A continuous device and method for preparing 2,5-furan dicarboxylic acid by coupling multistage series reaction and constant boiling rectification water removal

Abstract

The application discloses a kind of multistage series reaction and constant boiling rectification water removal coupling 2,5-furan dicarboxylic acid continuous preparation device and method.The continuous preparation device is by 2-6 gap reaction kettle of coupling constant boiling rectification water removal series connection composition.The steps of the method are as follows:1) single gap reaction kettle stable operation;2) multistage series reaction kettle stable continuous operation;3) continuously adding hexahydroxydicarboxylic acid and / or hexahydroxydicarboxylic acid salt to the first stage gap reaction kettle, reaction at 100~140 ℃;4) the reaction product from the last stage gap reaction kettle is obtained after cooling, crystallization, recrystallization 2,5-furan dicarboxylic acid product.The application realizes 2,5-furan dicarboxylic acid continuous production, substrate concentration can be increased to 30%, reaction selectivity is good, space-time yield is high, product uniformity is good, suitable for large-scale industrial application, with good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of multi-stage series fully mixed flow continuous reaction in the chemical industry, specifically relating to a continuous preparation apparatus and method for 2,5-furandicarboxylic acid by coupling multi-stage series reaction and azeotropic distillation for dehydration. Background Technology

[0002] 2,5-Furandicarboxylic acid (abbreviated as 2,5-FDCA, CAS No.: 3238-40-2) is a monomer for the biodegradable plastic polyethylene furanoate (PEF). It also has broad application prospects in pharmaceuticals, fine chemicals, and solvents. In 2004, it was listed by the U.S. Department of Energy as one of twelve biomass-based platform compounds, indicating huge future demand. The structural formula of 2,5-FDCA is as follows:

[0003]

[0004] Currently, the mainstream route for the preparation of 2,5-FDCA starts from glucose / fructose, first dehydrates and cyclizes it to generate 5-hydroxymethylfurfural (5-HMF), and then oxidizes it to obtain the final product. However, due to the high reactivity and poor stability of 5-HMF, and the difficulty in separation, the preparation cost is high, which severely restricts the industrialization of this route.

[0005] 2,5-FDCA can also be prepared from hexoses by first oxidizing them to obtain hexonic acid, followed by dehydration and cyclization. The advantages of this route include: a short process; the raw materials can be an aqueous solution of a mixture of hexoses with low purity requirements; and the intermediate product, hexonic acid, is very stable and relatively easy to separate. Currently, significant breakthroughs have been achieved in the preparation of hexonic acid using both chemical and biological methods, making low-cost preparation of hexonic acid possible. Therefore, the hexonic acid route for the preparation of 2,5-FDCA has broad development prospects.

[0006] The reaction formula for the catalytic dehydration cyclization of hexonic acid and / or hexonic acid salt to prepare 2,5-FDCA is as follows (taking gluconic acid as an example):

[0007]

[0008] As can be seen from the previous reaction formula, for every 1 mole of 2,5-FDCA produced, 3 moles of water are generated. Experiments show that the water content has a huge impact on the reaction. The increase in water content will greatly reduce the selectivity of the product 2,5-FDCA, thus affecting the yield. To this end, the research group of the applicants of this patent filed an application for an apparatus and method for preparing 2,5-furandicarboxylic acid from hexanoic acid (salt) by coupling dehydration cyclization and azeotropic distillation (Lv Xiuyang, Lv Xilei, Zheng Liping, Xu Haifeng, Chen Xujie, Jiang Yuxi, Xu Ling, Li Yanchen. Apparatus and method for preparing 2,5-furandicarboxylic acid from hexanoic acid (salt) by coupling dehydration cyclization and azeotropic distillation, ZL202010215086.5 (authorization date: May 17, 2022)). This method, by adding an entrainer that can form an azeotrope with water, distills the water out in a timely manner through azeotropic distillation, reducing the occurrence of side reactions and thus significantly improving the yield of the product 2,5-FDCA. However, the following problems still need to be solved:

[0009] • The substrate concentration should not exceed 10%, i.e., 0.1 kg hexanoic acid (salt) / L catalyst-reaction solvent solution. Exceeding this concentration will significantly reduce the yield of 2,5-FDCA, while a substrate concentration of 10% is not high enough for industrial production.

[0010] • Intermittent operation results in batch-to-batch variations, affecting the uniformity of product quality.

