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CN-122010970-A - Method for purifying pyromellitic dianhydride and pyromellitic dianhydride

CN122010970ACN 122010970 ACN122010970 ACN 122010970ACN-122010970-A

Abstract

The invention discloses a method for purifying pyromellitic dianhydride and pyromellitic dianhydride, wherein the purity of the pyromellitic dianhydride is more than or equal to 99.99 percent, the free acid value is lower than 1 weight percent, preferably lower than 0.5 weight percent, more preferably 0.01-0.2 percent, the particle diameter D10 of the pyromellitic dianhydride is 100-140 mu m, and the particle diameter D90 is 140-150 mu m; the solvent in the mixed material comprises dioxane and acetone, and (2) the crude homogeneous anhydride concentrated solution is subjected to first cooling crystallization treatment and second cooling crystallization treatment to obtain homogeneous anhydride crystals, the crystals are washed in an inert gas atmosphere, and finally drying treatment is carried out, wherein the cooling rate of the first cooling crystallization treatment is higher than that of the second cooling crystallization treatment. The homogeneous anhydride product obtained by the invention has the characteristics of high purity (up to 99.99wt percent), low free acid value (down to 0.04wt percent), small and uniform homogeneous anhydride crystal granularity, and the like, and has good application prospect.

Inventors

  • WANG ANG
  • GU LONGQIN
  • FANG MIN
  • CHEN BINGXU
  • CHEN LIANG
  • ZENG WEI

Assignees

  • 中国石油化工股份有限公司
  • 中石化（上海）石油化工研究院有限公司

Dates

Publication Date
20260512
Application Date
20241111

Claims (10)

  1. 1. A method for purifying pyromellitic dianhydride, characterized in that the method comprises the following steps: (1) Filtering and concentrating the mixed material containing the crude pyromellitic dianhydride to obtain a crude pyromellitic dianhydride concentrated solution; the solvent in the mixed material comprises dioxane and acetone; (2) Performing first cooling crystallization treatment and second cooling crystallization treatment on the crude homogeneous anhydride concentrated solution to obtain homogeneous anhydride crystals; The cooling rate of the first cooling crystallization treatment is higher than that of the second cooling crystallization treatment; the second cooling crystallization treatment is performed in the presence of a seed crystal of homogeneous anhydride.
  2. 2. The purification method according to claim 1, wherein, In the step (1), the step of (a), The mass ratio of dioxane to acetone is 0.05-0.90, preferably 0.05-0.50, more preferably 0.20-0.30, and/or The mass ratio of the solvent to the crude anhydride in the mixture is 12-18, and/or, In the step (2), the step of (C), The cooling rate of the first cooling crystallization treatment is 1.5-19 ℃ per minute, preferably 3.5-17 ℃ per minute, more preferably 6.5-9 ℃ per minute higher than the cooling rate of the second cooling crystallization treatment; More preferably, the process is carried out, The first cooling rate is 3-20deg.C/min, preferably 5-18deg.C/min, more preferably 8-10deg.C/min, and/or The cooling rate of the second cooling crystallization treatment is 1.0-1.5 ℃ per minute; More preferably, the initial temperature of the first cooling crystallization process is 55 to 60 ℃, and the initial temperature of the second cooling crystallization process is 45 to 50 ℃.
  3. 3. A purification method according to claim 1 or 2, wherein, The temperature of the filtration is 40-50℃, and/or The concentration temperature is 55-60℃, and/or The mass ratio of the solvent in the crude pyromellitic dianhydride to the crude pyromellitic dianhydride in the crude pyromellitic dianhydride concentrated solution is 5-7.
  4. 4. A purification method according to any one of claim 1 to 3, wherein, The conditions of the first cooling crystallization treatment include: the final temperature of cooling is 45-50 ℃.
  5. 5. A purification method according to any one of claim 1 to 4, The conditions of the second cooling crystallization treatment include: the final temperature of cooling is 0-5 ℃; The temperature keeping time of the end point temperature is 1-3h.
  6. 6. A purification method according to any one of claim 1 to 5, wherein, The seed crystal mass is 0.01-5wt%, preferably 0.05-2wt%, more preferably 0.1-1wt% and/or the mass of the crude pyromellitic dianhydride The seed crystal has a particle diameter of 50-250 μm, preferably 80-150 μm, more preferably 80-100 μm, and/or The seed crystal is pyromellitic dianhydride with the purity of 99.00-99.99%.
  7. 7. A purification method according to any one of claim 1 to 6, wherein, The crude pyromellitic dianhydride is crude pyromellitic dianhydride prepared by gas phase oxidation of durene and/or The content of pyromellitic dianhydride in the crude pyromellitic dianhydride is 90-99wt%.
  8. 8. A purification method according to any one of claim 1 to 7, The inert gas is selected from nitrogen and/or argon.
  9. 9. A purification method according to any one of claim 1 to 8, wherein, The drying conditions include: vacuum degree of 0.8-1bar, and/or At a temperature of 55-60℃, and/or The time is 2-3h.
  10. 10. The pyromellitic dianhydride is characterized in that the purity of the pyromellitic dianhydride is more than or equal to 99.99 percent, the free acid value is lower than 1 weight percent, preferably lower than 0.5 weight percent, more preferably 0.01-0.2 percent, the particle size D10 of the pyromellitic dianhydride is 100-140 mu m, and the particle size D90 is 140-150 mu m.

