Preparation method of 2,5-furandicarboxylic acid compounds

Abstract

This disclosure discloses a method for preparing 2,5-furandicarboxylic acid (FDCA) compounds. The method includes providing a hexose diacid compound, an acid catalyst, and an ionic liquid; and dehydrating the hexose diacid compound in the ionic liquid under the catalysis of the acid catalyst to form a 2,5-furandicarboxylic acid compound; wherein the ionic liquid comprises a cationic moiety selected from pyridinium, pyridazinium, pyrimidinium, pyrazinium, oxazinium, thiazinium, imidazoline, pyrazolium, thiazoline, isothiazinium, oxazolium, isoxazolium, or triazolium and an anionic moiety selected from halide anions.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering. Specifically, this invention relates to a method for preparing 2,5-furandicarboxylic acid compounds by acid catalysis using ionic liquids as the reaction medium. Background Technology

[0002] Polyethylene terephthalate (PET) is one of the most widely used polymer materials in modern life. PET is derived from the polycondensation of purified terephthalic acid (PTA) and ethylene glycol, both based on fossil resources. With environmental pollution, global warming, and resource crises caused by fossil resource use becoming increasingly prominent concerns, governments and industries in major economies worldwide have made the preparation of new materials from renewable biomass resources a strategic development direction. 2,5-furandicarboxylic acid (FDCA), derived from biomass and comparable to PTA, was one of the 12 most important platform compounds selected by the U.S. Department of Energy in 2004 from over 300 bio-based compounds. Its molecular structure is similar to PTA, both possessing a cyclic conjugated system and containing two carboxylic acid groups. Polyethylene furanoate (PEF polyester), made from FDCA and renewable ethylene glycol, is a 100% renewable polyester. Its carbon dioxide emissions over its entire lifecycle are 70% lower than those from producing PET polyester. Compared to traditional PET polyester, PEF polyester has 10 times the oxygen barrier properties and 6-10 times the carbon dioxide barrier properties, significantly extending the shelf life of food and beverages. Furthermore, PEF polyester has superior mechanical properties compared to traditional PET polyester, making it a viable alternative in applications such as automotive parts, cables, apparel fabrics, carpets, and films.

[0003] Over the past two decades, more and more people have been trying to produce FDCA from renewable biomass resources (cellulose, starch, glucose, fructose, etc.) in order to reduce dependence on traditional fossil fuels.

[0004] FDCA can be obtained by air oxidation of 5-hydroxymethylfurfural (HMF). The catalyst can be a Co / Mn / Br homogeneous system (CN102040571A, CN102648191A, CN109651311A) or a supported noble metal heterogeneous system (US 10,654,819 B2). However, due to the instability of HMF, the cost of separation and purification is high, which in turn leads to the high cost of FDCA prepared by this route.

[0005]

[0006] FDCA can also be derived from the dehydration of a hexose diacid (WO2017 / 083297A1, WO2019 / 014393A1, CN107417651A). The hexose diacid can be gluconic acid, galactonic acid, etc.

[0007]

[0008] Currently, most FDCA synthesis focuses on the first chemical pathway, which involves the dehydration of fructose to produce HMF, followed by oxidation with various catalysts to generate FDCA. This pathway faces two challenges: first, the intermediate HMF has low volatility and a low decomposition temperature, making it a difficult molecule to separate; second, the oxidation of HMF to FDCA is not particularly efficient, requiring noble metal catalysts, low-concentration reaction conditions, and pH control. Due to these challenges, commercial production from HMF to FDCA is not yet possible.

[0009] Alternatively, FDCA can be prepared via the dehydration and cyclization of a hexacarbon sugar diacid. However, traditional methods using acids such as sulfuric acid (H₂SO₄), hydrobromic acid (HBr), methanesulfonic acid (MSA), and trifluoromethanesulfonic acid (TfOH) for catalytic dehydration yields low rates. This necessitates the addition of excess halides such as LiBr and NaBr to promote the reaction and increase the FDCA yield. However, the presence of halides like LiBr and NaBr often leads to the generation of HX at high temperatures, causing pressure in the reaction system. Furthermore, the byproducts such as HBr impose extremely stringent requirements on the selection of reaction equipment.

[0010] US9,701,652B2 reported the preparation of FDCA by sulfuric acid-catalyzed dehydration of glycosaminoglycans or mucilage in 1-butyl-3-methyl-imidazolium hydrogen sulfate ionic liquid. Although no excess halide was added, the FDCA yield was low, with the highest reported yield being only 52%, and the vast majority of experiments yielding FDCA in the range of 0-30%.

