Liquid Mole Fraction Research Articles

Electrical conductivity and dipolar relaxation of binary dimethylimidazolium chloride–water solutions: A molecular dynamics study

The non-thermal response of neat dimethylimidazolium chloride salts and their binary mixtures with water have been investigated by means of non-equilibrium molecular dynamics simulation at an electric field intensity of 10 − 3 V/Å, in terms of electrical conductivity and dipolar relaxation (as metrics of translational and rotational response, respectively). Using Green-Kubo and transient time correlation function (TTCF) analysis, the electrical conductivity of each system has been estimated. It was found that the systems' conductivity at 450 K increased, while dipolar relaxation times for both water molecules and dimethylimidazolium ions decreased, with decreasing ionic liquid mole fraction. This indicates greater scope for accelerated response to external electric fields in less associated ionic liquids.

Electrical Conductivity of Caprolactam Tetrabutylammonium Bromide Ionic Liquids in Aqueous and Alcohol Binary Systems

The electrical conductivities of binary systems of caprolactam tetrabutylammonium bromide ionic liquid + solvent (solvent = water, ethanol, 2-propanol, 1-butanol) systems were measured at ionic liquid mole fractions from (3.60·10−4 to 6.82·10−2) and temperatures from (290.55 to 342.25) K. The conductivities of the mixtures increase with increasing temperature, increasing concentration of ionic liquid, and decreasing caprolactam/tetrabutylammonium bromide mole ratio in the ionic liquid. The conductivity values of the binary systems (ionic liquid + solvent) decrease with the solvent in the following order: water > ethanol > 2-propanol > 1-butanol.

Vapor−Liquid Equilibria of Binary Systems of Ethene Oxide + Dodecane, Ethene Oxide + 1-Decanol, and Ethene Oxide + 1-Dodecanol and Prediction with the Predictive Soave−Redlich−Kwong (PSRK) Equation of State

Vapor−liquid equilibrium (VLE) measurements have been made for the binary systems ethene oxide + dodecane at four temperatures from (303.15 to 393.15) K, ethene oxide + 1-decanol at three temperatures from (303.15 to 363.15) K, and ethene oxide + 1-dodecanol at four temperatures from (313.15 to 433.15) K for varying mole fractions. An adiabatic calorimeter was used as a static apparatus for the VLE measurement. The obtained temperature, pressure, and liquid mole fraction data (T−p−x data) were used for fitting binary interaction parameters for the predictive Soave−Redlich−Kwong equation of state (PSRK EoS). The applicability of fitted parameters to other systems containing identical structural groups is shown by means of the binary system ethene oxide + 2-methylpropane and ethene oxide + 1-dodecanol.

Phase equilibria study of { N-butylquinolinium bis{(trifluoromethyl)sulfonyl}imide + aromatic hydrocarbons, or an alcohol} binary systems

Quinolinium ionic liquid has been prepared from 1-butylquinolinium bromide as a substrate. The work includes specific basic characterization of synthesized compound by NMR spectra, elementary analysis and water content. The basic thermal properties of the pure IL, i.e. melting and glass-transition temperatures, as well as the enthalpy of fusion have been measured using a differential scanning microcalorimetry technique (DSC). (Solid + liquid) phase equilibria (SLE) and (liquid + liquid) phase equilibria (LLE) for the binary systems: ionic liquid (IL) N-butylquinolinium bis{(trifluoromethyl)sulfonyl}imide, {([BQuin][NTf 2]) + aromatic hydrocarbon (benzene, or toluene, or methylbenzene, or propylbenzene, or thiophene), or an alcohol (ethanol, or 1-butanol, or 1-hexanol, or 1-octanol, or 1-dodecanol)} have been determined at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (260 to 330) K. For the binary systems, the simple eutectic diagrams were observed with immiscibility in the liquid phase with an upper critical solution temperature (UCST). For mixtures with alcohols, it was observed that with increasing chain length of an alcohol the solubility decreases and the UCST increases. In the case of mixture (IL + benzene, or alkylbenzene, or thiophene) the eutectic systems with mutual immiscibility in the liquid phase with very high UCSTs were observed. These points were not detectable with our method and they were observed at low ionic liquid mole fraction. Densities at high temperatures were determined and extrapolated to T = 298.15 K. Well-known UNIQUAC, and NRTL equations have been used to correlate experimental SLE data sets. For the systems containing immiscibility gaps {IL + an alcohol} parameters of the LLE correlation equation have been derived using only the NRTL equation.

