U.S. patent application number 15/140866 was filed with the patent office on 2016-08-18 for subcritical water assisted oil extraction and green coal production from oilseeds.
The applicant listed for this patent is Tyton Biosciences, LLC. Invention is credited to Igor Kostenyuk, Sandeep Kumar, Peter J. Majeranowski, Sergiy Popov.
Application Number | 20160237377 15/140866 |
Document ID | / |
Family ID | 50545116 |
Filed Date | 2016-08-18 |
United States Patent
Application |
20160237377 |
Kind Code |
A1 |
Kumar; Sandeep ; et
al. |
August 18, 2016 |
SUBCRITICAL WATER ASSISTED OIL EXTRACTION AND GREEN COAL PRODUCTION
FROM OILSEEDS
Abstract
Provided herein are methods of optimizing energy recovery from
oilseeds. The methods disclosed provide at least the ability to
swell oilseeds and disrupt the cell walls (hulls) without changing
the functionality and quality of oil; the process integration of
oil extraction and green coal production to maximize the energy
recovery in the form of crude oil and green coal from oilseeds; and
heat integration during processing stages including subcritical
water pretreatment, oil extraction, and subcritical water
carbonization to minimize the process heat requirement.
Inventors: |
Kumar; Sandeep; (Norfolk,
VA) ; Popov; Sergiy; (Norfolk, VA) ;
Majeranowski; Peter J.; (Norfolk, VA) ; Kostenyuk;
Igor; (Danville, VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tyton Biosciences, LLC |
Danville |
VA |
US |
|
|
Family ID: |
50545116 |
Appl. No.: |
15/140866 |
Filed: |
April 28, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14437846 |
Apr 23, 2015 |
9328312 |
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PCT/US13/64966 |
Oct 15, 2013 |
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15140866 |
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61717219 |
Oct 23, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10L 2290/544 20130101;
C11B 1/104 20130101; C10L 5/44 20130101; C11B 1/10 20130101; C10L
2200/0484 20130101; C11B 1/04 20130101; Y02E 50/30 20130101; Y02E
50/10 20130101 |
International
Class: |
C11B 1/10 20060101
C11B001/10; C11B 1/04 20060101 C11B001/04; C10L 5/44 20060101
C10L005/44 |
Claims
1. A process for optimizing energy recovery from an oilseed
comprising: pretreating whole oilseeds with subcritical water at a
pretreatment temperature; separating pretreated oilseeds from a
pretreated liquid phase; and extracting oil from the pretreated
oilseeds using an organic solvent.
2. The process of claim 1, wherein the pretreatment temperature is
between about 180.degree. C. and 220.degree. C.
3. The process of claim 1, wherein pretreating occurs for a period
between 5 minutes and 60 minutes.
4. The process of claim 1, wherein the whole oilseeds are one or
more of cotton seeds, rapeseeds, mustard seeds, jathopha seeds,
sunflower seeds, safflower seeds, tobacco seeds, sesame soybeans,
cotton seeds, flaxseeds, and canola seeds.
5. The process of claim 1, wherein the organic solvent is selected
from n-hexane, ethanol, methanol, chloroform, acetone,
dichloromethane, and petroleum ethers.
6. The process of claim 1 further comprising: separating a solid
phase from the oil after extraction; producing green coal from the
solid phase with subcritical water carbonization of the solid phase
at a carbonization temperature.
7. The process of claim 6 further comprising: producing green coal
also from the pretreated liquid phase with subcritical water
carbonization of the liquid phase at the carbonization
temperature.
8. The process of claim 6, wherein the pretreatment temperature is
between about 180.degree. C. and 220.degree. C.
9. The process of claim 6, wherein pretreating occurs for a period
between 5 minutes and 60 minutes.
10. The process of claim 6, wherein the whole oilseeds are one or
more of cotton seeds, rapeseeds, mustard seeds, jathopha seeds,
sunflower seeds, safflower seeds, tobacco seeds, sesame soybeans,
cotton seeds, flaxseeds, and canola seeds.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/437,846, filed Apr. 23, 2015, which is a 35
U.S.C. 371 national stage of International Patent Application No.
