DISQUAC Interaction Parameters Research Articles

Solid-liquid equilibria for dibenzofuran or Xanthene + Heavy Hydrocarbons: Experimental measurements and modelling

The solid–liquid equilibria (SLE) phase diagrams have been determined using a DSC technique for dibenzofuran + n-C21, or + n-C31, or + n-C41 mixtures. The three systems show a eutectic point. Values of the eutectic temperature and of the heat of melting have been also evaluated and used to determine the eutectic composition of the systems by means of the Tamman’s plots. The dependence of deviations from ideality of dibenzofuran + aromatic hydrocarbon mixtures with size, shape, and of the degree of alkylation of the hydrocarbon has been investigated. At this end, we have considered SLE data available in the literature for solutions including benzene, acenaphthene, phenanthrene, anthracene, biphenyl, chrysene, toluene, or diphenylmethane. Dibenzofuran + n-alkanes systems show positive deviations from the ideal solution model, which increase with the alkane size. The mentioned deviations are stronger in the corresponding xanthene solutions. DISQUAC interaction parameters have been obtained for the (aromatic/ether) and (aliphatic/ether) contacts in dibenzofuran or xanthene + aromatic hydrocarbon, or + n-alkane mixtures. Better fitting is obtained with DISQUAC model compared to the Ideal Solubility Model, or UNIFAC model. Finally, the COSMO-RS model was used to predict the eutectic coordinates for the binary systems Dibenzofuran + n-alkanes (n-C21, or n-C31 or n-C41). Excellent agreement was obtained only for the eutectic temperature.

Thermodynamics of mixtures containing a fluorinated benzene and a hydrocarbon

Fluorobenzene, or 1,4-difluorobenzene or hexafluorobenzene + alkane mixtures and hexafluorobenzene + benzene, or + toluene, or + 1,4-dimethylbenzene systems have been investigated using thermodynamic properties from the literature and through the application of the DISQUAC and UNIFAC (Dortmund) models and the concentration-concentration structure factor (SCC(0)) formalism. DISQUAC interaction parameters for the contacts F/alkane and F/aromatic have been determined. UNIFAC interaction parameters available in the literature for these contacts have been used along calculations. Both models predict double azeotropy for the C6F6 + C6H6 system, although in different temperature ranges. TheHmE values of the fluorobenzene, or 1,4-difluorobenzene + n-alkane systems are positive and are accurately described by the models using interaction parameters independent of the n-alkane. This means that no Patterson’s effect exists in such mixtures. DISQUAC calculations allow state that such conclusion is still valid for C6F6 + n-alkane mixtures. DISQUAC provides better results than UNIFAC on CpmE of solutions involving n-alkanes, or on HmE of C6F6 + aromatic hydrocarbon systems. Mixtures with alkanes are characterized by interactions between like molecules, which are mainly of dispersive type, which is supported, e.g, by the negative CpmE values of these systems. It is shown that structural effects can contribute largely to HmE. This is investigated in terms of the excess molar internal energy at constant volume, UVmE, whose values are determined for the investigated solutions. For mixtures with a given n-alkane, the relative variation of HmE and UVmEwith the fluorohydrocarbons is different.HmEvalues change in the sequence C6F6 > 1,4-C6H4F2 > C6H6 > C6H5F, while UVmE changes in the order: 1,4-C6H4F2 > C6H6≈ C6H5F > C6F6 . C6F6 + aromatic hydrocarbon mixtures are characterized by interactions between unlike molecules as it is demonstrated by their negative HmE values. The application of the SCC(0) formalism reveals that homocoordination is more important in C6F6 + n-alkane mixtures than in the corresponding systems with C6H5F, and that heterocoordination is dominant in the solutions of C6F6 with an aromatic hydrocarbon.

Liquid–Liquid Equilibria for 2-Phenylethan-1-ol + Alkane Systems

The liquid–liquid equilibrium (LLE) curves for 2-phenylethan-1-ol (2-phenylethanol, 2PhEtOH) + octane, + decane, + dodecane, + tetradecane or + 2,2,4-trimethylpentane have been determined by a method of turbidimetry using a laser scattering technique. Experimental results reveal that the systems are characterized by an upper critical solution temperature (UCST), which increases linearly with the number of C atoms of the n-alkane. In addition, the LLE curves have a rather horizontal top and become skewed to higher mole fractions of the n-alkane, when its size increases. For a given n-alkane, UCST decreases as follows: phenol > phenylmethanol > 2-PhEtOH, indicating that dipolar interactions decrease in the same sequence. This has been ascribed to a weakening in the same order of the proximity effects between the phenyl and OH groups of the aromatic alkanols. DISQUAC interaction parameters for OH/aliphatic and OH/aromatic contacts in the investigated systems are reported. Phenol, or phenylmethanol or 2-PhEtO...

