Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-05-16
2002-01-15
Padmanabhan, S (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S017000, C568S451000, C536S004100, C536S018500, C556S016000, C556S021000, C556S136000
Reexamination Certificate
active
06339174
ABSTRACT:
The present invention relates to a catalyst and to its use for the hydroformylation of olefinically unsaturated compounds having from 9 to 18 carbon atoms using hydrogen and carbon monoxide at superatmospheric pressure.
It is known that metals of group VIII of the Periodic Table of the Elements can be used for catalyzing addition reactions onto olefinically unsaturated compounds. The catalyst is frequently used as a solid which is insoluble in the reaction medium (heterogeneous catalysis).
One catalytic addition reaction of the olefins which is important from the point of view of industrial utility is hydroformylation. Here, aldehydes and alcohols are prepared by reaction of olefins with carbon monoxide and hydrogen, with the aldehydes and alcohols containing one more carbon atom than the starting olefin. The catalyst used is customarily used in a homogeneous phase with the olefin. The reaction is preferably catalyzed by hydridometal carbonyls of metals of group VIII of the Periodic Table. Apart from cobalt, which is widely used industrially as catalyst metal, rhodium has achieved increasing importance for, preferably, the hydroformylation of lower olefins. In contrast to cobalt, rhodium allows the reaction to be carried out at low pressure, and, in addition, straight-chain n-aldehydes are preferentially formed when using terminal olefins and iso-aldehydes are formed only in subordinate amounts. Furthermore, the hydrogenation of the olefinic compounds to form saturated hydrocarbons occurs to a significantly lesser extent in the presence of rhodium catalysts than when cobalt catalysts are employed.
In the processes introduced in the industry, the rhodium catalyst is used in the form of modified hydridorhodium carbonyls which contain additional ligands which may be used in excess. Ligands which have been found to be particularly useful are tertiary phosphines or phosphites. Their use makes it possible to reduce the reaction pressure to values below 30 MPa. However, the separation of the reaction products and the recovery of the catalysts dissolved homogeneously in the reaction product present problems in this process. In general, the reaction product is distilled from the reaction mixture. However, owing to the thermal sensitivity of the aldehydes and alcohols formed, this route can be employed in practice only in the hydroformylation of short-chain olefins. Here and in the following, the term “short-chain olefins” refers to olefins having not more than 8 carbon atoms in the molecule. The hydroformylation of long-chain olefins or olefinic compounds having functional groups forms products which have a high boiling point and cannot be separated by distillation from the homogeneously dissolved rhodium catalyst complex. The thermal stress on the material being distilled leads to thick oil formation and thus to considerable losses of desired products and of catalyst by decomposition of the rhodium complexes. Here and in the following, the term “long-chain olefins” refers to olefins having more than 8 carbon atoms in the molecule.
The problem of thermal decomposition is avoided if two-phase catalysis is used. Here, there are two liquid, mutually immisible phases of which one, namely the organic phase, comprises the olefin and the other, usually polar phase, comprises the catalyst. Solubility of the catalyst in the polar phase is a prerequisite for use of this process. On an industrial scale, an aqueous phase is used as polar phase and a rhodium complex is used as catalyst. The solubility of the catalyst in the aqueous phase is achieved here by use of sulfonated triarylphosphines as constituents of the complex. In this process variant, the catalyst is separated from the reaction product after the hydroformylation reaction is complete simply by separation of aqueous and organic phases, i.e. without distillation and thus without additional thermal process steps. Such a process is described, for example, in DE-C 26 27 354. A particular feature of this procedure is that n-aldehydes are formed with high selectivity from terminal olefins and only subordinate amounts of iso-aldehydes (i.e. aldehydes branched in the &agr; position relative to the aldehyde group) are formed. Besides sulfonated triarylphosphines, carboxylated triarylphosphines are also used as constituents of water-soluble rhodium complexes.
The use of water-soluble catalysts has also proven useful in the hydroformylation of lower olefins, in particular propene and butene. However, if higher olefins such as pentene or hexene are used, the reaction rate decreases noticeably. The economics of the reaction on an industrial scale are frequently no longer satisfactory when using olefins having more than four carbon atoms. In order to increase the conversion and/or the selectivity of the reaction to n-aldehydes in the hydroformylation of higher olefins by means of water-soluble catalysts, specific amphiphilic reagents or solubilizers have also been used. The addition of these materials leads to an improvement in mass transfer between the individual phases and thus the miscibility of aqueous catalyst phase and organic phase.
Thus, DE 31 35 127 A1 describes the hydroformylation of olefins using amphiphilic reagents. Table 7 shows that the hydroformylation of 1-dodecane by means of rhodium and monosulfonated triphenylphosphine (3-Ph
2
PC
6
H
4
SO
3
Na) without addition of an amphiphilic reagent leads to a conversion of 56% (Example 77), while the addition of a specific, long-chain alkyl ethoxylate of the formula C
12
H
25
(OCH
2
CH
2
)
23
OH (marketed by ICI Chemicals under the trade name Brij 35®) leads to a reduction in the conversion to 37% (Example 78).
DE 34 12 335 likewise relates to the hydroformylation of olefins using quaternary ammonium salts. As can be seen from Table 4, the hydroformylation of hexene by means of rhodium and trisodium tri(m-sulfophenyl)phosphine without addition of a solubilizer leads to a conversion of 36% (Example 10), while an addition of 2.5% of triethylene glycol (Example 14) or of 5% of polyglycol 200 (Example 11) gives a conversion of only 43.5% and 43%, respectively. In contrast, a very high conversion, namely 86%, is achieved by addition of 2.5% of trimethylhexadecylammonium bromide as solubilizer. This document shows that only the addition of quaternary ammonium salts results in an appreciable increase in the conversion. On the other hand, neither the addition of triglycols or polyglycols nor a doubling of the amount of these materials (from 2.5 to 5%) results in a significant increase in the conversion.
A disadvantage of the use of quaternary ammonium salts as amphiphilic reagents is, however, their poor biodegradability. Thus, for example, the presence of quaternary ammonium salts in wastewater leads to considerable difficulties in wastewater treatment. A further disadvantage of the use of amphiphilic reagents and solubilizers is that the increase in the miscibility of aqueous catalyst phase and organic phase achieved using these compounds is accompanied by an increased solubility of the organic phase in the aqueous phase and of the aqueous phase in the organic phase. In this way, amphiphilic reagent and solubilizer as well as rhodium and water-soluble phosphine can to an increasing extent get into the organic phase and be discharged with the organic phase after phase separation. The discharge of these substances via the organic phase is naturally undesirable, since corresponding amounts of new substances have to be added to the aqueous phase, which, particularly in respect of rhodium, is associated with considerably increased costs.
Furthermore, if relatively large amounts of amphiphilic reagents or solubilizers are added, i.e. the aqueous catalyst phase and the organic phase become increasingly miscible, the demixing required for phase separation no longer takes place or does not take place to an unsatisfactory extent as a result of the formation of emulsions or solutions. This occurs particularly in the case of those amphiphilic reagents which can also be used as surfactants or foam formers. Th
Bierman, Muserlian and Lucas
Celanese Chemicals Europe GmbH
Padmanabhan S
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