Methanol-water Mixtures Research Articles

Structure study of water in alcohol-water binary system based on Raman spectroscopy

The structure of water and the interaction between in the binary mixture of methanol-water and isopropanol-water at various mole fractions of alcohols were investigated by Raman spectroscopy. The results show that the tetrahedral hydrogen bonding network of water molecules is expanded at 0 < X methanol < 0.4, and the coordination number of water molecules becomes lower at 0.4 < Xmethanol < 0.5, which is due to the aggregation of methanol molecules under hydrophobic hydration as the molar fraction of methanol increases, resulting in a decrease in the total area of interaction between hydrophobic groups and water molecules in solution. In turn, the hydrophilic groups of methanol molecules break the hydrogen bonds between water molecules by forming hydrogen bonds with the free water molecules around them. When Xmethanol > 0.5, the hydrogen bonding network of water molecules becomes loose and eventually exists in solution as clusters of varying sizes. Due to the difference in chain length, the number of alkyl groups in isopropanol and methanol is different, so the hydrophobic group interacts with water more strongly and has a stronger effect on “breaking up” the water clusters.

ОПИСАНИЕ ТЕРМОДИНАМИЧЕСКОГО РАВНОВЕСИЯ НЕИДЕАЛЬНЫХ РАСТВОРОВ ПО ДАННЫМ О ПОВЕРХНОСТНОМ НАТЯЖЕНИИ

The paper considers the estimation of the thermodynamic equilibrium of binary solutions according to the data on their surface tension. The parameters of the Margulis model for acetone-water and methanol-water mixtures are estimated

Nucleation Behavior in a Transformation of the Amorphous State to the Crystalline State during Antisolvent Crystallization

The liquid-mediated phase transformation of an amorphous form to a crystalline heptahydrate form of guanosine 5′-monophosphate was studied in antisolvent crystallization using methanol–water mixtures as solvents. Three steps were monitored: the formation of the amorphous form, dissolution of the amorphous form, and growth of the heptahydrate crystals using in situ Raman spectroscopy, focused beam reflectance measurement (FBRM), and particle vision measurement (PVM) and off-line methods like viscosity, thermal gravimetric analysis (TGA), and powder X-ray diffraction (PXRD). Effects of the antisolvent fraction, initial concentration, and addition rate of the antisolvent on the transformation process were discussed. Solid forms, solute concentration, particle size, counts, induction time, metastable zone width, solution viscosity, and amorphous slurry viscosity were all measured for 18 experiment runs. The induction time of the crystalline hydrate increased with the supersaturation but decreased with the increasing viscosity of the amorphous slurry. Both are not as expected. The induction time correlates nicely in the opposite direction with the viscosity of the amorphous slurry concentration. The amorphous slurry viscosity is about 20 times higher than the solution viscosity. Viscosity of the amorphous slurry was discovered to be a crucial factor influencing the transition of the amorphous slurry to the crystalline form in the pre-exponential component of the classical nucleation rate equation. The metastable zone boundaries of the amorphous and heptahydrate crystalline forms were shown in a plot of the solute concentration versus the mass fraction of methanol in the mixed solvent. The amorphous and heptahydrate crystalline forms can be selectively produced under all the conditions of this study. The pre-exponential factor of the nucleation rate equation factor is crucial in comprehending the transformation from an amorphous to a crystalline state.

α-Fe2O3 Nanoparticles/Iron-Containing Vermiculite Composites: Structural, Textural, Optical and Photocatalytic Properties

