Thiolation of methanol with H2S using core-shell structured ZSM-5@t-ZrO2 catalyst

Abstract

Core-shell structured ZSM-5@t-ZrO2 catalysts were prepared by a hydrothermal coating method, and their physicochemical properties, catalytic performance, and deactivation behavior in thiolation reactions were studied using a ZSM-5/t-ZrO2 physically-blended catalyst as a comparison. Reactions using the core-shell ZSM-5@t-ZrO2 catalyst were carried out at a pressure of 0.7 MPa, 370 °C, a H2S:CH3OH molar ratio of 2:1, and a N2 flow rate of 90 ml·min−1. The conversion of CH3OH, and the selectivity and yield of CH3SH under these conditions were 92.07%, 90.89%, and 83.68%, respectively, and the catalytic lifetime was longer than 30 h. Compared with the ZSM-5/t-ZrO2 physically-blended catalyst, the CH3SH yield and the catalytic lifetime of the core-shell structured ZSM-5@t-ZrO2 catalyst were higher by 5.37% and 150%, respectively. The unique reaction pathway of the shell (t-ZrO2, Lewis (L) base active site)-core (ZSM-5, Brǿnsted (B) acid active site) and the Lewis-Brønsted acid active center based on a composite solid-solution interface were mainly responsible for the high activity of the thiolation reaction. Meanwhile, the formation of a micro-mesoporous system increased the diffusion of molecules and reduced the deactivation rate of carbon- and sulfur-containing deposits. Generally, carbon- and sulfur-containing substances deposited on catalysts were mainly composed of polymethylbenzene, polymethyl naphthalene, cyclic elemental sulfur, and other compounds containing CS and SS bonds. Finally, the core-shell structured catalysts showed excellent resistance to deactivation by carbon- and sulfur-containing deposits.