Alkylation of aromatics: Part I. Reaction network of the alkylation of phenol by methanol on ushy zeolite

Abstract

The alkylation of phenol with methanol was studied at 473 K, at atmospheric pressure in a flow reactor, in the presence of ultrastable (US) HY zeolite. The effect of the conversion rate on the product distribution shows that anisole, ortho- and para-cresols ( o-/p-cresol molar ratio = 1.5) are the primary products of the reaction. O-alkylation is about three times as fast as C-alkylation. The transformation of the primary products (anisole and o-cresol), pure or in mixture with methanol was also studied under the same conditions. Anisole disproportionates into methylanisoles and phenol. The reaction is assumed to occur through methyl transfer between a protonated and a non-protonated anisole molecule. Direct isomerization of anisole into cresols does not occur. The alkylation of phenol by anisole leads to cresols and methylanisoles as primary products. This reaction is about twice as fast as the disproportionation of anisole. The rate of formation of cresols from phenol apparently does not depend on the alkylating agent (methanol or anisole). However, phenol inhibits anisole disproportionation. Pure o-cresol does not react. Its alkylation by methanol gives mainly o-methylanisole and 2,4- and 2,6-dimethylphenols.