CA1178298A

CA1178298A - Method for extractive processing of cobalt-containing catalysts used in hydrocarboxylating

Info

Publication number: CA1178298A
Application number: CA000366535A
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: 1984-11-20
Also published as: JPS6315022B2; ATA602480A; EP0032524B1; EP0032524A3; DE2949939C2; AT382328B; PL125152B1; ES497619A0; DE2949939A1; JPS5697546A; ES8200637A1; RO80380A; PL228389A1; EP0032524A2

Abstract

ABSTRACT
A method is disclosed of processing spent cobalt-containing catalysts for re-use in hydrocarboxylation reactions. The reaction mixture obtained after reacting olefins with carbon monoxide and water or alkanol is oxidized and the cobalt-containing residue is treated with a C1 to C4 carboxylic acid and water. The resulting organic and aqueous phases are separated and the cobalt is recovered from the carboxylic acid/water phase in the form of the carboxylic acid salt. This salt is returned to the hydro-carboxylation reaction for re-use.

Description

1.~'7~

This invention relates to a method of processing cobalt-containing catalysts used in hydrocarboxylation react;ons.
It is known that fatty acids, and fatty acid derivatives, can be procluced by reacting olefins with carbon monoxide and an ll-acid component, for example water or alkanol, in the presence oE a catalyst containing a metal of group VIII of the periodic system of the elements and optionally a promotor IJ. FALBE, "Synthesen mit Kohlenmonoxid", Springer-Verlag, Berlin, Heidelberg, New York, 1967).
A specially preferred variant of this so-called hydrocarboxylating reaction involves carrying out the reaction in the presence of cobalt-contaill-ing catalysts. According to one particularly preferred embodiment, a promotor is also added, more particularly pyridine or a nonortho-substituted alkyl-pyridine.
One substantial problem associated Wit}l this homogeneously cataly~ed reaction is the recovery of the relatively costly cobalt from the reaction mixture in a form in which it may be re-used as a catalyst.
A method described in German AS 2159139 attempts to solve this pro-blem by carrying out the reaction of olefin and carbon monoxide in the pre-sence of an excess of alkanol and paraffin, or by adding paraffin after the reaction has been completed. This results in the formation of a two-phase mixture. The lower phase, consisting mainly of alkanol and promotor, contains at the most about 97% of the cobalt used as the catalyst. The upper paraf-finic phase consists mainly of unreacted olefin and reaction products.
The lower phase which contains still-active catalyst may be re-used in the reaction, but the advantage of this is more than out-weighed by a loss of about 3% of the cobalt used. A hydrocarboxylating process can, in effect, be regarded as economically satisfactory only if the cobalt contained in the ~7~

paraffinic stage is also recovered. In the view of the excess alkanol and the addition of paraffin required for the process, however~ it would be very costly.
Another method for recovering cobalt is described in United States Patent 3507891, and this is characterized in that the cobalt is recovered to--gether with the residue of the processing of the reaction mixture by distilla-tion.
In this connection, if the reaction mixture is subjected, prior to the distillation process, to an oxidizing treatment, with air for example, the catalyst is recovered in a form from which the active catalyst-species is re-built only ~mder hydrocarboxylating condit:ions. An oxid:iz:ing treatment of thereaction mixture can be dispensed with only if alkyl pyridines are used as promotors, since, in the presence of these promotors, heat-st.able complexes are formed under distillation conditions~ and these retain their act:iv:ity.
Although the method according to Uni-ted States Patent 3507891 does provide for largely complete recovery of the cobalt used, it fails, like the method according to German AS 2159139, to provide a means for separating high boiling point substances and other detrimental contaminants arising unavoid-ably as by-products of each hydrocarboxylating process.
It was ther~fore the purpose of the invention to develop a method, as simple as possible and largely loss-free, for processing the cobalt-contain-ing catalysts used in hydrocarboxylating, which also permits separation of high boiling point and detrimental contaminants.
This purpose is achieved in that the reaction mixture is distilled after an oxidizing treatment, the resulting cobalt-conta:ining distillation residue being treated with water and a carboxylic acid containing from l to 4 carbon atoms, the resulting phases being separated, and the cobalt being re-~ ~ 7~3~

