Alkanol Systems Research Articles

Volumetric, transport and acoustic properties of binary mixtures containing alkanol at 298.15–318.15 K

The measurement of density (ρ), viscosity (η) and ultrasonic speed (u) have been conducted at T = 298.15 K–318.15 K and at 0.1 MPa to study the intermolecular interactions between p–chlorotoluene with alkanol (C1–C2). These data were utilized to derive the excess properties like excess molar volume (VmE), deviation in viscosity (Δη), excess free energy of activation (ΔG*E), deviation in ultrasonic speed (Δu), and excess isentropic compressibility (κsE) for binary mixtures. Utilizing the VmE values, partial molar volume and excess partial molar volume were calculated. The Δη and κsE were investigated using theoretical models such as the Singh model and ab initio approach, which yielded interactional parameters that not only indicate the extent of unlike interactions and depolymerization of self–associated alkanol but also predicts the Δη and κsE for these systems. The conclusions of the ab initio approach were further validated by the Singh model for viscosity. The u data were further interpreted by various correlations and theories. Regarding correlation, Nomoto’s correlation demonstrated high predictive power for ultrasonic speed data, respectively, compared to other correlations. The resulting excess properties were fitted to Redlich–Kister polynomial equations. The VmE values were observed to be negative for p–chlorotoluene + alkanol systems at all temperatures. The study of the binary mixtures is significant because it sheds light on the nature of intermolecular interactions which has practical implications in areas such as chemical synthesis, solvent selection, and understanding the effects of solvents on reaction rates and product yields.

Thermodynamic and structural study of DMPC-alkanol systems.

The thermodynamic and structural behaviors of lamellar dimyristoylphosphatidylcholine-alkanol (abbreviation DMPC-CnOH, n = 8-18 is the even number of carbons in the alkyl chain) systems were studied by using DSC and SAXD/WAXD methods at a 0-0.8 CnOH : DMPC molar ratio range. Up to n≤ 10 a significant biphasic effect depending on the main transition temperature tm on the CnOH concentration was observed. Two breakpoints were revealed: turning point (TP), corresponding to the minimum, and threshold concentration (cT), corresponding to the end of the biphasic tendency. These breakpoints were also observed in the alkanol concentration dependent change in the enthalpy of the main transition ΔHm. In the case of CnOHs with n > 10 we propose a marked shift of TP and cT to very low concentrations; consequently, only increase of tm is observed. A partial phase diagram was constructed for a pseudo-binary DMPC-C12OH system. We suggest a fluid-fluid immiscibility of the DMPC-C12OH system above cT with a consequent formation of domains with different C12OH contents. At a constant CnOH concentration, the effects of CnOHs on ΔHm and bilayer repeat distance were found to depend predominantly on the mismatch between CnOH and lipid chain lengths. Observed effects are suggested to be underlined by a counterbalancing effect of interchain van der Waals interactions and headgroup repulsion.

Accounting for quadrupolar interactions in the CPA equation of state: A modelling approach for binary mixtures of CO2 or benzene with n-alkanes and 1-alkanols

The Cubic Plus Association (CPA) equation of state (EoS) is extended with the theory for quadrupolar molecules of Gross, yielding the CPA-G model. CPA-G is compared to the recently developed qCPA, which uses the polar theory of Larsen and coworkers. Each model requires an additional adjustable parameter for quadrupolar molecules.The models are evaluated by means of their ability to model the phase equilibria of binary mixtures of CO2 or benzene with n-alkanes and 1-alkanols, as well as binary mixtures of quadrupolar molecules. A refined technique of accounting for cross-association in the CO2 + 1-alkanol systems is proposed, allowing an improved description of these systems without the use of a binary interaction parameter. Accounting for cross-association in the benzene + 1-alkanol systems investigated in this work did not lead to improved results. Both CPA-G and qCPA provide significant improvements over nonpolar CPA in both n-alkane and 1-alkanol mixtures, with excellent results obtained in the subcritical region without the use of binary interaction parameters. qCPA continues to provide excellent predictions in the supercritical region, while CPA-G overestimates the solubility pressures in the supercritical region. Both quadrupolar models can qualitatively predict the existence of three-phase equilibrium in the CO2 + n-alkane and CO2 + 1-alkanol systems. The simple combining rules used for cross-quadrupolar interactions in both CPA-G and qCPA do not take molecular orientation into account and are unable to truly capture the phase behaviour in the CO2 + benzene system.

