The impact of transition metals (Cr, Mn, and Co) on the performance of the 10%Ni/Al2O3-10%CeO2 catalysts in combined CO2 reforming and partial oxidation of methane

Abstract

This study explores the efficacy of Cr, Mn, and Co promoters in enhancing the performance of 10%Ni/Al₂O₃-10%CeO₂ catalysts during methane combined reforming process, emphasizing improved metal dispersion and reduced carbon formation. The supports and catalysts were synthesized through mechanochemical and impregnation methods, respectively, and characterized using XRD, BET, TPR, TPO, and FESEM analyses. The synthesized catalysts exhibited a high BET surface area, ranging from 195 to 172 m² g^-1, along with a mesoporous structure characterized by pore sizes between 2 and 12 nm. The introduction of Cr significantly enhanced catalyst performance, resulting in 70.5 % CH₄ and 69.1 % CO₂ conversions in dry reforming. TPO analysis indicated reduced carbon deposition on promoted catalysts by enhancing Ni dispersion and carbon reactivity. The 10%Ni–3%Cr/Al₂O₃-10%CeO₂ catalyst demonstrated stability over 440 min at 700 °C, achieving 84.9 % CH₄ and 68.1 % CO₂ conversions in combined reforming. The TPO analysis indicated an absence of carbon deposition on the catalyst surface during combined reforming, which was corroborated by the FESEM analysis. Furthermore, the influence of operating parameters on catalyst efficiency in both dry and combined reforming processes was investigated. As GHSV increased from 8000 to 24,000 ml/h.gcat, CH₄ conversion declined in dry reforming and combined reforming, dropping from 77 % to 66 % and from 86 % to 84 %, respectively. Also, in both processes, increasing the oxidizer contents (CH₄: CO₂ from 2:1 to 1:2, CH₄: CO₂: O₂ from 1:1:0 to 1:1:0.35) led to an increase in CH₄ conversion, while CO₂ conversion decreased.