Effect of preparation method on structure and catalytic activity of Cr-promoted Cu catalyst in glycerol hydrogenolysis

Relationships between surface structure and catalytic properties were investigated for a series of copper chromium catalysts. The catalysts were prepared using methods involving impregnation and precipitation, and their catalytic activities were evaluated for the hydrogenolysis of glycerol. Catalyst (10I and 50I) prepared by the impregnation method contained a mixed phase of both individual copper and chromium oxide structures, while the catalyst (50P) prepared by precipitation showed a single phase, with a copper chromite spinet structure (CuCr2O4). XPS data indicated that, after the reduction step, the copper species in the impregnated catalyst was reduced to Cu-0, but the catalyst prepared by the precipitation method retained a spinet structure evidenced by the large amount of Cu2+ species. In hydrogenolysis reactions, the precipitated catalyst showed a higher catalytic activity than the impregnated catalyst. Thus, the reduced copper chromite spinet structure, which constitutes a single phase, appears to be responsible for the high catalytic activity in the hydrogenolysis of glycerol to propylene glycol.