Process for the preparation of 2,5-furandicarboxylic acid compounds

Abstract

This invention relates to a method for preparing 2,5-furandicarboxylic acid 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 the 2,5-furandicarboxylic acid compound. 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. The acid catalyst comprises trifluoromethanesulfonic acid. The general structural formula of the hexose diacid compound is R1OOC(CHOH)4COOR2, and the structure of the 2,5-furandicarboxylic acid compound is shown in formula (I). This method offers mild reaction conditions; good FDCA selectivity and high yield; high product purity; simple operation; and low pollution.

Description

[0001] This application is filed on March 10, 2022, and the invention is entitled "2,5". This is a divisional application of patent application number 202210234062.3, entitled "Method for making furan dicarboxylic acid compounds". Technical Field

[0002] This invention belongs to the field of chemical engineering. Specifically, this invention relates to a method for preparing 2,5-dimethylaminopropionate (2,5-dimethylaminopropionate) by acid catalysis using ionic liquid as the reaction medium. Methods for processing furanyl dicarboxylic acid compounds. Background Technology

[0003] 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. Comparable to PTA is 2,5-dimethylformamide, which can be derived from biomass. Furandicarboxylic acid (2,5) Furandicarboxylic acid (FDCA) is 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), produced from FDCA and renewable ethylene glycol, is a 100% renewable polyester. Its carbon dioxide emissions over its entire life cycle are 70% lower than those from producing PET polyester. Compared to traditional PET polyester, PEF polyester has 10 times higher oxygen barrier properties and higher oxygen content (6%). With 10 times the carbon dioxide barrier properties, PEF polyester can significantly extend the shelf life of food and beverages. Furthermore, PEF polyester boasts superior mechanical properties compared to traditional PET polyester, making it a viable alternative to PET polyester in applications such as automotive parts, cables, apparel fabrics, carpets, and films.

[0004] 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.

[0005] FDCA can be from 5 Hydroxymethyl sulphuraldehyde (HMF) is obtained by air oxidation. 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.

[0006]

[0007] 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.

[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 on 1 Butyl 3 methyl The preparation of FDCA using imidazole hydrogen sulfate ionic liquids via sulfuric acid-catalyzed dehydration of glycosaminoglycans or mucilages, despite the absence of excess halides, results in low FDCA yields. The highest reported yield is only 52%, and most experiments yield less than 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] In order to overcome one or more deficiencies of the prior art, one of the objectives of this disclosure is to provide an improved 2,5 A method for preparing furanoic acid (FDCA) compounds, the invention provides 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 low environmental pollution throughout the production process.

[0013] This disclosure provides a method for preparing 2,5 A method for producing furanyl dicarboxylic 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 2,5-dicarboxylic acid. Furan dicarboxylic acid compounds; wherein the ionic liquid 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.

[0014] For example, the nitrogen atom of the ionic liquid has a C1 atom selected from straight-chain or branched chains. 10alkyl, cyclohexyl, phenyl Asia C1 3. Substituents of alkyl or phenyl groups.

[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 Dimethyliodide imidazole, 1 Ethyl 3 Methylimidazole, 1 Butyl 3 Methylimidazole iodide, 1,3 Dimethyl imidazole bromide, 1 Ethyl 3 Methylimidazolium bromide, 1 Butyl 3 Methylimidazolium bromide, 1,3 Dimethyl imidazole chloride, 1 Ethyl 3 Methylimidazole, 1 Butyl 3 Methylimidazole, 1 Jiji 3 Methylimidazole, 1 Jiji 3 Methylimidazolium bromide, 1 Jiji 3 Methylimidazole, 1 methyl 3 Propyl iodide imidazole, 1 methyl 3 Propyl imidazole bromide, 1 methyl 3 Propyl imidazole chloride, 1 decyl 3 Methylimidazole, 1 decyl 3 Methylimidazolium bromide, 1 decyl 3 Methylimidazole iodide, 1,3 Diisopropyl imidazole chloride, 1,3 Diisopropylimidazolium bromide, 1,3 Diisopropylimidazolium iodide, 1,3 Di-tert-butyl imidazole chloride, 1,3 Di-tert-butyl imidazole bromide, 1,3 Di-tert-butylimidazolium iodide, 1,3 Dicyclohexyl imidazole chloride, 1,3 Dicyclohexyl imidazole bromide, 1,3 Dicyclohexylimidazolium iodide, 1 Ethylpyridine bromide, 1 Ethylpyridine chloride, 1 One or more of ethylpyridine iodide. For example, the ionic liquid is selected from 1 Ethyl 3 Methylimidazolium bromide, 1 Butyl 3 Methylimidazolium bromide, 1 One or more of ethylpyridine bromide.