covered from the carboxylic acid/water stage in the form of a carboxylic acid saltO
Thus, the invention provides a method for processing a spent cobalt-containing catalyst used in reacting olefins with carbon monoxide and water or alkanols, wherein the reaction mixture is oxidizecl and the cobalt-containing residue left from distilling the oxidized discharge from the hydrocarboxylation is treated with a carboxylic acid containing from 1 to 4 carbon atoms and water, the resulting organic and aqueous phases are separated, the cobalt being recovered from the carboxylic acid/water phase in the form of the corresponding carboxylic acid salt, and thereafter, if necessary, being converted into another carboxylic acid saltO
In principle, the method according to ehe invention may be used ~or all hydrocarboxylating reactions carricd out in the presence of a cobalt-containing catalyst (e,g, those according to United States Patent 3507891 and German Patent Application P 2912489~8)o In this connection, above all the choice of the olefin used is not critical, i.e. it is possible to use both straight chain or branched a-olefins and olefins with internal double bonds.
Olefins with more than one double bond, and those with substituents, e.g. aryl-, cyano-, carboxymethyl- and hydroxyl- groups are also suitable.
It is customary to use olefins having from 2 to 40, preferably from 4 to 20 carbon atoms, obtained by methods known to the state of the art. For example, ~-olefins may boe obtained by synthesis reaction of ethylene according to ZIEGLER or by wax-cracking, whilc olefins with internal double bonds may be obtained by dehydrating or chlorinating and subsequent dehydrochlorinating of paraffinsu In this last-mentioned process, it is customary to use paraffin fractions, i.e. mixtures of paraffins having different C-numbers, so that the olefins obtained also do not have uniform C-numbers. In addition to this all ~ 3 -3-conceivable isomeric forms are naturally included among the olefin mixtures.
In addition to pure, optionally substituted, olefins, it is also possible to use those containing parafflns. The paraffin content arises from the fact that complete reaction is not achieved in the production of ole~ins and the unreacted paraffins are not separated, or are not completely separated.
ln addition to the oleflns used, the H-acid~compound, which is reacted w1th the olefin and the carbon monoxide, is also non-critical. Both water and alkannls having from l to 20, preferably from l to 4, carbon atoms may be used.
Moreo~er, the cobalt compound used in hydrocarboxylation is also immaterial~ Cobalt carbonyls are just as suitable as carboxylic acid cobalt salts and cobalt salts with inorganic acids.
It i~ preferable to use carboxyllc acid cobalt salts, the anions~
of which occur in the ~orm o~the corresponding carboxylic acids or carboxylic ac~d esters during hydrocarboxylation.
f a so-oal~led promotor is used in addition to the cobalt compound, preferred promotors are pyridine, all non-ortho-substituted alk~l-pyridines, and N-methyl-pyrrolidone~
~ ianlly,~ the reaction conditions under which the hydrocarboxylation is carried out are im~ater~al to the mebhod according to the invention. ~enerally speaking, hydroxycarboxylat-ing processes are carried out at temperatures of from 80 to 300, preferably from 150 to~220C, with carbon monoxide pressures of from lO to 800, preferably from lOO to 300 bars.
~ owever, the oxldizing treatment of the reaction mlxture, ` -4-~,~

:`: ' ' .

prior to the recovery of the cobalt, with oxygen or an oxygen-containing gas, preferably air, at temperatures of from 20 to 150, preferably from 70 to 120C, is advantageous in the present method.
This treatment, which has already been described in lines 21 to 43, column 4 of United States Patent 3 507 891, and in paragraph 2 on page 5 of German Patent Application P 29 12 489.8, is continued until the cobalt compounds which, in the following processing by distillation lead to the separation of metallic cobalt, are decomposed by oxidation.
In the subsequent processing by distillation, the volatile components of the reaction mixture are separated either in a single step or stepwise, at sump temperatures not exceeding 350C. The cobalt-content of the resulting distillation residue should amount to from 2 to 30, preferably from Ll to 15%, by weight.
According to the invention, the cobalt-containing residue may be processed in whole or in part. If only partial processing is used, the proportion of cobalt-containing residue to be processed is go~erned by the level of catalytic activity desired for hydro-carboxylation, the amount of ballast substances, such as high boilers, acceptable, and the complexity and cost of the process.
For more ccn~enient handling, it may be desirable to dilute the cobalt-con-taining residue with one or more solvents.
~uitable solvents are such as do not, in the subsequent carboxylic acid/water treatment, prevent the formation of two separate phases~ for example paraffins, preferably those having from 5 to 10 carbon atoms, or aromatics, preferably benzene, toluene or xylene.