[0011] Therefore, there is still a need in the market for an improved method for preparing FDCA to overcome one or more of the aforementioned defects in the prior art. Summary of the Invention

[0012] To overcome one or more deficiencies of the prior art, one of the objectives of this disclosure is to provide an improved method for preparing 2,5-furancarboxylic acid (FDCA) compounds, which offers one or more of the following advantages: carried out under normal pressure; mild reaction conditions; good FDCA selectivity; high FDCA yield; short reaction time; high purity of the prepared product; simple operation; and minimal environmental pollution throughout the production process.

[0013] This disclosure provides a method for preparing 2,5-furandicarboxylic acid (FDCA) compounds, the method comprising: providing an aldaric acid compound, an acid catalyst, and an ionic liquid; and dehydrating the aldaric acid compound in the ionic liquid under the catalysis of the acid catalyst to form a 2,5-furandicarboxylic acid compound; wherein the ionic liquid comprises a cationic portion selected from pyridinium, pyridazinium, pyrimidinium, pyrazinium, oxazinium, thiazinium, imidazolineium, pyrazolium, thiazolineium, isothiazinium, oxazolium, isoxazolium, or triazolium and an anionic portion selected from halide anions.

[0014] For example, the nitrogen atom of the ionic liquid has a carbon atom selected from straight-chain or branched chains. 1-10 Alkyl, cyclohexyl, phenyl-C 1-3 Alkyl or phenyl substituents.

[0015] For example, the ionic liquid includes halide anions selected from chlorine, bromine, or iodine.

[0016] Preferably, the ionic liquid is selected from 1,3-dimethylimidazolium iodide, 1-ethyl-3-methylimidazolium iodide, 1-butyl-3-methylimidazolium iodide, 1,3-dimethylimidazolium bromide, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium iodide, 1-hexyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium chloride, 1-methyl-3-propylimidazolium iodide, 1-methyl-3-propylimidazolium bromide, 1- The ionic liquid is selected from one or more of methyl-3-propyl imidazolium chloride, 1-decyl-3-methyl imidazolium chloride, 1-decyl-3-methyl imidazolium bromide, 1-decyl-3-methyl iodide imidazolium, 1,3-diisopropyl imidazolium chloride, 1,3-diisopropyl imidazolium bromide, 1,3-diisopropyl imidazolium iodide, 1,3-di-tert-butyl imidazolium chloride, 1,3-di-tert-butyl imidazolium bromide, 1,3-di-tert-butyl imidazolium iodide, 1,3-dicyclohexyl imidazolium chloride, 1,3-dicyclohexyl imidazolium bromide, 1,3-dicyclohexyl imidazolium iodide, 1-ethylpyridine bromide, 1-ethylpyridine chloride, and 1-ethylpyridine iodide. For example, the ionic liquid is selected from one or more of 1-ethyl-3-methyl imidazolium bromide, 1-butyl-3-methyl imidazolium bromide, and 1-ethylpyridine bromide.

[0017] For example, the hexacarbon sugar dicarboxylic acid compounds are derived from biomass materials.

[0018] For example, the hexacarboxylic acid compounds are selected from gluconic acid, dimethyl gluconic acid, diethyl gluconic acid, dipropyl gluconic acid (n-propyl and isopropyl), dibutyl gluconic acid (n-butyl, isobutyl, and tert-butyl), diethylene glycol gluconic acid, dipropylene glycol gluconic acid, dibutyl gluconic acid, sodium gluconic acid, potassium gluconic acid, calcium gluconic acid, 1,4-lactone gluconic acid, 6,3-lactone gluconic acid, 1,4:6,3-dilactone gluconic acid, galactonic acid, dimethyl galactonic acid, diethyl galactonic acid, dipropyl galactonic acid (n-propyl and isopropyl), dibutyl galactonic acid (n-butyl, isobutyl, and tert-butyl), diethylene glycol galactonic acid, and so on. Dipropylene glycol galactobionic acid, dibutyl galactobionic acid, sodium galactobionic acid, potassium galactobionic acid, calcium galactobionic acid, 1,4-galactobionic acid, 6,3-galactobionic acid, 1,4:6,3-dilactobionic acid, mannose, dimethyl mannose, diethyl mannose, dipropyl mannose (n-propyl and isopropyl esters) One or more of the following: dibutyl mannose (n-butyl, isobutyl, and tert-butyl mannose), diethylene glycol mannose, dipropylene glycol mannose, dibutyl mannose, sodium mannose, potassium mannose, calcium mannose, 1,4-lactone mannose, 6,3-lactone mannose, and 1,4:6,3-dilactone mannose.

[0019] For example, the acid catalyst is selected from one or more of hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, p-trifluoromethanesulfonic acid, acetic acid, trifluoroacetic acid, and phosphotungstic acid. Preferably, the acid catalyst comprises trifluoromethanesulfonic acid.

