Mole Fraction Of Ethanol Research Articles

Solubility, Solution Thermodynamics, and Preferential Solvation of Amygdalin in Ethanol + Water Solvent Mixtures.

The equilibrium solubility of amygdalin in [ethanol (1) + water (2)] mixtures at 293.15 K to 328.15 K was reported. The thermodynamic properties (standard enthalpy ΔsolnH°, standard entropy ΔsolnS°, and standard Gibbs energy of solution ΔsolnG°) were computed using the generated solubility data via van’t Hoff and Gibbs equations. The dissolution process of amygdalin is endothermic and the driving mechanism in all mixtures is entropy. Maximal solubility was achieved in 0.4 mole fraction of ethanol at 328.15 K and the minimal one in neat ethanol at 293.15 K. Van’t Hoff, Jouyban–Acree–van’t Hoff, and Buchowski–Ksiazczak models were used to simulate the obtained solubility data. The calculated solubilities deviate reasonably from experimental data. Preferential solvation parameters of amygdalin in mixture solvents were analyzed using the inverse Kirkwood–Buff integrals (IKBI) method. Amygdalin is preferentially solvated by water in ethanol-rich mixtures, whereas in water-rich mixtures, there is no clear evidence that determines which of water or ethanol solvents would be most likely to solvate the molecule.

Distribution coefficients of salicylic acid and methyl salicylate in high-pressure CO2 – water - ethanol systems

Vapor-liquid distribution coefficients (KD) of salicylic acid (SA) or methyl salicylate (MeS) in CO2 - water - ethanol systems were measured under flow conditions of water/ethanol ratios of (1 to 4) mol/mol at (313 to 353) K and (10 to 20) MPa. The KD of SA and MeS increased with pressure at constant temperature and with increasing water/ethanol ratios. Selectivity of SA versus MeS was highest (ca. 120) at water/ethanol feed ratios of 4 mol/mol, at 313 K and 20 MPa. Solute KD values followed trends of the liquid phase ethanol activity coefficients. A three-constant empirical relationship was developed that uses the pure CO2 reduced density and the feed ethanol mole fraction on a CO2-free basis as parameters to reliably correlate KD data and MeS/SA selectivities. The empirical relationship was also found to be applicable to flavonoid KD data in CO2 - water - ethanol systems.

Thermo-Acoustic Properties of (Ethanol + n-Heptane) Binary Mixtures from 293.35 to 433.89 K and up to 5.0 MPa

The experimental speeds of sound for the binary system of ethanol (1) + n-heptane (2) with the mole fractions of ethanol being (0.100, 0.300, 0.500, 0.700, and 0.900) were measured by Rayleigh-Bril...

Density and Viscosity of CO2 + Ethanol Binary Systems Measured by a Capillary Viscometer from 308.15 to 338.15 K and 15 to 45 MPa

Density and viscosity of CO2 + ethanol binary systems were measured by a high-pressure capillary viscometer at different ethanol mole fractions of 0, 0.067, 0.135, 0.203, 0.271, and 1 with temperat...

Ice formation and growth in supercooled water–alcohol mixtures: Theory and experiments with dual fiber sensors

Increased knowledge on fluid-solid phase transitions is needed, both when they are undesired and can impair process operations, and when strict control is required in fields such as food technology, the pharmaceutical industry and cryogenic CO2 capture. We present experimental results and theoretical predictions for the solid-formation and melting temperatures of ice in four binary water–alcohol mixtures containing methanol, ethanol, 1-propanol and 1-butanol. A dual fiber sensor set-up with a fiber Bragg grating sensor and a thin-core interferometer is used to detect the solid-formation. The predictions of melting temperatures with the cubic plus association equation of state combined with an ice model are in good agreement with experiments, but deviations are observed at higher alcohol concentrations. The measured degree of supercooling displays a highly non-linear dependence on the alcohol concentration. A heterogeneous nucleation model is developed to predict the solid-formation temperatures of the binary alcohol–water mixtures. The predictions from this model are in reasonable agreement with the measurements, but follow a qualitatively different trend that results in systematic deviations. In particular, the predicted degree of supercooling is found to be an essentially colligative property that increases smoothly with alcohol concentration. Experimental results are also presented for the growth rate of ice crystals in water–ethanol mixtures. For pure water, the measured crystal growth rate is 10.2 cm/s at 16 K supercooling. This is in excellent agreement with previous results from the literature. The crystal growth rate observed in ethanol–water mixtures however, can be orders of magnitude lower, where a mixture with 2% mole fraction ethanol has a growth rate of 2 mm/s. Further work is required to explain the large reduction in crystal growth rate with increasing alcohol concentration and to reproduce the behavior of the solid-formation temperatures with heterogeneous nucleation theory.

