Catalytic hydrodesulfurization by supported organometallic sulfide clusters and topotactic molybdenum nitride.

摘要

An analysis of the catalytic hydrodesulfurization (HDS) properties of novel organometallic sulfide clusters and high surface area molybdenum nitride is presented. Experimental procedures for the synthesis, characterization, and catalytic evaluation of both types of catalysts are described. The analysis shows that the catalytic properties of the clusters depend on the ratio of ruthenium and cobalt and that the clusters decompose at industrial HDS temperatures. The work also shows that the molybdenum nitride may be suitable for industrial HDS.; The novel catalysts were composed of {dollar}rm Hsb2SRusb3(CO)sb9{dollar}, {dollar}rm HSRusb2Co(CO)sb9{dollar}, {dollar}rm SRuCosb2(CO)sb9{dollar}, and (Co{dollar}rm sb3Ssb2(CO)sb7rbrack sb2{dollar} supported on carbon and alumina. FTIR and mass spectroscopy (MS) were used to monitor temperature programmed decomposition of the supported clusters. Significant amounts of H{dollar}sb2{dollar}O were detected as products of decomposition. TPD/MS of {dollar}rm Hsb2SRusb3(CO)sb9{dollar} labelled with C{dollar}sp{lcub}18{rcub}{dollar}O indicated that the H{dollar}sb2{dollar}O evolved during TPD was mostly formed from the support surface, not the cluster-bound carbonyls. Kinetic measurements show the mixed-metal cluster catalysts are more active at 150{dollar}spcirc{dollar}C but less active at elevated temperatures than catalysts containing only one metal component. A structural model is presented for the decomposed, mixed-metal catalysts in which an overlayer of cobalt masks the catalytic activity of ruthenium.; Molybdenum nitride with surface areas up to 108 m{dollar}sb2{dollar}/g was synthesized. The surface area was found to depend on synthesis temperature profile, mass transfer, and passivation procedure. Passivated and sulfided catalysts retained the bulk structure of Mo{dollar}sb2{dollar}N. X-ray diffraction and Raman spectroscopy showed no evidence for MoO{dollar}sb3{dollar} or MoS{dollar}sb2{dollar} formation in fresh catalysts or catalysts sulfided at 673 K. Thiophene desulfurization activity was measured at 673 K over a broad range of Mo{dollar}sb2{dollar}N surface areas and reactor conditions. Kinetic data indicate that butane, butenes, and butadiene can be formed directly by thiophene desulfurization. A system of reaction pathways was proposed to account for the observed thiophene desulfurization selectivities.