Synthesis and study of catalysts with perovskite-based supports for cyclic CO2 methanation

In recent years, carbon capture is emerging as a valid solution to close the carbon loop for processes with unavoidable CO2 emissions. Upon capture, CO2 can be either stocked or converted into value-added molecules. The present study focuses on a combined CO2 capture and conversion process, leading to methane production. Dual functional materials have served this purpose. In the first part of this work, five catalysts with a low ruthenium loading and perovskite-based supports (SrTiO3 and BaCeO3) were synthetized via solid-state route. The active metal phase was introduced into the materials using different approaches. In two cases, Ru was deposited on the support surface via impregnation, while in the others, Ru was incorporated as a B-site ion into the perovskite matrix and subsequently exsolved through thermal treatment in a reducing environment, forming nanoparticles on the surface. Additionally, the effect of the sintering temperature (1000°C and 1400°C) was investigated for one of the exsolved catalysts. In the second part of the study, catalyst performance was evaluated in the direct methanation reaction (P=1 bar, T =200°C-400°C, H2/CO2=4) to assess material behaviour under reaction conditions. In these circumstances, a kinetic study was conducted to estimate the apparent activation energy. Subsequently, cyclic methanation tests were conducted (P=1 bar, T =300°C). Each cycle consisted of a CO2 adsorption step followed by a methanation reaction step, during which hydrogen was supplied to the reactor. The results allowed a comparison between the performance of the exsolved catalysts and the impregnated ones. The study of the prepared and tested materials was completed with their characterization using XRD to investigate their surface crystalline structure, H2-TPR to evaluate their reducibility, TEM to gain insights into particles morphology, FESEM, EDX and CO pulse to estimate the surface Ru metal particle dispersion, and N2 physisorption at 77K to assess specific surface area of the samples. The main goal of this work is therefore to investigate the performance of perovskite-based materials in a field where they have been scarcely explored, with the aim of contributing to the development of more efficient catalytic systems for CO2 valorization.