Electronic and structural modifications of ruthenium catalysts by sulfur.

摘要

The reversible catalytic selectivity, which is defined as the rate of hydrogenolysis to hydrogenation ratio, for thiophene hydrodesulfurization (HDS) over sulfided ruthenium catalysts depends on the procedure used to presulfide these catalysts. XPS and SIMS have been used to examine the surface phases responsible for the various selectivity regimes. XPS results demonstrate similar reversible trends in surface composition, but only show a 12% increase in lattice sulfur concentration after sulfidization in 100% H;This transition is more evident using SIMS where substantial differences are observed. Sulfidization in 100% H;Deuterium and hydrogen adsorption in conjunction with static SIMS also exhibit significant differences as evidenced by newly formed SH;In an effort to model the hydrogenolysis pathway over sulfided ruthenium catalysts, the adsorption, desorption and decomposition of thiophene have been investigated over clean and sulfur precovered Ru(0001) using TPD, TPRS, AES, SIMS and TPSS. On the clean surface, initial thiophene coverages crack at 95K to form decomposition products on the surface. At 300K, surface dehydrogenation is observed along with the formation of a bound C