Prediction of vapor-liquid equilibrium from excess enthalpy data for binary ether +n-alkane or cyclohexane mixtures

Vapor liquid equilibrium (VLE) is successfully predicted from excess enthalpy H^E data for binary ether + n-alkane or cyclohexane mixtures. Parameters for the continuous linear association model (CLAM) and for the UNIQUAC Model for the excess Gibbs energy G^E were determined from H^E data measured at a low temperature (ambient temperature). These parameters are used to predict VLE data at low and high temperatures. The dependence of the accuracy of predictions on the set of H^E data chosen to evaluate the parameters and on the model for G^E are discussed.     

Multilayer adsorption from multicomponent liquid mixtures on solid surfaces

Multilayer adsorption of multicomponent liquid mixtures on homogeneous and heterogeneous solid surfaces is discussed. Heterogeneity effects of the adsorbent surface have been taken into account in calculation of mole fractions of the components in the first adsorbed layer. The model calculations, illustrating multilayer and heterogeneity effects, have been performed for adsorption of ternary liquid mixtures.

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Mehrschicht-Adsorption von flüssigen Mehrkomponentenmischungen auf festen Oberflächen

Zusammenfassung Es wird die Mehrschichtadsorption auf homogenen und heterogenen Oberflächen diskutiert. Bei der Berechnung der Molbrüche der Komponenten der ersten adsorbierten Schicht wurden Heterogenitäts-Effekte berücksichtigt. Die Modellrechnungen wurden an ternären flüssigen Mischungen vorgenommen.

     

Statistical thermodynamics of adsorption from multicomponent liquid mixtures on heterogeneous solid surfaces

The statistical thermodynamics of adsorption from multicomponent liquid mixtures on heterogeneous solid surfaces is discussed by assuming the cell adsorption model and ideal adsorbed phase.Two integral representations for the adsorption isotherm are proposed: one based onn-dimensional energy distribution function (i.e., each adsorption site is characterized by adsorption energies of all components), and the other based on distribution of differences of adsorption energies ofn-1 components in relation to adsorption energy of the chosen component (i.e., each adsorption site is characterized byn-1 differences of adsorption energies of the components in relation to adsorption energy of the chosen component).The expressions for differential adsorption heat for adsorption from binary liquid mixtures have been derived from both integral equations.

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Statistische Thermodynamik der Adsorption aus flüssigen Mehrkomponentenmischungen auf heterogenen festen Oberflächen

Zusammenfassung Die statistische Thermodynamik der Adsorption von aus mehreren Komponenten bestehenden flüssigen Mischungen auf heterogenen festen Oberflächen wird für das Modell der Zellenadsorption bei ideal adsorbierter Phase diskutiert.Zwei Integraldarstellungen der Adsorptionsisotherme werden vorgeschlagen: eine auf einen-dimensionale Verteilungsfunktion der Energie gestützte (das heißt, jede Adsorptionsstelle wird durch Adsorptionsenergien von allen Komponenten charakterisiert); die andere basiert auf der Verteilung der Unterschiede von Adsorptionsenergien dern-1-Komponenten in bezug auf die Adsorptionsenergie der ausgewählten Komponente (das heißt, jede Adsorptionsstelle wird durchn-1-Unterschiede charakterisiert. Formeln für differentiale Adsorptionswärmen für die Adsorption aus binären flüssigen Mischungen sind von beiden Integral-Gleichungen abgeleitet worden.

     

Excess thermodynamic properties of binary liquid mixtures containing dimethylsulfoxide at 30°C

The exess volumes of mixing of dimethylsulfoxide with n-, sec- and tertbutylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine and cyclohexylamine have been measured as a function of composition at 30°C by a dilatometric method. For all amines V^E values are negative over the entire mole fraction range. The results are attributed to the interaction between unlike molecules.     

