Showing papers on "Hexane published in 2005"
TL;DR: The chemical compositions of the upper phases and the lower phases of 55 Arizona systems made with various alkanes (pentane, hexane, heptane, isooctane and cyclohexane) were determined by gas chromatography and Karl Fischer titration.
Abstract: Countercurrent chromatography (CCC) is a separation technique that uses a biphasic liquid system; one liquid phase is the mobile phase, the other liquid phase is the stationary phase. Selection of the appropriate liquid system can be a problem in CCC, since it is necessary to select both the “column” and the mobile phase at the same time as the first is completely dependent on the second. A range of systems with various proportions of solvents were developed to ease this choice; 23 variations of the heptane/ethyl acetate/methanol/water biphasic liquid system were labeled A to Z. This range proved to be extremely useful and became the popular Arizona (AZ) liquid system. However, authors often replace the heptane with hexane. In this work, the chemical compositions of the upper phases and the lower phases of 55 Arizona systems made with various alkanes (pentane, hexane, heptane, isooctane and cyclohexane) were determined by gas chromatography and Karl Fischer titration. The test mixture separated consisted of five steroid compounds. The lower phases were found to have similar compositions when different alkanes were used, but the upper phases were found to change. Exchanging heptane for hexane or isooctane produced minimal changes in the CCC chromatogram, while changing the proportions of the solvents resulted in an exponential change in the retention volumes. The high density of cyclohexane made liquid stationary phase retention difficult. All Arizona systems equilibrated within 30 min, but were not stable: water slowly hydrolyzed the ethyl acetate (as shown by a continuous decrease in the pH of the lower aqueous phase), especially in the water-rich systems (early alphabet letters).
129 citations
TL;DR: In this paper, the authors aimed at screening solvent systems of varying polarities to identify suitable solvents for efficient and practical enzymatic glycerolysis, and found that the tertiary alcohols tert-butanol and tert-pentanol were the only pure solvers suitable for a fast reaction with an acceptably high formation of MAG.
Abstract: This study was aimed at screening solvent systems of varying polarities to identify suitable solvents for efficient and practical enzymatic glycerolysis. Several pure solvents and solvent mixtures were screened in a batch reaction system consisting of glycerol, sunflower oil, and Novozym® 435 lipase. Out of 13 solvents tested, tert-butanol and tert-pentanol were the only pure solvents suitable for a fast glycerolysis reaction with an acceptably high formation of MAG. In these systems, MAG contents of 68–82% were achieved within a few hours. Mixtures of tert-butanol/hexane, tert-pentanol/hexane, and tert-butanol/tert-pentanol in varying ratios also gave high MAG contents (58–78%). The tertiary alcohols tert-butanol and tert-pentanol, or mixtures of one of them with hexane, seemed to be the best choice among the solvents tested with respect to reaction efficiency, practical industrial applications, and steric hydroxyl group hindrance, which suppresses the ester formation with FA.
106 citations
TL;DR: In this article, a single-step sol-gel method was used for the determination of the Bronsted acid sites/Lewis acid sites ratio, determination of specific surface area (BET method), average pore diameter (BJH method), and catalytic activity in the n-hexane isomerization reaction.
Abstract: Sulfated TiO 2 was prepared by a single-step sol–gel method, in which the hydrolysis and sulfation occur in the same step, varying some conditions of the preparation method. The characterization was carried out by thermogravimetric analysis, infrared absorption spectroscopy, Raman spectroscopy, pyridine adsorption infrared spectroscopy for the determination of the Bronsted acid sites/Lewis acid sites ratio, determination of the specific surface area (BET method), average pore diameter (BJH method) and catalytic activity in the n -hexane isomerization reaction. In the infrared spectra it was verified that the sulfate is coordinated to the titanium in a chelate form, while in the Raman spectra it was observed that the samples are in an anatase crystalline form. Catalytic tests of the n -hexane conversion at 100 and 200 °C were carried out. At 100 °C, it was observed that the selectivity for isomerization and catalytic stability are higher than at 200 °C, however, at 100 °C the conversion is lower than at 200 °C. Among the structural and textural properties investigated, it was found that the samples which had greater average pore diameters and a higher Bronsted acid sites/Lewis acid sites ratio were the ones which showed greater catalytic activity.
