Cu-based mixed metal oxide catalysts for WGSR: Reduction kinetics and catalytic activity

This communication reports the effects of Mn/Cr on the reducibility and catalytic activity of Cu-Fe-Mn and Cu-Fe-Cr mixed oxide catalysts for the water gas shift reaction (WGSR). The reduction kinetics of the mixed oxide catalysts is investigated using TPR data, nucleation/nuclei growth models, and a power law model. Based on the statistical indicators, it is concluded that a second-order power law model describes the reduction of all catalysts adequately. The estimated activation energy for the reduction of the Cu-Fe-Mn catalyst is low compared to the Cu-Fe-Cr catalyst. The TPR analysis of the catalysts reveals that the addition of Mn significantly improved the reducibility of Cu-oxide species, which is consistent with the low activation energy for reduction of the Cu-Fe-Mn catalyst. In a flow type reactor, the Cu-Fe-Mn catalyst showed highest CO conversion at around 220°C, achieving a high specific reaction rate compared to the Cu-Fe-Cr catalyst. The enhanced reducibility of Cu-Fe-Mn catalyst played the key role in the high conversion of CO. These results are comparable with the results obtained for a commercial Cu-ZnO/Al₂O₃ catalyst, which was evaluated under the same reaction conditions.