Method for producing muconic acids and furans from aldaric acids

Abstract

The present invention relates to selective catalytic dehydroxylation method of aldaric acids for producing muconic acid and furan chemicals, which can be used directly in fine chemical and polymer applications (FCA/FDCA) and as intermediates in the preparation of industrially significant chemicals, such as terephthalic acid, adipic acid, caprolactone, caprolactam, nylon 6.6, 1,6-hexanediol and multiple pharmaceutical building blocks (MA/MAME).

Claims

1. A method for producing muconic acid from aldaric acid, wherein the method is also capable of producing furan chemicals, the method comprising selective catalytic dehydroxylation of the aldaric acid by heating the aldaric acid with a solvent and a reductant in a pressurized container to temperatures between 90 to 300 C. in the presence of a transition metal catalyst for a pre-determined reaction time and purifying the resulting product(s), wherein the catalysis is directed towards muconic acid by using catalytic temperatures between 90 and 150 C. and towards furan chemicals by using catalytic temperatures between 150 and 300 C.

2. The method according to claim 1, wherein the aldaric acid is galactaric acid having formula I: ##STR00010##

3. The method according to claim 1, wherein the catalysis is selectively directed towards muconic acid by using a catalytic temperature between 100 and 150 C.

4. The method according to claim 1, wherein the catalysis is selectively directed towards furan chemicals by using catalytic temperatures between 150 and 250 C.

5. The method according to claim 1 for producing compounds having structural formulas II, III, VIII and IX by using temperatures between 90 and 150 C. ##STR00011##

6. The method according to claim 1 for producing compounds having structural formulas IV-VII by using temperatures between 150 and 300 C. ##STR00012##

7. The method according to claim 1, wherein the transition metal catalyst is selected from rhenium, palladium, vanadium and molybdenum catalysts.

8. The method according to claim 1, wherein the catalyst is methyl trioxo rhenium.

9. The method according to claim 1, wherein the catalyst is used at a ratio of 1.0 to 10 mol-% per aldaric acid with mucic acid or mucic acid alkyl ester.

10. The method according to claim 1, wherein the reductant is hydrogen.

11. The method according to claim 1, wherein the solvent is selected from methanol, ethanol or butanol.

12. The method according to claim 1, wherein the pressure inside the container is adjusted to a level of 1 to 20 bars with hydrogen gas.

13. The method according to claim 1, wherein the reaction time is 1 minute to 70 hours.

14. The method according to claim 1, wherein the reaction time is 1 to 70 hours when targeting towards MA/MAME and 1 minute to 60 minutes when targeting towards furan chemicals.

15. The method according to claim 1, wherein the purification comprises filtering any solid precipitate, washing the precipitate with alcohol, drying the washed product(s) and subsequently evaporating the organic phase and using a chromatography for recovering the desired products.

16. The method according to claim 1, wherein the transition metal catalyst is selected from rhenium catalysts.

17. The method according to claim 1, wherein the catalysis is selectively directed towards muconic acid by using a catalytic temperature of 120 C.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 describes the two temperature controlled routes from galactaric acid to muconic acid and furans via rhenium catalyzed dehydroxylation reactions.

EMBODIMENTS

(2) The present invention relates to the production of sugar acid platform chemicals, more precisely muconic acid and furans, such as furoic acid and furandicarboxylic acid, from aldaric acid(s) via selective catalytic dehydroxylation.

(3) Aldaric acids are a group of sugar acids, where the terminal hydroxyl groups of the sugars have been replaced by terminal carboxylic acids, and are characterized by the formula HOOC(CHOH).sub.nCOOH. Nomenclature of the aldaric acids is based on the sugars from which they are derived. For example, glucose is oxidized to glucaric acid, galactose to galactaric acid and xylose to xylaric acid. Unlike their parent sugars, aldaric acids have the same functional group at both ends of their carbon chain. Thus, two different aldaric acids can produce the same muconic acid.

(4) According to one preferred embodiment of the present invention, the method comprises heating the aldaric acid with a solvent and a reductant in a pressurized container to temperatures between 90 to 300 C. in the presence of a transition metal catalyst for a pre-determined reaction time and purifying the resulting product or products.