[0011] • Intermittent operation requires long auxiliary time (heating, cooling, etc.) and has low space-time yield (the amount of the desired product obtained per unit volume of equipment per unit time). Summary of the Invention

[0012] The technical problem this invention aims to solve is the low substrate concentration, low space-time yield, and poor product uniformity encountered during the catalytic dehydration and cyclization of hexanoic acid (salt) to 2,5-furandicarboxylic acid using a batch reactor. The hexanoic acid and / or hexanoic acid salts described in this patent include gluconic acid and its salts, galactonic acid (also known as mucoic acid) and its salts, mannonic acid and its salts, etc., and the types of hexanoic acid salts include potassium salts, sodium salts, calcium salts, etc.

[0013] To address the issue of low substrate concentration, this invention employs a continuous feeding technique, where the reaction occurs simultaneously with the feeding in the first-stage gap reactor, ensuring that the actual concentration of the reactants within the reactor remains low. Coupled with azeotropic distillation technology, the generated water is distilled off promptly, guaranteeing high reaction selectivity and yield. Furthermore, by introducing a multi-reactor series fully mixed-flow continuous reaction technique, the process is made continuous, thereby resolving the problems of low space-time yield and poor product uniformity.

[0014] To achieve the above objectives, this invention provides a continuous preparation apparatus and method for 2,5-furandicarboxylic acid through a multi-stage series reaction coupled with azeotropic distillation for dehydration. This invention is achieved through the following technical solution:

[0015] A continuous preparation apparatus for 2,5-furandicarboxylic acid is provided, which couples a multi-stage series reaction with azeotropic distillation for dehydration. The continuous preparation apparatus consists of multiple intermittent reactors connected in series, wherein the number of intermittent reactors connected in series is 2-6. Each intermittent reactor includes a dehydration cyclization reactor, a distillation column, a condenser, and a phase separator. The dehydration cyclization reactor is connected to the distillation column, and the top of the distillation column is connected to the condenser and the phase separator. The phase separator is connected to the top of the distillation column.

[0016] Preferably, the number of intermittent reactors connected in series is 3 to 4.

[0017] A continuous method for preparing 2,5-furandicarboxylic acid by coupling a multi-stage series reaction and azeotropic distillation for dehydration, the method comprising the following steps:

[0018] 1) Stable operation of a single-gap reactor: Turn on the reactor agitator and reactor jacket heating steam, and add the mixture of reaction solvent and catalyst, and entrainer to the dehydration cyclization reactor in sequence. The vapor phase containing water, entrainer and reaction solvent undergoes vapor-liquid mass transfer with the liquid phase refluxed from the upper layer of the phase separator in the distillation column. The reaction solvent enters the liquid phase and returns to the reactor. The azeotropic vapor phase formed by the entrainer and water is distilled from the top of the column and enters the condenser for condensation. The condensate separates into layers in the phase separator. The upper layer of entrainer is refluxed and the lower layer of water is released. The mass ratio of reaction solvent to catalyst in the mixture of reaction solvent and catalyst is 20:1 to 100:15.

[0019] 2) Stable and continuous operation of multi-stage series reactors: The mixture of reaction solvent and catalyst is continuously added to the first-stage interstitial reactor, and the bottom of the reactor flows to the next stage at the same flow rate until the last interstitial reactor. The space time of a single interstitial reactor is 20 min to 2 h.

[0020] 3) Hexonic acid and / or hexonic acid salt are continuously added to the first-stage gap reactor and reacted at a reaction temperature of 100-140°C, wherein the mass flow ratio of hexonic acid and / or hexonic acid salt to the mixture of reaction solvent and catalyst in step 2) is 1:10-3:10.

[0021] 4) The reaction product flowing out of the last-stage gap reactor is cooled, crystallized, and recrystallized to obtain 2,5-furandicarboxylic acid. The crystallization mother liquor is returned to the first-stage gap reactor after impurity removal.

[0022] Preferably, the reaction solvent in step 1) is sulfolane, 3-methylsulfolane, 3-cyclobutene sulfone, dimethyl sulfone, diethyl sulfone, n-butane sulfone, methylphenyl sulfone, or diphenyl sulfone. The above reaction solvents all contain sulfone compounds, and their structural formulas, melting points, and boiling points are shown below.

[0023]

[0024] Preferably, the catalyst in step 1) is sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid, or trifluoromethanesulfonic acid.

[0025] Preferably, the entrainer in step 1) is cyclohexane, benzene, toluene, xylene, or anisole. The azeotropic points and compositions of these entrainers with water are as follows:

[0026] The azeotropic point of cyclohexane and water is 68.95℃, and the azeotropic composition is: cyclohexane 91.6% and water 8.4%.

