Influence of Hollow ZSM-5 Zeolites Prepared by Treatment with Different Alkalis on the Catalytic Conversion of Methanol to Aromatics

The influence of hollow ZSM-5 catalysts prepared with two different kinds of alkalis on catalytic performances in methanol to aromatics was studied. It was found that benzene, toluene, and xylene (BTX) selectivities of hollow catalysts were higher than the parent ZSM-5 catalyst due to increasing mesopore volumes and acid strength. Meanwhile, the catalyst prepared by NaOH treatment exhibited higher BTX selectivity than the catalyst prepared by tetrapropylammonium hydroxide treatment. The reason was that the concentration of strong acid sites, Brønsted acid sites, and framework alumina in channel crossings was higher than that of the catalyst prepared by NaOH treatment. All these favored the formation of aromatics. Moreover, the introduction of hollow structures with mesopores improved diffusion behaviors of species and reduced the deactivation rate of the catalysts. However, a relatively higher deactivation rate was obtained over the NaOH-treated sample due to increasing strong acid sites.