Positive Effect of Carbon Monolith Porosity Sealing with MgO in the CO ₂ Hydrogenation to CH ₄ Using NiO‐CeO ₂ Active Phase

Abstract Carbon monolith supports have been manufactured using 3D printed channels template and resorcinol‐formaldehyde carbonizable resin. These carbon monoliths were loaded with NiO‐CeO 2 nanoparticles (Np) as the active phase and tested for CO 2 hydrogenation to CH 4 , focusing on the effect of sealing the carbon porosity with MgO. The MgO coating improves CO 2 conversion to CH 4 by preventing the NiO‐CeO 2 nanoparticles from settling within the microporous structure of the carbon support, where gas diffusion limitations hinder access to the active phase. This was confirmed by SEM images, which evidence the introduction of NiO‐CeO 2 (Np) into the carbon matrix of the bare carbon monolith support and the accumulation of the active phase at the surface of the monolith channels once the porosity is sealed. Other characterization techniques like N 2 adsorption and Hg porosimetry, confirm that the porosity is blocked by MgO. On the other hand, it has been demonstrated that there is not a relevant chemical effect of MgO on the NiO‐CeO 2 (Np) catalytic performance for the carbon monoliths supported catalysts, because the contact between the MgO and NiO‐CeO 2 phases is poor due to the dispersing effect of carbon.