Method for preparing dimethyl furandicarboxylate from furfural

Abstract

The invention discloses a method for synthesizing dimethyl furandicarboxylate from furfural, and the method realizes the preparation of 2, 5-dimethyl furandicarboxylate from furfural through a three-step reaction. Comprising the following steps: 1, carrying out oxidative esterification on furfural to obtain methyl furoate, 2, carrying out an acetylation reaction on the methyl furoate to obtain 5-acetyl-2-methyl furoate, and 3, carrying out a Claisen reaction on the 5-acetyl-2-methyl furoate and dimethyl carbonate to realize an oxygen insertion process to directly prepare 2, 5-dimethyl furandicarboxylate. The method has the advantages that a large amount of cheap furfural is used as a raw material, a recarburization process is realized through acetylation reaction, reaction conditions are mild, and 2, 5-site positioning of a furan ring is accurate; in the oxygen insertion process of the third step, oxygen does not need to participate in the reaction, the reaction process is safer and milder, and the product is easy to separate in a sublimation mode.

Description

Technical Field

[0001] The present application relates to the technical field of catalytic synthesis, and in particular to a synthesis method for efficiently preparing dimethyl 2,5-furandicarboxylate from furfural. Background Art

[0002] Dimethyl 2,5-furandicarboxylate (FDME) is an important chemical intermediate derived from 2,5-furandicarboxylic acid (FDCA), and it shows great application potential in multiple fields. Dimethyl 2,5-furandicarboxylate is an important precursor for synthesizing the bio-based polyester material PEF. Compared with the traditional petroleum-based polyethylene terephthalate (PET), PEF has better gas barrier properties, thermal stability and mechanical strength, and is derived from renewable plant resources. At present, the production of the synthesis precursor dimethyl 2,5-furandicarboxylate of PEF has not been industrialized, and the production cost is relatively high, which limits the large-scale application of PEF.

[0003] Currently, the main routes for synthesizing dimethyl 2,5-furandicarboxylate (FDME) include the oxidative esterification method of 5-hydroxymethylfurfural (HMF), the method of inserting CO2 into furoic acid, etc.

[0004] FDME is directly obtained from HMF through the oxidative esterification reaction of HMF in methanol. Zou et al. 1 , 2 applied the homogeneous Co-Mn-Br-acetic acid system, which is an oxidation system for oxidizing p-xylene to terephthalic acid industrially, directly to the oxidation of HMF. The high-concentration conversion of HMF in the Co-Mn-Br-acetic acid system was achieved. However, the inherent instability of HMF limits this process. In many cases, an alkali needs to be added to obtain a high yield, and there are many by-products.

[0005] Banerjee et al. [3] developed a new route for preparing FDCA by using CO2 molecules to react with furoic acid to grow the carbon chain. They used cesium carbonate as the base and inserted CO2 between the C-H bonds of furoic acid to obtain 2,5-furandicarboxylic acid. This process has short steps and high yields, and the theoretical atom utilization rate is 100%. At the same time, it can also consume CO2, alleviating the greenhouse effect to a certain extent. However, this process also has some deficiencies. For example, the reaction occurs at the interface of the molten salt and CO2, that is, the liquid-gas interface. When the reaction system is enlarged, it is difficult for the interface to expand correspondingly, resulting in a decrease in the reaction rate and yield.

[0006] In summary, in the current production route of dimethyl 2,5-furandicarboxylate, there are mainly problems such as unstable reaction raw materials, difficulty in scaling up the reaction, and harsh reaction conditions. Based on this, the present application provides a novel synthetic route that is mild, efficient, and environmentally friendly. It uses biomass-based furfural, which is widely available, to prepare dimethyl 2,5-furandicarboxylate. The route is simple, the selectivity of each step product is high, and in this process, no oxygen is required for the oxygenation reaction, the reaction process is safer and milder, and the product separation and purification are convenient. Summary of the Invention

[0007] The present application provides a method for preparing dimethyl 2,5-furandicarboxylate from furfural through a three-step process.

