Catalytic hydrolysis of methyl mercaptan and methyl thioether on hydroxyl-modified ZrO2: a density functional theory study.

Abstract

The purification and removal of organic sulfur from natural gas is conducive to increasing the added value of natural gas and reducing environmental pollution. In this study, the adsorption properties of methyl mercaptan (CH3SH), dimethyl sulfide (C2H6S) and H2O on the surface of hydroxyl-modified ZrO2 were investigated using density functional theory (DFT) calculations. Additionally, a reaction mechanism was proposed for hydroxyl-modified ZrO2 catalyzing the hydrolysis of CH3SH and C2H6S. The chemisorption of H2O molecules on the catalyst surface is attributed to H-O and H-Zr bonds. The chemisorption of CH3SH and C2H6S on the catalyst surface is attributed to Zr-S bonds. Competitive adsorption between the three gases exists only between CH3SH and C2H6S. It reveals the water-resistant properties of hydroxyl-modified ZrO2 in desulfurization. The adsorption energies of the three gas molecules on the hydroxyl-modified ZrO2 surface are in the order of CH3SH - (Zr) > C2H6S - (Zr) > H2O - (OH). The natural hydrolysis of CH3SH and C2H6S is a heat-absorbing process that cannot occur spontaneously. The rate-determining step for CH3SH catalytic hydrolysis is the formation of CH3O. The fracture of CH3SHO is the rate-determining step for C2H6S catalytic hydrolysis. The depletion of the surface hydroxyl groups can be replenished by the dissociation of H2O molecules. Hydroxyl-modified ZrO2 facilitated the hydrolysis process of CH3SH to a greater extent than that of C2H6S. This study provides theoretical guidance for industrial applications and the design of hydroxyl-containing hydrolysis catalysts.