Surface species formed during CO and CO{sub 2} hydrogenation over Rh/TiO{sub 2}(W{sup 6+}) catalysts investigated by FTIR and mass spectroscopy

Journal Article · Fri Sep 15 04:00:00 EDT 1995 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1995.1229· OSTI ID:273839

Zhang, Z; Kladi, A; Verykios, E ^[1]

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1. Univ. of Patras (Greece)

Surface species formed over Rh/TiO{sub 2} (W{sup 6+}) catalysts during CO and CO{sub 2} hydrogenation were investigated by in situ FTIR spectroscopy and transient techniques. It was found that at least four carbon-containing species, namely, linear CO, bridged CO, active carbon (C{sub {alpha}}), and less-active carbon (C{sub {beta}}), exist on Rh crystallites, while formate and/or carbonate and/or hydrocarbonate species are on the TiO{sub 2} support. A reduction of CO coverage by 25-40% and a shift of the linear CO band to higher wavenumber values by 10 {approximately} 14 cm{sup -1} were observed under CO and CO{sub 2} hydrogenation upon doping the TiO{sub 2} carrier with small amounts of W{sup 6+} cations (<1 at.%). This implies that the Rh-CO bond is significantly weakened by doping, presumably due to an alteration of the electronic structure of the TiO{sub 2} carrier, which modifies the electronic state of surface Rh via electronic interactions at the metal-support interface. The concentrations of the C{sub {alpha}} and C{sub {beta}} species on Rh crystallites and carbon-containing species on the support were also found to be influenced by doping. While the concentration of the C{sub {alpha}} species (including CH{sub x} species) was reduced and that of the C{sub {beta}} species was enhanced with increasing W{sup 6+} dopant content, the concentration of the carbonate and/or hydrocarbonate species on the carrier exhibited a maximum at a W{sup 6+} content of 0.11 {approximately} 0.22 at.%. It is reasoned that hydrogen chemisorption is favored on the doped catalysts, as the CO coverage and the strength of the Rh-CO bond are significantly reduced. This has twofold consequences which result in a large increase of the CO and CO{sub 2} hydrogenation activity. 47 refs., 11 figs., 3 tabs.

• OSTI ID: 273839
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 156; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

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