Synthesis of Mordenite

Figure 3.7 Effect of pH on the crystallization rate for the synthesis of mordenite at 300 °C. Reproduced with permission from [3]. Copyright (1982) Academic Press, New York...

No lithium-containing mordenites have been found in natural occurrences these are calcium, sodium mordenites with varying but small contents of potassium. The first probable synthesis of mordenite in 1927 by Leonard (10) was the autoclaved product of reacting sodium carbonate solution with spodumene. Although the product, identified tentatively as mordenite( ) was not analyzed, the results of our studies suggest that he synthesized a Na,Li-mordenite. 

Phase studies in the siliceous portion of the lithia system and the lithia-soda system resulted in the synthesis of mordenites with the same coexisting phases—analcimes, phillipsites, quartz, opaline silica, and crystalline alkali silicates—as had been found in the soda system. Whereas the starting materials used as reactants are not critical parameters in the synthesis of these zeolites in the soda system, the choice of reactants is a predominant factor in lithia-containing systems to produce these phases. The mechanism is not understood yet but the sensitivity of these... 

D. E. Vaughan (W. R. Grace Co., Clarksville, Md. 21029) In view of the report of widespread occurrence of mordenite lake bed deposits (Sheppard, page 279), the low-temperature synthesis of mordenite is of some interest and importance. Would you care to comment on and correlate the experimental and field evidence ... 

Domine D, Quobex J (1968) Synthesis of mordenite. In Barrer RM (ed) Molecular sieves. Society of Chemical Industry, London, p 78... 

Selective synthesis of ethylenediamine from ethanolamine over modified H-mordenite catalyst... 

The synthesis of ethylenediamine (EDA) from ethanolamine (EA) with ammonia over acidic t3pes of zeolite catalyst was investigated. Among the zeolites tested in this study, the protonic form of mordenite catalyst that was treated with EDTA (H-EDTA-MOR) showed the highest activity and selectivity for the formation of EA at 603 K, W/F=200 g h mol, and NH3/ =50. The reaction proved to be highly selective for EA over H-EDTA-MOR, with small amounts of ethyleneimine (El) and piperazine (PA) derivatives as the side products. IR spectroscopic data provide evidence that the protonated El is the chemical intermediate for the reaction. The reaction for Uie formation of EDA from EA and ammonia required stronger acidic sites in the mordenite channels for hi er yield and selectivity. 

Sand, L.B. (1968) Synthesis of large-port and small-port mordenites. Mol. Sieves, Pap. Conf, 1967, 71-77. 

Boveri, M., Marquez-Alvarez, C., Laborde, M.A., and Sastre, E. (2006) Steam and add dealumination of mordenite charaderization and influence on the catalytic performance in linear alkylbenzene synthesis. Catal. Today, 114, 217-225. 

As mentioned above, the main types of zeoHtes in industrial catalytic application today are Zeolite Y (FAU) and its variants, ZSM-5 and SUicahte (MFI), Mordenite (MOR) and Beta (BEA). After the first commercial synthesis of X and Y zeolites in the mid- to late 1940s by workers at the Union Carbide Corporation [21, 22],... 

Fig. 2. Composition diagram for the reactant and suitable temperature for synthesis of high silica mordenite.

This study showed that the overall crystallization processes for mor-denite, zeolite X, and zeolite A were similar. However, the physical properties of the crystallizing system determine the rate-limiting step for a particular zeolite synthesis. In the case of mordenite in which both the viscosity of the batch composition and the morphology of seed crystals were varied, it was observed that diffusion in the liquid phase was the ratedetermining step. For zeolite X the actual growth rate on the crystal-liquid interface was the rate-limiting factor as shown by identical conversion rates for the seeded and unseeded systems. For zeolite A in the system chosen, both processes influenced the conversion rate. 