[0027] The azeotropic point of benzene and water is 69.3℃. The composition of the azeotrope is: benzene 91.1% and water 8.9%.

[0028] The azeotropic point of toluene and water is 84.1℃, and the azeotropic composition is: toluene 80.84% ​​and water 19.16%.

[0029] The azeotropic point of xylene and water is 92.0℃, and the azeotropic composition is: xylene 62.5% and water 37.5%.

[0030] The azeotropic point of anisole and water is 95.5℃, and the azeotropic composition is: anisole 59.5% and water 40.5%.

[0031] The space time of the intermittent reactor mentioned in step 2) refers to the ratio of the effective volume of the reactor to the volumetric flow rate of the feed. The space time of a single intermittent reactor is 20 min to 2 h, and the total space time is 40 min to 12 h.

[0032] In step 3), the hexonic acid is one or more of galactosic acid, gluconic acid, and mannonic acid; the hexonic acid salt is one or more of potassium gluconic acid monosodium gluconic acid monosodium gluconic acid monosodium gluconic acid calcium gluconic acid.

[0033] Preferably, the mass flow ratio of the hexanoic acid and / or hexanoic acid salt in step 3) to the mixture of reaction solvent and catalyst in step 2) is 15:100 to 1:4.

[0034] The volumes of the multi-stage series reactors can be the same or different, preferably the same; the reaction temperatures of the multi-stage series reactors can be the same or different, preferably, the reaction temperatures gradually increase from low to high, such as a three-stage series reactor, where the temperatures of the first, second, and third stages are 100℃, 115℃, and 130℃, respectively.

[0035] The operating pressure of distillation column D is 1 atm, with 3 to 10 theoretical plates. Packed columns are recommended. The boiling point difference between the reaction solvent and the azeotrope determines the ease of separation. The larger the boiling point difference, the easier the separation and the fewer theoretical plates required. Conversely, the smaller the boiling point difference, the more difficult the separation and the more theoretical plates required.

[0036] Beneficial effects

[0037] Compared with existing technologies, the substrate concentration of this invention can be increased to 30%, i.e., 0.3 kg hexanoic acid (salt) / L catalyst-reaction solvent solution. The timely removal of water generated during the reaction using an entrainer ensures high selectivity. The space-time yield is increased by more than 100% compared to intermittent techniques (Lv Xiuyang, Lv Xilei, Zheng Liping, Xu Haifeng, Chen Xujie, Jiang Yuxi, Xu Ling, Li Yanchen. Apparatus and method for preparing 2,5-furandicarboxylic acid from hexanoic acid (salt) by coupling dehydration cyclization and azeotropic distillation, ZL 202010215086.5 (authorization date: May 17, 2022)). Simultaneously, product uniformity is significantly improved. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a continuous preparation apparatus for 2,5-furandicarboxylic acid, which couples a two-stage series reaction with azeotropic distillation for dehydration.

[0039] Figure 2 This is a schematic diagram of a continuous preparation apparatus for 2,5-furandicarboxylic acid, which couples a three-stage series reaction with azeotropic distillation for dehydration.

[0040] Figure 3 This is a schematic diagram of a continuous preparation apparatus for 2,5-furandicarboxylic acid, which couples a four-stage series reaction with azeotropic distillation for dehydration.

[0041] Figure 4 This is a schematic diagram of a continuous preparation apparatus for 2,5-furandicarboxylic acid, which couples a five-stage series reaction with azeotropic distillation for dehydration.

[0042] Figure 5 This is a schematic diagram of a continuous preparation apparatus for 2,5-furandicarboxylic acid, which couples a six-stage series reaction with azeotropic distillation for dehydration.

[0043] The attached diagrams are labeled as follows: First-stage dehydration cyclization reactor R1, Second-stage dehydration cyclization reactor R2, Third-stage dehydration cyclization reactor R3, Fourth-stage dehydration cyclization reactor R4, Fifth-stage dehydration cyclization reactor R5, Sixth-stage dehydration cyclization reactor R6, First-stage distillation column D1, Second-stage distillation column D2, Third-stage distillation column D3, Fourth-stage distillation column D4, Fifth-stage distillation column D5, Sixth-stage distillation column D6, First-stage condenser C1, Second-stage condenser C2, Third-stage condenser C3, Fourth-stage condenser C4, Fifth-stage condenser C5, Sixth-stage condenser C6, First-stage phase separator S1, Second-stage phase separator S2, Third-stage phase separator S3, Fourth-stage phase separator S4, Fifth-stage phase separator S5, Sixth-stage phase separator S6. Detailed Implementation

[0044] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0045] Product analysis method: The reaction product 2,5-FDCA was quantified by HPLC (Agilent 1260, UV detector) using the external standard method. Chromatographic conditions were as follows: Agilent Hi-Plex H 300*7.7mm column; mobile phase: 5 mmol / L sulfuric acid aqueous solution; flow rate: 0.6 mL / min; column temperature: 65℃; injection volume: 20 μL; detection wavelength: 265 nm.

