U.S. patent application number 12/645547 was filed with the patent office on 2011-06-23 for method for recovering bitumen from oil sand.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Gregory Allen O'Neil, John Aibangbee Osaheni.
Application Number | 20110147276 12/645547 |
Document ID | / |
Family ID | 44149594 |
Filed Date | 2011-06-23 |
United States Patent
Application |
20110147276 |
Kind Code |
A1 |
O'Neil; Gregory Allen ; et
al. |
June 23, 2011 |
METHOD FOR RECOVERING BITUMEN FROM OIL SAND
Abstract
In one aspect, the present invention provides a method for
recovering bitumen from an oil sand, the method comprising: (a)
contacting a bitumen-containing oil sand with a first solvent
mixture of cyclohexane and ethanol to provide an extraction mixture
comprising a sand phase and an organic phase; (b) separating the
sand phase from the organic phase comprising bitumen, ethanol and
cyclohexane; (c) separating an azeotropic mixture comprising
cyclohexane and ethanol from the organic phase; and (d) recovering
bitumen from the organic phase. The first solvent mixture comprises
from about 95 to about 65 percent cyclohexane and from about 5 to
about 35 percent ethanol.
Inventors: |
O'Neil; Gregory Allen;
(Clifton Park, NY) ; Osaheni; John Aibangbee;
(Clifton Park, NY) |
Assignee: |
GENERAL ELECTRIC COMPANY
SCHENECTADY
NY
|
Family ID: |
44149594 |
Appl. No.: |
12/645547 |
Filed: |
December 23, 2009 |
Current U.S.
Class: |
208/390 |
Current CPC
Class: |
C10G 1/042 20130101 |
Class at
Publication: |
208/390 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Claims
1. A method for recovering bitumen from an oil sand, the method
comprising: (a) contacting a bitumen-containing oil sand with a
first solvent mixture of cyclohexane and ethanol to provide an
extraction mixture comprising a sand phase and an organic phase,
the first solvent mixture comprising from about 95 to about 65
percent cyclohexane and from about 5 to about 35 percent ethanol;
(b) separating the sand phase from the organic phase comprising
bitumen, ethanol and cyclohexane; (c) separating an azeotropic
mixture comprising cyclohexane and ethanol from the organic phase;
and (d) recovering bitumen from the organic phase.
2. The method according to claim 1, further comprising a drying
step in which the organic phase is treated with a drying agent.
3. The method according to claim 2, wherein the drying agent
comprises anhydrous recovered oil sand.
4. The method according to claim 1, wherein the first solvent
mixture is used in an amount corresponding to a weight ratio of
first solvent mixture to oil sand in a range from about 3 to 1 to
about 500 to 1.
5. The method according to claim 1, wherein the first solvent
mixture comprises about 70 percent cyclohexane and about 30 percent
ethanol.
6. The method according to claim 1, wherein the contacting is
carried for a period of time ranging from about 0.1 hour to about
24 hours.
7. The method according to claim 1, wherein the contacting is
carried out a temperature in a range from about 25.degree. C. to
about 150.degree. C.
8. The method according to claim 1, wherein the recovering bitumen
from the organic phase is carried out prior to separating the
azeotropic mixture from the organic phase.
9. The method according to claim 8, wherein the recovering bitumen
comprises centrifugation of the organic phase is carried out at a
temperature in a range from about minus 40.degree. C. to about
25.degree. C.
10. The method according to claim 1, wherein the recovering bitumen
from the organic phase is carried out following separating the
azeotropic mixture from the organic phase.
11. The method according to claim 1, wherein the separating the
azeotropic mixture is carried out by distillation at a pressure in
a range from about 0.1 atmosphere to about 5 atmosphere.
12. The method according to claim 1, wherein the separating the
azeotropic mixture is carried out by distillation at ambient
pressure.
13. The method according to claim 1, further comprising a step of
transporting the organic phase to a second location remote from a
first location at which the contacting is carried out.
14. The method according to claim 13, wherein the transporting
comprises transport by pipeline.
