CN114853775A - Method for refining pyromellitic dianhydride - Google Patents
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Abstract
The invention discloses a method for refining pyromellitic dianhydride in the field of chemical production, which comprises the steps of dissolving, filtering, oxidizing, distilling, crystallizing, filtering and drying to obtain a target product, wherein during dissolving, acetone and acetonitrile are adopted to prepare a mixed solvent according to the weight ratio of (2-4) to 1, and the weight ratio of crude anhydride to the mixed solvent is 1 (4-12); when in oxidation, ozone-containing air is introduced into the filtrate for oxidation; the invention can realize the reflux temperature lower than the boiling point of acetonitrile, so that the refining energy consumption is reduced. The introduction of ozone can oxidize methyl carboxylic acid impurities into corresponding aromatic acid, and other aromatic diacid and triacid anhydride are easily dissolved in acetone and acetonitrile, so that the impurities cannot be separated out and enter the pyromellitic dianhydride during crystallization, the pure pyromellitic dianhydride is white, the content of the obtained pyromellitic dianhydride impurities is low, the product quality is improved, and the purification energy consumption is low; the finished product of the refined anhydride has the characteristics of good purity, high melting point, high yield and uniform granularity.
Description
Technical Field
The invention relates to a method for refining pyromellitic dianhydride, in particular to a method for obtaining refined pyromellitic dianhydride from crude pyromellitic dianhydride by an oxidation-crystallization method, belonging to the technical field of chemical industry.
Background
Pyromellitic dianhydride, abbreviated as pyromellitic anhydride, and abbreviated as PMDA in english. The pyromellitic dianhydride is an important organic chemical raw material. The pyromellitic dianhydride is an important raw material for producing polyimide resin and films, matting agents, plasticizers, epoxy resin curing agents, polyester resin crosslinking agents, phenolic resin stabilizers and the like. Polyimide is a new material with high temperature resistance, low temperature resistance, radiation resistance and impact resistance, and has excellent electrical property and mechanical property, and has important application irreplaceable by other engineering plastics in aerospace and electromechanical industries. With the increasing market usage of polyimide, the demand for the polyanhydride as the main raw material for synthesizing the polyanhydride is increasing day by day.
In recent years, the maleic anhydride monomer is increasingly applied to the preparation of high-performance and high-tech material products at home and abroad, and the purity and the use requirements of the maleic anhydride product are higher and higher, so that the research on improving the purity and the application performance of the product and the industrialization of establishing a proper process technology are urgent and necessary.
The existing synthesis route of the pyromellitic anhydride is divided into two routes, wherein the first route is a durene gas-phase air oxidation method which comprises the processes of gasification, oxidation, trapping, hydrolysis decoloration, filtration, refining and the like; the second one is durene liquid phase air oxidation method, which comprises the processes of material preparation, oxidation, crystallization and centrifugation, dehydration to anhydride, refining, acetic acid recovery and the like. The former is a production process adopted by most manufacturers, and the latter is in the research and development test stage.
Shenyang chemical 1993(1), 31-32 Zhang Wei and the like, and a purification method of pyromellitic dianhydride is reported in the literature, and at present, there are three types, (1) a generated gas trapping method, including direct trapping and fractional trapping; (2) solvent methods, including washing, crystallization and complex separation; (3) sublimation methods, including low pressure sublimation and hot gas flow entrainment.
The coatings industry 2006, 36(11): 4-Dingzhiping et al reported that the gas-phase catalytic oxidation of durene to give pyromellitic dianhydride is a complex heterogeneous catalytic process consisting of a series of reactions. In the reaction process of the vanadium-titanium oxide catalyst, the oxidation of durene is an exothermic reaction, and certain strong acid points can be generated on the catalyst bed TiO under the high-temperature condition, so that durene can generate a series of demethylation or disproportionation reactions to generate o-xylene, pseudocumene, mesitylene and the like, which are respectively oxidized into phthalic anhydride, trimellitic anhydride, trimesic acid and the like. Resulting in a low yield of pyromellitic dianhydride. Meanwhile, the equipment flow and the operation process thereof are complex, the three wastes are seriously polluted, the operation cost is high, and the product meeting the application performance requirement is difficult to prepare. According to the difference of vapor pressure of each component at the same temperature, the method can directly and selectively desublimate and crystallize the pyromellitic anhydride from the gas product generated by gas-phase oxidation by controlling the suitable trapping temperature condition and selecting equipment with a special structure, thereby achieving the purpose of refining.
