Alkanol Mixtures Research Articles

Thermodynamics of mixtures containing polycyclic aromatic hydrocarbons

The DISQUAC group contribution model has been applied to the study of mixtures containing a polycyclic aromatic compound, naphthalene, phenanthrene, anthracene or pyrene, and an organic solvent, n-alkane, cyclohexane or 1-alkanol. The corresponding interaction parameters are reported. Systems with alkanes are characterized by dispersive parameters only. For naphthalene + 1-alkanol mixtures, the aromatic/OH contacts are represented by dispersive and quasichemical parameters. The latter are equal to those encountered in 1-alkanol + benzene, or + alkylbenzene mixtures for such contacts. DISQUAC provides good results on molar excess enthalpies, H E , solid–liquid equilibria, SLE, and vapor–liquid equilibria over a wide range of temperature for the investigated mixtures. In PAH + n-alkane systems, there is an enthalpy-entropy compensation effect in solutions with long alkanes, and no Patterson's effect is observed. Solubility of naphthalene in hexane or 1-hexanol is similar, and lower than that of 1-alkanol in alkane. This seems to indicate that interactions between unlike molecules are not so relevant as in 1-alkanol + benzene mixtures.

Viscosimetric behaviour of n-alkanols with triethylene glycol monomethyl ether at different temperatures

The thermodynamic functions of activation for viscous flow have been evaluated from the dynamic viscosity values of binary mixtures considering Eyring's transition state theory. Kinematic viscosities and densities of binary mixtures containing triethylene glycol monomethyl ether + (2-propanol or 2-butanol or 2-pentanol) over the whole mole fraction range of triethylene glycol monomethyl ether, at four different temperatures and atmospheric pressure were determined. Viscosity deviations and excess Gibbs energies of activation for viscous flow were calculated. All the values of viscosity deviations are negative, at all temperatures. The molar enthalpy of activation for viscous flow and molar entropy of activation for viscous flow functions were obtained. These functions with concentration of the triethylene glycol monomethyl ether show a minimum. These mixtures show a similar behaviour to that of the hydrocarbon–alkanol mixtures. The Grunberg–Nissan and Katti–Chaudrhi parameters were calculated and viscosity data were analyzed on the basis of their treatment.

Limiting activity coefficients in binary mixtures of 1-alkanols and ethylbenzene

Limiting activity coefficients in binary mixtures of six lower 1-alkanols (C 1–C 6) and ethylbenzene were determined employing alternatively the techniques of inert gas stripping and comparative ebulliometry. For each case, the suitable technique was chosen on the basis of the limiting relative volatility of the solute. Measurements were typically carried out at four temperatures covering a range of 30 K and were done with a good precision (1–3%). The new data were compared with available literature information on both the activity coefficient and calorimetric partial molar excess enthalpy at infinite dilution. All the critically evaluated information was merged and processed simultaneously to produce the recommended temperature dependences of the limiting activity coefficients. The performance of leading prediction methods (UNIFAC, modified UNIFAC, ASOG, MOSCED, DISQUAC) was further examined using this data.

A quasi-chemical nonrandom lattice fluid model for phase equilibria of associating systems

The contribution from Veytsman statistics for associating is combined with the quasi-chemical nonrandom lattice fluid (QLF) equation of state developed by the present authors. The physical contribution is characterized by temperature independent molecular parameters, representing close packed volume of a mer, segment numbers and energy parameters of a pure fluid, and a binary interaction parameter for a mixture. The chemical part is represented by the internal energy and entropy of the associating system. The resulting quasi-chemical nonrandom associating lattice fluid equation of state was applied to describe thermodynamic properties of pure fluids and phase equilibria of mixtures. The absolute chemical potentials which are derived from the canonical partition function are presented by using the fundament thermodynamic relations to consistently calculate phase equilibrium properties. The results for alkane–alkanol and alcohol–alkanol mixtures were found satisfactory for most systems when compared with the quasi-chemical nonrandom lattice fluid model and the statistical associating fluid theory model.

Modification of dipeptides by alkyl chloroformate—alkanol mixtures for analysis by gas chromatography/mass spectrometry with electron and chemical ionization and collisional activation: Differentiation of isomers

A possibility of dipeptide derivatization by alkyl chloroformate—alkanol (Alk = Me, Et, Pr, Bu) mixed reactants for their determination and differentiation of isomers in mixtures by gas chromatography/mass spectrometry with electron and chemical ionization and collisional activation was studied. Prospects for using derivatization by mixtures of methyl chloroformate with 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoropropanol, and 2,2,3,3,4,4,4-heptafluorobutanol were shown. Diagnostic ions that make it possible to determine the amino acid sequence in dipeptides and distinguish residues of isomeric leucine and isoleucine were revealed.

