Phase equilibrium measurements and thermodynamic modelling for the systems involving valeric acid, ethanol, ethyl valerate and water plus CO2

Abstract

This work reports phase equilibrium measurements for binary, ternary, quaternary and five components mixtures of CO2, ethanol, valeric acid, water and ethyl valerate at high pressures. Experiments were carried out using a high-pressure variable-volume view cell with operating temperatures ranging from 303.15K to 353.15K and pressures up to 15MPa. The CO2 mole fraction ranged from 0.4780 to 0.9412 for the binary system {CO2(1)+valeric acid(2)}, from 0.3801 to 0.9811 for {CO2(1)+ethyl valerate(2)}, from 0.5649 to 0.9193 for the ternary system {CO2(1)+ethanol(2)+valeric acid(3)} at an ethanol to valeric acid mole ratio of (3:1) and from 0.5907 to 0.9373 for {CO2(1)+ethanol(2)+ethyl valerate(3)} at an ethanol to ethyl valerate mole ratio of (1:1). For the quaternary {CO2(1)+ethanol(2)+water(3)+ethyl valerate(4)} and the five components system {CO2(1)+ethanol(2)+valeric acid(3)+water(4)+ethyl valerate(5)} fixed compositions were investigated at CO2 mole fraction of 0.7336 and 0.7211, respectively, while the mole ratio of other compounds were fixed at typical esterification conditions. For the systems investigated, vapour-liquid (VL), liquid-liquid (LL) and vapour-liquid-liquid (VLL) phase transitions were observed. The experimental data sets were successfully modeled using the Peng-Robinson cubic equation of state with the Boston-Mathias alpha function and using the van der Walls quadratic mixing rule. The PR-BM showed good performance in the prediction of the phase transitions for the ternary, quaternary and five components systems based on the binary interaction parameters obtained from the binary CO2+valeric acid, CO2+ethyl valerate and CO2+ethanol experimental data.