Method for removing impurities from reaction solution for producing biphenyltetracarboxylic acid

Abstract

The application provides a method for removing impurities in a reaction solution for producing biphenyltetracarboxylic acid, and relates to the technical field of refining.The method for removing impurities in the reaction solution for producing biphenyltetracarboxylic acid comprises the following steps: (1) adjusting the pH value of a coupling reaction end point solution of biphenyltetracarboxylic acid to alkaline, adding a composite reducing agent, and performing a reduction reaction to obtain a reduction reaction solution; (2) performing first solid-liquid separation on the reduction reaction solution to obtain a filtrate; (3) adjusting the pH value of the filtrate to acidic and then performing heat preservation, and performing second solid-liquid separation after the heat preservation is completed to obtain a crude biphenyltetracarboxylic acid product.The method is environmentally friendly and safe, can reduce the refining frequency and wastewater generation in the production process of biphenyltetracarboxylic acid, and greatly reduces the environmental protection and raw material costs.

Description

Technical Field

[0001] The invention relates to the technical field of refining, and in particular to a method for removing impurities from a reaction solution in the production of biphenyltetracarboxylic acid. Background Art

[0002] 3,3',4,4'-Biphenyltetracarboxylic dianhydride (S-BPDA) is produced from 4-chlorophthalic anhydride or a mixture of 4-chlorophthalic acid monosodium salts prepared using phthalic anhydride. 3,3',4,4'-biphenylether tetracarboxylic acid (S-BPTA) is obtained through catalytic dechlorination coupling, acidification, and purification. S-BPTA can be obtained by anhydrating the S-BPTA. After the catalytic dechlorination coupling, the impurities in the reaction system are primarily unreacted chlorophthalic acid compounds and phthalic acid. After acid precipitation, a diphenylether tetracarboxylic acid content exceeding 99% is obtained, with chlorophthalic acid being the primary impurity. However, separation of chlorophthalic acid from 3,3',4,4'-biphenylether tetracarboxylic acid is difficult and requires multiple purification steps.

[0003] 2,3,3',4'-Biphenyltetracarboxylic dianhydride (a-BPDA) is produced from 4-chlorophthalate and 3-chlorophthalate through catalytic dechlorination, coupling, acidification, and purification to obtain 2,3,3',4'-biphenyltetracarboxylic acid (a-BPTA). a-BPTA can be further purified by anhydrating. After the catalytic dechlorination, the impurities in the reaction system are primarily unreacted chlorophthalic acid compounds and phthalic acid. After acid precipitation, a diphenyl ether tetracarboxylic acid (DTE) with a concentration exceeding 97% is obtained, with chlorophthalic acid being the primary impurity. However, separation of chlorophthalic acid from 2,3,3',4'-DTE is difficult and requires multiple purification steps.

[0004] Biphenyltetracarboxylic acid is dehydrated to produce biphenyltetracarboxylic dianhydride, which is an imide monomer. As the demand for imides increases significantly, companies are in urgent need of finding an environmentally friendly and safe treatment method to reduce the number of refining times and wastewater generation during the production of biphenyltetracarboxylic acid, thereby greatly reducing environmental protection and raw material costs. Summary of the Invention

[0005] The present invention aims to provide a method for removing impurities from a reaction solution produced by biphenyltetracarboxylic acid. The method is environmentally friendly and safe, can reduce the number of refining times and wastewater generation during the production of biphenyltetracarboxylic acid, and greatly reduces environmental protection and raw material costs.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for removing impurities from a reaction solution produced by biphenyltetracarboxylic acid, comprising the following steps:

[0008] (1) adjusting the pH value of the end point solution of the biphenyltetracarboxylic acid coupling reaction to alkaline, adding a composite reducing agent, and performing a reduction reaction to obtain a reduction reaction solution;

[0009] (2) performing a first solid-liquid separation on the reduction reaction liquid to obtain a filtrate;

[0010] (3) The pH value of the filtrate is adjusted to acidic and then kept warm. After the heat preservation is completed, a second solid-liquid separation is performed to obtain a crude product of biphenyltetracarboxylic acid.

[0011] Preferably, the alkalinity in step (1) is a pH value of 12 to 13.