Experimental and Computational Study on the Properties of Pure and Water Mixed 1-Ethyl-3-methylimidazolium l-(+)-Lactate Ionic Liquid

Ionic liquids have attracted great attention, from both industry and academe, as alternative fluids for a large collection of applications. Although the term green is used frequently to describe ionic liquids in general, it is obvious that it cannot be applied to the huge quantity of possible ionic liquids, and thus, those with adequate environmental and technological profiles must be selected for further and deeper studies, from both basic science and applied approaches. In this work, 1-ethyl-3-methylimidazolium L-(+)-lactate ionic liquid is studied, because of its remarkable properties, through a wide-ranging approach considering thermophysical, spectroscopic, and computational tools, to gain a deeper insight into its complex liquid structure, both pure and mixed with water, thus implying the main factors that would control the technological applications that could be designed using this fluid. The reported results shows a strongly structured pure ionic liquid, in which hydrogen bonding, because of the hydroxyl group of the lactate anion, develops a remarkable role, together with Coulombic forces to determine the fluid's behavior. Upon mixing with water, the ionic liquid retains its structure up to very high dilution levels, with the effect of the ionic liquid on the water structure being very large, even for very low ionic liquid mole fractions. Thus, in water solution, the studied ionic liquid evolves from noninteracting ions solvated by water molecules toward large interacting structures with increasing ionic liquid content.

Using 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate as an Entrainer for the Extractive Distillation of Ethanol + Water Mixtures

Isobaric vapor−liquid equilibria (VLE) for the ethanol + water + [emim][triflate] ternary system have been obtained at 100 kPa using a recirculating still. The ethanol + water binary system was also obtained. Furthermore, data were simulated with the Mock’s electrolyte nonrandom two-liquid (NRTL) model, using the solvent−solvent interaction parameters obtained from VLE data of the ethanol + water system and taking the solvent−ionic liquid (IL) interaction parameters for the other binary systems from previous works. The agreement between experimental and calculated data is very good, showing the predictive capacity of the model. The addition of [emim][triflate] produces the disappearance of the ethanol + water azeotrope when the mole fraction of ionic liquid in the liquid phase is greater than 0.023 at 100 kPa. The effect of [emim][triflate] on the ethanol + water system has been compared with that produced by other ionic liquids reported in the literature.

Vapor–liquid equilibria and density measurement for binary mixtures of o-xylene + NMF, m-xylene + NMF and p-xylene + NMF at 333.15 K, 343.15 K and 353.15 K from 0 kPa to 101.3 kPa

Isothermal vapor–liquid equilibria at 333.15 K, 343.15 K and 353.15 K for three binary mixtures of o-xylene, m-xylene and p-xylene individually mixed with N-methylformamide (NMF), have been obtained at pressures ranged from 0 kPa to 101.3 kPa over the whole composition range. The Wilson, NRTL and UNIQUAC activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Peng–Robinson equation of state in calculating the vapor mole fraction. Liquid and vapor densities were measured by using two vibrating tube densitometers. The excess molar volumes of the liquid phase were also determined. Three systems of o-xylene + NMF, m-xylene + NMF and p-xylene + NMF mixtures present large positive deviations from the ideal solution and belong to endothermic mixings because their excess Gibbs energies are positive. Temperature dependent intermolecular parameters in the NRTL model correlation were finally obtained in this study.