Thermodynamic behaviour of alkyl lactate–alkanol systems

Abstract This work reports densities and speeds of sound of some alkyl lactates + alkanols binary mixtures over the whole composition range at T = 298.15 K and p = 0.1 MPa. The studied systems were methyl lactate or ethyl lactate with methanol, ethanol, 1-propanol, or 1-butanol. From experimental results, excess molar volumes and excess isentropic compressibilities have been calculated. Furthermore, excess molar enthalpies were experimentally determined at T = 298.15 K and p = 0.1 MPa. Finally, the excess properties were correlated with composition and discussed taking into account the associated character of both components, alkyl lactates and alkanols. From this analysis it has been concluded that excess properties values depend mainly on the length of the alkyl chain of the alkanol.

Hydrogen Bonding Interactions of m-Chlorotoluene with 1-Alkanol Analyzed by Thermodynamic, Fourier Transform Infrared Spectroscopy, Density Functional Theory, and Natural Bond Orbital.

Fourier transform infrared spectroscopy (FT-IR) has been employed to obtain information about the nature of interactions in the liquid solutions of pure solvents and their mixtures of m-chlorotoluene (MCT) with 1-alkanol systems at different mole fractions. Furthermore, densities (ρ) and speeds of sound (u) of binary mixtures of MCT with a set of five 1-alkanols, namely, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, and 1-heptanol, were measured as a function of composition at 298.15 K. From the experimental quantities, the excess volumes (VE), isentropic compressibility (ks), and excess isentropic compressibility (ksE) were calculated for the binary mixtures over the entire composition range and under the atmospheric pressure. These excess properties (VE) and (ksE) were correlated with the Redlich–Kister polynomial equation. Additionally, theoretical density functional theory calculations and natural bond orbital analyses were carried out to further discern the nature and strength of interactions between MCT and 1-alkanols. Moreover, the recorded FT-IR spectra-derived excess properties and quantum chemically derived data revealed the presence of interactions between component molecules in binary liquid solutions.

Thermodynamics of mixtures containing aromatic nitriles

The coexistence curves of liquid-liquid equilibrium (LLE) for the mixtures: phenylacetonitrile + heptane, + octane, + nonane, + cyclooctane, or + 2,2,4-trimethylpentane and for 3-phenylpropionitrile + heptane, or + octane are reported. Aromatic nitrile + alkane, + aromatic hydrocarbon or + 1 alkanol systems are investigated using a set of thermophysical properties: phase equilibria (solid-liquid, SLE, vapour-liquid, VLE and LLE), excess molar functions, enthalpies (HmE), isochoric internal energies (UVmE), isobaric heat capacities (CpmE) and volumes (VmE), and the Kirkwood’s correlation factor. Due to proximity effects between the phenyl and the CN groups, dipolar interactions between molecules of aromatic nitriles are stronger than those between molecules of isomeric linear nitriles. Dipolar interactions become weaker in the order: 3-phenylpropionitrile > phenylacetonitrile > benzonitrile. Benzonitrile+aromatic hydrocarbon mixtures are characterized by dispersive interactions and structural effects. The latter are more important in systems with phenylacetonitrile. Structural effects are also present in benzonitrile+n-alkane, or+1-alkanol+mixtures. The systems mentioned above have been studied using DISQUAC. Interaction parameters for contacts where the CN group in aromatic nitriles participates are given. DISQUAC describes correctly any type of phase equilibria, CpmE of benzonitrile+hydrocarbon mixtures and HmE of benzonitrile+cyclohexane, or 1-alkanol systems. Large differences encountered between theoretical HmE values and experimental data for some solutions are discussed. 1-Alkanol+benzonitrile mixtures are also investigated by means of the ERAS model. ERAS represents well HmE of these systems. The VmE curves of solutions with longer 1-alkanols are more poorly described, which has been explained in terms of the existence of structural effects.

Insights into the structure and dynamics at the hexadecane droplet–water interface in the presence of 1-alkanols as emulsifiers: Molecular dynamics studies

The structure and dynamics at the surface of nanoscopic hexadecane droplets immersed in aqueous phase with and without emulsifiers (1-alkanols of varying chain length; pentanol, heptanol, decanol and dodecanol) have been studied using atomistic molecular dynamics simulations. The nature of layering of alcohol molecules on the oil droplet is governed by the hydrophobicity of alkanols. Longer chain alkanols are more likely to penetrate into the oil droplet. The probability of tangential orientation of hexadecane molecules at the interface decreases with decreasing hydrophobic environment around the droplet. The interfacial hexadecane molecules show greater probability to obtain a puckered conformation in binary oil–water system than in ternary oil–water–alkanol systems. Decrease in hydrophobic interaction between hexadecane and water molecules due to the efficient screening of oil surface by longer chain alkanols in ternary oil–water–alkanol systems leads to greater survival probability of water molecules in the oil–water interfacial layer and enhancement in life time of H-bonds formed between alcohol and water molecules.

