Fundamental studies of desulfurization processes: reaction of methanethiol on ZnO and Cs/ZnO

The reaction of methanethiol on ZnO and Cs promoted ZnO surfaces has been studied with synchrotron based photoemission and thermal desorption spectroscopy. On ZnO, methanethiol undergoes selective reaction to produce carbon monoxide (37–58%), methane (23–38%), formaldehyde (12–15%), ethane (1–11%), and a mixture of ethylene and acetylene (3–13%). At low temperatures (<100 K), methanethiol reacts to yield thiolate intermediate bound to Zn2+ cations. The thiolate is stable to 500 K. Above this temperature, C–S bond cleavage occurs to yield methyl intermediate and atomic S. Carbon is removed from the surface as gaseous products above 500 K, and atomic sulfur remains bound to the zinc sites of the surface. Submonolayer amounts of cesium do not have a significant promotional effect on C–S bond cleavage, whereas Cs multilayers are found to significantly lower the activation barrier for C–S bond cleavage. This study illustrates the chemistry associated with the desulfurization of thiols on a catalytically relevant oxide surface.