Mole Fraction Of Methanol Research Articles

Solubility and preferential solvation of some non-steroidal anti-inflammatory drugs in methanol + water mixtures at 298.15 K

ABSTRACTThe equilibrium solubilities of naproxen (NAP), ketoprofen (KTP), and ibuprofen (IBP) in methanol + water binary mixtures at 298.15 K were determined and the preferential solvation parameters were derived by means of the inverse Kirkwood–Buff integrals (IKBI) method. These drugs are very sensitive to specific solvation effects. The preferential solvation parameters by methanol δx1,3 are negative in water-rich mixtures but positive in compositions from 0.32 in mole fraction of methanol to pure methanol. It is conjecturable that in the former case the hydrophobic hydration around aromatic rings and/or methyl groups plays a relevant role in the solvation. The higher solvation by methanol in mixtures of similar co-solvent compositions and in methanol-rich mixtures could be explained in terms of the higher basic behaviour of this co-solvent interacting with the hydroxyl group of the drugs. Moreover, drug solubilities were correlated by using the modified nearly ideal binary solvent/Redlich–Kister model obtaining average percentage deviations (APDs) lower than 9.0%.

Reduction of gas emission via optimization of purified purge gas recycle ratio for conversion of CO2 to methanol

The current study highlights the significance of optimum recycle purge gas ratio (Φ) to methanol synthesis reactor calculated via a one dimensional modeling of process and also proposes an environmentally friendly process. Moreover, Differential Evolution (DE) method is applied to maximize methanol mole fraction. The purge gas of this process includes about 60% hydrogen, 20% carbon monoxide and carbon dioxide and 20% nitrogen and methane. Burning of such these gases is not economical and environmentally friendly process, thus recycling the purge gas is a reliable work. Although complete restoration of the purge gas is environmentally friendly, it is not an economical process. In order to prevent accumulation of inert gases such as nitrogen and methane, a purge gas line is attached to the recycling stream. In addition, a nitrogen purification unit has been proposed in the present study. Nitrogen is separated from the recycle gas stream by a novel metallic membrane; furthermore, nitrogen is converted to ammonia during the purification process. The increase in methanol production in Optimized Reactor Configuration (ORC) is 41% compared with the one in Industrial Configuration (IC). The optimum recycle ratio is 0.41 in ORC while this parameter is 2.19 in IC and zero in Fresh Feed Configuration (FFC). Simulation results show that Stoichiometry Number (SN) is reduced to 2.1 at the entrance of reactor; moreover, methanol production rate increases in ORC. Furthermore, the capability of ORC for producing ammonia is 305mol/h. Enhancement in methanol and ammonia productions demonstrate the superiority of ORC to the previous configurations.

Correlation of solubility and prediction of the mixing properties of rosmarinic acid in different pure solvents and in binary solvent mixtures of ethanol + water and methanol + water from (293.2 to 318.2) K

The solubility of rosmarinic acid was measured in water, ethanol, methanol, and in the binary solvent mixtures (ethanol+water) and (methanol+water), with different molar fraction values for ethanol and methanol, from (Xsolv=0.10 to 0.90), over a temperature range of (T=293.15, 298.15, 303.15, 308.2, 313.15 and 318.15) K. With increasing temperature and molar fraction of ethanol and methanol, the solubility of rosmarinic acid increased from 0.26 to 0.46 and from 0.28 to 0.49 respectively. The experimental solubility values were well correlated by the modified Apelblat equation. From the measured solubility data, the thermodynamic properties enthalpy of dissolution (ΔsolHRA) and entropy of dissolution (ΔsolSRA) of rosmarinic acid, during the dissolution process in water, ethanol, methanol, and binary solvent mixtures (ethanol+water) and (methanol+water), could be calculated based on these fits. The results indicate that the dissolution process is endothermic.

