Effect of Supports on Copper-Based Catalysts for Dimethyl Oxalates Hydrogenation

Catalytic hydrogenation of dimethyl oxalate was studied over copper catalyst supported on three kinds of silica: silica sol, silica gel, fumed silica, named CS1, CS2, CS3 respectively. The Cu/SiO_2 catalyst supported on silica sol was prepared by the homogeneous deposition-precipitation of the mixture of aqueous cuprammonia complex and silica sol. Those catalysts supported on silica gel and fumed silica were obtained by the heterogeneous deposition-precipition of aqueous solution of Cu(NO)_3 and ammonia. (Activity) evaluation results show that at 468 K, the catalyst CS1 presents best performance. XRD (X-ray diffraction) patterns show there are CuO on oxidized catalysts CS2 and CS3, but not on oxidized CS1. (After) reduction,the content of Cu_2O increases from CS3 to CS1.XPS(X-ray photoelectron spectroscopy)analysis indicates that the ratio of Cu_2O/Cu~0 also increases as with the same sequences. These results suggest that the activity of catalyst is improved with the increase of Cu_2O.