Increasing Methanol Concentration Research Articles

Comparative conductimetric studies of salicylic acid in methanol–water mixtures at 25 °C

Conductivity data of salicylic acid in methanol–water mixtures were measured at 25°C. The data were analyzed in two methods, the Hsia–Fuoss’s and Fuoss 78’s conductance equations and a comparison was made. The two methods concern the derivation of thermodynamic association constants and limiting molar conductivities for all solvent compositions. The limiting equivalent conductance decreases with the increase of methanol content in the binary mixtures over the whole range of the solvent composition, but the variation does not give a constant value of Walden product. The electrolytes were found to be practically completely associated in all studied solvent mixtures. The association constant of acid decreases with the increase in relative permittivity of the mixtures. The values of ionic coefficients of self diffusion and the ionic conductance at infinite solutions were estimated.

Non-isothermal modeling of a small passive direct methanol fuel cell in vertical operation with anode natural convection effect

A two-dimensional, non-isothermal model is presented for a small passive direct methanol fuel cell (DMFC) in vertical operation. The effect of natural convection at the anode in the fuel reservoir is considered. The coupled heat and mass transport of the whole cell, along with the electrochemical reactions occurring in the passive DMFC are modeled. The comprehensive model is solved numerically by the finite element method and validated against the experiment results reported in this paper. The numerical results show that when in vertical operation, the cell temperature increases gradually from the bottom of the cell to the top of the cell, resulting from natural convection at the anode. A higher cell temperature will lead to stronger natural convection in the fuel reservoir, which will in turn lead to a larger temperature difference across the cell. The results also indicate that the rate of methanol crossover increases with increasing methanol concentration from 1 M to 4 M. When incrementally increasing the current densities, the rate of methanol crossover decreased at low methanol concentration of 1 M–2 M but increased at high methanol concentration of 3 M–4 M.

Investigating the effect of operating parameters on the open circuit voltage of a passive DMFC

The variations of the open circuit voltages (OCVs) were studied in a passive air-breathing direct methanol fuel cell with an air-breathing cathode using Nafion 115 as the electrolyte membrane. The effects of some operating parameters such as cell temperature, cell orientation, and also methanol concentration on the OCV of fabricated fuel cell were investigated experimentally. The experimental results showed that the OCV values depend strongly on the cell orientation, cell temperature, and methanol concentration. The OCV values decrease with an increase in methanol concentration and cell temperature. Also, the OCV values in vertical orientation are lower than the OCV values in other orientations.

Effects of concentration, temperature and solvent composition on density and apparent molar volume of the binary mixtures of cationic-anionic surfactants in methanol–water mixed solvent media

The accurate measurements on density of the binary mixtures of cetyltrimethylammonium bromide and sodium dodecyl sulphate in pure water and in methanol(1) + water (2) mixed solvent media containing (0.10, 0.20, and 0.30) volume fractions of methanol at 308.15, 318.15, and 323.15 K are reported. The concentrations are varied from (0.03 to 0.12) mol.l-1 of sodium dodecyl sulphate in presence of ~ 5.0×10-4 mol.l-1 cetyltrimethylammonium bromide. The results showed almost increase in the densities with increasing surfactant mixture concentration, also the densities are found to decrease with increasing temperature over the entire concentration range, investigated in a given mixed solvent medium and these values are found to decrease with increasing methanol content in the solvent composition. The concentration dependence of the apparent molar volumes appear to be negligible over the entire concentration range, investigated in a given mixed solvent medium and the apparent molar volumes increase with increasing temperature and are found to decrease with increasing methanol content in the solvent composition.

