TRIPHASIC SYSTEM FOR DIRECT CONVERSION OF SUGARS TO FURANDICARBOXYLIC ACID

Abstract

There is provided a one-pot process for the conversion of sugars to furancarboxylic acids, such as 2,5-furancarboxylic acid (FDCA), in a triphasic system (e.g. water or tetraethylammonium bromide (TEAB)—methyl isobutyl ketone (MIBK)—water). In this reaction setup, sugars are first converted to 5-hydroxymethylfurfural (HMF) in a first phase. Then HMF is then extracted into a second phase and transferred to a third phase of water. In the third phase HMF is converted to the furancarboxylic acid. The overall acid yields obtainable are between about 78% and 50% for conversion from fructose and glucose, respectively. The invention further relates to an apparatus for the triphasic reaction. The apparatus comprises two chambers which allow for the chemically separated reaction of the sugars and the intermediate of the sugars to form the final product in one process. The process according to the invention may be useful for industrial fabrication.

Claims

1. A one-pot method of producing furandicarboxylic acid from carbohydrate, the method comprising: a) reacting the carbohydrate via a dehydration reaction to produce an intermediate in a first solvent phase; b) contacting the first solvent phase with a second solvent phase at a first contact area; c) extracting the intermediate to the second solvent phase; d) contacting the second solvent phase directly with a third solvent phase at a different contact area; c) oxidizing the intermediate to produce the furandicarboxylic acid in the third solvent phase.

2-39. (canceled)

40. The method of claim 1, wherein the carbohydrate is selected from the group consisting of glucose, fructose and cellulose; preferably glucose or fructose; or more preferably, the intermediate is 5-hydroxymethylfurfural; or more preferably, the furandicarboxylic acid is 2,5-furandicarboxylic acid.

41. The method of claim 1, wherein the first solvent phase is tetraethylammonium bromide.

42. The method of claim 1, wherein the first solvent phase is an aqueous solution, preferably comprising NaCl.

43. The method of claim 1, wherein the second solvent phase is selected to allow diffusion of the intermediate through the second solvent phase to the third solvent phase.

44. The method of claim 1, wherein the second solvent phase is selected to at least partially chemically isolate the dehydration step and the oxidation step and is optionally selected to be immiscible with the first solvent phase and the third solvent phase.

45. The method of claim 1, wherein the second solvent phase is capable of dissolving the intermediate.

46. The method of claim 1, wherein the second solvent phase is selected to reduce prevent furandicarboxylic acid from dissolving therein.

47. The method of claim 1, wherein the second solvent phase is an organic solvent, preferably being selected from C.sub.4-6 alkyl alcohol, C.sub.3-8 alkyl ketone and mixtures thereof and most preferably is methyl isobutyl ketone or ethyl methyl ketone.

48. The method of claim 1, wherein the distribution ratio of 5-hydroxymethylfurfural in the first solvent phase and the second solvent phase is more than about 0.1, and preferably about 1.5 to about 3.5.

49. The method of claim 1, wherein the third solvent phase is capable of dissolving furandicarboxylic acid.

50. The method of claim 1, wherein the third solvent phase is an aqueous solution which optionally comprises sodium carbonate.

51. The method of claim 1, wherein the oxidation step is carried out in the presence of oxygen and a catalytic system, wherein the catalytic system is preferably a supported catalytic system comprising gold-palladium/hydrotalcite and more preferably Au.sub.8Pd.sub.2/hydrotalcite.

52. The method of claim 1, wherein the oxidation step is conducted at a temperature of about 95° C. and optionally comprises converting the intermediate in the third solvent phase to a second intermediate, preferably 5-hydroxymethyl-2-furancarboxylic acid, which is optionally converted to furandicarboxylic acid in the third solvent phase.

53. The method of claim 1, wherein the carbohydrate is glucose and wherein the dehydration step is carried out in the presence of a catalytic system comprising an acidic ion exchange resin and CrCl.sub.3 and is optionally conducted at a temperature of about 90° C. to about 100° C.; or is further optionally conducted at a temperature of about 110° C. to about 130° C.

