U.S. patent application number 12/261806 was filed with the patent office on 2009-08-13 for method for separating saturated and unsaturated fatty acid esters and use of separated fatty acid esters.
Invention is credited to Shailendra Bist, Samia Mohtar, Bernard Y. Tao.
Application Number | 20090199462 12/261806 |
Document ID | / |
Family ID | 40937679 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090199462 |
Kind Code |
A1 |
Bist; Shailendra ; et
al. |
August 13, 2009 |
METHOD FOR SEPARATING SATURATED AND UNSATURATED FATTY ACID ESTERS
AND USE OF SEPARATED FATTY ACID ESTERS
Abstract
The present invention provides a composition comprising methyl
esters derived from vegetable oils having less than about 3% by
weight of saturated fatty acid methyl esters and a cloud point of
less than about -30.degree. C. A method for making the lowered
cloud point composition is also disclosed in which vegetable
derived methyl esters, urea and alcohol are mixed under sufficient
heat to form a homogenous mixture. The mixture is then cooled to a
temperature where a solid phase and a liquid phase are formed. The
solid phase is enriched in saturated fatty acid methyl esters and
the liquid phase is enriched in unsaturated fatty acid methyl
esters. The solid phase is separated from the liquid phase.
Finally, unused urea and methanol are removed from the liquid phase
to form a liquid composition having a cloud point of less than
about -30.degree. C. and less than about 3% by weight saturated
fatty acid methyl esters.
Inventors: |
Bist; Shailendra; (Long
Beach, CA) ; Tao; Bernard Y.; (Lafayette, IN)
; Mohtar; Samia; (West Lafayette, IN) |
Correspondence
Address: |
BOSE MCKINNEY & EVANS LLP
111 MONUMENT CIRCLE, SUITE 2700
INDIANAPOLIS
IN
46204
US
|
Family ID: |
40937679 |
Appl. No.: |
12/261806 |
Filed: |
October 30, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11690540 |
Mar 23, 2007 |
|
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12261806 |
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Current U.S.
Class: |
44/385 |
Current CPC
Class: |
Y02P 30/20 20151101;
C10G 2300/1011 20130101; Y02E 50/10 20130101; Y02E 50/13 20130101;
C11B 7/0083 20130101; C10L 1/19 20130101; C10L 1/026 20130101; C11C
3/003 20130101 |
Class at
Publication: |
44/385 |
International
Class: |
C10L 1/18 20060101
C10L001/18 |
Claims
1. A composition, comprising: methyl esters derived from vegetable
oils, the methyl esters comprising less than about 3% by weight of
saturated fatty acid methyl esters; and the composition having a
cloud point of less than about -30.degree. C.
2. The composition of claim 1, wherein the methyl esters consist
essentially of methyl oleate, methyl linoleate and methyl
linolenate.
3. The composition of claim 2, wherein the methyl linolenate
comprises less than about 10% by weight of the methyl esters.
4. The composition of claim 3, wherein the methyl stearate
comprises less than about 0.1% by weight of the methyl esters.
5. The composition of claim 3, wherein the methyl linoleate
comprises at least about 50% by weight of the methyl esters.
6. The composition of claim 4, wherein the methyl linoleate
comprises at least about 60% by weight of the methyl esters.
7. The composition of claim 1, wherein the cloud point is less than
about -35.degree. C.
8. The composition of claim 1, wherein the cloud point is less than
about -40.degree. C.
9. The composition of claim 1, wherein the cloud point is less than
about -45.degree. C.
10. The composition of claim 1, wherein the cloud point is less
than about -50.degree. C.
11. The composition of claim 1, wherein the cloud point is less
than about -55.degree. C.
12. The composition of claim 1, wherein the methyl esters comprise
less than about 2% saturated methyl esters.
13. The composition of claim 1, wherein the methyl esters comprise
less than about 1.5% saturated methyl esters.
14. The composition of claim 1, wherein the methyl esters comprise
less than about 0.5% saturated methyl esters.
15. The composition of claim 1, wherein the vegetable oils from
which the methyl esters are derived comprise soy oil.
16. The composition of claim 1, further comprising a petroleum
based component.
17. The composition of claim 16, wherein the petroleum based
component comprises fossil fuel derived diesel fuel.
18. The composition of claim 1, comprising less than about 1%
methyl stearate.
19. The composition of claim 1, comprising less than about 0.5%
methyl stearate.
20. The composition of claim 1, comprising less than about 0.1%
methyl stearate.
21. The composition of claim 1, further comprising animal fat
derived methyl esters.
22. A method of lowering the cloud point of methyl esters derived
from vegetable oil, comprising: mixing vegetable derived methyl
esters, urea and alcohol with sufficient heat to form a homogenous
mixture; cooling the homogeneous mixture to a temperature where a
solid phase and a liquid phase are formed, the solid phase being
enriched in saturated fatty acid methyl esters and the liquid phase
being enriched in unsaturated fatty acid methyl esters; separating
the solid phase from the liquid phase; and removing alcohol and
unused urea from the liquid phase to form a liquid composition
having a cloud point of less than about -30.degree. C. and less
than about 3% by weight saturated fatty acid methyl esters.
23. The method of claim 22, wherein the alcohol comprises
methanol.
24. The method of claim 23, further comprising, before the step of
forming the homogeneous mixture, mixing vegetable derived oil,
sodium hydroxide and methanol to form the vegetable derived methyl
esters.
25. The method of claim 24, wherein the homogeneous mixture
contains methanol in an amount of about 3 to 10 times by weight of
the amount of the fatty acid methyl ester.
26. The method of claim 25, wherein excess methanol is provided in
the step of mixing the vegetable derived oil, sodium hydroxide and
methanol to form the vegetable derived methyl esters, whereby
adding methanol during the step of forming the homogeneous mixture
is unnecessary.
27. The method of claim 23, further comprising separating glycerin
from the vegetable derived methyl esters before the step of forming
the homogeneous mixture.
28. The method of claim 22, wherein the ratio of urea to methyl
esters in the homogeneous mixture is from about 0.9:1 to about
1:1.
29. The method of claim 22, wherein the solid phase is separated
from the liquid phase by filtration, centrifugation, sedimentation,
or decantation of the liquid phase.
30. The method of claim 22, wherein the liquid composition
comprises less than about 2 percent by weight of saturated fatty
acid methyl esters.
31. The method of claim 22, wherein the liquid composition
comprises less than about 1.5 percent by weight of saturated fatty
acid methyl esters.
32. The method of claim 22, wherein the removal of the alcohol is
by evaporation.
33. The method of claim 22, wherein the removal of the alcohol is
by applying vacuum.
34. The method of claim 22, wherein the removal of unused urea is
by washing with acidified water, wherein the washed unused urea is
separated by a liquid-liquid centrifugal extractor or by a gravity
separation.
35. The method of claim 22, wherein the yield of the liquid
composition is at least 43% by weight of the vegetable-derived
methyl esters used to form the homogeneous mixture.
36. The method claim of 35, wherein cloud point of the liquid
composition is less than -34.degree. C.
37. The method claim of 35, wherein cloud point of the liquid
composition is less than -40.degree. C.
38. The method claim of 35, wherein cloud point of the liquid
composition is less than -50.degree. C.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 11/690,540, filed Mar. 23, 2007, which claims
priority to U.S. patent application Ser. No. 11/668,865, filed Jan.
30, 2007, now abandoned, which claims priority to U.S. patent
application Ser. No. 11/068,104, filed Feb. 28, 2005, which claims
priority to U.S. Provisional Patent Application Ser. No.
60/547,992, filed Feb. 26, 2004, all of which are hereby
incorporated by reference in their entirety.
BACKGROUND OF THE DISCLOSURE
[0002] The present invention generally relates to fatty acid
esters, more particularly, to a method for preparation and
separation of fatty acid esters. A multitude of energy crises
stemming from supply disruption as well as significantly increasing
demand for fossil fuels by industrialized nations in the past few
decades have spawned motivation for development of alternative fuel
sources. Additionally, since there are finite reserves of crude oil
from which petroleum based fuels are derived, there is also
motivation to develop renewable fuel sources. A substantial amount
of effort has recently been made to develop biodiesel fuels from
renewable sources.
[0003] Soy methyl ester (SME) or methyl soyate, the chemical
description of which is provided below, is a common organic acid
ester precursor for producing biodiesel. Organic acids, as the name
indicates, are organic compounds with acid-like properties. One
common group of organic acids are carboxylic acids, which have a
"--COOH tail." Esters constitute a class of organic acid compounds
where at least one --OH member is replaced by an alkoxy group
(--O--C.sub.nH.sub.2+1). In the case of methyl acetate ester, for
example, a methoxy group (--O--CH.sub.3), which is the simplest
form of an alkoxy, has replaced the --OH group in acetic acid
CH.sub.3COOH. This results in CH.sub.3COOCH.sub.3, or methyl
acetate ester. This chemical reaction is commonly termed
esterification. Diagram 1, found below, shows the chemical bond
structures for these compounds.
##STR00001##
[0004] Fatty acids consist mainly of carbon chains and hydrogen
atoms. These chains can be short with a small number of carbon
atoms, e.g., butyric acid (CH.sub.3CH.sub.2CH.sub.2COOH), or long
with large number of carbon atoms, e.g., oleic acid
CH.sub.3(CH.sub.2).sub.7CH.dbd.CH(CH.sub.2).sub.7COOH. Fatty acids
may include single and double bonds between carbon atoms. A
saturated fatty acid has the maximum number of hydrogen atoms
covalently bound to each carbon atom in the chain of carbon atoms,
i.e., a saturated fatty acid has no double bonds. An unsaturated
fatty acid has at least one double bond between two carbon atoms.
Diagram 2, found below, shows an example of saturated and
unsaturated fatty acids.
##STR00002##
[0005] SME is produced by the transesterification of soybean oil
with methanol in the presence of a catalyst. Transesterification
results in a class of organic reactions where one ester is
transformed into another ester by interchanging at least one
alkoxy. The catalyst is often an acid or base.
[0006] SME profile by percent and by molecular weight is given in
Table 1, below.