[0008] The present application adopts the following technical solutions:

[0009]

[0010] A method for synthesizing dimethyl 2,5-furandicarboxylate, the synthesis method comprising the following steps:

[0011] (1) Add furfural, a catalyst, and methanol to a reaction kettle, conduct air displacement by introducing pure oxygen, maintain the oxygen pressure at 0.1 - 2.0 MPa, raise the temperature of the reactor to 50°C - 180°C, continuously react for 1 h - 12 h, and obtain methyl furoate through separation.

[0012] (2) Weigh 5 g of solid acid particles with a particle size of 20 - 40 mesh and fill them into a fixed-bed glass reaction tube. Heat the reaction tube to 50°C - 180°C, and use a plunger pump to pump a mixed solution of methyl furoate and acetic anhydride into the catalyst bed layer at a flow rate of 0.05 m1·min -1 . Separate and purify the reaction product and the solvent by vacuum distillation to obtain methyl 5-acetyl-2-furoate.

[0013] (4) Add methyl 5-acetyl-2-furoate, a catalyst, and dimethyl carbonate to a reaction kettle, displace the air by introducing nitrogen, maintain the nitrogen pressure at 0.1 - 6.0 MPa, raise the temperature of the reactor to 160°C - 260°C, continuously react for 1 h - 12 h, and obtain dimethyl 2,5-furandicarboxylate through separation.

[0014] 2. The synthesis method according to claim 1, wherein the catalyst in step (1) is gold supported on metal oxides such as MgO, CaO, BaO, TiO2, Al2O3, etc.

[0015] In step (1), the molar ratio of furfural to methanol is 1:10 - 1:100.

[0016] One or more of solid phosphoric acid, sulfonated zirconium, Amberlyst, Nafion, molecular sieve HBEA, HUSY, HZSM-5, HMOR, etc. in step (2).

[0017] The molar ratio of acetic anhydride to methyl furoate in step (2) is 0.1 - 5.

[0018] In step (3), the catalyst is a combination of one or more of CeO2, MgO, ZrO2, La2O3, magnesium aluminum hydrotalcite, sodium methoxide, sodium carbonate, and sodium bicarbonate.

[0019] In step (3), the molar ratio of methyl 5-acetyl-2-furoate to dimethyl carbonate is 1:10 - 1:100.

[0020] The above at least one technical solution adopted in this application can achieve the following beneficial effects:

[0021] This application uses inexpensive and easily available furfural as a raw material. First, it is oxidized and esterified under the action of a gold / oxide catalyst to produce methyl furoate. Then, under the action of a solid acid, it is acetylated with acetic anhydride to produce methyl 5-acetyl-2-furoate. After distillation and purification, a catalyst and dimethyl carbonate are added to methyl 5-acetyl-2-furoate, and finally an oxygenation reaction is realized to produce dimethyl 2,5-furandicarboxylate. Compared with the traditional furan carbon-increasing method, this method has mild reaction conditions, accurate product orientation effect, and high product selectivity. And this method avoids the oxidation step of directly using oxygen as the oxygen source, making the whole process safer and more convenient. This application realizes the efficient preparation of dimethyl 2,5-furandicarboxylate from furfural. Specific embodiments

[0022] To make the purpose, technical solution and advantages of this application clearer, the technical solution of this application will be clearly and completely described below in conjunction with specific embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

[0023] Example 1

[0024] (1) Preparation of methyl furoate by oxidation and esterification of furfural

[0025] The oxidation and esterification reaction is carried out in a kettle reactor. Weigh 0.1 g of furfural and 0.02 g of Au / MgO and add them to a 20 mL reaction kettle, and then add 8 mL of methanol. After the reactor is sealed, the air in it is replaced with oxygen at least three times, and finally 0.5 MPa O2 is filled. The stirring rate is 500 rpm, the reactor is heated to 100 °C, and maintained for 2 h.

