Effect of the quadrupolar contribution of CO2 on the vapor–liquid equilibria and surface tensions of CO2–hydrocarbon binary mixtures

• An EOS was established by combining PCP-SAFT with DGT.
• The bulk and interfacial properties of CO2–hydrocarbon mixtures were investigated.
• The phase behaviors of non-polar CO2 and quadrupolar CO2 were compared.
• The effect of the quadrupolar contribution of CO2 was demonstrated.

An equation of state (EOS) was established by combining the perturbed-chain polar statistical associating fluid theory (PCP-SAFT) with density-gradient theory (DGT). The bulk and interfacial properties of carbon dioxide (CO2)–butane, CO2–decane, CO2–benzene, CO2–cyclohexane and CO2–tetradecane binary mixtures were investigated. To illustrate the effect of the quadrupolar contribution of CO2 on the bulk and interfacial properties, the calculated vapor–liquid equilibria (VLE) and surface tensions were compared with those calculated from the perturbed-chain statistical associating fluid theory (PC-SAFT) and DGT, in which CO2 was treated as non-polar molecule. Results showed that by taking into account the quadrupolar contribution of CO2, both the VLE and surface tensions of CO2–hydrocarbon binary mixtures can be significantly improved compared with the experimental data.