The influence of functional end groups on the high-pressure phase equilibria of long chain molecules in supercritical propane

The influence of various functional end groups on the high-pressure phase equilibria of long chain molecules in supercritical propane was studied by comparing the bubble/dew point pressure of a range of long chain molecules. All long chain molecules had a hydrocarbon segment containing 14 carbon atoms but different functional end groups. Insufficient published data exists for phase equilibria of these types of molecules in supercritical propane, thus prompting experimental work. Bubble/dew point measurements in the temperature range 375-410 K were conducted in a high-pressure phase equilibrium cell to determine the influence of the functional end groups. The alkane (with no functional end group) is the most soluble, followed by the ethyl ester, the methyl ester and the alcohol. The carboxylic acid is the least soluble. The influence of the functional end groups may be explained by considering the structure and polarity of the end groups. It was found that an increase in polarity and/or a decrease in shielding of the polar groups resulted in a decrease in the solubility of the molecules, which in turn resulted in an increase in the bubble/dew point pressures. (C) 2008 Elsevier B.V. All rights reserved.