Process for the production of 5-hydroxymethylfurfural in the presence of organic catalysts from the thiourea family

Abstract

A process for the transformation of a feed of at least one sugar into 5-hydroxymethylfurfural, contacting the feed with one or more organic catalysts in the presence of at least one solvent, said solvent being water or an organic solvent, alone or as a mixture, at a temperature in the range 30 C. to 200 C., and at a pressure in the range 0.1 MPa to 10 MPa, in which said organic catalysts are selected from compounds from the thiourea family with general formula R1NHC(S)NHR2, in which the groups R1 and R2 are aromatic groups optionally having a heteroatom, linear or branched alkyl groups, which may or may not be cyclic, and alkyl groups with at least one heteroatom, which may be linear or branched, which may or may not be cyclic, said groups R1 and R2 possibly being substituted or unsubstituted and which may be identical or different.

Claims

1. A process for the transformation of a feed comprising at least one sugar into 5-hydroxymethylfurfural, in which said feed is brought into contact with one or more organic catalysts in the presence of at least one solvent, said solvent being water or an organic solvent, alone or as a mixture, at a temperature in the range 30 C. to 200 C., and at a pressure in the range 0.1 MPa to 10 MPa, in which said organic catalysts are selected from compounds from the thiourea family with general formula R1NHC(S)NHR2, in which the groups R1 and R2 are selected from aromatic groups comprising or not comprising a heteroatom, linear or branched alkyl groups, which may or may not be cyclic, and alkyl groups comprising at least one heteroatom, which may be linear or branched, which may or may not be cyclic, said groups R1 and R2 possibly being substituted or unsubstituted and which may be identical or different.

2. The process as claimed in claim 1, in which said sugar is selected from oligosaccharides and monosaccharides, alone or as a mixture.

3. The process as claimed in claim 2, in which the monosaccharides are selected from glucose, mannose and fructose, used alone or as a mixture.

4. The process as claimed in claim 2, in which the oligosaccharides are selected from saccharose, lactose, maltose, isomaltose, inulobiose, melibiose, gentiobiose, trehalose, cellobiose, cellotriose, cellotetraose and oligosaccharides obtained from the hydrolysis of said polysaccharides obtained from the hydrolysis of starch, inulin, cellulose or hemicellulose, used alone or as a mixture.

5. The process as claimed in claim 1, in which said groups R1 and R2 are selected from aromatic groups comprising a heteroatom, said heteroatom being selected from nitrogen, phosphorus and oxygen.

6. The process as claimed in claim 5, in which said groups R1 and R2 selected from the groups pyridine, phosphole and furan.

7. The process as claimed in claim 1, in which said groups R1 and R2 are selected from aromatic groups containing 6 to 14 carbon atoms and not comprising a heteroatom, which may or may not be fused.

8. The process as claimed in claim 7, in which the aromatic groups containing 6 to 14 carbon atoms are selected from phenyl, naphthyl, phenanthryl and anthracyl groups.

9. The process as claimed in claim 1, in which said groups R1 and R2 are selected from non-cyclic alkyl groups containing 1 to 12 carbon atoms, which may be linear or branched, selected from the groups methyl, ethyl, propyl, isopropyl, butyl, pentyl and hexyl.

10. The process as claimed in claim 1, in which said groups R1 and R2 are selected from cycloalkyl groups containing 3 to 8 carbon atoms selected from cyclopentyl, cyclohexyl, cycloheptyl and bicyclo[2.2.2]octyl groups.

11. The process as claimed in claim 1, in which said groups R1 and R2 are selected from alkyl groups and/or cycloalkyl groups comprising at least one tertiary amine function.

12. The process as claimed in claim 11, in which said groups R1 and R2 are selected from N,N-dimethylethylamine, N,N-dimethylcyclohexylamine, N-methylpiperidine and aza-bicyclo[2.2.2]octyl.

13. The process as claimed in claim 1, in which said organic catalyst is 1-(3,5-bis-trifluoromethylphenyl)-3-cyclohexyl thiourea.

14. The process as claimed in claim 1, in which said organic catalyst is 1-(4-methoxyphenyl)-3-phenyl thiourea.

15. The process as claimed in claim 1, in which said solvent is an organic solvent selected from alcohols, ethers, esters, lactones, cyclic carbonates, nitriles, amides, sulphones, sulphoxides and ammonium salts, alone or as a mixture.