54. The method of claim 1, wherein the carbohydrate is fructose and wherein the dehydration step is carried out in the presence of a catalytic system comprising an acidic ion exchange resin.

55. An apparatus for use in converting carbohydrate into furandicarboxylic acid in a one-pot process, the apparatus comprising: a first chamber, which is preferably cylindrical in shape, fluidly connected to a second chamber, which is preferably cylindrical in shape and preferably of the same dimension as the first chamber, by a conduit, wherein the first chamber comprises a dividing means, which preferably has a height of about 10% to about 50% of the height of the first chamber, to at least partially separate the first chamber into a first subzone and a second subzone, wherein the first subzone defines a first reaction zone for producing an intermediate from the carbohydrate and the second chamber defines a second reaction zone for producing furandicarboxylic acid from the intermediate, wherein the conduit, the dividing means and the second subzone are configured to at least partially chemically isolate the first and second reaction zones and wherein optionally the dividing means extends from the base of the first chamber.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0072] The accompanying drawings illustrate a disclosed embodiment and serve to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition or the limitation of the invention.

[0073] FIG. 1 shows a reaction scheme of the conversion pathway from HMF to FDCA in the water phase.

[0074] FIG. 2 shows an illustration of a triphasic system for the direct conversion of carbohydrates such as sugars to furandicarboxylic acid such as FDCA.

[0075] FIG. 3 shows schematic illustrations of examples of triphasic reactors.

[0076] FIG. 4 shows (a) a photograph of the triphasic reaction setup in Example 2a, (b) the obtained FDCA yield vs. reaction time, (c) the HPLC detection results for the reaction in phase III after 5 h, 10 h, 20 h and 30 h, and (d) the HPLC detection results for the reaction in phase III after 5 h.

[0077] FIG. 5 shows in (a) a schematic design of an apparatus in accordance with an embodiment of the present disclosure, and (b) a photograph of the apparatuses used in the examples.

[0078] FIG. 6 shows the TEM and XRD of a prepared Au.sub.8Pd.sub.2/HT catalyst used in the examples.

[0079] FIG. 7 shows a .sup.1H NMR spectrum of isolated FDCA product prepared from Example 2a.

EXAMPLES

[0080] Non-limiting examples of the invention and a comparative example will be further described in greater detail, which should not be construed as in any way limiting the scope of the invention.

[0081] Materials:

[0082] The carbohydrates used in the examples were D-Glucose and D-Fructose from Alfa Aesar (Massachusetts, USA). TEAB, HMF, FDCA, and Amberlyst®-15 were purchased from Sigma-Aldrich (Missouri, USA). MIBK was purchased from Merck (New Jersey, USA).

[0083] All the chemicals were used directly without any pre-treatment.

[0084] Product Analysis:

[0085] In the examples, HMF and FDCA were analyzed by HPLC (Agilent Technologies, California, USA, 1200 series) and confirmed with isolation yield. HPLC working conditions were column (Agilent Hi-Plex H, 7.7×300 mm, 8 μm), solvent 10 mM H.sub.2SO.sub.4, flow rate 0.7 ml/min, 25° C., UV detector, 280 nm for HMF and 254 nm for FDCA. The retention times for detected compounds were 20.7 min, 24.4 min, 29.4 min and 36.5 min for FDCA, HFCA, FFCA and HMF, respectively. Fructose and glucose were measured using a Sugar Analyzer (DKK-TOA Corporation, Japan. Model: SU-300).

[0086] Characterization:

[0087] In the examples, the product was characterized by .sup.1H and .sup.13C NMR (Bruker, Massachusetts, USA, AV-400). The Au.sub.8Pd.sub.2/HT catalyst was characterized by TEM (FEI Tecnai F20) and XRD (PANalytical x-ray diffractometer, X'pert PRO, with Cu Kα radiation at 1.5406 Angstroem). The TEM and XRD characterization results of the Au.sub.8Pd.sub.2/HT catalyst are shown in FIG. 6.

Example 1

[0088] The Au.sub.8Pd.sub.2/HT catalyst was prepared in this example.

