共查询到20条相似文献,搜索用时 15 毫秒
1.
《The Journal of Supercritical Fluids》2007,39(3):312-318
The solubilities of caffeine in supercritical CO2, supercritical CO2 + water, supercritical CO2 + ethanol, and supercritical CO2 + water + ethanol were measured with a circulation-type apparatus combined with an on-line Fourier transform infrared (FT-IR) spectrometer at 313.2 K and 15.0 MPa. The solubilities of caffeine were determined with the peak absorbances of caffeine at 1190 cm−1. The solubilities of caffeine increase until water is saturated in supercritical CO2. The maximum increase rate is 22%. In CO2 + caffeine + ethanol system, the solubilities of caffeine increase with increasing the concentration of ethanol. The solubility of caffeine becomes five times when 1000 mol m−3 of ethanol is added. In CO2 + caffeine + water + ethanol system, the solubilities of caffeine are smaller than those with single entrainer of water or ethanol. The shape of the peaks of two CO stretching bands for caffeine were changed by the addition of ethanol. It was confirmed that the interaction species of caffeine interacting with ethanol are produced by deconvolution of the CO stretching bands. The enhancement of solubility for caffeine in supercritical CO2 by the addition of ethanol is due to the hydrogen bonding between caffeine and ethanol. 相似文献
2.
Essential oil was extracted from yarrow flowers (Achillea millefolium) with supercritical CO2 at pressure of 10 MPa and temperatures of 40–60 °C, and its composition and yield were compared with those of hydrodistillate. The yield of total extract, measured in dependence on extraction time, was affected by extraction temperature but not by particle size of ground flowers. CO2-extraction of cuticular waxes was lowest at 60 °C. Major essential oil components were camphor (26.4% in extract, 38.4% in distillate), 1,8-cineole (9.6% in extract, 16.2% in distillate), bornyl acetate (16.7% in extract, 4.3% in distillate), γ-terpinene (9.0% in extract, 9.4% in distillate), and terpinolene (7.6% in extract, 3.9% in distillate). Compared to hydrodistillation, the yield of monoterpenes was lower due to their incomplete separation from gaseous CO2 in trap but the yield of less volatile components like monoterpene acetates and sesquiterpenes was higher. Hydrolysis of γ-terpinene and terpinolene, occuring in hydrodistillation, was suppressed in supercritical extraction, particularly at extraction temperature of 40 °C. 相似文献
3.
A new industrial process for extracting cocoa butter and xanthines with supercritical carbon dioxide
This research explores the feasibility of extracting cocoa butter and xanthines (theobromine and caffeine) from cocoa beans
with supercritical CO2. It is difficult to carry out the extraction with CO2 alone in the temperature range 40–90°C at pressures between 80 to 300 bar. However, the addition of a polar cosolvent, such
as ethanol, greatly enhances solubilities, especially that of cocoa butter. Based on experimental investigations and theoretical
inference, the design of a potential industrial process for extracting cocoa butter and xanthines is proposed, in which ethanol
is used as cosolvent, and distillation is used to separate and regenerate ethanol. The pressure required is much less than
that for CO2 alone as specified in the patent literature. 相似文献
4.
Kiyoshi Matsuyama Kenji Mishima Ken‐Ichiro Hayashi Hideharu Ishikawa Hideto Matsuyama Toru Harada 《应用聚合物科学杂志》2003,89(3):742-752
The rapid expansion from a supercritical solution with a nonsolvent (RESS‐N) was applied to the formation of polymeric microcapsules containing medicines such as p‐acetamidophenol, acetylsalicylic acid, 1,3‐dimethylxanthine, flavone, and 3‐hydroxyflavone. A suspension of medicine in carbon dioxide (CO2) containing a cosolvent and dissolved polymer was sprayed through a nozzle to atmospheric pressure. The pre‐expansion pressure was 10–25 MPa, and the temperature was 308–333 K. The polymers were poly(L ‐lactic acid) (molecular weight = 5000), poly(ethylene glycol) (PEG; PEG4000, molecular weight = 3000; PEG6000, molecular weight = 7500; and PEG20000, molecular weight = 20,000), poly(methyl methacrylate) (molecular weight = 15,000), ethyl cellulose (molecular weight = 5000), and PEG–poly(propylene glycol)–PEG triblock copolymer (molecular weight = 13,000). The solubilities of the polymers as coating materials and these medicines as core substance were very low in CO2. However, the solubilities of these polymers in CO2 significantly increased with the addition of low molecular weight alcohols as cosolvents. After RESS‐N, polymeric microcapsules were formed according to the precipitation of the polymer caused by a decrease in the solvent power of CO2. This method offered three advantages: (1) enough of the coating polymers, which were insoluble in pure CO2, dissolved; (2) the microparticles of the medicine were encapsulated without adhesion between the particles because a nonsolvent was used as a cosolvent and the cosolvent remaining in the mixture was removed by the gasification of CO2; and (3) the polymer‐coating thickness was controlled with changes in the feed composition of the polymer for drug delivery. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 742–752, 2003 相似文献
5.
