A method for preparing 2,5-furandicarboxylic acid and its intermediates

Abstract

This invention discloses a method for preparing 2,5-furandicarboxylic acid and its intermediates. The method involves reacting alkyl furoate and paraformaldehyde in an acid solution with a mass percentage concentration of 0.1%-10%, under the catalysis of a Lewis acid containing metal ions, at a temperature of 50-90°C, to generate alkyl 5-hydroxymethyl furoate. This method can obtain the target product in high yield with fewer steps while reducing the amount of acid used. Furthermore, using this alkyl 5-hydroxymethyl furoate as a raw material, 2,5-furandicarboxylic acid can be prepared with high selectivity. The overall process involves relatively few steps, produces less waste, is more environmentally friendly, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a method for preparing 2,5-furandicarboxylic acid and its intermediates. Background Technology

[0002] 2,5-Furfurandicarboxylic acid (FDCA, structural formula: 2,5-furandicarboxylic acid is an important new type of chemical product with broad market application prospects. It can replace terephthalic acid (PTA) and is widely used in the preparation of high-performance engineering plastics such as polyester, epoxy resin, polyamide, and polyurethane. In addition, 2,5-furandicarboxylic acid itself can also be used as a chemical raw material and pharmaceutical intermediate.

[0003] Currently, the main method for synthesizing 2,5-furandicarboxylic acid is based on 5-hydroxymethylfurfural (HMF, structural formula: FDCA is prepared from fructose and glucose through an oxidation reaction. However, this method has the following main problems: ① HMF is mainly prepared by dehydrating fructose and glucose. If FDCA is to replace terephthalic acid in the preparation of polyester materials, it will compete with food for resources. Moreover, the price of the raw material 5-hydroxymethylfurfural is relatively high. ② HMF itself has poor stability and is difficult to separate. In addition, there are many intermediates in the process of oxidizing HMF to prepare FDCA. The oxidation is difficult and the selectivity is poor. The catalysts used are often precious metal catalysts, which are expensive and cannot be produced on a large scale.

[0004] Another synthetic method uses furoic acid (structural formula: Using furoic acid as a raw material, Zhou Guangyuan et al. from the Dalian Institute of Chemical Physics first prepared potassium furoate, which was then disproportionated with carbon dioxide under high temperature and pressure to generate FDCA. This route uses furoic acid derived from non-grain biomass, but it has high equipment requirements, poor selectivity, and certain difficulties in large-scale production. Liu Lang et al. developed a chloromethylation route to prepare FDCA using furoic acid as a raw material. After esterification with concentrated sulfuric acid, chloromethylation, hydrolysis, and finally oxidation with potassium permanganate, FDCA was obtained. The reaction equation is as follows:

[0005]

[0006] However, the esterification, chloromethylation, hydrolysis, and oxidation processes in this furoic acid-chloromethylation route all have some problems to varying degrees. For example, the esterification step not only requires concentrated sulfuric acid, which places high demands on the equipment, but also requires the addition of alkali to neutralize the waste liquid after the reaction, resulting in high levels of waste. In addition, the vacuum distillation step in the post-treatment may carry away the product, and when unreacted raw materials such as methanol are distilled off, the equilibrium will shift, and the product will become a raw material, resulting in a relatively low yield. In the chloromethylation and hydrolysis processes, not only are large amounts of hydrogen chloride or alkali solution required, resulting in a lot of waste, but the overall yield of the two steps is also low. In the oxidation process, potassium permanganate oxidation is used, which has high raw material and auxiliary material costs, low oxidation selectivity, and also high levels of waste. In addition, the route is also relatively long, which is not conducive to industrial production. Summary of the Invention

[0007] The purpose of this invention is to overcome one or more shortcomings of the prior art and provide an improved method for preparing 2,5-furandicarboxylic acid intermediates (the compound shown in formula (I)), which can obtain the target product in high yield with fewer steps while reducing the amount of acid used.

[0008] The present invention also provides another method for preparing 2,5-furandicarboxylic acid intermediate (the compound shown in formula (Ⅰ)) using furoic acid as a starting material.