Investigation of the effects of methanol presence on characteristics of sulfonated aromatic electrolyte membranes: Molecular dynamics simulations

Effects of methanol solvent on characteristics of water–methanol solvated sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) membranes were investigated at different methanol concentrations and temperatures using molecular dynamics simulations. Simulation results showed phase segregation of membrane on the uptake of methanol. Analysis of S–S RDFs revealed that the distance between sulfonic acid groups increased by increasing methanol concentration. Using RDFs of SPPO chains to solvent molecules, it was found that sulfonic acid groups were more solvated with water while aromatic backbone of SPPO exhibited stronger affinity toward methanol. From cluster size distribution examination, it was understood that larger solvent clusters formed at lower methanol concentrations. Diffusivity of water molecules decreased and that of methanol enhanced with an increase in methanol uptake. Calculated methanol diffusion coefficients were smaller in SPPO compared with Nafion, in agreement with experimental observations. Furthermore, increasing the temperature improved diffusivities for all permeants.

Spherical Polymer Brushes in Solvents of Variable Quality: An Experimental Insight by TEM Imaging

The spherical micelle and vesicle composed of [PW12O40](3-) and poly(styrene-b-4-vinylpyridinium methyl iodide) are regarded as a model system to study spherical polymer brushes (SPBs) in solvents of various quality. The pure repulsions occur for the brush chains in the chloroform solution and chloroform/methanol mixture with a methanol volume ratio of 9.1%, where the grafted polystyrene chains have a relatively extended conformation. Further increase in the methanol concentrations leads to the presence of the intra/inter-brush van der Waals attractions. Transmission electron microscopy studies show that there is a coexistence of isolated and oligomeric SPBs and multi-SPB aggregates (MSAs) with the methanol content from 17% to 23%. Only MSAs are detected with the increasing methanol content. Both the corona and core shrink significantly in the isolated and oligomeric SPBs and MSAs. The full interpenetration of the grafted chains is observed between the cores in the oligomeric SPBs and MSAs.

Fate of anticancer drug ellipticine in reverse micelles in aqueous and methanolic environment: A photophysical approach

The present investigation explored a detailed photophysics of an anticancer agent ellipticine, in AOT reverse micelle using steady state and time resolved spectroscopy. We observed that ellipticines are entrapped as a cationic species in AOT/hexane system. Increase in water content in reverse micelles, entraps more number of cationic species while increase in methanol content causes switch over of cationic ellipticine to a neutral species. Unlike in pure methanol, we did not observe any solvent assisted proton transfer in AOT/hexane/methanol system. This unique observation was explained by the inhomogeneity of methanol entrapped in AOT/hexane system.

Chromatographic Behavior of Aromatic Diamines in Hydro-Organic, Micellar and Submicellar Reversed Phase Liquid Chromatographic Modes

The chromatographic behavior (retention, elution strength, efficiency, peak asymmetry and selectivity) of some aromatic diamines in the presence of methanol with or without anionic surfactant SDS in the four different reversed phased liquid chromatographic (RPLC) modes, i.e., hydro-organic, micellar (MLC), low submicellar (LSC) and high submicellar (HSC), was investigated. In the three surfactant-mediated modes, the surfactant monomers coat the stationary phase even up to 70 % methanol; this results in the suppression of peak tailing (by masking the silanol groups on the stationary phase). In MLC and HSC, the solute retention decreases by increasing the surfactant concentration, while this situation was reversed in LSC. In the region between MLC and HSC modes (25–50 % methanol), retention of late eluting solutes was increased by increasing methanol content which is seemingly due to disaggregation of SDS micelles. Changes in selectivity were observed after changing the concentrations of SDS and methanol, in a greater extent when concentration of SDS was changed. Among the four studied RPLC modes, HSC showed the best efficiency with nearly symmetrical peaks. Prediction of retention of solutes in HSC based on a mechanistic retention model combined with Pareto-optimality method allowed the full resolution of target diamines in practical analysis times.

