PROCESS FOR THE PRODUCTION AND SEPARATION OF 5-HYDROXYMETHYLFURFURAL WITH QUATERNARY AMMONIUM SALTS

Abstract

The present invention relates to a process for the production and separation of 5-hydroxymethylfurfural (HMF) comprising the steps of: (1) dehydrating at least one saccharide selected from the group consisting of monosaccharides having 6 carbon atoms and disaccharides, oligosaccharides and polysaccharides formed from units having 6 carbon atoms or mixtures thereof, in the presence of water and of at least one quaternary ammonium salt, at a temperature between 80-130° C., obtaining a reaction mixture comprising the quaternary ammonium salt, HMF and any unreacted saccharide; and (2) subjecting the said reaction mixture to at least one membrane separation operation selected in the group consisting of nanofiltration, reverse osmosis, electrodialisis and their combinations, obtaining an aqueous permeate comprising HMF and a retentate comprising quaternary ammonium salt, wherein both the dehydration of step (1) and the separation operations of step (2) are carried out in the absence of organic solvents.

Claims

1. A process for the production and separation of 5-hydroxymethylfurfural (HMF), which is carried out in the absence of an organic solvent, the process comprising the steps of: 1) dehydrating at least one saccharide selected from the group consisting of monosaccharides having 6 carbon atoms and disaccharides, oligosaccharides and polysaccharides formed from units having 6 carbon atoms or mixtures thereof, in the presence of water and of at least one quaternary ammonium salt, at a temperature between 80-130° C., obtaining a reaction mixture comprising the quaternary ammonium salt, HMF and any unreacted saccharide; 2) subjecting the said reaction mixture to at least one membrane separation operation selected in the group consisting of nanofiltration, reverse osmosis, electrodialisis and their combinations, obtaining an aqueous permeate comprising HMF and a retentate comprising quaternary ammonium salt.

2. The process according to claim 1, wherein step 2) comprises one or more nanofiltration operations.

3. The process according to claim 1, wherein said process comprises, before step 2), a preliminary purification step for the removal of high molecular weight compounds.

4. The process according to claim 3, wherein in the said preliminary purification step comprises one or more operations selected from: decantation, centrifugation, microfiltration or ultrafiltration.

5. The process according to claim 1, comprising, at the end of step 1) and before separation step 2) a step of diluting the reaction mixture with water.

6. The process according to claim 1, wherein said quaternary ammonium salt has formula R3R′N+X−, wherein: R, equal or different, represents a substituted or unsubstituted C1-C16 alkyl group; R′ belongs to the group consisting of: hydrogen, substituted or unsubstituted C1-C16 alkyl group, substituted or unsubstituted monocyclic aryl group; X− represents an anion selected from chloride, bromide, iodide, fluoride, hydroxide, BF4− and PF6.

7. The process according to claim 1, wherein said quaternary ammonium salt has a molecular mass equal to or greater than 220 g/mol.

8. The process according to claim 7, wherein said membrane of step 2) is a nanofiltration membrane.

9. The process according to claim 1, wherein the weight ratio between quaternary ammonium salt and saccharide at the beginning of step 1) is less than 5:1.

10. The process according to claim 1, wherein said saccharide is fructose and, at the beginning of step 1), water is present in amounts less than 10% by weight with respect to the sum of quaternary ammonium salt and fructose.

11. The process according to claim 1, wherein step 1) is carried out in the presence of an acid catalyst.

12. The process according to claim 1, wherein the reaction time of step 1) is comprised from 1 minute and 240 minutes.

13. A composition of HMF having a purity of said HMF of more than 98.5% by weight and comprising at least one quaternary ammonium salt in a quantity, converted into nitrogen atom, of more than 0 and less than 0.25% by weight with respect to the weight of HMF.

14. The composition according to claim 13, wherein said composition further comprises one or more components selected from the group consisting of: organic acids, compounds with at least one keto or aldehyde function (different from HMF), dimers, oligomers and humins, formed as by-products of the reaction of dehydration of the starting saccharides, in a total amount less than 1% by weight with respect to the weight of HMF.

15. The composition according to claim 13, wherein said composition comprises furfural, wherein the weight ratio between furfural and HMF is less than 0.10%.

16. The composition according to claim 13, wherein said composition comprises an amount of fructose that is less than 3% by weight with respect to the weight of HMF.