[0046] The yield of 2,5-furandicarboxylic acid in this invention is a molar yield, calculated using the following formula:

[0047]

[0048] Example 1

[0049] use Figure 1 The apparatus shown is a continuous preparation device for 2,5-furandicarboxylic acid, which couples a two-stage series reaction and azeotropic distillation for dehydration. The number of intermittent reactors connected in series is 2. The dehydration cyclization reactor is connected to the distillation column. The top of the distillation column is connected to a condenser and a phase separator. The phase separator is connected to the top of the distillation column.

[0050] The first-stage intermittent reactor includes a first-stage dehydration and cyclization reactor R1, a first-stage distillation column D1, a first-stage condenser C1, and a first-stage phase separator S1; the second-stage intermittent reactor includes a second-stage dehydration and cyclization reactor R2, a second-stage distillation column D2, a second-stage condenser C2, and a second-stage phase separator S2.

[0051] The volume of both the first-stage dehydration cyclization reactor R1 and the second-stage dehydration cyclization reactor R2 is 10L.

[0052] The experimental steps are as follows:

[0053] 1) Stable operation of a single-gap reactor: Turn on the reactor agitator (stirring speed 300 r / min) and reactor jacket heating steam, add 5 L of the mixture of reaction solvent and catalyst and 1 L of entrainer to the dehydration cyclization reactors R1 and R2 respectively. The water produced by the reaction forms a vapor phase with the entrainer and reaction solvent. In the distillation column, it undergoes vapor-liquid mass transfer with the liquid phase refluxed from the upper layer of the phase separator. The reaction solvent enters the liquid phase and returns to the reactor. The azeotropic vapor phase formed by the entrainer and water is distilled from the top of the column and enters the condenser for condensation. The condensate separates into layers in the phase separator. The upper layer of entrainer is refluxed and the lower layer of water is released. Stable operation of azeotropic distillation for dehydration;

[0054] 2) Stable and continuous operation of two-stage series reactors: A mixture of reaction solvent and catalyst is continuously added to the first-stage gap reactor, and the bottom of the first-stage reactor flows to the next-stage gap reactor at the same flow rate, thus ensuring stable operation of the two-stage series continuous reaction;

[0055] 3) Hexose disodium salt is continuously added to the first-stage gap reactor and reacted at the set reaction temperature. The two-stage series reaction and azeotropic distillation dehydration coupling device are continuously and stably operated.

[0056] 4) The molar yield of 2,5-FDCA was obtained by sampling, HPLC analysis and calculation of the reaction product flowing out of the second-stage gap reactor. The reaction product was collected and then cooled, crystallized and recrystallized to obtain 2,5-furandicarboxylic acid product. The mother liquor of crystallization was returned to the first-stage gap reactor after impurity removal.

[0057] The experimental results are shown in Table 1 below. The reaction raw materials are: potassium gluconate monophosphate, the reaction solvent is sulfolane, the catalyst is sulfuric acid, and the entrainer is anisole.

[0058] Table 1

[0059]

[0060] Example 2

[0061] use Figure 2 The continuous preparation apparatus for 2,5-furandicarboxylic acid, which is coupled with a three-stage series reaction and azeotropic distillation for dehydration, shown in Example 1, has three interstitial reactors connected in series, while the rest remain unchanged. The third-stage interstitial reactor includes a third-stage dehydration and cyclization reactor R3, a third-stage distillation column D3, a third-stage condenser C3, and a third-stage phase separator S3.

[0062] The volumes of the first-stage dehydration cyclization reactor R1, the second-stage dehydration cyclization reactor R2, and the third-stage dehydration cyclization reactor R3 are all 10L.