[0012] Preferably, the composite reducing agent in step (1) comprises two or three of 40% hydrazine hydrate, acetaldehyde, methanol and sodium formate.

[0013] Preferably, the end point liquid of the biphenyltetracarboxylic acid coupling reaction in step (1) is obtained by coupling reaction with halogenated phthalic acid as raw material; and the mass ratio of the composite reducing agent to the sodium salt of halogenated phthalic acid is 0.45-0.55:1.

[0014] Preferably, the temperature of the reduction reaction in step (1) is 140-150° C.; and the time of the reduction reaction is 4-6 hours.

[0015] Preferably, the acidity in step (3) is a pH value of 0.3 to 2.

[0016] Preferably, the insulation temperature in step (3) is 80-90° C., and the insulation time is 0.5-1 h.

[0017] Preferably, after the second solid-liquid separation in step (3), the process further comprises: top-washing the obtained filter cake with hot water and drying it to obtain a crude product of biphenyltetracarboxylic acid.

[0018] Preferably, the drying temperature is 105-130° C., and the drying time is 2-5 hours.

[0019] Preferably, the mass content of biphenyltetracarboxylic acid in the crude biphenyltetracarboxylic acid product is ≥99.8%.

[0020] The present invention provides a method for removing impurities from a biphenyltetracarboxylic acid production reaction liquid, comprising the following steps: (1) adjusting the pH value of a biphenyltetracarboxylic acid coupling reaction end point liquid to alkaline, adding a composite reducing agent, and performing a reduction reaction to obtain a reduction reaction liquid; (2) performing a first solid-liquid separation on the reduction reaction liquid to obtain a filtrate; (3) adjusting the pH value of the filtrate to acidic and then heat-insulating it, and after the heat-insulating is completed, performing a second solid-liquid separation to obtain a crude biphenyltetracarboxylic acid product. In the present invention, the impurities in the biphenyltetracarboxylic acid coupling reaction end point liquid are mainly sodium salts of unreacted chlorophthalic acid compounds, and the present invention uses a composite reducing agent to reduce these impurities to sodium phthalate; after the acid adjustment, the sodium phthalate is converted into phthalic acid, and the phthalic acid is dissolved in hot water for easy removal. The present invention performs chemical dechlorination before separating the materials, and performs heat preservation treatment after acid adjustment to complete the separation of soluble impurities and products. The method is simple, effective, environmentally friendly and safe, can reduce the number of refining times and wastewater generation in the production process of biphenyltetracarboxylic acid, and greatly reduces environmental protection and raw material costs. DETAILED DESCRIPTION

[0021] The present invention provides a method for removing impurities from a reaction solution produced by biphenyltetracarboxylic acid, comprising the following steps:

[0022] (1) adjusting the pH value of the end point solution of the biphenyltetracarboxylic acid coupling reaction to alkaline, adding a composite reducing agent, and performing a reduction reaction to obtain a reduction reaction solution;

[0023] (2) performing a first solid-liquid separation on the reduction reaction liquid to obtain a filtrate;

[0024] (3) The pH value of the filtrate is adjusted to acidic and then kept warm. After the heat preservation is completed, a second solid-liquid separation is performed to obtain a crude product of biphenyltetracarboxylic acid.

[0025] The present invention adjusts the pH value of the biphenyltetracarboxylic acid coupling reaction endpoint solution to alkaline, adds a composite reducing agent, and performs a reduction reaction to obtain a reduction reaction solution. In the present invention, the biphenyltetracarboxylic acid coupling reaction endpoint solution preferably includes a 3,3',4,4'-biphenyltetracarboxylic acid coupling reaction endpoint solution or a 2,3,3',4'-biphenyltetracarboxylic acid coupling reaction endpoint solution. In the present invention, the composition of the biphenyltetracarboxylic acid coupling reaction endpoint solution preferably includes: 28-30wt% of tetrasodium biphenyltetracarboxylic acid salt, ≤0.5wt% of disodium 4-chlorophthalic acid salt, 2-3wt% of disodium phthalic acid salt, and the balance is solvent water.

[0026] In the present invention, the alkalinity is preferably a pH value of 12 to 13, more preferably 12.29 to 12.51. In the present invention, sodium hydroxide is preferably used to adjust the pH value of the end point solution of the biphenyltetracarboxylic acid coupling reaction to alkaline.

