A method for preparing 2,5-furandicarboxylic acid from furfural

Abstract

The invention belongs to the technical field of 2,5-furandicarboxylic acid preparation, and in particular to a method for preparing 2,5-furandicarboxylic acid using furfural as raw material. Comprise the following steps: (1) pretreatment of furfural: furfural and alcohol compound are catalyzed under acidic ion resin, and acetalization reaction is carried out to obtain the acetal compound of furfural and alcohol compound; (2) under stirring condition, acetal compound is added dropwise to the mixed liquid of acylating agent and ionic liquid, reacts 1-2 hours, then adds catalyst and continues to react 3-5 hours, and the product of post-processing acylation reaction is obtained 5-acyl furfurals; (3) 5-acyl furfurals are mixed with hydrogen peroxide, catalyst is added, oxidation reaction is carried out, after reaction terminates, the product after oxidation reaction is washed, recrystallized, and white crystals are obtained, i.e. 2,5-furandicarboxylic acid. The present invention adopts furfural to obtain 2,5-furandicarboxylic acid by acylation reaction, and cost is low, reaction is mild, purity is high, and yield is high.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of 2,5-furandicarboxylic acid, and particularly relates to a method for preparing 2,5-furandicarboxylic acid by utilizing furfural as a raw material. Background Art

[0002] 2,5-Furandicarboxylic acid (FDCA) is an important compound for the production of biomass-derived polymers such as polyester, polyurethane, and polyamide. It can also be used as a bio-based alternative to the bio-based raw material polyethylene terephthalate (PET). FDCA has the same carbon number as glucose, its aromaticity is weaker than that of the benzene ring, and it is easily degraded, making it widely used.

[0003] Currently, the preparation of 2,5-furandicarboxylic acid (FDCA) primarily involves an acylation reaction between furoic acid and an acylating agent to produce the intermediate 2-acyl-5-furandicarboxylic acid, followed by pH adjustment to obtain 2,5-furandicarboxylic acid. Alternatively, FDCA is obtained through a two-step acylation reaction using furan as the starting material. All of these preparation methods suffer from drawbacks such as expensive raw materials and relatively intense reactions.

[0004] The present invention provides a method for preparing 2,5-furandicarboxylic acid using furfural as a raw material. The method is a completely new preparation process. Currently, there are no public technical reports on preparing 2,5-furandicarboxylic acid using furfural as a raw material. This is because the aldehyde groups in furfural are highly active. During the acylation reaction, the aldehyde groups in the furfural are easily polymerized, making it difficult to obtain acyl furfural, resulting in an extremely low yield of the final 2,5-furandicarboxylic acid.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] To address the aforementioned deficiencies in the prior art for preparing 2,5-furandicarboxylic acid, the present invention provides a method for preparing 2,5-furandicarboxylic acid from furfural. The present invention utilizes furfural as a cheaper raw material, resulting in a milder reaction system, providing a novel, low-cost method for preparing 2,5-furandicarboxylic acid.

[0007] The present invention is achieved through the following technical solutions:

[0008] The present invention provides a method for preparing 2,5-furandicarboxylic acid from furfural, comprising the following steps:

[0009] (1) Under anhydrous conditions, the acylating agent and the ionic liquid are mixed to obtain a transparent mixed liquid A;

[0010] (2) Pretreatment of furfural: Furfural and alcohol compounds are subjected to acetalization reaction under the catalysis of acidic ion resin to obtain acetal compounds of furfural and alcohol compounds;

[0011] (3) under stirring conditions, the acetal compound obtained in step (2) is added dropwise to the mixed liquid A obtained in step (1), and the reaction is carried out for 1-2 hours, and then a catalyst is added and the reaction is continued for 3-5 hours, and then the product of the acylation reaction is post-treated to obtain 5-acylfurfural;

[0012] In this step, since the acylation reaction is relatively easy to proceed, the catalyst is not added in the first 1-2 hours to avoid a violent reaction, a temperature rise, and the volatilization of the raw materials, which may affect the progress of the acylation reaction. Then, in order to make the acylation reaction more thorough, the catalyst is added after 1-2 hours of the acylation reaction to promote a more complete acylation reaction.

[0013] (4) The 5-acylfurfural obtained in step (3) is mixed with hydrogen peroxide, a catalyst is added, and an oxidation reaction is carried out. After the reaction is completed, the product after the oxidation reaction is washed and recrystallized to obtain white crystals, namely 2,5-furandicarboxylic acid.

