Carbon Dioxide Reforming of Methane Over Co/Al 2 O 3 Catalysts Doped with Manganese

The manganese-promoted cobalt supported on gamma alumina was prepared following the incipient wetness impregnation method and employed as a catalyst for carbon dioxide reforming of methane. The addition of manganese has changed the physicochemical properties of the original material. The Co 3 O 4 crystallite size was decreased from 12.14 to 8.66 nm, suggesting a higher metal dispersion. The activation of the catalyst precursor was more effective with less energy required. Notably, the carbon dioxide adsorption over the catalyst surface was greatly enhanced in the presence of 1 wt% manganese. Taken all together, the manganese-promoted catalyst showed an outperformance with higher activity and stability in comparison with the pristine. At 973 K, 1 atm, CH 4 /CO 2 ratio of 1, the addition of 1 wt% Mn into 5Co/Al 2 O 3 led to notable increases in CH 4 (15.2%) and CO 2 (17.68%) conversions. Also, the stability of Mn-promoted was much higher compared to pristine catalyst with only 0.3 wt% of undesirable coke formed. Meanwhile, it was 4.94 wt% in the case of 5Co/Al 2 O 3 at the same operating condition. Furthermore, the role of carbon dioxide adsorption in carbon dioxide reforming of methane was investigated. At a proper combination of carbon dioxide activation and methane dissociation, the catalytic activity can be significantly enhanced with much lower activation energies for the feedstock gases. Nevertheless, when the adsorption of carbon dioxide was dominant, catalytic activity was much lower and the deactivation occurred rapidly.