Showing papers on "Hexane published in 1995"
TL;DR: Investigation of the lipase catalyzed transesterification reaction in supercritical carbon dioxide with a special emphasis on determining the extent of any interaction between the enzyme and carbon dioxide suggests that the enzyme undergoes shear inactivation in hexane.
Abstract: We have previously demonstrated that the activity of the lipase (Candida cylindracea) catalyzed transesterification reaction between methylmethacrylate and 2-ethylhexanol in supercritical carbon dioxide is comparatively low. In this article, we have investigated the same reaction in supercritical carbon dioxide with a special emphasis on determining the extent of any interaction between the enzyme and carbon dioxide. Transesterification reaction rates in hexane and supercritical carbon dioxide are compared at different temperatures. In supercritical carbon dioxide, temperature was found to have no significant effect on reaction rate in the range of 40 degrees to 55 degrees C. Above 55 degrees C, however, the reaction rate increased significantly as a function of temperature. It appears that carbon dioxide forms reversible complexes with the free amine groups on the surface of the enzyme. Direct evidence of modification was obtained using mass spectroscopy to detect the extent of modification of a pure protein. The kinetics of the reaction have been studied in hexane, and they obey a ping-pong bi-bi mechanism with inhibition by 2-ethylhexanol. The effect of bubbling carbon dioxide and/or fluoroform on the reaction rate in hexane at different temperatures suggests that the enzyme undergoes shear inactivation in hexane. (c) 1995 John Wiley & Sons, Inc.
109 citations
TL;DR: In this paper, an enzymatic treatment with carbohydrases was performed either simultaneously with or prior to the hexane extraction of oil from soya grits, which increased the oil extractability by 5% of the extractable oil.
88 citations
TL;DR: In this paper, the pϱT behavior of ethanol, hexane and its mixture has been investigated with the aim to cover the whole region from low pressure-low temperature thermodynamic excess properties up to the critical curve.
79 citations
TL;DR: In this paper, the lasing performance and wavelength tunability of a novel high efficiency copolymer poly[(2, 5, 2‘, 5'tetraoctyl), TOP•PPV, pumped with third harmonic radiation of a Nd:YAG laser, was studied in various organic solvents.
Abstract: The lasing performance and wavelength tunability of a novel high efficiency copolymer poly[(2, 5, 2‘, 5‘‐tetraoctyl)‐p‐terphenyl‐4,4‘‐ylene vinylene‐p‐phenylene vinylene], TOP‐PPV, pumped with third harmonic radiation of a Nd:YAG laser, was studied in various organic solvents. The results were compared with Coumarin 120 and Coumarin 47 in ethanol under identical experimental conditions. The efficiency of the TOP‐PPV copolymer in hexane exceeds that of both coumarin dyes with more than 50%. The laser emission of the polymer dye in hexane is tunable in the wavelength region between 414 and 456 nm (Δλ=38 nm).
75 citations
TL;DR: In this paper, the extraction of six essential oil components of rosemary (Rosmarinus officinalis L.) was carried out at atmospheric pressure in an electrically and mechanically modified domestic microwave oven.
Abstract: Extraction experiments were carried out at atmospheric pressure in an electrically and mechanically modified domestic microwave oven, with temperature changes monitored by a gas thermometer. The rates of extraction were measured of six essential oil components of rosemary (Rosmarinus officinalis L.) and detailed results are given for α-pinene and for 1,8-cineole. Major differences of behaviour were found according to whether the solvent employed was hexane, ethanol, or a mixture of 10 mol% hexane + 90 mol% ethanol. Simulated microwave extraction plots generated from the data of a series of thermostatted solvent extractions showed faster extraction rates than expected from the temperature changes. The rates of extractions were affected by the intensity of the microwave energy, the dielectric properties, size and composition of the workload, and the shape of the extracting vessel. Scanning electron micrographs showed that the kinetics and mechanism of the extractions were related to structural changes in the oil-containing glands
67 citations
TL;DR: In this article, the solvent-to-meal ratio was 10:1 (vol/wt) for hexane and 10:2 for heptane for ground cottonseed.