[0009] The present invention also provides a method for preparing 2,5-furandicarboxylic acid.

[0010] To achieve the above objectives, the present invention employs the following technical solution:

[0011] A method for preparing a compound of formula (I), the method comprising: reacting a compound of formula (II) and paraformaldehyde in an acid solution with a mass percentage concentration of 0.1%-10% under the catalysis of a Lewis acid containing metal ions at a temperature of 50-90°C to generate a compound of formula (I).

[0012]

[0013] In equation (I) or equation (II), R is C 1-4 alkyl.

[0014] According to some preferred aspects of the invention, the acid in the acid solution is an inorganic acid.

[0015] According to some preferred aspects of the invention, the molar ratio of the acid in the acid solution to the compound represented by formula (II) is 0.01-1.0:1, further 0.01-0.5:1, and even further 0.01-0.25:1.

[0016] According to some preferred and specific aspects of the invention, the acid solution is one or more combinations selected from hydrochloric acid, aqueous sulfuric acid, aqueous nitric acid, and aqueous phosphoric acid.

[0017] According to some preferred aspects of the invention, the mass percentage concentration of the acid solution is 0.1%-5%. Further, the mass percentage concentration of the acid solution is 0.3%-4%. In some embodiments of the invention, the mass percentage concentration of the acid solution is 0.5%-3%.

[0018] According to some preferred aspects of the invention, the reaction is carried out at 60-80°C.

[0019] According to some preferred aspects of the present invention, the molar ratio of the paraformaldehyde to the compound represented by formula (II) is 0.5-3.0:1, further 0.6-2.0:1, and even further 0.8-1.6:1.

[0020] According to some preferred aspects of the invention, the Lewis acid is a metal halide salt.

[0021] Furthermore, the metal in the metal halide salt is zinc, aluminum, or tin.

[0022] According to some preferred and specific aspects of the invention, the Lewis acid is one or more selected from zinc chloride, aluminum chloride, tin chloride, zinc bromide, and tin bromide.

[0023] According to one specific aspect of the invention, the Lewis acid is zinc chloride.

[0024] According to some preferred aspects of the invention, the molar ratio of the Lewis acid to the compound represented by formula (II) is 0.05-3.0:1, further 0.05-1.5:1, even further 0.05-1.0:1, and still further 0.05-0.5:1.

[0025] In some preferred embodiments of the present invention, the reaction is carried out in a one-pot process, which includes adding the compound of formula (II), paraformaldehyde, acid solution, and Lewis acid to a reaction vessel, heating, and maintaining the temperature for reaction.

[0026] Furthermore, after the reaction is complete, the unreacted compound (II) and the product compound (I) are extracted using an organic solvent. The aqueous phase is reused for the next batch of reaction, and the compound (II) is recovered in the oil phase to obtain the compound (I).

[0027] Further, the organic solvent is selected from one or more combinations of chloroform, 1,2-dichloroethane, methyl tert-butyl ether, ethyl acetate, propyl acetate, and 2-methylfuran. According to one specific aspect of the invention, the organic solvent is methyl tert-butyl ether.

[0028] In some embodiments of the present invention, in formula (I) or formula (II), R is methyl or ethyl. When R is methyl, the compound represented by formula (II) is methyl furoate, and when R is ethyl, the compound represented by formula (II) is ethyl furoate.

[0029] Another technical solution provided by the present invention: a method for preparing a compound represented by formula (Ⅰ), the method comprising:

[0030] (1) Make furoic acid and C 1-4 Alkyl alcohols undergo esterification to produce the compound shown in formula (II);

[0031]

[0032] (2) The compound shown in formula (II) and paraformaldehyde are reacted in an acid solution with a mass percentage concentration of 0.1%-10% under the catalysis of Lewis acid containing metal ions at a temperature of 50-90℃ to produce the compound shown in formula (I).

[0033]

[0034] In equation (I) or equation (II), R is C 1-4 alkyl.

[0035] According to some preferred aspects of the invention, in step (1), the esterification reaction is carried out in the presence of a catalyst, which is a strongly acidic resin.

