Pentane thermodynamic properties

Heintz, A., Lehman, J.K., and Wertz, Ch., Thermodynamic properties of mixtures containing ionic liquids. 3. Liquid-liquid equilibria of binary mixtures of l-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide with propan-l-ol, butan-l-ol, and pentan-l-ol, /. Chem. Eng. Data, 48, 472, 2003. 

TABLE 2-236 Thermodynamic Properties of 2-Methyl Pentane (Isohexane)... 

Vapor-Kquid equilibrium data of poly(isobutylene) in n-pentane and n-heptadecane Data extract from Landolt-Bornstein VIII/6D3 Polymers, Polymer Solutions, Physical Properties and their Relations I (Thermodynamic Properties Equilibria of Ternary Polymer Solutions) ... 

Ambrose, D., Sprake, C.H.S., Townsend, R., 1975. Thermodynamic properties of organic oxygen compounds XXXVn. Vapour pressures of methanol, ethanol, pentan-1 -ol, and octan-1 -ol from the normal boiling temperature to the critical temperature. J. Chem. Thermodyn. 7,185-190. 

We have a dilemma we need a high-quality solvent to insure that the polymer remains in solution when it is formed but we need a solvent whose quality can be easily adjusted to induce the polymer to drop out of solution. How can we resolve it First, we need to know the thermodynamic variables that cause the occurrence of an LCST (chapter 3). The key variable in this instance is the chemical nature of the solvent or, to a first approximation, the critical properties of the solvent. Decreasing the solvent quality shifts the LCST curve to lower temperatures, and it is this variable that we wish to manipulate to force the polymer out of solution. To demonstrate the effect of solvent quality on the location of the LCST curve, consider the difference in LCST behavior for the same polymer, polyisobutylene, in two different solvents, n-pentane and cyclooctane. The LCST curve for the polyisobutylene-rt-pentane system begins at 70°C, while for the polyisobutylene-cyclooctane system it begins at 300°C (Bardin and Patterson, 1969). Cyclooctane, which has a critical temperature near 300°C, is a much better solvent than n-pentane, which has a critical temperature near 200°C, probably because cyclooctane has a greater cohesive energy density that translates into a lower thermal expansion coefficient, or equivalently, a lower free volume. Numerous examples of LCST behavior of polymer-solvent mixtures are available in the literature, demonstrating the effect of solvent quality on the location of the LCST (Freeman and Rowlinson, 1960 Baker et al., 1966 Zeman and Patterson, 1972 Zeman et al., 1972 Allen and Baker, 1965 Saeki et al., 1973, 1974 Cowie and McEwen, 1974). 

In addition, the CO2 continuous phase exhibits solvent properties typical of hydrocarbon solvents such as pentane or hexane [34-36] that have a very high capacity for lower polarity organic solutes. More details about the solvent properties and thermodynamics of these and other supercritical systems are given in a companion chapter by McFann and Johnston in this book (Chapter 9). 

Most highly polar and ionic species are not amenable to processing with desirable solvents such as carbon dioxide or any other solvent such as water that has a higher critical temperature well above the decomposition temperature of many solutes. In such instances, the combination of the unique properties of supercritical fluids with those of micro-emulsions can be used to increase the range of applications of supercritical fluids. The resulting thermodynamically stable systems generally contain water, a surfactant and a supercritical fluid (as opposed to a non-polar liquid in liquid micro-emulsions). The possible supercritical fluids that could be used in these systems include carbon dioxide, ethylene, ethane, propane, propylene, n-butane, and n-pentane while many ionic and non-ionic surfactants can be used. The major difference between the liquid based emulsions and the supercritical ones is the effect of pressure. The pressure affects the miscibility gaps as well as the microstracture of the micro-emulsion phase. 

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