CeO_2及其含量对Au-Pd/ZnO催化剂甲醇部分氧化制氢性能的影响

Effect of CeO_2 on the performances of CeO_2-ZnO supported Au-Pd catalysts for hydrogen production by methanol partial oxidation

采用聚合物保护乙醇还原法制备了不同Zn/Ce摩尔比的Au-Pd/ZnO-CeO2催化剂,考察了CeO2掺入量对Au-Pd/ZnO-CeO2催化剂甲醇部分氧化制氢反应性能的影响,并运用XRD、TPR、CH3OH(CO2)-TPD、比表面积测定等技术对催化剂进行了表征。结果表明,CeO2的掺入提高了Au-Pd/ZnO催化剂的活性、氢选择性和稳定性,当n(Zn)/n(Ce)=7/3时催化剂活性最佳,598K甲醇的转化率和氢气选择性分别达到99%和64%,反应20h后催化剂的活性仍保持在95%以上。这归因于在该摩尔比时载体的比表面积最大、活性组分与载体的相互作用最强、催化剂的碱中心和对反应物甲醇的吸附量最大,这些均有利于甲醇部分氧化制氢反应性能的提高。

The Au-Pd/ZnO-CeO2 catalysts with different Zn/Ce ratios were prepared by poly （N-vinyl-2-pyrrolidone）（PVP）-stabilized ethanol reduction method, and the effects of ceria on the catalytic performances of Au-Pd/ZnO-CeO2 catalysts for partial oxidation of methanol were investigated. XRD, TPR, TPD and nitrogen adsorption-desorption were used to characterize the properties of the catalysts. The results showed that the addition of ceria could improve the activity, hydrogen selectivity and stability of the Au-Pd/ ZnO catalysts, and the best catalytic activity （99% methanol conversion） and hydrogen selectivity （64%） were obtained over the catalyst with the Zn/Ce molar ratio of 7：3 at 598 K, and the methanol conversion remained above 95% after 20 hours reaction over this catalyst. The support with the Zn/Ce molar ratio of 7：3 had the largest surface area, the strongest interaction between the active species and the support, and the most alkali sites and absorption of methanol in the catalyst, and all of these were advantageous to the catalytic performance enhancement.