[0036] According to the present invention, when a strong acid resin is selected as the catalyst for the esterification reaction, on the one hand, it can be recycled and reused, and no alkali neutralization is required during post-treatment, reducing the generation of waste. On the other hand, practice has shown that the use of strong acid resin has also resulted in a significantly improved yield, and the post-treatment is simpler, requiring only direct filtration, which avoids the loss of the target product due to complex post-treatment processes, further ensuring the yield. In addition, the strong acid resin can also be recycled and reused, reducing production costs.

[0037] Further, the strong acid resin is selected from one or more of Lanxess SP-112H, S-200KR, S-108, Blue Depth LS-51, 001X4, D001, and Solanite C100E, C100EDL, and C100EFG. According to one specific aspect of the invention, the strong acid resin is Blue Depth LS-51.

[0038] Furthermore, the mass ratio of the strong acid resin to the furoic acid is 0.3-30:1, further 0.3-20:1, even further 0.3-10:1, and still further 0.8-6:1.

[0039] Furthermore, in step (1), the esterification reaction is carried out at a temperature of 60-150°C.

[0040] Further, in step (1), the C 1-4 The molar ratio of alkyl alcohol to furoic acid is 10-100:1, further 10-80:1, even further 10-50:1, and still further 10-30:1.

[0041] Another technical solution provided by the present invention: a method for preparing 2,5-furandicarboxylic acid, the method comprising:

[0042] (1) Make furoic acid and C 1-4 Alkyl alcohols undergo esterification to produce the compound shown in formula (II);

[0043]

[0044] (2) The compound shown in formula (II) and paraformaldehyde are reacted in an acid solution with a mass percentage concentration of 0.1%-10% under the catalysis of Lewis acid containing metal ions at a temperature of 50-90℃ to produce the compound shown in formula (I).

[0045]

[0046] In equation (I) or equation (II), R is C 1-4 alkyl;

[0047] (3) React the compound shown in formula (Ⅰ) with an oxidant under alkaline conditions, and then acidify to obtain 2,5-furandicarboxylic acid;

[0048]

[0049] According to some preferred aspects of the present invention, in step (3), the oxidant is one or more selected from alkali metal hypochlorite, alkali metal chlorite, hydrogen peroxide, peroxytert-butanol, and alkali metal perchlorate.

[0050] In some embodiments of the present invention, in step (3), the oxidant is one or more of sodium hypochlorite, sodium chlorite, hydrogen peroxide, tert-butanol peroxide, and sodium perchlorate.

[0051] Further, in step (3), the molar ratio of the oxidant to the compound shown in formula (I) is 2.0-3.0:1, further 2.0-2.8:1, and even further 2.0-2.4:1.

[0052] Furthermore, in step (3), the reaction is carried out at 5-40°C, and further at 10-30°C.

[0053] Further, in step (3), the reaction is carried out at a pH of 9-11. In some embodiments, the reaction can be controlled to proceed at a pH of 9-11 by adding an alkali or an aqueous solution thereof (e.g., including but not limited to sodium hydroxide or an aqueous solution thereof).

[0054] Furthermore, in step (3), the reaction is carried out in the presence of a catalyst, which is a metal oxide.

[0055] According to some preferred aspects of the invention, the metal oxide is one or more combinations selected from copper oxide, nickel oxide, cobalt oxide, and manganese oxide.

[0056] Furthermore, the amount of catalyst added, by mass percentage, is 1%-50% of the amount of the compound shown in formula (I), further 1%-30%, and even further 1%-20%.

[0057] In some embodiments of the present invention, the acidification involves adding hydrochloric acid, sulfuric acid aqueous solution, nitric acid aqueous solution, or phosphoric acid aqueous solution, and the concentration can be selected to be relatively high, for example, concentrated hydrochloric acid. Furthermore, the pH value of the system after acidification is controlled to be less than 1, preferably less than 0.5.

[0058] In some embodiments of the present invention, step (3) includes: adding the compound shown in formula (Ⅰ) into a reaction vessel, adding a metal oxide, controlling the pH of the system to 9-11 by adding an alkali or its aqueous solution, then adding an oxidant at 10-30°C, controlling the pH of the system to remain at 9-11 during the addition of the oxidant, keeping the reaction at a constant temperature after the addition, and then acidifying, filtering, washing, and drying.

