Fuel from air: NiO-CeO2 nanoparticles, MgO and beta zeolite dual function materials for direct CO2 capture and hydrogenation to CH4

• Efficient dual-functional materials (DFM) based on MgO and NiO-CeO 2 on β-zeolite were presented. • DFM showed capabilities on both capturing CO 2 from air and its hydrogenation into CH 4 . • CO 2 capture step from air at 35 °C retained the 77 % of the inlet CO 2 . • Rapid heating to 350 °C under H 2 enabled to convert the 45 % of captured CO 2 into CH 4 . Dual function materials based on NiO-CeO 2 nanoparticles and MgO supported on beta zeolite have been prepared and tested for direct capture of CO 2 from air and further hydrogenation to CH 4 . Catalysts characterisation shows highly microporous materials with good dispersion of the NiO-CeO 2 active phase on the zeolite carrier and a slight blockage of zeolite pores. H 2 -TPR and XPS characterisation reveal that the beta zeolite improves the reducibility of the dispersed NiO-CeO 2 active phase. Among the synthesis methods tested, impregnation-calcination is more convenient than zeolite crystallization in the presence of NiO-CeO 2, leading to materials with higher catalytic activity in the CO 2 methanation reaction. On the contrary, the NiO-CeO 2 loading had little effect in the range studied (10, 20 %). The presence of MgO disrupts the intrinsic high catalytic performance of NiO-CeO 2 , but this penalty is not encountered when both MgO and NiO-CeO 2 are dispersed on the beta zeolite support. CO 2 capture from air at 35 °C, studied by thermogravimetry, suggests that CO 2 chemisorption on MgO and NiO-CeO 2 prevails with regard to physisorption on beta zeolite. In situ DRIFTS analysis showed that the mechanism of CO 2 adsorption involved carbonate and bicarbonate species and revealed that isolated silanol groups of the beta zeolite can act as CH 4 trapping sites. Therefore, the MgO and NiO-CeO 2 containing beta zeolite catalyst is an adequate dual function material to capture CO 2 directly from air and catalyse the hydrogenation of the CO 2 captured to CH 4 .