Exploring the possibility to use Li-exchanged zeolites as catalyst for CO2 hydrogenation

Converting CO2 emissions from industrial processes into synthetic fuels, such methane, using green hydrogen represents an interesting tool to manage the surplus production of energy from intermittent renewable sources using a greenhouse gas [1]. The occurrence of CO2 methanation, based on the Sabatier reaction, requires the use of a catalyst consisting in an active metal (generally Ni or Ru) supported on mesoporous or microporous materials, as alumina, SBA-15, MCM-41 and zeolites [2]. Addition of alkali, most of all to alumina, strongly improves the CO2 adsorption capacity thus increasing the overall catalytic performances [3]. Alkali cations also modify the basicity of zeolites enhancing the CO2 adsorption/activation [2]. Low silica type X zeolite (LSX) was found a promising CO2 sorbent, Li-LSX showing excellent performance [4]. Dispersion of an active metal on the zeolite provides the catalytic functionality to produce methane from adsorbed CO2 and H2 [1, 2]. The alkali metal is generally exchanged whereas the active transition metal cation is more commonly introduced by impregnation. Nevertheless, the location of the active metal cation in the zeolite plays a crucial role in determining both activity and selectivity [5] and a close contact between adsorbed CO2 and H2 is a key factor for the catalytic reaction [3]. Attempts to exchange Ru in ZSM5 have been reported using suitable precursors and the performance of the exchanged zeolite was found better than that of the Ru-impregnated counterpart even if for a reaction different from methanation [6]. In this work the CO2 adsorption capacity of commercial Li-LSX pellets was explored in order to evaluate the possibility to use this material as support for methantion catalysts after the dispersion of Ru, investigating the possible routes to introduce the noble metal. References: [1] Bacariza, M. C., Graça, I., Lopes, J. M., Henriques, C. ChemCatChem 2019, 11, 2388-2400. [2] Bacariza, M. C., Graça, I., Lopes, J. M., Henriques, C. Micropor. Mesopor. Mater. 2018, 267, 9-19. [3] Cimino, S., Boccia, F., Lisi, L. J. CO2 Utiliz. 2020, 37, 195-203. [4] Kodasma, R., Fermoso, J., Sanna, A., Chem. Eng. J. 2019, 358, 1351-1362. [5] Wei, L., Kumar, N., Haije, W., Peltonen, J., Peurla, M., Grénman, H., de Jong, W., Molecular Catalysis 2020, 494, 111115. [6] Yan, P., Kennedy, E., Stockenhuber, M., J. Catal. 2021, 396, 157-165.