|Author||Haruta, M. ♦ Tsubota, S. ♦ Kobayashi, T. ♦ Kageyama, H. ♦ Genet, M. J.|
|Source||United States Department of Energy Office of Scientific and Technical Information|
|Subject Keyword||INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY ♦ COAL, LIGNITE, AND PEAT ♦ CARBON MONOXIDE ♦ OXIDATION ♦ GOLD COMPLEXES ♦ CATALYTIC EFFECTS ♦ ABSORPTION SPECTROSCOPY ♦ CATALYST SUPPORTS ♦ CHEMICAL REACTION KINETICS ♦ COBALT OXIDES ♦ HETEROGENEOUS CATALYSIS ♦ IRON OXIDES ♦ SORPTIVE PROPERTIES ♦ TEMPERATURE DEPENDENCE ♦ TEMPERATURE RANGE 0065-0273 K ♦ TEMPERATURE RANGE 0273-0400 K ♦ TITANIUM OXIDES ♦ CARBON COMPOUNDS ♦ CARBON OXIDES ♦ CATALYSIS ♦ CHALCOGENIDES ♦ CHEMICAL REACTIONS ♦ COBALT COMPOUNDS ♦ COMPLEXES ♦ IRON COMPOUNDS ♦ KINETICS ♦ OXIDES ♦ OXYGEN COMPOUNDS ♦ REACTION KINETICS ♦ SPECTROSCOPY ♦ SURFACE PROPERTIES ♦ TEMPERATURE RANGE ♦ TITANIUM COMPOUNDS ♦ TRANSITION ELEMENT COMPLEXES ♦ TRANSITION ELEMENT COMPOUNDS ♦ Chemical & Physicochemical Properties ♦ Coal, Lignite, & Peat- C1 Processes- (1987-)|
|Abstract||Gold can be highly dispersed on a variety of metal oxides by coprecipitation and deposition-precipitation followed by calcination in air. The small gold particles are hemispherical in shape and stabilized by epitaxial contact, dislocations, or contact with an amorphous oxide layer. Such supported gold differs in catalytic nature from unsupported gold particles and exhibits high catalytic activities for low-temperature oxidation of CO. Especially, gold supported on TiO[sub 2], [alpha]-Fe[sub 2]O[sub 3], Co[sub 3]O[sub 4], NiO, Be(OH)[sub 2], and Mg(OH)[sub 2] is very active even at temperatures below 0[degrees]C. Among the gold catalysts supported on TiO[sub 2], [alpha]-Fe[sub 2]O[sub 3], and Co[sub 3]O[sub 4] the turnover frequencies for CO oxidation per surface gold atom are almost independent of the kind of support oxides used and increase sharply with a decrease in diameter of gold particles below 4 nm. Small gold particles not only provide the sites for the reversible adsorption of CO but also appreciably increase the amount of oxygen adsorbed on the support oxides. In the temperature range -10 to 65[degrees]C, the activation energies for CO oxidation were 8.2 kcal/mol (Au/TiO[sub 2]), 8.4 kcal/mol (Au-[alpha]-Fe[sub 2]O[sub 3]), and 3.9 kcal/mol (Au/Co[sub 3]O[sub 4]). The rate of CO oxidation is zero order with respect to CO for the three catalysts, and 0.2-0.3 for Au/TiO[sub 2] and Au/Co[sub 3]O[sub 4] and zero order for Au/[alpha]-Fe[sub 2]O[sub 3] with respect to O[sub 2]. By taking into consideration TPD and FT-IR data, a mechanism is proposed in which CO adsorbed on gold particles migrates toward the perimeter on support oxides and there it reacts with adsorbed oxygen to form bidentate carbonate species. The decomposition of the carbonate intermediate is considered to be rate-determining. 57 refs., 13 figs., 1 tab.|
|Learning Resource Type||Article|
|Publisher Place||United States|
|Journal||Journal of Catalysis|
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