Vapor–liquid equilibria and density measurement for binary mixtures of toluene, benzene, o-xylene, m-xylene, sulfolane and nonane at 333.15 K and 353.15 K

Isothermal vapor–liquid equilibria at 333.15 K and 353.15 K for four binary mixtures of benzene + nonane, toluene + o-xylene, m-xylene + sulfolane and o-xylene + sulfolane have been obtained at pressures ranged from 0 to 101.3 kPa over the whole composition range. The Wilson, NRTL and UNIQUAC activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Peng–Robinson equation of state in calculating the vapor mole fraction. Liquid and vapor densities of these solutions were measured by using two vibrating tube densitometers. The excess molar volumes of the liquid phase were also determined. The P– x– y phase behavior indicates that mixtures of m-xylene + sulfolane, o-xylene + sulfolane and benzene + nonane present large positive deviations from the ideal solution and belong to endothermic mixings because their excess Gibbs energies are positive.

Preparation and catalytic use of silica-polymer core–shell microspheres with imidazolium-styrene copolymer shells

Silica-polymer core–shell microspheres with imidazolium-styrene copolymer shells were prepared by polymerization of acidic ionic liquids with styrene in the presence of 3-mercaptopropyltrimethoxysilane (MPTMS)-modified silica, in water–ethanol mixed solvent. It was found that the thickness of the copolymer shells and the amounts of ionic liquids contained in the shells depended largely on reaction parameters such as the emulsifier, and the type and mole fraction of acidic ionic liquid. Unlike the neat imidazolium-styrene copolymers, the silica-polymer core–shell microspheres were insoluble in organic solvents. Moreover, they retained the properties of the imidazolium-styrene copolymers while affording improved mechanical strength due to their core–shell structure. The core–shell microspheres can be used as efficient catalysts for acetalization of carbonyl compounds with methanol under mild reaction conditions.

Isobaric Vapor−Liquid and Liquid−Liquid Equilibria for Chloroform + Methanol + 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate at 100 kPa

Isobaric vapor−liquid equilibria for the binary system chloroform + methanol as well as the vapor−liquid equilibria for the chloroform + methanol + [emim][triflate] ternary system have been obtained at 100 kPa using a recirculating still. The ternary ionic liquid (IL) system presents an immiscibility zone at high chloroform composition, which increases with the temperature. Liquid−liquid equilibria for this system have also been determined. The measured ternary vapor−liquid equilibrium data were correlated using the Mock’s electrolyte nonrandom two-liquid (NRTL) model which reproduces reasonably well the experimental values and predicts the total disappearance of the azeotrope when the mole fraction of ionic liquid in the liquid phase is 0.25. The immiscibility does not affect the use of [emim][triflate] as the entrainer for the complete chloroform + methanol separation.

Isothermal vapor–liquid equilibria for binary mixtures of hexane, heptane, octane, nonane and cyclohexane at 333.15 K, 343.15 K and 353.15 K

Isothermal vapor–liquid equilibria at 333.15 K, 343.15 K and 353.15 K for four binary mixtures of hexane + heptane, heptane + octane, cyclohexane + octane and cyclohexane + nonane have been obtained at pressures ranged from 0 to 101.3 kPa. The NRTL, UNIQUAC and Wilson activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Soave–Redlich–Kwong equation of state in calculating the vapor mole fraction. Liquid and vapor densities were also measured by using two vibrating tube densitometers. Phase behaviors of the P– x– y diagrams indicate that three mixtures of hexane + heptane, heptane + octane, cyclohexane + octane were close to the ideal solution. However, the cyclohexane + nonane mixture presents a large positive deviation from the ideal solution. Only the cyclohexane + octane mixture is negative in the excess Gibbs energy indicates that it is an exothermic system.

