Hydrothermal synthesis of zeolites

Hydrothermal synthesis of zeolites

137 ~y~rother~a~ synthesis of zeolites Mark T Weller* and Sandra E Dannl Recent developments have included the synthesis of new, large pore zeolite...

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137

~y~rother~a~ synthesis of zeolites Mark T Weller*

and Sandra E Dannl

Recent developments have included the synthesis of new, large pore zeolite structures, zeotypes and metal substituted zeolites, along with the in situ investigation of zeolite synthesis and control of morphoiogies. In terms of new zeolite structures there is increasing realisation of the aim to specifically design templates to control reolite structures, and the use of the fluoride ion as a mediating agent has been influential. In terms of zeotypes considerable effort has been directed at transition metal containing systems, particularly those of cobalt, with the potential to generate redox active catalytic centres. Growth of zeolite films on substrates has also been developed and progress is being made in studying directly, using diffraction and NMR techniques, the crystallisation of zeolites.

templates, sometimes synthesised specifically to induce a particular pore geometry. Often computer modelling and structural work define the interaction between the template and framework and the use of larger, more complex templates frequently leads to an open pore system with channels formed from 12- and 14-membered rings. Another notable influence has been the addition of anions, particularly fluoride ions, to reaction mixtures to facilitate and direct reactions, however, these anions are not often incorporated into the final product. Figure 1

Addresses *Department of Chemistry, University of Soffth~pto~, Highfield, Southampton SO1 7 1BJ, UK; e-mail: [email protected] :Department of Chemistry, Loughborough University, Loughborough LEl 1 3TU, UK; e-mail: [email protected] Current Opinion in Solid State & Materials Science 1998, 3:137-l

43

Electronic identifier: 1359-0286-003-00137 0 Current Chemistry ISSN 1359-0286

Introduction The purpose of this review is to highlight the advances achieved in the hydrothermal synthesis of zeolites in the past 1-2 years. Zeolites have been reviewed previously in this journal, most notably in volume 1 where articles on recent discoveries, future prospects and membranes were included. The material covered in this review is restricted to macroscopic crystalline materials and four salient areas are reviewed; new zeolite structures, known zeolite structures with different structuraf compositions (doped structures), zeotypes with zeolite morphoiogies and new methods of crystallisation/in situ crystallisation studies. As far as this review is concerned the term zeolite has been restricted to crystalline materials with nanoporous structures constructed mainly with aluminosilicate or silicate units; some nonaluminosilicate frameworks which have zeolite structures are discussed if their synthesis and structural chemistry are significant. Developments in the syntheses of mesoporous structures are not covered and hydrothermal synthesis of nonzeolitic frameworks (e.g titanosilicates and many noncobalt, transition metal phosphates), which is a rapidly developing area in its own right, also lies mainly outside the scope of this review.

Current Okion

in Solid State&Mater&

Science

The structure of SSZ-4211104 shown as connected SiO, tetrahedra. The structure is viewed down the c direction and the undulating channel shown.

New zeolite structures

SSZ-42 ternplated using the N-benzyl-1,4-diazabicyclo [2.2.2] octane cation has a unique one-dimensional channel system as shown in Figure 1 [l”]. These channels consist of l&membered rings and have side walls similar to those found in zeolite p. C;omputer modelling indicates that the template molecule fits into the side pockets along the direction of the main channel. The adsorption properties of this material are exceptional for a one-dimensional material and are similar to those of a two-dimensional structure due to the presence of the large cage or pockets lying atong the channels.

The number of zeolite structures continues to develop, and recent work indicates that synthesis routes have become better directed with the use of carefully chosen

This large pore silica has also been described, as ITQ-1, in two artictes by Camblor and co-workers [2’,3’], The

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Synthesis and reactivity of solids

synthesis described in this work is an example of the use of fluoride ions as mediators in zeolite synthesis; the template used in this case was the N-benylquinuclidinium cation. Furthermore structure solution was again achieved from X-ray powder data rather than from single crystal methods. The relatively thin walls in this material produce a large void volume of 0.21 cm3/g similar to that of the well-known zeolite B.

