CATALYTIC HYDRODESULFURIZATION BY SUPPORTED BIMETALLIC SULFIDE CLUSTER CATALYSTS

The synthesis, characterization, and thiophene hydrodesulfurization (HDS) activities of novel organometallic sulfide cluster catalysts are presented. The catalysts are composed of H2SRu3(CO)9, HSRu2Co(CO)9, SRuCo2(CO)9, and [(Co3S2(CO)7]2 supported on carbon and gamma-Al2O3. Although the clusters decompose at industrial HDS temperatures, the catalytic properties of the cluster catalysts at lower temperatures depend on the ratio of ruthenium and cobalt. Temperature-programmed decomposition (TPD) of the supported clusters in flowing hydrogen was monitored using FT-IR and mass spectrometry (MS). Temperatures of decomposition (as determined by the maximum rate of CO evolution) follow the order H2SRu3(CO)9 > HSRu2Co(CO)9 > SRuCo2(CO)9 > [Co3S2(CO)7]2. Significant amounts of H2O are detected as products of cluster decomposition on alumina. TPD/MS data of H2SRu3(CO)9 labeled with (CO)-O-18 indicate that the H2O evolved is mostly formed from the alumina surface and not from cluster-bound carbonyls. Kinetics measurements at 150-degrees-C show that the mixed-metal cluster catalysts are more active for thiophene desulfurization than catalysts containing only one metal component. This trend is reversed at higher temperatures and for catalysts sulfided at 400-degrees-C; that is, the mixed-metal catalysts are less active for thiophene desulfurization than catalysts containing only one metal component. The carbon-supported cluster catalysts are more active for thiophene hydrodesulfurization and more selective for butane formation than catalysts supported on gamma-Al2O3.