15. A method for recovering bitumen from an oil sand, the method
comprising: (a) contacting in-situ a bitumen-containing oil sand in
a subsurface deposit with a first solvent mixture of cyclohexane
and ethanol to provide an extraction mixture, a sand phase and an
organic phase, the first solvent mixture comprising from about 95
to about 65 percent cyclohexane and from about 5 to about 35
percent ethanol; (b) removing the organic phase comprising bitumen,
cyclohexane and ethanol from the subsurface deposit; (c) separating
an azeotropic mixture comprising cyclohexane and ethanol from the
organic phase; and (d) recovering bitumen from the organic
phase.
16. The method according to claim 15, wherein the order of steps
(a)-(d) is first (a) then (b) then (c) then (d).
17. The method according to claim 15, further comprising a drying
step in which the organic phase is treated with a drying agent.
18. The method according to claim 15, wherein the first solvent
mixture is used in an amount corresponding to a weight ratio of
first solvent mixture to oil sand in a range from about 0.5 to 1 to
about 50 to 1.
19. The method according to claim 15, wherein the separating the
azeotropic mixture is carried out by distillation at a pressure in
a range from about 0.1 atmosphere to about 5 atmosphere.
20. A method for recovering bitumen from an oil sand, the method
comprising: (a) contacting at ambient temperature a
bitumen-containing oil sand with a first solvent mixture comprising
about 69 cyclohexane and about 31 percent ethanol to provide an
extraction mixture comprising a sand phase and an organic phase;
the first solvent mixture being used in an amount corresponding to
a weight ratio of first solvent mixture to oil sand in a range from
about 3 to 1 to about 500 to 1; (b) separating the sand phase from
the organic phase comprising bitumen, ethanol and cyclohexane; (c)
separating an azeotropic mixture comprising cyclohexane and ethanol
from the organic phase; and (d) recovering bitumen from the organic
phase.
Description
BACKGROUND
[0001] The invention relates generally to a method for recovering
oil from oil bearing sand, and more particularly to a recovering of
such oil in form of bitumen by a method that includes contacting
bitumen-containing sand with a liquid medium.
[0002] The world population, especially in the developed and
developing industrial countries, consumes enormous amounts of
energy. It is estimated that about half of the amount of energy
consumed comes from petroleum products. As the traditional sources
of oil are being exhausted, and as increased demand supports a
relatively high price for oil in the global marketplace, there is a
growing need for the development of alternate sources of oil.
[0003] One such alternate source of oil is oil bearing sands such
as oil shale and tar sands. Despite the fact that enormous amounts
of oil are present in the oil shale and tar sand deposits and the
fact that such deposits are located in many of the most
technologically advanced countries (including the United States and
Canada), the amounts of oil actually obtained from these deposits
are significantly lower than the amount of oil obtained from
traditional oil sources. The reason for this seeming paradox is
that oil in the oil shale and tar sands is more difficult and
expensive to recover than oil from a traditional oil source.
[0004] A number of processes for the recovery of oil from oil sands
have been explored over the past few years. These processes include
direct combustion (heating or retorting), solvent extraction, water
flotation and many variations of these processes to extract oil
from the oil sands. Organic material recoverable from oil sands is
at times referred to as bitumen. However currently known processes
for the extraction of oil in form of bitumen from oil sands face
both technical and economic challenges. One important technical
disadvantage of known processes is the relatively low recovery rate
of bitumen from a treated oil sand. For example, in a water
flotation process only about 50 to about 70 percent of the bitumen
is recovered from the oil sand. It is difficult to separate and
recover bitumen from oil sands because the organic material
comprising the oil sand is both a complex chemical mixture and may
be bound to the inorganic components of the oil sand and/or
physically trapped within the interstices of the sand component of
the oil sand. Thus, a variety of bitumen recovery schemes involve
the application of heat to the oil sand or solvent treatment of the
oil sand in order to enhance the recovery of bitumen from the
sand.
[0005] One known method of recovering useful organic material from
oil sands is referred to as the retorting method, which involves
heating the oil sand and recovering a distillate. A serious
limitation of the retorting method is that it is energy and capital
intensive and produces as a by-product a spent sand which may
require further treatment before it can be disposed of
appropriately. The energy intensiveness of the process can be
better appreciated by considering the cost of sustained heating of
large volumes of oil sand at high temperature. Generally
temperatures employed in the retorting process range between about
500.degree. C. and about 800.degree. C. Large capital expenditures
are needed for equipment used to heat the oil bearing sand, even if
the heating is carried out in situ. The oil recovered from oil
sands by conventional processes, such as retorting, is not
identical in composition to the conventional crude oil recovered
from the ground and for many applications such oil sand oil has to
be further treated by distillation, coking of residue and/or
hydrogenation to achieve the required characteristics.
