Vapor–liquid equilibria for CO2–fermentation alcohol mixtures: Application of a new group contribution equation of state to isomeric compounds

This study provides vapor–liquid equilibrium data that can be used for the separation of trace components from fermentation alcohol with supercritical CO2. C4 and C5 alcohols were selected as key components among the trace components of fermentation alcohols because these are impurities that can be produced during the process and separation is necessary from alcohol aqueous solutions. Vapor–liquid equilibrium data were measured for the systems of CO2–1,3-butanediol, CO2–1,2-butanediol, CO2–iso-amylalcohol, CO2–2-methylbutanol, and CO2–iso-butanol at 313.2 and 333.2 K at pressures from 4 to 15 MPa. The experimental results demonstrated that the isomers exhibited a slightly different phase behavior for the binary mixtures of CO2 at the range studied. The group contribution equation of state (GC-EOS) proposed by Skjold-Jorgensen [S. Skjold-Jorgensen, Fluid Phase Equilib. 16 (1984) 317–351] was modified to allow application to isomers by considering the contact surface area between molecular pairs. The new model could predict the phase behavior of the binary mixtures of CO2 and C4/C5 alcohols contained in fermentation alcohols.