17. A method comprising: oxidizing the HMF composition according to claim 13 to form 2,5-furandicarboxylic acid.

Description

EXAMPLES

Example 1

[0115] Step 1)

[0116] 350 g of water and 11.5 kg of a quaternary ammonium salt (tetrabutylammonium bromide, TBAB) were progressively added to a vessel having a useful volume of 20 l with a thermostatic jacket and fitted with stirring means, raising the mixture to a temperature of 80° C. 5 kg of fructose were then added. The mixture was heated to 95-100° C. with stirring and 50 g of a 5 M aqueous solution of sulfuric acid was added. The mixture was held at atmospheric pressure for a reaction time of approximately 15 minutes.

[0117] At the end of the reaction the mixture was diluted in water in a ratio of 1:1 by weight (quenching). The quenching product so obtained was analysed by HPLC-UV using a “Phenomenex Gemini NX-C18” 150 mm×3.0 mm×5 μm column (flow: 0.5 mL/min; column temperature: 30° C.) and a 1% by volume aqueous solution of HCOOH (A) and acetonitrile (B) as eluents using the following gradient (Table 1):

TABLE-US-00002 TABLE 1 % vol. % vol. min A B 0 95 5 5 90 10 10 60 40 15 10 90 17 10 90 20 95 5 22 95 5

[0118] The mixture substantially comprised HMF, TBAB, unreacted fructose, water and sulfuric acid. The HMF yield in the mixture obtained at the end of the reaction, determined by HPLC analysis with external calibration, was 83% by weight in comparison with the theoretical obtainable from the starting fructose.

[0119] The quenching product was then further diluted by adding a quantity of water equal to approximately 10 times the weight of the quenching product at ambient temperature. Step 2) The resulting mixture (pH: 3.8) underwent a preliminary ultrafiltration step using a ceramic membrane with pores of 20 nm diameter (nominal cut-off 20,000 Da), at an operating temperature of between 25° C. and 45° C. (membrane surface area: 0.36 m.sup.2; permeate flow: 400 L/h/m.sup.2), with two diafiltration steps following a permeation step.

[0120] The permeate was then sent to a step of nanofiltration using polyamide membrane with a nominal cut-off of 150-300 Da (membrane surface area: 2.4 m.sup.2) at a temperature of between 25° C. and 45° C., applying a pressure of 30 bar (permeate flow: 60-10 L/h/m.sup.2). With two diafiltration steps following a permeation step saline rejection of 99.8% relative to the TBAB was achieved. Finally, the permeate resulting from the nanofiltration step was sent to an osmotic filtration step to concentrate the HMF solution, using a polypiperazine amide seawater membrane (membrane surface area: 2.8 m.sup.2), at an average temperature of 35° C. and a pressure of 30-35 bar (permeate flow: 26-20 L/h/m.sup.2). Through two diafiltration steps following a permeation step a solution of approximately 60.10 g/l of HMF was obtained. HPLC analysis of this solution confirmed a recovery yield of approximately 81.8% of 5-hydroxymethylfurfural with a TBAB concentration of less than 1% by weight.

Example 2

[0121] The procedure in Example 1 was replicated performing the nanofiltration step twice. Before nanofiltration the pH of the permeate obtained from the ultrafiltration step was adjusted to a value of approximately 6.5 through the addition of NaOH.

[0122] At the end of the osmotic filtration step an HMF composition, which when subjected to HPLC-UV analysis as in previous Example 1) showed to be 99.8% pure and have an overall furfural, hydroxymethylketone and levulinic acid content of 0.06% by weight, was obtained.

[0123] Analysis of the composition by IC-CD chromatography yielded a nitrogen content of 0.001% by weight. The nitrogen content was determined stoichiometrically following quantification of the ammonium cation by means of an external standard performing the chromatographic analysis with a Metrosep C4-100 column (100 mm×4.0 mm×5 μm; flow: 1.0 mL/min; column temperature: 30° C.) and, as eluent, a mixture of aqueous nitric acid (7.5 mmol/L) and 20% v/v acetonitrile.

[0124] IC-PAD analysis of the same composition performed using a Metrosep Carb 2 column (250 mm×4.0 mm×5 μm; flow: 0.7 mL/min; column temperature: 30° C.) and isocratic elution of a 200 mM aqueous solution of NaOH revealed a residual fructose content of 0.1%.

Example 3 Comparative

[0125] A preheating and a dehydration reaction were performed in a stirred autoclave, maintaining the same weight ratios between the reactants and according to the same procedure as described in Example 3 of WO 2016/059205. In more detail, 693.8 g of Tetraethylammonium bromide, TEAB) were fed to a batch stirred autoclave with a useful volume of 2 L fitted with an oil thermostatic jacket. In the same autoclave 30.3 g of distilled water were added, setting the temperature of the thermostatic bath to 100° C. When the internal mixture temperature raised up to 85° C., 278.2 g of fructose were charged in the autoclave. During preheating, the charging operations have been realized under nitrogen flow.