[0006] Another approach to recovering oil from an oil bearing sand
has been to extract the oil with one or more solvents. Thus,
extractive separation of bitumen from oil sands using organic
solvents such as hydrocarbons and is known. In addition, extracting
oil from oil shale using a variety of organic solvents at elevated
temperatures and at elevated pressures has also been tried. Known
extraction processes have not been entirely successful because they
employ organic solvents which are generally quite expensive
relative to the value of the recovered bitumen and may require the
use of high temperatures and high pressures. The use of high
temperatures and/or pressures, in turn, necessitates the use of
sophisticated and expensive equipment. The solvent employed may
itself have a very strong affinity for the sand being treated, and
thus recovery of the solvent employed may present an additional
technical challenge and economic issue.
[0007] There remains a need for the efficient recovery of useful
bitumen from oil sand which is responsive to the economic realities
of recovering a relatively low-value organic product from an
abundant natural resource and the ecological imperative of doing so
in a manner consistent with the highest principles of environmental
stewardship.
BRIEF DESCRIPTION
[0008] In one aspect, the present invention provides a method for
recovering bitumen from an oil sand, the method comprising: (a)
contacting a bitumen-containing oil sand with a first solvent
mixture of cyclohexane and ethanol to provide an extraction mixture
comprising a sand phase and an organic phase; (b) separating the
sand phase from the organic phase comprising bitumen, ethanol and
cyclohexane; (c) separating an azeotropic mixture comprising
cyclohexane and ethanol from the organic phase; and (d) recovering
bitumen from the organic phase. The first solvent mixture comprises
from about 95 to about 65 percent cyclohexane and from about 5 to
about 35 percent ethanol.
[0009] In another aspect, the present invention provides a method
for recovering bitumen from an oil sand, the method comprising: (a)
contacting in situ a bitumen-containing oil sand in a subsurface
deposit with a first solvent mixture of cyclohexane and ethanol to
provide an extraction mixture comprising a sand phase and an
organic phase; (b) removing the organic phase comprising bitumen,
cyclohexane and ethanol from the subsurface deposit; (c) separating
an azeotropic mixture comprising cyclohexane and ethanol from the
organic phase; and (d) recovering bitumen from the organic phase.
The first solvent mixture comprising from about 95 to about 65
percent cyclohexane and from about 5 to about 35 percent
ethanol.
[0010] In yet another aspect, the present invention provides a
method for recovering bitumen from an oil sand, the method
comprising: (a) contacting at ambient temperature a
bitumen-containing oil sand with a first solvent mixture comprising
about 69 cyclohexane and about 31 percent ethanol to provide an
extraction mixture comprising a sand phase and an organic phase;
(b) separating the sand phase from the organic phase comprising
bitumen, ethanol and cyclohexane; (c) separating an azeotropic
mixture comprising cyclohexane and ethanol from the organic phase;
and (d) recovering bitumen from the organic phase. The first
solvent mixture being used in an amount corresponding to a weight
ratio of first solvent mixture to oil sand in a range from about 3
to 1 to about 500 to 1.
DETAILED DESCRIPTION
[0011] In the following specification and the claims, which follow,
reference will be made to a number of terms, which shall be defined
to have the following meanings.
[0012] The singular forms "a", "an" and "the" include plural
referents unless the context clearly dictates otherwise.
[0013] "Optional" or "optionally" means that the subsequently
described event or circumstance may or may not occur, and that the
description includes instances where the event occurs and instances
where it does not.
[0014] It is also understood that terms such as "top," "bottom,"
"outward," "inward," and the like are words of convenience and are
not to be construed as limiting terms. Furthermore, whenever a
particular feature of the invention is said to comprise or consist
of at least one of a number of elements of a group and combinations
thereof, it is understood that the feature may comprise or consist
of any of the elements of the group, either individually or in
combination with any of the other elements of that group.
