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United States Patent |
6,204,400
|
Roberts
,   et al.
|
March 20, 2001
|
Process for the preparation of derivatives of fatty acids
Abstract
The preparation of a mixture comprising branched fatty acids and
oligomerised fatty acids comprises contacting a source of unsaturated
fatty acids or their derivatives with an ionic liquid.
Inventors:
|
Roberts; Glyn (Wallasey, IE);
Lok; Cornelis Martinus (Wirral, IE);
Adams; Christopher John (Wirral, IE);
Seddon; Kenneth Richard (Donaghadee, IE);
Earle; Martyn John (Belfast, IE);
Hamill; Jennifer Therese (Belfast, IE)
|
Assignee:
|
Unichema Chemie BV (Gouda, NL)
|
Appl. No.:
|
242428 |
Filed:
|
October 12, 1999 |
PCT Filed:
|
July 7, 1997
|
PCT NO:
|
PCT/EP97/03641
|
371 Date:
|
October 12, 1999
|
102(e) Date:
|
October 12, 1999
|
PCT PUB.NO.:
|
WO98/07679 |
PCT PUB. Date:
|
February 26, 1998 |
Foreign Application Priority Data
Intern'l Class: |
C09F 007/00 |
Field of Search: |
554/156,26
|
References Cited
U.S. Patent Documents
3090807 | May., 1963 | Illing et al. | 554/156.
|
4371469 | Feb., 1983 | Foglia et al. | 554/26.
|
Primary Examiner: Carr; Deborah D.
Attorney, Agent or Firm: Pillsbury Madison & Sutro Intellectual Property Group
Claims
What is claimed is:
1. Process for the preparation of a mixture comprising branched fatty acids
and oligomerised fatty acids, wherein a source comprising unsaturated
fatty acids or derivatives thereof, is contacted with an ionic liquid.
2. Process according to claim 1, characterized in that the source comprises
at least 50% by weight of fatty acids or derivatives thereof, having at
least one unsaturated carbon-carbon bond in the fatty acid chain.
3. Process according to claim 2, characterized in that the fatty acid
feedstock or derivative thereof, comprises of at least 80% by weight of
unsaturated fatty acid or derivatives thereof.
4. Process according to claim 1, characterized in that at least 50% by
weight of fatty acids or derivatives thereof have a fatty acid chain
length of between 10 and 24 carbon atoms.
5. Process according to claim 4, characterized in that the fatty acid
feedstock or derivative thereof comprises at least 40% by weight of oleic
acid or derivative thereof.
6. Process according to claim 5, characterized in that the fatty acid
feedstock or derivative thereof comprises of at least 70% by weight of
oleic acid.
7. Process according to any of claim 1, characterized in that the fatty
acid derivative is an alkyl ester of a fatty acid.
8. Process according to claim 7, characterized in that the fatty acid
derivative is an ester of fatty acid and an alcohol having 1-4 carbon
atoms.
9. Process according to claim 1, characterized in that the ionic liquid
comprises a binary ionic liquid.
10. Process according to claim 1, characterized in that the ionic liquid
comprises a metal(III) chloride and/or an organic halide.
11. Process according to claim 10, characterized in that the metal(III)
chloride is aluminium(III) or iron(III) chloride.
12. Process according to claim 10, characterised in that the organic halide
is an unsymmetrical imidazolium halide or a pyridinium halide.
13. Process according to claim 12, characterized in that the unsymmetrical
imidazolium halide is 1-methyl-3-ethylimidazolium chloride.
14. Process according to claim 1, characterized in that it is carried out
at temperatures below 150.degree. C., or preferably at temperatures below
50.degree. C.
15. Process according to claims 1, characterized in that the reaction is
performed under atmospheric pressure.
16. Process according to claim 1, characterized in that the ionic
liquid:fatty acid reactant ratio is larger than 1:1, preferably at least
3:1.
17. Process according to claim 1, characterized in that substantially no
aromatic dimers are produced during the reaction.
18. Process according to claim 1 in which the products are separated from
the reactants and ionic liquid.
19. Process according to claim 18 in which the imadazolium or pyridinium
halide is separated from the product/AlCl.sub.3 adduct by extraction with
a polar solvent.
20. Process according to claim 18 in which the product is liberated from
the product/AlCl.sub.3 adduct by hydrolysis in water.
Description
The present invention relates to a process for the preparation of a mixture
of branched and oligomeric fatty acids, by contacting a composition
comprising unsaturated straight chain fatty acids with an ionic liquid.