PCT/US2013/064966 filed on Oct. 15, 2013, claiming priority to U.S.
Provisional Patent Application Ser. No. 61/717,219 filed on Oct.
23, 2012, all incorporated herein by reference in their
entireties.
BACKGROUND
[0002] Oilseeds are grains that are valuable for the oil content
they produce. Some of these oilseeds are cotton seeds, rapeseeds,
mustard, sunflower, safflower, tobacco seeds, sesame soybeans,
cotton seed, flaxseed, and canola seed. The oil content in these
seeds depends on the type of plants, but it is common to get 15-50
weight % of oil in the total seed mass. Table 1 shows the oil
content in some common seeds on a dry basis:
TABLE-US-00001 Moisture Oil/Fat content content Seeds (wt %) (wt %)
Cotton 5 15-25 Rape 9 40-45 Mustard 7 25-45 Sesame 5 25-50
Sunflower 5 25-50 Safflower 5 25-30 Tobacco 7 35-45
[0003] Oilseeds are used chiefly to produce vegetable oil and
oilseed meal, which in turn are used to produce food fats and oil
products, as well as animal feed for poultry, hogs, and cattle.
Other applications are in soap-making, cosmetics, detergents, or as
an ingredient in other foods.
[0004] Recently, non-food bases oils (e.g., tobacco seeds, cotton
seeds) are being envisioned as a renewable feedstock for producing
biodiesel or other alternative fuels. The procedures to extract oil
from seeds are generally solvent extraction and pressing. At
commercial scales, the seeds are subjected to a number of
processing steps prior to oil extraction. The oilseed is first
cleaned to remove trash, dirt, and sand before subjecting the
oilseeds to mechanical extraction such as pressing or solvent
extraction process. The conventional method of pressing the seeds
leaves too much high value oil in the seed cakes. Therefore,
solvent extraction methods are used to maximize the oil
extracted.
[0005] Solvent extraction achieves more complete oil recovery than
mechanical extraction but requires a thorough preparation of the
feedstock (e.g. drying, cleaning, dehulling, conditioning, flaking,
cooking/tempering, pre-pressing, etc.) Solvent extraction removes
the oil from a flaked seed or oil-cake by treating the flaked seed
or oil-cake with non-polar solvents such as hexane. FIGS. 1A and 1B
illustrate the major steps involved in oil extraction using
pressing and solvent extraction. These processes are generally
expensive and have some well-known challenges, such as additional
seed preparation stages, use of dry seeds, primer pressing, steam
cooking to facilitate the solvent extraction process, long
extraction time, loss of volatile compounds, and the generation of
large amount of toxic solvent/chemical waste. Accordingly, improved
processes are desired.
SUMMARY
[0006] Disclosed herein are processes for optimizing energy
recovery from an oilseed. Energy recovery is optimized by producing
both crude oil and green coal from the oilseeds. One method
disclosed herein comprises pre-treating whole oilseeds with
subcritical water at a pretreatment temperature, separating
pretreated oilseeds from a pretreated liquid phase and extracting
crude oil from the pretreated oilseeds using an organic
solvent.
[0007] The method can further comprise separating a solid phase
from the crude oil after extraction and producing green coal from
the solid phase with subcritical water carbonization of the solid
phase at a carbonization temperature. The method can further
comprise also producing green coal from the pretreated liquid phase
with subcritical water carbonization of the liquid phase at the
carbonization temperature.
[0008] The methods disclosed provide at least the ability to swell
oilseeds and disrupt the cell walls (hulls) without changing the
functionality and quality of oil; the process integration of oil
extraction and green coal production to maximize the energy
recovery in the form of crude oil and green coal from oilseeds; and
heat integration during processing stages including subcritical
water pretreatment, oil extraction, and subcritical water
carbonization to minimize the process heat requirement.
[0009] The integrated processes disclosed provide several major
advantages over conventional processes including higher oil yield,
shorter extraction time, tolerance to high moisture content of the
feedstock, elimination of preparation stages, and utilization of
the extracted solid residue for green coal production.