Chinese patent CN1970560A provides a method for producing pyromellitic dianhydride by purifying pyromellitic acid. In the absence of acetic anhydride, the crude pyromellitic acid is first partially converted to pyromellitic anhydride by heating, and then the mixture is heated in the presence of acetic anhydride to completely anhydrize the pyromellitic acid. The pyromellitic dianhydride obtained by the method not only contains almost no pyromellitic monoanhydride and other monoanhydrides derived from impurities and has less discoloration, but also has the advantages of no blockage caused during transportation, storage and use, and the like.
Chinese patent CN101580509A reports a method for producing electronic grade pyromellitic dianhydride from secondary captured crude anhydride. Comprises the following steps: washing the second catching crude anhydride; dehydrating and decoloring; recrystallizing; and (5) drying. One of the advantages. The process flow is short. Thereby saving energy; secondly, because the refining process is carried out in a closed device, the environment is not damaged; thirdly, because the separated crystallization mother liquor is recycled, the yield of pyromellitic dianhydride can be improved, the consumption of a dehydrating agent and a decolorizing agent is saved, the economy is realized, and the energy consumption can be saved; fourthly, the purity of the obtained pyromellitic dianhydride can reach more than 99 percent; fifthly, the pyromellitic dianhydride obtained by the method can meet the purity grade requirement for synthesizing an electronic-grade PI film.
The gas phase products produced by the gas phase air oxidation of durene are reported by 4 Wusha et al, proceedings of Harbin university of technology 2009, 14(4), which contain, in addition to the main product, the maleic anhydride, phthalic anhydride and some intermediate acids, such as 4, 5-dimethyl diacid (4, 5-DMPA), 5-methyl trimellitic acid (5-MTA), 2, 5-dimethyl triacid (2, 5-DMPA), 4, 6-dimethyl triacid (4, 6-DMPA) and the like.
According to the research of liquid-phase air oxidation technology, a pyromellitic acid (PMA) mixture generated by liquid-phase air oxidation of durene is crystallized, centrifuged and dehydrated into anhydride to obtain crude anhydride, wherein impurities comprise Phthalic Anhydride (PA), para/isophthalic acid (PTA/IPA), trimellitic anhydride (TMA), 5-methyl trimellitic acid, pyromellitic monoanhydride (PMMA) and the like.
According to the patent and literature reports, the solvents of the homogeneous anhydride solvent recrystallization method comprise: water, acetic acid, acetic anhydride, acetone, butanone, pentanone, cyclohexanone, ethyl acetate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, dioxane-acetic anhydride, benzene-tetrahydrofuran, diethyl ether-acetone, ethyl acetate-petroleum ether, and the like. For example, wangshan et al summarize solvent refining: primary solvent complexing recrystallization, secondary solvent thermal modification of crystal form and mixed solvent recrystallization; the use of a dioxane-acetic anhydride mixed solvent as a solvent for recrystallization is also discussed. The mixed solvent containing acetic anhydride with the concentration of less than 50 wt% has high effect, refining yield of about 80% and purity of crude anhydride raised from 95% to 99.4%.
The disadvantages are that: the purity of crude anhydride in the current market is 92-98%; the purity of the refined anhydride is about 99.5 percent, and the yield is about 80 percent. The existing gas phase trapping method, sublimation method or recrystallization method has the problems of low quality, low yield and uneven particle size.
Disclosure of Invention
The invention aims to provide a method for refining pyromellitic dianhydride, which has the advantages of low impurity content of the obtained pyromellitic dianhydride, capability of effectively eliminating the color graying and yellowing of the pyromellitic dianhydride, improvement of the product quality and low purification energy consumption.