(5) Particularly, the method comprises a selective catalytic dehydroxylation of aldaric acid(s), wherein the catalysis is selectively directed towards muconic acid by using catalytic temperatures between 90 and 150 C., such as 100 to 120 C. and preferably of about 100 C. On the other hand, said catalysis can be selectively directed towards furans by using catalytic temperatures between 150 and 300 C., such as 150 to 250 C. and preferably of about 200 C. However, all the compounds II to IX are also being produced at temperatures between 120 and 150 C. The reaction temperatures can be selected and adjusted based on targeted products, as e.g. described in the examples below. The reaction typically starts from galactric acid, but other aldaric acids, such as glucaric acid, may also be used.

(6) As previously said, the catalysis of the present invention can be selectively directed towards muconic acid route or furan route by only adjusting the reaction temperature and time. Such surprising and advantageous finding has not been disclosed before in the art.

(7) One important aspect of the invention is to select an efficient and functional combination of catalyst, solvent and reductant. Earlier attempts in the prior art have failed to facilitate the use of light (i.e. short) alcohols, such as methanol, ethanol and n-butanol, for the reduction step. The inventors of the present invention have managed to develop such a combination providing excellent results towards the desired end-products. Thus, an example of such a combination is to use methyl trioxo rhenium catalyst together with a light alcohol such as methanol as a solvent together with hydrogen as a reductant. The products obtained from the muconic acid route, when using galactaric acid as the aldaric acid and such catalyst/reductant/solvent combination as described herein, comprise muconic acid (MA) and methyl muconate (MAME). Consequently, the furan route provides products such as furoic acid (FCA), furoic acid methyl ester (FCAME), furandicarboxylic acid (FDCA) and furandicarboxylic acid methyl ester (FDCAME).

(8) However, other transition metal catalysts besides rhenium, such as molybdenum, vanadium and palladium catalysts, may also be used.

(9) One major advantage of using the above mentioned combination is that the hydrogen results in H.sub.2O as a byproduct, thus leaving only an alcohol solvent, such as methanol, which is easy to wash or distil off in the purification steps. Hydrogen can also be recycled and it is cheaper compared to other prior art reductants, such as 1-butanol. Other reductants than alcohols are also problematic in the purification step and must be physically removed. Thereby the method is particularly green and produces only low amounts of waste.

(10) The method as herein described is also able to be performed at lower temperatures compared to the prior art methods, where the energy consumption remains low. Relating to the previous, the reaction time is set between 1 minute to 70 hours, preferably between 1 to 2 hours and in particular between 1 to 60 minutes, making the method even more energy efficient. However, the reaction time depends on the targeted product. Typically longer times (such as 48 to 70 hours) are necessary for obtaining MA/MAME and shorter times (1 minute to 60 minutes, preferably 1 minute to 10 minutes) are applicable when producing furan products.

(11) The purification of the produced products comprises filtering any solid precipitate, washing the precipitate with alcohol and drying the washed product(s) for example by evaporation. The organic phase having the desired product(s) of the present invention is subsequently evaporated and then purified, for example, by silica column chromatography. The results are confirmed by further analysis methods generally known in the art.

(12) The present invention is illustrated by the following non-limiting examples. It should be understood, however, that the embodiments given in the description above and in the examples are for illustrative purposes only, and that various changes and modifications are possible within the scope of the claims.

EXAMPLES

(13) Numbering and structural formulas of the relevant chemical compounds of the following examples:

Galactaric Acid (I)

(14) ##STR00001##

2,4-Hexanedioic Acid (2E, 4E) (II)

(15) ##STR00002##

2,4-Hexanedioic Acid 1,6-dimethyl Ester (2E, 4E) (III)

(16) ##STR00003##

2-Furancarboxylic Acid (IV)

(17) ##STR00004##

2-Furancarboxylic Acid Methyl Ester (V)

(18) ##STR00005##

2,5-Furandicarboxylic Acid (VI)

(19) ##STR00006##

2,5-Furandicarboxylic Acid 2,5-dimethyl Ester (VII)

(20) ##STR00007##

2,4-Hexanedioic Acid 1,6-diethyl Ester (2E, 4E) (VIII)

(21) ##STR00008##

2,4-Hexanedioic Acid 1,6-dibutyl Ester (2E, 4E) (IX)

(22) ##STR00009##

(23) General Method

(24) Reactions were conducted in 25 ml Teflon coated pressure vessels. Product yields were determined using GC-FID with external calibration for each product compound. Standard esterification methods of the corresponding carboxylic acids were used to produce the ester standards for the calibrations. The results were confirmed using GC-MS and NMR analyses.

