The Effect of La2O3 on Pd Close-Coupled Catalysts

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Palladium close-coupled catalysts were prepared by impregnation method with different amounts of La 2 O 3 as a promoter. Low temperature N 2 adsorption-desorption, X-ray diffraction, H 2 -temperature programmed reduction (H 2 -TPR), CO-chemisorption, and X-ray photoelectron spectroscopy (XPS) were used to characterize the effect of La 2 O 3 on the physicochemical properties of the prepared catalysts. Their catalytic activities toward C 3 H 8 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 La 2 O 3 significantly improves catalytic performance and enhances the thermal resistance of the catalysts. H 2 -TPR results suggest that the addition of La 2 O 3 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 La 2 O 3 also improves the dispersion of the Pd species and decreases the mean particle size of palladium. The optimal loading amount of La 2 O 3 is 10%. ：采用浸渍法制备了不同 La 2 O 3 含量的 Pd 密偶催化剂. 使用低温 N 2 吸附-脱附、X 射线衍射、H 2 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 La 2 O 3 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, La 2 O 3 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. H 2 -TPR 结果表明 La 2 O 3 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, La 2 O 3 的添加提高了 Pd 物种的分散, 降低了 Pd 的平均颗粒度. La 2 O 3 的最佳添加量为 10%. Adding La 2 O 3 to Pd close-coupled catalysts as a promoter can improve their catalytic performance toward C 3 H 8 conversion and the optimum La 2 O 3 content is 10%.