Surface characterization of copper(II) oxide-zinc oxide methanol-synthesis catalysts by x-ray photoelectron spectroscopy. 1. Precursor and calcined catalysts

TLDR: A surface characterization of the precursor and calcined copper oxide-zinc oxide (CuO-ZnO) catalysts prepared both by coprecipitation and by impregnation methods was carried out by using x-ray photoelectron spectroscopy (XPS) as mentioned in this paper.

Abstract: A surface characterization of the precursor and calcined copper oxide-zinc oxide (CuO-ZnO) catalysts prepared both by coprecipitation and by impregnation methods was carried out by using x-ray photoelectron spectroscopy (XPS). Strong oxide-oxide interactions were found to result in the formation of several surface copper species in the coprecipitated catalysts. With the catalysts containing 80-30 wt % CuO, it is proposed that the CuO structure is distorted to produce amorphous copper oxide phases in the surface layer. The copper species in the catalysts with > 80 wt % CuO are composed of the Cu/sup 2 +/ ions in crystalline CuO and the amorphous phases. As for the catalysts containing less than 30 wt % CuO XPS results showed the presence of Cu/sup 2 +/ ions, which dissolved substitutionally in the ZnO lattice and formed highly covalent bondings with oxygen anions. In contrast to the coprecipitated catalysts, the impregnated catalysts showed no appreciable interactions between copper and zinc oxides. The surface copper species in the precursor catalysts were attributed to copper hydroxycarbonate in the high copper content catalysts and to the copper in zinc hydroxycarbonate in the low copper content catalysts. 5 figures, 3 tables.