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

[0018] For example, the hexacarbon sugar diacid 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 gluconic acid, dipropylene gluconic acid, dibutyl gluconic acid, sodium gluconic acid, potassium gluconic acid, calcium gluconic acid, and gluconic acid. 1,4 lactone, gluconic acid 6,3 lactone, gluconic acid 1,4:6,3 Dilactone, galactobionic acid, dimethyl galactobionic acid, diethyl galactobionic acid, dipropyl galactobionic acid (n-propyl and isopropyl), dibutyl galactobionic acid (n-butyl, isobutyl, and tert-butyl), diethylene glycol galactobionic acid, dipropylene glycol galactobionic acid, dibutyl galactobionic acid, sodium galactobionic acid, potassium galactobionic acid, calcium galactobionic acid 1,4 lactone, galactoside 6,3 lactone, galactoside 1,4:6,3 Dilactone, mannose, dimethyl mannose, diethyl mannose, dipropyl mannose (n-propyl and isopropyl), dibutyl mannose (n-butyl, isobutyl, and tert-butyl), diethylene glycol mannose, dipropylene glycol mannose, dibutyl mannose, sodium mannose, potassium mannose, calcium mannose, mannose 1,4 lactone, mannose 6,3 lactone, mannose 1,4:6,3 One or more of the dilactones.

[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, the reaction system is introduced with organic solvents selected from 1,4... One or more organic solvents including dioxane, dimethyl sulfoxide, sulfolane, dimethylformamide (DMF), dimethylacetamide (DMA), and glycol dimethyl ether.

[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°C. 180℃. 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 numerical range listed herein is intended to include all subranges within that range and any combination of the endpoints of that range or subrange, such as 1. Integers in 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 the subrange 1. 3.1 4.1 10, 2 4.2 Level 10.

[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, hexose diacid compounds refer to compounds 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., C1). 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 atoms, 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 glycol gluconic acid, sodium gluconic acid, potassium gluconic acid, calcium gluconic acid, and gluconic acid. 1,4 lactone, gluconic acid 6,3 lactone, gluconic acid 1,4:6,3 Dilactone, galactobionic acid, dimethyl galactobionic acid, diethyl galactobionic acid, dipropyl galactobionic acid (n-propyl and isopropyl), dibutyl galactobionic acid (n-butyl, isobutyl, and tert-butyl), diethylene glycol galactobionic acid, dipropylene glycol galactobionic acid, dibutyl galactobionic acid, sodium galactobionic acid, potassium galactobionic acid, calcium galactobionic acid 1,4 lactone, galactoside 6,3 lactone, galactoside 1,4:6,3 Dilactone, mannose, dimethyl mannose, diethyl mannose, dipropyl mannose (n-propyl and isopropyl), dibutyl mannose (n-butyl, isobutyl, and tert-butyl), diethylene glycol mannose, dipropylene glycol mannose, dibutyl mannose, sodium mannose, potassium mannose, calcium mannose, mannose 1,4 lactone, mannose 6,3 lactone, mannose 1,4:6,3 One or more of the dilactones.

[0034] 2,5 Furan dicarboxylic acid compounds in this application 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., C1), and alkyl groups (e.g., C1). 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 10 Alkyl indicates that it contains 1 An alkyl group with 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 C1. C6 alkyl. C1 Representative examples of 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), and 3 Pentyl (C5), Neopentyl (C5), 3 methyl 2 Butyl (C5), tert-amyl (C5), and n-hexyl (C6), etc.

