Cesium Induced Changes in the Acid–Base Properties of Metal Oxides and the Consequences for Methanol Thiolation

Cs+-modified γ-alumina, titania anatase, and zirconia in the absence of WS2 are active catalysts for methanol thiolation. Pyridine and CO adsorptions via IR show that Cs+ cations induce higher concentrations and strength of base sites. Reaction rates are similar on all three catalysts, indicating that the Cs+ cations are part of the dominating active sites. Methanol thiolation shows similar apparent activation energies, decreasing with Cs+ concentration. Reaction orders close to 0.5 for both reactants suggest that all three metal oxides and their alkali-metal-modified counterparts follow the identical base-catalyzed Langmuir–Hinshelwood mechanism. A reaction between the surface alcoholate and the corresponding sulfhydryl groups is hypothesized to be the pathway for reaction.