[0014] The present application now converts the aldehyde group into acetal after the furfural is subjected to acetalization reaction with an alcohol compound, and protects the aldehyde group to avoid the side reaction of the aldehyde group reacting to generate polyfurfural groups in the acylation reaction.

[0015] Preferably, the molar mass ratio of the acylating agent to the ionic liquid in step (1) is 0.1 mol:50-60 g.

[0016] Preferably, the acylating agent in step (1) is acetic anhydride, acetyl chloride or propionyl chloride; and the ionic liquid is one or more of triethylamine hydrochloride-aluminum trichloride, 1-butyl-3-methylimidazole hydrochloride and tetrabutylammonium bromide.

[0017] Preferably, the molar ratio of furfural to alcohol compound in step (2) is 1:3-5, the temperature of the acetalization reaction is 50-100° C., and the pressure is 0.1-1.0 MPa.

[0018] Preferably, the alcohol compound is one or more of methanol, ethanol or butanol; and the acidic ion resin is sulfonic acid styrene resin.

[0019] Preferably, in step (3), the amount of furfural and mixed liquid A is 1:(1.5-3) in terms of the molar ratio of the acylating agent to furfural, and the amount of the catalyst added is 1-5 wt% of the mass of the acylating agent;

[0020] The catalyst is one or more of anhydrous aluminum chloride, ferric chloride and zinc chloride.

[0021] Preferably, the reaction temperature in step (3) is 10-30°C, the reaction pressure is 0.01-0.05 MPa, and the stirring condition is a stirring speed of 300-500 rpm; when furfural is added dropwise to the mixed solution A, the dropping speed is adjusted to ensure that the temperature rise of the mixed material is within 5°C.

[0022] Preferably, in the post-treatment step of step (3), the acylation product in the reaction product is extracted with petroleum ether at an extraction temperature of 30-50°C for 3-5 times, the extracted product is washed with a 1wt% NaOH solution at a washing temperature of 20-30°C, and the washed product is then dehydrated and vacuum distilled to obtain 5-acylfurfural; in the process of washing the extracted product with the NaOH solution, the catalyst of the acylation reaction can be removed, and the acetal can be decomposed to restore the original aldehyde group and alcohol to obtain 5-acylfurfural, and the acetal will not undergo disproportionation reaction, thereby ensuring the purity of the product.

[0023] The vacuum pressure of the vacuum distillation is -0.0996 MPa to -0.1 MPa, and the temperature of the bottom of the tower is 70-150°C.

[0024] Preferably, the hydrogen peroxide in step (4) is 20-30 wt% hydrogen peroxide, the catalyst is copper, and the temperature of the oxidation reaction is 30-45°C.

[0025] Preferably, the amount of the catalyst used in step (4) is 10 wt% of the mass of the 5-acylfurfural; and the molar ratio of the 5-acylfurfural to hydrogen peroxide is greater than 1:1.5.

[0026] Compared with the prior art, the present invention has the following effects:

[0027] 1. This application uses furfural, which has a lower cost, as a raw material to prepare 2,5-furandicarboxylic acid, which has good economic benefits.

[0028] 2. The present invention uses alcohol compounds and furfural for acetalization pretreatment to convert more active aldehyde groups into acetals, thereby protecting the aldehyde groups from participating in the acylation reaction and reducing the occurrence of side reactions. At the same time, after the acylation reaction, the product after the acylation reaction is washed to remove the catalyst while simultaneously reducing the aldehyde groups. Then, a mild oxidation reaction is carried out to obtain the current product 2,5-furandicarboxylic acid, thereby improving the yield.

[0029] 3. The present invention uses an ionic liquid as the reaction medium for the acylation reaction, rather than an organic solvent system or an aqueous solution system. Since the ionic liquid has strong polarity and a high boiling point, and has a large difference in polarity and boiling point from the product 2,5-furandicarboxylic acid, it is beneficial to separate the product. In combination with the post-treatment step, the purity of the product can be further improved.

[0030] 4. The present invention mixes the prepared 5-acylfurfural with hydrogen peroxide, and reacts under mild conditions with a catalyst to obtain the target product 2,5-furandicarboxylic acid, thereby saving energy and simplifying the reaction. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] Unless otherwise specifically stated, the numerical value set forth in these embodiments does not limit the scope of the present invention. Technology and methods known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology and methods should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments can have different values.