Supercritical fluid extraction of volatile oil from Lippia alba (Mill.) cultivated in Aragón (Spain)
The objective of this study is the supercritical extraction of the volatile oil from Lippia alba (Mill.) cultivated in Aragón. The influence of extraction pressure and temperature and cosolvent percentage on overall yield and volatile oil composition was studied. The supercritical extraction conditions were optimized using the 2007 crop; operating at 35.0 MPa, 40 °C and 5% of ethanol as cosolvent, 2009 and 2011 crops were also tested. Supercritical fluid extract compositions and overall yields were compared with the extracts obtained by conventional extraction techniques such as hydrodistillation (HD) and organic solvent extraction (OSE). Four terpenoids (linalool, 1,8-cineole, β-caryophyllene and β-caryophyllene oxide) were selected as target compounds and their content in the different extracts was monitored by gas chromatography. Linalool was selected as indicator of the plant adaptation to the commercial purposes. HD is the technique that provides the highest percentage of linalool in all the extracts, but showed always the lowest overall yields; whereas, SFE extracts provides a good balance between the overall yield and presence of the four target compounds. 相似文献
6.
This study highlights the possibility of supercritical carbon dioxide for extracting phenolic compounds from bamboo leaves that have shown antioxidant and anticancer activities. The CO2 extraction solvent was modified by adding ethanol–water mixture cosolvent of different concentrations to allow extraction of both polar and non-polar compounds. Conventional Soxhlet extraction was also done to investigate the advantages of supercritical extraction over the conventional extraction method. For addition of 5% (mol) of a 25:75 (mol:mol) ethanol–water mixture solvent to CO2, the highest amount of polyphenols (7.31 ± 0.06 mg/g bamboo leaves in catechin equivalents) and radical scavenging activity (3.65 ± 0.05 mg/g bamboo leaves in BHA equivalents) at 20 MPa and 95 °C, could be obtained among the mixture cosolvents studied. For Soxhlet extraction with a 25:75 (mol:mol) ethanol–water mixture, 1.48 times the amount of phenolic compounds (10.85 ± 0.52 mg/g bamboo leaves in catechin equivalents), could be isolated compared with the supercritical extraction method, however, the radical scavenging activity (3.30 ± 0.05 mg/g bamboo leaves in BHA equivalents) was 0.90 times lower than the extract obtained from the supercritical extraction method. The seven major antioxidative compounds identified from the SC-CO2 extraction method were: (1) dl-alanine, (2) gluconic acid, (3) phosphoric acid, (4) ß-siosterol, (5) β-amyrene, (6) α-amyrin acetate and (7) friedelin. 相似文献
7.
X.-H. Lu Q.-H. Xia D. Zhou S.-Y. Fang A.-L. Chen Y.-L. Dong 《Catalysis communications》2009,11(2):106-109
Catalytic selective epoxidation of mixed biolefins with air over nanosized Co3O4 catalyst under mild ultrasonic conditions has been first reported. When the styrene/α-pinene molar ratio was 1:5, the highest conversions were, respectively, reached 81.8 mol% for styrene and 76.1 mol% for α-pinene, with the epoxidation selectivity of 84.1% (styrene oxide) and 94.6% (α-pinene oxide), notably higher than those of the conventional reactions under magnetic stirring. An intermolecular electron-transfer phenomenon between conjugated styrene and electron-rich α-pinene was revealed by UV–vis spectra, which was considerably important for the enhancement of reactivities of both olefinic molecules observed experimentally. 相似文献
8.
