Cu-ZnO-Al_2O_3-ZrO_2/HZSM-5催化剂上CO_2加氢合成二甲醚

采用共沉淀法和机械混合法合成了Cu-ZnO-Al2O3-ZrO2/HZSM-5双功能催化剂,研究了该催化剂催化CO2加氢合成二甲醚反应的性能,考察了HZSM-5分子筛的硅铝比、反应温度和反应压力对CO2转化率、二甲醚选择性和收率的影响。实验结果表明,随硅铝比的增大,二甲醚选择性和收率呈峰形变化特性;随反应温度的升高,CO2转化率增加,二甲醚选择性降低;而随反应压力的升高,二甲醚选择性增加。当硅铝比(n(SiO2)∶n(Al2O3))为50、反应温度和压力为250℃和3.0 MPa时,CO2转化率达到19.6%,二甲醚的选择性和收率分别为47.0%和9.2%。H2-TPR,NH3-TPD,XRD表征结果显示,Cu-ZnO-Al2O3-ZrO2/HZSM-5双功能催化剂中HZSM-5分子筛的结构没有明显变化,但硅铝比的变化影响双功能催化剂的酸性,HZSM-5分子筛的加入使Cu的还原温度降低。

Synthesis of Dimethyl Ether by CO2 Hydrogenation over Cu-ZnO-Al2O3-ZrO2/HZSM-5 Catalyst

Cu-ZnO-Al2O3-ZrO2/HZSM-5 bifunctional catalysts were prepared by coprecipitation and mechanical mixing method,and were characterized by means of H2-TPR,NH3-TPD and XRD.The hydrogenation of CO2 to dimethyl ether(DME) over the catalysts was studied.The effect of n(SiO2)∶n(Al2O3) in the HZSM-5 zeolite,reaction temperature and pressure on the catalyst performance in the hydrogenation were investigated.The conversion of CO2,and selectivity and yield to DME were 19.6%,47.0% and 9.2% respectively over Cu-ZnO-Al2O3-ZrO2/HZSM-5 catalyst with the n(SiO2)∶n(Al2O3) 50 under the reaction conditions of 250 ℃ and 3.0 MPa.With the rise of reaction temperature,the conversion of CO2 increased while the selectivity to DME decreased.The selectivity to DME increased with the increase of reaction pressure.The characterization results showed that the HZSM-5 zeolite structure was not changed,but surface acid strength of the catalysts was affected by the change of n(SiO2)∶n(Al2O3),and the reduction temperature of Cu decreased due to the addition of HZSM-5 zeolite.