Metal-oxide promoted Ni/Al2O3 as CO2 methanation micro-size catalysts

The Power-to-Gas concept has the challenge to convert the excess of renewable electricity to synthetic natural gas, composed mainly by methane, through CO2 methanation. The superior heat transfer capacity of micro-structured reactors offers a suitable alternative for an efficient control of the reaction temperature. In the present work, the strategy of adding large amount of metal oxide promoters (15 wt.%) to nickel supported on micro-size catalysts (d(p) = 400-500 mu m) is presented. The addition of CeO2, La2O3, Sm2O3, Y2O3 and ZrO2 was clearly beneficial, as the corresponding metal-oxide promoted catalysts exhibited higher catalytic performance than Ni/Al2O3 and the commercial reference Meth (R) 134 (T = 200-300 degrees C, P = 5 bar.g). This increase of catalytic activity is attributed to the higher amount of CO2 adsorbed on the catalyst. Among the selected promoters, La2O3 showed the highest catalytic activity (X-CO2 = +20% at 300 degrees C) due to the enhancement of nickel reducibility, nickel dispersion and the presence of moderate basic sites. In addition, Ni-La2O3/Al2O3 was stable for one week, while the unpromoted catalyst exhibited a slight decline in its activity. Accordingly, the technical catalyst proposed in this study could be used directly in compact reactors for CO2 methanation with much higher activity than the commercial reference.