Figure 2

Previous attempts at the preparation of VPI-8 produced very small crystallites which were unsuitable for use in an ab initio structure determination due to the broadening of the X-ray reflections. Relatively large crystals of VPI-8 (4 pm), suitable for crystallographic work, have been produced using seed crystals [4”]. Single crystal electron diffraction experiments showed the crystals to be free of twinning and faulting and confirmed the tetragonal structure with a = 13.053 and c = 5.037 A. However, it was identification of the pinwheel building unit by HRTEM which provided the key to the full structure solution. The framework contains large l&membered rings running parallel to c separated by walls comprising of 5 and 6-membered rings. Two possible topologies were recognised although neither appeared to be preferred on stereochemical grounds. The biscyclopentadienyl cobalt (III) ion has recently been used to template a number of zeotypes which had previously required an amine to form, for example AlPO,-5. By using a large organometallic template, with methylatedcyclopentadienyl rings, a new high silica zeolite, UTD-1, with a 14-membered ring system was produced [5’,6]. The 14-membered elliptical pores represent one of the largest pore structures known for a zeolite. The reaction mixture consisting of a solution of 18% aqueous solution of (CpMe&Co(OH), NaOH and fumed SiO, were combined to form a gel of molar ratio 0.12.5:1:0.1:60H20 and aged for one hour. After transference to a teflon-lined autoclave the reactor was heated to 175°C under static conditions for two days. The mineral melinolite, K,Ca2[Al&,0,,].Z4H20 is a naturally occurring zeolite and exists in other cation forms, for example as a barium containing system; the material is structurally similar to phillipsite. Structural analysis of a synthetic zeolite of this type, termed zeolite W, has been carried out on powdered material grown from gels containing both potassium and sodium [7’]. The product, which contains only potassium as the nonframework cation, differs from the naturally occurring forms only in terms of the distribution of cations within the g-ring channels. The relationship between structure and ion type in this material would be worth studying further through detailed ionexchange and structural work. Another zeolite form of silica, SSZ-16, but with smaller pores has been reported [8’]. Again careful choice of template is required to maximise yield of the framework; however, many similar diquarternary ammonium cations

Current ODinion in Solid State & hktemls

The main cavity of the SSZ-16

SC;--=

structure.

direct its formation. Generally a tetramethylene system is optimum, though three and five bridge units have also been successfully employed. The structure directing agent provides an excellent fit for the large elongated cage in SSZ-16, (Figure ‘2). The structure is isomorphous with that of the aluminophosphate AlP04-52 with stacks of gmelinite cages. The largest windows to the main cages are only eight rings though there exists the potential for catalytic reactions involving small molecules such as NO,. Two zeolites currently of considerable importance as regards their ion-exchange properties are heulandite/clinoptilolite and zeolite P (gismondine type). The synthesis and structure of zeolite P and heulandite have been addressed by Khodabandeh and Davis [9] who have demonstrated a facile route to a heulandite via zeolite Pl. Zeolite Pl was formed by treatment of perlite glass with basic carbonate solutions and this was subsequently converted to heulandite by treatment with calcium ions. This conversion ofzeolite structures may be similar to the formation of zeolite A and then sodalite which occurs in high alumina/aluminosilicate/sodium hydroxide solutions.

Hydrothermal synthesis of zeolites Weller and Dann

Figure 3

139

zeolite) has not been previously fully characterised due to difficulties in producing a defect free material. An allsilica ZSM-11 has been prepared using the N,N-diethyl3,5-dimethylpiperidium cation as a template in a hydrothermal reaction at 150-170% [12’]. The use of this template is crucial in order to inhibit the formation of ZSM-5 (MFI). Structure investigation, as part of this work, using SEM, TEM and high resolution powder X-ray diffraction have confirmed that this material has a defect free high symmetry structure.

Current Opinion in Solid State & Materials Science

The large 14sring pore of the CIT-5 structure;

only the T atoms are

shown.

Zeolite P with a high aluminium content, Si:Al, 1:l (MAP, maximum aluminium P) and small uniform particle size may be obtained through seeding of vigorously stirred reaction mixtures [lo’]. The tight particle size distribution coupled with the micron sized crystallites and the unusual framework flexibility lead to unique, favourable ion-exchange and water sorption properties. These properties of MAP, resulting from the framework structure and the ability to maximise the aluminium content, clearly demonstrate the ability to tailor zeolite frameworks for specific applications. A further development of large pore systems, required for catalytic application on large molecules, has occurred with the synthesis and structural characterisation of CI’I5 [ll”] a high silica zeolite with 14-membered rings, (Figure 3). The templating agent used for this material was the complex cation N( 16)-methylsparteinium at 175°C in a high silica gel. A key feature of this synthesis was incorporation of lithium into the reaction mixture, however, this alkali metal is not incorporated into the zeolite, which is formally described as a pure silica. The structure is built from a zig-zag ladder of a four membered ring cross-linked by five ring units. Normally systems with such open structural features such as a 14-membered ring channel deliver poor thermal stability but remarkably the framework of CIT.5 seems to be stable to above 900°C. The structure shows a high degree of order which may confer this stability. Pentasil-based structures, particularly that of ZSM-5, have been studied due to their excellent catalytic properties. The pentasil-based structure of ZSM-11 (MEL type