Conductance in isodielectric mixtures. III.i-butyronitrile with chlorobenzene,o-dichlorobenzene,p-dichlorobenzene, 1,2-dichloroethane,andn-pentanol

The conductance of tetrabutylammonium tetraphenylboride, picrate, perchlorate, and nitrate has been measured at 25°C in mixtures ofi-butyronitrile with chlorobenzene,o-dichlorobenzene,p-dicholorobenzene, 1,2-dichloroethane, andn-pentanol covering the range of dielectric constants 10D20. In these mixtures of polar solvents, both association constants and ionic mobilities depend on ion-solvent interaction energies and on free volume in a manner that is specific for each system. This failure of the primitive model (rigid charged spheres in a continuum) is shown to be the consequence of short-range spatial and energetic interactions between ions and adjacent solvent molecules.     

Thermodynamics of mixtures containing unsaturated hydrocarbons by quasichemical group contributions

The quasichemical group surface interaction method was tested for its ability to correlate and predict vapor-liquid equilibrium (VLE) and molar excess enthalpy (H ^E ) in binary systems 1-octyne-1-propanol, 1-nonyne-1-propanol, 1-nonyne-1-butanol, 1-butylcyclopentene-nonane, 1-butylcyclopentene-1-butanol and 3-ethylcyclopentene-1-butanol. All computations involve using the few sets of group parameters obtained for CHC/OH by a change of the number of H ^E experimental points and the minimization function. For alkylcyclopentene systems, acyclic C=C group parameter as well as those of cyclic C=C and special cyclopentene groups have been used. The results have been compared with those obtained previously by the Wilson and UNIFAC methods.Communicated at the Festsymposium celebrating Dr. Henry V. Kehiaian's 60^th birthday, Clermont-Ferrand, France, 17–18 May 1990     

Volumes of mixtures of alcohols in water at 25°C

Many studies support the idea that alcohols in water undergo microphase transitions which are, in many respects, similar to micellization. To investigate the interactions in these systems even further, the volumes of transfer of normal alcohols of intermediate chain length, kept near infinite dilution, were measured from water to aqueous solutions of 2-propanol and 2-butoxyethanol. These results were compared with the volumes of transfer of the same alcohols to aqueous solutions of octyldimethylamine oxide, a well-characterized non-ionic surfactant. The trends observed are all very similar, exhibiting in many cases a maximum in the transition region. This tends to confirm the formation of mixed aggregates in aqueous mixtures of alcohols, but, in a general way, it is also shown that the magnitude of an extremum in the functions of transfer is related to the relative hydrophobicities of the present solutes, the extremum appearing in most cases only when the transferred solute is more hydrophobic than the main solute.     

Thermodynamics of liquid mixtures containing n-alkanes and strongly polar components: VE and C P E of mixtures with either pyridine or piperidine

Excess molar volumes V _E and excess molar heat capacities C _P ^/E at constant pressure have been obtained, as a function of mole fraction x₁, for several binary liquid mixtures belonging either to series I: pyridine+n-alkane (C_lH_2l+2), with l=7, 10, 14, 16, or series II: piperidine+n-alkane, with l=7, 8, 10, 12, 14. The instruments used were a vibrating-tube densimeter and a Picker flow microcalorimeter, respectively. V ^E of pyridine+n-heptane shows a S-shaped composition dependence with a small negative part in the region rich in pyridine (x₁>0.90). All the other systems show positive V ^E only. The excess volumes increase with increasing chain length l of the n-alkane. The excess molar heat capacities of the mixtures belonging to series II are all negative, except for a small positive part for piperidine+n-heptane in the region rich in piperidine (x₁>0.87). The C _P ^/E at the respective minima, C _P ^/E (x_1,min ), become more negative with increasing l, and the x_1,min values range from about 0.26 (l=7) to 0.39 (l=14). Most interestingly, mixtures of series I exhibit curves of C _P ^/E against x₁ with two minima and one maximum, the so-called W-shape curves.Dedicated to Professor A. Néckel on the occasion of his 65^th birthday. Communicated in part at the XVII^èmes Journées de Calorimétrie, d'Analyse Thermique et de Thermodynamique Chimique, Ferrara, Italy, 27–30 October, 1986.     

