共查询到20条相似文献,搜索用时 109 毫秒
1.
用超临界溶剂在半连续装置上对中温煤焦油沥青(MCTP)进行了抽提和分离,考察了抽提段的实验条件对灰分和吡啶不溶物(PI组分)脱除率的影响;在分离段使用升温和/或降压法、精馏法调节MCTP族组成分布,并用分步抽提法调节MCTP的族组成。实验表明:用甲苯为超临界溶剂抽提可脱除全部灰分,PI组分也可在较低的压力下选择性地脱除;采用升温和/或降压法对抽出物可进行一定程度的分离,但对庚烷可溶物(HS组分)分离的选择性不高;采用精馏法可选择性地脱除HS组分,但尚需改进设备进一步提高分离效率;采用分步抽提法用石油醚作一次抽提溶剂可高选择性地脱除HS组分,其选择性在95%以上。 相似文献
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高温煤焦油的超临界萃取分馏研究 总被引:5,自引:0,他引:5
采用正戊烷溶剂,在超临界状态下,于220℃和5MPa~15MPa循序升压条件下,将高温煤焦油萃取分馏为10个液相窄馏分和1个固相沥青产物;切割深度达78.36%,萃余沥青收率为21.64%,明显低于常规蒸馏沥青收率。研究发现,所用高温煤焦油的初馏分萃取收率最高,随着萃取压力的增加,较低压力段一次萃取液相馏分的收率迅速减少;压力达到10 MPa,液相馏分总收率趋于峰值。元素分析和色质联用分析数据表明,随着萃取压力的增加,一次萃取获得窄馏分的碳氢原子比逐渐增加,平均环数和相对分子质量均逐渐增大,萃取馏分逐渐变重。 相似文献
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Marković S Marković Z Engelbrecht JP McCrindle RI 《Journal of chemical information and computer sciences》2002,42(1):82-86
The relationship between the rate of supercritical fluid extraction of polycyclic aromatic hydrocarbons (PAHs) from coal-tar pitch and some topological invariants are examined. The aim is to explain the appearance of a minimum value on the activation energy/molar mass curve of the PAHs. Rate constants are approximated using spectral moment expansion. It is shown that the size of the PAHs determines more than 95% of the extraction rate. Activation energy for the extraction of the PAHs was found to increase with increasing molar mass. The appearance of a minimum value on the activation energy/molar mass curve is the consequence of experimental difficulties resulting from the tendency of lower members of the PAHs to sublime. 相似文献
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Mechanisms that control the extraction rates of essential oil from savory (Satureja hortensis) and polycyclic aromatic hydrocarbons (PAHs) from historically-contaminated soil with hot water and supercritical carbon dioxide were studied. The extraction curves at different solvent flow-rates were used to determine whether the extractions were limited primarily by the near equilibrium partitioning of the analyte between the matrix and solvent (i.e. partitioning thermodynamics, or the "elution" step) or by the rate of analyte desorption from the matrix (i.e. kinetics, or the "initial desorption" step). Two simple models were applied to describe the extraction profiles obtained with hot water and with supercritical CO2: (1) a model based solely on the thermodynamic distribution coefficient KD, which assumes that analyte desorption from the matrix is rapid compared to elution. and (2) a two-site kinetic model which assumes that the extraction rate is limited by the analyte desorption rate from the matrix, and is not limited by the thermodynamic (KD) partitioning that occurs during elution. For hot water extraction, the thermodynamic elution of analytes from the matrix was the prevailing mechanism as evidenced by the fact that extraction rates increased proportionally with the hot water flow-rate. This was also confirmed by the fact that simple removal calculations based on a single KD (for each essential oil compound) gave good fits to experimental data for flow-rates from 0.25 to 4 ml/min. In contrast, supercritical CO2 extraction showed only minimal dependence on flow-rate, and the simple KD model could only describe the initial 20-50% of the extraction. However, a simple two-site kinetic model gave a good fit for all CO2 flow-rates tested. The results of these investigations demonstrated that very simple models can be used to determine and describe extractions which are limited primarily by partitioning thermodynamics, or primarily by desorption kinetics. Furthermore, these results show that the time required for the recovery of essential oil from savory with hot water can be minimized by increasing flow-rate, with little change in the total volume of water required. In contrast, raising the flow-rate of supercritical CO2 has little effect on the mass of essential oils recovered per unit of time, indicating that optimal recovery of these compounds with supercritical CO2 (amount recovered for the lowest amount of CO2) requires longer extraction times rather than faster flow-rates. 相似文献