TABLE-US-00001 TABLE 1 Typical SME profile Fatty Molecular Percent
of Acid Carbon Weight Melting SME by Name Design Formula and
Structure (g/mole) Point (.degree. C.) Weight methyl palmi- tate
C16:0 ##STR00003## 270.5 30.5 10.3 methyl stearate C18:0
##STR00004## 298.5 39.1 4.7 methyl oleate C18:1 ##STR00005## 296.5
-19.8 22.5 methyl lino- leate C18:2 ##STR00006## 294.5 -34.9 54.1
methyl lino- lenate C18:3 CH.sub.3(CH.sub.2CH.dbd.CH).sub.3
(CH.sub.2).sub.7CO.sub.2CH.sub.3 292.5 -57 8.3
[0007] Biodiesel produced by typical methods suffers from a
crystallization phenomenon when temperatures decrease. Although
this crystallization phenomenon is not limited to biodiesel, the
temperature at which biodiesel begins to crystallize is
substantially higher than petroleum-based diesel fuel. The
crystallized constituents can clog fuel filters in vehicles using
biodiesel and thereby cut off the fuel supply to the engine. The
temperature at which two phases, i.e., the liquid and solid phases
start to separate, thus producing a cloudy mixture, is referred to
as cloud point (C.P.). Saturated fatty acid esters constituents
have a higher C.P. than unsaturated fatty acid esters. To lower the
temperature at which crystallization occurs and thereby lower the
C.P. of the fuel, several techniques are often used, examples of
which include blending with petroleum-based diesel, introducing
additives, and winterization. Winterization refers to removal of
saturated fatty acids, e.g., C16:0 and C18:0, and in some cases
mono-unsaturated fatty acids, e.g., C18:1, that cause the biodiesel
product to crystallize at an undesirably high temperature. The
removal process is typically by filtration of the crystallized
particles of the saturated and in some cases mono-unsaturated fatty
acids which leaves a mixture having a greater amount of unsaturated
fatty acids compounds with lower C.P., thereby lowering the C.P. of
the biodiesel so produced.
[0008] The winterization process has gained more interest in recent
years. Winterization by itself produces low yields, i.e., a
substantial portion of the starting material is lost during the
filtration process. Therefore, use of compounds which improve the
winterization process, typically referred to as "improvers," is
essential. One process which includes the addition of improvers is
referred to as fractionation, which uses the crystallization
properties of esterified fatty acids to separate a mixture into low
and high melting point liquid fractions. During fractionation,
these improvers create inclusion compounds/complexes. This process
includes a host constituent having a series of cavities or landing
sites for attachment by a second chemical constituent, commonly
referred to as the guest. The compound resulting from the
combination of the host and the guest is called an "inclusion
compound." The forces that hold the host and the guest constituents
together are van der Waals type forces. That is, no covalent bonds
form between the guest and the host. Clathrates are one type of
inclusion compound in which the spaces in the host constituent are
enclosed on all sides, causing a "trapping effect."
[0009] There are three different types of fractionation: dry
fractionation, detergent fractionation, and solvent fractionation.
Solvent fractionation has received a substantial amount of interest
in recent years. It is an efficient process by which one group of
esterified fatty acid constituents are separated from another
group. The differing solubility of the groups is the key to success
with this process. Several advantages are offered by solvent
fractionation as compared to dry fractionation. For example, dry
fractionation requires a longer crystallization period than solvent
based fractionation; and solvent fractionation substantially
increases the chance of crystallization in one round rather than
multiple stages as may be the case with dry fractionation.
Conversely, solvent based fractionation requires more energy and
the solvents are costly, although in many cases they are recovered
in solvent recovery schemes.
[0010] The prior art method of thermal crystallization
(winterization) followed by filtration (with or without solvent)
utilizes the difference in crystallization temperature of the
saturated and unsaturated components of SME. The saturated
components crystallize at a higher temperature and can be removed
via filtration, centrifugation, etc. However, a significant amount
of co-crystallization occurs. Co-crystallization occurs when during
the winterization process certain unsaturated components also
crystallize and are thus also removed, resulting in high losses of
the preferred unsaturated fatty acid methyl esters (FAME). To
obtain a C.P. of -16.degree. C., almost 75% of the starting
material was removed in the work reported by Dunn et al. See R. O.
Dunn, M. W. Shockley, and M. O. Bagby, "Improving the
Low-Temperature Properties of Alternative Diesel Fuels: Vegetable
Oil-Derived Methyl Esters," JAOCS, Vol. 73, No. 12 (1996), PP
1720-1721. Additionally, these techniques involve cooling to very
low temperatures and require processing times of days.
[0011] Also, the amount of saturated or monounsaturated molecules
which are extracted from the fatty acid compound has been shown to
have an effect on the C.P. For instance, Dunn et al. in two
published articles suggest a linear relationship in the depression
in C.P. as a function of reduction of saturate constituents. See,
Dunn et al. "Improving the low-temperature properties of
alternative diesel fuels: Vegetable oil-derived methyl esters"
published in 1996, and "Winterized Methyl Esters from Soybean Oil:
An Alternative Diesel Fuel with Improved Low-Temperature Flow
Properties" published in 1997. In the latter article, Dunn et al.
describe a linear relationship between total concentration of
saturate constituents and C.P., as described in equation (1), found
below:
CP=1.4403*(Total Saturates)-24.8 (1)
FIG. 1 titled as prior art graphically shows the linear
relationship described by Dunn's equation (1) between the C.P. and
the total saturates.
[0012] In the 1996 article, Dunn et al. reported a winterization
process resulting in a C.P. of -16.degree. C. having final
components of C16:0 (4.3, % by wt), C18:0 (1.3, % by wt), C18:1
(30.3, % by wt), C18:2 (49.6, % by wt), C18:3 (11.9, % by wt), and
others (2.6, % by wt). In the same paper, Dunn et al. suggested a
laboratory experiment resulting in a C.P. of -23.degree. C. C.P.
for a pure solution of unsaturated C18 components, presumably
C18:1, C18:2, and C18:3, i.e., a saturate concentration of 0. That
is, according to Dunn et al., a drop of 7.degree. C. is to be
expected in going from a normal winterization process having a C.P.
of -16.degree. C., to -23.degree. C. with zero concentration of
saturated components. Extension of the linear relationship, as
shown in FIG. 1, or by use of equation (1), places the point at
which the line crosses the abscissa, i.e., saturate concentration
of 0, at -24.8.degree. C. This confirms that Dunn et al. in both
the 1996 and 1997 articles contemplated a further but small
depression of C.P. as the concentration of the saturates approaches
zero. In fact, immediately after presenting the laboratory data
directed at the removal of all saturates, in the 1996 article Dunn
et al. stated "[w]interization may prove to be effective in
removing nearly all saturated long methyl esters from SME. However,
complete removal of saturated methyl esters may not be recommended
because doing so would significantly reduce their ignition
quality." P. 1721, JAOCS, Vol. 73 no. 12 (1996). Therefore, in
addition to predicting a linear relationship, Dunn et al. concluded
that the extra 7.degree. C. of C.P. depression in going from
-16.degree. C. at saturate concentration of about 6% by weight
(C16:0:4.3% by wt, and C18:0:1.3% by weight) in a typical
winterization process to a C.P. of -23.degree. C. for 0% saturate
components, experimentally, and -24.8.degree. C. based on equation
(1), was not advisable.
[0013] In other prior art work, urea, also known as carbamide with
the chemical formula (NH.sub.2).sub.2CO, has been used in the
winterization process. Urea is used to form inclusion compounds
with long chain organic compounds. This was first discovered and
reported by F. Bengen in a German patent filed in 1940. See Bengen,
F., German Patent Application 0. Z. 12438, Mar. 18, 1940. Later
studies from the late forties to the early fifties reported the
selectivity of urea in forming complexes with long chain organic
molecules. (See citations in the Reference section.) This
selectivity was found to be based on: a) Carbon chain length, b)
presence of unsaturation in the molecule, and c) degree of
unsaturation. The formation of these complexes was found to be a
useful technique for the separation of a mixture of saturated and
unsaturated organic compounds, e.g., fractionation of a mixture of
free fatty acids. Various techniques for the formation of such
complexes were also studied, however, with little or no focus on
process parameters. Hayes et al. worked on the fractionation of
fatty acids and studied various process parameters that affect the
formation of urea inclusion complexes, product yields, and the
composition of fractions obtained. U.S. Pat. Nos. 5,106,542 and
5,243,046 to Traitler et al. describe the art of fractionating
fatty acid mixtures via urea inclusion. U.S. Pat. No. 5,679,809 to
Bertoli et al. ("the '809 patent") describes the concentration of
polyunsaturated fatty acid ethyl esters via urea inclusion.
[0014] In solvent fractionation, urea dissolves in ethanol,
methanol, or other solvents as an early step in producing inclusion
compounds. The goal of solvent-based fractionation, as explained in
the '809 patent, is to remove saturated and monounsaturated fatty
acid ethyl esters. The '809 patent teaches heating the mixture of
ester, urea, and ethanol to a particular temperature until the urea
is dissolved. The mixture is then cooled to allow certain molecules
to form a solid phase. The solid phase is separated from the liquid
phase by filtration or centrifugation. The liquid phase is further
processed to partly remove ethanol, and the desired ethyl esters
enriched with polyunsaturated fatty acids are then extracted by
washing the remaining liquid phase with an acidic liquid.
[0015] As cloud points of approximately -20.degree. C. are too high
for many cold weather uses of biodiesel, such as in vehicles, there
is still a need for an improved process to lower C.P. of biodiesel
to an acceptable level.
REFERENCES
[0016] 1. Bengen, F., German Patent Application 0. Z. 12438, Mar.
18, 1940. [0017] 2. Swern, D. "Urea and Thiourea Complexes in
Separating Organic Compounds," Industrial and Engineering
Chemistry, Vol. 47, 216-221, 1955. [0018] 3. Swern, D., Parker, W.