The purpose of the invention is realized as follows: a method for refining pyromellitic dianhydride comprises the following steps:
(1) dissolving: mixing and stirring acetone and acetonitrile in a dissolving kettle uniformly, then adding crude anhydride containing pyromellitic dianhydride into the dissolving kettle, continuously heating and refluxing until the crude anhydride is dissolved, wherein the reflux temperature is 60-70 ℃; wherein, the purity of the pyromellitic dianhydride contained in the raw material of the crude anhydride is 92-98%, the weight ratio of acetone to acetonitrile is (2-4) to 1, and the weight ratio of the crude anhydride to the mixed solvent is (4-12);
(2) and (3) filtering: filtering to remove insoluble impurities under a thermal state;
(3) and (3) oxidation: introducing air containing ozone into the filtrate for oxidation;
(4) and (3) distillation: distilling under normal pressure to remove a part of solvent;
(5) and (3) crystallization: cooling and crystallizing the residual mother liquor, and controlling the stirring speed at the same time until crystals are separated out;
(6) filtering-drying: and (5) filtering and drying the crystallized material to obtain a qualified finished product of the refined anhydride.
In the invention, acetone and acetonitrile are mixed into a mixed solvent according to the weight ratio of (2-4) to 1, the mixed solvent has higher saturation solubility of pyromellitic dianhydride at 60-70 ℃ than that of the pyromellitic dianhydride in single acetone, and the solubility of the pyromellitic dianhydride is very low at the crystallization temperature, the crystallization temperature is basically normal temperature, and the crystallization operation is convenient. Meanwhile, the boiling point of acetone is 56 ℃, the boiling point of acetonitrile is 81 ℃, the difference between the boiling points of the acetone and the acetonitrile is large, the acetone and the acetonitrile cannot be subjected to azeotropy at the temperature of 60-70 ℃, only the acetone is evaporated and refluxed, and the acetone boiling and refluxing can generate enough driving force, so that the pyromellitic dianhydride can be quickly dissolved. Meanwhile, the reflux temperature lower than the boiling point of acetonitrile can be realized, so that the refining energy consumption is reduced. At 60-70 ℃, a small amount of diacid or triacid impurities in the crude anhydride have certain solubility, the impurities mainly comprise methyl benzene diacid, methyl trimellitic acid, terephthalic acid, isophthalic acid and trimellitic anhydride, after the impurities are dissolved in a mixed solvent, the subsequent oxidation reaction can be smoothly carried out, the methyl carboxylic acid impurities can be oxidized into corresponding aromatic acid through the introduction of ozone, and other aromatic diacid and triacid anhydride are easily dissolved in acetone and acetonitrile, so that the impurities can not be separated out and enter into pyromellitic dianhydride during crystallization, the pure pyromellitic dianhydride is white instead of graying or yellowing, and the subsequent application of the pure pyromellitic dianhydride can not be influenced. The acetone and the acetonitrile and the dosage proportion thereof selected by the invention are the preferable schemes considering factors in the aspects of reflux dissolution, normal-temperature crystallization, impurity removal, purification energy consumption and the like. The obtained pyromellitic dianhydride has low impurity content, can effectively eliminate the grey and yellow color of the pyromellitic dianhydride, improves the product quality, and has low purification energy consumption; the finished product of the refined anhydride has the characteristics of good purity, high melting point, high yield and uniform granularity.
The invention is further improved in that in the step (1), the reflux temperature is 65 ℃, and the weight ratio of the acetone to the acetonitrile in the mixed solvent is preferably 3: 1; the weight ratio of the crude anhydride to the mixed solvent is preferably 1: 8.
The further improvement of the invention is that in the step (3), the content of the ozone in the air is 2-4vt%, the continuous introducing time is 20-40min, and the aeration quantity per hour is 60-80 times of the volume of the mixed solvent. Preferably, the content of the ozone in the air is 3vt%, the continuous introducing time is 30min, and the ventilation quantity per hour is 70 times of the volume of the mixed solvent.
The further improvement of the invention is that the mixed solvent with 1/3-4/5 times of weight is removed by atmospheric distillation. It is preferable to distill off 2/3 times by weight of the mixed solvent.
The further improvement of the invention is that in the step (5), the crystallization temperature is 15-25 ℃, the stirring speed is 30-300r/min, and the cooling speed is 0.35-1 ℃/min. Preferably, the crystallization temperature is 20 ℃, the stirring speed is 135r/min, and the cooling speed is 0.7 ℃.
The further improvement of the invention is that in the step (6), a vacuum filtration dryer is adopted for drying, the vacuum degree is 0.08-0.09MPa, and the drying temperature is 75-85 ℃.
