Separation Effects of Renewable Solvent Ethyl Lactate on the Vapor-Liquid Equilibria of the Methanol plus Dimethyl Carbonate Azeotropic System

Ethyl lactate, which is an expected renewable solvent, was tested as an entrainer candidate for the separation of the binary methanol + dimethyl carbonate (DMC) azeotropic system by extractive distillation. Isobaric vapor liquid equilibria (VLE) for two binary constituent systems, that is, methanol + DMC and DMC + ethyl lactate of the methanol + DMC + ethyl lactate ternary system, were determined by an ebulliometric method at pressures of (40.00 to 101.3) kPa. The experimental VLE data were fitted by the nonrandom two-liquid (NRTL) model. Predictions of the binary systems were also performed by the NIST-modified universal functional activity coefficient (UNIFAC) group contribution model. The separation effects of ethyl lactate were examined by two methods: residue curve map and relative volality alpha(12) using the binary NRTL parameters. Both sets of calculated results indicated that ethyl lactate can be used as entrainer. Compared to other entrainers reported in the previous works, ethyl lactate would be a more potential entrainer for breaking the methanol + DMC azeotropic system by extractive distillation, considering not only the minimum liquid mole fraction of the entrainer, but also the corresponding boiling point of the ternary system, viscosity, molecular weight, and price. Finally, the measurements of VLE for the methanol + DMC + ethyl lactate ternary system were also done, and these behaviors were compared with the predictions using binary NRTL parameters and the NIST-modified UNIFAC model.