Halomethanes in tri-n-octylamine and squalane mixtures at infinite dilution

The retention behavior of eight halomethanes and four saturated hydrocarbons was measured in gas chromatographic stationary phases consisting in tri-n-octylamine (TOA), squalane (SQ) and six TOA+SQ mixtures, at 55.0, 58.5, 62.5 and 65.0°C. Equlibrium constants for complex formation were extracted from experimental data by using a lattice model developed by Martire. The results may be interpreted in terms of the formation of weak hydrogen-bonded complexes, with sociation constants of about 0.13 L-mol^–1 for haloforms and 0.07 L-mol^–1 for dihalomethanes at 60°C.     

Excess thermodynamic properties of binary liquid mixtures containing cyclohexylamine at 30°C

The excess volumes of mixing of cyclohexylamine with n-hexane, n-heptene, n-octane, n-nonane, benzene, toluene, nitrobenzene, chlorobenzene and bromobenzene have been measured at 30°C. For all systems except for n-hexane, V ^E is positive over the entire mole fraction range. For the n-hexane mixtures, a sigmoid curve is obtained with negative V ^E at high mole fraction of amine.     

An improvement for the excess enthalpy prediction by UNIFAC. 1. Binary mixtures containing alkanes

The UNIFAC model is tested for its ability to correlate and predict binary excess enthalpies. Besides the alkanes containing systems from earlier work, those for ester-alkane mixtures are also investigated. The model is fitted to binary excess enthalpy data. The influence of group surface area parameters is also examined by using values based on the van der Waals surface areas Q_s multiplied for all the groups by the factor n. A significant improvement of H^E calculation in most of the systems considered is observed if the factor n is taken equal to 3.     

Pervaporation of dichloromethane from multicomponent aqueous systems containing n-butanol and sodium chloride

In this paper, pervaporation (PV) of dichloromethane (DCM) from binary and multicomponent systems at different feed concentrations and temperatures using a commercial hydrophobic membrane CMX-GF-010-D (CELFA AG, Switzerland) is reported. Coupling effects are studied by permeating DCM/n-butanol/water ternary mixtures. The effect of sodium chloride on the process performance is also evaluated by PV of ternary DCM/sodium chloride/water and quaternary DCM/n-butanol/sodium chloride/water mixtures. PV performance was evaluated by permeate flux and enrichment factor. Further, permeance was calculated for pure water, DCM/water and DCM/n-butanol/water systems at 40 °C.     

ViscosityB-coefficients for lithium perchlorate in ethylene glycol-water mixtures

Viscosities and densities of lithium perchlorate solutions in different ethylene glycol-water compositions have been measured at 25.0 and 35.0 °C. From these data, the correspondingB-coefficients of theJones-Dole equation have been determined. TheB-value depends on the solvent composition and it reaches a maximum in the water-rich region. This behaviour is analysed in terms of ionic solvation and solvent structure.

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Viskositäts-B-Koeffizienten für Lösungen von Lithiumperchlorat in Ethylenglykol-Wasser-Mischungen

Zusammenfassung Es wurden die Dichten und Viskositäten für Lösungen von Lithiumperchlorat in verschieden zusammengesetzten Ethylenglykol-Wasser-Mischungen bei 25 °C und 35 °C gemessen. Auf Grund der erhaltenen Daten wurden dieB-Koeffizienten in den entsprechendenJones-Dole-Gleichungen für die relative Viskosität bestimmt. DieB-Werte hängen von der Zusammensetzung des Lösungsmittels ab und erreichen im wasserreichen Konzentrationsgebiet ein Maximum. Dieses Verhalten wird in Hinblick auf die Ionensolvatation und die Struktur des Lösungsmittels analysiert.

     

Ab initio calculations of electrostatic potentials and deformation densities for a series of choline ester model systems

Ab initio LCAO-MO-SCF calculations using a double zeta basis set have been performed for the methyl esters of acetic acid, carbamic acid, methylcarbonic acid, and trifluoracetic acid, in order to model the corresponding choline esters. The systems have been compared by means of population analyses, electron density differences, electrostatic potentials and potential differences. The significance of the electrostatic potential in connection with crystal structure and packing has been studied. The differences in the proton affinity of the compounds have been correlated to differences in the potentials.     

