Alkanol Mixtures Research Articles

Liquid-liquid equilibria for (2-hydroxy benzaldehyde + n-alkane) mixtures. Intermolecular and proximity effects in systems containing hydroxyl and aldehyde groups

The liquid-liquid equilibrium (LLE) curves have been determined for the 2-hydroxyl-benzaldehyde (salicylaldehyde, SAC) + CH3(CH2)nCH3 mixtures (n = 5,6,7,8,9). The equilibrium temperatures were determined observing, by means of a laser scattering technique, the turbidity produced on cooling when a second phase takes place. All the systems show an upper critical solution temperature, which linearly increases with n. Intermolecular effects have been investigated in alkanol + benzaldehyde systems using data from the literature. Interactions in 1-alkanol mixtures are mainly of dipolar type. The corresponding excess molar enthalpies, HmE, are large and positive, which reveals that interactions between like molecules are dominant. Interactions between unlike molecules are stronger for the methanol-containing system. For the other mixtures, the enthalpy of the 1-alkanol-benzaldehyde interactions remains more or less constant. At 298.15 K and equimolar composition, the replacement of a linear polar solvent by the isomeric aromatic one leads to increased HmE values in systems with a given 1-alkanol. The phenol + benzaldehyde system shows strongly negative deviations from the Raoult’s law. Proximity effects have been examined in SAC + hydrocarbon mixtures. Alkane-containing systems are essentially characterized by dipolar interactions, while dispersive interactions are prevalent in the solution with benzene. All the mixtures have been treated in terms of DISQUAC. The interaction parameters for the OH/CHO contacts and for the SAC/aromatic and SAC/alkane contacts have been reported. DISQUAC provides a correct description of the thermodynamic properties considered. In the case of SAC systems, this is done by defining a new specific group HO–C–C–CHO for salicylaldehyde.

Study of molecular interactions and preferential solvation in binary mixtures of cyclohexane and (C5–C10) 1-alkanol by Kirkwood-Buff integrals

Mixtures formed by cyclohexane + 1-alkanol have been investigated in the framework of the Kirkwood–Buff theory of solution. The alcohols considered are 1-pentanol up to 1-decanol. Data for the Kirkwood–Buff integrals, Gij excess or deficit number of molecules around the central ones, Δnij and coefficients of linear solvation, δij are reported. For solutions with a given cyclohexane, the increase in the CH2 groups of alcohols chain causes a decrease in G12 by the following sequences: 1-decanol > 1-nonanol > 1-octanol > 1-heptanol > 1-hexanol > 1-pentanol. The comparison of G12 and other calculated parameters for cyclohexane + 1-alkanol mixtures reveals that the interactions between similar molecules are more outstanding and the decrease in the alkyl chain of alcohols leads to the weakening of interactions related to the self–association of 1-alkanol, differences in the free volumes, hydrophobic interactions, and structural changes. These trends are consistent with experimental data on the excess molar volumes.

Molecular interaction studies based on transport, thermodynamic and excess properties of aniline and alkanol mixtures at varying temperatures

Density (ρ) data at 303.15 K–318.15 K, Sound speed (u) and viscosity (η) data at 303.15 K–313.15 K for the binary mixtures of aniline with 1-alkanols were measured over the entire composition range. The 1-alkanols included in this work were 1-propanol, 1-butanol, 1-pentanol and 1-hexanol. The experimental data were used to compute excess molar volume (VmE), excess isentropic compressibility (кSE) and deviation in viscosity (Δη). The excess data and deviation in viscosity (Δη) data were analyzed and correlated using Redlich-Kister and Hwang polynomial type equations. Also the experimental sound speed data were considered in terms of Schaff's collision factor theory (CFT) and Jacobson free length theory (FLT). Further, for all the measured viscosity values, the average absolute percentage deviation (AAPDs) values were obtained using various predictive and correlative models and the results were compared for prognostic analysis. Furthermore, the deviations of the measured properties in the investigation were examined in terms of divergent intermolecular interactions that exist among the constituent molecules.