E., "Application of Urea Complexes in the Purification of Fatty
Acids, Estes, and Alcohols. 1. Oleic Acid from Inedible Animal
Fats," JAOCS, 431-434, 1952. [0019] 4. Newey, H. A., Shokal, E. C.,
Mueller, A. C., Bradley, T. F., "Industrial and Engineering
Chemistry," Vol. 42, 2538-2540, 1950. [0020] 5. Schlenk, H.,
Holman, R. T., "Separation and Stabilization of Fatty Acids by Urea
Complexes," Journal of American Chemical Society, vol. 72,
5001-5005, 1950. [0021] 6. Hayes, D. G., Bengtsson, Y. C., Alstine,
J. M. V., Setterwall, F., "Urea Complexation for the Rapid,
Ecologically Responsible Fractionation of Fatty Acids from Seed
Oil," vol. 75, JAOCS, 103-1409, 1998. [0022] 7. Hayes, D. G.,
Bengtsson, Y. C., Alstine, J. M. V., Setterwall, F., "Urea-Based
Fractionation of Seed Oil Samples Containing Fatty Acids and
Acylglycerols of Polyunsaturated and Hydroxy Fatty Acids," Vol. 77,
JAOCS, 207-213, 2000. [0023] 8. Hayes, D. G., "Free Fatty Acid
Fractionation via Urea Inclusion Compounds," Vol. 13, INFORM,
832-833, 2002. [0024] 9. Hayes, D. G., Alstine, J. M. V., Asplund,
A. L., "Triangular Phase Diagrams to Predict the Fractionation of
Free Fatty Acid Mixtures via Urea Complex Formation," Separation
Science and Technology, Vol. 36, 45-58, 2001. [0025] 10. Lee, L. A.
Johnson and E. G. Hammond, "Reducing the Crystallization
Temperature of Biodiesel by Winterizing Methyl Soyate," JAOCS, Vol.
73, No. 5 (1996). [0026] 11. R. O. Dunn, M. W. Shockley, and M. O.
Bagby, "Improving the Low-Temperature Properties of Alternative
Diesel Fuels: Vegetable Oil-Derived Methyl Esters," JAOCS, Vol. 73,
No. 12 (1996). [0027] 12. R. O. Dunn, M. W. Shockley, and M. O.
Bagby, "Winterized Methyl Esters from Soybean Oil: An Alternative
Diesel Fuel With Improved Low-Temperature Flow Properties," Oil
Chemical Research, Society of Automotive Engineers, Inc., 1997.
[0028] 13. Diks, R. M. M., Lee, M. J., "Production of Very Low
Saturate Oil Based on the Specificity of Geotrichum Candidum
Lipase," JAOCS, Vol. 76, No. 4, 1999. [0029] 14. Shimada, Y.,
Maruyama, K., Okazaki, S., Nakamura, M., Sugihara, C., "Enrichment
of Polyunsaturated fatty Acids with Geotrichum Candidum Lipase,"
JAOCS, Vol. 71, 951-953, 1994. [0030] 15. U.S. Pat. No. 5,678,809,
"Concentration of Polyunsaturated Fatty Acid Ethyl Esters and
Preparation Thereof." [0031] 16. U.S. Pat. No. 5,106,542, "Process
for the Continuous Fractionation of a Mixture of Fatty Acids."
[0032] 17. U.S. Pat. No. 5,243,046, "Process for the Continuous
Fractionation of a Mixture of Fatty Acids." [0033] 18. U.S. Pat.
No. 6,444,784 B1, "Wax Crystal Modifiers." [0034] 19. U.S. Pat. No.
6,409,778 B1, "Additive for Biodiesel and Biofuels." [0035] 20.
International Publication No. WO 99/62973, "Wax Crystal Modifiers
Formed Form Dialkyl Phenyl Fumarate." [0036] 21. International
Publication No. WO 00/32720, "Winterized Paraffin Crystal
Modifiers." [0037] 22. U.S. Pat. No. 3,961,916, "Middle Distillate
Composition with Improved Filterability and Process Thereof."
[0038] 23. U.S. Pat. No. 5,726,048, "Mutant of Geotricum Candidum
Which Produces Novel Enzyme System to Selectively Hydrolyze
Triglycerides." [0039] 24. U.S. Pat. No. 6,537,787, "Enzymatic
Methods for Polyunsaturated Fatty Acid Enrichment." [0040] 25. U.S.
Pat. No. 5,470,741, "Mutant of Geotrichum Candidum Which Produces
Novel Enzyme System to Selectively Hydrolyze Triglycerides." [0041]
26. Kocherginsky et al., "Mass Transfer of Long Chain Fatty Aids
Through Liquid-Liquid Interface Stabilized by Porous Membrane,"
Separation Purification Technology, Vol. 20, 197-208, 2000. [0042]
27. U.S. Pat. No. 4,542,029, "Process for Separating Fatty Acids."
[0043] 28. U.S. Pat. No. 4,049,688, "Process for Separating Esters
of Fatty Acids by Selective Adsorption." [0044] 29. U.S. Pat. No.
4,129,583, "Process for Separating Crystallizable Fractions from
Mixtures Thereof." [0045] 30. Maeda, K., Nomura, Y., Tai K., Uneo,
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[0046] The above references 1-30 are incorporated herein by
reference.
SUMMARY OF THE INVENTION
[0047] Embodiments of the present teachings are related to lowering
cloud point of a vegetable derived composition having methyl esters
by fractionating saturated and mono-unsaturated components of
methyl esters in the composition.
[0048] According to one exemplary embodiment, a composition is
disclosed having methyl esters derived from vegetable oils. The
methyl esters comprise less than about 3% by weight of saturated
fatty acid methyl esters. The composition has a cloud point of less
than about -30.degree. C.
[0049] The methyl esters in certain embodiments comprise methyl
oleate, methyl linoleate and methyl linolenate. The methyl
linolenate may comprise less than about 10% by weight of the methyl
esters. The methyl stearate comprises less than about 0.1% by
weight of the methyl esters. The methyl linoleate comprises at
least about 50% or at least about 60% by weight of the methyl
esters.
[0050] Cloud point of the composition can be selected, but for most
cold weather applications envisioned, the composition has a cloud
point that is less than about -35.degree. C. In another embodiment,
the composition has a cloud point that less than about -40.degree.
C. In still another embodiment, the composition has a cloud point
less than about -45.degree. C.
[0051] In another embodiment, the composition has a cloud point
less than about -50.degree. C.
[0052] In yet another embodiment, the composition has a cloud point
is less than about -55.degree. C.
[0053] In one embodiment, the methyl esters in the composition
comprise less than about 2% saturated methyl esters. In another
embodiment, the methyl esters in the composition comprise less than
about 1.5% saturated methyl esters. In another embodiment, the
methyl esters in the composition comprise less than about 0.5%
saturated methyl esters.
[0054] In one embodiment, the vegetable from which the composition
is derived comprises soy oil. In another embodiment, the
composition includes material comprising a petroleum based
component, wherein the petroleum based component comprises fossil
fuel derived diesel fuel. In another embodiment, the composition
includes material comprising animal fat derived methyl esters.
[0055] In one embodiment, the composition comprises less than about
1% methyl stearate. In another embodiment the composition comprises
less than about 0.5% methyl stearate. In yet another embodiment the
composition comprises less than about 0.1% methyl stearate.
[0056] In one exemplary embodiment, a method of lowering the cloud
point of methyl esters derived from vegetable oil is disclosed. The
method includes mixing vegetable derived methyl esters, urea and
alcohol with sufficient heat to form a homogenous mixture. The
homogeneous mixture is cooled to a temperature where a solid phase
and a liquid phase are formed, the solid phase being enriched in
saturated fatty acid methyl esters and the liquid phase being
enriched in unsaturated fatty acid methyl esters. The solid phase
is separated from the liquid phase, and methanol and unused urea
are removed from the liquid phase to form a liquid composition
having a cloud point of less than about -30.degree. C. and less
than about 3% by weight saturated fatty acid methyl esters.
[0057] In one embodiment of the above method, the alcohol comprises
methanol. Also, the method further comprises, before the step of
forming the homogeneous mixture, the step of mixing vegetable
derived oil, sodium hydroxide and methanol to form the vegetable
derived methyl esters. In certain embodiments, the homogeneous
mixture contains methanol in an amount of about 3 to 10 times by
weight of the amount of the fatty acid methyl ester. Excess
methanol is provided in the step of mixing the vegetable derived
oil, sodium hydroxide and methanol to form the vegetable derived
methyl esters. Adding methanol during the step of forming the
homogeneous mixture is therefore unnecessary.
[0058] In another embodiment, the method further comprises
separating glycerin from the vegetable derived methyl esters before
the step of forming the homogeneous mixture. In another embodiment
of the method, the ratio of urea to methyl esters in the
homogeneous mixture is from about 0.9:1 to about 1:1. In another
embodiment, the solid phase is separated from the liquid phase by
filtration, centrifugation, sedimentation, or decantation of the
liquid phase. In yet another embodiment, the liquid composition
comprises less than about 2 percent by weight of saturated fatty
acid methyl esters. In another embodiment of the method, the liquid
composition comprises less than about 1.5 percent by weight of
saturated fatty acid methyl esters. In yet another embodiment of
the method, the step of removal of methanol is by evaporation.
Alternatively, the step of removal of methanol can be by applying
vacuum. In another embodiment of the method, unused urea is removed
by washing with acidified water, and the washed unused urea can be
separated by a liquid-liquid centrifugal extractor or by a gravity
separation.
[0059] In one embodiment of the method, the yield of the liquid
composition is at least 43% by weight of the vegetable-derived
methyl esters used to form the homogeneous mixture and the cloud
point of the liquid composition is less than -34.degree. C. The
cloud point of the liquid composition, however, can be less than
-40.degree. C. or less than -50.degree. C.
