Dealkylation of alkyl-substituted aromatic hydrocarbons in the presence of an aluminosilicate catalyst Communication 3. Kinetics of the dealkylation of o- and p-chlorocumenes

Abstract

1. The main reaction of chlorocumene cracking is the cleavage of the isopropyl group in the form of propylene and the formation of chlorobenzene. The reactions of hydrogen redistribution, isomerization and polymerization occur to an insignificant degree and apply only to the decomposition products of the isopropyl carboniumion. 2. The kinetics of dealkylationof o- and p-chlorocumenes under the indicated conditions follows the Frost equation. 3. The activation energy of cleavage of the isopropyl group from the benzene ring increases from 17,500 to 21,500 for o-chlorocumene or 24,200 cal/mole for p-chlorocumene, depending on the position of the chlorine atom relative to the isopropyl group, after the replacement of a hydrogen atom in the cumene molecule by chlorine. The retention of the passivating influence of the chlorine atom with respect to electrophilic substitution reactions even under the conditions of catalytic cracking may be regarded as confirmation of the ionic character of the catalytic reactions of hydrocarbons over aluminosilicates.