CO2 methanation over Ru- and Ni/Al2O3 catalysts: Effect of preparation solvent on performance and surface chemistry

Ru/Al 2 O 3 and Ni/Al 2 O 3 catalysts were prepared and investigated in the CO 2 hydrogenation reaction. 0.5 wt% Ru/Al 2 O 3 , 2 wt% Ni/Al 2 O 3 , and 13.6 wt% Ni/Al 2 O 3 catalysts were prepared by using a modified incipient wetness impregnation with a main focus on the effect of solvent selection and catalyst pretreatment conditions on the catalyst reduction, activity, selectivity, activation energy, and morphology. In-depth characterizations, including FT-IR, FE-SEM, and XRD, were performed on the catalysts, and an operando study was carried out on the best-performing Ru-catalysts in CO x transient experiments at 523 K. The investigation revealed that employing ethanol as the solvent for preparation results in a catalyst with improved properties and activity. Furthermore, coupling solvent selection with various pretreatment conditions demonstrated that specific pretreatments can significantly affect the catalyst properties, activity, and morphology. Operando IR confirmed the mechanism and the effect of CO reported in the literature, even if a different distribution of carbonyl species was detected. • The effect of solvent and pretreatment on Ru/Al 2 O 3 catalysts was successfully investigated. • A limited effect of solvent selection was observed for the Ni-based materials. • The best solvent for Ru-based catalyst is E, followed by a N 2 + N 2 /H 2 temperature treatment. • Operando supports the monohydrogencarbonate-formate mechanism occurring on 0.5Ru/A.