Perspective of dimethyl ether as fuel: Part I. Catalysis

Perspective of dimethyl ether as fuel: Part I. Catalysis

Journal of CO₂ Utilization 32 (2019) 299–320 Contents lists available at ScienceDirect Journal of CO2 Utilization journal homepage: www.elsevier.com...

3MB Sizes 0 Downloads 16 Views

Journal of CO₂ Utilization 32 (2019) 299–320

Contents lists available at ScienceDirect

Journal of CO2 Utilization journal homepage: www.elsevier.com/locate/jcou

Review article

Perspective of dimethyl ether as fuel: Part I. Catalysis Ujjal Mondal, Ganapati D. Yadav



T

Department of Chemical Engineering, Institute of Chemical Technology, Nathalal Parekh Marg, Mumbai 400019, India

ARTICLE INFO

ABSTRACT

Keywords: Dimethyl ether (DME) Syngas CO2 Catalysis Multi-metal catalysts Fuel Methanol LPG CCS Multi-phase reactors

Dimethyl ether (DME) is heralded as the cleanest high-efficiency compression ignition fuel as a substitute for diesel. DME's autoignition property and high octane number are favorable to use it as a substitute for diesel and also LPG as a cooking fuel. DME can be synthesized from different routes such as coal, petroleum and biomass including various greenhouse gases. Huge amounts of greenhouse gases (CO and CO2) are generated in coal or petroleum operated thermal power plants and released in the atmosphere. Roughly 5–10% of total CO2 emission can be utilized for fuel and chemical production. CO2 capture and sequestering (CCS) plants only can be sustainable if supported by DME synthesis plant with a capacity of 3000–7500 TPD. DME can be produced from CO2 using innovative catalysts, reactors and separators. Part I of this review is a representation of the innovative strategies which have been reported for the production of DME from different sources of raw materials, catalysts and influence of operational parameters on DME selectivity and yield. The critical gaps are identified and further, research potentials are given in Part I. However, the industrial processes using a variety of reactor configurations affect the overall capex and opex. The production of syngas, irrespective of the source, is the first step in DME synthesis, which is then followed by conversion into DME using a battery of reactors and separators. A critical analysis is presented and future scope is outlined in Part II.

1. Introduction The UN Sustainable Development Goals for the world are indeed challenging and consequently finding reliable and economic resources for energy will depend on the science and technology of converting different waste products, waste energy and finding new resources. The energy and environment problems are intertwined due to the fast depletion of natural resources and a huge build-up of greenhouse gases in the atmosphere. Among different natural energy resources such as crude oil, coal, and natural/shale gases, crude oil is depleting very fast. The transportation industry happens to be the primary cause of oil delpetion; it consumes roughly 57% of total petroleum production. According to some estimates (e.g., BP Energy), the crude oil supply will run out by ∼2055. Electric cars are introduced to restrain air pollution but the problem is still unsolved as most of the power plants are operating on coal and petroleum as the primary non-renewable energy sources. The power plants are releasing a huge amount of greenhouse gases (COX, SOX, NOX) into the environment. The lifetime of the natural resources has been reduced dramatically and their overuse will lead to energy supply shortages for future generations. These problems have propelled to research and innovation in the development of new clean energy



alternatives, which have to be renewable and can be utilized in the industry without any major modification of the present infrastructure. The three main characteristics of the energy supply chain which are essential for any type of energy infrastructure are the energy generation, storage, and distribution and utilization [1]. Dimethyl ether (DME), or methoxymethane (IUPAC name) is the cleanest high-efficiency compression ignition fuel because of its autoignition property. It is the simplest and safer aliphatic ether which is known to be far from being toxic, carcinogenic, teratogenic, mutagenic compound and corrosive. DME is an environmentally benign compound and upon release it is photochemically degraded to CO2 and H2O a within few hours and will not deplete the ozone layer or build up greenhouse gas [2]. Apart from its use as fuel, DME is a higher grade propellant used for the synthesis of many safer healthcare products vis-à-vis conventional petroleum-based routes. It is estimated that the total worth of the DME industry will be approximately $ 9.7 billion by 2020 [1] which is divided in mainly four categories mainly, (1) LPG blend, (2) diesel replacement as a transportation fuel, (3) gas turbine fuel in power generation sector, and (4) chemical precursor for different chemicals (for instance, olefins and petrochemicals). China is the largest DME producer utilizing 90% of total DME production for LPG blending. Other

DOI of original article: https://doi.org/10.1016/j.jcou.2019.02.006 Corresponding author. E-mail addresses: [email protected], [email protected] (G.D. Yadav).

https://doi.org/10.1016/j.jcou.2019.02.003 Received 24 January 2019; Accepted 7 February 2019 Available online 23 April 2019 2212-9820/ © 2019 Elsevier Ltd. All rights reserved.

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

DME with the addition of a very little methanol and water is a good alternative to diesel for transportation sector and small-scale power generation industry. Based on Lower Heating Value (LHV), 1.2 L of DME is equivalent to 1 L of diesel. Because of higher octane number (55–60) with a low boiling point (−25 °C), it requires little modification of existing diesel engine to utilize DME as a fuel. Inside diesel engine, DME burns without sooting which is similar to an oxygenated fuel additive and it also enhances favorable air/fuel mixture inside the engine. DME has a very low vapor pressure and is chemically and physically stable. Thus, DME can be used as an aerosol propellant and can replace chlorofluorocarbon (CFC), Freon and R-134, which are the main contributors to ozone layer depletion. DME is used as a feedstock for a variety of chemicals such as acetic acid [9,10], methyl acetate [11–13], aromatics [14,15], gasoline [11], light olefins [16–18], higher ethers, oxygenates, etc. [19,20]. As the fuel cell technology matures, the opportunity of DME as fuel in a hybrid vehicle is very high. DME is a hydrogen carrier and it can be reformed to produce syngas (H2 + CO) at a lower temperature (120–150 °C) when compared with other fuels like diesel, gasoline, and methane (above 650 °C). DME can be catalytically converted to other useful chemicals by reacting with syngas such as formaldehyde [21], methyl acetate [22], and ethanol [23]. Other usages of DME include as solvent, kiln fuel for ceramics, and for welding and cutting plus brazing applications.

Fig. 1. The overall trend of papers published in the area of DME synthesis.

countries such as Egypt, Indonesia, South Korea, Vietnam, and India have also started evaluating or establishing manufacturing DME units. A number of research articles have been published over the years on DME synthesis (Fig. 1), particularly during the last two decades. The highest number of articles were published in 2011 due to its perceived great potential as a fuel inviting the attention of researchers in academia and industry. It is thus timely to review the scope of DME and its potential as a fuel and precursor for a number of chemicals, and industrial processes. The current review is thus written in two parts highlighting all areas concerning DME synthesis using various catalysts, and the reactor and separation strategies. The scope of Part I is to highlight the recent advancement of DME synthesis which includes various innovative reaction systems, catalysts and their synthetic protocols to get high activity, and effect of operational parameters on DME selectivity and yield.

3. History of DME production DME was developed as an aerosol propellant in 1963 by Akzo Nobel. From 1970 global oil prices started to increase and Amoco was the first company to invest in R and D of DME [24]. Until 1975 DME was produced as a by-product (3–5%) along with methanol in a high-pressure production process [25]. A German patent filed in 1980 mentioned that DME was present in methanol based fuel [26]. In 1990 a US patent was published on the operation of a diesel engine with 95% DME [27]. National Institute for Petroleum and Energy Research laboratories at Bartlesville in the US was the first to test DME in diesel engines in the 1980s [5]. In 1995, Haldor Topsoe, Amoco, and Navistar International Corporation jointly started an investigation on the large-scale synthesis of DME and concluded that methanol dehydration is a suitable technology for DME production. Amoco consortium was the first to justify the use of DME as a non-polluting ultra-clean fuel with diesel engines, which can meet the 1995 ULEV (California Ultra Low Emissions Vehicle) regulations in the category of medium-duty vehicles. In Europe, Volvo was the first company to carry out trials on buses with bio-DME. DME blending in LPG (20% vol./vol.) is more convenient than using DME as a diesel replacement because for the latter purpose, engines have to be modified accordingly. Enhancement of blending of DME from 20 to 30% does not need any major infrastructure other than the storage capacity of LPG industry [5,28]. The use of DME as a gas turbine fuel was started by Toyo Engineering, Haldor Topsoe Chiyoda Corporation and Snamprogetti/

2. DME properties and applications A comparison of the physico-chemical properties of different conventional fuels which could be replaced by DME is shown in Table 1. According to the World LP Gas Association (WLPGA), DME can be used as a mixture or separately as a substitute in the LPG industry [4]. About 15–20 vol.% of DME blending in LPG will not affect the current LPG infrastructure for storage, distribution, and usage [5]. DME gas can be liquefied by pressurizing at 0.57 MPa at 20 °C or by cooling to −25 °C at atmospheric pressure. The similar physical properties of LPG and DME, allow DME to be used as a substitute for propane and butane in LPG as a cooking fuel. The well established LPG industry infrastructure can be also used for DME without difficulty [6,7]. Around the world, the number of vehicles running on LPG is increasing. Currently, there are more than 10 million LPG operated cars on the road. DME can be synthesized from biomass and, especially bio-DME can be used as a blending agent with LPG (15–20 vol.) [8]. Table 1 Comparison of properties of different fuels (information extracted from [3,4]). Properties

DME

MeOH

Methane

LPG

Gasoline

Diesel

Chemical formula Molecular weight (Da) Boiling Point (°C) Vapour pressure at 20 °C Liquid density at 20 °C g/cm3 Specific gravity (25 °C/4 °C) Flammability limits in Air, Vol% Wobbe Index, kJ/m3 Cetane No. Calorific Value LHV, kcal/kg

CH3OCH3 46.07 −24.9 5.1 0.67 0.661 3.4–17 46198 55–60 6925

CH3OH 32.04 64.6 – 0.79 0.786 5.5–36 – 5 4800

CH4 16.04 −161.5 – 0.42 0.55 5–15 48530 0 12000

C2-C5 44.09 −42 8.4 0.49 0.51 0.94–2.1 69560 5 11950

C4-C12 100–105 35–200 – 0.71–0.77 0.739 1.9–8.4 – 4–20 11110

C3-C25 ≈200 180–360 – 0.832 0.82–0.95 0.6–7.5 – 40–55 10800

300

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

ENI [8,24], and also due to a joint effort of three major institutions, namely, Electric Power Development Corporation of Japan (EPDC), BP Amoco and General Electric Co. of US [29]. In Japan, a 1.15 MW DME fueled diesel power plant was established by FE Holdings, Daihatsu and Iwatani Corporation [30]. Haldor Topsoe has developed advanced solid oxide fuel cell technology which can use DME directly which eventually increases the thermal efficiency of small-scale power generation plant [8]. Chinese companies are converting coal into olefins such as ethylene and propylene via methanol to olefins (MTO) process. Others include Lurgi's methanol to propylene (MTP) process and Honeywell's advanced MTO process. Both processes utilize coal gas as a raw material to produce methanol followed by DME production and finally, DME is reacted to produce olefins. In 2001 International DME Association was established followed subsequently by China DME Association (CDA), Japan DME Forum (JDF) and Korea DME Forum (KDF). In 2016 Shenhuya group and Dow Chemical Company of China announced to invest US $10 billion to produce olefins from MTO process. Amoco along with Indian Oil Corporation Limited (IOCL) and Gas Authority of India Limited (GAIL) formed a joint venture in 1998 to promote DME in the Indian power market which was less competitive and less risky for investment at that time. Biomass derived catalytic DME synthesis is being pursued by Indian researchers.

On the contrary according to Gates and Johanson [35], methanol molecules are absorbed on the two adjacent acid sites of the catalyst. Kiviranta-Paakkonen et al. proposed Eley–Rideal (ER) model for the methanol dehydrogenation reaction, where one molecule of methanol is absorbed on the acidic site of catalyst while other reacting molecule remains in the bulk phase [32]. Ha et al. [36] studied a number of methanol dehydration reactions and concluded that at the beginning of the reaction two methanol molecules are non-dissociatively adsorbed on two acidic sites of an acidic catalyst (m-ZSM-5). Then those two adsorbed methanol molecules form an intermediate which instantly rearranges itself to form methyl carboxyneum ion and carbenium ion or two methyl carboxyneum ions. The second step was regarded as the rate determining step [36]. DME formation from methanol is also demonstrated by associative and dissociative pathways and both the reactions are proposed to carry out on the Brønsted acid site [37–39]. Methanol to dimethyl ether (MTD) reaction with ZSM-22 catalyst has been studied on the basis of density function theory (DFT) by Moses and Nørskov [40] who proposed that both the associative and dissociative pathways are responsible for methanol conversion but the dissociative pathway is faster than the former with similar dependency on acidic site. They have established a linear correlation between the strength of acidic site and activation energy and proposed that weaker acid sites produce higher activation energies. In the case of two-step dissociative pathway, DME synthesis step is a bit slower than the water releasing step. Hence, DME formation is the rate determining step for the dissociative pathway. Cassone et al. [41] have done computational analysis based on ab initio molecular dynamics method to study a novel electrochemical pathway to produce DME from methanol. The indirect process of DME synthesis from CO2 is shown in Fig. 3. For the methanol synthesis process, matured methanol-synthesis catalysts are used and a majority of them are copper based catalysts. While for the methanol dehydration process, acidic catalysts like zeolite, alumina and sulphuric acid have been used. Thus with the existing catalyst technology setting up a DME plant is rather cheap but the output is a mixture of methanol, water, and DME which has to be distilled for purification, separation, and recycling. Methanol cost is one of the deciding factors for DME price which it is generally double the cost of methanol [3,42]. Despite disadvantages, most of the DME plants operate with indirect synthesis process where a solid acid catalyst (usually alumina) is used for vapour phase dehydration of methanol. H2SO4 is also used as an acid catalyst by some industries, e.g. Jiutai Energy Group of China. and the reaction mechanism is shown below (Eqs. (5) and (6)). The advantages of this process are that the sulphuric acid can be recycled several times and the weakened acid is used as a raw material in the fertilizer industry; this liquid phase catalytic dehydration process can reduce the process cost by one-third of actual cost [43].

4. DME synthesis Coal or petroleum operated thermal power plants generate huge quantities of CO and CO2 greenhouse gases and technologies must be developed for CO2 capture and sequestering (CCS) facility. The economy of the CCS plant only could be sustainable when it is supported by DME synthesis plant with a capacity of 3000–7500 TPD [28]. DME can be synthesized via two synthesis routes: (1) indirect synthesis or two-step process, (2) direct synthesis or single step process. The direct synthesis process comprises a single reactor process where both reactions occur over a bifunctional catalyst. Linde/Lurgi, Haldor Tospoe, Uhde, Toyo Engineering, and Mitsubishi Gas Chemical Company are holding the licenses for the single-step DME synthesis technology. 4.1. Indirect method The indirect process is a dual-step catalytic process in which methanol is synthesized from syngas or CO2 in the first reactor and then it is dehydrated to produces DME in the second reactor. MGC, Toyo, Udhe, and Lurgi are the companies which are developing DME production technology by indirect synthesis [28]. In the presence of an acidic catalyst, methanol is dehydrated to DME wherein the by product water acts as a reaction inhibitor by competing with methanol for protons (Fig. 2). Kinetic modeling of methanol dehydration has been reported in the literature and a majority concludes that the methanol dehydration reaction (Eq. (1)) follows either Eley–Rideal kinetic model or Langmuir–Hinshelwood [31–33].

2CH3 OH

° H298

CH3 OCH3 + H2 O

=

23.5 kJ/mol

(1)

CH3OH + O CH3+

2−





↔ CH3O + OH



+ CH3O ↔ CH3OCH3

(5)

CH3HSO4 + CH3OH → CH3OCH3+H2SO4

(6)

4.2. Direct method

According to Bandiera and Naccache [34], the mechanism of DME formation by methanol dehydration involves two adjacent sites on the catalyst surface, i.e., one acidic site (H+) and another adjacent basic site (O2−). Methanol is protonated on the acidic site to form [CH3·OH2]+ which is instantly converted to CH3+ and H2O (Eq. (2)). One methanol molecule is converted to CH3O− and OH− on the adjacent basic site (Eq. (3)). Finally, DME is formed by combining two activated species (CH3+ and CH3O−) (Eq. (4)). CH3OH + H+ ↔ [CH3·OH2]+ → CH3+ + H2O

CH3OH + H2SO4 → CH3HSO4+H2O

Though the direct or one-pot synthesis of DME from syngas is a onestep process, it involves three reactions, i.e. methanol formation by syngas hydration, methanol dehydration and water-gas shift (WGS) reaction (Eqs. (7)–(9)). Hydrogen produced in the WGS reaction is used in the methanol synthesis reaction and methanol (Eq. (7)) is thereafter dehydrated to DME. These reactions are conducted in a single reactor packed with a bifunctional catalyst for the simultaneous occurrence of the reactions. The overall reaction of the syngas to dimethyl ether (STD) process can be expressed as Eq. (10).

(2) (3)

CO + 2H2

(4) 301

CH3 OH

° H298 =

90.6 kJ/mol

(7)

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

Fig. 2. Indirect method of DME synthesis via methanol dehydration reaction [32,35].

2CH3 OH

H2 O + CO 3CO + 3H2

CH3 OCH3 + H2 O

H2 + CO2

° H298 =

° H298 =

CH3 OCH3 + CO2

23.4 kJ/mol

23.4 kJ/mol ° H298

=

245.8 kJ/mol

is produced via syngas hydration. The single step conversion method is getting more attention in the industry because of the higher one pass conversion of syngas and it requires a lower supply of hydrogen to produce DME in comparison to dual step process. Thermodynamic analysis of direct DME synthesis from syngas and CO2 reaction has been done by Moradi et al. [44] and Ateka et al. [45]. By comparing the heat generation between Eqs. (9) and (14), it can be concluded that the use of CO2 in the direct synthesis process produces less heat and thus the reaction is more thermodynamically stable and the catalyst bed overheating problem with syngas can be avoided. However, H2O formation during the reaction promotes the catalyst deactivation and reduces DME yield. Another advantage of using CO2 is its higher oxidation power compared to syngas and the presence of CO2 in the supplied reaction gas mixture influences the active site of catalyst to produce more methanol [46]. Commercialization of DME production from syngas is not economically viable as it requires a higher amount of energy and releases greenhouse gases into the atmosphere via water-gas shift reaction. DME production has to adopt new technologies to be more energy efficient and environment-friendly. Utilization of CO2 for the purpose of DME production can be a noble way to prevent accumulation of greenhouse gas in the environment. The present technology is not mature enough to convert CO2 into DME with higher conversion rate and selectivity. This is an equilibrium limited reaction and if the produced water can be withdrawn from the reactor, the equilibrium can shift toward DME synthesis.

(8) (9) (10)

CO2 is hydrogenated to produce DME and like in the STD process, methanol is formed as an intermediate product followed by DME synthesis through methanol dehydration. Both methanol synthesis and methanol etherification reactions occur in parallel (Eqs. (11) and (12)) along with the reverse water-gas shift (rWGS) reaction as a side reaction (Eq. (13)). The overall reaction of CO2 hydrogenation to produce DME is given by Eq. (14).

CO2 + 3H2 2CH3 OH

H2 + CO2

2CO2 + 6H2

CH3 OH + H2 O

° H298 =

49.4 kJ/mol

(11)

CH3 OCH3 + H2 O

° H298 =

23.4 kJ/mol

(12)

H2 O + CO

° H298 = 41.4 kJ/mol

CH3 OCH3 + H2 O

° H298 =

122.2 kJ/mol

(13) (14)

The direct method of DME synthesis is more practical as both the reactions are performed in a single reactor and thus the operational cost will be less (Fig. 4). Integration of methanol formation and methanol esterification reaction makes the whole process more thermodynamically favorable as the methanol formation from syngas hydrogenation is exothermic and reversible (Eq. (1)). The formation of water molecules during methanol dehydration reaction (Eq. (8)) is also beneficial for hydrogen generation in WGR reaction (Eq. (9)). The reactions (Equations (7), (8) and (9)) produce a synergic effect on reaction equilibrium and as more methanol is converted to DME, more methanol

4.3. Other routes Methane has a high potential to be used as a precursor for DME production via a dual-step synthesis process. Firstly methane is

Fig. 3. The indirect process of DME synthesis from the gaseous mixture of CO2 and H2. 302

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

Fig. 4. the Direct process of DME synthesis from the gaseous mixture of CO2 and H2.

transformed into methyl halide (such as CH3Cl, CH3Br) by reacting with hydrogen halide via oxidative halogenation reaction and then methyl halide is converted to higher hydrocarbons including DME via hydrolysis and carbonylation reactions [47–52]. Yang et al. [47] have reported the conversion of methane into methyl bromide by reacting with oxygen and hydrogen bromide over Rh/SiO2 catalyst. One of the problems associated with this reaction is that ony ∼10% methane is converted to CO and CO2. You et al. [48] co-fed CO and CO2 along with methane and HBr/H2O in the oxidative halogenation reactor to produce CH3Br and avoided generation of CO2.Then the produced methyl bromide was hydrolyzed to produce DME over a metal chloride catalyst supported on silica (ZnCl2/SiO2). Corrosion of the reactor is a common problem when methyl halide is used as a precursor. This issue was resolved by Prakash et al. [49] who utilized poly(4-vinyl pyridine) as a catalyst in the place of liquid amines. Methyl halide is also used to synthesize DME and methyl acetate as a by-product via oxidative carbonylation reaction by reacting with CO and Cu2O in the presence of SbF5/graphite as a catalyst [50]. Methanol and DME were produced when the mixed oxide was used as a catalyst for the oxidative carbonylation of methyl bromide [51,52].