[0036] The reaction of this disclosure is shown in the following reaction formula, wherein a hexacarbon sugar diacid compound undergoes dehydration and cyclization in an ionic liquid in the presence of an acid catalyst to form 2,5 Furanodicarboxylic acid (FDCA) compounds,

[0037] 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.

[0038] 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.

[0039] 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, those described in K.N. Marsh et al., Fluid Phase Equilibria 219 (2004), 93. 98 and J.G. Huddleston et al., Green Chemistry 2001, 3, 156 164 describes an ionic liquid that is liquid at room temperature.

[0040] FDCA yield = molar amount of FDCA product / molar amount of hexacarbon sugar diacid compound 100%.

[0041] The inventors unexpectedly discovered that when using an ionic liquid containing an anionic moiety selected from halide anions, 2,5-carboxylic acid compounds prepared by dehydration cyclization of hexacarbon sugar diacid compounds... The FDCA yield is high for furanyl dicarboxylic acid compounds, and it is believed that ionic liquids not only serve as reaction media, but also provide halide anions to aid in the catalysis of the reaction.

[0042] 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.

[0043] 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 C1... 10 Alkyl, cyclohexyl, phenylmethylene, phenylethylene, phenylpropylene, phenyl, etc.

[0044] In one embodiment, the ionic liquid comprises a halide anion selected from chlorine, bromine, or iodine. For example, the ionic liquid is selected from 1,3... Dimethyliodide imidazole, 1 Ethyl 3 Methylimidazole, 1 Butyl 3 Methylimidazole iodide, 1,3 Dimethyl imidazole bromide, 1 Ethyl 3 Methylimidazolium bromide, 1 Butyl 3 Methylimidazolium bromide, 1,3 Dimethyl imidazole chloride, 1 Ethyl 3 Methylimidazole, 1 Butyl 3 Methylimidazole, 1 Jiji 3 Methylimidazole, 1 Jiji 3 Methylimidazolium bromide, 1 Jiji 3 Methylimidazole, 1 methyl 3 Propyl iodide imidazole, 1 methyl 3 Propyl imidazole bromide, 1 methyl 3 Propyl imidazole chloride, 1 decyl 3 Methylimidazole, 1 decyl 3 Methylimidazolium bromide, 1 decyl 3 Methylimidazole iodide, 1,3 Diisopropyl imidazole chloride, 1,3 Diisopropylimidazolium bromide, 1,3 Diisopropylimidazolium iodide, 1,3 Di-tert-butyl imidazole chloride, 1,3 Di-tert-butyl imidazole bromide, 1,3 Di-tert-butylimidazolium iodide, 1,3 Dicyclohexyl imidazole chloride, 1,3 Dicyclohexyl imidazole bromide, 1,3 Dicyclohexylimidazolium iodide, 1 Ethylpyridine bromide, 1 Ethylpyridine chloride, 1 One or more of ethyl iodide pyridine.

[0045] In one specific embodiment, the ionic liquid is selected from 1 Ethyl 3 Methylimidazolium bromide, 1 Butyl 3 Methylimidazolium bromide, 1 One or more of ethylpyridine bromide.

[0046] 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.

[0047] 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.

[0048] In one implementation, no organic solvent was introduced into the reaction system.

[0049] In another embodiment, an organic solvent is introduced into the reaction system. Introducing an organic solvent may be beneficial in reducing the viscosity of the ionic liquid. For example, the reaction system may incorporate a solvent selected from 1,4-dimethylformamide (DMI). One or more organic solvents including dioxane, dimethyl sulfoxide, sulfolane, dimethylformamide (DMF), dimethylacetamide (DMA), and glycol dimethyl ether.

[0050] 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°C. 180°C. In a preferred embodiment, the reaction temperature is 120°C. 160℃.

[0051] 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%.

[0052] 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%.

