Thermodynamics of sulfur chemisorption on metals. II. Alumina-supported ruthenium

Abstract

Isosteric heats of chemisorption of sulfur on alumina‐supported ruthenium have been determined by measuring the equilibrium ratio of H2S/H2 in contact with the solid in a closed gas‐recirculation system. At low coverage the heat of chemisorption with respect to 1/2 S2(g) was found to be −215±15 kJ mol−1. With increasing coverage it decreased to −174±10 kJ mol−1, a value comparable to the heat of formation of bulk ruthenium sulfide. For equal coverage with sulfur, the thermodynamicchemical potential of alumina‐supported ruthenium exceeds that of alumina‐supported nickel by approximately one order of magnitude. The binding strength of adsorbed sulfur is 432±15 kJ mol−1 for Ru and 464±15 kJ mol−1 for Ni.