TRANSPORT PHENOMENA IN SUPERCRITICAL FLUID EXTRACTION

A scaling analysis is performed to study transport phenomena in the supercritical fluid extraction process. Two typical systems, one solid-fluid and one liquid-fluid, are investigated. Characteristic velocities and time scales of each transport process are determined by force balances. The dominant driving force in each existing phase and the race-determining factor of the entire system are identified. Enhancements of practical applications towards more energy efficient operations are suggested. For situations with insufficient solute transport, different methods of improvement are discussed.     

MODELING ANALYTICAL TESTS OF SUPERCRITICAL FLUID EXTRACTION FROM SOLIDS WITH LANGMUIR KINETICS

A model for the analytical supercritical fluid extraction (SFE) tests from solid samples in which desorption of the solute from the surface of the solid is the rate determining step is presented. The desorption process is described by the Langmuir kinetics. The two stages of the test (static and dynamic) are modeled, where each of the two phases (solid and supercritical fluid) are considered well mixed. The resulting ordinary differential equations are solved analytically for the static stage and numerically for the dynamic stage. Dimensionless curves of concentrations of the two phases and fractional recovery during the two stages of the tests are predicted. These curves are characterized by two dimensionless parameters for the static stage, the equilibrium constant and the fractional initial capacity, in addition to one parameter for the dynamic stage, the desorption coefficient. The model provides a good fit to experimental results for SFE from solids. The trends in the fitted parameters with respect to pressure and temperature are in agreement with theory.     

超临界流体萃取天然药物的研究现状及发展趋势

综述近年来迅速发展起来的超临界萃取技术在天然药物提取中的研究现状，并对其今后的发展方向和趋势进行分析和讨论     

超临界流体喷淋萃取塔流体力学特性和传质性能

在内径为25mm的连续逆流喷淋塔内进行了流体力学特性和质量传递性能的研究,实验压力为(8～14)MPa,实验温度为35℃,实验体系为CO_2/异丙醇/水和CO_2/乙醇/水.建立了描述连续逆流超临界流体喷淋萃取塔的流体力学关联式,根据双膜理论,建立了用于计算液相总体积传质系数的质量传递模型.流体力学关联式和质量传递模型的计算值与实验结果符合较好.     

EFFECTS OF ENTRAINERS ON THE PHASE EQUILIBRIUM OF SUPERCRITICAL FLUID EXTRACTION PROCESS

A flow apparatus was set up for measuring the solubility of a solid solute in a supercritical fluid withthe presence of a small amount of entrainer.The solubilities of biphenyl,diphenylamine and benzoic acid insupercritical carbon dioxide with one of the selected entrainers which were ethanol,acetone and n-hexanerespectively,were obtained in the pressure range of 10—32 MPa and the temperature range of 308—318K.Asolvolytic association theory has been proposed to explain the mechanism of entrainer effect,and theexperimental results were reasonably analysed.According to the solvolytic association theory,the association equa-tion of state was adopted to correlate the experimental data with good accuracy.     

应用超临界技术进行废水处理

超临界技术是一种新兴的废水处理技术，它主要包括超临界流体萃取和超临界水氧化两种，本文论述了这两种技术的应用研究，应用前景，存在的问题和研究方向。     

A STUDY ON SUPERCRITICAL FLUID EXTRACTION OF L-PROLINE

The extraction of L-proline from the fermentation broth filtrate with the supercritical fluid was studied. It has been proved that L-proline and most amino acids are hardly dissolved in the pure supercritical carbon dioxide fluid. When the methyl alcohol was added as an entrainer in L-proline solution or carbon dioxide fluid, the solubility of L-proline in the supercritical fluid would be greatly increased, but ethyl alcohol was unsatisfactory as an entrainer.The influences of extraction pressure, temperature, time, flow rate of fluid, concentrations of L-proline and entrainer on the yield of L-proline have been investigated for searching the optimal extraction conditions.     

