Method for preparing 2, 5-furandicarboxylic acid by using tubular fluidized bed reactor and taking 5-hydroxymethylfurfural as raw material
By using copper oxide catalyst and activated carbon treatment in a tubular fluidized bed reactor, the problems of low synthesis efficiency and poor safety in traditional batch reactors for FDCA were solved, achieving efficient, safe and continuous production of FDCA.
Patent Information
- Application Number
- CN202511059015.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-30
- Publication Date
- 2025-11-21
AI Technical Summary
In the existing technology, the selective oxidation of 5-hydroxymethylfurfural (HMF) to prepare 2,5-furandicarboxylic acid (FDCA) suffers from problems such as expensive catalysts and deactivation, and the synthesis efficiency and safety are low in traditional batch reactors, which limits its industrial production.
A copper oxide catalyst was prepared using a tubular fluidized bed reactor and a salicylic acid-ethanol composite template agent. The catalyst was then oxidized in an aqueous phase using 5-hydroxymethylfurfural and sodium hypochlorite, followed by activated carbon decolorization and purification to achieve efficient synthesis of FDCA.
It enables safe, rapid, and continuous production of FDCA, improves synthesis efficiency, solves the problems of slow production speed and poor safety in traditional reactors, and reduces catalyst costs.
Smart Images
Figure CN120987889A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical technology, specifically relating to a method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material in a tubular fluidized bed reactor. Background Technology
[0002] The selective oxidation of 5-hydroxymethylfurfural (HMF) is the main method for synthesizing 2,5-furandicarboxylic acid (FDCA), but due to the high cost of raw materials and the lack of large-scale synthesis processes, FDCA has not yet been industrialized. Therefore, the design of efficient catalysts and the development of catalytic processes are current research hotspots. Compared with homogeneous catalysts, heterogeneous catalysts have significant advantages in solid-liquid separation and catalyst recovery. Noble metal catalysts such as Pd, Au, and Pt can use oxygen or air as oxidants to efficiently oxidize HMF to FDCA at relatively high temperatures (65–130 °C), but the high cost of these catalysts and catalyst deactivation issues limit their large-scale application. Compared with noble metal catalysts, inexpensive metal oxides such as Cu, Ni, and Co have weaker activity and can effectively catalyze the oxidation of HMF to FDCA in the presence of sodium hypochlorite as an oxidant. However, the low synthesis efficiency and poor safety of FDCA in traditional batch reactors restrict its industrial production. Summary of the Invention
[0003] The purpose of this invention is to provide a method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material in a tubular fluidized bed reactor.
[0004] This invention provides a safe, rapid, and continuous method for synthesizing 2,5-furandicarboxylic acid (FDCA), which utilizes a tubular fluidized bed reactor with extremely high mass transfer efficiency to achieve efficient FDCA synthesis. This method solves the problems that limit the industrial production of FDCA, such as slow synthesis rate (greater than 2 hours), inability to produce continuously, and poor safety, in traditional reactors.
[0005] The present invention discloses a method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material in a tubular fluidized bed reactor. The method first involves preparing a copper oxide catalyst using a salicylic acid-ethanol composite template agent. The specific steps are as follows:
[0006] (1) Preparation of copper oxide catalyst
[0007] A soluble copper salt aqueous solution was added to a salicylic acid-ethanol aqueous solution and stirred until evenly dispersed. Then, an alkaline precipitant was slowly added dropwise to the resulting mixed solution while stirring to obtain a precursor complex solution. The precursor complex solution was then transferred to a hydrothermal reactor for hydrothermal reaction. After the reaction was completed, the mixture was cooled to room temperature, centrifuged and filtered to obtain a solid product. After washing, drying, and grinding, a nanorod-shaped copper oxide catalyst powder was obtained.
[0008] (2) Oxidative Synthesis
[0009] In a tubular fluidized bed reactor, 5-hydroxymethylfurfural and sodium hydroxide are catalyzed by copper oxide catalyst and oxidized by sodium hypochlorite in the aqueous phase. After separating the catalyst, 2,5-furandicarboxylic acid reaction stock solution is obtained.
[0010] (3) Preprocessing
[0011] Activated carbon was added to the 2,5-furandicarboxylic acid reaction stock solution obtained in step (2) to remove the residual active chlorine-containing substances in the stock solution. After centrifugation, the purified 2,5-furandicarboxylic acid stock solution was obtained.