Solubility and preferential solvation of acetaminophen in methanol + water mixtures at 298.15 K

ABSTRACTThe equilibrium solubility of acetaminophen in methanol + water binary mixtures at 298.15 K was determined and correlated with the Jouyban–Acree model. Preferential solvation parameters by methanol (δx1,3) were derived from their thermodynamic solution properties by means of the inverse Kirkwood–Buff integrals method. δx1,3 values are negative in water-rich mixtures but positive in compositions from 0.32 in mole fraction of methanol to pure methanol. It is conjecturable that in the former case, the hydrophobic hydration around non-polar groups plays a relevant role in the solvation. The higher solvation by methanol in mixtures of similar cosolvent compositions and methanol-rich mixtures could be explained in terms of the higher basic behavior of this cosolvent.

Molecular Dynamics Simulation of Na+–Cl– Ion-Pair in Water–Methanol Mixtures under Supercritical and Ambient Conditions

Constrained molecular dynamics simulations have been performed to investigate the structure and thermodynamics of Na(+)-Cl(-) ion-pair association in water-methanol mixtures under supercritical and ambient conditions in dilute solutions. From the computed potentials of mean force (PMFs) we find that contact ion pairs (CIPs) are more stable than all other associated states of the ion pairs in both ambient and supercritical conditions. Stabilities of CIPs increase with increase in the mole fraction of methanol. In supercritical conditions, major changes in PMFs occur as we go from x(methanol) = 0.00 to x(methanol) = 0.50. The stable solvent shared ion pair (SShIP) which occurs in x(methanol) = 0.00 and 0.25, vanishes when x(methanol) is 0.50 or greater. The stabilities of these ion pairs increase with increasing temperature. Local structures around the ions are studied using the radial distribution functions, density profiles, angular distribution functions, running coordination numbers and excess coordination numbers. Preferential solvation analysis shows that both Na(+) and Cl(-) ions are preferentially solvated by water. From the calculation of enthalpies and entropies, we find that Na(+)-Cl(-) ion-pair association in water-methanol binary mixtures is endothermic and driven by entropy both in ambient as well as under supercritical conditions.

Solvation of o-hydroxybenzoic acid in pure and modified supercritical carbon dioxide, according to numerical modeling data

The dissolution of an elementary fragment of crystal structure (an o-hydroxybenzoic acid (o-HBA) dimer) in both pure and modified supercritical (SC) carbon dioxide by adding methanol (molar fraction, 0.035) at T = 318 K, ρ = 0.7 g/cm3 is simulated. Features of the solvation mechanism in each solvent are revealed. The solvation of o-HBA in pure SC CO2 is shown to occur via electron donor-acceptor interactions. o-HBA forms a solvate complex in modified SC CO2 through hydrogen bonds between the carboxyl group and methanol. The hydroxyl group of o-HBA participates in the formation of an intramolecular hydrogen bond, and not in interactions with the solvent. It is concluded that the o-HBA-methanol complex is a stable molecular structure, and its lifetime is one order of magnitude higher than those of other hydrogen bonds in fluids.

Modeling Phase Equilibria for the Glycine–NH4Cl–Methanol–Water System and Its Application for the Industrial Monochloroacetic Acid Process

As a continuation of our previous study, this work focuses on the determination and modeling of phase equilibria for the mixed-solvent electrolyte system containing glycine, ammonium chloride (NH4Cl), methanol, and water. This electrolyte is used in the monochloroacetic acid (MCA) process for glycine production. The solubilities for the NH4Cl–methanol–water and glycine–NH4Cl–methanol–water systems were determined from 283.15 to 323.15 K. The MSE model embedded in the OLI platform was modified by regressing experimental data through adjustment of the UNIQUAC and the middle-range interaction parameters. With the new model parameters, solubilities in the quaternary system were predicted with excellent agreement. The average absolute deviations between the prediction and the experimental solubility are 3.46 and 0.54% for glycine and NH4Cl, respectively. OLI Stream Analyzer 9.1 was used with this new MSE model to investigate the effect of the methanol composition and temperature on the yield of glycine crystallization in the MCA process. It was found that a methanol mole fraction of 0.65–0.70 at ambient temperatures was optimal for enhancing the theoretical yield of glycine to 96.5% while minimizing the methanol consumption.

