负载Pd催化剂的表面碱性和NO吸附关系

催化消除汽车尾气中氮氧化物（ＮＯｘ）物种在大气环境保护方面有着重要意义．随着环保法规的越来越严格，研制活性更高，稳定性更好的 ＮＯｘ催化剂势在必行．贵金属 Ｐｔ、Ｐｄ、Ｒｈ三效催化剂（ＴＷＣ）能够同时去除 ＮＯｘｓ、ＣＯ、ＨｘＣｙ三种污染物，生产工艺比较成熟．其中Ｒｈ是公认的促使ＮＯｘ还原为Ｎ２的最有效组分，但Ｒｈ的价格较高且资源贫乏，限制了其实际应用．所以人们一直尝试采用一种廉价的替代品．单Ｐｄ的三效催化剂，由于其相对低廉的价格，较好的耐高温性能，有可能是合适的选择［１－２］．此外，以ＮＨ３为还…

Correlation of the Basicity with the Adsorption of NO on Supporte Pd Catalysts

The adsorption of CO_2 and NO on supported Pd catalysts has been studied by using TPD-MS method and the adsorbed surface species were discussed based on literatures. The amount and intensity of basic sites increase when promoter Li is added, whereas the amount of basic sites decreases when Ce is added. It is found that there are three kinds of basic sites with different intensity on the catalyst surface. On sample Pd/Al_2O_3 and Pd/Al_2O_3-Li_2O, large amount of CO desorption species is detected, this shows some CO_2 on the surface being decomposed. There is no such effect on the sample Pd/Al_2O_3-CeO_2. After analyzing the TPD profiles of NO adsorption on catalysts, it is found that both the NO desorption amount and the shapes of desorption peaks change remarkably when promoter Li or Ce is added. In the case of Li, the γ-peak (nitrate and nitrite species on surface) of NO desorption increases, the intermediate N_2O desorbs at higher temperature. In the case of Ce, the α-peak (species on the Brönstesd acidic sites ) of NO desorption decreases, and N_2O desorbs at lower temperature.