5.1. Methanol formation reaction 5.1.1. Copper based catalysts BASF was the first company to commercially produce methanol from syngas containing CO2 by using ZnO-Cr2O3 as a hydrogenation catalyst. In 1960 ICI introduced copper zinc oxide alumina catalyst for selective production of methanol from naphtha/natural gas under milder reaction conditions. Thereafter a lot of research was done on Cu-ZnO based catalyst combined with other metals. Among them Cu-ZnO based catalysts prepared by co-precipitation method have shown higher conversion and selectivity. The metallic Cu clusters in Cu-ZnO-Al2O3 are the active sites for methanol synthesis and WSG reactions; and the conversion and selectivity are dependent on copper dispersion and metal surface area [58–60]. A typical example of the commercial catalyst is Cu-ZnO-Al2O3, which is usually composed of 50–70 mol% of CuO, 20–50 mol% of ZnO and 5–20 mol% Al2O3. According to Chinchen et al. [61], ZnO is the bestperforming oxide among MnO, Cr2O3, and SiO2 in terms of various functionalities and it shows a good promoting effect for methanol synthesis but not for rWSR reaction [62]. The primary role of ZnO is to provide an optimum dispersion of metallic Cu, by acting as a geometric spacer between the Cu nanoparticles which leads to higher number of active sites on which syngas conversion to methanol takes place [55]. The other functions of zinc oxide are to hinder sintering of copper particles as well as to disperse catalyst poison such as Cl and S to reduce poisoning. The ratio of Cu+/Cu° is also appropriately maintained by ZnO by creating Cu+-O-Zn active sites, as both the Cu states are important in methanol formation. da Silva et al. [63] concluded that ZnO is responsible for the strong metal-support interaction with Cu nanoparticles, which were referred to as “methanol active copper”. The size of the copper particle and its dispersion over the support material are greatly varied with the type of precipitant, Cu/Zn molar ratio, calcination temperature, etc. although excessive ZnO is responsible for deactivation of the catalyst. Thorhauge et al. [64] have demonstrated the role of Zn particles on Cu dispersion and its influence on syngas to methanol conversion. Le Valent et al. [65] have developed a mathematical model of methanol synthesis reaction on core-shell Cu-ZnO catalyst to correlate successfully the number of Cu-ZnO contact points with observed catalytic activity. Further addition of trivalent ions (M3+) such as Al3+ in Cu/ZnO catalyst leads to the enhanced thermal and chemical stability of the catalyst, higher Cu dispersion and metal surface area [66]. Based on previous studies Sugawa et al. [67] have proposed the following order of activity of different metals for methanol formation from CO2:

5. Catalysts for DME synthesis Many challenges still exist for DME production despite several efforts during the last few years. The development of a highly active and efficient catalyst for CO and CO2 hydrogenation is still a distant dream. One pot DME synthesis (direct method) from either syngas or CO2 involves two separate reactions (methanol formation and methanol dehydrogenation). The catalyst should perform as a redox function which first turns gases into alcohol which is dehydrated to the ether on an acid site. As stated earlier the indirect method of DME synthesis involves both the reactions in separate reactors whereas the direct method is more attractive since it alleviates the thermodynamic constraints of methanol synthesis from CO2 or CO and leads to higher conversion as well as selectivity [53–55]. It is highly recommended by the industry to use a single pot synthesis technique for DME synthesis to reduce production cost [55,56]. Other than the metal function and acid function of the of bi-functional catalyst, some other important factors also influence the productivity of the one-pot process, such as (i) preparation method of the catalyst, (ii) sintering of the copper particle, and (iii) catalyst deactivation. It is very important to know that the product distribution of direct DME synthesis reaction does not only depend on the thermodynamics of the reaction but also on the reaction kinetics. The heat conduction properties of the bi-functional catalyst are very low and the reaction process is carried out in the range of 523–673 K and pressure of 10–50 bar [57,58]. In the case of the indirect process, irrespective of the process followed, the productivity is highly dependent on the catalyst properties. In the following section, the effect of metal function and acid function on the DME synthesis is discussed.

Cu ≫ Co = Pd = Re > Ni > Fe ≫ Ru = Pt > Os > Ir = Ag = Rh > Au Water generation during hydrogenation of CO2 for methanol production leads to the unsatisfactory performance of Cu-ZnO-Al2O3, since alumina possesses strong hydrophilic property; and in order to solve this problem, lower hydrophilic promoters have been adopted such as ZrO2 [68,69]. Various Cu based zirconia catalysts have been reviewed by Raudaskoski et al. [70] who have described how Zr promoted high 303

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

Cu dispersion results in higher conversion and more methanol selectivity. To further enhance the performance of ZrO2 containing Cu based ternary catalyst, additional promoters have been incorporated such as Ti [68]. Cu-ZnO-ZrO2-TiO2 quaternary catalyst prepared by oxalate precipitation method led to higher conversion and selectivity due to the presence of both the promoters Zr and Ti. The addition of Zr and Ti in the catalyst structure led to a decrease in crystallite size of CuO, ZnO and increased CuO-ZnO interaction [68]. Angelo et al. [71] have studied the effect of CeO2 as a promoter in Cu-ZnO-Al2O3 catalyst and found that CeO2 addition decreases the Cu crystalline size and does not benefit the reaction in any way. Garciani et al. [72] have introduced a new site for CO2 activation and hydrogenation on the ceria-copper interface. They have shown that the hydrogenation reaction on CeOx/ Cu (100) is 200 times higher than Cu (100) and 14 times higher than Cu-ZnO. Fornero et al. [73] have shown that Cu-Ga2O3-ZrO2 catalyst performed better than Cu-Ga2O3 and Cu-ZrO2 catalysts. Other than the foregoing metal promoters, various other metal and non-metal promoters have been added in to the Cu-ZnO bi-metallic system for methanol synthesis; these include Mn [74], Cr [75], Au [76], La [77], Ce [77], V [78], graphene [79], carbon [74,80] or mixture [77,81,82] among them. It was observed that Zr, Al, and Ga showed the maximum activity in terms of conversion and selectivity [83]. Among a number of catalysts studied, LaCr0.5Cu0.5O3 and Cu-ZnO-Ga2O3/SiO2 have shown better methanol formation rate with high selectivity (as high as 99.5%), but their stability and scalability have not been tested [84]. Martin et al. [85] have studied the activity of In2O3/ZrO2 catalyst for methanol synthesis from CO2 hydrogenation at very low pressure compared to conventional system. They have achieved 100% methanol selectivity compared to Cu-ZnO catalyst and shown 1000 h time on stream (TOS) stability.

η-Al2O3 > γ-Al2O3 ≫ θ-Al2O3 ≫ (χ + γ)-Al2O3 ≫ δ-Al2O3 > αAl2O3 ≈ κ-Al2O3 γ-Al2O3 forms Lewis acid site during the calcination process and although it is very active, it strongly binds to water molecules and gets deactivated instantly. Xu et al. [96] studied the effect of water content, reaction temperature, and catalyst acidity on methanol conversion and in this regard, a number of catalysts with different acidity (different silica content) such as γ-Al2O3, amorphous alumina-silica, titania modified zirconia, and HZSM-5 have been considered. Water molecules block the active sites of the catalyst, and it was reported that γ-Al2O3 was the most affected whereas HZSM-5 the least. More acidic catalyst shows an increase in the activity of the catalyst. γ-Al2O3 is affected by water content because it possesses the most number of strong Lewis acid sites to adsorb water molecules [97]. 5.2.2. Zeolites and modified zeolies Considerable attention is focused on the use of zeolites as a solid acid catalyst for methanol dehydration reaction. Zeolites are crystalline aluminosilicates which are widely studied for their shape selectivity which comes from their well-defined microporous structure. The shape selectivity can be further tuned as per the reaction by turning the opening and special orientation of the channels, size, and location of the cases. Zeolites possess both Brosted and Lewis acid sites and the distribution, number, position and strength of these acid sites are the main deciding factors for catalytic activity [98]. The main advantage of zeolite is the stronger acid sites, which allows the reaction to be carried out at low reaction temperature [99,100] Vishwanathan et al. [99] reported 80% conversion of methanol to DME at 230 °C by HZSM-5 catalyst, while γ-Al2O3 required a higher temperature of 320 °C to reach the same conversion [99]. Olefins and coke formed through some undesired side reactions at the high strength acid sites of zeolites and blocking of pore structure by coke molecules were the main reasons for deactivation of zeolites [101]. Catizzone et al. [102] have investigated several types of zeolites for methanol dehydration reaction based on the channel openings (8–12 membered rings) and channel orientation (1-,2- and 3-dimensional channel orientations). One dimensional zeolite such as MTW or MOR have shown high DME selectivity at 240 °C but deposition of coke leads to early deactivation of the catalyst. With medium pore opening the 1-D zeolite turn over number (TON) was better and it showed good resistance to coke deposition. SAPO-34, MFI, and BEA are 3-D channel zeolites which have been investigated by the same research group who found that despite the small channel openings (3.8 Å) of SAPO-34, it showed high DME selectivity, but it rapidly got deactivated by coke deposition [102,103]. When channel intersection and channel openings have a similar size such as MFI and BAE structure, higher stability was observed with coke deposition [104]. Tang et al. [105] have studied ZSM-5-MCM-41 composite catalyst which is both microporous and macroporous, having a better activity for methanol dehydration [106]. Several studies on FER zeolites for the methanol dehydration reaction have shown high DME yield. Catizzone et al. [107] have investigated FER zeolites with different acidity (governed by Si/Al ratio) for methanol dehydration reaction. Higher aluminum content increases methanol conversion and Lewis acid sites are more active at a lower temperature (240–160 °C) than Bronsted acid sites [108]. The activity of zeolites can be further improved by decreasing surface acid strength or decreasing total number of acid sites of the catalyst. The strength of acidic sites of the solid acid catalyst is of great importance, as DME formation occurs at the low acidic side (Lewis acid) and DME is further converted to olefins on strong acid sites. Several reports have appeared on Na, Mg, Zn, Zr impregnated HZSM-5 catalyst for DME synthesis from methanol and it was demonstrated that with these metal impregnation strong acidity was decreased which reduced coke deposition [109]. Khandan et al. [110] have shown with

5.1.2. Palladium-based catalysts A number of Pd based catalysts have also been developed for methanol synthesis by hydrogenation of CO and CO2 such as Cu/SiO2 [86], Li-Pd and Na-Pd [87], Pd-Ga2O3 [88], Pd-βGa2O3 [89], Ga2O3 promoted Pd-SiO2 [90,91], Pd-Cu/SiO2 [69], and Pd-ZnO [92]. Koizumi et al. [93] have reported that methanol synthesis from CO2 by Pd catalyst can be further improved by adopting two strategies such as (i) using uniform mesoporous support for the catalyst (SBA-15, MCM-41), and (ii) use of alkali/alkaline earth metal additives. 5.2. Methanol Dehydration to DME 5.2.1. Alumina The second step of indirect DME synthesis is the dehydration of methanol for which generally solid acid catalysts are employed, and the most desired properties of the solid acid catalyst require them to be hydrophobic, stable at high temperature, highly active and selective for the desired product. One of the earliest studies reported that DME was formed by methanol dehydration using alumina as a catalyst at the temperature range of 300–400 °C [94]. Methanol dehydration process has several licensors around the globe such as Linde/Lurgi, Haldor Tospoe, Toyo Engineering, Mitsubishi Gas Chemical Company (Japan), Uhde, China Southwestern Research Institute of Chemical Industry and China Energy. This reaction can be carried out in either the liquid or vapor phase, depending on the catalyst used, at suitable reaction temperature (100–300 °C) and pressure (1–20 bar). Among the solid acid catalysts applied for methanol dehydration, alumina and zeolites are the most popular as they are stable at high temperature and pressure, having a high surface area, low cost and most of the acid sites have lower acidity (Lewis acid site). Sung et al. [95] have investigated different crystalline phases of alumina for the methanol dehydration reaction and concluded that γ-Al2O3 showed the second highest catalytic activity among other phases and the order of activity of different phases was as follows:

304

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

incorporation Zr in HZSM-5 framework DME yield increases from 53 to 92%. Kim et al. [111] have studied γ-Al2O3 impregnated HZSM-5 catalyst for methanol dehydration reaction and obtained 50% conversion with 99% DME selectivity.

an industrially applied mature catalyst which is well researched. Like syngas, CO2 is also converted to DME by a physical mixture of CZA and γ-Al2O3 catalysts [124–126]. Takeguchi et al. [127] have studied DME synthesis from a mixture of CO and H2 by physically mixed Cu/ZnO/ Al2O3/Cr2O3/Ga2O3 and silica-modified γ-Al2O3 catalysts. Silica loading increases the Bronsted sites and catalyst surface area. Other studies have reported that when γ-Al2O3 was modified with niobium sulfate (Nb2(SO4)3) and treated with 0.1 mol NH4F solution, both the surface area and acidity of the catalyst increased [128]. Joo et al. [129] have suggested that strong acidic sites on γ-Al2O3 converted methanol and DME into CO through reforming reaction and thus prior treatment of γ-Al2O3 and HZSM-5 with sodium carbonate and formaldehyde would increase the number of weak acid sites. A huge number of studies have been reported on the effect of different promoters on the Cu-metal functions in the hybrid bi-metal catalyst such as Ga [130], Mn [131], Pd [132], La [133], Zr [82–84], Y [134], magnesia [130], as well as carbon nanotubes [135], etc. and the effect of different promoters on Cu dispersion, activity, and selectivity of DME have been discussed. According to Venugopal et al. [134] among the different promoters (Ga, Zr, La, Y) in CZA catalyst, yttrium (Y) showed the highest CO conversion (70%) and DME selectivity of 47.7% which was due to Cu particle grain growth and surface area. Different functionalities of various promoters enhance the catalyst activity of CZA catalyst; for instance, Ga increases the inverse spillover of hydrogen [130], and Zr increases the crystalline size of Cu [136], etc. MgO modified γ-Al2O3 dehydration catalysts in hybrid form also have been studied to witness better CO conversion and DME activity [130]. When alumina content is more than 50 wt% in Cu/ZrO2 and calcination temperature is more than 500 °C, CZA catalyst itself can be used as a hybrid catalyst [137]. Gel type slurry catalyst made up of CZA with AlOOH binder showed good catalytic activity for DME synthesis as AlOOH acts as methanol dehydration catalyst [138]. Various mesoporous catalysts also have been extensively reported for the one-pot synthesis of DME from CO and CO2. Jiang et al. [139] prepared a mesoporous Cu-γ-Al2O3 catalyst with different Cu mol ratio by evaporation induced self-assembly method and it showed excellent CO conversion (72%) and DME selectivity (69%) at 310 °C and 50 bar pressure. Wang et al. [140] prepared mesoporous Al2O with highly dispersed Cu by combustion synthesis method and it showed good activity with high DME selectivity for 56 h time on stream (TOS). Zeolite-based catalysts have been used as an acid function in a bifunctional catalyst as the hydrophobic nature of zeolite is responsible for the higher activity at the lower reaction temperature, which makes the methanol formation step thermodynamically more favorable [141–143]. Zeolites of proton and non-proton form (HZSM-5 and ZSM5), ferrierite, zeolite-Y, and mordenite are among the most famous zeolites used as an acid function in DME synthesis. Ramos et al. [144] investigated different solid acid catalysts mixed with a commercially available methanol synthesis catalysts such as porous alumina (alumina-C), non-porous alumina (alumina-D), tungstated zirconia (WZrO2), sulfated zirconia (S-ZrO2), and HZSM-5. HZSM-5 was the most active catalyst among the rest when employed for DME synthesis from CO, which was due to the higher number of Bronsted acid sites present on HZSM-5. Cu-Mn-Zn supported on HY zeolites, modified via ion exchange with rear earth (Nd, La, Ce, Sm, Pr, and Eu) [145] and transition (Ni, Co, Fe, Cr, and Zr) [145] metals, as hybrid catalysts have been utilized for DME synthesis. The effect of Si/Al (30, 80, 280) ratio of HZSM-5 and HY catalyst in CZA-zeolite on CO conversation and DME selectivity has been studied by Xie et al. [146]. In their case, the lowest CO conversion of 46.7% and the highest DME selectivity 70.4% were observed with HZSM-5 (Si/Al = 280) whereas the highest CO conversion of 87.7% and the lowest DME selectivity of 65.9% was achieved with HZSM-5(Si/Al = 30). García-Trenco et al. [147] and others have shown that CZA-zeolite catalysts are deactivated due to Cu sintering as Cu2+ ions (and sometimes Zn ions also) migrate to the HZSM-5 and increase the number of Lewis acid sites. In order to modify and study

5.2.3. Heteropolyacid (HPA) Heteroplyacids (HPAs) are also used as catalysts in methanol dehydration reaction. Keggin-type HPAs, which are represented as H8−n[Xn+M12O40], where “X” is heteroatom (such as Al3+, P5+, Si4+, etc.), “n” is the oxidation state and “M” is the metal ion, are the most commonly used. The heteroatom in the HPAs possesses highly acidic Bronsted acid site. Thus HPA performs better at lower reaction temperature compared to zeolites. Carr et al. [38] have done methanol dehydration reaction over Keggin type HPA clusters with different heteroatoms (X = P5+, Si4+, Al3+, and Co2+) and proposed that the reaction mechanism follows associative reaction pathway. Alharbi et al. [112] have studied the activity of HPA in methanol dehydration reaction and compared results with zeolite with different acidity (Si/ Al = 10–120) in terms of the turn over reaction frequency (TOF) and acid strength of the catalyst. HPA containing tungsten/phosphorus (HPW) showed TOF of 53 h−1 whereas the most active zeolite, HZSM5 had TOF of 1 h−1. Ladera et al. [113] have proposed that the activity of HPAs can be further enhanced by using TiO2 as support as it enhances the accessibility of the methanol molecules to the proton site of HPAs. 5.2.4. Ion exchange resin (IER) Ion exchange resins (IER) are also employed for methanol dehydration reaction. IER is a copolymer of divinyl benzene/styrene and sulfonic acid is present in the IER structure. The main advantage of using IER as an acid catalyst is the use of low reaction temperature in the range of 30–150 °C [114,115]. The activity can be further improved by incorporation of Lewis acid site through reaction with aluminum chloride or boron trifluoride [116]. Hosseininejad et al. [117] have shown that Amberlyst 35 has the highest catalytic activity among other IERs, γ-alumina, and zeolites (HY, HZSM5, HM zeolites) at the temperature range of 110–135 °C. 5.2.5. SBA-15 and HMS supported catalysts Tokey et al. [118] have synthesized alumina impregnated SBA-15, a mesoporous structure aluminosilicate, by one-pot hydrothermal synthesis and used it for DME production by the methanol dehydration reaction demonstrating methanol conversion value close to equilibrium conversion with 100% DME selectivity. Al-HMS with different Si/Al ratio has been synthesized by Sabour et al. [119] and tested for DME production by methanol dehydration reaction. Al-HMS with Si/Al ratio of 10 showed the best catalytic activity with methanol conversion of 89% with 100% DME selectivity. When the Si/Al ratio was increased, the conversion increased but DME selectivity decreased. 5.3. Direct method of DME production One pot conversion of CO and CO2 to DME is challenging and energetically unfavorable. Suitable reaction conditions and efficient catalyst are required to carry out such reactions. During DME synthesis reaction from CO2, CO and water are produced by reverse water gas shift (rWGS) reaction and other hydrocarbons are also formed from methanol. A large quantity of water formation which is a big problem during DME synthesis from CO2, as it creates a thermodynamic limitation for methanol formation and methanol dehydration reaction, and thus the DME yield is lower when CO2 is used as compared to CO. Many reports can be found on syngas to DME (STD) reactions with physical mixtures of catalysts used for methanol synthesis and methanol dehydration (e.g. Cu/ZnO/Al2O3 and γ-Al2O3). It was reported that CO conversion increased from 50 to 93% and DME selectivity from 34 to 52% when the reaction temperature was elevated to 240–290 °C with CO: H2 mole ratio of 2 [120–123]. Cu/ZnO/Al2O3 (CZA) catalyst is 305

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

the influence of acid sites of zeolites, modification of HZSM-5 catalyst with a number of basic oxides (i.e., MgO, ZnO, CaO, and Sb2O3) and transition metals (Zr and Fe) was carried out and it was found that due to acid sites being shifted to weaker strength, DME selectivity was improved [148,149]. Pure and modified ferrierite has become quite popular for the direct DME synthesis from CO, as modified ferrierite is highly DME selective and stable at high reaction temperature. Montesano et al. [150] studied the influence of zeolite structure and topology on DME yield and concluded that the main reason for ferrierite activity was that it provides a path for small molecule diffusion (i.e. MeOH and DME). Prasad et al. [151] also reported higher activity and stability of CZA/HFER catalyst for DME synthesis compared to HZSM-5, HY, and NaY. Many studies have shown that CZA/Zr incorporated HFER catalyst showed higher catalytic activity than HZSM-5 and Yzeolites. Zr modification of FER has resulted in low Cu surface area with presence of a required number of acid sites for DME synthesis [123,152]. Naik et al. [124] compared the catalytic activity of γ-Al2O3 and HZSM-5 (Si/Al = 60) by mixing with CZA catalyst for direct conversion of CO2 to DME in a fixed bed reactor at 260 °C and 5 MPa. HZSM-5 was more active in terms of CO2 conversion (30% vs 20%) and DME selectivity (75% vs 5%) and it also possessed better catalyst stability. So it was concluded that the use of γ-Al2O3 acid function in the hybrid catalyst is very disadvantageous when single pot CO2 to DME conversion reaction is considered. Ge et al. [153] observed that for good conversion and yield of DME, both the active sites of catalyst should be in close proximity. Frusteri et al. have investigated the function of an acid catalyst in the hybrid catalytic system, which was prepared via geloxalate precipitation of CuZnZr precursors on HZSM-5 (Si/ Al = 27–127) [154]. It was found out that acidity of zeolite has to be tuned accordingly to achieve highest DME selectivity along with good resistance to water deactivation. HZSM-5 with Si/Al ratio of 127 gave the highest methanol conversion but poor resistance to water deactivation. HZSM-5 with Si/Al of 27 offered poor methanol conversion but good water resistance and that HZSM-5 with Si/Al ratio 38 was the best for one step CO2 to DME conversion and water resistance [154]. Other than the acidic property, the textual properties of zeolites also influence the catalytic activity for CO2 conversion. Therefore Frusteri et al. [155] prepared hybrid grains of the catalyst by co-precipitating CuZnZr on different zeolites with different channel supports (FER, MOR, MFI) for direct synthesis of DME from CO2. During the catalyst testing, the following trend of catalyst activity was observed,