Abstract: For many years, commercial-grade hexane has been the preferred solvent for extracting oil from cottonseed. Recent environmental and health concerns about hexane may limit the use of this solvent; therefore, the need for a replacement solvent has become an important issue. Heptane is similar to hexane, but does not have the environmental and health concerns associated with the latter. On a laboratory scale, delinted, dehulled, ground cottonseed was extracted with hexane and heptane. The solvent-to-meal ratio was 10:1 (vol/wt). The yield and quality of the oil and meal extracted by heptane were similar to that extracted by hexane. Extraction temperature was higher for heptane than for hexane. A higher temperature and a longer time were required to desolventize miscella from the heptane extraction than from the hexane extraction. Based on these studies, heptane offers a potential alternative to hexane for extracting oil from cottonseed.
54 citations
TL;DR: In this paper, a high-performance liquid chromatography column (hexane/acetonitrile as solvent, ultraviolet detection) was used to analyze the fatty acid distribution (as fatty acid methyl esters) of a representative sample of hydrogenated oil.
Abstract: A silver-ion high-performance liquid chromatography column (hexane/acetonitrile as solvent, ultraviolet detection) was used to analyze the fatty acid distribution (as fatty acid methyl esters) of a representative sample of hydrogenated oil. Fractions containingcis- andtrans-18:1 isomers were readily separated. The positional fatty acid isomers were separated by rechromatographing these fractions. The elution order and percent compositions were compared with results obtained by gas chromatography. Of the Δ8 to Δ14trans-18:1 isomers, only the Δ8 and Δ9 pair could not be separated. The Δ8 and Δ9cis-18:1 pair also could not be separated, and the Δ10 isomer was poorly separated from this pair. Area percents were comparable to results obtained by gas chromatography.
51 citations
TL;DR: In this article, solvent debinding of alumina green bodies shaped by powder injection molding is investigated, and a shrinking core is observed at the early stage of 50 °C solvent debindings.
47 citations
TL;DR: In this article, the Redlich-Kister equations were fitted to a binary mixture of 2-methylpropan-2-ol with hexane, benzene, propan-2ol, methanol, ethanol, and water at 3032 K.
Abstract: Densities (e), refractive indices (n), absolute viscosities (η), and static dielectric constants (E) have been measured over the entire range of composition for binary mixtures of 2-methylpropan-2-ol with hexane, benzene, propan-2-ol, methanol, ethanol, and water at 3032 K Excess molar volumes were fitted to Redlich-Kister equations
44 citations
TL;DR: Comparison of the degree of enzyme hydration reached in nonpolar solvents with that obtained in air shows that adsorption of strongly bound water is hardly affected by the low dielectric medium, but adsorptions of loosely bound water are significantly reduced, which suggests that the hydrophobic regions of the protein surface are preferentially solvated by solvent molecules.
Abstract: A very sensitive NMR method has been developed for measuring deuterated water bound to proteins suspended in nonpolar solvents. This has been used to determine the amount of bound water as a function of water activity for subtilisin Carlsberg suspended in hexane, benzene, and toluene and for alpha-chymotrypsin in hexane. The adsorption isotherms for subtilisin in the three solvents are very similar showing that water activity can be usefully employed to predict the amount of water bound to proteins in nonpolar organic media. Comparison of the degree of enzyme hydration reached in nonpolar solvents with that obtained in air shows that adsorption of strongly bound water is hardly affected by the low dielectric medium, but adsorption of loosely bound water is significantly reduced. This suggests that the hydrophobic regions of the protein surface are preferentially solvated by solvent molecules, and that in a nonpolar environment formation of a complete monolayer of water over the protein surface is thermodynamically unfavorable. (c) 1995 John Wiley & Sons, Inc.