[0027] In the present application, the composite reducing agent preferably comprises two or three of 40% hydrazine hydrate, acetaldehyde, methanol and sodium formate, more preferably a composite reducing agent of 40% hydrazine hydrate and acetaldehyde, a composite reducing agent of methanol and sodium formate, or a composite reducing agent of 40% hydrazine hydrate, methanol and sodium formate. In specific embodiments of the present application, when the composite reducing agent is a composite reducing agent of 40% hydrazine hydrate and acetaldehyde, the mass ratio of the 40% hydrazine hydrate and acetaldehyde is 1.1:1.5; when the composite reducing agent is a composite reducing agent of methanol and sodium formate, the mass ratio of the methanol and sodium formate is 1.5:7; when the composite reducing agent is a composite reducing agent of 40% hydrazine hydrate, methanol and sodium formate, the mass ratio of the 40% hydrazine hydrate, methanol and sodium formate is 0.8:0.7:0.9.

[0028] In the present application, the 40% hydrazine hydrate refers to hydrazine hydrate with a mass concentration of 40%; the solvent is water.

[0029] In the present application, the biphenyl tetracarboxylic acid coupling reaction end-point liquid is preferably obtained by coupling reaction using halogenated phthalic acid as raw material, and the specific preparation method is described in Chinese patent 200910074886.3. In the present application, the preparation method of the biphenyl tetracarboxylic acid coupling reaction end-point liquid preferably comprises: preparing a 3-10% alkali solution, adding 4-halogenated phthalic acid into the alkali solution, and the COOH:OH - molar ratio = 1:2-3, dissolving; adding a palladium-carbon-potassium iodide binary composite catalyst, and dropping an alcohol at 80-100°C, the effective hydroxyl group addition amount of the alcohol and the 4-halogenated phthalic acid have a molar ratio of 1:1-3, the dropping time is 3-8 hours, and the reaction is completed to obtain the biphenyl tetracarboxylic acid coupling reaction end-point liquid.

[0030] In the present application, the mass ratio of the composite reducing agent and the sodium salt of halogenated phthalic acid is preferably 0.45-0.55:1. In specific embodiments of the present application, the mass ratio of the composite reducing agent and the disodium salt of 4-chlorophthalic acid is 0.45-0.55:1.

[0031] In the present application, the temperature of the reduction reaction is preferably 140-150°C, more preferably 145°C; and the time of the reduction reaction is preferably 4-6h. In the present application, the reduction reaction is preferably carried out in a closed environment; the atmosphere of the reduction reaction is preferably hydrogen or air; and the pressure is preferably 0.2-0.6 MPa.

[0032] In the present application, the main impurity in the biphenyl tetracarboxylic acid coupling reaction end-point liquid is the sodium salt of the unreacted chlorophthalic acid compound, and the composite reducing agent is used to reduce these impurities into sodium phthalate.

[0033] After the reduction reaction solution is obtained, the reduction reaction solution is subjected to first solid-liquid separation to obtain a filtrate. Preferably, the reduction reaction solution is first cooled and then subjected to first solid-liquid separation. In the present application, the first solid-liquid separation is preferably filtration. In the present application, the temperature of the first solid-liquid separation is preferably 80-90°C, more preferably 80-85°C.

[0034] After the filtrate is obtained, the pH value of the filtrate is adjusted to be acidic, and then the filtrate is subjected to heat preservation. After the heat preservation is completed, second solid-liquid separation is performed to obtain a crude 3,3',4,4'-biphenyltetracarboxylic acid. In the present application, the acidity is preferably pH 0.3-2, more preferably 0.82-1.1. Preferably, the pH value of the filtrate is adjusted to be acidic by using a hydrochloric acid solution. In the present application, the mass concentration of the hydrochloric acid solution is preferably 30%.

[0035] In the present application, the temperature for adjusting the pH value of the filtrate is preferably 80-90°C, more preferably 85°C. By adjusting the pH value, sodium phthalate is converted into phthalic acid, and phthalic acid is dissolved in hot water, which facilitates removal.

[0036] In the present application, the temperature of the heat preservation is preferably 80-90°C, more preferably 85°C; and the heat preservation time is preferably 0.5-1h. By heat preservation, it is ensured that the acid adjusting process is complete.