95 citations
TL;DR: Sorption equilibrium and kinetics of hexane isomers were studied in commercial pellets of zeolite BETA in the form HBEA with a Si/Al ratio of 150, between temperatures of 423 and 523 K and partial pressures up to 0.3 bar as mentioned in this paper.
89 citations
TL;DR: In this article, d-Limonene, a safe agricultural byproduct, was used to extract rice bran oil and compared against hexane, a petroleum product widely used as a solvent for extracting edible oil.
Abstract: d-Limonene, a safe agricultural by-product, was used to extract rice bran oil and compared against hexane, a petroleum product widely used as a solvent for extracting edible oil. The yield of crude rice bran oils extracted with both solvents in percentage by weight was obtained. The quality of crude rice bran oil was analyzed. The yield and quality of crude rice bran oil from the limonene-based solvent extraction were almost equivalent to those from the hexane-based operation. The optimum solvent-to-rice bran ratio and extraction time required for d-limonene extraction of oil, based primarily on crude rice bran oil yield, have been determined to be 5:1 and 0.5 hr, respectively. Despite the absence of antioxidants during the limonene recovery step with vacuum evaporation, the quantity of the oxidation products in the recovered limonene was <1% (wt) of the original limonene solvent. The application of d-limonene solvent as an alternative to hexane in edible oil extraction could potentially eliminat...
81 citations
TL;DR: Comparison with Soxhlet and hot hexane extractions showed that the percentages of FAMEs are similar in all the extracts and they agree with the data in the bibliography.
80 citations
TL;DR: In this article, the authors extract oil and tocopherols from almond seeds using supercritical carbon dioxide and compare this extraction with a traditional solvent method using a 10-l vessel.
Abstract: The objective of this study was to extract oil and tocopherols from almond seeds using supercritical carbon dioxide and to compare this extraction with a traditional solvent method. Oil and tocopherol extraction rates were determined as functions of the pressure (350-550 bar), temperature (35-50 ◦ C) and CO2 flow rate (10-30 kg h −1 ), using a 10-l vessel. The effects of matrix particle size on extraction yield were also studied and it was demonstrated that extraction yield is greatly influenced by particle size. Maximum recovery was obtained in the first 2-3 h of extraction at a pressure of 420 bar, a temperature of 50 ◦ C and a flow rate of 30 kg h −1 CO2. These results suggest that the elevated initial oil and tochopherol solubility is related to the increased proportion of fatty acids in the initial extract. The results were compared with those obtained when hexane/methanol was used as a solvent. 2005 Society of Chemical Industry
74 citations
TL;DR: In this article, a response surface methodology was used to determine the effects of solvent flow rate (2, 3 and 4 g/min), pressure, pressure and temperature on apricot kernel oil in supercritical carbon dioxide.
Abstract: Response surface methodology was used to determine the effects of solvent flow rate (2, 3 and 4 g/min), pressure (30, 375 and 45 MPa), temperature (40, 50 and 60 °C), and co-solvent concentration (0, 15 and 3 wt% ethanol) on oil yield of apricot (Prunus armeniaca L) kernel oil in supercritical carbon dioxide (SC-CO2) All the parameters had significant effects on oil yield as well as the interactions between solvent flow rate and pressure, and between pressure and temperature Oil yield increased with increased parameters The oil yield was represented by a second-degree polynomial equation The maximum oil yield from the response surface equation was obtained as 026 g/g kernel for 15 min extraction of 5 g apricot kernel particles (particle diameter<0850 mm) with 4 g/min solvent flow rate containing 3 wt% ethanol at 45 MPa and 60oC The response surface equation predicted the experimental oil yield with a 10% error The fatty acid compositions of apricot kernel oils extracted with SC-CO2 and hexane were similar
68 citations
TL;DR: In this article, the authors studied the degumming of soybean oil using an ultrafiltration membrane prepared from polyethersulphone (PES) and showed that up to 89% of the phospholipids were removed when the miscella was ultrafiltered.
