超临界流体萃取-论文

宁夏大学硕士生考试考查卷面纸～～学年度第学期姓名学号院（所、部）年级专业研究方向课程考试方式Supercritical Fluid ExtractionAbstract:Solvent extraction is an important mass transfer unit operation. Supercritical fluid extraction (SFE), a sustainable green technology leads a wide range of applications since the past decade. Background of supercritical fluid extraction technology was introduced and overview of the technology of supercritical fluid extraction was also introduced. Focused on the method of enhanced extraction and industrial applications of supercritical fluid extraction technology.Keywords:solvent extraction,supercritical fluid extraction technology, enhance, industrial applicationSupercritical Fluid Extraction1.The background of solvent extractionExtraction techniques play a unique role in analytical chemistry. At the same time, extraction generally is relegated to a support role and it has just been within the past 15 years or so that the importance of extraction technology has been recognized for its role in the generation of quality analytical information [1].Solvent extraction is an important mass transfer unit operation. In this process, the solute is of different distributions between two immiscible or partially miscible in the liquid phases, which can achieve the purpose of separating or purifying the liquid mixtures [2]. Solvent extraction is usually operated at room temperature or low temperature. With the characteristics of low energy consumption, it is more suitable for the separation of heat-sensitive substances and easily realizing the economic countercurrent operation, which is conducive to continuous mass production. Its range of applications throughout the field of petroleum, chemical, hydrometallurgy, medicine, nuclear, biological engineering, mew materials, environmental protection, etc.. Solvent extraction method has advantages of high selectivity and efficient separation.Solvent extraction began in the 1840s. According to historical records, there were researchers extracted uranyl nitrate with diethyl ether in the analysis. During the early twentieth century, using solvent extraction to run the aromatics extraction process in the Oil Industry, it indicated the starting of industrial application. From 60 years 20th Century, solvent extraction technology has been applied in Petrochemical and Hydrometallurgical Industry on great scale. So far, the solvent extraction has developed in several aspects as supercritical fluid extraction [3], two-phase aqueous extraction, microwave extraction, membrane extraction, reversed micellar extraction, electro-extraction, ultrasonic solvent extraction, predispersed solvent extraction, nonequilibrium solvent extraction.2.The development of supercritical fluid extractionSupercritical fluid extraction (SFE), a sustainable green technology leads a wide range of applications since the past decade.It is a more developed technique which uses a supercritical fluid as extraction solvent. It derived from 1960s and developed rapidly in chemical separation techniques. SFE is an innovative, clean and environmental friendly technology with particular interest for the extraction of essential oil from plants and herbs [4]. SFE can be used on separation, purification, concentration, drying, the sterilization process, the polymerization reaction, and the actual production. Its scope of application has been included organic chemicals, petroleum, pharmaceutical, food, environmental protection, analytical chemistry, textile dyeing, pulp and paper, paint, fine ceramics, wood processing corrosion and other fields.SFE is based on the solvating properties of supercritical fluid (SF), which can be obtained by employing pressure and temperature above the critical point of a compound, mixture or element. Extraction by SF depends on some intrinsic tunable natures of supercritical fluid like temperature, pressure and some extrinsic features like the characteristics of the sample matrix, interaction with targeted analysts and many environmental factors [5,6]. By proper controlling of SFE parameters, the extractability of supercritical fluid can also be modified which enable this process to find its field from food to pesticide researches [7]. Mo r eover, a higher degree of freedom can be obtained in extraction by SFE than the conventional methods, which means the number of tunable properties goes higher in SFE. Thus, the tunable properties of SFE make this process more unique, sensitive and specific in compared with conventional extraction methods [8].It says that the main technical feature of SFE is the use of SF at the critical temperature and the critical pressure, which have the ability to dissolve many substances. The almost liquid-like density of supercritical fluids promotes solubility, and the gas-like viscosity and