[0012] (4)Acidification
[0013] The 2,5-furandicarboxylic acid purified stock solution obtained in step (3) was acidified, centrifuged and dried to obtain solid 2,5-furandicarboxylic acid;
[0014] (5) Alkali dissolution treatment
[0015] The 2,5-furandicarboxylic acid solid obtained in step (4) was subjected to alkali dissolution, activated carbon decolorization, acidification, centrifugation, and drying to obtain a 2,5-furandicarboxylic acid composition.
[0016] (6) Purification treatment
[0017] The 2,5-furandicarboxylic acid composition obtained in step (5) was purified to obtain the purified 2,5-furandicarboxylic acid.
[0018] Furthermore, in step (1), the soluble copper salt is any one of copper sulfate pentahydrate, copper chloride, copper nitrate, or copper acetate, and its aqueous solution concentration is 0.1–0.15 mol / L; the salicylic acid-ethanol aqueous solution is prepared by mixing 6 mM salicylic acid-ethanol solution with deionized water at a volume ratio of 1:2–4; the molar ratio of salicylic acid to soluble copper salt is 1:2–6;
[0019] The alkaline precipitant is any one of sodium hydroxide aqueous solution, ammonia water or sodium carbonate aqueous solution, and the pH of the reaction system is in the range of 8 to 10 after the alkaline precipitant is added.
[0020] The hydrothermal reaction temperature is 100–200°C, and the hydrothermal reaction time is 8–15 hours;
[0021] The washing process involves alternating between deionized water and ethanol 2-3 times, and the drying temperature is 50-80℃.
[0022] Step (2) is carried out in a tubular fluidized bed reactor (reactor structure as follows) Figure 2As shown, the reactor is made of corrosion-resistant materials such as titanium. It has a tubular structure with internal cooling pipes, also made of titanium. The cooling pipes can be straight or coiled, depending on the required heat exchange area. Each cooling pipe has a cooling water inlet and outlet, with the inlet at the bottom and the outlet at the top. An external jacket, welded to the reactor body and made of the same material, is fitted with a jacket water inlet and outlet, also with the inlet at the bottom and the outlet at the top. Temperature and pressure monitoring are located on the side of the reactor to display the reaction temperature and to monitor catalyst concentration through pressure differential changes. A lower head, made of corrosion-resistant materials such as titanium, is installed at the bottom of the reactor and connected to it via a flange. The lower head has catalyst and sodium hypochlorite inlets at its lower part and a 5-hydroxymethylfurfural inlet on its side to ensure uniform heat distribution. An upper head, also made of corrosion-resistant materials such as titanium, is installed at the top of the reactor and connected to it via a flange, with a material outlet.
[0023] The copper oxide catalyst prepared in step (1) is prepared into a suspension and then pumped into the bottom of the reactor along with sodium hypochlorite aqueous solution and NaOH aqueous solution. The material flows from the bottom to the top of the reactor. Then, 5-hydroxymethylfurfural aqueous solution is pumped into the reactor from a position higher than the sodium hypochlorite feed position as a separate feed. Under the action of the catalyst, it begins to react with sodium hypochlorite. Cooling water (temperature range of 10-30℃) is circulated in the reactor jacket and cooling pipes to remove the heat generated by the reaction. Multiple reactors can be set up in series to increase the residence time of the reaction. The reacted material is discharged from the material outlet at the top of the reactor and enters the catalyst separator to separate the copper oxide catalyst for recycling. Then, 2,5-furandicarboxylic acid reaction stock solution is obtained.
[0024] The mass ratio of available chlorine (calculated as chlorine gas) in 5-hydroxymethylfurfural, sodium hydroxide, sodium hypochlorite, and copper oxide catalyst is 0.5–1.5: 0.5–1.5: 1–3: 0.5–1.5;
[0025] The reaction temperature inside the reactor is controlled at 25–45°C by cooling water, and the residence time of the reactants in the reactor is 0.2–0.5 h.
[0026] The effective chlorine concentration (calculated as chlorine gas) in the sodium hypochlorite aqueous solution is 7-13%.
