Hydroformylation process

Details Hydroformylation process Hydroformylation process

1999-03-04

2001-12-18

Killos, Paul J. (Department: 1623)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S909000, C585S531000, C560S232000

Reexamination Certificate

active

06331656

ABSTRACT:

The present invention relates to a process for the hydroformylation of olefins having from 12 to 100 carbon atoms at pressures of from 100 to 400 bar and at from 100 to 200° C. using a cobalt catalyst and separation of the catalyst, with the extraction of the catalyst being carried out in the presence of an emulsion breaker and using a downstream coalescence stage.
The hydroformylation of olefins using a cobalt catalyst at from 100 to 200° C. and pressures of from 100 to 400 bar is a well-tried process in industry (Ullmanns Enzyklopädie der Technischen Chemie, Volume 7, Pages 120ff).
In such a process, the cobalt catalyst is generally used in the form of the acetate or formate or else in the form of soluble salts of higher carboxylic acids, eg. as cobalt ethylhexanoate. Preferably, cobalt formate or cobalt acetate is fed in as an aqueous solution in amounts of from 0.1 to 3 percent by weight, based on the olefin to be hydroformylated. Further details may be found in the monograph by J. Falbe, New Syntheses with Carbon Monoxide, Springer Verlag, 1970, 162-165.
For reasons of economics and to free the hydroformylation product of catalyst, the cobalt which is present in the form of cobalt carbonyl or cobalt hydridocarbonyl has to be separated off as completely as possible and returned to the synthesis stage.
This is usually achieved, according to DE-A 24 04 855, U.S. Pat. No. 2,404,855 by treating the oxo reaction mixture with molecular oxygen in the presence of aqueous acid. The cobalt is thus oxidized from the oxidation state −1 to +2 and can then be removed by extraction with the aqueous solution. The aqueous extract is separated off, for example, by decantation, in a phase-separation vessel or in other apparatuses suitable for this purpose.
Other methods (see Ullmanns Enzyklopädie der Technischen Chemie, Vol. 7, p. 123) employ the thermal decomposition of the cobalt carbonyls for separating them from the reaction mixture. For this purpose, the CO partial pressure is lowered by depressurizing the reaction product and superheating steam is introduced. The precipitated cobalt hydroxide, oxide or metal is then separated off mechanically or by dissolving in HNO
3
.
In another embodiment, the reaction product containing the cobalt hydridocarbonyl is scrubbed using an aqueous sodium carbonate solution which takes up the acid hydridocarbonyl. The catalyst can be set free again from the aqueous phase using, for example, sulfuric acid and can be recirculated.
It is also possible to combine various cobalt removal methods. Thus, DE-A 30 26 900 U.S. Pat. No. 3,932,523 proposes, in a first step, extracting the cobalt hydridocarbonyl from the organic phase in the form of the complex salt Co(CO(CO)
4
)
2
using an aqueous cobalt(II) salt solution and, in a second step, removing residues of the cobalt catalyst by treatment with air and acid.
The reaction product which has been freed of cobalt can then be processed further in a customary manner, eg. by distillation, hydrogenation or hydrogenative amination.
While short-chain olefins are now hydroformylated predominantly at relatively low pressures in the presence of rhodium catalysts, the hydroformylation of higher olefins having 12 and more carbon atoms using cobalt catalysts has retained its importance.
An application of the hydroformylation reaction using a cobalt catalyst which is of particular interest is, according to EP-A 244 616, the hydroformylation of polybutenes or polyisobutenes to give polybutyl- or polyisobutylaldehydes, alcohols or esters.
A subsequent hydrogenated amination of the oxo product gives polybutylamines or polyisobutylamines, which are valued components for the formulation of lubricants and fuel additives.
However, owing to the high viscosity and the surface-active properties of the oxo products of the polyisobutenes, an effective removal of the cobalt catalyst used can be achieved only with difficulty. Polyisobutene oxo products tend to form an intimate bond with the cobalt carbonyl from which the catalyst is extremely difficult to isolate. Although thermal cobalt removal would effectively destroy the carbonyls, separating off the cobalt hydroxide by, for example, filtration is hard to imagine because of the high viscosity.
Likewise, cobalt removal methods based on extraction of the cobalt hydridocarbonyl, either with oxidation of the cobalt from −1 to +2 or with retention of the oxidation state, have their limitations. Here, the tendency of the polyisobutene oxo products to form stable emulsions with aqueous phases is a noticeable disadvantage.
Since the hydroformylation reaction using a cobalt catalyst is carried out at elevated pressures of from 100 to 400 bar, it is necessary in all process variants to depressurize the crude product to pressures of customarily less than 50 bar for further work-up.
This often results, particularly in the case of a multiphase depressurization with an aqueous solution being introduced for the cobalt extraction, in strong shear fields which favor the formation of emulsions. The high energy input during dispersion causes the formation of very small droplets; a fine dispersion or emulsion is formed.
If water-in-oil emulsions are present owing to the phase ratio between aqueous and organic phases, these are additionally stabilized by the high viscosity ratio between aqueous and organic phases. Depending on the operative conditions, these emulsions of aqueous and organic phases can be stable for a number of days. As a result, the circulation of the aqueous phase is as impossible as the further processing of the hydroformylated polyisobutene.
However, to carry out the hydroformylation economically it is necessary to achieve complete separation and recirculation of the cobalt catalyst used after passage through the reaction stage, since this, on the one hand, lowers the costs for the process and on the other hand the further processing in the subsequent process stages is made significantly easier.
It is an object of the present invention to carry out the hydroformylation in such a way that the cobalt catalyst used can be virtually completely separated off and substantially circulated, and an oxo product suitable for further processing, ie. largely free of cobalt, is obtained.
We have found that this object is achieved by a process for the hydroformylation of olefins having from 12 to 100 carbon atoms in the presence of a cobalt carbonyl catalyst at pressures of from 100 to 400 bar and at from 100 to 200° C., depressurization and recovery of the cobalt catalyst by extraction with an aqueous acid solution in the presence of atmospheric oxygen, wherein
(a) the extraction is carried out in the presence of a polymeric emulsion breaker selected from the group consisting of alkoxylated compounds containing amino, imino or OH groups, and
(b) to achieve complete phase separation in the organic phase still containing small amounts of aqueous phase, the formation of relatively large droplets of the dispersed aqueous phase is effected in a coalescence stage, preferably with the aid of a packed column.
Suitable emulsion breakers are alkoxylated compounds as are customarily used in the petroleum industry for removing the salt-containing water. These are, for example, (a) oligo- and polyamines and -imines alkoxylated with propylene oxide and possibly ethylene oxide in addition and also (b) alkoxylated alkylphenol-formaldehyde resins and (c) ethylene oxide/propylene oxide block polymers and also (d) their polymeric acrylic esters as are described in DE-A 22 27 546 and DE-A 24 35 713 (a); DE-A 20 13 820 (b); DE-A 15 45 250 (c); and DE-A 43 26 772 (d).
Particular preference is given to using an emulsion breaker which is obtained by reacting polyethylenimine having a MW of from 10,000 to 50,000 with propylene oxide and optionally ethylene oxide in amounts such that the content of alkoxy units is from 90 to 99% by weight.
The amount of demulsifier which is added to achieve the desired effect is from about 0.1 to 100 g per metric t of the organic material used, preferably from 2 to 20 g

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