Micellization and Solvation Properties of Newly Synthesized Imidazolium- and Aminium-Based Surfactants

This work aimed to study the solvation properties of newly synthesized cationic surfactants: 1-hexyl-1-methyl-1H-imidazol-1-ium bromide (R6Im), 1-dodecyl-1-methyl-1H-imidazol-1-ium bromide (R12Im), N,N,N-tributylhexan-1-aminium bromide (R6N4), and N,N,N-tributyldodecan-1-aminium bromide (R12N4) in water and ethanol–water solvents with a 0.237 mole fraction of ethanol at 298.15 K using conductivity, refractive index, surface tension, and density measurements. Critical micelle concentration (CMC) for the synthesized surfactants was determined and discussed. Thermodynamic parameters including association constant, molal volume, and polarizability were calculated and discussed. Some surface properties of surfactants including excess surface concentration and minimum area per molecule were also calculated and discussed. A good agreement was found between the CMC values obtained from different techniques, such as conductivity, refractive index, and surface tension. Imidazolium surfactants had been proved to decrease the CMC and increase the association constant with the increase of ethanol mole fraction, while tributylamine had been proved to increase the CMC and decrease the association constant with the increase of ethanol mole fraction. Also, imidazolium surfactants had been proved to have higher CMC than tributylamine, which may be related to higher solvation of imidazolium surfactants than that of tributylamine. Both surfactants (R12Im) and (R12N4) were proved to have lesser CMC.

Molecular Mechanism for Azeotrope Formation in Ethanol/Benzene Binary Mixtures through Gibbs Ensemble Monte Carlo Simulation.

Azeotropes have been studied for decades due to the challenges they impose on separation processes but fundamental understanding at the molecular level remains limited. Although molecular simulation has demonstrated its capability of predicting mixture vapor-liquid equilibrium (VLE) behaviors, including azeotropes, its potential for mechanistic investigation has not been fully exploited. In this study, we use the united atom transferable potentials for phase equilibria (TraPPE-UA) force field to model the ethanol/benzene mixture, which displays a positive azeotrope. Gibbs ensemble Monte Carlo (GEMC) simulation is performed to predict the VLE phase diagram, including an azeotrope point. The results accurately agree with experimental measurements. We argue that the molecular mechanism of azeotrope formation cannot be fully understood by studying the mixture liquid-state stability at the azeotrope point alone. Rather, azeotrope occurrence is only a reflection of the changing relative volatility between the two components over a much wider composition range. A thermodynamic criterion is thus proposed on the basis of the comparison of partial excess Gibbs energy between the components. In the ethanol/benzene system, molecular energetics shows that with increasing ethanol mole fraction, its volatility initially decreases but later plateaus, while benzene volatility is initially nearly constant and only starts to decrease when its mole fraction is low. Analysis of the mixture liquid structure, including a detailed investigation of ethanol hydrogen-bonding configurations at different composition levels, reveals the underlying molecular mechanism for the changing volatilities responsible for the azeotrope.

