Extra-large pore zeolites

2 DESIGN OF EXTRA-LARGE PORE ZEOLITES AND OTHER MICROPOROUS AND MESOPOROUS CATALYSTS 

A great demand exists for (hydro)thermally stable, crystalline structures with pore sizes in the 10-20 A size range that feature tetrahedral frameworks to allow 

The presence of three-membered rings has also been suggested to be advantageous in the quest for crystalline mesoporous materials.[50] The lack of crystallinity, which is a general feature of this class of materials, has been ascribed to their low framework density. For a range of crystalline framework materials a correlation between the framework density and the size of the smallest ring size in the structure has been established.1611 If this correlation is applied to mesoporous materials, which have typical void fractions 0.5, then the presence of three-membered rings becomes clearly beneficial in the quest to render these structures crystalline. 

3 HIERARCHICAL PORE ARCHITECTURES COMBINING MICROPOROUS AND MESOPOROSITY 

The inherent limitations of the use of zeolites as catalysts, i.e. their small pore sizes and long diffusion paths, have been addressed extensively. Corma reviewed the area of mesopore-containing microporous oxides,[67] with emphasis on extra-large pore zeolites and pillared-layered clay-type structures. Here we present a brief overview of different approaches to overcoming the limitations regarding the accessibility of catalytic sites in microporous oxide catalysts. In the first part, structures with hierarchical pore architectures, i.e. containing both microporous and mesoporous domains, are discussed. This is followed by a section on the modification of mesoporous host materials with nanometre-sized catalytically active metal oxide particles. 

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Cano, M.L., Cozens, F.L., Garcia, H., Marti, V. and Scaiano, J.C. (1996). Intrazeolite photochemistry. 13. Photophysical properties of bulky 2,4,6-triphenylpyrylium and tritylium cations within large- and extra-large-pore zeolites. J. Phys. Chem. 100, 18152-18157... 

Paillaud, J.-L., Harbuzaru, B., Patarin, J., and Bats, N. (2004) Extra-large-pore zeolites with two-dimensional channels formed by 14 and 12 rings. Science, 304, 990. 

Tontisirin, S. and Ernst, S. (2007) Zeolite SSZ-53 an extra-large-pore zeolite with interesting catalytic properties. Angew. Chem. Int. Ed., 46, 7304-7306. 

Zwijnenburg, M. A., Bromley, S. T., Jansen, J. C. and Maschmeyer, T. Toward understanding extra-large-pore zeolite energetics and topology a polyhedral approach, Chem. Mater., 2004, 16, 12-20. 

T. Wessels, Ch. Baerlocher, L.B. McCusker, and E.J. Creyghton, An Ordered Form of the Extra-large-pore Zeolite UTD-1 Synthesis and Structure Analysis from Powder Diffraction Data. J. Am. Chem. Soc., 1999, 121, 6242-6247. 

B. Harbuzaru, J.L. Paillaud, J. Patarin, and N. Bats, Extra-large-pore Zeolites with Two-dimensional Channels formed by 14- and 12-rings. Science, 2004, 304, 990-992. 

Figure 1. New Concept for Extra-Large Pore Zeolite Synthesis [37]...

P-07 - Investigation of hydrocarbon adsorption on large and extra-large pore zeolites... 

Large and extra-large pore zeolites with one-dimensional channel systems (SSZ-24, SSZ-31, SSZ-42, SSZ-48, CIT-5, UTD-1 and VPI-5) are investigated with hydrocarbon adsorption using a series of adsorbates with varying molecule sizes. Valuable input from adsorption for the determination of zeolite structures is demonstrated with zeolite SSZ-42 that contains an undulating, one-dimensional 12-MR charmel system. The adsorptive properties of two newer zeolites with unknown structures, SSZ-53 and SSZ-55, are discussed. The observed adsorptive characteristics provide useful information for the structure characterization of novel zeolites. 

EPR, polyaromatic ionisation 14-P-18 Extra-large pore zeolites PL-3... 

Extra-large-pore zeolites (at least 14-membered rings with pore sizes around 1.0 nm)—e.g., aluminosilicates CIT-5, UTD-1. aluminophosphates (VPI-5, JDF-20, gallophosphate. cloverite). 

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