Dilute Aqueous Ethanol Research Articles

Effect of sessile binary droplet evaporation at different ambient temperatures on interfacial profile near the triple line

Heat and mass transfer near the triple line of an evaporating droplet contains complex physics, while the mechanisms of evaporation influenced by the ambient temperature remain unclear. This paper describes an experimental study of interfacial profile near the triple line during evaporation of pure water and binary mixtures including dilute aqueous ethanol and n-butanol solutions at different ambient temperatures. The difference of interfacial profile between single and multi-component sessile evaporative droplets were experimentally demonstrated. The result shows that the thin film evaporation of the binary droplets is greatly suppressed when the ambient temperature drops. The thin film thickness reduces with the time under various ambient temperature conditions which are below 25 °C. The thickness difference at between 0 s and 40 s decreases in the order of water, ethanol solution and n-butanol solution. For water droplet, the critical thin film thickness at which the evaporation mode changes decreases with increasing ambient temperature, which is opposite to the binary droplets. Meanwhile, the rate of change of thin film thickness increases with increasing ambient temperature for water or ethanol solution, while it decreases with increasing temperature for n-butanol solution, which is attributed to the contact line energy barrier that decreases with increasing ambient temperature.

Photophysics of Zinc Porphyrin Aggregates in Dilute Water-Ethanol Solutions.

Dimeric and multimeric aggregates of a model metalloporphyrin, zinc tetraphenylporphyrin (ZnTPP), have been produced in a controlled manner by incrementally increasing the water content of dilute aqueous ethanol solutions. Steady state absorption, fluorescence emission, and fluorescence excitation spectra have been measured to identify the aggregates present as a function of solvent composition. The dynamics of the excited states of the aggregates produced initially by excitation in the Soret region have been measured by ultrafast fluorescence upconversion techniques. Only the monomer produces measurable emission from S2 with a picosecond lifetime; all Soret-excited aggregates, including the dimer, decay radiationlessly on a femtosecond time scale. The S1 state is the only significant product of the radiationless decay of the S2 state of the excited monomer, and the aggregates also produce substantial quantum yields of S1 fluorescence when initially excited in the Soret region. The resulting fluorescent aggregates all decay on a subnanosecond time scale, likely by a mechanism that involves dissociation of the excited monomer from the excitonic multimer. The ZnTPP dimers excited at their ground state geometries in the Soret region exhibit a dynamic behavior that is quite different from those produced following noncoherent triplet-triplet annihilation under the same conditions. The important implications of these observations in determining the aggregation conditions promoting efficient photon upconversion by excitonic annihilation in a variety of media are thoroughly discussed.

Ca(OH)2-Catalyzed Condensation of Aldehydes with Methyl ketones in Dilute Aqueous Ethanol: A Comprehensive Access to α,β-Unsaturated Ketones.

Cheap, abundant but seldom-employed Ca(OH)2 was found to be an excellent low-loading (5–10 mol%) catalyst for Claisen-Schmidt condensation of aldehydes with methyl ketones under mild conditions. It was interesting that dilute aqueous ethanol (20 v/v%) was unexpectedly discovered to be the optimal solvent. The reaction was scalable at least to 100 mmol and calcium could be precipitated by CO2 and removed by filtration. Evaporation of solvent directly afforded the product in the excellent 96% yield with high purity, as confirmed by its 1H NMR spectrum.

Recovery of Dilute Aqueous Acetone, Butanol, and Ethanol with Immobilized Calixarene Cavities

Macrocyclic calixarene molecules were modified with functional groups of different polarities at the upper rim and subsequently grafted to mesoporous silica supports through a single Si atom linker. The resulting materials were characterized by thermogravimetric analysis, UV-visible spectroscopy, nitrogen physisorption, and solid-state NMR spectroscopy. Materials were then used to separate acetone, n-butanol, and ethanol from dilute aqueous solution, as may be useful in the recovery of fermentation-based biofuels. For the purpose of modeling batch adsorption isotherms, the materials were considered to have one strong adsorption site per calixarene molecule and a larger number of weak adsorption sites on the silica surface and external to the calixarene cavity. The magnitude of the net free energy change of adsorption varied from approximately 15 to 20 kJ/mol and was found to decrease as upper-rim calixarene functional groups became more electron-withdrawing. Adsorption appears to be driven by weak van der Waals interactions with the calixarene cavity and, particularly for butanol, minimizing contacts with solvent water. In addition to demonstrating potentially useful new sorbents, these materials provide some of the first experimental estimates of the energy of interaction between aqueous solutes and hydrophobic calixarenes, which have previously been inaccessible because of the insolubility of most nonionic calixarene species in water.

