Modifications of surface properties of a H-2-treated RuS2/SiO2 catalyst: Aparallel between low-temperature COFTIR spectroscopy and model reactions

A silica-supported ruthenium sulfide catalyst was progressively reduced by hydrogen at increasing temperatures (423-673 K). The resulting modification of the surface properties was characterized by low-temperature CO adsorpti on FTIR spectroscopy and by test reactions such as CH3SH condensation and 1 -butene hydrogenation. On the nonreduced catalyst, CO adsorption spectra sh owed the presence of bands, indicating various CO forms on Ru sites in a su lfur-rich environment. When sulfur was progressively removed from the ruthe nium sulfide phase, the number of coordinatively unsaturated Ru sites incre ased with the simultaneous formation of metallic Ru microdomains. A compari son of measurements of adsorption and catalytic activity showed that a rich sulfur environment was needed for the condensation of CH3SH to CH3SCH3, a reaction that required acidic sites, while butene hydrogenation required hi ghly depleted Ru sites. These results show that, upon reduction, RuS2 becam e less acidic and increasingly more metallic. (C) 2000 Academic Press.