[0063] The experimental steps are as follows:

[0064] 1) Stable operation of a single-gap reactor: Turn on the reactor agitator (stirring speed is 300 r / min) and reactor jacket heating steam, add 5L of reaction solvent and catalyst mixture and 1L of entrainer to the dehydration cyclization reactors R1, R2 and R3. The water produced by the reaction forms a vapor phase with the entrainer and reaction solvent. In the distillation column, it undergoes vapor-liquid mass transfer with the liquid phase refluxed from the upper layer of the phase separator. The reaction solvent enters the liquid phase and returns to the reactor. The azeotropic vapor phase formed by the entrainer and water is distilled from the top of the column and enters the condenser for condensation. The condensate separates into layers in the phase separator. The upper layer of entrainer is refluxed and the lower layer of water is released. Stable operation of azeotropic distillation for dehydration.

[0065] 2) Stable and continuous operation of three-stage series reactors: A mixture of reaction solvent and catalyst is continuously added to the first-stage interstitial reactor, and the mixture flows to the next interstitial reactor at the same flow rate from the bottom of the first-stage interstitial reactor until the last interstitial reactor, thus achieving stable operation of the three-stage series continuous reaction.

[0066] 3) Add hexonic acid or hexonic acid salt to the first-stage gap reactor continuously, react at the set reaction temperature, and continuously and stably operate the three-stage series reaction and azeotropic distillation dehydration coupling device.

[0067] 4) The molar yield of 2,5-FDCA was obtained by sampling, HPLC analysis and calculation of the reaction product flowing out of the third-stage gap reactor. The reaction product was collected and then cooled, crystallized and recrystallized to obtain 2,5-furandicarboxylic acid product. The mother liquor of crystallization was returned to the first-stage gap reactor after impurity removal.

[0068] The experimental results are shown in Table 2 below. The reaction solvent was sulfolane, the catalyst was sulfuric acid, and the entrainer was toluene.

[0069] Table 2

[0070]

[0071] Example 3

[0072] use Figure 2 The continuous preparation apparatus for 2,5-furandicarboxylic acid, which is coupled with a three-stage series reaction and azeotropic distillation for dehydration, shown in Example 1, has three interstitial reactors connected in series, while the rest remain unchanged. The third-stage interstitial reactor includes a third-stage dehydration and cyclization reactor R3, a third-stage distillation column D3, a third-stage condenser C3, and a third-stage phase separator S3.

[0073] The volumes of the first-stage dehydration cyclization reactor R1, the second-stage dehydration cyclization reactor R2, and the third-stage dehydration cyclization reactor R3 are 10L, 20L, and 10L, respectively.

[0074] The experimental steps are as follows:

[0075] 1) Stable operation of a single-gap reactor: Turn on the reactor agitator (stirring speed 300 r / min) and reactor jacket heating steam. Add 5 L of a mixture of reaction solvent and catalyst and 1 L of entrainer to dehydration cyclization reactors R1 and R3. Add 10 L of a mixture of reaction solvent and catalyst and 2 L of entrainer to dehydration cyclization reactor R2. The water produced by the reaction forms a vapor phase with the entrainer and reaction solvent. In the distillation column, it undergoes vapor-liquid mass transfer with the liquid phase refluxed from the upper layer of the phase separator. The reaction solvent enters the liquid phase and returns to the reactor. The azeotropic vapor phase formed by the entrainer and water distills from the top of the column and enters the condenser for condensation. The condensate separates into layers in the phase separator. The upper layer of entrainer is refluxed, and the lower layer of water is released. Stable operation of azeotropic distillation for dehydration;

[0076] 2) Stable and continuous operation of three-stage series reactors: A mixture of reaction solvent and catalyst is continuously added to the first-stage interstitial reactor, and the mixture flows to the next interstitial reactor at the same flow rate from the bottom of the first-stage interstitial reactor until the last interstitial reactor, thus achieving stable operation of the three-stage series continuous reaction.

[0077] 3) Hexose disodium salt is continuously added to the first-stage intermittent reactor and reacted at the set reaction temperature. The three-stage series reaction and azeotropic distillation dehydration coupling device are continuously and stably operated.

[0078] 4) The molar yield of 2,5-FDCA was obtained by sampling, HPLC analysis and calculation of the reaction product flowing out of the third-stage gap reactor. The reaction product was collected and then cooled, crystallized and recrystallized to obtain 2,5-furandicarboxylic acid product. The mother liquor of crystallization was returned to the first-stage gap reactor after impurity removal.

[0079] The experimental results are shown in Table 3 below. The reaction raw materials are: potassium gluconate monopotassium salt and the entrainer is xylene.