[0053] 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 1.0 M NaOH solution, then further diluted with water to dissolve the ionic liquid and all substrates and products, and then sampled for 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 that 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 substrate hexose diacid and the formation of FDCA. This method employs Hi... A Plex H column (300 mm x 7.7 mm) was used. The mobile phase was 5 mmol / L dilute sulfuric acid aqueous solution, the flow rate was 0.6 mL / min, the column temperature was 40 °C, and the injection volume was 20 μL. Using this chromatographic method, the retention time of the 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.

[0054] This disclosure describes the preparation of 2,5-carbohydrate diacid compounds via acid-catalyzed dehydration and cyclization in an ionic liquid system. Furan dicarboxylic acid (FDCA) is being developed using ionic liquids 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 proceed under normal pressure without the need for depressurization, exhibiting high efficiency. The reaction can be completed in 1–5 hours at 160℃. The reaction conditions are relatively mild, FDCA exhibits good selectivity, and the product purity is high. The entire production process has minimal environmental pollution, making it suitable for industrial production.

[0055] Example 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.

[0056] Experiment 1 below 36. Using potassium gluconate monopotassium as a raw material for hexose diacid compounds, using 1 Ethyl 3 Methylimidazolium bromide, 1 Butyl 3 Methylimidazolium bromide or 1 Ethylpyridine bromide is used as an ionic liquid, with trifluoromethanesulfonic acid, methanesulfonic acid, or sulfuric acid as the acid catalyst, as shown in Table 1. 2,5-dimethylformamide (2,5-dimethylformamide) was prepared by dehydration and cyclization under the reaction conditions listed in 4. Furandicarboxylic acid (FDCA).

[0057] Taking Experiment 1 as an example, 0.099 g (0.4 mmol) of potassium gluconate was added to a thick-walled pressure-resistant tube. Ethyl 3 Methylimidazolium bromide 0.61 g (3.2 mmol) and trifluoromethanesulfonic acid 0.36 g (2.4 mmol) were used. The mixture was heated to 120 °C and reacted for 1 h. After the reaction was complete, 1 M NaOH aq was added to adjust the pH of the system to 8–10. After the reaction solution was completely dissolved, a small amount of the solution was diluted with 5 mmol H₂SO₄ aqueous solution and the reaction conversion was analyzed by HPLC. The yield of FDCA was 86.7%.

[0058] Table 1: In 1 Ethyl 3 The synthesis of FDCA using trifluoromethanesulfonic acid as a catalyst in methylimidazolium bromide

[0059] Note: [a], [b], and [c] respectively added 5 wt%, 10 wt%, and 20 wt% water to the reaction system; [d] Add 4.48 equivalents of ethylene glycol to the reaction system; [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.

[0060] Table 2: Use of methanesulfonic acid / sulfuric acid in 1 Ethyl 3 Synthesis of FDCA from methyl imidazole

[0061] Table 3: Use of trifluoromethanesulfonic acid in 1 Synthesis of FDCA from ethylpyridine bromide

[0062] Table 4: Use of trifluoromethanesulfonic acid in 1 Butyl 3 Synthesis of FDCA from methyl imidazole

[0063] Several experiments on the preparation of FDCA 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 FDCA yield could reach a maximum of 93.5% (experimental). 6) Under the same experimental conditions, when the reaction temperature is increased to 150℃ and the reaction time is 0.5h, the yield of FDCA can reach 85.9% (experimental). 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℃ for 5 h, the yield of FDCA could reach 81.5% (experimental). 15). When 5 wt% H2O is added to the reaction system and the reaction is carried out at 120℃ for 5 h, the yield of FDCA can still reach 81.5% (experimental). 18). Adding the polar solvent sulfolane to the reaction system did not affect the reaction results (Experiment 22). 24). High FDCA conversion rates can still be achieved using other ionic liquids in the reaction (Experiment 25). 36).

