共查询到20条相似文献,搜索用时 15 毫秒
1.
Lourdes Casas Casimiro Mantell Miguel Rodríguez Ascensión Torres Francisco A. Macías Enrique J. Martínez de la Ossa 《Journal of separation science》2009,32(9):1445-1453
The kinetics of the supercritical fluid extraction of bioactive compounds from sunflower using CO2 as solvent were studied in order to establish an efficient method for this extraction. The influence of time of extraction at different solvent flow rates was investigated. The extraction pressure and temperature were optimized in previous studies and these values used were 400 bar and 50°C. The extraction yields and the bioactivity levels of the extracts were also analysed. The results indicate that the most appropriate extraction time is between 120 and 180 min depending on the solvent flow and the pretreatment of the sample. The dried sample extracted at 40 g/min, the congealed sample extracted at the same flow and 180 min, and the dried sample extracted at 25 g/min for 120 min showed the best activity profiles. The extractions were carried out in a pilot plant with an extraction vessel with a capacity of 2 L. 相似文献
2.
The dependence of Mentha pulegium L. (pennyroyal) essential oil composition, obtained by supercritical carbon dioxide (SC-CO2), with the following parameters: pressure, temperature, extraction time (dynamic), and modifier (methanol) was studied. The results were also compared with those obtained by conventional hydrodistillation method in laboratory conditions. Regarding the percentages of menthone (30.3%) and pulegone (52.0%), the optimum SFE results were obtained at the following experimental conditions: pressure=100 atm, T=35 °C, dynamic time=10 min, and Vmodifier=0 μl. The results of hydrodistillation showed that the major components of M. pulegium L. were pulegone (37.8%), menthone (20.3%), and piperitenone (6.8%). The evaluation of the composition of each extract was performed by gas chromatography-mass spectrometry. 相似文献
3.
Dry ice-originated supercritical and liquid carbon dioxide extraction of organic pollutants from environmental samples 总被引:1,自引:0,他引:1
Packed in a high-pressure vessel and under calculated conditions, dry ice can be used as a source of carbon dioxide for supercritical CO2 extraction or liquid CO2 of organic compounds from environmental samples. Coupled with a fluid modifier such as toluene, dry ice-originated supercritical CO2 (Sc CO2) achieves quantitative extraction of many volatile organic compounds (VOCs) and semivolatile organic compounds (SOCs) including polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and polychlorinated biphenyls (PCBs) from solid matrices. Compared to contemporary manual or automated supercritical fluid extraction (SFE) technologies, this novel technique simplifies SFE to a minimum requirement by eliminating the need of a high-pressure pump and any electrical peripherals associated with it. This technique is highly suitable to analytical areas where sample preservation is essential but difficult in the sampling field, or where sample collection, sample preparation, and analysis are to be done in the field. 相似文献
4.
Takayuki Iijima 《Tetrahedron letters》2007,48(30):5309-5311
A comparative analysis of the reactions between sodium phenoxide and CO2 under the gaseous and supercritical conditions has demonstrated the preferential effect of supercritical conditions for promoting the reactivity of CO2. A significant increase in product yield was obtained in supercritical CO2 compared to reactions undertaken in gaseous CO2. 相似文献
5.
Capillary supercritical fluid chromatography has been directly coupled with supercritical fluid extraction using modified carbon dioxide. The mixed fluids were prepared with a single pump on-line mixing system. The most important step in the SFE-SFC interface was the elimination of the modifier solvent. This was achieved by use of a coupled trap, 0.1 mm i.d. and 0.53 mm i.d. capillary tubing connected in series, with the collected solutes refocused on the second (0.53 mm i.d.) trap before transfer into the separation column. This enabled complete elimination of various modifier solvents and high efficiency collection of the solutes. The effect of the modifier on trapping efficiency was investigated using methanol, ethanol, dichloromethane, hexane, and toluene at a variety of concentrations. n-Eicosane was, for example, trapped quantitatively by modified carbon dioxide containing up to 13 % (w/w) methanol. The use of the technique has been demonstrated by selective extraction of n-paraffins, fatty acid methyl esters, and alcohols from a silica matrix; the effect of different modifiers on the extraction of a mixture of pesticides from soil has also been investigated. 相似文献
6.