Zeolite-p has commanded considerable interest in recent years due to its three-dimensional open pore structure and potential for forming a chiral framework. One problem with this material has been the presence of large numbers of defects associated with Si-O- or Si-OH units in those materials synthesised with typical Si:Al ratios of S-100. Recent work has reported the unseeded synthesis of pure silica zeolite-p using fluoride media [ 131. The fluoride ions seem to be occluded into the pores with the tetraethylammonium template negating the need for a framework charge associated with the connectivity defects. The structure remains a mixture of the polymorphs of this phase. Other publications on zeolites [14-221 have concerned synthesis using modified routes, for example using different templates such as crown ethers, or further structural characterisation of known zeolite frameworks. Examples of this structural work include changes in framework geometry as a function of silicon:aluminium ratio or determination of the template position.

Zeotypes While zeolites are strictly defined as aluminosilicate frameworks (though the aluminium level can be zero) other structurally related materials but without silicon and/or aluminum in the framework have been the focus of considerable attention. It is not the purpose of this review to discuss this work in detail but where it impinges on hydrothermal synthesis of true zeolites, for example through structural analogies, work of considerable note is discussed. STA-1, a microporous magnesium aluminophosphate was ternplated from aluminium hydroxide/magnesium acetate/phosphoric acid gels using diquinuclidinium ions [(C,H,,N-(CH,),(NC,Hr$]z+ n = 7-9 at 190°C for 48 h [‘23”]. STA-1 has the large pore volume and low framework density expected for such a large templating molecule. This work illustrates well how designing a particular organic template can lead to a designed framework. The structure consists of l&ring channels running in two orthogonal directions in the crystal which are also linked in the third direction (Figure 4). Introduction of various anions into gel mixtures can radically alter the product nature. For example a new zeotype, UiO-7 [24], was obtained from a fluoride modified

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Synthesis and reactivity of solids

Figure 4

charge compensation framework following

Current ODinion in Solid State & Materials Science

The framework of STA-1 viewed down the b direction showing the 12sring openings. Only the connections between the T atoms are shown.

gel with the well known tetramethylammonium hydroxide template. The introduction of the.fluoride ion directs the reaction profile away from the normally formed sodalite type phase to a more open strutture. Reaction was carried out by crystallisation of a pseudoboehmite/phosphoric acid mixture with HF at 150°C. The structure solution of UiO-7 shows the developments taking place towards using several methods to obtain a structure where good single crystals are not available. In this case the structure was determined from a combination of synchrotron X-ray data, MASNMR data and through simulated annealing computational work. The structure determination in this case used the high quality diffraction data to obtain the unit cell parameters and possible space groups. From this, possible framework geometries consistent with structure symmetry were generated and tested against the diffraction data. In this instance one good fit was achieved and the basic structure then refined using the powder diffraction data. The structure contains an unusual two-dimensional eight-ring channel system, as in SAPO-40, but in this material the units are tilted producing a narrower pore system. The existence of UiO-6 has also recently been reported [25’]; this material is a l&ring ALP04 with one-dimensional channels.

aluminophosphate

Beryllophosphate and berylloarsenate analogues of the zeolite RHO were prepared by the hydrothermal reaction of beryllium nitrate, group (V) acid and alkali metal hydroxides in a gel [26]. Transformation of the gel to the microcrystalline product was achieved by heating in vacuum at 70°C. Despite the low temperature required for synthesis and good ion-exchange properties, these materials have very poor thermal stability. Attempts to improve stability, by exchange reactions, were largely unsuccessful except for divalent calcium and barium where the higher charge imparts better stability by

for the highly dehydration.

negatively

charged

The introduction of high levels of redox active metal sites in known zeolite structures remains a highly desirable goal of the synthetic chemist. A number of materials of this type are described in the later sections. An alternative route to materials containing transition metal centres in porous systems is the incorporation of large transition metal clusters of the anti-Keggin type [27] into a framework. Vanadium-based polyhedra of the general formula with -0.1
Modified structures Introduction of other transition metal species at reasonable levels into zeolite structures to enhance and modify catalytic activity remains the goal of the synthetic chemist. However, incorporation of transition metals other than cobalt into well-known zeolite frameworks is frequently difficult due to their preference for higher coordination environments than tetrahedral. Characterisation of such materials also needs to be undertaken rigorously to demonstrate that the transition metal dopant is actually in the framework. The synthesis of a zeolite having a silicon to iron ratio of 11:l is therefore of note [41’]. This iron silicate adopting the ferrierite (FER or ZSM-35) structure was obtained by addition of iron (III) sulphate to a silicate gel and crystallisation at 150°C for 1.5-20 days. Confirmation that the iron was incorporated into the zeolite framework was obtained from a significant increase in the unit cell parameters over those of ferrierite, adsorption characteristics and photoelectron spectroscopy. The replacement of iron by aluminum in this structure should alter its acid characteristics and, hopefully, reduce the effects of coking during isomerisation reactions The selectively and Lewis acidity of zeolitic materials can be modified by substitution of framework cations by transition metals. Trace amounts of nonframework iron, introduced by the addition of iron nitrate into the hydrothermal synthesis reaction mixture, have been shown to promote

