Note: Descriptions are shown in the official language in which they were submitted.
CA 02540300 2006-03-17
Oil Extraction
BACKGROUND
Oil has been routinely recovered from oil-bearing plants for thousands of
years. A large variety of plants produce sufficient quantities of oil that can
be
processed into edible or industrial products.
Oil from oil-bearing plants is typically extracted by solvents. Solvent
extraction is a mass-transfer process in which one or more materials are
transported
from a mixture to a solvent phase, resulting in their separation from the
mixture.
Various organic solvents have been used for commercial extraction. However,
there
still exists a need in developing a cost-effective solvent and environment-
friendly
extraction process for recovering oil from oil-bearing plants.
SUMMARY
This invention is based on the discovery that a triglyceride can be readily
extracted from an oil-bearing seed by using a fatty acid alkyl ester as a
solvent.
In one aspect, this invention features a method of producing a triglyceride
solution. The method includes contacting a liquid fatty acid alkyl ester and a
substance containing triglyceride (e.g., at 15-180 C or 25-150 C) so that the
triglyceride is dissolved into the fatty acid alkyl ester to form a
triglyceride solution.
Preferably, the fatty acid alkyl ester is obtained, prior to the contacting
step, by
reacting alcohol (e.g. a C1-C8 primary or secondary alcohol) with triglyceride
extracted from the same triglyceride-containing substance. Exemplary alcohols
include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-
pentanol,
isopentanol, neopentanol and n-hexanol. The fatty acid alkyl ester and the
triglyceride-containing substance can be mixed at a weight ratio ranging from
1:2 to
10:1 (e.g., from 1:1 to 6:1).
The triglyceride-containing substance can be oil-bearing seed. The term "oil-
bearing seed" refers to any plant seed suitable for oil extraction. Examples
of oil-
bearing seed include, but are not limited to, soybean, peanut, sunflower seed,
rapeseed, corn (e.g., corn germs or distillers dried corn grains), jatropha
seed, karanja
seed, neem seed, mahua seed, castor bean, rubber seed, cotton seed, palm
kernel,
olive, almond kernel, babassu seed, ben seed, cardoon seed, camelina seed,
linseed,
hazelnut kernel, hemp seed, mustard seed (e.g., Ethiopian mustard seed and
Indian
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mustard seed), jojoba seed, poppy seed, safflower seed, sesame seed, wheat
grain, sal
seed, crambe seed, cuphea seed, nahor seed, and tobacco seed. Alternatively,
the
triglyceride-containing substance can be obtained from parts other than seed
in certain
oil-bearing plants. The term "oil-bearing plant" refers to any plant that
contains oil in
any part (e.g., seed or fruit) and is suitable for oil extraction. Examples in
addition to
those listed above include, but are not limited to, rice bran, palm (e.g.,
palm fruit
pulp), yellowwood, and algae.
The fatty acid alkyl ester described above can contain a C 1-C8 primary or
secondary alkoxy moiety or a C6-C24 fatty acid moiety. The term "alkoxy"
refers to
a straight or branched, saturated or unsaturated, non-aromatic hydrocarbon
moiety
containing an oxygen radical, such as -OCH3 or -OCH=C2H4. The term "fatty
acid"
mentioned herein refers to a straight or branched, saturated or unsaturated
monobasic
organic acid. Exemplary fatty acids include, but are not limited to, caproic
acid,
caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid,
margaric acid,
stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric
acid,
palmitoleic acid, oleic acid, linoleic acid, linolenic acid, cis-11-eicosenoic
acid, and
erucic acid. Exemplary fatty acid alkyl esters include, but are not limited
to, fatty acid
methyl esters, fatty acid ethyl esters, fatty acid n-propyl esters, fatty acid
isopropyl
esters, fatty acid n-butyl esters, fatty acid isobutyl esters, fatty acid n-
pentyl esters,
fatty acid isopentyl esters, fatty acid neopentyl esters, and fatty acid n-
hexyl esters.
Typically, the fatty acid alkyl ester can have a boiling point of 150-500 C.
The details of one or more embodiments of the invention are set forth in the
description below. Other features, objects, and advantages of the invention
will be
apparent from the description and from the claims.
DETAILED DESCRIPTION
This invention relates to extracting a triglyceride from an oil-bearing plant
using a fatty acid alkyl ester as a solvent at a certain temperature (e.g., 15-
180 C) to
obtain an extraction solution. When the oil-bearing plant contains a high oil
content,
the plant can be optionally pressed or squeezed to remove a portion of the oil
before
extraction. If desired, the oil-bearing plant can also be pulverized to
facilitate
extraction.