Quantitative analysis of microfluidic mixing using microscale schlieren technique

In this study, we discuss the employment of microscale schlieren technique to facilitate measurement of inhomogeneities in a micromixer. By mixing dilute aqueous ethanol and water in a T-microchannel, calibration procedures are carried out to obtain the relation between the concentration gradients and grayscale readouts under various incident illuminations, concentrations of aqueous ethanol solution, and knife-edge cutoffs. We find that to broaden measuring range with minimal error, the luminous exitance should be tuned to have a reference background with an average grayscale readout of 121, and dilute aqueous ethanol solution with a mass fraction of 0.05 should be used along a 50 % cutoff. For concentration gradients greater than 6.8 × 10−3 or below −2.5 × 10−2 μm−1, the calibration curves show great linearity. Correspondingly, the discernable limit of our microscale schlieren system is 2.3 × 10−5 μm−1 for a positive refractive index gradient and −8.6 × 10−5 μm−1 for a negative refractive index gradient. Once the relation between concentration gradients and grayscale readouts is known, the concentration distribution in a microfluidic can be reconstructed by integrating its microscale schlieren image with appropriate boundary conditions. The results prove that the microscale schlieren technique is able to provide spatially resolved, noninvasive, full-field measurements. Since the microscale schlieren technique is directly linked to the measurement of a refractive index gradient, the present method can be easily extended to other scalar quantifications that are related to the variation of refractive index.

Variation in seed dormancy in Echinochloa and the development of a standard protocol for germination testing. II: Breaking dormancy in seeds unresponsive to light or dark conditions alone by using heat and ethanol pretreatment

A recently established method for the germination of Echinochloa seeds recognised and accounted for variation in responses to light and darkness. This method used parallel light and dark tests and was successful in promoting germination in most seed lots. However, some samples exhibited deeper dormancy and were not fully responsive to either test. In the present study, we employed warm pretreatments where seeds were exposed to dilute aqueous ethanol solutions to attempt to break their dormancy. Based on tests of five Echinochloa accessions, we propose a new, follow-up protocol that can be used on samples unresponsive to the established method. The additional step involves a 3-day dark pretreatment at 35-37°C, imbibing the seeds in ~0.25M ethanol (aq). After this pretreatment, the seeds should be germinated for 14 days at 20/30°C (16 hours/ 8 hours) with half held in darkness and the other half exposed to an 8-hour light cycle.

Preparation and benchmarking of thin film supported PTMSP-silica pervaporation membranes

Supported silica filled poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membranes were optimised in terms of silica filler loading and top layer thickness, and applied in the pervaporative separation of dilute aqueous ethanol and butanol mixtures (5 wt.%). Addition of hydrophobic silica clearly increased the permeate flux at the expense of the alcohol/water selectivity. Based on its maximal pervaporation separation index (PSI) an optimum was found for a 25 wt.% silica filled membrane with a PTMSP separating layer of 2.4 μm thickness. This membrane exhibited a flux of 9.5 kg m −2 h −1 in combination with an ethanol/water separation factor of 18.3. In the pervaporation of a butanol/water mixture, a flux of 9.5 kg m −2 h −1 and accompanying separation factor of 104 was obtained. A benchmark of this optimised supported PTMSP-silica nanohybrid membrane against two commercially available PDMS-based membranes clearly demonstrated the superior flux/selectivity combination of the prepared thin film silica filled PTMSP membranes in the removal of alcohols from dilute aqueous mixtures. Compared to the commercial membranes, a 4- and 3-fold increase in flux and a 2- and 3-fold increase in alcohol/water separation factor was observed for the optimised supported PTMSP-silica membrane in the separation of a 5 wt.% ethanol/water and butanol/water mixture, respectively.