3~9~3 Carboxylic acids having from 1 to 4 carbon atoms are suitable for treating cobalt-containing residue~ optionally diluted with sol~ents. Preferred are acetic acid and/or propionic acid.
At least 2 moles of carboxylic acid per gram-atom of cobalt are needed. It is usual to operate with from 2 to 250, preferably from 2 to ]00 moles of carboxylic acid per gram-atom of cobalt.
As far as the method according to the invention is concerned, it is immaterial whether the water required for treatment and phase-separation is added together with, or after, the carboxylic ac-id.
The amt3unt of water added must be sufficient to ef~ect separation into an organic upper phase and a lower aqueous carboxylic acid phase containing the cobalt in dissolved form.
The amount of water is usually from 0.1 to 10 times the weight of the carboxylic acid.
The treatment o~ the cobalt-containing catalyst residue may be carried out in any suitable equipment, for example stirring-vessels, cascade stirring=vessels or counterflow extractors.
The treatment temperature, which is preferably in the range of 20 to 100C~ should, in general, not exceed the boiling point of the lowest boiling component of the two phase mixture.
Separation of the phases formed into a suitable apparatus, for example a separating funnel t3r settler, follows treatment with carboxylic acid and water, possibly after a certain waiting time.
This separate step can be omitted if adequate phase separation occurs during treatment, as for example in the counterflow extractor.

Both the treatment of the cobalt-containing catalyst residue with carboxylic acid and water, and the possibly necessary subsequent phase separation, may be repeated as often as necessary, and either continuously or intermittently, for the purpose of increasing cobalt recovery.
Water and excess carboxylic acid are then separated from the optionally united cobalt-containing phase, for example by distillation. The cobalt salt of the carboxylic acid is left.
Unless this cobalt salt of the carboxylic acid dissolves in the reactants used in hydrocarboxylation, and this solution can be returned without difficulty to the hydrocarboxylating process, it should be con~erted as a final step. This lnvolves reaction with a carboxylic acid, tne cobalt sa].-t of which is then soluble :Ln at least one of the reactants. For e~ample, cobalt acetate, which is insoluble in higher alkanols, olefins, and any promoters us-ed, may be converted, with the aid of 2-ethylhexanoic acid, for example, into so called cobalt octoate which is soluble in alkanols ha~ing a C nu~ber 2 2. The acetic acid released in the above reaction may be separated by distilling and returned to the process~

-6a-~., ~ ~' .~ ~.7~3~318 The organic phase, more or less free from cobalt, is either dis-carded or, if the economics of the process so require, is processed, for example by distillation. Any solvent added for the purpose of diluting the cobalt-containing residue may thereby be recovered, while the carboxylic acid arising at this stage may be re-used, for example at any suitable location in the method according to the invention.
As already indicated, the method according to the invention may be used successfully for all hydrocarboxylating processes in which use is made of a cobalt-containing catalyst.
The following Examples illustrate the method according to the inven-tion. All percentages are percentages by weight, unless otherwise indicated.
~xample 1 __ llydrocarboxylation In a 5-litre VA stirring autoclave, 1680 g of a static isomeric mix-ture of linear dodecenes with internal double bonding ~l-dodecene proportion <
1%~, 800 g of methanol, 167 g of a 10% Co-tridecanoate, and 279 g of ~-pico-line, are reacted at 180C with CO having an ll2 content of 2% by volume, at a hot pressure of 200 bars. After 3 h, the reaction is halted with an olefin yield of 87%.
Oxidizing treatment of the reaction product.
T1le entire reaction product amounting to 3126 g, is treated in a trickle-column (length: 1 m; inside diameter 2.5 cm), filled with Raschig rings at 80C in counterflow with 100 litres of air/h. The time of residence of the liquid phase entering from above is 15 min.
Catalyst processing.
Methanolg ~-picoline, unreacted dodecene and tridecanoic-acid methylester are separated from the so pretreated reaction-discharge by step-wise distillation. After the ester-fraction has been separated, there remains a residue of 19g g having a cobalt content of 8.43%.
The cobalt-containing residue is heated with a mixture of 400 g of acetic acid and 400 g of water for 1 h under reflux. lhe resulting phases are separated in a heatable separating fulmel at 90C. This produces an upper organic phase weighing 188 g. The lower aqueous acetic acid phase weighs 810 g and has a cobalt content of 2.04%. Thus 99.1% of the total cobalt used as the hydrocarboxylating catalyst is located in the aqueous acetic acid phase.
The upper organic phase is again mixed with 376 g of a mixture of equal parts by weight of acetic acid ancl water, is boiled for 15 minutes ullder reflux, the resulting phases being separatecl in a heatable separating funnel at 90 C. The upper organic phase thus obtained weighs 184 g. 'Ih~ lower aqueous acetic ac.id phase weighs 3gO g and has a cobalt content of 0.037~.
The two aqueous acetic acid phases obtained by extraction, and con-taining 99.95% of the cobalt used as the hydrocarboxylating catalyst are united and are concentrated in a rotary evaporator, in a water-jet vacuum, and at a bath temp~rature of 55CJ until dry. This produces 63.4 g of a violet crystalline solid having a cobalt content of 26.3%.
~ e-use of the recovered cobalt as a hydrocarboxylating catalyst.
. .. .. _ The hydrocarboxylation described at the beginning of Example 1 is repeated under the same conditions, except that the catalyst is now a mixture, dissolved in methanol, of 63.4 g of the violet crystalline solid and 33 mg of cobalt acetate (replacing the cobalt losses). The reaction, again halted after 3 h, produces the same results as the hydrocarboxylation described at the beginning of the Example.
Example 2 The hydrocarboxylation described in Example 1 is repeated, except ~ ~t7~