[0059] According to the present invention, in step (3), the ester is hydrolyzed during the oxidation of alcohol to carboxylic acid.

[0060] According to the present invention, in step (3), the compound shown in formula (I) is used as a raw material for oxidation. The raw material has good stability and is easy to oxidize. Furthermore, alkali metal hypochlorite, alkali metal chlorite, hydrogen peroxide, peroxide tert-butanol and alkali metal perchlorate, which are more commonly used in industry, are used for oxidation. In particular, alkali metal hypochlorite is not only cheaper, but also has high selectivity. The reaction yield of this step is high, and can even reach more than 95%.

[0061] Furthermore, according to the present invention, the process of the present invention can prepare 2,5-furandicarboxylic acid with relatively few process steps, which is beneficial for large-scale industrial production.

[0062] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0063] Through extensive experimental analysis during the practical process, the inventors of this invention concluded that the chloromethylation reaction does not proceed directly from methyl furoate to methyl 5-chloromethyl-2-furanoate. Instead, it first generates the intermediate methyl 5-hydroxymethyl-2-furanoate, followed by the chlorinated product. Furthermore, practical experience revealed that this methyl 5-hydroxymethyl-2-furanoate facilitates hydroxyl oxidation with better selectivity. Based on this, this invention provides a process for preparing alkyl 5-hydroxymethyl-2-furanoate and its derivatives, and a process for preparing 2,5-furandicarboxylic acid using these as raw materials. In particular, when preparing alkyl 5-hydroxymethyl-2-furanoate from alkyl furoate, the use of a low-concentration acid solution and a relatively high temperature resulted in an unexpectedly high yield. This significantly reduces the amount of acid used, and the separated acid solution can be reused, resulting in virtually no wastewater generation, making it more environmentally friendly and beneficial for industrial applications. Detailed Implementation

[0064] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0065] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0066] Example 1

[0067] This example provides a method for preparing 2,5-furandicarboxylic acid, and its synthetic route is as follows:

[0068]

[0069] The preparation method of this 2,5-furandicarboxylic acid includes:

[0070] (1) Preparation of methyl furoate

[0071] 200.02 g of furoic acid, 599.99 g of Blue Depth LS-51 resin, and 1143.60 g of methanol were weighed into a 3 L reaction flask and placed in a water bath for heating and stirring. After reaching the reflux temperature (T = 68 °C), the mixture was kept at this temperature for 30 h. After cooling to room temperature, the mixture was filtered, and the resin was washed with a small amount of methanol. After recovering the methanol from the filtrate, the mixture was distilled to obtain 220.78 g of methyl furoate, with a yield of 98.10%.

[0072] (2) Preparation of methyl 5-hydroxymethylfurfural

[0073] The methyl furoate prepared above was added to a 2L reaction flask. 63.09g of paraformaldehyde (molecular weight 30.03, calculated based on formaldehyde molecular weight), 47.72g of zinc chloride, and 638.30g of 1% dilute hydrochloric acid were weighed out. The mixture was heated and stirred. When the temperature reached 70℃, the reaction was maintained for 8 hours. After cooling to room temperature, methyl tert-butyl ether was added for extraction three times, each time 500g. The organic phases were combined, and after recovering the methyl tert-butyl ether by distillation, 1.10g of methyl furoate was distilled out. 246.84g of 5-hydroxymethyl furoate was further distilled out. The reaction conversion rate was 99.50%, and the yield was 90.76%.

[0074] (3) Preparation of 2,5-furandicarboxylic acid (FDCA)

[0075] 100.01 g of the methyl 5-hydroxymethylfurfural prepared above and 2.0 g of nickel oxide were weighed into a 2 L reaction flask. 50 g of sodium hydroxide aqueous solution with a concentration of 0.004 g / L was added to control the pH value at 10 ± 1. When T = 20 °C, a 10% sodium hypochlorite aqueous solution was slowly added dropwise, while a 5% sodium hydroxide aqueous solution was used to control the pH value of the reaction at 10 ± 1. The dropwise addition was carried out over 15 h, and a total of 1048.85 g of 10% sodium hypochlorite aqueous solution was added. The reaction was kept at this temperature for 1 h, and then acidified with 37% concentrated hydrochloric acid until the pH value was less than 0.5. After filtration, washing, and drying, 95.10 g of FDCA product was obtained, with a yield of 95.12%.