Investigation of bubble diameter and flow regime between water and dilute aqueous ethanol solutions in an airlift reactor

In this study, the effect of ethanol addition into pure water and its concentration on bubble diameter, gas hold-up and flow regimes were investigated in an airlift reactor. Air and water with ethanol (concentration ranging from 0%–1%, v/v) were as dispersed and continuous phases, respectively. Superficial gas velocity was considered as an effective parameter. Bubble size distribution was measured by photography and picture analysis at various concentrations of ethanol and various velocities of gas. Alcohol concentration enhancement caused bubble diameter to decrease. Furthermore, the bubbles diameter in pure water was nearly 4 times higher than that of ethanol with concentration of 1% (v/v) and also was 3.4 times higher than that of ethanol with concentration of 0.25% (v/v) at the highest aeration gas velocity inlet. For ethanol solutions in lower superficial gas velocity, a homogenous flow regime was observed. This trend continued to inlet gas velocity of about 0.4 cm/s. The transition flow regime occurred after this datum although in pure water, a homogenous flow regime was observed up to a superficial gas velocity of 0.7 cm/s. The gas hold-up in dilute ethanol solutions were more than (around 2 times) that of pure water and increased with increasing concentration of ethanol in those solutions.

Vapor phase synthesis of nanofibrous carbon materials from water-ethanol mixtures

We present a detailed study of the pyrolytic synthesis of nanofibrous carbon materials (NCMs) from ethanol and various water-ethanol mixtures on a nickel catalyst at temperatures from 400 to 700°C. In the synthesis from 96% ethanol, the initial deposition rate increases with temperature, but this is accompanied by a substantial decrease in catalyst life. The addition of water to the reaction system considerably increases the catalyst life. One possible reason for this is that water vapor prevents carbonization of the catalyst particles. At the same time, above 600°C the rate of NCM deposition from a 50% water-ethanol mixture is considerably slower. At 550°C and lower temperatures, the rate of NCM deposition from water-ethanol mixtures (based on ethanol consumption) changes insignificantly. Our results demonstrate that NCMs can be synthesized even from very dilute (down to 10 vol %) aqueous ethanol solutions. The participation of water vapor in chemical processes that take place in the reaction zone is discussed.

Enzyme-like Acceleration for the Hydrolysis of a DNA Model Promoted by a Dinuclear Zn(II) Catalyst in Dilute Aqueous Ethanol

The rates and products of cleavage of methyl (2-chloro-4-nitrophenyl) phosphate (2) promoted by a dinuclear Zn(II) complex (3) of 1,3-bis-N,N'(1,5,9-triazacyclododecyl)propane along with 1 equiv of ethoxide were investigated in ethanol solution containing small amounts of water (8 mM <or= [H2O] <or= 2.1 M) at 25 degreesC and sspH 7.9. The kinetics of decomposition of 5 x 10(-5) M 2 in the presence of varying [3] (0.03 mM <or= [3] <or= 0.12 mM) in ethanol containing 28 mM water show very strong saturation binding which is analyzed to give fitted values for the complex dissociation constant (Kd) and maximum catalytic rate constant (kcatmax) of 3.2 x 10(-8) M and 1.47 x 10(-3) s(-1). Product analysis indicates that the reaction in ethanol containing 28 mM and 2.1 M water produces 46% and 93% of the hydrolysis product (methyl phosphoric acid), with the remainder being ethanolysis product (ethyl methyl phosphate). Analysis of the kinetics of the reaction at 28 mM water indicates that second order rate constant for the catalytic reaction, given as kcatmax/Kd, is 4.6 x 104 M(-1) s(-1), is a factor of 8.4 x 10(10) larger than the second order rate constant (k2EtO) for the ethoxide promoted reaction of 2 in ethanol (5.5 +/- 0.3) x 10(-7) M(-1) s(-1). A more detailed analysis that considers the relative acidities of water and ethanol in ethanol solvent indicates that at sspH 7.9, the ethanolysis is accelerated by 2.3 x 10(14) times relative to the computed ethoxide reaction at that sspH, while the hydrolysis is accelerated by >or=1.6 x 10(17) times relative to the background hydroxide reaction, suggesting that complex 3 promotes the hydrolysis at least 1000 times more effectively than ethanolysis.

Synthesis and characterization of a novel hyperbranched polyether

AbstractA hyperbranched polyether has been synthesized by a single‐step nucleophilic displacement polymerization technique between cyanuric chloride and the sodium salt of bisphenol‐A. The effects of various reaction parameters on the yield, and molecular weight, as measured by the intrinsic viscosity of the polymer, have been studied. The synthesized polymer has been characterized by FT‐IR, UV and 1H NMR spectroscopies, elemental analysis, solubility and viscosity measurements. The polymer is soluble in highly polar solvents such as N,N‐dimethylacetamide, N,N‐dimethylformamide and dimethyl sulfoxide, partially soluble in dilute aqueous NaOH solution, methanol, ethanol, chloroform, etc., but insoluble in water and non‐polar hydrocarbon solvents. The solubility parameter of the hyperbranched polymer has also been measured experimentally. Copyright © 2004 Society of Chemical Industry

