超临界CO2清洗技术

介绍了超临界CO2清洗的工艺及其应用,分析了超临界CO2清洗在技术、经济及环保方面的特点。     

Oxidative stability of walnut oils extracted with supercritical carbon dioxide

Supercritical carbon dioxide (SC-CO₂) was used to partially defat walnuts, and the oxidative stability of the extracted walnut oils was assessed. The SC-CO₂-extracted oils were less stable during accelerated storage in the dark than was pressed walnut oil, as determined by PV, headspace analysis by solid-phase microextraction, and sensory methods. The SC-CO₂-extracted oils, however, exhibited greater photo-oxidative stability than did pressed walnut oil by all of these methods, possibly because of the presence of chlorophyll in the pressed oil. Oxidative stability indices and tocopherol contents were significantly lower in the SC-CO₂-extracted oils than in pressed oil.     

Quality of wheat germ oil extracted by liquid and supercritical carbon dioxide

The extraction of wheat germ oil by liquid and supercritical CO₂ is described from the point of view of both operative method and pretreatment of raw material. The best conditions for wheat germ oil extraction are: pressure, 150 bar; temperature, 40°C; and solvent flow rate, 1.5 L/min at standard temperature and pressure. The yields and fatty acid compositions obtained are very similar to those resulting from the conventional extraction process using hexane as solvent (8.0 wt%), although a higher-quality oil is obtained by using CO₂ as solvent (free fatty acids, 12.4%; tocopherol content, 416.7 mg tocopherol/g wheat germ oil). These factors lead to the conclusion that the extraction process using CO₂ could be economically competitive with the conventional process, since it considerably simplifies the oil refinement stages and completely eliminates the solvent distillation stage, which are the most costly processing steps in terms of energy consumption.     

Extraction of essential oil from geranium (Pelargonium graveolens) with supercritical carbon dioxide

This study investigated the supercritical fluid extraction (SFE) of geranium essential oil from geranium (Pelargonium graveolens) using supercritical carbon dioxide solvent. The extraction yield was measured as a function of pressure, temperature and carbon dioxide flow rate. At low pressure (10 MPa) and high temperature (343 K), waxes were co‐extracted with the essential oil, resulting in artificially elevated essential oil extraction yields as no method was available with the SFE apparatus used to separate co‐extracted waxes and oil. At high pressure (30 MPa) and low temperature (313 K), the amount of wax co‐extracted decreased. Under these ‘optimum’ conditions, the extraction yield increased with decrease in flow rate giving a maximum extraction yield of 2.53%. All samples were analyzed by gas chromatography–mass spectrometry and the effect of pressure and extraction time on oil composition was studied. The percentage compositions of terpene hydrocarbons, terpenols, geraniol and geranyl esters were significantly affected by pressure and extraction time. The oil samples obtained by SFE were also compared with commercially obtained steam distilled samples. All major components of the commercially obtained oils were present in the SFE‐obtained oils; however, the percentage composition of the major components differed greatly between steam distilled and SFE oils. Copyright © 2005 Society of Chemical Industry     

PP/超临界CO2连续挤出发泡成型

以超临界CO2为发泡剂,在连续挤出发泡过程中研究了超临界CO2用量对高熔体强度均聚聚丙烯(PP)发泡成型过程的影响.随着超临界CO2用量的增加,发泡挤出机口模压力降低,试样发泡倍率降低,泡孔尺寸变小,泡孔密度提高.在w(CO2)为3%,5%时,得到发泡倍率最高为13左右的PP发泡材料.w(CO2)为7%,发泡温度为12...     

超临界二氧化碳技术的应用进展

超临界流体(SCF)因其具有很多优异特性而广泛应用于各个领域。主要介绍了超临界二氧化碳流体技术在萃取、制备超细颗粒材料、化学反应、酶催化、高分子科学、化学分析以及精密仪器清洗几个领域中的应用进展。     

超临界CO_2流体萃取植物油的实验研究

建立了一套超临界流体萃取实验装置,就大豆和花生两种植物油超临界流体萃取进行了较为详细的实验研究.在探讨了压力、温度、颗粒度、空隙率以及时间等对萃取率的影响之后,获得了指导实际生产的最佳工艺参数条件.     

超临界CO_2萃取水冬瓜油

研究了用超临界ＣＯ２流体从水冬瓜果实中提取油品的工艺,探索了操作压力、温度、流量及时间对水冬瓜油的萃取率的影响。分析了萃取条件与油品质量的关系,并综合得出了超临界ＣＯ２萃取水冬瓜油的最佳萃取条件。     