61 citations
TL;DR: In this article, the authors used configurational-bias Monte Carlo (CBMC) simulations to determine the sorption isotherms for hexane isomers (n -hexane, 2-methylpentane and 2,2-dimethylbutane) in MOR zeolite.
59 citations
TL;DR: In this paper, X-ray diffraction (XRD) and inverse gas chromatography (IGC) were used to characterize parent and exchanged zeolites for hexane oxidation.
Abstract: Hexane deep oxidation was studied over NaX and CaA zeolites modified by ion exchange with transition metals (Mn2+, Co2+, Fe3+), the percentage of ion exchanged, determined by ICP-MS, varying between 39 and 98%. Parent and exchanged zeolites were characterized by X-ray diffraction (XRD), N2 physisorption, temperature-programmed reduction (TPR), oxygen and ammonia temperature-programmed desorption (TPD) and inverse gas chromatography (IGC). Catalytic activities were evaluated through the recording of light-off curves in a pulsed microreactor, catalytic activity being correlated with physicochemical properties of the solids (crystallinity, surface acidity, adsorption properties and morphological parameters). As general trend, CaA zeolites are more active than NaX zeolites. Mn-exchanged CaA zeolite was the most active catalyst for hexane oxidation, whereas the addition of Fe to the zeolites leads to strong chemical and morphological changes in the parent zeolite.
TL;DR: In this article, the reaction of (dpp-bian)Na(Et2O) with one equiv. of iPrMgCl in hexane and Et2O was characterized by elemental analysis, UV/Vis and NMR spectroscopy, as well as by single-crystal X-ray diffraction.
Abstract: The reaction of (dpp-bian)Na(Et2O) with one equiv. of iPrMgCl in hexane affords (dpp-bian)Mg-iPr(Et2O) (1) whereas (dpp-bian)Mg(Et2O)2 (2) is formed when this reaction is carried out in Et2O as a result of isopropyl radical elimination. Compound 1 which is stable in hexane and Et2O also decomposes in THF with elimination of isopropyl radicals yielding (dpp-bian)Mg(THF)2. The reaction of (dpp-bian)Na2(Et2O)3 with two equiv. of iPrMgCl in Et2O produces 2 and iPr2Mg, which then interact to give (dpp-bian)(Mg-iPr)2(Et2O) (3) when treated with hexane or toluene. Compounds 1–3 were characterized by elemental analysis, UV/Vis and NMR spectroscopy, as well as by single-crystal X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
TL;DR: In this paper, the authors analyzed the properties of the DMC + hexane, heptane, and chlorobenzene binary mixture and found that the excess molar volumes for these three binary systems were positive over the whole composition range at all temperatures.
Abstract: Densities and viscosities for the dimethyl carbonate (DMC) + (hexane, heptane, chlorobenzene) binary systems have been experimentally determined from (293.15 to 353.15) K and at normal atmospheric pressure over the entire mole fraction range. Other mixing properties of interest such as the excess molar volumes and the viscosity deviations have also been obtained for each of the systems. The obtained properties have been compared with those reported by other authors in the literature and have been analyzed in terms of the molecular interactions present in this kind of mixture. The excess molar volumes for these three binary systems were positive over the whole composition range at all temperatures. On the contrary, the deviations of viscosity for DMC + hexane and DMC + heptane are negative, and those for DMC + chlorobenzene are very small.
TL;DR: With this model system, it is shown that the enzyme enantioselective properties are under the control of the amount of water present in the organic media, which is similar to the aqueous simulation at 5-10% of water content.
TL;DR: In this article, a resistance-in-series model has been adapted to deal with a conventional solvent or a non-conventional solvent in subcritical conditions, and two kinds of applications have been chosen to test its validity: extraction of ethanol or acetone from an aqueous solution by subcritical carbon dioxide or propane in a single-fiber module, and extraction of sulfur aroma compounds by hexane.