[0010] The most energy-intensive and costly stage in the production
of fuels from oil-based feedstock is extraction and purification of
oils derived from the biomass feedstock. The processes disclosed
herein concentrate on extraction and purification of oil from the
biomass, and in particular from oilseeds. With the use of the
disclosed processes, as much as 85% of the energy content in
oilseeds is expected to be recovered in the form of products such
as crude oil and green coal. The extracted oils can be readily
converted into biodiesel through the well-studied
transesterification process or into renewable diesel and advanced
biofuels (jet fuel, green diesel) through the catalytic
hydrodeoxygenation process, as examples. Valuable byproducts are
also produced which can be used in the cosmetics/pharmaceutics
industry. The green coal produced from the residue has application
as a solid fuel.
[0011] These and other aspects of the present disclosure are
disclosed in the following detailed description of the embodiments,
the appended claims and the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention is best understood from the following detailed
description when read in conjunction with the accompanying
drawings. It is emphasized that, according to common practice, the
various features of the drawings are not to-scale. On the contrary,
the dimensions of the various features are arbitrarily expanded or
reduced for clarity. Included in the drawings are the following
figures:
[0013] FIG. 1A illustrates major steps involved in conventional oil
extraction from oilseeds via pressing;
[0014] FIG. 1B illustrates major steps involved in conventional oil
extraction from oilseeds via solvent extraction;
[0015] FIG. 2 is a flow diagram of the processes disclosed
herein;
[0016] FIG. 3 is a table of different oilseeds and their
corresponding weights after subcritical water pretreatment;
[0017] FIG. 4 is a graph showing the pH of the aqueous phase after
subcritical water pretreatment;
[0018] FIG. 5 is a graph showing the total organic carbon of the
aqueous phase after subcritical water pretreatment;
[0019] FIG. 6 is a table of the oil yields from both ground seeds
and seeds subjected to subcritical water pretreatment;
[0020] FIG. 7 is a table of the oil yields from both ground seeds
and seeds subjected to subcritical water pretreatment on a raw seed
basis;
[0021] FIG. 8 is a graph of the fatty acid concentrations in the
oils extracted from both the ground seeds and the seeds subjected
to subcritical water pretreatment;
[0022] FIG. 9A is a graph illustrating the mass distribution of
products from oilseeds after the processes disclosed herein;
[0023] FIG. 9B is a graph illustrating the energy (ECR)
distribution of products from oilseeds after the processes
disclosed herein; and
[0024] FIG. 10 is a flow diagram of the material balance of the
processes disclosed herein.
DETAILED DESCRIPTION
[0025] Subcritical water is a non-toxic, environmentally benign,
inexpensive, and green solvent which can be used as an alternative
to conventional organic solvents generally used in the solvent
extraction process, such as n-hexane. Liquid water below the
critical point is referred to as subcritical water. In the
subcritical region, the ionization constant (K.sub.w) of water
increases with temperature and is about three orders of magnitude
higher than that of ambient water, and the dielectric constant
(.di-elect cons.) of water drops from 80 to 20. A low .di-elect
cons. allows subcritical water to dissolve organic compounds, while
a high K.sub.w allows subcritical water to provide an acidic medium
for the hydrolysis of biomass components. Because of its tunable
solvent properties, subcritical water can be employed to extract
many organic components from biomass.
[0026] Subcritical water pretreatment, also referred to herein as
hydrothermal pretreatment, of the oilseeds increases the
accessibility to the oils encased inside the hulls. The subcritical
water swells oilseeds to disrupt the seed walls (hulls) without
changing the functionality and quality of oil. The subcritical
water increases the Brunauer-Emmett-Teller (BET) surface area, the
pore volume and the pore diameter. Cell walls, in general, are
organized in a conventional framework. The basic framework is
highly polymeric. Interspersed within the framework are lower
molecular weight polymers, inorganic, and non-monomeric compounds.