diffusivity make extraction and purification faster compared to extraction and purification by conventional (liquid) solvents [9]. In addition, supercritical fluids have no interfacial surface tension, because of the absence of liquid/gas phase boundary in supercritical state. High product quality can be accomplished by fine-tuning pressure and temperature conditions of the supercritical fluid. The extraction can be selective to some extent by controlling the density of the medium and the extracted material is easily recovered by simply depressurizing, allowing the supercritical fluid to return to the gas phase leaving no or little solvent residues. Temperature increases lead to the improved extraction capabilities of more traditional techniques such as Soxhlet extraction. The new generation of enhanced extraction technologies is based on the use of temperatures above the atmospheric boiling point of the extracting solvent. In SFE, pressure is applied to the extraction system so that these high temperatures (critical temperatures) can be achieved. Thus, the specific components can be isolated from a liquid or a solid. Further, supercritical extracts were often recognized of superior quality when compared with those produced by hydro-distillation or liquid-solid extraction. The common SCF are carbon dioxide (CO2), ammonia, ethylene, propylene, and water etcetera. Compared with traditional separation methods, SFE is of high speed on separation and high extraction efficiency. SCF possess dual characteristics of both gas and liquid. With a strong ability to dissolve, smooth flowing property and delivery performance, it‟s easy to adjust the extraction process. Its low power consumption making it suitable for the extraction and purification of the less volatile and heat-sensitive substances.Supercritical CO2 is selective, there is no associated waste treatment of a toxic solvent, and extraction times are moderate. SFE has traditionally focused on carbon dioxide as theextracting solvent. Due to its chemical and physical properties (low critical pressure and temperature) CO2 has become the major solvent for SFE. The extraction behavior of the 16 EPA-PAHs in CO2-SFE has been studied thoroughly and can be summarized as follows:1)Low molecular weight PAHs (LMW, molecular weights 128-178) can be extractedwith pure carbon dioxide,2)High molecular weight PAHs (HMW, molecular weights 202-278) can only beextracted efficiently using modifiers together with CO2,3) A higher extraction temperature (120℃ towards 60℃) provides a better recoveryof all PAHs although the HMW-PAHs are more affected than the LMW-PAHs,4)The addition of small amounts of water generally improves the extractability ofPAHs due to the swelling effect of the matrix [10].Based on these findings an official method was established by the US Environmental Protection Agency [11] which was used in interrelated studies with minor modifications. The method is divided into three discrete steps: In step 1, the more volatile PAHs are extracted using pure CO2 at a rather low density and temperature. In step 2, the less volatile PAHs are removed at a higher density and temperature and by adding modifiers (dichloromethane and methanol) to the CO2. A short step 3 with pure CO2 is used to purge the whole system thereby removing traces of modifier. Some research are clearly confirmed that the frequently mentioned “matrix effect”in SFE might be minimized by using this multistep extraction approach applying different extraction conditions.On the other hand, CO2 is a nonpolar solvent, so small amount of alcohols or other polar organic solvents are added in an attempt to increase the fluid polarity. With the advent of pressurized liquid extraction (PLE) and other techniques, SFE applications appear to have reverted to CO2-only extractions without the use of organic cosolvents. One area where CO2extraction has been prevalent is the isolation of essential oils and other natural products.By applying untrasound during the SFE of algal samples, extraction pressure, temperature, and time were reduced while the extraction yield was simultaneously improved.It is thought that the ultrasound aided in disrupting cell walls or the energy of interaction between the analyte and the algae matrix.During the development of SFE to date, instrument quality has varied tremendously.3.The future of supercritical fluid extractionIn most laboratories, decades-old extraction procedures are still commonplace.Yet the development of instrumental analysis techniques has grown exorbitantly, especially since the development of enabling technologies, such as the transistor and microprocessor control, and still continues to grow. This is rightly so. SFE offers several advantages, including reduced consumption of hazardous organic