Fatty acids are versatile building blocks in various parts of the chemical
industry, ranging from lubricants, polymers, solvents to cosmetics and
much more. Fatty acids are generally obtained by hydrolysis of
triglycerides of vegetable or animal origin. Naturally occurring
triglycerides are esters of glycerol and generally straight chain, even
numbered carboxylic acids, in size ranging from 10-24 carbon atoms. Most
common are fatty acids having 12, 14, 16 or 18 carbon atoms. The fatty
acids can either be saturated or contain one or more unsaturated bonds.
Long, straight chain saturated fatty acids (C10:0 and higher) are solid at
room temperature, which makes them difficult to process in a number of
applications. The unsaturated long chain fatty acids like e.g. oleic acid
are liquid at room temperature, so easy to process, but are unstable
because of the existence of a double bond. Derivatives of fatty acids that
are branched (i.e. branched fatty acids) mimic the properties of the
straight chain in many respects, however, they do not have the
disadvantages associated with them. For example branched C18:0
(commercially known as isostearic acid) is liquid at room temperature, but
is not as unstable as unsaturated C18:1, since the unsaturated bonds are
prone to oxidation. Therefore, branched fatty acids are for many
applications more desirable than straight chain fatty acids.
Apart from branched fatty acids other fatty acid derivatives, such as
oligomerised fatty acids, find use in similar and other applications.
Oligomeric fatty acids refer to materials prepared by coupling of the
monomer units, of which typically dimeric and trimeric species are desired
building blocks in plastics, the personal care industry, lubricants,
etcetera.
Mixtures comprising oligomerised fatty acids and branched fatty acids can
be likewise useful.
Currently, branched and oligomeric fatty acids are obtained by
isomerisation/oligomerisation of the straight chain, unsaturated fatty
acids. The reaction is conventionally carried out using a clay catalyst,
and is generally performed at high temperature (e.g. 250.degree. C.). A
common process is the preparation of branched C18:0 and dimerised C18
(i.e. C36 dicarboxylic acids) from unsaturated straight chain C18:1 (or
also C18:2). A disadvantage in this conventional process is that
substantial amounts of aromatic dimers are formed. Such compounds are
undesirable for a number of reasons, of which the most notable are: they
do not contribute to the properties desired, and they can present a health
hazard. The latter precludes the use of conventional dimer acids for
certain highly desirable applications in the personal product and
cosmetics industries.
In addition, the prior art processes suffer from the disadvantage that
although a reasonable amount of polymerised product is obtained, the ratio
of dimerised to trimerised and higher fatty acids is fixed and cannot
easily be tuned to market demand.
Hence, there is a need for a process for the preparation of a mixture
comprising branched and oligomeric fatty acids, in which mixture the
concentration of aromatic dimers is low, or preferably substantially zero.
It has now been found that the above objectives can be met by a process for
the preparation of a mixture comprising branched fatty acids and dimerised
fatty acids, wherein a source comprising unsaturated fatty acids or
derivatives thereof, is contacted with an ionic liquid.
An ionic liquid is herein to be understood as a salt (or a mixture of
salts) in its liquid form (i.e. molten).
Preferably, to lead to the desired products, in the process according to
the invention, the source comprises at least 50% by weight of fatty acids
or derivatives thereof, having at least one unsaturated carbon-carbon bond
in the fatty acid chain. It is also preferred that at least 50% by weight
of said fatty acids or derivatives of fatty acids have a fatty acid chain
length of between 8 and 24 carbon atoms. A preferred fatty acid in this
respect is oleic acid or derivatives thereof.
Regarding the derivatives in the source as mentioned, esters are preferred,
with alkylesters being the most preferred. Of these alkylesters, the most
preferred ones are the fatty acid esters of alcohols having 1-4 carbon
atoms, e.g. methanol, ethanol, propanol. Hence, a preferred source for
performing the reaction according to the invention comprises oleic acid,
methyl oleate, and/or ethyl oleate.
With respect to the type of ionic liquid, a wide variety of possibilities
exists. However, it will be clear that the preferred ionic liquids are the
ones that are liquid at relatively low temperatures. Although some salts
have very high melting points (i.e. common NaCl has a melting point of
approx. 850.degree. C.), there are salts known which melt under less
severe conditions. An example of such salts are mixtures of two or more
salts. In the case in which a mixture of two salts is used, the resulting
ionic liquid is called a binary ionic liquid. Hence, it is preferred that
in the process as set out above the ionic liquid comprises a binary ionic
liquid.
