HMF preparation catalysed by anolyte fraction

Abstract

The present invention relates to a method for the production of 5-hydroxymethylfurfural (HMF), which converts a fructose-containing component using a catalytically active anolyte fraction, which has been produced by electrolysis of water, at a temperature of 90 to 200° C. and for obtaining an HMF-containing product mixture, wherein advantageously a high HMF selectivity is achieved with significantly lower by-product formation.

Claims

1. A method for the production of 5-hydroxymethylfurfural (HMF) comprising the steps: a) providing a fructose-containing component, b) producing a catalytically active anolyte fraction by electrolysis of water, c) mixing the fructose-containing component and the catalytically active anolyte fraction to obtain a reaction solution, d) converting the fructose present in the reaction solution to HMF at a temperature of 90° C. to 200° C. to obtain a liquid HMF-containing product mixture, and e) obtaining a liquid HMF-containing product mixture.

2. The method of claim 1, wherein the water for the electrolysis is fully demineralized water.

3. The method of claim 1, wherein the water for the electrolysis comprises a salt selected from the group consisting of alkaline halides, alkaline earth halides, alkaline nitrates, alkaline earth nitrates, alkaline sulfates, alkaline earth sulfates, citrates, acetates, tartrates, oxalates, glycolates, gluconates and mixtures thereof.

4. The method according to claim 3, wherein the water for the electrolysis comprises 0.01 to 2.5 wt.-% of salt (based on the total weight of the water).

5. The method according to claim 1, wherein the pH of the catalytically active anolyte fraction is 1.5 to 4.5.

6. The method according to claim 1, wherein the fructose-containing component is a solid fructose-containing component or a liquid fructose-containing component.

7. The method according to claim 1, wherein in method step c) a reaction solution with a carbohydrate content of 5 to 50 wt.-% (dry matter carbohydrate in relation to the total weight of reaction solution) is obtained and used in method step d).

8. The method according to claim 1, wherein in method step c) a reaction solution with a fructose content of 40 to 100 wt.-% (dry matter fructose in relation to dry matter of the carbohydrate content of the reaction solution) is obtained and used in method step d).

9. The method according to claim 1, wherein the ratio of the carbohydrate content (dry matter) of the fructose-containing component to the catalytically active anolyte fraction (total weight) in the reaction solution is 0.01-2.5.

10. The method according to claim 1, wherein the ratio of fructose content (DM) of the fructose-containing component to catalytically active anolyte fraction (total weight) in the reaction solution is 0.01-2.5.

11. The method according to claim 1, wherein the fructose-containing component provided in step a), the anolyte fraction or both are set to a temperature of 90° C. to 200° C. before step c) or wherein the reaction solution obtained in step c) is set to a temperature of 90° C. to 200° C.

12. The method according to claim 1, wherein the process is carried out such that a fructose conversion of 1 to 50 mol-% is achieved in method step d).

13. The method according to claim 1, wherein the method is set so that in method step d) an HMF selectivity of 60 to 100 mol-% is obtained.

14. The method according to claim 1, wherein the method is carried out continuously.

15. The method according to claim 1, wherein apart from the catalytically active anolyte fraction, no further catalytically active component is used in the process.

16. The method according to claim 1, comprising the following step: f) cooling the liquid HMF product mixture to a temperature of 20 to 80° C.

17. The method according to claim 1, comprising the following step: g) filtration, decolorization and/or purification of the liquid HMF product mixture.

18. The method according to claim 1, comprising the following step: h) setting the liquid HMF product mixture to a dry matter content of 20 to 70 wt.-%.

19. The method according to claim 1, comprising the following steps: i) purification of the liquid HMF product mixture using chromatography, ultra- and/or nanofiltration, extraction with a suitable extractant, adsorption on a suitable material and subsequent targeted desorption and/or electrodialysis to separate at least one HMF fraction, and j) obtaining at least one HMF fraction.

20. The method according to claim 19, wherein the liquid HMF product mixture is separated in step i) using chromatography into at least four fractions comprising an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction and in step j) at least an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction is obtained.

21. The method according to claim 20, wherein the fructose fraction obtained in method step j) is recycled into step a).

22. The method according to claim 20, wherein the glucose fraction obtained in method step j) is used for the production of ethanol.

23. The method according to any of claim 20, wherein the organic acid fraction obtained in method step j) is used to isolate levulinic and formic acid.

