Measurement of Vapor–Liquid Equilibrium Data for Binary Systems CO₂ + Ethyl Propionate, Methyl Propionate, Ethyl Acetate, and Ethyl Isobutyrate at 253.15 K

In order to improve the decarbonization capacity of the absorbent in the syngas purification process in industry, selecting and developing more efficient physical solvents has become a breakthrough direction. Considering that ester solvents have great potential for absorbing CO2, in this work, vapor–liquid equilibrium (VLE) data were measured for the binary system of CO2 + ethyl propionate, methyl propionate, ethyl acetate, and ethyl isobutyrate at 253.15 K. Herein, the operating pressure ranges from 0.3 to 1.7 MPa. The experimental data were correlated by Peng–Robinson (PR) and Soave–Redlich–Kwong (SRK) equations of state with van der Waals (vdW) mixing rules. Among the aforementioned equations, the PR equation of state correlates the experimental data better above 1.2 MPa. Moreover, it can be found that ethyl acetate has the best CO2 absorption performance, followed by methyl propionate, ethyl propionate, and ethyl isobutyrate. In addition, the average absolute relative deviations of the molar fractions of CO2 in the vapor phase and measured pressures were calculated for each system. As a result, the overall deviations were less than 0.02% and 4%, respectively, indicating that the measured experimental values are stable and reliable. This work will not only provide a reference for screening efficient CO2 absorption solvents but also provide the basic thermodynamic data for the syngas purification process.