Preparation of aldehydes

Details Preparation of aldehydes Preparation of aldehydes

1997-04-18

1998-03-03

Geist, Gary

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

Organic compounds

Oxygen containing

568454, 568451, 568483, C07C 4500

Patent

active

057236801

DESCRIPTION:

BRIEF SUMMARY
This is the U.S. National Stage Application of PCT/EP95/04506 filed Nov. 16, 1995 now WO/96/16012 published May 30, 1996.
The present invention relates to a process for the preparation of aldehydes and/or alcohols by the hydroformylation of olefins of more than 3 carbon atoms by means of a bare rhodium catalyst homogeneously dissolved in the reaction medium, at superatmospheric pressure and at elevated temperatures, and separation of the rhodium catalyst from the liquid reaction mixture.
The hydroformylation of olefins with carbon monoxide and hydrogen in the presence of transition metal catalysts is known. While .alpha.-olefins can be very readily hydroformylated using rhodium-containing, phosphine-modified catalysts (cf. J. Falbe, Ed: New Syntheses With Carbon Monoxide, Springer, Berlin 1980, page 55 et seq.), this catalyst system is not very suitable for internal olefins and internal branched olefins nor for olefins with more than 7 carbon atoms (cf. Falbe, page 95 et seq.). Thus, internal carbon-carbon double bonds are hydroformylated only very slowly in the presence of such a catalyst. Since the hydroformylation product is as a rule separated by distillation from the catalyst dissolved homogeneously in the reaction system and the boiling point of the aldehyde formed in the hydroformylation increases with increasing number of carbon atoms and chain length to temperatures at which the rhodium-containing catalyst decomposes, this hydroformylation method is uneconomical for the hydroformylation of olefins of more than 7 carbon atoms. In the hydroformylation of polymeric olefins, for example of polyisobutene, the catalyst containing a noble metal cannot be recovered in reusable form.
On the other hand, internal olefins and internal branched olefins can advantageously be hydroformylated using bare rhodium, ie. rhodium compounds which are dissolved homogeneously in the hydroformylation medium and are not modified with phosphorus-containing ligands, such as phosphines or phosphites. Such rhodium catalysts which have not been modified with phosphines or phosphites and their usefulness as a catalyst for the hydroformylation of the abovementioned classes of olefins are known (cf. Falbe, page 38 et seq.). The terms bare rhodium or bare rhodium catalysts are used in this application for rhodium hydroformylation catalysts which, in contrast to conventional rhodium hydroformylation catalysts, are not modified with ligands, particularly phosphorus-containing ligands, such as phosphine or phosphite ligands, under the hydroformylation conditions. Carbonyl or hydrido ligands are not understood as meaning ligands in this sense. It is assumed in the technical literature (cf. Falbe, page 38 et seq.) that the rhodium compound HRh(CO).sub.4 is the catalytically active rhodium species in the hydroformylation with bare rhodium catalysts, although this has not been definitively proven owing to the many chemical mechanisms taking place side by side in the hydroformylation reaction zone. Merely for the sake of simplicity, we make use of this assumption in this application too, without intending to restrict the scope of protection of the present application if at some time in the future a rhodium species other than the stated one should prove to be the actual catalytically active species. The bare rhodium catalysts form under the conditions of the hydroformylation reaction from rhodium compounds, for example rhodium salts, such as rhodium(III) chloride, rhodium(III) nitrate, rhodium(III) acetate, rhodium(II) acetate, rhodium(III) sulfate or rhodium(III) ammonium chloride, from rhodium chalkogenides, such as rhodium(III) oxide or rhodium(III) sulfide, from salts of oxo acids of rhodium, for example the rhodates, from rhodium carbonyl compounds, such as Rh.sub.4 (CO).sub.12 and Rh.sub.6 (CO).sub.16, or from organo rhodium compounds, such as acetonylacetonatorhodium dicarbonyl or cyc10octadienerhodium acetate or chloride, in the presence of CO/H.sub.2 mixtures, which are usually referred to as synthesis gas. For carrying out hydrofor

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