少量CeO_2的添加对Pd/La-Al_2O_3密偶催化剂三效性能的影响  

Effects of the addition of small quantities of ceria on the catalytic behavior of Pd-only close-coupled catalysts during automobile exhaust elimination

作　　者：阳雪[1] 杨林颜 林嗣煜 周仁贤[1] 

机构地区：[1]浙江大学化学系催化研究所,浙江杭州310028

出　　处：《催化学报》2014年第8期1267-1280,共14页

基　　金：supported by the National High Technology Research and Development Program of China (863 Program; 2011AA03A406);Zhejiang Leading Team of Science and Technology Innovation (2009R50020)~~

摘　　要：以La改性的Al2O3为载体,采用共吸附浸渍法制备了一系列不同CeO2含量的单Pd密偶催化剂,并对其进行了表征.PdOx和CeO2之间的强相互作用改善了Pd0再氧化为PdO的能力,同时增强了反应条件下硝酸盐,亚硝酸盐和异氰酸盐在载体上的吸附.因此适量CeO2的添加明显改善了新鲜催化剂对HC和NOx的催化性能,且当CeO2添加量为2%时催化效果最佳.Pd-Ce界面上PdOx和CeO2间强相互作用也使得PdOx物种在高温时仍能以小颗粒的形式分散在载体上,从而显著地提高催化剂的热稳定性.经1100°C高温老化后,CeO2(2%–4%)的存在明显拓宽了HC和NOx的操作窗口,这对于提高单Pd密偶催化剂在汽车尾气处理上的催化性能有重要意义.A series of La‐Al2O3 supported Pd‐Ce close‐coupled catalysts were synthesized by a co‐adsorption impregnation method and subsequently investigated. In the case of fresh catalysts, the presence of an optimal concentration of ceria obviously promoted the catalytic activity during HC and NOx eliminations, owing to the interaction between the palladium oxide species（PdOx） and CeO2 that improves the oxidation of Pd0 to PdO and enhances the adsorption of nitrite/nitrates and isocyanate intermediate species on the support under reaction conditions. Pd‐Ce（2.0）/La‐Al2O3 catalyst（where 2.0 is the wt% of CeO2） exhibited the highest catalytic activity for HC and NO eliminations. Following aging at 1100 °C, the operational window for HC and NOx conversions was broadened and the thermal stability of the catalysts was also improved as a result of the presence of an appropriate quantity of ceria（2.0–4.0 wt%）. The enhanced interactions between PdOx and CeO2 evidently led to the formation of a Pd‐O‐Ce system, stabilizing PdOx species with smaller particle sizes at high tem‐peratures. This result is significant since it suggests a means of improving the catalytic performance of Pd‐only close‐coupled catalysts during automobile exhaust elimination.

关 键 词：单钯密偶催化剂 催化性能 氧化铈 热稳定性 原位红外光谱 

分 类 号：O643.36[理学—物理化学] O614.332[理学—化学]