Showing papers on "Hexane published in 1994"
TL;DR: In this article, the microwave heating characteristics of extraction mixtures consisting of rosemary or peppermint leaves suspended in hexane, ethanol and hexane + ethanol mixtures were studied.
Abstract: The microwave heating characteristics of extraction mixtures consisting of rosemary or peppermint leaves suspended in hexane, ethanol and hexane + ethanol mixtures were studied. The temperature rises were found to depend on the dielectric properties of the solvents and the leaves in question. The rates of extraction of several essential oil constituents increased with increasing power output between ca 200 and 640 W but not in a proportional way. Scanning electron micrographs of the leaves showed that the extraction rates were related to structural changes in the oil-containing glands.
73 citations
TL;DR: Binary diffusion coefficients for infinitely dilute solutions of acetone, benzene, toluene, m-xylene, 1,3,5trimethylbenzene, and naphthalene in hexane, in dodecane, and in cyclohexane were measured from 303.2 to 333.2 K and at 16.0 MPa using the Taylor dispersion technique as mentioned in this paper.
Abstract: Binary diffusion coefficients for infinitely dilute solutions of acetone, benzene, toluene, m-xylene, 1,3,5trimethylbenzene, and naphthalene in hexane, in dodecane, and in cyclohexane were measured from 303.2 to 333.2 K and at 16.0 MPa using the Taylor dispersion technique. In addition, the measurements for 0andp-xylenes, vitamin y3, linoleic acid methyl ester, indole, dl-limonene, vitamin A acetate, vitamin E, and vitamin K1 in hexane and vitamin y3 and linoleic acid methyl ester in dodecane were made at the limited conditions. The D12 results in the three solvents are expressed by the equation DldT = a$ with average absolute deviation of 5.2%) where 17 is the solvent viscosity and a and p are constants related to the solute molar volume a t the normal boiling point. For the D12 measured in this study this correlation is as accurate as Nakanishi’s correlation which is superior to other correlations examined.
47 citations
TL;DR: In this paper, the kinetics of immobilized lipase-catalyzed esterification of oleic acid and methanol in hexane were investigated, and the reaction follows Michaelis-Menton kinetics as observed from the relationship of initial rate of the reaction.
Abstract: The kinetics of immobilized lipase-catalyzed esterification of oleic acid and methanol in hexane were investigated. The reaction follows Michaelis-Menton kinetics as observed from the relationship of initial rate of the reaction, both as a function of enzyme and of substrate concentration. Inhibition by excess of methanol has been identified. The kinetic constants have been measured for the reaction in the absence of any significant external diffusional limitations. The kinetics of the enzymatic reaction are suggested to agree with a Ping-Pong Bi Bi mechanism.
46 citations
TL;DR: In this paper, the authors derived a predictive equation for the solubility of anthracene in binary hydrocarbon + alcohol mixtures based upon Mobile Order theory, which was used to test the limitations and applications of expressions derived from mobile order theory.
42 citations
TL;DR: In this paper, a column with a simple isocratic mobile phase of acetonitrile in hexane and flame ionization detection was employed to separate and quantitate triacylglycerol species of vegetable oils.
Abstract: Silver ion high performance liquid chromatography with a commercially available column with a simple isocratic mobile phase of acetonitrile in hexane and flame ionization detection was employed to separate and quantitate triacylglycerol species of vegetable oils. Coconut, palm, cottonseed, olive, safflower, sunflower, corn, pumpkinseed, linseed, soybean, and canola oils were analyzed, as well as randomized corn and soybean oils, and the blends and interesterified products of corn and soybean oil with cottonseed oil stearine. Fractionated triacylglycerol species were identified by gas chromatography of their methyl esters. Triacylglycerol composition was obtained by reversed phase and silver ion high performance liquid chromatography of the same oil. Oil fatty acid composition was determined by gas chromatography of the transmethylated oil and correlated with that calculated from the triacylglycerol composition by silver ion chromatography of the same oil. The triacylglycerol separation was mostly...
40 citations
TL;DR: A two-phase solvent extraction system consisting of alkanol-ammonia-water and hexane was employed for the simultaneous extraction of oil and detoxification of flaxseed meal as discussed by the authors.