24. The method according to claim 19, wherein the HMF fraction obtained in method step j) is oxidized directly and is oxidized in a further step to 2,5-furandicarboxylic acid (FDCA) without the need for further purification.

25. The method according to claim 1, wherein the pH of the catalytically active anolyte fraction is 2 to 3.

26. The method according to claim 1, wherein the fructose-containing component is fructose, a fructose syrup or a fructose solution.

Description

(1) The figures show:

(2) FIG. 1 is a schematic representation of the reactor system used according to the invention.

(3) FIG. 2 is a schematic representation of the method according to the invention, wherein the components provided in step a) are initially mixed in step b) and the reaction solution obtained is subsequently heated and an HMF fraction is obtained after the purification step h) (step i)).

(4) FIG. 3 is a schematic representation of the method according to the invention analogous to FIG. 2, wherein in step h) a column chromatographic separation is carried out and an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction is obtained (step i)).

(5) FIG. 4 is a schematic representation of the method according to the invention, wherein the components provided in step a) are heated separately from one another and are only subsequently mixed in step b) to obtain a reaction solution, and wherein an HMF fraction is obtained after purification step h) (step i)).

(6) FIG. 5 is a schematic representation of the method according to the invention analogous to FIG. 4, wherein a column chromatographic separation is carried out in step h) and an HMF fraction, a glucose fraction, a fructose fraction and an organic acid fraction is obtained (step i)).

EXAMPLES

(7) In the method according to the invention, a fructose-containing component which has a variable ratio of fructose to glucose and a catalytically active anolyte fraction are used as starting materials. The catalytically active anolyte fraction is produced in a water ionizer (Titanion SE Ultra) from deionized water mixed with the appropriate electrolyte. The fructose-containing component is mixed with the catalytically active anolyte fraction so that a reaction solution with a dry matter content of 20 to 40 wt.-% (DM carbohydrate based on the total weight of the reaction solution) is obtained. The reaction solution obtained in this way is pumped into the heated “heating zone” of the tubular reactor (outer diameter 8 mm, inner diameter 6 mm, length 630 mm) with the aid of an HPLC pump and is converted there. The tubular reactor is designed as a double-tube counterflow heat exchanger, wherein the temperature is controlled by means of a thermal oil in the outer jacket. The thermal oil is tempered by means of a thermostat. After the “heating zone” there is a direct transition to the “cooling zone.” This is also designed as a double-tube heat exchanger in counterflow (outer diameter of the product-carrying tube 8 mm, inner diameter 6 mm, length 125 mm). The reaction solution is cooled to room temperature within the “cooling zone” and the conversion is stopped. The product mixture is then filtered through a metal sintered filter (pore size 7 μm) and any insoluble humic substances that may have formed are removed. The pressure in the reactor system is set with the aid of a pressure holding valve so that boiling of the reaction solution and thus the occurrence of vapor bubbles is avoided (approx. 1 MPa at 180° C.).

(8) The following examples show the implementation of the method according to the invention with different fructose-containing components, differently prepared catalytically active anolyte fractions, different DM contents and at different temperatures.

(9) In all experiments, samples were taken during the test and analyzed by means of HPLC (BIORAD Aminex 87-H, 5 mmol/l sulfuric acid, 50° C.). The fructose conversion, HMF selectivity and the balance were then calculated from the analytical results (balance=(total of unconverted sugar, HMF and formic acid (in mol)*100/sugar used (in mol)). Levulinic acid is not taken into account in the balance, since one molecule of formic acid and one molecule of levulinic acid are produced from one molecule of HMF.

Example 1: HMF Synthesis with Catalytically Active Anolyte Fraction Based on 0.18% NaCl at 170° C. (MMR 112)

(10) A fructose syrup with 95% fructose purity and a DM content of 70% was used as the fructose-containing component. The catalytically active anolyte fraction was produced from an electrolyte solution which contained 0.18 wt.-% of sodium chloride and which had a pH of 2.3. The fructose syrup was diluted with the catalytically active anolyte fraction to a DM content of 20% DM carbohydrate. This reaction solution was then converted with a residence time of 5.6 min in the heating zone at a temperature of 170° C. (temperature of the thermal oil).