Modeling of the Mixture Critical Locus with a Modified Cubic Plus Association (CPA) EoS: Aromatics, Ketones, Ethers, Diethyl Carbonate, and THF

The description of the critical data of a mixture is of importance for various applications such as supercritical processes, reactions close to the critical temperature, or safety design in piping. In a previous work, we have shown that a modified cubic-plus-association (CPA) equation of state is able to provide an accurate representation of critical points for mixtures of associating compounds or for mixtures of associating compounds with hydrocarbons. In the present work, this study is extended to mixtures containing associating and solvating compounds. Binary and ternary mixtures of alkanols, diethylamine or water with ketones, aromatics, ethers, tetrahydrofuran, or diethyl carbonate are studied. Binary interaction parameters are fitted from subcritical LLE or VLE data. For the binary mixtures, when analyzing the curves of Tc and Pc versus composition, the average deviation on Pc is below 2.4%, while the average ΔTc is below 2.5 K. Three ternary mixtures are also investigated. For these, deviations are...

FT-IR studies and excess thermodynamic properties of binary liquid mixtures 2-(2-butoxyethoxy) ethanol with 1-hexanol, 1-octanol and 1-decanol at different temperatures

Abstract In continuation to our prior investigational studies on the interactions between binary mixtures of alkoxy alkanols and alcohols, here, we report the thermo-physical properties and spectra analysis of 2-(2-butoxyethoxy) ethanol with CH3(CH2)3OC2H4O(CH2)2OH, viz., 1-hexanol CH3(CH2)5OH, 1-octanol CH3(CH2)7OH and 1-decanol CH3(CH2)9OH over the entire composition range at T = (293.15, 298.15, 303.15, 308.15 and 313.15) K. The experimental data of densities and speeds of sound were used to calculate the values of excess functions and deviations in properties. The evaluated properties from experimental data have been construed in terms of the difference in the size of the molecule as well as the strength of specific and non-specific interactions between components of the mixture. The excess functions and their deviations have also been correlated using Redlich-Kister type polynomial equation by the method of least-squares for the estimation of the binary coefficients and the standard deviations. The FT-IR technique has been used to scrutinize the –OH interactions between the binary mixtures and inestimable to spot the influence on the structural variation in the alcohols.

HPLC-MS separation and detection of dialkyl phosphonates and trialkyl phosphites in reaction mixtures of 1-alkanols with phosphorous trichloride

To evaluate the rationality and separation conditions of alkyl esters of phosphorous P(III) and P(V) acids using reversed phase HPLC with mass spectrometric detection, the analyses of reaction mixtures of two 1-alkanols (1-butanol and 1-heptanol) with PCl 3 in the presence of N,N-dimethyl aniline (for pH correction) have been carried out. In accordance with the previous results, these mixtures preferably contain trialkyl phosphites (RO) 3 P and dialkyl phosphonates (RO) 2 PH=O. However, the results of HPLC-MS analyses indicate the prevalence of oxidation products P(III) ® P(V) in the composition of these mixtures, namely trialkyl phosphates (RO) 3 OP. In accordance with this scheme, the appearance of diheptyl phosphate (C 7 H 15 O) 2 P(=O)-OH is caused by the oxidation of diheptyl phosphonate. Possible reasons of such discrepancies in the composition of reaction mixtures are discussed. One of them may be oxidation of P(III) derivatives by air oxygen during storage, or, tentatively, due to electrochemical reactions during electrospray ionization. The reaction mixture of 1-heptanol with PCl 3 contains two components with the same molecular weights ( M = 294) and identical mass spectra, but strongly different retention parameters ( t R 5.4 and 16.0 min). The second of them is diheptyl phosphonate. To explain the appearance the first of them, existence of more hydrophilic prototropic tautomer (C 7 H 15 O)P-OH (contains hydroxyl group in the molecule) was proposed. Comparing the analytical results obtained in positive and negative modes of detection indicates that the first of them seems to be more effective for detection of alkyl esters of P(III) and P(V) phosphorous acids. Keywords : Trialkyl phosphites, dialkyl phosphonates, reversed phase HPLC, MS-detection, determination in reaction mixtures, oxidation products DOI: http://dx.doi.org/10.15826/analitika.2018.22.3.014 (Russian) Igor G. Zenkevich, Tatiana I. Pushkareva, Vlada E. Nosova St. Petersburg State University, Universitetskii prosp., 26, St. Petersburg, 198504, Russian Federation

Insights into Glycol Ether-Alkanol Mixtures from a Combined Experimental and Theoretical Approach.

