草酸盐热分解法制备CeO_2负载CuO催化剂用于CO优先氧化反应

采用草酸盐热分解-浸渍法制备了一系列不同CuO负载量的CuO/CeO_2催化剂,并将其用于CO优先氧化(PROX)研究.当CuO负载量为10%时催化剂活性最高,具有温区最宽且温度最低的CO完全转化窗口(96~160℃),并且当反应温度低于131℃时,产物中CO2选择性始终保持100%.研究结果表明,当负载少量CuO时,Cu~(2+)离子会进入CeO_2晶格形成固溶体;进一步提高CuO负载量会导致CuO在CeO_2表面聚集.对于CuO/CeO_2催化剂,形成Cu-Ce固溶体会在催化剂表面生成大量的表面氧空位和Ce3+;Ce3+则与Cu~(2+)作用产生更多的表面Cu~+,而Cu~+是CO PROX的活性中心,因此表面Ce3+含量的提高和Cu-Ce之间相互作用的增强是活性提高的主要原因.与普通沉淀-浸渍法制备的CuO/CeO_2催化剂相比,草酸盐热分解-浸渍法制备的催化剂更有利于Cu-Ce固溶体的形成,从而具有更多的表面Ce3+和更强的表面Cu-Ce相互作用,因此具有更高的CO优先氧化活性.

CuO Catalyst Supported on CeO2 Prepared by Oxalate Thermal Decomposition Method for Preferential Oxidation of CO

A series of CuO/ CeO2 catalysts with different CuO loadings was prepared via oxalate thermal decomposition-impregnation method for the CO preferential oxidation(PROX) reaction. The catalyst with 10%CuO loading has the best activity, with the lowest and the widest CO full conversion temperature window of 96—160 ℃, and 100% selectivity to CO2 below 131℃. The results indicate that the Cu-Ce solid solution is formed when a small amount of CuO is loaded. However, the increased CuO loading will result in the aggregation of CuO on the surface of CeO2 , which is unfavorable to form the solid solution. For the CuO/ CeO2 catalysts, the formation of Cu-Ce solid solution can inevitably generate surface oxygen vacancy and Ce3+, which can react with the Cu2+ to produce Cu+ through the balance of Ce3++Cu2+﹦ Ce4++Cu+. As the Cu+ is the active center for the CO PROX, the increased surface Ce3+ content and the strengthened interaction be-tween CuO and CeO2 can enhance the CO PROX activity of the catalyst. Compared with the CuO/ CeO2 cata-lysts prepared by precipitation-impregnation method, the catalysts prepared by oxalate thermal decomposition-impregnation method have the higher surface Ce3+ content and stronger interaction between Cu and Ce, resul-ting in the better CO PROX activity.