Marek Rogalski

Ebulliometers modified for the accurate determination of vapour—liquid equilibrium

Abstract The modifications of ebulliometers for the accurate determination of vapour—liquid equilibrium at pressures between 5 and 300 kPa and temperatures from 300 to 500 K are described. The measurements can be performed with or without the determination of the composition of the liquid and vapour phases at equilibrium. The proposed method is suitable for determinations at very low concentrations (limiting values of activity coefficients) and for whole range of concentrations. The ability of the proposed ebulliometers to reach the operation at steady state in a short time after changing the thermodynamic parameters makes possible isothermal as well as isobaric measurements. The procedure for the calculation of the composition of the liquid phase at equilibrium from the composition of the sample introduced into the ebulliometer is given. The accuracy of results obtained is limited only by the purity of the substances used and by the precision of weighing and introduction of the samples into the ebulliometer. To illustrate the performance of the proposed modified ebulliometers, the experimental results obtained for the systems N-methylpyrrolidone—cyclohexane, N-methylpyrrolidone—butylbenzene, and chlorobenzene—hexane are given.

Activity coefficients at infinite dilution of organic compounds in 1-(meth)acryloyloxyalkyl-3-methylimidazolium bromide using inverse gas chromatography.

Activity coefficients at infinite dilution, gammainfinity, of organic compounds in two new room-temperature ionic liquids (n-methacryloyloxyhexyl-N-methylimidazolium bromide (C10H17O2MIM)(Br) at 313.15 and 323.15 K and n-acryloyloxypropyl-N-methylimidazolium bromide(C6H11O2MIM)(Br)) were determined using inverse gas chromatography. Phase loading studies of the net retention volume per gram of packing as a function of the percent phase loading were used to estimate the influence of concurrent retention mechanisms on the accuracy of activity coefficients at infinite dilution of solutes in both ionic liquids. It was found that most of the solutes were retained largely by partition with a small contribution from adsorption and that n-alkanes were retained predominantly by interfacial adsorption on ionic liquids studied in this work. The solvation characteristics of the two ionic liquids were evaluated using the Abraham solvation parameter model.

Vapour—liquid equilibria in binary systems formed by N-Methylpyrrolidone with hydrocarbons and hydroxyl derivatives

Abstract The vapour—liquid equilibria (VLE) determined by an ebulliometric total pressure method under isothermal conditions for binary systems formed by N -methylpyrrolidone with hexane (333.25 and 343.15 K), dodecane (393.25 K), cyclohexane (333.25 and 354.15 K), methyl-cyclohexane (354.15 and 373.25 K), benzene (333.25 and 354.15 K), toluene (362.15 and 383.35 K), propylbenzene (352.15 and 373.75 K), butylbenzene (352.15 and 373.75 K), propanol-1 (354.15 K), hexanol-1 (351.75 and 393.35 K) and at 393.55 K for cyclohexanol, 4-methylphenol and 2,4-dimethylphenol are reported. The vapour pressures of the pure substances are given. The least squares analysis of VLE data by means of the Redlich-Kister equation is given.

A new ebulliometric technique. Vapour-liquid equilibria in the binary systems ethanol-n-heptane and ethanol-n-nonane

Abstract Berro, C., Rogalski, M. and Peneloux, A., 1982. A new ebulliometric technique. Vapour-liquid equilibria in the binary systems ethanol-n-heptane and ethanol-n-nonane. Fluid Phase Equilibria, 8: 55–73. This paper considers a modification to a recirculation still described previously by Berro et al. (1975). The ebulliometric apparatus is coupled to a closed flow system allowing continuous densimetric analysis of liquid and vapour phase compositions. Vapour-liquid equilibria have been measured for two systems: ethanol-n-heptane, at 303.27 (T-P-x data only) and 343.17 K; and ethanol-n-nonane, at 343.21 K. The experimental data were reduced using the observed-deviation method (Neau and Peneloux, 1981). The results of the reduction are presented and discussed.

Modifying the Peng Robinson equation for a homogeneous representation of pure fluid PVT properties

Abstract Peng-Robinson volume corrected equation was modified to yield homogeneous representation of PVT properties of pure fluids. A correcting term which significantly contributes only in the vicinity of the critical point was added. The resulting equation is not cubic any longer but preserves general characteristics of cubic EOS far from the critical point and yields, at the same time, very satisfactory representation of near critical fluid properties.