[0026] After the reaction was completed, product analysis was performed on a GC-MS QP-2010ultra, and the chromatographic column model was Rtx-5Si1 MS (30m×0.25mm×0.25μm). The external standard method was used to calculate the yield of the liquid product and the carbon balance. The chromatographic analysis results showed that the conversion rate of furfural was 100%, and the yield of methyl furoate was 98%.

[0027] (2) Preparation of methyl 5-acetyl-2-furoate by acetylation of methyl furoate

[0028] The acetylation reaction of methyl furoate was carried out in a fixed-bed reactor. 5 g of 20-40 mesh HBEA particles were weighed and filled into a glass reaction tube (inner diameter 1.2 cm). The reaction tube was heated to 100 °C, and a mixture of furan and acetic anhydride (molar ratio of acetic anhydride to methyl furoate = 5) was pumped into the catalyst bed at a flow rate of 0.05 m1·min- 1 and reacted for 2 h.

[0029] After the reaction was completed, product analysis was performed on a GC-MS QP-2010ultra, and the chromatographic column model was Rtx-5Si1 MS (30m×0.25mm×0.25μm). The external standard method was used to calculate the yield of the liquid product and the carbon balance. The chromatographic analysis results showed that the conversion rate of the reactant was 90%, and the yield of methyl 5-acetyl-2-furoate was 85%.

[0030] (3) Preparation of dimethyl 2,5-furandicarboxylate by Claisen reaction of methyl 5-acetyl-2-furoate

[0031] The Claisen reaction was carried out in a batch reactor. 1 g of methyl 5-acetyl-2-furoate and 0.5 g of ZrO2 were weighed and added to a 100 mL reaction kettle, and 50 mL of dimethyl carbonate (DMC) was added. After the reactor was sealed, the air in it was replaced with nitrogen at least three times, and finally 0.5 MPa N2 was filled, the stirring rate was 500 rpm, the reactor was heated to the specified temperature and maintained for 2 h.

[0032] After the reaction was completed, product analysis was performed on a GC-MS QP-2010ultra, and the chromatographic column model was Rtx-5Si1 MS (30m×0.25mm×0.25μm). The external standard method was used to calculate the yield of the liquid product and the carbon balance. The chromatographic analysis results showed that the conversion rate of methyl 5-acetyl-2-furoate was 100%, and the yield of dimethyl 2,5-furandicarboxylate was 95%.

[0033] Example 2

[0034] (1) Preparation of methyl furoate by oxidative esterification of furfural

[0035] The oxidative esterification reaction is carried out in a batch reactor. Weigh 0.1 g of furfural and 0.02 g of Au / CaO and add them into a 20 mL reaction kettle, then add 8 mL of methanol. After the reactor is sealed, replace the air in it with oxygen at least three times, and finally fill it with 0.5 MPa of O2. The stirring rate is 500 rpm, the reactor is heated to 100 °C and maintained for 4 h.

[0036] After the reaction is completed, the product analysis is completed on a GC-MS QP-2010ultra, and the chromatographic column model is Rtx-5Si1 MS (30 m × 0.25 mm × 0.25 μm). The external standard method is used to calculate the yield of the liquid product and the carbon balance. The chromatographic analysis results show that the conversion rate of furfural is 100%, and the yield of methyl furoate is 92%.

[0037] (2) Preparation of methyl 5-acetyl-2-furoate by acetylation of methyl furoate

[0038] The acetylation reaction of methyl furoate is carried out in a fixed-bed reactor. Weigh 5 g of solid phosphoric acid particles with a mesh size of 20-40 and fill them into a glass reaction tube (tube diameter 1.2 cm). The reaction tube is heated to 80 °C, and a mixture of furan and acetic anhydride (the molar ratio of acetic anhydride to methyl furoate = 5) is pumped into the catalyst bed at a flow rate of 0.05 ml·min- 1 and the reaction lasts for 4 h.