Isothermal vapor–liquid equilibria for binary mixtures of benzene, toluene, m-xylene, and N-methylformamide at 333.15 K and 353.15 K

Isothermal vapor–liquid equilibrium (VLE) at 333.15 K and 353.15 K for four binary mixtures of benzene + toluene, benzene + N-methylformamide, toluene + m-xylene and toluene + N-methylformamide have been obtained at pressures ranged from 0 kPa to 101.3 kPa. The NRTL, UNIQUAC and Wilson activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Soave–Redlich–Kwong equation of state in calculating the vapor mole fraction. Liquid and vapor densities were also measured by using two vibrating tube densitometers. The P– x– y diagram and the activity coefficient indicate that two mixtures of benzene + toluene and toluene + m-xylene were close to the ideal solution. However, two mixtures containing N-methylformamide present a large positive deviation from the ideal solution. The excess Gibbs energy in the benzene + toluene mixture is negative indicates that it is an exothermic system.

An Experimental Investigation on Heat Transfer Characteristics for Micro-Capillary Evaporator

An experimental investigation on heat transfer characteristics for a kind of micro-capillary groove evaporator has been carried out in this article. The binary liquid mixture used in this experiment was composed of 2-Methylpentane and methanol. The experimental results showed that when the liquid mixture mole fraction X1 (2-Methylpentane):X2 (methanol) equals to 1:9, the enhanced heat transfer effect was the best. This kind of binary liquid mixture was applied for all three evaporators with different dimensions; the optimal ratio of depth on the width of the micro-groove for the evaporator was obtained. Compared with the available results in the previous studies, the experimental results showed that the temperature of the heated surface could be reduced in the range of 10°–20° at the same heat flux. The experimental results showed that this kind of evaporator could be capable of cooling for high-power electronic chips.

Solvent effects on the reaction rate and selectivity of synchronous heterogeneous hydrogenation of cyclohexene and acetone in ionic liquid/alcohols mixtures

Synchronous heterogeneous catalytic hydrogenation of cyclohexene and acetone, catalyzed by Pt/Al2O3, was carried out in solutions of 2-hydroxy ethylammonium formate (a room temperature ionic liquid, RTIL) with ethanol and propan-1-ol at 25°C. Rate constants and selectivity of the reaction (relative to cyclohexene hydrogenation) increase with mole fraction of the ionic liquid (IL). The reactants tendency to the catalyst surface increases by addition of the ionic liquid and thus the reaction rate increases, especially for cyclohexene hydrogenation. Consequently the selectivity to cyclohexene hydrogenation was increased. Single-parameter correlations of logkvs.π* (dipolarity/polarizibility) gives reasonable results in the solution. The increase of the reaction rate with π* is attributed to the non-polar nature of the reactants.

Local Structures in PEO-[C2mim]CF3SO3 Electrolytes Used in Electrochemical Double-Layer Capacitors

Polymer electrolytes containing room-temperature ionic liquids have tremendous potential for use in electrochemical double-layer capacitors. In this report, the local structure of one family of ionic-liquid-based polymer electrolytes (PEO complexed with 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, [C2mim]CF3SO3) is correlated to trends in the conductivity and thermal properties of the materials. Conductivities dramatically increase as the mole fraction of the ionic liquid is increased in the polymer electrolyte. Concomitantly, melting point onset temperatures for PEO decrease with increasing amounts of ionic liquid. IR and Raman spectroscopy suggest that the [C2mim]+ cations are weakly coordinated by oxygen atoms of the polymer backbone, and there is some degree of ionic association at higher mole fractions. The lack of strong PEO-[C2mim]+ interactions might explain, in part, why this system has much higher conductivities compared to other PEO-MCF3SO3 (M = Li, Na, K, etc.) polymer electrolytes at equivalent salt compositions.

