CO2 reforming of methane over Ni and/or Ru catalysts supported on mesoporous KIT-6: Effect of promotion with Ce
Abstract
CO2 reforming of methane was studied over Ni and/or Ru supported on KIT-6 and KIT-6 promoted with Ce catalysts synthesized using the wet impregnation technique. The percent of nickel and ruthenium in all catalysts was fixed at 15 wt% and/or 1 wt% respectively. All catalysts were calcined at 550 °C and characterized by XRD, N2 adsorption/desorption, H2-TPR and CO2-TPD. All catalysts exhibited type IVa isotherms attributed to their mesoporous nature. Ce promotion resulted in a significant destruction of the porous structure which was demonstrated by the change in the shape of the isotherm as well as decreased surface areas and pore volumes. H2-TPR profiles showed reduction peaks corresponding to the reduction of agglomerated RuO2 species as well as different NiO species that are either free or in interaction with the support. It was noticed that the incorporation of Ce impaired the interactions between the active phase and the support. CO2-TPD profiles demonstrated that promoting the catalysts with Ce increased their basicity. Among the non-promoted catalysts, Ni-Ru/KIT-6 presented enhanced active phase dispersion, reducibility, and the highest basicity which resulted in an ameliorated catalytic performance. However, the promoted Ni-Ru/Ce-KIT-6 catalyst exhibited much higher activity and stability after 12 h on stream despite the formation of graphitic carbon resulting from the decomposition of methane.