A PROCESS FOR THE HYDROFORMYLATION OF CONJUGATED DIENES

Abstract: A process for the hydroformylation of a conjugated diene which comprises reacting a conjugated diene with carbon monoxide and hydrogen in the presence of a complex of rhodium with a polydentate ligand containing trivalent phos­ phorus bearing substituted or unsubstituted aryl groups and in which ligand any of two P-atoms are separated by a chain of two carbon atoms.

Description: A PROCESS FOR THE HYDROFORMYLATION OF CONJUGATED DIENES Hydroformylation of conjugated dienes with the aid of rhodium catalysts is known. From the Journal of Molecular Catalysis, 2 (19y), pp. 211-218 it is known that a conjugated diene may be hydroformylated under high pressure with a rhodium catalyst and a tert.-phosphine as a co-catalyst. Dependent on the choice of the co-catalyst used in the hydroformylation the yield of linear saturated mono-aldehyde generally ranges from about 30 to 60%, based on the conjugated diene. A number of byproducts, such as dialdehydes, unsaturated mono-aldehydes and a small amount of high-boiling product, are formed. Applicant has now found a process for the hydroformylation of conjugated dienes wherein the content of the by-products is suppressed and the amount of linear product is considerably improved. The invention provides a process for the hydroformylation of a conjugated diene by reacting a conjugated diene with carbon monoxide and hydrogen, characterized in that the reaction is carried out in the presence of a complex of rhodium with a polydentate ligand containing trivalent phosphorus bearing substituted or unsubstituted aryl groups and in which ligand any of the two P-atoms are separated by a chain of two carbon atoms. In British Patent Specification 988,941 is disclosed a process for the preparation of an aldehyde and/or alcohol wherein an olefin is reacted with carbon monoxide and hydrogen in the presence of a complex containing in the molecule a transition metal having an atomic number from 23 to 32, 40 to 51 or 57 to 84 and at least one molecule of a biphyllic ligand containing trivalent phosphorus, arsenic or antimony as a catalyst. Although according to the description polydentate phosphorus-containing ligands are disclosed as co-catalysts, no conclusions could be drawn that with the catalyst used in the process according to the present invention still better results in selectivity to linear products could be obtained, since when mono-unsaturated compounds are replaced by conjugated dienes a higher amount of branched products is expected. It has further been proved that a polydentate phosphoruscontaining ligand, having aliphatic groups bound to P, has no activity at all. Moreover, in the specification all examples relate to the use of cobalt as catalyst metal in the complex, and no special attention is drawn to rhodium. The polydentate ligand used in the process according to the invention preferably contains substituted or unsubstituted phenyl groups bound to trivalent P. Suitable substituents bound to the phenyl group comprise alkyl groups, alkoxy groups and halogen atoms. More preferably the polydentate ligand contains at least one moiety: EMI2.1 Examples of polydentate ligands are those having the chemical formula: EMI2.2 Generally, the hydroformylation according to the invention is carried out under rather mild conditions. Preferrred reaction temperatures are in the range of from 50 to 200 C and more preferred temperature from 80 to 130 C and preffered pressures (as the sum of the pressure of hydrogen and carbon monoxide) range of from 3 to 35 bars. Generally, the molar ratio of hydrogen to carbon monoxide is in the range of from 0.5 to 12. The amount of catalyst may vary within wide ranges, but generally the molar ratio of catalyst to diene is in