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A study of the kinetics and mechanism of chemical reactions in supercritical fluids is considered. An experimental procedure was proposed for examining reversible chemical reactions in supercritical water. The reaction kinetics of 2-propanol dehydration in supercritical water was studied. It was found that the uncatalyzed reactions of olefin hydrogenation by hydrogen dissolved in supercritical water occur at high rates near the critical point of water. The experimental data on the dehydration of 2-propanol in supercritical water are adequately described by first-order reaction rate equations. The rate constants and activation energies of 2-propanol dehydration near the critical point of supercritical water were found. 相似文献
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Effect of sample handling on alkaloid and mineral content of aqueous extracts of greater celandine (Chelidonium majus L.) 总被引:4,自引:0,他引:4
The authors examined the extraction of alkaloids from the greater celandine (Chelidonium majus L.) by different methods (traditional pressing and tea making, microwave and supercritical fluid extraction). The extractants were water and propylene glycol. For comparison of the extraction methods, the yield was evaluated according to total alkaloid content measured by spectroscopy. The highest alkaloid yield was obtained by microwave extraction and by making tea. Distribution of the components was studied by thin-layer chromatography and densitometry. The concentration and the ratio of alkaloid components in extracts are significantly different depending on the extraction method. The solution obtained by supercritical fluid extraction contains coptisine and chelidonine, while berberine could be obtained by microwave extraction only. Extracts with high coptisine content were obtained by supercritical fluid extraction, followed by pressing and microwave extraction. Mineral element content of the drug and extracts was also determined by inductively coupled plasma atomic emission spectrometry. Element content (Na, Ca, Fe) was found to be highest in microwave extracts. 相似文献
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Three different extraction methods (ultrasonic extraction (USE), Soxhlet extraction (SOX) and supercritical fluid extraction
(SFE)) were compared for the extraction of pyrethrins from chrysanthemic flowers and commercial insecticide powder. Allethrin
was extracted from paper strips. All extracts and the kinetics were analyzed by supercritical fluid chromatography and flame
ionization detector.
Received: 18 January 1999 / Revised: 29 June 1999 / /Accepted: 30 June 1999 相似文献
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Three different extraction methods (ultrasonic extraction (USE), Soxhlet extraction (SOX) and supercritical fluid extraction
(SFE)) were compared for the extraction of pyrethrins from chrysanthemic flowers and commercial insecticide powder. Allethrin
was extracted from paper strips. All extracts and the kinetics were analyzed by supercritical fluid chromatography and flame
ionization detector.
Received: 18 January 1999 / Revised: 29 June 1999 / /Accepted: 30 June 1999 相似文献
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用水蒸气蒸馏和超临界CO2提取方法对川芎药材中的化学成分进行提取,用气相色谱-质谱联用技术(GC-MS)对提取物进行分析,分别鉴定出30和34个化合物,测定了其相对含量。 结果表明,水蒸气蒸馏和超临界CO2提取物的主要成分均为(Z)-藁本内酯。 超临界CO2提取方法能提取出较多的川芎药效物质,如丁基酞内酯、丁烯基酞内酯、川芎内酯A、(Z)-藁本内酯、(E)-藁本内酯和川芎内酯I。 而水蒸气蒸馏提取物中除了川芎药效物质外,还含有较多的萜烯类化合物。 结果表明,超临界CO2对川芎药效物质的提取比水蒸气蒸馏法的效率高。 通过对川芎中带不饱和侧链与饱和侧链内酯类化合物质谱裂解规律的解析归纳,鉴别了川芎中不饱和侧链内酯类化合物如(Z)-藁本内酯、(E)-藁本内酯、丁烯基酞内酯和川芎内酯I以及饱和侧链内酯类化合物如丁基酞内酯和川芎内酯A。 相似文献
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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
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Optimization of supercritical fluid extraction-gas chromatography of methylmercury in marine samples
R. Cela-Torrijos M. Miguns-Rodríguez A. M. Carro-Díaz R. A. Lorenzo-Ferreira 《Journal of chromatography. A》1996,750(1-2):191-199
Two-level factor designs were used to optimize the supercritical fluid extraction (SFE) of methylmercury (Me---Hg) in marine samples, which were subsequently analysed by gas chromatography-electron capture detection (GC-ECD). Several variables potentially affect to extraction efficiency and kinetics. The factors studied were: CO2 flow-rate and density, extraction cell temperature, static extraction time, nozzle and trap temperature, amount of hydrochloric acid and contact time between the acid and the sample before to extraction. The extraction kinetics was studied in all experiments by splitting extracts at 2, 7, 17 and 37 min. The results suggest that only the extraction cell temperature is statistically significant. The optimized SFE procedure to extract Me---Hg was validated by means of three available reference materials having certified methylmercury content. 相似文献
