由合成气制备C_2含氧化合物用铑基催化剂中各组分间的相互作用

THE INTERACTIONS OF THE ACTIVE COMPONENTS IN Rh BASED CATALYSTS FOR THE SYNTHESIS OF C 2 OXYGENATES FROM SYNGAS

采用ＴＰＲ，ＥＰＲ，ＩＲ，ＸＰＳ等手段对由合成气制备Ｃ２含氧化合物的Ｒｈ基催化剂中各活性组分间的相互作用进行了研究．ＴＰＲ实验表明，Ｍｎ的存在除了促进金属铑在担体表面的分散，增加还原过程的耗氢量外，还使Ｒｈ物种的还原温度显著升高；少量Ｌｉ的加入导致氢向载体ＳｉＯ２的溢流，使体系的还原特性发生了明显的变化．原位ＥＰＲ和ＸＰＳ研究显示，添加剂与Ｒｈ相互作用，在催化剂表面形成了稳定的复合氧化物．助剂Ｍｎ主要起着吸引电子的作用，使还原后的催化剂表面上Ｒｈ＋物种的含量增加；相反，作为给电子助剂，Ｌｉ的加入稳定了表面Ｒｈ０物种．

Rh based catalysts which are used for the synthesis of C 2 oxygenates through syngas were investigated by TPR, EPR, XPS and IR methods. TPR results indicate that the addition of Mn to the Rh/SiO 2 system inhibited the reduction of the Rh component, while reduction of the Mn component itself appeared to be enhanced. Corresponding EPR experiments suggest that the addition of the Mn component resulted in the formation of Rh Mn mixed oxides. The existence of the Li species serving as an electron donor gives rise to metallic Rh in the catalyst, as evidenced by the XPS results. IR spectra of adsorbed CO indicate that the existence of Mn in the catalyst improved the dispersion of Rh and enhanced the concentration of Rh + species on the surface. The addition of Li promoted the formation of Rh 0 species. Moreover, the addition of Li to the Rh/SiO 2 system might cause the spillover of hydrogen from the Rh species to the SiO 2 support.