Ammonia/Ethanol Mixture for Adsorption Refrigeration

Adsorption refrigeration has become an attractive technology due to the capability to exploit low-grade thermal energy for cooling power generation and the use of environmentally friendly refrigerants. Traditionally, these systems work with pure fluids such as water, ethanol, methanol, and ammonia. Nevertheless, the operating conditions make their commercialization still unfeasible, especially owing to safety and cost issues as a consequence of the working pressures, which are higher or lower than 1 atm. The present work represents the first thermodynamic insight in the use of mixtures for adsorption refrigeration and aims to assess the performance of a binary system of ammonia and ethanol. According to the Gibbs’ phase rule, the addition of a component introduces an additional degree of freedom, which allows to adjust the pressure of the system varying the composition of the mixture. The refrigeration process was simulated with isothermal- isochoric flash calculations to solve the phase equilibria, described by the Peng-Robinson-Stryjek-Vera (PRSV) equation of state for the vapor and liquid phases and by the ideal adsorbed solution theory (IAST) and the multicomponent potential theory of adsorption (MPTA) for the adsorbed phase. In operating condenser and evaporator, pressure levels around atmospheric pressure can be achieved using an ammonia/ethanol mixture with a mole fraction of ethanol in the range of 0.70−0.75. A good agreement in the predictions of the adsorbed phase composition was also reported using the IAST and the MPTA methods.

Hesperetin Solubility in Aqueous Co-solvent Mixtures of Methanol and Ethanol: Solute Descriptors, Solvent Effect and Preferential Solvation Analysis

Solubility data for hesperetin in pure solvents and alcohol-rich regions of aqueous mixtures of methanol and ethanol were used to derive the solute descriptors for solubility prediction of hesperetin by using the Abraham solvation parameter model. Solubility data in aqueous mixtures of methanol and ethanol were analyzed by the linear solvation energy relationships approach to provide detailed insight into the solvent effect. In this regard, energy terms for solute–solvent and solvent–solvent interactions were defined in terms of dipolarity–polarizability, hydrogen bond basicity, hydrogen bond acidity and Hildebrand solvent parameter. Results indicate that the main contribution was from solvent–solvent interactions represented by the cavity term. Preferential solvation analysis was performed with the help of inverse Kirkwood–Buff integrals approach. Local composition and preferential solvation parameter were calculated as a function of mole fraction of methanol and ethanol. Results show that hesperetin is preferentially surrounded by water in water-rich regions, whereas methanol or ethanol are preferred in other compositions. This observation was discussed in terms of the solute hydrophobic hydration and specific hydrogen bonding interactions.

Maraviroc in aqueous co-solvent solutions of n-propanol, ethanol, dimethyl sulfoxide and N,N-dimethylformamide: Solubility determination, preferential solvation and solvent effect analysis

The liquid–solid equilibrium and solubility of maraviroc in co-solvent mixtures of n-propanol, ethanol, dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) plus water was obtained via the saturation shake-flask technique between 278.15 K and 323.15 K under 101.2 kPa. For the four aqueous co-solvent mixtures investigated, the mole fraction solubility of maraviroc increased with the increase in the temperature and mass fraction of n-propanol, ethanol, DMSO and DMF. The maximum solubility values of maraviroc were observed in the neat co-solvents. The dependence of the maraviroc solubility on the solvent composition and temperature was mathematically correlated by means of the Jouyban-Acree model. The obtained values of relative average deviation (RAD) and root-mean-square deviation (RMSD) were no more than 4.16 × 10−2 and 49.13 × 10−6, respectively. KAT-LSER model was implemented to get quantitative information about solvent effect on the variation of solubility data. The variation in the maraviroc solubility was dependent upon the hydrogen-bond donation and cavity term in n-propanol + water and ethanol + water mixtures; and the cavity term was the dominant term in the (DMSO + water) and (DMF + water) mixtures. Quantitative study was made for the local mole fraction of ethanol (n-propanol, DMSO and DMF) and water around the maraviroc by the Inverse Kirkwood–Buff integrals method applied to the solubility data determined. Maraviroc was preferentially solvated by ethanol or n-propanol for the aqueous co-solvent mixtures of ethanol or n-propanol in intermediate and ethanol/n-propanol-rich compositions. It was conjecturable that maraviroc could act mainly as a Lewis acid in front to the ethanol or n-propanol molecules. However in the {n-propanol (1) + water (2)} mixture with compositions 0 < x1 < 0.20, ethanol (1) + water (2) mixture with compositions 0 < x1 < 0.25 and DMF/DMSO mixtures within entire compositions, maraviroc was preferentially solvated neither by co-solvent (1) nor by water.

