Highly efficient separation and equilibrium recovery of H₂/CO₂ in hydrate-based pre-combustion CO₂ capture

Gas hydrate-based CO₂ capture processes have attracted considerable attention due to their potentials for energy-efficient pre-combustion CO₂ capture. Recent investigations have explored the use of tailored-wettability porous silica gels, highlighting benefits in thermodynamic and kinetic efficiencies, specifically characterized by low energy requirements and rapid formation. However, achieving high purity levels for both H₂ and CO₂ is crucial for practical implementation. Consequently, identifying and optimizing an effective separation route becomes imperative. In this study, we examined the thermodynamic stability, gas uptake, and separation factors of THF (5.56 mol%) + H₂ + CO₂ hydrates with varying compositions (H₂:CO₂ = 80:20, 60:40, 30:70, or 20:80 mol%) in C0 and C1 silica gel (functionalized by monofunctional alkylsilanes (X-(CH₃)₂-Si-C_n)) systems with SDS (0 or 500 ppm). Pressure-composition diagrams for THF + H₂ + CO₂ systems in C0 and C1 silica gel were meticulously measured. Notably, the C1 silica gel system without SDS demonstrated good thermodynamic stability, substantial gas uptake, and a significant separation factor. Based on the pressure-composition diagram of the C1 silica gel system, we proposed a highly efficient route for separating H₂ and CO₂. This proposed cyclic process involves a three-stage reactor and achieve to gas hydrate-based pre-combustion CO₂ capture, yielding a purity of approximately 91 % H₂ and 94 % CO₂. The present findings provide valuable insights into optimizing the wettability of porous media and efficient separation routes, demonstrating the feasibility of a gas hydrate-based pre-combustion carbon dioxide capture process.