Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2000-11-15
2002-02-12
Owens, Amelia (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S214000, C549S323000, C549S324000
Reexamination Certificate
active
06346629
ABSTRACT:
The present invention relates to a process for producing butyrolactones by carbonylating alkynes with carbon monoxide in the presence of water over a rhodium catalyst and precipitating the rhodium catalyst by immediate hydrogenation of the carbonylation reaction mixture, removing and recycling the catalyst and recovering the butyrolactone from the filtrate.
WO 97/07111 discloses reacting alkynes with carbon monoxide and water in the presence of transition metal catalysts, especially rhodium, to obtain butyrolactones. As stated by Takaski Joh et. al. in Inorganica Chi. Acta, 220 (1994) 45, 2(5H)-furanones are formed as intermediates. The 2(5H)-furanones can be converted into butyrolactones by hydrogenation in situ or separately. Complete hydrogenation to butyrolactones is obtained by forcing the carbonylation reaction in the presence of water, which may give rise to hydrogen as a result of the water gas equilibrium, by adding hydrogen during the carbonylation, or by subsequent hydrogenation of the isolated 2(5H)-furanones.
However, the butyrolactone production process of WO 97/07111 has proved unsatisfactory with regard to catalyst removal and reuse. True, after the synthesis effluent has been worked up, i.e., the butyrolactones have been recovered by distillation, the dissolved catalyst remaining behind in the distillation residue can be reused. But this has the disadvantage that, on the one hand, the catalyst cannot be separated from the distillation residue and therefore there will be a buildup of high boilers in the course of repeated recycling, and, on the other, the repeatedly reused catalyst provides distinctly reduced selectivity and activity with regard to the desired conversion into butyrolactones.
There is therefore a need for a simple process for isolating ideally all the rhodium carbonylation catalyst without loss of activity for recycling into the reaction.
Numerous processes have been described for removing rhodium in the field of hydroformylation. In U.S. Pat. No. 4,400,547 the crude oxo product is contacted after the reaction with a ligandizing compound such as triphenylphosphine and the aldehyde is distilled off as product. The distillation residue is then treated with oxygen to deligandize the catalyst and recover the rhodium in an active form. However, this does not provide a way of separating rhodium and distillation residue.
The removal of rhodium from high boiling hydroformylation residues is also described in U.S. Pat. No. 3,547,964. The residues are treated with hydrogen peroxide in the presence of acids such as formic acid, nitric acid or sulfuric acid to convert the rhodium into a water-soluble form. However, the cost of hydrogen peroxide and its problematical handling put limits on the use of this technique in industry.
EP-A 584 720 B1 discloses an optionally two-stage extraction process wherein rhodium is recovered in the form of a complex from the distillation residues of products of the oxo process. In the first stage, the residues are treated with oxygen or an oxygen-containing gas in the presence of a monocarboxylic acid and of the alkali metal salt of the monocarboxylic acid. The residue is then extracted with water, and the rhodium, which is present as a water-soluble compound, passes into the aqueous phase. This process is not practicable in the present case, since the rhodium complex has proven to be difficult to extract quantitatively from the butyrolactone synthesis reactor effluent.
Other processes, for example as described in DE-A 43 26 076, concern the recovery of rhodium by ashing, i.e., burning, the organic constituents. The rhodium thus recovered cannot be reused immediately, but requires a further workup.
It is an object of the present invention to provide a simple and economical process for isolating ideally all the rhodium carbonylation catalyst without loss of activity for recycling into the reaction.
We have found that this object is achieved, surprisingly, by a process for producing butyrolactones of the general formula I
where R
1
and R
2
are each hydrogen, alkyl, hydroxyalkyl, substituted or unsubstituted aryl or substituted or unsubstituted trialkylsilyl, by reacting alkynes of the general formula II
R
1
—C≡C—R
2
II,
where R
1
and R
2
are each as defined above, with preferably not less than 4 equivalents of carbon monoxide and preferably not less than 2 equivalents of water in the presence of a rhodium catalyst under pressures from 20 to 300 bar and hydrogenating the unhydrogenated 2(5H)-furanone intermediates, which comprises
a) reacting the carbonylation reaction mixture immediately (i.e., without removal of the 2(5H)-furanone target product or of a mixture thereof with butyrolactone) with hydrogen at from 150 to 250° C.; preferably from 180 to 230° C., and from 100 to 300 bar, preferably from 150 to 200 bar,
b) removing the precipitated catalyst and returning it into the carbonylation reaction, and
c) subjecting the catalyst-free reaction mixture to a distillation to recover the butyrolactone.
Surprisingly, more than 99% of the catalyst used is recovered and even frequent repetition of the operation or a prolonged continuous run does not harm the selectivity and activity of the catalyst.
True, WO 97/07111 states in paragraph 5 on page 7 that it can be sensible to produce only mixtures comprising predominantly butyrolactone. These mixtures can then be fed “directly” into the hydrogenation or be separated into their individual components, butyrolactone and furanone. However, there is no teaching in the cited reference that hydrogenating the reaction mixture while it still contains the catalyst will under certain conditions precipitate the catalyst, which may then be removed and returned into the reaction. On the contrary, the only relevant example (8) utilizes a specific hydrogenation catalyst, in fact a palladium catalyst, to hydrogenate the 2(5H)-furanone at atmospheric pressure and room temperature only after it has been freed from catalyst.
For stage (a) of the process of the invention, the carbonylation reaction mixture is subjected to a hydrogenation with hydrogen at pressures from 20 to 300 bar, preferably from 150 to 250 bar, especially from 180 to 220 bar, immediately after the residual CO pressure has been released, without prior removal of the 2(5H)-furanone intermediates formed or of the butyrolactones already formed. The hydrogenation converts the rhodium carbonyl catalyst into an insoluble form (it is believed through removal of some of the carbonyl groups and, it is believed, through formation of a rhodium cluster) and the 2(5H)-furanones to the corresponding butyrolactones. The reaction temperature for the hydrogenation is generally within the range from 0 to 300° C., preferably within the range from 50 to 150° C., while the reaction time for the hydrogenation is generally within the range from 0.1 to 24 h, preferably within the range from 0.5 to 5 hours.
The reaction gives rise to a solid material which contains the catalyst and which can be removed by common methods such as, for example, filtration, centrifugation or sedimenting. At the same time, any 2(5H)-furanone present is completely and very selectively hydrogenated to the butyrolactone. The precipitated catalyst can be used for renewed butyrolactone syntheses without significant loss of activity or selectivity. The sequence of carbonylation/catalyst precipitation/catalyst removal/ carbonylation can be repeated more than once. The precipitation of the catalyst is virtually quantitative each time; the reactor effluent contains less than 1% of the initial rhodium in homogeneous solution.
The process of the invention is useful for all catalysts suitable for the butyrolactone synthesis described. Preference is given to the catalysts Rh
6
(CO)
16
, Rh
4
(CO)
12
, Rh(CO)
2
acac, [codRhCl]
2
, RhCl
3
*3H
2
O and Rh(OAc)
3
.
The amount of catalyst used is generally within the range from 0.01 to 10 mmol per mole of alkyne. The precipitated, removed and recycled catalysts are present as compounds of unknown structure; however,
Brunner Melanie
Henkelmann Jochem
Rahn Ralf-Thomas
Rheude Udo
BASF - Aktiengesellschaft
Keil & Weinkauf
Owens Amelia
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