Abstract: This work focuses on the modeling of solvent-extraction processes carried out in a hollow-fiber membrane contactor (HFC). A resistance-in-series model has been adapted to deal with a conventional solvent or a nonconventional solvent in subcritical conditions. Two kinds of applications have been chosen to test its validity: extraction of ethanol or acetone from an aqueous solution by subcritical carbon dioxide or propane in a single-fiber module, and extraction of sulfur aroma compounds by hexane. Modifications in membrane characteristics and operating parameters have been investigated to determine optimal conditions. Simulations carried out with carbon dioxide have shown that the resistance in the solvent boundary layer is always negligible, whereas, in the case of hexane, the resistance in the aqueous boundary layer is always predominant. For the application with subcritical carbon dioxide, optimal values of feed and solvent velocities have been obtained. These thresholds correspond to the point where the resistance in the membrane becomes predominant. © 2005 American Institute of Chemical Engineers AIChE J, 2005
TL;DR: In this article, the authors investigated the production of fatty acid ethyl esters (FAEEs) from soybean oil using n-hexane as solvent and two commercial lipases as catalysts, Novozym 435 and Lipozyme IM.
Abstract: This work investigated the production of fatty acid ethyl esters (FAEEs) from soybean oil using n-hexane as solvent and two commercial lipases as catalysts, Novozym 435 and Lipozyme IM. A Taguchi experimental design was adopted considering the variables temperature (35–65°C), addition of water (0–10 wt/wt%), enzyme (5–20 wt/wt%) concentration, and oil-to-ethanol molar ratio (1:3–1:10). It is shown that complete conversion in FAEE is achieved for some experimental conditions. The effects of process variables on reaction conversion and kinetics of the enzymatic reactions are presented for all experimental conditions investigated in the factorial design.
TL;DR: In this paper, the textural characterization of MCM-41 has been employed and converged with nitrogen adsorption results in the case of n -hexane and 1-hexene.
TL;DR: Lipase-catalyzed kinetic resolution of various 1-arylethanols was performed in supercritical carbon dioxide (scCO2), in hexane and without solvent.
Abstract: Lipase-catalyzed kinetic resolution of various 1-arylethanols was performed in supercritical carbon dioxide (scCO2), in hexane and without solvent. The use of scCO2 enhances reactivity especially w...
Journal Article•
TL;DR: In this paper, a twin inhibition was observed for the esterification reaction between ethanol and isovaleric acid using immobilized lipase from Rluzomucor miehei in hexane and in mixed solvent system.
Abstract: A twin inhibition is observed for the esterification reaction between ethanol and isovaleric acid using immobilized lipase from Rluzomucor miehei in hexane and in mixed solvent system. The observed bi-substrate inhibitionpattern follows a Ping-Pong Bi-Bi mechanism with dead-end inhibition of enzyme by both the substrates. An increase in K m value for alcohol in mixed solvent (0.645 M) than in hexane (0.256 M), indicates that the enhanced salvation of ethanol in mixed solvent results in lower degree of inhibition.
TL;DR: In this paper, the retention times for these test solutes were determined and Flory-Huggins parameters were calculated and values of these physico-chemical parameters characterizing the examined materials were arranged in a matrix form.
TL;DR: A fast, efficient and reproducible recovery procedure for periplasmic l-asparaginase from two distinctly related gram-negative bacteria, Enterobacter aerogenesand Pseudomonas aeruginosa, is presented and it is shown that they possess different permeability characteristics.
TL;DR: The aim of this work is to define more precisely the interactions between oil contaminant and water, i.e. the influence of the intensity of interaction between the oil contaminants and water on its chemical composition.
