Direct Dimethyl Ether (DME) synthesis from natural gas

Direct Dimethyl Ether (DME) synthesis from natural gas

Studies in Surface Science and Catalysis, volume 147 X. Bao and Y. Xu (Editors) 9 Elsevier B.V. All rights reserved. 379 Direct Dimethyl Ether (DME)...

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Studies in Surface Science and Catalysis, volume 147 X. Bao and Y. Xu (Editors) 9 Elsevier B.V. All rights reserved.

379

Direct Dimethyl Ether (DME) synthesis from natural gas Takashi Ogawa, Norio Inoue, Tutomu Shikada, Osamu Inokoshi, Yotaro Ohno DME Development Co., Ltd, Shoro-koku Shiranuka-ch, Hokkaido, 088-0563 Japan ABSTRACT Dimethyl Ether (DME) is a clean and economical alternative fuel which can be produced from natural gas. The properties of DME are very similar to those of LPG. DME can be used for various fields as a clean and easy-to-handle fuel, such as power generation, transportation, home heating and cooking, etc. An innovative process of direct synthesis of DME from synthesis gas has been developed. 5 tons per day DME production pilot plant (5TPD) project had finished very successfully in FY2001, and 100 tons per day DME production demonstration plant (100TPD) project started in FY2002. These projects are supported and funded by Ministry of Economy, Trade and Industry (METI). This JFE Direct DME Synthesis will open a new way to economical DME mass production. 1. INTRODUCTION DME synthesis from synthesis gas (syn-gas: H2+CO gas) has been developed for these years [1-3]. JFE (formally NKK) Corporation has been making remarkable progress in a development of direct DME synthesis from syn-gas with a liquid phase slurry reactor [4-7]. DME is the simplest ether having the chemical formula of CH3OCH3. It is colorless gas, and sulfur and nitrogen free. As its vapor pressure is about 0.6 MPa at 25~ DME is easily liquefied under light pressure. DME is also a very clean diesel substitute that does no exhaust black smoke [8]. Table 1 shows physical properties and combustion characteristics of DME and other relating fuels. DME can be distributed and stored by using LPG handling technology, which means DME does not need costly LNG tankers or LNG terminals [9]. Once natural gas is converted to DME, it will provide a competitive new altemative measure to transport natural gas.

380 Table 1 Physical Properties of DME and other fuel [Properties] DME P r o p a n e Methane CH4 Chemical formula C H 3 O C H 3 C3H8 231 111.5 Boiling point (K) 3 247.9 0.49 Liquid density (g/cm @293K) 0.67 1.52 0.55 Specific gravity (vs. air) 1.59 9.3 Vapor pressure (atm @293K) 6.1 2.1-9.4 5-15 Explosion limit 3.4-17 (5) * 0 Cetane number* 55-60 91.25 36.0 Net calorific value (MJ/Nm3) 59.44 46.46 50.23 28.90 Net calorific value (MJ/kg) * Estimated value

Methanol Diesel CH3OH 337.6 180-370 0.79 0.84 5.5-36 0.6-6.5 5 40-5 21.1 41.86

2. DIRECT DME SYNTHESIS PROCESS Table 2 shows reactions concerning with direct DME synthesis and their reaction heats. There are mainly two overall reaction routes that synthesize D M E from syn-gas, reaction (1) and (2). The reaction (1) synthesizes DME in three steps, which are reaction (3), (4) and (5). When the three reactions (3, 4, 5) take place simultaneously, the syn-gas conversion rises dramatically. Separation of by-product CO2 from unreacted syn-gas is much easier compared with separation of by-product water (in the case of reaction (2)). Because of these reasons, JFE Direct DME Synthesis focused the development of the catalyst system and its reaction process on the reaction (1). Typical reaction conditions are 240-280 [~ and 3.0-7.0 [MPa]. The standard condition is 260 [~ and 5.0 [MPa]. Catalyst loading ratio W/F is 3.0-8.0 [kg-catalyst * h/kg-mol]. Table 2 DME synthesis reaction formulas Reaction 3CO+3H2 2CO+4H2 2CO+4H2 2CHBOH CO+H20

Reaction heat [kJ/mol-DME] -246 CH3OCH3+H20 -205 2CH3OH - 182 CH3OCH3+H20 - 23 CO2+H2 - 41 CH3OCH3+CO2

Table 3 DME synthesis from natural gas in the direct DME synthesis plant Unit Reaction (ATR) 2CH4 at-02 + CO2 ~ 3CO + 3H2 + H20~, (DME Synthesis Reactor) 3CO+ 3H2 --* CH3OCH3 (DME) + CO2 (DME Plant Total)

