Note: Descriptions are shown in the official language in which they were submitted.
1 1 ~2563
A.527(L)
PROCESS FOR THE SELECTIVE HYDROGENATION OF FATTY ACID
DERIVATIVES AND SELECTI~ELY HYDROGENATED FATTY ACID
DERIVATIVES
The present invention relates to a process for the
selective hydrogenation of unsaturated fatty acid
derivatives. In particular the present invention relates
to a process for the selective hydrogenation of fatty acid
derivatives containing, in addition to fatty acids having
two double bonds, fatty acids having more than two double
bonds.
An area of major commercial importance in which such
fatty acid derivatives occur is that of fats and oils which
consist mainly of a mixture of triglyceride esters of fatty
acids. The fatty acids usually contain about 16 to about
22 carbon atoms and may be saturated, e.g. stearic acid;
mono-unsaturated, e.g. oleic acid; di-unsaturated, e.g.
linoleic acid; or tri-unsaturated, e.g. linolenic acid or
may even be unsaturated to a greater degree.
In the field of technology relating to oils and fats
it is common to hydrogenate oils in order to remove at
least partly the unsaturation present so as to obtain
hydrogenated oil having the desired properties, such as a
higher melting point and/or increased stability.
During the hydrogenation a number of reactions take
place, both successively and simultaneously. For
N2E27N
~ 1 ~25~
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example, in the hydrogenation of an oil containing
linolenic acid, the hydrogenation reactions can be
represented by the following simplified scheme:
linolenic acid-~Kl linoleic acid _~K2 oleic acid
_~ K3 stearic acid~
the rate constants of the reactions being indicated by
Kl, K2, etc. In addition side reactions occur, such
as displacement and isomerisation of double bonds.
Isomerisation gives rise to the conversion of cis-double
bonds into trans-double bonds, the corresponding oils
containing the trans-acids usually having a higher melting
point. Oils and fats which have a high content of stearic
acid have a melting point that for most applications is too
high to be organoleptically acceptable. Formerly it was
therefore usual to direct the hydrogenation in such a way
that as little stearic acid was formed as possible, but
that a high content of trans-oleic acid was still obtained,
so that the oil had the desired melting point. Nowadays
it is considered less desirable to apply cis-trans
isomerisation since there is a preference for liquid,
though stable, oils, which can be used as such or can serve
as an ingredient for soft margarines which can be stored in
the refrigerator.
The selectivity values of the hydrogenation reactions
are usually defined as follows:
K2 Kl
I II
K3 K2
When the SI value of-the reaction is high, small
amounts of saturated acids are obtained. With a high
SII value it is possible to hydrogenate linolenic acid
~ 1 ~;2563
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and still retain a high percentage of the essential fatty
acid linoleic acid. An isomerisation-selectivity value,
abbreviated to Si, indicates the amount of trans-isomers
formed in relation to the degree of hydrogenation. As
has alrady been observed, it is now desirable that the
hydrogenation be influenced in such a way that the S
value is as low as possible.
The selection of catalysts with which to perform the
hydrogenation reaction can thus be important in order to
~O ensure as far as possible that the desired hydrogenation
reaction preferentially occurs and that only a minimum of
isomerisation takes place.
A catalytic process which aims to hydrogenate
selectively fatty acid derivatives containing more than two
double bonds with a minimum of isomerisation is disclosed
in European Patent Application No. 0 021 528. In
EP-A-0021528 the selective hydrogenation of triglyceride
oils such as soya bean oil, rapeseed oil, linseed oil and
fish oils is described in which fatty acids having ~ore
than two double bonds are reduced to fatty acids having two
double bonds in the presence of other fatty acids having
two double bonds, so-called essential fatty acids, whose
content in the oil remains high. In addition
isomerisation to the trans form of naturally occurring
fatty acids having cis-double bonds is relatively low, so
that stable liquid oils can be obtained which can be used
as such or can be used in margarines that remain soft at
refrigerator temperatures. A selectivity SII of at most
about 10 is claimed for the process described in
EP-A-0021528, which comprises hydrogenating at a
temperature of from -20C to 100C in the presence of a
catalyst comprising palladium, platinum, rhodium or iridium
which has been treated with dry ammonia in a molar ratio of
ammonia to catalytically active metal of at least 100:1.
It is stated that with increasing levels of ammonia
treatment the selectivity achieved in hydrogenation
1 J 62~63
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decreases and that when the mole ratios of ammonia to
catalytically active metal are higher than 2000:1 no
further increase in selectivity is achieved.
