Studies on the active species and on dispersion of Cu in Cu/SiO2 and Cu/Zn/SiO2 for hydrogen production via methanol partial oxidation

The partial oxidation of methanol to hydrogen (CH3OH+12O2→2H2+CO2) was investigated over Cu/SiO2 and Cu/Zn/SiO2 catalysts prepared by deposition–precipitation method. The effects of Cu loadings in Cu/SiO2 and different Cu/Zn ratios in Cu/Zn/SiO2 catalysts on activities have been investigated in detail. The kinetic results show that the catalyst with 10% Cu loading (Cu/Zn 7:3) exhibits the highest CH3OH conversion and H2 selectivity than other catalysts. The results of XRD and XPS characterizations indicate that Cu0 species in catalysts is an active species for high activity, but Cu+ species inhibits the partial oxidation of methanol to hydrogen. The appropriate introduction of Zn results in higher dispersion of Cu0, which leads to high activity of the catalysts for hydrogen generation. However, overloading of Zn results in the formation of bigger crystallites of Cu2O in the catalyst which decreases the activity of the catalyst.