[0126] In dehydration step (Step 1 according to the process of WO 2016/059205), at a temperature of 97° C. a slurry consisting of 13.6 g of heterogeneous catalyst (10% HPW/SiO.sub.2) mixed with 25.7 g of water has been charged to the autoclave. The system has been kept at this temperature and pressure for about 5 minutes more. The vacuum has then been applied until 23 mbar to remove water. The reaction time in the autoclave, from the charging of catalyst to drying, was approximately of 68 minutes. The product consisted of HMF, TEAB, unreacted fructose and a water content of 7.13 g.sub.H2O residual/g.sub.HMF (%) H2O.sub.residual/HMF percent weight ratio).

[0127] As in separation step 2) of Example 3 of WO 2016/059205, products obtained in step 1) have been discharged from the reactor and passed to a second stirred vessel (extractor) having a volume of 5 l, held at a temperature of 70° C., to which approximately 2 l of 2-butanone were charged. After 2 h mixing, the organic phase was collected and filtered under vacuum (100-300 mbar) on a sintered glass filter with porosity of 10-16 μm to separate out the solid phase containing the TEAB and fructose from the organic solvent containing the extracted HMF.

[0128] The HMF was then recovered by evaporation of the 2-butanone from the liquid phase. The evaporation was performed at about 65° C. in two steps, the first at 400 mbar and the second at 150 mbar.

[0129] A yield of approximately 89% of HMF having a purity of approximately 98% by weight was obtained.

[0130] Analysis of the HMF composition by IC-CD chromatography yielded a nitrogen content of 1.05% by weight. The nitrogen content was determined stoichiometrically following quantification of the ammonium cation as described above in Example 1 according to the present invention.

Example 4

[0131] Step 1)

[0132] In a batch apparatus of 20 L of volume, about 350 gr of water were heated to a temperature of 90° C. When the temperature of water reached 90° C., about 8 kg of tetraethylammonium bromide (TEAB) were added to the apparatus and mixed with water. At a temperature of 85-90° C., 5 Kg of fructose were added to the mixture and the complete dissolution of TEAB has been observed. Finally, 50 g of a catalytic solution of H2SO4 5M was added to the mixture at a pressure of 1.8 bar and an increase of temperature to 100-103° C. was observed.

[0133] The reaction time was of 15 minutes starting from the adding of catalyst. The HMF in the product was quantified by using the HPLC method described in the example 1.

[0134] At the end of the dehydration reaction the mixture was diluted in water in order to obtain the following composition (pH=2.1): Hydroxymethylfurfural 10% wt and tetraethylammonium bromide (TEAB) 22% wt (i.e. the weight ratio of HMF over TEAB is 1:2).

[0135] Step 2) Electrodialysis was performed on a stack operated in three-compartment mode with 10 cell-pairs consisting of AR103/CR67 membranes. A heavy cation membrane CR64LMR was placed at the anode electrode and a heavy anion membrane AR103QDR was placed next to the cathode. The stack was fed via 3 pumps from 3 tanks containing separate streams for the electrode rinse: Stream 1: Starting feed solution; Stream 2: Brine (starting fluid is RO water); Stream 3: Electrode rinse, an H2SO4 solution at 15 mS/cm.

[0136] The electric current applied was limited to 7.5 amps. 4 L of starting feed solution (i.e. the diluted mixture from step 1, 33% mass dry) was charged in the feed solution compartment (Starting feed conductivity: 29167 μS/cm). The process temperature was kept at 30° C. During the process, the conductivity of brine and of feed solution was monitored.

[0137] A decrease in amperage was observed after 50 minutes although conductivity of all solution was still high, possibly indicating membrane fouling.

[0138] The stack was operated at an initial voltage of 5V. The test was runned untill amperage dropped to 0.5 amps. The test was stopped when the final feed conductivity reached a plateau of 9875 μS/cm. The test duration was of 250 minutes.

[0139] With the aim to verify the desalting during the process, intermediate samples at 90 min (±14200 ρS/cm) and at 120 min (±12000 ρS/cm) were collected. The obtained results are reported in Table 2:

TABLE-US-00003 TABLE 2 Desalting RUN 1 (%) Starting Feed — (stream 1) Feed 90 min. 53.9 Feed 120 min. 73.0 Feed 250 min. 79.1 (5-HMF stream)

[0140] The removal of TEA+Br− from the HMF solution has been obtained with a recovery of 79.1% TEAB in final brine stream.