CO2 methanation on Mg-promoted Fe catalysts

This paper deals with the hydrogenation of CO2 to CH4 and H2O on Fe catalysts. An extensive screening of various promoters for an alpha-Fe2O3 precursor was carried out providing Mg as most effective. Thus, a systematic series of Mg/Fe2O3 catalysts with different Mg contents was prepared and thoroughly characterized by X-ray diffraction, N-2 physisorption, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Additionally, the carbonaceous species formed in CO2 hydrogenation were analyzed by temperature-programmed hydrogenation. From characterization and catalytic results, a structure-activity correlation was derived showing that the methanation was predominately referred to surface carbon and Fe carbide species. Consequently, the catalyst with a Mg load of 2 wt.% exhibited the highest CH4 production. Finally, the best catalyst was evaluated under practical operation conditions (8 bar, 10,000 h(-1)). In these tests, CH4 was formed as the major product revealing highest yield of 32% (400 degrees C).