Vapor–Liquid Interfacial Properties of CO2 Mixtures for Sequestration Applications: Molecular Simulations, Classical Density Functional Theory, and Equations of State

Experimentally determining interfacial tension (IFT) for compositions relevant to CO2 transport is challenging. We address this using molecular dynamics (MD) simulations and perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state with classical density functional theory. We compute phase equilibria and interfacial properties of pure CO2 and CO2–CH4, CO2–Ar, CO2–N2, and CO2–H2 mixtures at 220–273 K. Both approaches accurately estimate CO2 phase equilibria and IFTs. For binary mixtures, phase equilibria computed using PC-SAFT agree well with experiments when kij ≠ 0. IFTs computed from PC-SAFT depend strongly on kij, while MD simulations systematically overpredict IFTs. The IFT decreases with increasing pressure, least pronouncedly for H2-containing mixtures. Binary mixtures exhibit interfacial enrichment of the light boiling component, decreasing with increasing temperature and pressure. Semiempirical Parachor and Winterfeld–Scriven–Davis models capture IFT–pressure trends with mixture-dependent accuracy. These results improve predictions of metastable limits and provide key insights for fast-transient multiphase CO2 flow modeling.