Methane Reforming Utilizing Vibrational Excitation

― Frontier of Plasma-Driven Catalysis ―

Abstract

Plasma-assisted heterogeneous catalysis for CH₄ conversion attracts keen attention because the strong C-H bond breaking is possible via vibrational excitation of CH₄ at low temperature. Similarly, vibrational excitation of CO₂ possesses unique reactivity in heterogeneous catalysis. This paper provides a kinetic analysis of nonthermal plasma-assisted CH₄ dry reforming to elucidate the drastic reaction promotion mechanism. Lanthanum-modified Ni/Al₂O₃ catalyst was combined with dielectric barrier discharge at 5 kPa and 400–700℃. Activation energy decreases from 91.0 kJ/mol to 44.7 kJ/mol which was well correlated with the state-specific gas-surface reactivity of vibrationally excited CH₄ on Ni surface. Reactivity of plasma-excited CO₂ is discussed by the in situ DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) under the influence of CO₂ plasma, showing the plasma-excited CO₂ promotes the formation of surface carbonate species (CO₃^2－) : co-operative activation of CO₂ is the key to enhancing overall reforming performance.