BRIEF DESCRIPTION OF DRAWINGS
[0060] The above-mentioned and other advantages of the present
invention and the manner of obtaining them, will become more
apparent and the invention itself will be better understood by
reference to the following description of the embodiments of the
invention taken in conjunction with the accompanying drawings,
wherein:
[0061] FIG. 1 is a graph showing a linear relationship between
saturate concentration and C.P. taught by the prior art;
[0062] FIG. 2a is a schematic showing process steps involved in
producing SME;
[0063] FIG. 2b is a schematic showing process steps involved in
fractionation of SME in accordance with the current teachings;
[0064] FIG. 3 is a graph of fuel flow rate versus power range;
[0065] FIG. 4 is a graph of controlled emission of Jet A fuel and
soy methyl ester blends for carbon monoxide;
[0066] FIG. 5 is a graph of controlled emission of Jet A fuel and
soy methyl ester blends for nitrogen dioxide;
[0067] FIG. 6 is a graph of controlled emission of Jet A fuel and
soy methyl ester blends for nitrogen monoxide;
[0068] FIG. 7 is a graph showing cloud point depression as a
function of SME:urea:ethanol/methanol and also showing remaining
methyl esters in the treated product;
[0069] FIG. 8 is a graph of percent extracted SME vs. extracted
species;
[0070] FIG. 9a is a graph of C.P. vs. percent saturates
illustrating how the current teachings differ from prior art
predictions;
[0071] FIG. 9b is a graph of C.P. vs. percent saturated fatty
acids, monounsaturated fatty acids, and polyunsaturated fatty
acids;
[0072] FIG. 10 is a graph of yield vs. C.P.; and
[0073] FIG. 11 is a graph of C.P. vs. urea ratio to the starting
material.
DETAILED DESCRIPTION
[0074] The embodiments of the present invention described below are
not intended to be exhaustive or to limit the invention to the
precise forms disclosed in the following detailed description.
Rather, the embodiments are chosen and described so that others
skilled in the art may appreciate and understand the principles and
practices of the present invention.
[0075] These teachings relate to the fractionation/separation of
fatty acid methyl esters, e.g., SME, into saturated fatty acid-rich
and unsaturated fatty acid-rich fractions via the use of urea
inclusion/urea complexation. Operation of diesel engines using
renewable energy sources including triglycerides-derived fuels is
known, as is the challenge of overcoming negative properties of
these triglycerides-derived fuels, e.g., the gelling of bioderived
diesel (biodiesel) at higher temperatures than petroleum derived
fuels. The composition of typical un-winterized biodiesel from SME
is as given in table 2.
TABLE-US-00002 TABLE 2 Composition of SME based biodiesel Fatty
Acid Methyl Ester % by Weight Methyl Palmitate (C 16:0) .sup.1 10.3
Methyl Sterate (C18:0) 4.7 Methyl Oleate (C18:1) 22.5 Methyl
Linoleate (C 18:2) 54.1 Methyl Linolenate (C18:3) 8.3 .sup.1 The
parenthetical reference (Cnn:n) indicates the number of carbon
atoms of the molecule on the left side of the colon followed by the
number of carbon-carbon double bonds in the molecule on the right
hand side of the colon.
[0076] Referring to FIG. 2a, transesterification of a starting
material is shown. Transesterification reactants comprise a fatty
acid source, e.g., soy oil, an alcohol, and a catalyst. Methanol is
typically chosen as the reactant for SME transesterification,
resulting in formation of the methyl ester from triglycerides. A
hydroxide catalyst is typically used to accelerate the
transesterification, although the reaction also responds to acid
catalysis. Generally, mineral acids or mineral bases are selected
as transesterification catalysts.
[0077] Typically, the transesterification of fatty acids from soy
oil is considered "commercially complete" after a reaction time of
from one to three hours at reaction conditions. Total time of
reactants in the reaction vessel may exceed these times if it is
necessary to heat reactants to reaction temperature in situ. In
commercial settings, completion of the transesterification occurs
when continuation of the transesterification cannot economically be
maintained. Commercial completion may be influenced by many factors
related to the equipment involved. Examples of these factors are
capital cost/depreciation status, operating expense, size,
geometry, separation equipment available, raw material cost, labor
cost, or even the time of day as it relates to an operator's shift
change.
[0078] The range of possible fat sources is not limited. Commercial
fat sources are generally chosen from oilseeds, often locally
produced, such as soybeans and canola. The carbon content of fatty
acids from such sources ranges from 16 to 22 carbon atoms per fatty
acid molecule.
[0079] In one embodiment, transesterification of raw materials of
fats is most commonly accomplished by supplying fats and alcohol in
the molar ratio of 1 mole fat (triglycerides) to 3 moles alcohol.
Although the process is operable outside this ratio, unreacted raw
materials result. The reaction is observed to be nearly
stoichiometric although it may be advantageous to add excess
alcohol to the esterification step as will be discussed below. One
percent catalyst by weight of fat is sufficient to facilitate the
reaction at a commercially acceptable rate. Insufficient catalyst
results in a slowed reaction; excess catalyst is not observed to
significantly increase the reaction rate and may require additional
separation effort at the completion of the reaction.
[0080] An example of the transesterification process is shown in
FIG. 2a. Sodium Hydroxide (NaOH) is mixed with methanol, creating
methoxide in methanol. The mixture produces heat. Fatty acids (in
this case soy oil), are added to the methoxide mixture. The
transesterification reaction generates glycerin and methyl esters.
If a period of quiescence is allowed, the glycerin phase will
separate from the methyl esters at the completion of the
transesterification, forming a liquid phase of methyl ester on top
of a liquid phase of glycerin. The phases may then be separated by,
e.g., decanting the methyl esters. Other phase separation methods
such as a centrifugation may be used to accelerate and enhance the
separation of glycerin from the methyl ester. The exemplary
technique for the above-described transesterification process is
illustrated by the following example.
Transesterification of Soy Oil to Produce Un-Winterized SME
Example:
[0081] Transesterification of soy oil with methanol in a vessel was
completed with 6 molar parts methanol to 2 molar parts refined soy
oil. NaOH as a catalyst at the rate of 1% by weight of soy oil was
included. The liquid components were heated to 65.degree. C. The
condition was maintained for one hour with continuous mixing. The
resulting two phases (upper layer--soybean methyl esters, methanol,
impurities; bottom layer-glycerol, residual catalyst, impurities)
were separated by decantation, using a 1000 ml separatory funnel.
Analysis of the methyl ester phase disclosed the composition by
weight in Table 3a.
TABLE-US-00003 TABLE 3a Soy Oil Methyl Ester Fatty Acid Methyl
Ester % by Weight Methyl Palmitate (C 16:0) .sup.1 10.9 Methyl
Stearate (C18:0) 4.1 Methyl Oleate (C18:1) 25.9 Methyl Linoleate (C
18:2) 53.0 Methyl Linolenate (C 18:3) 6.1 Others traces Total
Saturates 15.0 C.P. (.degree. C.) 3
[0082] For purpose of comparison, compositions of other vegetable
oils are listed in table 3b, while compositions of the fats of some
land and marine animals are listed in table 3c.
TABLE-US-00004 TABLE 3b* Fatty Acid Composition of Some Vegetable
Oils (%) Oil C10:0 C12:0 C14:0 C16:0 C18:0 C18:1 C18:2 C18:3 Cocoa
butter 26 3.5 37 2.5 Coconut 7 48 17 8 3 6 2 Corn 11 3 27 57
Cottonseed 0.8 25 2 18 53 0.1 Olive 1 15 2.6 67 13 1 Palm 1 46 5 39
9 0.4 Palm kernel 3.6 50 16 8 2 15 1 Peanut 10 3 52 29 Rapeseed 3 1
25 17 8.5 Safflower 6 2 14 74 0.4 Soybean 11 3.5 22 54 8 Sunflower
7 4 17 71 0.3
TABLE-US-00005 TABLE 3c* Fatty Acid Composition of Some Vegetable
Oils (%) C4:0- Oil 12:0 C14:0 C16:0 C18:0 C18:1 C18:2 C18:3 C20:5
C22:6 Beef tallow 3 26 22 42 2 0.2 Butter 12 10.8 26 10.3 28 2 1
Chicken 0.9 22 10 41 20 2 Lard 1.3 24 15.5 46 9 0.3 Mackerel 6 16 3
15 2 1 5 9 *Source: Bailey Industrial Oil and Fat Products,
5.sup.th edition, 1996, Vol. 1, Edible Oil and Fat Products:
General Applications, Y. H. Hui, editor Wiley Interscience, John
Wiley and Sons, Inc.
[0083] Biodiesel derived from SME has proven to be an extender,
additive, or replacement for petroleum-based diesel fuel and
heating oil. Studies are ongoing for using biodiesel as an aviation
turbine fuel extender. A challenge posed by biodiesel is its poor
cold flow properties. The total content of saturates is about
14-15% (wt/wt) and causes the C.P. to be about 0.degree. C. and
pour point to be about -2.degree. C. to -4.degree. C. This limits
the use of SME at low temperatures. Various efforts have been made
to reduce or depress the C.P. of SME, e.g., 1) removal of saturated
components, 2) use of cold flow additives, 3) use of branched chain
alcohol esters, and 4) combinations thereof.
[0084] The popular method for removal of saturate components is
winterizing or cold filtering. Various studies have been conducted;
however, these methods have very low yields for any significant
reduction in the C.P. Cold flow additives have been successful in
lowering the P.P. (Pour Point), but have little or no effect on the
C.P.
[0085] These teachings disclose a C.P. reduction ranging from about
-2.degree. C. to about -57.degree. C. by a controlled removal of
the saturated, and in some cases, mono-unsaturated fractions by
clathration and subsequent separation. The remaining
polyunsaturated fatty acid fractions yields range from 98%-41% of
the starting material, i.e., SME. The process parameters of greater
significance are: 1) urea/FAME/Alcohol (weight/weight/weight
ratio), and 2) the temperature to which the methyl ester clathrate
mixture is cooled. The rate of cooling appears to play a lesser
role in the formation of urea clathrates and therefore separation
of saturated from unsaturated fatty acid methyl ester.
[0086] Referring to FIG. 2b, starting material composed of SME,
urea, and solvent in the form of alcohol (methanol or ethanol) is
mixed in reactor 100 to start the fractionation process. Although
the starting material shown in FIG. 2b is SME, resulting from the
transesterification process whereby glycerol is decanted from the
fatty acids, the starting material for the process shown in FIG. 2b
can contain glycerol. The mixture in reactor 100 is heated to
60-65.degree. C. to achieve a homogenous mixture to facilitate
formation of clathrates.