S. Dowy A. Braeuer K. Reinhold-Lpez A. Leipertz 《The Journal of Supercritical Fluids》2009,50(3):265-275
Laser based Raman and elastic light scattering measurements were performed to study the process of mixture formation and the influence of the solute paracetamol onto the phase behaviour of the pseudo-binary system ethanol/CO2 in the supercritical antisolvent process. From the Raman based technique, mole fraction and partial density distributions of CO2 were obtained. The mole fraction distributions indicate a rapid mixture formation with fast supersaturation of the solute. At the same time, the increase of the CO2 partial density at conditions considerably above the mixture critical point (MCP) indicate a change from a homogeneous supercritical to a multi-phase subcritical flow. This phase change goes along with particle precipitation. Thus, the results of our investigations proof, why past approaches failed to generate amorphous paracetamol nanoparticles with the system paracetamol/ethanol/CO2 above the MCP. Process parameters like injection pressure (20.0–35.0 MPa), chamber pressure of CO2 (7.5–17.5 MPa), temperature (313–333 K) and solute concentration (0–5 wt%) were varied. 相似文献
9.
Using a specially created experimental setup, the crossover character of a change in solubility is determined, and the approximate pressure at the upper crossover point is found (≈19 MPa). The modification of carbon dioxide with chloroform is shown to increase its solubility by 2–2.5 times on average within the above range of conditions. The supercritical CO2 fluid extraction (SCFE) process is studied as it applies to the regeneration of LD-265 alumopalladium hydrogenation catalyst. Dimethylsulfoxide and ethanol are selected as cosolvents (modifiers). Maximum regeneration efficiency is established at a 5.5–6.5 wt % concentration of cosolvents, and dimethylsulfoxide proves to be a more efficient cosolvent than ethanol. The diene and bromine numbers and styrene and methylcyclopentadiene conversions obtained on catalysts regenerated via SCFE satisfy the requirements for catalytic systems used in the selective hydrogenation of dienes in a benzene–toluene–xylene fraction. 相似文献
10.
桉叶素的纯化 总被引:2,自引:0,他引:2
对云南某香料公司生产的某批桉叶油进行了全组成分析,结果为桉叶素、柠檬烯、对聚伞花素、γ-萜品烯、月桂烯、α-蒎烯、β-蒎烯、α-水芹烯、芳樟醇、松油烯-4-醇、α-松油醇和未知成分的质量分数分别为86.98%、9.10%、0.89%、0.79%、0.57%、0.54%、0.27%、0.39%、0.16%、0.02%、0.03%和0.12%。物性分析表明,主要杂质与桉叶素具有相近的沸点和溶解性质,而熔点相差较大,因而确定采用管式熔融结晶技术对桉叶素进行纯化。40次实验结果表明,采用w(桉叶素)≈80%的桉叶油为原料,通过二次重结晶,即首先将原料在-20~-30℃结晶,缓慢发汗至0.5℃,得到w(桉叶素)≥95%的中间产品;再重结晶一次,可得w(桉叶素)≥99.5%的最终产品。实验结果再现性好。 相似文献
11.
Natamycin, an antimicrobial agent sparingly soluble in water, was incorporated into alginate films in order to produce antimicrobial packaging, using three different approaches: the conventional loading method, when natamycin is added directly to the polymeric aqueous film-forming solution; the immersion procedure, by which a previously prepared films is contacted with natamycin solution, and by the supercritical solvent impregnation (SSI) method, with loading tests performed in CO2 containing natamycin, with and without addition of cosolvent (ethanol, 10% molar). The loading capacities were evaluated, as well as the influence on physical attributes of the films and on the release behavior of natamycin in water. The conventional method led to films heterogeneities with high surface roughness, and the immersion technique evinced several disadvantages like low incorporation yields, and negative influence on water vapor permeability and on the swelling degree of the film. The supercritical method showed that longer contact times and the use of ethanol as a cosolvent increased the natamycin loading yields and led to homogeneous films, where SSI (CO2 + EtOH) process produced visually attractive and tranlucent films. 相似文献
12.
