Zeolites templates

Quaternary ammonium bromides and hydroxides (quats) are applied as templates in the synthesis of zeolites with relatively high Si/Al ratio. Examples will be given of the use of mon-, di-, poly- and associated quats as templates in zeolite growth. Templated zeolites of the MFI-type can be grown in a lateral or in an axial way onto metal supports, providing promising composite systems, for separation and catalysis, respectively. 

Delprato, F., Delmotte, L., Guth, J.L, and Huve, L. (1990) Synthesis of new silica-rich cubic and hexagonal faujasites using crown-ether based supramolecules as templates. Zeolites, 10, 546. 

Among the inorganic templates, zeolite produces more regulated pores as compared to the silica template. If nano-channels in zeolite are completely filled with carbonaceous precursor and then the carbon materials are extracted from the zeolite framework, one can obtain the porous carbon of which structure reflects the porosity of the original zeolite template. The ordered mesoporous silica templates, e.g., MCM-4 838,39,47 and SBA-1547 have been employed to prepare the ordered porous carbons by the procedures involving the pore filling of the silica template with carbonaceous precursor followed by carbonization and silica dissolution. The resulting pore sizes of the ordered mesoporous carbons are smaller than about 10 nm. 

F. Delprato, L. Delmotte, J.L. Guth, and L. Huve, Synthesis of New Silica-rich Cubic and Hexagonal Faujasites using Crown-ether-based Supramolecules as Templates. Zeolites, 1990, 10, 546-552. 

P.A. Cox, J.L. Casci, and A.P Stevens, Molecular Modelling of Templated Zeolite Synthesis. 

Carbon precursor Template zeolite Carbonization conditions Pore structure parameters ... 

Calcination of the as-prepared forms of organically templated zeolites and substituted aluminophosphates in oxygen at ca. 500 °C removes the organics to leave the protonic forms, where the protons are in the form of bridging hydroxyls (Scheme 6.1). These balance the negative framework charge... 

The dynamic character of the template-zeolite interactions has only been studied recently [39]. Experimental data (solid state and NMR between -120 C and 20°C), as well as molecular dynamic (MD) calculations at -150 C, -120 C and 0 C, indicate that the tetramethylammonium (TMA) ion occluded in the beta cage of sodalite has a considerable degree of rotational freedom. Figure 10, even at low temperature. MD shows that this rotational freedom originates from the dynamics of the zeolite lattice the distance between... 

Calorimetric measurements of acidity of H-ZSM-5 zeolites synthesized by hydrothermal processes with and without the aid of a template, with various Si/Al ratios (17, 41, 54, 73, 111), have shown a higher acidity of the non-templated samples in number and strength, especially for low Si/Al ratios, while the two series of samples exhibited close behaviors when Si/Al > 37. This can be explained by the possible presence of more Lewis acid sites in the non-templated zeolites [183,184]. 

ShiraUtar VP, Clearfield A. Synthesis of the molecular sieve ZSM-5 without the aid of templates. Zeolites 1989 9 363-70. 

Synthesis of ionic liquid templated zeolite like structures... 

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