(11) Fructose conversion: 31.6%

(12) HMF selectivity: 81.2%

(13) Formic acid selectivity: 4.5%

(14) Levulinic acid selectivity: 2.3%

(15) Balance: 96%

Example 2: HMF Synthesis with Catalytically Active Anolyte Fraction Based on 0.625% NaCl at 170° C. (MMR 114)

(16) A fructose syrup with 95% fructose purity and a DM content of 70% was used as the fructose-containing component. The catalytically active anolyte fraction was produced from an electrolyte solution which contained 0.625 wt.-% of sodium chloride and which had a pH of 2.3. The fructose syrup was diluted with the catalytically active anolyte fraction to a DM content of 20%/c DM carbohydrate. This reaction solution was then converted with a residence time of 5.6 min in the heating zone at a temperature of 170° C. (temperature of the thermal oil).

(17) Fructose conversion: 35.0%

(18) HMF selectivity: 80.6%

(19) Formic acid selectivity: 5.2%

(20) Levulinic acid selectivity: 2.3%

(21) Balance: 95.6%

Example 3: HMF Synthesis with Catalytically Active Anolyte Fraction Based on 1% NaNO.SUB.3 .at 165° C. (MMR 117)

(22) A fructose syrup with 95% fructose purity and a DM content of 70% was used as the fructose-containing component. The catalytically active anolyte fraction was produced from an electrolyte solution which contained 1.0 wt.-% of sodium nitrate and which had a pH of 2.2. The fructose syrup was diluted with the catalytically active anolyte fraction to a DM content of 20% DM carbohydrate. This reaction solution was then converted with a residence time of 5.6 min in the heating zone at a temperature of 165° C. (temperature of the thermal oil).

(23) Fructose conversion: 19.97%

(24) HMF selectivity: 81.8%

(25) Formic acid selectivity: 2.9%

(26) Levulinic acid selectivity: 1.6%

(27) Balance: 97.23%

Example 4: HMF Synthesis with Catalytically Active Anolyte Fraction Based on 0.25% NaNO.SUB.3 .at 165° C. (MMR 117/2)

(28) A fructose syrup with 95% fructose purity and a DM content of 70% was used as the fructose-containing component. The catalytically active anolyte fraction was produced from an electrolyte solution which contained 0.25 wt.-% of sodium nitrate and which had a pH of 2.2. The fructose syrup was diluted with the catalytically active anolyte fraction to a DM content of 20% DM carbohydrate. This reaction solution was then converted with a residence time of 5.6 min in the heating zone at a temperature of 165° C. (temperature of the thermal oil).

(29) Fructose conversion: 16.5%

(30) HMF selectivity: 86.5%

(31) Formic acid selectivity: 3.1%

(32) Levulinic acid selectivity: 1.5%

(33) Balance: 98.6%

Example 5: HMF Synthesis with Catalytically Active Anolyte Fraction Based on 0.18% NaCl at 165° C. with 30% DM (MMR 137)

(34) A fructose syrup with 85% fructose purity and a DM content of 75% was used as the fructose-containing component. The catalytically active anolyte fraction was produced from an electrolyte solution which contained 0.18 wt.-% of sodium chloride and which had a pH of 2.3. The fructose syrup was diluted with the catalytically active anolyte fraction to a DM content of 30% DM carbohydrate. This reaction solution was then converted with a residence time of 5.6 min in the heating zone at a temperature of 165° C. (temperature of the thermal oil).

(35) Fructose conversion: 17.6%

(36) HMF selectivity: 88.2%

(37) Formic acid selectivity: 4.7%

(38) Levulinic acid selectivity: 2.1%

(39) Balance: 97.9%

Example 6: HMF Synthesis with Catalytically Active Anolyte Fraction Based on 0.18% NaCl at 165° C. with 40% DM (MMR 136)

(40) A fructose syrup with 85% fructose purity and a DM content of 75% was used as the fructose-containing component. The catalytically active anolyte fraction was produced from an electrolyte solution which contained 0.18 wt.-% of sodium chloride and which had a pH of 2.3. The fructose syrup was diluted with the catalytically active anolyte fraction to a DM content of 40% DM carbohydrate. This reaction solution was then converted with a residence time of 5.6 min in the heating zone at a temperature of 165° C. (temperature of the thermal oil).