Hydrothermal synthesis of reolites Weller and Dann

catalytic activity in the aromatisation of n-hexane 1421. Further chemistry involving substitution of framework aluminium has also been reported, though the levels of incorporation of the dopant ions are lower and evidence for their successful incorporation less robust [43-46].

Cobalt containing systems A range of cobalt-phosphate-based zeotype structures have been synthesised, as reported by Feng and colleagues [47]. Framework analogues which have been prepared include, analcine, chabazite, thomsonite, sodalite, merlionite and pbi!Iipsite, with synthesis conditions typical of those used in zeolite formation. A variety of organic amines uere used as templates and the framework charge could be varied by changing factors such as the cobalt to phosphate ratio. Difficulties in synthesising zeolite analogues in this system result from the host-guest charge mismatch where the framework charge is too negative to be balanced by the positive charge of most protonated amines. This work followed the initial synthesis of a cobalt gallium phosphate of the gismondine type by Cowley and Chippindale [48]. In comparison with the aluminosilicat~s, frameworks containing the BOh unit have been poorly studied despite enhancement of catalytic properties achieved by even small amounts of boron substitution, A new open framework cobalt borophosphate [49] has been synthesised using boric acid, phosphoric acid and cobalt trisethylenediamine trichloride. The channels are formed from polyhedra sharing corners in the sequence P04-CoQ,-P04-B04P04-B04-P04-Coo4 in a wavelike, oblong fashion. The short-axis of the opening is about 5.21 A and the long axis 7.6 A (O-O distances?. A novel cobalt-gallium phosphate with a microporous structure has been reported [SO] and cobalt has also been incorporated into the aluminophosphate ALPO-34 [Sl].

141

of uniform habit and size. Perchlorate appeared to have the greatest effect on the speed of crystallisation; in the case of zeolite Y it also appeared to improve selectivity in phase formation, where the normal zeolite P impurity remained undetected in the mother liquor two hours after complete crystallisation of zeolite Y. Other synthesis methods involving induction heating and crystallisation in a strong gravitational field have also been described [54,55].

Controlled reolite morphologies Several papers in the last eighteen months have dealt with the synthesis of zeolite films which have potential applications as membranes, in optoelectronic devices and in sensors. Three phases grown in this way are zeolite A [56’], ZSM-5 [.57’] and zeolite L [SS]. Of note here is the development of the technique of depositing nanocrystals of the zeolite from zeolite suspensions. Zeolite crystals are grown in solution until they reach a critical size and then deposited onto a substrate by dipping it into the nanosol; the nanounits are generally deposited in an ordered arrangement. The use of such membranes in the separation of alcoholether mixtures has also been described. The technique uses a pervaporation method employing an Na-Y membrane grown hydrothermally on a porous alumina support [59]. This membrane consisted of randomly oriented crystallites but very high selectivities were obtained, particularly for alcohol ether combinations having large differences in molecular size.

In situ studies

ZSM-5, zeolite-fi and hexagonal Y (EMT) have been successfully synthesised by heating gels using microwaves [.52’]. The enhancement of single-phase crystallisation reduces reaction times -from days/hours to minutes; long reaction times at low temperature have previously been necessary to reduce the formation of impurity phases. The use of microwaves to reduce the cryscallisation time of useful zeolites may make the synthesis of such products more industrially viable.

The direct observation of zeolite crystallisation and formation remains a goal of the synthetic chemist. Because of the hydrothermal nature of these reactions, coupled with long nucleation times and subsequent rapid crystal growth, such studies are still problematical, though progress is being made. Such results provide a significant advance on previous studies of zeolite formation where the reaction mixture was separated or quenched. Solid state NMR methods, %i and 27Al have been used by Shi eta/. [60’] to observe the direct formation of zeolite A from aluminosilicate gels. These results currently throw little additional light on the nucleation/growth mechanism as they were obtained at a fairly low temperature, 65°C and the technique is therefore not really applicable to most conditions used in zeolite synthesis.

