超临界二氧化碳的最新应用

据有关资料报导:利用超临界二氧化碳来萃取天然植物的探索工作正在篷勃发展。利用二氧化碳作超临界萃取剂进行萃取,是在轻工、化工、食品、医药及精细化工等方面很有发展前途的一项新分离技术。超临界二氧化碳具有密度高、粘度低、扩散系数和节电常数大的特性,以二氧化碳作溶剂具有消毒、不自燃,价廉又易得等优点。从天然植物中提取有效成份,以取代传统的溶剂萃取方法,可大幅度提高产物的纯度,且工艺过程简便又安全可靠。     

超临界或高压CO2中无限稀释扩散系数的模拟

采用分子动力学模拟的方法对超临界二氧化碳的自扩散系数及甲醇和乙醇在超临界二氧化碳中的无限稀释扩散系数进行了模拟计算。结果表明,分子动力学模拟方法可较准确地反映二氧化碳的扩散性质,计算无限稀释扩散系数取得了与实验值较吻合的结果。采用这种新方法可以准确有效的地预测超临界体系的扩散性质,将会更加广泛应用于工程设计,因此分子动力学模拟作为先进的研究手段会得到越来越广泛的应用。     

超临界二氧化碳流体萃取分离技术

超临界流体的扩散系数比一般液体的扩散系数高一个数量级,而粘度要低一个数量级。与液-液萃取系统相比,超临界流体萃取系统具有较快的传质和萃取速度,因此能有效地对固体样品进行萃取分离。常用的超临界流体有乙烯、氙气、一氯三氟乙烷、二氧化碳、乙烷、一氧化二氮、一氟甲烷、丙烷、氨等,应用领域也从早期的天然香料提取扩展到食品、环境保护、农药、烟草、中药等行业,超临界萃取技术越来越受到国际科技届的广泛关注。但该技术应用于工业化生产尚需一定时日,还需要进一步降低操作成本和设备的造价。     

超临界流体快速膨胀法制备超细氟比洛芬粒子

文章选用二氧化碳作为超临界溶剂,采用超临界溶液快速膨胀技术制备超细氟比洛芬药物粒子,在较宽的温度压力范围内测定了氟比洛芬在超临界二氧化碳中的溶解度,考察了各种操作参数对药物粒子粒径的影响,研究了药物粒子粒径随各种操作参数的变化规律。结果表明：在实验考察的范围内,氟比洛芬的溶解度较小,在10-5~10-7之间（摩尔分率）,溶解度随着温度和压力的升高而增大。同时实验结果表明：粒径随预膨胀压力的升高而减小;一定范围内随接收距离的增大而增大;在萃取温度较低的情况下,粒子粒径基本随着萃取温度的升高而减小;随着萃取温度的升高,在相对较高预膨胀温度下,粒径随着萃取温度升高而增大。     

超临界流体快速膨胀法制备超细阿昔洛韦粒子

以二氧化碳作为超临界溶剂,采用超临界溶液快速膨胀技术制备得到超细阿昔洛韦药物粒子,在一定的温度和压力情况下,测定了阿昔洛韦在超临界二氧化碳中的溶解度,考察了各种操作参数对药物粒子粒径的影响,研究了药物粒子粒径随各种操作参数的变化规律。结果表明:阿昔洛韦在超临界二氧化碳中的溶解度较小,在10-5~10-6之间(摩尔分率),溶解度随着温度和压力的升高而增大,不存在文献中所报道的反向区。同时实验结果表明:药物粒子粒径变化对预膨胀温度最敏感,粒径随预膨胀温度的升高而减小;一定范围内随收集距离的增大而增大;在萃取温度较低的情况下,粒子粒径基本随着萃取温度的升高而减小;随着萃取温度的升高,在相对较高预膨胀温度下,粒径随着萃取温度升高而增大。     

超临界流体技术及应用现状

重点介绍了超临界流体的特殊理化性质,主要包括密度、粘度、扩散系数、介电常数等,对超临界流体技术在萃取、颗粒制造、环境治理、化学反应等领域的应用现状进行了综述,并对该技术的未来发展趋势进行了展望。     

绿色产业超临界技术最新研究进展-在化学反应工程中的应用

超临界流体技术具有许多传统技术所没有的快速、高效、低能耗、污染少等优点，而且超临界流体无毒，不燃，不污染环境，可以设计实现许多新型、高效的绿色化工过程。介绍了超临界流体的密度、粘度、扩散系数等物理化学性质及其对化学反应的影响。重点论述了超临界水的性质、超临界流体在化学反应工程研究中的应用和由超临界流体实现的绿色化工过程。     

苦荞活性组分在SC-CO_2/CH_3OH中无限稀释扩散系数的测定及计算

为了测定苦荞活性组分(芦丁与山奈酚-3-O-芸香糖苷)在超临界二氧化碳-甲醇(SC-CO_2/CH_3OH)体系中的无限稀释三元扩散系数,采用色谱峰扩展法在温度为308.15～323.15K,压力为8～14MPa进行实验,考察了压力、温度、密度及夹带剂等因素对扩散系数的影响规律,结果表明三元扩散系数随压力、密度及夹带剂质量分数的升高而减小,随温度的升高而增大。分别采用了修正的Wilke-Chang、He-1997及Dymond-Hildebrand-Batschinski模型对相关溶质分子在SC-CO_2/CH_3OH中的三元扩散系数进行理论关联及预测,计算结果与实验数据比较发现,Dymond-Hildebrand-Batschinski模型的预测效果最佳,芦丁与山奈酚-3-O-芸香糖苷组分的平均绝对偏差分别为2.48%和3.71%。     

