Dynamic extraction of a crude oil and its vacuum residue was carried o
ut with supercritical carbon dioxide and propane to understand the nat
ure of the extraction and partitioning processes as a function of pres
sure and temperature. The overall extraction performance of a solvent
was governed by a complex interplay between extraction efficiency and
feedstock volatility (heaviness). The extraction efficiency and extrac
tive power of the solvent were linked to the solvent density, which in
creases with pressure. Enhanced solvating power of the solvent near th
e critical temperature of the pure solvent was evident when the extrac
tion yields with respect to temperature were evaluated. Composition va
riations during an extraction sequence were determined by simulated di
stillation analysis of extracted samples. The results showed that the
earlier extracts contained lighter compounds and the later extracts pr
ogressively heavier compounds. Differences in composition between extr
acted samples assessed by g.c.-m.s. provided evidence of composition v
ariations. Copyright (C) 1996 Elsevier Science Ltd.