Thermodynamics of liquid–vapor phase equilibrium in dimethyl sulfoxide–alkanol systems in the range of 293.15–323.15 K

Liquid–vapor phase equilibria in dimethyl sulfoxide–alkanol (1-propanol, 1-butanol, and tert-butanol) binary systems are studied using a static method. The total saturated vapor pressure in the temperature range of 293.15–323.15 K is measured. The partial pressures of dimethyl sulfoxide and alkanes have been calculated via integrating the Gibbs–Duhem equation. Excess molar Gibbs energies are described by the Redlich–Kister equation, and the correlation parameters are calculated. The nature of the deviation from the ideal behavior of these solutions is explained by allowing for the presence of competing homo- and heteromolecular interactions and the considerable effect of the length of the alkanols’ hydrocarbon chains has on the values of the thermodynamic parameters.

Excess molar enthalpies of binary mixtures of formamide with butanol at 298.15 K: Application of Prigogine–Flory–Patterson theory and Treszczanowicz–Benson association model

Excess molar enthalpies (HmE) of formamide (1)+1-butanol or 2-methyl-1-propanol or 2-methyl-2-propanol (2) mixtures have been measured at 298.15K over the entire composition range using flow micro calorimeter. The excess enthalpy data along with previously published excess volumes data (VmE) (M. Rani, S. Maken, J. Ind. Eng. Chem. 18 (2012) 1694) have been utilised to study the thermodynamics of molecular interactions in terms of Prigogine–Flory–Patterson theory and Treszczanowicz–Benson association model with a Flory contribution term. The Treszczanowicz–Benson model was developed for alkane+alkanol systems considering Mecke–Kempter type of association in alkanol. In this paper the Treszczanowicz–Benson association model was applied, for the first time, to binary mixtures containing both components associated (butanol and formamide) through hydrogen bonding. In both the cases, when either of formamide or butanol was assumed to be associated, the calculated HmE and VmE values compared reasonably well with the corresponding experimental data, but the agreement is not very impressive for excess enthalpy in formamide+2-methyl-2-propanol mixtures. Extent of inter-molecular H-bonding in formamide and butanols in their binary mixtures was also reflected in their molar enthalpy of association of H-bonding ΔhH0.

Measurement and correlation of vapor–liquid equilibria for alkane + alkanol and alkane + alkanediol systems with group contribution COSMOSPACE model

The infinite dilution activity coefficients were measured for alkanes (hexane, octane and decane) in alkanols (1-decanol, 1-dodecanol and 1-tetradecanol) and alkanes (hexane, octane and decane) in alkanediols (1,2-ethanediol and 1,3-propanediol) systems by a gas stripping method. A group contribution COSMOSPACE (conductor-like screening model surface-pair activity coefficient equation) model was proposed to calculate the activity coefficients of alkane+alkanol and alkane+alkanediol systems. The molecules are divided into three segments based on the electric charges of atoms. Segment OH is OH group. Segment CH2+ is CH2 adjacent to OH. Segment CH2 is the remaining alkyl group except segment CH2+. The Flory–Huggins term of a modified ASOG is used as the combinatorial term. The infinite dilution activity coefficients of 1-alkanols in alkanes, alkanes in 1-alkanols and alkanes in alkanediols are correlated well by using the group contribution COSMOSPACE model. The activity coefficients in finite concentration range for alkane+alkanol systems are also correlated with good accuracy.

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.

The Interaction of Cationic Gemini Surfactant 1,4-Butanediyl-α,ω-bis(dimethylcetylammonium bromide) with Primary Linear Alkanols

The critical micelle concentration (CMC) of cationic gemini surfactant 1,4-butanediyl-α, ω-bis(dimethylcetylammonium bromide; C16-C4-C16) with and without additives (primary linear alcohols: butanol (C4OH), pentanol (C5OH), hexanol (C6OH), heptanol (C7OH), octanol (C8OH)) is measured by surface tension measurements using a du Noüy tensiometer in aqueous solution at 303 K. The CMC of C16-C4-C16 decreased with increasing alcohol concentration and the effect followed the order: C8OH > C7OH > C6OH > C5OH > C4OH. The surfactant concentration required to reduce the surface tension of the solvent by 20 mN/m, C20, ratio of C20 and CMC, maximum surface excess, Γmax, and minimum surface area per molecule, Amin, were evaluated from surface tension versus log Ct (Ct is the total surfactant concentration) plots. Mixed micelles were formed and the CMC values of the mixtures were used to compute βm, the interaction parameter for mixed micelle formation in aqueous medium, βσ, the interaction parameter for mixed monolayer formation at the aqueous solution/air interface, and the respective activity coefficients (f1 and f2). The standard Gibbs energy of adsorption was also evaluated. We observed synergism in C16-C4-C16/alkanol systems at all concentration ratios.