[0080] Table 3

[0081]

[0082]

[0083] Example 4

[0084] use Figure 3 The continuous preparation apparatus for 2,5-furandicarboxylic acid, which is coupled with a four-stage series reaction and azeotropic distillation for dehydration, shown in Example 1, has four interstitial reactors connected in series, while the rest remain unchanged. The third-stage interstitial reactor includes a third-stage dehydration and cyclization reactor R3, a third-stage distillation column D3, a third-stage condenser C3, and a third-stage phase separator S3. The fourth-stage interstitial reactor includes a fourth-stage dehydration and cyclization reactor R4, a fourth-stage distillation column D4, a fourth-stage condenser C4, and a fourth-stage phase separator S4.

[0085] The volumes of the first-stage dehydration cyclization reactor R1, the second-stage dehydration cyclization reactor R2, the third-stage dehydration cyclization reactor R3, and the fourth-stage dehydration cyclization reactor R4 are all 10L.

[0086] The experimental steps are as follows:

[0087] 1) Stable operation of a single-gap reactor: Turn on the reactor agitator (stirring speed 300 r / min) and reactor jacket heating steam, add 5L of reaction solvent and catalyst mixture and 1L of entrainer to dehydration cyclization reactors R1, R2, R3 and R4. The water produced by the reaction forms a vapor phase with the entrainer and reaction solvent, which undergoes vapor-liquid mass transfer with the liquid phase refluxed from the upper layer of the phase separator in the distillation column. The reaction solvent enters the liquid phase and returns to the reactor. The azeotropic vapor phase formed by the entrainer and water distills from the top of the column and enters the condenser for condensation. The condensate separates into layers in the phase separator. The upper layer of entrainer is refluxed and the lower layer of water is released. Stable operation of azeotropic distillation for dehydration;

[0088] 2) Stable and continuous operation of four-stage series reactors: A mixture of reaction solvent and catalyst is continuously added to the first-stage interstitial reactor, and the mixture flows to the next interstitial reactor at the same flow rate from the bottom of the first-stage interstitial reactor until the last interstitial reactor, thus achieving stable operation of the four-stage series continuous reaction.

[0089] 3) Hexose disodium salt is continuously added to the first-stage intermittent reactor and reacted at the set reaction temperature. The four-stage series reaction and azeotropic distillation dehydration coupling device are continuously and stably operated.

[0090] 4) The molar yield of 2,5-FDCA was obtained by sampling, HPLC analysis and calculation of the reaction product flowing out of the fourth-stage gap reactor. The reaction product was collected and then cooled, crystallized and recrystallized to obtain 2,5-furandicarboxylic acid product. The mother liquor of crystallization was returned to the first-stage gap reactor after impurity removal.

[0091] The experimental results are shown in Table 4 below. The reaction raw materials are: potassium gluconate monophosphate, the reaction solvent is sulfolane, the catalyst is sulfuric acid, and the entrainer is benzene.

[0092] Table 4

[0093]

[0094] Example 5

[0095] use Figure 4The 2,5-furandicarboxylic acid continuous preparation apparatus shown is a five-stage series reaction coupled with azeotropic distillation for dehydration. Compared with the apparatus in Example 1, the number of intermittent reactors connected in series is 5, while the rest remain unchanged. The third-stage intermittent reactor includes a third-stage dehydration cyclization reactor R3, a third-stage distillation column D3, a third-stage condenser C3, and a third-stage phase separator S3. The fourth-stage intermittent reactor includes a fourth-stage dehydration cyclization reactor R4, a fourth-stage distillation column D4, a fourth-stage condenser C4, and a fourth-stage phase separator S4. The fifth-stage intermittent reactor includes a fifth-stage dehydration cyclization reactor R5, a fifth-stage distillation column D5, a fifth-stage condenser C5, and a fifth-stage phase separator S5.

[0096] The volumes of the first-stage dehydration cyclization reactor R1, the second-stage dehydration cyclization reactor R2, the third-stage dehydration cyclization reactor R3, the fourth-stage dehydration cyclization reactor R4, and the fifth-stage dehydration cyclization reactor R5 are all 10L.

