A process for the production of dimethyl 2,5-furandicarboxylate from furfural

Abstract

This application discloses a method for preparing dimethyl 2,5-furandicarboxylate through a three-step reaction. The method includes the following steps: First, furfural is oxidatively esterified to methyl 2-furanate under the catalysis of a gold-based catalyst. Second, methyl 2-furanate is acetylated to prepare methyl 5-acetyl-2-furanate. Third, methyl 5-acetyl-2-furanate is reacted with dimethyl carbonate via a Claisen reaction to achieve oxygenation and obtain dimethyl 2,5-furandicarboxylate. Its advantages are: This application uses furfural, a cheap, readily available, and structurally stable bulk chemical, as a raw material and develops a highly efficient and green catalytic system for the preparation of dimethyl 2,5-furandicarboxylate.

Description

Technical Field

[0001] This application relates to the field of catalytic synthesis technology, and in particular to a synthetic method for preparing dimethyl 2,5-furandicarboxylate from furfural. Background Technology

[0002] 2,5-Furfurandicarboxylic acid (FDCA), due to the presence of an aromatic ring in its molecular structure, is used as a monomer to synthesize polyethylene 2,5-furandicarboxylate (PEF), a bio-based biodegradable plastic that can replace polyethylene terephthalate (PET) with higher mechanical strength and better gas barrier properties. Therefore, 2,5-furandicarboxylic acid (FDCA) was selected by the U.S. Department of Energy as one of the 12 most promising bio-based platform compounds.

[0003] However, when FDCA is used as a monomer, its poor solubility often necessitates higher polymerization temperatures, which can easily lead to decarboxylation side reactions and hinder the polymerization process. Dimethyl 2,5-furandicarboxylate (FDCM), as a derivative of FDCA, has a lower boiling point and is readily soluble in many common solvents. Furthermore, when FDCM is used as a monomer in a transesterification-condensation reaction with ethylene glycol, the resulting small-molecule product is methanol rather than water, which is more easily removed from the reaction system, thus accelerating the reaction rate. FDCM is also more stable under polymerization conditions and less prone to side reactions. Therefore, FDCM is a more ideal bio-based platform compound to replace petroleum-based polyester monomers than FDCA.

[0004] Current research on the preparation of FDCM mainly focuses on oxidative esterification using 5-hydroxymethylfurfural (HMF) as a raw material. However, the active hydroxymethyl group in HMF easily causes intermolecular condensation, resulting in poor stability and slow progress in industrial production.

[0005] In summary, developing an efficient catalytic system for the preparation of FDCM using inexpensive bio-based raw materials is of great research significance. Furfural is a readily available and inexpensive bulk chemical; biomass such as corn cobs and camellia shells can be used as raw materials for furfural production, and its industrial production is already well-established. Based on this, this application provides a green and efficient novel synthetic route to prepare dimethyl 2,5-furandicarboxylate from the widely available bulk chemical furfural. Summary of the Invention

[0006] A method for synthesizing dimethyl 2,5-furandicarboxylate, the method comprising the following steps: (1) Preparation of gold-based catalysts Chloroauric acid hydrate and metal oxide were added to 40 g of water and stirred at 25-100 °C for 1-4 h. After cooling to room temperature, the mixture was filtered, dried, and then heat-treated in air at 200-600 °C for 1-8 h before cooling to obtain a gold-based catalyst.

[0007] (2) Add furfural, gold-based catalyst and methanol to the reactor, wherein the amount of methanol is 10-200 times the mass of furfural and the amount of gold-based catalyst is 0.1-2 times the mass of the raw material furfural; introduce molecular oxygen as oxygen source and maintain the pressure at 0.1-2 MPa, raise the reactor temperature to 80-160 °C, continue the reaction for 1-12 h and then cool to room temperature, filter, and separate and purify by vacuum distillation to obtain methyl furoate.

[0008] (3) Mix the acid catalyst with acetic anhydride and stir vigorously in an oil bath at 100-180 °C. Add methyl 2-furoate dropwise and continue stirring for 1-6 h. Cool to room temperature, neutralize with saturated sodium bicarbonate aqueous solution, extract with ethyl acetate, collect the organic layer by rotary evaporation, and obtain methyl 5-acetyl-2-furoate by column chromatography.

[0009] (4) Add methyl 5-acetyl-2-furfuryl ester, catalyst and dimethyl carbonate to the reactor, purge with nitrogen to replace air and keep the nitrogen pressure at 0.1-5 MPa, raise the reactor temperature to 200-260 °C and continue the reaction for 1-12 h, and obtain dimethyl 2,5-furandicarboxylate by separation.

[0010] The metal oxide in step (1) is one or more combinations of MgO, Al2O3, CeO2, ZrO2, La2O3, TiO2, magnesium aluminum hydrotalcite, and magnesium aluminum spinel.

[0011] The mass ratio of chloroauric acid hydrate to metal oxide in step (1) is 0.005-0.1.