Solid-liquid equilibria of eicosane, tetracosane or biphenyl + 1-octadecanol, or + 1-eicosanol mixtures

A differential scanning calorimetric (DSC) technique has been used to obtain solid-liquid equilibrium temperatures for n-C20, or n-C24, or biphenyl + 1-octadecanol, or + 1-eicosanol mixtures. All the systems show a simple eutectic point. The final composition of these points is determined on the basis of the Tamman plots using values of the eutectic heat and of the heat of melting, which are also reported. Deviations of activity coefficients (γ) from unity for the mentioned mixtures and for the systems n-C24 or n-C28 + cyclododecane, or + cyclododecanol and for dodecane + cyclohexanol are discussed in terms of the alcohol self-association and size effects. Mixtures with alkanols show positive (γ− 1) values. Such differences are larger for the cyclohexanol system, as this is the most self-associated alcohol considered. Size effects lead to slightly negative (γ− 1) values for cyclododecane solutions. Using the regressed parameters, DISQUAC provides a good description of the phase diagrams for the mixtures under consideration and improves results from the UNIFAC (Dortmund) model. The influence of size effects on the DISQUAC interaction parameters is discussed.

Thermodynamics of Mixtures Containing Amines. XV. Liquid–Liquid Equilibria for Benzylamine + CH3(CH2)nCH3 (n = 8, 9, 10, 12, 14)

Coexistence curves for the liquid–liquid equilibria (LLE) of 1-phenylmethanamine (benzylamine) + CH3(CH2)nCH3 (n = 8, 9, 10, 12, 14) have been determined using the critical opalescence method by means of a laser scattering technique. All of the LLE curves show an upper critical solution temperature (UCST), which increases with increasing n. For systems including a given n-alkane, the UCST decreases in the sequence aniline > 2-methylaniline (o-toluidine) > benzylamine > N-methylaniline > pyridine. This means that amine–amine interactions become weaker in the same order. Most of the DISQUAC interaction parameters for the aliphatic/amine (a,n) and aromatic/amine (b,n) contacts previously determined for solutions with aniline, o-toluidine, or N-methylaniline have been used for the representation of the LLE data. Only the first dispersive interaction parameter of the (a,n) contact has been modified. The coordinates of the critical points are correctly represented by the model.

Thermodynamics of Mixtures Containing Aromatic Alcohols. 1. Liquid–Liquid Equilibria for (Phenylmethanol + Alkane) Systems

The liquid–liquid equilibrium (LLE) curves for (phenylmethanol + CH3(CH2)nCH3) mixtures (n = 5, 6, 8, 10, 12) have been obtained by the critical opalescence method using a laser scattering technique. All of the systems show an upper critical solution temperature (UCST). In addition, the LLE curves have a rather horizontal top, and their symmetry depends on the alkane size. The UCST increases almost linearly with n. For systems including a given alkane and phenol or phenylmethanol, the UCST is much higher than that of the corresponding mixtures with hexan-1-ol or heptan-1-ol. This reveals that dipolar interactions are stronger in solutions with aromatic alcohols. Preliminary DISQUAC interaction parameters for OH/aliphatic contacts in the investigated systems were obtained. It is remarkable that the coordinates of the critical points of (phenol or phenylmethanol + alkane) mixtures can be described using the same quasichemical interaction parameters for the OH/aliphatic and OH/aromatic contacts.

Thermodynamics of Mixtures Containing Amines. X. Systems with Cyclic Amines or Morpholine

Cyclic amine or morpholine + organic solvent mixtures have been investigated in terms of DISQUAC and of the Kirkwood–Buff formalism. The amines considered are cyclohexylamine; (c-CH2)uNH (u = 2–7) and (c-CH2)uN–CH3 (u = 4,5). The organic solvents are alkanes and methanol or ethanol. The DISQUAC interaction parameters are reported. The model describes correctly a whole set of thermodynamic properties: vapor–liquid equilibria (VLE); excess Gibbs energies, GmE; excess enthalpies, HmE; excess heat capacities at constant pressure, CP,mE; and partial excess enthalpies at infinite dilution, H1E,∞, as well as the main features of the Kirkwood–Buff integrals. In (c-CH2)uNH + C6H12 mixtures, amine–amine interactions become weaker with increased u values. This is supported by the corresponding decrease of HmE and H1E,∞ and of the effective dipole moment. Interactions between amine molecules are also weakened when passing from a primary cyclic amine to an isomeric tertiary cyclic amine. The existence of an aromatic ring in the amine, as in aniline or pyridine, leads to stronger amine–amine interactions. Dipolar interactions between morpholine molecules are stronger than those between piperidine molecules, and reveal the existence of proximity effects between the two groups of morpholine. In systems with alkanes, interactions between amine molecules are preferred to those between unlike molecules. In piperidine + methanol and pyrrolidine + ethanol systems, the mixture structure is close to random mixing.