[0020] In one embodiment, no co-catalyst selected from lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide, barium bromide, ferric bromide, ferrous bromide, nickel bromide, copper bromide, cuprous bromide, zinc bromide, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrabutylammonium bromide is added to the reaction system.

[0021] In one embodiment, no organic solvent is added to the reaction system. In another embodiment, one or more organic solvents selected from 1,4-dioxane, dimethyl sulfoxide, sulfolane, dimethylformamide (DMF), dimethylacetamide (DMA), and glycol dimethyl ether are introduced into the reaction system.

[0022] In one embodiment, the water content in the reaction medium is less than 10%, preferably less than 5%.

[0023] In one embodiment, the dehydration reaction temperature is 100-180°C. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this invention.

[0025] This invention may be implemented in other specific forms without departing from its essential attributes. It should be understood that, without conflict, any and all embodiments of this invention can be combined with technical features of any or more other embodiments to obtain further embodiments. This invention includes such combinations to obtain further embodiments.

[0026] All publications and patents mentioned in this disclosure are incorporated herein by reference in their entirety. In the event of any conflict between the use or terminology used in any publications and patents incorporated by reference and the use or terminology used in this disclosure, the use and terminology of this disclosure shall prevail.

[0027] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0028] As used herein, the words “comprising,” “containing,” or “including” mean that the element preceding the word encompasses the elements listed following the word and their equivalents, without excluding other elements. The terms “containing” or “comprising (including)” as used herein can be open-ended, semi-closed, or closed-ended. In other words, the terms also include “consistently composed of” or “composed of”.

[0029] Unless otherwise indicated in the working embodiments or elsewhere, all figures set forth in the specification and claims expressing the amount of material, reaction conditions, duration, and quantitative properties of the material shall be understood to be modified by the term “about” in all cases. It should also be understood that any range of numbers listed in this application is intended to include all subranges within that range and any combination of the endpoints of that range or subranges; for example, integers 1-20 include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20, and also include subranges 1-3, 1-4, 1-10, 2-4, 2-10, etc.

[0030] This disclosure should be interpreted as consistent with the laws and principles of chemical bonding. In some cases, it may be necessary to remove a hydrogen atom to accommodate a substituent at a given position.

[0031] In this application, a hexose diacid compound refers to a compound having the structural formula R1OOC(CHOH)4COOR2, wherein R1 and R2 are each independently selected from hydrogen, alkali metals (e.g., lithium, sodium, or potassium), alkaline earth metals (e.g., calcium or magnesium), and alkyl groups (e.g., C). 1-6 Alkyl), -CH2-(CH2)x-CH2OH (e.g., x is 0, 1, 2, 3 or 4), aralkyl (e.g., benzyl and phenethyl), and aryl (e.g., phenyl). When R1 and R2 are hydrogens, it is a hexacarbon sugar diacid, such as gluconic acid, galactonic acid, and mannonic acid.

[0032] In one embodiment, the hexose diacid compound is derived from biomass materials. For example, pectin can be extracted from biomass materials (such as the peels and cores of fruits like citrus, grapefruit, lemon, apple, pear, and hawthorn, as well as the pomace after juicing), and the pectin can be hydrolyzed with pectinase to form galacturonic acid, which is then oxidized to form galactobacic acid. As another example, alginic acid can be extracted from biomass materials such as brown algae like kelp or Sargassum, and then hydrolyzed to form guluronic acid and / or mannuronic acid, which is then oxidized to form guluronic acid and / or mannobacic acid.

[0033] For example, hexose diacid compounds can be selected from gluconic acid, dimethyl gluconic acid, diethyl gluconic acid, dipropyl gluconic acid (n-propyl and isopropyl), dibutyl gluconic acid (n-butyl, isobutyl, and tert-butyl), diethylene glycol gluconic acid, dipropylene glycol gluconic acid, dibutyl gluconic acid, sodium gluconic acid, potassium gluconic acid, calcium gluconic acid, 1,4-lactone gluconic acid, 6,3-lactone gluconic acid, 1,4:6,3-dilactone gluconic acid, galactonic acid, dimethyl galactonic acid, diethyl galactonic acid, dipropyl galactonic acid (n-propyl and isopropyl), dibutyl galactonic acid (n-butyl, isobutyl, and tert-butyl), diethylene glycol galactonic acid, and so on. Dipropylene glycol galactobionic acid, dibutyl galactobionic acid, sodium galactobionic acid, potassium galactobionic acid, calcium galactobionic acid, 1,4-galactobionic acid, 6,3-galactobionic acid, 1,4:6,3-dilactobionic acid, mannose, dimethyl mannose, diethyl mannose, dipropyl mannose (n-propyl and isopropyl esters) One or more of the following: dibutyl mannose (n-butyl, isobutyl, and tert-butyl mannose), diethylene glycol mannose, dipropylene glycol mannose, dibutyl mannose, sodium mannose, potassium mannose, calcium mannose, 1,4-lactone mannose, 6,3-lactone mannose, and 1,4:6,3-dilactone mannose.