The Conductance Percolation and Droplets Dimension of AOT in Alkanol Systems

The conductance behaviors of AOT in alkanol (hexanol, heptanol, octanol, and decanol) reverse microemulsions have been investigated. The percolation phenomenon induced by water is observed in the water/AOT/decanol system at 15°C and 30°C, and the water/AOT/octanol system at 15°C. The percolation phenomenon of water/AOT/alkanol systems is discussed from the interaction between the hydroxy group of alkanol and the polar group of AOT, droplets diffusion coefficient, and the rate constant for droplets collision. The droplets size and diffusion coefficient of the water/AOT/alkanol systems have also been studied by modifying the water concentration. The results show that hydrodynamic diameter of droplets decreases and diffusion coefficient increases with the increasing of water content, which may be explained by the polarity of alkanol phase.

Densities and Excess Molar Volumes of N-Methylmorpholine + 1-Alkanol Systems at 298.15 K

Densities, ρ, of pure N-methylmorpholine (1) + ethanol (2), + 1-propanol (2), + 1-butanol (2), + 1-pentanol (2), + 1-hexanol (2), and + 1-octanol (2) and their binary mixtures were measured using a digital vibrating tube densimeter at 298.15 K. Excess molar volumes, VE, of the binary mixtures were calculated from density values. Excess molar volumes of binary mixtures of N-methylmorpholine (1) + ethanol (2) and + 1-propanol (2) show an S-shaped dependence on composition with positive values in the N-methylmorpholine-rich region and negative values at the opposite extreme. The excess molar volume is positive over the mole fraction range for N-methylmorpholine (1) + 1-butanol (2), + 1-pentanol (2), 1-hexanol (2), and + 1-octanol (2) systems. All experimental VE values were fitted to the Redlich–Kister equation.

High-pressure vapor–liquid equilibria for CO 2 + alkanol systems and densities of n-dodecane and n-tridecane

An apparatus based on the static-analytic method was used to measure the vapor–liquid equilibria (VLE) for CO 2 + alkanol systems. Equilibrium measurements for the CO 2 + 1-propanol system were performed from 344 to 426 K. For the case of the CO 2 + 2-propanol system, measurements were made from 334 to 443 K, and for the CO 2 + 1-butanol were obtained from 354 to 430 K. VLE data were correlated with the Peng–Robinson equation of state using the classical and the Wong–Sandler mixing rules. Moreover, compressed liquid densities for the n-dodecane and n-tridecane were obtained via a vibrating tube densitometer at temperatures from 313 to 363 K and pressures up to 25 MPa. The Starling and Han (BWRS), and The five-parameter Modified Toscani-Swarcz (MTS) equations were used to correlate them. The experimental density data were compared with those from literature, and with the calculated values obtained from available equations for these n-alkanes.

Measurement of Density and Viscosity of Binary 1-Alkanol Systems (C8−C11) at 101 kPa and Temperatures from (283.15 to 313.15) K

In this paper, we present the experimental values of the density and dynamic viscosity, obtained at 101 kPa, for binary systems containing 1-octanol, 1-nonanol, 1-decanol, and 1-undecanol over the entire range of mole fractions and at the following temperatures: (283.15, 288.15, 293.15, 298.15, 303.15, 308.15, and 313.15) K. The experimental viscosity data have been correlated by means of a model previously developed in our group. The binary interaction parameters of this model are also presented. The agreement between experimental and calculated values is quite good. The overall mean relative standard deviations are 0.2 % for the system 1-octanol + 1-nonanol, 0.5 % for the system 1-octanol + 1-decanol, 0.7 % for the system 1-octanol + 1-undecanol, 0.2 % for the system 1-nonanol+1-decanol, 0.6 % for the system 1-nonanol + 1- undecanol, and 0.2 % for the system 1-decanol + 1-undecanol.