Vermiculite two-dimensional mixed-layer interstratified structures are a very attractive material for catalysis and photocatalysis. The iron-containing vermiculite from the Palabora region (South Africa) and its samples, which calcined at 500 and 700 °C, were studied in comparison with the α-Fe2O3 nanoparticles/vermiculite composites for the first time as photocatalysts of methanol decomposition, which is an organic pollutant and an efficient source for hydrogen production. The aim of the work was to characterize their structural properties using X-ray fluorescence, X-ray diffraction, infrared spectroscopy, nitrogen physisorption, diffuse reflectance UV-Vis spectroscopy and photoluminescence spectroscopy to explain the photocatalytic effects. The photocatalytic test of the samples was performed in a batch photoreactor under UV radiation of an 8W Hg lamp. The photocatalytic activity of vermiculite–hydrobiotite–mica-like layers at different water hydration states in the interstratified structure and the substitution ratio of Fe(III)/Al in tetrahedra can initiate electrons and h+ holes on the surface that attack the methanol in redox processes. The activity of α-Fe2O3 nanoparticle photocatalysts stems from a larger crystallite size and surface area. The hydrogen production from the methanol–water mixture in the presence of vermiculites and α-Fe2O3 nanoparticles/vermiculite composites was very similar and higher than the yield produced by the commercial TiO2 photocatalyst Evonik P25 (H2 = 1052 µmol/gcat.). The highest yield of hydrogen was obtained in the presence of the Fe/V–700 composite (1303 µmol/gcat after 4 h of irradiation).

Potential one-pot synthesis of spherical magnesium silicate powder by mechanical milling

Synthetic magnesium silicate finds applications in adsorbents, catalysis, pharmaceuticals, foods, cosmetics, and in oil industry. This study introduces a method for potential one-pot preparation of narrowly sized, spherical magnesium silicate powders. After initial synthesis by precipitation from magnesium sulphate and sodium metasilicate solutions, the magnesium silicate precursor was ball-milled with two immiscible liquids, forming a particle-loaded emulsion. Hexane formed the continuous phase; the droplet phase was formed by either acetonitrile, methanol, or water-methanol mixtures. Suspended precursor particles were refined, their fragments became trapped in the droplets, where they were eventually compacted into composite spheres. Prepared spherical powders were characterized using scanning electron microscopy, nitrogen sorption, and low angle laser light scattering. The synthesized powders exhibited narrow size distributions with modes from 3.3 to 92 μm. The spherical powders showed an enhanced flowability and had specific surface areas comparable to or higher than the precipitated precursor powders.

Improving the efficiency of an aircraft power plant with a turboprop engine based on water-methanol mixture injection

This paper considers a technique for modernizing the power plant (PP) of a regional aircraft. The modernization is based on the injection of water or a water-methanol mixture into the compressor or combustion chamber of a turboprop engine (TPE). An algorithm has been developed for the thermodynamic calculation of TPE parameters, taking into consideration the injected mixture; the mathematical model (MM) has been improved. Methodical studies of the operability and range of application of the improved MM were carried out. The results of mathematical modeling were validated. For verification, the AI-450M turboshaft engine produced by GP Ivchenko-Progress (Ukraine) was used as an object of research. Based on the improved MM, a software module has been developed to study the performance characteristics of a regional aircraft with a TPE. The influence of water injection and a water-methanol mixture on the TPE operating process and the operational characteristics of a regional passenger aircraft has been studied. The proposed measures could be implemented in existing TPEs. This would allow the operation of aircraft without significant modernization of the airport infrastructure. For TPE, the injection of water and a water-methanol mixture is an alternative way of boosting in order to temporarily improve performance. A given modernization technique could improve the TPE power up to ~10 %, as well as reduce the amount of harmful emissions. The results obtained showed a satisfactory convergence of estimated and experimental data. The error of the results under the accepted assumptions does not exceed 3 %. The calculation results demonstrate the advantages of injection at the take-off stage of the aircraft to reduce the take-off distance (up to 45 % in hot conditions TAMB=+30 °C) and reduce the time of climbing the echelon (~10 %)

Crystallization of Mn(II) and Cd(II) Complexes in A Water-Methanol System: Tartrate vs Nicotinamide Ligand Selectivity