[0015] Approximating language, as used herein throughout the
specification and claims, may be applied to modify any quantitative
representation that could permissibly vary without resulting in a
change in the basic function to which it is related. Accordingly, a
value modified by a term or terms, such as "about", is not to be
limited to the precise value specified. In some instances, the
approximating language may correspond to the precision of an
instrument for measuring the value. Similarly, "free" may be used
in combination with a term, and may include an insubstantial
number, or trace amounts, while still being considered free of the
modified term.
[0016] As discussed in detail below, embodiments of the present
invention include a method for recovering bitumen from an oil sand,
the method comprising: (a) contacting a bitumen-containing oil sand
with a first solvent mixture of cyclohexane and ethanol to provide
an extraction mixture comprising a sand phase and an organic phase;
(b) separating the sand phase from the organic phase comprising
bitumen, ethanol and cyclohexane; (c) separating an azeotropic
mixture comprising cyclohexane and ethanol from the organic phase;
and (d) recovering bitumen from the organic phase.
[0017] As used herein "oil sands" also includes but not limited to
tar sands, extra heavy oils, oily sludge wastes, oil-bearing
diatomites, oil shales, tar saturated sandstones and the like.
Further, oil sands as used herein also include mined oil sands as
well as crude output from steam assisted gravity drainage processes
(SAG-D processes). The methods provided by the present invention
may be applied to both mined oil sands (oil sands removed from a
first location to a second location for treatment), and subsurface
oil sand deposits. When applied to a subsurface oil sand deposit
the method is at times herein referred to as an in-situ recovery
method, and for example, the oil sand is said to be contacted in
situ with the first solvent mixture to provide an extraction
mixture.
[0018] Oil sands are a type of bitumen deposit which may be found
as deposits near the surface of the earth or in subsurface
deposits. Oil sand deposits located near the surface of the earth
may be mined using surface mining techniques and transported from a
first location where the oil sand is mined to a second location
where the oil sand is subjected to treatment for bitumen recovery.
In one embodiment, the oil sand is a subsurface deposit not readily
accessible using surface mining techniques.
[0019] The oil sands may comprise a mixture of sand, clay, water,
organometallic compounds, and a dense and viscous form of petroleum
also known as bitumen. Oil sands may also be referred to as
"unconventional oil" or "crude bitumen". Bitumen is especially
prone to the formation of highly stable emulsions due to its
chemical complexity which varies from deposit to deposit, its
occurrence in nature with water containing a variety of inorganic
species, and the considerable shear forces that the contents of an
oil deposit may experience during capture by a man-made
conduit.
[0020] As noted, the present invention provides a method in which a
bitumen-containing oil sand is contacted with a first solvent
mixture. The first solvent mixture includes a mixture of
cyclohexane and ethanol. In one embodiment, the first solvent
mixture includes cyclohexane and ethanol in a ratio from about 95
weight percent to about 65 weight percent of cyclohexane and from
about 5 weight percent to about 35 weight percent of ethanol based
on the total weight of the first solvent mixture. In another
embodiment, the first solvent mixture includes a mixture of
cyclohexane and ethanol in a ratio from about 90 weight percent to
about 65 weight percent of cyclohexane and from about 10 weight
percent to about 35 weight percent of ethanol based on the total
weight of the first solvent mixture. In yet another embodiment, the
first solvent includes a mixture of cyclohexane and ethanol in a
ratio from about 70 weight percent cyclohexane and about 30 weight
percent of ethanol based on the total weight of the first solvent
mixture. In a particular embodiment, the first solvent mixture
comprises cyclohexane and ethanol in a ratio from about 69 weight
percent cyclohexane and about 31 weight percent ethanol based on
the total weight of the first solvent mixture.
[0021] In one embodiment, the first solvent is used in an amount
corresponding to a weight ratio of first solvent mixture to the oil
sand in a range from about 3 to 1 to about 500 to 1. In another
embodiment, the first solvent is used in an amount corresponding to
a weight ratio of first solvent mixture to oil sand in a range from
about 3 to 1 to about 50 to 1. In yet another embodiment, the first
solvent is used in an amount corresponding to a weight ratio of
first solvent mixture to oil sand in a range from about 3 to 1 to
about 10 to 1.
