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%.
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 fiom 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%.
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