Modifying Ni active sites with Ga and Co and optimizing reactant feed conditions to improve low temperature activity and stability in the dry reforming of methane

Abstract

Dry reforming of methane (DRM) converts greenhouse gases (CO₂ and CH₄) to syngas. Supported Ni catalysts are commonly employed to take advantage of their activity and earth abundance. Still, most such catalysts deactivate either due to coking at lower temperatures or sintering at higher ones. Great importance has been placed on developing catalysts to achieve stability and high H₂/CO. In this work, Ni–Ga/Al₂O₃, Ni/CeO₂/ZrO₂, and Ni–Co/Ce₂O₃/La₂O₃ and other catalysts have been explored for DRM at lower than usual temperatures. Reactant feed ratios and co-feeding of H₂O and CO were explored in kinetics studies at these temperatures and a range of partial pressures. A Ni–Ga/Al₂O₃ demonstrated enhanced low-temperature DRM activity and a H₂/CO ratio of one throughout 160 h time onstream. However, this improvement was accompanied by a high coking rate, which could ultimately impact stability. For the Ni/rare earth oxide catalysts, there was little to no coking at standard conditions, and coking/deactivation could be further reduced either by higher (than 1 : 1) CO₂ : CH₄ feed ratios or modest H₂O co-feeding. Kinetics studies showed that increasing CO₂ partial pressure accelerated DRM for redox-capable catalysts, that low CO partial pressures did not inhibit the reaction, and that water addition both suppressed coke formation and stabilized the active Ni phase, water effectively functioning as a promoter of DRM.