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Liquid to vapor–liquid, liquid–liquid to vapor–liquid–liquid, and liquid to liquid–liquid transition pressures of (α-olefin + n-hexane + LLDPE) systems were measured using a newly constructed and verified synthetic-visual high-pressure cell and metallocene linear low-density polyethylene (LLDPE: M̅ w = 199 kg·mol–1, M̅ w/M̅ n = 2.62, 2.56 mol % 1-hexene). New phase behavior data are reported for a quasibinary (n-hexane + LLDPE) system at polymer mass percentages of w P = (0.5–5) wt % and quasiternary (α-olefin + n-hexane + LLDPE) systems for w P = 3 wt % and polymer-free α-olefin mass percentages of up to 3 wt % ethylene, 20 wt % 1-butene, 100 wt % 1-hexene, 30 wt % 1-octene, and 30 wt % 1-decene. The reported data span temperatures of T = (380–470) K and pressures of P = (0.5–13) MPa. They show that (i) transition temperatures and pressures change linearly with α-olefin mass fraction in the solvent; (ii) the C2 to C6 α-olefins decrease, and the C8 to C10 α-olefins increase the transition temperatures; and (iii) ethylene has a significant antisolvency effect. The measured data are correlated and predicted successfully with the modified Sanchez–Lacombe equation of state.

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Vapor–liquid equilibrium (VLE) and vapor–liquid–liquid equilibrium (VLLE) data were measured for the ethanol/diisopropyl ether (DIPE)/water, n-propanol/DIPE/water, and n-propanol/2,2,4-trimethylpentane (isooctane)/water systems at 101.3 kPa. The data were carefully measured in a Guillespie type still, equipped with an ultrasonic homogenizer. The VLE data were found to be thermodynamically consistent, and the LLE part of the VLLE data followed a regular profile according to the Othmer–Tobias correlation. VLLE were observed in the temperature ranges of (334.19 to 336.29) K, (335.31 to 345.76) K, and (347.74 to 352.31) K for the ethanol/DIPE/water, n-propanol/DIPE/water, and n-propanol/isooctane/water systems, respectively. These VLLE regions encompassed wide ranges for water and entrainer composition, with alcohol mole fractions of up to approximately 0.4. The ethanol/DIPE/water and n-propanol/isooctane/water systems displayed ternary heterogeneous azeotropes at (334.19 and 347.74) K, respectively. However, no ternary heterogeneous azeotrope was found for the n-propanol/DIPE/water system. The measured data were subsequently modeled in Aspen Plus with the nonrandom two-liquid (NRTL), universal functional UNIFAC(VLE), UNIFAC(LLE), and universal quasichemical UNIQUAC activity coefficient models, applying the default regression parameters built into Aspen Plus. UNIFAC(VLE) predicted the ethanol/DIPE/water system most accurately, while UNIQUAC performed the best for the n-propanol/DIPE/water. However, none of these models could predict the n-propanol/isooctane/water system with acceptable accuracy. The results of this study strongly support proposals that DIPE or di-n-propyl ether (DNPE) could be used as effective entrainers for alcohol dehydration, replacing the more traditional entrainers like benzene and cyclohexane.

New subatmospheric vapor−liquid equilibrium (VLE) data for five binary 1-alcohol + n-alkane systems are presented. An all-glass dynamic recirculating still was used to measure the phase behavior of the 1-pentanol + n-nonane, 1-hexanol + n-decane, 1-heptanol + n-undecane, 1-octanol + n-dodecane, and 1-decanol + n-tetradecane systems at 40 kPa. Each of the five systems displayed an azeotrope, indicating complex molecular interactions. Thermodynamic modeling was conducted with (1) the NRTL activity coefficient model, (2) the predictive Soave− Redlich−Kwong (PSRK) group contribution equation of state (EoS) with original UNIFAC model parameters, and (3) PSRK with newly regressed NRTL parameters. The models, in order of decreasing performance, were NRTL > PSRK (with UNIFAC) > PSRK (with NRTL). Therefore, the PSRK with UNIFAC parameters G E -EoS investigated in this article showed that accurate 1-alcohol + n-alkane VLE data can be predicted without the need to first measure experimental data.

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A new association scheme for sPC-SAFT, denoted as 2C, is presented for more-accurate predictions of 1-alcohol/water phase equilibria than with the 2B or 3B association schemes. This 2C association scheme consists of one bipolar association site and one negative electron donor site and is a combination of the 1A and 2B/3B association schemes. The performance of the 2C scheme is evaluated and compared to the 2B and 3B schemes by modeling the vapor–liquid equilibria and liquid–liquid equilibria of alcohol/water, alcohol/alcohol and alcohol/alkane mixtures. Liquid–liquid equilibria of multicomponent systems are also considered. Compared to sPC-SAFT with the 2B or 3B schemes, sPC-SAFT-2C provides improved phase equilibria predictions for the investigated alcohol/water vapor–liquid systems, as well as for liquid–liquid equilibria of water/alcohol/alkane and water/alcohol/alcohol ternary systems. However, a slight deterioration in the prediction of binary alcohol/alkane phase equilibria is observed with the 2C scheme, compared to the 2B scheme. Furthermore, related VLE predictions with sPC-SAFT-2C compare well to predictions with the Cubic-Plus-Association (CPA) equation of state.