[0022] In one embodiment, the contacting of the bitumen-containing
oil sand with the first solvent mixture is carried out for a period
of time ranging from about 0.1 hour to about 24 hours. In another
embodiment, the contacting of the bitumen-containing oil sand with
the first solvent mixture is carried out for a period of time
ranging from about 3 hour to about 15 hours. In one embodiment, the
contacting of the bitumen-containing oil sand and the first solvent
mixture is carried out at a temperature a range from about
25.degree. C. to about 150.degree. C. In another embodiment, the
contacting of the bitumen-containing oil sand and the first solvent
mixture is carried out at a temperature a range from about
45.degree. C. to about 120.degree. C. In yet another embodiment,
the contacting is carried out at ambient temperature. In one
embodiment, steam may be contacted with the extraction mixture.
[0023] The contacting of the bitumen-containing oil sand with the
first solvent provides an extraction mixture. The extraction
mixture includes a sand phase and an organic phase. The organic
phase includes bitumen, ethanol and cyclohexane. The sand phase is
separated from the organic phase. The separation of the sand phase
from the organic phase may be carried out by techniques known to
one skilled in the art. In one embodiment, the separation of the
sand phase and the oil phase may be carried out by gravity
separation, i.e. a separation in which the product is subjected to
defined gravitational forces tending to separate the heavier sand
from the lighter fluids. Examples of gravitational separation
include but are not limited to centrifugation, separation using a
hydrocyclone, rotary filtration, simple filtration, and the like.
In one embodiment, a hydrocyclone separation is employed which
includes a plurality of separating stages. In certain embodiments,
the sand phase obtained following contact with the first solvent
mixture may be discarded as bitumen-free and solvent-free sand. In
certain other embodiments, the sand phase may be separated from the
extraction mixture and thereafter be subjected to a second stage of
extraction. In embodiments in which the oil sand is being treated
in situ, the organic phase is removed from the spent sand phase by
bringing the organic phase to the surface. In embodiments involving
in situ contacting of an oil sand with the first solvent mixture in
a subsurface deposit, the first solvent mixture is introduced into
the subsurface deposit via at least one solvent inlet conduit. The
organic phase resulting from the contacting of the oil sand with
the first solvent mixture is thereafter removed via one or more
outlet conduits. In one embodiment, the solvent inlet conduit also
serves as the outlet conduit. In one embodiment, the solvent inlet
conduit delivers the first solvent to a subsurface oil sand deposit
while a plurality of outlet conduits arrayed radially about the
edge of the subsurface oil sand deposit removes the resultant
organic phase comprising bitumen, cyclohexane and ethanol. In order
to enhance the recovery of bitumen and solvent from the subsurface
oil sand deposit, the first solvent mixture may be heated prior to
or during contact with the subsurface oil sand. In one embodiment,
an inert gas or steam is used to enhance the removal of the organic
phase from the subsurface oil sand deposit. In one embodiment,
carbon dioxide is used to enhance the removal of the organic phase
from the subsurface oil sand deposit.
[0024] The organic phase separated from the sand phase may be
treated in order to separate and recover the cyclohexane and
ethanol employed and to recover the bitumen component of the
organic phase. In one embodiment, the organic phase is subjected to
conditions under which the cyclohexane and ethanol is removed from
the organic phase by distillation. In various embodiments
cyclohexane and ethanol are recovered as an azeotropic mixture
comprising about 69% cyclohexane and about 31% ethanol. As is
demonstrated herein, the use of an azeotropic mixture of
cyclohexane and ethanol provides a two-fold advantage in that the
azeotropic mixture has a significantly lower boiling point
(64.9.degree. C.) than either of its constituents solvents
cyclohexane (80.7.degree. C.) and ethanol (78.degree. C.); and the
extraction efficiency of cyclohexane-ethanol mixture with respect
to bitumen recovery is superior to the pure solvents. The lower
boiling point of the azeotropic mixture allows recovery of the
first solvent mixture for reuse at a lower cost since less energy
is required to effect its distillation. Thus, in one embodiment, an
azeotropic mixture of cyclohexane and ethanol is separated from the
organic phase. Those of ordinary skill in the art will understand
that a cyclohexane-ethanol mixture comprising 69% cyclohexane and
31% ethanol will have essentially the same composition before and
after distillation. When an azeotropic mixture (also sometimes
referred to as constant boiling mixture) is boiled the resulting
vapor has the same ratio of the constituents cyclohexane and
ethanol, as the original mixture. The separating of the azeotropic
mixture from the organic phase may be carried out by several
methods known to one skilled in the art for example distillation,
pressure swing distillation, extractive distillation, chemical
action separation, pervaporation, vapor permeation and the like. In
one embodiment, the separating the azeotropic mixture is carried
out by distillation. In one embodiment, the distillation is carried
out at a pressure in a range from about 0.1 atmospheres to about 5
atmospheres. In another embodiment, the separating the azeotropic
mixture is carried out by distillation at ambient pressure.
