Phase Equilibria of Long-Chain Carboxylic Acids in Supercritical Propane

Abstract

This paper presents data on the phase behavior of long-chain acids (octanoic acid, decanoic acid, dodecanoic acid, hexadecanoic acid, octadecanoic acid, and docosanoic acid) in supercritical propane. The data were measured for acid mass fractions w acid = (0.0149 to 0.652) in the temperature range T = (375 to 412) K, and the phase transition occurred at pressures in the range p = (3.7 to 11.2) MPa. The data showed no temperature inversions yet does hint toward possible three-phase regions at low temperatures for acids with 10 or more carbon atoms. The data shows a linear relationship between the phase transition pressure and the temperature at constant composition. Additionally, for acids with 10 or more carbon atoms, at constant temperature and mass fraction, a linear relationship exists between the phase transition pressure and the number of carbon atoms.

High-Pressure Phase Behavior of CO2 + (C12/C14 n-Alkane and/or C8/C10 Carboxylic Acid and/or C12/C14 Methyl Ester) Systems

“…A previous study has shown that, in supercritical propane, the behaviors of n -carboxylic acids systems are approximately similar to the binary phase behavior of a propane + n -alkane system where the n -alkane has double the carbon number of the n -carboxylic acid. This was explained by the dimerization effect observed for n -carboxylic acids, where two acids hydrogen bond in such a way that a “double molecule” is formed.…”