Ru-Promoted CO2 activation for oxidative dehydrogenation of propane over chromium oxide catalyst†
Catalytic oxidative dehydrogenation of lower alkanes with CO2 is an attractive alternative for commercialized dehydrogenation processes not only due to its higher thermodynamic limit but also because it could help reduce anthropogenic CO2. Here, we studied the catalytic behavior of a Ru-modified conventional SiO2-supported chromium oxide catalyst and obtained insights into the structure–property relationship for oxidative dehydrogenation of propane (ODP) with CO2. The catalyst exhibits a volcano-shape propylene production rate trend as Ru loading increases up to 3 wt%. The optimal catalyst with 1 wt% Ru showed a two-fold enhancement in the propylene production rate compared with the unmodified chromium oxide catalyst. We show that a small amount of Ru could help activate CO2 and remove adsorbed H2 on the catalyst surface to shift the equilibrium of the direct dehydrogenation reaction, resulting in an increase in its activity without breaking the C–C bonds. Higher loadings of Ru lead to a decrease in activity and selectivity due to the large amount of adsorbed CO2 that blocks propane adsorption, as well as the high activity of Ru for the reforming reaction of propylene and CO2. This work demonstrates a new modification of the conventional chromium catalyst for the ODP reaction and its effects on catalytic performance.