Detailed Description
Example 1:
firstly, adding a mixed solvent prepared from 3 parts of acetone and 1 part of acetonitrile (in a weight ratio of 3: 1) into a reaction container, and stirring; then adding 0.5 part of 98 percent crude anhydride (the weight ratio of the crude anhydride to the mixed solvent is 1: 8) into a reaction vessel, continuously heating and refluxing until the crude anhydride is basically dissolved, wherein the reflux temperature is 65 ℃; then removing insoluble impurities by hot filtration;
introducing air containing 3.5vt% ozone into the filtrate at 65 deg.C for oxidation, and maintaining for 30min, wherein the introduction amount of air is 60-80 times of the solvent volume/hr; 1/2 wt% of solvent was then distilled off; then cooling the residual mother liquor to 20 ℃, wherein the cooling rate is 1 ℃/min, and the stirring rate is controlled to be 135r/min at the same time until crystals are separated out; then the crystallized material passes through a vacuum filtration dryer, the vacuum degree is maintained at 0.08-0.09MPa, the temperature is 75-85 ℃, and the time is 60min, thus obtaining a finished product of refined anhydride, the appearance of which is white powdery crystal.
The invention provides a method for refining pyromellitic dianhydride, in particular to an oxidation-crystallization method. Researches show that trace methyl carboxylic acid impurities in crude pyromellitic dianhydride (crude anhydride for short) can be converted into corresponding aromatic acid through ozone oxidation, and the aim of eliminating grey and yellow color of the pyromellitic dianhydride is fulfilled; secondly, the small amount of impurities of diacid or triacid anhydride (0.6-2.5 wt% of terephthalic acid, 0.5-1.9wt% of isophthalic acid, 0.9-3.6wt% of trimellitic anhydride) is different from the solubility of pyromellitic anhydride in acetone and acetonitrile (see table 1 below).
TABLE 1 solubility of acids/anhydrides in acetone and acetonitrile (g/100 g) Table
The solubility law of the acid/anhydride in different solvents and temperatures is summarized in the table: the homogeneous anhydride is greater than the partial anhydride is greater than the isophthalic acid is greater than the terephthalic acid; acetone (acetone/acetonitrile mixed solvent) is more than acetonitrile at normal temperature, and acetone (acetone/acetonitrile mixed solvent) is more than acetonitrile at high temperature. These physical properties in turn lead to differences in crystallization during the temperature reduction. At 56 ℃, the solubility of the pyromellitic dianhydride in the acetone/acetonitrile mixed solvent is 14.9 g/solvent 100g, and at 65 ℃, the acetone content in the solvent is reduced and the acetonitrile content is increased because the acetone is already boiled, and the solubility of the pyromellitic dianhydride approaches to 16 g/solvent 100 g; at 20 ℃, the solubility of pyromellitic dianhydride in the mixed solvent is 8.0 g/solvent 100g, which is lower than that in acetone. Therefore, the crystallization is more favorable, in addition, when the mixed solvent is crystallized, a part of the solvent is distilled, the distilled acetone is mainly acetone due to the low boiling point of the acetone, the content ratio of the acetonitrile is increased along with the reduction of the acetone, the solubility of the pyromellitic dianhydride in the distilled mixed solvent is less than 8.0 g/100g of the solvent, and the solubility of the pyromellitic dianhydride in the acetonitrile is closer to 2.0 g/100g of the solvent; therefore, the acetone/acetonitrile mixed solvent is adopted, the lower reflux dissolution temperature can be realized, the crystallization can be carried out at normal temperature, the yield is higher, and the purification energy consumption is low.
Example 2-1:
example 1 was followed except that 92% crude anhydride was used.
Example 2-2:
example 1 was followed except that 95% crude anhydride was used.
Comparative example 2-a
The procedure is as in example 1, except that 91% crude anhydride, pale yellow powdery crystals are used.
Analysis and test: the purity of the product is determined by High Performance Liquid Chromatography (HPLC) with reference to GB/T26792-2019; the melting point adopts an automatic melting point instrument; the particle size is measured by a dry particle size analyzer.
TABLE 2 comparison table of the influence of crude anhydride purity on the quality and yield of refined anhydride
According to the comparison results in the table, the raw material purity is high, and the finished product purity and yield are high, so that the purity of the crude anhydride is preferably more than or equal to 92 percent, and more preferably 98 percent.