[0034] In this application, 2,5-furandicarboxylic acid compounds refer to compounds having the structural formula... Compounds wherein R1 and R2 are each independently selected from hydrogen, alkali metals (e.g., lithium, sodium, or potassium), alkaline earth metals (e.g., calcium or magnesium), alkyl groups (e.g., C4, 24, 25, 26 ... 1-6 Alkyl), -CH2-(CH2)x-CH2OH (e.g., x is 0, 1, 2, 3 or 4), aralkyl (e.g., benzyl and phenethyl), and aryl (e.g., phenyl). When R1 and R2 are hydrogen, it is 2,5-furandicarboxylic acid.

[0035] In this application, alkyl refers to a straight-chain or branched saturated hydrocarbon group consisting only of carbon and hydrogen atoms. For example, C1-C 10Alkyl refers to an alkyl group containing 1-10 carbon atoms. Typical alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, nonyl, and decyl. In some embodiments, it is a C1-C6 alkyl group. Representative examples of C1-C6 alkyl groups include, but are not limited to, methyl (C1), ethyl (C2), n-propyl (C3), isopropyl (C3), n-butyl (C4), tert-butyl (C4), sec-butyl (C4), isobutyl (C4), n-pentyl (C5), 3-pentyl (C5), neopentyl (C5), 3-methyl-2-butyl (C5), tert-pentyl (C5), and n-hexyl (C6).

[0036] The reaction disclosed herein is shown in the following reaction formula, wherein a hexose diacid compound undergoes dehydration and cyclization in an ionic liquid in the presence of an acid catalyst to form a 2,5-furandicarboxylic acid (FDCA) compound.

[0037]

[0038] In this application, an acid catalyst refers to a Bronsted acid capable of donating a proton. For example, an acid catalyst is selected from one or more of hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid (MsOH), trifluoromethanesulfonic acid (TfOH), benzenesulfonic acid, p-toluenesulfonic acid, p-trifluoromethanesulfonic acid, acetic acid, trifluoroacetic acid, and phosphotungstic acid.

[0039] In a preferred embodiment, the acid catalyst comprises trifluoromethanesulfonic acid. For example, the acid catalyst is trifluoromethanesulfonic acid, or the acid catalyst is a mixture of trifluoromethanesulfonic acid and one or more acids selected from hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, p-trifluoromethanesulfonic acid, acetic acid, trifluoroacetic acid, and phosphotungstic acid.

[0040] In this application, an ionic liquid refers to a salt that is liquid at the reaction temperature and is composed entirely of anions and cations. Ionic liquids preferably have a melting point of less than 180°C, more preferably less than 160°C, even more preferably less than 120°C, and particularly less than 100°C. Ionic liquids include, for example, ionic liquids that are liquid at room temperature as described by KN Marsh et al., Fluid Phase Equilibria 219 (2004), 93-98, and J. G. Diddleston et al., Green Chemistry 2001, 3, 156-164.

[0041] FDCA yield = (molar amount of FDCA product / molar amount of hexacarbon sugar diacid compound) * 100%

[0042] The inventors unexpectedly discovered that the FDCA yield was high when using an ionic liquid containing an anionic moiety selected from halide anions to prepare 2,5-furan dicarboxylic acid compounds by dehydration cyclization of hexacarbon sugar diacid compounds. It is believed that the ionic liquid not only serves as a reaction medium but also provides halide anions to aid in the catalysis of the reaction.

[0043] In one embodiment, the ionic liquid used comprises a cationic portion selected from pyridinium, pyridazineium, pyrimidineium, pyrazineium, oxazineium, thiazineium, imidazolineium, pyrazolium, thiazolineium, isothiazolium, oxazolium, isoxazolium, or triazolium and an anionic portion selected from halide anions.

[0044] Those skilled in the art will understand that one or more (e.g., 1, 2, or 3) nitrogen atoms of pyridinium, pyridazineium, pyrimidineium, pyrazineium, oxazineium, thiazineium, imidazoleium, pyrazolium, thiazolylium, isothiazolium, oxazolium, isoxazolium, or triazolium in the cationic moiety of the ionic liquid may have substituents. For example, the substituents are selected from straight-chain or branched C atoms. 1-10 Alkyl, cyclohexyl, phenylmethylene, phenylethylene, phenylpropylene, phenyl, etc.

