Study of reverse water gas shift reaction by TPD, TPR and CO 2 hydrogenation over potassium-promoted Cu/SiO 2 catalyst

Abstract

The reverse water gas shift (RWGS) reaction over Cu/SiO 2 with and without potassium promoter was studied by means of CO 2 hydrogenation, temperature programmed reduction (TPR) and temperature programmed desorption (TPD). After addition of even a little amount of potassium, Cu/K 2O/SiO 2 obviously offers better catalytic activity than Cu/SiO 2. The coverage of formate species increases on Cu/K catalyst. TPD of CO 2 adsorbed on Cu/K 2O/SiO 2 and TPR profile of Cu/K 2O/SiO 2 showed that new active sites could be created at interface between Cu and K. The main role of K 2O was to provide catalytic activity for decomposition of formates, besides acting as a promoter for CO 2 adsorption. A new reaction mechanism was suggested. Hydrogen was dissociatively adsorbed on Cu and could spill over to K 2O to associate with CO 2. This resulted in the formation of formate species for the production of CO.