Catalysis by crystalline aluminosilicates: IV. Attainable catalytic cracking rate constants, and superactivity

Abstract

Crystalline aluminosilicate zeolite catalysts possessing a number of different crystal structures and ionic forms are characterized by rate constants for the cracking of n-hexane of from one to more than four orders of magnitude greater than the activity of conventional amorphous siliceous oxide cracking catalysts. Some are highly molecular shape selective at similarly high “superactivities.” Product spectra change with the temperature at which activity is achieved. Apparent activation energies are remarkably uniform. Catalysts can now be made that span a wide range of activities, from ones that crack at conventionally high temperatures to those that approach the low-temperature performance of acid catalysts of the aluminum-hydrogen halide type.