The synthesis of Ti-mordenite has been conducted by reaction of TiCl4 with dealuminated mordenite or by hydrothermal synthesis (Section IV.F). The evidence for the incorporation of titanium is limited. The UV-visible spectra show that, in addition to the transition at 48,000 cm- , assigned to isolated Tiiv in tetrahedral coordination, there is also an absorption at 35,000 cm-, indicating extra-framework Ti02. The catalytic properties in oxidation reactions with H202 are significantly different from those of Ti02 deposited on mordenite, but they are limited to the hydroxylation of benzene and the oxidation of w-hexane (Kim and Cho, 1993). 

Machado et al. (1) studied the synthesis of monolaurin from lauric acid and glycerol employing commercial Beta, Y, and Mordenite zeolites as catalysts. The optimized conditions for the monolaurin synthesis... 

With TPA the very fast nucleation prevents the formation of other zeolitic phases while the stability prevents transformations to other products. TEA, on the other hand, may be used for the synthesis of other Si-rich zeolites such as mordenite, ZSM-12, -20, —25, beta, and Nu-2 (20) as well since it evidently exerts no specific structure-directing influence during nucleation. Depending on the precise gel composition and synthesis conditions, it can thus easily be envisaged that other zeolites may form which are stabilized by TEA incorporation. 

We should remember that low temperature zeolite synthesis started with Milton s gel synthesis of A and X in the early 1950 s(l). Large pore zeolites were substantially unavailable at that time. Natural faujasite was rare as it still is. Large port mordenite was still ten years in the future as were zeolites L and Omega. Zeolites were regarded as ion exchangers or as selective sorbents, not as catalysts. 

Results from diverse experimental methods were combined to arrive at structure proposals for ECR-1, a typical example of a microcrystalline zeolite. The zeolite features a 12-ring single channel, formed by a regular alternation of connected sheets of mordenite and mazzite. Crucial clues to the structure came from the HREM observation of a mazzite epitaxial overgrowth on an ECR-1 crystal. Electron and x-ray diffraction, infra-red spectroscopy and synthesis phase relationships were essential additional data sources. 

The proposed structure for ECR-1 was solved by accumulating evidence from many "traditional" sources, such as the synthesis phase relationships, powder x-ray diffraction (PXD) and electron diffraction (ED), molecular probe sorption, infra-red analysis (IR) and electron microscopy (EM). Initial unsuccessful models were based on extended merlinoite frameworks, followed by modifications based on mordenite. The observation of crystal overgrowths of mazzite in high resolution lattice images was the key to recognizing the compatibility of mordenite and mazzite structural layers, and that intimate intergrowth of the two structures was possible. 

An analogous process has been used industrially for the synthesis of 2,6-di-isopropylnaphthalene from naphthalene and propylene in the presence of H-mordenite, another shape-selective zeolite (Equation 7). Oxidation of... 

Other shapes of organocations do not produce SSZ-13 and, instead, give a slower synthesis of pentasil zeolites (mordenite, ZSM-5, beta) or no conversion product at all. Hiis was observed for linear substituents on charged nitrogen. Two groups were considered (1) homologous tetraalkyl ammonium compounds and... 

Titanium Silicalite-2 (TS-2), structurally similar to TS-1, could be prepared likewise using tetrabutylammonium hydroxide as the template [13, 14]. Titanium aluminum Beta (Ti,Al-[3) was prepared by hydrothermal synthesis from amorphous silica, sodium aluminate, tetraethyltitanate and tetraethylammonium hydroxide [15]. The presence of A1 was necessary for the crystallization of the product. Al-free Titanium Beta (Ti-[3) could be obtained in the presence of particular templates, such as dibenzyldimethylammonium hydroxide [16]. Titanium Mordenite (Ti-MOR), conversely, was obtained by post-synthesis insertion of Ti to dealuminated Mordenite [17]. Ti-MWW (Ti-MCM-22) was obtained by the synthesis of the lamellar precursor of Ti,B-MCM-22 followed by acid treatment to remove most of the boron and extra-framework Ti and finally calcination to burn out the template and bring about the condensation of lamellae into the three-dimensional MWW structure [18]. Ti is present in a number of different environ-... 

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