that 111.3 g of cobalt naphthenate, having a cobalt content of 15%, is used as the hydrocarboxylation catalyst.
The oxidizing treatment of the hydrocarboxylation reaction product is carried out under the same conditions as in Example 1.
The residual sump product of stepwise distillation of the reaction mixture, pretreated by oxidation, is 132.7 g of a residue contai:ning 12.6% of cobalt.
This residue is treated, as in Example 1, by extracting it twice The united aqueous acetic acid phases are concentrated to dryness as in Example 1 and produce 64.5 g of a violet crystalline solid ha~ing a coba]t content of 25.8%. This is the equivalent of a 99.7% cobalt reco~ery.
Example 3 Example 1 is repeated, except that only 30p of the cobalt-containing residue left fro~ distilling the oxidized discharge from the hydrocarboxylation is processed. The amounts of acetic acid and water used for the extraction treatment are reduced to match the lesser amount of residue. The end-product of the catalyst process~ing is 19~2 g of a violet crystalline solid contain-ing 26.1% of cobalt. This corresponds to a 99.9% cobalt recovery, ~n relation to the amount of cobalt-containing residue treated.
19.2 g of the violet crystalline solid, and 20 mg of cobalt acetate (to replace the cobalt losses), are dissolved in methanol and are used, in conjunction with the 70% of untreated cobalt residue, as the hydrocarboxylation catalyst. Conditions are as in the hydrocarboxylation described at the beginning of ~ _9_ ~7~ B

Example 1. After 3 h of reaction, the olefin yield is 86%.
Example 4 Example 1 is repeated, but the cobalt-containing residue remaining as the sump residue of the distillation process is mixed with 200 ml of n-hexane before being processed. In this case, the cobalt-reco~ery achievable is 99.97%.
Example 5 Example 1 is repeated, except that the acetic acid used ~or extraction is replaced by the same amount by weight of propionic acid.
The end-product of the catalyst processing is a violet paste which dissolves in alkanols such as methanol~ ethanol and y -p1:coline and contains 99.85% of the cobalt used as the hydro-carboxylation c~talyst.
Example 6 Example 1 is repeated, except that only 50% of the amount of water indicated in Example 1 is used ~or -the extractive catalyst processing. Achievable cobalt-recovery amounts to 99.85%.
Example 7 Example 1 is~ repeated, except that the 800 g of methanol used in the hydrocarboxylation is replaced by the same amount by weight of ethanol~
~ n order to be able to return to the reaction the violet crystalline solid left as the end-product of the catalyst processing, which product contains 99.9% of the cobalt used as the hydrocarboxylat~on catalyst, as a solution in one Or the rJ~

reactants used in the hydrocarboxylation, the said solid is converted into another carboxylic acid salt. To this end, 64.2 g of the violet crystalline solid, which is not sufficiently soluble in any of the reactants, is mixed with 150.3 g of 2-ethyl-hexanoic acid, and this is heated in a water-~et vacuum until no more acetic acid or water is distilled off.
~ fter replacement of the cobalt losses, the cobalt-octoate thus obtained is re-used as an ethanol solution as a catalyst for hydrocarboxylation, under the conditions described at the beginning of Example 7. There is no difference in the reaction results obtained with the two hydrocarboxylation ~ lOa-1~7~
approaches in Example 7.
Example 8 Example 1 is repeated, except that the dodecene is replaced by 1960 g of ~-tetradecene. The resulting cobalt-recovery amo~mts to 99.88%.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
l. A method for processing a spent cobalt-containing catalyst used in reacting olefins with carbon monoxide and water or alkanols, wherein the reaction mixture is oxidized and the cobalt-containing residue left from distilling the oxidized discharge from the hydrocarboxylation is treated with a carboxylic acid containing from 1 to 4 carbon atoms and water, the resulting organic and aqueous phases are separated, the cobalt being recovered from the carboxylic acid/water phase in the form of the corresponding carboxylic acid salt, and thereafter, if necessary, being converted into another carboxylic acid salt.
2. A method according to claim 1, wherein acid or propionic acid is used as the carboxylic acld.