[0089] Au.sub.8Pd.sub.2/HT was prepared according to a known method (G. S. T. Yi, S. P.; Li, X. K.; Zhang, Y. G., ChemSusChem 2014).

[0090] 0.1 mmol of HAuCl.sub.4 and 0.025 mmol of NaPdCl.sub.4 were dissolved in 40 ml of water. To this solution, 1 g of hydrotalcite was added, followed by addition of NH.sub.3 aqueous solution (29.5%, 0.425 ml) until pH=10. The solution was vigorously stirred for 6 h and refluxed for 30 min at 373 K. The resulting solid was filtered, washed thoroughly with water and heated at 473 K overnight.

Example 2a

[0091] A one-pot conversion of fructose to FDCA in a triphasic reactor (shown in FIG. 5b) was conducted in this example. A photograph of the triphasic reaction setup with reactants used in this example is shown in FIG. 4a.

[0092] 0.18 g fructose (1 mmol), 0.91 g TEAB, 0.09 ml water, and 0.018 g smashed amberlyst-15 were added to phase I of the reactor. The reactor was pre-heated to 95° C. and stirred with a magnetic stirrer to melt and mix all the reactants.

[0093] 0.25 g Au.sub.8Pd.sub.2/HT catalyst, 0.106 g of Na.sub.2CO.sub.3 (1 mmol), and 10 ml of water were added to the other side of the reactor (phase III).

[0094] 4 ml of MIBK was added on top of phase I and phase III.

[0095] The reactor was put in an oil bath pre-heated to 95° C.

[0096] Oxygen gas was bubbled into phase III during the reaction, with water added if the water level decreased. Every 5 hours, an aliquot of solution was taken out from phase III (right chamber shown in FIG. 4a) for HPLC analysis. The reaction was conducted for 30 hours. FIG. 4b shows the FDCA yield versus reaction time. For the first 10 hours, FDCA yield increased almost linearly over time. The FDCA yield topped at 20 hours with 78% FDCA overall yield. Thereafter, the FDCA yield decreased slowly at the 25-hour and 30-hour points, which may due to the degradation of FDCA over prolonged reaction time.

[0097] The FDCA product was isolated and analysed in Na.sub.2CO.sub.3 by .sup.1H NMR and the characterization results are shown in FIG. 7.

[0098] The reaction progress of the triphasic system was also monitored by analysis of the FDCA yield in phase III with HPLC. As shown in FIG. 4c, the FDCA yield gradually increased from 5 hours to 20 hours and reached a maximum yield of 78% at 20 hours.

[0099] As shown in FIG. 4d, after 5 hours of reaction in phase III, only HFCA (retention time at 24 min) and FDCA (retention time at 21 min) could be detected. Almost no HMF was observed (HMF retention at 37 min). As expected, a high content of HMF was detected only in MIBK (phase II) and TEAB (phase I) (results not shown). This indicates that the conversion of HMF to FDCA is via the HFCA intermediate (as shown in FIG. 1), and the conversion from HMF to HFCA is fast. Once HMF was diffused to phase III, it was quickly converted to HFCA, and then converted to FDCA.

Example 2b

[0100] To study the kinetic process in the triphasic reactor of Example 2a, a step-by-step reaction was conducted, using the same amounts of chemicals as in Example 2a.

[0101] Firstly, the conversion of fructose to HMF in TEAB was carried out according to a known method (S. P. Simeonov, J. A. S. Coelho, C. A. M. Afonso, ChemSusChem 2012, 5, 1388-1391) but modified by using a lower reaction temperature of 95° C. This is in the consideration of the reaction in phase III, where the optimized reaction temperature is 95° C.

[0102] The conversion of fructose to HMF in TEAB was a fast reaction. It was completed after 30 min with HMF yield of 86% in this example.

[0103] The reaction was then upgraded to a bi-phasic system, with 4 ml of MIBK added on top as an extraction layer. TEAB is immiscible with MIBK and thus, a clear interface between TEAB and MIBK was maintained during the reaction. After 30 min reaction at 95° C., for 1 mmol of fructose, 0.6 mmol of HMF was detected in TEAB, and 0.22 mmol of HMF in MIBK. The HMF distribution ratio between MIBK and TEAB was therefore about 1:2.7.