The distribution ratio (DM) of Pd(II) by the extraction with 2-methyl-8-quinolinol (HMQ) was determined using the supercritical carbon dioxide medium (SF-CO2) and organic solvent media such as perfluoro-methylcyclohexane, heptane, cyclohexane, carbon tetrachloride and benzene. From experimental results of the slopes of log DM versus pH plot and log DM versus HMQ concentration plot, the extracted species both in the SF-CO2 extraction (SFE) and the solvent extraction (SE) were determined to be Pd(MQ)2. The distribution constant of HMQ (KD,HMQ) in the SFE and SE systems were determined from the dependence of the distribution ratio of HMQ (DHMQ) on the pH. A linear relationship was observed between log KD,HMQ and the solubility parameter (δ) of the extraction medium based on the regular solution theory in both the SFE using SF-CO2 at the pressure of 8.5–40 MPa and the SE systems. The difference in the slope of the log KD,HMQ versus δ plot between the SFE and the SE systems is attributable to the extent of the specific interaction of the solute HMQ with the solvent molecules, i.e. CO2 molecules and the organic solvent molecules. The DM versus δ plot obtained under a given extraction condition using SF-CO2 (11–40 MPa) and organic solvents showed clear linearity. The DM obtained using SF-CO2 at relatively low pressure range from 8.5 to 11 MPa was independent of the pressure and the δ of SF-CO2, which coincides with the experimental fact that the solubility of Pd(MQ)2 in the SF-CO2 at 8.5–11 MPa was practically constant. 相似文献
7.
John M. Stubbs 《Fluid Phase Equilibria》2011,305(1):76-82
The partitioning of ethylbenzene between poly(ethylene glycol) (PEG) and supercritical carbon dioxide was studied at 308.15, 328.15 and 348.15 K and 10, 15.5 and 20 MPa with PEG-400, 600 and 900 using Monte Carlo molecular simulation. The effect of a cosolvent was also studied with either 5% ethane or 5% n-octane added. Ethylbenzene favored the supercritical phase most when the density was highest, and while ethane had little effect, the addition of n-octane increased the amount of solute dissolved in carbon dioxide. Increasing polymer molecular weight led to more solute in the PEG-rich phase. This coincides with a higher amount of dissolved carbon dioxide that preferentially solvates ethylbenzene. 相似文献
8.
Trofim I. Trofimov Maxim D. Samsonov Yurri M. Kulyako Boris F. Myasoedov 《Comptes Rendus Chimie》2004,7(12):443
Dissolution of individual actinide oxides (Th, U, Pu, Np), or their mechanical mixtures, as well as of solid solutions U–Pu, U–Np, U–Am and U-Pu-Eu oxides in supercritical fluid carbon dioxide (SF-CO2) containing the complex of tri-n-butyl phosphate (TBP) with nitric acid (TBP–HNO3) has been investigated. The effect of the calcination temperature of solid solutions of dioxides on the separation of actinides during supercritical fluid extraction (SFE) has been studied as well. It was shown for the first time that milligram amounts of uranium dioxide could be quantitatively dissolved in (SF-CO2) containing the TBP–HNO3 complex and efficiently separated from Pu, Np, and Th during SFE of mechanical mixture of these oxides. On the contrary, both U and Pu are quantitatively dissolved in SF-CO2–TBP–HNO3 during SFE from solid solutions of U–Pu dioxide. An increase of the calcination temperature of the mixed U(IV)–Pu(IV) dioxide from 850 to 1200 °C has no influence on the relative extraction yield of these actinides during SFE. To cite this article: T. Trofimov et al., C. R. Chimie 7 (2004).