[0033] Example 1

[0034] A method for preparing 2,5-furandicarboxylic acid from furfural comprises the following steps:

[0035] (1) Under anhydrous conditions, in a double-row vacuum tube operating system, 0.1 mol of acetyl chloride (acylating agent) was mixed with 50 g of triethylamine hydrochloride-aluminum trichloride (aluminum trichloride mass content of 50-60 wt%) (ionic liquid) to obtain a transparent mixed liquid A;

[0036] (2) Pretreatment of furfural: 1 mol of furfural was mixed with 3 mol of methanol, and acetalization reaction was carried out under the catalysis of sulfonic acid styrene resin at a temperature of 60°C and a pressure of 0.5 MPa to obtain an acetal compound of furfural and methanol;

[0037] (3) under stirring, the acetal compound obtained in step (2) is added dropwise to the mixed liquid A obtained in step (1), and the reaction is carried out for 2 hours. Then, anhydrous aluminum chloride is added as a catalyst and the reaction is continued for 3 hours. The product of the acylation reaction is then post-treated to obtain 5-acylfurfural; the amount of anhydrous aluminum chloride added is 3% of the mass of acetyl chloride (acylating agent) in the mixed liquid A;

[0038] The post-treatment step comprises: extracting the acylated product from the reaction product with petroleum ether (boiling range of about 70° C.), the extraction temperature being 50° C., the volume ratio of the extractant petroleum ether to the extracting liquid being 1:1, extracting 3-5 times, washing the extracted product with a 1wt% NaOH solution at a washing temperature of 20-30° C., and then dehydrating and vacuum distilling the washed product (vacuum pressure of -0.0996 to -0.1 MPa, bottom temperature of 100° C.) to obtain 5-acetylfurfural.

[0039] In this step, since the acylation reaction is relatively easy to proceed, the catalyst is not added within the first 2 hours to avoid a violent reaction, a temperature rise, and the volatilization of the raw materials, which may affect the progress of the acylation reaction. Then, in order to make the acylation reaction more thorough, the catalyst is added after 2 hours of the acylation reaction to promote a more complete acylation reaction.

[0040] (4) The 5-acetylfurfural obtained in step (3) was mixed with 30 wt% hydrogen peroxide (molar ratio of 1:2), and a catalyst copper of 10 wt% of the mass of 5-acetylfurfural was added, and an oxidation reaction was carried out at 45°C. After the reaction was completed, the product after the oxidation reaction was washed and recrystallized to obtain white crystals, namely 2,5-furandicarboxylic acid, with a purity of 98.5% and a yield of 52.2%.

[0041] Example 2

[0042] A method for preparing 2,5-furandicarboxylic acid from furfural comprises the following steps:

[0043] (1) Under anhydrous conditions, 0.1 mol of propionyl chloride (acylating agent) was mixed with 60 g of N-methyl-4-butylimidazole hydrochloride (ionic liquid) in a double-row vacuum tube operating system to obtain a transparent mixed liquid A;

[0044] (2) Pretreatment of furfural: 1 mol of furfural was mixed with 5 mol of methanol and ethanol (the molar ratio of methanol to ethanol was 1:1), and acetalization reaction was carried out at a temperature of 100°C and a pressure of 1.0 MPa under the catalysis of sulfonic acid styrene resin to obtain an acetal compound of furfural, methanol and ethanol;

[0045] (3) under stirring, the acetal compound obtained in step (2) is added dropwise to the mixed liquid A obtained in step (1), and the reaction is carried out for 1 hour. Then, anhydrous aluminum chloride is added as a catalyst and the reaction is continued for 5 hours. The product of the acylation reaction is then post-treated to obtain 5-acylfurfural; the amount of anhydrous aluminum chloride added is 5% of the mass of propionyl chloride (acylating agent) in the mixed liquid A;

[0046] The post-treatment step comprises: extracting the acylated product from the reaction product with petroleum ether (boiling range of about 70° C.), the extraction temperature being 30° C., the volume ratio of the extractant petroleum ether to the extracting liquid being 0.5:1, extracting 3-5 times, washing the extracted product with a 1wt% NaOH solution at a washing temperature of 20-30° C., and then dehydrating and vacuum distilling the washed product (vacuum pressure of -0.0996 to -0.1 MPa, bottom temperature of 100° C.) to obtain 5-propionylfurfural.

