The supercritical fluid extraction (SFE) of bitumens from four major U
inta Basin (Utah) oil sand deposits was studied with propane solvent.
The deposits studied included Whiterocks, Asphalt Ridge, PR Spring and
Sunnyside. The bitumens from these deposits differed widely in physic
al and chemical properties. The volatilities (components with boiling
point < 811 K) were 46.6, 53.5, 45.4 and 40.9 wt.%; the molecular weig
hts were 653, 426, 670 and 593 kg/kg mel; and the asphaltene contents
(n-pentane insolubles) were 2.9, 6.8, 19.3 and 23.6 wt.% for the White
rocks, Asphalt Ridge, PR Spring and Sunnyside bitumens, respectively.
The SFE experiments were carried out at five conditions, combinations
of three different pressures (5.6 MPa, 10.4 MPa, and 17.3 MPa) and thr
ee temperatures (339 K, 380 K and 422 K). The cumulative extraction yi
eld increased with increase in solvent density at all operating condit
ions for the four bitumens. A maximum yield of 45 wt.% was obtained at
the highest solvent density with the Whiterocks bitumen. The extracti
on products were significantly upgraded liquids relative to the bitume
ns. Comparatively lighter fi actions were extracted in the earlier sta
ges of extraction for all the four bitumens, whereas heavier extracts
were obtained at higher extraction-solvent densities. The asphaltene c
ontents of the residual fractions were significantly higher than the a
sphaltene contents predicted on a prorated basis for all four bitumens
. This trend was due to the extraction of cosolubilizing components th
at kept the asphaltenes in suspension in the bitumen. It was concluded
that solute polarity played a significant role in the extraction yiel
ds of the four bitumens. The Whiterocks bitumen, which was the least p
olar bitumen based on asphaltenes content, gave higher extraction yiel
ds compared to the bitumens from the other three deposits at all five
operating conditions. The Sunnyside bitumen with the highest asphalten
e content gave the lowest extraction yield at all five conditions. The
Asphalt Ridge and PR Spring bitumens with intermediate polarity (base
d on asphaltene content) gave intermediate extraction yields with the
Asphalt Ridge bitumen extraction yields higher than the PR Spring bitu
men. Preliminary modeling of the extraction process using the Peng-Rob
inson cubic equation of state and a pseudocomponent lumping scheme pro
vided a reasonable match with the experimental data for Whiterocks and
PR Spring bitumens. (C) 1998 Elsevier Science B.V. All rights reserve
d.