The solvent properties of subcritical water in the range of
120-220.degree. C. are used for 5 to 60 minutes of pretreatment
time to hydrolyze the amorphous or water-soluble components of cell
walls and enhance the solvent's accessibility for extracting oils
in the subsequent stage. With the removal of amorphous components
after subcritical water pre-treatment, surface modifications (e.g.
creation of cracks and pores) occur as a result of mild hydrolysis
over the cell wall surface. As non-limiting examples, oilseeds
include cotton seeds, rapeseeds, mustard seeds, sunflower seeds,
safflower seeds, jathopha seeds, tobacco seeds, sesame soybeans,
cotton seeds, flaxseeds, and canola seeds.
[0027] FIG. 2 is a flow diagram of a process for producing crude
oil and green coal from oilseeds. As illustrated, in step 10, the
oilseeds are subjected to subcritical water pre-treatment.
[0028] The temperature range of 120-220.degree. C. for the
pretreatment is selected based on the hydrolyzing properties of
subcritical water for biopolymers. Above 220.degree. C.,
subcritical water starts hydrolyzing biomass polymers (cellulose,
proteins) to water-soluble compounds that leads to liquefaction of
biomass components as well as hydrolysis of oils to fatty acids. In
other words, the oilseed cell material (i.e., hulls) would be
liquefied as oxygenated hydrocarbons in the aqueous phase during
such extraction procedures. Due to the higher
liquefaction/extraction temperature used (250-350.degree. C.), the
quality of oil is not preserved and part of oil is hydrolyzed to
fatty acids. Furthermore, no wet cake is produced.
[0029] Because swelling the oilseeds rather than liquefying the oil
seeds is desired, the subcritical water pretreatment temperature is
at or kept below 220.degree. C. This not only helps in protecting
oil quality, but also preserving the oilseed cell materials or
hulls which can be used for the green coal production in
subcritical water.
[0030] The oil is extracted from the pretreated seeds using organic
solvents in step 12. Organic solvents such as n-hexane, ethanol,
methanol, chloroform, acetone, dichloromethane, and petroleum
ethers can be used for the oil extraction from the subcritical
water pretreated seeds. Extraction can be performed using a Soxhlet
extraction apparatus, as a non-limiting example. The liquid phase
and solid phases are separated after extraction, with the liquid
phase being crude oil 14 which can be further processed for use as
a biofuel.
[0031] The solid phase is a wet cake 16. The wet cake 16 is
subjected to subcritical water carbonization, also referred to
herein as hydrothermal carbonization, in step 18 to make green coal
20 from the wet cake recovered after the oil extraction. The
subcritical water carbonization process occurs in the temperature
range of 220-300.degree. C. The subcritical water from the
pretreatment step 10 has dissolved organic compounds and can also
undergo subcritical water carbonization in step 18. The subcritical
water product and the wet cake can be fed together or separately.
The temperature of the subcritical water product assists in
reducing costs as the temperature is increased in the subcritical
water carbonization step 18. Therefore, the process heat
requirements are reduced.
[0032] The disclosed processes provide the following: [0033] A
comparable oil yield; [0034] Seed preparation stages (cleaning,
decortications, and milling/grinding) are eliminated in the
disclosed process. [0035] Oilseeds with high moisture content can
be directly used without the need for additional drying. [0036]
Extracted oil looks transparent and is free from suspended solids
when compared to the conventional solvent extraction process.
[0037] Lower extraction time is required to obtain comparable oil
yield. [0038] Wet cake residue after oil extraction is used for the
green coal production. [0039] Batch, semi-batch, and continuous
flow reactors can be used for the pretreatment and subcritical
water carbonization. [0040] Microwave heating can be used during
subcritical water pretreatment and subcritical water carbonization
process. Microwave assisted processes will require less than five
minutes of processing time.
[0041] The integrated approach of oil extraction and production of
green coal from oilseeds provides a unique opportunity to maximize
the overall energy recovery from oilseeds. To quantify the amount
of energy being retained in extracted oil and the green coal with
respect to the initial energy input from oilseeds, energy
conversion ratio (ECR) is defined as:
ECR ( % ) = ( Weight of oil * HHV of oil Weight of oilseeds * HHV
of oilseeds ) * 100 + ( Weight of green coal * HHV of green coal
Weight of oilseeds * HHV of oilseeds ) * 100 ##EQU00001##
[0042] In subcritical water based processes, water is kept in the
liquid phase by applying pressure. Thus latent heat typically
required for the phase change of water from liquid to vapor phase
(2.26 MJ/kg of water) is not necessary. Because the latent heat is
not required, the energy requirement is reduced compared to steam
based processes. As an example, 2.869 MJ/kg of energy is required
to convert ambient water to steam at 250.degree. C. and 0.1 MPa,
whereas only 0.976 MJ/kg (about one third of the energy) is
required to convert ambient water to subcritical water at
250.degree. C. and 5 MPa. This also means that the energy contained
in the subcritical water is insufficient to vaporize the water on
decompression. Further, it is possible to recover much of the heat
(more than two thirds of the heat) from subcritical water.