[0097] The experimental steps are as follows:

[0098] 1) Stable operation of a single-gap reactor: Turn on the reactor agitator (stirring speed 300 r / min) and reactor jacket heating steam, add 5L of reaction solvent and catalyst mixture and 1L of entrainer to dehydration cyclization reactors R1, R2, R3, R4 and R5. The water produced by the reaction forms a vapor phase with the entrainer and reaction solvent, which undergoes vapor-liquid mass transfer with the liquid phase refluxed from the upper layer of the phase separator in the distillation column. The reaction solvent enters the liquid phase and returns to the reactor. The azeotropic vapor phase formed by the entrainer and water distills from the top of the column and enters the condenser for condensation. The condensate separates into layers in the phase separator. The upper layer of entrainer is refluxed and the lower layer of water is released. Stable operation of azeotropic distillation for dehydration;

[0099] 2) Stable and continuous operation of five-stage series reactors: The reaction solvent and catalyst mixture is continuously added to the first-stage interstitial reactor, and the mixture flows to the next interstitial reactor at the same flow rate from the bottom of the first-stage interstitial reactor until the last interstitial reactor, so as to achieve stable operation of five-stage series continuous reaction.

[0100] 3) Hexose disodium salt is continuously added to the first-stage intermittent reactor and reacted at the set reaction temperature. The five-stage series reaction and azeotropic distillation dehydration coupling device are continuously and stably operated.

[0101] 4) The molar yield of 2,5-FDCA was obtained by sampling, HPLC analysis and calculation of the reaction product flowing out of the fifth-stage gap reactor. The reaction product was collected and then cooled, crystallized and recrystallized to obtain 2,5-furandicarboxylic acid product. The mother liquor of crystallization was returned to the first-stage gap reactor after impurity removal.

[0102] The experimental results are shown in Table 5 below. The reaction raw materials are a mixture of potassium gluconate monosodium salt and sodium gluconate monosodium salt in a 1:1 mass ratio. The reaction solvent is sulfolane. The catalyst is sulfuric acid. The entrainer is cyclohexane.

[0103] Table 5

[0104]

[0105]

[0106] Example 6

[0107] use Figure 5 The 2,5-furandicarboxylic acid continuous preparation apparatus shown is a six-stage series reaction coupled with azeotropic distillation for dehydration. Compared with the apparatus in Example 1, the number of intermittent reactors connected in series is 6, while the rest remain unchanged. The third-stage intermittent reactor includes a third-stage dehydration cyclization reactor R3, a third-stage distillation column D3, a third-stage condenser C3, and a third-stage phase separator S3. The fourth-stage intermittent reactor includes a fourth-stage dehydration cyclization reactor R4, a fourth-stage distillation column D4, a fourth-stage condenser C4, and a fourth-stage phase separator S4. The fifth-stage intermittent reactor includes a fifth-stage dehydration cyclization reactor R5, a fifth-stage distillation column D5, a fifth-stage condenser C5, and a fifth-stage phase separator S5. The sixth-stage intermittent reactor includes a sixth-stage dehydration cyclization reactor R6, a sixth-stage distillation column D6, a sixth-stage condenser C6, and a sixth-stage phase separator S6.

[0108] The volumes of the first-stage dehydration cyclization reactor R1, the second-stage dehydration cyclization reactor R2, the third-stage dehydration cyclization reactor R3, the fourth-stage dehydration cyclization reactor R4, the fifth-stage dehydration cyclization reactor R5, and the sixth-stage dehydration cyclization reactor R6 are all 10L.

[0109] The experimental steps are as follows:

[0110] 1) Stable operation of a single-gap reactor: Turn on the reactor agitator (stirring speed is 300 r / min) and reactor jacket heating steam, add 5 L of reaction solvent and catalyst mixture and 1 L of entrainer to the dehydration cyclization reactors R1, R2, R3, R4, R5 and R6. The water produced by the reaction forms a vapor phase with the entrainer and reaction solvent. In the distillation column, it undergoes vapor-liquid mass transfer with the liquid phase refluxed from the upper layer of the phase separator. The reaction solvent enters the liquid phase and returns to the reactor. The azeotropic vapor phase formed by the entrainer and water is distilled from the top of the column and enters the condenser for condensation. The condensate separates into layers in the phase separator. The upper layer of entrainer is refluxed and the lower layer of water is released. Stable operation of azeotropic distillation for dehydration.

[0111] 2) Stable and continuous operation of six-stage series reactors: The reaction solvent and catalyst mixture is continuously added to the first-stage interstitial reactor, and the mixture flows to the next interstitial reactor at the same flow rate from the bottom of the first-stage reactor until the last interstitial reactor, so as to achieve stable operation of the six-stage series continuous reaction.

[0112] 3) Hexose disodium salt is continuously added to the first-stage intermittent reactor and reacted at the set reaction temperature. The six-stage series reaction and azeotropic distillation dehydration coupling device are continuously and stably operated.

