Alkylation of phenol and m-cresol over zeolites

The alkylation of phenols and phenol derivatives such as m-cresol are important reactions in a sequence of syntheses for the production of many important fine chemicals. Specifically it is of great importance to develop catalysts and processes, which are able to selectively produce one or other particular isomer or derivative. This paper presents results of an investigation into the alkylation of phenol and m-cresol, respectively, using methanol in the former case and propene in the latter. The catalysts of choice were H-ZSM-5 and H-MCM-22. In the case of phenol methylation it was found that controlling diffusivity by increasing crystal size was most conducive to the formation of p-cresol. H- MCM-22 showed a high selectivity to p-cresol. In the case of m-cresol propylation the selectivity over H-ZSM-5 to thymol was greater than 90% at conversions of around 50%, and 80% at conversions of around 85%. This high selectivity to thymol was considerably greater than reported in previous papers. In both systems mild reaction temperature and pressure conditions were desirable so as to minimize the formation of oligomeric products of methanol (via dimethyl ether) and propene, which could cause deactivation of the zeolite.