Highly-selective CO2 conversion via reverse water gas shift reaction over the 0.5wt% Ru-promoted Cu/ZnO/Al2O3 catalyst

The reverse water gas shift (RWGS) reaction can be potentially used to convert captured CO2 into renewable synthetic fuels via syngas generation. However, this conversion pathway has not been yet realized because of a number of technological challenges, including a lack of catalysts which possess satisfactory catalytic performance. In this paper, the RWGS reaction over a 0.5 wt% Ru-promoted 40 wt% Cu/ZnO/Al2O3 catalyst is studied. Due to the Ru addition, CO2 conversion was improved more than two-fold as compared to the baseline Cu/ZnO/Al2O3 catalyst. The catalyst stability was significantly improved as well. Although Ru is known for its high activity in methanation reactions, the 0.5 wt% Ru-Cu/ZnO/Al2O3 catalyst maintained complete selectivity to CO formation. In order to investigate this intriguing finding, the catalyst was studied by XRD, SEM-EDS, STEM-EDS, and TPR, revealing the possibility of the formation of Ru-Cu core-shell nanoparticles. Further investigation have shown that the Ru-support interaction is also a crucial factor affecting the catalyst selectivity. To extrapolate the experimentally measured data, a rate expression was derived and kinetic parameters were estimated. The resulting reaction rate expression was implemented to assess the catalyst performance under a wider range of operating conditions.