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Abstract: Sm2O3 doped ZrO2-based catalysts (Sm2O3–ZrO2 composite oxide) were prepared by co-precipitation and their physical properties (texture and structure) and chemical properties (acid–base and redox) were characterized with the methods of N2 adsorption–desorption isotherm, powder X-ray diffraction, Raman spectroscopy, NH3 and CO2 temperature programmed desorption and H2 temperature programmed reduction. The catalytic performances of the catalysts (activity and selectivities) were evaluated in the CO hydrogenation to isobutene and isobutane (isosynthesis) under the reaction conditions of 673K, 5.0MPa, and 650h−1. The relationship between the catalytic performance and the physical/chemical properties of Sm2O3–ZrO2 catalysts were also examined. The catalytic activity and selectivity of the Sm2O3–ZrO2 catalysts varied with Sm2O3 doping. The physical properties of the catalysts, such as cumulative pore volumes, average pore diameters and crystal sizes had some influences on the activity and selectivity in the isosynthesis. CO conversion increased with an increase in the amount of the acidic sites on the surface of Sm2O3–ZrO2 catalysts, while iso-C4 percentage in total hydrocarbons increased with an increase in the amount of the basic sites. The addition of Sm2O3 into ZrO2 enhanced the reducibility of Sm2O3–ZrO2 catalysts. The highest CO conversion (21.6%) and C4 selectivity (41.8%) were obtained over the catalyst that had a maximum amount of H2 consumptions (57.7μmolg−1) in the TPR measurement for Sm2O3–ZrO2 catalysts. A coordination of the acid–base properties and the redox property may play important role for the improvement of the catalytic performances of the isosynthesis. [Copyright &y& Elsevier]

Enhancement of methanol selectivity in the products of the direct selective oxidation of methane with CH4-O2-NO in a gas-phase reaction was examined using a Cu-ZnO/SiO2 catalyst. Two types of Cu-ZnO/SiO2 catalysts were prepared with different compositions: 3:7:90 (denoted as CZS-1) and 5:5:90 (CZS-2) as the weight percent ratios of CuO:ZnO:SiO2. Both CH3OH and CH2O were observed as C1-oxygenates at 550 °C in the gas-phase selective oxidation of CH4 in CH4-O2-NO without a catalyst, but then only CH3OH was observed in the presence of the CZS-1, in addition to the direct gas-phase selective oxidation of methane. The catalyst temperature was 250 °C and the reaction pressure was 0.4 MPa. CH3OH, CO and CO2 selectivities increased and CH2O selectivity decreased in the presence of the Cu-ZnO/SiO2, in comparison to the values in the absence of the catalyst. We, therefore, suggested that three reactions: i.e. the hydrogenation reaction of CH2O, the dissociation reaction of CH2O, and the WGSR, progressed simultaneously on the Cu-ZnO/SiO2 catalyst in CH4-O2-NO.Since the selectivity of CH3OH did not vary during the variation of reaction temperatures from 150 °C up to 350 °C over the Cu-ZnO/SiO2 catalyst, we assumed that SiO2 was a favorable support to enhance the selectivity of CH3OH in a wider catalyst temperature region. [Copyright &y& Elsevier]