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~ g one and half years of 5TPD experimental period, six continuous plant operations were conducted. Total plant operation time reached 4,300 hours, and total DME production reached about 400 tons. Picture 1 shows the plant. Since natural gas was not available at the plant site, LPG and Coal Bed Methane were used as feedstock. Fig. 2 shows typical 5TPD resuks of once-through conversion and selectivity. The once-through CO conversion reached higher than 50% at 260 ~ and 5 MPa. The DME catalyst system did not generates undesirable heavier by-products such as oil, wax or higher alcohols. The degradation of the catalyst activity was confirmed to be lower than 10 points of the initial value after 1,000 hours. Table 4 Product selectivity and DME quality of 5 TPD a. Product C-mol ratio : DME / (DME + Methanol) b. Product H-mol ratio : H20 / (DME + Methanol + H20) c. DME purity d. Impurity of DME : Methanol+ H20

0.91 [-] 0.013 [-] 99.9 [%] < 100 pp

382 Table 4 shows typical product selectivity and typical product DME quality of 5 TPD (CO2 was eliminated from the products). DME once-through yield was as much as 90%. Very small amount of H20 was produced. Fig. 3 shows a typical example of the material balance of 5TPD. When DME yield achieved 5.7 tons per, total CO conversion reached almost 95% in this material balance.

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DME Development Co., Ltd, started five year DME 100TPD project with funds provided by METI in 2002. Fig. 4 shows the schedule of 100TPD project. Fig. 5 shows the overview of 100TPD. The targets of the development with 100TPD operation are as follows; a. To achieve targeted reactor performance. O Total syn-gas conversion > 95% O Selectivity ofDME > 90% O Purity ofDME > 99% b. To operate the demo-plant continuously more than three months. c. To establish scale-up technology of the slurry reactor. d. To establish operation procedure. 5. ECONOMICS OF DME PRODUCTION FROM NATURAL GAS

Based on the results of 5TPD project and economic assumptions, the CIF price of DME is estimated. DME is produced at natural gas field and transported to Japan. As a result of a calorie-equivalent based sensitivity analysis, Table 4 shows the results of feasible DME production study based on natural gas feedstock, DME plant scale and transportation distance. Estimated DME CIF price (3.7-5 US$ / MMBTU) is lower than those of LPG and Diesel oil and almost similar to LNG CIF price in Japan [ 10].

384 Table 4 Study of Feasible DME Production Area Gas price Plantscale Production FOB price Transport CIF price (Size of gas field) (DME) distance (DME) [US$/MMBm] [ton/d] [kton/y] [USS/MMBtu] [kin] [USS/MMBtu] West Australia 1.0 2,500 830 4.4 7,000 5.0 (Large scale) 1.0 5,000 1,650 3.8 7,000 4.4 1.0 10,000 3,330 3.3 7,000 4.0 South East Asia 1.25 5,000 1,650 4.1 5,000 4.6 (Middle scale) 1.25 10,000 3,330 3.7 5,000 4.1 Middle East 0.5 2,500 830 3.7 12,000 4.8 (Large scale) 0.5 5,000 1,650 3.1 12,000 4.2 0.5 10,000 3,330 2.6 12,000 3.7 6. CONCLUSION JEF Direct DME Synthesis technology successfully finished 5 TPD project with sufficient achievement. Based on these results, DME Development Co., Ltd, is now conducting a 100TPD project to establish commercial DME production technology. 100 t/d DME production will start in 2004. The DME energy flow system would promote utilization of stranded medium and small scale natural gas field to produce an easy-to-handle fuel and to supply to the Asia-Pacific Region in the furore.

ACKNOWLEDGEMENT The authors would like to express sincere appreciation for Agency of Natural Resources and Energy, Coal Division (METI) for their long term financial support.

REFERENCES [1] J.B. Hansen et al: SAE950063 (Feb. 1995) [2] Air products and Chemicals: DOE/PC/90018-T7 (June. 1993) [3] D. Romaini et al: The 2nd International Oil, Gas & Petrochemical Congress, Tehran 16-18 (May, 2000) [4] Y. Ohno: Energy total engineering, vol.20, No.1 (1997), p.45 [5] Y. Ohno et al: Preprints of Papers Presented at the 213th ACS National Meeting, Div. Of Fuel Chemistry, p. 705, San Francisco (1997) [6] T. Ogawa et al: Proceedings of the 14th Annual International Pittsburgh Coal Conference and Workshop, 30-3004, Taiyuan, China (1997) [7] T. Ogawa et al: The AIChE 2000 Spring National Meeting, "Oxygenated Fuels", Atlanta, UAS, (Mar.5-9, 2000) [8] T. Fleisch: SAE950061 (Feb. 1995) [9] Y. Kikkawa et al: Oil & Gas Journal (Apr.6, 1998), p.55 [10] u Arldo et al: Gas 2002 Indonesia, Jakarta, Indonesia (Jan. 14, 2002)