Solubility study of carbon dioxide in pentaerythritol esters: Based on SAFT-VR-Mie equation of state

Abstract

Lubricants are almost necessary for carbon dioxide systems in the energy, chemical, and refrigeration industries. The study of the solubility behavior of lubricants with working fluids requires a proper equation of state as necessary tools. The solubility of CO2 in synthetic precursors for polyol esters lubricants has been investigated by SAFT-VR-Mie EoS with variable fluid potential, including pure component pentaerythritol esters (PEC) molecules and CO2-PECs mixed system. The correlations between the molecular parameters in SAFT-VR-Mie EoS and mass of PECs with different branched lengths are given under the constraints of experimental PρT data. According to the parameterized molecular model, the prediction of the critical point and the constant-pressure specific heat of the PECs is introduced in this work. The dissolution balance model of CO2 in PECs was developed by the quantitative model of temperature and molecular mass dependent molecular interaction factor kij. The explanation for the variation of the interaction factors is given by the analysis of the intermolecular volume differences effect, and the extension of this model to commercial lubricants still proves to be valid and accurate.