Mechanism of Low Pressure Plasma-Assisted CO2 Hydrogenation Over Ni-USY by Microsecond Time-resolved FTIR Spectroscopy

Zeolite H-USY doped with nickel (14% wt.) was used as a catalyst in the plasma-assisted CO2 hydrogenation under partial vacuum. CO was found to be the main product of the reaction and it is generated by plasma-assisted CO2 dissociation in the gas phase. The CO2 molecules vibrationally excited by plasma are also adsorbed on metallic nickel as formates which are further transformed into linear carbonyls. These species are then hydrogenated to form methane. Since the catalyst presents a low basic behavior, methane is produced from hydrogenation of linear carbonyls on nickel surface rather than from carbonates species. A detailed mechanism for this reaction assisted by plasma (glow discharge) is proposed using Operando time-resolved FTIR spectroscopic data.