[0027] In step (3), the removal of residual active chlorine-containing substances in the 2,5-furandicarboxylic acid reaction stock solution involves dechlorinating the 2,5-furandicarboxylic acid reaction stock solution with activated carbon. The operating temperature is 20-40℃. The effective chlorine content in the reaction solution is monitored every half hour (using potentiometric titration). When the effective chlorine content is <10mg / L, it is considered that there is no effective chlorine residue in the reaction solution. After centrifugation and filtration to remove the activated carbon, the purified 2,5-furandicarboxylic acid stock solution is obtained. The particle size of the activated carbon used is less than 100μm. 1-3g of activated carbon needs to be added for every 1 liter of purified 2,5-furandicarboxylic acid stock solution prepared.
[0028] In step (4), concentrated hydrochloric acid with a concentration of 10-12 mol / L is used to adjust the pH of the 2,5-furandicarboxylic acid purification stock solution to 1.0-1.5 for acidification.
[0029] In step (5), alkali dissolution involves adding the obtained 2,5-furandicarboxylic acid solid to an aqueous NaOH solution for complete dissolution to obtain an FDCA solution, with m(FDCA):m(NaOH):m(H2O) = 1:0.6:15-40; activated carbon decolorization involves mixing the alkali-dissolved FDCA solution with activated carbon and stirring, with m(FDCA):m(C) = 20-40:1, and stirring for 0.5-1 h; acidification involves adding 10-12 mol / L hydrochloric acid to the FDCA solution after activated carbon decolorization and filtration, maintaining the system temperature at 15-25°C during the addition until the pH of the reaction solution is 0.5-1.0; the liquid phase purity of the 2,5-furandicarboxylic acid mixture obtained after centrifugation and drying (including 2,5-furandicarboxylic acid and impurities, including at least one of halogenated monocarboxyl compounds, dialdehyde compounds, and dicarboxyl compounds) is 99%-99.99%.
[0030] In step (6), the 2,5-furandicarboxylic acid composition is purified by dispersing the 2,5-furandicarboxylic acid composition in an eluent, refluxing and slurrying, centrifuging and drying to obtain the purified 2,5-furandicarboxylic acid. The eluent is a mixture of a polar solvent with a boiling range of 80 to 170°C and a monocarboxylic acid. The polar solvent is at least one of 1,4-dioxane, isopropanol and n-butanol. The monocarboxylic acid is a monocarboxylic acid with a nonpolar end, and is at least one of formic acid, acetic acid, propionic acid, isobutyric acid and n-valeric acid.
[0031] The halogenated monocarboxyl compounds in the impurities are at least one of 5-chloro-2-furanoic acid, 5-bromo-2-furanoic acid, 4-bromo-2-furanoic acid, and 3-bromo-2-furanoic acid; the dialdehyde compounds are at least one of bis-(5-formylfurfuryl) ether, 2,2'-bisfuran-5,5'-dicarboxaldehyde, adipaldehyde, and succinal; and the dicarboxyl compounds are at least one of bis-(5-carboxyfurfuryl) ether, 2,2'-bisfuran-5,5'-dicarboxylic acid, and succinic acid.
[0032] The mass ratio of the 2,5-furandicarboxylic acid composition to the eluent is 1:3 to 8; in the eluent, the mass ratio of the polar solvent to the monocarboxylic acid is 0.1 to 4:1.
[0033] The steps for reflux pulping and elution are as follows:
[0034] R1: The 2,5-furandicarboxylic acid composition is dispersed in the eluent and first pulped at temperature T1 with rotation speed n for time t; then, under rotation speed m, it is cooled to temperature T2 at a cooling rate K. The filter cake obtained after filtration is washed with the eluent and then pressed dry.
[0035] R2: Disperse the filter cake that has been washed and pressed dry in step R1 in the eluent, first pulp it at temperature T1 and speed n for time t; then, under the condition of speed m, cool it down to temperature T2 at a cooling rate K, and after filtration, wash the obtained filter cake with the eluent and press it dry.
[0036] R3: Repeat step R2 1 to 3 times, and finally dry the washed and pressed filter cake.
[0037] Wherein, T1 = 90~140℃, t = 1~2h, n = 200~600rpm; T2 = 20~40℃, m = 100~200rpm, K = 5~10℃ / min. Attached Figure Description
[0038] Figure 1 Flowchart of the process for preparing 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural;
[0039] Figure 2 Schematic diagram of a tubular fluidized bed reactor.