[0104] Separately, the conversion of HMF (prepared from fructose) to FDCA was conducted in 10 ml water, with 0.25 g of Au.sub.8Pd.sub.2/HT catalyst and 1 mmol Na.sub.2CO.sub.3. The reaction was conducted at 95° C. with O.sub.2 bubbling and was completed in 7 hours with almost quantitative yield of FDCA.

[0105] As described above and in FIG. 4b, the whole process from fructose to FDCA was completed at nearly 20 hours, with a total yield of 78% FDCA. This indicates that the mass transfer of HMF from phase I to phase III via MIBK was the bottle neck, which slowed down the whole process.

Example 3

[0106] In this example, the conversion of glucose to FDCA was performed. The direct conversion of glucose to FDCA in a triphasic reactor is more challenging than the conversion of fructose to FDCA, as glucose needs to be isomerized to fructose.

[0107] In the triphasic reactor (shown in FIG. 5b), 0.18 g glucose (1 mmol), 0.91 g TEAB, 0.09 ml water, 0.018 g smashed amberlyst-15 and 0.0266 g CrCl.sub.3.6H.sub.2O (0.1 mmol) were added to phase I of the reactor to convert glucose to HMF. TEAB was used as the reaction media and amberlyst-15/CrCl.sub.3 was selected as catalysts.

[0108] Phase I was initially conducted at 95° C. However, after 7 hours of reaction, only negligible amount of FDCA was detected, with the glucose conversion at only 7.2%. The low glucose conversion may due to the low reaction temperature in phase I.

[0109] The reaction in phase I was improved upon by conducting the reaction at 120° C. for 30 min. To achieve this, the triphasic reactor setup was tilted to heat only the phase I chamber of the reactor. After that, the temperature was lowered down to 95° C., and the whole reactor was heated in the same oil bath.

[0110] 0.25 g Au.sub.8Pd.sub.2/HT catalyst, 0.106 g of Na.sub.2CO.sub.3 (1 mmol), and 10 ml of water were used in the other side of reactor (phase III).

[0111] 4 ml of MIBK was added on top of phase I and phase III.

[0112] Oxygen was bubbled in reactor III during the reaction, with water added if the water level decreased.

[0113] In this example, 50.2% of FDCA yield was achieved with a full conversion of glucose. The results are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Entry Reactiontime (h) HFCA yield (%) FDCA yield (%) 1 10 28.2 26.1 2 20 17.0 42.9 3 30 6.6 50.2 4 40 3.4 49.6 5 50 0.9 48.4

Example 4

[0114] In this example, in the conversion of fructose to FDCA, saturated NaCl aqueous solution was used as the reaction media in phase I of the triphasic system.

[0115] The reaction conditions used were 0.18 g fructose, 0.6 ml 0.25 M HCl (NaCl saturated), 4 ml MIBK, 0.1 g Au—Pd/HT, 10 ml H.sub.2O and 1 mmol Na.sub.2CO.sub.3.

[0116] The reaction was conducted at 95° C. and an overall FDCA yield of 41% was achieved, as shown below in Table 2.

TABLE-US-00002 TABLE 2 Entry Reaction time (h) HFCA yield (%) FDCA yield (%) 1 5 13.3 12 2 10 14.8 26 3 20 2.9 41 4 30 0.9 38

[0117] In conclusion, a triphasic reactor that can convert sugars to FDCA in one-pot has been demonstrated. Overall FDCA yields of 78% and 50% were achieved with fructose and glucose feedstock, respectively. Kinetic studies showed that the phase transfer of HMF from phase I to phase III was the main bottle neck which slowed down the overall reaction.

INDUSTRIAL APPLICABILITY

[0118] The one pot method of the invention may be useful as a method to convert sugars to furandicarboxylic acid. The high yield obtained in a simplified set-up may have a use for commercial production of furandicarboxylic acids derived from biomass. 2,5-furandicarboxylic acid can be made which has numerous applications as mentioned in the background section. An improved new apparatus has been further disclosed which allows for running the one pot process with good phase separation.

[0119] It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.