40 citations
TL;DR: In this paper, the vapor-liquid equilibria for the five alkanol + alkane binary systems were measured by a flow-type apparatus at 298.15 K. The experimental results obtained were correlated by several equations for activity coefficients.
Abstract: The vapor-liquid equilibria for the five alkanol + alkane binary systems methanol + hexane, methanol + heptane, ethanol + hexane, ethanol + heptane, and ethanol + octane were measured by a flow-type apparatus at 298.15 K. The values of the activity coefficient are greater than unity. The experimental results obtained were correlated by several equations for activity coefficients, and these correlations are compared.
35 citations
TL;DR: In this article, the copolymer-propane cloud-point curve was analyzed at 170°C and 2800 bar (280 MPa) for poly(ethylene-co-(31 mol%) methyl acrylate) at ∼5 wt% in propane and in hexane.
33 citations
TL;DR: In this article, the authors investigated the molecular evaporation and condensation processes from high-temperature liquid n−C6H14 and n‐C16H34 films with molecular dynamics simulations.
Abstract: Energetic, structural, and dynamical properties of solid‐to‐liquid and liquid‐to‐vapor interfaces and molecular evaporation and condensation processes from high‐temperature liquid n‐C6H14 and n‐C16H34 films were investigated with molecular dynamics simulations. For hexadecane all evaporation events occurred via monomers while for hexane, evaporation of monomers as well as dimers were observed. For both alkane liquids the molecular evaporation mechanism is found to be sequential in nature, starting with an end segment of a molecule leaving the surface and subsequently the evaporation of the molecule occurs via sequential ‘‘dragging’’ of the rest of the molecule. The condensation coefficients of vapor molecules onto the liquid surface are estimated as ∼0.9 for hexane and ∼1 for hexadecane. Evaporation is accompanied by significant molecular conformational changes. In hot liquid n‐C16H34 the trans (t) and gauch (g+ and g−) dihedral conformations are distributed as (t,g+,g−)=(66,17,17) while in the vapor the distribution is almost uniform with a large decrease in the fraction of trans conformations, i.e., (33,31,36). On the other hand, for the shorter alkane hot liquid (t,g+,g−)=(72,14,14) while in the vapor the fraction of trans conformations is increased, i.e., (83,10,7). These results are discussed in light of theoretical treatments of evaporation processes.
30 citations
TL;DR: In this article, the authors used supercritical carbon dioxide (SC-CO2) to extract cottonseed lipids with and without a cosolvent, ethanol or 2-propanol (IPA).
Abstract: Extraction of cottonseed lipids with supercritical carbon dioxide (SC-CO2) was conducted with and without a cosolvent, ethanol or 2-propanol (IPA). At 7000 psi and 80°C, the reduced pressure, temperature and density of SC-CO2 was at 6.5, 1.17 and 1.85, respectively; the specific gravity was 0.87. Under these conditions, CO2 is denser than most liquid extraction agents such as hexane, ethanol and IPA. The extraction of cottonseed with SC-CO2 gave a yield of more than 30% (moisture-free basis). This is comparable to yields obtained by the more commonly used solvent, hexane. The crude cottonseed oil extracted by SC-CO2 was visually lighter than refined cottonseed oil. This was substantiated by colorimetric measurements. No gossypol was detected in the crude oil. However, crude oil extracted by SC-CO2, to which less than 5% of ethanol or IPA as co-solvent was added, containedca. 200 ppm of gossypol, resulting in the typical dark color of cottonseed crude oil with gossypol. CO2 extracted a small amount of cottonseed phosphatides, about one-third of that extracted by pure ethanol, IPA or hexane. A second extraction with 100% ethanol or IPA after the initial SC-CO2 extraction produced a water-soluble lipid fraction that contained a significant amount of gossypol, ranging between 1500 and 5000 ppm. Because pure gossypol is practically insoluble in water, this fraction is believed to be made up of gossypol complexed with polysaccharides and phosphatides.