Ligand selectivity of tartrate vs nicotinamide in a water-methanol system has been observed in the crystallization of Mn(II) and Cd(II) complexes. These complexes were crystallized at room temperature by a layered solution technique using a water-methanol mixture solvent in a M(II):tartrate:nicotinamide (M = Mn, Cd) molar ratio of 1:1:2. Complexes of M(II)-nicotinamide and M(II)-tartrate were also prepared for data comparison. Analysis of the crystals by infrared spectroscopy, powder-X-ray diffraction and qualitative anion test showed that in a presence of both tartrate and nicotinamide, the Mn(II) forms neutral Mn(II)-tartrate hydrate complex, whereas the Cd(II) forms ionic Cd(II)-nicotinamide chloride complex. In the case of Mn(II) complex, tartrate tend to coordinate as ligand than the nicotinamide, although molar ratio of nicotinamide was doubled than that of tartrate ligand. In contrast, the neutral nicotinamide ligand is more predominant to coordinate in the Cd(II) complex than the anionic tartrate. The tartrate-nicotinamide ligand selectivity in the crystallization of Mn(II) and Cd(II) complexes is likely due to the use of tartrate salt as precursor and the choice of solvent mixture. In addition, powder-XRD analysis confirms that there was no indication of M(II)-tartrate and M(II)-nicotinamide that co-crystallized together at the same time by both metal ions.

Study of Interactions of Acetaminophen in Water and Water–Methanol Mixture at T = 298.15–313.15 K: A Conductivity Approach with Solution Thermodynamics

Study of Interactions of Acetaminophen in Water and Water–Methanol Mixture at T = 298.15–313.15 K: A Conductivity Approach with Solution Thermodynamics

Frequency and wave type effects on extractability of oleuropein from olive leaves by moderate electric field assisted extraction

The moderate electrical field (MEF) process was used to reduce the process time (t) of oleuropein extraction from olive leaves. MEF process was performed with methanol-water (4:1 v/v) with sine wave-SN and square wave-SQ at 30 V/cm with different frequencies (1, 1000, and 2000 Hz). The conventional extraction (CE) method was performed for 8 h in methanol-water (4:1 v/v) mixture at 40 °C. The effects of MEF conditions on t, effective electrical conductivity (EEC), cell disintegration (Zc) and extraction performance coefficient (EPC) were determined. SN provided desired extraction yield in a shorter time than SQ (p < 0.05). The necessary extraction time for target extraction yield (21.6 ± 1.0 mg Oleuropein/g dm) increased as the frequency decreased (p < 0.05). SN resulted in higher Zc values compared to SQ (p < 0.05). EPC of MEF was higher than CE (p < 0.05). It is concluded extractability of the oleuropein at any given extraction time could be improved by MEF compared to CE.

Electro-Osmotic Flow of Water–Methanol Mixtures Through Nafion Membranes Revisited: Composition and Temperature Dependence

The electro-osmotic drag coefficient of water and methanol mixtures through Nafion 117 membranes was measured as a function of the composition at several temperatures between 25 and 60°C using a two-compartment capillary cell with Ag/AgCl electrodes. The electro-osmotic water drag in HCl aqueous solutions is higher than that reported in measurements where the membrane is in contact with pure water; hence, all the reported results were performed at the same acid concentration. It was found that the drag coefficient for pure methanol is about 40% higher than that for water at all the temperatures studied as a consequence of the expanded nanostructure of Nafion in methanol. The drag coefficients of the water–methanol mixtures exhibit a high non-linearity, which can be explained by considering the Nafion sorption in the binary solvent. The electro-osmotic flow in pure methanol is similar to that of 5 M methanol aqueous solutions, which opens the opportunity to use pure methanol in DMFCs. The methanol crossover due to permeability can be minimized. Controversial results with previous studies are also addressed.