超临界二氧化碳介入的α-松油醇催化合成1，8-桉叶素

提出超临界二氧化碳介入α-松油醇异构合成1,8-桉叶素的方法,并采用二极管阵列检测器测量超临界二氧化碳下α-松油醇/环己烷体系的最大吸收波长研究二氧化碳加入量与极性的关系。考察了溶剂体系极性、溶剂量和二氧化碳压力对磷钨酸/聚离子液体（PW/PIL）催化剂催化α-松油醇异构合成1,8-桉叶素的影响,并探讨了超临界二氧化碳介质中,PW/PIL催化剂催化α-松油醇异构合成1,8-桉叶素可能的反应机理。开发了一种绿色高效的1,8-桉叶素合成工艺,当环己烷/α-松油醇的质量比10∶1,PW/PIL催化剂/α-松油醇的摩尔比0.0163∶1,CO₂压力19.0 MPa,50℃反应8 h时,α-松油醇的转化率为89.3%,1,8-桉叶素的选择性为54.6%。研究表明,超临界二氧化碳起到共溶剂、膨胀溶剂、降低溶剂体系极性的三重作用,从而改善了催化剂的团聚现象,提高了1,8-桉叶素的选择性。     

超临界二氧化碳在非常规油气藏开采中的应用研究

超临界二氧化碳具有接近于气体的低黏度和高扩散系数,又具有接近于液体的高密度,这些性质引起了国内外石油行业的广泛关注,并将其引入油气藏开发。研究结果显示,超临界二氧化碳非常适合应用在非常规油气藏的开采作业中。我国的非常规油气藏储量丰富,但采收率普遍较低,将超临界二氧化碳引入非常规油气藏的开发很有必要。本文分析了超临界二氧化碳在非常规油气藏开采中的钻井、压裂、驱油及除垢洗井等作业过程中的技术原理和特点,认为,超临界二氧化碳弥补了水基钻井液或压裂液的不足,提高了效率,减少了污染,适用性好,并总结了超临界二氧化碳在非常规油气藏中的未来发展和总体优势。     

Modeling of drug solubility in supercritical carbon dioxide using equation of state based on hole theory with molecular surface charge density

Equation of state based on hole theory with molecular surface charge density was developed for the modeling of drug solubility in supercritical carbon dioxide. In the hole theory, the density change of supercritical carbon dioxide can be represented by the number of holes in the system. The molecular interaction energy parameter was estimated using the interactions of segments on the molecular surface given by a quantum calculation using conductor-like screening model. The only one parameter, coordination number around a molecule was fitted to the experimental data of the drug solubility in supercritical carbon dioxide. The solubilities of the eighteen drugs in supercritical carbon dioxide were modeled by the equation of state with the molecular surface charge density. The effect of the molecular pair for the coordination number on the correlated results was investigated. It is found that the results using the fitted parameter of the solute–solute pair coordination number result in the modeling performance better than those of carbon dioxide–solute coordination number. The results of the modeling of drug solubility in supercritical carbon dioxide are compared with the experimental data. The average absolute relative deviation between the experimental and calculated results of the solubility for the drug composed of C, H and O atoms acetylsalicylic acid, benzoic acid, ferulic acid, (S)-naproxen, p-benzoquinone, propyl gallate, salicylic acid and vanillic acid is 0.38 smaller than those for compounds including N, F, I and S atoms, amical-48, benzocaine, caffeine, carbamazepine, (±)-flurbiprofen, methimazole, phenazopyridine, theobromine, theophylline and uracil, 0.59.     

超临界CO2中CTFE和VAc共聚物的制备及表征

以超临界CO2为反应介质,制备了三氟氯乙烯（CTFE）和醋酸乙烯酯（VAc）共聚物。研究了反应过程中压力的变化与反应进度的关系,考察了单体配比对聚合反应及聚合物的结构与性能的影响情况,并对聚合物的性能进行了研究。结果表明,反应过程中压力的变化与反应的进度是同步的,通过控制单体配比,可以得到不同结构、不同氟含量的聚合物。     

未改性聚丙烯纤维的超临界染色研究进展

综述了未改性聚丙烯纤维的超临界染色研究进展。在超临界二氧化碳中,染料可以扩散至纤维内部,与传统的方法相比,染色结果有很大的提高。超临界二氧化碳作为未改性聚丙烯纤维染色媒介是可行的。有25篇参考文献。     

