Hydrogenation of CO2 over skeletal copper surfaces containing precipitated ZnO

Catalysts have been prepared by precipitating different amounts of ZnO on the surface of skeletal copper particles. The precursor copper catalysts were prepared by fully leaching CuAl2 particles with concentrated NaOH solutions in the presence and absence of sodium chromate. The resulting catalysts contained surface zinc oxide concentrations in the range 0-1.36 mg per m(2) of catalyst surface. The influence of different concentrations of ZnO on the surface of skeletal copper was examined by the hydrogenation of CO2 using a mixture of 24% CO2/76% H-2 at 4 MPa, 493-533 K and space velocities up to 410 700 h(-1): The catalysts were found to be highly active and selective for methanol synthesis. Methanol synthesis activity increased linearly with ZnO loadings with a maximum being reached at a loading of around 1.1 mg m(-2) for higher surface area skeletal copper prepared by leaching in the presence of chromate. ZnO loadings were also shown to improve the selectivity of CO2 hydrogenation over copper by reducing the formation of CO by the reverse water-gas shift reaction.