Bioenergetic Strategy for the Biodegradation of p-Cresol by the Unicellular Green Alga Scenedesmus obliquus

Cultures from the unicellular green alga Scenedesmus obliquus biodegrade the toxic p-cresol (4-methylphenol) and use it as alternative carbon/energy source. The biodegradation procedure of p-cresol seems to be a two-step process. HPLC analyses indicate that the split of the methyl group (first step) that is possibly converted to methanol (increased methanol concentration in the growth medium), leading, according to our previous work, to changes in the molecular structure and function of the photosynthetic apparatus and therefore to microalgal biomass increase. The second step is the fission of the intermediately produced phenol. A higher p-cresol concentration results in a higher p-cresol biodegradation rate and a lower total p-cresol biodegradability. The first biodegradation step seems to be the most decisive for the effectiveness of the process, because methanol offers energy for the further biodegradation reactions. The absence of LHCII from the Scenedesmus mutant wt-lhc stopped the methanol effect and significantly reduced the p-cresol biodegradation (only 9%). The present contribution deals with an energy distribution between microalgal growth and p-cresol biodegradation, activated by p-cresol concentration. The simultaneous biomass increase with the detoxification of a toxic phenolic compound (p-cresol) could be a significant biotechnological aspect for further applications.

Hydrogen production by methanol–water solution electrolysis with an alkaline membrane cell

The basic concept of methanol–water solution electrolysis with an alkaline membrane and the experimental studies are presented. The measurements were performed with a membrane electrode assembly consisting of an anion exchange membrane, Pt/C cathode and either PtRu/C or Pt/C anode. Hydrogen production efficiency was measured and the effects of temperature and methanol concentration on the electrolysis performance were investigated. PtRu was found to be a better catalyst at low potentials and the hydrogen was produced with a high efficiency. The results indicate that the favored kinetics and mass transport at high temperatures result in increased hydrogen production. Additionally, it was found that, increasing methanol concentration decreased the performance of the electrolysis as the membrane morphology changes as a function of the concentration.

Zinc Ion Doped Solid-Phase Extraction of Eicosapentaenoic Acid and Docosahexaenoic Acid from Antarctic Krill

Antarctic krill crude extracts contain high levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Accordingly, the solid phase extraction of EPA and DHA from Antarctic krill crude extracts has attracted significant research interest. This study compared the extraction of EPA and DHA from Antarctic krill crude extracts using an aminopropyl, zinc ion-doped silica, and C18 and zinc ion-doped C18 solid-phase column. The best extraction effect was obtained using the zinc ion-doped C18 SPE with water containing methanol as the eluant. The efficiency increased gradually with increasing methanol concentration from 12.5 to 25% in the washing stage, and when pure methanol (5.0 mL) or acetonitrile (3.0 mL) was used as the eluant. To detect EPA and DHA, the acids were first converted to their methyl esters and detected by gas chromatography with flame ionization detection (GC–FID). In the zinc ion-doped C18 elution fractions, EPA and DHA were isolated from the crude extracts in high yield (85–91% (r2 = 4.8–6.3%)).

English

Two field experiments were carried out at Kafr El-Garayda Village, Bialla Center, Kafr El-Sheikh Governorate, Egypt during 2010/2011 and 2011/2012 seasons to study the effect of methanol and boron foliar spraying on growth, yield and quality of sugar beet. This aimed to study four aqueous methanol solutions control without 0, 15, 30 and 45% (v/v) sprayed three times during growth stages which occupied the vertical plots and four boron concentrations control without 0, 40, 80 and 120 ppm as boric acid applied as foliar spray- ing at two times during growth season and assigned in the horizontal plots. Results indicated that foliar application of 30% methanol solution significantly increased all studied characters i.e. total chlorophyll, leaf area/plant, foliage and root fresh weight, foliage and root length and root diameter, total soluble solids, sucrose and apparent purity per- centages, root, top and sugar yields/ha, whereas harvest index was decreased. Moreover, increasing methanol concentration to 45% tend- ed to decrease all above mentioned characters. Application of 80 ppm boron significantly improved root yield and its attributes and root quality, on contrarily harvest index was decreased. Maximum top, root, sugar yields/ha and root quality produced by foliar spraying of 30% methanol and 80 ppm boron.