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Summary An analytical supercritical fluid extraction (SFE) technique, followed by GC/MS, was developed to separate and determine the volatile components in Chinese herbal medicine. Three kinds of herbs, frankincense, myrrh, andEvodia rutaecarpa were extracted and analyzed. The extraction was carried out using supercritical fluid CO2 at 20 MPa and 50°C. The main factors affecting the efficiency and selectivity of the extraction are discussed. The results revealed the potential of supercritical fluid extraction as an analytical procedure for the study of medicinal plants. 相似文献
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Several investigations on the extraction of dioxins from soil and fly ash with supercritical fluid have been reported; however, few of them describe the influence of components on the extraction. We extracted dioxins from eight samples with different values of organic carbon content and surface area with supercritical CO(2) at a temperature of 463 K, a pressure of 40 MPa, and using 10% toluene as an entrainer. We researched the influence of the characteristics of soil and fly ash on supercritical CO(2) extraction of dioxins. The results revealed that the extraction efficiencies of PCDD/DFs and PCBs were high for all soil samples, while that of fly ash samples decreased with the increase in organic carbon content and surface area. The extraction efficiencies of dioxins from four standard samples, activated carbon, humic acid, alumina, and florisil, were also examined. The results revealed that the extraction efficiencies were strongly influenced by activated carbon like components present in the samples. 相似文献
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比较了烟叶中油分的萃取方法,分别采用超声、索氏、ASE加速溶剂和CO2超临界萃取方法萃取烟叶中的油分,萃取物再经硅胶氧化铝柱分离成3种不同极性的馏分,馏分使用气相色谱分离,质谱鉴定结构.在同时考虑萃取率和萃取物组成成分的基础上最终选择索氏萃取.通过对萃取溶剂和萃取时间进行单因素试验,确定了最佳萃取条件为:萃取溶剂三氯甲烷,萃取时间16 h.方法所得组分全面,有利于后期卷烟配方的调整与设计. 相似文献
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A preparative supercritical fluid extraction system is described and was used with supercritical carbon dioxide to extract the active insecticide components pyrethrin I (PI) and pyrethrin II (PII) successfully from pyrethrum flower. A high-performance liquid chromatography method was developed and was used to separate and analyze the supercritical carbon dioxide extracts. Extraction efficiencies under several different extraction conditions were examined. Under the conditions examined, the most effective extractions of PI and PII (140 +/- 18 mg and 55 +/- 9 mg per 100 g of dry pyrethrum flower powder) were performed at 40 degrees C and 1200 psi. The results showed that extraction efficiencies of supercritical carbon dioxide are much better than those of n-hexane for pyrethrins I and II. During the extraction process, the most efficient extraction period was the first 3 h of the experiment. 相似文献
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M. W. Raynor I. L. Davies K. D. Bartle A. A. Clifford A. Williams J. M. Chalmers B. W. Cook 《Journal of separation science》1988,11(11):766-775
The combination of supercritical fluid extraction, high resolution capillary supercritical fluid chromatography, and Fourier transform infrared microspectrometry is described for the separation and identification of polycyclic aromatic hydrocarbons in a coal tar pitch. The variable solvating power of the supercritical fluid was utilized to selectively fractionate the sample. The fluid extract was decompressed through a frit restrictor into the sample cavity of a cooled microvalve injector, where the analytes were deposited and concentrated for subsequent chromatographic analysis. Several of the analytes separated in the chromatograph were collected on a potassium bromide disc at a solvent elimination inter-face for subsequent infrared analysis involving the use of an infra-red microscope accessory. The spectra obtained show the power of this detection technique for distinguishing between isomers. 相似文献