Study of Electrical Conductivity for Salt Diclofenac Potassium in Water and Water-Methanol Mixtures at Different Temperatures

This paper traces the conductivity of diclofenac potassium salts in the low concentrations in water and mixtures of water and methanol (10%, 20% and 30% aqueous methanol) at different temperatures (288.15, 293.15, 298.15, 303.15 and 308.15 K). The conductivity data were analyzed using the Lee-Wheaton conductivity equation to obtain the values ​​of equivalent conductivity at infinite dilution “∧o”, association constants (KA), the association diameter (R) and Walden product (Λ0η0). The results showed that diclofenac potassium salt behaves as weak electrolytes in the solvents used. Moreover, standard thermodynamic parameters of the association (change value in: Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) were calculated and discussed. The results showed that the values ​​of molar conductivity, the distance parameter between the ions (R) and association constants (KA) increase with increasing temperature at the best fit value of the standard deviation (σ). The thermodynamic results also indicated that the ion association process is endothermic (+ΔH) and spontaneous (- ΔG) and increasing degrees of freedom (+ΔS).

Kinetic Monte Carlo simulation of hydrogen production from photocatalytic water splitting in the presence of methanol by 1 wt% Au/TiO2

In this research, using the kinetic Monte Carlo simulation (KMC), the hydrogen production from a water-methanol mixture using Au/TiO2 photocatalyst is investigated. A mechanism is proposed, and the rate constants of the reaction steps are specified. The reaction rate constants of different steps and the concentration of the active sites on the photocatalyst surface were determined. An excellent match between simulated and experimental data confirms the results. The electron-hole pair production, methanol adsorption on the photocatalyst surface, and electron-hole recombination steps are considered the most critical steps. To study the effects of independent variables (initial concentration of methanol, photocatalyst dosage, pH, and time of reaction) on the produced hydrogen, a combination of KMC simulation and design of experiment was employed. The concentration of photocatalysis has the highest and pH has the lowest effect on the hydrogen production. The optimal conditions for photocatalytic hydrogen production are presented.

Copper-Catalyzed Azide-Alkyne Cycloaddition of Hydrazoic Acid Formed In Situ from Sodium Azide Affords 4-Monosubstituted-1,2,3-Triazoles.

We report a copper-catalyzed cycloaddition of hydrogen azide (hydrazoic acid, HN3) with terminal alkynes to form 4-substituted-1H-1,2,3-triazoles in a sustainable manner. Hydrazoic acid was formed in situ from sodium azide under acidic conditions to react with terminal alkynes in a copper-catalyzed reaction. Using polydentate N-donor chelating ligands and mild organic acids, the reactions were realized to proceed at room temperature under aerobic conditions in a methanol–water mixture and with 5 mol % catalyst loadings to afford 4-substituted-1,2,3-triazoles in high yields. This method is amenable on a wide range of alkyne substrates, including unprotected peptides, showing diverse functional group tolerance. It is applicable for late-stage functionalization synthetic strategies, as demonstrated in the synthesis of the triazole analogue of losartan. The preparation of orthogonally protected azahistidine from Fmoc-l-propargylglycine was realized on a gram scale. The hazardous nature of hydrazoic acid has been diminished as it forms in situ in <6% concentrations at which it is safe to handle. Reactions of distilled solutions of hydrazoic acid indicated its role as a reactive species in the copper-catalyzed reaction.

Catalytic Oxidative Desulfurization of Heavy Naphtha Fraction Over a PMN550 Catalyst, Reactivity and a Kinetic Model