43 citations
TL;DR: In this paper, the retention behavior of certain members of these isomer sets and the resulting impact of modifier selection and concentration was demonstrated, and the retention characteristics on calcium hydroxide and electronic absorption spectra allowed assignment of geometric configurations to some of the resolved peaks.
Abstract: HPLC methodology employing a calcium hydroxide stationary phase selective for separations of phytofluene, ζ-carotene, γ-carotene, α-carotene, and β-carotene geometric isomer sets was developed. The retention behavior of certain members of these isomer sets and the resulting impact of modifier selection and concentration was demonstrated. Pertinent modifications for specific analytical situations are recommended. Individual purified carotenoids were isomerized by iodine catalysis. Resolution of phytofluene isomers was achieved using hexane, that of α-carotenes using 0.1% p-methylanisole in hexane, that of β-carotenes using 2.0% p-methylanisole in hexane, that of ζ-carotenes using 1.4% benzyl ether in hexane, and that of γ-carotenes using 2.45% benzyl ether in hexane. Retention characteristics on calcium hydroxide and electronic absorption spectra allowed assignment of geometric configurations to some of the resolved peaks. These methods may be used, with modifications where necessary, to analyze isomeric sets of carotenes and to isolate individual isomers.
TL;DR: In this article, five solvents, n-heptane, isohexane, cyclopentane and neohexane were compared with commercial hexane using a bench-scale extractor.
Abstract: Hexane has been used for decades to extract edible oil from cottonseed. However, due to increased regulations affecting hexane because of the 1990 Clean Air Act and potential health risks, the oil-extraction industry urgently needs alternative hydrocarbon solvents to replace hexane. Five solvents,n-heptane, isohexane, neohexane, cyclohexane, and cylopentane, were compared with commercial hexane using a benchscale extractor. The extractions were done with a solvent to cottonseed flake ratio of 5.5 to 1 (w/w) and a miscella recycle flow rate of 36 mL/min/sq cm (9 gal/min/sq ft) at a temperature of 10 to 45°C below the boiling point of the solvent. After a 10-min single-stage extraction, commercial hexane removed 100% of the oil from the flakes at 55°C; heptane extracted 100% at 75°C and 95.9% at 55°C; isohexane extracted 93.1% at 45°C; while cyclopentane, cyclohexane, and neohexane removed 93.3, 89.4, and 89.6% at 35, 55, and 35°C, respectively. Each solvent removed gossypol from cottonseed flakes at a different rate, with cyclopentane being most and neohexane least effective. Based on the bench-scale extraction results and the availability of these candidate solvents, heptane and isohexane are the alternative hydrocarbon solvents most likely to replace hexane.
01 Jan 1995
TL;DR: In this article, the pendant drop technique has been used to measure interfacial tension of hexane/water plus Triton X-100 interface and the results of the measurements are reported together with the interpretation of these data.
Abstract: Measurements of interfacial tension of hexane/water plus Triton X-100 interface have been made by the pendant drop technique. The results of the measurements are reported together with the interpretation of these data. The main result is that in the range of concentrations under examination the Freundlich isotherm describes the system with a great accuracy.
TL;DR: A static-based apparatus with capillary sampling has been used to measure vapor-liquid equilibria up to 112 MPa at three temperatures around 323, 373, and 423 K.
Abstract: A static-based apparatus with capillary sampling has been used to measure vapor-liquid equilibria up to 112 MPa at three temperatures around 323, 373, and 423 K for the following systems: hydrogen sulfide+hexane, +cyclohexane, +benzene, +pentadecane, and +(hexane+pentadecane)
TL;DR: The investigation of the dependence of antioxidant stoichiometry on TH oxidation product distribution for reactions in hexane, acetonitrile, and in phosphatidylcholine liposomes implies that competing reaction pathways contribute similarly to the antioxidant chemistry of TH.
