Ultralarge pore zeolites

Zeohte Y with an average crystal size of 80 run was synthesized by optimizing the synthetic composition and the addition of NaCl [42]. Van Grieken et al. [43] synthesized nanocrystalline ZSM-5 with crystal sizes ranging from 10 to 100 nm through hydrothermal crystallization of supersaturated homogeneous mixtures 

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Corma, A., Diaz-Cabanas, M.J., Rey, E., Nicolopoulus, S., and Boulahya, K. (2004) lTQ-15 the first ultralarge pore zeolite with a bi-directional pore system formed by intersecting 14- and 12-ring channels, and its catalytic implications. Chem. Commun., 2004,1356. 

A. Corma, M.J. DIaz-Cabanas, F. Rey, S. Nicolopoulus, and K. Boulahya, ITQ-15 The First Ultralarge Pore Zeolite with a Bi-directional Pore System formed by Intersecting 14- and 1-ring Channels, and its Catalytic Implications. Chem. Commun., 2004, 1356-1357. 

However, zeolite-like materials with ultralarge pores such as Cloverite (20 T, 0.6 x 1.32 nm), VPI-5 (18 T, 1.27 nm), AIPO4-8 (14 T, 0.79 x 0.87 nm) were recently synthesized. A comparison between the pore openings of zeolites and the kinetic diameter of guest molecules shows clearly that zeolites can be used for molecular sieving. It should however be stressed that these values are temperature-dependant temperature increases both the flexibility of the guest molecules and the breathing motions of the host zeolite pore mouth and framework. 

Corma Canos, A. Navarro Villalba, T. Perez Pariente, J. Stmcmre Material of the Zeolite Type With Ultralarge Pores and a Lattice Comprised of Silicone and Titanimn Oxides Its Synthesis and Utilization for the Selective Oxidation of Organic Products. 5783167, 1998. 

Szostak, R., Kuvadia, R., Brown, J. and Thomas, T.L. (1989) "Ultralarge pore molecular sieves characterization of the 14A pore mineral, cacoxenite", in P.A. Jacobs and R.A. van Santen (eds.). Zeolites Facts, Figures, Future, Studies in Surface Science and Catalysis, 49, Elsevier, Amsterdam, pp. 439-446. 

Figure 8.4 Tailored design of zeolites for the enhancement of the accessibility to active sites, (a) Ultralarge-pore size zeolites, (b) nanocrystal zeolites, (c) delaminated zeolites, and (d) hierarchical zeolites.

Considering the size of the channels, they are conventionally defined as ultralarge (> 12-), large (12-), medium (10-), or small (8-membered ring) pore materials depending on the smallest number of O or T (T = Si, Al) atoms that limit the pore aperture of the largest channel, and whose diameter varies between 5 and 20 A. A summary of the different types of zeolites is shown in table 2. 

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