Extraction of rice brain oil using supercritical carbon dioxide and propane

Extraction of rice bran lipids was performed using supercritical carbon dioxide (SC−CO₂) and liquid propane. To provide a basis for extraction efficiency, accelerated solvent extraction with hexane was performed at 100°C and 10.34 MPa. Extraction pressure was varied for propane and SC−CO₂ extractions. Also, the role of temperature in SC−CO₂ extraction efficiency was investigated at 45,65, and 85°C. For the SC−CO₂ experiments, extraction efficiencies were proportional to pressure and inversely proportional to temperature, and the maximal yield of oil achieved using SC−CO₂ was 0.222±0.013 kg of oil extracted per kg of rice bran for conditions of 45°C and 35 MPa. The maximal yield achieved with propane was 0.224±0.016 kg of oil per kg of rice bran at 0.76 MPa and ambient temperature. The maximum extraction efficiencies of both SC−CO₂ and propane were found to be significantly different from the hexane extraction baseline yield, which was 0.261±0.005 kg oil extracted per kg of rice bran. A simulated economic analysis was performed on the possibility of using SC−CO₂ and propane extraction technologies to remove oil from rice bran generated in Mississippi. Although the economic analysis was based on the maximal extraction efficiency for each technology, neither process resulted in a positive rate of return on investment.     

Solubility of fatty acids in supercritical carbon dioxide

The solubilities of lauric, linoleic, myristic, oleic, palmitic and stearic acid in supercritical carbon dioxide (SC-CO₂) at different pressures and temperatures were measured. The solubility values obtained in this work were compared with previously published data, and possible causes for observed discrepancies were discussed. The solubilities of the six fatty acids were modeled by Chrastil’s equation, and estimated model parameters were used to plot the solubility isotherms of fatty acids at 313, 323 and 333°K (40, 50 and 60°C) as a function of SC-CO₂ density. The comparison of solubility isotherms of fatty acids and vegetable oil suggests that separation of fatty acids from triglycerides might be possible by using SC-CO₂ at densities less than 700 kg/m³. From the effect of temperature on fatty-acid and vegetable-oil solubility, it seems that the extraction yield could be increased without sacrificing the selectivity of SC-CO₂ for fatty acids by choosing a higher operating temperature. The data also suggest that fractionation of certain fatty acids might be possible by manipulating the processing conditions. Given the values of the constants, Chrastil’s equation could serve as a guideline for choosing appropriate processing conditions and predicting the effect of pressure and temperature of SC-CO₂ on solute solubility.     

Lipase-catalyzed glycerolysis of soybean oil in supercritical carbon dioxide

The transesterification of soybean oil with glycerol, 1,2-propanediol, and methanol by an immobilized lipase in flowing supercritical carbon dioxide for the synthesis of monoglycerides is described. A lipase from Candida antarctica was used to catalyze the reaction of soybean oil with glycerol, 1,2-propanediol, ethylene glycol, and methanol. Reactions were performed in supercritical carbon dioxide at a density of 0.72 g/L and at a flow rate of 6 μL/min (expanded gas). The substrates were added at flows ranging from 2.5 to 100 μL/min. Monoglycerides were obtained at up to 87 wt%, and fatty acid methyl esters at nearly 100 wt%. The reactivity of the alcohols paralleled the solubility of the substrate in liquid carbon dioxide. Glycerol has the slowest reaction rate, only 2% of that of methanol.     

Acylation of glucose catalysed by lipases in supercritical carbon dioxide

The acylation of glucose with lauric acid in a reaction catalysed by two Candida lipases and a Mucor miehei lipase in supercritical carbon dioxide (SCCO₂) was investigated. A linear dependence of the reaction rate on enzyme concentration was observed. Studies on the effect of temperature on enzyme activity showed that Candida antarctica lipase remains stable at temperatures as high as 70°C. Non-immobilised Candida rugosa lipase was found to have a temperature optimum at 60°C. The acylation reaction rate depended on the initial water activity of both substrates and enzyme; the optimum was 0·75 for Candida antarctica lipase, 0·53 for Candida rugosa lipase, and between 0·3 and 0·5 for Mucor miehei lipase. Candida rugosa lipase was most active at a molar ratio of sugar: acyl donor of 1: 3, while the optimum ratio was found to increase to 1: 6 when the reaction was catalysed by Candida antarctica and Mucor miehei lipases. © 1998 SCI     

Off-flavor removal from soy-protein isolate by using liquid and supercritical carbon dioxide

The efficacy of liquid carbon dioxide (L-CO₂), supercritical carbon dioxide (SC-CO₂), and SC-CO₂ containing 5% ethanol in the removal of off-flavors from soybean protein isolate was studied. Medium-chain aldehydes:n-butanal,n-pentanal, andn-hexanal; ketones: 2-butanone, 2-pentanone, and 2-hexanone; and alcohols: 1-butanol and 2-butanol; were the major compounds extracted. The extractions were performed at a constant fluid density of 901 kg/m³ with 100, 500, and 1000 standard liter of carbon dioxide. None of the treatments had a detrimental effect on soy-protein functionality. Headspace gas chromatography (GC) and sensory analysis of the treated samples were compared with the untreated soy isolate (control). In general, L-CO₂ was the least effective, and SC-CO₂ was the most effective in removing the off-flavor volatiles. Addition of ethanol as an entrainer did not improve the efficiency of off-flavor removal by SC-CO₂. The results of sensory analysis correlated well with the GC analysis. Sensory analysis of a 33% (wt/vol) slurry of treated soy-protein isolate had more off-flavor notes than the dry soy isolate. Dry and slurried treated soy-protein isolates had significantly less off-flavors and significantly more acceptability than the untreated control.     