According to a first aspect of the present invention
there is provided a process for the selective
hydrogenation of unsaturated fatty acid derivatives having
fatty acid moieties containing more than two double bonds
- and fatty acid moieties containing two double bonds, the
process comprising catalytic hydrogenation at a temperature
of from -20C to 100C in the presence of ammonia and a
catalyst comprising at least one member selected from the
group consisting of palladium, platinum, iridium and
rhodium characteristed in that ammonia is present at a
level of at least 1.8 mol/l with respect to the said fatty
acid derivative.
It is to be understood that the present invention
extends to the fatty acid derivatives so hydrogenated and
to products incorporating the separated hydrogenated fatty
acid derivatives.
We have now discovered tha-t as the amount of ammonia
is increased above the maximum level described in
EP-A-0021528 the selectivity SII value continues to rise.
The actual SII value achieved in a particular case
depends on the fatty acid derivative, the catalyst and the
reaction conditions employed. Employing for example a
palladium catalyst we have found however that SII values
of above about 10 can usually be achieved. In some
instances even SII values of more than 14 have been found
at an ammonia concentration of 4 mol/l with respect to the
fatty acid derivative. The selectivity of platinum as a
catalyst i5 in general known to be less than that of
palladium. However by means of the present process the
SII value is nonetheless increased even when platinum is
employed. We have also found that the amount of ammonia
when calculated with respect to the amount of fatty acid
derivative present gives a better correlation with
I 1 6~563
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selectivity SII, than when measured with respect to the
amount of catalyst present.
The present invention can thus provide a process that
is easy to perform and that employs as a raw material dry
ammonia which is not only readily available and relatively
cheap, but which can also be removed readily from the
hydrogenated fatty acid derivative.
As in the process described in ~P A-0021528 the
present process can reduce the formation of trans-isomers
to a low level. Unlike the process described in
EP-A-0021528 however the present process can in addition
give further increases in SII values.
According to a second aspect of the present invention
there is provided a fatty acid derivative which has been
prepared by hydrogenation characterised in that the fatty
acid derivative has an SII value (as hereinbeEore
defined) of at least 10.
Preferably the fatty acid derivative has in addition a
trans isomerisation content of less than lO mol %. The
20 , actual amount will depend on the catalyst, the derivative
and the reaction conditions employed. For example where
the fatty acid derivative contains a high percentage of
fatty acid moieties having more than two double bonds such
as for instance in linseed oil the opportunity for
trans-isomerisation to occur is greater and greater
isomerisation may occur. Preferably however the fatty
acid derivative has a trans-isomerisation content of less
than 5 mol %. Moreover the fatty acid derivative
preferably has a SII value of at least 14 to l5~
In carrying out the present process the amount of
ammonia present is preferably at least 2.5 mol/1 with
respect to the fatty acid derivative employed. A
preferred upper limit for the ammonia concentration is 8
mol/l with respect to the fatty acid derivative employed.
More preferably not more than 4 mol/l is employed~
~ 1 6~3
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As catalytically active metals, of which Pd and Pt are
preferred, alloys of these metals can alternatively be
used. Such catalytically active metals can contain
so-called promotors, i.e. metals promoting the effect of
the catalyst as far as its activity and/or selectivity are
con~erned, such as Cu, Ag, Au, Zn, Sn, Zr, Hf, V, Nb, Ta,
Cr, Mo, ~ or Mn.
The catalyst can be used in the form of a porous
metal, preferably in the form of small particles suspended
in the system, such as palladium powder or a metal sol,
obtained by reduction of a soluble compound of the metal
with a reducing organo-metal compound. The metallic
constituent can alternatively be supplied on a carrier.
Suitable carriers for the catalyst include carbon, silicon
oxide, aluminium oxide, kieselguhr and an ion-exchanging
resin.
The amount of catalytically active metal which is
employed in the hydrogenation, is not critical and may vary
from about l mg/kg to about lO g/kg, preferably fro~ 35
mg/kg to lg/kg, calculated on the basis of the metal
catalyst with respect to the compound to be hydrogenated.
The optimum amount depends inter alia on the form of the
catalyst, whether the catalyst has been applied on a
carrier or not, on the unsupported surface area of the
catalyst, on the catalytic activity of the metal that is
used and on the amount of ammonia that is to be added.
Conversely the activity, selectivity and the formation
of trans-isomers that are effected in the hydrogenation
with the addition of a certain amount of ammonia will
~0 depend on the amount and the type of catalyst. In
addition the quality of the fatty acid derivative and any
prior treatment it may have had can influence the
hydrogenation characteristics of the various amounts of
- ammonia added.