29 citations
TL;DR: In this paper, the dynamic viscosity of four binary alkanol + alkane mixtures of ethanol and 1-propanol with hexane and heptane was measured at 298.15 K and in a pressure range from atmospheric to 520 bar.
Abstract: Measurements are reported for the dynamic viscosity of four binary alkanol + alkane mixtures of ethanol and 1-propanol with hexane and heptane. The measurements were conducted at 298.15 K and in a pressure range from atmospheric to 520 bar. A self-centering falling body viscometer was used for the measurements. All four systems exhibit negative viscosity deviations over the full composition and pressure ranges. The experimental data are discussed in terms of the specific interactions involved in the systems.
TL;DR: In this article, the HPLC behavior of the tocol components was studied under various mobile phase conditions, including hexane or cyclohexane, in binary and ternary mobile phases.
TL;DR: In this paper, the authors discuss the solubility of anthracene in binary alkane + 2-butanol solvent mixtures, and show that it is solvable in both binary and binary solvability.
Abstract: Article discussing the solubility of anthracene in binary alkane + 2-butanol solvent mixtures.
TL;DR: In this article, the solvent effect on the Menshutkin SN2 reaction of CH3X (X = Cl, Br, I) has been studied using multicavity self-consistent reaction field (MCa SCRF).
Abstract: The solvent effect on the Menshutkin SN2 reaction of CH3X (X = Cl, Br, I) has been studied using multicavity self-consistent reaction field (MCa SCRF). Two dielectric media, corresponding to hexane and water, have been modelled. The linear and nonlinear structures of the reaction complexes have been used to model the reaction path. The reaction field due to the solvent stabilizes significantly both the transition state and the local minimum of the product of the reaction. The structure of the complexes corresponding to other minima in the reaction path is also discussed. Our results indicate that the reactions of ammonia with methyl chloride, methyl bromide and methyl iodide are exothermic (except methyl iodide in hexane) even in the gas phase, due to the formation of different products (complex between the electroneutral HX and CH3NH2). In hexane, the ion pair CH3NH3+X– is formed, whereas in water the reaction results in free ions. A full scheme of the reaction in different media is presented.
TL;DR: The association behavior of a maleic anhydride-grafted ethylenepropylene copolymer, EP(60/40), has been studied by several methods in hexane and THF.
Abstract: The association behavior of a maleic anhydride-grafted ethylenepropylene copolymer, EP(60/ 40), has been studied by several methods in hexane and THF. The concentration-dependent apparent hydrodynamic diameters (D H ) of EP (60/40) have been determined at 25°C by dynamic light scattering. D H have been found to increase exponentially in both solvents. However, in THF D H are much smaller and their increase with increasing concentrations of EP(60/40) is less steep than that in hexane.
TL;DR: Soybean, wheat germ, sunflower and peanut oils were extracted with supercritical carbon dioxide modified with pentane in this article, which was optimized by chemometric methods using as frontier limits; supercritical pressures of 50 to 150 atm, supercritical temperatures of 60 to 100°C and extraction times of 5 to 15 min.
Abstract: Soybean, wheat germ, sunflower and peanut oils were extracted with supercritical carbon dioxide modified with pentane. The extractions were optimized by chemometric methods using as frontier limits; supercritical pressures of 50 to 150 atm, supercritical temperatures of 60 to 100°C and extraction times of 5 to 15 min. The oils extracted with CO2/pentane were compared to those obtained through conventional extraction methods using hexane.
TL;DR: In this article, the parathion-specific antiserum was encapsulated in reverse micelles composed of Aerosol OT and having aqueous centres, and a solution of parathions in hexane was then allowed to compete for antibody binding sites with the antigen-coated surface of a microtitre plate.