Investigation of Nucleate Pool Boiling of Saturated Pure Liquids and Ethanol-Water Mixtures on Smooth and Laser-Textured Surfaces

ABSTRACTNucleate pool boiling experiments were performed on plain and five laser-textured stainless-steel foils using saturated pure water, 100% ethanol, 0.4% and 4.2% mole fraction ethanol – water mixtures. All laser-textured samples contained untreated, smooth 0.5 mm wide regions and intermediate textured surfaces, that differ in the width of the laser patterned regions (from 0.5 mm to 2.5 mm). For smooth surfaces, we measured significant decreases in average heat transfer coefficients (HTC) and increases in bubble activation temperatures in comparison with the laser-textured surfaces for all the tested working fluids. Significant enhancement in HTC (280%) on a textured heating surface with 2.5-mm-wide laser pattern was recorded using pure water. For pure ethanol, the highest enhancement of 268% was achieved on a heating surface with 1.5-mm-wide laser pattern. The highest enhancement of HTC for the tested binary mixtures was obtained using 2.0-mm wide-laser-textured regions (HTC improved by 235% and 279% for the 0.4% and 4.2% mixtures, respectively). Our results indicate that laser texturing can significantly improve boiling performance when the intervals of the laser-textured patterns are close to the capillary lengths of the tested fluids.

Heat and mass transfer in the boundary layer during evaporation of aqueous solutions of ethanol and acetone into air and superheated vapor components of solutions

A stationary flow of three-component gas in a laminar boundary layer on a flat plate is considered at adiabatic evaporation of a two-component liquid film. Numerical modelling were carried out at atmospheric pressure, air flow velocity of 2 m/s and temperature from 20 to 500 °C in the whole range of concentrations of a low-boiling component of binary solutions: ethanol/water, acetone/water, and acetone/ethanol. Data on the local specific evaporation rate of ethanol/water and acetone/water solutions into dry air and superheated mixture of ethanol, acetone and water vapors were obtained depending on the temperature of the inlet flow. Composition of superheated vapor mixture was taken to be equilibrium relative to the liquid solution. With an increase in the molar fraction of ethanol or acetone in the water solution, the evaporation rate increases, and when evaporated into superheated vapor, the growth of evaporation rate with increasing vapor temperature is significantly higher than at evaporation into air. With an increase in ethanol or acetone concentration in the liquid solution, the inversion temperature decreases from down to 155…165°C.

Thermodynamic Properties of Water−Ethanol Films Formed between Hydrophobic Surfaces. Part I.

Based on thermodynamic reasoning we claim that long-ranged, solvophobic surface forces may arise in thin films of associated liquids due to formation of linear aggregates composed of spheroidal, nano-sized molecular clusters. Supposedly, these aggregates can span a narrow gap between two hydrofobic solid surfaces submerged in the film-forming liquid phase, thus giving rise to attraction. Such aggregates are apparantly generated in thin water and water–ethanol films, especially below room temperature and for high mole fractions of water or ethanol, respectively. The surface force recorded for a pure water with film thickness larger than about 20 nm are found to be proportional to the number of bridging cluster aggregates per unit area that cross the mid-plane of a thin film. Moreover, the long-range-ness (decay length) was seen to depend inversely on the work of formation of the elongated middle part of a bridging cluster aggregate. Furthermore, addition of small amounts of ethanol rapidly reduce the surface force generated for pure water films with thickness of a few hundred nm.

