CA1178611A

CA1178611A - Method of processing cobalt-containing catalysts used in hydrocarboxylating

Info

Publication number: CA1178611A
Application number: CA000366538A
Authority: CA
Inventors: Peter Hofmann
Original assignee: Chemische Werke Huels AG
Current assignee: Huels AG; Evonik Operations GmbH
Priority date: 1979-12-12
Filing date: 1980-12-11
Publication date: 1984-11-27
Also published as: RO81104B; PL125154B1; ES8200236A1; RO81104A; DE2949878A1; JPS56133034A; AT382532B; JPS6315021B2; PL228360A1; ATA602380A; EP0032525A2; ES497618A0; EP0032525A3; EP0032525B1

Abstract

ABSTRACT
A method is disclosed of processing spent cobalt-containing catalysts for re-use in hydrocarboxylation reactions. The cobalt-containing residue from the reaction mixture is hydrated and the resulting metallic cobalt-containing product is treated with an acid to form a cobalt salt. This salt may, if necessary, be converted to a different salt soluble in the hydro-carboxylation reaction mixture, and is returned to the reaction mixture for re-use.

Description

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 ; ' 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.
.
2016 g of a mixture of 40 mole% of n-undecene, 40 mole% of n-dodecene, : ` :

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.

-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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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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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of processing a spent cobalt-containing catalyst used in the reaction of olefins with carbon monoxide 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 necessary, is converted into another cobalt salt.

2. A method according to claim 1, wherein the hydration is carried out in the presence of a solvent.

3. A method according to claim 1, wherein the metallic cobalt is dissolved at elevated temperature and with a flow of oxygen-containing gas passing through it, in an aqueous carboxylic acid containing from 1 to 4 carbon atoms.

4. A method according to claim 3, wherein the acid is aqueous acetic acid.