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.
Partially presented at the AOCS 1993 Annual Meeting & Expo in Anaheim, California. 相似文献
13.
YAG precursors were synthesized by the urea method in aqueous solution using supercritical carbon dioxide and ethanol fluid drying technique, respectively. The composition of the precursors, the phase formation process and the properties of the calcined powders were investigated by means of XRD, IR, TG/DSC, BET, TEM and SEM. Compared with the classically prepared powders at room temperature in air, the amorphous precursor dried by supercritical CO2 fluid was loosely agglomerated and directly converted to pure YAG at about 900 °C. The resultant YAG powders showed good dispersity with an average crystallite size about 20 nm and specific surface area of 52 m2 g−1. However, the precursor dried by supercritical ethanol fluid was crystalline. Extensive phase segregation occurred during the drying process and resulted in the formation of separate phases such as monoclinic Y(OH)3 and pseudoboehmite. YAM and YAP phases appeared in the calcination process and phase pure were not detected until 1200 °C. 相似文献
14.
Precipitation polymerizations of acrylic acid (AA) in compressed carbon dioxide (65 bar) with different cosolvents, acetic acid, ethanol, and tetrahydrofuran, were studied. Analyses by viscosity measurement and differential scanning calorimetry indicate that the cosolvents have a pronounced effect on the properties of the product. Scanning electron microscopy shows that the products progress from microparticles to bicontinuous networks to fibers with the change of cosolvents and reaction conditions. Measurement of the volume expansion (ΔV%) of the liquid phase containing different cosolvents indicates that the miscibility of compressed CO2 with the liquid phase is dependent on the cosolvent. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1876–1880, 2003 相似文献
15.
16.
Supercritical separation processes for a multi-component mixture of solutes are of practical interest. In this study, the experimental equilibrium solubilities of two solute mixtures, p-toluenesulfonamide (p-TSA) and sulfanilamide (SNA), in supercritical carbon dioxide (SC CO2) were measured at temperatures of 308, 318 and 328 K and pressures in the range of 11.0-21.0 MPa using a dynamic flow method. The effect of cosolvent on the multi-component system was investigated by the addition of a 3.5 mol% ethanol. In the ternary system (p-TSA + SNA + CO2), the solubility of SNA increased as compared to its binary system (SNA + CO2), while the solubility of p-TSA decreased. In the quaternary system (p-TSA + SNA + ethanol + CO2), a significant solubility enhancement was observed for both p-TSA and SNA. The selectivity, which is thought to imply the intermolecular interactions between p-TSA and SNA, was also enhanced by the presence of ethanol so that the two solutes could be separated by a max. purity of 99.4%. The influence of the hydrogen bond interaction on solubility was discussed. The equations of Chrastil, Méndez-Santiago and Teja, and their modified forms were used to correlate the experimental data. 相似文献
17.
《The Journal of Supercritical Fluids》2007,40(3):330-337
In this study, the extraction of jojoba seed oil obtained from jojoba seed using both supercritical CO2 and supercritical CO2+ethanol mixtures was investigated. The recovery of jojoba seed oil was performed in a green and high-tech separation process. The extraction operating was carried out at operating pressures of 25, 35 and 45 MPa, operating temperatures of 343 and 363 K, supercritical fluid flow rates of 3.33 × 10−8, 6.67 × 10−8 and 13.33 × 10−8 m3 s−1, entrainer concentrations of 2, 4 and 8 vol.%, and average particle diameters of 4.1 × 10−4, 6.1 × 10−4, 8.6 × 10−4 and 1.2 × 10−3 m. It was found that a green chemical modifier such as ethanol could enhance the solubilities, initial extraction rate and extraction yield of jojoba seed oil from the seed matrix as compared to supercritical CO2. In addition, it was found that the solubility, the initial extraction rate and the extraction yield depended on operating pressure and operating temperature, entrainer concentration, average particle size and supercritical solvent flow rate. The solubility of jojoba seed oil and initial extraction rate increased with temperature at the operating pressures of 35 and 45 MPa and decreased with increasing temperature at the operating pressure of 25 MPa. Furthermore, supercritical fluid extraction involved short extraction time and minimal usage of small amounts entrainer to the CO2. About 80% of the total jojoba seed oil was extracted during the constant rate period at the pressure of 35 and 45 MPa. 相似文献
18.