Epoxidation of propylene with H2O2 catalyzed by supported TS-1 catalyst in a fixed-bed reactor: Experiments and kinetics

The epoxidation of propylene with H2O2 catalyzed by a supported TS-1 catalyst in a fixed-bed reactor has been studied. The effects of methanol concentration (40–70wt.%), hydrogen peroxide concentration (5–20wt.%), propylene pressure (0.2–0.6MPa) and temperature (35–50°C) on the reaction are investigated. The experimental results show that the reaction rate increases with the increase in methanol concentrations, hydrogen peroxide concentrations, propylene pressure and temperature; the activation energy of the reaction is 46.8kJmol−1 and the reaction orders with respect to hydrogen peroxide and propylene are 0.32 and 0.68, respectively. The reaction was modeled with Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) models, and the results show that the kinetic model of Eley–Rideal with H2O2 being adsorbed can give the best fit among the models compared for the epoxidation of propylene with H2O2.

Quantitative analysis of fungicide azoxystrobin in agricultural samples with rapid, simple and reliable monoclonal immunoassay

This work presents analytical performance of a kit-based direct competitive enzyme-linked immunosorbent assay (dc-ELISA) for azoxystrobin detection in agricultural products. The dc-ELISA was sufficiently sensitive for analysis of residue levels close to the maximum residue limits. The dc-ELISA did not show cross-reactivity to other strobilurin analogues. Absorbance decreased with the increase of methanol concentration in sample solution from 2% to 40%, while the standard curve became most linear when the sample solution contained 10% methanol. Agricultural samples were extracted with methanol, and the extracts were diluted with water to 10% methanol adequate. No significant matrix interference was observed. Satisfying recovery was found for all of spiked samples and the results were well agreed with the analysis with liquid chromatography. These results clearly indicate that the kit-based dc-ELISA is suitable for the rapid, simple, quantitative and reliable determination of the fungicide.

Short-time microscopic dynamics of aqueous methanol solutions

In this paper we present the picosecond vibrational dynamics of a series of methanol aqueous solutions over a wide concentration range from dense to dilute solutions. We studied the vibrational dephasing and vibrational frequency modulation by calculating the time correlation functions of vibrational relaxation by fits in the frequency domain. This method is applied to aqueous methanol solutions xMeOH–(1 − x)H2O, where x = 0, 0.2, 0.4, 0.6, 0.8 and 1. The important finding is that the vibrational dynamics of the system become slower with increasing methanol concentration. The removal of many-body effects by having the molecules in less-crowded environments seems to be the key factor. The interpretation of the vibrational correlation function in the context of Kubo theory, which is based on the assumption that the environmental modulation arises from a single relaxation process and applied to simple liquids, is inadequate for all solutions studied. We found that the vibrational correlation functions of the solutions over the whole concentration range comply with the Rothschild approach, assuming that the environmental modulation is described by a stretched exponential decay. The evolution of the dispersion parameter α with dilution indicates the deviation of the solutions from the model simple liquid and the results are discussed in the framework of the current phenomenological status of the field.

On the Solubility of Carbon Dioxide in Binary Water–Methanol Mixtures

The solubility of carbon dioxide in binary mixtures of water and methanol containing up to 12.37 mass % methanol has been measured at temperatures between 298 K and 333 K at atmospheric pressure. The solubility increases with increasing methanol content, but the influence is, at least at low temperatures, much smaller than linear interpolation would suggest. Employing the van't Hoff equation for ideal solutions, a correlation has been proposed that fits the measurements for up to 8.16 mass % methanol in water.