[0087] Subsequent to heating, the mixture in reactor 100 is cooled
to precipitate the clathrates. The mixture is cooled to a final
temperature of between 20-25.degree. C. While the rate of cooling
does not have an important effect in the final composition of the
mixture, the final temperature is a crucial parameter in the
process affecting yield and the amount by which saturated
components are removed from the mixture. For example, cooling down
to 20-25.degree. C. has provided acceptable yields while removing
high amounts of saturated compounds. Constant stirring is important
throughout the process. The cooling will result in a fractional
crystallization of the mixture, giving rise to the formation of two
phases: 1) solid phase or precipitate having urea complexes (mainly
clathrates of saturated fatty acids and urea); and 2) liquid phase
or filtrate having methanol (mainly unsaturated fatty acids and
urea). This fractionation process can be repeated in several steps,
generally referred to as step fractionation, on the same sample to
obtain the desired composition and properties of the final
product.
[0088] The liquid-solid mixture is transferred to liquid-solid
separation station 102 where centrifugation, filtration, or other
techniques may be employed to separate liquids from solid
clathrates. Extraction and purification of the mixture having
mainly unsaturated fatty acids and urea is accomplished by
centrifugal separation, vacuum filtration, or by using conical
decantation tank to precipitate the solids. The liquid that is
separated from the solid clathrates is then transferred to solvent
recovery station 104 to remove the solvent. Solvent recovery
station 104 is a closed vessel in which the liquid is heated to
evaporate and recover the solvent, e.g., methanol 105. Solvent
recovery can also be accomplished by applying vacuum to the closed
vessel. In one embodiment, an evaporator equipped with an internal
detector can be used which stops the heating process whenever the
evaporator detects that no more solvent is being evaporated. In
another embodiment a rotary evaporator can be used having a
water-bath that is at about 60.degree. C., having a vacuum of
between 15-25 mm Hg. The recovered methanol 105 is then transferred
to reactor 100 to supplement the solvent used in the starting
material. The solvent recovered liquid extract is then washed by
acidified water in mixer 106 (60.degree. C., pH 3-4) to dissolve
the remaining urea (around 100 ml water for each 170 g of urea),
before going through liquid-liquid separation station 108 to
extract low C.P. SME 124 as well as urea brine 116. Optionally,
hexane or another suitable organic solvent can be added to improve
the extraction of the remaining unsaturated methyl esters. The
water/solvent phases are separated either by a liquid-liquid
centrifugal extractor or by gravity separation (decantation) of
phases.
[0089] Raffinate solids 110 extracted from liquid-solid separation
station 102 are mixed with water in mixer 112 and transferred to
liquid-liquid separation station 114 to extract urea brine 116 and
high C.P. SME 120. The raffinate solids 110 are washed with warm
water to dissolve the urea inclusion compounds (UIC). The upper
layer containing the methyl esters is decanted or siphoned in
liquid-liquid separation station 114. Urea brine 116 coming from
liquid-liquid separation stations 108 and 114 is combined and dried
in dryer 122 to produce urea 118 that can be re-used in reactor
100. If this results in a hardened form of urea, it is recommended
to grind it before recycling it into the process.
[0090] Depending upon the desired C.P. reduction, a particular
proportion of urea/FAME/Alcohol as starting material is chosen.
Affecting the C.P. reduction is also the terminal temperature to
which the mixture is cooled in reactor 100. In one embodiment of
the current teachings, the mixture is allowed to cool to room
temperature. Additionally, the fatty acid starting materials in the
transesterification process affect the cloud point. Various
combinations of these parameters are possible for the same C.P.
reduction. The urea/FAME ratio may range from 0.0:1 to 1:1 wt/wt.
The alcohol/FAME ratio may range from 3:1 to 10:1 wt/wt.
[0091] Exemplary methods in accordance with these teachings add an
alcohol, such as methanol, as a urea solvent and urea for
fractionation or clathration. By weight, the ratio of urea to FAME
may be in the range from 0.1:1 to 1:1. It is also envisioned that a
ratio greater than 1 part urea to 1 part FAME can be used if a very
low CP is desired. Urea forms solid phase clathrates with the
saturated fatty acid esters.
[0092] Sufficient alcohol should be added to dissolve all urea that
is added. A sufficient amount of alcohol results in a ratio of
alcohol to the methyl ester which ranges from 3:1 to 10:1 wt/wt.
Excess alcohol decreases the tendency to produce urea clathrates,
thus, decreases the efficiency of the process. Alcohol present
after clathrate formation is often separated from the predominantly
unsaturated ester by methods utilizing the relative vapor pressures
of the two components, for example, distillation or flash
evaporation. Economic considerations encourage limiting alcohol to
an amount necessary to dissolve the added urea.
[0093] Methanol is preferred for esterification. Use of methanol as
the solvent for urea in preference to C2-C4 alcohols eliminates the
need to store and handle additional reagents for separation of
fatty acid methyl esters. After formation of the FAME and glycerin,
a convenient manufacturing sequence separates the glycerin phase
from the fatty acid ester phase, followed by addition of urea and
alcohol to the FAME. The urea and alcohol may be added separately
or as a solution of urea dissolved in alcohol. An option afforded
by the use of methanol as urea solvent is the convenient
continuation of the process by conducting the subsequent
clathration step in the same vessel used for the ester formation.
By continuing the process in the same vessel with methanol as the
solvent, capital investment is reduced by eliminating additional
process steps to first remove residual methanol prior to addition
of C2-C4 alcohols.
[0094] In one embodiment, excess methanol may be provided in the
esterification step such that the addition of solvent during the
clathration stage can be reduced or eliminated. In another
embodiment it is possible to proceed directly from esterification
to clathration without removing glycerin. In this embodiment,
glycerin is removed as a final stage, as are clathrates.
[0095] Dissolution of urea in methyl ester is accomplished by
stirring alcohol in the solution at temperatures in the range of
50-75.degree. C. The rate of heating of the mixture has not been
observed to have a significant effect on the yield of the product
or the C.P. achieved.
[0096] It has been observed that the cooling rate has little
influence on the C.P. Yields are impacted more significantly by the
terminal temperature to which a mixture is cooled. Cooling the
mixture of saturated fatty acid esters urea clathrates, unsaturated
fatty acid methyl esters, excess/unreacted methyl alcohol,
excess/unreacted urea, and optionally, glycerin, to temperatures of
20 to 25.degree. C. provides economically acceptable yields
resulting in high clathrate formation of saturated esters compounds
and thereby in high removal of saturates without the need for
refrigeration.
[0097] The solid phase including clathrates of the saturated methyl
esters may be separated from the liquid phase comprising
unsaturated-methyl-esters, methanol, dissolved urea, and
optionally, glycerin by convenient solid-liquid separation means
such as filtration or centrifuge, as indicated by liquid-solid
separation station 102.
[0098] If present, glycerin may be removed from the liquid phase.
Alcohol present in the liquid phase that is rich in unsaturated
fatty acid esters may be recovered by evaporation at a temperature
between 30-50.degree. C. (e.g., in a closed vessel under vacuum, as
indicated by solvent recovery station 104). The remaining filtrate
is then washed with warm acidic water (60-70.degree. C., pH 3-4) to
remove urea and alcohol, as indicated by liquid-liquid separation
station 108. The water wash may be carried out in steps, washing
the filtrate with warm, acidified water in each step, or in a
continuous manner. Suitable purity of filtrate may be achieved with
single or multiple step washes with water volumes equal to the
filtrate volume. Continuous washing is successful with 3-4 water
volumes.
[0099] The saturate rich fraction, indicated by high temperature
SME 120 in FIG. 2b, may be obtained from the raffinate by
dissolving and washing with warm acidified water (60-70.degree. C.,
pH 3-4) in the liquid-liquid separation station 114. The warmed
saturate rich fraction phase separates from the aqueous phase. The
saturate rich fraction has utility such as a hydrocarbon source in
chemical manufacturing or additives to heating oil and other heavy
oils or fuels where C.P. is not a critical property. Urea can be
recovered for re-use by evaporation of the wash water or by thermal
dissociation, as indicated by dryer station 122.
[0100] The exemplary technique is illustrated by the following
examples. A summary of these examples is found in table 4. In Table
4 FAME constituents are listed for each example. Additionally,
resulting C.P., cooling rate, % by weight of starting SME and the
proportions of SME to urea to ethanol is listed for each
example.
TABLE-US-00006 TABLE 4 Experiment Number Base 1 2 3 4 Methyl
Palmitate (C16:0) 9.2 6.3 1.6 2.3 2.1 Methyl Stearate (C18:0) 3.8
1.4 0 0 0 Methyl Oleate (C 18:1) 23.5 24.6 21.9 22.5 24.0 Methyl
Linoleate (C18:2) 55.3 59.6 69.5 68.5 66.0 Methyl Linoleniate
(C18:3) 7.6 8.1 7.0 6.8 7.5 Others 0.7 0.02 0.03 0.02 0.01 Total
Saturates 12.9 7.7 1.6 2.3 2.1 Cooling rate (.degree. C./min) 1.2
1.2 1.3 10.7 Cooled downed temperature (.degree. C.) 20 20 30 20 %
by Wt of starting SME 78.4 66.4 75.9 64.9 SME/Urea/EtOH (g/g/mL)
24.1/ 24.1/ 24.1/ 24.1/ 10.1/ 18.0/ 16.0/ 16.0/ 160 160 160 160
C.P. (.degree. C.) 0 -10 -26 -16 -23
Example 1
[0101] Soy methyl ester prepared as described is analyzed for
composition. The starting soy methyl ester had the composition and
properties according to Table 5:
TABLE-US-00007 TABLE 5 Percentage by Weight Fatty Acid Methyl Ester
Composition Methyl Palmitate (C 16:0) 9.2 Methyl Stearate (C18:0)
3.8 Methyl Oleate (C18:1) 23.5 Methyl Linoleate (C18:2) 55.3 Methyl
Linolenate (C 18:3) 7.6 Others 0.7 Total Saturates 12.9 C.P.
(.degree. C.) 0
[0102] 24.1 g of soy methyl ester and 10.1 g of urea were added to
160 mL of ethanol and the mixture was heated to 67.degree. C., with
constant stirring. A homogenous mixture was obtained with all the
urea dissolving at this temperature. The mixture was then cooled at
a rate of 1.2.degree. C./min to a final temperature of 20.degree.
