Advancing decarbonization: experimental perspectives on CO2 methanation

Carbon dioxide capture, conversion and storage (CCCS) technologies are becoming crucial in representing a route for the use of carbon dioxide as C1 building block1. On the other side, renewable energies face the issue of intermittency, so the surplus energy from renewable resources could be stored in the guise of green hydrogen, which however still lacks a capillary distribution network. It can be used for CO2 methanation as an interesting solution, due to wide methane grid existing worldwide and the clear regulatory framework. In our study the methanation of carbon dioxide was approached thanks to the use of two continuous experimental setups. Specific focus is put on the direct methanation of biogas streams to obtain upgraded biomethane. The initial catalysts screening was performed in an Incoloy 800 tubular reactor under atmospheric pressure. Subsequently, high-pressure tests and Gas Hourly Space Velocity (GHSV) screening in the range of 3000 h-1 to 400000 h-1 were conducted using a PID FR-50, equipped with a SS-316 tubular reactor and a continuous G/L separator. Numerous materials were used to support the Ni active phase, such as Al2O3, ZrO2, TiO2, ZSM-5, SiO2, MgO and CeO2. Catalysts were obtained through the use of various techniques, including wet-impregnation, sol-gel, co-precipitation, radio frequency (RF) thermal plasma and Ultrasound-Assisted synthesis technique. The effect of mixed supports, such as Al2O3/CeO2 and ZrO2/CeO2 has been investigated as well. Testing has been done both on pure CO2 streams, supposed coming from a CO2 capture process, and on biogas streams, without prior separation. Several catalysts showed interesting performance and, among them, 36% Ni/Al2O3 and 36% Ni/ZSM-5 achieved high CO2 conversion, approaching the thermodynamic equilibrium. Overall, the use of Ni catalysts, despite the relatively high loading, has proven to be suitable for methanation, presenting an alternative to noble metal-based catalysts. References: [1] S.A. Theofanidis, A.N. Antzaras, A.A. Lemonidou, Curr. Opin. Chem. Eng. 39 (2023) 100902. [2] M. Tommasi, S.N. Degerli, G. Ramis, I. Rossetti, Chem Eng Res Des. 201 (2023) 457–482. Acknowledgments This study was carried out within the Agritech National Research Center and received funding from the European Union Next-Generation EU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 – D.D. 1032 17/06/2022, CN00000022).