Therefore, if 1 kg of water is to be heated to subcritical water
condition at 250.degree. C. for the subcritical water carbonization
process/oil extraction stage, it will require about 1 MJ/kg of
process heat.
[0043] Subcritical water pretreatment is an efficient process that
allows avoiding grinding and other preparation of seeds to obtain
cleaner oil suitable for biodiesel production. Higher oil yields
were obtained when n-hexane is used as a solvent as compared to
ethanol. The solids residue after oil extraction (wet cake) allows
producing green coal using the wet cake and liquid generated during
subcritical water pretreatment of the oilseeds. Subcritical water
carbonization of the wet cake and liquid to produce green coal is
an efficient means to utilize the oilseed residue. The heating
value of green coal is comparable to that of bituminous grade coal
and thus can have potential applications in co-firing or other
solid fuels applications.
[0044] A study was conducted using different oilseeds. The five
types of oilseeds are used: cottonseeds, flaxseeds, yellow mustard
seeds, canola (rape) seeds, and tobacco seeds. The cottonseeds were
obtained from a local farm in Virginia, the flaxseeds, mustard
seeds, and canola seeds were purchased accordingly from Superior
Nut Company, Cambridge, Mass., Penzeys Spices, Wauwatosa, W I, and
Seedland, Wellborn, Fla. The tobacco seeds were provided by Tyton
BioSciences, Danville, Va. All the seeds were dried overnight in an
oven at 65.+-.3.degree. C., packed in plastic bags, and stored in a
dark and dry place at room temperature before being used. The
moisture content of the seeds, determined with a moisture meter
Denver Instrument IR 35 by drying the ground seeds at 105.degree.
C. to constant weight, was <1%.
[0045] Subcritical water pretreatment (or hydrothermal
pretreatment) of the seeds was carried out in a 500 mL batch
reactor with a Parr 4848 controller at 120.+-.1, 150.+-.1,
180.+-.1, and 210.+-.1.degree. C. (the respective autogenous
pressures were 30, 100, 250, and 500.+-.5 psi) for 30 minutes with
continuous stirring at 300 RPM. In a typical experiment, the
reactor was loaded with 30 grams of the seeds and 300 mL of
deionized water, sealed, and kept under the above conditions. After
cooling down to the room temperature, the solid and liquid phases
were separated by vacuum filtration. The solid phase (pretreated
seeds) was dried in an oven at 65.+-.3.degree. C. overnight until
the moisture content was below 1%. After the subcritical water
pretreatment, the oilseeds became dark but were not crushed and
retained the original shapes. The weight of the seeds after the
subcritical water pretreatment is provided in FIG. 3.
[0046] The aqueous phase was analyzed for pH and total organic
carbon (TOC) with Shimadzu TOC.sub.VPN analyzer. The results of the
analyses are provided in FIGS. 4 and 5, respectively. The
subcritical water pretreatment of the oilseeds promotes hydrolysis
of the seed starches and proteins and extraction of them to the
aqueous phase. As seen from FIG. 4, pH of the aqueous phase is
reducing with increasing reaction temperature, which can be
explained by the partial degradation of the hydrolyzed
carbohydrates to organic acids. As seen in FIG. 5, TOC is
increasing due to intensifying carbohydrate and protein extraction
rate. The aqueous phase was collected and stored at 4.degree. C.
for using in the subcritical water carbonization of extracted
oilseeds experiments.