C. The urea inclusion compounds (clathrates) formed were separated
by filtration. The filtrate was then heated to 30.degree. C. and
70% of the starting volume of ethanol was recovered via evaporation
under vacuum. The remaining filtrate was twice washed with equal
volumes of water (60.degree. C., pH 3). 18.8 g of fractionated soy
methyl ester (78.4% by wt of the starting soy methyl ester) was
recovered with the composition and properties according to Table 6.
Recovered ethanol is available for re-use in the process.
TABLE-US-00008 TABLE 6 Percentage by Weight Fatty Acid Methyl Ester
Composition Methyl Palmitate (C 16:0) 6.3 Methyl Stearate (C18:0)
1.4 Methyl Oleate (C18:1) 24.6 Methyl Linoleate (C18:2) 59.6 Methyl
Linolenate (C 18:3) 8.1 Others 0.02 Total Saturates 7.7 C.P.
(.degree. C.) -10
Example 2
[0103] 24.1 g of soy methyl ester having the composition according
to Table 5 and 18.0 g of urea were added to 160 mL of ethanol and
the mixture was heated to 73.degree. C., with constant stirring. A
homogenous mixture was obtained with all the urea dissolving at
this temperature. The mixture was then cooled at a rate of
1.2.degree. C./min to a final temperature of 20.degree. C. The urea
inclusion compounds formed were then separated by filtration. The
filtrate was then heated to 30.degree. C. and 52% of the starting
volume of ethanol was recovered via evaporation under vacuum. The
filtrate was twice washed with equal volumes of water (60.degree.
C., pH 3). 16.0 g of fractionated soy methyl ester (66.4% by wt of
the starting soy methyl ester) was recovered with the composition
and properties according to Table 7.
TABLE-US-00009 TABLE 7 Percentage by Weight Fatty Acid Methyl Ester
Composition Methyl Palmitate (C16:0) 1.6 Methyl Stearate (C18:0)
0.0 Methyl Oleate (C18:1) 21.9 Methyl Linoleate (C 18:2) 69.5
Methyl Linolenate (C 18:3) 7.0 Others 0.03 Total Saturates 1.6 C.P.
(.degree. C.) -26
Example 3
[0104] 24.1 g of soy methyl ester having the composition according
to Table 5 and 16.0 g of urea were added to 160 mL of ethanol and
the mixture was heated to 72.degree. C., with constant stirring. A
homogenous mixture was obtained with all the urea dissolving at
this temperature. The mixture was then cooled at a rate of
1.3.degree. C./min to a final temperature of 30.degree. C. The urea
inclusions compounds formed were then separated by filtration. The
filtrate was then heated to 30.degree. C. and 63% of the starting
volume of ethanol was recovered via evaporation under vacuum. The
filtrate was twice washed with equal volumes of water (60.degree.
C., pH 3). 18.3 g of fractionated soy methyl ester (75.9% by wt of
the starting soy methyl ester) was recovered with the composition
and properties according to Table 8.
TABLE-US-00010 TABLE 8 Percentage by Weight Fatty Acid Methyl Ester
Composition Methyl Palmitate (C 16:0) 2.3 Methyl Stearate (C18:0)
0.0 Methyl Oleate (C18:1) 22.5 Methyl Linoleate (C18:2) 68.5 Methyl
Linolenate (C 18:3) 6.8 Others 0.02 Total Saturates 2.3 C.P.
(.degree. C.) -16
Example 4
[0105] 24.1 g of soy methyl ester having the composition according
to Table 5 and 16.0 g of urea were added to 160 mL of ethanol and
the mixture was heated to 72.degree. C., with constant stirring. A
homogenous mixture was obtained with all the urea dissolving at
this temperature. The mixture was the cooled at a rate of
10.7.degree. C./min to a final temperature of 20.degree. C. The
urea inclusions compounds formed were then separated by filtration.
The filtrate was then heated to 30.degree. C. and 63% of the
starting volume of ethanol was recovered via evaporation under
vacuum. The filtrate was twice washed with equal volumes of water
(60.degree. C., pH 3). 15.6 g of fractionated soy methyl ester
(64.9% by wt of the starting soy methyl ester) was recovered with
the composition and properties in Table 9.
TABLE-US-00011 TABLE 9 Percentage by Weight Fatty Acid Methyl Ester
Composition Methyl Palmitate (C 16:0) 2.1 Methyl Stearate (C18:0)
0.0 Methyl Oleate (C18:1) 24.0 Methyl Linoleate (C 18:2) 66.0
Methyl Linolenate (C 18:3) 7.5 Others 0.01 Total Saturates 2.1 C.P.
(.degree. C.) -23
Examples 5-7
[0106] Fuel for turbine engines is specified by ASTM standard
D-1655. Plant sourced oils have limited penetration in to the
market for turbine fuel.
[0107] A commercially sourced soybean oil derived fatty acid methyl
ester, the properties of which are described in Table 5, was
fractionated as described herein. The "as obtained" fraction
analysis and the fraction analysis after processing appears in
Table 11. The fractionated soy methyl ester of Examples 5-7 was
then blended with the Commercial Jet A fuel to yield the properties
which are listed in Table 10.
TABLE-US-00012 TABLE 10 Turbine Fuel 9 Parts Jet A: 7 Parts Jet A:
9 Parts Jet A: Property- 1 Part 3 Parts 1 Part Measurement ASTM D
Fractionated SME Fractionated SME Fractionated SME Units 1655
Example 5 Example 6 Example 7 Density-kg/m.sup.3 775-840 817.8
831.4 817.8 Viscosity cSt g- maximum 8.0 5.5 -- -- 20.degree. C.
Freeze Point- maximum -40.degree. C. -42.degree. C. -41.degree. C.
-40.degree. C. 1 .degree. C. Net Heat of minimum 42.8 42.7 41.4
42.6 Combustion- MJ/kg Acid Value- maximum 0.01 0.016 0.028 0.016
mgKOG/g
TABLE-US-00013 TABLE 11 Com- Fractionated Fractionated Fractionated
mercial SME SME SME SME Example 5 Example 6 Example 7 Component
Percent by Weight methyl palmitate 9.2 3.5 1.3 6.5 methyl stearate
3.8 0.2 0.1 0.5 methyl oleate 23.5 29.0 28.2 28.7 methyl linoleate
55.3 58.1 60.6 56.0 methyl linolenate 7.6 9.2 9.8 8.3 unknown 0.7 0
0 0
[0108] The fractionated soy methyl ester was blended with Jet A
fuel in the ratios indicated in Table 10 which yielded the
properties that are indicated in Table 10. The blended fuel has
demonstrated that the requirements of ASTM D-1655 are attainable
with blends including soy methyl ester.
[0109] Combustion studies of soy methyl ester blends with
commercial Jet A show non-critical deviation from the combustion of
commercial Jet A fuel. An Allison stationary 250 turbine having a
relatively low compression ratio of 6.2:1 was used for the
combustion study. FIG. 3 shows the fuel flow rate over a power
range from 40 to 70 RPM % for Jet A fuel, and soy methyl ester
blends of 10%, 20% and 30% with Jet A fuel.
[0110] Controlled emissions for Jet A and soy methyl ester blends
are shown in FIG. 4 for carbon monoxide, FIG. 5 for nitrogen
dioxide, and FIG. 6 for nitrogen monoxide.
Example 8
[0111] 24.0 g of soy methyl esters and 16.8 g of urea were added to
120 mL of methanol and the mixture was heated to 55.degree. C.,
with constant stirring. The starting SME was prepared according to
the example which followed the discussion of transesterification
process and which was titled "Transesterification of soy oil to
produce un-winterized SME example." A homogenous mixture was
obtained with all the urea dissolving at this temperature. The
mixture was then cooled in a water bath to 25.degree. C. The urea
clathrates were then separated by filtration. Methanol was
recovered from the filtrate by flash evaporation. The filtrate was
washed two times with equal volumes of water (60.degree. C., pH of
3). 12.4 g of fractionated soy methyl ester (51.7 by wt of the
starting soy methyl ester) was recovered with the composition and
properties according to Table 12.
TABLE-US-00014 TABLE 12 Fractionated Soy Methyl Ester Percentage by
Weight Fatty Acid Methyl Ester Composition Methyl Palmitate (C16:0)
2.3 Methyl Stearate (C18:0) 0 Methyl Oleate (C18:1) 24.4 Methyl
Linoleate (C18:2) 66.0 Methyl Linolenate (C18:3) 7.3 Others
(>C20) traces Total Saturates 2.3 C.P. (.degree. C.) -23
Example 9
[0112] 24.0 grams of soy methyl esters, prepared according to
transesterification of soy oil to produce un-winterized SME
example, and 19.2 grams of urea were added to 120 ml of methanol.
The mixture was heated to 55.degree. C., with constant stirring.
After all components were dissolved, the mixture was cooled down to
25.degree. C. in a water bath; the urea clathrates formed were
separated by filtration. The methanol from the filtrate was removed
by flash evaporation. The filtrate was then washed twice with equal
volume of water (60.degree. C., pH of 3). 10.7 g of fractionated
SME (yield=44.6%) was recovered with the composition and properties
according to Table 13.
TABLE-US-00015 TABLE 13 Percentage by Weight Fatty Acid Methyl
Ester Composition Methyl palmitate (C16:0) 1.7% Methyl Stearate (C
18:0) 0% Methyl Oleate (C18:1) 24.2% Methyl Linoleate (C 18:2)
66.1% Methyl Linolenate (C18:3) 8.0% Others (>C20) Traces Total
saturated fatty acids 1.7% C.P. (.degree. C.) -34
Example 10
[0113] 24.0 g of soy methyl ester, prepared according to
transesterification of soy oil to produce un-winterized SME
example, and 24.0 g of urea were added to 120 mL of methanol. The
mixture was heated to 55.degree. C., with constant stirring. The
homogenous mixture obtained was then cooled in a water bath to 25
to 20.degree. C. The urea clathrates were separated by filtration.
Methanol was removed from the filtrate by flash evaporation. The
filtrate was washed two times with equal volumes of water
(60.degree. C., pH of 3). 10.3 g of fractionated soy methyl ester
(42.9% by wt of the starting soy methyl ester) was recovered with
the composition and properties according to Table 14.