solvents, higher sample throughput, cleanness and safety, environmental friendliness, expeditiousness, simplicity,quantitativeness and favorable solvation capacity which approaches that of a liquid. The unique properties exhibited by supercritical fluids have already been applied for the analysis of pesticide residues in solid samples [12,13], plant materials [14,15].Extractions using “hot water” are still finding their niche in the world of analytical sample preparation. The technique is commonly referred to as subcritical water extraction, since the practitioners of this approach come from an SFE background; other terms, like hot water extraction or superheated water extraction, are found in the literature. Regardless, the approach is identical to PLE-applied pressure allows the use of the solvent at temperatures above the atmospheric boiling point. The major difference is that water loses its “effective polarity” at these high temperatures, so both nonpolar and polar solutes may potentially be extracted with a single solvent at different temperatures. Again, the initial applications were in the environmental arena, but research is branching into other areas. Ozel and Kaymaz [16] demonstrated that in the range of 100-150 °C water was able to quantitatively extract essential oils more efficiently than steam distillation or Soxhlet extraction. Kasia and Ikehara [17] used the hot water technique in the stepwise extraction of proteins and carbohydrates from soybeans. Small- and medium-sized carbohydrates and proteins were extracted, but not those with higher molar mass. While hot water extractions have the advantage of the complete elimination of organic solvents, whether this technique finds increasing use in analytical laboratories will depend on the reluctance to use temperatures in the 150-250 °C range and the more lengthy solvent (water) evaporation times.SFE is regarded as a green process because it does not use chemical solvents with drastic environmental impacts. Some applications of SFE have already been commercialized and some are emerging [18]. But still now it is considered as a ……black box design‟‟ of process, because of the complex interaction of affecting factors and lack of knowledge on the in-depth fluid dynamics of supercritical fluid in extraction [19]. Simple approximations of experimental units are possible to con struct in this ……black box design‟‟, but detail point-to-point process and extraction principle are beyond measurable.It should be noted that, on the one hand, the characteristics of the molecular structure of CO2 itself, weak Van der Waals forces and low dielectric constant make it not suitable for extraction of polar or large molecular weight substances; on the other hand, due to the supercritical CO2extraction of material mostly solid base materials and these materials accumulate in the basket in the extraction, the extraction of the material once more, and the more greater accumulation of uneven density. Making the shortcomings of supercritical CO2 extraction of low mass transfer efficiency, time-consuming and not higher yield target component present in the process.For the current limitations of supercritical CO2extraction, proposing a variety ofimprovements to improve extraction efficiency and expand its range of applications. Expanding the scope of the extraction, the common method of adding different polar co-solvent (such as methanol, ethanol, acetone, etc.) and adding special surfactant [such as bis(2-ethylhexyl) succinate sulfonate] is formed reverse microemulsion system. In terms of improving the efficiency of mass transfer, mass transfer enhancement proposed various methods of enhanced ultrasound, electric and microwave strengthening. A major advantage of these enhanced physical field will not introduce foreign substances, physical strengthening methods are all green. Wherein due to the directivity of the ultrasonic wave, high quality medium large vibration acceleration and frequency, to produce cavitation in the liquid medium, and the device is stable, inexpensive and easy to implement in combination with other devices, which is believed to strengthen the most promising one method of mass transfer.In order to extend the scope and improve the efficiency of supercritical CO2 extraction, four enhanced technologies including supercritical CO2extraction with modifier (SCE), supercritical CO2 extraction with ultrasound combined modifier (USCE), supercritical CO2 reverse microemulsion extraction (SCRME) and supercritical CO2 reverse microemulsion extraction with ultrasound (USCRME) were applied to optimize the process. Their extracting kinetic models were built based on transfer theory and principle of mass balance [20]. As matters turned out, the USCRME technology not only can improve the diffusion