Finding a replacement for the toxic hexavalent chromium oxide in commercial iron oxide-based high temperature water-gas shift (HT-WGS) catalyst is of current environmental concern. Previous studies in developing Cr-free catalysts mainly focus on ex-situ characterization on catalysts bulk structure. In the present study, CuO/MO_x-Fe₂O₃ catalysts promoted by Si, Al, Cr or Mg were studied with XRD, in situ Raman, HS-LEIS, BET, transient C¹⁶O₂ → C¹⁸O₂ isotopic switch, steady-state WGS activity test and CO-TPR to elucidate their structure-activity relationships. The Mg and Al are homogeneously distributed within both fresh and activated catalysts as texture promoters, while the Si exists as discrete SiO₂ that is covered by iron oxides. During the HT-WGS reaction, the Mg promoter resulted in the poorest thermally stability and least amount of metal-metal oxide interface, and the Si promoter inhibited the reducibility of surface oxygen. Only the Al promoter was found to yield a catalyst that possessed similar catalyst structure, comparable thermostability and activity with the Cr-promoted catalyst. This work demonstrates the importance of in situ characterization to the rational design of Cr-free iron oxide based HT-WGS catalysts.

在商用的基于氧化铁的高温水煤气变换（HT-WGS）催化剂中寻找有毒的六价铬氧化物的替代品是当前环境关注的问题。以前开发无铬催化剂的研究主要集中在对催化剂本体结构的异位表征。在本研究中，用XRD，原位拉曼，HS-LEIS，BET，瞬态C ¹⁶ O ₂  →C ¹⁸ O ₂研究了由Si，Al，Cr或Mg促进的CuO / MO _x -Fe ₂ O ₃催化剂。同位素开关，稳态WGS活性测试和CO-TPR来阐明它们的构效关系。Mg和Al作为质地促进剂均匀分布在新鲜催化剂和活化催化剂中，而Si则以离散的SiO _2的形式存在，并被氧化铁所覆盖。在HT-WGS反应过程中，Mg促进剂导致最差的热稳定性和最少的金属-金属氧化物界面数量，而Si促进剂抑制了表面氧的还原性。发现仅Al助催化剂产生的催化剂具有与Cr促进的催化剂相似的催化剂结构，可比的热稳定性和活性。这项工作证明了原位表征对于无铬氧化铁基HT-WGS催化剂合理设计的重要性。