Methane dry reforming over well-dispersed Ni catalyst prepared from perovskite-type mixed oxides

Methane dry reforming with carbon dioxide was performed using perovskite-type mixed oxide catalysts, La_1-xSr_xNiO₃ (x = 0, 0.1) and La_2-xSr_xNiO₄ (x = 0-1) at 600-900°C and atmospheric pressure. Catalytic activity and resistance against coke formation were varied with the type of perovskite and the amount of Sr-substitution. LaNiO₃ showed high activity without coke formation while La₂NiO₄ did not show any activity. Among Sr-substituted catalysts, La_0.9Sr_0.1NiO₃ and La_1.8Sr_0.2NiO₄ had the highest catalytic activity without coke formation. For these catalysts, initially the catalytic activity increased with time and then reached a steady state. The XRD spectra of used catalysts showed that catalysts were transformed to mixed phases of La₂O₂CO₃ and SrCO₃ with highly dispersed Ni metal during the reaction. This transformation could be caused by the removal of lattice oxygen by Sr-substitution, which was promoted by the reducing atmosphere of the reaction (CH₄/CO₂ = 1). The enhanced catalytic activity of Sr-substituted perovskite could come from dual active sites, La₂O₃ for CO₂ adsorption and Ni for CH₄ activation.