Abstract: In oil spill investigations, one of the most important steps is a proper choice of approaches that imply an investigation of samples taken from different sedimentary environments, samples of oil contaminants taken in different periods of time and samples taken at different distances from the oil spill. In all these cases, conclusion on the influence of the environment, microorganisms or migration on the oil contaminants' composition can be drawn from the comparison of chemical compositions of the investigated contaminants. However, in case of water contaminants, it is very important to define which part of organic matter has been analyzed. Namely, previous investigations showed that there were some differences in chemical composition of the same oil contaminant depending on the intensity of its contact with ground water. The aim of this work is to define more precisely the interactions between oil contaminant and water, i.e. the influence of the intensity of interaction between the oil contaminant and water on its chemical composition. The study was based on a comparison of four fractionated extracts of an oil pollutant, after they had been analyzed in details. Oil polluted surface water (wastewater canal, Pancevo, Serbia) was investigated. The study was based on a comparison of four extracts of an oil contaminant: extract 1 (decanted part), and extracts 2, 3 and 4 (extracted by shaking for 1 minute, 5 minutes and 24 hours, respectively). The fractionated extracts were saponified with a solution of KOH in methanol, and neutralized with 10% hydrochloric acid. The products were dissolved in a mixture of dichloromethane and hexane, and individually fractionated by column chromatography on alumina and silica gel (saturated hydrocarbon, aromatic, alcohol and fatty acid fractions). n-Alkanes and isoprenoid aliphatic alkanes, polycyclic alkanes of sterane and triterpane types, alcohols and fatty acids were analyzed using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). δ13CPDB values of individual n-alkanes in the aliphatic fractions were determined using gas chromatography-isotope ratio monitoring-mass spectrometry (GC-irmMS). and discussion. Extracts 1 and 2 are characterized by uniform distribution of n-alkanes, whereas extract 3 is characterized by an even-numbered members dominating the odd-ones, and extract 4 showed a bimodal distribution. Extract 1 is characterized by the least negative δ13CPDB values of C19-C26 n-alkanes. Sterane and triterpane analysis confirmed that all extracts originated from the same oil contaminant. n-Fatty acids, C19-C24, in all extracts are very low, being somewhat higher in extract 4. Even-numbered n-alcohols, C12–C16, were identified in the highest concentration in extract 3. It was assumed that algae were responsible for the composition of extract 3. Furthermore, a possible reason for higher concentrations of C19–C26 n-alkanes and C19–C24 fatty acids in extract 4 is the formation of inclusion compounds with colloidal micelles formed between the oil contaminant's NSO-compounds and water. It was undoubtedly confirmed that there were specific differences in the compositions of the different extracts depending on the intensity of the interaction between the oil contaminant and the surface water.
Recommendation and Outlook. When comparing the composition of oil contaminants from different water samples (regardless of the ultimate investigation goal) it is necessary to compare the extracts isolated under the same conditions, in other words, extracts that were in the same or very similar interaction with water.
TL;DR: In this article, the performance of ultrasonic and Soxhlet extraction using hexane, dichloromethane, ethylacetate/methyl-tert-butylether (1/3, v/v) and hexane/acetone (1 /1, v /v) for the analysis of seventeen insecticides in sediments was evaluated.
Abstract: The performance of ultrasonic and Soxhlet extraction using hexane, dichloromethane, ethylacetate/methyl-tert-butylether (1/3, v/v) and hexane/acetone (1/1, v/v) for the analysis of seventeen insecticides in sediments was evaluated. The contents of the extracts differed severely. The extracts obtained with ethylacetate/methyl-tert-butylether (1/3, v/v) and hexane/acetone (1/1, v/v) were dark yellow to green, whereas the extracts obtained with dichloromethane and hexane were light yellow and clear respectively. This is due to higher solubility of matrix compounds in ethylacetate/methyl-tert-butylether (1/3, v/v) and hexane/acetone (1/1, v/v). High loads of coextracted matrix compounds lead to matrix effects in the evaporation step of GC–MS measurements. This is known as matrix induced response enhancement effect. Matrix effects and recoveries were checked by analysis of spiked sediments. The suitable choice of extraction method in connection with an appropriate solvent separates the analytes from matrix compounds. Matrix effects are reduced and recoveries of spiked samples are improved.
TL;DR: In this paper, the luminescence quenching of Ru( byp ) 3 2 + as a means of monitoring oxygen in hexane at room temperature has been examined and compared with typical sol-gel materials.