TABLE-US-00016 TABLE 14 Percentage by Weight Fatty Acid Methyl
Ester Composition Methyl Palmitate (C 16:0) 0 Methyl Stearate
(C18:0) 0 Methyl Oleate (C18:1) 19.2 Methyl Linoleate (C 18:2) 72.3
Methyl Linolenate (C 18:3) 8.5 Others (>C20) traces Total
Saturates 0 C.P. (.degree. C.) -57
[0114] Referring to FIG. 7, a bar graph as shown that illustrates
reduction in cloud point achieved by a process in accordance with
these teachings as a function of the proportion of SME, urea and
methanol starting materials. FIG. 7 represents experiments 8-10 as
well as other experiments. Data points corresponding to experiments
8-10 are marked accordingly in FIG. 7. Data points corresponding to
the other experiments are marked as 11-15, and data corresponding
to these experiments are presented in Table 15.
TABLE-US-00017 TABLE 15 Data point 11 12 13 14 15 SME: Urea (120 ml
of methanol) 1:0 1:0.2 1:0.3 1:0.4 1:0.5 Methyl Palmitate (C16:0)
10.9 9.9 7.0 5.8 4.3 Methyl Stearate (C18:0) 4.1 4.2 2.0 1.4 0.0
Methyl Oleate (C 18:1) 25.9 25.5 26.8 25.5 27.4 Methyl Linoleate
(C18:2) 53.0 54.5 57.6 60.5 60.5 Methyl Linoleniate (C18:3) 6.1 5.9
6.6 6.8 7.8 Total Saturates 15.0 14.1 9.0 7.2 4.3 C.P. (.degree.
C.) 5 -1 -7 -8 -13
[0115] Each bar in FIG. 7 represents an individual process to
achieve cloud point reduction. The height of an individual bar
represents the yield at the completion of the process, with higher
yields shown on the left hand side of the graph. The relative
amounts of starting materials are printed below each bar. As shown,
the relative proportion of SME to methanol is the same for all
runs, 1 to 5. Moving from left to right on the graph of FIG. 7,
however, the amount of urea in the starting material incrementally
increases from zero (0) parts (bar on far left) to one (1) part
(bar on far right). Finally, the relative proportion of each
individual fatty acid, e.g., C16:0, C18:0, etc., is indicated by
the different cross-hatched segments of the individual bars. For
example, the bar on the far left hand side has about 2.1 g C16:0,
1.2 g C18:0, 5.8 g C:18:1, 13.1 g C:18:2 and 1.8 g C:18:3.
Resulting cloud point is plotted on the y-axis as a solid line
connected by the data points as shown.
[0116] FIG. 7 shows that lower cloud points are achieved as the
relative proportion of urea increases. A C.P. data point is shown
in the center of each bar, indicating the cloud point associated
with the composition of the starting material. For example, the bar
on the far left hand side of the graph corresponding to a starting
material having a proportion of 1:0:5 of SME, urea and ethanol (or
methanol), has a C.P. of 3.degree. C.
[0117] A solid line connecting the C.P. data points is shown in
FIG. 7. This solid line shows that the corresponding cloud point
achieved varies from 3.degree. C. to -57.degree. C. as the
proportion of urea to SME is increased from 0 to 1. Specifically,
the C.P. decreases from 3.degree. C. to -8.8.degree. C. according
to the four consecutive data points on the left hand side of the
graph. This drop is associated with a urea increase from 0 to 0.4,
in relative proportion, while SME and ethanol (or methanol)
proportions are held constant. This decrease of 3.degree. C. to
-8.8.degree. C. for the first four data points represents about 20%
of the overall decrease in C.P. (decrease of 3.degree. C. to
-57.degree. C.). Conversely, the last four data points,
corresponding to urea proportions of 0.5 to 1 represent a drop of
C.P. from -12.degree. C. to -57.degree. C. This drop represents 75%
of the overall decrease in C.P. This data illustrates a significant
decrease in C.P. when urea proportion is increased from 0.5 to
1.
[0118] Additionally, FIG. 7 shows the relationship between the
fatty acid profiles achieved at the end of the process based on the
amount of urea used in the starting material. For example, the
fatty acid profile of the bar shown on the far left hand side of
the graph is given above. As the percentage of saturates (C16:0 and
C18:0) in the fatty acid profile decreases, the C.P. decreases
accordingly. For example, in the bar on the far left hand side of
the graph, associated with a urea to SME ratio of 0, the percentage
of saturates (C16:0 and C18:0) is about 14% (about 3.3 g out of the
about 24.0 g total fatty acids). The C.P. corresponding to this bar
is 3.degree. C. The bar in the center of the graph associated with
a urea proportion of 0.5 shows a saturate percentage of about 4%.
The C.P. corresponding to this bar is -12.degree. C. The bar on the
right hand side of the graph associated with a urea proportion of
0.8 shows a saturate percentage of about 1.9%. The C.P.
corresponding to this bar is -34.degree. C. Finally, the bar on the
far right hand side of the graph has a saturate percentage of 0%
while having a C.P. of -57.degree. C. Therefore, the C.P. decreases
significantly as the last of saturates, C16:0, are removed from the
fatty acid profile. Specifically, 38% of the overall C.P. decrease
occurs as urea proportion is increased from 0.8 to 1.0.
[0119] As discussed above, the prior art teachings of Dunn et al.,
predict a straight line relationship between the amount of
saturated components removed and the reduction in cloud point. Dunn
et al. predicted that this straight line can be extrapolated to
compositions having no saturated components. However, quite
surprisingly and remarkably, the inventors of the instant
application have found that the reduction in cloud point as the
last few percent of saturated components is removed is not linear.
In stark contrast to the teachings of Dunn et al., the inventors
have found that the cloud point of composition having very low
amounts of saturated components is far lower than Dunn et al.
predicted. For example, one of skill in the art can readily
recognize that the slope of the line extending from left to right
in FIG. 7 steepens significantly between the third to the last and
last bar, as shown. This dramatic change in slope is unexpected,
and directly contradicts the straight line relationship taught by
the prior art.
[0120] FIG. 7 also shows that C18:0 is removed prior to complete
removal of C16:0. This is shown in the bars associated with urea
proportions of 0.4 and 0.5. That is, a small amount of C18:0 is
found in the fatty acid profile shown in the bar associated with
urea proportion of 0.4. However, no C18:0 is found in the bar
associated with urea proportion of 0.5. In fact, as urea
proportions are increased to 0.7 and 0.8, only a small amount of
C16:0 saturates remain in the corresponding fatty acid profiles.
The reason C18:0 saturates are removed prior to removal of C16:0 is
that the urea inclusion compounds are formed favoring longer
straight chain hydrocarbons. Thus, C18:0 is thus preferentially
removed, before C16:0.
[0121] In addition, it can be observed from FIG. 7 that the amounts
of C18:3, polyunsaturated component of the fatty acid profiles, are
not significantly affected as the urea proportion is increased from
0 to 1. This is to be contrasted with other unsaturated components,
C18:1 and C18:2. Specifically, large portions of the C18:2
polyunsaturated components as well as the C18:1 monounsaturated
components are lost as urea proportion is increased from 0 to 1.
The loss of unsaturated components is apparently due to the
indiscriminate clathration of these components when saturated
components are no longer abundantly present in the mixture.
[0122] Another observation that can be made from FIG. 7 is that the
yield at the lowest C.P., associated with the bar at the far right
hand side of the graph, is about 46% of the starting SME, shown in
the bar at the far left hand side of the graph. However, the yield
does not decrease significantly as the C.P. decreases from
-34.degree. C. to -57.degree. C. This can be appreciated from the
last two bars on the right hand side of the graph.
[0123] Referring to FIG. 8, a graph of % extracted SME vs.
extracted species is presented. The graph in FIG. 8 shows the way
different constituents of the fatty acid profile change over the
range of experiments shown in FIG. 7. All of the constituents start
at 100% at the right hand side of the graph. There are 8 data
points for each constituent except for C18:0, which only has 4 data
points. Each data point corresponds to the percentage of one of the
fatty acid constituents in the fatty acid profile of a particular
experiment shown in FIG. 7. Different fatty acid constituents are
represented with different symbols. For example, C18:0 is
represented by solid squares, C16:0 by solid diamonds, C18:1 by
solid triangles, C18:2 by hollow diamonds and C18:3 by letter "X".
Vertical bars are included in the graph in order to facilitate
reading data points on the graph.
[0124] The graph in FIG. 8 demonstrates how constituent of the
fatty acid profile reduce as the amount of urea is increased in the
starting material. The horizontal axis in FIG. 8 titled "%
Ext.sub.SME" represents the percentage of fatty acids extracted at
the end of each experiment shown in FIG. 7. The vertical axis in
FIG. 8 represents the percentage of the remaining fatty acid
constituents in each experiment as compared to the amount of those
constituents in the starting material (indicated by the bar on the
far left hand side of FIG. 7). The horizontal axis is a
representation of the overall yield. For example, a yield of 70%,
shown approximately at the center of the horizontal axis in FIG. 8,
corresponds to the fifth bar from the left hand side in FIG. 7,
having urea proportion of 0.5. The total amount of fatty acids
extracted is about 16.5 g. This amount represents about 70% of the
starting fatty acids shown in the far left hand bar in FIG. 7,
which totals about 24.0 g. Referring to FIG. 7, of the approximate
amount of 16.3 g of extracted fatty acids, associated with the bar
representing urea proportion of 0.5, about 0.6 g is C16:0 (about
25% of the 2.4 g of starting C16:0), about 4.4 g is C18:1 (about
76% of the 5.8 g of starting C18:1), about 9.9 g is C18:2 (about
76% of the starting 13.0 g of C18:2), and about 1.4 g is C18:3
(about 82% of the starting 1.7 g of C18:3). These values are shown
in FIG. 8. For example, the dotted line going through 70% of %
Ext.sub.SME shows no C18:0 (represented by a solid square), about
25% C16:0 (represented by a solid diamond), about 76% C18:1
(represented by a solid triangle), about 76% C18:2 (represented by
a hollow diamond), and about 82% C18:3 (represented by a letter
"X"). Regression results showing best fit curves are seen as solid
lines and curves in FIG. 8. These solid lines and curves assist in
determining % Ext.sub.spicies at any % Ext.sub.SME between about
44% and 100% of % Ext.sub.SME.
