PROCESS FOR THE MANUFACTURE OF A SATURATED ALCOHOL

Abstract

The present invention relates to a process for the manufacture of a saturated primary alcohol from an unsaturated aliphatic ester comprising the steps of: a) Providing an aliphatic ester having at least one carbon-carbon double bond; b) Carrying out a metathesis of said ester in the presence of a ruthenium carbene-based catalyst thereby obtaining a first reaction mixture; c) Adding a ligand and a base to the first reaction mixture, wherein the ligand comprises at least one donor atom chosen from the group consisting of a nitrogen atom and a phosphorus atom thereby obtaining a second reaction mixture comprising an ester product resulting from the metathesis reaction; d) Carrying out a homogeneous hydrogenation of the ester-product resulting from the metathesis, thereby obtaining a saturated primary alcohol. Further, the present invention relates to a catalyst for the hydrogenation of esters and to a process for the hydrogenation of esters using said catalyst.

Claims

1. Process for the manufacture of a saturated primary alcohol from an unsaturated aliphatic ester comprising the steps of: a) Providing an aliphatic ester having at least one carbon-carbon double bond; b) Carrying out a metathesis of said ester in the presence of a ruthenium carbene-based catalyst thereby obtaining a first reaction mixture; c) Adding a ligand and a base to the first reaction mixture, wherein the ligand comprises at least one donor atom chosen from the group consisting of a nitrogen atom and a phosphorus atom thereby obtaining a second reaction mixture comprising an ester product resulting from the metathesis reaction; d) Carrying out a homogeneous hydrogenation of the ester-product resulting from the metathesis, thereby obtaining a saturated primary alcohol.

2. Process according to claim 1, wherein a second compound having at least one carbon-carbon double bond is provided in step a) together with the aliphatic ester having at least one carbon-carbon double bond.

3. Process according to claim 1, wherein a step b1) is carried out after step b) and before step c) comprising adding an olefin to the first reaction mixture and carrying out a second metathesis between the ester product resulting from the metathesis reaction in step b) and the olefin.

4. Process according to claim 3, wherein the olefin is a cyclic olefin and step b1) is a ring-opening-metathesis polymerisation.

5. Process according to claim 1, wherein the ester provided in step a) is an ester of an unsaturated fatty acid.

6. Process according to claim 1, wherein the catalyst has the formula (I): ##STR00003## wherein m and n are independently numerals between 0 and 2, X is a ionic ligand chosen from the group consisting of halides, phenoxy, alkoxy and hydroxyl, R is chosen from the group consisting of an unsubstituted linear alkyl, a substituted linear alkyl, an unsubstituted aryl and a substituted aryl, R is chosen from the group consisting of an unsubstituted trialkylphosphine, a substituted trialkylphosphine, an unsubstituted tricycloalkylphosphine, a substituted tricycloalkylphosphine, an unsubstituted triarylphosphine, a substituted triarylphosphine, an unsubstituted pyridine, a substituted pyridine, an unsubstituted pyrazine and a substituted pyrazine; and R is chosen from the group consisting of a substituted imidazole-2-ylidene or a substituted dihydroimidazole-2-ylidene, an unsubstituted trialkylphosphine, a substituted trialkylphosphine, an unsubstituted tricycloalkylphosphine, a substituted tricycloalkylphosphine, an unsubstituted triarylphosphine, a substituted triarylphosphine.

7. Process according to claim 1, wherein the ligand has the formula (1): NH.sub.2CH.sub.2CH.sub.2P(R.sup.7).sub.3, wherein R.sup.7 is chosen from the group consisting of alkyl, cycloalkyl, aryl.

8. Process according to claim 1, wherein the base is an alkoxide of an alkali metal.

9. Process according to claim 1, wherein after step b), the ester product of the metathesis is isolated before carrying out the hydrogenation in step d).

10. Process according to claim 1, wherein the process is carried out without isolating the ester product of the metathesis, before carrying out the homogeneous hydrogenation.

11. Ruthenium-based catalyst suitable for homogeneous hydrogenation of esters obtainable by the process comprising step of: i) Dissolving the catalyst as defined in formula (I) in a solvent; ii) Dissolving a ligand comprising at least one donor atom chosen from the group consisting of a nitrogen atom and a phosphorus atom in a solvent; iii) Mixing the solutions obtained in i) and ii) and adding a base thereby obtaining a ruthenium-based catalyst in solution suitable for the homogeneous hydrogenation of esters.

12. Process for the homogeneous hydrogenation of an ester into an alcohol comprising contacting an ester with hydrogen in the presence of a ruthenium-based catalyst as defined in claim 10.

13. Process according to claim 12, carried out under a hydrogen pressure below 100 bar and at a temperature below 250 C.

14. Process according to claim 13, wherein the hydrogen pressure is in the range from 10 to 70 bar and the temperature is in the range from 55 C. to 85 C.

Description

EXAMPLES

Example 1: Self-Metathesis and Hydrogenation to Produce an ,-Diol

[0044] In a N2 glove-box, catalyst (Ia) was placed into a 5 mL vial. 4-methyl pentenoate was added and the reaction mixture was stirred at 30 C. for 3 h. Ethylene gas was produced. The ligand NH.sub.2CH.sub.2CH.sub.2P(C.sub.6H.sub.5).sub.2 was dissolved in 1 ml of dry THF. The metathesis reaction mixture was added to the ligand solution. After stirring, the reaction mixture was added to a vial containing t-BuOK. The reaction was placed in the hydrogenation reactor under 50 bar of hydrogen at 70 C. for 16 h.

[0045] The conversion yield was determined based on the initial 4-methyl pentenoate and converted into the desired product: 1,8-octane diol. The yield of the metathesis reaction was 88%, the yield of the hydrogenation reaction was 95%, therefore the overall yield was 84%.

Example 2: Cross-Metathesis and Hydrogenation to Produce an Alcohol

[0046] In a N.sub.2 glove-box, catalyst (Ib) was placed into a 5 mL vial. A mixture of styrene and methyl acrylate was added and the reaction mixture was stirred at 30 C. for 3 h. Ethylene gas was produced.

[0047] The ligand NH.sub.2CH.sub.2CH.sub.2P(C.sub.6H.sub.5).sub.2 was dissolved in 1 ml of dry THF. The metathesis reaction mixture was added to the ligand solution. After stirring, the reaction was added to a vial containing t-BuOK. The reaction was placed in the hydrogenation reactor under 50 bar of hydrogen at 70 C. for 16 h.

[0048] The conversion yield was determined based on the initial styrene and converted into the desired product: 3-phenyl propanol. The yield of the metathesis reaction was 66%, the yield of the hydrogenation reaction was 89%, therefore the overall yield was 59%.

Comparative Experiments

[0049] ,-diols can be prepared by metathesis of fatty acid ester/hydrogenation using 2 different catalysts: the metathesis catalyst used above and a traditional ester hydrogenation catalyst such as an heterogeneous catalyst operating at very high pressure (>150 bar) and temperature (>250 C.). Such a process absolutely requires isolation of the product after the first metathesis step, two different catalysts and a dedicated high pressure reactor. Such a process is therefore not as versatile and cost-effective as the process according to the present invention.

[0050] In processes wherein the metathesis catalyst was not modified by the addition of ligand and used as such in the hydrogenation reaction, the ester group remained unchanged during the hydrogenation step indicating that the unmodified metathesis catalyst is not active towards ester hydrogenation. These processes did not allow to produce alcohols from esters.