Abstract: Using CO as the probe molecule, infrared diffuse reflectance spectroscopy was used to study the adsorption of Pd⁃Ag/Al2O3 catalysts prepared by impregnation method and the carbon monoxide adsorption on the support and a series of changes in the surface species of the catalyst. The results showed that in the Pd⁃Ag/Al2O3 catalytic system, due to the different order of silver addition, the active center of the catalyst was affected by the electronic effect and the geometric effect, which caused the surface species adsorption morphology of the catalyst after CO adsorption. It was found that there was no bridge adsorption of CO on Pd⁃Ag/Al2O3⁃LM⁃2 catalyst when CO was adsorbed and desorbed before and after heating. The characteristic peak intensity of HCO〖_3^-〗 was found decreased with the increase of CO adsorption and desorption temperature. At the same time, the adsorption characteristic peak of HCOO- was relatively enhanced, and the consistent growth and decline relationship between the two indicated that HCO〖_3^-〗 was converted to HCOO- during the heating process.

Key words: Pd?Ag/Al2O3 catalyst, In?situ infrared diffuse reflection, Carbon monoxide, Adsorption and conversion

摘要： 采用原位漫反射红外光谱技术，研究CO探针分子在浸渍法制备的Pd⁃Ag/Al2O3催化剂及Al2O3载体上的吸附行为。根据催化剂表面吸附CO后表面物种吸附形态的不同，可以判断不同制备方法所得Pd⁃Ag/Al2O3催化剂上活性中心Pd原子受到助剂Ag原子的电子效应和几何效应不同。研究发现，升温前后吸附和脱附CO时，只有Pd⁃Ag/Al2O3⁃LM⁃2催化剂上不存在CO的桥式吸附，且发现随着CO的吸附和脱附温度的升高，HCO_3的特征峰强度相对减弱，与此同时HCOO-的吸附特征峰相对增强，两者一致的消长关系说明HCO〖_3^-〗在升温的过程中转变为HCOO-。

关键词: Pd?Ag/Al2O3催化剂, 原位红外漫反射, CO, 吸附与转化