Deformation of Nanoporous Carbons Induced By Multicomponent Adsorption: Insight from the SAFT-DFT Model

Deformation of nanoporous materials during gas adsorption has been attracting considerable attention due to various applications, including energy and gas storage, carbon capture, and separation. While most practical applications involve multicomponent mixtures, most experimental and theoretical works deal with single-component adsorption. Here, we study the specifics of adsorption-induced deformation during the displacement of methane by carbon dioxide from carbon nanopores, a process of paramount importance for secondary gas recovery and carbon sequestration in shale and coal formations. Density functional theory calculations augmented by the perturbed-chain statistical associating fluid theory (SAFT-DFT) and grand canonical Monte Carlo (GCMC) simulations are employed to model the adsorption of CH4–CO2 mixtures on carbon slit nanopores of various sizes. We found a nonmonotonic behavior of adsorption deformation with increasing pressure and varying mixture composition that is explained by the peculiarities of molecule packings confined in nanoscale pores. The SAFT-DFT method is shown to produce results in agreement with atomistic GCMC simulations at a fraction of the computational cost. The SAFT-DFT method can be extended to study the adsorption selectivity and deformation effects for complex mixtures, including hydrocarbons and CO2.