[0113] 4) The molar yield of 2,5-FDCA was obtained by sampling, HPLC analysis and calculation of the reaction product flowing out of the sixth-stage gap reactor. The reaction product was collected and then cooled, crystallized and recrystallized to obtain 2,5-furandicarboxylic acid product. The mother liquor of crystallization was returned to the first-stage gap reactor after impurity removal.

[0114] The experimental results are shown in Table 6 below. The reaction raw materials are a mixture of potassium gluconate monophosphate and calcium gluconate monophosphate in a 1:1 mass ratio. The reaction solvent is sulfolane. The catalyst is sulfuric acid. The entrainer is toluene.

[0115] Table 6

[0116]

[0117] As can be seen from the above embodiments and experimental data, while ensuring high reaction selectivity and yield, the substrate concentration of the scheme described in this invention can be increased to 30%, which is a significant improvement compared to the current technology where the substrate concentration cannot exceed 10%. At the same time, the space-time yield of this invention is also significantly improved compared to the existing intermittent technology.

[0118] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for continuous preparation of 2,5-furan dicarboxylic acid by coupling multistage series reaction and azeotropic distillation for water removal, characterized in that, The method is prepared by a continuous preparation device composed of 2-6 gap reactors in series, each gap reactor includes a dehydration cyclization reactor, a rectifying tower, a condenser and a phase separator, wherein the dehydration cyclization reactor is connected with the rectifying tower, the top of the rectifying tower is connected with the condenser, the condenser is connected with the phase separator, and the top of the phase separator is connected with the top of the rectifying tower; the method comprises the following steps: 1) Single gap reactor stable operation: open the reactor stirring and reactor jacket heating steam, add the mixed solution of reaction solvent and catalyst, and entraining agent into the dehydration cyclization reactor in sequence, the vapor phase containing water, entraining agent and reaction solvent is subjected to vapor-liquid mass transfer with the liquid phase refluxing in the upper layer of the phase separator in the rectifying tower, the reaction solvent enters the liquid phase and returns to the reactor, the azeotrope vapor phase formed by the entraining agent and water is distilled from the top of the tower and enters the condenser for condensation, the condensed liquid is separated into two layers in the phase separator, the upper layer is the entraining agent refluxing, and the lower layer is water releasing, wherein the mass ratio of the reaction solvent to the catalyst in the mixed solution of reaction solvent and catalyst is 20:1-100:15; 2) Multi-stage series reactor stable continuous operation: continuously add the mixed solution of reaction solvent and catalyst into the first stage gap reactor, and flow to the next stage with the same flow rate at the bottom until the last stage gap reactor; 3) Continuously add hexose diacid and / or hexose diacid salt into the first stage gap reactor, wherein the mass flow ratio of the hexose diacid and / or hexose diacid salt to the mixed solution of reaction solvent and catalyst in step 2) is 1:10-3:10; 4) The reaction product flowing out from the last stage gap reactor is cooled, crystallized and recrystallized to obtain 2,5-furan dicarboxylic acid product, and the crystallization mother liquor is returned to the first stage gap reactor after impurity removal; Wherein, the reaction temperature of the gap reactor is 100-140℃, the reaction temperature of the first stage gap reactor is 100-130℃, the reaction temperature of each subsequent gap reactor is not less than the reaction temperature of the first stage gap reactor, and the space-time of a single gap reactor is 20min-2h.

2. The method of claim 1, wherein, The number of gap reactors in series is 3-4.

3. The method of claim 1, wherein, In step 1), the reaction solvent is cyclobutane sulfone, 3-methyl cyclobutane sulfone, 3-cyclobutene sulfone, dimethyl sulfone, diethyl sulfone, n-butyl sulfone, methyl phenyl sulfone and diphenyl sulfone.

4. The method of claim 1, wherein, In step 1), the catalyst is sulfuric acid, p-toluene sulfonic acid, methyl sulfonic acid and trifluoromethanesulfonic acid.

5. The method of claim 1, wherein, In step 1), the entraining agent is cyclohexane, benzene, toluene, xylene and anisole.

6. The method of claim 1, wherein, In step 3), the hexose diacid is one or more of galactaric acid, glucaric acid and mannaric acid; and the hexose diacid salt is one or more of glucaric acid monopotassium salt, glucaric acid monosodium salt and calcium glucarate.

7. The method of claim 1, wherein, In step 3), the mass flow ratio of the hexose diacid and / or hexose diacid salt to the mixed solution of reaction solvent and catalyst in step 2) is 15:100-1:4.

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