A Novel Coprecipitation Path to a High-Performing Ni/MgO Catalyst for Carbon Dioxide Methanation

Abstract

The novel crystalline bimetallic single-source precursor (Ni1–xMgx)12(CO3)8(OH)6O · y H2O with x = 0–0.5 can be converted into a highly active Ni/MgO CO2 methanation catalyst. All stages of preparation, namely, coprecipitation, crystallization, calcination, and reduction, as well as the spent catalysts have been comprehensively analyzed using powder X-ray diffraction, physisorption, transmission electron microscopy, and other techniques. The scalable synthesis allows attaining unusually high surface areas around 230 m2 g−1 for the calcined precatalyst Ni1–xMgxO. During reduction, this oxide solid solution separates into metallic Ni and Ni-depleted oxide to form the active catalyst with finely interdispersed nanoparticles of both components with a high porosity. A high methane production rate is observed in a CO2/H2 (1:4) feed at high space velocities of ≈150 Lh−1 g−1. This performance is competitive with an industrial methanation catalyst and depends strongly on the Ni:Mg ratio utilized in the synthesis. For an equimolar ratio, the new catalyst is found to be 4 times as active as the benchmark. Due to the nanoscaled microstructure, the novel material can stabilize very high Ni loadings (≤77 wt%) with only minor sintering effects at a reaction temperature of 240–280 °C. This material thus closes the gap between thermally unstable Raney-type and conventional lower loaded impregnated industrial catalysts.