Cu-Ce-O/γ-Al_2O_3的CO氧化性能

采用柠檬酸络合法制备一系列不同铜铈比的Cu-Ce-O/γ-Al_2O_3催化剂,用XRD、H2-TPR对其进行表征,采用连续固定床微反装置对Cu-Ce-O/γ-Al_2O_3催化剂CO催化氧化活性进行评价。结果表明,Cu-Ce-O/γ-Al_2O_3催化剂的XRD图谱中除归属于γ-Al_2O_3的晶相峰外,还出现CuO和CeO_2的晶相峰。高温水热引起活性组分CeO_2的晶粒聚集、长大和尖晶石结构CuAl2O4物质的生成;CuO-CeO_2之间的共生共存与相互作用,使得Cu-Ce-O/γ-Al_2O_3催化剂中具有非完整结构的Cu2+1-xCu+x]O1-12x12x]增多,Cu+离子和氧空位增多,有利于其H2-TPR还原峰温度向低温区偏移,有利于提高其CO的催化氧化活性,使得Cu-Ce-O/γ-Al_2O_3催化剂的TCO50和TCO90降低。Cu与Ce物质的量比为5∶5制备的Cu-Ce-O/γ-Al_2O_3-55催化剂的TCO50和TCO90分别降至最低的162℃和199℃,表明此时的Cu-Ce-O协同效应最佳;CuO-CeO_2二相的共生共存与相互作用有利于减少高温水热环境下活性组分的聚集和晶粒长大,有利于Cu-Ce-O/γ-Al_2O_3催化剂能够保持较高的CO催化氧化活性。

The performances of CO oxidationover Cu-Ce-O/γ-Al2O3 catalyst

A series of Cu-Ce-O/γ-Al₂O₃ catalysts with different Cu/Ce ratio were prepared by citrate method and characterized by XRD,H₂-TPR and testedactivityfor oxidation of carbon monoxide in continuous micro-fixed bed reactor.The results showed that there werecrystalline peaks of CeO₂ and CuO in Cu-Ce-O/γ-Al₂O₃ catalysts besides γ-Al₂O₃.High temperature hydrothermal conditioninduced aggregation and grain growth of active components and the formation of CuAl₂O₄ in the Cu-Ce-O/γ-Al₂O₃ catalyst.The amount of $Cu^{2+}_{1-x}Cu^{+}_{x}]O_{1-\frac{1}{2}x}□\frac{1}{2}x]$ increased because of the intergrowth between CuO and CeO₂,Cu⁺and oxygen vacancy increased,the H₂-TPR reduction peak shifted to the low temperature region.The catalytic oxidation activity of CO was improved so that $T^{CO}_{50}$ and $T^{CO}_{90}$ of Cu-Ce-O/γ-Al₂O₃ catalyst were reduced.The $T^{CO}_{50}$ and $T^{CO}_{90}$ of Cu-Ce-O/γ-Al₂O₃-55-catalyst were reduced to 162 ℃ and 199 ℃ respectively when Cu∶Ce ratio was 5∶5,here the synergidtic effect was the best.The interaction between CuO and CeO₂ inhibited aggregation and grain growth of the active components in the high temperature hydrothermal environment which was beneficial to maintain high activity of CO catalytic oxidation of Cu-Ce-O/γ-Al₂O₃ catalyst.