[0025] Recovery of bitumen from the organic phase may be carried
out by techniques known to one skilled in the art such as
centrifugation, filtration and the like. In one embodiment,
recovering of the bitumen from the organic phase includes reducing
the temperature of the organic phase to effect precipitation of the
bitumen from the organic phase and thereafter centrifuging of the
mixture to further separate the bitumen from the organic phase. In
one embodiment, the centrifugation of the organic phase is carried
out at a temperature in a range from about minus 40.degree. C. to
about 25.degree. C. In another embodiment, the centrifugation of
the organic phase is carried out at a temperature in a range from
about minus 5.degree. C. to about 20.degree. C. In one embodiment,
centrifugation results in the formation of a lower bitumen layer
and a supernatant liquid comprised chiefly of the first solvent
mixture. The supernatant liquid may be decanted from the lower
bitumen layer following centrifugation. In one embodiment, the
recovery of the bitumen from the organic phase is carried out prior
to separating the azeotropic mixture from the organic phase. In
another embodiment, the recovery of bitumen from the organic phase
is carried out following separating the azeotropic mixture from the
organic phase. In one embodiment, the extraction mixture is
distilled to provide an "overhead" stream comprising an azeotropic
mixture of cyclohexane and ethanol and a "bottoms" stream of
bitumen fluid. Such a process is amenable to continuous process
steps operated at steady state.
[0026] In one embodiment of the present invention, the method
further includes a drying step in which the organic phase is
treated with a drying agent prior to separation of the azeotropic
mixture comprising cyclohexane and ethanol. Non-limiting examples
of drying agents include anhydrous salts such as calcium chloride
(CaCl.sub.2), sodium sulfate (Na.sub.2SO.sub.4), calcium sulfate,
magnesium sulfate (MgSO.sub.4), and the like. In one embodiment,
the sand phase after separation from the organic phase (spent sand)
may be heated to remove any residual water and may be employed as a
drying agent in the drying step.
[0027] In some embodiments, the method includes a step of
transporting the organic phase to a second location remote from a
first location at which the contacting is carried out. In one
embodiment, the transporting comprises transport by pipeline.
[0028] In various embodiments, the bitumen recovered may be
transported and eventually upgraded into higher value products, for
example synthetic oil. In one embodiment, the bitumen obtained
after the recovery step includes less than about 1 parts per
million (ppm) of impurities such as vanadium, nickel and sulfur
compounds. In another embodiment, less than about 1 ppm of
impurities such as vanadium compounds.
[0029] In another aspect of the present invention a method for
recovering bitumen from an oil sand that includes (a) contacting
in-situ a bitumen-containing oil sand in a subsurface deposit with
a first solvent mixture of cyclohexane and ethanol to provide an
extraction mixture, a sand phase and an organic phase, the first
solvent mixture comprising from about 95 to about 65 percent
cyclohexane and from about 5 to about 35 percent ethanol; (b)
removing the organic phase comprising bitumen, cyclohexane and
ethanol from the subsurface deposit; (c) separating an azeotropic
mixture comprising cyclohexane and ethanol from the organic phase;
and (d) recovering bitumen from the organic phase. In one
embodiment, the order of the steps may be interchangeable. In
another embodiment, the order of steps (a)-(d) is first (a) then
(b) then (c) then (d).
[0030] In another embodiment, the methods includes (a) contacting
at ambient temperature a bitumen-containing oil sand with a first
solvent mixture comprising about 69 cyclohexane and about 31
percent ethanol to provide an extraction mixture comprising a sand
phase and an organic phase; the first solvent mixture being used in
an amount corresponding to a weight ratio of first solvent mixture
to oil sand in a range from about 3 to 1 to about 500 to 1; (b)
separating the sand phase from the organic phase comprising
bitumen, ethanol and cyclohexane; (c) separating an azeotropic
mixture comprising cyclohexane and ethanol from the organic phase;
and (d) recovering bitumen from the organic phase.