Abstract: Oxidation ofR,R,R-α-tocopherol (vitamin E; TH) by peroxyl radicals generated from the azo initiator azobis(2,4-dimethylvaleronitrile) in acetonitrile, hexane, or in phospholipid liposomes yields 8a-(alkyldioxy)tocopherone adducts, 8a-(hydroxy)tocopherone, and their hydrolysis product α-tocopherolquinone TH oxidation also yields 4a,5-epoxy- and 7,8-epoxy-8a-(hydroperoxy)tocopherones and their respective hydrolysis products 2,3-epoxy-α-tocopherolquinone and 5,6-epoxy-α-tocopherolquinone. Previous work indicates that the distribution of TH oxidation products varies with reaction environment. We investigated the dependence of antioxidant stoichiometry on TH oxidation product distribution for reactions in hexane, acetonitrile, and in phosphatidylcholine liposomes. Yields of 8a-substituted tocopherones were highest in hexane and lowest in phosphatidylcholine liposomes. In contrast, yields of epoxide products were highest in the liposome system and lowest in hexane. Yields of α-tocopherolquinone were similar in all three systems. Antioxidant stoichiometry, measured by the inhibited autoxidation method, was approximately 2.0 peroxyl radicals trapped per TH consumed in acetonitrile and in liposomes. In hexane, a slightly larger stoichiometric factor of approximately 2.5 was measured. This may, in part, reflect the generation of more reactive alkoxyl radicals in hexane. The reaction environment thus markedly affects the balance between competing TH oxidation pathways but produces comparatively little effect on antioxidant stoichiometry. These results imply that competing reaction pathways contribute similarly to the antioxidant chemistry of TH.
TL;DR: In this paper, the isotherms of five n -alkanes: propane, butane, pentane, hexane, and heptane in 13 X zeolite have been measured by microgravimetry.
TL;DR: In this paper, the viscosities, densities and refractive indices of nine binary liquid systems containing n-alkane + isomers of hexane have been determined at 298.15 K. The results with these models agree with experimental data with an average absolute deviation of less than 0.6%.
Abstract: In this paper the viscosities, densities, and refractive indices of nine binary liquid systems containing n-alkane + isomers of hexane have been determined at 298.15 K. The viscosity values were fitted to the McAllister three-body model and the Redlich-Kister-type equation. The results with these models agree with experimental data with an average absolute deviation of less than 0.6%. The nine binary liquid systems studied were hexadecane with 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, and 2,3-dimethylbutane; dodecane with 2-methylpentane, 2,2-dimethylbutane, and 2,3-dimethylbutane; and tetradecane with 2-methylpentane and 2,3-dimethylbutane.
TL;DR: In this article, a procedure to determine total oil content of pecan was developed for samples weighing 500 and 10 mg by supercritical fluid extraction (SFE) with carbon dioxide as the extraction solvent, and chilled hexane as the trapping solvent.
Abstract: A procedure to determine total oil content of pecan was developed for samples weighing 500 and 10 mg by supercritical fluid extraction (SFE) with carbon dioxide as the extraction solvent, and chilled hexane as the trapping solvent. Fatty acid methyl esters (FAMEs) were prepared from the total lipid fraction by using either an aliquot (500 mg starting weight) or the entire extract (10 mg starting weight). Total oil content obtained for either sample size with SFE was similar to that obtained with an organic solvent extraction technique. The fatty acid composition for the total lipid fraction of oils extracted with SFE was the same as for oils extracted with organic solvents, and oil composition did not change during SFE. Both oil yield and fatty acid composition were similar to those reported previously for pecan. Samples could be extracted and placed into FAME-derivatizing reagents in one day, and fatty acid composition of the total lipid fraction could be determined by gas-liquid chromatography the next day. The procedure, as demonstrated for pecan, should be suitable for other oilseeds, especially those containing low amounts of water.