Example 1 Catalytic Dehydroxylation of Galactaric Acid (I) for the Production of Compounds II-VII

(25) Galactaric acid (1.0 g, 4.76 mmol), methyl trioxo rhenium (0.12 g, 0.47 mmol, 10 mol %) and methanol (10 ml) were charged in the reaction vessel. The reaction vessel was pressurised with hydrogen and heated up to the reaction temperature (Table 1). After the indicated reaction time the mixture was cooled down to room temperature, any solid precipitate was filtered, washed with methanol (5 ml) and dried. The solvent fraction was concentrated in a rotary evaporator. Purification was by flash silica column chromatography. The different fractions were analysed with GC-FID, GC-MS and NMR.

(26) TABLE-US-00001 TABLE 1 Experiments with galactaric acid with MTO/MeOH T Gas, time Yield (%) # ( C.) (bar) (h) II III IV V VI VII 1 100 H.sub.2 (5) 70 0.1 10.7 0.1 2 100 H.sub.2 (10) 48 0.02 6.7 0.03 0.17 0.09 0.13 3 120 H.sub.2 (5) 48 12.3 0.08 0.09 0.12 4 150 H.sub.2 (5) 70 0.1 0.4 3.1 5.2 0.2 1.4 5 200 H.sub.2 (5) 2 0.8 0.9 11.2 1.9 1.7 0.6 6 200 H.sub.2 (5) 1 0.1 1.6 9.6 14.7 0.6 2.3 7 200 H.sub.2 (5) 0.25 0.87 1.4 6.09 14.0 0.88 3.6

Example 2 Catalytic Dehydroxylation of Galactaric Acid (I) for the Production of Compound VIII

(27) Galactaric acid (1.0 g, 4.76 mmol), methyl trioxo rhenium (0.12 g, 0.47 mmol, 10 mol %) and ethanol (10 ml) were charged in the reaction vessel. The reaction vessel was pressurised with hydrogen and heated up to the reaction temperature (Table 2). After the indicated reaction time the mixture was cooled down to room temperature, any solid precipitate was filtered, washed with ethanol (5 ml) and dried. The solvent fraction was concentrated in a rotary evaporator. The different fractions were analysed with GC-FID, and GC-MS.

(28) TABLE-US-00002 TABLE 2 Experiments with galactaric acid with MTO/EtOH Yield T Gas, time (%) # ( C.) (bar) (h) VIII 8 120 H.sub.2 (5) 48 19.2

Example 3 Catalytic Dehydroxylation of Galactaric Acid (I) for the Production of Compound IX

(29) Galactaric acid (1.0 g, 4.76 mmol), methyl trioxo rhenium (0.12 g, 0.47 mmol, 10 mol %) and 1-butanol (10 ml) were charged in the reaction vessel. The reaction vessel was pressurised with hydrogen and heated up to the reaction temperature (Table 3). After the indicated reaction time the mixture was cooled down to room temperature, any solid precipitate was filtered, washed with butanol (5 ml) and dried. The solvent fraction was concentrated in a rotary evaporator. The different fractions were analysed with GC-FID, and GC-MS.

(30) TABLE-US-00003 TABLE 3 Experiments with galactaric acid with MTO/BuOH Yield T Gas, time (%) # ( C.) (bar) (h) IX 9 120 H.sub.2 (5) 48 21.4

Example 4 Purification of Mucic Acid Methyl Ester from Reaction #1

(31) After the solvent fraction was concentrated to give a purple powder (528 mg) it was dissolved into acetone (10 g) and then added to silica gel (1 g). This was then evaporated to a powder and eluted from a flash column (11 cm silica gel) with solvent 10% ethyl acetate/90% hexane. Removal of the solvent from the product fractions gave compound III as a white powder, 110.4 mg, 8.2% yield. .sup.1H NMR (D6-DMSO) 3.70 (6H, s, CH.sub.3), 6.49 (2H, d, J 13.95 alkene H), 7.40 (2H, d, J 13.95, alkene H). .sup.13C NMR (D6-DMSO) 165, 141, 128, 51. GC-MS m/z 170.

CITATION LISTPATENT LITERATURE

(32) 1. WO 2010/144862 A2 2. FR2723945

CITATION LISTNON-PATENT LITERATURE

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