The extraction process can be performed by methods well known in the art.
As an example, it can be carried out by mixing a pulverized oil-bearing plant
and a
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fatty acid alkyl ester in a continuous stirred-tank reactor for a
predetermined period of
time. As another example, it can be carried out continuously by bring
together,
without mixing, a pulverized oil-bearing plant and a fatty acid alkyl ester in
a plug
flow reactor or a fixed bed reactor through a counter-current flow, a co-
current flow,
or a combination of both flows. The extraction process can be carried out by
either a
batch method or a flow method. Typically, a flow method can be used to help
maintain reasonable manufacturing costs.
The extraction can be performed at different temperatures. Generally,
extraction at a higher temperature (e.g., above 35 C) recovers more oil.
However,
high temperature extraction may also produce more impurities (e.g., phosphorus
and
moisture). The weight ratio between the solvent and the oil-bearing plant used
in the
extraction process depends on various factors, e.g., the type of the oil-
bearing plant
and the oil content in the oil-bearing plant. For example, one can use a low
weight
ratio for extracting a prepressed oil-bearing plant, from which a portion of
the oil in
the plant has been removed. Typically, the weight ratio is in the range of 1:2
to 10:1.
Other extraction conditions (e.g., the extraction time) can be determined
empirically.
The fatty acid alkyl ester used in the extraction process can be prepared by
known methods. For example, a fatty acid alkyl ester can be prepared by an
esterification reaction between an alcohol (e.g., ethanol) and a fatty acid
(e.g., stearic
acid). As another example, a fatty acid alkyl ester can be prepared by a
transeterification reaction between an alcohol and a triglyceride, such as the
transeterification reactions described in U.S. Patent Application 10/945,339.
Preferably, the fatty acid alkyl ester is prepared from a C 1-C4 alcohol.
Extractions
with such a fatty acid alkyl ester generally produce a triglyceride solution
that
contains less impurities (e.g., phosphorus and moisture). The triglyceride
used to
prepare the fatty acid alkyl ester can be obtained from a plant different from
the plant
to be extracted. Preferably, the triglyceride is obtained from a plant that is
the same
as the plant to be extracted. In that case, the triglyceride extracted from
the plant is
identical to the triglyceride used to prepare the extraction solvent (i.e.,
the fatty acid
alkyl ester). As a result, if the extracted triglyceride is subsequently used
to prepare
the fatty acid alkyl ester via a transesterification reaction, the fatty acid
alkyl ester in
an extraction solution can be used as a solvent for the reaction and therefore
needs not
to be separated from the extracted triglyceride.
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After the extraction process, the fatty acid alkyl ester can be optionally
separated from the extracted triglyceride by partially or completely removal
from an
extraction solution. The removal step can be carried out by distillation using
a
vacuum column, a short-path vacuum distillation unit, or any other suitable
device
known in the art. Whether to remove the fatty acid alkyl ester partially or
completely
from an extraction solution or to remove it at all depends on various factors,
such as
the ratio between the fatty acid alkyl ester and the extracted triglyceride
and the end
use of the extracted triglyceride.
The extracted triglyceride can be further processed for use in the food and
pharmaceutical industries. It can also be used as a raw material for preparing
fatty
acid alkyl esters or fatty alcohols. Fatty acid alkyl esters are useful as
diesel fuels,
lubricant oils, or chemical intermediates. Fatty alcohols are useful as
surfactants in
detergent industry.
The specific examples below are to be construed as merely illustrative, and
not
limitative of the remainder of the disclosure in any way whatsoever. Without
further
elaboration, it is believed that one skilled in the art can, based on the
description
herein, utilize the present invention to its fullest extent.
Example 1
Soybeans were first ground into a powder and sieved through a filter having a
size of 40 mesh (about 425-520 m). Soybean powder having an average particle
size
of less than 40 mesh, which is similar to a dehulled powder, was collected and
used
for oil extraction.
The soybean powder obtained above was dried until it had a moisture content
of less than 6 wt%. The powder was then extracted using soybean based fatty
acid
methyl esters (FAMEs) as a solvent in a beaker with agitation. The soybean
based
FAMEs were previously prepared by a transesterification reaction between
methanol
and triglycerides obtained from soybean.