[0064] Experiment 37 38. As shown in Table 5 below, using potassium gluconate monopotassium as a raw material for hexose diacid compounds, 1 Ethyl 3 Methylimidazolium hydrogen sulfate, as an ionic liquid, was used as an acid catalyst and prepared by dehydration and cyclization under the reaction conditions listed in Table 5. Furandicarboxylic acid (FDCA).

[0065] Table 5: Use of sulfuric acid in 1 Ethyl 3 Synthesis of FDCA from methylimidazolium hydrogen sulfate

[0066] Experiment 37 38 uses 1 Ethyl 3 The yields of FDCA from methylimidazolium hydrogen sulfate and sulfuric acid were significantly lower.

[0067] Experiment 39 40 As shown in Table 6 below, using potassium gluconate monopotassium as a raw material for hexose diacid compounds, 1 Ethyl 3 Methylimidazolium hexafluorophosphate was used as an ionic liquid, and trifluoromethanesulfonic acid was used as an acid catalyst to prepare 2,5-methylimidazolium hexafluorophosphate via dehydration and cyclization under the reaction conditions listed in Table 6. Furandicarboxylic acid (FDCA).

[0068] Table 6: Use of trifluoromethanesulfonic acid in 1 Ethyl 3 Synthesis of FDCA from methylimidazolium hexafluorophosphate

[0069] Experiment 41 42 As shown in Table 7 below, using potassium gluconate monophosphate as a raw material for hexose diacid compounds, 1 Ethyl 3 Methylimidazolium tetrafluoroborate was used as an ionic liquid, and trifluoromethanesulfonic acid was used as an acid catalyst to prepare 2,5-methylimidazolium tetrafluoroborate via dehydration and cyclization under the reaction conditions listed in Table 7. Furandicarboxylic acid (FDCA).

[0070] Table 7: Use of trifluoromethanesulfonic acid in 1 Ethyl 3 Synthesis of FDCA from methylimidazolium tetrafluoroborate

[0071] Experiment 43 44 As shown in Table 8 below, using potassium gluconate monopotassium as a raw material for hexose diacid compounds, using 1 Ethyl 3 Methylimidazolium trifluoromethanesulfonate was used as an ionic liquid, and trifluoromethanesulfonic acid was used as an acid catalyst to prepare 2,5-methylimidazolium trifluoromethanesulfonate via dehydration cyclization. Furandicarboxylic acid (FDCA).

[0072] Table 8: Use of trifluoromethanesulfonic acid in 1 Ethyl 3 Synthesis of FDCA from methylimidazolium trifluoromethanesulfonate

[0073] Experiment 39 44 uses trifluoromethanesulfonic acid as a catalyst, and the ionic liquid is 1. Ethyl 3 Methylimidazolium hexafluorophosphate, 1 Ethyl 3 Methylimidazolium tetrafluoroborate or 1 Ethyl 3 Methylimidazolium trifluoromethanesulfonate, their yields for preparing FDCA were significantly lower than those using 1 in Table 1. Ethyl 3 Yield of FDCA prepared by methyl imidazole bromide.

[0074] Compared with the prior art, this disclosure has one or more of the following advantages: 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. 2) Ionic liquids act as both reaction co-catalysts and reaction solvents, avoiding the need to add strongly polar aprotic solvents (such as sulfolane, dimethyl sulfoxide, 1,4-dimethylolpropane, etc.) as required in existing technologies. Dioxane (dioxane), the entire production process has relatively low environmental impact; 3) The reaction time is relatively short, generally 1 to 5 hours to complete; 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; 5) The FDCA product obtained after post-processing has high purity; 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.

[0075] Experiment 45 47. As shown in Table 9 below, D Using potassium gluconate monophosphate as a raw material, sulfolane as a solvent, and NaBr or LiBr as an additive, 2,5-gluconate monophosphate monophosphate was obtained by dehydration and cyclization under TfOH acid catalysis. Furan dicarboxylic acid, the reaction temperature is 120-160℃.

[0076] Table 9: Synthesis of FDCA using trifluoromethanesulfonic acid under sodium bromide / lithium bromide conditions

[0077] Note: [h] Sodium bromide; [i] Lithium bromide.