[0045] In one embodiment, the ionic liquid comprises a halide anion selected from chloride, bromine, or iodine. For example, the ionic liquid is selected from 1,3-dimethylimidazolium iodide, 1-ethyl-3-methylimidazolium iodide, 1-butyl-3-methylimidazolium iodide, 1,3-dimethylimidazolium bromide, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium iodide, 1-hexyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium chloride, 1-methyl-3-propylimidazolium iodide, 1-methyl-3-propylimidazolium bromide, 1-methyl-3-propylimidazolium bromide, 1-methyl-3-propylimidazolium iod ... The following are one or more of the following: 1-decyl-3-methyl imidazolium chloride, 1-decyl-3-methyl imidazolium bromide, 1-decyl-3-methyl imidazolium iodide, 1,3-diisopropyl imidazolium chloride, 1,3-diisopropyl imidazolium bromide, 1,3-diisopropyl imidazolium iodide, 1,3-di-tert-butyl imidazolium chloride, 1,3-di-tert-butyl imidazolium bromide, 1,3-di-tert-butyl imidazolium iodide, 1,3-dicyclohexyl imidazolium chloride, 1,3-dicyclohexyl imidazolium bromide, 1,3-dicyclohexyl imidazolium iodide, 1-ethylpyridine bromide, 1-ethylpyridine chloride, and 1-ethylpyridine iodide.

[0046] In one specific embodiment, the ionic liquid is selected from one or more of 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, and 1-ethylpyridine bromide.

[0047] In one embodiment, a co-catalyst is added to the reaction system, for example, the co-catalyst is selected from one or more of lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide, barium bromide, ferric bromide, ferrous bromide, nickel bromide, copper bromide, cuprous bromide, zinc bromide, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrabutylammonium bromide.

[0048] In another embodiment, no cocatalyst selected from lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide, barium bromide, ferric bromide, ferrous bromide, nickel bromide, copper bromide, cuprous bromide, zinc bromide, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrabutylammonium bromide is added to the reaction system.

[0049] In one implementation, no organic solvent was introduced into the reaction system.

[0050] In another embodiment, an organic solvent is introduced into the reaction system. Introducing an organic solvent may help reduce the viscosity of the ionic liquid. For example, one or more organic solvents selected from 1,4-dioxane, dimethyl sulfoxide, sulfolane, dimethylformamide (DMF), dimethylacetamide (DMA), and glycol dimethyl ether may be introduced into the reaction system.

[0051] The reaction temperature disclosed herein typically does not exceed 180°C, for example, at 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C. Too low a reaction temperature is detrimental to water evaporation and also hinders the shortening of the reaction time. Too high a reaction temperature may trigger side reactions. In one embodiment, the reaction temperature is 100-180°C. In a preferred embodiment, the reaction temperature is 120-160°C.

[0052] The reaction raw materials and reaction media disclosed herein are expected to have a low water content, for example, less than 10 wt%. In a preferred embodiment, the water content is less than 5 wt%, 4 wt%, 3 wt%, 2 wt%, or 1 wt%.

[0053] The reaction raw materials and reaction media disclosed herein are preferably intended to have a low alcohol (e.g., ethanol or ethylene glycol) content, for example, less than 5 wt%. In a preferred embodiment, the alcohol content is less than 4 wt%, 3 wt%, 2 wt%, or 1 wt%.

[0054] During or at the end of the reaction, a quantitative sample is extracted from the reaction mixture for analysis. For example, the reaction sample can be diluted for high-performance liquid chromatography (HPLC) analysis in two ways: 1) the sample is neutralized with 1.0M NaOH solution, then further diluted with water to dissolve the ionic liquid and all substrates and products, followed by HPLC detection; 2) the sample is directly dissolved in dimethyl sulfoxide (DMSO) for analysis. The dilution degree varies from 5 to 30 times for each experiment to ensure the diluted sample concentration is within an appropriate range for analysis using a PDA UV detector. HPLC analysis is used to analyze the conversion of the reaction mixture, monitoring the consumption of the hexose diacid substrate and the formation of FDCA. The method employs a Hi-Plex H, 300 mm x 7.7 mm HPLC column, with a mobile phase of 5 mmol / L dilute sulfuric acid aqueous solution, a mobile phase flow rate of 0.6 mL / min, a column temperature of 40 °C, and an injection volume of 20 μL. Using this chromatographic method, the retention time of the raw material hexose diacid was 10.2 min, and the retention time of FDCA was 22.5 min. The content of FDCA in each sample was accurately determined using the external standard method.

[0055] This disclosure utilizes a hexose diacid compound in an ionic liquid system under acid catalysis to prepare 2,5-furandicarboxylic acid (FDCA). The invention uses an ionic liquid as the reaction medium, replacing or reducing the use of other polar solvents. High conversion and FDCA yields (up to 93.5%) can be achieved without the addition of additional halides. The reaction can be carried out under normal pressure without the need for depressurization, exhibiting high efficiency; the reaction can be completed in 1–5 hours at 120–160°C. The reaction conditions are relatively mild, resulting in good FDCA selectivity and high product purity. The entire production process has minimal environmental pollution and is suitable for industrial production.

