ChemInform Abstract: Hydrogenation of Carbon Dioxide over Copper‐Zirconia Catalysts Prepared by in situ Activation of Amorphous Copper‐Zirconium Alloy.

Abstract

Abstract Amorphous Cu 7 Zr 3 has been applied as precursor for the preparation of copper on zirconia catalysts used for carbon dioxide hydrogenation. The catalysts were prepared by in situ activation of the precursor in CO 2 /H 2 and CO/H 2 reactant gas mixtures. During this activation, the initially low activity of the amorphous alloy increased largely and reached finally a steady state. Structural and chemical changes of the amorphous precursor during its transition to the active stable catalysts were investigated using gas adsorption, X-ray diffraction, N 2 O-titration, Auger electron spectroscopy and scanning electron microscopy. The as-prepared catalysts consisted of copper predominantly present as metal particles and stabilized by amorphous zirconium dioxide. XRD indicated that the metallic copper particles existed in two forms, as small, probably disordered particles and as larger crystalline particles. The most important changes the amorphous CuzZr alloy underwent during in-situ activation were: (i) oxidation of zirconium to zirconium oxides; (ii) segregation of copper from the bulk onto the surface; and, (iii) partial crystallization. The activity and the selectivity behaviour of the Cu/ZrO 2 derived from the amorphous Cu 7 Zr 3 alloy were found to be similar as those of Cu/ZrO 2 prepared by coprecipitation of the corresponding metal nitrates. This suggests that the copper sites active for carbon dioxide hydrogenation are in both preparations of similar nature.