CO2 Conversion into Methane Over Ru/CeO2 Catalysts Prepared From Different Metal Ion Precursors

Anthropogenic CO2 from aerospace cabin, or CO2 from outdoor atmosphere, such as the Martian atmosphere, may be converted into methane and water by the Sabatier reaction. Ru-based materials are suitable catalysts for methanation due to their high activity and selectivity. A previous study of a Ru/CeO2 catalyst prepared by one-pot hydrothermal synthesis from metal nitrate solutions, showed good activity for CO2 methanation with very high selectivity towards CH4 against CO (98 % at 350 °C), and high stability over time-on-stream, appearing as a promising and reliable Sabatier catalyst for in-situ resource utilization of CO2. In this study, four Ru/CeO2 catalysts were synthesized by one-pot hydrothermal method starting from different metal ions precursors, such as ruthenium(III) chlorine or nitrosyl nitrate salts, and cerium(III) nitrate or ammonium cerium(IV) nitrate salts. The catalytic tests showed that the nature of the metal precursor strongly affects the catalytic performances of the Ru/CeO2 system. The two catalysts prepared starting from RuCl3 showed higher activity than those prepared from the most used Ru(NO)(NO3)3 precursor, whereas one formulation produced an inactive material. The time-on-stream test (TOS), carried out for 40 hours in the range of 300-500 °C, revealed no activity nor selectivity loss. To understand the effect of the precursor nature on the material, a deep physical-chemical characterization of samples is needed. Some preliminary results on the surface morphology and Ru reducibility and dispersion obtained by XRD, BET-BJH, H2-TPR and H2-TPD, RAMAN and XPS are reported.