Methanation of CO₂ over Yb-Promoted Ni/Al₂O₃ Catalysts Prepared by Solution Combustion

Introducing a proper promoter into Ni-based catalysts for CO2 methanation is an effective method to improve their catalytic performance. In this work, we prepare a series of Yb-modified Ni/Al2O3 catalysts by a solution combustion approach and characterize them using various techniques, including nitrogen adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed hydrogen reduction (H2-TPR), hydrogen desorption (H2-TPD), carbon dioxide desorption (CO2-TPD), Fourier transform infrared (FTIR), and Thermogravimetric/differential thermal (TG/DTA), and test their CO2 methanation activity in a fixed-bed reactor under conditions of 200–500 °C, 0.1–2 MPa, space velocities ranging from 7200 to 16,200 h–1, and feed molar ratios of H2/CO2 from 1 to 4. We found that Yb modification promotes the dispersion of reducible NiO on Al2O3 and simultaneously leads to the creation of new Yb-involved CO2 chemisorption sites responsible for the improved catalytic activity and stability of Ni/Al2O3 catalysts for CO2 methanation so that the Yb-modified Ni/Al2O3 catalysts exhibit higher catalytic activities than Ni/Al2O3 catalysts without Yb.