[0047] The next step is Soxhlet extraction of the oilseeds with
n-hexane. 10 grams of both ground seeds and seeds pretreated at
120, 150, 180, and 210.degree. C. were extracted with 200 mL of
hexane in a Soxhlet apparatus for 120 minutes (8 cycles). After the
extraction, hexane was removed by vacuum evaporation to constant
weight, and the oil was gravimetrically quantified and labeled. The
oil yield (in g/100 g of dry seeds) after each extraction was
calculated from the mass of extracted oil and the mass of seeds
used for the extraction. The extracted seeds were dried in an oven
at 65.+-.3.degree. C. and stored at room temperature for analyses
and using in the subcritical water carbonization experiments. The
results of the oil extraction from the pretreated and ground seeds
are provided in FIG. 6.
[0048] As can be seen from FIG. 6, the oil yields from all the
seeds pretreated at 180 and 210.degree. C. were significantly
higher than from the respective ground seeds. The oil yield from
the cotton, flax, mustard, canola, and tobacco seeds pretreated at
210.degree. C. was higher than from the respective ground seeds by
11.6%, 35.3%, 31.3%, 32.9%, and 23.2% accordingly and reached as
much as 82% for canola seeds. The oils extracted from the seeds
pretreated at 180 and 210.degree. C. typically had darker color
than the oils extracted from respective ground seeds, which can be
explained by the presence of colloid carbon particles as well as
free fatty acids (FFAs) as a result of the partial degradation of
triacylglycerols at higher temperatures.
[0049] Calculations of the oil yields on a raw (unpretreated) seed
basis showed that oil yields of most of the seeds pretreated at
210.degree. C. exceeds the oil yield of respective ground seeds by
up to 6%. The results of the oil extraction from the pretreated and
ground seeds on a raw seed basis are provided in FIG. 7. This
phenomenon can be explained by the more porous structure of the
pretreated seeds with greater surface area compared to that of the
ground seeds, which makes the oils more accessible to solvents such
as n-hexane. The partial hydrolysis and removal of the
carbohydrates and proteins from the oilseeds to the aqueous phase
in the pretreatment step changes the oilseeds structure and
increases their porosity and surface area. In order to confirm
this, BET surface area and pore size/volume analysis was performed
on the extracted oilseeds as described below.
[0050] In order to add value to the subcritical water pretreatment
and oil extraction process, extracted canola seeds pretreated at
210.degree. C. were subjected to subcritical water carbonization in
a 500 mL batch reactor equipped with a Parr 4848 controller. 10
grams of the extracted seeds and 300 mL of the aqueous phase
obtained after the seeds' pretreatment were loaded into the
reactor, sealed, and kept under the temperature of 300.degree. C.
and autogenous pressure of 1220.+-.5 psi for 60 minutes. After the
reactor was cooled down to ambient temperature, the solid and
liquid phases were separated by vacuum filtration and the solid
phase was dried in an oven at 65.+-.3.degree. C. overnight. The dry
weight of the carbonized solids (green coal) was 5.5 g (55 wt
%).
[0051] Elemental analysis of the raw, pretreated, extracted, and
carbonized canola seeds was carried out with ThermoFinnigan Flash
EA 1112 automatic elemental analyzer and higher heating values of
all the samples were calculated using Dulong's formula. The results
of the analysis are provided in Table 2.
TABLE-US-00002 TABLE 2 HHV*, Sample N, wt % C, wt % H, wt % O, wt %
MJ/kg Raw canola seeds 3.227 58.39 9.293 29.09 27.837 Pretreated
canola 1.273 67.441 10.647 20.64 34.38 seeds Extracted canola 5.152
50.218 6.148 38.482 18.898 seeds Canola seedcake 4.868 64.221 6.606
24.305 26.466 green coal *HHV was calculated using Dulong's
formula: HHV (MJ/kg) = 33.5 (C %) + 142.3 (H %) - 15.4 (O %) - 14.5
(N %)
[0052] As can be seen from the above table, the extracted canola
seeds contain a high amount of nitrogen, which indicates a high
protein content that can find a proper application. If carbonized
with subcritical water, it gives green coal of a good quality (26.5
MJ/kg) comparable with bituminous coal.