TL;DR: In this paper, a cottonseed processing mill with a 270 MT/day (300 tons/day) capacity agreed to test both isohexane and heptane with their expander-solvent process.
Abstract: Hexane has been used for decades to extract oil from cottonseed and is still the solvent of choice for the edible-oil industry. Due to increased regulations as a result of the 1990 Clean Air Act and potential health risks, the edible-oil extraction industry urgently needs an alternate hydrocarbon solvent to replace hexane. Based on laboratory-scale extraction tests, two hydrocarbon solvents, heptane and isohexane, were recommended as potential replacements for hexane. A cottonseed processing mill with a 270 MT/day (300 tons/day) capacity agreed to test both solvents with their expander-solvent process. Extraction efficiencies of isohexane and heptane, judged by extraction time and residual oil in meal, refined and bleached color of miscella refined oil, and solvent loss, were comparable to that of hexane. However, fewer problems were encountered with the lower-boiling isohexane than with the higher-boiling heptane. With isohexane, the daily throughput increased more than 20%, and natural gas consumption decreased more than 40% as compared to hexane.
TL;DR: In this article, a kinetic study of ethyl myristate formation by esterification of myristic acid with ethanol catalysed by a lipase from Mucor miehei immobilized on Duolite A 568, has been carried out.
Abstract: A kinetic study of ethyl myristate formation by esterification of myristic acid with ethanol catalysed by a lipase from Mucor miehei immobilized on Duolite A 568, has been carried out.The reaction was done in a two liquid phase system in which the non-aqueous solvent was supercritical carbon dioxide (P= 12.5 MPa, T = 323 K) or n-hexane (P = 0.1 MPa, T = 323K). In heteregenous catalysis, it is important to study the internal mass transfer limitation. For this, the support was sieved into different size series (from 300 to 600 mm) and the reaction was carried out for each size series. The samples were analyzed by gas chromatography and the esterification was shown to follow Ping Pong Bi Bi kinetics with competitive substrate inhibition. The Thiele modulus values show that there is, in the hexane case, a diffusional control while in SCCO2 media, we obtained an intermediate rate between reactional and diffusional rates.
TL;DR: In this paper, the solubility of coal tar pitches in several organic solvents and the semiquantitative gas chromatographic analysis of the corresponding volatile fraction extracts are discussed.
TL;DR: In this paper, the authors measured the rates and extents of extraction for three major constituents of peppermint oil, namely 1,8-cineole, menthone and menthol, using leaves of the black mint (Mentha x piperita L.).
Abstract: The rates and extents of extraction have been measured for three major constituents of peppermint oil, namely 1,8-cineole, menthone and menthol, using the leaves of the black mint (Mentha x piperita L.). The solvents used were hexane, ethanol and mixtures of composition 90mol% ethanol + 10mol% hexane and 90mol% hexane + 10 mol% ethanol. The extractions were carried out isothermally at 25, 35 and 45°C as well as in an electrically and mechanically modified domestic microwave oven where the temperature increase varied from c. 10 to 30°C. The rates of both isothermal and microwave extractions were sensitive to the solvent employed and decreased in the order 90mol% hexane > 90 mol% ethanol > hexane > ethanol. The rates of microwave extraction were also affected by the microwave power output and the size of the sample load. The activation energies for the extractions were in the range 30-90 kJ mol -1 , again dependent on the solvent used. Scanning electron microscopy on the spent leaves provided evidence of a link between the kinetics of extraction and structural changes on the glands.
TL;DR: In this paper, the dynamical structures are qualitatively estimated by dynamic light scattering and the rheological measurements for sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/water/nhexane/sodium chloride.
Abstract: The dynamical structures are qualitatively estimated by the dynamic light scattering and the rheological measurements for sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/water/n-hexane/sodium chloride...
TL;DR: In this article, photodeselenation of the corresponding 2,4,5,6-tetraselena-1,3-digermabicyclo[2.1.1]hexane, obtained by photodeselination of 2.4.5.