Résumé
Dissolution d’oxides d'actinides et extraction d’éléments dans le dioxide de carbone supercritique contenant le complexe tri-n-butylphosphate–acide nitrique. La dissolution d’oxydes de Th, U, Pu et Np, de leurs mélanges et de solutions solides U–Pu, U–Np, U–Am et U–Pu–Eu dans le dioxyde de carbone supercritique (CO2-SC) contenant le complexe tri-n-butyl phosphate–acide nitrique (TBP–HNO3) a été étudiée, et notamment l’effet de la température de calcination des solutions solides. On montre que quelques milligrammes de UO2 peuvent être dissous dans le système CO2-SC–TBP–HNO3 et être séparés de Pu, Np et Th en traitant un mélange d’oxydes. En revanche, U et Pu sont dissous dans la phase CO2-SC–TBP–HNO3 durant le traitement des solutions solides U(IV)–Pu(IV). Une augmentation de la température de calcination de 850 à 1200 °C de ces solutions solides n’a pas d’effet sur le rendement d’extraction des actinides. Pour citer cet article : T. Trofimov et al., C. R. Chimie 7 (2004). 相似文献9.
Oxidative degradation of nylons was carried out using nitrogen dioxide (NO2) as the oxidizing agent and supercritical carbon dioxide (scCO2) as the reaction medium. Seven typical nylons were studied: three ring opening polymerization type nylons (nylon-6, -11 and -12) and four condensation co-polymerization type nylons (nylon-4/6; -6/6; -6/9 and -6/12). All the nylons decomposed in the NO2/scCO2 system under relatively mild conditions (140 °C, 1 h, and 10 MPa) and provided aliphatic α, ω-diacids such as succinic, glutaric and adipic acids in good yields. The product distribution of these α, ω-diacids strongly depended on the reaction conditions such as temperature, time and amount of NO2, but not on the total pressure. Furthermore, the proportions of the products were affected by the type of nylon. A mechanism is proposed and a detailed discussion regarding the degradation of nylon in the NO2/scCO2 system is provided. 相似文献
10.
Soyoung Kwon Kyoungwon Lee Hwayong Kim Youn-Woo Lee Won Bae 《Colloid and polymer science》2008,286(10):1181-1191
The free radical copolymerization of N-vinyl-2-pyrrolidone and 2-methylene-1,3-dioxepane was carried out in supercritical carbon dioxide (scCO2) using three kinds of dispersants and 2,2′-azobisisobutyronitrile as the initiator. Polymerization was performed with fluorinated
polymeric dispersants synthesized in scCO2 using the solution polymerization method and commercially available siloxane-based surfactant. Spherical biocompatible and
biodegradable polymeric particles were prepared within the sub-micron size range. The effect of various ratios of the comonomer,
reaction temperature, and concentration of initiator, in addition to the types and concentrations of the dispersants, on the
particle size and morphology was investigated. The particle size and particle size distribution of copolymer particles were
controlled using the above mentioned experimental parameters. Glass transition temperatures of copolymers were varied according
to the comonomer ratios used. 相似文献
11.
This work has been developed using a sylvestral fruit tree, native to the Brazilian forest, the Eugenia uniflora L., one of the Mirtaceae family. The main goal of the analytical study was focused on extraction methods themselves. The method development pointed to the Clevenger extraction as the best yield in relation to SFE and Soxhlet. The SFE method presented a good yield but showed a big amount of components in the final extract, demonstrating low selectivity. The essential oil extracted was analyzed by GC/FID showing a large range of polarity and boiling point compounds, where linalool, a widely used compound, was identified. Furthermore, an analytical solid phase extraction method was used to clean it up and obtain separated classes of compounds that were fractionated and studied by GC/FID and GC/MS. 相似文献
12.