[0037] In the present application, the second solid-liquid separation is preferably filtration. After the second solid-liquid separation, preferably, the obtained filter cake is washed with hot water, dried, and then a crude 3,3',4,4'-biphenyltetracarboxylic acid is obtained. In the present application, the temperature of the filtration is preferably 80-90°C, more preferably 85°C. In the present application, the temperature of the hot water is preferably 80-90°C. In the present application, 3,3',4,4'-biphenyltetracarboxylic acid is substantially insoluble at this temperature, but phthalic acid is soluble in hot water, and thus phthalic acid in the crude 3,3',4,4'-biphenyltetracarboxylic acid can be removed.

[0038] In the present application, the temperature of the drying is preferably 105-130°C, more preferably 110-115°C; and the drying time is preferably 2-5h, more preferably 2-3h.

[0039] In the present application, the mass content of 3,3',4,4'-biphenyltetracarboxylic acid in the crude 3,3',4,4'-biphenyltetracarboxylic acid is preferably ≥99.8%, more preferably ≥99.85%.

[0040] In the present application, after the second solid-liquid separation, a filtrate containing phthalic acid is also obtained. The filtrate containing phthalic acid is cooled and then filtered to obtain phthalic acid. In the present application, the temperature after the cooling is preferably 30°C. In the present application, the purity of the phthalic acid is preferably ≥99%.

[0041] The method provided by the present invention is simple and effective, avoids the generation of large amounts of wastewater and hazardous waste during repeated refining processes, and does not cause secondary pollution.

[0042] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] In the embodiment, the end point liquid of the biphenyltetracarboxylic acid coupling reaction is a 3,3',4,4'-biphenyldianhydride coupling catalytic dechlorination coupling liquid, and the preparation method is referred to Example 1 in Chinese Patent 200910074886.3.

[0044] The organic matter in the coupling liquid of 3,3',4,4'-biphenyldianhydride coupling catalytic dechlorination is 29.8wt% of tetrasodium biphenyltetracarboxylate, 0.49wt% of disodium 4-chlorophthalate, and 2.3wt% of disodium phthalate.

[0045] Example 1

[0046] Take 1000g of biphenyltetracarboxylic acid coupling reaction end point liquid, adjust the base pH to 12.4 with 6.2g of sodium hydroxide, add 2.6g of composite reducing agent (1.1g of 40% hydrazine hydrate, 1.5g of acetaldehyde), put into autoclave, warm up to 150℃, react for 4h, and the reaction is complete. The content of 4-chlorophthalic acid disodium salt in the gained reduction reaction liquid is 0.02wt%; the reduction reaction liquid is cooled to 80℃, filtered, and the filtrate is added with 397.9g of 30wt% hydrochloric acid to adjust the pH to 0.82. After acid adjustment is complete, it is incubated at 85℃ for 1h. After incubation is complete, it is filtered at 85℃, and the filter cake is top washed with 100g and 90℃ hot water. After the top washing is complete, it is dried (temperature is 110℃, time is 3h) to obtain 231.1g of biphenyltetracarboxylic acid dry product. The purity of biphenyltetracarboxylic acid is 99.91wt%.

[0047] Example 2

[0048] Take the end of the coupling reaction of biphenyl tetracarboxylic acid liquid 1000g, adjust the pH to 12.51 with sodium hydroxide 7.1g, add composite reducing agent 2.2g(methanol 1.5g, sodium formate 0.7g), put into autoclave, heat to 145℃, react for 6h, after the reaction is completed, the content of 4-chloro phthalic acid disodium salt in the obtained reduction reaction liquid is 0.02wt%; cool the reduction reaction liquid to 80℃, filter, add 30wt% hydrochloric acid 402.7g to the filtrate to adjust the pH to 0.32, after the acid adjustment is completed, keep at 85℃ for 1h, after the keeping is completed, filter at 85℃, use 100g, 90℃ hot water to top wash the filter cake, after the top washing is completed, dry(drying temperature is 110℃, time is 3h), obtain biphenyl tetracarboxylic acid dry product 232g, the purity of biphenyl tetracarboxylic acid is 99.9wt%.