用超临界二氧化碳法制备超强吸水剂

以N，N’-亚甲基双丙烯酰胺(BIS)为交联剂，研究了疏水性单体丙烯酸十八酯(OA)与亲水性单体丙烯酸(AA)在超临界二氧化碳中的聚合反应，制备了超强吸水剂。结果表明，65℃、压力大于13MPa时，制备的产物都为白色固体粉末。用超临界二氧化碳萃取技术可以对产物进行纯化，50℃、20MPa下，产物经超临界二氧化碳萃取2次后纯度可大于95％，4次后单体残留率为0．28％。该超强吸水剂的吸水率有一定下降，然而保水率却得到提高。     

Extraction of phospholipids from canola with supercritical carbon dioxide and ethanol

The potential use of supercritical (SC)-CO₂/ethanol mixture for the extraction and fractionation of phospholipids (PL) from flaked canola seeds, canola meal, and acetone insolubles (AI) was investigated. PL extraction was possible when ethanol was used as a cosolvent in SC-CO₂. PL recovery of 20.8% was achieved when canola flakes were extracted at 70°C and 55.2 MPa with SC-CO₂/10%EtOH after iol removal with neat SC-CO₂. Soaking of canola meal with ethanol prior to SC-CO₂/EtOH extraction increased PL recovery to 30.4%. PL content of the extracts increased with decreasing triglyceride concentration in the feed material and increasing amounts of ethanol added to SC-CO₂ or used for soaking. Fractionation of Al gums resulted in extracts containing 50% PL, of which 90% was phosphatidylcholine (PC); but yields were low, even after soaking treatment, due to caking. SC-CO₂/EtOH mixture may be used to extract PC-enriched PL from flaked canola seeds, canola meal, and AI. However, further research is needed to improve extraction efficiency.     

苯甲酸在含夹带剂的超临界CO2中溶解度的研究

采用流动法研究和测定了苯甲酸在35、50℃下,10.0—30.0MPa范围内,在纯超临界CO2和含醇系列夹带剂的超临界CO2中的溶解度。实验研究表明,醇系列夹带剂的加入均可明显增大苯甲酸的溶解度,但4种醇的增强作用随着碳链的增加而略有减弱。论述了温度、压力对溶解度的影响,并用Sovova方程对实验数据进行了回归。     

Absorption of low molecular weight solutes into polyurethane in supercritical carbon dioxide

Absorption of a series of low molecular weight solutes into polyurethane was investigated in supercritical carbon dioxide with different conditions. The effect on the amount of solutes absorbed in polyurethane due to these factors such as pressure, temperature, absorption time, decompression time, the character of solutes, and the amount of cosolvent was examined by a gravimetric method. The absorption mechanism was discussed. The desorption of solutes in polyurethane showed a dependence on the logarithm of time. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3162–3168, 2000     

Lipase-catalyzed alcoholysis with supercritical carbon dioxide extraction 1: Influence of flow rate

A combined process of lipase (E.C. 3.1.1.3) catalysis and extraction of product with supercritical carbon dioxide was studied. The effect of different flow rates of the extraction fluid on the selective removal of the ethyl esters (EE) synthesized in a lipase-catalyzed alcoholysis of cod liver oil with ethanol was investigated. The faster the flow rate, the faster the extraction rate and the higher the recovery of EE. For example, after a 270-min extraction, the total recovery of EE was 1520 mg for a flow rate of 0.3 liter carbon dioxide at atmospheric pressure and room temperature/min (NL/min) as compared to 250 mg when 0.015 NL/min was used. The concentration of EE in the carbon dioxide was found to decrease with increasing flow rate, which indicates that the rate of diffusion of EE limits their extraction at fast flow rates. A high flow rate was found to result in a more selective extraction of EE, i.e., less amounts of other lipid components present in the reaction mixture were coextracted with the EE. Further, by increasing the flow rate, the equilibrium of the reaction was shifted slightly toward ester synthesis. An increase in the flow rate from 0.015 to 0.075 NL/min resulted in an approximately 10% increase in total conversion (from 73 to 82%), whereas only a negligible increase was obtained when the flow rate was increased further to 0.15 NL/min.     

超临界CO_2萃取青皮挥发油的工艺研究

采用正交实验法对超临界CO2萃取中药青皮挥发油的最佳工艺条件进行优选。以挥发油得率为考察指标,探讨了萃取压力、萃取温度、萃取时间三因素在不同水平下对青皮挥发油得率的影响,并与水蒸气蒸馏法进行了比较。研究表明,萃取压力对挥发油得率有显著影响,萃取温度及时间影响不显著,各因素作用主次关系为:压力>温度>时间。优选得到的最佳工艺为:萃取压力25 MPa,萃取温度35℃,萃取时间1.5 h,得率为1.3197%,比水蒸气蒸馏法提高2.4倍,时间减少78.57%。超临界CO2萃取收率高、耗时短、品质好。     

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.