Theo W. de Loos

Modelling of liquid–liquid equilibria of mixed solvent electrolyte systems using the extended electrolyte NRTL

Abstract Liquid–liquid equilibria of mixed solvent electrolyte systems were correlated using an extended electrolyte NRTL model. The electrolyte NRTL expression for the activity coefficients has been modified by taking into account the derivatives to the solvent composition of the physical properties and by a new Bronsted–Guggenheim (BG) expression. In addition to some ternary mixed solvent electrolyte systems, the model has been applied to the quaternary systems that are of importance in the extraction process of e-caprolactam: water+e-caprolactam+solvent+ammonium sulfate (AS). The liquid–liquid equilibria of the ternary and quaternary systems involved and the mean activity coefficients of the salt+water systems were used simultaneously to obtain the adjustable parameters. The results are compared to the original electrolyte NRTL of Chen.

Phase behavior of hyperbranched polymer systems: experiments and application of the perturbed-chain polar SAFT equation of state.

Vapor-liquid equilibrium data for systems of hyperbranched polymer (HBP) and carbon dioxide are reported for temperatures of 285-455 K and pressures up to 13 MPa. The bubble-point pressures of (CO2 + hyperbranched polyester) and of (CO2 + hyperbranched polyglycerol + CH3OH) samples with fixed compositions were measured using a Cailletet apparatus. The system (CO2 + polyglycerol + CH3OH) also exhibits a liquid-liquid phase split characterized by lower critical solution temperatures. For this system cloud point curves and vapor-liquid-liquid bubble-point curves were also measured. Moreover, a thermodynamic model has been developed for HBP mixtures in the framework of the perturbed-chain polar statistical association fluid theory (PCP-SAFT) equation of state accounting for branching effects. There is no additional binary interaction parameter introduced along with the branching contributions to the model. Although the miscibility gap in the system (CO2 + polyglycerol + CH3OH) is not predicted by the model, PCP-SAFT including branching effects gives a good representation of the bubble-point curves of this system at temperatures lower than the lower solution temperature (LST).

Solubilities of CO 2 , CH 4 , C 2 H 6 , and SO 2 in ionic liquids and Selexol from Monte Carlo simulations

Monte Carlo simulations are used to calculate the solubility of natural gas components in ionic liquids (ILs) and Selexol, which is a mixture of poly(ethylene glycol) dimethyl ethers. The solubility of the pure gases carbon dioxide (CO2), methane (CH4), ethane (C2H6), and sulfur dioxide (SO2) in the ILs 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Cnmim][Tf2N], n = 4, 6), 1-ethyl-3-methylimidazolium diethylphosphate ([emim][dep]), and Selexol (CH3O[CH2CH2O]nCH3, n = 4, 6) have been computed at 313.15 K and several pressures. The gas solubility trend observed in the experiments and simulations is: SO2 > CO2 > C2H6 > CH4. Overall, the Monte Carlo simulation results are in quantitative agreement with existing experimental data. Molecular simulation is an excellent tool to predict gas solubilities in solvents and may be used as a screening tool to navigate through the large number of theoretically possible ILs.

6 Vapour—liquid equilibrium at high pressure

Publisher Summary It is impossible to perform vapor–liquid equilibrium (VLE) measurements at high pressure for all kind of systems, using one technique only; therefore, the authors have divided the experimental methods for the determination of high-pressure VLE into two groups based on the way the compositions are measured. This chapter makes a classification according to the way the phase equilibrium are obtained—that is, closed- and open-circuit methods. Closed-circuit methods can be divided into static-synthetic and static-analytic methods. These methods have the advantage that the system investigated can be equilibrated for a sufficient time-period, so that the equilibrium is assured. On the other hand, open-circuit methods involve a separator that permits collecting all the circulating phases in equilibrium. Equilibrium is attained during the circulation of a mixture. The major advantages of this method, also known as the “dynamic method,” are the short equilibration times and the possibility for use with nonmetallic materials.

Upper-critical-solution-temperature behavior of the system polystyrene + methylcyclohexane. Influence of CO2 on the liquid-liquid equilibria

Abstract Experimental cloud-point data are reported for polystyrene + methylcyclohexane systems in the vicinity of the upper critical solution temperature (UCST). Two samples of polystyrene were used. One is nearly monodisperse with MW = 31,600 and MN = 29,100. The other has MW = 250,000 and MN = 64,000. Experimental pressures range from 1 MPa to 14 MPa. Experimental temperatures range from 297 K to 306 K for the lower molar mass polymer in methylcyclohexane and 323 K to 331 K for the higher molar mass polymer in methylcyclohexane. The mass fractions of the polymer range between 0.03 and 0.27 for the monodisperse sample and between 0.02 and 0.14 for the other. Data are also reported on the influence of CO2 on the phase behavior of the monodisperse sample in methylcyclohexane for two polymer mass fractions.

Enzymatic Reaction in Organic Solvents and Supercritical Gases

The enzymatic esterification of glycidol and butyric acid, catalysed by porcine pancreatic lipase (ppl), has been performed in different organic solvents and compared with equilibrium conversions estimated from theory. Preliminary results show that the predicted equilibrium conversions were in good agreement with experiments for most of the organic solvents tested. In different organic solvents the enzyme exhibited enantioselectivity. It appears that the more polar the organic solvent, the higher was the selectivity towards the R-isomer. Conversions were also predicted for supercritical solvents. The conversion in supercritical carbon dioxide was predicted to be greater than that in the organic solvents. Moreover, the conversion in carbon dioxide was predicted to be greater than that in supercritical ethane. In the phase behavior of the glycidol and carbon dioxide binary two liquid phase coexisted near the critical point of pure carbon dioxide. Taking into account the three phase (liquid-liquid-vapor) lines of glycidol-carbon dioxide, the gas phase reaction conditions should be selected at temperatures above 310 K and pressures above 80 bar.