[0056] Example

[0057] The following examples are provided to further illustrate the invention. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following examples, unless otherwise specified, can be performed under standard conditions for such reactions or as recommended by the manufacturer. Unless otherwise specified, all experimental materials and reagents used are commercially available.

[0058] Experiments 1-36 below use potassium gluconate monophosphate as a raw material for hexose diacid compounds, and 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, or 1-ethylpyridine bromide as ionic liquids. Trifluoromethanesulfonic acid, methanesulfonic acid, or sulfuric acid are used as acid catalysts to prepare 2,5-furandicarboxylic acid (FDCA) through dehydration and cyclization under the reaction conditions listed in Table 1-4.

[0059] Taking Experiment 1 as an example, 0.099 g (0.4 mmol) of potassium gluconate monophosphate, 0.61 g (3.2 mmol) of 1-ethyl-3-methylimidazolium bromide, and 0.36 g (2.4 mmol) of trifluoromethanesulfonic acid were added to a thick-walled pressure-resistant tube. The temperature was raised to 120 °C and the reaction was carried out for 1 h. After the reaction was completed, 1 M NaOH aq was added to the reaction system to adjust the pH to 8-10. After the reaction solution was completely dissolved, a small amount of solution was taken and diluted with 5 mmol H2SO4 aqueous solution to make up the volume. The reaction conversion was detected by HPLC. The yield of FDCA was 86.7%.

[0060] Table 1: Synthesis of FDCA using trifluoromethanesulfonic acid catalyzed in 1-ethyl-3-methylimidazolium bromide

[0061]

[0062] Note: [a], [b], and [c] respectively added 5 wt%, 10 wt%, and 20 wt% water to the reaction system;

[0063] [d] Add 4.48 equivalents of ethylene glycol to the reaction system;

[0064] [e], [f], and [g] were respectively added to the reaction system in the form of 0.3 mL, 0.5 mL, and 1.0 mL sulfolane.

[0065] Table 2: Synthesis of FDCA in 1-ethyl-3-methylimidazolium bromide using methanesulfonic acid / sulfuric acid

[0066]

[0067] Table 3: Synthesis of FDCA using trifluoromethanesulfonic acid in 1-ethylpyridine bromide

[0068]

[0069] Table 4: Synthesis of FDCA using trifluoromethanesulfonic acid in 1-butyl-3-methylimidazolium bromide

[0070]

[0071] Several experiments on FDCA preparation were conducted in this disclosure. When the mass ratio of ionic liquid to potassium gluconate substrate was 6.1, TfOH was 6.0 eq, and the reaction was carried out at 120°C for 5 h, the highest FDCA yield reached 93.5% (Experiment-6). Under the same experimental conditions, increasing the reaction temperature to 150°C for 0.5 h resulted in an FDCA yield of 85.9% (Experiment-7). When the mass ratio of ionic liquid to potassium gluconate substrate was adjusted to 3.8, TfOH was 5.0 eq, and the reaction was carried out at 120°C for 5 h, the FDCA yield reached 81.5% (Experiment-15). Adding 5 wt% H₂O to the reaction system and reacting at 120°C for 5 h still resulted in an FDCA yield of 81.5% (Experiment-18). Adding the polar solvent sulfolane to the reaction system did not affect the reaction results (Experiments 22-24). High FDCA conversion rates were also achieved using other ionic liquids in the reaction (Experiments 25-36).

[0072] Experiments 37-38, as shown in Table 5 below, used potassium gluconate monophosphate as the raw material for a hexose diacid compound, 1-ethyl-3-methylimidazolium hydrogen sulfate as the ionic liquid, and sulfuric acid as the acid catalyst to prepare 2,5-furandicarboxylic acid (FDCA) through dehydration and cyclization under the reaction conditions listed in Table 5.

[0073] Table 5: Synthesis of FDCA using sulfuric acid in 1-ethyl-3-methylimidazolium hydrogen sulfate

[0074]

[0075] Experiments 37-38 used 1-ethyl-3-methylimidazolium hydrogen sulfate and sulfuric acid, and the yield of FDCA was significantly lower.

[0076] Experiments 39-40, as shown in Table 6 below, used potassium gluconate monophosphate as the raw material for hexose diacid compounds, 1-ethyl-3-methylimidazolium hexafluorophosphate as the ionic liquid, and trifluoromethanesulfonic acid as the acid catalyst to prepare 2,5-furandicarboxylic acid (FDCA) through dehydration and cyclization under the reaction conditions listed in Table 6.