Abstract: Immunoaffinity methods are presently finding limited applications in environmental analysis because many target compounds are best handled in non-polar solvents such as hexane. These solvents can be detrimental to protein molecules, particularly when the solvating water which is necessary for bioactivity is lost. Consequently, a generic immunoassay principle which would allow the provision of samples dissolved in hexane was sought. A competitive enzyme-linked immunosorbent assay (ELISA) method for the measurement of aqueous parathion was developed, optimized and then adapted to the measurement of the analyte without its prior removal from hexane. The parathion-specific antiserum was encapsulated in reverse micelles composed of Aerosol OT and having aqueous centres, and a solution of parathion in hexane was then allowed to compete for antibody binding sites with the antigen-coated surface of a microtitre plate. The calibration graph for the hexane-compatible ELISA method is displaced from its aqueous counterpart in correspondence with the partition coefficient of parathion between water and hexane, this method being about 104-fold more sensitive. It is probable that the thermodynamic barrier to the transfer of parathion from an organic bulk phase to the aqueous interior of a reverse micelle balances the antigen–antibody binding strength and thus reduces the potency of parathion as an antigenic competitor. Means are suggested for tuning the calibration graph of the hexane-compatible ELISA method to the analyte concentration range that is of interest.
TL;DR: In this article, the effect of modifying the solvent with isopropanol, which competes for adsorption sites and modifies the solvent polarity, was studied in hexane.
Abstract: Diffuse reflectance Fourier transform infrared spectroscopy was used to observe adsorption complexes of oleic acid and isopropanol (IPA) on silicic acid in hexane. The spectra provide definite evidence of the molecular nature of the surface interaction. In addition, the effect on oleic acid adsorption of modifying the solvent with IPA, which competes for adsorption sites and modifies the solvent polarity, was studied. Oleic acid adsorption was reduced in the presence of an equimolar IPA concentration in hexane, relative to that from hexane alone. This could be explained by a combination of competitive adsorption of IPA and IPA interacting with oleic acid in solution. IPA, in solution, and silica are probably competing for the lipid. This is additional evidence that suggests that lipid adsorption onto silicic acid is influenced by competitive adsorption. The adsorption of oleic acid and IPA, from a mixture of the two in hexane, was controlled by (i) the equilibrium between surface-bound species and molecules in solution and (ii) the polar interaction between oleic acid and IPA in solution. Thus, washing pre-bound oleic acid with hexane removed only a small amount of oleic acid, while washing with a solution of IPA in hexane removed most of the pre-bound oleic acid.
TL;DR: In this paper, US-Y zeolite was used to adsorb eight aromatic nitrogen compounds dissolved in hexane, hexane + hexadecane, Hexane + naphthalene and hexane+ hydrotreated shale oil.
TL;DR: In this paper, the solubility of anthracene in binary alkane + 2-methyl-1-propanol solvent mixtures was investigated and the results showed that it is solubile in both binary and binary alkane.
Abstract: Article on the solubility of anthracene in binary alkane + 2-methyl-1-propanol solvent mixtures.
TL;DR: A polarity test mix consisting of acetophenone, N,N-dimethylaniline, naphthalene, 2-naphthol, and n-tetracosane was spiked onto sand and extracted with carbon dioxide modified with acetonitrile, methanol, or toluene as discussed by the authors.
Abstract: A polarity test mix consisting of acetophenone, N,N-dimethylaniline, naphthalene, 2-naphthol, and n-tetracosane was spiked onto sand and extracted with carbon dioxide modified with acetonitrile, methanol, or toluene. The extracts were collected in chloroform, hexane, methanol, or a mixed collection solvent consisting of equal parts chloroform-hexane-methanol. The mixed collection solvent which showed excellent recoveries for pure CO2, had the worst recoveries of all the collection solvents with modified CO2. Overall hexane was the best collection solvent studied for these analytes under these extraction conditions.
TL;DR: In this article, the rates and extents of extraction into hexane, ethanol and two mixtures of hexane + ethanol (10.1 mol% hexane and 89.7 mol% ethanol) of six essential oil constituents of the leaves of rosemary (Rosmarinus officinalis L.) have been measured.
