CO选择性氧化用Cu_1Zr_1Ce_9O_δ催化剂的红外光谱研究

DRIFTS Study of Cu_1Zr_1Ce_9O_δ Catalysts for Selective CO Oxidation

采用共沉淀法制备了Cu1Zr1Ce9Oδ催化剂,用于富氢气体中CO的选择性氧化反应,利用原位漫反射红外光谱技术考察了Cu1Zr1Ce9Oδ催化剂表面上的吸附物种和反应中间产物。研究发现,H2,O2和CO物种竞争吸附于Cu1Zr1Ce9Oδ表面相同的吸附位上。氢气预处理会引起Cu1Zr1Ce9Oδ催化剂上Cu+物种的深度还原,降低了CO的吸附量。氧气预处理为催化剂提供了较多的活性氧物种,同时抑制了Cu+物种的深度还原。氦气预处理仅起到净化催化剂表面的作用。180℃时Cu1Zr1Ce9Oδ催化剂在2938.7和2843.8cm-1处出现桥式和双齿型甲酸根物种的红外吸收峰。Cu1Zr1Ce9Oδ催化剂上活性较高的氧阴离子在常温下即可将催化剂表面上吸附的CO氧化成表面碳酸根。甲酸根和碳酸根物种占据Cu1Zr1Ce9Oδ催化剂的吸附中心,导致催化剂活性降低。300℃下用氦气吹扫Cu1Zr1Ce9Oδ催化剂表面,双齿型的甲酸根物种分解生成碳酸根物种,碳酸根物种再继续分解生成CO2,释放出催化剂表面的吸附位,恢复了Cu1Zr1Ce9Oδ催化剂的活性。

The Cu1Zr1Ce9Oδ catalysts synthesized with coprecipitation method were used into the selective CO oxidation in hydrogen-rich gas.The adsorbed species and the intermediates on Cu1Zr1Ce9Oδ catalysts were examined by in-situ diffuse reflectance FTIR spectroscopy （in-situ DRIFTS） technique.It was found that hydrogen,oxygen and CO in the feed stream were adsorbed competitively at the same adsorption sites on the surface of Cu1Zr1Ce9Oδ catalysts.The pretreatment with hydrogen caused the deep reduction of Cu＋ species to Cu0 species and decreased the capacity of CO adsorption on the catalyst surface.The Cu1Zr1Ce9Oδ catalyst pretreated with oxygen offered more active oxygen species and inhibited the deep reduction of Cu＋ species.The helium pretreatment only purified the surface of Cu1Zr1Ce9Oδ catalyst.Two IR bands at 2 938.7 and 2 843.8 cm-1 due to bridged formate and bidentate formate species appeared at 180 ℃.The active oxygen anion of Cu1Zr1Ce9Oδ catalyst could react with CO and produce carbonate species at room temperatures.The carbonate and formate species occupied the adsorption sites and deteriorated the catalytic performance of Cu1Zr1Ce9Oδ.Flushing the Cu1Zr1Ce9Oδ catalyst with helium at 300 ℃,the bidentate formate species on the catalyst surface decomposed to monodentate carbonate species and then further decomposed to CO2,which could release the adsorption sites and restore well the catalytic activity.