EPA和DHA在超临界流体色谱柱中的传质动力学

用超临界流体色谱 (SFC)法研究了EPA和DHA在C18上的吸附和传质性能 .建立了色谱动力学模型并获得了模型参数 ,较好地拟合了实验流出曲线 .结果表明吸附平衡、轴向弥散、流体相传质和颗粒内有效扩散都是影响SFC分离EPA和DHA的重要因素     

聚丙烯纤维的超临界流体染色

以超临界二氧化碳为介质研究了分散染料在聚丙烯及混纺织物上的染色能力．结果表明,选用合适的分散染料可使织物在较短时间内染色,而且产品颜色十分均匀．在16～26MPa和80～120℃范围内,染料在织物上的着色量较高且随温度和压力变化不大．     

超临界流体技术

简述了超临界流体技术在萃取分离、化学反应工程、环境保护、材料科学等方面的应用,并对其发展前景进行了展望．     

水溶液中硫酸钾晶体生长动力学

The single crystal growth rates of potassium sulfate in pure aqueous solution under different conditions were determined by photomicrography in a flow system for crystal growth. The effects of themain controlling factors, such as supersaturation, crystal size, solution velocity and crystal growth temperature, on crystal growth rates of potassium sulfate were discussed in detail by using non-linear regression from the experimental data, and several empirical relationships were given. The results showed that the growth rates of crystals increased with supersaturation, crystal size, solution velocity and temperature. Moreover supersaturation was the most important controlling factor influencing growth rates of crystals, crystal size and solution velocity were the secondary and temperature was the least.Furthermore, It was found that the growth rate of crystals along the [100] crystallographic axis was higher than that along the [001] in the same condition. The effect of every factor on crystal growth rates along the [100] crystallographic axis was stronger than that along the [001].     

超临界流体干燥法制备炭气凝胶

以间苯二酚和甲醛为原料, Ca(OH)2为催化剂,经溶胶—凝胶过程得水凝胶 ;以超临界 CO2干燥水凝胶,得到网络间充满气体的固态材料气凝胶,再经高温热解得炭气凝胶。 TEM表征结果显示：气凝胶和炭气凝胶均具有规则的纳米网络结构,网络节点粒径约 10 nm,典型网络孔径小于 50 nm。     

超临界流体结晶技术研究进展

综述了超临界流体结晶技术的理论和应用进展，重点介绍了三种超临界流体结晶技术：超临界溶液快速膨胀结晶法，超临界流体抗溶剂结晶法和超临界流体梯度结晶分离法，并指出了它们的研究方向。     

超临界流体技术与超细粉体制备

综述了超临界流体应用于制备超细粉体的研究现状、主要研究成果和应用前景。介绍了超临界溶液快速膨胀(RESS)法,超临界流体抗溶剂(GAS)法,超临界气体抗溶剂沉淀(PCA)法,超临界逆向结晶(SRC)法,超临界流体渗透(SFI)技术,超临界干燥(SCFD)法和超临界流体化学反应法等,近年来开发的一些新方法和新工艺。分析了这些新工艺新方法的原理、特点、技术上的可行性、应用前景、目前达到的水平与存在的问题,以及今后的发展所需要解决的关键问题等。     

重金属的超临界络合萃取动力学

引　言超临界ＣＯ2 络合萃取是去除重金属的一种清洁高效的方法 .其原理是利用络合剂与带电的离子通过配位键生成电中性的、弱极性的、稳定的、易溶于超临界ＣＯ2 的络合物 ,从而可被超临界ＣＯ2萃取[1] .该技术具有萃取速度快、萃取率高、萃取温度较低、生物兼容性好和无毒、无污染等优点 .近年来 ,对土壤、河床污泥以及从模拟的滤纸和砂土上萃取金属离子的研究 ,国外已有大量报道[2 ] ,但从真实体系中萃取痕量重金属的报道则很少[3] .中药以其丰富的资源、独特的疗效、毒副作用小等优点已引起了世界各国的关注 .然而 ,由于环境污染、炮制…     