Recommended Vapor–Liquid Equilibrium Data. Part 4. Binary Alkanol–Alkene/Alkyne Systems

The recommended vapor–liquid equilibrium (VLE) data for binary mixtures of alkanols with alkenes and alkynes have been selected after critical evaluation of all data reported in the open literature up to the end of 2003. The evaluation procedure consisted in combining the thermodynamic consistency tests, data correlation, comparison with enthalpy of mixing data, and comparison of VLE data for various mixtures. The data were correlated with Wilson equation as well as with equation of state appended with chemical term (EoSC) proposed by Góral. The recommended data for 18 systems are presented in the form of individual pages containing tables of data, figures, and auxiliary information. Each page corresponds to one system and contains three isotherms (spaced by at least 15K) and one isobar (preferably at 101.32kPa). Experimental gaps were completed with the predicted data.

Thermodynamics of 1-alkanol + aromatic compound mixtures. Systems with dimethylbenzene, ethylbenzene or trimethylbenzene

Binary mixtures of 1-alkanols and ethylbenzene, dimethylbenzenes or trimethylbenzenes have been studied in the framework of the DISQUAC model. The interaction parameters for the hydroxyl/aromatic contacts are reported. DISQUAC represents well a set of thermodynamic properties: vapor-liquid equilibria (VLE), liquid–liquid equilibria (LLE), molar excess enthalpies ( H E) and the concentration–concentration structure factor ( S CC(0)). The model predicts correctly H E of 1-alkanol + 1,4-dimethylbenzene + cyclohexane systems using binary parameters only, that is neglecting ternary interactions. The available database on H E and molar excess volume ( V E) is examined in order to gain insight into the interactions present in the studied mixtures: (i) dipolar interactions are stronger in systems with benzene; (ii) interactions between unlike molecules decrease with the increase of the chain length of the 1-alkanol for solutions with a given aromatic hydrocarbon; (iii) self-association of 1-alkanols is more important in systems with alkylbenzenes than in those including benzene; (iv) benzene is a more active molecule than other aromatic compounds when breaking the alcohol structure.

Second-order thermodynamic derivative properties of selected mixtures by the soft-SAFT equation of state

We have discussed the capability of the soft-SAFT equation of state (EoS) to predict second order thermodynamic derivative properties of pure fluids in a recent paper [F. Llovell, L.F. Vega, J. Phys. Chem. B 110 (2006) 11427–11437]. The goal of this work is to extend these calculations to selected binary mixtures. The equation was applied in a semi-predictive manner: the pure component molecular parameters needed to apply soft-SAFT to experimental systems were obtained by fitting vapor–liquid equilibrium data and used, without further fitting, to calculate isochoric and isobaric heat capacities of selected alkane + n-alkane and n-alkane + 1-alkanol binary mixtures; isentropic compressibility coefficients and the speed of sound of selected n-alkane + 1-alkanol mixtures were calculated following the same procedure. We have used the crossover soft-SAFT equation which explicitly incorporates a renormalization group term in order to take into account the long range fluctuations appearing in the near critical region. Soft-SAFT was able to capture the qualitative behavior of the mixture properties studied, for a wide range of conditions, showing quantitative agreement with experimental data in some of the cases. As a further test to the equation, we have also calculated excess properties. The equation was able to capture the non-ideal behavior upon mixing experienced by these properties. This work shows the robustness of the molecular parameters and the equation to calculate properties not included in the fitting procedure, in a predictive manner.

Density and surface tension variation with temperature for n-nonane + 1-hexanol

New experimental densities and surface tensions for n-nonane + 1-hexanol at 288.15, 298.15 and 308.15 K are reported. Densities were measured with an Anton Paar DMA 4500 densimeter, and surface tensions using a Lauda TVT2 automated tensiometer, which uses the principle of the pending drop volume. The experimental data of pure liquids and mixtures have been used to calculate excess molar volumes and surface tension deviations of n-nonane + 1-hexanol as a function of mole fractions. A comparative study of these properties together with those available in the literature for the n-alkane + 1-alkanol mixtures has been performed. In addition, the magnitude of these experimental quantities is discussed in terms of the nature and type of intermolecular interactions in binary mixtures.

Thermodynamics of mixtures containing alkoxyethanols: Part XIX. Systems with linear monoethers or 1-alkanols

Alkoxyethanol + linear monoether, or + 1-alkanol mixtures have been investigated in terms of the DISQUAC and ERAS models and using the so-called concentration–concentration structure factor, S CC(0). DISQUAC and ERAS interaction parameters are reported. DISQUAC describes consistently a whole set of thermodynamic properties: vapor–liquid equilibria, VLE, molar excess functions as Gibbs energy, G E, enthalpy, H E, or heat capacity at constant pressure, C P E and S CC(0). In the framework of DISQUAC, the intramolecular H-bonds between the O and OH of the cellosolve are independent, except for short chain ethers, of the molecular environment (linear ether, or 1-alcohol). ERAS describes systems with dibutylether by means of a large physical contribution to the excess thermodynamic properties. The model overestimates the self-association of the lower 1-alkanols in their mixtures with 2-alkoxyethanols, which leads to a poor representation of the properties of such systems. Mixtures with dibutylether are characterized by homocoordination with interactions which can be assumed to be of dipolar type. In systems with 1-alkanols, interactions between like and unlike molecules and structural effects are compensated, and S CC(0) is nearly ideal.

