Ce改性的Rh-UiO-66-Zr催化剂对合成气制乙醇的影响

Effect of Ce introduced Rh-UiO-66-Zr catalyst in syngas converting to ethanol

  • 摘要: 在合成气直接合成乙醇过程中,Rh基催化剂对乙醇等C2含氧化合物具有良好的选择性而持续成为研究热点。本工作利用UiO-66作为载体,将金属Ce4 +引入UiO-66-Zr的Zr6O4(OH)4金属节点替换部分金属Zr4 +形成Zr6−xCexO4(OH)4金属节点,从而较为精确地对合成气制备乙醇活性位点问题进行研究。XRD、TG、Raman、BET、H2-TPR、XPS和in-situ DRIFTS等表征结果显示,随着UiO-66Zr6O4(OH)4节点上金属Ce4 +的引入,催化剂上形成了-(Zr-O)-Rh-(O-Ce-位点,而在Rh/UiO-66-Zr催化剂上形成的-(Zr-O)-Rh-(O-Zr)-位点,结合催化反应评价结果发现,乙醇活性位点数量显著提升。由于Rh物种与-(O-Zr)-物种的相互作用较强,Rh与-(O-Ce)-位点的相互作用较弱,这种相互作用的势差有利于电子的高效率传输。另一方面,-(Zr-O)-Rh-(O-Ce)-可以稳定合成气制备乙醇的关键中间体,从而促进乙醇的形成。

     

    Abstract: In the process of direct synthesis of ethanol from syngas, rhodium-based catalysts continue becoming a hot topic because of their high selectivity for C2 oxygen-containing compounds such as ethanol. In this work, UiO-66 was used as a support to introduce the metal Ce4 + species into the Zr6O4(OH)4 metal node of UiO-66-Zr to replace some of the metal Zr4 + species formation Zr6−xCexO4(OH)4 metal nodes, so as to accurately study the problem of ethanol activity sites for the preparation of syngas. The characterization results of XRD, TG, Raman, BET, H2-TPR, XPS, and in-situ DRIFTS showed that with the introduction of metal Ce4 + species at the UiO-66 Zr6O4(OH)4 node, -(Zr-O)-Rh-(O-Ce)-sites were formed on the catalyst, and -(Zr-O)-Rh-(O-Zr)-sites were formed on the Rh/UiO-66-Zr catalyst. Combined with the evaluation results of the catalytic reaction, the number of ethanol active sites was significantly increased. Because of the interaction between Rh species and -(O-Zr)-species is stronger than Rh species with -(O-Ce)- sites, the potential difference of this interaction favors the efficient transport of electrons. On the other hand, -(Zr-O)-Rh-(O-Ce)- can stabilize the key intermediates for the preparation of ethanol from syngas, which can promote the formation of ethanol.

     

/

返回文章
返回