Cu-Ni双金属催化剂的XPS研究

XPS study of Cu-Ni bimetallic catalyst

采用XPS方法研究了以不同方式引入Ni的Cu Ni/Al2 O3 双金属催化剂的表面结构及不同处理条件对催化剂表面结构的影响。发现催化剂表面存在表面铝酸盐物种 ,且Ni的存在会促进表面铝酸盐物种的生成。催化剂经H2 还原处理或经CO2 加氢反应后均要发生表面重构。Ni的存在会影响表面重构过程从而影响催化剂的活性和选择性 ,在所研究的含Ni催化剂上 ,CO2 加氢反应经历了生成双齿表面吸附中间物的过程。

The surface structure of CuNi bimetallic catalysts and its variation with different treatment conditions were studied by XPS techiqueThe effect of the chemical state of Ni before the impregnation of Cu in catalyst preparation on the surface structure and its variation were also investigatedIt is found that Cu atom approaches the surface of Al_2O_3 when it is supportedSurface aluminates are formed on the surface of the catalysts and the presence of Ni favorites the formation of surface aluminatesThe surface content of Cu is increased when Ni existed in reduced form before the introduction of Cu,while the opposite is true when Ni existed in oxidized form before introduction of CuSurface reconstruction is observed when the samples studied are reduced in H_2 or treated under CO_2 hydrogenation conditionThe hydrogenation of CO_2 enriches the surface contenrt of Cu species comparing to reductionAfter CO_2 hydrogenation treatment,Cu species is observed to migrate to the surface of the catalyst in the absence of Ni,while in the presence of Ni surface is remarkably decreasedBidentate CO_2 adsorptive species with the two O of CO_2 cooordinated to metal atoms is a possible intermediate in the hydrogenation of CO_2 over Ni containing catalyst studied