Density and Relative Permittivity for 1-Alkanols + Dodecane at 298.15 K

Densities and relative permittivities at a frequency of 30 kHz for the binary mixtures of 1-alkanols, CnH2n+1OH for n = 1 to 10, + dodecane were measured for the mole fraction range of 1-alkanol between 0 and 0.1 at a temperature of 298.15 K. By using Debye and Frohlich equations, the apparent dipole moments (μ) of 1-alkanols were calculated, and the limiting values (μ0) were determined by extrapolating to infinite dilution. The value of μ0 decreased with increasing hydrocarbon length of the 1-alkanol. The present results were compared with our previous measurements in cyclohexane and heptane. Methanol had the same μ0 value irrespective of solvent, while μ0 for 1-alkanols with n ≥ 2 showed a lower value in dodecane than those found in cyclohexane and heptane. The excess partial molar volumes of 1-alkanols at infinite dilution decreased with increasing n.

Apparent Dipole Moments of 1-Alkanols in Cyclohexane and n-Heptane, and Excess Molar Volumes of (1-Alkanol + Cyclohexane or n-Heptane) at 298.15 K

Excess molar volumes and relative permittivities at a frequency of 30 kHz were determined precisely for the binary mixtures of 1-alkanols, C n H2n+1OH for n = 1 to 10, with cyclohexane or n-heptane to the mole fraction of 1-alkanol, x, to 0.1 at a temperature of 298.15 K. Apparent dipole moments, μ, of the 1-alkanols were calculated by using the Frohlich equation, and the limiting values, μ0, were determined by extrapolating to infinite dilution. The solvent effect on μ0 was very small. The value of μ0 was largest in methanol and decreased with increasing n. It was found that the alkanols were isolated up to x ≈ 0.003. The threshold of molecular interaction beyond this critical mole fraction was ascertained by means of FT-IR spectra. The dipole moments of the 1-alkanols for n = 1–4 were evaluated by ab initio calculations. The average values of μ0 for the rotational configurations calculated by assuming the Boltzmann distribution agreed excellently with the observed ones. The excess partial molar volumes of 1-alkanols determined at the infinite dilution depended on n as well as the solvent. These results are discussed from the viewpoint of the interactions between the solute and solvent molecules.

Recommended Vapor—Liquid Equilibrium Data. Part 3. Binary Alkanol—Aromatic Hydrocarbon Systems

AbstractFor Abstract see ChemInform Abstract in Full Text.

Recommended Vapor–Liquid Equilibrium Data. Part 3. Binary Alkanol–Aromatic Hydrocarbon Systems

The recommended vapor–liquid equilibrium (VLE) data for mixtures of alkanols with benzene and alkylbenzenes have been selected after critical evaluation of all data reported in the open literature up to the middle of 2002. The evaluation procedure consisted in combining the thermodynamic consistency tests, data correlation, comparison with enthalpy of mixing data, and comparison of VLE data for various mixtures. The data were correlated with equations based on local compositions concept as well as with equation of state appended with chemical term (EoSC) proposed by Góral. The recommended data for 29 systems are presented in the form of individual pages containing tables of data, figures and auxiliary information. Each page corresponds to one system and contains three isotherms (spaced by at least 15 K) and one isobar (preferably at 101.32 kPa). Experimental gaps were completed with the predicted data.

Thermodynamics of liquid mixtures containing a very strongly polar compound: Part 6. DISQUAC characterization of N, N-dialkylamides

Systems of N, N di( n-alkylamides) (hereafter, N, N-dialkylamides) with alkane, benzene, toluene, 1-alkanol or 1-alkyne have been investigated in the framework of the DISQUAC model. The corresponding interaction parameters are reported. They change regularly with the molecular structure of the mixture components. This variation is similar to those encountered when treating other systems in terms of DISQUAC. The model describes consistently a whole set of thermodynamic properties: liquid–liquid equilibria (LLE), vapor–liquid equilibria (VLE), solid–liquid equilibria (SLE), molar excess Gibbs energies ( G E), molar excess enthalpies ( H E), molar excess heat capacities at constant pressure ( C P E), partial molar excess properties at infinite dilution, enthalpies and heat capacities. The model also provides good results for the Kirkwood–Buff integrals and for the linear coefficients of preferential solvation. For ternary systems, DISQUAC predictions on VLE and H E, obtained using binary parameters only, are in good agreement with the experimental data. A short comparison between DISQUAC and Dortmund UNIFAC results is shown. DISQUAC improves UNIFAC results on H E and C P E, magnitudes which strongly depend on the molecular structure. The investigated mixtures behave similarly to those characterized by thermodynamic properties which arise from dipolar interactions. Association/solvation effects do not play, as a whole, an important role in the studied systems. This may explain that the ERAS model fails when representing the thermodynamic properties of dimethylformamide + 1-alkanol mixtures.