[0076] Example 2

[0077] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that the temperature is controlled at 50°C and the reaction is maintained at that temperature for 20 hours during the preparation of methyl 5-hydroxymethylfurfural. The conversion rate is 90.65%, and the yield is 83.55%.

[0078] Example 3

[0079] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that the temperature is controlled at 60°C and the reaction is maintained at that temperature for 12 hours during the preparation of methyl 5-hydroxymethylfurfural. The conversion rate is 95.1%, and the yield is 86.60%.

[0080] Example 4

[0081] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that the temperature is controlled at 90°C during the preparation of methyl 5-hydroxymethylfurfural. The conversion rate is 100%, and the yield is 81.44%.

[0082] Example 5

[0083] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that the temperature is controlled at 80°C during the preparation of methyl 5-hydroxymethylfurfural. The conversion rate is 100%, and the yield is 87.31%.

[0084] Example 6

[0085] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that the mass concentration of dilute hydrochloric acid used in the preparation of methyl 5-hydroxymethylfurfural is 5%. The conversion rate is 100%, and the yield is 78.46%.

[0086] Example 7

[0087] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that the mass concentration of dilute hydrochloric acid used in the preparation of methyl 5-hydroxymethylfurfural is 3%. The conversion rate is 100%, and the yield is 83.71%.

[0088] Example 8

[0089] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that in the preparation of methyl 5-hydroxymethylfurfural, the mass concentration of dilute hydrochloric acid used is 0.5%, and the reaction is maintained at this temperature for 15 hours. The conversion rate is 95.01%, and the yield is 84.41%.

[0090] Example 9

[0091] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that in the preparation of methyl 5-hydroxymethylfurfural, the mass of 1% dilute hydrochloric acid used is 1600.22 g. The conversion rate is 100%, and the yield is 89.17%.

[0092] Example 10

[0093] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that in the preparation of methyl 5-hydroxymethylfurfural, dilute sulfuric acid with a mass concentration of 1.31% is used instead of dilute hydrochloric acid, and the molar amount of sulfuric acid in the dilute sulfuric acid is controlled to be half the molar amount of hydrogen chloride in the dilute hydrochloric acid. The conversion rate is 100%, and the yield is 85.52%.

[0094] Example 11

[0095] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that in the preparation of methyl 5-hydroxymethylfurfural, dilute nitric acid with a mass concentration of 1.71% is used instead of dilute hydrochloric acid, and the molar amount of nitric acid in the dilute nitric acid is controlled to be the same as the molar amount of hydrogen chloride in the dilute hydrochloric acid. The conversion rate is 100%, and the yield is 84.90%.

[0096] Example 12

[0097] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that in the preparation of methyl 5-hydroxymethylfurfural, the amount of zinc chloride used is 30.05 g, and the reaction is maintained at this temperature for 16 h. The conversion rate is 96.90%, and the yield is 87.42%.

[0098] Example 13

[0099] This example provides a method for preparing 2,5-furandicarboxylic acid, which is basically the same as in Example 1, except that zinc chloride is replaced with an equimolar amount of tin chloride in the preparation of methyl 5-hydroxymethylfurfural. The conversion rate is 100%, and the yield is 85.5%.

[0100] Example 14

[0101] This example provides a method for preparing 2,5-furandicarboxylic acid, and its synthetic route is as follows:

[0102]

[0103] The preparation method of this 2,5-furandicarboxylic acid includes:

[0104] (1) Preparation of ethyl furoate

[0105] 200.0 g of furoic acid, 600.01 g of Blue Depth LS-51 resin, and 1150.30 g of ethanol were weighed into a 3 L reaction flask and placed in a water bath for heating and stirring. After reaching the reflux temperature (T = 80 °C), the mixture was kept at this temperature for 30 h. After cooling to room temperature, the mixture was filtered, and the resin was washed with a small amount of ethanol. After recovering the ethanol from the filtrate, the mixture was distilled to obtain 244.82 g of ethyl furoate, with a yield of 97.90%.