Permittivity Measurements of Mixtures as a Function of their Composition for Microwave Heating Improving

Microwave heating is a more efficient alternative to conventional heating in the chemical reactions field due to its positive effects on conversion and reaction kinetics. Dielectric properties of substances and mixtures are important for the optimization of microwave heating processes; notwithstanding this, specific databases are poor and far from being complete, and in the scientific literature only a few data regarding these properties can be found. Dielectric properties are represented by permittivity, which is a complex measure of a substance behaviour in the presence of an electromagnetic field and depends on the field frequency, as well as on the temperature and composition of the chemical system under study. In this work, some real and imaginary parts of permittivity measurements were carried out using a specially designed measurement system. The apparatus was tested in the estimation of permittivity values in water-ethanol mixtures, varying their composition. The results were compared to literature data and fitted with available literature models to verify their trend as a function of composition. The permittivity real part values increase with reducing the molar fraction of ethanol, whereas the imaginary part decreases, according to the values of water and ethanol permittivity reported in the literature. The regressions carried out to describe the permittivity dependence on composition prove that the measured values can be well described by the models taken into account.

Study of solvation of substituted propylbenzene in ethanol-water solutions under subcritical conditions by molecular dynamics

Solutions of 2-methoxy-4-(2′-hydroxypropyl)phenol (PrPh) in water and water-ethanol mixtures (0.020, 0.115, 0.285 mol fraction of ethanol) at temperature 573 K and densities corresponding to an experimental pressure of 23 MPa have been simulated by molecular dynamics. Distribution of components in the fluid bulk and in the PrPh solvate shell has been researched. Numbers and lifetimes of hydrogen bonds between the components have been determined, and tendencies to selective solvation have been analyzed. It has been shown that PrPh molecules form stable long-lived hydrogen bonds with water and ethanol. An increase in ethanol concentration leads to a decrease in the number of hydrogen bonds formed by PrPh and to an increase in their lifetime that indicates growing stability of the solvate complexes. The local mole fraction of ethanol around PrPh is lower than its average mole fraction in the fluid, i.e., the PrPh solvate shells mainly consist of water molecules.

Modelling of ethanol pyrolysis in a commercial CVD reactor for growing carbon layers on alumina substrates

Chemical vapour deposition (CVD) is widely used for preparation of pyrolytic carbons from various precursors. The prediction of deposition kinetics requires deep understanding of all transport phenomena involved. In this work, we perform the computational modelling of ethanol pyrolysis in a commercial CVD reactor (a tube furnace). The reactor is employed for growing carbon layers on alumina substrates. The inlet gas flow is produced by evaporating azeotrope ethanol/water mixture and mixing it with inert gas (argon). The modelling is performed in 3D and 2D statements using Marinov mechanism with 57 species participating in 383 reactions. The heat and species transport is taken into account with temperature dependent physical properties. It is shown that the inlet gas velocity in the 2D statement should be corrected for a meaningful comparison with the 3D case. A good agreement is found between species mole fractions at the substrate position for 3D and 2D statements at low volume flow rates, while at high flow rates some deviations are observed. The temperature at the substrate position is found to be lower than at the reactor wall due to inflow of a colder gas. The main pyrolysis products at moderate temperatures (around 900 °C) are water, ethylene, hydrogen, carbon monoxide, and methane. With increasing temperature, the mole fractions of hydrogen, acetylene, and carbon monoxide increase, while those of water and methane become smaller. With increasing ethanol/water volume flow rate, the mole fractions of ethanol and pyrolysis products saturate at some constant values due to incomplete thermal decomposition of ethanol in the reactor volume. The rise of argon flow rate leads to the decrease of pyrolysis products mole fractions due to decrease of residence time. The obtained results can be employed for simulating and analyzing pyrolysis processes in realistic CVD reactors with complex geometry as well as for the development of coupled gas phase and surface reaction model of carbon layer deposition on nanoporous substrates.

