Highly para-selective alkylation of toluene with methanol over modified superfine nano-ZSM-5 aggregates

Alkylation between toluene and methanol is a promising route to produce para-xylene (PX). ZSM-5 zeolite commonly used as a catalyst in toluene alkylation with methanol, has been paid extensive attention. In this study, synthesis of superfine nano-ZSM-5 aggregates with fast mass transfer and controllable acid properties were realized before modification in an simple way. Firstly, nano-ZSM-5 aggregates with fast mass transfer was synthesized combined with a dual-silica source and a low-temperature crystallization method. The acid properties, such as W/S and LASs/BASs, were adjusted during low-temperature crystallization. Secondly, the mass transfer ability was further enhanced by introducing more irregular pore structures via alkali treatment method, meanwhile, the acid properties were further optimized to obtain increased W/S and LAS/BAS ratios, which had positive on the catalytic performance. After SiO₂ modification, the obtained Si/AH-NTZ-130 catalyst displayed excellent performance with the PX selectivity approaching 80%. Moreover, the optimized Si/P-AH-NTZ-130 was stable for 120 h, with a PX selectivity of nearly 100%.