[0078] Experiment 45 The advantages and disadvantages of technical solution 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.

[0079] Experiment 48 51 with D Using potassium gluconate monophosphate as a raw material, sulfolane as a solvent, and tetrabutylammonium bromide (TBAB), tetramethylammonium bromide (TMAB), or tetraethylammonium bromide (TEAB) as additives, 2,5-dimethylammonium bromide was obtained by dehydration and cyclization under TfOH acid catalysis. Furan dicarboxylic acid, reaction temperature is 120℃.

[0080] Table 10: Synthesis of FDCA using trifluoromethanesulfonic acid under tetrabutylammonium bromide / tetramethylammonium bromide / tetraethylammonium bromide conditions

[0081] Notes: [j] Tetrabutylammonium bromide; [k] Tetramethylammonium bromide; [l] Tetraethylammonium bromide.

[0082] Experiment 48 The advantages and disadvantages of the 51 technical solution 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.

[0083] Experiment 52 54. Using galactosic acid as a raw material, 1 Ethyl 3 Methylimidazolium bromide, as an ionic liquid, undergoes dehydration and cyclization under TfOH acid catalysis to yield 2,5-methylimidazolium bromide. Furan dicarboxylic acid, reaction temperature is 120℃.

[0084] Table 11: Using galactobionic acid as a raw material and trifluoromethanesulfonic acid in 1 Ethyl 3 Synthesis of FDCA from methyl imidazole

[0085] Experiment 52 54 indicates that galactoic acid can replace D. Potassium gluconate monopotassium is used in the method of this disclosure to synthesize FDCA.

[0086] 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 for preparing 2,5-furandicarboxylic acid compounds, characterized in that, 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-dimethylformamide (DDI). Furanodicarboxylic acid compounds; The ionic liquid 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; The acid catalyst comprises trifluoromethylsulfonic acid; The general structural formula of the hexacarbon sugar diacid compounds is R1OOC(CHOH)4COOR2, wherein R1 and R2 are each independently selected from hydrogen, alkali metals, alkaline earth metals, alkyl groups, and so on. CH2 (CH2) x CH2OH, aralkyl and aryl groups; The 2,5 The structures of furanyl dicarboxylic acid compounds are shown in formula (I). Equation (I), In formula (I), R1 and R2 are each independently selected from hydrogen, alkali metals, alkaline earth metals, alkyl groups, and so on. CH2 (CH2) x CH2OH, aralkyl and aryl.

2. The method according to claim 1, wherein, In the general structural formula of the six-carbon sugar diacid compounds The alkali metal is selected from lithium, sodium, or potassium; and / or The alkaline earth metal is selected from calcium or magnesium; and / or The alkyl group is C1. 6-alkyl; and / or The CH2 (CH2) x In CH2OH, x is 0, 1, 2, 3, or 4; and / or The aryl group is benzyl and / or phenethyl; and / or The aryl group is phenyl; Preferably, The hexose diacid compounds are selected from gluconic acid, dimethyl gluconic acid, diethyl gluconic acid, di-n-propyl gluconic acid, diisopropyl gluconic acid, di-n-butyl gluconic acid, diisobutyl gluconic acid, di-tert-butyl gluconic acid, diethylene glycol gluconic acid, dipropylene glycol gluconic acid, dibutyl glycol gluconic acid, sodium gluconic acid, potassium gluconic acid, calcium gluconic acid, and gluconic acid. 1,4 lactone, gluconic acid 6,3 lactone, gluconic acid 1,4:6,3 Dilactone, galactobionic acid, dimethyl galactobionic acid, diethyl galactobionic acid, di-n-propyl galactobionic acid, diisopropyl galactobionic acid, di-n-butyl galactobionic acid, diisobutyl galactobionic acid, di-tert-butyl galactobionic acid, diethylene glycol galactobionic acid, dipropylene glycol galactobionic acid, dibutyl galactobionic acid, sodium galactobionic acid, potassium galactobionic acid, calcium galactobionic acid, galactobionic acid 1,4 lactone, galactoside 6,3 lactone, galactoside 1,4:6,3 Dilactone, mannose, dimethyl mannose, diethyl mannose, di-n-propyl mannose, diisopropyl mannose, di-n-butyl mannose, diisobutyl mannose, di-tert-butyl mannose, diethylene glycol mannose, dipropylene glycol mannose, dibutyl mannose, sodium mannose, potassium mannose, calcium mannose, mannose 1,4 lactone, mannose 6,3 lactone, mannose 1,4:6,3 One or more of the dilactones.