The standard Gibbs energy of adsorption from the bulk at the surface of liquid mixtures: reinterpretation of Traube's rule: Analysis of the Δ adsG0 contributions under the Extended Langmuir model

In this paper, it is shown that the symmetrically normalized activity coefficient of the solute in the bulk solution, γ B b , makes a non-negligible contribution to the standard Gibbs energy of adsorption of solute from the bulk at the surface of binary liquid mixtures, Δ ads G 0. With a view to defining this change with practical purposes, we selected the pure solute and a surface pressure π of 1 mN m −1 as standard states for the bulk and surface phases, respectively. Besides, we assumed availability of data in the highly dilute region, where the two-dimensional ideal equation of state holds. In this way, Δ ads G 0 = − RT ln ( π / γ B b x B ) . When γ B b is taken into account, Traube's rule (that ln ( π / x B ) x B → 0 increases linearly with chain length in the water + 1-alkanol series) does not imply that Δ ads G 0 increases linearly with chain length. On the contrary, together with the fact that in this series ln( γ B b , ∞ ) increases with chain length at the same rate as ln ( π / x B ) x B → 0 , Traube's rule implies that Δ ads G 0 is constant in this series. This can be interpreted in molecular terms as indicating that in highly dilute solutions the hydrocarbon chain of alkanol molecules at the surface does not lie in or on the surface (as is implied by a linear increase in Δ ads G 0 with chain length), but resides completely in the gas phase, as is now known to be true. The constancy of Δ ads G 0 also explains why water + 1-alkanol systems share the same π versus γ B b x B curve except at high surface concentrations, where the degree of discrepancy is in any case limited by the small differences in surface tension among the pure alkanols. We conclude by using the “Extended Langmuir” model of surface behaviour to split Δ ads G 0 into five distinct physically meaningful contributions.

The standard Gibbs energy of adsorption from the bulk at the surface of liquid mixtures: reinterpretation of Traube's ruleAnalysis of the ΔadsG0 contributions under the Extended Langmuir model

In this paper, it is shown that the symmetrically normalized activity coefficient of the solute in the bulk solution, γBb, makes a non-negligible contribution to the standard Gibbs energy of adsorption of solute from the bulk at the surface of binary liquid mixtures, Δ adsG0. With a view to defining this change with practical purposes, we selected the pure solute and a surface pressure π of 1 mN m -1 as standard states for the bulk and surface phases, respectively. Besides, we assumed availability of data in the highly dilute region, where the two-dimensional ideal equation of state holds. In this way, Δ adsG0 = -RT ln(π/γBbxB). When γBb is taken into account, Traube's rule (that ln(π/xB)xB→0 increases linearly with chain length in the water + 1-alkanol series) does not imply that ΔadsG0 increases linearly with chain length. On the contrary, together with the fact that in this series ln(γBb,∞) increases with chain length at the same rate as ln(π/xB)xB→0, Traube's rule implies that ΔadsG0 is constant in this series. This can be interpreted in molecular terms as indicating that in highly dilute solutions the hydrocarbon chain of alkanol molecules at the surface does not lie in or on the surface (as is implied by a linear increase in ΔadsG0 with chain length), but resides completely in the gas phase, as is now known to be true. The constancy of ΔadsG0 also explains why water + 1-alkanol systems share the same π versus γBbxB curve except at high surface concentrations, where the degree of discrepancy is in any case limited by the small differences in surface tension among the pure alkanols. We conclude by using the "Extended Langmuir" model of surface behaviour to split ΔadsG0 into five distinct physically meaningful contributions. © 2004 Elsevier B.V. All rights reserved.

Measurement and Correlation of Excess Molar Enthalpies for Ethylene Glycol + Alkanol Systems at the Temperatures (298.15, 308.15, and 323.15) K

Excess molar enthalpies for a series of ethylene glycol + alkanol (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol) systems were measured over the entire molar composition range at (298.15, 308.15, and 323.15) K under atmospheric pressure using a flow-type isothermal microcalorimeter. The values of HE increase slightly with increasing temperature for all of the ethylene glycol + n-alkanol (methanol, ethanol, 1-propanol, and 1-butanol) systems over the entire composition range. In addition, a dependence of HE on the chain length of the n-alkanol was observed. However, the same temperature dependency as in the ethylene glycol + n-alkanol systems was not observed for ethylene glycol + 2-alkanol (2-propanol and 2-butanol) systems. The experimental results were compared with values correlated using the Redlich−Kister equation.

Vapor-Liquid Equilibria for n-Pentane + Alkanol Systems near the Critical Region

Vapor-Liquid Equilibria for n-Pentane + Alkanol Systems near the Critical Region