[0040] Table 1: Performance data of the products from the examples
[0041]
[0042]
[0043] The mass of the liquid after catalyst separation = total feed amount at reactor inlet - amount of catalyst; the reaction liquid after catalyst separation is sampled and sent to a liquid chromatography instrument for analysis to obtain the HMF content and FDCA content. Detailed Implementation
[0044] Example 1
[0045] (1) Catalyst preparation: A 0.1 mol / L copper sulfate pentahydrate aqueous solution was prepared. The salicylic acid-ethanol aqueous solution was prepared by mixing 6 mM salicylic acid-ethanol solution with deionized water at a volume ratio of 1:3. The molar ratio of the added template agent salicylic acid to copper sulfate pentahydrate was 1:2. The two were stirred and mixed evenly. A 50% NaOH aqueous solution was used as an alkaline precipitant and slowly added dropwise under stirring until the pH of the solution reached 9, thus obtaining the precursor complex solution. The precursor complex solution was transferred to a hydrothermal reactor and aged at 120°C for 10 hours. After the reaction solution cooled to room temperature, it was centrifuged and filtered to obtain the product. The product was washed three times with deionized water and ethanol to remove impurities. The washed product was placed in an oven and dried at 60°C. Subsequently, the dried product was ground to obtain nanorod-shaped copper oxide catalyst powder, denoted as CuO-S, with a yield of 98-99%.
[0046] (2) Oxidative synthesis: Prepare a mixture of 9.4 kg of 5-hydroxymethylfurfural aqueous solution with a mass fraction of 50%, 100 L of sodium hypochlorite aqueous solution with an effective chlorine (calculated as chlorine) mass concentration of 11%, 6.8 kg of NaOH aqueous solution with a mass fraction of 50%, and 50 L of CuO-S aqueous solution with a mass fraction of 5%.
[0047] The mixture of 100L of sodium hypochlorite aqueous solution with an effective chlorine (calculated as chlorine gas) mass concentration of 11%, 6.8kg of NaOH aqueous solution with a mass fraction of 50%, and 50L of CuO-S aqueous solution with a mass fraction of 5% was pumped together from... Figure 2 The tubular fluidized bed reactor shown is fed through the bottom inlet, where 9.4 kg of the above-mentioned 50% (by mass) 5-hydroxymethylfurfural aqueous solution is added. Figure 2 The 5-hydroxymethylfurfural inlet at the bottom side of the tubular fluidized bed reactor shown is pumped into the reactor. By adjusting the flow rate, the residence time of the material in the reactor is ensured to be between 10 min and 20 min. Figure 2 As shown, the tubular fluidized bed reactor is equipped with temperature monitoring. Cooling water enters the reactor through both the coil water inlet and the jacket water inlet, carrying away the heat of the reaction, and flows out through the coil water outlet and the jacket water outlet, controlling the reaction temperature at 36℃. After the reaction is complete, the cooling water flows out through the coil water outlet and the jacket water outlet, respectively. Figure 2 The material flows out of the top outlet of the tubular fluidized bed reactor shown in Table 1.
[0048] Example 2
[0049] (1) Catalyst preparation: A 0.1 mol / L copper chloride solution was prepared. The salicylic acid-ethanol aqueous solution was prepared by mixing 6 mM salicylic acid-ethanol solution with deionized water at a volume ratio of 1:3. The molar ratio of the added template agent salicylic acid to copper chloride was 1:2. The two were stirred and mixed. A 50% NaOH solution was used as an alkaline precipitant and slowly added dropwise with stirring until the pH of the solution reached 9, thus obtaining the precursor complex solution. The precursor complex solution was transferred to a hydrothermal reactor and aged at 120°C for 10 hours. After the reaction solution cooled to room temperature, it was centrifuged and filtered to obtain the product. The product was washed three times with deionized water and ethanol respectively to remove impurities. The washed product was placed in an oven and dried at 60°C. Subsequently, the dried product was ground to obtain copper oxide powder, denoted as CuO-Cl, with a yield of 98-99%.
[0050] (2) Oxidative synthesis: The reaction conditions are the same as in Example 1, except that the catalyst is changed to CuO-Cl. After the reaction solution is completely reacted, the reaction mixture is then... Figure 2 The material flowed out of the top outlet of the tubular fluidized bed reactor shown in Table 1;
[0051] (3) Pretreatment: After the reaction solution passes through the catalyst separator, the 2,5-furandicarboxylic acid reaction stock solution is obtained; at 30°C, the stock solution is dechlorinated according to the ratio of purified stock solution: activated carbon = 1L: 2g. The activated carbon removes the residual active chlorine-containing substances in the stock solution. After centrifugation, the activated carbon is filtered out to obtain the 2,5-furandicarboxylic acid purified stock solution.
