Study of reverse water gas shift reaction by TPD, TPR and CO2 hydrogenation over potassium-promoted Cu/SiO2 catalyst

The reverse water gas shift (RWGS) reaction over Cu/SiO2 with and without potassium promoter was studied by means of CO2 hydrogenation, temperature programmed reduction (TPR) and temperature programmed desorption (TPD). After addition of even a little amount of potassium, Cu/K2O/SiO2 obviously offers better catalytic activity than Cu/SiO2. The coverage of formate species increases on Cu/K catalyst. TPD of CO2 adsorbed on Cu/K2O/SiO2 and TPR profile of Cu/K2O/SiO2 showed that new active sites could be created at interface between Cu and K. The main role of K2O was to provide catalytic activity for decomposition of formates, besides acting as a promoter for CO2 adsorption. A new reaction mechanism was suggested. Hydrogen was dissociatively adsorbed on Cu and could spill over to K2O to associate with CO2. This resulted in the formation of formate species for the production of CO.