[0053] In order to evaluate the possible degradation of the canola
seed oil in a pretreatment step, fatty acid (FFA) concentrations
were determined in all the extracted oils. The oils were titrated
with 0.1% NaOH solution, and the results obtained are shown in FIG.
8. As seen from FIG. 8, the FFA concentrations are increasing
slightly with increasing pretreatment temperature. Therefore, the
degradation of the extracted oils at the pretreatment temperatures
studied was insignificant.
[0054] Additionally, the oils extracted from the raw and pretreated
at 210.degree. C. canola seeds were analyzed with SRI-GC8610C
chromatograph equipped with Restek MXT-WAX capillary column and a
flame ionization detector (FID) to compare their FFA profiles.
Helium at 19 psi was used as a carrier gas. The temperature program
was as follows: the initial oven temperature 120.degree. C., hold
for 3 min, ramp at 20.degree. C./min to 220.degree. C., hold for 10
min; injector temperature 230.degree. C., detector temperature
250.degree. C.
[0055] The oil samples were subjected to transesterification with
methanol and NaOH (0.35% methoxide). The obtained fatty acid methyl
esters (FAMEs) were washed with deionized water, re-dissolved in
n-hexane, separated from the water phase, dried over anhydrous
Na.sub.2SO.sub.4, recovered by vacuum evaporation, and dissolved in
chloromethane (1:10). 1 .mu.L of each sample was injected into the
column. FAMEs were identified by comparing their retention times
and peak areas to those of the standards. The FFA profiles of the
both samples were consistent with known canola seed oil profiles.
The composition of the oils extracted from the ground seeds and
seeds pretreated at 210.degree. C. is shown in Table 3.
TABLE-US-00003 TABLE 3 Fatty acid composition, wt % Palmitic
Stearic Oleic Linoleic Linolenic Sample (16:0) (18:0) (18:1)
(18:2n6) (18:3n3) Ground 7.9 .+-. 0.5 2.0 .+-. 0.5 57.2 .+-. 0.5
19.7 .+-. 0.5 13.2 .+-. 0.5 seeds Pretreated 7.8 .+-. 0.5 2.0 .+-.
0.5 57.0 .+-. 0.5 20.5 .+-. 0.5 12.7 .+-. 0.5 seeds
[0056] No significant difference was observed in composition of the
oils extracted from the ground seeds and the pretreated canola
seeds, indicating no degradation.
[0057] BET analysis was carried out with NOVA 2000e surface area
and pore size analyzer (Quantachrome Instruments). The ground seeds
and seeds pretreated at 210.degree. C. after Soxhlet extraction
were used for the analysis. The results shown in Table 4 were
obtained:
TABLE-US-00004 TABLE 4 Surface area, m.sup.2/g Pore volume, cc/g
Pore diameter, .ANG. Sample (MultiBET) (HK method) (Kr87) Raw seeds
1.265 7.096 * 10.sup.-4 20.745 Pretreated seeds 5.336 88.40 *
10.sup.-4 43.998
[0058] As seen from the table, the surface area, pore volume, and
pore size for the hydrothermally pretreated canola seeds were
greater than those for the raw seeds. This explains the faster oil
extraction and the higher oil yields from the pretreated seeds on a
raw seeds basis.
[0059] As it can be clearly seen from FIGS. 6 and 7, the
subcritical water pretreatment and extraction process for all the
oilseeds pretreated at 180 and 210.degree. C. provided
significantly higher oil yields than those from the respective
ground seeds. The oil yield from the cotton, flax, mustard, canola,
and tobacco seeds pretreated at 210.degree. C. was higher than from
the respective ground seeds by 11.6%, 35.3%, 31.3%, 32.9%, and
23.2% respectively and reached as much as 82% for canola seeds.
Calculations of the oil yields on a raw (unpretreated) seed basis
showed that oil yields of the flax, mustard, and canola seeds
pretreated at 210.degree. C. exceeded the oil yield of respective
ground seeds by 3.43, 6.03, and 6.18% respectively. From BET
analysis of the surface area and pore size/volume of the extracted
canola seeds (Table 4), it can be seen that all the characteristics
for the pretreated seeds were greater than those for the respective
ground seeds. The hydrothermal pretreatment makes the oil more
accessible for n-hexane and explains the faster oil extraction and
higher oil yield from the pretreated seeds on a raw seeds basis
without significant degradation of the extracted oil (FIG. 8, Table
3).
