Alkylation and dealkylation of benzene and its homologs in presence of aluminosilicates

Abstract

1. The catalytic treatment of a mixture of benzene, xylenes, and other polymethylbenzenes in presence of synthetic aluminosilicates is accompanied by dealkylation reactions and alkyl-transfer reactions leading to the formation of toluene in appreciable amount. The extent to which each of these reactions participitates in the process is found to be directly related to the value of the applied pressure. 2. The use of an elevated pressure is of decisive importance for maximum formation of toluene. With increase in pressure the yield of toluene increases, attaining a maximum in the range 10–20 atm. The optimum conditions for the reaction were determined. 3. The predominant reaction resulting in the formation of toluene at elevated pressure is demethylation of xylenes and polymethylbenzenes with simultaneous methylation of benzene. A small part is played in the formation of toluene by the migration of methyl groups of xylenes with formation also of trimethylbenzenes. The readiness with which methyl groups are eliminated tends to increase as their number in the benzene nucleus increases. 4. In the reaction of coupled alkylation and dealkylation in a mixture of benzene and o-xylene, isomeric transformation of o-xylene into the meta and para isomers occurs.