Additivity model calculations of UHF spin densities and charge densities in methyl-substituted radical cations

By use of a heteroatom model for the methyl group and an additivity model for spin densities, the unrestricted Hartree-Fock after annihilation (UHFAA) results for the radical cations of naphthalene, 1-methylnaphthalene and 2-methylnaphthalene are used to predict the spin densities in the -electron approximation in the corresponding cations of di-, tri- and tetramethylnaphthalenes. The additivity model approach is shown to be equally successful for charge densities.     

Temperature dependence of the volumetric properties of binary mixtures containing oxaalkane +n-heptane

Excess molar volumes of mixtures of n-heptane + 2,5-dioxahexane and n-heptane + 2,5,8-trioxanonane were determined from density measurentents at 5, 15, 25 and 35°C. These results allowed the following mixing quantities to be reported in all range of concentrations: , (v ^E /T) _P and (h ^E /P) _T , at 25°C. The obtained values were then compared with the calculated values by using the Flory theory and the Nitta-Chao theory of liquid mixtures. The results are discussed in terms of order or disorder creation.     

Excess Molar Volumes of Binary Mixtures of Acetonitrile with n-Alkanols at 25°C

Molar excess volumes of acetonitrile with ten n-alkanols (from methanol to decanol) were determined from density measurements at 25°C and normal atmospheric pressure, using a vibrating-tube densimeter. V ^E for acetonitrile + methanol mixtures are negative over the entire range of mole fractions. The ethanol and propanol mixtures exhibit sigmoidal curves and positive values are obtained for all remaining mixtures. The results for V ^E were compared with those obtained using several theoretical models.     

Thermodynamics of binary mixtures: Volumes,heat capacities,and dilution enthalpies for then-pentanol+2-methyl-2-butanol system

The densities, heat capacities, and dilution enthalpies ofn-pentanol+2-methyl-2-butanol mixtures have been measured, in many cases as a function of temperature, over the complete mole fraction range. Excesses thermodynamic properties, apparent and partial molar heat capacities, volumes and expansibilities were derived. The concentration and temperature dependences of these functions are discussed in terms of the variations of the structure of the system caused by the participation of the two alcohol molecules (with quite different steric hindrance of the alkyl chain around the-OH group) in the dynamic intermolecular association process through hydrogen bonding.     

Surface tensions and surface heats of mixing of mixtures containing bromobenzene at 293.15 and 303.15 K

Surface tensions of mixtures of bromobenzene with cyclohexane, benzene,o-, m-, andp-xylene have been determined by the capillary rise method at 293.15 and 303.15 K. The data have been used to check the various theories of surface tension of liquid mixtures. The surface heats of mixing have been computed at 293.15 K as a function of composition.

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Oberflächenspannungen und Oberflächen-Mischungswärmen von Mischungen mit Brombenzol als eine Komponente, bei 293,15 und 303,15 K

Zusammenfassung Die Oberflächenspannungen von Mischungen von Brombenzol mit Cyclohexan, Benzol undo-, m- undp-Xylol wurden mit der Kapillarmethode bei 293,15 und 303,15 K bestimmt. Die Daten wurden zur Überprüfung verschiedener Theorien der Oberflächenspannung herangezogen. Die Oberflächen-Mischungswärmen wurden für 293,15 K berechnet.

     

Variation of some microscopic properties with composition in 2-methoxyethanol and 1,2-ethanediol mixtures

Selected microscopic properties, namely E_T(30) polarity, Kamlet-Taft solvatochromic parameters and dissociation constant of picric acid, have been correlated with solvent composition in 2-methoxyethanol/1,2-ethanediol mixtures. Theoretical and semi-empirical equations which embody preferential solvation of the solute and show standard deviations lower than 0.01 for solvatochromic parameters and 0.03 for pK values have been proposed.