[0060] Table 5 and FIGS. 9A and 9B provide the mass and energy
distribution of all products obtained during the subcritical water
pretreatment and extraction of canola seeds at 210.degree. C.
Energy conversion ratios (ECRs) were calculated for both oil and
green coal using the data from Table 2 and the following
formulae:
ECR.sub.O=(m.sub.O*HHV.sub.O/(m.sub.S*HHV.sub.S)100% (1)
ECR.sub.C=(m.sub.O*HHV.sub.O/m.sub.S*HHV.sub.S)100% (2)
[0061] Where m.sub.O--mass of the oil extracted, g [0062]
HHV.sub.O--heating value of the oil, MJ/kg [0063] m.sub.S--mass of
the oilseeds, g [0064] HHV.sub.S--heating value of the oilseeds,
MJ/kg [0065] m.sub.C--mass of the green coal produced, g [0066]
HHV.sub.C--heating value of the coal, MJ/kg
[0067] As seen from FIGS. 9A and 9B, the integrated process obtains
55% oil and 25% green coal from the canola seeds, which energy
content accounted to 71 and 24% respectively (the overall ECR was
95%).
TABLE-US-00005 TABLE 5 Energy content, Sample Mass, g Mass, wt %
HHV, KJ/g KJ ECR, % Raw seeds 10.00 100.00 27.80 278.00 100.00 Oil
5.50 55.00 36.00 198.00 71.22 Green coal 2.48 24.80 26.50 65.72
23.64 Soluble 2.02 20.20 7.07 14.28 5.14 organics
[0068] To determine the process yields, mass balance around
subcritical water pretreatment of the canola seeds, solvent oil
extraction, and subcritical water carbonization of the seedcake was
developed and summarized in FIG. 10. The raw canola seeds (100 kg,
on a dry basis) were subjected to the hydrothermal pretreatment at
210.degree. C. for 30 minutes yielding 63.7 kg of partially
hydrolyzed seeds and 32.7 kg of water-soluble organic products. The
pretreated seeds were extracted with n-hexane for 90 minutes
yielding 55.0 kg of oil and 12.3 kg of extracted seedcake. The
latter was mixed with the water-soluble organic products from the
pretreatment step, subjected to the subcritical water carbonization
at 300.degree. C. for 60 minutes, and resulted in producing 24.8 kg
of green coal and 20.2 kg of water-soluble organics, which was
further recycled for the next subcritical water carbonization step.
The integrated process produces 55% high quality oil, which can be
used for biodiesel production, and 25% green coal, thus utilizing
80% of the canola seeds with an overall ECR of 95%.
[0069] The subcritical water pretreatment and extraction is a novel
integrated process that employs hydrothermal pretreatment and oil
extraction steps followed by hydrothermal carbonization of the
extracted seeds. The integrated process provides several major
advantages over conventional processes: higher oil yield, shorter
extraction time, tolerance to high moisture content of the
feedstock, avoiding preparation stages, and utilization of the
extracted solid residue for green coal production. The disclosed
process can be integrated with biodiesel productions. The
integration of oil extraction with green coal production adds value
to the extracted oil and increases the overall ECR of the oilseeds
up to 95%. Hydrothermal pretreatment of oilseeds is an efficient
step that makes it possible to significantly increase the oil yield
during the following solvent extraction step. The higher oil yield
obtained from hydrothermally pretreated seeds and faster oil
extraction compared to that of ground seeds can be explained by the
partial hydrolysis of carbohydrates and proteins, thus making the
solid phase richer in oils and increasing its surface area and pore
size/volume. The disclosed integrated process can be an efficient
way of simultaneous oil extraction and solid fuels production from
different oilseeds.
[0070] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiments but, on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims, which
scope is to be accorded the broadest interpretation so as to
encompass all such modifications and equivalent structures as is
permitted under the law.
* * * * *