Syngas production for steelmaking applications via dry reforming of methane using rare earth-containing aerogel catalysts: Evaluation of resistance to deactivation by coke deposition

Abstract

This study investigates the performance of Ni-Al₂O₃ aerogel catalysts, both unpromoted and promoted with rare earth oxides (La and Nd), in the dry reforming of methane for syngas production, with a focus on their application in the direct reduction of iron oxides. Additionally, the catalyst synthesis offers further advantages during the aerogel drying step, owing to the use of CO₂ as the drying medium. For comparison purposes, a Ni-Al₂O₃ xerogel was also prepared and characterized to highlight the benefits of supercritical drying in aerogel synthesis. The influence of reaction temperature (600–800 °C) and rare earth promotion (La, Nd) on CH₄ and CO₂ conversion, H₂ and CO production, and carbon deposition was investigated using a gaseous mixture containing CH₄/CO₂ (molar ratio 1:1). CH₄ and CO₂ conversions increased while carbon deposition decreased with the increase in temperature. Reverse water-gas shift, reverse Boudouard reaction, and CO reduction were the primary parallel reactions observed. The addition of rare earth promoters further improved catalyst performance, particularly La-promoted catalysts, which exhibited higher activity (0.34 and 0.67 mmol g_cat⁻¹ min⁻¹ for CH₄ and CO₂, respectively). Carbon deposition profile was monitored along the reaction time, and all catalysts tested showed a net zero carbon deposition rate after 24 h of operation. Deactivation was not measured due to the hollow morphology of the deposited carbon nanotubes. The H₂/CO ratio (around 0.3–0.5) of the produced synthesis gas makes it suitable for iron reduction in steelmaking.