Effect of competitive adsorption on the deformation behavior of nanoslit-confined carbon dioxide and methane mixtures

Abstract

Understanding the behaviors of nanoslit-confined carbon dioxide and methane mixtures is of great importance in geological storage of carbon dioxide (CO2) and extraction of methane (CH4) from shale/coalbeds. Herein, the effects of pore width, bulk mixture composition, and geographic depth on the mixture adsorption and pore deformation tendency are studied by using the classical density functional theory. The solvation pressure against pore width shows an oscillating distribution, indicating a deformation transition from expansion to contraction in nanopores. A high recovery ratio of CH4 can be found in small pores at low temperatures and under high bulk pressure. For the 0.68 nm pore, a remarkably high optimal recovery ratio is identified at the geographic depth of about 0.2 km, while for the pores with pore width of 0.9–1.2 nm a modest optimal recovery ratio locates at the depth of about 0.5–1.0 km. This work provides a thorough understanding of the adsorption and deformation behavior of slit-confined mixtures.