Desulfurization of heavy naphtha by a catalytic oxidation process combining hydrogen peroxide with organic and inorganic acids and in the presence of a PMN550 catalyst. This study was conducted to find out the effect of many variables on the efficiency of the process, especially the effect of hydrogen peroxide, the amount of acid, temperature, residence time, weight of the catalyst (0.01-0.6) g, temperature (20-120) C, residence time (20-140) minutes, ratio hydrogen peroxide to heavy naphtha (0.1-0.6) ml and ratio acid to heavy naphtha (0.01-0.175) ml. The catalytic oxidation process depends on all of the above variables. Desulphurization of heavy naphtha using organic and inorganic oxidizers in combination with hydrogen peroxide, glacial acetic acid, phthalic acid, malic acid, sulfuric acid and formic acid. The maximum removal of sulfur was with sulfuric acid and formic acid, which are 50%, 55%, respectively. the catalytic oxidation process carried out In two steps: the first step was the catalytic oxidation at a moderate temperature and atmospheric pressure, and the second step was to extract the oxidized mixture with a methanol-water mixture. The efficiency of the catalytic oxidation process carried out in the presence of PMN550 reached 99%. The catalyst was manufactured in the laboratory and a set of catalyst tests were performed on it FT-IR, AFM, BET, XRD, and XRF, which It has proven its efficacy. Mathematical models of the relevant reactions were developed to match the experimental results by obtaining the optimal kinetic parameters. Using optimization methods, the maximum conversion rate was 99%, at a temperature of 90°C, a residence time 60 minutes and the initial concentration was 651.3ppm.

A columnar regular-porous stainless steel reaction support with high superficial area for hydrogen production

To improve hydrogen production (HP) performance of regular-porous structure (RPS), a columnar RPS with small specific surface area and high superficial area is developed. A numerical simulation model of regular-porous stainless steel structure (RPSSS) is established. Subsequently, heat transfer performance, pressure loss, temperature, methanol concentration, H 2 concentration distributions and HP performance of the columnar RPSSS with small specific surface area and high superficial area and the body-centered cubic RPSSS with high specific surface area and small superficial area are compared. Then, temperature, methanol concentration, H 2 concentration distributions and HP performance of axial and longitudinal size-enlarged columnar RPSSSs are studied. The results show that compared to the body-centered cubic RPSSS, the columnar RPSSS has higher methanol conversion, larger H 2 flow rate and higher CO selectivity. Especially in the condition of 300 °C wall temperature and 12 mL/h methanol-water mixture injection rate (MWMIR), the methanol conversion, H 2 flow rate and CO selectivity of the columnar RPSSS are increased by 12.3%, 9.24% and 30%, respectively, indicating that the superficial area of RPSSS is more important for its HP performance compared to its specific surface area. Compared to the longitudinal size-enlarged columnar RPSSS, the axial size-enlarged columnar RPSSS has higher methanol conversion, larger H 2 flow rate and higher CO selectivity. This research work provides a new method for the optimization of hydrogen production reaction support (HPRS). Hydrogen production numerical simulation model of columnar regular-porous stainless steel reaction support. • A columnar regular-porous hydrogen production reaction support is proposed. • A numerical simulation model of regular-porous stainless steel structure is built. • Heat transfer ability and pressure loss of regular-porous structure are studied. • Temperature and reactant concentration of regular-porous structure are explored. • Hydrogen production performance of regular-porous structure is investigated.

A Localized Enantioselective Catalytic Site on Short DNA Sequences and Their Amphiphiles.

A DNA-based artificial metalloenzyme (ArM) consisting of a copper(II) complex of 4,4′-dimethyl-2,2′-bipyridine (dmbipy-Cu) bound to double-stranded DNA (dsDNA) as short as 8 base pairs with only 2 contiguous central pairs (G for guanine and C for cytosine) catalyzes the highly enantioselective Diels–Alder reaction, Michael addition, and Friedel–Crafts alkylation in water. Molecular simulations indicate that these minimal sequences provide a single site where dmbipy-Cu is groove-bound and able to function as an enantioselective catalyst. Enantioselective preference inverts when d-DNA is replaced with l-DNA. When the DNA is conjugated to a hydrophobic tail, the obtained ArMs exhibit enantioselective performance in a methanol–water mixture superior to that of non-amphiphilic dsDNA, and dsDNA-amphiphiles with more complex G•C-rich sequences.

