Ceria as a new support of noble metal catalysts for hydrocarbon reactions:chemisorption and catalytic studies

Metal/cerium-oxide systems were practically not studied in hydrocarbon reac tions. Chemisorption properties-in temperature programmed reduction, hydrog en adsorption, and H-2/O-3 titration-and catalytic behavior of ceria-suppor ted Pt and Ph catalysts with different metal loadings and with two pre-redu ction temperatures (LTR, T-R= 573 K and HTR, T-R= 773 K) were investigated. Pt/CeO2 was tested in transformation of n-hexane while Rh/CeO2 in ring ope ning of methylcyclopentane (MCP), Higher spillover activity was found for t he LTR Ph samples than for HTR ones. The opposite was true for Pt. The Rh/c eria samples showed ordinary catalytic behavior: structure insensitivity wa s observed for the first C-C bond cleavage of MCP on Rh/ceria and the furth er reaction of the ring opening intermediates was affected by the surface h ydrogen concentration. The Pt/LTR samples showed catalytic properties simil ar to EUROPT-1, while the HTR samples were different, namely the higher spi llover activity caused high C-5-cyclization selectivity on the catalyst wit h low metal loading, and surprisingly high hydrogenolysis selectivity on th at with higher metal loading. (C) 2001 Elsevier Science B.V. All rights res erved.