MASS TRANSFER IN A SEMIBATCH SUPERCRITICAL FLUID EXTRACTION CONTACTOR FOR LIQUID MIXTURES

The problem of mass transfer in a semibatch Supercritical Fluid Extraction contactor for liquid mixtures has been considered both theoretically and experimentally. The multicomponent mass transfer model is applied to the case of a gaseous solvent rising through the liquid to be extracted. The results obtained with this model are compared with those calculated by using a liquid-liquid extraction model recently extended to supercritical extraction contactors. A simplified model is developed and all of the models considered are tested on the basis of experimental data points. Experiments are carried out in a semi-batch pilot-size apparatus and results are presented for the systems Ethanol-Water-CO₂ at 17.0 MPa, 308 K and Isopropanol-Water-CO₂ at 10.3 MPa, 313 K. Models based on the gas-liquid extraction approach are capable of representing the concentration versus time profiles at the extractor, while the liquid-liquid approach predicts lower extraction effectiveness.     

KINETICS OF PHENOL EXTRACTION FROM AQUEOUS PHASE BY SULFURIC ACID SALTS OF TRIOCTYLAMINE

The kinetics of the extraction of phenol from the aqueous phase by sulfuric acid salts of trioctylamine (TOA salts) in kerosene and the stripping of phenol from the organic phase by sodium hydroxide solution were studied using a constant interfacial area cell. Measurements of the extraction and stripping rates were made by measuring the time-dependent phenol concentrations in the aqueous phase. It is found that the extraction rate of phenol is strongly dependent on the initial concentration of phenol in the aqueous phase and on the initial concentration of TOA salts in the organic solvent. However, the effect of the total sulfate concentration and the acidic concentration on the extraction rate are not significant. The stripping rate is only a function of the initial concentration of phenol in the TOA salt-organic phase. By analyzing the experimental data, it was recognized that the extraction of phenol occurs at the interface, rather than in the bulk of the solution. The diffusion resistance, rather than the resistance of chemical reaction, is the rate-controlling step for the phenol extraction. Based on the experimental data, simple expressions of the extraction rate and stripping rate of phenol were obtained.     

含乙醇废水的超临界水氧化反应动力学及反应机理

研究了等温平推流反应器中乙醇的超临界水氧化反应（SCWO）,反应温度475～550 ℃、压力22～30 MPa、停留时间0.6～63.7 s、氧气与乙醇摩尔浓度比4.56～9.09.一氧化碳和二氧化碳分别是反应中间产物和最终产物.随停留时间增大、温度升高,乙醇去除率增大,压力和氧气浓度变化对过程无显著影响.以幂指数方程描述乙醇SCWO动力学,乙醇和氧气的反应级数分别为1和0,计算值和实验值相差基本在10%以内.超临界条件下分别以过氧化氢和氧气为氧化剂时乙醇的氧化反应无明显差别,亚临界条件下过氧化氢氧化速率大于氧气.基于对此现象的分析,作者推测：无论以过氧化氢或氧气作为氧化剂,在超临界水中,它们之间可以通过一系列自由基反应迅速达到平衡,且各物种的平衡分布与初始分布无关,体系的主要氧化过程在平衡分布下进行.     

采用均匀设计法优化木材亚/超临界乙醇-水萃取过程参数

在间歇高压釜实验装置上,采用均匀设计法优化了木材亚／超临界乙醇－水萃取过程参数。研究结果表明,当混合溶剂中水的质量分数为６０％ ,温度为２９０℃和溶木比为１５∶１（此时系统压力为７．８ ＭＰａ）时,能获得最高的木材转化率和萃取物产率,大约９０％ 的木材变成了可溶组分,这为木材液化开辟了新的技术途径。