(223a) Catalysis In a Pocket: The MCM-22 Story

MCM-22 (MTW) is among a unique class of multidimensional pore shape selective zeolites wherein the principal locus for catalysis is in 12 member ring (12-MR) surface pockets. The zeolite contains two independent pore systems, both of which are accessed through rings comprised of ten tetrahedral (T) atoms (such as Si, Al, and B). One of these pore systems is defined by two-dimensional, sinusoidal channels and the other is defined by large 12-MR supercages with an inner free diameter of 0.71 nm and a height of 1.82 nm. Virtually all acid catalyzed reactions take place in pockets formed from the surface termination of the 1.82 nm high and 0.71 nm diameter supercages. The zeolite has been evaluated and found promising for a number of acid-catalyzed reactions. Most importantly, it has been found to be unusually selective for aromatic alkylation in the presence of a wide range of olefins under liquid phase conditions.