[0125] It is envisioned that experimental results using different
starting material as indicated in FIG. 7 can be provided to a
mathematical analysis package, e.g., SAS, for the purpose of
fitting a curve to the experimental results. Such a mathematical
analysis package can perform a regression analysis and provide a
formula relating C.P. to molar or weight fraction of the
constituents of a starting material. Such a formula will
advantageously provide an analytical tool for predicting C.P. of a
particular mixture by knowing the species of a fatty acid profile
that make up the mixture. For example, by knowing the molar or
weight fractions of C16:0, C18:0, C18:1, C18:2, and C18:3 of a
particular mixture, a corresponding C.P. can be calculated.
[0126] In addition to the effect of the amount of urea in the
urea/FAME/alcohol mixture on the C.P., the starting material in the
transesterification process, i.e., the source of starting fatty
acid, also affects the C.P. Referring to FIG. 9a, a graph of C.P.
vs. % saturates is provided. In FIG. 9a the C.P. depression
discussed in the prior art is compared with the C.P. depression
according to the current teachings. The C.P. depression according
to the current teachings is designated by "Tao soybean." Of
particular interest are C.P. depression of "dunn 97 solvent," "dunn
96," and "Gomez." The linear graph of "dunn 97" corresponds to FIG.
1, titled prior art, which shows a C.P. depression from about
0.degree. C. to about -16.degree. C. Similarly, "dunn 97 solvent"
represents Dunn et al. (1997 article) winterization using solvents,
and "Gomez" indicate C.P. depression in the range of about
0.degree. C. and 2.degree. C. to about -10.degree. C. and
-5.degree. C., respectively.
[0127] Further referring to FIG. 9a, the line shown in FIG. 1 is
shown again based on the actual data points, designated as "solvent
dunn 96." The line is extrapolated so that it meets the vertical
axis at about, -25.degree. C. Dunn used SME in the experiment for
which the results are shown in FIG. 9a.
[0128] The amount of saturated fatty acids, i.e., C16:0 and C18:0,
that remain at the end of the clathration process controls the
cloud point. This concept is shown in FIG. 9b which shows
experimental data from different starting material, examples of
which are provided in Table 3b. The experimental data corresponding
to FIG. 9b is presented in Table 16. Each data point corresponding
to polyunsaturated, monounsaturated, and saturated fatty acids
indicates percent weight of the corresponding constituents as
compared to the whole. For example, in experiment number 1, 6%, by
weight, are polyunsaturated fatty acids, 25.5% are monounsaturated
fatty acids, and 11.5% are saturated fatty acids.
TABLE-US-00018 TABLE 16 Exp. No. 1 2 3 4 5 6 7 8 9 10 C.P. -5 -1 -6
-7 -8 -13 -16 -18 -22 -28 PUFA* 63 60.4 64.3 64.2 67.3 68.4 18.7
69.4 33.7 36.7 MUFA** 25.5 25.5 24.1 26.8 25.5 27.4 78.3 24.9 63.5
61.5 SFA*** 11.5 14.1 11.6 9.0 7.2 4.3 3.1 5.7 2.8 1.8 Exp. No. 11
12 13 14 15 16 17 18 19 C.P. -28 -34 -37 -37 -38 -39 -49 -52 -57
PUFA* 73.3 74.1 41.3 48.4 37.1 39.3 90.9 90.8 80.8 MUFA** 24.4 24.1
58.2 51.6 61.6 59.8 9.1 9.2 19.2 SFA*** 2.3 1.7 0.5 0 1.3 1 0 0 0
*PUFA indicates polyunsaturated fatty acids, e.g., C18:2 and C18:3
**MUFA indicates monounsaturated fatty acids, e.g., C18:1 ***SFA
indicates saturated fatty acids, e.g., 16:0 and C18:0.
[0129] In experiments 10 and 15, for example, the amounts of PUFA
and MUFA are approximately the same, i.e., 36.7% vs. 37.1, and
61.5% vs. 61.6%. However, the SFA are different by 0.5%, i.e., 1.8%
vs. 1.3%. The difference in percent SFA results in a drop in C.P.
of 10.degree. C. In contrast to these experiments, experiments 1
and 2 reveal a much smaller lowering of C.P. in the presence of a
much larger drop in SFA. For example, a difference of 2.6% in SFA,
i.e., 14.1% vs. 11.5%, results in a 5.degree. C. drop in C.P. This
observation further strengthens the point that very small amounts
of SFA remaining in the end composition could produce ultra low
C.P., lower than -30.degree. C. Moreover, as the percent SFA
remaining in the end composition reaches about 1-2%, further
removing small amounts of SFA, e.g., 0.5%, results in larger drops
in C.P., e.g., 10.degree. C. This shows that the relationship
between the amount of saturated fatty acids and CP becomes
nonlinear after most of the saturated fatty acids are removed.
Conversely, where large amounts of SFA remain in the end
composition, e.g., about 11-14%, further removing large amounts of
SFA, e.g., 2.6%, results in relatively smaller drops in C.P., e.g.,
5.degree. C.
[0130] In another embodiment, the product from the fractionation
process, according to the current teachings, can be used to treat
petroleum based fuel to improve cold flow properties of the
petroleum based diesel fuel. Two types of diesel fuel are commonly
used. Diesel number 2, which contains a higher amount of paraffin,
has a cloud point of about -28.degree. C. Diesel number 1 has a
cloud point of about -40.degree. C. Traditionally, diesel number 1
is blended with diesel number 2 for cold-weather operation. Adding
fractionated esters from the current process, which is rich in
polyunsaturated fatty acids, to diesel number 2 will improve C.P.
of the blend. This is advantageous since blending fuel with diesel
number 1 in large quantities is not desirable for diesel engine
operation due to lubricity difference between diesel number 1 and
number 2. However, addition of polyunsaturated-rich fractionated
esters to diesel number 2 will not have the same lubricity
disadvantages. It is well known that addition of
polyunsaturated-rich fractionated esters will actually improve
lubricity.
[0131] Referring to FIG. 10, a graph of yield vs. C.P. is
presented. Yield is affected by the processes of the current
teachings. In order to lower C.P., relative concentration of
saturated molecules are diminished which negatively affects yield.
FIG. 10 shows the resulting SME yield as a function of the desired
C.P. For example, at -57.degree. C. the yield is at about 46% the
starting SME. A substantial portion of the remaining 54% of the
starting SME is removed as high temperature SME (see reference
numeral 120 in FIG. 2b). As mentioned above, there are various
utilities for high temperature SME such as a hydrocarbon source in
chemical manufacturing or additives to heating oil and other heavy
oils where C.P. is not a critical property. Therefore, the high
temperature SME cannot be viewed as waste.
[0132] Referring to FIG. 11 impact of the amount of urea on C.P.
used in processing different starting material is shown. This graph
shows that an effective starting material from the group of
starting material listed in FIG. 11 is SME. Independent of the
chosen starting material, the amount of urea generally causes
depression of the C.P. with SME showing the largest amount of C.P.
depression.
[0133] Applicants' method as disclosed enables the fractionation of
fatty acid methyl esters based on saturated vs. unsaturated
molecules from mixtures of saturated and unsaturated fatty acid
methyl esters. Separated fractions may be achieved with the desired
unsaturated fraction comprising from 15 to 0% by weight saturated
fatty acid methyl esters, from 10 to 45% by weight monounsaturated
fatty acid methyl esters, and from 50 to 85% polyunsaturated fatty
acid methyl esters.
[0134] The C.P. for mixtures of saturated and unsaturated fatty
acid methyl esters may be reduced by preferably 10.degree. C., more
preferably 25.degree. C. to 60.degree. C. below the C.P. of the
unfractionated fatty acid methyl ester mixture.
[0135] It is envisioned that for many cold weather uses, biodiesel
in accordance with these teachings should have a cloud point that
is less than about -30.degree. C. Other cold weather applications
may require the biodiesel to have a cloud point less than about
-40.degree. C., or less than about -45.degree. C., or even less
than about -50.degree. C. These teachings provide a composition
having a cloud point of as low as -57.degree. C. (see Example 10)
and a method of making the same.
[0136] As one of skill in the art can appreciate from the examples
above, these surprisingly low cloud points are achieved when almost
all of the saturated fatty acid components, i.e., more than about
97%, are removed. In accordance with these teachings, the amount of
saturated fatty acid components in the final product should be less
than about 3%, more preferably less than about 2%. To achieve cloud
points of less than -40.degree. C. or less than about -50.degree.
C., the amount of saturated fatty acid components should be less
than about 3%, depending on the feedstock.
[0137] The experiments above also empirically show that
surprisingly low cloud points are achieved in a composition with a
small relative amount of C18:3 components. With reference to FIG.
7, the last three bars on the right hand side represent
compositions having cloud points of -23.degree. C., -34.degree. C.
and -57.degree. C., respectively. The amounts of C18:3 in these
compositions range from about 7.3% to about 8.5%. It is thus
envisioned that compositions with low cloud points in accordance
with these teachings may have C18:3 components of less than about
10%. Indeed, cloud points approaching -40.degree. C. were achieved
with pure sunflower oil (see FIG. 10), which has less than 0.5%
C18:3 components, but has 71% C18:2 components.
[0138] Additionally, empirical data show that very low C.P.'s may
be achieved without a significant corresponding sacrifice in
yields. For example, to achieve a cloud point of -23.degree. C.,
yield was about 52% (resulting SME compared to starting SME),
whereas for a cloud point of -57.degree. C., yield was about 43%.
Surprisingly, yield was substantially unaffected when lowering
cloud point from -34.degree. C. to -57.degree. C., as the yield was
lowered only by about 2%.
[0139] While exemplary embodiments incorporating the principles of
the present invention have been disclosed hereinabove, the present
invention is not limited to the disclosed embodiments. Instead,
this application is intended to cover any variations, uses, or
adaptations of the invention using its general principles. Further,
this application is intended to cover such departures from the
present disclosure as come within known or customary practice in
the art to which this invention pertains and which fall within the
limits of the appended claims.
* * * * *