[0039] After the reaction is completed, the product analysis is completed on a GC-MS QP-2010ultra, and the chromatographic column model is Rtx-5Si1 MS (30 m × 0.25 mm × 0.25 μm). The external standard method is used to calculate the yield of the liquid product and the carbon balance. The chromatographic analysis results show that the conversion rate of the reactants is 100%, and the yield of methyl 5-acetyl-2-furoate is 90%.

[0040] (3) Dimethyl 2,5-furandicarboxylate is formed by the Claisen reaction of methyl 5-acetyl-2-furoate

[0041] The Claisen reaction is carried out in a batch reactor. Weigh 1 g of methyl 5-acetyl-2-furoate and 0.5 g of magnesium-aluminum hydrotalcite and add them into a 100 mL reaction kettle, then add 50 mL of dimethyl carbonate (DMC). After the reactor is sealed, replace the air in it with nitrogen at least three times, and finally fill it with 0.5 MPa of N2. The stirring rate is 500 rpm, the reactor is heated to the specified temperature and maintained for 2 h.

[0042] After the reaction was completed, product analysis was performed on a GC-MS QP-2010ultra, and the chromatographic column was of the Rtx-5Si1 MS type (30 m × 0.25 mm × 0.25 μm). The external standard method was used to calculate the yield of the liquid product and the carbon balance. The chromatographic analysis results showed that the conversion rate of methyl 5-acetyl-2-furoate was 100%, and the yield of dimethyl 2,5-furandicarboxylate was 93%.

[0043] Example 3

[0044] (1) Preparation of methyl furoate by oxidative esterification of furfural

[0045] The oxidative esterification reaction was carried out in a batch reactor. 0.1 g of furfural and 0.02 g of Au / Al2O3 were weighed and added to a 20 mL reaction kettle, and 8 mL of methanol was added. After the reactor was sealed, the air in it was replaced with oxygen at least three times, and finally 0.5 MPa O2 was charged. The stirring rate was 500 rpm, the reactor was heated to 100 °C and maintained for 2 h.

[0046] After the reaction was completed, product analysis was performed on a GC-MS QP-2010ultra, and the chromatographic column was of the Rtx-5Si1 MS type (30 m × 0.25 mm × 0.25 μm). The external standard method was used to calculate the yield of the liquid product and the carbon balance. The chromatographic analysis results showed that the conversion rate of furfural was 100%, and the yield of methyl furoate was 95%.

[0047] (2) Acetylation of methyl furoate to prepare methyl 5-acetyl-2-furoate

[0048] The acetylation reaction of methyl furoate was carried out in a fixed-bed reactor. 5 g of 20-40 mesh HZSM-5 particles were weighed and filled into a glass reaction tube (inner diameter 1.2 cm). The reaction tube was heated to 80 °C, and a mixture of furan and acetic anhydride (molar ratio of acetic anhydride to methyl furoate = 5) was pumped into the catalyst bed at a flow rate of 0.05 m1·min -1 and reacted for 2 h.

[0049] After the reaction was completed, product analysis was performed on a GC-MS QP-2010ultra, and the chromatographic column was of the Rtx-5Si1 MS type (30 m × 0.25 mm × 0.25 μm). The external standard method was used to calculate the yield of the liquid product and the carbon balance. The chromatographic analysis results showed that the conversion rate of the reactant was 100%, and the yield of methyl 5-acetyl-2-furoate was 95%.

[0050] (3) Formation of dimethyl 2,5-furandicarboxylate from methyl 5-acetyl-2-furoate via Claisen reaction

[0051] The Claisen reaction was carried out in a batch reactor. 1 g of methyl 5-acetyl-2-furoate and 0.5 g of sodium carbonate were weighed and added into a 100 mL reaction kettle, and 50 mL of dimethyl carbonate (DMC) was added. After the reactor was sealed, the air in it was replaced with nitrogen at least three times, and finally 0.5 MPa of N2 was charged. The stirring rate was 500 rpm. The reactor was heated to the specified temperature and maintained for 2 h.