[0077] Table 6: Synthesis of FDCA using trifluoromethanesulfonic acid in 1-ethyl-3-methylimidazolium hexafluorophosphate

[0078]

[0079] Experiments 41-42, as shown in Table 7 below, used potassium gluconate monophosphate as the raw material for hexose diacid compounds, 1-ethyl-3-methylimidazolium tetrafluoroborate as the ionic liquid, and trifluoromethanesulfonic acid as the acid catalyst to prepare 2,5-furandicarboxylic acid (FDCA) through dehydration and cyclization under the reaction conditions listed in Table 7.

[0080] Table 7: Synthesis of FDCA using trifluoromethanesulfonic acid in 1-ethyl-3-methylimidazolium tetrafluoroborate

[0081]

[0082] Experiments 43-44, as shown in Table 8 below, used potassium gluconate monophosphate as the raw material for a hexose diacid compound, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate as the ionic liquid, and trifluoromethanesulfonic acid as the acid catalyst to prepare 2,5-furandicarboxylic acid (FDCA) via dehydration cyclization.

[0083] Table 8: Synthesis of FDCA using trifluoromethanesulfonic acid in 1-ethyl-3-methylimidazolium trifluoromethanesulfonate

[0084]

[0085] Experiments 39-44 used trifluoromethanesulfonic acid as a catalyst and 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium tetrafluoroborate, or 1-ethyl-3-methylimidazolium trifluoromethanesulfonate as the ionic liquid. The yield of FDCA prepared by these liquids was significantly lower than that prepared by using 1-ethyl-3-methylimidazolium bromide as shown in Table 1.

[0086] Compared with the prior art, this disclosure has one or more of the following advantages:

[0087] 1) The reaction can yield FDCA in high yield under normal pressure, and does not require a vacuum. Furthermore, the reaction at high temperatures does not produce large amounts of hydrogen halide vapor, thus avoiding the need for special pressure-resistant reactors and other equipment, resulting in lower equipment requirements.

[0088] 2) Ionic liquids act as both reaction co-catalysts and reaction solvents, which avoids the need to add some strongly polar aprotic solvents (such as sulfolane, dimethyl sulfoxide, 1,4-dioxane) in the reaction of existing technologies, and the whole production process is less harmful to the environment.

[0089] 3) The reaction time is relatively short, generally 1 to 5 hours to complete;

[0090] 4) The operation is simple, FDCA has good selectivity and high yield, with the highest yield reaching 85-95% and good reaction stability, making it very suitable for industrial production;

[0091] 5) The FDCA product obtained after post-processing has high purity;

[0092] 6) The reaction process can be controlled by adding acid dropwise. The reaction is essentially a reaction controlled by adding materials, which reduces the production safety risk.

[0093] Experiments 45-47, as shown in Table 9 below, used potassium D-gluconic acid as the raw material, sulfolane as the solvent, and NaBr or LiBr as the additive. Under TfOH acid catalysis, 2,5-furandicarboxylic acid was obtained by dehydration cyclization at a reaction temperature of 120-160℃.

[0094] Table 9: Synthesis of FDCA using trifluoromethanesulfonic acid under sodium bromide / lithium bromide conditions

[0095]

[0096] Note: [h] Sodium bromide; [i] Lithium bromide.

[0097] The advantages and disadvantages of the technical schemes in Experiments 45-47 are: 1) The reaction will produce HX at high temperature, so pressure-resistant and corrosion-resistant equipment is required, which places high demands on the equipment; 2) The amount of Bronsted acid and halides used in the reaction is large; 3) A large amount of acidic waste gas and waste are generated.

[0098] Experiments 48-51 used potassium D-gluconic acid as a raw material, sulfolane as a solvent, and tetrabutylammonium bromide (TBAB), tetramethylammonium bromide (TMAB), or tetraethylammonium bromide (TEAB) as additives. The 2,5-furandicarboxylic acid was obtained by dehydration and cyclization under TfOH acid catalysis at a reaction temperature of 120℃.

[0099] Table 10: Synthesis of FDCA using trifluoromethanesulfonic acid under tetrabutylammonium bromide / tetramethylammonium bromide / tetraethylammonium bromide conditions

[0100]

[0101] Notes: [j] Tetrabutylammonium bromide; [k] Tetramethylammonium bromide; [l] Tetraethylammonium bromide.

[0102] The advantages and disadvantages of the technical scheme in Experiments 48-51 are: 1) The amount of Bronsted acid and halides used in the reaction is relatively large; 2) A large amount of acidic waste gas and waste are generated.

[0103] Experiments 52-54 used galactosic acid as a raw material and 1-ethyl-3-methylimidazolium bromide as an ionic liquid. The reaction was carried out by dehydration and cyclization under TfOH acid catalysis to obtain 2,5-furandicarboxylic acid at a reaction temperature of 120℃.

