Thiolation behaviors of methanol catalyzed by bifunctional ZSM-5@t-ZrO2 catalyst

The catalytic properties of bifunctional ZSM-5@t-ZrO 2 catalyst for methanol thiolation were revealed by using methanol and H 2 S as probe molecules. Taking the ZSM-5/t-ZrO 2 physically-blended catalyst, pure ZSM-5 and t-ZrO 2 as control catalysts, we investigated the characteristics of adsorption and transformation of different reaction molecules on or over different catalysts by combination of in-situ diffuse reflectance Fourier transform infrared spectroscopy (Drifts) and a variety of techniques including XRD, XPS, XRF, FT-IR, N 2 adsorption-desorption, CO 2 /NH 3 -TPD, and DSC. The results showed that the synergistic effect of acid sites between ZSM-5 phase and t-ZrO 2 phase in the bifunctional catalyst enhanced the adsorption and dissociation of methanol molecules, while the base sites in t-ZrO 2 phase were mainly responsible for the adsorption and dissociation of H 2 S molecules. Due to the small specific surface area of pure t-ZrO 2 catalyst, precursor species for sulfur deposition and carbon deposition were easily formed. Presulfurization could improve the initial activity of methanol thiolation and shorten the induction period. The dissociation of H 2 S at the base sites was the rate-determining step of the bimolecular reaction, and the appropriate increase of base sites in the bifunctional components could construct the matching formation rate of sulfhydryl and methoxy groups. At the same time, the special composite structure and meso-microporous system of ZSM-5@t-ZrO 2 could effectively reduce the formation rate of carbon and sulfur deposits.