The catalytic activity of Ru and Ir supported on Eu₂O₃ for the reaction, CO₂ + CH₄ ⇄ 2 H₂ + 2 CO: a viable solar-thermal energy system

Abstract

Methane and carbon dioxide which often co-exist in nature, constitute valuable potential resources both for the storage of solar (thermal) energy and the convenient production of synthesis gas. Ru and Ir supported on Eu₂O₃ are effective catalysts for the reforming of methane with carbon dioxide to produce synthesis gas with no significant coke formation even after prolonged activity. Ru catalysts show onset of activity around 673 K reaching a maximum at about 973 K. Loadings as low as 1% by weight of Ru are highly effective. Ir catalysts show onset around 823 K reaching a maximum conversion in excess of 94% with respect to CO₂ at 1023 K for a 1% loading of the metal. X-ray absorption studies on the spent Ru/Eu₂O₃ catalysts indicate the presence of the reduced metal, primarily in the form of large spherical particles (> 30 Å) of hexagonal structure. 5% Ir supported on Eu₂O₂ was found to transform an equimolar mixture of H₂ and CO to methane and carbon dioxide with a 42% conversion with respect to H₂ at around 848 K and atmospheric pressure. A 5% loading of Ru on Eu₂O₃ produced a 14% conversion with respect to H₂ at 973 K under similar conditions.