Heat capacity estimations using equations of state

Abstract Five equations of state accurately expressing the vapor pressures of hydrocarbons were used to estimate Δ C p , the difference between liquid and ideal gas heat capacities. It was observed that two equations of state giving equally accurate vapor pressures can yield very different Δ C p estimates. The consequences are investigated and discussed.

Equation of state associated with activity coefficient models to predict low and high pressure vapor–liquid equilibria

Abstract A simple and thermodynamically consistent method is presented to establish an equation of state for mixtures by using activity coefficient model parameters. All current solution models such as NRTL, van Laar, UNIFAC, or any other thermodynamic model can be used. The main feature of the method presented is that only a single scaling factor value determined at a given reference temperature is required to predict the vapor–liquid equilibria in a wide range of temperature and pressure. The performance of the method is tested on the prediction of the vapor–liquid equilibria at low, moderate, and high pressures for six binary systems (methanol−benzene, acetone−water, methanol−acetone, methanol−water, ethanol−water, and 2-propanol−water) and a ternary system (acetone−water−methanol). For comparison, vapor–liquid equilibrium calculations were carried out with the Wong and Sandler method by using the PRSV equation of state associated with the van Laar and scaling factors. On the whole, it is found that at high pressures both methods give similar predictions but at low pressures the proposed method gives sometimes better results than that of Wong and Sandler method.

Modelling of the phase behaviour of mixtures in the critical region using the augmented Peng-Robinson equation of state

Abstract The Peng-Robinson equation extended to the PVT property representation in the critical point neighbourhood (PRA equation) was used to calculate binary pressure-composition and pressure-density diagrams. The modified excess function at constant packing fraction model was used to take into consideration binary interactions. In the case of binary systems exhibiting the mixture critical point, calculation results were satisfactory and substantially improved with respect to those obtained using the volume corrected Peng-Robinson (PRC) equation.

Charge sensitivity approach to mutual polarization of reactants: molecular mechanics perspective

AbstractCharge sensitivity analysis (CSA) in force-field atoms resolution was applied to describe the mutual polarization of reactants as well as charge-transfer (CT) effects. An inclusion complex of β-cyclodextrin with salicylic acid was used as a model system. Three CSA models were taken into account and verified on a Born–Oppenheimer molecular dynamics (BOMD) trajectory. The models differed in terms of the equilibrium conditions imposed on the system. It was demonstrated that mutual polarization is an important source of stabilization, in contrast to the results obtained from static charge calculations. The energy lowering induced by CT was small and comparable to the CT stabilization that occurs in hydrogen-bonded systems. All models correctly described the main topological features of the BOMD energy surface. CSA in force-field atoms resolution qualitatively reproduced the charge reorganization accompanying hydrogen-bond formation. It was shown that CSA parameters are very sensitive to the bond formation process, which suggests that they could be applied in reactive force fields as detectors of newly formed chemical bonds. FigureFukui function detector of bond formation during molecular dynamics simulations of inclusion complex of b-cyclodextrin with salicylic acid.

Physico-Chemical Properties and Phase Behavior of the Ionic Liquid-β-Cyclodextrin Complexes

The solubility of β-cyclodextrin (β-CD) in ionic liquids (ILs) and the activity coefficients at infinite dilution ( γ13∞) of more than 20 solutes (alkanes, aromatic hydrocarbons, alcohols) were measured in four chosen ionic liquids, their mixtures with β-CD, and in the β-CD at high temperatures from 338 to 398 K using the inverse gas chromatography. The intermolecular interactions, inclusion complexes and the possible increasing of the solubility of β-CD in water using the IL are presented. The solubility of β-CD in ten chosen hydrophobic ILs at the temperature T = 423 K was detected. The solid-liquid phase diagrams (SLE) of {IL (1) + β-CD (2)} binary systems at the high mole fraction of the IL were measured for three systems (1-ethyl-3-methylimidazolium chloride, [EMIM][Cl], 1-ethyl-3-methylimidazolium bromide, [EMIM][Br]; and for 1-butyl-3-methylimidazolium chloride, [BMIM][Cl]). The eutectic points were determined at the high IL concentration for all binary systems. The intermolecular interaction and the possibility of inclusion complexes of the IL and/or solvents with β-CD were discussed. The infrared spectroscopy, IR was used for the description of the intermolecular interactions in the (β-CD + IL) systems. It was shown via the activity coefficients at infinite dilution results that the inclusion complexes are dependent on the temperature. The addition of β-CD to the IL does not improve the selectivity of the separation of the aliphatics from aromatics.