Density, Surface Tension, and Refractive Index of Octane + 1-Alkanol Mixtures at T = 298.15 K

Surface tension and refractive index for binary mixtures of {octane + ethanol, + 1-propanol, + 1-butanol, + 1-pentanol, + 1-hexanol, + 1-heptanol, and + 1-octanol}, and density for {octane + ethanol} have been measured at T = 298.15 K for the whole composition range. From the experimental data we extract excess molar volumes, surface tension deviations, and changes of refractive index. All these experimental data are compared among them and with previous results of the binary mixtures hexane + 1-alkanol and dibutyl ether + 1-alkanol. Also we compare our present results with other published data when available.

Experimental study and modelling using the ERAS-Model of the excess molar volume of acetonitrile–alkanol mixtures at different temperatures and atmospheric pressure

Densities of {(1− x)CH 3(CH 2) n−1 OH + xCH 3CN} for n=1, 2, 3 or 4 have been determined as a function of composition at 288.15, 293.15, 298.15 and 303.15 K at atmospheric pressure using a vibrating-tube densimeter (Anton Paar DMA 4500, resolution 1×10 −5 g cm −3). Excess molar volumes were calculated. The V m E values were negative for acetonitrile–methanol mixtures and sigmoid for acetonitrile–alkanols (C 2–C 4) mixtures over the complete mole fraction range. V m E values increase in a positive direction with increase in chain length of the alkanols and with the temperature. The Extended Real Associated Solution Model (ERAS-Model) calculations allowing for self-association for the alkanols and complex formation between acetonitrile and alkanols have been used to correlate experimental data. The model is able to reproduce the asymmetrical V m E behavior of the studied systems, although agreement between theoretical and experimental values is less satisfactory for some concentration ranges.

Limiting activity coefficients in binary mixtures of 1-alkanols and toluene

Limiting activity coefficients in binary mixtures of six lower 1-alkanols (C 1–C 6) and toluene were determined employing alternatively the techniques of inert gas stripping (IGS) and comparative ebulliometry (EBU). For each case, the suitable technique was chosen on the basis of the limiting relative volatility of the solute. Measurements were typically carried out at four temperatures covering a range of 30 K and were done with a good precision (1–3%). The new data were compared with available literature information on both the activity coefficient and calorimetric partial molar excess enthalpy at infinite dilution. All the critically evaluated information was merged and processed simultaneously to produce the recommended temperature dependencies of the limiting activity coefficients. The performance of leading prediction methods (UNIFAC, modified UNIFAC, ASOG, MOSCED, DISQUAC) was further examined using this data. An attempt was also made to interpret the behavior of the systems studied using a non-athermal association model.

Micellar behaviour of cetyltrimethylammonium bromide in N-methyl acetamide—alkanol and N, N-dimethyl acetamide—alkanol mixtures

The critical micelle concentration (c.m.c.) of Cetyltrimethylammonium bromide (CTAB) micellar solution, containing methanol, ethanol, n-propanol, n-butanol and n-pentanol in N-methyl acetamide (NMA) and in N, N-dimethyl acetamide (DMA) has been determined using electrical conductivity and surface tension measurements at various temperatures. Both methods show that micelles are formed in NMA and in DMA solution in absence and in presence of n-alkanols. Critical micelle concentrations have also been measured as a function of the concentration of alcohol added. It is suggested that alcohol addition leads to an increase in NMA and in DMA penetration into the micellar interface that depends on the alcohol chain length. The results are discussed in terms of: (1) alcohol penetration of the micelles, and (2) solvent structuring. Thermodynamic parameters were evaluated for micellar systems in absence and in presence of n-alkanols to further explain the results.

Correlation, verification and prediction of vapour–liquid equilibria using equation of state with association term: II. Alcohols + non-aliphatic hydrocarbons

An equation of state with association term was used to correlate all available binary VLE data sets for mixtures of alkanols with non-aliphatic hydrocarbons. The self association of alkanols was described using a uniform set of parameters. The cross association between alkanols and aromatic compounds was taken into account. The verification of the VLE data for mixtures of alkanols and non-aliphatic hydrocarbons is described and recommended data are given. The method of prediction of the VLE in the investigated mixtures is described. The recommended data were compared with the results of the prediction.