Ru-Promoted CO2 activation for oxidative dehydrogenation of propane over chromium oxide catalyst

Abstract

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.