Non-equilibrium plasma-assisted dry reforming of methane over shape-controlled CeO2 supported ruthenium catalysts

Abstract

In this report, CeO₂ and SiO₂ supported 1 wt% Ru catalysts were synthesized and studied for dry reforming of methane (DRM) by introducing non-thermal plasma (NTP) in a dielectric barrier discharge (DBD) fixed bed reactor. From quadrupole mass spectrometer (QMS) data, it is found that introducing non-thermal plasma in thermo-catalytic DRM promotes higher CH₄ and CO₂ conversion and syngas (CO + H₂) yield than those under thermal catalysis only conditions. According to the H₂-TPR, CO₂-TPD, and CO-TPD profiles, reducible CeO₂ supported Ru catalysts presented better activity compared to their irreducible SiO₂ supported Ru counterparts. For instance, the molar concentrations of CO and H₂ were 16% and 9%, respectively, for plasma-assisted thermo-catalytic DRM at 350 °C, while no apparent conversion was observed at the same temperature for thermo-catalytic DRM. Highly energetic electrons, ions, and radicals under non-equilibrium and non-thermal plasma conditions are considered to contribute to the activation of strong C–H bonds in CH₄ and C–O bonds in CO₂, which significantly improves the CH₄/CO₂ conversion during DRM reaction at low temperatures. At 450 °C, the 1 wt% Ru/CeO₂ nanorods sample showed the highest catalytic activity with 51% CH₄ and 37% CO₂ conversion compared to 1 wt% Ru/CeO₂ nanocubes (40% CH₄ and 30% CO₂). These results clearly indicate that the support shape and reducibility affect the plasma-assisted DRM reaction. This enhanced DRM activity is ascribed to the surface chemistry and defect structures of the CeO₂ nanorods support that can provide active surface facets, higher amounts of mobile oxygen and oxygen vacancy, and other surface defects.