6. Effect of catalyst preparation method A number of methods for synthesizing hybrid catalysts have been reported in the literature such as co-precipitation [131,161], sol–gel [137], precipitating sedimentation [162], impregnation [163], and wet chemical methods [164]. Among them, the co-precipitation and physical mixing methods are the most widely used preparation methods for hybrid catalysts. Co-precipitation method involves the co-precipitation of active functions of methanol synthesis catalyst (MSC) over an aqueous or organic solution of precursors of methanol dehydration catalyst (MDC). The physical mixing of both the MSC and MDC functions is the other method. There are a few drawbacks of this method however such as the uncontrolled size distribution of the particles, random active site distribution on the catalyst surface and aggregation of catalyst particles during precipitation. Ahmad et al. [164] have compared the hybrid catalyst preparation method for STD reaction including impregnation, co-precipitation, co-precipitation-impregnation, co-precipitation sedimentation, and oxalate methods. According to their study oxalate, coprecipitation and co-precipitation sedimentation are better performing methods of hybrid catalyst preparation among the rest. In recent years, a number of innovative STD catalyst preparation methods have been proposed and developed; among them, sonochemical assisted, physical sputtering, and core-shell catalyst are the most popular. When the coprecipitation method is coupled with the ultrasound irradiation, the ultrasound waves lead to a high nucleation rate limiting particle growth and enhance the interaction between particles and fragments of aggregates of the catalyst [165]. Allahyari et al. [166] have prepared CuO-ZnO-Al2O3/HZSM-5 nanocatalyst by the sonochemical method and it was reported that longer irradiation time led to bigger CuO crystals, higher surface area along with smaller particle aggregates and uniform active site distribution. Khosbin et al. [167] compared the activity of STD nanocatalyst prepared by co-precipitation-ultrasound and co-precipitation- physical mixing method. It was found that catalyst prepared by the former method showed better catalytic activity (50.5% CO conversion and 55% DME selectivity) in comparison to the latter method (CO conversion 16.5% and DME selectivity of 38%) at identical reaction conditions. Hosseini et al. [168] prepared nanocrystalline γAl2O3 by sol–gel method and found that catalyst prepared by the sol–gel method showed higher activity than that prepared with precipitation method. The non-aqueous sol–gel method showed even better activity than aqueous sol–gel one. Some other advantages of the sol–gel method include low-temperature preparation method, a high degree of purity, ability to control pore volume and pore size distribution. Irrespective of the catalyst preparation method adopted, the catalytic activity decreases with TOS due to the migration of copper particle, sintering [169], oxidation, coke deposition [144,170], the strong interaction between the CZA and methanol dehydration catalyst [171] and partially with the impurities present in syngas [172]. Therefore, many scientists have proposed a different approach to maximizing the stability of the Cu-based catalyst. Garciá-Trenco et al. [173] confined Cu nanoparticles inside the pores of zeolite to improve the stability of catalyst in DME synthesis. In a different approach, Cu-ZnO particles were confined inside the pores of mesoporous silica (SBA-15) to avoid direct contact between CZA and SBA-15 surface [174]. This approach eliminated any kind of detrimental interaction, as well as sintering of Cu particles from the catalyst structure and further analysis with HRTEM, showed the presence of Cu nanoparticles size of 5–6 nm. This catalyst preparation approach has been proved to be more effective than physical grinding or mixing method. Millimeter size capsule catalyst is also employed for STD reaction where CZA core is covered by a thin layer of acidic zeolite shell [175]. This method is advantageous as very less amount of by-product is formed and high DME selectivity achieved, because the active sites on the surface of CZA catalyst and the acid sites of MDC do not much

CuZnZr/FER > CuZnZr/MOR > CuZnZr/MFI Lower mass transfer limitation was offered by FER as metal oxide anchored on the lamellar crystals of the FER zeolite generates more number of Lewis acid and CO2 gets activated on those sites. There are several other reasons for the deactivation of zeolite catalysts, among which the most common mechanisms are: (i) coke deposition on the active site of the catalyst, and (ii) pore blockage inside the zeolite channels by carbonaceous compounds. It is experimentally proved that coke deposition in zeolite is very much dependent on the shape of the channels [156] and zeolites with large pores are more prone to coke formation compared to medium pore size zeolites [157]. Deactivation of zeolite can be controlled by incorporation of Na into the zeolite structure; it leads to moderate number of Bronsted acid sites and decreases the acid strength of the HZSM-5 [121]. One of the other methods for enhancing the resistance to carbon formation is by creating a silicalite shell around the HZSM-5 [158,159]. Ateka et al. [160] have established a kinetic model of direct synthesis of DME from syngas and CO2 using CuO-ZnO-MnO/SAPO-18 bifunctional catalyst in a fixed bed isothermal reactor. The kinetics was established by considering that all reactions occurred during both methanol synthesis and methanol dehydration reaction.

306

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

interact. Methanol produced on CZA catalyst has to diffuse through the acidic sites of HZSM-5 on the shell side to get converted into DME [176]. This coated capsule catalyst is not the perfect catalyst for direct DME synthesis as multiple defects and cracks are formed on the zeolite shell side during acidic hydrothermal synthesis which leads to a decrease in CO conversion. A second layer of silicate-1 zeolite on the HZSM-5 shell was given as a protective layer [175,177] for HZSM-5 layer. Pd/SiO2 core encapsulated with dual layer coating has shown good catalytic activity for DME synthesis. SiO2 has been used as adhesive for the preparation of SAPO encapsulated MSC cores (Cr/ZnO [178], CZA [54]). Urea hydrolysis assisted simple homogeneous precipitation method was also reported to prepare core-shell structure of [email protected] catalyst for STD reaction [179]. Sánchez-Contador and coworkers [180] have investigated the advantage of the core-shell structure of [email protected] over simple physically mixed catalyst CZZSAPO-11 for DME synthesis from the mixture of CO and CO2 gases in fixed bed reactor. The core-shell structure enables separation of the methanol synthesis and methanol dehydration reactions and therefore H2O produced in the dehydration reaction will not affect the methanol formation on metallic function. As a result, methanol while diffusing out of the core, will be converted to DME in the shell side of the catalyst. Nowadays a number of innovative capsule catalysts have been synthesized for STD reaction [182,183]. Zeng et al. [163] proposed a dry sputtering method which is an alternative to a wet chemical method and is environmentally benign. They have synthesized a highly dispersed Cu-Zn nano-alloy coated HZSM-5 catalyst via the physical sputtering method. A wide range of particle size distribution of impregnated catalyst was observed from 5 to 15 nm and after calcination followed by reduction, active Cu5Zn8 nanolayer was formed. This nano alloyed and well-dispersed catalyst showed good syngas conversion and high DME selectivity.

deposition occurs on the catalyst surface. Some other studies have proved that the presence of water attenuates coke formation on metal sites. The main origin of the coke is the adsorbed methoxy ions on metal sites and water content controls the presence of methoxy ion on the catalyst surface [60,123]. 7.2. Effect of different feed compositions Direct DME synthesis process is reported to be more thermodynamically advantageous compared to two-step process and the equilibrium conversion of feed gas (CO and/or CO2) depends upon the reaction temperature and feed gas composition [190]. Syngas can be tailor-made according to the required composition of H2 and CO, for a different use. Among the different syngas production methods catalytic partial oxidation (CPO) produces the required H2/CO ratio for the application in DME synthesis. The increase in H2 proportion in the feed gas mixture enhances CO conversion but for WGS reaction the opposite trend is observed, because the reaction order for methanol synthesis reaction is 2 and for WGS reaction it is 1. Moradi et al. [191] have reported that CO conversion is increased from 48.23% to 78.40% at constant space velocity (SV) of 1100 mLN/(g-cat.h) when H2/CO ratio is changed from 1 to 2. In the STD process, CO conversion is not dependent on the methanol dehydration step when the intrinsic methanol formation rate is much slower than the methanol dehydration rate [46]. With increasing H2/CO ratio, methanol synthesis rate is accelerated and CO conversion enhanced as H2 rich environment favors methanol formation and is the highest at 2:1 ratio [184]. At a low content of H2 in syngas (H2/CO = 1:1), H2 becomes the limiting reactant and the methanol formation rate becomes very slow with overall low DME yield. Higher H2/CO ratio (2:1) suppresses the WGS reaction, which consumes the produced water in a methanol dehydration reaction. Thus by increasing the H2 proportion results into the accumulation of water molecules which leads to deactivation of catalyst [191]. Along with H2, CO2 is also produced in the WGS reaction. Some studies reported that CO2 removal before DME synthesis enhances the yield and high purity CO2 can also be achieved [192]. Otherwise, CO2 is adsorbed on the catalyst surface faster than CO and H2 [157]. Thus the presence of CO2 in the reactor has to be regulated as both CO conversion and DME selectivity are decreased in high CO2 concentration [193,194]. Bayat and Dogu [190] have investigated the effect of CO/CO2 ratio on overall DME yield and carbonaceous gas (CO + CO2) conversion by keeping H2/(CO + CO2) ratio constant. They have achieved a very high DME selectivity of 90% at 275 °C with a feed gas composition of 4:1 (CO/CO2). Erene et al. [195] investigated the effect of H2/CO2 ratio on CO2 conversion and DME selectivity. The highest DME selectivity is observed at 8:1 ratio and the lowest at 1:1. At H2/CO2 ratio of 1:1, significant coke deposition was observed on the acid function and the transformation of oxygenates (methanol and DME) depended on the acid function of the catalyst. Thus the increased quantity of hydrogen increases the yield of oxygenates. Ateka et al. [196] investigated the valorization of CO2 for DME synthesis from the feed gas (a mixture of H2, CO, and CO2) on CZA/S-18 bifunctional catalyst. The CO2 content in the feed is varied with the molar ratio of CO2/COx, from 0.0 to 0.5. According to their findings, DME yield is decreased with the co-feeding of CO2, which is in a good agreement with other studies. With the syngas feed, the DME yield is reported to reach as high as 14.6%, and when CO2 is introduced at a CO2/COx molar ratio of 0.25, the DME yield reduced to 6.6%. The presence of CO2 has a very moderate effect on the product distribution, the selectivity of oxygenates remained remarkably high (< 95%) with paraffin selectivity less than 1%. When the H2/COx molar ratio is varied from 3 to 4 in the feed gas (CO2/ COx > 0.4), the DME yield is slightly enhanced, but for lower value CO2/COx ratio, the opposite trend was observed (Fig. 5). Maximum CO2 conversion of 10% is achieved at CO2/COx of 0.4 and H2/COx ratio of 4.

7. Effect of operating parameters on DME selectivity 7.1. Water production during DME synthesis Direct DME synthesis processes utilizing CO-rich or CO2-rich feedstock have different extent of water generated during the course of the reaction. DME synthesis from methanol dehydration process is responsible for water generation. The produced water is often consumed by the water gas shift (WGS) reaction (Eq. (9)) when CO-rich feed gas is used and H2 is produced from the WGS reaction, which is again utilized in CO hydrogenation reaction [19]. WSG acts as a chemical wheel which gives the syngas based DME synthesis process extra kinetic flexibility to reduce water accumulation and accelerate the methanol hydrogenation reaction [184]. But in the case of CO2 rich feed, reverse water-gas shift (rWGS) reaction is responsible for additional water generation and CO production [185] (Eq. (13)). Therefore it is essential to remove water from the system, otherwise decrease in DME selectivity is inevitable. The higher water content in the system is also unsuitable for methanol generation step by hydrogenation reaction, as CO and CO2 have to compete with water molecules to get adsorbed on the metallic sites of MSC [123,186]. In situ removal of water can accelerate rWGS reaction to produce more CO from CO2 and DME synthesis will be improved. In the case of CO-rich feed gas, removal of water can accelerate the methanol dehydration reaction and enhance the DME selectivity [187]. Carvill et al. [188] have shown that sorption-enhanced reaction process could be useful for water removal by adsorption and Iliuta et al. [189] have also adopted sorption-enhanced reaction method for in situ water removal for DME synthesis in fixed bed reactor and studied the effect of different parameters. DME synthesis with in situ water removal can improve DME selectivity compared to that without water removal [189]. But according to Sierra et al. [123] removal of water can lead to deactivation of Cu-ZnO-Al2O3 catalyst as coke 307

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

Fig. 5. Effect of the CO2/COX ratio in the feed on the product yield (a) and selectivity (b) and effect of the H2/COX ratio on the yield of DME (c) and selectivity (d) for different CO2/COX molar ratios in the feed. Reaction conditions: 275 °C; 30 bar; 10.18 (g-cat) h (molC)−1; feed, H2 + CO + CO2. Reproduced from [196].

7.3. Effect of feed supply rate

methanol selectivity (1.5%). Liu et al. [198] investigated the effect of various space velocities (1500 to 3000 mLN g-cat−1 h−1) on CO2 conversion and DME selectivity. It was reported that when SV was increased to 3000 mLN/ (gcat h), CO2 conversion is decreased along (27.9 to 22.3%) with DME selectivity (64.6 to 58.5%). Similar observations were also made by Zhao et al. [199] who reported that when SV was increased to 3500 mLN. g-cat−1 h−1 from 1500 mLN g-cat−1 h−1, then DME selectivity was decreased to 47.5 from 63.1%.

Feed supply rate is an important parameter for DME synthesis in any reactor system and it is represented by many units such as space velocity (SV), gas hourly space velocity (GHSV), and space-time (ST). At constant H2/CO ratio, CO conversion increases when space velocity (SV) is decreased but when SV is reduced beyond a certain point CO conversion cannot be enhanced. At higher SV, the fast feeding of reactant gas mixture promotes high mass transfer rate, but it comes with the cost of the contact time between the reacting species and the catalyst. Moradi et al. [191] observed that CO conversion is increased from 71.51% to 89.52%, when SV was reduced from 1000 mLN/(g-cat.h) to 500 mLN/(g-cat.h) at constant H2/CO ratio (2:1). However, further increase in CO conversion was not reported for SV less than 500 mLN/(g-cat.h). Hayer et al. [58] investigated DME synthesis in a microchannel reactor from syngas. Experimentally they confirmed that with increasing the space velocity from 4500 to 60000 mLN/(g-cat-h), the CO conversion decreased. Initially, it increased to maximum at 9000 mLN/(g-cat-h) as the corresponding feed rate increased, but after that, it decreased due to short residence time. Increase in SV also decreases the selectivity of DME due to the consecutive product formation from methanol. Kumar and Srivastava [197] studied syngas conversion into DME in fluidized bed reactor and reported that DME productivity initially increased with an increase in GHSV from 80 to 1000 h−1, but it decreased above 1400 h−1. It was reported that at turbulent flow the CO conversion, DME selectivity, and yield were higher. CO conversion was very low at bubbling bed flow regime (GHSV = 80 h−1). Beyond GHSV of 1000 h−1 flow regime changed to turbulent flow and both CO conversion as well as DME selectivity increased. Ateka et al. [196] investigated the effect of space-time (2.5–20 g-cat h (molc)−1) by varying the catalyst mass at different molar flow rates on DME yield from syngas in a high pressure fixed bed reactor. They observed that by increasing the space-time CO conversion and DME yield were increased with negligible paraffin selectivity and little

7.4. Effect of reaction temperature The reaction temperature plays a big role in reversible exothermic reactions such as DME synthesis from syngas or mixture of CO2 and H2. In the beginning, the reaction is under kinetic control at low temperature and by increasing the reactor temperature, the reaction rate can be enhanced. As the reaction progresses and tends to achieve reaction equilibrium, the reactor temperature starts to increase and as a result, the overall conversion is reduced. Thus any reaction process involving exothermic reversible reaction should be operated in such a way that along the reactor length the reactor temperature should decrease. Kumar and Srivastava [197] studied the effect of temperature on DME synthesis from syngas in a slurry phase reactor at 230 and 250 °C. A similar conversion was achieved at both reaction temperatures, although at the end of the reaction, a minor difference in productivity was observed. Reaction at 250 °C showed better selectivity than at 230 °C along most of the reactors. Lu et al. [184] have concluded that DME synthesis catalyst should not be exposed to a temperature higher than 270 °C otherwise the catalyst activity will be reduced due to sintering of Cu metallic sites which was also confirmed by others [200,201]. Kumar and Srivastava [197] explained that with increasing the temperature, the selectivity also increases because at higher temperatures activity of methanol dehydration catalyst is higher than that of methanol synthesis catalyst. It was 308

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

Fig. 6. Effect of temperature on CO conversion and DME selectivity. Reaction condition: catalyst CZA/HZSM-5 (prepared by impregnation, co-precipitation–physically mixing and co-precipitation–ultrasound methods), H2/CO molar ratio of 2, GHSV of 600 cm3N/(g-cat.h) [167].

Fig. 7. Effect of pressure on CO conversion and DME selectivity. Reaction condition: catalyst CZA/HZSM-5 (prepared by impregnation, co-precipitation–physically mixing and co-precipitation–ultrasound methods), H2/CO molar ratio of 2, GHSV of 600 cm3N/(g-cat.h) [167].

suggested that 250 °C was the best reaction temperature for DME synthesis in slurry phase reactor. DME synthesis from syngas in fixed bed reactor has been studied in the presence of CuO-ZnO-MnO/SAPO-18 bifunctional catalyst, and the reaction temperature was varied in the range of 250–350 °C. It was reported that the highest DME yield was obtained at 275 °C and above 300 °C an increase in paraffin yield (methane is most selective among all C1–C3 molecules) was observed. In the temperature range of 250–275 °C DME selectivity was found to be > 95% but it was reduced to 65% when the reaction temperature was increased to 350 °C [202]. Khosbin and Haghighi [167] investigated DME synthesis from CO in the range of 200–300 °C and their results are shown as CO conversion and DME selectivity in Fig. 6. It shows that CO conversion increases up to 275 °C but thereafter it decreases when the temperature is increased to 300 °C. DME selectivity decreases as the reaction temperature is increased. Zhau et al. [199] examined the effect of temperature on CO2 conversion and DME selectivity. It was found that with the increase in temperature from 240 to 260 °C, CO2 conversion and DME selectivity were also increased (20.9% and 63.1%, respectively). But further increase up to 280 °C decreased both CO2 conversion and DME selectivity. The hydrogenation of CO2 is a reversible reaction and therefore an increase in temperature causes enhancement of reverse reaction and a decrease in DME selectivity. Zha et al. [203] had reported that when the temperature was increased to 282 °C from 262 °C, DME selectivity was decreased to 30.9% from 45.1%. Liu et al. [198] also had reported that when reaction temperature was increased from 240 to 260 °C DME selectivity was increased to 64.5%, but a sharp decrease in DME selectivity (47.5%) was observed when the temperature was increased to 280 °C.

7.5. Effect of operational pressure According to the thermodynamic analysis of DME synthesis reaction, the reaction pressure has a positive effect on overall DME yield. Many researchers have reported that with increasing reaction pressure both the CO conversion and DME selectivity increase. So it is evident that the equilibrium conversion of CO for the methanol synthesis reaction is enhanced by the consumption of methanol in the methanol dehydration reaction. The negative effect of elevated pressure on direct DME synthesis has also been reported as water is produced in both methanol synthesis and methanol dehydration reactions. Increase in the partial pressure of water suppresses the CO conversion by blocking the active sites for methanol dehydration reaction. Erena et al. [201] investigated the effect of pressure from 10–50 bar on the direct DME synthesis from a mixture of CO, CO2, and H2 gases. CO conversion was increased when operating pressure was elevated to 50 bar. Hydrogenation of CO and CO2 leads to a decrease in a number of moles, and consequently, when pressure is elevated, hydrogenation reactions are favored over WGS reaction. The methanol synthesis reaction is the limiting step of this process. Thus it can be understood that by increasing pressure, the rate of methanol dehydration reaction is also elevated. The composition of the hydrocarbons in the product stream is also affected by the variation of pressure, and the fraction of C1–C4 paraffin increased in comparison to C5* paraffin [195]. Therefore it is very clear that at elevated pressure (up to 50 bar) the hydrogenation of light olefins (intermediate products obtained methanol and DME) predominates over single condensation reactions (aromatization, alkylation, oligomerization). Jia et al. [204] investigated DME synthesis

309

Catalyst

CuO-ZnO-MnO/SAPO-18

Cu-ZnO/γ-Al2O3

Pd-Ga NP/γ-Al2O3

Cu-Zn NP/HZSM-5

Cu-ZnO-ZrO2/SAPO-11

SAPO-11 nanocrystals (20–30 nm) CuO-ZnO-Al2O3/SAPO-18

Cu-infiltrated Zr doped SBA-15

Cu–Zn/Al2O3; sol-gel method

CuO/ZnO/Al2O3 & HZSM-5

CuO/ZrO2 + montmorillonite K10 (modified by 3 wt% of Ga, Cr, Mn and Ag) Cu–Fe–Ce/HZSM-5 with 3.0 wt% CeO2

Cu.ZnO/Al2O3 or Nb2O5

Cu based MSC (C18W019) + Silicotungstic acid impregnated mesoporous alumina ([email protected])

Diatomite catalysts modified using nitric acid

CuO-ZnO-MnO/SAPO-18

CuO-Fe2O3-CeO2/HZSM-5

Cu/mesoAL(HT)

CuO–ZnO–Al2O3/HZSM-5

MgO/HZSM-5

Cu-Zn-Zr/MFI Zeolite

Cu–Fe–Zr/HZSM-5

Cu/ZnO/Al2O3 & HZSM-5 (modified with MgO, CaO & BaO) Cu/Zn/Al citric/TPA- K10

CuO–ZnO–Al2O3 and SiO2-ZSM-5

Cu–ZnO–Al2O3–ZrO2 (with different Zr ratio) and γ-Al2O3

Synthesis method

Direct method

Direct method

Direct method

Direct method

Direct method

Indirect method Direct method

Direct method

Direct method

Direct method

Direct method

Direct synthesis

Direct method

Direct method

310

Indirect method

Direct synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Indirect synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Direct synthesis

270

260

280–360

260

240–280

180–240

200–300

260

250

240–280

270–350

250–350

275

250/270

240–280

220–300

250

220

250

260 275

275

250–300

250–300

220–260

275

Temperature, °C

5

2

4

4

2–4

5

2

5

2–4

3

0.1

5

3

2–4

4

1–5

0.9

3.3

0.1 3

3

5

2

5

3

Pressure, MPa

Table 2 Effect of different catalysts and process parameters on selectivity for DME synthesis in fixed bed reactor.

