Modeling the Phase Behavior of Carbon Dioxide Solubility in Deep Eutectic Solvents with the Cubic Plus Association Equation of State

Abstract

The thermodynamic modeling of a new generation of solvents, deep eutectic solvents (DESs) is investigated. Because hydrogen bonding is a dominant molecular interaction, the cubic plus association (CPA) equation of state (EoS) was chosen for modeling. This is the first study to model DES density and carbon dioxide solubility using CPA. Fifteen different DESs were chosen which have density data, as well as CO2 solubility data, available in the literature over wide temperature and pressure ranges. To date, this is the most extended and global databank of DESs which has been employed in relation to a complex EoS. The density data were used to optimize the CPA parameters. The CPA EoS proved to be capable of accurately modeling pure DES densities. The validity of the optimized CPA parameters was further validated with literature density data of mixtures of DES + water, which were estimated successfully by a purely predictive procedure. To calculate CO2 solubility in DES, all the possible association schemes of CO2 were investigated. It was concluded that the inert (no-association) scheme for CO2 was the most accurate (AARD% = 6.2), while at the same time being the simplest with fewer fitting parameters. The induced association (solvation) scheme (AARD% = 7.1) is also suitable. © 2017 American Chemical Society.