High-Pressure PVT Behavior of Natural Fats and Oils, Trilaurin, Triolein, and n-Tridecane from 303 K to 353 K from Atmospheric Pressure to 150 MPa

Abstract

High-pressure PVT data are lacking for many natural oil systems that are processed with supercritical fluids. In this work, we report on the PVT behavior of beef shank, beef tallow, coconut, palm, and palm kernel fats and castor, menhaden, linseed, olive, perilla, safflower, sesame, and soybean oils, each of which was characterized by a fatty acid distribution, iodine value, and saponification value. In addition, we report on the PVT behavior of pure components trilaurin, triolein, and tridecane. Well over 800 PVT data were measured with a static-type bellows apparatus. PVT behavior of the fats showed a marked change in crystallinity with increasing temperature and pressure. PVT behavior for the fats and oils above their melting point was similar, as expected, but could be explained in terms of molecular weight, iodine value, and to some extent, fatty acid composition. At a given temperature and pressure, the specific volume of the oils decreased with increasing iodine value. The data were correlated with the Tait, Peng-Robinson, Hederer-Peter-Wenzel, lattice, Flory, and simplified perturbed hard chain theory (SPHCT). As expected from their functional form, all cubic equations performed poorly in the compressed liquid region. Only the Tait, Flory, and SPHCT equations provided satisfactory correlation. SPHCT parameters were determined for all fats and oils. These parameters were generalized in terms of measurable oil properties, saponification value, and iodine value. The parameter, c, which is related to the number of degrees of freedom, was found to be slightly temperature dependent. With the correlated parameters, PVT behavior of the oils could be described to within 4.9% average error in pressure.