[0106] (2) Preparation of ethyl 5-hydroxymethylfurfural

[0107] Ethyl furoate prepared above was added to a 2L reaction flask. 62.95g of paraformaldehyde (molecular weight 30.03, calculated based on formaldehyde molecular weight), 47.61g of zinc chloride, and 636.88g of 1% dilute hydrochloric acid were weighed out. The mixture was heated and stirred. When the temperature reached 70℃, the reaction was maintained for 8 hours. After cooling to room temperature, methyl tert-butyl ether was added for extraction three times, with 500g added each time. The organic phases were combined, and after recovering methyl tert-butyl ether by distillation, 2.45g of ethyl furoate was distilled out. 267.86g of 5-hydroxymethyl ethyl furoate was then further distilled out. The reaction conversion rate was 99.0%, and the yield was 90.11%.

[0108] (3) Preparation of 2,5-furandicarboxylic acid (FDCA)

[0109] 109.00 g of the ethyl 5-hydroxymethylfurfural prepared above and 2.0 g of nickel oxide were weighed into a 2 L reaction flask. 50 g of sodium hydroxide aqueous solution with a concentration of 0.004 g / L was added to control the pH value at 10 ± 1. When T = 20 °C, a 10% sodium hypochlorite aqueous solution was slowly added dropwise, while a 5% sodium hydroxide aqueous solution was used to control the pH value of the reaction at 10 ± 1. The dropwise addition was carried out over 15 h, and a total of 1048.85 g of 10% sodium hypochlorite aqueous solution was added. The reaction was kept at this temperature for 1 h, and then acidified with 37% concentrated hydrochloric acid until the pH value was less than 0.5. After filtration, washing, and drying, 94.97 g of FDCA product was obtained, with a yield of 94.97%.

[0110] Comparative Example 1

[0111] The difference between Comparative Example 1 and Example 1 is that the preparation process of 5-hydroxymethyl furoate in step (2) is different. The other steps are the same as in Example 1. Specifically, 220.78g of the above-mentioned methyl furoate was added to a 2L reaction flask, and 63.09g of paraformaldehyde, 47.72g of zinc chloride, and 660.13g of 1,2-dichloroethane were weighed and placed in an oil bath for heating and stirring. When T=70℃, HCl was blown through the flask (rate 10L / h) for 8h. After the reaction was completed, the mixture was washed with water and the organic phase was distilled. No methyl furoate was found, and 112.81g of 5-chloromethyl furoate was obtained. 30.30g of 5-hydroxymethyl furoate was obtained, with a conversion rate of 100%, a chloromethyl yield of 37.03%, and a hydroxymethylation yield of 11.08%.

[0112] Comparative Example 2

[0113] The difference between Comparative Example 2 and Example 1 is that the temperature in step (2) of the preparation process of methyl 5-hydroxymethylfuronate is controlled at 35°C. The remaining steps are the same as in Example 1. In step (2) of the preparation process of methyl 5-hydroxymethylfuronate, the hydroxymethylation conversion rate is 32.07%, and the yield is 21.10%.

[0114] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0115] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for preparing a compound of formula (Ⅰ), characterized in that, The preparation method includes: reacting the compound shown in formula (II) and paraformaldehyde in an acid solution with a mass percentage concentration of 0.1%-10% under the catalysis of a Lewis acid containing metal ions at a temperature of 50-90℃ to generate the compound shown in formula (I); In equations (I) and (II), R is C 1-4 alkyl; The acid solution is selected from one or more of hydrochloric acid, sulfuric acid aqueous solution, nitric acid aqueous solution and phosphoric acid aqueous solution, and the Lewis acid is selected from one or more of zinc chloride, aluminum chloride, tin chloride, zinc bromide and tin bromide.

2. The method for preparing the compound of formula (Ⅰ) according to claim 1, characterized in that, The molar ratio of the acid in the acid solution to the compound shown in formula (II) is 0.01-1.0:

1.