Solvation structures of lithium halides in methanol–water mixtures

The potentials of mean force (PMFs) for the ion pairs, Li+Cl−, Li+Br− and Li+I− have been calculated in five methanol–water compositions. The results obtained are verified by trailing the trajectories and calculating the ion pair distance residence times. Local structures around the ions are studied using the radial distribution functions, density profiles, orientational correlation functions, running coordination numbers and excess coordination numbers. The major change in PMF is observed as the methanol mole fraction (xmethanol) is changed from 1.0 to 0.75. The stable contact ion pair occurring for xmethanol=1.0 becomes unstable at and below xmethanol=0.75. The preferential solvation data show that the halide ions are always preferentially solvated by water molecules. Although the lithium ion is preferentially solvated by methanol molecules, there is significant affinity towards water molecules as well.

Effect of the composition of methanol−water mixtures on tacticity of poly(N‐ethylacrylamide) gel

ABSTRACTTwo series of macroporous poly(N‐ethylacrylamide) (PNEAM) gels are synthesized in different composition of methanol–water mixtures (xm = 0, 0.06, 0.13, 0.21, 0.31, and 0.43; where xm = mole fraction of methanol) in presence as well as in the absence of 0.1M Y(OTf)3 Lewis acid as additive. The gels synthesized in the absence of Lewis acid are atactic and in the presence of the same are isotactic. Synthesis of the corresponding linear PNEAM homopolymers shows that, the isotacticity (meso dyad, %) of the resulted polymers increases for the gels prepared in the presence of Lewis acid (LA) and remains constant for the gel prepared in the absence of LA, respectively, with the increase in the concentration of the synthesis solvent methanol. SEM micrographs reveal that, the hydrogels synthesized in the presence of LA are more porous than the gels prepared in the absence of LA. Swelling ratio of all the hydrogels decreases with the increase in the temperature and LA gels show higher swelling ratio values than non LA gels (NLA). Deswelling rate of the hydrogels prepared in methanol–water mixture in presence of LA is faster than the hydrogels prepared in absence of LA. Moreover, reswelling rate increases with increase in the isotacticity of the PNEAM segment in the gel. All these results have been explained on the basis of the formation of highly porous hydrogels with higher isotactic PNEAM chain segment in the presence of LA in methanol–water mixtures. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41668.

Solubility and preferential solvation of meloxicam in methanol + water mixtures at 298.15 K

The equilibrium solubility of meloxicam in methanol+water binary mixtures at 298.15K was determined and the preferential solvation parameters were derived from their thermodynamic solution properties by means of the inverse Kirkwood–Buff integrals method. From solvent effect studies, it is found that this drug is sensitive to specific solvation effects. The preferential solvation parameter by methanol δx1,3, is negative in water-rich mixtures but positive in compositions from 0.30 in mole fraction of methanol to pure methanol. It is conjecturable that in the former case the hydrophobic hydration around aromatic rings and/or methyl groups plays a relevant role in the solvation. The more solvation by methanol in mixtures of similar co-solvent compositions and in methanol-rich mixtures could be explained in terms of the bigger basic behavior of the co-solvent interacting with hydrogen-donor groups of the drug.

