Dry reforming of methane with CO₂ over Gd (Co,Mn)O₃ perovskite-type oxides

Current trends aimed at reducing the environmental impact of human activity have led to the need for the development of efficient and sustainable catalytic systems for the methane dry reforming process. Moreover, the by-products of the primary greenhouse gases represent valuable raw materials for the petrochemical industry. These materials, which meet the requirements for activity, selectivity, and thermal and chemical stability, are complex oxides with a perovskite structure.

Gd(Co,Mn)O₃ complex oxides were prepared by the sol–gel method with citric acid and characterized by X-ray diffraction and Fourier-transform IR spectroscopy. Their oxygen non-stoichiometry was also investigated by iodometric titration. The catalytic properties of the samples were studied in a flow reactor at atmospheric pressure with a volume flow rate of 0.9-1.0 L/h and a CO₂:CH₄ ratio of 1:1.

It has been shown that the addition of manganese to the anionic sublattice of a complex oxide inhibits the conversion of carbon dioxide into methane. In samples containing manganese, the reaction temperature is shifted towards lower values, with X_50% conversions of CH₄ and CO₂ occurring at almost 300 K lower than in unsubstituted samples of cobalt. The synthesis gas ratio does not reach stoichiometric levels, which may be due to an increased side reaction of CO₂ reduction. Despite the lower catalytic activity, less surface carbonization was observed in complex oxides containing manganese. The formation of trace amounts of hydrocarbons suggests that the adsorption of methane on manganese atoms occurs mainly through the formation of CH_x species. These results suggest that catalytic systems based on Gd(Co,Mn)O₃ have potential for the production of synthesis gas through the conversion of carbon dioxide into methane.