Thermodynamics of mixtures containing oxaalkanes. 5. Ether + benzene, or +toluene systems

Linear or cyclic ether + benzene or +toluene mixtures have been investigated in terms of the DISQUAC and UNIFAC (Dortmund version) models as well as using the Kirkwood–Buff formalism. The corresponding DISQUAC interaction parameters are reported. The QUAC interaction parameters are independent of the aromatic compound, and those for l = 1 (Gibbs energy) and l = 3 (heat capacity) are also independent of the ether. DISQUAC correctly describes a whole set of thermodynamic properties of these systems: vapour–liquid equilibria, VLE, solid–liquid equilibria, SLE, molar excess enthalpy, H m E , molar excess isobaric heat capacity, C pm E , and Kirkwood–Buff integrals. DISQUAC improves meaningfully UNIFAC H m E results, which remarks that the accurate description of this property is difficult when proximity effects or cyclization are present. From values of the molar excess enthalpies at infinite dilution obtained from H m E data available in the literature, it is concluded that the increase of the number of –O– atoms in the ether or cyclization leads to stronger interactions between unlike molecules. Values of the Kirkwood–Buff integrals and of linear coefficients of preferential solvation reveal that the structure of the investigated systems is close to random mixing.

Thermodynamics of organic mixtures containing amines. X. Phase equilibria for binary systems formed by imidazoles and hydrocarbons: Experimental data and modelling using DISQUAC

(Solid + liquid) equilibrium (SLE) temperatures have been determined using a dynamic method for the systems (1 H -imidazole, + benzene, + toluene, + hexane, or + cyclohexane; 1 -methylimidazole + benzene, or + toluene, 2-methyl-1 H -imidazole + benzene, + toluene, or + cyclohexane, and benzimidazole + benzene). In addition (liquid + liquid) equilibrium (LLE) temperatures have been obtained using a cloud point method for (1 H -imidazole, + hexane, or + cyclohexane; 1 -methylimidazole + toluene, and 2-methyl-1 H -imidazole + cyclohexane). The measured systems show positive deviations from the Raoult’s law, due to strong dipolar interactions between amine molecules related to the high dipole moment of imidazoles. On the other hand, DISQUAC interaction parameters for the contacts present in these solutions and for the amine/hydroxyl contacts in (1 H -imidazole + 1-alkanol) mixtures have been determined. The model correctly represents the available data for the examined systems. Deviations between experimental and calculated SLE temperatures are similar to those obtained using the Wilson or NRTL equations, or the UNIQUAC association solution model. The quasichemical interaction parameters are the same for mixtures containing 1 H-imidazole, 1-methylimidazole, or 2-methyl-1 H-imidazole and hydrocarbons. This may be interpreted assuming that they are members of a homologous series. Benzimidazole behaves differently.

Thermodynamics of 1-alkanol + cyclic ether mixtures

1-Alkanol + cyclic ether mixtures have been investigated in terms of the DISQUAC and ERAS models and using the concentration–concentration structure factor ( S CC(0)). The corresponding interaction parameters are reported. DISQUAC interaction parameters for the systems 1-alkanol + 1,7,10,13,16-hexaoxacyclooctadecane (18CE) and methanol + 1,3,5-trioxane are also given. DISQUAC correctly describes a whole set of thermodynamic properties: vapor–liquid equilibria, VLE, molar excess enthalpies, H E, solid–liquid equilibria, SLE, and S CC(0) of the binary systems. H E of 1-alkanol + cyclic ether + alkane mixtures are fairly well represented by DISQUAC using binary parameters only. ERAS provides a semiquantitative description of the investigated mixtures due to the fact that main contribution to their thermodynamic properties is usually the physical one. 1-Alkanol + cyclic ether systems are characterized by dipolar interactions and homocoordination. Interactions between unlike molecules are stronger in mixtures with tetrahydrofuran (THF) or 1,3-dioxolane, when are compared with those present in solutions with tetrahydropyran (THP) or 1,4-dioxane. The DISQUAC interaction parameters underline that proximity effects are more relevant in systems with 1,3-dioxolane or 1,3,5-trioxane. THP, 1,4-dioxane and 18CE form a homologous series in the framework of DISQUAC.

Evaluation of the [formula omitted] interaction parameters using the DISQUAC group contribution model

Thermodynamic behaviour of the eight systems containing 1,1,2,2-tetrachloroethane and ethyl or propyl C 1C 4 alkanoates was interpreted in terms of the DISQUAC group contribution model. The DISQUAC dispersive interaction parameters for COO Cl contact were evaluated considering the quasichemical parameters are equal to zero. The molar excess Gibbs energies and the excess enthalpies were calculated using this model and compared with experimental data. The relation between the DISQUAC interaction parameters for COO Cl contact and the chain length of the alkanoate was established.

Calorimetric and phase equilibrium data for linear carbonates + hydrocarbons or + CCl 4 mixtures. Comparison with disquac predictions

The disquac interaction parameters for the linear organic carbonate—alkane, carbonate—cyclohexane, carbonate—benzene or —toluene, and carbonate—CCl 4 contacts are revised on the basis of new experimental data on vapor—liquid equilibria for dimethyl or diethyl carbonate + n-alkane mixtures. The new parameters differ slightly from the previous ones. The main conclusions remain valid. The quasichemical interchange coefficients for carbonate—alkane or —cyclohexane contacts, and the purely dispersive interchange coefficients for carbonate—benzene or —toluene and carbonate—CCl 4 contacts, show a relatively weak steric effect. The model provides a fairly consistent description of low pressure fluid phase equilibria (vapor—liquid, liquid—liquid and solid—liquid) and related excess functions (Gibbs energy and enthalpy) using the same set of parameters.