以碱土金属为助剂的CuO/CeO_2水煤气变换催化剂的催化性能

Catalytic behavior of CuO/CeO_2 water gas shift catalyst promoted by alkaline earth oxides

采用共沉淀法制备了系列CuO/CeO_2-MO(M=Mg、Ca、Sr和Ba)催化剂,通过X射线粉末衍射、M_2物理吸附、N_2O选择性化学吸附、H_2程序升温还原和循环伏安法等手段对催化剂的物化性能进行表征,考察了富氢条件下水煤气变换反应中碱土金属氧化物作为助剂对CuO/CeO_2催化剂性能的影响。结果表明,BaO作为助剂可降低载体CeO_2和CuO的晶粒度,有效增大催化剂的比表面积,提高铜组分的表面分散度,并有利于更多与载体表面氧空位有强相互作用的CuO物种的形成,从而获得较高的催化活性。MgO、CaO和SrO的添加对催化剂活性影响较小。关联活性数据和结构表征结果,推断CuO/CeO_2催化剂在水煤气变换反应中的有效活性位是与载体CeO_2表面氧空位强相互作用的单质Cu。

A series of CuO/CeO2-MO （M = Mg, Ca, Sr, Ba） catalysts for water-gas shift reaction were prepared by co-precipitation method. The effects of alkaline-earth oxides as modifiers on the structural properties, redox properties and catalytic activities of the CuO/CeO2 catalysts were studied in detail with the aid of XRD, Nz physical adsorption, selective N20 chemisorption, H2-TPR and cyclic voltammetry. The results showed that BaO as promoter decreased crystal size of CeO2 and CuO, enhanced specific surface area of the catalyst, improved Cu dispersion on catalyst surface, and was beneficial to the forma- tion of more CuO species interacted with surface oxygen vacancy on ceria, and as a consequence, higher catalytic activities were obtained. The addition of MgO, CaO and SrO had little influence on catalytic activities. From the correlation between catalytic behavior and characteristic results, it was suggested that the metallic copper （Cu2） interacted with surface oxygen vacancy on ceria was the most effective active site for water gas shift reaction over CuO/CeO2 catalysts.