Kirkwood−Buff Integrals in Aqueous Alcohol Systems: Aggregation, Correlation Volume, and Local Composition

The Kirkwood−Buff theory of solution was used to investigate the formation of clusters in aqueous alcohol solutions. The correlation volume (volume in which the composition differs from the bulk one) was calculated for the systems 1-propanol−water and tert-butyl alcohol−water and compared with the sizes of clusters determined by various physical techniques. The calculations indicated that two types of clusters, alcohol- and water-rich clusters, are present in the solutions. Their sizes, which depend on composition in a similar way, exhibit maxima in the water-rich region. The calculated values are in a satisfactory agreement with experiment. The composition inside the clusters (the local composition) was calculated as a function of the correlation volume for dilute aqueous methanol, ethanol, propanols, and tert-butyl alcohol solutions. The results were compared with the local compositions provided by the Wilson and NRTL equations.

Solubility of Potassium Dichromate in Dilute Aqueous Ethanol Solutions in the Temperature Range 283 K to 303 K

Solubility data for potassium dichromate in dilute aqueous ethanol solutions were determined at five temperatures (283, 288, 293, 298, and 303) K. The densities of the saturated solutions were also measured. The solubility data (283, 288, 293, and 298) K correlated well with the empirical equation ln x1 = A + Bx2 + Cx22 with an precision of ±1.5% where x1 and x2 are the mole fraction of potassium dichromate and ethanol in salt-saturated solutions and A, B, and C are fitted empirical constants depending on the temperature. The results indicate that at ambient temperatures of about 283 to 303 K, addition of less than 0.01 mass fraction of ethanol to an aqueous saturated solution of potassium dichromate caused “salting out” in the range between 33 and 43% of the mass of the salt.

Single crystals of inulin

Lamellar crystals of inulin were grown by crystallizing sharp fractions of low molecular weight inulin from dilute aqueous ethanol solutions. The crystals were analyzed using three-dimensional electron diffraction and X-ray powder diagrams. Two crystalline polymorphs were observed, depending on the hydration conditions: a hydrated form which indexed on an orthorhombic unit cell, with space group P2 12 12 1 and with cell dimensions of a = 1.670 nm, b = 0.980 nm and c (chain axis) = 1.47 nm, together with a pseudo-hexagonal semi-hydrated form with unit cell parameters a = 1.670 nm, b = 0.965 nm and c (chain axis) = 1.44 nm. These parameters, together with the density data, indicate that inulin crystallizes along a pseudo-hexagonal six-fold symmetry with an advance per monomer of 0.24 nm. The difference between the hydrated and the semi-hydrated unit cells does not seem to correspond to any change in the conformation of inulin, but rather to a variation in water content.

Production of high yield [13N] ammonia by proton irradiation from pressurized aqueous solutions

The method of direct production of large quantities of [13N]ammonia in the cyclotron water target for clinical cardiac studies by PET or synthetic uses was considered. Two main approaches based on the proton irradiation either of dilute aqueous ethanol solution under helium pressure or pure water pressurized by hydrogen were evaluated. Using ethanol as a target additive at the relatively low helium pressure of 400 KPa up to 22.2 GBq (600 mCi, EOB) of final product can be produced with radiochemical purity of more than 98%. Under comparable conditions the water target pressurized by hydrogen was about two times less effective for production of [13N]NH3 because of the formation of considerable amounts of [13N]N2. A possible mechanism of labelled nitrogen production was discussed.

Molecular and Crystal Structures of Inulin from Electron Diffraction Data

The crystal and molecular structures of inulin, the poly(2→1)-β-d-fructofuranan, hemihydrate and monohydrate, were determined by a constrained linked-atom least-squares (LALS) refinement, utilizing intensities measured from electron diffraction data and stereochemical restraints. Single crystals were grown from dilute aqueous ethanol solutions and their three-dimensional electron diffraction diagrams analyzed. In the hemihydrate form, there is half a molecule of water per fructosyl residue. In this allomorph, which corresponds to air-dried crystals, inulin adopts an orthorhombic P212121 space group with cell parameters a = 16.70 Å, b = 9.65 Å, and c (chain axis) = 14.4 Å. By using the base plane electron diffraction data combined with the upper layer line data, the best molecular model was refined to an R factor of 22.7% and R‘‘ factor of 22.3%. This model has two antiparallel sixfold helices centered on the twofold screw axes intersecting the base plane of the orthorhombic system. The six water molecules are distributed over eight sites in the unit cell. The helical conformation is characterized by φ = 66°, ψ = 154°, and ω = −82°. In the monohydrate form obtained when inulin crystals were kept in a moist environment, there is one molecule of water per fructosyl residue. The unit cell dimensions remained nearly the same (a = 16.70 Å, b = 9.80 Å, and c (chain axis) = 14.7 Å) but substantial differences in the electron diffraction intensities were observed. The best molecular model was refined to an R factor of 18.1% and an R‘‘ factor of 16.5% by using only hk0 reflections of the base plane electron diffraction data. Simulated diffraction patterns of this structure showed that its differences with the hemihydrate could be accounted for only by introducing extra water molecules into the gaps of the crystalline structure without major modification of the inulin conformation.

