Alkylation of Phenol with Methanol over ZSM-5 Zeolite

The catalytic performance of different molecular sieves in the alkylation of phenol with methanol to produce p-cresol was evaluated, and the acidity and structure of the catalysts were characterized using N₂ adsorption–desorption and Fourier transform infrared spectroscopy techniques. It was shown that the catalytic activity of molecular sieves was closely related to their acidic site number, specific surface area, and pore structure. Since Zeolite ZSM-5 (Zeolites Socony Mobil No. 5) has a relatively small amount of strong acid as well as a small pore size, it is favorable for the diffusion of p-cresol out of the pores. Therefore, focusing on ZSM-5, the effects of operating conditions such as weight hourly space velocity (WHSV), phenol/methanol (P/M) ratio, and reaction temperature on the catalytic performance were investigated. The results showed that increasing the WHSV, P/M ratio, and reaction temperature improved the selectivity to cresol. In addition, X-ray diffraction and Thermal Gravity/Differential Thermal Gravity characterization methods were also carried out for ZSM-5, and it was found that the deactivation of ZSM-5 was due to coke deposition and pore blockage on the active site and that the selectivity to cresol could be restored by regenerating the catalyst and covering the strong acid site, which resulted in the reduction of the strong acid site to increase the selectivity of the product.