Preferred binary ionic liquids comprise a metal(III) chloride and/or an
organic halide salt, e.g. [A].sup.+ X.sup.-. Also, inorganic halide salts
can be used. Suitable metal(III) chlorides include aluminium(III) chloride
and iron(III) chloride. Regarding the organic halide, an unsymmetrical
imidazolium or pyridinium halide has the advantage that
isomerisation/oligomerisation may now occur under mild conditions,
contrary to conventional processes. A preferred unsymmetrical imidazolium
halide is 1-methyl-3-ethyl imidazolium chloride.
A distinct advantage of the presently invented process over the known
processes is that there is no need to carry out a reaction for branching
and/or oligomerisation of fatty acids at elevated temperatures: as long as
the temperature is high enough for the salt which is used as the reaction
"solvent" (or medium) to be in its liquid form (i.e. molten). An
additional advantage is that substantially no aromatic and/or cyclic
dimers are formed in the process according to the invention.
Therefore, it is preferred that the process according to the invention is
carried out at temperatures below 250.degree. C. More preferred are
operating temperatures of below 150.degree. C., or even below 50.degree.
C., as long as the ionic liquid is chosen such that the mixture of ionic
liquid and reactants is a liquid. Some reaction systems are even active at
temperatures below 0.degree. C. At such temperatures, the amount at
cracked products obtained can be low, and following this, such a
temperature can be preferred for some cases.
As an additional advantage, there is no need for performing the reaction
under increased pressure, and therefore, it is preferred for the reaction
according to the invention to be carried out at atmospheric pressure.
Yet a further advantage of the present process is that long reaction times
are not needed. Generally, the reaction can be shorter than 60 minutes, in
many cases even shorter than 15 minutes.
In the process according to the invention, the ratio of ionic liquid:fatty
acid reactant is preferably larger than 1:1, preferably at least 3:1, and
most preferably at least 6:1.
In a practical set up, the process will be preferably be operated in a
(semi-)continuous way, and the products are separated from the reactants
and ionic liquid. The expensive unsymmetrical imadazolium or pyridinium
halide can be easily separated from the product by extraction with
solvents such as dichloromethane and hexane etc, together with mixtures
thereof. The imidazolium or pyridinium species can then be recycled
following evaporation or distillation of the solvent.
The invention is further illustrated by the following examples, which are
not to be interpreted as limiting the invention thereto.
EXAMPLE 1
Branching/Oligomerisation of Methyl Oleate
In a dry box, 1-methyl-3-ethylimidazolium chloride (3.55 g, 24.20 mmol) was
added to triply sublimed aluminium(III) chloride (6.45 g, 48.40 mmol), in
a 100 cm.sup.3 round bottomed flask, equipped with a dinitrogen inlet,
Teflon stirrer bar and a stopper. The two solids were left to stand for 1
h without stirring, at which point the melt had partially formed. The melt
was transferred to a fume cupboard and connected to a supply of
dinitrogen, and cooled to a reaction temperature of 0.degree. C. Methyl
oleate (3.56 g, 12.10 mmol, molar ratio of ionic liquid to methyl oleate
6:1) was added dropwise by pipette over a 10 minute period, and the whole
system kept under a constant stream of dinitrogen to prevent air/moisture
entering the reaction. The reaction was allowed to proceed for 1hr, at
which point the reaction mixture was quenched by the addition of water and
crushed ice (50 cm.sup.3). The resultant organic phase was then extracted
with 3.times.30 cm.sup.3 aliquots of dichloromethane. The combined organic
extracts were dried using MgSO.sub.4, filtered, and the solvent evaporated
using a rotary evaporator.
The various products were separated by flash chromatography on 100 g of
silica, using a gradient elution (500 ml of 2%, followed by 5%, followed
by 10% ethyl ethanoate in 40-60.degree. petroleum ether.) Following
separation the products were identified by a combination of .sup.1 H &
.sup.13 C NMR, GCMS and infra-red.
Selectivities for the various products obtained under these conditions are
presented in Table 1. This table also outlines the results of other
experiments performed in the same manner as outlined in this example but
using various ionic liquid:methyl oleate ratios, reaction times and
reaction temperatures.