(41) Fructose conversion: 15.5%

(42) HMF selectivity: 89.7%

(43) Formic acid selectivity: 5.5%

(44) Levulinic acid selectivity: 1.6%

(45) Balance: 98.2%

Example 7: Influence of the Fructose Purity on the HMF Selectivity in the HMF Synthesis with Catalytically Active Anolyte Fraction

(46) The fructose-containing components were fructose solutions with different fructose puritys (62%, 70%, 80%, 85%, 90% and 100%) and with a DM content of 30% in a catalytically active anolyte fraction. The catalytically active anolyte fraction was produced from an electrolyte solution which contained 0.18 wt.-% of sodium chloride and which had a pH of 2.3. These reaction solutions were then each converted with a residence time of 5.6 min in the heating zone at a temperature of 165° C. (temperature of the thermal oil).

(47) TABLE-US-00001 Fructose Fructose HMF- Formic acid Levulinic acid unit conversion Selectivity selectivity selectivity Balance [%] [%] [%] [%] [%] [%] 62 17.8 89.3 5.8 1.5 96.2 70 18.3 89.0 3.9 1.4 97.5 80 18.2 88.5 3.0 1.6 98.4 85 17.9 88.3 4.7 2.0 97.9 90 17.8 83.8 2.4 1.1 97.9 95 18.0 81.2 2.8 1.4 97.9 100 18.1 80.1 3.1 1.7 97.6

(48) As the purity of the fructose increases, the selectivity to HMF deteriorates with the same conversion.

Example 8: Influence of the Cation in the Production of the Catalyticaly Active Anolyte Fraction on the HMF Selectivity in the HMF Synthesis

(49) A fructose syrup with a fructose purity of 85% and a DM content of 75% was used as the fructose-containing component. This syrup was diluted with a catalytically active anolyte fraction based on various chloride salts (lithium, sodium, potassium chloride, each 0.18 wt.-%) to a dry matter content of 30% carbohydrate.

(50) These reaction solutions were then each converted with a residence time of 5.6 min in the heating zone at a temperature of 165° C. (temperature of the thermal oil).

(51) TABLE-US-00002 pH Chloride value content catalyt- catalyt- ically ically Fruc- Formic Levulinic active active tose HMF- acid acid anolyte anolyte conver- Selec- selec- selec- Bal- Electro- fraction fraction sion tivity tivity tivity ance lyte [-] [mg/l] [%] [%] [%] [%] [%] LiCl 2.2 1101 17.9 87.9 4.7 2.0 97.7 NaCl 2.3 793 17.6 88.2 4.7 2.1 97.9 KCl 2.3 645 17.2 86.8 2.9 1.1 97.9

Example 9: Comparative Experiment with 0.75% H.SUB.2.SO.SUB.4 .(without Catalytically Active Anolyte Fraction, State of the Art) at 135° C. and 30% DM (MMR 149)

(52) A fructose syrup with a fructose purity of 85% and a DM content of 75% was used as the fructose-containing component. This syrup was set to a dry matter content of 30% carbohydrate with deionized water and treated with 0.75% sulfuric acid.

(53) This reaction solution was then converted with a residence time of 5.6 min in the heating zone at a temperature of 135° C. (temperature of the thermal oil).

(54) Fructose conversion: 20.0%

(55) HMF selectivity: 73.2%

(56) Formic acid selectivity: 9.15%

(57) Balance: 96.1%

Example 10: Influence of the Chloride Concentration on Conversion and HMF Selectivity

(58) A fructose syrup with a fructose purity of 95% and a DM content of 75% was used as the fructose-containing component. This syrup was diluted to a dry matter content of 20% carbohydrate with catalytically active anolyte fractions based on different sodium chloride concentrations in the electrolysis (1.0 wt.-%, 0.625 wt.-%, 0.25 wt.-%, 0.18 wt.-%, 0, 10 wt.-% and 0.05 wt.-%).

(59) These reaction solutions were then each converted with a residence time of 5.6 min in the heating zone at a temperature of 165° C. (temperature of the thermal oil).

(60) TABLE-US-00003 Chloride concentration NaCl in the concentration reaction solution during during the Fructose HMF electrolysis HMB synthesis conversion selectivity Balance [%] [mg/l] [%] [%] [%] 1.0 4683 29.6 86.3 97.3 0.625 3272 30.5 85.1 97.2 0.25 1203 30 86.7 97.3 0.18 993 29.7 84.1 96.0 0.10 408 30.4 79.9 95.2 0.05 326 29.0 80.6 96.1

(61) Fructose conversion and HMF selectivity are largely independent of the chloride concentration over a range.