Young Hae Choi Jinwoong Kim Min Jeong Noh Eun Sun Choi Ki-Pung Yoo 《Chromatographia》1998,47(1-2):93-97
Summary Solubilities in supercritical CO2 of coumarin, four monosubstituted coumarin derivatives (4-hydroxycoumarin, 7-hydroxycoumarin, 7-methoxycoumarin, and 7-methylcoumarin)
and four disubstituted derivatives, (6,7-dihydroxycoumarin, 7-hydroxycoumarin-4-acetic acid, 7-methoxycoumarin-4-acetic acid,
and 7-hydroxy-4-methylcoumarin) were measured in the temperature range 35–50 °C and the pressure range 8.5–25 MPa. In general,
the substituted coumarin derivatives were less soluble than simple coumarin. It was also found that substitution at the C-4
position of coumarin tended to reduce the solubility more than substitution at the C-7 position. These solubility data are
essential for the systematic application of SFE and SFC of coumarin derivatives from plant sources. 相似文献
13.
Polypropylene (PP) was compounded with β-nucleating agent and injection-molded at 180 °C or 220 °C. The samples were subsequently treated by supercritical carbon dioxide (scCO2) at different temperatures. Results show that processing temperature and scCO2 treatment could strongly influence the tensile and impact properties of β-nucleated PP. In particular, the sample processed at 220 °C and treated at 120 °C exhibit much enhanced impact strength (4.8 times that of its untreated counterpart). FTIR, WAXD, SEM and DMA were performed to explore the effects of processing temperature and scCO2 treatment on structure of the samples. Deformation-induced plastic flow and micro-voids were also evaluated to construct structure-property relations. It was found that the influence of processing temperature on mechanical properties is mainly associated with the β-form content and β-crystalline morphology, while the structural changes in the crystalline lamellar scale may be responsible for the toughening effect of scCO2 treatment. 相似文献
14.
Gholamhossein Sodeifian Seyed Ali Sajadian Bizhan Honarvar 《Natural product research》2018,32(7):795-803
Extraction of oil from Dracocephalum kotschyi Boiss seeds using supercritical carbon dioxide was designed using central composite design to evaluate the effect of various operating parameters including pressure, temperature, particle size and extraction time on the oil yield. Maximum extraction yield predicted from response surface method was 71.53% under the process conditions with pressure of 220 bar, temperature of 35 °C, particle diameter of 0.61 mm and extraction time of 130 min. Furthermore, broken and intact cells model was utilised to consider mass transfer kinetics of extracted natural materials. The results revealed that the model had a good agreement with the experimental data. The oil samples obtained via supercritical and solvent extraction methods were analysed by gas chromatography. The most abundant acid was linolenic acid. The results analysis showed that there was no significant difference between the fatty acid contents of the oils obtained by the supercritical and solvent extraction techniques. 相似文献
15.
In the present work,effect of theattr action terms of four recently modified Peng-Robinson(MPR)equations of state on the prediction of solubility of caffeine,cholesterol,uracil and erythromycin was studied.The attraction terms of two of these equations are linear relative to the acentric factor and for the other two are exponential.It is found that the later show less deviation.Also interaction parameters for the studied systems are obtained and the percentage of average absolute relative deviation(%AARD)in each calculation is displayed. 相似文献
16.
17.
Fernando M. Lanas Mrio S. Galhiane Sandra R. Rissato Marco A. Barbirato 《Journal of separation science》1997,20(7):369-374
Toxicity evaluation of Dicofol to Astyanax bimaculatus schubarti, a characteristic fish species living in tropical rivers and lakes was carried out through LC50 – 96 Hours. These experiments were performed under laboratory controlled conditions with atmospheric air flow and dilution water at 25°C in the static mode, supercritical fluid extraction (SFE) with pure CO2 and CO2 modified with hexane and methanol were used at 50, 70, 80, and 100°C and 300 atm. Several collection modes were studied to extract Dicofol from fish samples. The extraction efficiencies were directly comparedd with those obtained after 8 h of Soxhlet extraction using the same clean-up with Florisil and analysis by HRGC/ECD and HRGC/MS as a confirmatory analytical technique. The SFE recoveries at temperatures lower than 80°C were typically lower than soxhlet recoveries; however a temperature increase enhanced the efficiency of SFE. The results showed that under certain conditions, supercritical fluid gave higher extractio power (extracted 11 % more pesticide), shorter extraction time, and lower solvent consumption than Soxhlet, thus affording an excellent alternative to the conventional method for extracting Dicofol from fish sample. 相似文献
18.