TL;DR: In this paper, the authors studied the behavior of several organic and inorganic membranes in the presence of organic solvents (hexane) for their application in edible oil processing, and found that hexane flux was higher through pretreated polyethersulfone (PES) membranes than through ceramic membranes with higher MWCO.
TL;DR: In this paper, the solubility of tritolylamine (TTA) in 12 solvents (hexane, heptane, n-octane, decane, hexadecane, toluene, benzene, 2propanol, propanol, 2-butanone, methanol, and ethanol) was measured gravimetrically and compared with the predictions obtained from the ideal solution and UNIQUAC equations.
Abstract: The solubility of tritolylamine (TTA) in 12 solvents (hexane, heptane, n-octane, decane, hexadecane, toluene, benzene, 2-propanol, propanol, 2-butanone, methanol, and ethanol) was measured gravimetrically and compared with the predictions obtained from the ideal solution and UNIQUAC equations. To use the UNIQUAC equation, the specific heat and heat of fusion of TTA were measured by differential scanning calorimetry (DSC). DSC results also indicated that TTA does not have any enantiotropically related polymorphs. It is shown that the UNIQUAC predictions are close to the measured solubility values. In addition, measurement of the solubility of TTA in hexane was performed by an on-line density meter. The results compared closely with those obtained with the gravimetric method. The solvents were chosen so that their polarity indexes cover a wide range.
TL;DR: The estimated finding by solubility parameters was supported by the results of soxhlet extraction and these solvents can be used to extract alpha-endosulfan, Endrin and HCB with the reliable recoveries.
TL;DR: The mean lifetimes of polyyne C 8 H 2 in hexane were determined at 50, 60, 80, and 100°C and in methanol at 60°C as mentioned in this paper.
TL;DR: In this paper, the solubility of oleic acid, linoleic acid and soybean oil were determined in supercritical carbon dioxide and in super critical carbon dioxide containing added hexane (10% v/v) at eight different pressures and at each of four different temperatures (35, 40, 45 and 50C).
Abstract: The solubilities of oleic acid, linoleic acid and soybean oil were determined in supercritical carbon dioxide and in supercritical carbon dioxide containing added hexane (10% v/v) at eight different pressures (136–372 atm) and at each of four different temperatures (35, 40, 45 and 50C). An ISCO supercritical fluid extraction system was used to determine the solubility of selected components of crude soybean oil; triacylglycerols, oleic acid and linoleic acid. An increase in density increased the solubility for all three components up to ~306 atm and 45C. The solubility for oleic acid was 2.10 ± 0.32 mg/mL (averaged over the entire range of conditions); for soybean oil, 1.40 ± 0.29 mg/mL; and for linoleic acid, 0.93 ± 0.26 mg/mL of supercritical fluid. On average, adding 10% hexane as a cosolvent to the supercritical carbon dioxide increased component solubility by ~40% at 35C and ~240% at 50C.
TL;DR: Effects of pore diameter of zeolites and ordering of molecules inside zeolite channels on the sorption energy of hexane are discussed.
Abstract: Sorption of n-hexane on monodimensional pure silica SSZ-35, CIT-5, ZSM-12, and ZSM-22 zeolites with different pore dimension and on recently synthesized ITQ-29 was studied by IR spectroscopic and computational chemistry methods. Heats of sorption of n-hexane on these zeolites was determined experimentally from the temperature dependence of the intensity of IR bands of sorbed hexane as well as from theoretical calculations. Calculations have shown the different orientations of sorbed hexane molecules inside zeolite channels, which depend on the type of zeolite and loading. At high loadings, ordering of hexane inside the channels is observed due to optimization of sorbate-sorbate and sorbate-zeolite interaction energies. Such ordering is responsible for the increase of the sorption energy. A decrease of the sorption energy upon increasing the pore dimension of zeolite was observed, in agreement with results previously published in the literature. Effects of pore diameter of zeolites and ordering of molecules inside zeolite channels on the sorption energy of hexane are discussed.