The use of Group VA and VIIA metal salts as promoters for selective crysrallisation of zeolites and their ability to increase the yield up to 4-6 times has been reported [53’]. Acid or Na/K salts of ions such as ClO,- or BrO,- are slowly added co the starting gel before it is transferred to teflon lined autoclaves before hydrothermal reaction. A range of zeolites with different pore sizes, for example, small (NU-1, FER), medium (ZSM-5) and large (beta and ZSM-12) have been synthesised using this methodology producing crystals

ln sitll diffraction experiments of zeolite growth are often hampered by the low levels of crystalline material and the time scales required to collect a reasonable diffraction profile. The development of a zeolitic phase, after nucleation, generally occurs too rapidly for all the stages to be observed using a laboratory source. These problems may be overcome by using high intensity synchrotron radiation as illustrated in the study of the synthesis of ULMJ [61’]. In this work a hydrothermal reaction occurring at 180°C

New synthesis methods

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Synthesis

and reactivity

of solids

was studied by acquiring energy dispersive X-ray diffraction patterns at 60 s intervals. Results showed the formation of a short lived previously unobserved intermediate.

Conclusions The hydrothermal synthesis of zeolites and zeotypes remains a fertile area of study with the development of new framework structures through the use of tailored templating. Clearly this area has a great potential for future development as more complex templates are designed specifically for directing the formation of particular pore structures and features. The use of other influential structure-directing agents in hydrothermal reactions, such as fluoride, oxoanions and lithium, even though they are often not incorporated into the final material, is also an area where further understanding needs to be developed and employed.

5. .

Balkus KJ, Biscotto M, Gabrielov AG: The synthesis and characterization of UTD-1: the first lage pore zeolite based on a 14 membered ring system. Studies Surf Sci Catal A 1997, 105:415-421. A large pore high silica zeolite with one-dimensional channels constructed from 14-membered rings. Interestingly this material; was not templated with an amine but rather a cyclopentadienyl cobalt (Ill) derivative. The structure is faulted and involves intergrowths of various crankshaft chains. 6.

7. .

Bieniok A, Bornholdt K, Brendel U, Baur WH: Synthesis and crystal structure of zeolite-w, resembling the mineral merlinoite. J Mater Chem 1996,6:271-275. Synthesis and structure determination of a potassium form of the MER framework, natural phase merlionite.

8

Lobo RF, Zones SI, Medrud RC: Synthesis and Rletveld refinement of the small-pore zeolite SSZ-16. Chem Mater 1996,8:24092411. The use of various templating agents in the formation of this smaller pore zeolite, B-ring windows, is described. The structure contains two small cage types of the gmelinite and AFT type. .

9.

Systems containing transition metals, either adopting zeolite structures or new framework geometries, have also recently seen rapid progress. While tetrahedral cobalt may be readily incorporated into frameworks other transition metals must also be targets if they can be stabilised in four -fold coordination at high levels within the structures. The final area where further rapid developments are likely to occur is in the in S&Uinvestigation of zeolite formation under hydrothermal conditions. High intensity X-ray and neutron beams, as well as the ability to carry out solid state NMR under high pressure conditions, promise significant advances of our understanding of zeolite formation and growth.

References and recommended

reading

Papers of particular interest, published within the annual period of review, have been highlighted as: l l

of special interest * of outstanding interest

1. ..

Chen CY, Finger LW, Medrud RC, Crozier PA, Chan IV, Harris TV, Zones SI: SSZ-42; the first high-silica large pore zeolite with an undulating one-dimensional channel system. Chem Commun 1997:1775-1776. __ _ _ Structure determination, using a combination of single crystal and powder methods, of SSZ-42 first described in World Patent 95/908793 1995. A likely site for the template molecule in the main channels is also shown. An unusual feature of this material is the sinusoidal main channel formed from 12 tetrahedral atoms. Same structure as ITQ-4 [2’,3’1.

2. .

Barrett PA, Camblor MA, Corma A, Jones RH, Villaescusa LA: Structure of [email protected]; a new pure silica polymorph containing large pores and a large void volume. Chem Meter 1997, 9:1713-l715. Same structure as in [l”] but determined from synchrotron data and reported first. The structures are essentially identical though a significant difference in one lattice parameter may result from very different calcination temperatures. 3. .

Camblor MA, Corma A, Villaescusa A: IT0 4: a new large microporous polymorph of silica. Chem Commun 1997:749-750. Initial report of IT04/SSZ-42 describing its synthesis in fluoride media.

4. ..