−1

H2: CO2 = 5:1; GHSV = 1500– 3000 mL.gcat−1h−1 H2/CO/CO2/N2 = 59.93:27.33:4.12:8.62 (vol%); GHSV = 1500 mL h−1 g−1 cat Syngas (CO:CO2:H2 = 5:30:65) GHSV = 3600 h−1 H2: CO = 2 GHSV = 3600 cm3 gas/g−1 cat h−1 Biomass derives syngas(H2/CO/CO2/CH4 = 52/24/23/1), GHSV = 1500 h−1

H2/CO = 3; space time (2.5–20 gcat h (molC)−1) H2/CO2 = 4; GHSV = 1500–3500 mL gcat−1 h−1 H2:CO:N2 = 63:31.5:5.5; SV = 2000 L/(kgcat.h) H2/CO = 2 (mole ratio) GHSV = 3600 cm/gcat/h MeOH:EtOH = 3:1 WHSV = 4 h−1 SV = 2500 NL/Kgcat/h; CO2:H2:N2 = 3:9:1

Plasma catalytic reactor = 11.0–15.0 kV, H2: C02 = 4:1 GHSV = 1500–3500 mL.gcat−1h−1 H2/CO2 = 3 SV = 10 h−1 H2/CO/CO2 = 50/40/10, Space time = 0.48 s gcat/mL. Total flow rate of feed gas = 25 ml/min MeOH:N2 = 1:4; total flow rate = 60 ml/min

Syngas AV = 800 N cm3/min/g H2 + CO2 = 6 m ml/min

H2/CO/Ar = 5.0/5.0/1.0 mL min

N2: MeOH = 240 (vol ratio) H2:CO2 = 3; CO2:COx = 0–0.5 St = 10.18 gcat. h (molC)−1; H2:CO2 = 3:1

Ar:N2:H2:CO = 5:2:1.5:1.5 Total flow = 50 mLNTP/min Ar:N2:H2:CO = 5:2:1.5:1.5 Total flow = 50 mLNTP/min H2:COx = 3; CO2:COx = 0.5; Space time = 2.5 gcat. h (molC)−1

DME =

35%

DME =

31%

CCOx = 36%

SDME = 90%

YDME = 26.0%

CCOx = 90%

S

CCO2 = 9%

YDME = 16.9%

CCO2 = 69.5%

S

YDME = 8%

CCO2 = 15%

YDME = 14.5%

CCOx = 9.5%

CMeOH = 80%

YDME = 6.5

CCOx = 9%

YDME = 25

YDME = 19.6 CCO = 40%

CCO = 30%

CCO2 = 60%

YDME = 21.

CCOx = 47%

H2:COx = 3; CO2:COx = 0–0.5; Space time = 5.2 gcat. h (molC)−1 H2:CO2:Ar:N2 = 15:15:60:10

Conversion & yield

Others essential factor

(continued on next page)

Samson et al. [222] Ordomsky et al. [169] Song et al. [223]

Mao et al. [221]

Frusteri et al. [154] Qin et al. [220]

Liu et al. [219]

Cai et al. [172]

Ham et al. [218]

Pranee et al. [217] Ateka et al. [202] Zhau et al. [199]

Bayat et al. [190]

Silva et al. [216]

Ateka et al. [206] Henrich et al. [207] Gentzen et al. [208] Gentzen et al. [209] SánchezContador et al. [181] Chen et al. [210] Ateka et al. [196] Atakan et al. [211] Takeishi et al. [212] Dadgar et al. [213] Kornas et al. [214] Su et al. [215]

Authors

U. Mondal and G.D. Yadav

Journal of CO₂ Utilization 32 (2019) 299–320

Core- shell structure catalyst (CuO–ZnO–[email protected] SiO2–Al2O3) Cu/ZnO/H-ZSM5 by by sputtering and impregnation methods CuZnAl/zeolite

Direct synthesis

250 270 260

Cu/ZnO/H-ZSM5 sputtering catalyst Cu–ZnO/γ-Al2O3

Core shell CuOZnO [email protected]

Undoped and doped γ-alumina spherical particles (CuO, CuO + ZnO) by sol-gel method core–shell like silicoaluminophosphate (SAPO-46) encapsulated Cr/ZnO capsule catalyst Ba2+ impregnated on γ-Al2O3

Cu/ZnO/Al2O3 and phosphate on γ-Al2O3

Mesoporous Cu/γ-Al2O3

Core-shell design CuO-ZnO/HZSM-5

CuO–ZnO–Al2O3 with acid catalyst NH4ZSM-5, HZSM-5 or γ-Al2O3

XNC-98/HZSM-5 = 4:1,

aluminum fluoride (AlF3) modified HZSM-5

CuO-ZnO-Al2O3 to pseudo-boehmite was 2/1 Al-SBA-15

hybrid CuZnAl/ZSM-5

CuO–ZnO–Al2O3/γ-Al2O3 with excess γ-Al2O3

Cu-Zn/γ-Al2O3

Double shell capsule catalyst Cr/ZnO–S–Z (S = neutral Silicalite-1 zeolite layer; Z = HZSM-5 layer) CuO/ZnO/Al2O3 and γ-alumina

Cu–ZnO/γ-Al2O3

Direct synthesis

Indirect synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Indirect Synthesis

Direct synthesis Indirect synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Direct synthesis

Indirect synthesis

Direct synthesis

311 250

220–260

300–350

260

225–325

260

220–260 120–450

180

220–280

200–260

257

280–325

250

260 –290

350

Up to 350

240–280

Direct synthesis Direct synthesis

Direct synthesis

262

Multi-walled carbon nanotubes promoted CuO–ZnO–Al2O3/ HZSM-5. CuO–Fe2O3–ZrO2/HZSM-5

260

250

220–320

Temperature, °C

Direct synthesis

Direct synthesis

Direct synthesis

Catalyst

Synthesis method

Table 2 (continued)

5

3–7

5

5

2–4

4

4 0.1

3

2

3

5

5

0.1

5

0.1

5

5 3.5

2–3.5

3

4

5

2–6

Pressure, MPa

−1

H2: 60–75%, N2: 9–12%, CO: 12–20%, CO2: 1–5%. GHSV = 1000–2500 mL/g h H2:CO = 2:1; space velocity (SV) = 4000 mL gcat−1 h−1

A mixture of 90 vol% syngas (molar composition: 66%H2/30%CO/ 4%CO2) and 10 vol% Ar. SV = 1700 mLsyngas/(gcat. h) H2/CO2 = 2/1 to 4/1 ST = 42.0 (g of catalyst) h (mol of carbon)−1 H2/CO = 1 GHSV = 3000 ml/g-cat.·h Ar 3.02%, CO 32.6%, CO2 5.16%, H2 59.22% in molar base

H2/CO2 = 2 (mol/mol) SV = 1600 h−1 syngas mixture (BOC gases) which contained (62% H2, 31% CO, 4% CO2 and 3% Ar) SV = 2400 ml h−1 g−1 cat H2/CO = 1 GHSV = 3000 ml/gcat.h MeOH SV = 40 ml h−h N2 SV = 6000 h−1 H2:CO: CO2 = 1.0/1.0/0.08 MeOH vapour + He = 44.4 cm3 min−1.

Syngas (H2/CO) = 2 GHSV = 8400 h−1 Syngas = CO(6 ml/min) + H2 (12 ml/min) + N2 (2 ml/min)

MeOH flow rate = 0.3–0.9 cm min

3

Syngas (H2/CO = 2) GHSV = 1000–4000 mL/(h gcat) Syngas (CO: 33.8 v%, CO2: 5.10 v%, Ar: 3.09 v%, balanced with H2; Wcatalyst/Fsyngas = 10 g h mol−1 Gas mixture = 90% syngas(66% H2/30% CO/4% CO2) + 10% Ar SV = 2550 cm3/(gcat.h) H2/CO2 = 3/1 GHSV = 1800 mL gcat−1 h−1 H2/CO2 = 5/1 GHSV= 1500–3000 mL gcat−1 ·h−1 Syngas (CO: 32.5%, CO2: 5.2%, Ar: 3.1%, balanced with H2) Syngas= H2/CO = 2 along with 5.6 mol% N2 GHSV = 2000 ml/gcat.h Syngas = H2/CO GHSV = 1500 mLh−1 gcat−1 2 mol% CH3OH mixed with N2 was fed into the reactor at a flow rate of 60 mL min−1 Syngas = 58.10% H2: 33.80% CO: 5.10% CO2: 3.09% Ar

Others essential factor

CCO = 13.7%

SDME = 61.9%

Space time yield = 5.08 mol/L/h CCO = 71.1%

SDME = 85.8%

SDME = 69% CCO = 79.3%

CCO = 74%

SDME = 45%

CCOx = 65%

SDME = 64.4%

CCOx = 93.8%

CCO = 30%

SDME = 49.3%

CCOx = 23.6%

CCOx = 75.0% SDME = 69.8%

SDME = 76.1%

CCOx = 11.5%

SDME = 63.1%

CCOx = 20.9%

YDME = 13%

Conversion & yield

(continued on next page)

Cheng et al. [238] Beak et al. [239]

Yang et al. [237]

Park et al. [236]

Erena et al. [60]

Liu et al. [235] Tokey et al. [118] Trenco et al. [171]

Zhang et al. [233] Yang et al. [234]

Abu-Dahrieh et al. [141]

Pinkaew et al. [178] Hoda et al. [230] Montesano et al. [231] Jiang et al. [139] Li et al. [232]

Wang et al. [183] Pillai et al. [229]

Zeng et al. [163] Ahn et al. [228]

Liu et al. [227]

García-Trenco et al. [226] Zha et al. [203]

Wang et al. [224] Sun et al. [225]

Authors

U. Mondal and G.D. Yadav

Journal of CO₂ Utilization 32 (2019) 299–320

225–350 1.660 2.180

6CuO–3ZnO–Al2O3/γ-Al2O3 and 6CuO–3ZnO–1Al2O3/ HZSM-5 bifunctional catalyst (JC207/HZSM5 [Si/Al = 38, MgO, Cao and ZnO])

γ-Al2O3

novel silicotungstic acid (STA) incorporated nanocomposite catalysts (silicate structured mesoporous catalysts TRC-62(L), TRC-82(L) and TRC-92(L)), mesoporous nanocrystalline γ-Al2O3

Nafion-Incorporated Silicate Structured Nanocomposite Mesoporous Catalysts

γ-Al2O3 derived from Nordstrandite Cu–ZnO–Al2O3 promoted with Zr or Ga on γ-Al2O3

CuO-ZnO- Al2O3/γ- Al2O3

1. Rh-SiO2 catalyst (0.406 wt% Rh in SiO2) 2. ZnCl2/SiO2

Cu/Zn/Al/HZSM-5

Cu–ZnO–Al2O3/Zr-ferrierite (CZA–ZrFER)

CuO–TiO2–ZrO2 (with various Ti and Zr molar ratios) + HZSM5 Cu-Zn-Al-M (M = Ga, La, Y, Zr)/γ- Al2O3

Direct synthesis

Indirect synthesis

Indirect synthesis

Indirect synthesis

Indirect synthesis Direct synthesis

Direct synthesis

Indirect synthesis

Direct synthesis

Direct synthesis

Direct synthesis

312

Direct synthesis

Indirect synthesis

Indirect synthesis

Direct synthesis

CuO-ZnO-Al2O3-ZrO2/HZSM-5 (SiO2:Al2O3 = 25)

CuO/ZnO/Al2O3 for methanol forming, γ-alumina for methanol dehydration Cu–ZnO–Al2O3/Zr-modified zeolites (Ferrierite, ZSM-5 and Y) Cu0.5(1+y)FeyZr2−y(PO4)3 y = (0, 0.5, 1.0, 1.5 and 2.0) commercially available γ- Al2O3

Direct synthesis

Direct synthesis

γ-Al2O3 and η-Al2O3 from boehmite and bayerite CuO–ZnO–Al2O3–ZrO2 + HZSM-5

Indirect synthesis

Direct synthesis

Indirect synthesis

Direct synthesis

CuO–ZnO–Al2O3 (Cu:Zn:Al ≈ 5:4:1 mass ratio)/γ-Al2O3

Direct synthesis

250

300

197–397

250

260

250

260

250–280

200

250

260

300 250

120–300

300

180–350

260–380

240–280

260

210–300

118–150 250–290

Macro porous sulphonic acid ion exchange resign bifunctional catalyst (JC207/HZSM5 [Si/Al = 25, 38, 50, 150])

Indirect synthesis Direct synthesis

Temperature, °C

Catalyst

Synthesis method

Table 2 (continued)

3

1.6

0.1

4

6

5

4.13

3

4

4.3

0.1

1–4

0.1 5

0.1

0.1

0.1–1.6

3

5

1-6

2.0 3

Pressure, MPa

MeOH = 0.55 ml/min GHSV = 26.07 h−1 H2/CO2 = 3 GHSV = 1600 h−1

H2/CO2 = 3 SV = 6000 mL/(g cat · h) Coal gasification H2/CO = 0.5 GHSV = 3000 l/kg-cat h CO/H2/CO2 (41/38/21) SV = 5550 ml/h gcat MeOH + Ar/Air = 2.4l/h

H2/CO = 1.5 GHSV = 6000–12000 h−1 GHSV = 6000

MeOH WHSV, (1.75–9.62 h−1) MeOH = 2.1 ml/min He = 23 ml/min Space Time = 0.27 s g cm-3 MeOH: Feed Gas = 0.48 MeOH, GHSV = 6000 H2:CO = 2:1 (SV) = 4000 mL gcat−1 h−1 H2/CO = 2–4 ST = 0.1–68.0 (g of catalyst) h (mol of reactants)−1 Reactant flow rate = 1 mmol/min (H2 + CO) 1. liquid 48 wt%HBr/H2O was 6.5 ml/h (CH4, O2, N2, CO, and CO2 were 20.0 ml/min, 5.0 ml/min, 5.0 ml/min, 3.0 ml/min, and 4.0 ml/min) 2. CH3Br, N2, and H2O (L) are 10.0 ml/min, 10.0 ml/min, and 0.5 ml/h) H2/CO = 2 GHSV = 3000 h−1 Tail gas recycled GHSV = 650-3000 h−1 CO/CO2/H2 = 41/21/38 (molar feed composition) SV = 5500 L/(kgcat h) Feed gas = CO2 (23.3%), H2 (64.5%) and N2 (the rest)

MeOH = 0.20 ml/min gas product from biomass gasification containing H2 42.1%, N2 13.4%, CO 33.9%, CH4 5.0%, CO2 5.6% SV = 1300 L/(kg. hr) H2/CO = 2–4; SV = 15.000 Nml/gcat/h reactant gas (CO2/3H2) GHSV = 3000 ml/gcat. h Biomass pyrolysis gas (H2 42.1%, N2 13.4%, CO 33.9%, CH4 5.0%, CO2 5.6%) SV = 1300 L/(kg hr) MeOH, SV = (W/F = 1.724 g/ml·min) MeOH = 2.1 mL/hr MeOH/He = 0.48 (vol/vol)

Others essential factor

SDME = 69%

CCO = 72%

CMeOH = 27.7–46.33%

YDME = 37%

CCOx = 6.9%

CMeOH = 100%

SDME = 61.1%

CCO = 35.2%

SDME = 61.1%

CCO = 47.6%

SDME = 93.5%

CCO = 13%

SDME = 64.5%

CCO2 = 28.4%

YDME = 20.9%

SDME = 45.2%

CCO2 = 46.2%

SDME = 64%

CCO = 87–90%

SDME = 92.1%

Conversion & yield

(continued on next page)

Pet'kov et al. [256] Mollavali et al. [257] Zhao et al. [258]

Kang et al. [255]

Yoo et al. [254]

An et al. [253]

Wang et al. [251] Venugopal et al. [134] Seo et al. [252]

Bae et al. [250]

Li et al. [249]

You et al. [248]

Sierra et al. [123]

Seo et al. [246] Kang et al. [247]

Keshavarz et al. [245] Ciftci et al. [89]

Moradi et al. [243] Ciftci et al. [244]

Xu et al. [242]

Naik et al. [124]

Hayer et al. [58]

Lei et al. [240] Xu et al. [241]

Authors

U. Mondal and G.D. Yadav

Journal of CO₂ Utilization 32 (2019) 299–320

Cu–Mn–Zn/zeolite Y modified with La, Ce, Pr, Nd, Sm and Eu Cu/ZnO/Al2O3 and SAPO-34 and -18

aluminum phosphate catalysts with Al/P = 1

Al2O3 on the Cu-ZnO-Al2O3-SiO2 catalysts prepd. by a pseudo sol-gel method 1. 0.1 wt% Ru/SiO2 2. RuCl3

Direct synthesis

Direct synthesis

Indirect synthesis

Direct synthesis

Cu-ZnO-ZrO2/Al2O3-HZSM-5

C301/HZSM-5 C301/γ-Al2O3 Cu-ZnO-X (X = Al2O3, Cr2O3, ZrO2 or Ga2O3

Direct synthesis

Direct synthesis

313 270 230–350

CuO/ZnO/γ-Al2O3

Pd/SiO2, Pd/Al2O3, modified Pd/Al2O3 and hybrid (phys. mixed) catalysts containing. Pd/SiO2 or Cu-Zn-Al (O) and γAl2O3

Direct synthesis

250

230–270

260–280

240

220–290

200–325

2. 150– 180

1. 530– 560

250

175–275

260

245

Temperature, °C

Direct synthesis

Direct synthesis

Direct synthesis

Direct synthesis

aluminum was 850–425 mm (about 18–35 mesh)and magnesium was 20–70 mesh (about 740–210 mm) power Copper catalyst (Süd-Chemie Catalysts Japan Inc., MDC-3) and γ-alumina Cu-Zn-Al/HZSM-5

Indirect synthesis

Indirect two step process

Catalyst

Synthesis method

Table 2 (continued)

1.1–5.1

3

1

4

8

5

1–3

0.1

3

0.1

4.2

2

Pressure, MPa

Syngas = (H2/CO/CO2/Ar) 60/30/5/5) Flow rate = 44 mmol/h H2/CO = 2 Space velocity = 1000−1 Syngas derived from CH4 catalytic partial oxidation (CPO) = H2:CO:N2:CO2:CH4 = 39.8″14.7:37.2:5.9:2.4 SV = 1500−1 H2 to (CO + CO2) equal to 2.6 GHSV = 927 ml/gcat.h Blast furnace gas CO/CO2/H2 = 4/4/1 Feed gas flowrate = 1.O x 10−6m3/sec H2/CO/CO2 = 64/31/5 (mol) GHSV = 2000 h−1 Based on carbon molecule H2/CO = 2/1 (5% CO2 was added in the case of methanol synthesis on Cu-Zn-Al catalyst) Contact time = 0.3–4.2 g-cat.-hr/mol.

20%CO2 and 80%H2 SV of 3200 h−1 1. HBr/H2O (40 wt% in water) = 4.0 mL/h. CH4 = 5 ml/min O2 = 15–20 ml/min 2. CH3Br = 0.5 g H2O = 0.4-0.7 g MeOH = 0.39 kg/dm3

H2/CO = 3/2 and SV = 1500 h−1 H2/CO = 1.5 GHSV = 3000 mL/gcat h MeOH = 2 ml/h

Others essential factor

CCO = 93%

SDME = 100%

CMeOH = 52%

SDME = 67%

CCO = 81%

CMeOH = 86%

CCO = 70%

SDME = 10.8%

CCO = 63.4%

SDME = 67%

CCO = 81%

Conversion & yield

Han et al. [270]

Li et al. [269]

Akiyama [268]

Wang et al. [56]

Hengyong [267]

Omata et al. [265] Jia et al. [266]

Usui et al. [264]

Kumar et al. [261] Wang et al. [262] Xu et al. [263]

Yoo et al. [260]

Jin et al. [259]

Authors

U. Mondal and G.D. Yadav

Journal of CO₂ Utilization 32 (2019) 299–320

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

reaction up to 100 bar and concluded that there is no significant enhancement of CO conversion beyond 50 bar and this result is very much similar to that of Erena et al. [205]. In slurry reactor, the effect of pressure has shown an additional effect, with increasing the pressure the bubble size decreases and as a result mass transfer coefficient increases, which influences the overall conversion. Kumar and Srivastava [197] also confirmed a similar phenomenon for DME synthesis reaction in fluidized bed reactor from syngas. Khosbin et al. [167] investigated the influence of reaction pressure from 10–40 bar on CO conversion and DME selectivity. A positive effect of reaction pressure has been reported on CO conversion and DME selectivity, as shown in Fig. 7. Table 2 summarizes different catalysts and operating parameters influencing the conversion, yield and selectivity of DME studied over recent years. Zhou et al. [199] varied the reaction pressure from 20–40 bar in one pot DME synthesis process to investigate the effect on CO2 conversion and DME selectivity. CO2 conversion was increased when reaction pressure was elevated to 30 bar, but when it was increased beyond 30 to 40 bar, CO2 conversion was decreased. DME selectivity was also shown to have a similar relationship with reaction pressure. The one-step CO2 to DME synthesis process is a series of volume decreasing reactions, and therefore by increasing pressure, the CO2 conversion can be enhanced. Zhou et al. [199] concluded that the decrease in CO2 conversion (17.2% from 20.9%) and DME selectivity (55.5% from 60.3%) might be due to water formation in the reactor when the pressure was elevated from 30 to 40 bar. Based on several studies, it was also concluded that 30 bar was the optimum pressure for one pot DME synthesis from CO2 [198,199,203].