The binary liquid mixtures of glycol ethers (glymes) + 1-alkanol were characterized from the microscopic and macroscopic viewpoints through a combined experimental and theoretical study. Structuring, dynamics, and intermolecular forces were determined using density functional theory and classical molecular dynamics methods. The macroscopic behavior was studied though the measurement of relevant physicochemical properties and Raman IR studies. The changes in intermolecular forces with mixture composition, temperature, and the effects from the types of glymes as well as 1-alkanols were considered. Hydrogen bonding in the mixed fluids, its changes upon mixing, and mixture composition showed a large effect on fluids' structure and determined most of the fluids' properties together with the presence of hydrophobic domains from long 1-alkanols.

Thermo physical and FT-IR study on binary mixtures of 2-isopropoxy ethanol and alcohols at different temperatures

As a continuation to our investigations on thermodynamic properties of binary mixtures of alkoxy alkanols with alcohols, the present paper reports the experimental data for the densities, speeds of sound and viscosities for the binary mixtures of 2-isopropoxy ethanol with alcohols. Densities and speeds of sound of 2-isopropoxy ethanol (CH3)2CH2OC2H4OH and alcohols namely1-hexanol C6H14O, 1-octanol C8H18O and 1-decanol C10H22O and their binary mixtures with 2-isopropoxy ethanol as a common component have been measured over the full range of composition at atmospheric pressure and at different temperatures 293.15, 298.15, 303.15, 308.15 and 313.15K and viscosities have also been measured at 298.15, 303.15 and 308.15K over the full range composition. The experimental data were used to calculate the values of excess molar volumes VmE, deviations in isentropic compressibility Δκs, deviations in speed of sound Δu, deviations in viscosity Δη and excess Gibbs free energies ΔG∗E at all mole fractions of (CH3)2CH2OC2H4OH. The observed variations of these parameters with composition and temperature are discussed in terms of the molecular interactions due to physical and chemical effects between the unlike molecules of the binary mixtures. Further, experimental densities were used to estimate partial molar volumes V¯m,1, excess partial molar volumes V¯m,1E and their limiting values at infinite dilution V¯m,i∞ and V¯m,iE,∞, respectively. These parameters, especially excess functions are found to be quite sensitive towards the intermolecular interactions in liquid mixtures. The excess functions and deviations have also been correlated using Redlich-Kister type polynomial equation by the method of least-squares for the estimation of the binary coefficients and the standard errors. A study of above discussed parameters is used to throw light on the interactions existing between the constituents of the binary mixtures. FT-IR technique has been used to scrutinize the –OH interactions between the binary mixtures and is very valuable to spot the influence on the structural variation in the alcohols.

Properties of Dialkylcarbonate + 1-Alkanol Mixtures at the Vacuum Interface

The properties of solutions formed by dialkylcarbonate + 1-alkanol solutions are studied using classic molecular dynamics simulations. The effects of solution composition, temperature, and dialkylcarbonate type have been analyzed. The structure at the interface was analyzed and compared with the bulk liquid phases, with special attention to surface composition, molecular orientation, and intermolecular forces. Evaporation rates were also calculated as a function of temperature. Reported results provide a detailed characterization of interfacial properties of the presented complex systems at the nanoscopic level for the first time.

Limiting activity coefficient measurements in binary mixtures of dichloromethane and 1-alkanols (C1–C4)

Limiting activity coefficients γ∞ in binary mixtures of dichloromethane with four lower 1-alkanols (C1–C4) were experimentally determined employing alternatively the techniques of inert gas stripping, comparative ebulliometry, Rayleigh distillation, and differential distillation. For each case, the suitable technique was chosen on the basis of the limiting relative volatility of the solute and/or volatility of the solvent. The measurements yielding data of good accuracy (relative standard uncertainty of γ∞ from 0.01 to 0.03) were carried out at several temperatures in the range from (283–333) K. The variation of limiting activity coefficients with temperature was fitted by a suitable two- or three-parameter equation and compared with available literature information on both limiting activity coefficients and calorimetric partial molar excess enthalpies at infinite dilution. The performance of the leading prediction method Modified UNIFAC was further examined using these new data. Concentration dependences of activity coefficients calculated from their infinite dilution values using van Laar equation were found to agree well with those inferred from reliable VLE data from the literature. The occurrence of an azeotropic point was tested for the systems under study and the temperature dependence of the azeotropic composition was estimated for mixtures of dichloromethane with methanol and ethanol.

