Improving the Adsorption Selectivity of CO₂/CH₄ by Strength, Shape and Kinetics

Gas separation by adsorption can be accomplished by three basic physical mechanisms: equilibria, kinetics, and steric effects. Equilibrium mechanisms rely on the strength of attraction between gas molecules and their substrate. For example, the interaction of CO₂ with a substrate is usually stronger than methane-substrate. As a result, the equilibrium mechanism presents a plausible strategy to separate carbon dioxide from mixtures. We have studied the adsorption of CO₂/CH₄ mixtures on various substrates by Monte Carlo and Molecular Dynamics simulations. Our findings show that on substrates including MOFs, carbon nanohorns and graphene, the selectivity of adsorption of CO₂/CH₄ at room temperature is low (near 1). We explore the kinetics and steric effects on the selectivity, finding that the combination of the three above-mentioned mechanisms can significantly boost the CO₂/CH₄ separation at 300K. In this talk, I will present a review of the various cases studied.