Vapor-liquid equilibrium for 1,4-butanediol, ethylene glycol and 3-methyl-1,5-pentanediol systems under different vacuum conditions

The utilization of 1,4-butanediol (BDO) spans across numerous sectors, underscoring its significance as a pivotal chemical. However, the separation of crude BDO still presents great challenges. Ethylene glycol (EG) and 3-methyl-1,5-pentanediol (MPD) are classical impurities in BDO crude products. In this paper, the pressure and temperature data of MPD components under high vacuum pressure were measured, and Antoine constant was obtained by fitting to supplement the basic data. The isobaric vapor-liquid equilibrium (VLE) data for the EG-BDO and BDO-MPD mixtures were experimentally measured at pressures of 1.0, 10.0, and 50.0 kPa. Meanwhile, the thermodynamic consistency of the experimental binary data was examined using the Herington area test. The experimental VLE data for binary systems were analyzed using the nonrandom two-liquid (NRTL) universal quasichemical (UNIQUAC) and Wilson activity coefficient models, demonstrating that the predicted outcomes showed excellent agreement with the measured data. Finally, the interaction energy between the components was calculated by molecular simulation to explain the gas-liquid equilibrium behavior. Therefore, this work provided guidance and basis for the separation of EG-BDO and BDO-MPD in high vacuum separation.