Catalytic hydrogenation of CO2 to methane over supported Pd, Rh and Ni catalysts

Abstract

As a step in production of so-called electrofuels, ambient pressure CO₂ hydrogenation has been investigated over different catalytic model systems based on metal particles (Pd, Rh and Ni) supported on various metal oxides (SiO₂, Al₂O₃ and CeO₂) and aluminosilicates (ZSM-5 and MCM-41) at different specific reactant ratios and temperatures between 150 and 450 °C. Catalytic activity and selectivity measurements in a flow reactor show that the highest CO₂ conversion towards methane is obtained for the Rh/Al₂O₃ and Rh/CeO₂ catalysts, followed by Ni/CeO₂. Generally, the results suggest that both the support material and reaction conditions play an important role in the hydrogenation process. Further, in situ diffusive reflectance infrared Fourier transform spectroscopy reveals the intermediate species during transient CO₂ hydrogenation over the Rh and Ni containing catalysts. Adsorption and dissociation of CO₂ occurs over the Rh/Al₂O₃ catalyst in the presence of H₂, resulting in the formation of linear Rh–CO species, while formates and carbonates are formed over the Rh/CeO₂ and Ni/CeO₂ catalysts, likely at the metal–support interface.