Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention relates to a method of processing cobal-t-containing cat-
alysts used in hydrocarboxylation.
It is known that fatty acids and corresponding fatty acid derivatives
can be produced by reacting olefins with carbon monoxide and an H-acid component,
for example water or alkanol, in the presence of a catalys-t containing a metal
of group VIII of the periodic system of elements and, if necessary, a promotor
(J. FALBE, "Synthese mit Kohlenmonoxid", Springer-Verlag, Berlin, Heidelberg, New
York, 1967).
A specially preferred variant of this reaction, known as hydrocarboxyl-
ating, involves carrying out the reaction in the presence of catalysts containingcobalt. According to one preferred embodiment, a promotor is also added, in par-
ticular pyridine or a non-orthosubstituted alkyl-pyridine.
One important problem wi-th this homogeneously catalyzed reaction is the
matter of recovering relatively costly cobalt from the reaction mixture in a form
which will allow it to be re~used as a catalyst.
According to German AS 2159139, this problem may be solved by carrying
out the reaction between the olefin and carbon monoxide in the presence of an
excess of alkanol and paraffin, or by adding paraffin at the completion of the
reaction. In this way a two-phase mixture is produced. The lower phase, consis-
ting predominantly of alkanol and promotors, contains, at the most, abou-t 97% of
the cobalt used as the catalyst. The upper paraffinic phase consists mainly of
unreacted olefins and reaction products.
The lower phase containing the catalyst in still active form, may be
re-used in the reaction, but the advantage of this is outweighed by the loss of
about 3% of the cobalt used. Now a hydrocarboxylating process can be regarded
as economically satisfactory if the cobalt contained in the paraffinic stage is
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also recovered. In any case, the necessary excess of alkanol and the addition
of paraffin make this process complex and costly.
Another process for recovering cobalt is described in United States
Patent 3507891 and is characterized in that the cobalt is recovered together
with the sumpof the distillative processing of the reaction mixture.
In this case, if the reaction mixture is subjected to an oxidizing
treatment, for example with air, prior to the distillative process, then the
catalyst is recovered in a form from which the active catalyst-species rebuilds
itself only under hydrocarboxylating conditions. An oxidizing treatment of the
reaction mixture can be dispensed with only if alkyl-pyridines are used as
promotors, since, in the presence of these promotors, thermostable complexes
are formed under distillation conditions, which retain their activity.
Although the process according to United States Patent 3507891 permits
almost complete recovery of the cobalt used, like the process according to
German AS 2159139, it fails to provide any way of separating high boiling point
substances and other detrimental contaminants which inevitably arise as by-
products of any hydrocarboxylating process.
It was therefore the purpose of the present invention to develop the
simplest possible, and largely loss-free, process ~or treating the cobalt-
containing catalysts used in hydrocarboxylating, which, at the same time, will
permit the separation of high boiling point and unwanted contaminants. ';
This purpose is achieved in that the reaction mixture is hydratedafter an oxidizing treatment and in that the resulting metallic cobalt is
separated and returned to the process after treatment with an acid to form a
compound soluble in at least one of the reactants.
Accordingly, the invention provides a method of processing a spent
cobalt-containing catalyst used in the reaction of olefins with carbon monoxide
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and water or alkanols by an oxidizing treatment, which comprises hydrating the
cobalt-containing residue remaining after the processing by distillation of the
oxidized discharge from the hydrocarboxylation, separating the metallic cobalt
thus produced and reacting it with an acid to form a cobalt salt which, if neces-
sary, is converted into another cobalt salt.
The process according to the invention may be applied, in principle, to
all hydrocarboxylating reactions carried out in the presence of a catalyst con-
taining cobalt (e.g. the processes according to United States Patent 3507891 andGerman Patent Application P 2912489.8). Above all, the choice of the olefin usedis non-critical, i.e. it is possible to use straight-chain or branched -olefinsand olefins with internal double bonding. However, olefins with more than one
double bond, and those with substituents, for example aryl-, cyano-, carboxymet-hyl- and hydroxyl groups, are also suitable.