The optimal operating conditions of a thermally double coupled, dual membrane reactor for simultaneous methanol synthesis, methanol dehydration and methyl cyclohexane dehydrogenation

In this study, the concept of thermally double coupled reactor is proposed as an alternative configuration to mix the energy efficient concept of coupling two exothermic with one endothermic reaction. In this multi-tubular fixed bed reactor, methanol synthesis and methanol dehydration, as two exothermic reactions occur in the inner and outer tubes while the methyl cyclohexane dehydrogenation, as an endothermic reaction takes place in the middle tube. Two water permselective membranes are also applied in the inner and outer tubes to remove water from both exothermic sides. Extraction of water as one of the main byproducts in the DME (dimethyl ether) and methanol synthesis processes increases the production rate and the catalyst life time. In this configuration, the operating conditions are optimized using a differential evolution method in order to maximize the outlet methanol and DME mole fractions of the inner and outer exothermic sides respectively. Then the optimized results of the thermally double couple dual membrane reactor are compared with the optimized thermally double couple reactor and the ones in conventional methanol and DME synthesis reactors. This comparison shows the superiority of this configuration to the conventional ones owing to the enhancement of methanol and DME mole fractions (10.9% and 19.5% increase compared with conventional ones respectively). Hydrogen and toluene, as two valuable products, are also produced in a favorable mode.

Influence of ions on molecular vibrations and hydrogen bonds in methanol–water mixtures: MD simulation study

Solutions of NaCl, MgCl2 and CaCl2 in methanol–water mixtures have been investigated by the molecular dynamics simulations. Special attention has been paid to the OH stretching frequencies and hydrogen bonds of the water and methanol molecules in the subsystems; the coordination shells of the ions and the bulk solvent. The influence of the ions on the properties of the solvent molecules is limited to the first coordination shells and it depends on the ion charge density. Thus all cations affect the intramolecular bonds, valence angles, and the dipole moment and the Cl− ion influences only the length and vibrations of the nearest OH bond of the water molecules, but it does not affect the properties of the methanol molecules. Though the influence of the cations on the solvent molecules is strong, the interactions between the solvent molecules enhance the molecular polarization. In consequence the induced dipole moment and the OH frequencies of the water and methanol molecules in the cation shells depend also on the methanol mole fraction. The shift of the OH stretching frequency correlates linearly with the induced dipole moment, but it does not correlate with the strength of the hydrogen bonds.

Effect of Methanol/Water Mixtures on the Lower Critical Solution Temperature of Poly(N-isopropylacrylamide)

ABSTRACTPoly(N-isopropylacrylamide) (PNIPAM) is a thermo-sensitive polymer that exhibits a lower critical solution temperature (LCST) around 305 K. Below the LCST, PNIPAM is soluble in water and above this temperature polymer chains collapse prior to aggregation. In the presence of methanol, electron paramagnetic resonance (EPR) spectroscopy suggests that, LCST of PNIPAM is depressed up to certain mole fraction of methanol (0.35 mole fraction) and it is speculated that addition of methanol affects the PNIPAM-water interactions. Above 0.35 mole fraction of methanol, LCST gets elevated to temperatures above ∼305 K (32°C) and cannot be detected up to 373 K (100 °C). The atomistic origin of this co-solvency effect on the LCST behavior is not completely understood. In the present study, we have used molecular dynamics (MD) simulations to investigate the effect of methanol-water mixtures on conformational transitions and the LCST of PNIPAM. We employ two different force fields i.e. polymer consistent force-field (PCFF) and CHARMM to study solvation dynamics and the PNIPAM LCST phase transition in various methanol-water mixture compositions (0.018, 0.09, 0.27, 0.5, and 0.98 mole fractions). Simulations are conducted at fully atomistic level for three different temperatures (260, 278, and 310 K) and radius of gyration (Rg) of PNIPAM chains was computed for determination of LCST behavior of PNIPAM.