[0012] The acid catalyst in step (3) is one or more of the following: phosphoric acid, solid phosphoric acid, zirconium sulfonate, Amberlyst, Nafion, molecular sieve HBEA, HUSY, HZSM-5, HMOR, etc.

[0013] The mass ratio of the acid catalyst to methyl furoate in step (3) is 1-3.

[0014] In step (3), the mass ratio of acetic anhydride to methyl furoate is 5-100.

[0015] In step (4), the catalyst is one or more of CeO2, MgO, ZrO2, La2O3, magnesium aluminum hydrotalcite, sodium methoxide, sodium carbonate, and sodium bicarbonate.

[0016] In step (4), the mass ratio of dimethyl carbonate to methyl 5-acetyl-2-furfuryl is 10-100.

[0017] In step (4), the mass ratio of the catalyst to methyl 5-acetyl-2-furfurylate is 0.5-2.

[0018] The above-mentioned technical solution adopted in this application can achieve the following beneficial effects: This application uses readily available and inexpensive furfural as a raw material, and oxidatively esterifies it under a gold-based catalyst to obtain methyl 2-furoate. After distillation and purification, it is acetylated with acetic anhydride under an acid catalyst to generate methyl 5-acetyl-2-furoate. After purification, a catalyst and dimethyl carbonate are added to the methyl 5-acetyl-2-furoate to achieve an oxygenation reaction to generate dimethyl 2,5-furandicarboxylate. Compared with the traditional method of oxidative esterification using HMF, this method produces a stable product and has a high raw material utilization rate. This application achieves efficient preparation of dimethyl 2,5-furandicarboxylate from furfural. Attached Figure Description

[0019] Figure 1 A flowchart of the synthesis route provided in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Example 1

[0022] (1) Preparation of gold-based catalysts

[0023] 0.01 g of chloroauric acid hydrate and 2 g of MgO were added to 40 g of water, stirred at 25 °C for 4 h, filtered and dried, and the mixture was heat-treated in air at 600 °C for 1 h and then cooled to obtain a gold-based catalyst.

[0024] (2) Add 0.1g furfural, 0.01g gold-based catalyst and 1g methanol to the reactor, introduce molecular oxygen as oxygen source, maintain the pressure at 0.1 MPa, raise the reactor temperature to 160 °C, continue the reaction for 1 h and then cool to room temperature, filter, and separate and purify by vacuum distillation to obtain methyl furoate, with a yield of 98%.

[0025] (3) Mix 1 g of phosphoric acid with 5 g of acetic anhydride and stir vigorously in an oil bath at 100 °C. Add 1 g of methyl 2-furfurylate dropwise and continue stirring for 6 h. Cool to room temperature, neutralize with saturated sodium bicarbonate aqueous solution, extract with ethyl acetate, collect the organic layer and evaporate by rotary evaporation. After column chromatography, the pure product methyl 5-acetyl-2-furfurylate was obtained with a yield of 99%.

[0026] (4) 1 g of methyl 5-acetyl-2-furfurylate, 0.5 g of CeO2 catalyst and 10 g of dimethyl carbonate were added to the reactor. Nitrogen gas was introduced to replace the air and the nitrogen pressure was maintained at 0.1 MPa. The reactor temperature was raised to 260 °C and the reaction was continued for 1 h. The yield of dimethyl 2,5-furandicarboxylate was 97% after separation.

[0027] Example 2

[0028] (1) Preparation of gold-based catalysts

[0029] 0.1 g of chloroauric acid hydrate and 1 g of Al2O3 were added to 40 g of water, stirred at 100 °C for 1 h, filtered and dried, and the mixture was heat-treated in air at 200 °C for 8 h and then cooled to obtain a gold-based catalyst.

[0030] (2) Add 0.1 g furfural, 0.2 g gold-based catalyst and 20 g methanol to the reactor, introduce molecular oxygen as oxygen source, maintain the pressure at 2 MPa, raise the reactor temperature to 80 °C, continue the reaction for 12 h and then cool to room temperature, filter, and separate and purify by vacuum distillation to obtain methyl furoate with a yield of 95%.

[0031] (3) Mix 3 g HZSM-5 with 100 g acetic anhydride and stir vigorously in an oil bath at 180 °C. Add 1 g methyl furoate dropwise and continue stirring for 1 h. Cool to room temperature, neutralize with saturated sodium bicarbonate aqueous solution, extract with ethyl acetate, collect the organic layer by rotary evaporation, and obtain pure methyl 5-acetyl-2-furfurylate by column chromatography with a yield of 99%.

[0032] (4) 1 g of methyl 5-acetyl-2-furfurylate, 2 g of sodium bicarbonate catalyst and 100 g of dimethyl carbonate were added to the reactor, nitrogen gas was introduced to replace the air and the nitrogen pressure was maintained at 5 MPa. The reactor temperature was raised to 200 °C and the reaction was continued for 12 h. The yield of dimethyl 2,5-furandicarboxylate was 99% after separation.

