Study of promoted Cu/ZnO and Cu/ZrO2 catalysts for dimethyl adipate hydrogenolysis†
Abstract
Two supports (ZnO, ZrO2) and four promoters (Al2O3, ZnO, CoOx, NiO) were investigated to design environmentally-friendly Cu-based hydrogenolysis catalysts. Both catalyst characterization and activity in dimethyl adipate hydrogenolysis were described. While ZrO2 improved the reducibility of CuO nanoparticles, these particles were less stable under reaction conditions. ZnO provided better stabilization and reduced coke formation. CoOx, used as a promoter, increased the surface availability of dissociated H2 and stabilized Cu nanoparticles with a high surface area. Conversely, Al2O3 or NiO promoters improved neither catalyst performance nor selectivity due to the higher number of acid–base sites. The essential role of ZnO, whether used as support or a single promoter, was attributed to Cu–ZnO synergy that enhanced the activity in dimethyl adipate hydrogenolysis and improved desired selectivity to hexane-1,6-diol. Overall, the hydrogenolysis activity (TOFH) was 5 times higher for ZnO-supported catalysts.