(51a) Synergistic Adsorption and Catalysis for CO2 Storage and Its Methanation (CSM) over Ni–K2CO3 Supported on Al2O3

Catalytic CO₂ Storage Methanation (CSM) is an emerging approach that integrates CO₂ capture, storage and catalytic utilization into a single material. In this work, we present a Ni-K₂CO₃/Al₂O₃-based catalyst for the CSM system designed to capture CO₂ directly from the air, store it via surface adsorption, and subsequently convert the stored CO₂ to methane through catalytic hydrogenation. Ni is generally used for CO₂ methanation, and K₂CO₃ serves as an effective CO₂ sorbent under ambient conditions.

Figure 1a demonstrates that the Ni-K₂CO₃/Al₂O₃ (Ni/K/Al) effectively operated in the CSM system. In addition, Ni/K/Al achieved a CO₂ capacity of 2.35 mmol/g, nearly three times higher than K₂CO₃/Al₂O₃ (K/Al). These results indicate that Ni is not only active for methanation but also promotes the generation of additional CO₂ adsorption sites. This synergistic enhancement for adsorption was attributed to the reductive decomposition of K₂CO₃ during H₂ pretreatment, forming KO^‒ superbase sites that enhance CO₂ adsorption.

XRD analysis (Figure 1b) confirmed K₂CO₃ decomposition in Ni/K/Al after H₂ pretreatment, as its peaks disappeared—unlike in K/Al where they remained—supporting the proposed mechanism. Additionally, a sharp metallic Ni peak appeared in Ni/K/Al, while Ni in Ni/Al formed inactive NiAl₂O₄ spinel, making it ineffective for methanation. These results suggest that K₂CO₃ suppresses strong Ni– Al₂O₃ interactions, preventing NiAl₂O₄ formation and promoting reducible Ni oxide dispersion on K₂CO₃, enhancing methanation activity.

This study demonstrated the critical role of interfacial interactions between Ni and K₂CO₃ in enabling efficient CSM. Ni facilitated the in-situ generation of active CO₂ adsorption sites through K₂CO₃ decomposition, while K₂CO₃ prevented NiAl₂O₄ formation and promoted Ni dispersion, which further confirmed the catalytic advantages of the Ni/K/Al system. We will discuss in greater detail during the presentation, along with additional performance data, characterization and reaction mechanisms for CMS at the upcoming AIChE meeting.