Phase Equilibrium Measurements and Thermodynamic Modeling of CO₂ + Diethyl Carbonate and CO₂ + Diethyl Carbonate + Ethanol Systems

This study presents new vapor–liquid equilibrium measurements and thermodynamic modeling for the binary system CO2 + diethyl carbonate (DEC) and the ternary system CO2 + DEC + ethanol. DEC is a promising biobased compound, applicable as a fuel additive and chemical intermediate. Its sustainable production through CO2-ethanol carbonylation has garnered interest under carbon capture and utilization frameworks. Using a high-pressure visual synthetic method, we measured phase transitions over a range of 30–80 °C and CO2 mole fractions from 0.50 to 0.90. The data were modeled using the Peng–Robinson equation of state with a van der Waals quadratic mixing rule (vdW2), showing excellent agreement (average absolute deviations ≤2.1 bar for binaries and ≤4.7 bar for ternaries). This contribution delivers a consistent data set for the ternary CO2 + DEC + ethanol system, aiding thermodynamic modeling and contributing to the development of clean technologies in the biofuels and sustainable chemical sectors.