CTFE与VAc共聚物的制备

在超临界CO2中制备三氟氯乙烯(CTFE)与乙酸乙烯酯(VAc)共聚物P(CTFE-co-VAc),考察了单体配比对聚合反应、产物结构及性能的影响,研究了共聚物的表面性能及其溶液黏度。控制单体配比可得到不同结构、不同氟含量的共聚物。当m(VAc)/m(CTFE)小于4∶16时,产物中y(CTFE)恒定在50%左右;氟含量是影响共聚物表面性能的关键因素,共聚物中CTFE单元的比例增加,则产物中氟含量增大,产物对溶剂的接触角变大,当产物中w(F)为29.16%时,聚合物膜的表面能最小,为0.028 J/m2;聚合物溶液黏度随共聚物中VAc结构单元比例增加而增大。     

Separation of alkanes and alcohols with supercritical fluids. Part I: Phase equilibria and viability study

The chemical conversion of detergent range alkanes (12-14 carbon atoms) to alcohols is often incomplete and results in a large amount of residual alkane. This paper shows that these alkanes and alcohols can be separated by supercritical fluids. Ethane, propane and carbon dioxide were selected as possible supercritical solvents while n-tetradecane and 1-dodecanol were selected to represent the alkane-alcohol mixture, as these would be the two most difficult compounds to separate in a C12 to C14 alkane-alcohol mixture. A phase behaviour study and relative solubility analysis revealed that both ethane and carbon dioxide show promise in separating n-tetradecane and 1-dodecanol. Propane was eliminated as possible solvent because the phase behaviour of n-tetradecane and 1-dodecanol in supercritical propane is too similar. A pilot plant study showed that both supercritical ethane and carbon dioxide can be used to separate n-tetradecane and 1-dodecanol, with indications that supercritical ethane may affect a superior separation. An economic analysis, considering the energy requirements, revealed that the most important parameter with regard to energy consumption is the solvent-to-feed ratio. The process utilising ethane is more energy intensive, yet the energy requirements for both processes compare well with other petrochemical separation processes using supercritical fluids. Further investigations with both ethane and carbon dioxide should be conducted to determine which of these two solvents are superior and to optimise the operating parameters.     

Development of activity coefficient model based on COSMO method for prediction of solubilities of solid solutes in supercritical carbon dioxide

A COSMO base activity coefficient model was newly developed to predict the solubilities of solid solutes in supercritical carbon dioxide. This activity coefficient model describes that the system is composed of the surface segments on the solvent molecule and vacancy unlike the conventional model based on COSMO method. The density change of supercritical fluid can be represented by the change of the surface area of the vacancy. This prediction model is referred to “COSMO-vac (vacancy)” model. The solubilities of 16 pharmaceuticals in supercritical carbon dioxide were predicted by COSMO-vac model. The averaged deviations between the logarithmic experimental and predicted results are smaller than unity. Furthermore, the predicted results for the solutes composed of only C, H and O atoms are better than those for the solutes including the other atoms. The percentage of the predicted results within the order of the experimental data at the pressure over 15 MPa is higher than that at the pressures below 15 MPa.     

Extraction of Fatty Acids from <Emphasis Type="Italic">Boletus edulis</Emphasis> by Subcritical and Supercritical Carbon Dioxide

Mushrooms contain many valuable compounds such as fatty acids, carbohydrates, lycopene, lovastatin, trace elements etc. As they are currently valued for biologically active substances, and as high pressure carbon dioxide fluid extraction has been documented as an effective method for preparing bioactive products from plant materials, subcritical and supercritical carbon dioxide extraction of Boletus edulis mushroom was performed. In the extracts obtained, the fatty acids were determined. Response surface methodology (RSM) was applied to investigate the effect of pressure and extraction time on the extraction yield. The analysis of variance showed that pressure and extraction time had a significant effect on the extraction yield in both investigated process. The interaction between pressure and extraction time had a significant effect only in supercritical extraction process of B. edulis. Higher extraction yields have been obtained by subcritical carbon dioxide, and higher linoleic acid content has been determined in extracts obtained by supercritical carbon dioxide.     

苯甲酸在含不同夹带剂的超临界CO2中的溶解度

利用流动法分别测定了苯甲酸在温度308.15, 318.15, 328.15 K、压力范围8.0~23.0 MPa时,在纯超临界CO2及以乙醇、乙酸乙酯、乙二醇为夹带剂的超临界CO2中的溶解度. 研究结果表明,三种夹带剂的加入均可以不同程度地提高苯甲酸的溶解度,其增大幅度为乙醇>乙二醇>乙酸乙酯. 此外还探讨了温度、压力对苯甲酸在超临界CO2中溶解度的影响,以及夹带剂的作用机理,并用Sovova方程对实验数据进行回归,得到了较满意的结果.     

超临界二氧化碳微乳液的研究和应用进展

综述了在超临界二氧化碳（SFC）中，能形成微乳液的表面活性剂（SAA）的结构特性，助SAA对SFC微乳液形成的影响以及SFC微乳液的研究现状，同时，介绍了紫外－可见吸收光谱、傅立叶－红外光谱、小角中子散射和小角X光散射等近代测试方法，及其在SFC微乳液形成及其结构特性研究中的应用。另对SFC微乳液在化学反应，生物活性物质及金属离子萃取，合成材料和清洗领域中的应用也进行了介绍。