Hydrodesulfurization of Dibenzothiophene Catalyzed by Supported Metal Carbonyl Complexes(Part 5) Catalysts for Hydrodesulfurization Prepared from Alumina-supported Ruthenium Carbonyl-Alkali Metal Hydroxide Systems.

Abstract

In hydrodesulfurization of dibenzothiophene (DBT) catalyzed by sulfided alumina-supported ruthenium compounds, the effects of addition of alkali metal hydroxide on the catalytic activity and product selectivity were investigated. When sodium hydroxide was added to catalysts derived from alumina-supported Ru3(CO)12, the conversion of DBT remarkably increased from 44 to 71%. It was essential to obtain the high catalytic activity and, therefore, that after the reaction of Ru3(CO)12 with sodium hydroxide, in advance, to give a ruthenium hydride Na[HRu3(CO)11], the hydride was supported on alumina. By the reaction of RuCl3, Ru(acac)3 (acac=acetylacetonate) and Ru3(CO)12 with cesium hydroxide and products supported on alumina, the activity increased in the order RuCl3-CsOH/Al2O3<Ru(acac)3-CsOH/Al2O3<Ru3(CO)12-3CsOH/Al2O3. When the amount of addition of alkali metal hydroxides increased in the alumina-supported ruthenium carbonyl system, the conversion of DBT increased and reached the maximum at M/Ru=2 (M=Na or Cs). Further addition of cesium decreased the activity. In Ru3(CO)12-nCsOH/Al2O3 systems, biphenyl was produced selectively. In order to elucidate these phenomenon, the measurements of NO chemisorption and X-ray photoelectron spectroscopy (XPS) before and after HDS were performed. The addition of cesium to Ru3(CO)12/Al2O3 increased the amount of NO chemisorption, indicating that the sulfided catalysts still had many coordinatively unsaturated sites. XP spectra showed that addition of appropriate amounts of cesium would stabilize ruthenium sulfide on alumina, even in pressurized hydrogen. Catalysts derived from a Ru3(CO)12-6CsOH/Al2O3 system showed activities comparable to that of Co-Mo/Al2O3.