[0033] Example 3

[0034] (1) Preparation of gold-based catalysts

[0035] 0.1 g of chloroauric acid hydrate and 2 g of a mixture of magnesium aluminum hydrotalcite and MgO were added to 40 g of water, stirred at 60 °C for 3 h, filtered and dried, and the mixture was heat-treated in air at 300 °C for 5 h and then cooled to obtain a gold-based catalyst.

[0036] (2) 0.2 g furfural, 0.1 g gold-based catalyst and 10 g methanol were added to the reactor, molecular oxygen was introduced as the oxygen source and the pressure was maintained at 1.2 MPa. The reactor temperature was raised to 130 °C and the reaction was continued for 6 h. After cooling to room temperature, the mixture was filtered and purified by vacuum distillation to obtain methyl 2-furfurylate with a yield of 93%.

[0037] (3) Mix 2 g Amberlyst 15 with 10 g acetic anhydride and stir vigorously in an oil bath at 130 °C. Add 1 g methyl furoate dropwise and continue stirring for 3 h. Cool to room temperature, neutralize with saturated sodium bicarbonate aqueous solution, extract with ethyl acetate, collect the organic layer, evaporate by rotary evaporation, and obtain pure methyl 5-acetyl-2-furfurylate with a yield of 99% after column chromatography.

[0038] (4) 1 g of methyl 5-acetyl-2-furfurylate, 1 g of sodium methoxide and 20 g of dimethyl carbonate were added to the reactor, nitrogen gas was introduced to replace the air, and the nitrogen pressure was maintained at 2 MPa. The reactor temperature was raised to 220 °C and the reaction was continued for 6 h. The yield of dimethyl 2,5-furandicarboxylate was 99% after separation.

[0039] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A process for the production of dimethyl 2,5-furandicarboxylate from furfural, characterized in that, The method includes the following steps: Preparation of gold-based catalyst: Chloroauric acid hydrate and metal oxide were added to 40 g of water, stirred at 25-100 °C for 1-4 h, cooled to room temperature, filtered, dried and then the mixture was heat-treated in air at 200-600 °C for 1-8 h and then cooled to obtain the gold-based catalyst. (2) Preparation of methyl furoate by furfural oxidation esterification: Furfural, gold-based catalyst and methanol are added to the reactor, wherein the amount of methanol is 10-200 times the mass of furfural and the amount of gold-based catalyst is 0.1-2 times the mass of raw furfural; molecular oxygen is introduced as the oxygen source and the pressure is maintained at 0.1-2 MPa. The reactor temperature is raised to 80-160 °C and the reaction is continued for 1-12 h. After cooling to room temperature, the mixture is filtered and purified by vacuum distillation to obtain methyl furoate. (3) Preparation of 5-acetyl-2-furfuryl methyl ester by acetylation of 2-furfuryl methyl ester: The acid catalyst was mixed with acetic anhydride and stirred vigorously in an oil bath at 100-180 °C. 2-furfuryl methyl ester was added dropwise and stirred continuously for 1-6 h. After cooling to room temperature, the mixture was neutralized with saturated sodium bicarbonate aqueous solution and extracted with ethyl acetate. The organic layer was collected and evaporated by rotary evaporation. After column chromatography, 5-acetyl-2-furfuryl methyl ester was obtained. (4) Preparation of dimethyl 2,5-furandicarboxylate by oxygen insertion reaction of methyl 5-acetyl-2-furfurylate: methyl 5-acetyl-2-furfurylate, catalyst and dimethyl carbonate are added to the reactor, nitrogen is introduced to replace the air, and the nitrogen pressure is maintained at 0.1-5 MPa. The reactor temperature is raised to 200-260 °C and the reaction is continued for 1-12 h. Dimethyl 2,5-furandicarboxylate is obtained by separation.

2. The method of claim 1, wherein, The metal oxide in step (1) is one or more combinations of MgO, Al2O3, CeO2, ZrO2, La2O3, TiO2, magnesium aluminum hydrotalcite, and magnesium aluminum spinel.

3. The method of claim 1, wherein, The mass ratio of chloroauric acid hydrate to metal oxide in step (1) is 0.005-0.

1.

4. The method of claim 1, wherein, The acid catalyst in step (3) is one or more of the following: phosphoric acid, solid phosphoric acid, zirconium sulfonate, Amberlyst, Nafion, molecular sieve HBEA, HUSY, HZSM-5, HMOR, etc.

5. The method of claim 1, wherein, The mass ratio of the acid catalyst to methyl furoate in step (3) is 1-3.

6. The method of claim 1, wherein, In step (3), the mass ratio of acetic anhydride to methyl furoate is 5-100.

7. The method of claim 1, wherein, In step (4), the catalyst is one or more of CeO2, MgO, ZrO2, La2O3, magnesium aluminum hydrotalcite, sodium methoxide, sodium carbonate, and sodium bicarbonate.

8. The method of claim 1, wherein, In step (4), the mass ratio of dimethyl carbonate to methyl 5-acetyl-2-furfuryl acid is 10-100.

9. The method of claim 1, wherein, In step (4), the mass ratio of the catalyst to methyl 5-acetyl-2-furfurylate is 0.5-2.

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