Improvement of extraction methods of Malian Cashew nut shell liquid-siftdesk

The extraction of cashew nut shell liquid (CNSL) was investigated using five solvents (water, water-methanol mixture, acetone, methanol and hexane) under different extraction conditions. Effects of process parameters such as extraction cycle, pressure, solvent volume and extraction duration were investigated. The best yields of extraction (51.7%) were obtained with water-methanol mixture by using an accelerated solvent extractor (ASE) under pressure at 100 bars. The extraction obtained with water at atmospheric pressure was close to ASE extraction (49.8%). However, the composition of CNSL varied among these different operating conditions. Chemical composition of the extracted oil by ASE or by atmospheric pressure extraction showed minor difference in their composition. The quality of the analyzed extracts was almost equal in cardol, cardanol, anacardol and anacardic acid contents.

Photocatalytic hydrogen generation from a methanol–water mixture in the presence of g-C3N4 and graphene/g-C3N4

Synthesis and application of g-C3N4 and graphene/g-C3N4 in H2 production from water splitting, using different g-C3N4 precursors.

Constant distillate composition of batch distillation column with variable reflux mode based on still pot concentration

The objective of this work is to control the constant distillate composition of batch distillation column xD. A new correlation developed involved the instant reflux ratio value R with a composition of the remaining mixture in the bottom pot (boiler) xB. Also adding the dynamic time as ahead time (+dt) to the control algorithm to increase the R to anticipate the changes in xD. +dt was calculated using an electroconductive tracer that was injected both in the bottom pot and in the top tray to estimate the upward and the downward dynamic time. The proposed correlation was successfully applied as a control strategy on a glass batch distillation pilot plant that has 5 cm diameter, 1 m long, eight sieve trays, and Methanol–Water mixture as a system. The real-time experimental runs of the suggested control algorithm applied by manipulating the reflux stream that affects the changes that happened in the top composition product to keep it constant. The proposed procedure shows a quick and stable response for distillate product composition during the operating time that minimizes and saves the energy supplied to the boiler. Moreover, the system gives a straight, smooth linear constant distillate product even in case of disturbing the system.

Optimal synthesis of nanosize seeds for secondary growth of high performance hydroxy-sodalite (H-SOD) zeolite membranes for small gas and water separations

Nanosize H-SOD particles were hydrothermally synthesized as seeds for the secondary growth of hydroxy-sodalite (H-SOD) zeolite membrane. The size and phase purity of H-SOD zeolite particles were carefully controlled by changing several hydrothermal conditions. Especially, NaOH concentration in the hydrothermal solution made a significant effect on the phase purity and particle size. The high phase purity particles with a mean diameter of 80 nm were successfully synthesized at a 3 M NaOH concentration and applied for secondary growth. Overall, uniform H-SOD zeolite membranes with various thicknesses (3, 7, and 9.5 μm) were prepared by varying secondary growth time. The 9.5 μm thick H-SOD zeolite membrane exhibited high H 2 /N 2 permselectivity of 95 at 473 K and a transmembrane pressure of 0.3 MPa. And, the pervaporation performance was evaluated for 90 wt% methanol-water mixture at 423 K, an elevated temperature. It showed a high water/methanol separation performance; its water/methanol separation factor was 2726 and the total flux, 1.02 kg/m 2 h. The high small gases and water separation performances were because interparticular voids between the nano size seeds were small and the surface of seed layer was flat. Therefore, the secondary growth remained a continuous zeolite layer with few non-zeolitic pores. In the present work, it was well proven experimentally that application of nanosize seed is an effective option to prepare high performance zeolite membrane in H-SOD zeolite system. • High purity H-SOD zeolite particles with a mean diameter of 80 nm were carefully prepared for the secondary growth of H-SOD zeolite membranes. • Synthesis temperature, time and NaOH concentrations played major roles on the particle size. • The H-SOD zeolite membranes prepared by using the nanosize seeds showed excellent performances for H 2 /CO 2 , H 2 /N 2 and water/methanol separations. • The good performance was due to smaller interparticular voids between nano size seeds and the increased surface flatness of seed coating layer.