[0104] Table 11: Synthesis of FDCA from galactobacic acid using trifluoromethanesulfonic acid in 1-ethyl-3-methylimidazolium bromide

[0105]

[0106] Experiments 52-54 show that galactopyric acid can replace potassium D-gluconic acid monophosphate in the synthesis of FDCA using the method disclosed herein.

[0107] While the invention has been described above using specific embodiments and examples, many variations and modifications will be apparent to those skilled in the art. Therefore, the described embodiments are to be considered illustrative rather than restrictive in all respects. Consequently, the scope of the invention is defined by the appended claims rather than the foregoing description. All variations within the meaning and scope of the claims should be included within the protection scope of this invention.

Claims

1. A method of making a 2,5-furan dicarboxylic acid compound, the method comprising providing a six-carbon sugar diacid compound, an acid catalyst, and an ionic liquid; and dehydration of the six-carbon sugar diacid compound in the ionic liquid catalyzed by the acid catalyst to form the 2,5-furan dicarboxylic acid compound; wherein the six-carbon sugar diacid compound is selected from one or more of gluconic acid, dimethyl gluconate, diethyl gluconate, di-n-propyl gluconate, di-i-propyl gluconate, di-n-butyl gluconate, di-i-butyl gluconate, di-t-butyl gluconate, diethylene glycol gluconate, dipropylene glycol gluconate, dibutylene glycol gluconate, sodium gluconate, potassium gluconate, calcium gluconate, gluconolactone-1,4-lactone, gluconolactone-6,3-lactone, gluconolactone-1,4:6,3-dilactone, galactaric acid, dimethyl galactarate, diethyl galactarate, di-n-propyl galactarate, di-i-propyl galactarate, di-n-butyl galactarate, di-i-butyl galactarate, di-t-butyl galactarate, diethylene glycol galactarate, dipropylene glycol galactarate, dibutylene glycol galactarate, sodium galactarate, potassium galactarate, calcium galactarate, galactarolactone-1,4-lactone, galactarolactone-6,3-lactone, galactarolactone-1,4:6,3-dilactone, wherein the ionic liquid comprises a cationic portion selected from pyridinium and imidazolium and an anionic portion selected from halide anions, wherein the acid catalyst comprises triflic acid.

2. The process of claim 1, wherein the ionic liquid has one substituent on the nitrogen atom selected from the group consisting of straight chain or branched C 1-10 alkyl, cyclohexyl, phenyl- C 1-3 alkyl, or phenyl.

3. The method of claim 1, wherein the ionic liquid comprises a halide anion selected from chloride, bromide, or iodide.

4. The method of claim 3, wherein the ionic liquid is selected from one or more of 1,3-dimethylimidazolium iodide, 1-ethyl-3-methylimidazolium iodide, 1-butyl-3-methylimidazolium iodide, 1,3-dimethylimidazolium bromide, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium iodide, 1-hexyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium chloride, 1-methyl-3-propylimidazolium iodide, 1-methyl-3-propylimidazolium bromide, 1-methyl-3-propylimidazolium chloride, 1-decyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium bromide, 1-decyl-3-methylimidazolium iodide, 1,3-diisopropylimidazolium chloride, 1,3-diisopropylimidazolium bromide, 1,3-diisopropylimidazolium iodide, 1,3-di-t-butylimidazolium chloride, 1,3-di-t-butylimidazolium bromide, 1,3-di-t-butylimidazolium iodide, 1,3-dicyclohexylimidazolium chloride, 1,3-dicyclohexylimidazolium bromide, 1,3-dicyclohexylimidazolium iodide, 1-ethylpyridinium bromide, 1-ethylpyridinium chloride, 1-ethylpyridinium iodide.

5. The process of claim 4 wherein the ionic liquid is selected from one or more of 1- ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1- ethylimidazolium pyridinium bromide.

6. The process of any one of claims 1 to 5 wherein the reaction system has not been charged with a promoter selected from lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide, barium bromide, iron bromide, ferrous bromide, nickel bromide, copper bromide, cuprous bromide, zinc bromide, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide.

7. The process of any one of claims 1 to 5 wherein the reaction system has not been charged with any organic solvent.

8. The process of any one of claims 1 to 5 wherein the reaction system has been charged with one or more organic solvents selected from 1,4-dioxane, dimethylsulfoxide, sulfolane, dimethylformamide, dimethylacetamide, glymes.

9. The process of any one of claims 1 to 5 wherein the water content of the reaction medium is below 10%.

10. The process of claim 8 wherein the water content of the reaction medium is below 5%.

11. The process of any one of claims 1 to 5 wherein the temperature of the dehydration is between 100 and 180°C.

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