Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-07-18
2004-08-17
Cheung, William (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
active
06777503
ABSTRACT:
The present invention relates to a process for the hydroformylation of olefins having from 20 to 400 carbon atoms by reaction of the olefins with synthesis gas in the presence of a cobalt carbonyl catalyst.
Hydroformylation, also known as the oxo process, is a process which has been carried out on an industrial scale for decades. In this process, olefins are reacted with mixtures of carbon monoxide and hydrogen in the presence of carbonyl complexes of metals of transition group VIII of the Periodic Table, in particular those of cobalt or rhodium, to produce aldehydes which have one more carbon atom (cf. the monograph “New Syntheses with Carbon Monoxide”, J. Falbe (editor), Springer Verlag 1980.
At present, cobalt is used virtually exclusively as catalytically active metal for the hydroformylation of relatively long-chain olefins. The known process variants of the cobalt-catalyzed hydroformylation differ, in particular, in the way in which the catalyst which is homogeneously dissolved in the reaction mixture is separated from the reaction products. For economic reasons and to free the hydroformylation product of catalyst, this has to be separated off as completely as possible and returned to the synthesis step. An elegant way of separating of the catalyst is to make the homogeneously dissolved catalyst heterogeneous in a liquid phase which is immiscible with the hydroformylation product.
For this purpose, it is customary, as described in DE-A-2404855, to treat the reaction mixture with molecular oxygen in the presence of aqueous acid. The cobalt is 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.
In the hydroformylation of short-chain olefins, the residual amount of cobalt remaining in the organic phase is usually less than about 2 ppm. As the chain length of the aldehyde/alcohol mixtures produced increases, i.e. at a number of carbon atoms of more than 12, the surface-active properties of the reaction products increase. This results in the finely dispersed liquid-liquid-gas dispersion which is initially formed in the cobalt removal step being stabilized and the droplet-droplet coalescence or droplet-interface coalescence being inhibited.
Only after relatively long residence times does the emulsion break up substantially into the two liquid, each homogeneous phases.
DE-AS-1285997 and U.S. Pat. No. 3,488,184 describe the removal of cobalt(II) salts from the reaction products of the oxo process by means of cation exchangers. Disadvantages in long-term industrial use are the swelling behavior of many ion-exchange resins in the presence of the aldehyde-containing reaction product and the complicated regeneration of the ion-exchange resins.
A particularly interesting application of the hydroformylation reaction using a cobalt catalyst is, according to EP-A-244616, the hydroformylation of polybutenes or polyisobutenes to give polybutyl or polyisobutyl aldehydes, alcohols or esters.
Due to the high viscosity and the surface-active properties of the oxo products of poly(iso)butenes, effective removal of the cobalt catalyst used can be achieved only with difficulty. In the oxidative decomposition of the cobalt carbonyls present in the output from the reactor in the presence of an acidic aqueous solution, extremely stable water-in-oil emulsions are formed. Phase separation on the basis of the density difference requires very long residence times, as a result of which economical separation under the earth's gravity is not possible.
WO 98/12235 describes the combined use of polymeric emulsion breakers and coalescence-promoting apparatuses in order to accelerate the phase separation of reaction products from the hydroformylation of olefins having from 12 to 100 carbon atoms. While this procedure succeeds in reducing the residual cobalt content of the C
12
-C
18
-olefins in the hydroformylation products to below 1 ppm, a residual cobalt content of from 6 to 9 ppm remains in (iso)butene oligomers having 20 carbon atoms or more formed as oxo products. These residual amounts of cobalt can have an adverse effect in the further processing of the hydroformylation products. Both in the work-up by distillation and in chemical reactions in the presence of hydrogen, e.g. hydrogenation or hydrogenative amination, solid deposits of cobalt salts or metallic cobalt can form in the apparatuses, and these impair mass and/or heat transfer. The deposits have to be removed periodically by mechanical or chemical means, e.g. by dissolution in nitric acid. These necessary measures are inconvenient and adversely affect the economics of the further processing steps.
WO 98/12235 points out the possibility of separating the finely dispersed residual water from the organic phase by means of electrostatic coalescence apparatuses in place of mechanical coalescence apparatuses.
Such electrostatic coalescence apparatuses have already been used in petroleum recovery for separating off salt-containing water which originates from the oil reservoirs and is present in emulsified form in the crude oil, cf., for example, “Encyclopedia of Chemical Processing and Design”, Vol. 17, p. 223, New York 1983; and Chem.-Ing.-Techn. 62 (1990), No. 7, p. 525. In the first literature reference, it is stated on p. 224 that: “all [electric] desalinators require the addition of washing water, usually in the range from 4 to 8% by volume, based on the crude input.”
It has been found that when an attempt is made to use an electrostatic coalescence apparatus for separating the organic phase, which still contains, for example, up to 5% by weight of water, obtained after aqueous work-up of a reaction product from the hydroformylation of poly(iso)butenes and subsequent phase separation, short circuits and deposition of metallic cobalt are observed, which is a drawback. This phenomenon is presumably due to the high electrical conductivity of the aqueous phase owing to the presence of dissolved cobalt(II) salts and the tendency of the emulsified water droplets to form string-of-beads-type aggregates in the field direction and the comparative ease of reduction of the cobalt(II) salts to metallic cobalt. These problems appear to be inherent in the system, and an obvious solution was not able to be found.
It is an object of the present invention to purify reaction products from the cobalt-catalyzed hydroformylation of olefins having from 20 to 400 carbon atoms to residual cobalt contents of 2 ppm or less, in particular 1 ppm or less, and to provide an efficient process for this purpose which is reliable in long-term industrial operation.
We have found that this object is achieved by a process for the hydroformylation of olefins having from 20 to 400 carbon atoms by reaction of the olefins with synthesis gas in the presence of a cobalt carbonyl catalyst and recovery of the cobalt catalyst by extraction of the reaction product with an aqueous acidic solution in the presence of oxygen and separation of the organic and aqueous phases, wherein
(a) the aqueous phase is separated from the organic phase by means of gravitational forces to the extent that the proportion of aqueous phase dispersed in the organic phase is 2% by weight or less, based on the organic phase,
(b) the organic phase obtained in step (a) is exposed to an electric field to coalesce the remaining dispersed aqueous phase.
In the process of the present invention, it is critical that the content of dispersed aqueous phase is reduced to 2% by weight or less, preferably 1% by weight or less, in particular 0.5% by weight or less, before the organic phase is passed to an electrocoalescence apparatus. No water is added to the organic phase which has been freed of the major part of the aqueous phase in this way. This finding is surprising, since it is contrary to the express advice in the prior art (cf. “Encyclopedia of Chemical Processing and Design” above, Vol. 17), accor
Borchert Gerhard
Diehl Klaus
Grenacher Armin Volker
Sauer Friedrich
Schwahn Harald
BASF - Aktiengesellschaft
Cheung William
Keil & Weinkauf
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