[0052] (4) Acidification: The obtained 2,5-furandicarboxylic acid purified stock solution was put into an acidification tank. The system temperature was maintained at 20℃. 12mol / L concentrated hydrochloric acid was used for acidification and the pH was controlled at 1.0. 2,5-furandicarboxylic acid was precipitated after acidification. After centrifugation, it was dried at 55℃ to obtain solid 2,5-furandicarboxylic acid. Samples were taken for testing and the results are shown in Table 1.
[0053] Example 3
[0054] Alkali dissolution treatment: The 2,5-furandicarboxylic acid solid obtained by acidification treatment in step (4) of Example 2 was subjected to alkali dissolution treatment, that is, the obtained 2,5-furandicarboxylic acid solid was added to NaOH aqueous solution, and the mass ratio of FDCA, NaOH and water added was 1:0.6:20. After complete dissolution, decolorization treatment was carried out according to the mass ratio of FDCA to activated carbon of 25:1, and the stirring time was 0.5h. After filtering the activated carbon, acidification treatment was carried out by adding 12mol / L hydrochloric acid and maintaining the system temperature at 20℃ until the pH of the reaction solution was 1.0. After centrifugation, it was dried at 55℃ to obtain the 2,5-furandicarboxylic acid composition. Samples were taken for testing, and the results are shown in Table 1.
[0055] Example 4
[0056] Take the sample obtained in Example 3, add 10 kg of 2,5-furandicarboxylic acid composition (2,5-furandicarboxylic acid with a liquid phase purity of 99.30%, 5-chloro-2-furancarboxylic acid with a liquid phase purity of 0.50%, and bis-(5-formylfurfuryl) ether with a liquid phase purity of 0.20%) to 5 kg of 1,4-dioxane, 2 kg of propionic acid, 30 kg of acetic acid, and 5 kg of formic acid as eluent. In the eluent tank, disperse and slurry at 90°C and 600 rpm for 1.5 h, then disperse at 150 rpm and cool to 40°C. Filter, and wash and press the filter cake with eluent.
[0057] 10 kg of washed and pressed filter cake was added to an eluent consisting of 5 kg of 1,4-dioxane, 2 kg of propionic acid, 30 kg of acetic acid, and 5 kg of formic acid. The mixture was dispersed and stirred in an eluent tank at 90°C and 600 rpm for 1.5 h. Then, the mixture was dispersed at 150 rpm and cooled to 40°C. The mixture was filtered, and the filter cake was washed and pressed dry with the eluent. This process was repeated three times. Finally, the washed and pressed filter cake was dried at 50°C to obtain purified 2,5-furandicarboxylic acid. HPLC analysis showed that the FDCA content was 99.998%, the 5-chloro-2-furancarboxylic acid content was 0.001%, and the bis-(5-formylfurfuryl) ether content was 0.001%. Other components were not detected.