3. The method for preparing the compound of formula (I) according to claim 2, characterized in that, The molar ratio of the acid in the acid solution to the compound shown in formula (II) is 0.01-0.5:

1.

4. The method for preparing the compound of formula (I) according to claim 3, characterized in that, The molar ratio of the acid in the acid solution to the compound shown in formula (II) is 0.01-0.25:

1.

5. A method for preparing the compound of formula (I) according to any one of claims 1-4, characterized in that, The mass percentage concentration of the acid solution is 0.1%-5%.

6. The method for preparing the compound of formula (I) according to claim 1, characterized in that, The reaction is carried out at 60-80°C; and / or the molar ratio of the paraformaldehyde to the compound shown in formula (II) is 0.5-3.0:

1.

7. The method for preparing the compound of formula (I) according to claim 1, characterized in that, The molar ratio of the paraformaldehyde to the compound shown in formula (II) is 0.6-2.0:

1.

8. The method for preparing the compound of formula (I) according to claim 7, characterized in that, The molar ratio of the paraformaldehyde to the compound shown in formula (II) is 0.8-1.6:

1.

9. The method for preparing the compound of formula (I) according to claim 1, characterized in that, The molar ratio of the Lewis acid to the compound shown in formula (II) is 0.05-3.0:

1.

10. The method for preparing the compound of formula (I) according to claim 9, characterized in that, The molar ratio of the Lewis acid to the compound shown in formula (II) is 0.05-1.5:

1.

11. The method for preparing the compound of formula (I) according to claim 10, characterized in that, The molar ratio of the Lewis acid to the compound shown in formula (II) is 0.05-1.0:

1.

12. The method for preparing the compound of formula (I) according to claim 11, characterized in that, The molar ratio of the Lewis acid to the compound shown in formula (II) is 0.05-0.5:

1.

13. The method for preparing the compound of formula (I) according to claim 1, characterized in that, The reaction is carried out in a one-pot process, which includes: adding the compound shown in formula (II), paraformaldehyde, acid solution, and Lewis acid to the reaction vessel, heating, and maintaining the temperature for reaction; and / or, in formulas (I) and (II), R is methyl or ethyl.

14. A method for preparing a compound of formula (I), characterized in that, The preparation method includes: (1) Make furoic acid and C 1-4 Alkyl alcohols undergo esterification to produce the compound shown in formula (II); (2) The compound shown in formula (II) and paraformaldehyde are reacted in an acid solution with a mass percentage concentration of 0.1%-10% under the catalysis of Lewis acid containing metal ions at a temperature of 50-90℃ to produce the compound shown in formula (I). In equations (I) and (II), R is C 1-4 alkyl; The acid solution is selected from one or more of hydrochloric acid, sulfuric acid aqueous solution, nitric acid aqueous solution and phosphoric acid aqueous solution, and the Lewis acid is selected from one or more of zinc chloride, aluminum chloride, tin chloride, zinc bromide and tin bromide.

15. The method for preparing the compound of formula (I) according to claim 14, characterized in that, In step (1), the esterification reaction is carried out in the presence of a catalyst, which is a strong acid resin.

16. The method for preparing the compound of formula (I) according to claim 15, characterized in that, The strong acid resin is selected from one or more of Lanxess SP-112H, S-200KR, S-108, Blue Depth LS-51, 001X4, D001, Purolite C100E, C100EDL, C100EFG.

17. The method for preparing the compound of formula (I) according to claim 15, characterized in that, The mass ratio of the strong acid resin to the furoic acid is 0.3-30:

1.

18. The method for preparing the compound of formula (I) according to claim 17, characterized in that, The mass ratio of the strong acid resin to the furoic acid is 0.3-20:

1.

19. The method for preparing the compound of formula (I) according to claim 18, characterized in that, The mass ratio of the strong acid resin to the furoic acid is 0.3-10:

1.

20. The method for preparing the compound of formula (I) according to claim 19, characterized in that, The mass ratio of the strong acid resin to the furoic acid is 0.8-6:

1.

