Isobaric Vapor–Liquid Equilibria of Binary Systems Containing Cyclohexane for the Separation of Phenolic Compounds from Biomass Fast Pyrolysis Oils

Biomass pyrolysis oil is considered to be a promising alternative to fossil energy for the synthesis of high value-added chemicals and fuels. 2-Methoxy-4-methyl phenol (MMP), 4-ethylphenol (EP), 3,5-dimethylphenol (DMP), and m-Cresol (MC) are the important phenolic compounds in pyrolysis oil. The investigation of phase equilibrium is crucial to design separation processes. In this work, the isobaric vapor–liquid equilibrium (VLE) experiment, correlation, and estimation of binary systems (cyclohexane + MMP/EP/DMP/MC) were investigated. The experimental data were verified by the Herington test and van Ness test, and all were thermodynamically consistent entirely. The binary energy interaction parameters were obtained by correlating the experimental data using NRTL, Wilson, and UNIQUAC activity coefficient models. The average absolute relative deviations (ARD %) of T, x1, and y1 correlated by NRTL, Wilson, and UNIQUAC models for four binary systems are below 0.2. In addition, the VLE data were correlated and estimated by the UNIFAC-DMD model. The new interaction parameters of the C–CH2 group in the UNIFAC-DMD model were obtained and used to estimate cyclohexane + DMP systems. The ARD % of T and y1 for cyclohexane + DMP systems were 1.02 and 0.43, respectively. The estimation accuracy of UNIFAC-DMD with new parameters was significantly improved.