Example 11: Effect of Electrolysis when Using DI and Tap Water

(62) Within the scope of these experiments, a reaction solution with a dry matter content of 20% based on a fructose syrup with a fructose purity of 85% and an original dry matter content of 75% (F85/75) was prepared. For dilution, firstly pure deionized water or pure tap water was used, and secondly catalytically active anolyte fraction of deionized or tap water formed during the electrolysis was used. The resulting reaction solutions were then reacted in the heating zone with a residence time of 5.6 min at 169° C. Through regular sampling and analysis of the samples by means of HPLC, conversion and selectivities were monitored and a carbon balance was drawn up. Table 1 shows the results obtained.

(63) TABLE-US-00004 TABLE 1 Test 2018MMR2 2018MMR4 2018MMR2 2017MMR166 Dilution Deionized Anolyte Tap Anolyte water water fraction water fraction from from deionized tap water water electrolysis pH value of 4.38 4.2 7.62 2.4 the reaction (pure solution deionized [-] water 6.24) Fructose 2.8 3.2 5.3 9.3 conversion HMF 76.3 84.6 29.2 82.8 selectivity [%] Levulinic 0 0 0 0.98 acid selectivity [%] Formic acid 0 0 4.45 2.47 selectivity Balance [%] 99.4 99.5 98.0 98.5

(64) The results show a clear improvement in terms of both fructose conversion and HMF and byproduct selectivity when using the respective anolyte fraction of deionized water and tap water compared to pure deionized or tap water.

Example 12: Effect of the Anolyte Fraction Concentration on the HMF Conversion

(65) As part of this series of experiments, a catalytically active anolyte fraction was first produced on the basis of a 0.18% sodium chloride solution. Starting from this anolyte fraction (100% anolyte fraction), various dilutions were then made with pure DI water (75% anolyte fraction/25% DI water, 50% anolyte fraction/50% DI water and 25% anolyte fraction/75% DI water). These mixtures were then each used to prepare a reaction solution with a dry matter content of 20% DM based on a fructose syrup with 85% fructose purity and an original dry matter content of 75%, which was then processed under the same reaction conditions (residence time 5.6 min in the heating zone, temperature 169° C.) were converted. Through regular sampling and analysis of the samples by means of HPLC, conversion and selectivities were monitored and a carbon balance was drawn up. Table 2 shows the results obtained.

(66) TABLE-US-00005 TABLE 2 Test 1 2 3 4 Dilution 100% 75% anolyte 50% anolyte 25% anolyte water anolyte fraction/25% fraction/50% fraction/75% fraction deionized deionized deionized water water water pH of the 2.2 2.4 2.6 2.9 reaction solution [-] Fructose 20.1 14.4 10.4 5.2 conversion HMF 87.9 89.0 91.9 100 selectivity [%] Levulinic acid 1.7 1.3 0.9 0 selectivity [%] Formic acid 3.3 1.6 2.2 0 selectivity [%] Balance [%] 97.7 98.1 99.6 100

(67) The results show a clear dependence of both the fructose conversion and the HMF and byproduct selectivities as well as the carbon balance on the concentration of the anolyte fraction. In comparison to pure deionized water or the anolyte fraction of deionized water (see Table 1), all experiments show a clear improvement, in particular with regard to the selectivity.

Example 13: Oxygen Content of Various Anolyte Fractions

(68) Different anolyte fractions were produced and examined with regard to their oxygen content and pH value by means of an oxygen meter 4100e Mettler Toledo. For comparison, the oxygen content of fully demineralized water was determined.

(69) TABLE-US-00006 O.sub.2 content Solution pH Temperature (mg/l) Deionized water 6.24 21.3 9.3 Anolyte fraction 3.0 23.1 19.4 from deionized water Anolyte fraction 2.31 21 2 20.6 from 0.3 wt.-% NaNO.sub.3 Anolyte fraction 1.98 21.5 27.5 from 0.5 wt.-% NaNO.sub.3 Anolyte fraction 1.92 21 2 25.8 from 1.0 wt.-% NaNO.sub.3 Anolyte fraction 1.87 22.2 25.6 from 2.0 wt.-% NaNO.sub.3 Anolyte fraction 2.14 21.5 19.4 from 0.2 wt.-% NaCl Anolyte fraction 1.98 21.6 26.81 from 0.5 wt.-% NaCl Anolyte fraction 2.02 21.4 24.2 from 1.0 wt.-% NaCl

(70) The results shown in the table show that all anolyte fractions have a significantly higher oxygen content than non-electrolyzed, fully deionized water.