Claims
1. A method for preparing 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural using a tubular fluidized bed reactor, comprising the following steps: (1) Preparation of copper oxide catalyst A soluble copper salt aqueous solution was added to a salicylic acid-ethanol aqueous solution and stirred until evenly dispersed. Then, an alkaline precipitant was slowly added dropwise to the resulting mixed solution while stirring to obtain a precursor complex solution. The precursor complex solution was then transferred to a hydrothermal reactor for hydrothermal reaction. After the reaction was completed, the mixture was cooled to room temperature, centrifuged and filtered to obtain a solid product. After washing, drying and grinding, the solid product was obtained as a nanorod-shaped copper oxide catalyst powder. (2) Oxidative Synthesis In a tubular fluidized bed reactor, 5-hydroxymethylfurfural and sodium hydroxide are catalyzed by copper oxide catalyst and oxidized by sodium hypochlorite in the aqueous phase. After separating the catalyst, 2,5-furandicarboxylic acid reaction stock solution is obtained. This tubular fluidized bed reactor has a tubular structure with internal cooling pipes. These cooling pipes are either straight or coiled, depending on the required heat exchange area. Each cooling pipe has a cooling water inlet and outlet, with the water inlet at the bottom and the outlet at the top. An external jacket, welded to the reactor body and made of the same material, is fitted with a jacket water inlet and outlet, also with the water inlet at the bottom and the outlet at the top. Temperature and pressure monitoring are located on the side of the reactor to display the reaction temperature and to monitor catalyst concentration based on pressure differential changes. A lower head is installed at the bottom of the reactor, connected via a flange. The lower part of the lower head has catalyst and sodium hypochlorite inlets, while a 5-hydroxymethylfurfural inlet is located on the side to ensure uniform heat distribution. An upper head is installed at the top of the reactor, connected via a flange, and has a material outlet at its upper part. (3) Preprocessing Activated carbon was added to the 2,5-furandicarboxylic acid reaction stock solution obtained in step (2) to remove the residual active chlorine-containing substances in the stock solution. After centrifugation, the purified 2,5-furandicarboxylic acid stock solution was obtained. (4)Acidification The 2,5-furandicarboxylic acid purified stock solution obtained in step (3) was acidified, centrifuged and dried to obtain solid 2,5-furandicarboxylic acid; (5) Alkali dissolution treatment The 2,5-furandicarboxylic acid solid obtained in step (4) was subjected to alkali dissolution, activated carbon decolorization, acidification, centrifugation, and drying to obtain a 2,5-furandicarboxylic acid composition. (6) Purification treatment The 2,5-furandicarboxylic acid composition obtained in step (5) was purified to obtain the purified 2,5-furandicarboxylic acid.
2. The method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material using a plug flow apparatus as described in claim 1, characterized in that: In step (1), the soluble copper salt is any one of copper sulfate pentahydrate, copper chloride, copper nitrate, or copper acetate, and its aqueous solution concentration is 0.1–0.15 mol / L; the salicylic acid-ethanol aqueous solution is prepared by mixing 6 mM salicylic acid-ethanol solution with deionized water at a volume ratio of 1:2–4, and the molar ratio of salicylic acid to soluble copper salt is 1:2–6; the alkaline precipitant is any one of sodium hydroxide aqueous solution, ammonia water, or sodium carbonate aqueous solution, and the pH of the reaction system is adjusted to be in the range of 8–10 after the alkaline precipitant is added; the hydrothermal reaction temperature is 100–200℃, and the hydrothermal reaction time is 8–15 hours; the washing process involves alternating washing with deionized water and ethanol 2–3 times, and the drying temperature is 50–80℃.
3. The method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material using a plug flow apparatus as described in claim 1, characterized in that: Step (2) involves preparing the copper oxide catalyst prepared in step (1) into a suspension, which is then pumped together with sodium hypochlorite aqueous solution and NaOH aqueous solution into the bottom of the reactor, with the material moving from the bottom to the top. Next, 5-hydroxymethylfurfural aqueous solution is pumped into the reactor as a separate feed from a position higher than the sodium hypochlorite feed position, where it begins to react with sodium hypochlorite under the action of the catalyst. Cooling water with a temperature range of 10–30°C is circulated through the reactor jacket and cooling pipes to remove the heat generated by the reaction. Multiple reactors are connected in series to increase the residence time of the reaction. After the reaction… The material is discharged from the top material outlet of the reactor and enters the catalyst separator to separate the copper oxide catalyst, thus obtaining the 2,5-furandicarboxylic acid reaction stock solution. The mass ratio of available chlorine in 5-hydroxymethylfurfural, sodium hydroxide, sodium hypochlorite, and copper oxide catalyst is 0.5–1.5:0.5–1.5:1–3:0.5–1.
5. The reaction temperature in the reactor is controlled at 25–45°C by cooling water, and the residence time of the reactants in the reactor is 0.2–0.5 h. The mass concentration of available chlorine in the sodium hypochlorite aqueous solution is 7–13%, expressed as chlorine gas.
4. The method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material using a plug flow apparatus as described in claim 1, characterized in that: In step (3), the removal of residual active chlorine-containing substances in the 2,5-furandicarboxylic acid reaction stock solution involves dechlorinating the 2,5-furandicarboxylic acid reaction stock solution with activated carbon. The operating temperature is 20-40℃. The effective chlorine content in the reaction solution is monitored every half hour. When the effective chlorine content is <10mg / L, it is considered that there is no effective chlorine residue in the reaction solution. After centrifugation and filtration to remove the activated carbon, the purified 2,5-furandicarboxylic acid stock solution is obtained. The particle size of the activated carbon used is less than 100μm. 1-3g of activated carbon needs to be added for every 1 liter of purified 2,5-furandicarboxylic acid stock solution prepared.
