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.

The lower critical end point temperatures of [ethylene + comonomer + n-hexane + linear low-density polyethylene (LLDPE)] systems are shown to be strongly correlated with solvent average molecular mass and mole fraction-averaged carbon number, but not solvent density or critical temperature. A synthetic-visual method is used to measure vapor–liquid, vapor–liquid–liquid, and liquid–liquid phase boundaries for quasiquaternary (ethylene + comonomer + n-hexane + LLDPE) systems for the 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, and 1-decene comonomers, and for quasiternary (ethane/n-decane/4-methyl-1-pentene + n-hexane + LLDPE) systems. The reported data span temperatures of T = (375–465) K and pressures of P = (0.5–15) MPa. In all systems, the mass fraction of the LLDPE (M̅ w = 199 kg·mol–1; M̅ w/M̅ n = 2.62; 2.56 mol % 1-hexene) was kept at 3 wt % and solvent compositions were chosen to represent conditions found in the solution polymerization process. The modified Sanchez–Lacombe equation of state can predict the quasiquaternary systems’ phase behavior with moderate accuracy using parameters adjusted to quasiternary data.

The effect of temperature on the liquid–liquid equilibrium (LLE) phase behavior of ternary (water + alcohol + entrainer) systems comprised of the alcohols ethanol, isopropanol, and n-propanol and the entrainers diisopropyl ether (DIPE), cyclohexane, and isooctane (excluding (water + n-propanol + DIPE)) was investigated for application to the decanter in heterogeneous azeotropic distillation. LLE data were measured at ambient pressure for the (water + isopropanol + cyclohexane), (water + isopropanol + isooctane), and (water + n-propanol + isooctane) systems at 308.2 and 318.2 K and for the (water + n-propanol + cyclohexane) and (water + ethanol + isooctane) systems at 318.2 K. These data, in conjunction with literature LLE data, show that temperature has an effect on all systems investigated. As temperature increases, the aqueous phase becomes depleted of and the organic phase becomes enriched in alcohol. It appears that component polarities play an important role in explaining the phase behavior. The systems were correlated with the NRTL and UNIQUAC ACMs in Aspen Plus V8.2, but reliable correlations were only obtained for the (water + ethanol + DIPE/cyclohexane/isooctane) and (water + ethanol/isopropanol/n-propanol + cyclohexane) systems. These correlations were used to simulate the decanter water recoveries over a range of temperatures.

No abstract

A simple method to predict the liquid–liquid (LL), vapor–liquid (VL), and vapor–liquid–liquid (VLL) boundaries of (solvent + polymer) systems found in the solution process is developed with theoretical justification. The method is developed using the (solvent + LLDPE) data of only two polymers and applied to the (solvent + polymer) data of 276 different systems containing 65 different solvent combinations (up to five solvent constituents) and 69 different nonaromatic hydrocarbon polymers with predominantly linear backbones. For data sets of interest to the solution process, lower critical end point (LCEP) temperatures and pressures can be estimated with average absolute deviations (AADs) of 4 K and 0.2 MPa, respectively. The effects of ethylene and/or comonomer addition and nitrogen addition are accurately predicted (VL/VLL: AAD = 0.2 MPa, n = 1084; LL: AAD = 0.5 MPa, n = 1115). Good results are obtained when extending the results of pure solvents to commercial-grade solvents.