The extraction process was carried out by using FAMEs at a solvent-to-
powder weight ratio of 6:1 at 35 C. The beaker was agitated at a revolution
per
minute (rpm) of 300. After 30 minutes of extraction, the content of the
miscella (i.e.,
the solution containing extracted oil) was determined. The oil content in the
miscella
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was determined by HPLC (JASCO model 1580; column: Luna Su C18, 2 m,
250*4.6 mm, Phenomenex, Torrance, CA; mobile phases: methanol, and
hexane/isopropyl alcohol (4:5); UV detector: UV-2075, JASCO Inc., Tokyo,
Japan).
The moisture content in the miscella was determined by the Karl-Fisher method
according to the operation manual, MKC-500 KF Moisture Titrator Kyoto
Electronic
Manufacturing Co. Ltd, Ver. 04, #595-0006. The phosphorus content in the
miscella
was determined according to American Oil Chemist's Society official method Ca
12-
55. The results showed that miscella contained a moisture content of 818 ppm,
a
phosphorus content of 14.4 ppm, and an oil content of 3.60 wt%. The weight of
the
extracted oil was 20% of that of the soybean powder.
The soybean powder was also successively extracted with FAMEs at a
reduced solvent-to-powder ratio in a beaker. Specifically, the powder was
extracted
twice at a solvent-to-powder ratio of 1: 1 by agitating the beaker at a rpm of
1,000 for
mintues. After the first extraction, the miscella contained a moisture content
of
15 989 ppm, a phosphorus content of 23.4 ppm, and an oil content of 14.08 wt%.
After
the second extraction, the miscella contained a moisture content of 1,428.3
ppm, a
phosphorus content of 14.23 ppm, and an oil content of 6.13 wt%. After two
extractions, the total weight of the extracted oil was 21.59% of that of the
soybean
powder.
Finally, the soybean powder obtained above was also extracted via a
conventional method. Specifically, the powder was extracted by Gerhardt's
Soxtherm
automated soxlet system using hexane as a solvent at a solvent-to-powder ratio
of 8:1
at 65 C. This method is described in Official and Tentative Methods, the
American
Oil Chemist Society, Vol. 1, AOCS Champaign Il (1980) Method Am 2-93. The
results show that the oil contained a phosphorus content of 265 ppm. The
weight of
the extracted oil was 18.8% of that of the soybean powder.
Example 2
Two types of oil-bearing seeds were extracted by FAMEs prepared from
triglycerides obtained from their corresponding oil sources. Specifically,
sunflower
seeds were extracted by sunflower seed based FAMEs and peanuts (ground nuts)
were
extracted by peanut based FAMEs.
Sunflower seeds were dehulled and ground into a powder having an average
particle size of less than 40 mesh. The powder was dried until it had a
moisture
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content of less than 6 wt%. It was then extracted twice in a beaker with
sunflower
seed based FAME at a solvent-to-powder ratio of 1:1. Each extraction was
conducted
by agitating the beaker at a rpm of 1,000 for 15 minutes at 35 C. After the
first and
second extractions, the miscella contained a moisture content of 794 and 831
ppm,
respectively, a phosphorus content of 49.6 and 47.8 ppm, respectively, and an
oil
content of 35.65 and 12.30 wt%, respectively. After two extractions, the total
weight
of the extracted oil was 54.83% of that of the sunflower seeds.
Peanuts were ground into a powder having an average particle size of less than
25 mesh (i.e., about 425-710 m) and then dried until it contained less than 6
wt /o of
moisture. The powder was then extracted four times in a beaker with peanut
based
FAMEs at a solvent-to-powder ratio of 1:1. Each extraction was conducted by
agitating the beaker at a rpm of 1,000 for 15 minutes at 35 C. After the
first, second,
third, and fourth extractions, the miscella contained a moisture content of
701, 690,
661, and 661 ppm, respectively, a phosphorus content of 23.5, 16.4, 0, and 0
ppm,
respectively, and an oil content of 31.4, 10.9, 2.63, and 0.78 wt%,
respectively. After
three extractions, the total weight of the extracted oil was 45.83% of that of
the
peanuts. After four extractions, the total weight of the extracted oil was
47.48% of
that of the peanuts.
Example 3
Soybeans were extracted by soybean based fatty acid ethyl esters (FAEEs).
Soybean based FAEEs were prepared by a transesterification reaction between
ethanol and triglycerides obtained from soybeans.
Soybeans were first ground into a powder having an average particle size of
less than 40 mesh and then dried until it had a moisture content of less than
6 wt%.