Description

Method for purifying pyromellitic dianhydride and pyromellitic dianhydride Technical Field The invention relates to a method for purifying pyromellitic dianhydride and pyromellitic dianhydride. Background Pyromellitic dianhydride (C10H 2O6, pyromellitic dianhydride, PMDA) is a chemical intermediate with high added value, and two bilaterally symmetrical anhydride groups can be subjected to polycondensation reaction with diamine compounds, so that the pyromellitic dianhydride is an important monomer for synthesizing polyimide. Polyimide has excellent mechanical property and dielectric property, and has been widely used in aerospace, electronic information and other high technology industries. With the increasing development of downstream industry chains, the demand for polyanhydrides as a main raw material is also shifted from original electrical grade products to high-purity electronic grade products. At present, the production method of the homoanhydride mainly adopts a durene gas-phase oxidation process, and the reaction process is a complex multiphase selective oxidation process, so that anhydride (trimellitic anhydride and phthalic anhydride) byproducts, aldehydes and acids (trimesic acid) byproducts are also included in the crude product, and the requirements of subsequent polymer grade products are difficult to meet. It is therefore necessary to develop an efficient process for refining crude homoanhydride. The prior studies (modern chemical industry, 1994 (01): 31-32 Zhang Wei, etc., petrochemical industry (07): 505-510[2024-01-10] Wang Yushan, etc.) show that the refining method for the crude product of the maleic anhydride mainly comprises a sublimation condensation method, a generated gas trapping method and a solvent method. Sublimation condensation is a refining method used in early industrial stage, including a reduced pressure sublimation method and a hot air carrying method. The decompression sublimation method is to condense all the generated gas, decompress and sublimate the gas under the condition of vacuum and 300 ℃ and cool and condense the crystallized gas to obtain refined homoanhydride. The disadvantage of this method is that the operation flow of condensation-sublimation-condensation is complex, the equipment cost is large, and the product is easily decomposed during sublimation. The hot air carrying method is to add the crude product into the hot inert air flow directly and continuously to sublimate the crude product, and then to sublimate and trap the sublimated crude product to obtain the high-purity homoanhydride. CN211635279U recognizes that a large amount of gas must be used for carrying out the method, and the heat exchange efficiency of the gas heating and cooling device is severely required, especially the cooling efficiency of the cooling device is higher, if the cooling efficiency is too low, the desublimated fine particle product cannot be captured fast, and the purity of the desublimated homoanhydride is finally reduced. The generated gas trapping method utilizes the difference of vapor pressure of the maleic anhydride and other byproducts, and realizes the selective trapping of the multistage trapping device by controlling the temperature gradient of the multistage trapping device and the trapping device with a special structure. The disadvantage of this process is that it is necessary to select a catalyst with good properties, otherwise it is difficult to obtain a product with high yield and purity. Solvent methods include washing methods, recrystallization methods, and complexation separation methods. The washing method is to wash out impurities and byproducts by using a solvent, and CN113583016A proposes a refining method by using methyl tert-butyl ether (MTBE) as the solvent, and refining is realized by using the principle that the solubility of the maleic anhydride in MTBE is extremely low and the solubility of other impurities (maleic acid, meta acid and meta anhydride) is higher. The method has the defects that the washed solvent is difficult to recycle, the energy consumption is high, the product has quality loss, and the refined product is easy to have solvent residues. The recrystallization method is to dissolve the crude anhydride with solvent and then recrystallize to finish purification, and CN100475820C provides a solvent recrystallization refining method, which mainly comprises the steps of mixing the crude anhydride, a dehydrating agent and a decolorizing agent for reaction, filtering, crystallizing the filtrate in a crystallization kettle, and filtering and drying to obtain a refined product. The method has the advantages of simple process flow, low energy consumption, higher yield of refined products, cyclic utilization of crystallization mother liquor and good economy. The solvent recrystallization method is a refining method widely used in industry at present, but the technical problems of low purity of refined products, high free acid value of produc