Do metal-oxide promoters of Cu hydrogenolysis catalysts affect the Cu intrinsic activity?

Abstract

The well-established ester hydrogenolysis process has to be further improved to reduce its high energy demand and to replace used Adkins CuCr catalysts by chromium-free alternatives. In this study, the copper-based catalyst was modified by ZnO, ZnO with Al2O3 or MgO to elucidate the metal-oxide influence on catalyst structure, activity, performance and stability in ester hydrogenolysis. The catalysts composition, structure and physico-chemical properties were examined by AAS, XRD, TPR, BET, N2O-RFC, TGA-MS, NH3-TPD and CO2-TPD. It was confirmed that copper itself possesses high intrinsic activity for ester hydrogenolysis but the unpromoted copper species were very unstable. All used metal oxides were proven to be structural promoters stabilizing copper species and increasing the number of active sites. Consequently, they enhanced remarkably catalyst performance in dimethyl adipate conversion despite the decreased intrinsic activity of Cu active sites. All prepared catalysts outperformed a commercial CuCr catalyst in dimethyl adipate hydrogenolysis.