On the effect of Li or Na doping on Ru/TiO2 catalyst for CO2 methanation

Metal-support interactions can widely affect or even dominate the catalytic activity, selectivity, and stability of supported Ru nanoparticles during the CO2 methanation. In this work, we report on the effects of doping a Ru/TiO2 catalyst with either Li or Na (3 % wt.) with the general aim to provide a large pool of surface basic sites of weak/medium strength capable to promote CO2 adsorption and methanation at low temperature. However, catalytic kinetic measurements show that both alkali metals hinder the activity of the parent catalyst by different mechanisms. Detailed catalysts characterization (by XRD, porosimetric analysis, CO-DRIFTS, CO2-TPD and H2-TPSR) and operando DRIFTS experiments are used to evaluate the specific impact on the type of CO2-derived adsorbed and intermediate species and on possible reaction pathways by also comparing the results with analogue Ru-catalysts supported on γ-Al2O3