Plasma-Induced Micro-combustion for the Synthesis of Ni–M/SiO2 (M = La, Ce, Zr) Catalysts with High Selectivity toward CO2 Methanation

With La, Ce, and Zr as doping additives, Ni-based catalysts were prepared using a plasma-induced micro-combustion method. X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, H2 temperature-programmed desorption, CO2 temperature-programmed desorption, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) were used to characterize the as-synthesized catalysts. The results illustrated that the catalysts after doping exhibited higher reducibility and a stronger interaction between the metal and support compared with SiO2-supported Ni catalyst without additives. The additives increased the electron density around metal Ni and oxygen vacancies of the support, which promoted the CO2 and hydrogen adsorption. The catalysts were used in CO2 methanation, and the 10Ni-3La/SiO2 catalyst exhibited the highest turnover frequency of 0.517 s–1 and especially the highest CH4 selectivity of 85% at 280 °C under a high space velocity of 120 000 mL/(gcat·h). DRIFTs analysis confirmed adding additives, especially La and Ce, could accelerate the integration of CO2 species with dissociated H to generate formate intermediate, which facilitated methane formation.