Selectivity to branched/oligomeric fatty esters can be tailored to demand
by controlling either the reaction rate or the ratio of ionic liquid:fatty
acid reactant. Short reaction times and low temperatures favouring the
production of branched monomer and dimer moieties, long reaction
times/high temperatures favouring the production of trimer and higher
polymeric species. Similarly high dilution of the unsaturated fatty ester
feedstocks in the ionic liquid catalyst/solvent system favour the
production of branched and dimer moieties.
Analysis of the dimer fractions obtained from all these experiments, by
NMR, revealed the complete absence of cyclic or aromatic structures.
TABLE 1
Effective of ionic liquid: reactant mole ratio, reaction temperature
and reaction on time on product selectivity.
Mol rat. Temp/.degree. C. Reac. time mins % BM % LM % DIM % TRIM
% Poly % Crac
3:1 -40 10 26 1 38 19 <10 0
3:1 0 10 20 1 19 30 <20 5
1.1:1 -40 10 17 1 18 43 20 0
1.1:1 25 10 25 2 14 32 20 0
(BM = Branched monomer, LM = Linear monomer, DIM = Dimer, TRIM = trimer,
Poly = Polymer, Crac = Cracked products) * Note the oligomeric fractions
in this experiment were not separated.
The cracked products observed are sweet smelling volatile low molecular
fatty acid esters.
EXAMPLE 2
Effect of Reaction Temperature
Example 1 has been repeated using the same conditions, except that the
ionic liquid : fatty acid reactant ratio is now 6:1, and the reaction has
been performed at various temperatures (see table 2). All other conditions
remained the same.
TABLE 2
Effect of temperature at a ionic liquid: fatty
acid reactant ratio = 6:1
% Trimer &
Temperature/ higher % Cracked
.degree. C. % Monomer % Dimer polymers products
-40 13.5 .5 80.9 1.1
-10 17.4 3.2 54.6 24.7
0 18.3 6 49.3 26.4
8 21.1 5.3 50.3 23.3
25 20.5 15.7 43.8 19.9
50 16.1 9.6 34.6 39.7
60 14 11.4 33.5 41.1
120 11.9 5.8 32.3 50.0
EXAMPLE 3
Effect of Water Addition
In a dry box, 1-methyl-3-ethylimidazolium chloride (3.55 g, 24.20 mmol) was
added to a triply sublimed aluminium(III) chloride (6.45 g, 48.40 mmol) in
a 100 cm.sup.3 round bottomed flask, equipped with a dinitrogen inlet,
Teflon stirrer bar and a stopper. The two solids were left to stand for 1
h without stirring (to avoid excessive reaction rate and heat build up)
until the melt had partially formed. The melt was then stirred for 4 h at
which point the aluminium(III) chloride had reacted. The melt was then
transferred to a fume cupboard to and connected to a supply of dinitrogen.
A mixture of methyl oleate (3,50 g, 12.0 mmol, 50 mol %) and water (0.10
g, 0.1 ml) was added dropwise and stirred at room temperature for 1.5 h.
Water and crushed ice (50 cm.sup.3) was added and the product was
extracted with dichloromethane (3.times.30 cm.sup.3). The combined organic
extracts were dried (MgSO.sub.4), filtered and the solvent evaporated on a
rotary evaporator. This gave 3.10 g of a straw coloured oil.
The various products were separated by flash chromatography on 100 g of
silica, using a gradient elution (500 ml of 2%, followed by 5%, followed
by 10% ethyl ethanoate in 40-60.degree. petroleum ether.) Following
separation the products were identified by a combination of .sup.1 H &
.sup.13 C NMR, GCMS and infrared.
Selectivities for the various products obtained under these conditions are
listed below:
Cracked products*: 21%
Monomer + dimer: 38%
Trimer + polymer: 42%
*: the cracked products comprise mainly branched fatty acids having between
7 and 18 carbon atoms. NMR analysis of the dimer fractions reveals the
absence of cyclic or aromatic structures.
EXAMPLE 4
Alternative Extraction to Preserve 1-methyl-3-ethylimadazolium Chloride
In a dry box, 1-methyl-3-ethylimadazolium chloride (3.55 g, 24.20 mmol) was
added to doubly sublimed aluminium(III) chloride (6.45 g, 48.40 mmol) in a
100 cm.sup.3 round bottomed flask, equipped with a dinitrogen inlet,
Teflon stirrer bar and a stopper. The two solids were left to stand for
0.5 hour without stirring (to avoid excessive reaction rate and heat build
up) until the melt had partially formed. The melt was then stirred for 3
hours until all the aluminium(III) chloride had reacted. The melt was
transferred to a fume cupboard and connected to a supply of dinitrogen.