[0047] (4) The 5-propionylfurfural obtained in step (3) was mixed with 20 wt% hydrogen peroxide (molar ratio of 1:3), and a catalyst copper of 10 wt% of the mass of 5-propionylfurfural was added, and an oxidation reaction was carried out at 30°C. After the reaction was completed, the product after the oxidation reaction was washed and recrystallized to obtain white crystals, namely 2,5-furandicarboxylic acid, with a purity of 96.8% and a yield of 49.5%.

[0048] Comparative Example 1

[0049] The preparation method of this comparative example is basically the same as that of Example 1, except that the pretreatment of furfural in step (2) is omitted, and furfural (instead of the acetal compound) is directly added dropwise to the mixed liquid A in step (3). The other steps are the same as those in Example 1.

[0050] The product 2,5-furandicarboxylic acid obtained in Comparative Example 1 had a purity of 97.8% and a yield of only 26.5%.

[0051] In Comparative Example 1, after omitting the furfural pretreatment step, furfural is directly reacted with an acylating agent. The aldehyde group on the furfural is highly active and easily polymerizes to form polyfurfural groups. There are many side reactions, resulting in the production of a small amount of 5-acetylfurfural, which in turn leads to a decrease in the yield of the product 2,5-furandicarboxylic acid produced by the oxidation reaction.

[0052] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing 2,5-furandicarboxylic acid from furfural, characterized in that: The steps include: (1) Under anhydrous conditions, the acylating agent and the ionic liquid are mixed to obtain a transparent mixed liquid A; The acylating agent is acetic anhydride, acetyl chloride or propionyl chloride; The ionic liquid is triethylamine hydrochloride-aluminum chloride; The molar mass ratio of the acylating agent to the ionic liquid is 0.1 mol:50-60 g; (2) Pretreatment of furfural: Furfural and alcohol compounds are subjected to acetalization reaction under the catalysis of acidic ion resin to obtain acetal compounds of furfural and alcohol compounds; (3) under stirring conditions, the acetal compound obtained in step (2) is added dropwise to the mixed liquid A obtained in step (1), and the reaction is carried out for 1-2 hours, and then a catalyst is added and the reaction is continued for 3-5 hours, and then the product of the acylation reaction is post-treated to obtain 5-acylfurfural; The catalyst in step (3) is one or more of anhydrous aluminum chloride, ferric chloride and zinc chloride; (4) The 5-acylfurfural obtained in step (3) is mixed with hydrogen peroxide, and a copper catalyst is added to carry out an oxidation reaction. After the reaction is completed, the product after the oxidation reaction is washed and recrystallized to obtain white crystals, namely 2,5-furandicarboxylic acid.

2. The method for preparing 2,5-furandicarboxylic acid from furfural according to claim 1, wherein The molar ratio of furfural to alcohol compound in step (2) is 1:3-5, the temperature of the acetalization reaction is 50-100° C., and the pressure is 0.1-1.0 MPa.

3. The method for preparing 2,5-furandicarboxylic acid from furfural according to claim 1, wherein The alcohol compound is one or more of methanol, ethanol or butanol; and the acidic ion resin is sulfonic acid styrene resin.

4. The method for preparing 2,5-furandicarboxylic acid from furfural according to claim 1, wherein The amount of the catalyst added is 1-5 wt% of the mass of the acylating agent.

5. The method for preparing 2,5-furandicarboxylic acid from furfural according to claim 1, wherein The reaction temperature in step (3) is 10-30° C., the reaction pressure is 0.01-0.05 MPa, and the stirring condition is a stirring speed of 300-500 rpm.

6. The method for preparing 2,5-furandicarboxylic acid from furfural according to claim 1, wherein In the post-treatment step of step (3), the acylated product in the reaction product is extracted with petroleum ether at an extraction temperature of 30-50° C. for 3-5 times, the extracted product is washed with a 1wt% NaOH solution at a washing temperature of 20-30° C., and the washed product is then dehydrated and vacuum distilled to obtain 5-acylfurfural; The vacuum pressure of the vacuum distillation is -0.0996 MPa to -0.1 MPa, and the temperature of the bottom of the tower is 70-150°C.

7. The method for preparing 2,5-furandicarboxylic acid from furfural according to claim 1, wherein The hydrogen peroxide in step (4) is 20-30 wt% hydrogen peroxide, and the temperature of the oxidation reaction is 30-45°C.

8. The method for preparing 2,5-furandicarboxylic acid from furfural according to claim 7, wherein: The amount of the catalyst copper used in step (4) is 10 wt% of the mass of the 5-acylfurfural.