coefficient and the extracted maximum extraction rate is also changed between the solid phase adsorbed solute fluid phase interface-desorption. Thus, the desorption equilibrium in favor of the direction toward the movement.SC-CO2 fluid as a novel chemical reaction medium or solvent, because it has many advantages and much people of all ages, as people continued to deepen its research work, associated with the gradual improvement of the underlying data and engineering technical problems to overcome, SC-CO2 fluid extraction and chemical reactions in SC-CO2 fluid is bound to get new development.With the popular people‟s environmental awareness and sustainable development strategies, people in chemical, food, pharmaceutical and other related industries have become increasingly demanding. The pursuit of high-quality, efficient, clean and green industrial development path will become a new trend. Supercritical fluid extraction technology is called green technology. And it is environmentally friendly and can be recycled, and many other features. So there are broad prospects for development of supercritical technology and huge future market. It is bound to bring us great social, economic and environmental benefits.参考文献[1] Raynie D.E. Modern Extraction Techniques. Anal. Chem.2006, 78:3997-4003.[2] Tang Y.L. Summary of solvent extraction. Hangzhou Chemical. 2003, 33(4):9-11.[3] Mantell C, Casas L, Rodríguez M, et al. Supercritical Fluid Extraction. John Wiley & Sons, Ltd.2013, 79-100.[4] Fornari T., Vicente G., Vázquez E., et al. Isolation of essential oil from different plants and herbs bysupercritical fluid extraction. Journal of Chromatography A. 2012, 1250: 34-48.[5] Cavalcanti, R.N., Meireles, M.A.A., Fundamentals of supercritical fluid extraction. Academic Press,Oxford, 2012. 2(07):117–133.[6] Pereira, C., Meireles, M.A. Supercritical fluid extraction of bioactive compounds: fundamentals,applications and economic perspectives. Food and Bioprocess Technology. 2010, 3 (3), 340–372. [7] Azmir, J., Zaidul, I., Rahman, M., Sharif, K., Mohamed, A., Sahena, F., Jahurul, M., Ghafoor, K.,Norulaini, N., Omar, A. Techniques for extraction of bioactive compounds from plant materials: a review. Journal of Food Eng.2013, 117 (4), 426–436.[8] Sharif, K. M.; Rahman, M. M.; Azmir, J.; Mohamed, A.; Jahurul, M. H. A.; Sahena, F.; Zaidul, I. S.M., Experimental design of supercritical fluid extraction – A review. Journal of Food Engineering 2014, 124 (0), 105-116.[9] Hasan, N.; Farouk, B., Mass transfer enhancement in supercritical fluid extraction by acoustic waves.The Journal of Supercritical Fluids2013, 80(0):60-70.[10] Berset J.D., Ejem M., Holzer R., et al. Comparison of different drying, extraction and detectiontechniques for the determination of priority polycyclic aromatic hydrocarbons in backgroundcontaminated soil samples. Analytica Chimica Acta.1999, 383(3): 263-275.[11] EPA method 3561, Revision 0, January 1995.[12] Asiabi H., Yamini Y., Moradi M., Determination of sulfonylurea herbicides in soil samples viasupercritical fluid extraction followed by nanostructured supramolecular solvent microextraction.The Journal of Supercritical Fluids2013, 84:20-28.[13] Asiabi H., Yamini Y., Tayyebi M., Moradi M., Vatanara A., Keshmiri K., Measurement andcorrelation of the solubility of two steroid drugs in supercritical carbon dioxide using semi empirical models, J. Supercritical Fluids 2013, 78:28–33.[14] Maksimovic S., Kesic Z., Lukic I., Milovanovic S., Ristic M., Skala D., Supercritical fluidextraction of curry flowers, sage leaves, and their mixture. The Journal of Supercritical Fluids2013, 84:1-12.[15] Wüst Zibetti A., Aydi A., Arauco Livia M., Bolzan A., Barth D., Solvent extraction and purificationof rosmarinic acid from supercritical fluid extraction fractionation waste: Economic evaluation and scale-up. The Journal of Supercritical Fluids2013, 83:133-145.[16] Ozel M.Z., Kaymaz H. Superheated water extraction, steam distillation and soxhlet extraction ofessential oils of origanum onites. Anal. Bioanal. Chem., 2004, 379:1127-1133.[17] Kasai N., Ikehara H. Stepwise extraction of proteins and carbohydrates from soybean seed. J. Agric.Food. Chem., 2005, 53(10):4245-4254.[18] Machida, H., Takesue, M., Smith, R.L., Green chemical processes with supercritical fluids:properties, materials, separations and energy. The Journal of Supercritical Fluids, 2011, 60:2–15. [19] Wang, J., Sun, Z., Dai, Y., Ma, S. Parametric optimization design for supercritical CO2 power cycleusing genetic algorithm and artificial neural network. Applied Energy, 2010, 87 (4):1317–1324. [20] Luo D.L., Xu B.C., Qiu T.Q., Liu J.X., Comparison and dynamic models of supercritical CO2extraction enhanced by different technologies, Modern Food Science and Technology, 2013,29:1921-1925.。