Direct production of p/m-cresol from catalytic methylation of phenol with methanol over MCM-22 zeolite: Acidity effect and reaction network

Abstract

The methylation of phenol with methanol is an environment-friendly and simple method for cresol production. In this work, the direct and selective production of p/m-cresol from phenol methylation was realized over the MCM-22 zeolite catalyst by sensitive regulation of the reaction temperature. On the one hand, the effect of zeolite acidity was investigated by varying SiO₂/Al₂O₃ ratio, and the strong Bronsted acid sites were indicated to be crucial for phenol methylation reaction. The MCM-22 zeolite with strong acidity and moderate porosity exhibited outstanding and stable catalytic performance with high phenol conversion (∼40 %), excellent cresol selectivity (>95 %) and flexible product composition (p-cresol/cresols ∼40 % or m-cresol/cresols ∼50 %). On the other hand, the reaction network of phenol methylation was refined. It was demonstrated that, in addition to the direct production of cresols from C-alkylation of phenol, the cresols could also be produced by the transalkylation between phenol and anisole yield from phenol O-alkylation. This work not only develops a novel eco-friendly p/m-cresol production method, but also deepens people's knowledge of the reaction mechanism of phenol methylation.