Freyhardt CC, Lobo RF, Khodabenah S, Lewis JE, Tsapatsis M, Yoshikawa M. Camblor MA. Pan M. Helmkamo MM. Zones SI. Davis ME: VPI-8: A high silica molecular s&e with a novel ‘pinwheel’ building unit and its implications for the synthesis of extra-large pore molecular sieves. J Am Chem Sot 1996, II 8:7299-7310. The structure of the high-silica VPI-8 investigated using a range of techniques, particularly HRTEM. is described. The structure contains an unusual complex or tertiaj building unit which link together to produce one-dimensional channels constructed from 12 tetrahedral atoms.

Lobo RF, Tsapatsis M, Freyhardt CC, Khodabandeh S, Wagner P, Chen C-Y. Balkus KJ, Zones SI. Davis ME: Characterisation of the extra-large reolite UTD-1. JAm Chem Sot 1997 119:0474-0404.

Khodabandeh S, Davis ME: Synthesis of a heulandite-type zeolite by hydrothermal conversion of zeolite Pl. Chem Commun 1996:1205-l 206.

10. .

Adams CJ, Araya A, Carr SW, Chapple AP, Franklin KR, Graham P, Minihan AR, Osinga TJ, Stuart JA: Zeolite map: the new detergent zeolite. Studies Surf Sci Catal 1997, 105:1667-l 674. Synthesis of a zeolite P (GIS framework) with a silicon to aluminium ratio of 1:l and control of particle size at the 1 000 A level. The product is a commercial builder with enhanced properties relative to zeolite A. 11. *

Wagner P, Yoshikawa M, Lovallo M, Tsuji CIT-5 a high silica zeolite with 14-ring 1997:2179-2180. A new one-dimensional system with a large templated using the N(l6)-methylsparteinium strate exceptional thermal stability to 900%. l

K, Taspatsis M, Davis ME: pores. Chem Commun pore diameter (14 T atoms) cation. The materials demon-

12. .

Terasaki 0, Ohsuna T, Sakuma H, Watanabe D, Nakagawa Y, Medrud RC: Direct observation of pure MEL type zeolite. Chem Mater 1996.8:463-468. Synthesis and strhcture investigation, using HREM and synchrotron powder diffraction, of a MEL type material. The product shows no evidence of stacking fault of ZSM derived materials. 13.

Camblor MA. Corma A. Valencia S: Soontaneous nucleation and growth of a pure silica zeolite beta iree of connectivity defects. Chem Commun 1996:2365-2366.

14. Chen CSH, Schlenker JL, Wentzek SE: Synthesis and characterization of synthetic zeolite ECR-1. Zeolites 1996, 17:393-400. 15. Camblor MA, Correll C, Corma A, Diaz Cabanas M-J, Nicolpoulos S, Gonzalez Calbet JM, Vallet-Regi M: A new microporous polymorph of silica isomorphous to zeolite MCM-22. Chem Mater 1996, 8:2415-241% 16. Chatelain T, Patarin J, Farre R, Petigny 0, Schultz P: Synthesis and characterization of 1 E-crown-6 ether-containing KFI-type zeolite. Zeolites 1996, 17:328-333. 17. Yang SY, Evmiridis NP: Synthesis and characterization of an offretite/erionite type zeolite Microporous Mater 1996, 6:l Q-26. 16. Day VW, Finnie DJ, Han PD, Klemperer WG, Marquart TA, Payne DA: The ZSM-39 reolite dodecasil-3C - a new ferroic material. In Abstracts of Papers of the American Chemical Society 1996, 211:557. 19. Chen CSH, Schlenker JL, Wentzek SE: Synthesis and characterisation of synthetic zeolite ECR-1. Zeo/ites 1996, 17:393-400. 20. Zones SI, Nakagawa Y, Yuen LT, Harris TV: Guest/host interactions in high silica zeolite synthesis: 14.2.1.Oltricyclodecanes as template molecules. J Am Chem Sot 1996, 1 l&7558-7567. 21. Camblor MA, Bong Hong S, Davis ME: Unexpected contraction of a zeolite framework upon isomorphous substitution of Si by Al. Chem Commun 1996:425-426. 22. Borade RB, Clearfield A: Synthesis of beta-zeolite with high-levels of tetrahedral aluminium. Chem Commun 1996:625-626.

Hydrothermal

Noble GW, Wright PA, Lightfoot P, Morris RE, Hudson KJ, Kvick A, Graafsma H: Microporous magnesium aluminophosphate STA-1. Synthesis with a rationally designed template and structure elucidation by microcrystal diffraction. Angew Chem Int Ed Engl 1997, 36:81-83. A directed synthesis of a novel framework usmg a deslgned template. Linear dinuclidinium ions were used to promote pore formation. Structure analysis was again by powder X-ray diffraction using synchrotron radiation.

23. ”

24.