Molecular interactions and theoretical estimation of ultrasonic speeds using scaled particle theory in binary mixtures of 3-chloroaniline and 1-alkanols (C6–C10) at different temperatures

Density (ρ), speed of sound (u) and viscosity (η) have been measured for the binary mixtures of 3-chloroaniline with 1-alkanols (1-hexanol, 1-heptanol, 1-octanol, 1-decanol) over the entire composition range at (303.15, 308.15, 313.15, and 318.15) K. By using this data, the excess volume (VE), excess isentropic compressibility (κsE), deviation in viscosity (Δη) and excess Gibbs free energy of activation of viscous flow (G⁎E) have been calculated and were fitted to Redlich–Kister polynomial equation. The excess molar volumes, excess isentropic compressibility, deviation in viscosity and excess Gibbs energy of activation of viscous flow have been analyzed in terms of declustering and breaking of H-bonds in alkanols and alkyl chain of the 1-alkanols between unlike molecules. Moreover, the theoretical ultrasonic speeds are computed based on the scaled particle theory and compared with the experimentally measured values.

Simultaneous modeling of VLE, LLE and VLLE of CO2 and 1, 2, 3 and 4 alkanol containing mixtures using GC-PPC-SAFT EOS

A polar version of the group contribution PC-SAFT equation of state (GC-PPC-SAFT; Tamouza et al., 2004; NguyenHuynh et al., 2008) combined with a method for correlation/prediction of binary interaction parameters kij (NguyenHuynh et al., 2008) is here applied to model vapor–liquid, liquid–liquid and vapor–liquid–liquid phase equilibria of CO2+alkanol mixtures simultaneously.A cross-association interaction between CO2 and alkanol had to be taken into account to model/predict the mixtures equilibria accurately. The cross-association parameters were evaluated using the so-called CR1 mixing rules supported by ab initio computations.Extensive prediction tests on CO2+alkanol mixtures involving linear and branched alkanols are carried out. The results obtained showed that in most cases, the correlation and prediction calculations are qualitatively and quantitatively satisfactory: the overall deviations on liquid phase and vapor phase are respectively ΔX=3–4% and ΔY=1–2%.

Prediction of the vapor–liquid equilibria and speed of sound in binary systems of 1-alkanols and n-alkanes with the simplified PC-SAFT equation of state

Prediction of speed of sound is a challenging task for any equation of state because it needs the first- and second-order derivatives of the Helmholtz free energy with respect to both temperature and volume. Equally challenging is the simultaneous predictions of phase behavior and speed of sound (or other derivative properties) with satisfactory accuracy over wide temperature, pressure and composition conditions. This work presents the prediction of the vapor–liquid equilibria and speed of sound in binary mixtures of 1-alkanols and n-alkanes using the simplified PC-SAFT equation of state with pure component parameters estimated in different ways. All results are straight predictions, i.e. no binary interaction parameters are used. With the parameters presented in this work, the predicted overall percent average absolute deviations are, respectively, around 6.1% for the saturation pressure for 1533 experimental data points in the temperature range from 273 to 493K, and 1.7% for the speed of sound for 2490 experimental data points at temperature between 293 and 318K and pressure up to 120MPa. The results reveal that it is possible to simultaneously model the vapor–liquid equilibria and speed of sound with a satisfactory accuracy for 1-alkanols and n-alkanes binary systems within the PC-SAFT framework.

Density and Viscosity Measurements of Binary Alkanol Mixtures from (293.15 to 333.15) K at Atmospheric Pressure

Density and viscosity of binary mixtures of {x1isobutanol + x21-propanol}, {x1isobutanol + x22-propanol}, and {x13-amino-1-propanol + x21-propanol} were measured over the entire composition range and from temperatures (293.15 to 333.15) K at ambient pressure. The excess molar volumes and viscosity deviations were calculated and correlated by the Redlich–Kister and McAllister equations, respectively. The excess molar volumes are negative over the entire mole fraction range for all of the mixtures and become more negative with increasing temperature. The viscosity deviations of the binary mixtures are negative in the entire composition range and decrease with increasing temperature.

