A Study on CO2 Hydrogenation Using a Ceria-Zirconia Mixed Oxide (CexZr1-xO2)-Supported Fe Catalyst

Fe-impregnated CexZr1-xO2 supports were studied for CO2 methanation at 300, 400, and 500 degrees C under pressures 1 bar to 30 bars using a H-2/CO2 (4:1 v/v) mixture, and their performance was compared to Fe-impregnated ZrO2. The variables affecting performance included temperature, pressure, and iron and cerium loadings. The iron loading that resulted in maximum CH4 selectivity and yield was 10 wt %. At 500 degrees C, Fe-CexZr1-xO2 increased the CO2 uptake of the catalyst and its conversion to CO and CH4 by more than 50% compared to Fe-ZrO2. As a result, CH4 yield monotonically increased with temperature, but for Fe-ZrO2, it gradually decreased with temperature. Contrarily, at lower temperatures, Fe-ZrO2 gave higher CO2 conversion and CH4 yield. The highest CH4 yield was 25% with 10% Fe-Ce0.1Zr0.9O2 at 500 degrees C and 30 bars. This composition was also found to be highly stable over a continuous testing period of 100 h at 500 degrees C and 20 bars. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies indicated the possibility of a formate-assisted pathway of CH4 formation on Fe-CexZr1-xO2.