Oxidation of 5-hydroxy-2-furanone to maleates

Abstract

The invention is directed to a process for preparing maleic acid or a derivative thereof, the process comprising a step b) of oxidizing 5-hydroxy-2(5H)-furanone and/or cis--formylacrylic acid to maleic acid or a derivative thereof by contacting the 5-hydroxy-2(5H)-furanone and/or cis--formylacrylic acid with molecular oxygen (O.sub.2) in the presence of a catalyst. In a particular embodiment, the step b) is preceded by a step a) of oxidizing a furanic compound according to formula I into the 5-hydroxy-2(5H)-furanone and/or cis--formylacrylic acid, ##STR00001##
wherein R.sup.1 is H, CH.sub.2OH, CO.sub.2H or CHO and R.sup.2 is H, OH, C.sub.1-C.sub.6 alkyl or O(C.sub.1-C.sub.6 alkyl), or esters, ethers, amides, acid halides, anhydrides, carboximidates, nitriles, and salts of formula I.

Claims

1. A process for preparing maleic acid or a derivative thereof, said process comprising a step b) of oxidizing 5-hydroxy-2(5H)-furanone and/or cis--formylacrylic acid to maleic acid or a derivative thereof by contacting said 5-hydroxy-2(5H)-furanone and/or cis--formylacrylic acid with molecular oxygen (O.sub.2) in the presence of a catalyst.

2. The process according to claim 1, wherein said catalyst comprises a transition metal, metal salt, metal oxide or a phosphate.

3. The process according to claim 1, wherein said catalyst comprises a solid support selected from the group consisting of zirconia, silica, activated carbon, aluminum oxide, zinc oxide, and titanium dioxide.

4. The process according to claim 1, wherein said 5-hydroxy-2(5H)-furanone and/or cis--formylacrylic acid is/are liquid or dissolved in a solvent when contacted with said O.sub.2.

5. The process according to claim 4, wherein said solvent comprises an organic solvent or an aqueous solvent.

6. The process according to claim 1, wherein said step b) is carried out under a pressure of at least 5 bar.

7. The process according to claim 1, wherein said step b) is carried out at a temperature in the range of 20 to 200 C.

8. The process according to claim 1, wherein said step b) is carried out in a continuous reactor.

9. The process according to claim 1, wherein said step b) is preceded by a step of providing 5-hydroxy-2(5H)-furanone and/or cis--formylacrylic acid in an isolated formulation.

10. The process according to claim 1, wherein the derivative of maleic acid is one or more selected from the group consisting of maleic anhydride, fumaric acid, succinic acid, succinonitrile, putrescine, malic acid, and salts, anhydrides, amide, imides and esters of any of these compounds.

11. The process according to claim 1, wherein said step b) of oxidizing said 5-hydroxy-2(5H)-furanone and/or cis--formylacrylic acid to maleic acid or a derivative thereof is preceded by a step a) of oxidizing a furanic compound according to formula I into said 5-hydroxy-2(5H)-furanone and/or cis--formylacrylic acid, ##STR00004## wherein R.sup.1 is H, CH.sub.2OH, CO.sub.2H or CHO and R.sup.2 is H, OH, C.sub.1-C.sub.6 alkyl or O(C.sub.1-C.sub.6 alkyl), esters, ethers, amides, acid halides, anhydrides, carboximidates, nitriles, and salts of formula I.

12. The process according to claim 11, wherein said step a) comprises electrochemically oxidizing the furanic compound in an aqueous electrolyte solution.

13. The process according to claim 12, wherein said step a) and said step b) are carried out in said aqueous electrolyte solution.

14. The process according to claim 12, wherein said step a) is followed by an intermediate extraction step of extracting said 5-hydroxy-2(5H)-furanone and/or cis--formylacrylic acid with an organic solvent and wherein said step b) is carried out in said organic solvent.

15. The process according to claim 11, wherein said step a) comprises electrochemically oxidizing the furanic compound in an aqueous electrolyte solution comprising an acid.

16. The process according to claim 11, wherein said step a) comprises electrochemically oxidizing the furanic compound in an aqueous electrolyte solution comprising a mineral acid.

17. The process according to claim 11, wherein said step a) comprises electrochemically oxidizing the furanic compound in an aqueous electrolyte solution comprising a mineral acid selected from the group consisting of hydrochloric acid (HCl), nitric acid (HNO.sub.3), phosphoric acid (H.sub.3PO.sub.4), sulfuric acid (H.sub.2SO.sub.4), boric acid (H.sub.3BO.sub.3), hydrofluoric acid (HF), hydrobromic acid (HBr), perchloric acid (HClO.sub.4) and hydroiodic acid (HI).

18. The process according to claim 17, wherein the mineral acid is sulfuric acid.

19. The process according to claim 1, wherein said process further comprises converting said maleic acid into one or more of its derivatives selected from the groups consisting of maleic anhydride, fumaric acid, succinic acid, succinonitrile, putrescine, malic acid, and salts, anhydrides, amide, imides and esters of any of these compounds.

20. The process according to claim 1, wherein said catalyst comprises a transition metal, metal salt, metal oxide or a phosphate of which the metal is selected from the group consisting of cobalt, manganese, vanadium, molybdenum, copper, silver, gold, palladium, platinum and ruthenium.

21. The process according to claim 1, wherein said catalyst comprises a transition metal, metal salt, metal oxide or a phosphate of which the metal is gold.