Some strategies have been taken up for direct DME synthesis process from syngas and CO2, but it is a two-step process. The main obstacles of the process are the catalyst deactivation due to water generation and coke deposition on the surface of the acid catalyst. Copper-based multicomponent catalysts have been studied extensively. The vastly used CO2 or syngas hydrogenation catalyst is Cu/ZnO/Al2O3 (CZA) and for the methanol dehydration reaction, acidic catalysts are needed. Compared to the syngas to DME (STD) process, DME synthesis from CO2 produces more amount of water leading to catalyst poisoning. A vast array of catalysts have been tested for acid function for methanol dehydration reaction. HZSM-5 shows the highest water tolerability and activity. Catalyst preparation methods also have a profound effect on catalyst properties, and it is found that co-precipitation- sedimentation and co-precipitation coupled with ultrasound irradiation were the most suitable catalyst preparation methods for achieving high catalyst activity. Many studies have employed core-shell structure of bifunctional catalyst wherein CZA catalyst is covered by a thin layer of acidic catalyst (HZSM-5). This type of catalyst configuration shows high DME selectivity and less amount of by-product formation. The performance of any DME synthesis process is hugely affected by several operating parameters. A majority of the DME synthesis study has been carried out in the temperature range of 200–300 °C and pressure range up to 70 bar. For the conversion of CO2 to DME, the optimum operational pressure is 30 bar and temperature 270–275 °C. Direct conversion of CO2 is very difficult as more amount of water is produced via rWGS reaction. Therefore co-feeding of CO with the feed gas can convert water into H2 via WGS reaction and CO2 conversion will increase. Comparatively syngas conversion is much easier, and the highest conversion and DME selectivity are achieved in the range of 250–260 °C and at pressure of 40 bar. The molar ratio of H2 and CO2 also has a pronounced effect on DME selectivity and CO2 conversion. At a higher molar ratio of H2/CO2 (8:1) the highest DME selectivity is observed but as the molar ratio is decreased to 1:1, then CO2 conversion is increased, but DME selectivity is decreased as huge coke is deposited on the catalyst surface. Although a few pilot plant studies on DME synthesis are reported in recent times, most of the DME synthesis from various raw materials are only based on laboratory scale studies. To project DME as a future fuel for our society, new studies encompassing process optimization and scale-up of one-pot DME synthesis and economic aspects of an efficient and practical DME synthesis plant must be explored. More and more research on the noble catalyst development has to be taken up for getting the most active, reusable, economical and highly water tolerant catalyst. Feed type, its cost and supply rate is a very important factor for DME synthesis process, and its effect on DME selectivity and syngas gas and/CO2 conversion is dependent on the type and capacity of the reactor. Therefore optimization of the space velocity of the feed gas is of great importance for establishing a practical DME plant. The type of reactors and separators and their configurations have a great bearing on both fixed and operating costs of DME production. The production of syngas, irrespective of nature of feed, is critical in DME synthesis. Part II covers all these aspects. Overall, DME has a great future.

8. Conclusions Dimethyl ether (DME) has great potential as fuel and precursor for chemical manufacture. DME is the cleanest high-efficiency compression ignition fuel as a substitute for diesel. In order to establish DME production and utilization system, it is very important to establish the required infrastructure for raw material supply chain, DME synthesis process, and development of necessary machinery. The purpose of this review was to take stock of DME as fuel and find out the technological challenges in converting CO2 to DME. Fossil fuels are the largest source of energy, and the combustion of fossil fuels tends to generate a huge amount of greenhouse gases in the atmosphere. A large amount of greenhouse gases (CO and CO2) are generated in coal or petroleum operated thermal power plants and there is a dire need to provide a CO2 capture and sequestering (CCS) facility to deal with this huge pollution. However, the economy of the CCS plant only can be sustainable when it is supported by dimethyl ether synthesis plant with a production capacity in the range of 3000–7500 metric ton per day. Tremendous work has been done to explore the most suitable reaction conditions for DME synthesis. Bio-DME is a very attractive alternative to diesel, which yields very low tailpipe emissions, near-zero amount of CO2 emission and thus there is no need to CO2 capture and sequestration in the bioDME plant. However, the production cost of DME is higher with presently available technologies when it is produced from natural gas, coal, and biomass because the conversion of raw materials to syngas is an expensive process. Methanol based indirect DME synthesis is comparatively safer as methanol production from syngas is a mature and well-established process. Companies like Linde/Lurgi, Haldor Hospice, Uhde, Toyo Engineering, and Mitsubishi Gas Chemical Company are holding the licenses for the single-step DME synthesis technology. MGC, Toyo, Udhe, and Lurgi are developing DME production technology based on indirect synthesis. A tabular summary of different studies of the DME synthesis processes, catalysts, and operating conditions was presented. Other routes of DME synthesis process which are already practised and being developed were discussed in detail.

Conflict of interest statement The authors declare no conflict of interest. Acknowledgement UM got financial support as D.S. Kothari Post-Doctoral Fellowship of UGC. GDY received support from R.T. Mody Distinguished Professor Endowment, Tata Chemicals Darbari Seth Distinguished Professor of Leadership and Innovation, and J.C. Bose National Fellowship, DST, Govt. of India.

314

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

References

US4892561A, (1990), https://doi.org/10.1074/JBC.274.42.30033.(51). [28] T.H. Fleisch, A. Basu, R.A. Sills, Introduction and advancement of a new clean global fuel: The status of DME developments in China and beyond, J. Nat. Gas Sci. Eng. 9 (2012) 94–107, https://doi.org/10.1016/j.jngse.2012.05.012. [29] A. Basu, M. Gradassi, R. Sills, T. Fleisch, R. Puri, Use of DME as a gas turbine fuel, (2001), https://doi.org/10.1115/2001-GT-0003 V002T01A003. [30] X. Wang, China MTBE: Risks, opportunities, and challenges, 16th IMPCA 2013 Asian Methanol Conference Global MTBE Overview Mexico South America (2019), www.methanolmsa.com/wp-content/uploads/2013/11/Wang-Xiaoshu.pdf. [31] S. Hosseininejad, A. Afacan, R.E. Hayes, Catalytic and kinetic study of methanol dehydration to dimethyl ether, Chem. Eng. Res. Des. 90 (2012) 825–833, https:// doi.org/10.1016/j.cherd.2011.10.007. [32] P.K. Kiviranta-Pääkkönen, L.K. Struckmann née Rihko, J.A. Linnekoski, A.O.I. Krause, Dehydration of the alcohol in the etherification of isoamylenes with methanol and ethanol, Ind. Eng. Chem. Res. 37 (1998) 18–24, https://doi.org/10. 1021/ie970454d. [33] M.A. Armenta, V.M. Maytorena, R.G. Alamilla, R. Valdez, A. Olivas, Thermodynamic and catalytic properties of Cu-and Pd-oxides over mixed γ–χ–Al2O3 for methanol dehydration toward dimethyl ether, Int. J. Hydrogen Energy 44 (2019) 7276–7287, https://doi.org/10.1016/j.ijhydene.2019.01.243. [34] J. Bandiera, C. Naccache, Kinetics of methanol dehydration on dealuminated Hmordenite: model with acid and basic active centres, Appl. Catal. 69 (1991) 139–148, https://doi.org/10.1016/S0166-9834(00)83297-2. [35] B.C. Gates, L.N. Johanson, The dehydration of methanol and ethanol catalyzed by polystyrene sulfonate resins, J. Catal. 14 (1969) 69–76, https://doi.org/10.1016/ 0021-9517(69)90357-1. [36] K.S. Ha, Y.J. Lee, J.W. Bae, Y.W. Kim, M.H. Woo, H.S. Kim, M.J. Park, K.W. Jun, New reaction pathways and kinetic parameter estimation for methanol dehydration over modified ZSM-5 catalysts, Appl. Catal. A Gen. 395 (2011) 95–106, https://doi.org/10.1016/j.apcata.2011.01.025. [37] R. Blaszkowski, R.A. Van Santen, The mechanism of dimethyl ether formation from methanol catalyzed by zeolitic protons, J. Am. Chem. Soc. 118 (1996) 5152–5153, https://doi.org/10.1021/ja954323k. [38] R.T. Carr, M. Neurock, E. Iglesia, Catalytic consequences of acid strength in the conversion of methanol to dimethyl ether, J. Catal. 278 (2011) 78–93, https://doi. org/10.1016/j.jcat.2010.11.017. [39] D. Lesthaeghe, V. Van Speybroeck, G.B. Marin, M. Waroquier, Understanding the failure of direct C-C coupling in the zeolite-catalyzed methanol-to-olefin process, Angew. Chemie - Int. Ed. 45 (2006) 1714–1719, https://doi.org/10.1002/anie. 200503824. [40] P.G. Moses, J.K. Nørskov, Methanol to dimethyl ether over ZSM-22: A periodic density functional theory study, ACS Catal. 3 (2013) 735–745, https://doi.org/10. 1021/cs300722w. [41] G. Cassone, F. Pietrucci, F. Saija, F. Guyot, J. Sponer, J.E. Sponer, A.M. Saitta, Novel electrochemical route to cleaner fuel dimethyl ether, Sci. Rep. 7 (2017) 1–9, https://doi.org/10.1038/s41598-017-07187-8. [42] D. Mao, W. Yang, J. Xia, B. Zhang, Q. Song, Q. Chen, Highly effective hybrid catalyst for the direct synthesis of dimethyl ether from syngas with magnesium oxide-modified HZSM-5 as a dehydration component, J. Catal. 230 (2005) 140–149, https://doi.org/10.1016/j.jcat.2004.12.007. [43] K. Takeishi, Dimethyl ether and catalyst development for production from syngas, Biofuels. 1 (2010) 217–226, https://doi.org/10.4155/bfs.09.16. [44] G.R. Moradi, J. Ahmadpour, F. Yaripour, J. Wang, Equilibrium calculations for direct synthesis of dimethyl ether from syngas, Can. J. Chem. Eng. 89 (2011) 108–115, https://doi.org/10.1002/cjce.20373. [45] A. Ateka, P. Pérez-Uriarte, M. Gamero, J. Ereña, A.T. Aguayo, J. Bilbao, A comparative thermodynamic study on the CO2 conversion in the synthesis of methanol and of DME, Energy. 120 (2017) 796–804. [46] G. Centi, S. Perathoner, Advances in catalysts and processes for methanol synthesis from CO2, in: M. De Falco, G. Iaquaniello, G. Centi (Eds.), CO2 A Valuab, Source Carbon, Springer London, London, 2013, pp. 147–169. [47] F. Yang, Z. Liu, W.S. Li, T.H. Wu, X.P. Zhou, The oxidative bromination of methane over Rh/SiO2 catalyst, Catal. Lett. 124 (2008) 226–232, https://doi.org/10.1007/ s10562-008-9462-0. [48] Q. You, Z. Liu, W. Li, X. Zhou, Synthesis of dimethyl ether from methane mediated by HBr, J. Nat. Gas Chem. 18 (2009) 306–311, https://doi.org/10.1016/S10039953(08)60122-X. [49] G.K.S. Prakash, J.C. Colmenares, P.T. Batamack, T. Mathew, G.A. Olah, Poly(4vinylpyridine) catalyzed hydrolysis of methyl bromide to methanol and dimethyl ether, J. Mol. Catal. A Chem. 310 (2009) 180–183, https://doi.org/10.1016/j. molcata.2009.06.018. [50] G.A. Olah, J. Bukala, Antimony pentafluoride/graphite catalyzed oxidative carbonylation of methyl halides with carbon monoxide and copper oxides (or copper/ oxygen) to methyl acetate, J. Org. Chem. 55 (1990) 4293–4297, https://doi.org/ 10.1021/jo00301a017. [51] X.P. Zou, M. Lorkovic, G.D. Stucky, P.C. Ford, J.H. Sherman, P. Grosso, Integrated process for synthesizing alcohols and ethers from alkanes, US 6472572B1, (2019). [52] I.M. Lorkovic, A. Yilmaz, G.A. Yilmaz, X.P. Zhou, L.E. Laverman, S. Sun, D.J. Schaefer, M. Weiss, M.L. Noy, C.I. Cutler, J.H. Sherman, E.W. McFarland, G.D. Stucky, P.C. Ford, A novel integrated process for the functionalization of methane and ethane: Bromine as mediator, Catal. Today. 98 (2004) 317–322, https://doi.org/10.1016/j.cattod.2004.07.058. [53] M. Farniaei, M. Abbasi, A. Rasoolzadeh, M. Reza, Enhancement of methanol, DME and hydrogen production via employing hydrogen permselective membranes in a novel integrated thermally double-coupled two-membrane reactor, J. Nat. Gas Sci. Eng. 14 (2013) 158–173, https://doi.org/10.1016/j.jngse.2013.06.010.

[1] S. Lee, S. Oh, Y. Choi, Performance and emission characteristics of an SI engine operated with DME blended LPG fuel, Fuel 88 (2009) 1009–1015, https://doi.org/ 10.1016/j.fuel.2008.12.016. [2] D.A. Good, J.S. Francisco, A.K. Jain, D.J. Wuebbles, Lifetimes and global warming potentials for dimethyl ether and for fluorinated ethers: CH3OCF3 (E143a), CHF2 OCHF2 (E134), CHF2 OCF3 (E125), J. Geophys. Res. Atmos. 103 (1998) 28181–28186, https://doi.org/10.1029/98JD01880. [3] Y. Adachi, M. Komoto, I. Watanabe, Y. Ohno, K. Fujimoto, Effective utilisation of remote coal through dimethyl ether synthesis, Fuel 79 (2000) 229–234, https:// doi.org/10.1016/S0016-2361(99)00156-8. [4] J.-A. Taupy, DME industry and association overview, 4th International DME Conference Stockholm (2010), http://www.aboutdme.org/aboutdme/files/ ccLibraryFiles/Filename/000000001633/DME4_IDA_Taupy.pdf. [5] M. Marchionna, R. Patrini, D. Sanfilippo, G. Migliavacca, Fundamental investigations on di-methyl ether (DME) as LPG substitute or make-up for domestic uses, Fuel Process. Technol. 89 (2008) 1255–1261, https://doi.org/10.1016/j. fuproc.2008.07.013. [6] L. Zhang, H.-T. Zhang, W.-Y. Ying, D.-Y. Fang, Intrinsic kinetic of methanol dehydration over Al2O3 catalyst, World Acad. Sci. Eng. Technol. 59 (2011) 1538–1543. [7] Z. Azizi, M. Rezaeimanesh, T. Tohidian, M.R. Rahimpour, Dimethyl ether: A review of technologies and production challenges, Chem. Eng. Process. Process Intensif. 82 (2014) 150–172, https://doi.org/10.1016/j.cep.2014.06.007. [8] T.H. Fleisch, A. Basu, R.A. Sills, Introduction and advancement of a new clean global fuel: the status of DME developments in China and beyond, J. Nat. Gas Sci. Eng. 9 (2012) 94–107, https://doi.org/10.1016/j.jngse.2012.05.012. [9] S. Clara, D.S. Rice, A. Yamasani, S. Jose, J.B. Parks, S. Clara, E. Millar, M. View, P.C. Richardson, A cetic acid reactive distillation process based on DME/methanol carbonylation, US 6,175,039 B1, (2012) doi:9168268. [10] B. Ru, X.B. Li, L.J. Zhu, G.H. Xu, Y.L. Gu, Gas-Phase Methanol Carbonylation for Dimethyl Ether and Acetic Acid Co-Production, Adv. Mater. Res. 554-556 (2012) 760–763 doi:10.4028/www.scientific.net/AMR.554-556.760. [11] K.C. Liang, F.M. Yeh, C.G. Wu, H.M. Lee, Gasoline production by dehydration of dimethyl ether with NH4-ZSM-5 catalyst, Energy Procedia 75 (2015) 554–559, https://doi.org/10.1016/j.egypro.2015.07.452. [12] A. Sardesai, S. Lee, T. Tartamella, Synthesis of methyl acetate from dimethyl ether using group VIII metal salts of phosphotungstic acid, Energy Sources 24 (2002) 301–317, https://doi.org/10.1080/00908310252888682. [13] S. Wang, W. Guo, L. Zhu, H. Wang, K. Qiu, K. Cen, Methyl acetate synthesis from dimethyl ether carbonylation over mordenite modified by cation exchange, J. Phys. Chem. C 119 (2015) 524–533, https://doi.org/10.1021/jp511543x. [14] Q. Zhang, Y. Tan, C. Yang, H. Xie, Y. Han, Characterization and catalytic application of MnCl2 modified HZSM-5 zeolites in synthesis of aromatics from syngas via dimethyl ether, J. Ind. Eng. Chem. 19 (2013) 975–980, https://doi.org/10. 1016/j.jiec.2012.11.019. [15] Z. Wang, T. He, J. Li, J. Wu, J. Qin, G. Liu, D. Han, Z. Zi, Z. Li, J. Wu, Design and operation of a pilot plant for biomass to liquid fuels by integrating gasification, DME synthesis and DME to gasoline, Fuel 186 (2016) 587–596, https://doi.org/ 10.1016/j.fuel.2016.08.108. [16] A.S. Al-Dughaither, H. De Lasa, Neat dimethyl ether conversion to olefins (DTO) over HZSM-5: Effect of SiO2/Al2O3 on porosity, surface chemistry, and reactivity, Fuel 138 (2014) 52–64, https://doi.org/10.1016/j.fuel.2014.07.026. [17] P. Pérez-Uriarte, A. Ateka, A.G. Gayubo, T. Cordero-Lanzac, A.T. Aguayo, J. Bilbao, Deactivation kinetics for the conversion of dimethyl ether to olefins over a HZSM-5 zeolite catalyst, Chem. Eng. J. 311 (2017) 367–377, https://doi.org/10. 1016/j.cej.2016.11.104. [18] P. Pérez-Uriarte, A. Ateka, A.T. Aguayo, A.G. Gayubo, J. Bilbao, Kinetic model for the reaction of DME to olefins over a HZSM-5 zeolite catalyst, Chem. Eng. J. 302 (2016) 801–810, https://doi.org/10.1016/j.cej.2016.05.096. [19] K.L. Ng, D. Chadwick, B.A. Toseland, Kinetics and modelling of dimethyl ether synthesis from synthesis gas, Chem. Eng. Sci. 54 (1999) 3587–3592, https://doi. org/10.1016/S0009-2509(98)00514-4. [20] Z. Nie, H. Liu, D. Liu, W. Ying, Intrinsic kinetics of dimethyl ether synthesis from syngas, J. Nat. Gas Chem. 14 (2005) 22–28. [21] H. Liu, P. Cheung, E. Iglesia, Structure and support effects on the selective oxidation of dimethyl ether to formaldehyde catalyzed by MoOx domains, J. Catal. 217 (2003) 222–232, https://doi.org/10.1016/S0021-9517(03)00025-3. [22] P. Cheung, A. Bhan, G.J. Sunley, E. Iglesia, Selective carbonylation of dimethyl ether to methyl acetate catalyzed by acidic zeolites, Angew. Chemie - Int. Ed. 45 (2006) 1617–1620, https://doi.org/10.1002/anie.200503898. [23] X. Li, X. San, Y. Zhang, T. Ichii, M. Meng, Y. Tan, N. Tsubaki, Direct synthesis of ethanol from dimethyl ether and syngas over combined H-mordenite and Cu/ZnO catalysts, ChemSusChem. 3 (2010) 1192–1199, https://doi.org/10.1002/cssc. 201000109. [24] T.H. Fleisch, A. Basu, M.J. Gradassi, J.G. Masin, Natural gas conversion IV, Stud. Surf. Sci. Catal. 107 (1997) 117–125, https://doi.org/10.1016/S0167-2991(97) 80323-0. [25] B. Prabowo, M. Yan, M. Syamsiro, R.H. Setyobudi, M.K. Biddinika, State of the art of global dimethyl ether production and its potentional application in Indonesia, Proc. Pakistan Acad. Sci. 54 (2017) 29–39. [26] H.J. Majunke, H. Müller Dr., Treibstoff und eine Verwendung desselben, DE3307091C2, (1984). [27] D. John, N. Vancouver, Methyl ether fuels for internal combustion engines,