Example 3-1:
the same procedure as in example 1 was repeated except that a mixed solvent prepared from acetone and acetonitrile in a weight ratio of 2:1 was used.
Example 3-2:
the same procedure as in example 1 was repeated except that a mixed solvent prepared from acetone and acetonitrile in a weight ratio of 4:1 was used.
Comparative example 3-a:
the same procedure as in example 1 was repeated, except that a mixed solvent prepared from acetone and acetonitrile in a weight ratio of 1:1 was used.
Comparative example 3-b:
the same procedure as in example 1 was repeated except that a mixed solvent prepared from acetone and acetonitrile in a weight ratio of 5:1 was used.
Comparative example 3-c:
the same procedure as in example 1 was repeated except that a mixed solvent prepared from acetone and acetic acid in a weight ratio of 2:1 was used.
Comparative example 3-d:
the same procedure as in example 1 was repeated except that a mixed solvent of acetone and acetic anhydride in a weight ratio of 2:1 was used.
Comparative examples 3-e:
the same procedure as in example 1 was repeated, except that 4 parts of acetone solvent was used.
Comparative example 3-f:
the same procedure as in example 1 was repeated, except that 4 parts of acetonitrile solvent was used.
TABLE 3 comparison table of influence of solvent weight ratio and kind on refined anhydride quality and yield
Therefore, the mixed solvent is preferably acetone and acetonitrile in a weight ratio of 2-4:1, preferably 3: 1.
Example 4-1:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:4, and the method is otherwise the same as the example 1.
Example 4-2:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:5, and the method is otherwise the same as the example 1.
Examples 4 to 3:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:6, and the method is otherwise the same as the example 1.
Examples 4 to 4:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:10, and the method is otherwise the same as the example 1.
Examples 4 to 5:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:12, and the method is otherwise the same as the example 1.
Comparative example 4-a:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:3, and the method is otherwise the same as that of the example 1.
Comparative example 4-b:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:2, and the method is otherwise the same as the example 1.
Comparative example 4-c:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:1, and the method is otherwise the same as the example 1.
Comparative examples 4-d:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:13, and the method is otherwise the same as the example 1.
Comparative examples 4-e:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:15, and the method is otherwise the same as the example 1.
Comparative example 4-f:
the weight ratio of the crude anhydride to the acetone acetonitrile mixed solvent is changed to 1:17, and the method is otherwise the same as the example 1.
TABLE 4 comparison table of the influence of the weight ratio of crude anhydride to mixed solvent on the quality and yield of refined anhydride
The results in the table show that the yield decreases with more mixed solvent, and the weight ratio of the crude anhydride to the mixed solvent is preferably 1:4 to 12. Preferably 1: 8.
Example 5-1:
example 1 was followed by using 2vt% ozone in air.
Example 5-2:
example 1 was followed by using 4vt% ozone in air.
Comparative example 5-a:
example 1 was followed by using air containing 5vt% ozone.
Comparative example 5-b:
example 1 was followed by using 6vt% ozone in air.
Comparative example 5-c:
example 1 was followed by using air containing 1vt% ozone.
Comparative examples 5-d:
the procedure of example 1 was followed except that "the filtrate was oxidized by introducing air containing 3.5vt% ozone".
TABLE 5 comparison table of influence of ozone concentration on quality and yield of refined anhydride
The results show that the purity and melting point are improved by introducing ozone at different concentrations, too much leads to peroxidation, and the purity and yield are reduced. The ozone concentration is preferably 2 to 4%, more preferably 3%.
Example 6-1:
1/3 wt% of the solvent was distilled off, the procedure was otherwise the same as in example 1.
Example 6-2:
1/2 wt% of solvent was distilled off, and the procedure was otherwise the same as in example 1.
Examples 6 to 3:
4/5 wt% of solvent was distilled off, and the procedure was otherwise the same as in example 1.
Comparative example 6-a:
the procedure "1/2 wt. solvent distilled off" was removed, and the procedure was otherwise the same as in example 1.
Comparative example 6-b:
the procedure was followed except that "5/6 wt% of the solvent was distilled off" to obtain pale yellow colored crystals, as in example 1.