Description

EXAMPLE 1: CONVERSION OF FURFURAL TO 5-HYDROXY-2(5H)-FURANONE

(1) The anode compartment of an H-cell was charged with 100 mL of 0.5 M aqueous sulfuric acid containing 50 mM of furfural. Conversion at 20 C. The cathode compartment of the H-cell was charged 100 ml of 0.5 M aqueous sulfuric acid. A 10 cm.sup.2 PbO.sub.2 electrode was activated by CV between 0.5-2,1V against SHE. The reference and working electrodes were made ready then a potential of 1.85 V vs. SCE was applied across the cell. Analysis after 7 hours shows 2:1 ratio of the reaction intermediate formyl-acrylic acid:maleic acid present, and 9:1 after 20 hours. The maximum total yield of the product (maleic acid and 5-hydroxy-2(5H)-furanone is 80%).

EXAMPLE 2: EXTRACTION OF CIS-3-FORMYLACRYLIC ACID/5-HYDROXY-2(5H)-FURANONE AND MALEIC ACID FROM ELECTROLYTE

(2) An equal volume of an electrolyte containing formyl-acrylic acid:maleic acid present in a ratio of about 1:10 and an organic solvent (Ethyl acetate, Dichloromethane, Toluene, 2-Methyltetrahydrofuran, Diethyl Ether) were mixed together intensely and then left to phase separate. Both the aqueous and organics phases were then analysed by HPLC to determine the relative levels of cis--formylacrylic acid/5-hydroxy-2(5H)-furanone and maleic acid in each of the phases:

(3) TABLE-US-00001 Aqueous Phase Organic Phase Maleic Maleic Furanone Acid Furanone Acid Ethyl Acetate 8.3% 54.8% 91.7 45.2% Dichloromethane 99.1% 100% 0.9% 0% Toluene 99.1% 100% 0.9% 0% 2-MethylTHF 41.3% 26.4% 58.7% 73.6% Diethyl Ether 65.9% 63.2% 34.1% 36.6%
The conditions using ethyl acetate were scaled up, with the organic phase being separated from the aqueous, dried over sodium sulfate, then concentrated in vacuo to yield a white solid product (400 mg). This was analyzed by NMR and confirmed to be a 2.7:1 ratio of cis--formylacrylic acid/5-hydroxy-2(5H)-furanone:maleic acid.

EXAMPLE 3: CONVERSION OF FURFURAL TO 5-HYDROXY-2(5H)-FURANONE

(4) To tow separate reactors were charged the cis--formylacrylic acid/5-hydroxy-2(5H)-furanone:maleic acid mixture (50 mg), 5% palladium on carbon (25 mg), and solvent (350 Leither 0.5M aqueous sulfuric acid or a pH 7 aqueous buffer solution of monopotassium phosphate and dipotassium phosphate). The reactors were then heated to 70 C. with stirring and oxygen was bubbled through the mixture. After 2 hours, the reactions were cooled to room temperature and analyzed by HPLC. In both cases, conversion of cis--formylacrylic acid/5-hydroxy-2(5H)-furanone to maleic acid was observed.

EXAMPLE 4: SOLVENTS FOR THE OXIDATION OF HFO TO MALEIC ACID

(5) An autoclave (10 ml) was charged with HFO, solvent (1 ml) and 10% Pd/C according to the Table 1 below.

(6) The reactor was sealed then flushed with nitrogen. The reactor was then charged to 10 bar of pressure with pure oxygen. The reactor was then heated to 85 C. and stirred for 15 hours. After cooling to ambient temperature, the pressure was released and the reactor flushed with nitrogen. The product solutions were then filtered to remove catalyst, then analyzed by high-performance liquid chromatography (HPLC), with the yield of maleic acid compiled in Table 1.

(7) TABLE-US-00002 TABLE 1 Solvent HFO (mg) Pd/C (mg) TOF/sec for MA* Water 10.0 5.7 0 0.5M Sulfuric Acid 8.3 4.1 0 Ethyl Acetate 7.0 9.1 155 Methylisobutylketone 5.5 4.4 265 Methyl-t-butyl ether 5.8 5.1 321 2-MeTHF 7.1 4.4 790 Dichloromethane 6.6 8.5 0 Acetic Acid 6.5 7.3 10 n-Heptane 6.0 3.7 276 Toluene 4.6 4.4 738 Acetonitrile 5.3 12.0 43 Acetone 4.6 12.0 108 Dimethyl Carbonate 5.4 4.1 115 Nitromethane 5.3 4.7 86 *TOF/sec for MA means turnover frequency of the catalyst for MA under those conditions

EXAMPLE 5: CATALYSTS FOR THE OXIDATION OF HFO TO MALEIC ACID IN TOLUENE

(8) An autoclave (10 ml) was charged with HFO (10.6 mg), toluene (1 ml) and catalyst according to the Table 2. The reactor was sealed then flushed with nitrogen. The reactor was then charged to 10 bar of pressure with pure oxygen. The reactor was then heated to 111 C. and stirred for 14 hours. After cooling to ambient temperature, the pressure was released and the reactor flushed with nitrogen. The product solutions were then filtered to remove catalyst, then analyzed by HPLC, with the results compiled in Table 2.

(9) TABLE-US-00003 TABLE 2 Solvent Catalyst (mg) TOF/sec for MA No Catalyst 0 Au/SiO2 94 3279 Pd/C 6.0 309 Pt/C 13 82 Ru/C 11 1464 * TOF/sec for MA means turnover frequency of the catalyst for MA under those conditions