Abstract: 1,3-Bis[tris(trimethylsilyl)methyl]-2,4,5-triselena-1,3-digermabicyclo[1.1.1]pentane 4, obtained by photodeselenation of the corresponding 2,4,5,6-tetraselena-1,3-digermabicyclo[2.1.1]hexane, shows a short Ge ⋯ Ge distance of 2.672 A; an Se ⋯ Se interaction in 4 is observed by 77Se NMR, X-ray analysis and electronic spectroscopy.
TL;DR: Results indicate good correlation between neurotoxic potency in vivo and quantitative production of adducts in vitro with both n-hexane and n-heptane derivatives.
TL;DR: In this article, a series of 4 and 5-oxoaldehydes were synthesized, purified, and characterized by gas chromatography, Gas chromatography-mass spectrometry, gas chromalysis-Fourier transform infrared spectrometer, and nuclear magnetic resonance spectrometers.
Abstract: As part of our efforts to identify volatile decomposition products in used frying oils, a series of 4- and 5-oxoaldehydes were synthesized, purified, and characterized by gas chromatography, gas chromatography-mass spectrometry, gas chromatography-Fourier transform infrared spectrometry, and nuclear magnetic resonance spectrometry. Oxoaldehydes have been proposed as possible precursors of alkylfurans, which have potential anticancer effects. In a model reaction 4-oxononanal was refluxed in hexane for 40 days and only trace amounts of 2-pentylfwan were produced, suggesting that it is not a major precursor of the furan. The volatile constituents of used frying oils obtained from commercial food processors were studied, and 4-oxohexanal, 4-oxooctanal, 4-oxononanal, and 4-oxodecanal were identified
TL;DR: In this article, an extraction and purification method for the isolation of metalloporphyrins from a heavy crude oil is reported, which is extracted from a Boscan crude oil by a Soxhlet extraction method and monitored by UV-Vis and graphite furnace atomic absorption spectroscopies.
Abstract: An extraction and purification method for the isolation of metalloporphyrins from a heavy crude oil is reported. The metalloporphyrins are extracted from a Boscan crude oil by a Soxhlet extraction method and monitored by UV-Vis and graphite furnace atomic absorption (GFAA) spectroscopies. The first fraction is extracted with methanol and the second one with acetonitrile; both fractions are purified by adsorption chromatography using hexane benzene and dimethylformamide/benzene mixtures to isolate the metalloporphyrin species according to their polarities. HPLC fractionation and SEC molecular weight distribution techniques are combined to characterize these fractions.
TL;DR: In this article, a modified column chromatography procedure for heavy crude oils and tar sand bitumens was used to determine categories of porphyrins and other related metal-containing species.
Abstract: Product oils from the LLNL Hot-Recycled-Solids (HRS) retorting process were separated to isolate and concentrate the metallopetropor-phyrins. A modified column chromatography procedure developed previously for heavy crude oils and tar sand bitumens was used. The fractions were then examined by UV-vis spectroscopy to determine categories of porphyrins and other related metal-containing species. No porphyrins were found in the hexane fraction (least polar fraction); Ni porphyrins were found in the methylene chloride fraction (moderate polar fraction); and a free-base porphyrin-like species was found in the methanol fraction (the most polar fraction) of some of the oils. The CH2Cl2 fractions were further examined to quantify the amount of porphyrins detected. In the whole oil samples examined, ∼ 40 wt % of the Ni was found as Ni petroporphyrins. The vacuum residua of two product oils had ∼ 20 wt % of the Ni bound as Ni por-phyrins indicating that the vacuum distillation process destroys porphyrins.
TL;DR: In this paper, a direct current discharge operated in a working gas mixture of Ar/ n -hexane/H 2 O was used to characterize the discharge conditions, and the plasma polymer films were deposited on a model polymer surface to be modified for wettability.