~5 In carrying out a process embodying the present
invention, the compound to be hydrogenated can
I 1 6~8~
_ 7 _ A.S27(~)
be dissolved or dispersed in an organic liquid such as
hydrocarbon, for instance hexane, or a ketone. Good
results can alternatively be obtained with alcohols, but in
that case alcoholysis or in the case of oils and fats
interesterification may take place; consequently, when
alcoholysis or interesterification is desired, alcohols can
be used.
The ratio of organic liquid to fatty acid derivative
is not critical but is preferably not higher than about
20:l. The hydrogenation can alternatively be carried out
on the fatty acid derivative in the absence of an added
solvent or the like.
In general the hydrogenation can be carried out in any
suitable apparatus such as a reaction vessel with a
~5 stirrer, or when done continuously in a series of reaction
vessels with stirrers. Good results can also be obtained
when hydrogenation takes place over a column of catalyst
particles.
Preferably the process is performed so that the
catalyst is pre-treated with dry ammonia before
hydrogenation commences. If desired liquid ammonia can be
employed. Preferably however the hydrogenation is carried
out by suspending the catalyst in the fatty acid derivative
to be hydrogenated or a solution or suspension thereof and
subsequently introducing dry ammonia, optionally under
pressure, until the desired ammonia concentration has been
reached, after which the hydrogenation is started by
introducing hydrogen. If desired, the hydrogen supplied
can contain still more ammonia.
The temperature at which the hydrogenation is carried
out should not exceed 100C. Good results with active
catalysts can be obtained at temperatures from -20C.
Preferably hydrogenation is arranged to take place at a
temperature of from 10C to 60C.
The reaction can be carried out under atmospheric
Il 1 ~2S~
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pressure or at a higher pressure. Preferably the pressure
will vary from l00 to 2500 kPa. ~iaturally, if it is
desired to work at a temperature above the boiling point of
any liquid employed, a pressure above atmospheric pressure
should be applied.
The process can be controlled in a known manner, for
example by stopping the hydrogenation when a previously
calculated amount of hydrogen has been absorbed. Catalyst
and ammonia removal can be performed in a conventional
manner.
Examples of fatty acid derivatives that can be
hydrogenated by means of the present process include:
triglyceride fats and oils such as soya bean oil, rapeseed
oil, linseed oil, fish oils, tallow and similar animal
~5 fats, palm oil; fatty acid esters, such as the methyl-,
ethyl- and other alkyl esters; soaps; and alcohols.
The hydrogenated products can be used as frying oils,
table oils, as raw material for margarine or as raw
material for the preparation of stable products such as
soaps, esters, etc. Conventional techniques can be
employed for their preparation.
Embodiments of the present invention will now be
described by way of example only with reference to the
following worked Examples.
In some of the Examples the sum of the amount of
components is less than l00~, as less important fatty acid
components such as Cl4_, Cl7_, C20_ a 22
acids have not been mentioned. The composition of the
substrates before and after hydrogenation is given in mol.%.
Other percentages have been calculated by weight.
In the Tables the fatty acids have been indicated by
the number of carbon atoms present therein and the number
of double bonds, i.e. Cl8:3 means linolenic acid and
isomers, Cl8:2 linoleic acid and isomers, etc.
B 3
- 9 - A.527(L)
EXAMPLE 1
Hydrogenations were carried out in an autoclave with a
volume of 1 dm3 and provided with a heating coil, through
which thermostated water could be passed, a stirrer, an
inlet for gases, a device for taking samples and a
manometer.
In the autoclave soya bean oil was hydrogenated at a
temperature of 25C and under a pressure up to 1200 kPa,
the partial pressure of hydrogen of which amounted to 200
kPa. In each experiment the autoclave was charged with
100 mg of palladium per kg of oil of a 5% Pd/C (5% of
palladium on a carbon carrier) catalyst, 250 ml of soya
bean oil and 250 ml of hexane. The reactor was degassed
several times, flushed with argon and charged with
different amounts of ammoniacal gas tsee column I of Table
I). Thereafter the reactor was charge with hydrogen and
at intervals hydrogen was introduced to bring the pressure
to 1200 kPa. The course of the hydrogenation was
followed on the basis of the intake of hydrogen as
20 . indicated by the manometer. At certain intervals samples
were taken to determine the fatty acid composition and the
trans-isomer content as indicated in Table I.