On-line anion exchange purification of [ 13N]NH 3 produced by 10 MeV proton irradiation of dilute aqueous ethanol

[ 13N]NH 3 prepared by irradiating dilute aqueous ethanol with 10 MeV protons is contaminated with small amounts of [ 18F]fluoride and [ 13N]NO 2 −/NO 3 −. The content of 18F is negligible at end of bombardment but increases as a function of time due to the longer half-life of 18F. We developed a simple on-line purification method in which the irradiated water directly passes through a small anion exchange column. Both the radionuclidic impurity [ 18F]fluoride and the radiochemical impurities [ 13N]NO 3 −/NO 2 − are efficiently removed by this procedure which results in highly pure (>99.9%) [ 13N]NH 3 preparations.

Enantioselective permeation through poly[γ-[3-(pentamethyldisiloxanyl)propyl]- l-glutamate] membranes

Poly ( l-glutamic acid ester) with 3-(pentamethyldisiloxanyl)propyl groups was prepared from poly(γ-methyl- l-glutamate) (PMLG) by ester exchange reaction. This polymer had an α-helical structure in the membrane prepared from 1,2-dichloroethane solution. The membrane forming ability of the polymer was better than that of PMLG. Optical resolution of (±)-tryptophan was achieved by pressure driven permeation through the membrane. The enantioselectivity was 16% enantiomeric excess (%ee) and the permeation rate was high (10 −6 g m/m 2 h). This enantioselective permeation continued for more than 160 h. With an increase in the disiloxane side chain contant, the permeation rate could be increased while maintaining the selectivity. Since the enantioselectivity for adsorption favoured the (+)-isomer and that for permeation favoured the (−)-isomer, enantioselective permeation was caused by suppression of the (+)-isomer permeation. It was suggested that the permeation of dilute aqueous tryptophan solution occurred mainly in the region of highly mobile disiloxane side chains, which had no asymmetric centers, by measurements and analysis of the pervaporation of dilute aqueous ethanol solution. Therefore it was believed that this siloxane region was small enough for the asymmetric centers in the main chain to recognize enantioselectively the permeating solute.

The crystal and molecular structure of V H amylose by electron diffraction analysis

The crystal and molecular structures of V H amylose were determined by a constrained linked-atom least-squares refinement, utilizing intensities measured from electron diffraction patterns and stereochemical restraints. Hexagonal platelet single crystals were grown from dilute aqueous ethanol solution and their electron diffraction diagrams analysed. These data indicated that the amylose chains were crystallized in hexagonal lattice with a  b  13.65 A ̊ , c ( chain axis)  8.05 A ̊ and space group P6 522. The best model obtained using the base plane data coupled with a stereochemical refinement yielded R  0.24 ( R ″  0.25). It corresponded to a system of left-handed 6-fold helices packed on an hexagonal net but with statistically random up/down chain disorder. A column of six water molecules was present within each helical repeat. Additionally, the gap between each pair of adjacent helices was bridged by two water molecules positioned so as to allow hydrogen bonding with chains of either sense. This proposed crystal structure differs somewhat from previous reports which invoked orthorhombic lattices and requires a regularly alternating arrangement of up and down chains to account for the intensity. Suggestions are made to account for these differences.

In-target production of [ 13N]ammonia via proton irradiation of dilute aqueous ethanol and acetic acid mixtures

A reliable, reproducible method has been developed for the in situ production of decicurie quantities of [ 13N]ammonia by proton irradiation of pressurized, dilute aqueous solutions of acetic acid and ethanol. Some of the parameters investigated for their effect on the 13N product distribution included dose, dose rate, solute concentration, target body material, beam strike volume and proton energy. For the conditions investigated, [ 13N]NH 3 was produced directly in the target in yields >75%.