16. The process as claimed in claim 15, in which the alcohols are selected from methanol, ethanol, propanols and butanols, and in which the ethers are selected from diethylether, dimethoxyethane, tetrahydrofuran and dioxane, and in which the esters are selected from ethyl formate and ethyl acetate, and in which the lactones are selected from -valerolactone and -butyrolactone, and in which the cyclic carbonates are selected from ethylene carbonate and propylene carbonate, and in which the nitriles are selected from acetonitrile and benzonitrile, and in which the amides are selected from dimethylformamide, diethylformamide and N-methylpyrrolidone, and in which the sulphones are selected from dimethylsulphone and sulpholane, and in which the sulphoxide is DMSO, and in which the ammonium salt is choline chloride, alone or as a mixture.

17. The process as claimed in claim 1, in which the temperature is in the range 50 C. to 200 C., and in which the pressure is in the range 0.1 MPa to 8 MPa.

18. The process as claimed in claim 1, in which the feed is introduced in a solvent/feed weight ratio in the range 0.1 to 200.

19. The process as claimed in claim 1, in which the organic catalysts from the thiourea family are introduced in a feed/organic catalyst(s) weight ratio in the range 1 to 1000.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a graph representing the change in the yield of the reaction for the production of 5-HMF starting from a sugar feed under different catalytic conditions.

EXAMPLES

(2) In the examples below, the glucose and the fructose used as the feed were commercially available and used without supplemental purification.

(3) The 3,5-trifluoromethylphenyl isothiocyanate, phenyl isothiocyanate, cyclohexylamine and p-anisidine used as precursors for the catalysts in accordance with the invention were commercially available and were used without supplemental purification.

(4) The Amberlyst 15 was commercially available and used without supplemental purification.

(5) The N-methylpyrrolidone, denoted NMP in the examples, used as a solvent, was commercially available and used without supplemental purification.

(6) For Examples 1 and 2 for the preparation of the catalysts from the thiourea family, the molar yield of thiourea was calculated by the ratio between the number of moles of thiourea obtained and the number of moles of isothiocyanate employed.

(7) For Examples 3 to 8 for the transformation of sugars into 5-HMF, the molar yield of 5-HMF was calculated by the ratio between the number of moles of 5-HMF obtained and the number of moles of sugar feed employed.

Example 1: Preparation of the Organic Catalyst Thiourea 1

(8) 3,5-trifluoromethylphenyl isothiocyanate (1.485 g, 5.5 mmol) and cyclohexamine (0.595 g, 6 mmol) were dissolved in anhydrous dichloromethane and the reaction medium was stirred overnight at ambient temperature. The solvent was then evaporated off under vacuum and the unrefined product obtained was purified by chromatography on a silica column, the mobile phase being a CH.sub.2Cl.sub.2/MeOH gradient. The mass of thiourea 1 obtained was 0.83 g. The molar yield corresponding to thiourea 1 was 41% after purification.

(9) Empirical formula: C.sub.15H.sub.16F.sub.6N.sub.2S; Molecular weight: 370.09 g.Math.mol.sup.1

(10) .sup.1H NMR ( (ppm), (CD.sub.3).sub.2CO, 300 MHz) 8.29 (s, 2H), 7.67 (s, 1H), 4.35-4.15 (m, 1H), 1.81-1.54 (m, 4H), 1.45-1.08 (m, 6H)

Example 2: Preparation of Organic Catalyst Thiourea 2

(11) Phenyl isothiocyanate (0.564 g, 4.17 mmol) and p-anisidine (0.510 g, 4.14 mmol) were dissolved in anhydrous dichloromethane and the reaction medium was stirred overnight at ambient temperature. The solvent was then evaporated off under vacuum and the unrefined product obtained was purified by recrystallization from an EtOH/acetone mixture. The mass of thiourea 2 obtained was 0.48 g. The molar yield corresponding to thiourea 2 was 45% after purification

(12) Empirical formula: C.sub.14H.sub.14N.sub.2OS; Molecular weight: 258.05 g.Math.mol.sup.1

(13) .sup.1H NMR ( (ppm), (CD.sub.3).sub.2CO, 300 MHz) 8.86 (br.s, 1H), 7.54-7.52 (m, 1H), 7.40-7.30 (m, 4H), 7.17-7.13 (m, 1H), 6.94-6.89 (m, 2H), 3.80 (s, 3H).

Example 3: Transformation of Fructose Using the Organic Catalyst Thiourea 1 (in Accordance with the Invention)

(14) The catalyst from Example 1 (0.046 g, 0.12 mmol) was added to a solution of fructose (2.0 g, 11.10 mmol) in NMP (20 g). The feed/catalyst weight ratio was 43.5. The solvent/feed weight ratio was 10. The reaction medium was then stirred at 120 C. for 6 h. The conversion of fructose to 5-HMF was followed by regularly removing an aliquot of solution which was instantly cooled to 0 C., re-dissolved in water and checked by ion chromatography. The 5-HMF yield after 6 h was 55%.

