Polymer-derived SiOC as support material for Ni-based catalysts: CO2 methanation performance and effect of support modification with La2O3

Abstract

In this study, we investigated Ni supported on polymer-derived ceramics as a new class of catalyst materials. Catalysts have to withstand harsh reaction conditions requiring the use of a support with outstanding thermal and mechanical stability. Polymer-derived ceramics meet these requirements and bring the additional opportunity to realize complex porous structures. Ni-SiOC and La-modified Ni-SiOC catalysts were prepared by wet impregnation methods with target concentrations of 5 wt% for both metal and oxide content. Polymer-derived SiOC supports were produced using a photoactive methyl-silsesquioxane as preceramic polymer. Catalysts were characterized by N₂-adsorption-desorption, XRD, SEM, H₂-TPR, and in-situ DRIFTS. CO₂ methanation was performed as a test reaction to evaluate the catalytic performance of these new materials at atmospheric pressure in the temperature range between 200°C and 400°C. XDR, H₂-TPR, and in-situ DRIFTS results indicate both improved dispersion and stability of Ni sites and increased adsorption capacities for CO₂ in La-modified samples. Also, modified catalysts exhibited excellent performance in the CO₂ methanation with CO₂ conversions up to 88% and methane selectivity >99% at 300°C reaction temperature. Furthermore, the pyrolysis temperature of the support material affected the catalytic properties, the surface area, the stability of active sites, and the hydrophobicity of the surface. Overall, the materials show promising properties for catalytic applications.

Keywords: carbon capture and utilization; catalyst stability; methanation; polymer-derived ceramics; silicon oxycarbide.