STRUCTURAL CHARACTERIZATION OF RHODIUM-CONTAINING HYDRODESULFURIZATION (HDS) CATALYSTS DERIVED FROM A LASER VAPORIZATION CLUSTER SOURCE

A series of highly dispersed Rh-based materials have been prepared by deposition of laser-generated gas-phase clusters onto an industrial-gr ade alumina. While the diameter of the gas-phase metal clusters could be kept at or below 1 nm, the average diameter of the resulting suppor ted Rh particles was always at least 1.5 nm. The reaction of the clust ers with either O-2 or C2H4 failed to prevent Rh aggregation on the al umina surface. The addition of O-2 upstream of the Rh target was suffi cient to form bulk Rh2O3, whereas downstream addition of O-2 or C2H4 t o the Rh clusters was insufficient to form Rh oxide particles. Most of the Rh-containing particles further aggregated during either sulfidin g or HDS testing. Nevertheless, the resulting rhodium sulfides were co mparable in activity to sulfided, commercial Co-Mo or Ni-Mo catalysts on a per gram of catalyst basis and superior on a per gram of metal ba sis. At low loadings (0.1 wt%), the cluster-derived catalysts were mor e hydrogen-efficient than the commercial catalysts. (C) 1997 Academic Press.