Akporiaye DE, Fjellvag H, Halvorsen EN, Hustveit J, Karlsson A, Lillerud KP: The synthesis and structure of UiO-7, a new molecular sieve. Chem Commun 1998:601-802.

25. .

Akporiaye DE, Fjellvag H, Halvorsen EN, Haug T, Karlsson A, Liilerud FP: UiO-6: a novel 12-ring AIP04 made in an inorganicorganic cation system. Chem Commun 1998:1553-l 554. Use of fluoride ions to promote the formation of new zeolite with I P-ring channels with a 8.2 A pore size. Structure determination from powder methods is facilitated by a short repeat along the pore direction. 28.

Nenoff TM, Parise JB, Jones GA, Galya LG, Corbin DR, Stucky GD: Flexibility of zeolite RHO framework. In-situ X-ray and neutron powder structural characterisation of cation-exchanged BePO and BeAsO RHO analogs. J Phys Chem 1996,100:14256-14268.

27.

Schindler M, Bauer WH: Insertion of functional groups into zeolites - a new construction principle for open microporous frameworks. Angew Chem Int Ed Engl 1997, 36:91-93.

28.

McCready DE, Balmer ML, Keefer KD: Experimental and calculated X-ray powder diffraction data for cesium titanium silicate, CsTiSisOs,,: a new zeolite. Powder Diffraction 1997, 12:40-42.

29.

Oliver S, Kuperman A, Lough A, Ozin GA: Synthesis and characterization of a fluorinated anionic aluminophosphate framework UT-6, and its high-temperature dehydrofluorination AIP04-CHA. J Mafer Chem 1997, 7:807-812.

30.

31.

Akporiaye DE, Dahl IM, Mostad HB, Wendelbo R: The synthesis and characterisation of SAPO-43. Zeolites 1996, 17:517-522.

32.

Zahedi-Niaki MH, Joshi PN, Kaliaguine S: Synthesis and characterisation of a novel titanium aluminophosphate molecular sieve with ATS structure TAPO-36. Chem Commun 1997:47-48.

33.

Schreyeck L, Synthesis of diazapolyoxa 1997:1241 -I

34.

D’agosto F, Stumbe J, Caullet P, Mougenel JC: the LTA type ALP04 in the presence of the macrocycle Kryptofiix 222. Chem Commun 242.

Kr Das T, Chandwadkar AJ, Sivasankar S: A rapid method of synthesising the titanium silicate ETS-I 0. Chem Commun 1998:1105-1108.

35.

Liu X, Thomas JK: Synthesis of microporous titanosilcates ETS-I 0 and ETS-4 using solid TiO, as the source of titanium. Chem Commun 1996:I 435-l 438.

38.

Natarajan S, Gabrial J-C, Cheetham AK: Synthesis and structure of a three dimensional open framework aluminophosphate [NHz(CH,)sNH,l+CHAI,PaO,,l-HzO. Chem Commun 1996:I 415. 1418.

37.

Paillaud J-L, Marler B, Kessler H: Synthsis and characterisation of the novel GIS type AIPO,:fNH,Me,llAI,P,Osfl. Chem Commun 1996:1293-l 294.

38

Weigel SJ, Weston SC, Cheetham AK, Stucky GD: Co-operative structure direction in the synthesis of microporous materials preparation and crystal structure of TREN-GaPO. Chem Mater 1997, 9:1293-l 295.

39.

Harrison WTA, Gier TE, Stucky GD, Broach RW, Bedard RA: NaZnPO,.H,O, an open framework sodium zincophosphate with a new chiral tetrahedral framework topology. Chem Mater 1998, 6:145-154.

40.

Behrens E, Poojaty DM, Clearfield A: Synthesis crystal structure and ion exchange properties of porous titanosilicates HM,Ti40,(Si0,),.4Hz0 (M = H, K, Cs), structural analogues of the mineral pharmacosiderite. Chem Mater 1996, 6:1238-l 244.

41. .

Borade RB, Clearfield A: Synthesis of an iron silicate with the ferrierite structure. Chem Commun 1998:2267-2288.

of zeolites

Weller and Dann

I43

Incorporation of significant levels of iron (- 10%) into the ferrierite structure by crystallisation from iron rich media. 42.

Ko YS, Ahn WS, Chae JH, Moon SH: Synthesis and characterization of iron modified L-type zeolite. Studies Surf Sci Cataf A 1997, 105:733-740.

43.

Sasidharan M, Kumar R: Synthesis, characterization and catalytic properties of ferri-silicate and gallo-silicate analogs of zeolite NCL-1. Catal Left 1996,38:245-249.

44.