EXAMPLES
Preparation of Oil Sand Models
[0031] Oil sand models were prepared as follows. Britesorb.RTM.
D350EL silica adsorbent (approximately 35 grams) was added to a
blender, together with approximately 100 g of Saudi heavy crude oil
and 200 g of petroleum ether. The resulting slurry was mixed for
about five minutes at room temperature and was then poured into
centrifuge tubes. Each tube was centrifuged, and the resulting
liquid fractions were decanted from the Britesorb.RTM. D350EL
solids containing crude oil. The solids were dried under vacuum at
80.degree. C. for about two hours. The dried solids were then
analyzed using a Thermogravimetric Analyzer (TGA). The percent
weight loss between the initial onset of devolatization and/or
decomposition at about 200.degree. C. to about 650.degree. C. was
interpreted to reflect the removal of the residual organic material
(oil components) from the adsorbent. The results indicated that the
model oil sands comprised about 34.2 wt. % oil components.
[0032] First solvent mixtures (wash solutions) comprising
cyclohexane and ethanol were prepared and are given in Table 1
together with data for the recovery of oil components.
[0033] Oil sand models were contacted with first solvent mixture as
follows. The oil sand model (0.5 g) was placed in a vial along with
about 13 g of the particular wash solution being tested. The
resulting slurry was mixed for about five minutes on an auto-shaker
at room temperature and poured into a centrifuge tube. The tube was
centrifuged and the resulting organic phase was decanted away from
the model sand phase. The model sand phase was contacted two
additional times with the same solvent mixture as before. The model
sand thus recovered was analyzed by thermogravimetric analysis
(TGA) to determine an amount of oil remaining on the solid
phase.
[0034] TGA was performed on 5-10 mg samples. The temperature was
increased at a rate of 10-20.degree. C./minute to the desired final
temperature in a range from about 650.degree. C. to about
700.degree. C. During the analysis the sample was exposed to a
constant flow of air at 0.04 standard cubic feet per hour. As the
temperature increased, oil components were volatilized and/or
decomposed and thereby removed from the solid adsorbent resulting
in a corresponding weight loss. The weight loss corresponds
precisely to the oil that was present within the adsorbent. By
knowing the amount of oil initial present in the model oil sand and
the amount of oil remaining after washing, an efficacy of the wash
step can be quantified. Exemplary results are set forth in Table 1
below. The data show the unique ability of solvent mixtures having
compositions comprising from about 95 to about 65 percent
cyclohexane and from about 5 to about 35 percent ethanol to effect
the removal of the oil components from the oil sand model.
TABLE-US-00001 TABLE 1 Cyclohexane Ethanol Oil Removed Vanadium TGA
(wt %) (wt %) (%) (ppm) % wt loss CEx. 1 100 0 41.4 -- -- CEx. 2 10
90 36.9 0.6 5.31 CEx. 3 0 100 35.4 <0.1 32.76 Ex. 1 90 10 99.3
-- -- Ex. 2 75 25 98.0 -- -- Ex. 3 50 50 71.8 -- -- Ex. 4 25 75
46.8 0.5 5.87
[0035] The foregoing examples are merely illustrative, serving to
exemplify only some of the features of the invention. The appended
claims are intended to claim the invention as broadly as it has
been conceived and the examples herein presented are illustrative
of selected embodiments from a manifold of all possible
embodiments. Accordingly, it is the Applicants' intention that the
appended claims are not to be limited by the choice of examples
utilized to illustrate features of the present invention. As used
in the claims, the word "comprises" and its grammatical variants
logically also subtend and include phrases of varying and differing
extent such as for example, but not limited thereto, "consisting
essentially of" and "consisting of." Where necessary, ranges have
been supplied; those ranges are inclusive of all sub-ranges there
between. It is to be expected that variations in these ranges will
suggest themselves to a practitioner having ordinary skill in the
art and where not already dedicated to the public, those variations
should where possible be construed to be covered by the appended
claims. It is also anticipated that advances in science and
technology will make equivalents and substitutions possible that
are not now contemplated by reason of the imprecision of language
and these variations should also be construed where possible to be
covered by the appended claims.
* * * * *