315

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav [54] R. Phienluphon, K. Pinkaew, G. Yang, J. Li, Q. Wei, Designing core (Cu/ZnO/ Al2O3)–shell (SAPO-11) zeolite capsule catalyst with a facile physical way for dimethyl ether direct synthesis from syngas, Chem. Eng. J. 270 (2015) 605–611, https://doi.org/10.1016/j.cej.2015.02.071. [55] A.T. Aguayo, J. Ereña, D. Mier, J.M. Arandes, M. Olazar, J. Bilbao, Kinetic modeling of dimethyl ether synthesis in a single step on a CuO–ZnO–Al2O3/γ-Al2O3 Catalyst, Ind. Eng. Chem. Res. 46 (2007) 5522–5530, https://doi.org/10.1021/ ie070269s. [56] Z. Wang, J. Wang, J. Diao, Y. Jin, The synergy effect of process coupling for dimethyl ether synthesis in slurry reactors, Chem. Eng. Technol. 24 (2001) 507–511 doi:10.1002/1521-4125(200105)24:5 < 507::AID-CEAT507 > 3.0.CO;2-0. [57] Y. Hu, Z. Nie, D. Fang, Simulation and model design of pipe-shell reactor for the direct synthesis of dimethyl ether from syngas, J. Nat. Gas Chem. 17 (2008) 195–200, https://doi.org/10.1016/S1003-9953(08)60051-1. [58] F. Hayer, H. Bakhtiary-Davijany, R. Myrstad, A. Holmen, P. Pfeifer, H.J. Venvik, Synthesis of dimethyl ether from syngas in a microchannel reactor-Simulation and experimental study, Chem. Eng. J. 167 (2011) 610–615, https://doi.org/10.1016/ j.cej.2010.09.080. [59] H. Bakhtiary-Davijany, F. Hayer, X.K. Phan, R. Myrstad, H.J. Venvik, P. Pfeifer, A. Holmen, Characteristics of an integrated micro packed bed reactor-heat exchanger for methanol synthesis from syngas, Chem. Eng. J. 167 (2011) 496–503, https://doi.org/10.1016/j.cej.2010.08.074. [60] J. Ereña, I. Sierra, A.T. Aguayo, A. Ateka, M. Olazar, J. Bilbao, Kinetic modelling of dimethyl ether synthesis from (H2 + CO2) by considering catalyst deactivation, Chem. Eng. J. 174 (2011) 660–667, https://doi.org/10.1016/j.cej.2011.09.067. [61] G.C. Chinchen, K. Mansfield, M.S. Spencer, The methanol synthesis-how does it work, Chemtech 11 (1990) 692–699. [62] J. Nakamura, I. Nakamura, T. Uchijima, Y. Kanai, T. Watanabe, M. Saito, T. Fujitani, Methanol synthesis over a Zn-deposited copper model catalyst, Catal. Letters. 31 (1995) 325–331, https://doi.org/10.1007/BF00808596. [63] R.J. da Silva, A.F. Pimentel, R.S. Monteiro, C.J.A. Mota, Synthesis of methanol and dimethyl ether from the CO2 hydrogenation over Cu·ZnO supported on Al2 O3 and Nb2O5, J. CO2 Util. 15 (2016) 83–88, https://doi.org/10.1016/j.jcou.2016.01. 006. [64] M. Thorhauge, S. Kuld, I. Chorkendorff, H. Falsig, C. Elkjaer, S. Helveg, J. Sehested, Quantifying the promotion of Cu catalysts by ZnO for methanol synthesis, Science 352 (2016) 969–974. [65] A. Le Valent, C. Comminges, C. Tisseraud, C. Canaff, L. Pinard, Y. Pouilloux, The Cu-ZnO synergy in methanol synthesis from CO2, Part 1: Origin of active site explained by experimental studies and a sphere contact quantification model on Cu + ZnO mechanical mixtures, J. Catal. 324 (2015) 41–49, https://doi.org/10. 1016/j.jcat.2015.01.021. [66] W.H. Chen, B.J. Lin, H.M. Lee, M.H. Huang, One-step synthesis of dimethyl ether from the gas mixture containing CO2 with high space velocity, Appl. Energy 98 (2012) 92–101, https://doi.org/10.1016/j.apenergy.2012.02.082. [67] S. Sugawa, K. Sayama, K. Okabe, H. Arakawa, Methanol synthesis from CO2 and H2 over silver catalyst, Energy Convers. Manag. 36 (1995) 665–668, https://doi. org/10.1016/0196-8904(95)00093-S. [68] X. Jiang, N. Koizumi, X. Guo, C. Song, Bimetallic Pd-Cu catalysts for selective CO2 hydrogenation to methanol, Appl. Catal. B Environ. 170-171 (2015) 173–185, https://doi.org/10.1016/j.apcatb.2015.01.010. [69] F. Arena, K. Barbera, G. Italiano, G. Bonura, L. Spadaro, F. Frusteri, Synthesis, characterization and activity pattern of Cu-ZnO/ZrO2 catalysts in the hydrogenation of carbon dioxide to methanol, J. Catal. 249 (2007) 185–194, https:// doi.org/10.1016/j.jcat.2007.04.003. [70] R. Raudaskoski, M.V. Niemela, R.L. Keiski, The effect of ageing time on co-precipitated Cu/ZnO/ZrO2 catalysts used in methanol synthesis from CO2 and H2, Top. Catal. 45 (2007) 57–60, https://doi.org/10.1007/s11244-007-0240-9. [71] L. Angelo, K. Kobl, L.M.M. Tejada, Y. Zimmermann, K. Parkhomenko, A.C. Roger, Study of CuZn MOx oxides (M = Al, Zr, Ce, CeZr) for the catalytic hydrogenation of CO2 into methanol, C.R. Chim. 18 (2015) 250–260, https://doi.org/10.1016/j. crci.2015.01.001. [72] E.L. Fornero, P.B. Sanguineti, D.L. Chiavassa, A.L. Bonivardi, M.A. Baltanás, Performance of ternary Cu-Ga2O3-ZrO2 catalysts in the synthesis of methanol using CO2-rich gas mixtures, Catal. Today 213 (2013) 163–170, https://doi.org/ 10.1016/j.cattod.2013.03.012. [74] G. Wang, Y. Zuo, M. Han, J. Wang, Copper crystallite size and methanol synthesis catalytic property of Cu-based catalysts promoted by Al, Zr and Mn, React. Kinet. Mech. Catal. 101 (2010) 443–454, https://doi.org/10.1007/s11144-010-0240-9. [75] S. Mehta, G.W. Simmons, K. Klier, R.G. Herman, Catalytic synthesis of methanol from COH2: II. Electron microscopy (TEM, STEM, microdiffraction, and energy dispersive analysis) of the CuZnO and Cu/ZnO/Cr2O3 catalysts, J. Catal. 57 (1979) 339–360, https://doi.org/10.1016/0021-9517(79)90001-0. [76] N. Pasupulety, H. Driss, Y.A. Alhamed, A.A. Alzahrani, M.A. Daous, L. Petrov, Studies on Au/Cu-Zn-Al catalyst for methanol synthesis from CO2, Appl. Catal. A Gen. 504 (2015) 308–318, https://doi.org/10.1016/j.apcata.2015.01.036. [77] H. Zhan, F. Li, P. Gao, N. Zhao, F. Xiao, W. Wei, L. Zhong, Y. Sun, Methanol synthesis from CO2 hydrogenation over La-M-Cu-Zn-O (M = Y, Ce, Mg, Zr) catalysts derived from perovskite-type precursors, J. Power Sources 251 (2014) 113–121, https://doi.org/10.1016/j.jpowsour.2013.11.037. [78] N. Kanoun, M.P. Astier, G.M. Pajonk, Catalytic properties of new Cu based catalysts containing Zr and/or V for methanol synthesis from a carbon dioxide and hydrogen mixture, Catal. Letters. 15 (1992) 231–235, https://doi.org/10.1007/ BF00765266. [79] V. Deerattrakul, P. Dittanet, M. Sawangphruk, P. Kongkachuichay, CO2 hydrogenation to methanol using Cu-Zn catalyst supported on reduced graphene oxide

nanosheets, J. CO2 Util. 16 (2016) 104–113, https://doi.org/10.1016/j.jcou.2016. 07.002. [80] N. Ahmed, Y. Shibata, T. Taniguchi, Y. Izumi, Photocatalytic conversion of carbon dioxide into methanol using zinc-copper-M(III) (M = aluminum, gallium) layered double hydroxides, J. Catal. 279 (2011) 123–135, https://doi.org/10.1016/j.jcat. 2011.01.004. [81] W. Wang, S. Wang, X. Ma, J. Gong, Recent advances in catalytic hydrogenation of carbon dioxide, Chem. Soc. Rev. 40 (2011) 3703–3727, https://doi.org/10.1039/ c1cs15008a. [82] L. Jia, J. Gao, W. Fang, Q. Li, Carbon dioxide hydrogenation to methanol over the pre-reduced LaCr0.5Cu0.5O3 catalyst, Catal. Commun. 10 (2009) 2000–2003, https://doi.org/10.1016/j.catcom.2009.07.017. [83] E. Catizzone, G. Bonura, M. Migliori, F. Frusteri, G. Giordano, CO2 recycling to dimethyl ether: State-of-the-art and perspectives, Molecules. 23 (2018) 1–28, https://doi.org/10.3390/molecules23010031. [84] W. Wang, S. Wang, X. Ma, J. Gong, W. Wang, Recent advances in catalytic hydrogenation of carbon dioxide, Chem. Soc. Rev. 40 (2011) 3369–4260, https:// doi.org/10.1039/c1cs15008a. [85] O. Martin, A.J. Martín, C. Mondelli, S. Mitchell, T.F. Segawa, R. Hauert, C. Drouilly, D. Curulla-Ferré, J. Pérez-Ramírez, Indium oxide as a superior catalyst for methanol synthesis by CO2 hydrogenation, Angew. Chem. Int. Ed. 55 (2016) 6261–6265, https://doi.org/10.1002/anie.201600943. [86] A. Gotti, R. Prins, Basic metal oxides as cocatalysts for Cu/SiO2 catalysts in the conversion of synthesis gas to methanol, J. Catal. 519 (1998) 511–519. [87 Y. Kikuzono, S. Kagami, S. Naito, T. Onishi, K. Tamaru, Selective hydrogenation of carbon monoxide on palladium catalysts, Faraday Discuss. Chem. Soc. 72 (1981) 135–143, https://doi.org/10.1039/DC9817200135. [88] T. Fujitani, M. Saito, Y. Kanai, T. Watanabe, J. Nakamura, T. Uchijima, Development of an active Ga2O3 supported palladium catalyst for the synthesis of methanol from carbon dioxide and hydrogen, Appl. Catal. A Gen. 125 (1995) 199–202, https://doi.org/10.1016/0926-860X(95)00049-6. [89] S.E. Collins, M.A. Baltanás, A.L. Bonivardi, An infrared study of the intermediates of methanol synthesis from carbon dioxide over Pd/β-Ga2O3, J. Catal. 226 (2004) 410–421, https://doi.org/10.1016/j.jcat.2004.06.012. [90] S.E. Collins, J.J. Delgado, C. Mira, J.J. Calvino, S. Bernal, D.L. Chiavassa, M.A. Baltanás, A.L. Bonivardi, The role of Pd-Ga bimetallic particles in the bifunctional mechanism of selective methanol synthesis via CO2 hydrogenation on a Pd/Ga2O3 catalyst, J. Catal. 292 (2012) 90–98, https://doi.org/10.1016/j.jcat. 2012.05.005. [91] D.L. Chiavassa, S.E. Collins, A.L. Bonivardi, M.A. Baltanás, Methanol synthesis from CO2/H2 using Ga2O3-Pd/silica catalysts: Kinetic modeling, Chem. Eng. J. 150 (2009) 204–212, https://doi.org/10.1016/j.cej.2009.02.013. [92] J. Díez-Ramírez, J.L. Valverde, P. Sánchez, F. Dorado, CO2 hydrogenation to methanol at atmospheric pressure: influence of the preparation method of Pd/ZnO catalysts, Catal. Letters. 146 (2016) 373–382, https://doi.org/10.1007/s10562015-1627-z. [93] N. Koizumi, X. Jiang, J. Kugai, C. Song, Effects of mesoporous silica supports and alkaline promoters on activity of Pd catalysts in CO2 hydrogenation for methanol synthesis, Catal. Today 194 (2012) 16–24, https://doi.org/10.1016/j.cattod.2012. 08.007. [94] P.D. Adkins, H. Perkins, The behavior of methanol over aluminum and zinc oxides, J. Phys. Chem. C. (2018) 221–224, https://doi.org/10.1021/j150284a006. [95] D.M. Sung, Y.H. Kim, E.D. Park, J.E. Yie, Correlation between acidity and catalytic activity for the methanol dehydration over various aluminum oxides, Res. Chem. Intermed. 36 (2010) 653–660, https://doi.org/10.1007/s11164-010-0201-y. [96] M. Xu, J.H. Lunsford, D.W. Goodman, A. Bhattacharyya, Synthesis of dimethyl ether (DME) from methanol over solid-acid catalysts, Appl. Catal. A Gen. 149 (1997) 289–301, https://doi.org/10.1016/S0926-860X(96)00275-X. [97] Y. Fu, T. Hong, J. Chen, A. Auroux, J. Shen, Surface acidity and the dehydration of methanol to dimethyl ether, Thermochim. Acta 434 (2005) 22–26, https://doi. org/10.1016/j.tca.2004.12.023. [98] A. Corma, State of the art and future challenges of zeolites as catalysts, J. Catal. 216 (2003) 298–312, https://doi.org/10.1016/S0021-9517(02)00132-X. [99] V. Vishwanathan, K. Jun, J. Kim, H. Roh, Vapour phase dehydration of crude methanol to dimethyl ether over Na-modified H-ZSM-5 catalysts, Appl. Catal. A Gen. 276 (2004) 251–255, https://doi.org/10.1016/j.apcata.2004.08.011. [100] Z. Azizi, M. Rezaeimanesh, T. Tohidian, M.R. Rahimpour, Dimethyl ether: A review of technologies and production challenges, Chem. Eng. Process. Process Intensif. 82 (2014) 150–172, https://doi.org/10.1016/j.cep.2014.06.007. [101] J.M. Campelo, F. Lafont, J.M. Marinas, M. Ojeda, Studies of catalyst deactivation in methanol conversion with high, medium and small pore silicoaluminophosphates, Appl. Catal. A Gen. 192 (2000) 85–96. [102] E. Catizzone, A. Aloise, M. Migliori, G. Giordano, General Dimethyl ether synthesis via methanol dehydration: Effect of zeolite structure, Appl. Catal. A Gen. 502 (2015) 215–220, https://doi.org/10.1016/j.apcata.2015.06.017. [103] E. Catizzone, A. Aloise, M. Migliori, G. Giordano, From 1-D to 3-D zeolite structures: performance assessment in catalysis of vapour-phase methanol dehydration to DME, Microporous Mesoporous Mater. 243 (2017) 102–111, https://doi.org/ 10.1016/j.micromeso.2017.02.022. [104] N. Khandan, M. Kazemeini, M. Aghaziarati, Determining an optimum catalyst for liquid-phase dehydration of methanol to dimethyl ether, Appl. Catal. A Gen. 349 (2008) 6–12, https://doi.org/10.1016/j.apcata.2008.07.029. [105] Q. Tang, H. Xu, Y. Zheng, J. Wang, H. Li, J. Zhang, Appl. Catal. A: Gen. Catalytic dehydration of methanol to dimethyl ether over micro – mesoporous ZSM-5/MCM41 composite molecular sieves, Appl. Catal. A Gen. 413-414 (2012) 36–42, https://doi.org/10.1016/j.apcata.2011.10.039.

316

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav [106] Z. Bai, H. Ma, H. Zhang, W. Ying, D. Fang, Simulation of a multi-stage adiabatic reactor with inter-stage quenching for dimethyl ether synthesis, Chem. Ind. Chem. Eng. Q. 20 (2014) 481–490. [107] E. Catizzone, A. Aloise, M. Migliori, G. Giordano, The effect of FER zeolite acid sites in methanol-to-dimethyl-ether catalytic dehydration, J. Energy Chem. 26 (2017) 406–415, https://doi.org/10.1016/j.jechem.2016.12.005. [108] Y. Hu, Z. Nie, D. Fang, Simulation and model design of pipe-shell reactor for the direct synthesis of dimethyl ether from syngas, J. Nat. Gas Chem. 17 (2008) 195–200, https://doi.org/10.1016/S1003-9953(08)60051-1. [109] S. Hassanpour, M. Taghizadeh, Preparation, characterization, and activity evaluation of H-ZSM-5 catalysts in vapor-phase methanol dehydration to dimethyl ether, Ind. Eng. Chem. Res. (2010) 4063–4069, https://doi.org/10.1021/ ie9013869. [110] N. Khandan, M. Kazemeyni, M. Aghaziarati, Dehydration of methanol to dimethyl ether employing modified H-ZSM-5 catalysts, Iran. J. Chem. Eng. 6 (2009) 3–11. [111] S.D. Kim, S.C. Baek, Y.-J. Lee, K.-W. Jun, M.J. Kim, I.S. Yoo, Effect of γ-alumina content on catalytic performance of modified ZSM-5 for dehydration of crude methanol to dimethyl ether, Appl. Catal. A Gen. 309 (2006) 139–143, https://doi. org/10.1016/j.apcata.2006.05.008. [112] W. Alharbi, E.F. Kozhevnikova, I.V. Kozhevnikov, Dehydration of methanol to dimethyl ether over heteropoly acid catalysts: The relationship between reaction rate and catalyst acid strength, ACS Catal. 5 (2015) 7186–7193, https://doi.org/ 10.1021/acscatal.5b01911. [113] R.M. Ladera, J.L.G. Fierro, M. Ojeda, S. Rojas, TiO2-supported heteropoly acids for low-temperature synthesis of dimethyl ether from methanol, J. Catal. 312 (2014) 195–203, https://doi.org/10.1016/j.jcat.2014.01.016. [114] A. Ciftci, N.A. Sezgi, T. Dogu, Nafion-incorporated silicate structured nanocomposite mesoporous catalysts for dimethyl ether synthesis, Ind. Eng. Chem. Res. 49 (2010) 6753–6762, https://doi.org/10.1021/ie9015667. [115] D. Varışlı, T. Doğu, Production of clean transportation fuel dimethylether by dehydration of methanol over nafion catalyst, Gazi Univ. J. Sci. 21 (2008) 37–41, https://doi.org/10.1016/S0140-6701(03)82853-9. [116] J.J. Spivey, Review: dehydration catalysts for the methanol/dimethyl ether reaction, Chem. Eng. Technol. (2010) 37–41, https://doi.org/10.1080/ 00986449108939946. [117] S. Hosseininejad, A. Afacan, R.E. Hayes, Catalytic and kinetic study of methanol dehydration to dimethyl ether, Chem. Eng. Res. Des. 90 (2011) 825–833, https:// doi.org/10.1016/j.cherd.2011.10.007. [118] K.C. Tokay, T. Dogu, G. Dogu, Dimethyl ether synthesis over alumina based catalysts, Chem. Eng. J. 184 (2012) 278–285, https://doi.org/10.1016/j.cej.2011.12. 034. [119] B. Sabour, M. Hassan, T. Hamoule, M. Rashidzadeh, Catalytic dehydration of methanol to dimethyl ether (DME) over Al-HMS catalysts, J. Ind. Eng. Chem. 20 (2014) 222–227, https://doi.org/10.1016/j.jiec.2013.03.044. [120] S. Ren, W.R. Shoemaker, X. Wang, Z. Shang, N. Klinghoffer, S. Li, M. Yu, X. He, T.A. White, X. Liang, Highly active and selective Cu-ZnO based catalyst for methanol and dimethyl ether synthesis via CO2 hydrogenation, Fuel 239 (2019) 1125–1133, https://doi.org/10.1016/j.fuel.2018.11.105. [121] M. Stiefel, R. Ahmad, U. Arnold, M. Döring, Direct synthesis of dimethyl ether from carbon-monoxide-rich synthesis gas: Influence of dehydration catalysts and operating conditions, Fuel Process. Technol. 92 (2011) 1466–1474, https://doi. org/10.1016/j.fuproc.2011.03.007. [122] S. Papari, M. Kazemeini, M. Fattahi, Mathematical modeling of a slurry reactor for DME direct synthesis from syngas, J. Nat. Gas Chem. 21 (2012) 148–157, https:// doi.org/10.1016/S1003-9953(11)60347-2. [123] I. Sierra, J. Ereña, A.T. Aguayo, J.M. Arandes, M. Olazar, J. Bilbao, Co-feeding water to attenuate deactivation of the catalyst metallic function (CuO-ZnO-Al2O3) by coke in the direct synthesis of dimethyl ether, Appl. Catal. B Environ. 106 (2011) 167–173, https://doi.org/10.1016/j.apcatb.2011.05.021. [124] S.P. Naik, T. Ryu, V. Bui, J.D. Miller, N.B. Drinnan, W. Zmierczak, Synthesis of DME from CO2/H2 gas mixture, Chem. Eng. J. 167 (2011) 362–368, https://doi. org/10.1016/j.cej.2010.12.087. [125] Q. Zhang, Y.Z. Zuo, M.H. Han, J.F. Wang, Y. Jin, F. Wei, Long carbon nanotubes intercrossed Cu/Zn/Al/Zr catalyst for CO/CO2 hydrogenation to methanol/dimethyl ether, Catal. Today 150 (2010) 55–60, https://doi.org/10.1016/j.cattod. 2009.05.018. [126] F. Zha, J. Ding, Y. Chang, J. Ding, J. Wang, J. Ma, Cu-Zn-al oxide cores packed by metal-doped amorphous silica-alumina membrane for catalyzing the hydrogenation of carbon dioxide to dimethyl ether, Ind. Eng. Chem. Res. 51 (2012) 345–352, https://doi.org/10.1021/ie202090f. [127] T. Takeguchi, K.I. Yanagisawa, T. Inui, M. Inoue, Effect of the property of solid acid upon syngas-to-dimethyl ether conversion on the hybrid catalysts composed of Cu-Zn-Ga and solid acids, Appl. Catal. A Gen. 192 (2000) 201–209, https://doi. org/10.1016/S0926-860X(99)00343-9. [128] S.H. Lima, A.M.S. Forrester, L.A. Palacio, A.C. Faro, Niobia-alumina as methanol dehydration component in mixed catalyst systems for dimethyl ether production from syngas, Appl. Catal. A Gen. 488 (2014) 19–27, https://doi.org/10.1016/j. apcata.2014.09.022. [129] O.S. Joo, K.D. Jung, S.H. Han, Modification of H-ZSM-5 and γ-alumina with formaldehyde and its application to the synthesis of dimethyl ether from syn-gas, Bull. Korean Chem. Soc. 23 (2002) 1103–1105, https://doi.org/10.5012/bkcs. 2002.23.8.1103. [130] S. Asthana, C. Samanta, A. Bhaumik, B. Banerjee, R.K. Voolapalli, B. Saha, Direct synthesis of dimethyl ether from syngas over Cu-based catalysts: Enhanced selectivity in the presence of MgO, J. Catal. 334 (2016) 89–101, https://doi.org/10. 1016/j.jcat.2015.10.020.