Antonia P. de los Ríos Francisco J. Hernndez-Fernndez Demetrio Gmez Manuel Rubio Francisca Toms-Alonso Gloria Víllora 《The Journal of Supercritical Fluids》2007,43(2):303
The synthesis of butyl propionate in a recirculating bioreactor in room temperature ionic liquid/supercritical carbon dioxide biphasic systems at 50 °C and 80 bar was studied. In these systems, α-alumina microporous membranes with immobilized Candida antarctica lipase B were coated with four different ionic liquids based on 1-n-alkyl-3-imidazolium cations and hexafluorophosphate and bis{(trifluoromethyl)sulfonyl}imide anions. Selectivity increased (reaching >99.5%) when room temperature ionic liquid/supercritical carbon dioxide biphasic systems were used rather than in supercritical carbon dioxide alone. To understand the behaviour of the enzyme and the mass-transfer phenomena in these biphasic systems, the reaction was also carried out in ionic liquids and in ionic liquid/hexane biphasic systems, and the ionic liquid/hexane partition coefficients of the compounds involved in the transesterification reaction were determined. It was observed that the activity in room temperature ionic liquid/supercritical carbon dioxide biphasic systems depends on the effect of the ionic liquid media on the enzyme and the diffusional limitations across the IL-layer around the biocatalyst. 相似文献
19.
Berka-Zougali B Ferhat MA Hassani A Chemat F Allaf KS 《International journal of molecular sciences》2012,13(4):4673-4695
Two different extraction methods were used for a comparative study of Algerian Myrtle leaf essential oils: solvent-free-microwave-extraction (SFME) and conventional hydrodistillation (HD). Essential oils analyzed by GC and GC-MS presented 51 components constituting 97.71 and 97.39% of the total oils, respectively. Solvent-Free-Microwave-Extract Essential oils SFME-EO were richer in oxygenated compounds. Their major compounds were 1,8-cineole, followed by α-pinene as against α-pinene, followed by 1,8-cineole for HD. Their antimicrobial activity was investigated on 12 microorganisms. The antioxidant activities were studied with the 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging method. Generally, both essential oils showed high antimicrobial and weak antioxidant activities. Microstructure analyses were also undertaken on the solid residue of myrtle leaves by Scanning Electronic Microscopy (SEM); it showed that the SFME-cellular structure undergoes significant modifications compared to the conventional HD residual solid. Comparison between hydrodistillation and SFME presented numerous distinctions. Several advantages with SFME were observed: faster kinetics and higher efficiency with similar yields: 0.32% dry basis, in 30 min as against 180 min for HD. 相似文献
20.
《Applied catalysis. B, Environmental》2007,69(3-4):99-108
Freestanding and crack-free titania–silica aerogels with high titanium content (i.e., Ti/Si = 1) were successfully prepared by adjusting the hydrolysis of the two alkoxide precursors to a comparable rate during the sol–gel processing. Two titania–silica aerogels were prepared by ethanol and CO2 supercritical drying methods. Well-dispersed, nanometer-sized anatase crystal domains (ca. 10 nm) were crystallized by high temperature, ethanol supercritical drying. The crystalline domains were solidly anchored to the aerogel network by Ti–O–Si bonds. Titania–silica aerogels prepared by CO2 supercritical drying method were devoid of TiO2 crystals. A molecular-level mixing was achieved and anatase TiO2 was only crystallized with difficulty by high temperature calcination (1073 K). Both aerogels were mesoporous and displayed similar open pore structure that is readily accessible to reactant molecules. However, only the titania–silica aerogel with anatase TiO2 prepared by ethanol supercritical drying was active for the gas phase, photocatalytic oxidation of volatile organic compounds (i.e., isopropanol and trichloroethylene). Catalysts prepared from Degussa P25 TiO2 displayed lower activity under similar reaction conditions. 相似文献