5. The method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material using a plug flow apparatus as described in claim 1, characterized in that: In step (4), concentrated hydrochloric acid with a concentration of 10-12 mol / L is used to adjust the pH of the 2,5-furandicarboxylic acid purification stock solution to 1.0-1.5 for acidification.
6. The method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material using a plug flow apparatus as described in claim 1, characterized in that: In step (5), alkali dissolution involves adding the obtained 2,5-furandicarboxylic acid solid to NaOH aqueous solution for complete dissolution to obtain FDCA solution, with m(FDCA):m(NaOH):m(H2O) = 1:0.6:15-40; activated carbon decolorization involves mixing the alkali-dissolved FDCA solution with activated carbon and stirring, with m(FDCA):m(C) = 20-40:1, and stirring for 0.5-1h; acidification involves adding 10-12mol / L hydrochloric acid to the FDCA solution after activated carbon decolorization and filtration, maintaining the system temperature at 15-25℃ during the addition until the pH of the reaction solution is 0.5-1.0; the liquid phase purity of the 2,5-furandicarboxylic acid mixture obtained after centrifugation and drying is 99%-99.99%, and the 2,5-furandicarboxylic acid mixture consists of 2,5-furandicarboxylic acid and impurities, the impurities being at least one of halogenated monocarboxyl compounds, dialdehyde compounds, and dicarboxyl compounds.
7. The method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material using a plug flow apparatus as described in claim 6, characterized in that: The halogenated monocarboxylic acid compounds in the impurities are at least one of 5-chloro-2-furanic acid, 5-bromo-2-furanic acid, 4-bromo-2-furanic acid, and 3-bromo-2-furanic acid; the dialdehyde compounds are at least one of bis-(5-formylfurfuryl) ether, 2,2'-bisfuran-5,5'-dicarboxaldehyde, adipaldehyde, and succinaldehyde; and the dicarboxylic acid compounds are at least one of bis-(5-carboxyfurfuryl) ether, 2,2'-bisfuran-5,5'-dicarboxylic acid, and succinic acid.
8. The method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material using a plug flow apparatus as described in claim 1, characterized in that: In step (6), the 2,5-furandicarboxylic acid composition is purified by dispersing the 2,5-furandicarboxylic acid composition in an eluent, followed by reflux slurry washing, centrifugation, and drying to obtain the purified 2,5-furandicarboxylic acid. The eluent is a mixture of a polar solvent with a boiling range of 80-170°C and a monocarboxylic acid. The polar solvent is at least one of 1,4-dioxane, isopropanol, and n-butanol, and the monocarboxylic acid is at least one of formic acid, acetic acid, propionic acid, isobutyric acid, and n-valeric acid.
9. The method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material using a plug flow apparatus as described in claim 8, characterized in that: The mass ratio of the 2,5-furandicarboxylic acid composition to the eluent is 1:3 to 8; in the eluent, the mass ratio of the polar solvent to the monocarboxylic acid is 0.1 to 4:
1.
10. The method for preparing 2,5-furandicarboxylic acid using 5-hydroxymethylfurfural as a raw material using a plug flow apparatus as described in claim 8, characterized in that: The steps for reflux pulping and elution are as follows: R1: The 2,5-furandicarboxylic acid composition is dispersed in the eluent and first pulped at temperature T1 with rotation speed n for time t; then, under rotation speed m, it is cooled to temperature T2 at a cooling rate K. The filter cake obtained after filtration is washed with the eluent and then pressed dry. R2: Disperse the filter cake that has been washed and pressed dry in step R1 in the eluent, first pulp it at temperature T1 and speed n for time t; then, under the condition of speed m, cool it down to temperature T2 at a cooling rate K, and after filtration, wash the obtained filter cake with the eluent and press it dry. R3: Repeat step R2 1 to 3 times to dry the washed and pressed filter cake; Wherein, T1 = 90~140℃, t = 1~2h, n = 200~600rpm; T2 = 20~40℃, m = 100~200rpm, K = 5~10℃ / min.