(655b) Investigation of the Role of Supports for Ni Based CO­2 Methanation

CO₂ hydrogenation to methane is a potential strategy for CO₂ utilization as methane can be readily used in existing natural gas infrastructure for power generation. Nickel as a methanation catalyst has been widely studied because of its promising activity, low cost, and high availability however there are challenges from coke formation and sintering. As one strategy to improve nickel catalysts, a variety of oxide supports are explored. Partially reducible supports in particular may improve metal dispersion, basicity, and redox potential of the catalyst which have been shown to improve performance. Here, we have investigated the nature of metal-support interactions, characterized CO₂ adsorption, and explored potential reaction pathways to inform improved design of Ni based catalysts.

We have prepared Ni catalysts on Al₂O₃, CeO₂, TiO₂, SiO₂, and mesoporous SiO₂ (SBA-15) by strong electrostatic adsorption. The resulting catalysts were characterized using XRD, physisorption, H₂-TPR, CO₂-TPD, chemisorption, and in-situ FTIR. With the exception of Ni/CeO₂, the studied catalysts with a lower onset of reduction were found to have a higher turnover frequency. Ni/CeO₂ was found to be the most active catalyst despite a moderate onset of reduction at 225 °C; this high activity is attributed to a high fraction of weak and medium strength basic sites and high, surface area normalized CO₂ adsorption. From in-situ FTIR, we observe only adsorbed CO species on inert supports (Ni/SiO₂ and Ni/SBA-15) while we observe carbonate and formate species on ‘active’ supports (Ni/Al₂O₃, Ni/TiO₂, Ni/CeO₂). So, we hypothesize that CO species are formed on Ni⁰ sites and for active supports, the CO species transfer to the support to form carbonate and formate species. We have shown how Ni structures and therefore reaction pathways for Ni catalysts vary across supports, leading to improved activity for catalysts on reducible supports.