Isobaric Vapor–Liquid Equilibrium Data for the Near-Boiling System 1,2,4-Trimethylbenzene + 1,3,5-Trimethylbenzene + Dimethyl Sulfoxide or Sulfolane at 101.3 kPa

For the separation of 1,3,5-trimethylbenzene (1,3,5-TMB) and 1,2,4-trimethylbenzene (1,2,4-TMB), dimethyl sulfoxide (DMSO) and sulfolane were chosen as solvents. The vapor–liquid-phase equilibrium (VLE) data of the binary systems 1,3,5-TMB + 1,2,4-TMB, 1,3,5-TMB + DMSO, 1,2,4-TMB + DMSO, 1,3,5-TMB + sulfolane, and 1,2,4-TMB + sulfolane were determined at 437.78 to 560.32 K and 101.3 kPa. The data were tested for thermodynamic consistency by the Herington method and the Wisniak L–W method. The VLE data were correlated by using Wilson, NRTL, and UNIQUAC thermodynamic models, and the binary interaction parameters of the three thermodynamic models were obtained. By analyzing the thermodynamic parameters and their RMSD and AAD, it was found that the NRTL model is more accurate and can be used to simulate systems containing 1,3,5-TMB, 1,2,4-TMB, DMSO, and sulfolane. The ternary VLE data of 1,3,5-TMB + 1,2,4-TMB + solvents were measured and compared with the predicted data of the NRTL model, and it was found that the predicted results were consistent with the experimental results. The research results proved that the two solvents, DMSO and sulfolane, greatly improved the separation of the 1,3,5-TMB + 1,2,4-TMB system, with sulfolane being more effective. The present work provides reliable basic data for the process development of the 1,3,5-TMB + 1,2,4-TMB system.