ADAPTATION OF THE FLORY-HUGGINS THEORY FOR MODELING SUPERCRITICAL SOLUBILITIES OF SOLIDS
ADAPTATION OF THE FLORY-HUGGINS THEORY FOR MODELING SUPERCRITICAL SOLUBILITIES OF SOLIDS
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DOI：
10.1021/ie00080a026
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发表时间：
1988-08-01
影响因子：
4.2
通讯作者：
THODOS, G
中科院分区：
文献类型：
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作者：
KRAMER, A;THODOS, G
无限稀溶液中溶质活度系数的 Flory-Huggins 方程已在应用中得到扩展，用于模拟超临界流体中固体的溶解度。该方程对系统使用单个可调节参数，已发现该参数强烈依赖于超临界溶剂的溶解度参数。迄今为止，对固体总溶解度参数解析为其分散性、极性和氢键贡献的分析不充分，阻碍了该参数的普遍相关性。然而，目前用超临界溶剂的溶解度参数对这个单一可调参数进行建模的方法克服了这一限制，并且还克服了与固溶质相关的经常无法获得的数据，例如其蒸气压和其他相关物理性质。超临界气体萃取在高度非挥发性和敏感有机化合物的分离和回收方面继续受到相当多的关注。这种分离方法是基于压缩气体能够将这些化学成分溶解在其基质中，超出其预期的挥发性，从而通过改变系统的温度和压力条件来实现它们的分离。从理论论证可以表明，当萃取温度在溶剂气体的临界温度附近进行并且压力保持在其临界压力之上时，这些重有机化合物的挥发性增强变得最大。目前的应用涉及使用易于获得的超临界溶剂，例如二氧化碳。对于这种特定溶剂，温度必须保持略高于其临界温度 (Tc= 304.2 K)，压力必须超过其临界压力 (Pc= 73.82 bar)。在这方面，值得注意的是，如 Zosel (1980) 指出的那样，超临界二氧化碳目前用于选择性地脱除生咖啡豆中的咖啡因，以及如 Hubert 和 Vitzthum (1980) 报道的那样，用于从烟叶中提取尼古丁以及从黑胡椒、肉豆蔻和辣椒等香料中去除活性成分。目前正在研究使用二氧化碳从大豆、玉米和棉花种子中提取油。此外，正如 Stahl 等人 (1980) 指出的，制药工业目前正在探索从植物中去除生物碱和精油，以回收吗啡、可待因、阿托品等药物。在这方面，Krukonis 等人（1979）指出他们成功地从植物材料中提取了抗肿瘤剂。 Squires 和 Paulaitis (1987) 以及 McHugh 和 Krukonis (1986) 在最近的出版物中讨论了超临界萃取的许多其他重要应用。
The Flory-Huggins equation for the activity coefficient of a solute in an infinitely dilute solution has been extended in applicationto model the solubility of solids in supercritical fluids. This equation utilizes for a system a single adjustable parameterwhich has been found to be strongly dependent on the solubility parameter of the supercritical solvent. The insufficient analysis for the resolution of the total solubility parameter of solids into their dispersion, polar, and hydrogen bonding con-tributions has so far hindered the correlation of this parameter in a generalized manner. However, the present approach for modeling this single adjustable parameter with the solubility parameter of the supercritical solvent overcomes this limitation and also thefrequently unavailable data associated with the solid solute such as its vaporpressure and other related physical properties.Supercritical gas extraction continues to receive con-siderable attention for the separation and recovery of highly nonvolatile and sensitive organic compounds. This method of separation is based on the ability of compressed gases to dissolve within their matrix these chemical con-stituents beyond their expected volatility and thus realize their separation upon altering the temperature and pres-sure conditions of the system. From theoretical arguments, it is possible to show that the volatility enhancement of these heavy organic compounds becomes greatest when the temperature of extraction is carried out in the vicinity of the critical temperature of the solvent gas and the pressure is maintained above its critical pressure. Present day applications involve the use of readily ac-cessible supercritical solvents such as carbon dioxide. For this particular solvent, the temperature must be kept slightly above its critical temperature (Tc= 304.2 K) and the pressure must exceed its critical pressure (Pc= 73.82 bar). In this context, it is worth noting that supercritical carbon dioxide is presently employed to selectively de-caffeinate green coffee beans as pointed out by Zosel (1980) and to extract nicotine from tobacco leaves and to remove the active ingredients from such spices as black pepper, nutmeg, and chilies as reported by Hubert and Vitzthum (1980). The use of carbon dioxide is being currently investigated for the extraction of oils from soybeans, corn, and cotton seeds. Furthermore, the pharmaceutical industry is presently exploring the removal of alkaloids and essential oils from plants for the recovery of such medicináis as morphine, codeine, atropine, and others as pointed out by Stahl et al.(1980). In this connection, Krukonis et al.(1979) indicate that they were successful in extracting antineoplastic agents from plant materials. Many other important applications of supercritical ex-traction are discussed in recent publications by Squires and Paulaitis (1987) and also by McHugh and Krukonis (1986).