Industrial Application of Shape-Selective Catalysis

In the 26 years since the term "shape-selective catalysis" was coined by P. B. Weisz and V. J. Frilette [1] to describe the unique catalytic properties of small pore molecular sieve zeolites, great strides in the use of shape-selective zeolites have been made, both scientifically and technologically. Since then, in addition to small pore zeolites, synthetic medium pore zeolites, such as ZSM-5 [2], ZSM-11 [3], ZSM-22 [4], ZSM-23 [5], ZSM-35 [6], ZSM-38 [7], ZSM-48 [8], etc., have been discovered. The availability of these synthetic medium pore zeolites has expanded the realm of "shape selectivity" beyond the original discovery of selective conversion of straight chain molecules to include certain branched molecules, single-ring aromatics, naphthenes, and nonhydrocarbons with a critical molecular dimension smaller than about 6 Å.