Isobaric Vapor−Liquid Equilibria for 1-Propanol + Water + 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate at 100 kPa

Isobaric vapor−liquid equilibria for the binary systems 1-propanol + water, 1-propanol + 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]), and water + [emim][triflate] as well as the vapor−liquid equilibria for the 1-propanol + water + [emim][triflate] ternary system have been obtained at 100 kPa using a recirculating still. Electrolyte NRTL fitting parameters for the 1-propanol + water and water + [emim][triflate] systems were calculated. The measured ternary data were correlated using Mock’s electrolyte NRTL model which reproduces reasonably well the experimental values. The results show that the addition of [emim][triflate] to 1-propanol + water produced an important salting-out effect, and the model predicts that at 100 kPa the azeotrope disappears when the mole fraction of ionic liquid in the liquid phase is greater than 0.34.

Activity coefficients and excess Gibbs energy of binary mixtures of N, N-dimethyl formamide with selected compounds at 95.5 kPa

Bubble point temperatures at 95.5 kPa, over the entire composition range, are measured for the binary mixtures of N, N-dimethyl formamide with: acetophenone, aniline, bromobenzene, chlorobenzene and N, N-dimethyl acetamide, employing a Swietoslawski-type ebulliometer. Liquid phase mole fraction versus bubble point temperature measurements are well represented by the Wilson model. Computed values of the activity coefficients and excess Gibbs energy are presented and discussed.

Densities and Viscosities of 1-Butyl-3-methylimidazolium Tetrafluoroborate + Molecular Solvent Binary Mixtures

The densities and viscosities of 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF4] ionic liquid with methyl formate, methyl acetate, ethyl formate, and acetone have been measured at 298.15 K. The excess molar volume VmE and the viscosity deviations Δη for the binary mixture have been calculated and were fitted to the Redlich−Kister polynomials. The values of VmE and Δη are negative over the whole composition range. The minima in VmE and Δη are observed at about mole fraction of the ionic liquid, x ≈ 0.3 and 0.7, respectively.

Kinetics study of a Diels‐Alder reaction in mixtures of an ionic liquid with molecular solvents

AbstractThe second‐order rate constants for cycloaddition reaction of cyclopentadiene with naphthoquinone were determined spectrophotometrically in various compositions of 1‐(1‐butyl)‐3‐methylimidazolium terafluoroborate ([bmim]BF4) with water and methanol at 25 °C. Rate constants of the reaction in pure solvents are in the order of water > [bmim]BF4 > methanol. Rate constants of the reaction decrease sharply with mole fraction of the ionic liquid in aqueous solutions and increase slightly to a maximum in alcoholic mixtures. Multi‐parameter correlation of logk2 versus solute–solvent interaction parameters demonstrated that solvophobicity parameter (Sp), hydrogen‐bond donor acidity (α) and hydrogen‐bond acceptor basicity (β) of media are the main factors influencing the reaction rate constant. The proposed three‐parameter model shows that the reaction rate constant increases with Sp, α and β parameters. Copyright © 2008 John Wiley & Sons, Ltd.

Kinetic study of heterogeneous catalytic hydrogenation of cyclohexene to cyclohexane in ionic liquid–alcohols mixtures

Abstract Heterogeneous catalytic hydrogenation of cyclohexene, catalyzed by Pt/Al2O3, was carried out in solutions of 2-hydroxyethylammonium formate (a room temperature ionic liquid, RTIL) mixed with methanol, ethanol and propan-2-ol at 25 °C. The rate constants of the reaction in ionic liquid alcohol mixtures were higher than alcohol alone. First-order rate constant of the reaction in the RTIL relative to propan-2-ol is approximately 28. Furthermore, the rate constant of the reaction increases with the mole fraction of the ionic liquid. Single-parameter correlations of log k vs. normalized polarity parameter ( E T N ), hydrogen-bond acceptor basicity (β) and hydrogen-bond donor acidity (α) do not give acceptable results in the solutions. In addition, log k does not show an acceptable dual-parameter correlation with π* (dipolarity/polarizibility, one of the Kamlet–Taft parameters for solvent that shows the dipolarity of the solvent) and α, π* and β and E T N and β. However single-parameter correlation of log k vs. π* gives reasonable results. The increase of the reaction rate with π* is attributed to the non-polar nature of the reactants.