Latham K, Williams CD, Duke CVA: The synthesis of iron cancrinite using tetrahedral iron species. Zeolifes 1996, 17:513-516.

45.

Prasad S, Haw JF: Solid state NMR study of magnesium incorporation in aluminophosphate of type 20. Chem Mater 1998, 8:881-867.

46.

Choudhary VR, Kinage AK, Belhekar AA: Hydrothermal synthesis of galloaluminosilicate (MFI) zeolite crystals having uniform size, morphology and Ga/AI ratio. Zeolites 1997, 18:274-277.

47.

Feng P, Bu X, Stucky GD: Hydrothermal syntheses and structural characterization of zeolite analogue compounds based on cobalt phosphate. Nature 1997,386:735-741.

48.

Cowley AR, Chippindale AM: Synthesis and characterization of &NH, J(+)lCoGaPzO,I(-1, A COGAPO analog of the zeolite gismondine. Chem Commun 1996673-674.

49.

Sevov SC: Synthesis and structure of CoBzPaO,z(OH). CzH,cNz: the first metal borophosphate with an open framework structure. Angew Chem lnf Ed EnglI998, 35:2830-2832.

50.

Chippindale AM, Cowley AR: CoGaPO-5: synthesis and crystal structure of (C,N,H,,),[Co,GasP,O,,l, a microporous cobalt-gallium phosphate with a novel framework topology. Zeolifes 1997, 16:176-l 81.

51.

Hill SJ, Williams CD, Duke CVA: The synthesis of high cobalt containing CoALPO-34. Zeofifes 1996, 17:291-296.

to

Loiseau T, Ferey G: Synthesis and crystal-structure of ULM-16, a new open-framework fluorinated gallium phosphate with 1 B-ring channels - Ga,(P04),F,.I.BNCsH,,.0.5H,O. J Mater Chem 1996, 6:1073-l 074.

synthesis

52. .

Bhaumik A, Belhekar AA, Kumar R: A new method for enhancing zeolite crystallisation by using oxyacids/salts of group VA and VIIA elements as promoters. Studies Surf Sci Catal A 1997, 105:141-145. Addition of simple inorganic oxoanions has been shown to increase the rate of formation of several zeolites by factors of 4-8. 53. .

Zhao JP, Cundy C, Dwyer J: Synthesis of zeolites in a microwave heating environment. Studies Surf Sci Catal A 1997, 105:I 81-l 85. Formation of zeolites ZSM-5, 8 and EMT under microwave heating conditions showing the formation of these phase with reduced impurities and shorter nucleation times. 54.

Kim WJ, Hayhurst DT, Lee SA, Lee MC, Lim CW, Yoo JC: Studies of the crystallisation of ZSM-5 under high gravitational force field. Studies Surf Sci Catal A I 997, 105: 157-l 6 1.

55.

Slangen PM, Jansen JC, van Bekkum H: Induction heating: a novel tool for zeolite synthesis. Zeolites 1997, 18:63-66.

58. .

Yan YA Chaudhuri SR, Sarkar A: Synthesis of oriented zeolite molecular sieve films with controlled morphologies. Chem Mater 1996, 8:473-479. Hydrothermal synthesis of ZSM-5 deposited as an oriented film on fused silica glass; crystals orientate with the b direction perpendicular to the surface. 57. .

Boudreau LC, Tsapatsis M: A highly oriented thin film of zeolite A. Chem Mater 1997, 9:1705-l 710. Deposition of zeolite A oriented along the (hO0) direction on a glass slide from nanosols containing 200-300 nm crystallites. 58.

Lovallo MC, Tsapatsis M, Okubo T: Preparation of an asymmetric zeolite L film. Chem Mater 1996, 8:1579-l 584.

59.

Kita H, lnoue T, Yasamura H, Tanaka K, Okamoto K: Na-Y zeolite membrane for the pervaporation separation of methanol-methyl tert butyl ether mixtures. Chem Commun 1997:45-46.

80. .

Shi J, Anderson MW, Carr SW: Direct observation of a zeolite A synthesis by in situ solid state NMR. Chem Mater 1996. 8:369375. Use of 27AI and ‘%i MASNMR and powder X-ray diffraction to observed the formation and growth of zeolite A in gel and solution phases. 81. .

Francis RJ, Proce SJ, Obrien S, Fogg AM, O’Hare D, Loiseau T, Ferey G: Formation of an intermediate during the hydrothermal synthesis of ULM-5 studied using time-resolved in situ X-ray powder diffraction. Chem Commun 1997:521-522. Use of synchrotron radiation to observe the formation of the gallophosphate ULM-5 in situ over a 70 minute period. Discovery of a previously unobserved intermediate phase.