载体对草酸二甲酯加氢铜基催化剂的影响

以草酸二甲酯加氢反应为基础,研究了二氧化硅载体对铜基催化剂加氢反应性能的影响。催化剂分别以气相硅溶胶、硅胶、二氧化硅为载体,采用沉淀沉积法制备了Cu/SiO2催化剂(wCu=0.20),分别记为CS1、CS2、CS3,催化剂的活性从CS3、CS2到CS1依次增加。XRD测试物相结构表明:氧化态CS2和CS3中存在CuO晶相,而氧化态CS1中活性组分呈无定形分布。还原态催化剂的XRD测试表明催化剂中有Cu2O和Cu0存在,且Cu2O/Cu0的比例按CS3、CS2、CS1顺序增加,XPS分析证实了3个催化剂表面Cu2O/Cu0的比例有相应的变化趋势。这说明Cu2O和Cu0与草酸二甲酯加氢反应活性相关,提高Cu2O的含量,可以提高催化剂的活性。

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.