Use is generally made of olefins having from 2 to 40, preferably from 4
to 20, carbon atoms, which may be obtained by methods known in-the prior art. For
example, -olefins may be obtained by the synthesizing reaction of ethylene acc-ording to ZIEGLER or by wax-cracking, while olefins wi-th internal double bonding
may be obtained by dehydrating or chlorinating followed by the dehydrochlorinat-ing of paraffins.
In this latter process, paraffin fractions are generally used, i.e.
mixtures of paraffins of different C-numbers, so that the olefins obtained also
do not have uniform C-numbers. Furthermore, all conceivable isomeric forms app-
ear in these olefin mixtures.
In addition to pure, optionally substituted olefins, it is possible to
use those containing paraffins. The reaSQn for the paraffin content is that com-plete reaction is not achieved in olefin production and the unreacted paraffins
are not separated, or not fully separated.
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No-t only the olefin used but also the H-acid compound which is reacted
with the olefin and carbon monoxide, is non-critical for the method according to
the invention. It is possible to use either water or alkanols having from 1 to
20, preferabIy from 1 to 4, carbon atoms.
It is also immaterial which cobalt compound is used in hydrocarboxylat-
ing. Cobalt carbonyls are just as suitable as carboxylic acid cobalt salts or
cobalt salts with inorganic acids. It is preferable to use cobalt carboxylates,
the anions of which are produced, during hydrocarboxylating, in the form of corr-
esponding carboxylic acids or carboxylic acid esters.
If a so-called promotor is used in addition to the cobalt compound,
preference is given to pyridine, all non-orthosubstituted alkyl-pyridines, and N-
methyl pyrrolidone.
Finally, the reaction conditions under which the hydrocarboxylation is
carried out are not important to the method according to the invention. Hydro-
carboxylation processes are generally carried out at temperatures of from 80 to
300, preferably from 150 to 220C, and with carbon monoxide pressures of from 10
to 800, preferably from 100 to 300 bars.
However, what is critical for the method according to the invention is
the oxidizing treatment of the reaction mixture, prior to the recovery of the co-
balt. The oxidation preferably utilizes oxygen or an oxygen-containing gas, pre-
ferably air, at temperatures of from 20 to 150, preferably from 70 to 120C. This
treatment, already described in lines 21 to 43, of column 4 of United States Pat-
ent 3507891, and in paragraph 2 on page 5 of German Patent Application P 2912489-
.8, is continued until the cobalt compounds which lead, during -the subsequent
distillation treatment, to the separation of metallic cobalt, are decomposed by
oxidizing.
In the subsequent distillation treatment, the volatile componen-ts of
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the reaction mixture are separated either in one step or in stages, at sump temp-
eratures up to a maximum of 350C. The cobalt conten-t of the resulting distilla-
tion residue should be from 2 -to 30, preferably from 4 to 15% by weight.
According to the invention, the cobalt-containing residue may be proce-
ssed as a whole or in part. If partial processing is decided upon, the amount of
cobalt-containing residue to be processed is governed by the level of catalyst
activity sought in hydrocarboxylating, by the acceptable amount of ballast subst-
ances, for example high boiling point agents, and by the cost and complexity of
the process~
The procedure according to the invention is advantageously as follows.
The distillation residue to be processed is subjected to a hydrating treatment at
elevated temperature and pressure which, surprisingly enough, may be carried out
without the addition of any special hydration catalyst. The temperature used is
generally from 20 to 300, preferably from l~0 to 220C. The hydrogen pressure
req~ired for hydration is genarally from 50 to 500, preferably from 150 to 300,
bars.
Although the cobalt-containing residue may also be hydrated in the abs-
ence of any solvent, it is desirable to use one. Suitable solvents are, for ex~
ample: alkanols, preferably methanol, paraffins, preferably having from 5 to 8
~0 carbon atoms, e.g. C5- fraction, hexane or cyclohexane, or carboxylic acids, pre-
ferably acetic or propionic acid. The amount of solvent used may advantageously
be from 0.1 to 10 times the weight of the distillation residue.
After hydrating for up to 10 hours, preferably up to 5 hours, the res-
ulting reaction mixture is broken down, for example, by filtering, into a residue
of metallic cobalt and an organic phase. It is desirable, in this connection, to
operate under an atmosphere of inert gas, e.g. nitrogen or argon, since the cob-
alt may arise in a very finely-divided, and therefore pyrophoric, form.