Masashi Haruki Fumiya Kobayashi Kazuya Kishimoto Shin-ichi Kihara Shigeki Takishima 《Fluid Phase Equilibria》2009,280(1-2):49-55
A new apparatus based on the circulation method was developed to measure the solubility of metal complexes in supercritical carbon dioxide (scCO2) at a wide range of temperatures and pressures. A UV–vis spectrometer, which was connected to a small saturation cell through optical fibers, was used to determine solubility. The solubilities of cobalt(III) acetylacetonate (Co(acac)3) and chromium(III) acetylacetonate (Cr(acac)3) in scCO2 were measured to check the validity of both the apparatus and the method and to accumulate new solubility data. The solubility data for Cr(acac)3 obtained in this study were in good agreement with the data reported in the literature.The measured solubilities of Co(acac)3 and Cr(acac)3 were also correlated with the empirical equation including the three adjustable parameters, based on the equation proposed by Chrastil. The parameters were determined by fitting the equation to the experimental data for each metal complex and the calculated results closely replicated the experimental data. 相似文献
19.
Zhang Y Liu C Yu M Zhang Z Qi Y Wang J Wu G Li S Yu J Hu Y 《Journal of chromatography. A》2011,1218(20):2827-2834
Accelerated solvent extraction (ASE) coupled with high-performance counter-current chromatography (HPCCC) was successfully used for the extraction and online isolation of five chemical constituents from the plant Hypericum perforatum L. The upper phase of the solvent system of ethyl acetate-methanol-water (5:2:5, v:v:v) was used as both the ASE solvent and the HPCCC stationary phase. Two hydrophobic compounds including 28.4 mg of hyperforin with a HPLC purity of 97.28% and 32.7 mg of adhyperforin with a HPLC purity of 97.81% were isolated. The lower phase of ethyl acetate-methanol-n-butanol-water (5:2:2.5:12, v:v:v:v) was used as both the ASE solvent and CCC stationary phase. Three hydrophilic compounds of 12.7 mg of 3,4,5-O-tricaffeoylquinic acid with a HPLC purity of 98.82%, 15.2 mg of 1,3,5-O-tricaffeoylquinic acid with a HPLC purity of 99.46% and 42.5mg of 3-O-caffeoylquinic acid with a HPLC purity of 96.90%, were obtained in a one-step extraction-separation process with less than 3h from 10.02 g of raw material of H. perforatum. The targeted compounds isolated, collected and purified by HPCCC were analyzed by high performance liquid chromatography (HPLC), the chemical structures of all five compounds above mentioned were identified by UV, MS and NMR. 相似文献
20.
Ring-opening suspension polymerization of l-lactide in supercritical CO2 (scCO2) was investigated in the presence of different stabilizer architectures based on poly(dimethyl siloxanes) (PDMS). Two amphiphilic AB type block copolymers, a graft copolymer, and an ester-capped PDMS were selected to find their efficacy as stabilizers for the synthesis of poly(l-lactide) (PLLA) in scCO2. The stabilizer’s efficiency was analyzed in terms of the molecular weight, yield, and particle morphology of PLLA. The block copolymers, poly(dimethylsiloxane)-b-poly(acrylic acid) (PDMS-b-PAA) and poly(dimethylsiloxane)-b-poly(methacrylic acid) (PDMS-b-PMA) were found to be effective, leading to the formation of fine, discrete PLLA microparticles. On the other hand, the graft copolymer, poly(dimethylsiloxane-g-pyrrolidonecarboxylic acid) (PDMS-g-PCA) and acetylated PDMS (PDMS-OAc) failed to give an enough stabilization to the PLLA due to their short polymer-philic chains, resulting in hard agglomerates. 相似文献