In Situ Modification of CuO-Fe2O3 by Nonthermal Plasma: Insights into the CO2-to-CH3OH Hydrogenation Reaction

Abstract

The hydrogenation of CO2 to CH3OH on the binary mixed metal oxides of CuO-Fe2O3 under nonthermal plasma discharge has been reported in this study. The catalysts are synthesized using the sol-gel route and characterized by XRD, FTIR, SEM, and XPS techniques. The impact of CuO mixing with Fe2O3 on CO2 conversion and CH3OH yield has been investigated. Herein, we have compared two distinct techniques, namely thermal and plasma catalytic processes. The overall outcome shows that the CO2 conversion and CH3OH production increase with an increase in CuO mixing with Fe2O3. The synthesized catalyst does not show significant CO2 conversion and CH3OH formation in the thermal catalytic process (100-250 °C). Interestingly, when plasma discharge is combined with thermal heating, CO2 conversion and CH3OH production significantly improve. The plasma discharges in the CO2/H2 gas stream, at low temperatures (<200 °C), reduce Cu+2 to Cu+1 and Fe+3 to Fe+2, which could probably enhance the CO2 conversion and CH3OH production. Among the catalysts prepared, 15% CuO-Fe2O3 exhibited the best catalytic activity with 13.2% CO2 conversion, 7.3% CH3OH yield, and a space-time yield of 13 mmolCH3OH/h gcat, with 4.67 kJ/L of specific input energy (SIE). The CH3OH space-time yield is 2.9-fold higher than that of the commercial catalyst Cu/ZnO/Al2O3, which is operated at 30 °C with 45.45 kJ/L SIE.