[0049] Example 3

[0050] Take the end of the coupling reaction of biphenyl tetracarboxylic acid liquid 1000g, adjust the pH to 12.51 with sodium hydroxide 7.1g, add composite reducing agent 2.2g(methanol 1.5g, sodium formate 0.7g), put into autoclave, heat to 145℃, react for 6h, after the reaction is completed, the content of 4-chloro phthalic acid disodium salt in the obtained reduction reaction liquid is 0.02wt%; cool the reduction reaction liquid to 80℃, filter, add 30wt% hydrochloric acid 402.7g to the filtrate to adjust the pH to 0.32, after the acid adjustment is completed, keep at 85℃ for 1h, after the keeping is completed, filter at 85℃, use 100g, 90℃ hot water to top wash the filter cake, after the top washing is completed, dry(drying temperature is 110℃, time is 3h), obtain biphenyl tetracarboxylic acid dry product 232g, the purity of biphenyl tetracarboxylic acid is 99.9wt%.

[0051] Comparative Example 1

[0052] Take the end of the coupling reaction of biphenyl tetracarboxylic acid liquid 1000g, cool to 85℃, filter, add 30wt% hydrochloric acid to the filtrate to adjust the pH to 0.86, after the acid adjustment is completed, keep at 85℃ for 1h, after the keeping is completed, filter at 85℃, use 100g, 90℃ hot water to top wash the filter cake, after the top washing is completed, dry(drying temperature is 110℃, time is 3h), obtain biphenyl tetracarboxylic acid dry product 234.1g, the purity of biphenyl tetracarboxylic acid is 99.59wt%.

[0053] Put the biphenyl tetracarboxylic acid dry product in 10 times purified water, cook in 100℃ water for 5h, cool, wash with water, dry to obtain biphenyl tetracarboxylic acid 229.6g, the purity is 99.76wt%.

[0054] In the art, it is difficult to improve the purity of the product of biphenyl tetraacetic acid to more than 99%, the method of the present application not only improves the purity of the product, but also simplifies the reaction steps, and reduces the generation of wastewater in the refining process. The filtrate after filtering the main product from the reaction solution after acid treatment is directly cooled to 30℃ to obtain 99% of phthalic acid.

[0055] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method for removing impurities from a biphenyltetracarboxylic acid production reaction solution, comprising the following steps: (1) adjusting the pH value of the end point solution of the biphenyltetracarboxylic acid coupling reaction to alkaline, adding a composite reducing agent, and performing a reduction reaction to obtain a reduction reaction solution; (2) performing a first solid-liquid separation on the reduction reaction liquid to obtain a filtrate; (3) adjusting the pH value of the filtrate to acidic and then keeping it warm, and after the insulation is completed, performing a second solid-liquid separation to obtain a crude product of biphenyltetracarboxylic acid; The composite reducing agent in step (1) is a composite reducing agent of 40% hydrazine hydrate and acetaldehyde, a composite reducing agent of methanol and sodium formate, or a composite reducing agent of 40% hydrazine hydrate, methanol and sodium formate; The temperature of the insulation in step (3) is 80-90° C.; After the second solid-liquid separation in step (3), the method further comprises: top-washing the obtained filter cake with hot water and drying it to obtain a crude product of biphenyltetracarboxylic acid; the temperature of the hot water in the hot water top-washing is 80-90°C.

2. The method according to claim 1, characterized in that The alkalinity in step (1) is a pH value of 12 to 13.

3. The method according to claim 1, characterized in that The end point liquid of the biphenyltetracarboxylic acid coupling reaction in step (1) is obtained by coupling reaction with halogenated phthalic acid as raw material; the mass ratio of the composite reducing agent to the sodium salt of halogenated phthalic acid is 0.45-0.55:

1.

4. The method according to claim 1, wherein The temperature of the reduction reaction in step (1) is 140-150° C.; the time of the reduction reaction is 4-6 hours.

5. The method according to claim 1, wherein The acidity in step (3) is a pH value of 0.3 to 2.

6. The method according to claim 1, characterized in that The insulation time of step (3) is 0.5 to 1 hour.

7. The method according to claim 1, characterized in that The drying temperature is 105-130° C., and the drying time is 2-5 hours.

8. The method according to claim 1, characterized in that The mass content of biphenyltetracarboxylic acid in the crude biphenyltetracarboxylic acid product is ≥99.8%.