CO2 hydrogenation on ruthenium: comparative study of catalyst supports†

To achieve a significant reduction in anthropogenic CO₂ in the near future, captured carbon has to be valorized. To this end, CO₂ may be activated using H₂ to form sustainable fuels (synthetic natural gas), platform chemicals (methanol) and higher hydrocarbons (modified Fischer–Tropsch process). In this work we synthesize Ru based catalysts from various commercially available support materials and test them under lower temperatures than usually employed at various partial pressures of CO₂ and H₂ using methanation as a model reaction. The results show Ru/TiO₂, Ru/ZrO₂ and Ru/Al₂O₃ as the most active catalysts with high activity, selectivity towards methane (>95%), and stability with little to no deactivation over 80 h. These most promising catalysts are further tested and kinetic parameters determined, which find reaction orders and activation energies in agreement with literature, but differing from catalyst to catalyst, hinting at complex reaction mechanisms including the support as well as the Ru. The TOF calculated for Ru/TiO₂ at 190 °C is 5.7 s⁻¹ and highlights it as the most active catalyst in this work. The study opens new and promising avenues for the valorization of CO₂, as well as a basis to compare future optimizations and advances in the field of Ru-based CO₂ conversion.