The organic phase resulting from the separation may be processed by
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distillation. At this time~ any solvent used during hydration may be recoveredJ
and the remaining products may be passed on for appropriate exploitation.
Since it is usually impossible to return the metallic cobalt as such
to a hydrocarboxylating process, it must be converted into a salt by treatment
with an inorganic acid or a carboxylic acid. Conversion of the metallic cobalt
with Cl- to C4- carboxylic acids, preferably acetic and/or propionic acids, has
been found particularly advantageous. In order to shorten the time required
for metallic cobalt to dissolve in organic acids, it is usual to operate at
an elevated temperature, e.g. under reflux, with simultaneous passage of an
oxygen-containing gas, e.g. air, and in the presence of water.
If the resulting cobalt salt is insoluble, or not sufficiently soluble
in the reactants used in the hydrocarboxylating process, a transformation is
required as the final step. This consists of a reaction with a carboxylic acid,
the cobalt salt of which is then soluble in at least one of the reactants. For
example, cobalt acetate, which is insoluble in the higher alkanols, in olefins,
and in the promotors used, if any, may be converted, with the aid of 2-ethyl-
hexane acid, into so-called cobalt octoate which is soluble in alkanols having
a C-number > 2. The acetic acid released during the above reaction may be
separated by distillation and returned to the process.
As already indicated, the method according to the invention may be
used successfully for all hydrocarboxylating processes in which a cobalt-
containing catalyst is used.
The following Examples illustrate the method according to the inven-
tion. Unless otherwise,indicated all percentages are p~rcentages by weight.
Example 1.
Hydrocarboxylation.
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2016 g of a mixture of 40 mole% of n-undecene, 40 mole% of n-dodecene,
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20 mole% of n-tridecene (olefins are present as a statistical isomer-mixture with
less than 1% of ~-olefin), 800 g of methanol, 167 g of a mixture of dodecanoic~,
tridecanoic- and tetradecanoic-acid cobalt (cobalt con-tent 10%), and 279 g Of r-
picoline, are reacted at 180C with CO having an H2 content of 2~ by volume, in a
5-litre ~7A-agitator au-toclave, at a hot pressure of 200 bars. AEter -three hours,
the reaction is interrupted with an olefin reaction of 83%.
Oxidizing treatment of the reaction product.
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The entire reaction product, amounting to 3495 g, is treated in a tric-
kle-column (length: 1 m; inside diameter: 2.5 cm) filled with Raschig rings, at
80C in counterflow with 100 litres of air/h~ The residence time in the trickle-
column of the liquid phase entering at the top is 15 minutes.
Catalyst processing.
The following are separated from the pre-treated reac-tion product by
stepwise distillation: methanol, y-picoline, unreacted olefin, and a mixture of
dodecanoic-, tridecanoic- and tetradecanoic-acid methyl ester. After the ester
fraction has been separated, there remains 205 g of a residue with a cobalt cont-
ent of 8.15%.
This cobalt-containing residue is taken up in 410 g of n-hexane and is
hydrated in a 2-litre VA-agitator autoclave for 5 h at 180C and at an H2 hot
~0 pressure of 300 bars. The discharge from the autoclave is filtered under an N2
protective gas atmosphere, and the filter cake is washed three times with a total
of 100 ml of n-hexane. The greyish-black, powdered filter cake weighs 19.72 g
and has a cobalt content of 83.5%. Thus 98.6% of the cobalt used as the hydro-
carboxylating catalyst is located in the filter cake.
The hexane is recovered from the filtrate by distillation. The cobalt-
containing filter cake is boiled under reflux for 2 hours in a mixture of 100 g
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of acetic acid and 100 g of water. 30 litres of air/h are passed through the
boiling mixture. The violet solution thus obtained is concentra-ted until dry in
a rotary evaporator, with a water-jet vacuum and a bath tempera-ture of 55C.
This produces 64.1 g of a violet, crystalline solid having a cobalt content of
25.7%.
Re-use of the recovered cobalt as
a hydrocarboxylating catalyst.