Water vapour monitoring in natural gas in the presence of methanol

Hygrometers for monitoring of water vapour (moisture) in natural gases have been investigated with respect to influence from methanol co-exposure, during a total of 34 days of experiments. The tested hygrometers are based on capacitor sensor, quartz crystal microbalance (QCM), electrolytic cell, fibre-optic sensor and conversion of water to ethyne with calcium carbide (CaC2-GC), respectively. In the latter technique ethyne was quantified by a gas chromatograph (GC). While monitoring moisture at the level of 45μmol/mol, the hygrometers were exposed to approximately (10, 170 and 750)μmol/mol gaseous methanol. The experiments were performed in the laboratory, using nitrogen as the matrix gas. Exposure to approximately 10μmol/mol methanol demonstrated no clear effect on the tested hygrometers. At the higher levels of 170μmol/mol and 750μmol/mol methanol, the readings from several hygrometers were affected. Taken into account the specified uncertainty of the hygrometers, only the electrolytic cell and one of the two tested capacitor sensors (Capacitor B) were significantly affected during the test period. They demonstrated severe misreading as a result of methanol exposure. The readings from the fibre-optic sensor drifted slowly upwards during exposure to the higher methanol levels. The drift speed increased with increasing methanol concentration. However, despite the drift, the readings from the fibre-optic sensor stayed within its specified uncertainty (±2°C) during the test period. The QCM made a minor shift to higher readings when exposed to 750μmol/mol methanol. Similar shifts were noticed for the two different brands of capacitor sensors tested. Both capacitor sensors also demonstrated a permanent downward drift during the experiments, one of them increasing the drift speed upon increased methanol concentration. The CaC2-GC did not show any clear influence from methanol. The results imply that methanol exposure should be taken into consideration when choosing equipment for moisture monitoring and when determining a quality control strategy for the monitoring.

Preparation of multilayered thin film fuel cell using titanium oxide as anodic catalyst via layer-by-layer assembly

The multilayered thin film fuel cells (multilayered-TFFCs) using anatase TiO2 as an anodic catalyst were successfully prepared by layer-by-layer (LbL) assembly technique. The electrode-membrane assembly (MEA) of the multilayered-TFFC, which had a total thickness of approximately 720nm, was constructed on a continuously porous glass substrate. The anode and the cathode were separated by the multilayered polymer electrolyte having a thickness of about 350nm. The amounts of anodic TiO2 nanoparticles and cathodic Pt nanoparticles were calculated to be 6.2μgcm−2 and 18μgcm−2, respectively. The open circuit voltage was obtained by ultraviolet (UV) irradiation and methanol supply, because electrons were derived from photocurrent and methanol oxidation. The resultant current densities increased with increasing methanol concentration and intensity of UV irradiation. The multilayered-TFFC with 5molL−1 methanol solution showed the maximum power density of 13μWcm−2 by UV irradiation of 20mWcm−2.

Controlled Drug Release from Silk Fibroin Films Treated with Methanol-water Mixtures

Silk fibroin (SF) films were prepared using a casting method and the structural change owing to treatment with methanol-water mixtures of different concentrations was investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results were used to reveal the influence of structure on the release dynamics of Rhodamine B, a model compound loaded in the SF matrix. In methanol concentration ranging from 50% to 90%, the content of silk II crystalline structure, constituted by β-sheet, first increased and then decreased with increasing methanol concentration in the mixtures, reaching a maxi- mum around 80%. It was found that Rhodamine B released from the SF film via Fickian mechanism, of which the diffusional exponent increased with increasing β-sheet content in the matrix, suggesting that the silk II crystal could be used as natural regulator for drug release from SF material.

Improvement of dispersion state and charge separation efficiency of hybrid films of ZnO nanoparticle/conjugated polymers by utilizing methanol as a volatile dispersant

This contribution introduces an efficient method for fabricating hybrid films of ZnO nanoparticle/conjugated polymers with improved charge separation efficiency. Methanol is utilized as a volatile dispersant for promoting the dispersion of ZnO nanoparticles in chlorobenzene. The increase of methanol concentration from 0 to 20% (v/v) results in systematic improvement of the particle dispersion. The suspensions of ZnO nanoparticles in these solvents are used to prepare hybrid films of poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and regioregular poly(3-hexylthiophene) (P3HT). The morphologies and optical properties of the hybrid films, prepared by spin casting, are investigated by atomic force microscopy, UV/vis absorption and photoluminescence (PL) spectroscopy. The hybrid films obtained from all systems are continuous and exhibit relatively smooth surface. The extent of polymeric chain aggregation in the hybrid films is hardly affected by the variation of solvent. However, the drop of about 60% of PL intensity is detected when the methanol is added into ZnO/MEH-PPV solution prior to the film preparation. The drastic decrease of PL intensity indicates significant improvement of charge separation efficiency in the hybrid films. The investigation of ZnO/P3HT hybrid films shows consistent results. Our approach is very efficient because the methanol completely evaporates during the fabrication of hybrid film.