~ 16~.~63
- - 10 - A. ~27(L)
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~ A.527~L)
EXA~5PLE 2
The procedure of Example 1 was repeated, durinq which
975 mmol of ammonia were added and the partial pressure of
hydrogen was increased to 1300 kPa.
The results are given in Table II.
1 ~62563
12 - A.527(L)
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0~:) ~ 1*~
V L~ Lr\
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- 13 - A.527(L)
EXAMPLE 3
Linseed oil was hydrogenated according to the
procedure described in Example I, but at a temperature of
25C and under a pressure of 1050 kPa. The autoclave was
charged with 200 mg palladium per kg of oil as a 5~ Pd/C
catalyst, 250 ml linseed oil and 250 ml hexane.
The added ammonia amounted 975 mmol.
The results are given in Table III.
TABLE III
HYDROGENATION FATTY ACID COMPOSITION (MOL%) TRANS S
TIME (MIN)_ C16:0 C18:0 C18:1 C18:2 C18:3 (MOL%)
Starting oil 6.0 4.6 13.5 14.8 53.8 ~1
420 6.0 4.3 30.4 54.6 2.0 24 13.1
The relatively high trans-isomerisation content arises
from the high C18:3 content in unhydrogenated linseed oil.
EXAMPLE 4
The procedure of Example I was repeated with the
exception that platinum was used as the catalyst. The
temperature employed was 35C and the pressure was 900 kPa.
The autoclave was charged with 150 mg platinum per kg of
oil as a 5% Pt/C catalyst and 500 ml soyabean oil. No
organic liquid was added.
The added ammonia amounted to 1050 mmol.
The results are given in Table IV.
TABLE IV
HYDROGENATION FATTY ACID COMPOSITION (MOL%) TRANS 5II
TIME ~MIN) C16:0 C18:0 C18:1 C18:2 C18:3 (mol~)
Starting oil 10.6 4.0 24.0 53.0 7.0 <1
144 10.6 5.4 34.3 45.8 2.0 2 5.1
5 ~ 3
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The relatively low SII value is due to the use of a
Pt cata lyst. The SII value obtained is however
substantially higher than tha~ obtained in a similar
experiment in which a lower amount of ammonia was employed.
As a comparative example, Example 7 from
EP-A-0021528 is reproduced below.
The hydrogenation of soyabean oil was carried out at
a pressure of up to 1000 ~Pa using platinum as a catalyst
at 20C in an autoclave of 0.3 dm volume, which was
provided with an inlet for gases, a manometer, a stirrer
and a sampling device.
The reactor was charged with 200 mg of a 5%
platinum-on-carbon catalyst, 25 ml soyabean oil and 75 ml
hexane. The autoclave was degassed two or three times,
flushed with nitrogen and charged with gaseous ammonia.
The reactor was subsequently charged with hydrogen.
The progress of the hydrogenation was followed on the basis
of the hydrogen uptake as indicated by the manometer. At
regular intervals samples were taken to determine the fatty
acid composition and the transisomer content. The
results are given in Table IVa.
TABLE IVa
-
gMOUl~ HYDRO- FATTY ACID COMPOSI~IO~ (MOI~%~
OE` G13~ATION (MOI~/o)
AMMO~IA TIME C16:0C18:0 C18:1 C18:2 C18:3
ADDl~D (M [~)
(MMOI,. ~
Starting
Oil 10.7 4.0 25.3 53.1 6.7 ~1
( 45 10.7 5.3 31.7 48.'14.1 ~1
( 90 10.6 6.1 37.9 43.1 2.2 C1
( 130 10.7 7.6 45.8 39.9 0.9 ~1
I ~ B~563
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EXAMPLE 5
-
Soya bean oil was hydrogenated to a C18:3 content of
1% to obtain an oil with good frying properties. The
hydrogenation was performed by a procedure similar to that
described in Example 1, but at a temperature of 35C and
under a pressure of 1050 kPa. An autoclave with a volume
of 2 dm was charged with 75 mg palladium per kg of oil
at a 5~ Pd/C catalyst and 1000 ml soya bean oil. No
organic liquid was added.
The added ammonia amounted to 1800 mmol.
The results are given in Table V.
TABLE V
HYDROGENATION FATTY ACID COMPOSITION (MOL%) TRANS S
TIME (MIN) C16:0 C18 0 C18:1 C18 2 C18:3 (MOL~)
-
Starting oil 10.6 4.0 24.0 53.0 7.0 <1
107 10.6 4.0 32.9 50.1 1.03 9 11.3