[0052] After the reaction was completed, the product analysis was completed on a GC-MS QP-2010ultra, and the chromatographic column model was Rtx-5Si1 MS (30 m×0.25 mm×0.25 μm). The external standard method was used to calculate the yield of the liquid product and the carbon balance. The chromatographic analysis results showed that the conversion rate of methyl 5-acetyl-2-furoate was 100%, and the yield of dimethyl 2,5-furandicarboxylate was 97%.

[0053] The above are only the embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A method for efficiently preparing dimethyl 2,5-furandicarboxylate from furfural, characterized in that: The synthesis method comprises the following steps: (1) Furfural is oxidized and esterified to produce methyl furoate: furfural, catalyst and methanol are added to a reaction kettle reactor, oxygen is introduced, and the oxygen pressure is maintained at 0.1-2 MPa. The reactor temperature is raised to a certain temperature, and the reaction is carried out at this temperature for 1-12 hours. After the reaction is completed, the reaction is cooled to room temperature, and methyl furoate is separated and purified to obtain methyl furoate. (2) Acetylation of methyl furoate to generate 5-acetyl-2-furoate methyl ester: adding methyl furoate, a solid acid catalyst, and acetic anhydride to a fixed bed or a reaction kettle reactor, raising the reactor temperature to a certain temperature, reacting at the temperature for 0.1-12 hours, filtering, neutralizing, and distilling after the reaction to obtain 5-acetyl-2-furoate methyl ester; (3) subjecting 5-acetyl-2-furoic acid methyl ester to Claisen reaction to generate 2,5-furandicarboxylic acid dimethyl ester: adding 5-acetyl-2-furoic acid methyl ester, a catalyst, and dimethyl carbonate to a reactor or a fixed bed reactor, maintaining the nitrogen pressure at 0.1-6 MPa, raising the reactor temperature to a certain temperature, reacting at this temperature for 2-12 hours, cooling to room temperature after the reaction is completed, and separating and purifying to obtain 2,5-furandicarboxylic acid dimethyl ester.

2. The synthetic method of methyl furoate as claimed in claim 1, characterized in that, The catalyst in step (1) is gold supported in metal oxides such as MgO, CaO, BaO, TiO2, Al2O3, etc. The catalyst preparation process is as follows: HAuCl4, metal oxide, and a base such as NaOH, Na2CO3, NaHCO3, etc. are mixed, dissolved in water, and heated in a water bath at a certain temperature for a period of time. The obtained product can be used for furfural oxidative esterification reaction after washing and drying.

3. The synthesis method according to claim 1, characterized in that In step (1), the molar ratio of furfural to methanol is 1:10-1:

100.

4. The synthesis method according to claim 1, characterized in that The reaction temperature in step (1) is 50-180°C.

5. The synthetic method of 5-acetyl-2-furoic acid methyl ester as claimed in claim 1, characterized in that, The solid acid in step (2) is one or more of solid phosphoric acid, sulfonated zirconium, Amberlyst, Nafion, molecular sieve HBEA, HUSY, HZSM-5, HMOR, etc.

6. The synthesis method according to claim 1, characterized in that In step (2), the molar ratio of methyl furoate to acetic anhydride is 0.1-5.

0.

7. The synthesis method according to claim 1, characterized in that The reaction temperature in step (2) is 50-180°C.

8. The method for synthesizing dimethyl 2,5-furandicarboxylate according to claim 1, characterized in that: The catalyst in step (3) is a combination of one or more of CeO2, MgO, ZrO2, La2O3, magnesium aluminum hydrotalcite, sodium methoxide, sodium carbonate, and sodium bicarbonate.

9. The synthesis method according to claim 1, characterized in that In step (3), the molar ratio of 5-acetyl-2-furoic acid methyl ester to dimethyl carbonate is 1:10-1:

100.

10. The synthesis method according to claim 1, characterized in that In step (3), the reaction temperature is 160-260°C.

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