Supported Binary Oxide Catalysts Containing CuO Coupled with Ga2O3 and SnO2

Two series of binary oxide catalysts (CuGa/SA and CuSn/SA) containing CuO coupled with Ga2O3 or SnO2 were prepared by dispersing the metal phases onto a high surface area acidic silica-alumina ( SA) support by an adsorption method. Similar total amounts of metals ( about 1.6 atom(Met) center dot nm(-2)) were deposited onto the support, in different proportions, to obtain samples with weight percent of copper varying from 3.3 to 6.5% The SA support was first covered by the copper precursor, Cu(C2H3O2)(2), and then gallium (Ga(NO3)(3) center dot H2O) or tin (SnCl4 center dot 5H(2)O) precursors were deposited on the dried Cu-containing sample. The calcined materials were characterized by surface techniques (N-2 adsorption and XPS), to detect the surface morphology and chemical state of metal species, and by FT-IR and adsorption calorimetry after CO adsorption. Nanosized metal phases were observed in every case. Besides Cu(II), the surfaces contained Cu(I) as well as Cu(delta(+)) ions ( with 1 < delta < 2) stabilized by the interaction with the acid centers of the support. Gallium oxide preferentially covered the copper oxide phase, while tin dioxide mainly deposited on the bare surface of the support. The reducibility properties of the different supported metal oxides were investigated by TPR from both the qualitative and quantitative points of view. The catalytic performances of the simple and binary surfaces were comparatively studied in different reactions ( decomposition and reduction of N2O and NO, and CH4 combustion) considered as test reactions to investigate the reducing or oxidizing properties of the materials. The observed differences in catalytic activity among the catalysts are discussed in relation with the surface composition and properties.