Ce-Zr-O2上CuO分散性对CO氧化活性的影响

采用柠檬酸法制备了Ce-Zr-O₂固溶体, 并负载了过渡金属和贵金属Pt, 其中, 以Cu作为活性组分, 在CO氧化反应中表现出最高的活性, CO完全转化的温度约为120 ℃, 明显高于负载1%Pt(质量分数)催化剂的活性. 掺杂少量Zr到CeO₂(Ce_0.8Zr_0.2O₂)中对Cu基催化剂有非常好的促进作用. 分别采用等体积浸渍法(IW)、 沉淀沉积法(DP)、 水热法(HT)以及柠檬酸法(CA)制备了Cu负载质量分数为20%的Cu/Ce_0.8Zr_0.2O₂催化剂. 结果表明, 由沉淀沉积法制备的Cu/Ce_0.8Zr_0.2O₂催化剂的活性最高, 在100 ℃时, CO可完全转化. TEM结果表明, CuO物种很好地分散在Ce_0.8Zr_0.2O₂上. 吸附实验数据表明, Cu基催化剂上CO与O₂之间较弱的竞争吸附是其活性高于Pt催化剂的主要原因. Cu基催化剂上的氧空位对促进O₂的吸附具有重要作用, 也是影响CO低温氧化的重要因素之一.

Influence of CuO on Ce-Zr-O2 Dispersion on Catalytic Properties in CO Oxidation†

Ce-Zr-O₂ solid solution was prepared by citric acid method and 10%M/Ce_0.8Zr_0.2O₂ (M=Co, Mn, Cu) and 1%Pt/Ce_0.8Zr_0.2O₂ were prepared by incipient-wetness impregnation method. It was found that Cu was the best active composition in CO oxidation over M/Ce_0.8Zr_0.2O₂, which CO was completely converted into CO₂ at ca. 120 ℃ and was more active than 1%Pt/Ce_0.8Zr_0.2O₂. It was found that the optimum ratio of Ce to Zr was 4, Cu/Ce_0.8Zr_0.2O₂ showed the best activity in CO oxidation. Deposition method(DP), incipient-wetness precipitation method(IW), hydro-thermal method(HT) and citric acid method(CA) were used to prepare 20%Cu/Ce_0.8Zr_0.2O₂ catalysts. Cu/Ce_0.8Zr_0.2O₂ prepared by deposition method showed better activity in CO oxidation, which CO was completely converted into CO₂ at ca. 100 ℃. The data from H₂-TPR showed that the redox of Cu/Ce_0.8Zr_0.2O₂ was not a determining factor to control the CO oxidation. TEM results showed that the CuO was well dispersed on Ce_0.8Zr_0.2O₂. Based on adsorption data of CO and O₂, the high activity of Cu-based catalyst should be ascribed to the week competitive adsorption between CO and O₂ over Cu/Ce_0.8Zr_0.2O₂. The oxygen vacancy on Ce_0.8Zr_0.2O₂ was a crucial factor to affect the CuO dispersion and to reduce the competitive adsorption between CO and O₂.