The hydrocarboxylating process described at the beginning of Example 1
is repeated under the same conditions, except that the catalyst used is a mixt-
ure r dissolved in methanol, of 64.1 g of the viole-t, crystalline solid and 920 mg
of cobalt acetate (to replace the loss of cobalt). The reaction, again interrup-
ted after three hours, produces the same result as the hydrocarboxylation descri-
bed at the beginning.
Example 2.
The hydrocarboxylation described in Example 1 is repeated, except that
111.3 g of cobalt naphthenate having a cobaIt content of 15% are used as the
hydrocarboxylating catalyst.
The oxidizing treatment of the reaction product of hydrocarboxylation
is carried out under the same conditions as in Example 1.
The residual product of stepwise distillation of the reaction mixture
pretreated by oxidizing comprises 137.5 g of residue containing 12.13% of cobalt.
This residue is hydrated under the same conditions as in Example 1.
The cobalt-containing filter cake obtained by filtration is dissolved as in Exam-
ple 1. After being concentrated to dryness, the solution thus obtained delivers
65.1 g of a violet, crystalline solid having a cobalt content of 25.4%. This
corresponds to a cobalt recovery of 99.0%.
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Example 3.
Example 1 is repeated, except that only 20% of the cobalt-containing
residue remaining after the processing by distillation of the oxidized dis-
charge from the hydrocarboxylation is processed, and the amount of n-hexane
used as a solvent in hydration is reduced accordingly. ~he end-product of this
treatment is 12.9 g of a violet, crystalline solid containing 25.6% of cobalt.
This corresponds to a cobalt recovery of 98.8% of the amount of cobalt-contain-
ing residue processed.
The said violet, crystalline solid, and 160 mg of cobalt acetate
~to replace the loss of cobalt), are dissolved in methanol and are used, together
with the 80% of unprocessed catalyst residue, as the hydrocarboxylation catalyst,
under the hydrocarboxylating conditions described at the beginning of Example
1. After a three hour reaction, the olefin reaction amounts to 83%.
Example 4.
Example 1 is repeated, except that the hydration and catalyst
processing are carried out at 160C and 200 bars of H2 hot pressure. The cobalt
thus recovered amounts to 98.5%
Example 5.
Example 1 is repeated, except that the n-hexane used as solvent for
~0 the hydration and catalyst processing is replaced by the same amount by weight
of methanol. The cobalt thus recovered amounts to 99.0%.
Example 6.
Example 5 is repeated, except that only half the amount by weight of
methanol is used as the solvent for the hydration and catalyst processing. The
cobalt thus recovered amounts to 98.7%.
Example 7.
Example 1 is repeated, except that the 800 g of methanol used in the
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hydrocarboxylation is replaced by the same amount by weight of ethanol.
The violet, crystalline solid which remains as the end-product of the
catalyst processing contains 98.4% of the cobalt used as the hydrocarboxylating
catalyst. In order to return this to the reaction as a solution in one of the `~
reactants used in the hydrocarboxylating process, it is converted into another
carboxylic acid salts as follows.
66.2 g of the violet, crystalline solid$ which is not sufficiently
soluble in any of the reactants, are mixed with 147.3 g of a mixture-produced
by hydrocarboxylation according to Example 1 - of dodecanoic-, tridecanoic- and
ln tetradecanoic-acids, and is heated in a water-jet vacuum until no further acetic
acid or water are distilled off. The fatty acid cobalt salt thus obtained is
used again, after replacement of the cobalt lost, in the form of an ethanol-
solution, as the hydrocarboxylation catalyst, under the same hydrocarboxylating
conditions as described at the beginning of Example 7. The results of reacting
the two hydrocarboxylating batches of Example 7 are identical.
Example 8.
Example 7 is repeated, except that the cobalt-containing filter cake
obtained by filtration is processed by replacing the acetic acid with the same
amount by weight of propionic acid.
The end-product of the catalyst processing is a violet, pasty product
which dissolves in ethanol and contains 98.5% of the cobalt used as the
hydrocarboxylating catalyst.
Example 9.
Example 1 is repeated, except that 1400 g of ~-decene are used instead
of the mixture of olefins with internal double bonding. The cobalt thus
recovered amounts to 98.9%.
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