La-promoted Ni/Mg-Al catalysts with highly enhanced low-temperature CO2 methanation performance

In this paper, we investigated the effect of adding lanthanum on the structure and low-temperature activity of the Ni/Mg-Al catalyst for CO2 methanation. A series of La-doped Ni/Mg-Al catalysts with different La loadings were synthesized by urea hydrolysis method. The results showed that La-promoted NiLax (x = 2, 5 and 8 wt%) catalysts exhibited higher low-temperature activity than the Ni catalyst without La added. In particular, the NiLa5 catalyst performed the best, getting as high as 61% CO2 conversion and nearly 100% CH4 selectivity at 250 °C, 0.1 MPa, and a WHSV of 45,000 mL g−1 h−1. Characterization results revealed that La effectively increased Ni dispersion and decreased Ni particle size. In addition, La could significantly increase the amount of moderate basic sites, which contributed to enhanced CO2 adsorption capacity. Compared with coprecipitation method, urea hydrolysis method was proved to be a more efficient approach for the Ni-based catalyst preparation, getting the Ni-based catalyst with higher Ni dispersion, larger CO2 adsorption capacity and thereby better catalytic performance.