3. The method according to claim 1, wherein, In formula (I), The alkali metal is selected from lithium, sodium, or potassium; and / or The alkaline earth metal is selected from calcium or magnesium; and / or The alkyl group is C1. 6-alkyl; and / or The CH2 (CH2) x In CH2OH, x is 0, 1, 2, 3, or 4; and / or The aryl group is benzyl and / or phenethyl; and / or The aryl group is phenyl; Preferably, the 2,5 Furan dicarboxylic acid compounds are 2,5 Furandicarboxylic acid.

4. The method according to claim 1, wherein, The nitrogen atom of the ionic liquid has a C1 atom selected from straight-chain or branched chains. 10 Alkyl, cyclohexyl, phenyl Asia C1 3. Substituents of alkyl or phenyl groups; and / or The ionic liquid includes halide anions selected from chlorine, bromine, or iodine; Preferably, The ionic liquid is selected from 1,3 Dimethyliodide imidazole, 1 Ethyl 3 Methylimidazole, 1 Butyl 3 Methylimidazole iodide, 1,3 Dimethyl imidazole bromide, 1 Ethyl 3 Methylimidazolium bromide, 1 Butyl 3 Methylimidazolium bromide, 1,3 Dimethyl imidazole chloride, 1 Ethyl 3 Methylimidazole, 1 Butyl 3 Methylimidazole, 1 Jiji 3 Methylimidazole, 1 Jiji 3 Methylimidazolium bromide, 1 Jiji 3 Methylimidazole, 1 methyl 3 Propyl iodide imidazole, 1 methyl 3 Propyl imidazole bromide, 1 methyl 3 Propyl imidazole chloride, 1 decyl 3 Methylimidazole, 1 decyl 3 Methylimidazolium bromide, 1 decyl 3 Methylimidazole iodide, 1,3 Diisopropyl imidazole chloride, 1,3 Diisopropylimidazolium bromide, 1,3 Diisopropylimidazolium iodide, 1,3 Di-tert-butyl imidazole chloride, 1,3 Di-tert-butyl imidazole bromide, 1,3 Di-tert-butylimidazolium iodide, 1,3 Dicyclohexyl imidazole chloride, 1,3 Dicyclohexyl imidazole bromide, 1,3 Dicyclohexylimidazolium iodide, 1 Ethylpyridine bromide, 1 Ethylpyridine chloride, 1 One or more of ethylpyridine iodide; preferably selected from 1 Ethyl 3 Methylimidazolium bromide, 1 Butyl 3 Methylimidazolium bromide, 1 One or more of ethylpyridine bromide.

5. The method according to claim 1, wherein, The acid catalyst further comprises one or more selected from hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, p-trifluoromethylbenzenesulfonic acid, acetic acid, trifluoroacetic acid, and phosphotungstic acid.

6. The method according to any one of claims 1-5, wherein, No co-catalysts 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, or tetrabutylammonium bromide were added to the reaction system.

7. The method according to any one of claims 1-5, wherein, No organic solvents were added to the reaction system.

8. The method according to any one of claims 1-5, wherein, The reaction system is introduced from 1,4 One or more organic solvents including dioxane, dimethyl sulfoxide, sulfolane, dimethylformamide, dimethylacetamide, and glycol dimethyl ether.

9. The method according to any one of claims 1-5, wherein, The water content in the reaction medium is below 10 wt%, preferably below 5 wt%.

10. The method according to any one of claims 1-5, wherein, The dehydration reaction temperature is 100°C. 180℃.

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