[131] Y. Tan, H. Xie, H. Cui, Y. Han, B. Zhong, Modification of Cu-based methanol synthesis catalyst for dimethyl ether synthesis from syngas in slurry phase, Catal. Today 104 (2005) 25–29, https://doi.org/10.1016/j.cattod.2005.03.033. [132] M.H. Huang, H.M. Lee, K.C. Liang, C.C. Tzeng, W.H. Chen, An experimental study on single-step dimethyl ether (DME) synthesis from hydrogen and carbon monoxide under various catalysts, Int. J. Hydrogen Energy 40 (2015) 13583–13593, https://doi.org/10.1016/j.ijhydene.2015.07.168. [133] Z. Li, J. Li, M. Dai, Y. Liu, D. Han, J. Wu, The effect of preparation method of the Cu-La2O3-ZrO2/γ-Al2O3 hybrid catalysts on one-step synthesis of dimethyl ether from syngas, Fuel 121 (2014) 173–177, https://doi.org/10.1016/j.fuel.2013.12. 050. [134] A. Venugopal, J. Palgunadi, J.K. Deog, O.S. Joo, C.H. Shin, Dimethyl ether synthesis on the admixed catalysts of Cu-Zn-Al-M (M = Ga, La, Y, Zr) and γ-Al2O3: The role of modifier, J. Mol. Catal. A Chem. 302 (2009) 20–27, https://doi.org/10. 1016/j.molcata.2008.11.038. [135] Q. Zhang, Y.Z. Zuo, M.H. Han, J.F. Wang, Y. Jin, F. Wei, Long carbon nanotubes intercrossed Cu/Zn/Al/Zr catalyst for CO/CO2 hydrogenation to methanol/dimethyl ether, Catal. Today. 150 (2010) 55–60, https://doi.org/10.1016/j.cattod. 2009.05.018. [136] J. Toyir, P.R. De la Piscina, J.L.G. Fierro, N. Homs, Catalytic performance for CO2 conversion to methanol of gallium-promoted copper-based catalysts: Influence of metallic precursors, Appl. Catal. B Environ. 34 (2001) 255–266, https://doi.org/ 10.1016/S0926-3373(01)00203-X. [137] G.R. Moradi, S. Nosrati, F. Yaripor, Effect of the hybrid catalysts preparation method upon direct synthesis of dimethyl ether from synthesis gas, Catal. Commun. 8 (2007) 598–606, https://doi.org/10.1016/j.catcom.2006.08.023. [138] Z. Gao, W. Huang, L. Yin, L. Hao, K. Xie, The structure properties of CuZnAl slurry catalysts prepared by a complete liquid-phase method and its catalytic performance for DME synthesis from syngas, Catal. Letters 127 (2009) 354–359, https:// doi.org/10.1007/s10562-008-9689-9. [139] H. Jiang, H. Bongard, W. Schmidt, F. Schüth, One-pot synthesis of mesoporous Cu–γ-Al2O3 as bifunctional catalyst for direct dimethyl ether synthesis, Microporous Mesoporous Mater. 164 (2012) 3–8, https://doi.org/10.1016/j. micromeso.2012.08.004. [140] Y. Wang, Y. Chen, F. Yu, D. Pan, B. Fan, J. Ma, R. Li, One-step synthesis of dimethyl ether from syngas on ordered mesoporous copper incorporated alumina, J. Energy Chem. 25 (2016) 775–781, https://doi.org/10.1016/j.jechem.2016.04. 014. [141] J. Abu-Dahrieh, D. Rooney, A. Goguet, Y. Saih, Activity and deactivation studies for direct dimethyl ether synthesis using CuO-ZnO-Al2O3 with NH4ZSM-5, HZSM-5 or γ-Al2O3, Chem. Eng. J. 203 (2012) 201–211, https://doi.org/10.1016/j.cej. 2012.07.011. [142] Y. Tavan, S.H. Hosseini, M. Ghavipour, M.R.K. Nikou, A. Shariati, From laboratory experiments to simulation studies of methanol dehydration to produce dimethyl ether - Part I: Reaction kinetic study, Chem. Eng. Process. Process Intensif. 73 (2013) 144–150, https://doi.org/10.1016/j.cep.2013.06.006. [143] J.J. Spivey, Review: Dehydration catalysts for the methanol/dimethyl ether reaction, Chem. Eng. Commun. 110 (1991) 123–142, https://doi.org/10.1080/ 00986449108939946. [144] F.S. Ramos, A.M.D. De Farias, L.E.P. Borges, J.L. Monteiro, M.A. Fraga, E.F. SousaAguiar, L.G. Appel, Role of dehydration catalyst acid properties on one-step DME synthesis over physical mixtures, Catal. Today 101 (2005) 39–44, https://doi.org/ 10.1016/j.cattod.2004.12.007. [145] J. Fei, Z. Hou, B. Zhu, H. Lou, X. Zheng, Synthesis of dimethyl ether (DME) on modified HY zeolite and modified HY zeolite-supported Cu-Mn-Zn catalysts, Appl. Catal. A Gen. 304 (2006) 49–54, https://doi.org/10.1016/j.apcata.2006.02.019. [146] Q. Xie, P. Chen, P. Peng, S. Liu, P. Peng, B. Zhang, Y. Cheng, Y. Wan, Y. Liu, R. Ruan, Single-step synthesis of DME from syngas on CuZnAl-zeolite bifunctional catalysts: The influence of zeolite type, RSC Adv. 5 (2015) 26301–26307, https:// doi.org/10.1039/c5ra02814k. [147] A. García-Trenco, A. Vidal-Moya, A. Martínez, Study of the interaction between components in hybrid CuZnAl/HZSM-5 catalysts and its impact in the syngas-toDME reaction, Catal. Today 179 (2012) 43–51, https://doi.org/10.1016/j.cattod. 2011.06.034. [148] D. Mao, X. Guo, Dimethyl ether synthesis from syngas over the admixed Cu/ZnO/ Al2O3 catalyst and alkaline earth oxide-modified HZSM-5 zeolite, Energy Technol. 2 (2014) 882–888, https://doi.org/10.1002/ente.201402071. [149] Q.-L. Xu, P. Lan, S.-P. Zhang, T.-C. Li, Y.-J. Yan, Effect of modified zeolite on onestep process of DME synthesis, Pet. Sci. Technol. 29 (2011) 439–448, https://doi. org/10.1080/10916460903117552. [150] R. Montesano, A. Narvaez, D. Chadwick, Shape-selectivity effects in syngas-todimethyl ether conversion over Cu/ZnO/Al2O3 and zeolite mixtures: Carbon deposition and by-product formation, Appl. Catal. A Gen. 482 (2014) 69–77, https:// doi.org/10.1016/j.apcata.2014.05.009. [151] P.S. Sai Prasad, J.W. Bae, S.H. Kang, Y.J. Lee, K.W. Jun, Single-step synthesis of DME from syngas on Cu-ZnO-Al2O3/zeolite bifunctional catalysts: The superiority of ferrierite over the other zeolites, Fuel Process. Technol. 89 (2008) 1281–1286, https://doi.org/10.1016/j.fuproc.2008.07.014. [152] S.-H. Kang, J.W. Bae, K.-W. Jun, H.S. Potdar, Dimethyl ether synthesis from syngas over the composite catalysts of Cu–ZnO–Al2O3/Zr-modified zeolites, Catal. Commun. 9 (2008) 2035–2039, https://doi.org/10.1016/j.catcom.2008.03.046. [153] Q. Ge, Y. Huang, F. Qiu, S. Li, Bifunctional catalysts for conversion of synthesis gas to dimethyl ether, Appl. Catal. A: Gen. 167 (1998) 23–30, https://doi.org/10. 1016/S0926-860X(97)00290-1. [154] F. Frusteri, G. Bonura, C. Cannilla, G.D. Ferrante, A. Aloise, E. Catizzone, M. Migliori, G. Giordano, Environmental stepwise tuning of metal-oxide and acid

317

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav

[155]

[156] [157] [158] [159] [160]

[161]

[162] [163]

[164]

[165]

[166]

[167]

[168]

[169]

[170] [171]

[172]

[173] [174] [175] [176]

[177]

sites of CuZnZr-MFI hybrid catalysts for the direct DME synthesis by CO2 hydrogenation, Appl. Catal. B Environ. 176-177 (2015) 522–531, https://doi.org/10. 1016/j.apcatb.2015.04.032. F. Frusteri, M. Migliori, C. Cannilla, L. Frusteri, E. Catizzone, A. Aloise, G. Giordano, G. Bonura, Direct CO2-to-DME hydrogenation reaction: New evidences of a superior behaviour of FER-based hybrid systems to obtain high DME yield, J. CO2 Util. 18 (2017) 353–361. H.J. Chen, C.W. Fan, C.S. Yu, Analysis, synthesis, and design of a one-step dimethyl ether production via a thermodynamic approach, Appl. Energy 101 (2013) 449–456, https://doi.org/10.1016/j.apenergy.2012.08.025. G.R. Moradi, F. Yaripour, P. Vale-Sheyda, Catalytic dehydration of methanol to dimethyl ether over mordenite catalysts, Fuel Process. Technol. 91 (2010) 461–468, https://doi.org/10.1016/j.fuproc.2009.12.005. A.A. Rownaghi, F. Rezaei, M. Stante, J. Hedlund, Selective dehydration of methanol to dimethyl ether on ZSM-5 nanocrystals, Appl. Catal. B Environ. 119-120 (2012) 56–61, https://doi.org/10.1016/j.apcatb.2012.02.017. F. Raoof, M. Taghizadeh, A. Eliassi, F. Yaripour, Effects of temperature and feed composition on catalytic dehydration of methanol to dimethyl ether over γ-alumina, Fuel 87 (2008) 2967–2971, https://doi.org/10.1016/j.fuel.2008.03.025. A. Ateka, J. Ereña, J. Bilbao, A.T. Aguayo, Kinetic modeling of the direct synthesis of dimethyl ether over a CuO–ZnO–MnO/SAPO–18 catalyst and assessment of the CO2 conversion, Fuel Process. Technol. 181 (2018) 233–243, https://doi.org/10. 1016/j.fuproc.2018.09.024. S.C. Baek, S.H. Kang, J.W. Bae, Y.J. Lee, D.H. Lee, K.Y. Lee, Effect of copper precursors to the activity for dimethyl ether synthesis from syngas over Cu-ZnO/γAl2O3 bifunctional catalysts, Energy Fuels 25 (2011) 2438–2443, https://doi.org/ 10.1021/ef200504p. Q. Ge, Y. Huang, F. Qiu, S. Li, Bifunctional catalysts for conversion of synthesis gas to dimethyl ether, Appl. Catal. A Gen. 167 (1998) 23–30, https://doi.org/10. 1016/S0926-860X(97)00290-1. C. Zeng, J. Sun, G. Yang, I. Ooki, K. Hayashi, Y. Yoneyama, A. Taguchi, T. Abe, N. Tsubaki, Highly selective and multifunctional Cu/ZnO/Zeolite catalyst for onestep dimethyl ether synthesis: Preparing catalyst by bimetallic physical sputtering, Fuel 112 (2013) 140–144, https://doi.org/10.1016/j.fuel.2013.05.026. R. Ahmad, D. Schrempp, S. Behrens, J. Sauer, M. Döring, U. Arnold, Zeolite-based bifunctional catalysts for the single step synthesis of dimethyl ether from CO-rich synthesis gas, Fuel Process. Technol. 121 (2014) 38–46, https://doi.org/10.1016/ j.fuproc.2014.01.006. R. Khoshbin, M. Haghighi, Direct conversion of syngas to dimethyl ether as a green fuel over ultrasound-assisted synthesized CuO–ZnO–Al2O3/HZSM-5 nanocatalyst: effect of active phase ratio on physicochemical and catalytic properties at different process conditions, Catal. Sci. Technol. 4 (2014) 1779–1792, https://doi.org/10. 1039/C3CY01089A. S. Allahyari, M. Haghighi, A. Ebadi, H. Qavam Saeedi, Direct synthesis of dimethyl ether as a green fuel from syngas over nanostructured CuO–ZnO–Al2O3/HZSM-5 catalyst: Influence of irradiation time on nanocatalyst properties and catalytic performance, J. Power Sources 272 (2014) 929–939, https://doi.org/10.1016/j. jpowsour.2014.07.152. R. Khoshbin, M. Haghighi, Direct syngas to DME as a clean fuel: The beneficial use of ultrasound for the preparation of CuO-ZnO-Al2O3/HZSM-5 nanocatalyst, Chem. Eng. Res. Des. 91 (2013) 1111–1122, https://doi.org/10.1016/j.cherd.2012.11. 017. Z. Hosseini, M. Taghizadeh, F. Yaripour, Synthesis of nanocrystalline γ-Al2O3 by sol-gel and precipitation methods for methanol dehydration to dimethyl ether, J. Nat. Gas Chem. 20 (2011) 128–134, https://doi.org/10.1016/S1003-9953(10) 60172-7. V.V. Ordomsky, M. Cai, V. Sushkevich, S. Moldovan, O. Ersen, C. Lancelot, V. Valtchev, A.Y. Khodakov, The role of external acid sites of ZSM-5 in deactivation of hybrid CuZnAl/ZSM-5 catalyst for direct dimethyl ether synthesis from syngas, Appl. Catal. A Gen. 486 (2014) 266–275, https://doi.org/10.1016/j. apcata.2014.08.030. J.H. Kim, M.J. Park, S.J. Kim, O.S. Joo, K.D. Jung, DME synthesis from synthesis gas on the admixed catalysts of Cu/ZnO/Al2O3and ZSM-5, Appl. Catal. A Gen. 264 (2004) 37–41, https://doi.org/10.1016/j.apcata.2003.12.058. A. García-Trenco, S. Valencia, A. Martínez, The impact of zeolite pore structure on the catalytic behavior of CuZnAl/zeolite hybrid catalysts for the direct DME synthesis, Appl. Catal. A Gen. 468 (2013) 102–111, https://doi.org/10.1016/j. apcata.2013.08.038. M. Cai, A. Palčić, V. Subramanian, S. Moldovan, O. Ersen, V. Valtchev, V.V. Ordomsky, A.Y. Khodakov, Direct dimethyl ether synthesis from syngas on copper-zeolite hybrid catalysts with a wide range of zeolite particle sizes, J. Catal. 338 (2016) 227–238, https://doi.org/10.1016/j.jcat.2016.02.025. A. García-trenco, A. Martínez, Direct synthesis of DME from syngas on hybrid CuZnAl/ZSM-5 catalysts: New insights into the role of zeolite acidity, Appl. Catal. A Gen. 412 (2012) 170–179, https://doi.org/10.1016/j.apcata.2011.10.036. A. García-Trenco, A. Martínez, A simple and efficient approach to confine Cu/ZnO methanol synthesis catalysts in the ordered mesoporous SBA-15 silica, Catal. Today. 215 (2013) 152–161, https://doi.org/10.1016/j.cattod.2013.03.005. G. Yang, D. Wang, Y. Yoneyama, Y. Tan, N. Tsubaki, Facile synthesis of H-type zeolite shell on a silica substrate for tandem catalysis, Chem. Commun. 48 (2012) 1263–1265, https://doi.org/10.1039/c2cc16713a. G. Yang, N. Tsubaki, J. Shamoto, Y. Yoneyama, Y. Zhang, Confinement effect and synergistic function of H-ZSM-5/Cu-ZnO-Al2O3 capsule catalyst for one-step controlled synthesis, J. Am. Chem. Soc. 132 (2010) 8129–8136, https://doi.org/10. 1021/ja101882a. G. Yang, M. Thongkam, T. Vitidsant, Y. Yoneyama, Y. Tan, N. Tsubaki, A double-

[178]

[179] [180]

[181]

[182]

[183] [184] [185]

[186] [187] [188] [189] [190]

[191] [192]

[193]

[194]

[195]

[196]

[197] [198] [199] [200] [201]

318

shell capsule catalyst with core-shell-like structure for one-step exactly controlled synthesis of dimethyl ether from CO2 containing syngas, Catal. Today 171 (2011) 229–235, https://doi.org/10.1016/j.cattod.2011.02.021. K. Pinkaew, G. Yang, T. Vitidsant, Y. Jin, C. Zeng, Y. Yoneyama, N. Tsubaki, A new core-shell-like capsule catalyst with SAPO-46 zeolite shell encapsulated Cr/ZnO for the controlled tandem synthesis of dimethyl ether from syngas, Fuel. 111 (2013) 727–732, https://doi.org/10.1016/j.fuel.2013.03.027. R. Nie, H. Lei, S. Pan, L. Wang, J. Fei, Z. Hou, Core-shell structured [email protected] catalysts for CO hydrogenation to dimethyl ether, Fuel. 96 (2012) 419–425, https://doi.org/10.1016/j.fuel.2011.12.048. M. Sánchez-Contador, A. Ateka, A.T. Aguayo, J. Bilbao, Direct synthesis of dimethyl ether from CO and CO2 over a core-shell structured [email protected] SAPO-11 catalyst, Fuel Process. Technol. 179 (2018) 258–268, https://doi.org/10. 1016/j.fuproc.2018.07.009. M. Sánchez-Contador, A. Ateka, P. Rodriguez-Vega, J. Bilbao, A.T. Aguayo, Optimization of the Zr content in the CuO-ZnO-ZrO2/SAPO-11 catalyst for the selective hydrogenation of CO + CO2 mixtures in the direct synthesis of dimethyl ether, Ind. Eng. Chem. Res. 57 (2018) 1169–1178, https://doi.org/10.1021/acs. iecr.7b04345. Y. Wang, W. Wang, Y. Chen, J. Zheng, R. Li, Synthesis of dimethyl ether from syngas using a hierarchically porous composite zeolite as the methanol dehydration catalyst, J. Fuel Chem. Technol. 41 (2013) 873–880, https://doi.org/10. 1016/S1872-5813(13)60037-7. Y. Wang, W. Wang, Y. Chen, J. Ma, J. Zheng, R. Li, Core–shell Ccatalyst CuO–ZnO–Al2O3 @Al2O3 for dimethyl ether synthesis from syngas, Chem. Lett. 42 (2013) 335–337, https://doi.org/10.1246/cl.121099. W.Z. Lu, L.H. Teng, W. De Xiao, Simulation and experiment study of dimethyl ether synthesis from syngas in a fluidized-bed reactor, Chem. Eng. Sci. 59 (2004) 5455–5464, https://doi.org/10.1016/j.ces.2004.07.031. M.P. Rohde, G. Schaub, S. Khajavi, J.C. Jansen, F. Kapteijn, Fischer-Tropsch synthesis with in situ H2O removal - Directions of membrane development, Microporous Mesoporous Mater. 115 (2008) 123–136, https://doi.org/10.1016/j. micromeso.2007.10.052. A. Erkiaga, G. Lopez, M. Amutio, J. Bilbao, M. Olazar, Influence of operating conditions on the steam gasification of biomass in a conical spouted bed reactor, Chem. Eng. J. 237 (2014) 259–267, https://doi.org/10.1016/j.cej.2013.10.018. J. Ereña, I. Sierra, M. Olazar, A.G. Gayubo, A.T. Aguayo, Deactivation of a CuO ZnO - Al2O3/γ-Al 2O3 catalyst in the synthesis of dimethyl ether, Ind. Eng. Chem. Res. 47 (2008) 2238–2247, https://doi.org/10.1021/ie071478f. B.T. Carvill, J.R. Hufton, M. Anand, S. Sircar, Sorption-enhanced reaction process, AIChE J. 42 (1996) 2765–2772, https://doi.org/10.1002/aic.690421008. I. Iliuta, M.C. Iliuta, F. Larachi, Sorption-enhanced dimethyl ether synthesisMultiscale reactor modeling, Chem. Eng. Sci. 66 (2011) 2241–2251, https://doi. org/10.1016/j.ces.2011.02.047. A. Bayat, T. Dogu, Optimization of CO2/CO ratio and temperature for dimethyl ether synthesis from syngas over a new bifunctional catalyst pair containing heteropolyacid impregnated mesoporous alumina, Ind. Eng. Chem. Res. (2016), https://doi.org/10.1021/acs.iecr.6b03001. G. Moradi, J. Ahmadpour, M. Nazari, F. Yaripour, Effects of feed composition and space velocity on direct synthesis of dimethyl ether from syngas, Ind. Eng. Chem. Res. 47 (2008) 7672–7679, https://doi.org/10.1021/ie800888z. K.B. Kabir, K. Hein, S. Bhattacharya, Process modelling of dimethyl ether production from Victorian brown coal-Integrating coal drying, gasification and synthesis processes, Comput. Chem. Eng. 48 (2013) 96–104, https://doi.org/10. 1016/j.compchemeng.2012.08.008. N. Diban, A.M. Urtiaga, I. Ortiz, J. Ereña, J. Bilbao, A.T. Aguayo, Influence of the membrane properties on the catalytic production of dimethyl ether with in situ water removal for the successful capture of CO2, Chem. Eng. J. 234 (2013) 140–148, https://doi.org/10.1016/j.cej.2013.08.062. M. Stiefel, R. Ahmad, U. Arnold, M. Döring, Direct synthesis of dimethyl ether from carbon-monoxide-rich synthesis gas: Influence of dehydration catalysts and operating conditions, Fuel Process. Technol. 92 (2011) 1466–1474, https://doi. org/10.1016/j.fuproc.2011.03.007. J. Erena, R. Garona, J.M. Arandes, A.T. Aguayo, J. Bilbao, Effect of operating conditions on the synthesis of dimethyl ether over a CuO-ZnO-Al2O3/NaHZSM-5 bifunctional catalyst, Catal. Today 107 (2005) 467–473, https://doi.org/10.1016/ j.cattod.2005.07.116. A. Ateka, J. Ereña, P. Pérez-Uriarte, A.T. Aguayo, J. Bilbao, Effect of the content of CO2 and H2 in the feed on the conversion of CO2 in the direct synthesis of dimethyl ether over a CuO-ZnO-Al2O3/SAPO-18 catalyst, Int. J. Hydrogen Energy 42 (2017) 27130–27138, https://doi.org/10.1021/ie071478f. M. Kumar, V.C. Srivastava, Simulation of a fluidized-bed reactor for dimethyl ether synthesis, Chem. Eng. Technol. 33 (2010) 1967–1978, https://doi.org/10. 1002/ceat.201000158. R. Liu, F. Zhu, Y. Steinberger, Effectiveness of afforested shrub plantation on ground-active arthropod communities and trophic structure in desertified regions, Catena 125 (2015) 1–9, https://doi.org/10.1016/j.catena.2014.09.018. X. Zhou, T. Su, Y. Jiang, Z. Qin, H. Ji, Z. Guo, CuO-Fe2O3-CeO2/HZSM-5 bifunctional catalzyst hydrogenated CO2 for enhanced dimethyl ether synthesis, Chem. Eng. Sci. 153 (2016) 10–20, https://doi.org/10.1016/j.ces.2016.07.007. J. Ereña, R. Garoña, J.M. Arandes, A.T. Aguayo, J. Bilbao, Direct synthesis of dimethyl ether from (H2 + CO) and (H2 + CO2) Feeds. Effect of feed composition, Int. J. Chem. React. Eng. 3 (2005), https://doi.org/10.2202/1542-6580.1295. J. Ereña, R. Garoña, J.M. Arandes, A.T. Aguayo, J. Bilbao, Effect of operating conditions on the synthesis of dimethyl ether over a CuO-ZnO-Al2O3/NaHZSM-5 bifunctional catalyst, Catal. Today. 107-108 (2005) 467–473, https://doi.org/10.

