Operando Ru and Ti K-Edge X-Ray Absorption Study of the Low-Temperature Sabatier Reaction on Ru/TiO₂ Catalysts

Stimulated by recent findings of a beneficial effect of a high-temperature treatment on the activity and selectivity of highly active and selective Ru/TiO₂ catalysts in the CO_x methanation, a detailed study of the dynamic changes in the chemical and structural properties is performed, induced by this treatment and their correlation with the changes in the catalytic performance of the catalyst. These changes are characterized by time-resolved operando X-ray absorption spectroscopy at the Ru and Ti K-edges, together with structural characterization by high-resolution transmission electron microscopy. The observation of differently long times required for the reduction of the oxidic Ru nanoparticles in CO-free CO₂/H₂ gas mixtures (1000 min) and in trace amounts of CO containing CO/CO₂/H₂ gas mixtures (100 min) under reaction conditions (190 °C, atmospheric pressure) correlates very well with the different times required for catalyst activation in these reaction gas mixtures.