the range of from 1:10,000 to 1:10. The catalyst, which is a complex of rhodium, may be built up from 1,5-cyclo-octadiene-rhodium(I) acetate or another rhodium source. (1,5-Cyclo-octadiene-rhodium(I) acetate occurs in the form of the dimer. In the Examples the calculations were made as if it is a monomer). The hydroformylation of the conjugated dienes is generally carried out in a hydrocarbon solvent. Preferred solvents are toluene, benzene, cyclohexane or methylcyclohexane. Examples of conjugated dienes, used in the process according to the present invention, are 1,3-butadiene, isoprene, 1,3-pentadiene, and conjugated dienes with more than 5 carbon atoms per molecule. The following Examples further illustrate the invention. EXAMPLE 1A A 100 ml stainless steel autoclave was charged with a solution of 0.02 mmol. of 1,5-cyclo-octadiene-rhodium(I) acetate and 0.1 mmol. of 1,2-bis(diphenyl.phosphino)ethane in 20 ml toluene and with 20.0 mmol. of freshly distilled 1,3butadiene under an atmosphere of argon. The autoclave was then pressurized with an equimolar mixture of hydrogen and carbon monoxide and heated to 120 C, the pressure in the autoclave being now 12 bars. After 3 hours at 1200C, the pressure had been dropped to 9 bars. The autoclave was then cooled to ambient temperature and the gases were flashed off at atmospheric pressure. A pale yellow liquid remained in the autoclave. This liquid was analyzed by gas chromatography and the constituents were identified by gas chromatography and nuclear magnetic resonance spectroscopy by comparison with authentic samples. The conversion of 1,3-butadiene was 75%, the selectivity to pentanals was 90%, of which 99% was n-pentanal. The by-product, a mixture of pentenals, was formed in an amount of only 5%, the remaining 5% were dialdehydes, which were not further identified. A number of Examples 1B-5 are given with different polydentate ligands, using the same method as described above. A number of comparative experiments A-F is also given. Unlike otherwise stated in the Table the reaction conditions are the same as those applied in Example 1A. The designation 0 in the chemical formulae means a phenyl group. TABLE EMI5.1 Example <SEP> Ligand <SEP> P/Rh <SEP> Reaction <SEP> %select- <SEP> % <SEP> linearity <SEP> turnover <tb> <SEP> atom <SEP> temp., <SEP> ivity <SEP> to <SEP> of <SEP> pentanals <SEP> mol. <SEP> C4/mol. <SEP> Rh.h. <tb> <SEP> ratio <SEP> C <SEP> pentanals <tb> <SEP> 1A <SEP> #2P(CH2)2P#2 <SEP> 10 <SEP> 120 <SEP> 90 <SEP> 99 <SEP> 250 <tb> <SEP> 1B <SEP> 4 <SEP> 95 <SEP> > 80 <SEP> 98 <SEP> 90 <tb> <SEP> 2 <SEP> -CH2-CH2-P#2 <tb> <SEP> #P <SEP> 3 <SEP> 120 <SEP> > 80 <SEP> 98 <SEP> 120 <tb> <SEP> -CH2-CH2-P#2 <tb> <SEP> -CH2-CH2-P#2 <tb> <SEP> 3 <SEP> P-CH2-CH2-P#2 <SEP> 4 <SEP> 120 <SEP> > 80 <SEP> 98 <SEP> 90 <tb> <SEP> -CH2-CH2-P#2 <tb> <SEP> 4 <SEP> #P2-CH=CH-P#2 <SEP> 10 <SEP> 120 <SEP> 80 <SEP> 98 <SEP> 150 <tb> <SEP> 5 <SEP> #P2-CH-CH2-P#2 <SEP> 4 <SEP> 95 <SEP> 90 <SEP> 98 <SEP> 200 <tb> <SEP> CH3 <tb> Comparative <SEP> #2P(CH2)4P#2 <SEP> 4 <SEP> 95 <SEP> < 20 <SEP> 80 <SEP> 80 <tb> Experiment <tb> <SEP> A <tb> TABLE (cont'd) EMI6.1 Example <SEP> Ligand <SEP> P/Rh <SEP> Reaction <SEP> %select- <SEP> % <SEP> linearity <SEP> turnover <tb> <SEP> atom <SEP> temp., <SEP> ivity <SEP> to <SEP> of <SEP> pentanals <SEP> mol. <SEP> C4/mol. <SEP> Rh.h. <tb> <SEP> ratio <SEP> C <SEP> pentanals <tb> Comparative <SEP> #2P(CH2)3P#2 <SEP> 4 <SEP> 95 <SEP> 20 <SEP> - <SEP> 30 <tb> Experiment <tb> <SEP> B <tb> <SEP> C <SEP> P#3 <SEP> 10 <SEP> 120 <SEP> - <SEP> - <SEP> < 6 <tb> <SEP> D <SEP> #P(CH2)10P#2 <SEP> 10 <SEP> 120 <SEP> 20 <SEP> - <SEP> 75 <tb> <SEP> E <SEP> #PCH2P#2 <SEP> 10 <SEP> 120 <SEP> - <SEP> - <SEP> < 3 <tb> <SEP> F <SEP> (CH3)2P(CH2)2P(CH3)2 <SEP> 10 <SEP> 120 <SEP> - <SEP> - <SEP> < 