Bubble point pressures of binary methanol/water mixtures in fine‐mesh screens

Binary methanol/water mixture bubble point tests involving three samples of fine‐mesh, stainless steel screens as porous liquid acquisition devices are presented in this article. Contact angles are measured as a function of methanol mass fraction using the Sessile Drop technique. Pretest predictions are based on a Langmuir isotherm fit. Predictions and data match for methanol mole fractions greater than 50% when pore diameters are based on pure liquid tests. For all three screens, bubble point is shown to be a maximum at a methanol mole fraction of 50%. Model and data are in disagreement for mole fractions less than 50%, which is attributed to variations between surface and bulk fluid properties. A critical Zisman surface tension value of 23.2 mN/m is estimated, below which contact angles can be assumed to be zero. Solid/vapor and solid/liquid interfacial tensions are also estimated using the equation of state analysis from Neumann and Good. Published 2013 American Institute of Chemical Engineers AIChE J 60: 730–739, 2014

An NMR study of a water-methanol solution sorbed in MF-4SK sulfonated cation-exchange membranes

Concentration dependences of self-diffusion coefficients (SDCs), self-diffusion activation energies for water and methanol, and chemical shifts of the protons of the hydroxyl groups δOH simultaneously in an external water-methanol solution and the solution sorbed in MF-4SK membranes have been studied by NMR. It has been revealed that the SDC of pure methanol and pure water sorbed in an MF-4SK membrane is 3–5 times lower than that outside the membrane. It has been found that, in the presence of a small amount of methanol, the SDC of water in the membrane is 1.5–2 times higher than the SDC of pure sorbed water. At a solution concentration of 0.1–0.5 mole fraction, the SDC values of water and methanol in the membrane vary only slightly and are about 6 × 10−6 and 4 × 10−6 cm2/s, respectively. It has been determined that the δOH value in the membrane is 100–200 Hz higher than that in the external solution. The observed increase in δOH and decrease in SDC in the membrane suggest that the state of the solution in the MF-4SK sulfonated cation-exchange membrane has significantly changed compared to the external solution. The effect of the implanted carbon phase (CP) on the SDC of water and methanol and δOH of the solution sorbed in the MF-4SK membranes containing the CP has been studied. It has been revealed that at a methanol mole fraction of up to 0.5, the introduction of 23 wt % CP decreases the SDC of the solution components by no more than 10–20%. At a methanol mole fraction of 0.25–0.5, the self-diffusion activation energies for methanol and water in the external and membrane solutions decrease by 5–7 kJ/mol.

The concept of integrated thermally double coupled reactor for simultaneous production of methanol, hydrogen and gasoline via differential evolution method

The concept of integrated thermally double coupled reactor is proposed as an alternative for reduction of environmental emissions and consumption of energy, minimizing capital and operating costs and increasing production and efficiency of the processes. The goal of this study is simultaneous production of hydrogen, methanol and high octane gasoline in a novel thermally double coupled reactor. This configuration is a multi-tubular reactor in which the required heat for the endothermic decalin dehydrogenation is provided by two exothermic reactions: methanol production and Fisher–Tropsch synthesis (FTS). Differential evolution (DE) method is also used in order to find the optimal operating conditions for the enhancement of methanol mole fraction as well as gasoline yield in the outlet of thermally double coupled reactor. The results of methanol production in the optimized thermally double coupled reactor are compared with the conventional methanol synthesis reactor. This comparison shows that in addition to higher methanol productivity in the optimized thermally double coupled reactor (10.52% increase compared with conventional methanol synthesis reactor), hydrogen, naphthalene and gasoline are also produced as an additional valuable products in a favorable mode.

Probing the Microscopic Aspects of 1-Butyl-3-Methylimidazolium Trifluoroacetate Ionic Liquid and Its Mixture with Water and Methanol: A Photophysical and Theoretical (DFT) Study