Determination of the solubility and thermodynamic properties of albendazole in a binary solvent of ethanol and water

ABSTRACT The solubility of albendazole (ABZ) in a binary system of ethanol and water were determined experimentally by using a static analytical method within the temperature range (288.95 to 317.25) K under atmospheric pressure (p = 0.1 MPa). It was observed that the solubility of ABZ is not only depended on temperature but also related to the mole fraction of ethanol. Additionally, the obtained solubility data were correlated by employing the CNIBS/R-K model, the modified Apelblat equation and the Jouyban–Acree model. The modified Apelblat equation was proven to give good representation of the experimental solubility data. On the base of the measured solubility, the thermodynamic properties of the dissolution process were calculated. Dissolution of ABZ in these mixed solvents is endothermic, non-spontaneous and enthalpy-driving. This study provides useful information for the design and development of dosage forms of ABZ.

Critical properties for the mixtures of ethanol and some biodiesel surrogates

Critical temperature Tc and critical pressure pc of the mixtures of ethanol and biodiesel surrogates (ethanol + methyl butanoate, ethanol + ethyl propanoate, ethanol + methyl hexanoate, methyl butanoate+ ethyl propanoate and ethanol + methyl butanoate + ethyl propanoate) were measured via a flow method. A linear decrease in Tc and an increase in pc of three binary mixtures can be observed with the increasing mole fraction of ethanol. Despite the mole fraction of ethyl propanoate increases, critical curves of the ternary mixture change almost linearly with the mole fraction of ethanol. Critical properties of the binary mixtures were interrelated with Redlich–Kister equations and PR-WS equations and predicted by He equations. Maximum AADs for Tc and pc using Redlich–Kister equations are 0.08% and 0.65%. There is a great agreement between our experimental data and calculated values from two correlations for the critical parameters of ternary mixture.

Experimental measurements, equilibrium study and model correlation of methyl paraben in ethanol and methanol aqueous solutions from = (293.15 to 323.15) K

Data on corresponding solid–liquid equilibrium of methyl paraben (MP) in methanol, ethanol and binary aqueous systems are essential for industrial design and further theoretical studies. By the gravimetric method, the solubility of MP in pure water and two binary mixed solvents (methanol + water, ethanol + water) were measured over the temperature range from 293.15 to 323.15 K at atmospheric pressure. According to the experimental results, it could be found that the solubility of MP in three tested pure and binary solvent systems increased with the rise of temperature at the measurable ranges. The solubility data of MP in both binary solvent systems increase with the increasing of mole fraction of methanol or ethanol. Van't Hoff equation modified Apelblat equation, Yaws equation and, λh equation model were applied to correlate the experimental solubility data of MP in pure and mixed solvent systems. Finally, the thermodynamic behavior of MP dissolution process were analyzed, and its standard molar enthalpy (ΔsolH°), Gibbs energy (ΔsolG°), and entropy (ΔsolS°) of MP dissolution in the studied systems were acquired. It was found that the dissolution processes of MP in the tested systems were non spontaneous, endothermic and entropy-driven.

Kinetic model for the ammoxidation of ethanol to acetonitrile

A comprehensive kinetic study, based on V-based catalysts (Vanadium Pyro-Phosphate, VPP, VOx/TiO2 and VOx/ZrO2), was modeled to retrieve the surface reaction mechanism and kinetic parameters for the ammoxidation of ethanol to acetonitrile. In all the cases, the catalysts showed a moderate to good acetonitrile selectivity, that in turn resulted correlated primarily to the reaction temperature, while the byproducts distribution was more influenced by the thermodynamic stability of the reacting mixture.A large and comprehensive collection of data on ammoxidation of C2 substrates for acetonitrile production was analysed and 5 groups of experiments on VOx-based catalysts (operating in the temperature range 250–450 °C) were selected. The base reactant was ethanol and ammonia and oxygen were fed in optimal ratios of 1:3–1:4 mol/mol.A kinetic model was then derived applying the Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach to accepted catalytic oxidation mechanisms: for every catalytic material, eight to ten reactions with rates described by the Arrhenius formula were employed. Fixing the reaction orders according to the mechanistic assumption and adjusting only the kinetic and adsorption parameters, the calculated molar fractions of ethanol, ammonia, acetonitrile and ethylene resulted in good agreement with the extensive collection of experimental data available.