Predicting the vapor-liquid equilibrium of carbon dioxide+alkanol systems by using an artificial neural network

A multi-layer feed-forward artificial neural network has been presented for accurate prediction of the vapor liquid equilibrium (VLE) of CO2+alkanol mixtures. Different types of alkanols namely, 1-propaol, 2-propanol, 1-butanol, 1-pentanol, 2-pentanol, 1-hexanol and 1-heptanol, are used in this study. The proposed network is trained using the Levenberg-Marquardt back propagation algorithm, and the tan-sigmoid activation function is applied to calculate the output values of the neurons of the hidden layers. According to the network’s training, validation and testing results, a six layer neural network is selected as the best architecture. The presented model is very accurate over wide ranges of experimental pressure and temperatures. Comparison of the suggested neural network model with the most important thermodynamic correlations shows that the proposed neuromorphic model outperforms the other available alternatives. The predicted equilibrium pressure and vapor phase CO2 mole fraction are in good agreement with experimental data suggesting the accuracy of the proposed neural network model for process design.

Application of the UNIFAC model for prediction of surface tension and thickness of the surface layer in the binary mixtures

Surface properties of binary mixtures of (alkanol with acetonitrile) have been measured by surface tension method at T = 298.15 K and atmospheric pressure. The UNIFAC method is used for calculation activity coefficients of surface and bulk phases. Also, the surface tension has been predicted based on the Suarez method. This method combines a model for the description of surface tension of liquid mixtures with a UNIFAC group contribution method for the calculation of activity coefficient. Two techniques for calculation of molar surface areas, based on Paquette areas and Rasmussen areas are tested. On comparing the computed values of surface tension by the present approaches with experimental data, satisfactory results have been observed. In addition, the relative Gibbs adsorption and the surface mole fraction have been evaluated using this model. It is possible to calculate the thickness of liquid–vapor interfaces starting from surface tension data. A novel procedure is developed to obtain the thickness of liquid–vapor interfaces as a function of composition in binary systems.

Viscous synergic behaviour and solvent–solvent interactions occurring in liquid mixtures of aqueous alkanols with some alkanoic acids

The densities and viscosities of six ternary mixtures of the water, monoalkanols; 1-propanol, 2-propanol and monoalkanoic acids; formic acid, acetic acid and propionic acid are determined over the entire range of composition at 298.15, 308.15 and 318.15 K. From the experimental observations, the viscous synergy and synergy interaction index are derived from the equations developed by Kalentunc-Gencer, Peleg and Howell, respectively. The speeds of the sound of these ternary mixtures have been measured over the whole composition range at the same temperatures, and also the excess molar volumes, the isentropic compressibilities and excess isentropic compressibilities have been evaluated from the experimental data.

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.

Application of the Flory Theory and of the Kirkwod−Buff Formalism to the Study of Orientational Effects in 1-Alkanol + Linear or Cyclic Monoether Mixtures

Orientational effects present in binary mixtures of 1-alkanols with linear or cyclic monoethers have been studied using the Flory model and the Kirkwood−Buff formalism. The alcohols considered are those from methanol to 1-decanol, and the ethers are the following: dimethylether (DME), diethylether (DEE), dipropylether (DPE), dibutylether (DBE), tetrahydrofuran (THF), and tetrahydropyran (THP). In terms of the Flory model, orientational effects have been investigated by analyzing the concentration dependence of the interaction parameter, X12, and comparing the deviations obtained between experimental molar excess enthalpies, HmE, and calculated values with an X12 parameter determined from HmE measurements at equimolar composition. Due to the facts that structural effects are relevant for many of the considered mixtures and their excess molar volumes, VmE, are negative, we have also determined the excess molar internal energies, UV,mE, and X12 parameters from these data. From the X12 variation with the alka...

Topological investigations of the molecular species and molecular interactions that characterize pyrrolidin-2-one + lower alkanol mixtures

Molar excess volumes, V E, molar excess enthalpies, H E, and speeds of sound data, u, of pyrrolidin-2-one ( i) + ethanol or propan-1-ol or propan-2-ol or butan-1-ol ( j) binary mixtures have been determined over entire composition range at 308.15 K. The observed speeds of sound data have been utilized to predict excess isentropic compressibilities, κ S E of the investigated binary mixtures. The observed excess thermodynamic properties V E, H E and κ S E have been analyzed in terms of Graph theory. The analysis of V E data by the Graph theory suggests that pyrrolidin-2-one exists mainly as a mixture of cyclic and open dimer; ethanol as a mixture of dimer and trimer; butan-1-ol and propan-2-ol as mixture of monomer and dimer and propan-1-ol as a dimer in the pure state, and their mixtures contain 1:1 molecular complex. The IR studies lend additional credence to the nature and extent of interactions for the proposed molecular entities in the mixtures. Also, it has been observed that V E, H E and κ S E values predicted by the Graph theory compare well to with their corresponding experimental values.