Considering the potential of mixed ionic liquid-cosolvent systems in wide range of applications, photophysical and theoretical studies on an industrially important ionic liquid, 1-butyl-3-methylimidazolium trifluoroacetate (BMIMTFA), and also its mixture with water and methanol have been investigated. Two organic dipolar solutes coumarin 153 (C153) and 2-aminonitrofluorene (ANF) have been used as the probe molecule for the present study. Steady-state absorption and emission spectral behavior of C153 has not been significantly influenced by both the cosolvents. However, excitation wavelength dependent measurements with ANF in the BMIMTFA-water and BMIMTFA-methanol show entirely different photophysical response. For BMIMTFA-methanol system the average solvation and rotational time is found to be less than that in BMIMTFA-water system. Quite interestingly, time-resolved fluorescence anisotropy measurements reveal two different solute-solvent coupling constant (C(obs)) even if same mole fraction of water and methanol is used for the mixed solvent systems. Theoretical calculations also reveal stronger intermolecular interaction between IL and methanol than that between IL and water. The present combined photophysical and theoretical calculations seem to suggest different microscopic structural organization in the two binary systems.

Single-chain mechanics of poly(N-isopropyl-acrylamide) in the water/methanol mixed solvent

The variation of the single-chain mechanics of poly(N-isopropyl-acrylamide) (PNIPAM) for the entire range of the methanol molar fraction (χmethanol) (0%–100%) in the water/methanol mixed solvent has been studied by AFM-based single-molecule force spectroscopy at room temperature (RT). In general, the single-chain mechanics of PNIPAM shows a reentrant variation upon the change of χmethanol from 0% to 100%. The possible mechanism for the reentrant variation of the single-chain mechanics is discussed. The current study may cast new light on the design of novel environmental responsive nano-devices in the future, when χmethanol changes from 16% to 0%.

Continuous biocatalytic conversion of the oil of corn distiller's dried grains with solubles to fatty acid methyl esters in supercritical carbon dioxide

A ‘green’ process based on supercritical fluid technology to extract and convert the oil of corn distiller's dried grains with solubles (DDGS) to fatty acid methyl esters (FAME) was developed. Supercritical carbon dioxide (SC-CO2)-extracted corn DDGS oil was converted into FAME in a continuous SC-CO2 bioreactor using immobilized lipase. The highest mass yield of 95.0% FAME was obtained at 19.4 MPa, 63 °C, at methanol mole fraction of 0.875 mol mol−1 of corn oil and methanol mixture. The CO2 flow rate at standard conditions of temperature and pressure (25 °C K, 101.3 kPa) was 720 cm3 min−1, with the substrate mixture flow of 27 mg min−1 at an enzyme loading of 2 g. The product with the highest FAME mass fraction contained 6.0% MAG, 0.61% DAG, 0.06% TAG and 0.01% glycerol. Performance of the bioreactor was also investigated over time. The FAME mass fraction of the product obtained over two days was 89.0%, whereas it decreased to 72.5%, 76.5% and 43.8% after 3, 4 and 5 days, respectively. FAME mass fraction of the product increased to 80.2% after treating the enzyme bed using pure SC-CO2 to remove residual components.

Ion Specificity at a Low Salt Concentration in Water–Methanol Mixtures Exemplified by a Growth of Polyelectrolyte Multilayer

By use of a quartz crystal microbalance with dissipation (QCM-D), we have investigated the specific ion effect on the growth of poly(sodium 2-acrylamido-2-methylpropanesulfonate)/poly(diallyldimethylammonium chloride) multilayer at a salt concentration as low as 2.0 mM in water-methanol mixtures. QCM-D results demonstrate that specific ion effect can be observed in methanol and water-methanol mixtures though it is negligible in water. Moreover, the specific ion effect is amplified as the molar fraction of methanol (xM) increases from 0% to 75% but is weakened again with the further increase of xM from 75% to 100%. Nuclear magnetic resonance measurements reveal that the counterion-polyelectrolyte segment interactions may not account for the observed ion specificity. By extending the Collins' concept of matching water affinities to methanol and water-methanol mixtures, we suggest that the ion-solvent interactions and the resulted counterion-charged group interactions are responsible for the occurrence of the specific ion effect. The conductivity measurements indicate that water and methanol molecules may form complexes, and the change of relative proportion of complexes with the xM causes the amplification or weakening of the specific ion effect.