Example 4: Transformation of Fructose Using the Organic Catalyst Thiourea 2 (in Accordance with the Invention)

(15) The catalyst from Example 2 (0.044 g, 0.17 mmol) was added to a solution of fructose (2.0 g, 11.10 mmol) in NMP (20 g). The feed/catalyst weight ratio was 45.5. The solvent/feed weight ratio was 10. The reaction medium was then stirred at 120 C. for 6 h. The conversion of fructose to 5-HMF was followed by regularly removing an aliquot of solution which was instantly cooled to 0 C., re-dissolved in water and checked by ion chromatography. The 5-HMF yield after 6 h was 59%.

Example 5: Transformation of a Mixture of Glucose and Fructose Using the Organic Catalyst Thiourea 1 (in Accordance with the Invention)

(16) The catalyst from Example 1 (0.046 g, 0.12 mmol) was added to a 50% by weight/50% by weight mixture of fructose and glucose (2.0 g, 11.10 mmol) in NMP (20 g). The feed/catalyst weight ratio was 43.5. The solvent/feed weight ratio was 10. The reaction medium was then stirred at 120 C. for 6 h. The conversion of fructose to 5-HMF was followed by regularly removing an aliquot of solution which was instantly cooled to 0 C., re-dissolved in water and checked by ion chromatography. The 5-HMF yield after 6 h was 58%.

Example 6: Transformation of a Mixture of Glucose and Fructose Using the Organic Catalyst Thiourea 2 (in Accordance with the Invention)

(17) The catalyst from Example 2 (0.044 g, 0.17 mmol) was added to a 50% by weight/50% by weight mixture of fructose and glucose (2.0 g, 11.10 mmol) in NMP (20 g). The feed/catalyst weight ratio was 45.5. The solvent/feed weight ratio was 10. The reaction medium was then stirred at 120 C. for 6 h. The conversion of fructose to 5-HMF was followed by regularly removing an aliquot of solution which was instantly cooled to 0 C., re-dissolved in water and checked by ion chromatography. The 5-HMF yield after 6 h was 60%.

Example 7, Comparative: Transformation of Fructose without a Catalyst (not in Accordance)

(18) Fructose (2.0 g, 11.10 mmol) was dissolved in NMP (20 g). The solvent/feed weight ratio was 10. The reaction medium was then stirred at 120 C. for 6 h. The conversion of fructose to 5-HMF was followed by regularly removing an aliquot of solution which was instantly cooled to 0 C., re-dissolved in water and checked by ion chromatography. The 5-HMF yield after 6 h was less than 1%.

Example 8, Comparative: Transformation of Fructose Using a Strong and Corrosive Acid Resin (Amberlyst 15) (not in Accordance)

(19) Amberlyst 15 (0.040 g) was added to a solution of fructose (2.0 g, 11.10 mmol) in NMP (20 g). The feed/catalyst weight ratio was 50. The solvent/feed weight ratio was 10. The reaction medium was then stirred at 120 C. for 6 h. The conversion of fructose to 5-HMF was followed by regularly removing an aliquot of solution which was instantly cooled to 0 C., re-dissolved in water and checked by ion chromatography. The 5-HMF yield after 6 h was 45%.

(20) The results showing the yield of 5-HMF from samples taken after 6 hours of reaction are summarized in Table 1. The results showing the change in the 5-HMF yield over the whole of the reaction period are illustrated in FIG. 1.

(21) TABLE-US-00001 TABLE 1 Example Feed Catalyst Time Yield (%) 3 Fructose Thiourea 1 6 h 55 4 Fructose Thiourea 2 6 h 59 5 Glucose + Thiourea 1 6 h 58 Fructose 6 Glucose + Thiourea 2 6 h 60 Fructose 7 Fructose No catalyst 6 h <1% 8 Fructose Amberlyst 6 h 45

(22) The reaction kinetics were faster and the 5-HMF yield was higher in the case in which low acidity organic catalysts from the thiourea family in accordance with the invention were used, compared with a strong sulphonic acid such as Amberlyst 15, namely approximately 60% molar yield of 5-HMF in the presence of thioureas, as opposed to 45% for the strong acid resin Amberlyst 15 after 6 hours of reaction.

(23) Thus, it appears that, unexpectedly considering the low acidity, non-corrosive and non-toxic nature of thioureas, it is significantly more advantageous to use the organic catalysts in accordance with the invention compared with a strong acid resin which is conventionally used for the transformation of sugars into 5-HMF.