助剂对Cu-ZnO-Al_2O_3-SiO_2催化剂性质和催化性能的影响

EFFECT OF PROMOTERS ON THE CATALYTIC PERFORMANCE AND PROPERTIES OF Cu - ZnO -AI_2O_3 - SiO_2 CATALYSTS

研究了助剂MgO、TiO2、ZrO2等对CO2直接加氢合成二甲醚的Cu-ZnO-Al2O3-SiO2催化剂性质和催化性能的影响,并用XRD、XPS、H2-TPD、CO2-TPD、H2-TPR等手段进行了表征。结果表明,助剂不同程度地促进了CuO和ZnO的分散;降低了Cu-ZnO-Al2O3-SiO2催化剂的TPR还原温度;加入的助剂富集于催化剂表面,除ZrO2以外的其他助剂均降低了催化剂表面Cu原子的浓度;助剂对H2、CO2吸附中心有调变作用;活性评价结果表明,CO2的转化率与表面Cu原子的浓度和催化剂吸附氢的能力有关,ZrO2是CO2加氢制二甲醚Cu-ZnO-Al2O3-SiO2催化剂的优良助剂。

Effect of various promoters(MgO,TiO2, ZrO2) on the performance and properties of Cu - ZnO-Al2O3 - SiO2 catalysts for the direct synthesis of dimethyl ether (DME) from CO2 hydrogenation were investigated. These catalysts were examined by using techniques of XRD,XPS,H2 - TPD,CO2 - TPD,H2 -TPR. The results show that in all catalyst systems promoters improve the dispersion of CuO, ZnO in different extent and decrease the reduction temperature of Cu - ZnO - Al2O3 - SiO2 catalysts. The promoters added are accumulated on the catalysts' surface, presencing of MgO or TiO12brings about decrease of Cu concentration on the catalyst surface while that of ZrO2 increases the surface concentration of Cu. The promoters also have the adjustment action of adsorption center to H2 and CO2 of Cu - ZnO - Al2O3 - SiO2 catalysts. The catalytic activity indicates that conversion rate of CO2 is related to the surface concentration of Cu and the adsorption ability of catalysts to H2, ZrO2 is a favorable promoter for the conversion of CO2 hydrogenation to dimethyl ether.