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav 1016/j.cattod.2005.07.116. [202] A. Ateka, P. Pérez-Uriarte, M. Sánchez-Contador, J. Ereña, A.T. Aguayo, J. Bilbao, Direct synthesis of dimethyl ether from syngas on CuO-ZnO-MnO/SAPO-18 bifunctional catalyst, Int. J. Hydrogen Energy. 41 (2016) 18015–18026, https://doi. org/10.1016/j.ijhydene.2016.07.195. [203] F. Zha, H. Tian, J. Yan, Y. Chang, Multi-walled carbon nanotubes as catalyst promoter for dimethyl ether synthesis from CO2 hydrogenation, Appl. Surf. Sci. 285 (2013) 945–951, https://doi.org/10.1016/j.apsusc.2013.06.150. [204] M. Jia, W. Li, H. Xu, S. Hou, Q. Ge, An integrated air–POM syngas/dimethyl ether process from natural gas, Appl. Catal. A Gen. 233 (2002) 7–12, https://doi.org/10. 1016/s0926-860x(02)00120-5. [205] J. Ereña, R. Garoña, J.M. Arandes, A.T. Aguayo, J. Bilbao, Effect of operating conditions on the synthesis of dimethyl ether over a CuO-ZnO-Al2O3/NaHZSM-5 bifunctional catalyst, Catal. Today. 107-108 (2005) 467–473, https://doi.org/10. 1016/j.cattod.2005.07.116. [206] A. Ateka, M. Sánchez-Contador, J. Ereña, A.T. Aguayo, J. Bilbao, Catalyst configuration for the direct synthesis of dimethyl ether from CO and CO2 hydrogenation on CuO–ZnO–MnO/SAPO-18 catalysts, React. Kinet. Mech. Catal. (2018) 1–18, https://doi.org/10.1007/s11144-018-1344-x. [207] T. Henrich, J. Abeln, M. Betz, Direct dimethyl ether synthesis: modelling of the kinetics from isothermal, Exp. Data Chemie Ing. Tech 90 (2018) 307–315, https:// doi.org/10.1002/cite.201600131. [208] M. Gentzen, D.E. Doronkin, T.L. Sheppard, J.-D. Grunwaldt, J. Sauer, S. Behrens, An intermetallic Pd2Ga nanoparticle catalyst for the single-step conversion of COrich synthesis gas to dimethyl ether, Appl. Catal. A Gen. 562 (2018) 206–214, https://doi.org/10.1016/j.apcata.2018.04.018. [209] M. Gentzen, D.E. Doronkin, T.L. Sheppard, J.-D. Grunwaldt, J. Sauer, S. Behrens, Bifunctional catalysts based on colloidal Cu/Zn nanoparticles for the direct conversion of synthesis gas to dimethyl ether and hydrocarbons, Appl. Catal. A Gen. 557 (2018) 99–107, https://doi.org/10.1016/j.apcata.2018.03.008. [210] Z. Chen, X. Li, Y. Xu, Y. Dong, W. Lai, W. Fang, X. Yi, Fabrication of nano-sized SAPO-11 crystals with enhanced dehydration of methanol to dimethyl ether, Catal. Commun. 103 (2018) 1–4, https://doi.org/10.1016/j.catcom.2017.09.002. [211] A. Atakan, P. Mäkie, F. Söderlind, J. Keraudy, E.M. Björk, M. Odén, Synthesis of a Cu-infiltrated Zr-doped SBA-15 catalyst for CO2 hydrogenation into methanol and dimethyl ether, Phys. Chem. Chem. Phys. 19 (2017) 19139–19149, https://doi. org/10.1039/c7cp03037a. [212] K. Takeishi, Y. Wagatsuma, H. Ariga, K. Kon, K. Shimizu, Promotional effect of water on direct dimethyl ether synthesis from carbon monoxide and hydrogen catalyzed by Cu–Zn/Al2O3, ACS Sustain. Chem. Eng 5 (2017) 3675–3680, https:// doi.org/10.1021/acssuschemeng.6b02915. [213] F. Dadgar, R. Myrstad, P. Pfeifer, A. Holmen, H.J. Venvik, Catalyst deactivation during one-step dimethyl ether synthesis from synthesis gas, Catal. Letters 147 (2017) 865–879, https://doi.org/10.1007/s10562-017-1971-2. [214] A. Kornas, R. Grabowski, M. Śliwa, K. Samson, M. Ruggiero-Mikołajczyk, A. Żelazny, Dimethyl ether synthesis from CO2 hydrogenation over hybrid catalysts: effects of preparation methods, React. Kinet. Mech. Catal. 121 (2017) 317–327, https://doi.org/10.1007/s11144-017-1153-7. [215] T. Su, X. Zhou, Z. Qin, H. Ji, Intrinsic kinetics for dimethyl ether synthesis from plasma activation CO2 hydrogenation over Cu-Fe-Ce/HZSM-5, ChemPhysChem 18 (2017) 299–309, https://doi.org/10.1002/cphc.201601283. [216] R.J. da Silva, A.F. Pimentel, R.S. Monteiro, C.J.A. Mota, Synthesis of methanol and dimethyl ether from the CO2 hydrogenation over Cu·ZnO supported on Al2 and Nb2, Biochem. Pharmacol. 15 (2016) 83–88, https://doi.org/10.1016/j.jcou.2016. 01.006. [217] W. Pranee, S. Neramittagapong, A. Neramittagapong, Environmental Effects Dimethyl ether synthesis from methanol over diatomite catalyst modified using nitric acid treatment, Energy Sources, Part A Recover. Util. Environ. Eff 38 (2016) 2244–2249, https://doi.org/10.1080/15567036.2015.1047065. [218] H. Ham, J. Kim, S.J. Cho, J. Choi, D.J. Moon, J.W. Bae, Enhanced stability of spatially con fi ned copper nanoparticles in an ordered mesoporous alumina for dimethyl ether synthesis from syngas, ACS Catal. (2016), https://doi.org/10. 1021/acscatal.6b00882. [219] S. Liu, J. Chen, Environmental effects reaction mechanism and kinetics of methanol produced to dimethyl ether reaction mechanism and kinetics of methanol produced to dimethyl ether, Energy Sources; Part A Recover. Util. Environ. Eff 37 (2015) 1591–1596, https://doi.org/10.1080/15567036.2011.642061. [220] Z. Qin, T. Su, H. Ji, J. Chen, Experimental and theoretical study of the intrinsic kinetics for dimethyl ether synthesis from CO2 over Cu – Fe – Zr/HZSM-5, AIChE J. 61 (2015) 11–13, https://doi.org/10.1002/aic. [221] D. Mao, X. Guo, Dimethyl ether synthesis from syngas over the admixed Cu/ZnO/ Al2O3 catalyst and alkaline earth oxide- modified HZSM-5 Zeolite, Energy Technol. 2 (2014) 882–888, https://doi.org/10.1002/ente.201402071. [222] K. Samson, A. Żelazny, M. Śliwa, R. Grabowski, M. Ruggiero–Mikołajczyk, Influence of Montmorillonite K10 modification with tungstophosphoric acid on hybrid catalyst activity in direct dimethyl ether synthesis from syngas, Catal. Lett. 144 (2014) 1884–1893, https://doi.org/10.1007/s10562-014-1359-5. [223] F. Song, Y. Tan, H. Xie, Q. Zhang, Y. Han, Direct synthesis of dimethyl ether from biomass-derived syngas over Effect of Zr-loading, Fuel Process. Technol. 126 (2014) 88–94, https://doi.org/10.1016/j.fuproc.2014.04.021. [224] Y. Wang, W. Wang, Y. Chen, J. Ma, R. Li, Synthesis of dimethyl ether from syngas over core – shell structure, Chem. Eng. J. 250 (2014) 248–256, https://doi.org/10. 1016/j.cej.2014.04.018. [225] J. Sun, G. Yang, Q. Ma, I. Ooki, A. Taguchi, T. Abe, Q. Xie, Y. Yoneyama, N. Tsubaki, Fabrication of active Cu–Zn nanoalloys on H-ZSM5 zeolite for enhanced dimethyl ether synthesis via syngas, J. Mater. Chem. A. 2 (2014)

8637–8643, https://doi.org/10.1039/C3TA14936F. [226] A. García-trenco, A. Martínez, The influence of zeolite surface-aluminum species on the deactivation of CuZnAl/zeolite hybrid catalysts for the direct DME synthesis, Catal. Today. 227 (2014) 144–153, https://doi.org/10.1016/j.cattod.2013. 09.051. [227] R. Liu, Z. Qin, H. Ji, T. Su, Synthesis of dimethyl ether from CO2 and H2 using a Cu – Fe – Zr / HZSM ‑ 5 catalyst system, Ind. Eng. Chem. Res. 52 (2013) 16648–16655, https://doi.org/10.1021/ie401763g. [228] C.-I. Ahn, J.W. Jeong, J.W. Bae, D.H. Lee, S.H. Um, Effects of Cu – ZnO content on reaction rate for direct synthesis of DME from syngas with bifunctional Cu – ZnO/ γ-Al2O3 Catalyst, Catal. Lett. 143 (2013) 666–672, https://doi.org/10.1007/ s10562-013-1022-6. [229] K.T. Pillai, R.V. Pai, S.S. Pathak, S.K. Mukerjee, S.K. Aggarwal, V.V. Vinogradov, A.V. Agafonov, A.V. Vinograodov, Synthesis of doped and undoped γ-alumina spherical particles by a new sol – gel hybrid process and their application for methanol dehydration, J Sol-Gel Sci Technol. 66 (2013) 145–154, https://doi.org/ 10.1007/s10971-013-2979-8. [230] S. Hoda, S. Morteza, F. Cavus, Synthesis of some baria-modified γ -Al2O3 for methanol dehydration to dimethyl ether, Res. J. Chem. Sci. 3 (2013) 57–62. [231] R. Montesano, D. Chadwick, Combined methanol and dimethyl ether synthesis from CO/H2: Phosphorus mediated deactivation, Catal. Comm. 29 (2012) 137–140, https://doi.org/10.1016/j.catcom.2012.09.031. [232] Z. Li, C. Yang, J. Li, J. Wu, A CuZnAl-based hybrid material for the direct synthesis of dimethyl ether from syngas, Adavance Materrials Eng. Mater 458 (2012) 261–264 doi:10.4028/www.scientific.net/AMR.457-458.261. [233] H. Zhang, W. Li, W. Xiao, Attrition resistant catalyst of direct dimethyl ether synthesis, Appl. Mech. Mater. 177 (2012) 97–101 doi:10.4028/www.scientific.net/AMM.174-177.97. [234] Q. Yang, M. Kong, Z. Fan, X. Meng, J. Fei, F. Xiao, Aluminum fluoride modified HZSM-5 zeolite with superior performance in synthesis of dimethyl ether from methanol, Energy Fuels 26 (2012) 4475–4480, https://doi.org/10.1021/ ef3006383. [235] L. Liu, W. Huang, J. Huang, Z. Gao, L. Yin, The Synthesis and catalytic activity of slurry catalyst for methanol dehydration to dimethyl ether, Energy Sources Part A Recover. Util. Environ. Eff. 34 (2012) 682–691, https://doi.org/10.1080/ 15567030903530582. [236] N. Park, T.J. Lee, Control of surface area and activity with changing precipitation rate in preparation of Cu-Zn based catalysts for dimethyl ether direct synthesis, Korean J. Chem. Eng. 28 (2011) 2076–2080, https://doi.org/10.1007/s11814011-0061-1. [237] G. Yang, M. Thongkam, T. Vitidsant, Y. Yoneyama, A double-shell capsule catalyst with core–shell-like structure for one-step exactly controlled synthesis of dimethyl ether from CO2 containing syngas, Catal. Today 171 (2011) 229–235, https://doi. org/10.1016/j.cattod.2011.02.021. [238] C. Cheng, H. Zhang, W. Ying, D. Fang, Intrinsic kinetics of one-step dimethyl ether synthesis from hydrogen-rich synthesis gas over bi-functional catalyst, Korean J. Chem. Eng. 28 (2011) 1511–1517, https://doi.org/10.1007/s11814-011-0018-4. [239] S. Baek, S. Kang, J.W. Bae, Y. Lee, D. Lee, K. Lee, Effect of copper precursors to the activity for dimethyl ether synthesis from syngas over Cu-ZnO/γ-Al2O3 bifunctional catalysts, Energy Fuels 25 (2011) 2438–2443, https://doi.org/10.1021/ ef200504p. [240] Z. Lei, Z. Zou, C. Dai, Q. Li, B. Chen, Synthesis of dimethyl ether (DME) by catalytic distillation, Chem. Eng. Sci. 66 (2011) 3195–3203, https://doi.org/10. 1016/j.ces.2011.02.034. [241] Q. Xu, P. Lan, K. Huang, Y. Yan, Effect of different ratios of Si-Al of zeolite HZSM-5 on the activity of bifunctional catalysts upon dimethyl ether synthesis effect of different ratios of Si-Al of zeolite HZSM-5 on the activity of bifunctional catalysts, Pet. Sci. Technol. 29 (2011) 1080–1092, https://doi.org/10.1080/ 10916460903502472. [242] Q. Xu, P. Lan, S. Zhang, T. Li, Y. Yan, Effect of modified zeolite on one-step process of DME synthesis effect of modified zeolite on one-step process of DME synthesis, Pet. Sci. Technol. 29 (2011) 439–448, https://doi.org/10.1080/ 10916460903117552. [243] G. Moradi, F. Yaripour, H. Abbasian, M. Rahmanzadeh, Intrinsic reaction rate and the effects of operating conditions in dimethyl ether synthesis from methanol dehydration, Korean J. Chem. Eng. 27 (2010) 1435–1440, https://doi.org/10. 1007/s11814-010-0238-z. [244] A. Ciftci, D. Varisli, T. Dogu, Dimethyl ether synthesis over novel silicotungstic acid incorporated nanostructured catalysts dimethyl ether synthesis over novel silicotungstic acid incorporated nanostructured catalysts, Int. J. Chem. React. Eng. 8 (2010) 1–15, https://doi.org/10.2202/1542-6580.2151. [245] A.R. Keshavarz, M. Rezaei, F. Yaripour, Nanocrystalline gamma-alumina: A highly active catalyst for dimethyl ether synthesis, Powder Technol. 199 (2010) 176–179, https://doi.org/10.1016/j.powtec.2010.01.003. [246] C. Won, K. Deok, K. Young, K. Sang, Dehydration of methanol over nordstrandite based catalysts for dimethyl ether synthesis, J. Ind. Eng. Chem. 15 (2009) 649–652, https://doi.org/10.1016/j.jiec.2009.09.037. [247] S.H. Kang, J.W. Bae, H.S. Kim, G.M. Dhar, K.W. Jun, Enhanced catalytic performance for dimethyl ether synthesis from syngas with the addition of Zr or Ga on a Cu-ZnO-Al2O3/γ- Al2O3 bifunctional catalyst, Energy Fuels 24 (2010) 804–810, https://doi.org/10.1021/ef901133z. [248] Q. You, Z. Liu, W. Li, X. Zhou, Synthesis of dimethyl ether from methane mediated by HBr, J. Nat. Gas Chem. 18 (2009) 306–311, https://doi.org/10.1016/S10039953(08)60122-X. [249] Y. Li, T. Wang, X. Yin, C. Wu, L. Ma, H. Li, Y. Lv, L. Sun, 100 t/a-Scale demonstration of direct dimethyl ether synthesis from corncob-derived syngas, Renew.

319

Journal of CO₂ Utilization 32 (2019) 299–320

U. Mondal and G.D. Yadav Energy 35 (2010) 583–587, https://doi.org/10.1016/j.renene.2009.08.002. [250] J.W. Bae, S.H. Kang, Y.J. Lee, K.W. Jun, Synthesis of DME from syngas on the bifunctional Cu-ZnO-Al2O3/Zr-modified ferrierite: Effect of Zr content, Appl. Catal. B Environ. 90 (2009) 426–435, https://doi.org/10.1016/j.apcatb.2009.04. 002. [251] S. Wang, D. Sen Mao, X.M. Guo, G.Z. Lu, Dimethyl ether synthesis from CO2 hydrogenation over CuO-TiO2-ZrO2/HZSM-5 catalysts, Catal. Commun. 27 (2011) 2651–2658, https://doi.org/10.1016/j.catcom.2009.02.001. [252] C.W. Seo, K.D. Jung, K.Y. Lee, K.S. Yoo, Influence of structure type of Al2O3 on dehydration of methanol for dimethyl ether synthesis, Ind. Eng. Chem. Res. 47 (2008) 6573–6578. [253] X. An, Y. Zuo, Q. Zhang, D. Wang, J. Wang, Dimethyl ether synthesis from CO2 hydrogenation on a CuO-ZnO-Al2O3-ZrO2/HZSM-5 bifunctional catalyst, Ind. Eng. Chem. Res. (2008) 6547–6554, https://doi.org/10.1021/ie800777t. [254] Y.D. Yoo, S.J. Lee, Y. Yun, Synthesis of dimethyl ether from syngas obtained by coal gasification, Korean J. Chem. Eng. 24 (2007) 350–353, https://doi.org/10. 1007/s11814-007-5045-9. [255] S.H. Kang, J.W. Bae, K.W. Jun, H.S. Potdar, Dimethyl ether synthesis from syngas over the composite catalysts of Cu-ZnO-Al2O3/Zr-modified zeolites, Catal. Commun. 9 (2008) 2035–2039, https://doi.org/10.1016/j.catcom.2008.03.046. [256] V. Pet’kov, M. Sukhanov, I. Shchelokov, N. Orekhova, E. Asabina, M. Ermilova, G. Tereshchenko, Synthesis, surface properties and catalytic activity of phosphates Cu0.5(1+y)FeyZr2−y(PO4)3 in methanol conversion, Solid State Sci. 10 (2008) 513–517, https://doi.org/10.1016/j.solidstatesciences.2007.12.005. [257] M. Mollavali, F. Yaripour, H. Atashi, S. Sahebdelfar, Intrinsic kinetics study of dimethyl ether synthesis from methanol on γ-Al2O3 catalysts, Ind. Eng. Chem. Res. 47 (2008) 3265–3273, https://doi.org/10.1021/ie800051h. [258] Y. Zhao, J. Chen, Effects of ZrO2 on the performance of CuO-ZnO-Al2O3/HZSM-5 catalyst for dimethyl ether synthesis from CO2 hydrogenation, J. Nat. Gas Chem. 16 (2007) 389–392. [259] D. Jin, B. Zhu, Z. Hou, J. Fei, H. Lou, X. Zheng, Dimethyl ether synthesis via methanol and syngas over rare earth metals modified zeolite Y and dual Cu-Mn-Zn catalysts, Fuel. 86 (2007) 2707–2713, https://doi.org/10.1016/j.fuel.2007.03. 011. [260] K. Sang, J. Kim, M. Park, S. Kim, O. Joo, K. Jung, Influence of solid acid catalyst on

[261]

[262] [263] [264] [265]

[266] [267] [268] [269]

[270]

320

DME production directly from synthesis gas over the admixed catalyst of Cu/ZnO/ Al2O3 and various SAPO catalysts, Appl. Catal., A Gen. 330 (2007) 57–62, https:// doi.org/10.1016/j.apcata.2007.07.007. V.S. Kumar, A.H. Padmasri, C.V.V. Satyanarayana, I.A. Kumar, Nature and mode of addition of phosphate precursor in the synthesis of aluminum phosphate and its influence on methanol dehydration to dimethyl ether, Catal. Commun. 7 (2006) 745–751, https://doi.org/10.1016/j.catcom.2006.02.025. J. Wang, C. Zeng, Al2O3 effect on the catalytic activity of Cu-ZnO-Al2O3-SiO2 catalysts for dimethyl ether synthesis from CO2 hydrogenation, J. Nat. Gas Chem. 14 (2005) 156–162. H.F. Xu, K.X. Wang, W.S. Li, X.P. Zhou, Dimethyl ether synthesis from methane by non syngas process, Catal. Letters. 100 (2005) 53–57, https://doi.org/10.1007/ s10562-004-3085-x. Y. Usui, C. Wakai, N. Matubayasi, M. Nakahara, Synthesis of dimethyl ether from supercritical methanol in the presence of aluminum, Chem. Lett. 33 (2004) 394–395, https://doi.org/10.1246/cl.2004.394. K. Omata, T. Ozaki, T. Umegaki, Y. Watanabe, N. Nukui, M. Yamada, Optimization of the temperature profile of a temperature gradient reactor for DME synthesis using a simple genetic algorithm assisted by a neural network, Energy Fuels 17 (2003) 836–841, https://doi.org/10.1021/ef0202438. M. Jia, W. Li, H. Xu, S. Hou, Q. Ge, An integrated air – POM syngas/dimethyl ether process from natural gas, Appl. Catal. A Gen. 233 (2002) 7–12. X.U. Hengyong, The synthesis of dimethyl ether from syngas obtained by catalytic partial oxidation of methane and air, Stud. Surf. Sci. Catal. 136 (2001) 33–38, https://doi.org/10.1016/S0926-860X(02)00120-5. T. Akiyama, Development of Cu/ZnO/Al2O3 catalyst for dimethyl fther wlixture synthesis from CO-CO2-H2, ISIJ Int. 38 (1998) 93–97, https://doi.org/10.2355/ isijinternational.38.93. J. Li, X. Zhang, T. Inui, Improvement in the catalyst activity for direct synthesis of dimethyl ether from synthesis gas through enhancing the dispersion of CuO/ZnO/ T-A12O3 in hybrid catalysts, Appl. Catal. A Gen 147 (1996) 23–33, https://doi. org/10.1016/S0926-860X(96)00208-6. Y.Z. Han, K. Asami, K. Fujimoto, Gas phase dimethyl ether synthesis from syngas, J. Japan Inst. Energy. 75 (1996) 42–48, https://doi.org/10.3775/jie.75.42.