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Co/Al2O3 and Co/Al2O3–BaO catalysts with low cobalt loading (0.1, 0.3 and 1 wt%) for the selective catalytic reduction (SCR) of NO x by C3H6 were prepared. The distribution of cobalt species was investigated by UV–vis diffuse reflectance spectroscopy and by H2-TPR in order to identify the active cobalt species in hydrocarbons (HC)-selective catalytic reduction (SCR). It was found that the nature of cobalt species strongly depends on the cobalt loading as well as on the properties of the support. The barium addition to the alumina slows down solid state diffusion processes, improving the thermal stability of the support and preventing diffusion of cobalt into the bulk. Highly dispersed surface Co2+ species over alumina were identified as active sites in the NO-SCR process. Accordingly, a high concentration of surface Co2+ sites in Co 1 wt%/Al2O3 improves the catalytic performance in NO-SCR, the long term stability as well as the water tolerance. On the contrary, the formation of Co3O4 particles in Co 1 wt%/Al2O3–BaO promotes the propylene oxidation by oxygen, decreasing the activity and selectivity of the catalyst in NO reduction. [ABSTRACT FROM AUTHOR]

The catalytic performance and the sulphur resistance of a Pd (0.7 wt%) catalyst supported over Co3O4(30 wt%)–CeO2(70 wt%) mixed oxide were investigated in the oxidation of methane under stoichiometric and lean conditions. The catalytic behaviour was compared with that of two reference catalysts, palladium supported over pure Co3O4 and CeO2. Catalysts were characterized by XRD, BET, XPS and FTIR measurements. Regeneration by a CH4-reducing treatment at 600 °C was investigated. [ABSTRACT FROM AUTHOR]

A catalyst with 0.7 wt% Pd load supported over Co3O4 oxide was investigated in the methane oxidation by operating under CH4/O2 stoichiometric conditions. The effect of the noble metal addition on the activity of bare Co3O4 was evaluated. Samples were characterized by BET, XRD, TPR and XPS analyses. The SO2 poisoning of Pd catalyst and Co3O4 was studied by performing CH4 oxidation tests under stoichiometric conditions in SO2 (1 ppm or 10 ppm). Experiments evidenced that in our conditions the low amount of SO2 doesn’t influence the Pd behaviour, whereas in presence of 10 ppm of SO2 some deactivation occurs that becomes more evident above 450 °C at which the catalyst doesn’t reach 100% of methane conversion. Catalytic tests performed over Co3O4 and the Pd supported catalyst, after a treatment at 350 °C for 15 h in 10 ppm SO2/He, suggest that Co3O4 is a sulphating support, as confirmed by XPS analysis. Therefore, an important role in lowering the sulphur poisoning of Pd may be played by Co3O4. [ABSTRACT FROM AUTHOR]

The reduction of a Pt 1%/Ce0.6Zr0.4O2 catalyst by CO in the absence of gaseous oxygen was studied by transient reactivity tests, temperature programmed surface reaction with CO, flow thermogravimetric tests and DRIFTS experiments, in order to obtain information generally on the OSC properties and, specifically, on the mechanism of CO oxidation over both, Pt catalyst and support-only sample (Ce0.6Zr0.4O2). The results of thermogravimetric experiments showed the presence of an induction time in the weight change % of the catalyst, depending on the CO concentration in the gas flow. This induction time could be related to the presence of two oxygen reactive sites. The first one leads to strongly chemisorbed CO2 or carbonate species, while the second, tentatively related to Pt/support interface sites, generates weakly chemisorbed CO2 species in reversible equilibrium with gaseous CO2. The concentration of CO and the presence of a co-feeding of gaseous CO2 significantly and non-linearly affected the presence and reactivity of these Pt/support interface sites, although the details of this effect should be better understood. [ABSTRACT FROM AUTHOR]

The reduction of a Pt 1%/Ce0.6Zr0.4O2 catalyst by CO in the absence of gaseous oxygen was studied by transient reactivity tests, temperature programmed surface reaction with CO, flow thermogravimetric tests and DRIFTS experiments, in order to obtain information generally on the OSC properties and, specifically, on the mechanism of CO oxidation over both, Pt catalyst and support-only sample (Ce0.6Zr0.4O2). The results of thermogravimetric experiments showed the presence of an induction time in the weight change % of the catalyst, depending on the CO concentration in the gas flow. This induction time could be related to the presence of two oxygen reactive sites. The first one leads to strongly chemisorbed CO2 or carbonate species, while the second, tentatively related to Pt/support interface sites, generates weakly chemisorbed CO2 species in reversible equilibrium with gaseous CO2. The concentration of CO and the presence of a co-feeding of gaseous CO2 significantly and non-linearly affected the presence and reactivity of these Pt/support interface sites, although the details of this effect should be better understood. [ABSTRACT FROM AUTHOR]