The Effect of La2O3 on Pd Close-Coupled Catalysts

Palladium close-coupled catalysts were prepared by impregnation method with different amounts of La2O3 as a promoter. Low temperature N2 adsorption-desorption, X-ray diffraction, H2-temperature programmed reduction (H2-TPR), CO-chemisorption, and X-ray photoelectron spectroscopy (XPS) were used to characterize the effect of La2O3 on the physicochemical properties of the prepared catalysts. Their catalytic activities toward C3H8 conversion were evaluated using a gas mixture that simulates the emissions from a gasoline engine. The results of catalytic activity indicate that the presence of La2O3 significantly improves catalytic performance and enhances the thermal resistance of the catalysts. H2-TPR results suggest that the addition of La2O3 increases the reductive ability of the catalysts and shifts the reduction temperature to a lower value. The XPS and CO-chemisorption results indicate that doping by La2O3 also improves the dispersion of the Pd species and decreases the mean particle size of palladium. The optimal loading amount of La2O3 is 10%.

摘要：采用浸渍法制备了不同 La2O3 含量的 Pd 密偶催化剂. 使用低温 N2 吸附-脱附、X 射线衍射、H2 程序升温还原、CO 化学吸附和 X 射线光电子能谱等技术考察了 La2O3 对催化剂性能的影响. 模拟汽车尾气条件考察了催化剂上丙烷的转化活性. 活性测试结果表明, La2O3 的添加能显著提高催化剂对丙烷的转化活性和催化剂的热稳定性. H2-TPR 结果表明 La2O3 的添加降低了催化剂的还原温度, 提高了催化剂的氧化还原性能. CO 化学吸附和 XPS 结果表明, La2O3 的添加提高了 Pd 物种的分散, 降低了 Pd 的平均颗粒度. La2O3 的最佳添加量为 10%.

Adding La2O3 to Pd close-coupled catalysts as a promoter can improve their catalytic performance toward C3H8 conversion and the optimum La2O3 content is 10%.Figure optionsDownload as PowerPoint slide