Abstract: The rates and extents of extraction into hexane, ethanol and two mixtures of hexane + ethanol (10.1 mol% hexane and 89.7 mol% hexane) of six essential oil constituents of the leaves of rosemary (Rosmarinus officinalis L.) have been measured. The data were fitted to a first order kinetic equation to yield rate constants (k) for the extraction of α-pinene, camphene, α-pinene, limonene, 1,8-cineole and camphor. The values of k increased between threefold and fiftyfold in the mixed solvents compared to values obtained in the pure solvents. Experiments carried out over the temperature range 25–45°C yielded activation energies of over 100 kJ mol−1 for every constituent, showing that the extraction of rosemary oil was a hindered process. Scanning electron micrographs showed that the kinetics and mechanism of the extractions are related to structural changes in the oil-containing glands. The partition constants of most of the components were found to be 0.7 for hexane extraction.
TL;DR: An analytical methodology has been developed for the direct analysis of neutral nitrogen compounds in diesel oil by HPLC with subsequent detection using MS and/or photodiode-array UV spectrometry as mentioned in this paper.
TL;DR: In this paper, a dynamic headspace gas chromatographic method was used to characterize vola- tiles and semivolatiles in supercritical fluid extracted (SFE) oil and from a hexane-extracted crude soybean oil.
Abstract: Soybean flakes were extracted with supercritical carbon dioxide to produce a solvent-free, good-quality soybean oil. Volatile compounds from the supercritical fluid extracted (SFE) oil and from a hexane-extracted crude soybean oil were analyzed by dynamic headspace gas chromatographic methods to deter- mine qualitative differences between the extraction methods. The major differ- ence in the volatile profiles was the higher concentration of hexane in the solvent-extracted oil. During the SFE process, volatile compounds were trapped on a porous polymer trap attached at the exhaust port of the SFE apparatus. The volatile profile obtained from the sorbent trap was found to be similar to the headspace profile from the SFE/soybean oil removed during the same extraction. In addition, crude soybean oil was heated in a stirred reactor and the volatiles, which were stripped by supercritical carbon dioxide in an attempt to improve oil properties, were collected on sorbent traps and analyzed by the above method for comparison. The described methodology permits the characterization of vola- tiles and semivolatiles in SFE soybean oil and can be used to monitor the extrac- tion and quality of the resultant oil.
TL;DR: In this article, the effect of counter anion on the activity and selectivity of hexane aromatization was studied and it was shown that the electron-rich Pt site formed through the interaction with KF or KCl may be responsible for the high activity.
Abstract: Potassium salts were added to the catalyst prepared by ion exchange of KL with [Pt(NH3)4]Cl2 and the effect of their counter anion on the activity and selectivity for hexane aromatization was studied. The catalyst to which KF was added showed the highest activity and selectivity for benzene formation; methylcyclopentane and hydroisomerization products were negligible. Although the catalyst with KCl added also exhibited excellent performance, the catalysts with KBr or KI added gave rise to low hexane conversion and benzene yield. Infra-red spectra of adsorbed CO revealed that the presence of the low frequency C-O stretching band is closely related to catalytic performance of the Pt/KL series catalysts. The electron-rich Pt site formed through the interaction with KF or KCl may be responsible for the high activity and selectivity for hexane aromatization.
TL;DR: In this article, the influence of initial nicotine concentration, temperature, and pH on the distribution coefficients of nicotine between hexane and water has been studied and the coefficient was found to be independent of initial concentration, over the range studied, but was temperature and pH dependent.
Abstract: The influence of initial nicotine concentration, temperature, and pH on the distribution coefficients of nicotine between hexane and water has been studied. The coefficient was found to be independent of initial concentration, over the range studied, but was temperature and pH dependent
TL;DR: In this paper, the kinetics of enzymatic hydrolysis of rice bran oil in organic solvent (n -hexane) by free and immobilized Candida lipolytica lipase were investigated in a batch reactor.
TL;DR: In this paper, it was shown that the anionic cyclopolymerization of bis(dimethylvinylsilyl)methane initiated by n-BuLi/TMEDA in hexane yields a polymer with six-membered rings.
Abstract: It is shown that the anionic cyclopolymerization of bis(dimethylvinylsilyl)methane initiated by n-BuLi/TMEDA in hexane yields a polymer with six-membered rings
TL;DR: In this article, the performance of hexane adsorption on some common soil constituents and simple mixtures of these constituents at 27°C was studied at zero relative humidity and the results showed that clays were significant adsorbents in both pure constituent and mixture experiments.