The powder was then extracted three times in a beaker with soybean based FAEEs
at
a solvent-to-powder ratio of 1: 1. Each extraction was conducted by agitating
the
beaker at a rpm of 1000 for 15 minutes at 35 C. After the first, second, and
third
extractions, the miscella contained a moisture content of 650, 652, and 694
ppm,
respectively, a phosphorus content of 39.4, 23.3, 16.0 ppm, respectively, and
an oil
content of 14.09, 5.93, and 1.05 wt%, respectively. After three extractions,
the total
weight of the extracted oil was 20.1 % of that of the soybean powder.
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Example 4
Soybeans were extracted by a method similar to that described in Example 3
except that soybean based fatty acid butyl esters (FABEs) were used as a
solvent.
Soybean based FABEs were prepared by a transesterification reaction between n-
butanol and triglycerides obtained from soybeans.
After the first, second, and third extractions, the miscella contained a
moisture
content of 576, 519, and 479 ppm, respectively, a phosphorus content of
27.32,13.49,
and 0.96 ppm, respectively, and an oil content of 15.93, 5.10, and 1.60 wt%,
respectively. After three extractions, the total weight of the extracted oil
was 21.6%
of that of the soybean powder.
Example 5
Soybeans were extracted by a method similar to that described in Example 4
except that the extractions were conducted at a reduced agitation rate, i.e.,
at a rpm of
500. Further, the extractions were conducted at four different temperatures,
i.e.,
35 C, 60 C, 100 C, and 150 C.
The results show that the total weight of the extracted oil increased at
higher
temperatures. Specifically, at 35 C, 60 C, 100 C, and 150 C, the total weights
of the
extracted oil were respectively 21.42, 23.25, 28.4, and 32.8% of those of
soybean
powder. The results also show that at 35 C, 60 C, 100 C, and 150 C, the
phosphorus
contents in a mixture containing a combination of miscella obtained after each
extraction were 16.2, 18.64, 48.32, and 91.12 ppm, respectively.
Example 6
Two oil-bearing seeds were extracted by FAMEs prepared from triglycerides
obtained from their corresponding oil sources and triglycerides obtained from
another
oil source. Specifically, sunflower seeds were extracted by sunflower seed
based
FAMEs and soybean based FAMEs, and peanuts (ground nuts) were extracted by
peanut based FAMEs and soybean based FAMEs.
Sunflower seeds were extracted with sunflower seed based FAMEs and
soybean based FAMEs using a method similar to that described in Example 2
except
that a solvent-to-powder ratio of 6:1 was used and that only one extraction
was
performed. After the extraction with sunflower seed based FAMEs and soybean
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based FAMEs, the miscella contained a moisture content of 466 and 856 ppm,
respectively, a phosphorus content of 10.6 and 12.78 ppm, respectively, and an
oil
content of 6.33 and 4.06 wt%, respectively. The total weight of the extracted
oil was
39.0% of that of the sunflower seeds when sunflower seed based FAMEs were used
as the solvent and 24.71 % of that of the sunflower seeds when soybean based
FAMEs
were used as the solvent.
Peanuts were extracted with peanut based FAMEs and soybean based FAMEs
using a method similar to that described in Example 2 except that the solvent-
to-
powder ratio was 6:1 and that only one extraction was performed. After the
extraction with peanut seed based FAMEs and soybean based FAMES, the miscella
contained a moisture content of 470 and 718 ppm, respectively, a phosphorus
content
of 19.36 and 10.0 ppm, respectively, and an oil content of 6.23 and 6.83 wt%,
respectively. The total weight of the extracted oil was 39.1 % of that of the
peanuts
when peanut based FAMEs were used as the solvent and 39.8% of that of the
peanuts
when soybean based FAMEs were used as the solvent.
The above results show that oil could be extracted from a plant seed using
FAMEs prepared from oil of the same plant seed and FAMEs prepared from oil of
a
different plant seed.
OTHER EMBODIMENTS
All of the features disclosed in this specification may be combined in any
combination. Each feature disclosed in this specification may be replaced by
an
alternative feature serving the same, equivalent, or similar purpose. Thus,
unless
expressly stated otherwise, each feature disclosed is only an example of a
generic
series of equivalent or similar features.
From the above description, one skilled in the art can easily ascertain the
essential characteristics of the present invention, and without departing from
the spirit
and scope thereof, can make various changes and modifications of the invention
to
adapt it to various usages and conditions.
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