稀土氧化物修饰的Cu-ZnO-Al_2O_3/HZSM-5催化剂二氧化碳加氢一步制备二甲醚的研究

Study on Cu-ZnO-Al_2O_3/HZSM-5 catalyst modified by rare earth oxides for direct synthesis of dimethyl ether by hydrogenation of carbon dioxide

本文采用高压固定床反应装置考察了添加2%稀土氧化物(La2O3和CeO2)的Cu-ZnO-Al2O3/HZSM-5催化剂CO2加氢一步合成二甲醚的催化性能。XRD和H2-TPR结果分析发现,添加稀土氧化物后阻止了部分Cu2+还原为非晶态Cu。在513K,反应压力为3.0MPa,反应空速为1000h-1的条件下,考察了CO2加氢一步合成二甲醚的催化性能。结果表明,添加La2O3和CeO2后,催化剂的催化活性以及二甲醚的选择性均大幅提高,反应20h,CO2转化率以及二甲醚选择性变化较小,说明该催化剂稳定性较好。

Direct synthesis of dimethyl ether （DME） from carbon dioxide by catalytic hydrogenation on Cu- ZnO-A1203/HZSM-5 catalyst modified by rare earth oxides （La203 and CeO2） was studied with the high pressure fixed bed reactor. The XRD and H2-TPR results indicated that the reduction of little of Cu2 ion were prevented. The catalytic properties of the catalyst was investigated at the 513K temperature, 3MPa reaction pressure and 1000h-t space velocity. The higher CO2 conversion was obtained on the Cu-ZnO-A12OJHZSM-5 catalyst modified by rare earth oxides. The stability of amorphous catalyst Cu-ZnO-A1203-CeO2/HZSM-5 was investigated by follow reaction conditions： 513K, 3 MPa, feed gas mixture carbon dioxide： hydrogen=l：4, reaction space velocity： 1000hq. The results showed that the CO2 conversion and DME selectivity change to a lesser extent within 20 hours, indicat- ing better stability of the catalyst.