10 <tb> <SEP> 2 <SEP> 120 <SEP> - <SEP> - <SEP> < 10 <tb> From the Table the following may be concluded: The presence of a chain of two carbon atoms, which are bound to P-atoms is essential since a chain of one, three, four or ten carbon atoms gives a low conversion and a low selectivity to n-pentanal. There is hardly any conversion using P3 as a ligand. The presence of a phenyl group is also essential, since when phenyl is replaced by an alkyl group, e.g. methyl group, the conversion is extremely low, notwithstanding the presence of a chain of two carbon atoms. EXAMPLE 6 A 100 ml stainless steel autoclave was charged with a solution of 1,5-cyclo-octadiene-rhodium(I) acetate (0.02 mmol.) and 1,2-bis(diphenylphosphino)ethane (0.10 mmol.) in benzene (20 ml) and with isoprene (20 mmol.) under an atmosphere of argon. The autoclave was then pressurized to 12 bars with an equimolar mixture of hydrogen and carbon monoxide and heated to 1200C. After 3 hours at 1200C the autoclave was cooled to ambient temperature and the gases were flashed off at atmospheric pressure. Analysis of the liquid revealed an almost quantitative conversion of isoprene with a selectivity to 3-methylpentanal of 38%. The turnover was 400 mmol. of isoprene/Rh.h.

Claims: CLAIMS 1. A process for the hydroformylation of a conjugated diene by reacting a conjugated diene with carbon monoxide and hydrogen, characterized in that the reaction is carried out in the presence of a complex of rhodium with a polydentate ligand containing trivalent phosphorus bearing substituted or unsubstituted aryl groups and in which ligand any of two P-atoms are separated by a chain of two carbon atoms. 2. A process as claimed in claim 1, characterized in that the polydentate ligand contains at least one moiety: EMI8.1 3. A process as claimed in claim 1 or 2, characterized in that the polydentate ligand has the formula: EMI8.2 4. A process as claimed in claim 1 or 2, characterized in that the polydentate ligand has the formula: EMI8.3 5. A process as claimed in claim 1 or 2, characterized in that the polydentate ligand has the formula: EMI8.4 6. A process as claimed in claim 1 or 2, characterized in that the polydentate ligand has the formula: 02P - CH2 - CH2 - P2 7. A process as claimed in claim 1, characterized in that the polydentate ligand has the formula: #2P-HC=CH-P#2 8. A process as claimed in any one of the preceding claims, characterized in that the reaction is carried out at a temperature in the range of from 500 to 2000C. 9. A process as claimed in claim 8, characterized in that the reaction is carried out at a temperature in the range of from 80 to 1300C. 10. A process as claimed in any one of the preceding claims, characterized in that the sum of the pressures of hydrogen and carbon monoxide is in the range of from 3 to 35 bars. 11. A process as claimed in any one of the preceding claims, characterized in that the molar ratio of hydrogen to carbon monoxide is in the range of from 0.5 to 12. 12. A process as claimed in any one of the preceding claims, characterized in that the molar ratio of rhodium complex to diene is in the range of from 1:10,000 to 1:10. 13. A process as claimed in any one of the preceding claims, characterized in that the reaction is carried out in a hydrocarbon solvent. 14. A process as claimed in claim 13, characterized in that the reaction is carried out in toluene. 15. A process as claimed in claim 1, substantially as hereinbefore described with reference to the Examples. 16. Products whenever prepared by a process as claimed in any one of the preceding claims.

Inventors: ROOBEEK, CORNELIS FRANCISCUS, VAN LEEUWEN, PETRUS W. N. M.
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1981
Main classification: C07C45
IPC codes: B01J31, C07B61, C07C47, C07C67, C07C45