The reaction vessel was cooled to 0.degree. C. with an ice bath and methyl
oleate (3.0 g, 10.0 mmol, 30 w/w %) was added dropwise over a fifteen
minute period. After a further 5 mins, dichloromethane (25 cm.sup.3) was
added and the product extracted with hexane (3.times.33 cm.sup.3
aliquots). The solvent was evaporated from the combined organic extracts
to give 3.31 g of the aluminium adduct of the products. A further 0.84 g
of adduct was obtained by washing the melt with 3.times.33 cm.sup.3
aliquots of 50:50 dichloromethane/hexane, followed by evaporation of the
solvent. The adducts were destroyed by addition of water (50 ml),
extracted with dichloromethane (2.times.20 ml), dried (MgSO.sub.4),
filtered and the solvent evaporated on a rotary evaporator. This gave a
total of 2.37 g of colourless oil (79% of starting product--Remainder is
accounted for by volatile products produced as a consequence of cracking
reactions). The extracts were separated by Kugelrohr distillation at 2
mmHg pressure.
Cracked products*: 21%
Monomer: 14%
Dimer: 8%
Trimer + Polymer: 57%
*: the cracked products comprise mainly branched fatty acids having between
7 and 18 carbon atoms. Analysis of the dimer fraction by NMR indicates the
absence of cyclic or aromatic dimer structures.
EXAMPLE 5
Effect of Iron Based Ionic Liquid on Fatty Acid Oligomerisation
Preparation of 58% Iron(III) Chloride
In a dry-box, triply sublimed FeCl.sub.3 (8.96 g, 55.2.times.10.sup.-3 mol)
was added to 1-ethyl-3-methyl imidazolium chloride (5.86 g,
40.times.10.sup.-3 mol). The two solids were left stirring overnight.
Oligomerisation of Methyl Oleate in 58% FeCl.sub.3 -[emim]Cl
In a dry box, 58% FeCl.sub.3 -[emim]Cl (14.82, 40.times.10.sup.-3 mol) was
transferred to a 3-necked 200 ml round-bottomed flask equipped with a
dinitrogen inlet, Teflon stirrer bar and stoppers. The melt was
transferred to a fume cupboard and connected to a supply of dinitrogen.
Methyl oleate (3.0 g, 3.4 cm.sup.3, 10.times.10.sup.-3 mol) was added
dropwise over a 10 minute period. The reaction mixture was left stirring
overnight. A sample was then removed from the reaction mixture and
quenched with distilled water. The product was extracted with
dichloromethane, dried (MgSO.sub.4) and the solvent removed on a rotary
evaporator. The sample was analysed by proton NMR which indicated that the
reaction was complete. The NMR also showed that some chlorination had
occurred. Distilled water was added to the bulk mixture to quench the
combined organic extracts were dried (MgSO.sub.4), filtered and the
solvent removed on a rotary evaporator.
A sample of the crude product (0.71 g) was separated by fractional
distillation under vacuum (2.0 mmHg) on a Kugelrohr apparatus. This
produced the following yields:
Monomer 0.23 g (32.4%)
Dimer 0.06 9 (8.5%)
Trimer + polymer 0.28 g (39.4%)
Cracked products 0.14 g (19.7%)
Crude Product
.sup.1 H NMR (500 MHz/CDCl.sub.3 /TMS) (.delta./ppm) 0.85-0.89 (d+t, 4H),
1.28-1.29 (m, 28H), 1.61 (m, 2H), 2.28-2.33 (t, 2H), 3.66-3.67 (s, 3H),
3.87-3.89 (m, 0.3H).
.sup.13 C NMR (75 MHz/CDCl.sub.3 /TMS) (.delta./ppm) 14.548, 23.103,
25.397, 25.580, 26.920, 29.584, 29.674, 29.736, 30.057, 32.002, 32.334,
34.582, 38.959, 52.064, 64.787, 174.763.
Note that GCMS showed that there was a high proportion (estimated to be
50%) of the monomer which had been chlorinated. A breakdown of the
products detected by GCMS results is given below:
Retention time/s M.sup.+ Product
544-552 242 C.sub.14 Methyl ester
580-591 256 C.sub.15 Methyl ester
612-631 270 C.sub.16 Methyl ester
654-657 284 C.sub.17 Methyl ester
688-734 298 C.sub.18 Methyl ester
766-881 332 Chlorinated C.sub.18
Methyl ester
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