21. The method for preparing the compound of formula (I) according to claim 14, characterized in that, In step (1), the esterification reaction is carried out at a temperature of 60-150°C; and / or, in step (1), the C 1-4 The molar ratio of alkyl alcohol to furoic acid is 10-100:

1.

22. The method for preparing the compound of formula (I) according to claim 14, characterized in that, In step (1), the C 1-4 The molar ratio of alkyl alcohol to furoic acid is 10-80:

1.

23. The method for preparing the compound of formula (I) according to claim 22, characterized in that, In step (1), the C 1-4 The molar ratio of alkyl alcohol to furoic acid is 10-50:

1.

24. The method for preparing the compound of formula (I) according to claim 23, characterized in that, In step (1), the C 1-4 The molar ratio of alkyl alcohol to furoic acid is 10-30:

1.

25. A method for preparing 2,5-furandicarboxylic acid, characterized in that, The preparation method includes: (1) Make furoic acid and C 1-4 Alkyl alcohols undergo esterification to produce the compound shown in formula (II); (2) The compound shown in formula (II) and paraformaldehyde are reacted in an acid solution with a mass percentage concentration of 0.1%-10% under the catalysis of Lewis acid containing metal ions at a temperature of 50-90℃ to produce the compound shown in formula (I). In equations (I) and (II), R is C 1-4 alkyl; The acid solution is selected from one or more of hydrochloric acid, sulfuric acid aqueous solution, nitric acid aqueous solution and phosphoric acid aqueous solution, and the Lewis acid is selected from one or more of zinc chloride, aluminum chloride, tin chloride, zinc bromide and tin bromide. (3) React the compound shown in formula (Ⅰ) with an oxidant under alkaline conditions, and then acidify to obtain 2,5-furandicarboxylic acid; 26. The method for preparing 2,5-furandicarboxylic acid according to claim 25, characterized in that, In step (3), the oxidant is one or more of the following: alkali metal hypochlorite, alkali metal chlorite, hydrogen peroxide, peroxytert-butanol, and alkali metal perchlorate.

27. The method for preparing 2,5-furandicarboxylic acid according to claim 25, characterized in that, In step (3), the molar ratio of the oxidant to the compound shown in formula (Ⅰ) is 2.0-3.0:

1.

28. The method for preparing 2,5-furandicarboxylic acid according to claim 27, characterized in that, In step (3), the molar ratio of the oxidant to the compound shown in formula (Ⅰ) is 2.0-2.8:

1.

29. The method for preparing 2,5-furandicarboxylic acid according to claim 28, characterized in that, In step (3), the molar ratio of the oxidant to the compound shown in formula (Ⅰ) is 2.0-2.4:

1.

30. The method for preparing 2,5-furandicarboxylic acid according to claim 25, characterized in that, In step (3), the reaction is carried out at 5-40°C.

31. The method for preparing 2,5-furandicarboxylic acid according to claim 30, characterized in that, In step (3), the reaction is carried out at 10-30°C.

32. The method for preparing 2,5-furandicarboxylic acid according to claim 25, characterized in that, In step (3), the reaction is carried out at a pH of 9-11.

33. The method for preparing 2,5-furandicarboxylic acid according to claim 25, characterized in that, In step (3), the reaction is carried out in the presence of a catalyst, which is a metal oxide.

34. The method for preparing 2,5-furandicarboxylic acid according to claim 33, characterized in that, The metal oxide is selected from one or more of copper oxide, nickel oxide, cobalt oxide, and manganese oxide.

35. The method for preparing 2,5-furandicarboxylic acid according to claim 33, characterized in that, The amount of catalyst added, by mass percentage, is 1%-50% of the amount of the compound shown in formula (Ⅰ).

36. The method for preparing 2,5-furandicarboxylic acid according to claim 35, characterized in that, The amount of catalyst added, by mass percentage, is 1%-30% of the amount of the compound shown in formula (Ⅰ).

37. The method for preparing 2,5-furandicarboxylic acid according to claim 36, characterized in that, The amount of catalyst added, by mass percentage, is 1%-20% of the amount of the compound shown in formula (Ⅰ).

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