TABLE 6 comparison table of influence of solvent distillation amount on quality and yield of refined anhydride
Therefore, the more solvent distilled, the higher the yield, the lower the purity and melting point, but the yield is too low without evaporation, and the particle size is too large; however, too much distillation can affect the color of the finished product. The mixed solvent is preferably distilled off in an amount 1/3 to 4/5 times by weight, and preferably 2/3.
Example 7-1:
the temperature decrease rate was 0.35 ℃/min, and the same as in example 1.
Example 7-2:
the temperature decrease rate was 0.7 ℃/min, and the same as in example 1.
Comparative example 7-a:
the temperature decrease rate was 1.05 ℃/min, and the same as in example 1.
Comparative example 7-b:
the temperature decrease rate was 0.3 ℃/min, and the same as in example 1.
TABLE 7 comparison table of influence of cooling rate on quality and yield of refined anhydride
According to the above results, the slower the cooling rate, the larger the crystal particle size, the less the influence of quality, and the too long crystallization time affects the crystallization efficiency. Therefore, the cooling rate is controlled to be 0.35-1.0 ℃/min.
Example 8-1:
the stirring rate was changed to 60r/min, and the procedure was otherwise the same as in example 1.
Example 8-2:
the stirring rate was changed to 100r/min, and the procedure was otherwise the same as in example 1.
Examples 8 to 3:
the stirring rate was changed to 200r/min, and the procedure was otherwise the same as in example 1.
Examples 8 to 4:
the stirring rate was changed to 300r/min, and the procedure was otherwise the same as in example 1.
Comparative example 8-a:
the stirring rate was changed to 20r/min, and the procedure was otherwise the same as in example 1.
Comparative example 8-b:
the stirring rate was changed to 310r/min, and the procedure was otherwise the same as in example 1.
TABLE 8 comparison table of the influence of stirring speed on the quality and yield of refined anhydride
According to the results in the table, the higher the stirring rate, the smaller the average particle size, and the less the change in purity. Therefore, the stirring rate is preferably 30 to 300 r/min.
In conclusion, the purity of the finished product of the refined anhydride obtained by the oxidation-crystallization method is more than or equal to 99.9 percent, the melting point is more than or equal to 287 ℃, the yield is more than or equal to 90 percent, and the particle size distribution D90100-150 um.
The invention is not limited to the above embodiment, and the reflux temperature can be selected to be 60-70 ℃ during dissolution; wherein, during oxidation, the content of ozone in the air is 2-4vt%, the continuous introducing time is 20-40min, and the air flow per hour is 60-80 times of the volume of the mixed solvent; during distillation, 1/3-4/5 times of the weight of the mixed solvent is removed by normal pressure distillation, the crystallization temperature is 15-25 ℃, the vacuum degree is 0.08-0.09MPa, and the drying temperature is 75-85 ℃. Within the range of the parameters, the smooth implementation of the invention can be ensured and the beneficial effects of the invention can be obtained.
The present invention is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts according to the disclosed technical contents, and these substitutions and modifications are all within the protection scope of the present invention.
Claims (9)
1. A method for refining pyromellitic dianhydride is characterized by comprising the following steps:
(1) dissolving: mixing and stirring acetone and acetonitrile in a dissolving kettle uniformly, then adding crude anhydride containing pyromellitic dianhydride into the dissolving kettle, continuously heating and refluxing until the crude anhydride is dissolved, wherein the reflux temperature is 60-70 ℃; wherein, the purity of the pyromellitic dianhydride contained in the raw material of the crude anhydride is 92-98%, the weight ratio of acetone to acetonitrile is (2-4) to 1, and the weight ratio of the crude anhydride to the mixed solvent is (4-12);
(2) and (3) filtering: filtering to remove insoluble impurities under a thermal state;
(3) and (3) oxidation: introducing air containing ozone into the filtrate for oxidation;
(4) and (3) distillation: distilling off a part of the solvent;
(5) and (3) crystallization: cooling and crystallizing the residual mother liquor, and controlling the stirring speed at the same time until crystals are separated out;
(6) filtering-drying: and (5) filtering and drying the crystallized material to obtain a qualified finished product of the refined anhydride.
2. The method according to claim 1, wherein the pyromellitic dianhydride is selected from the group consisting of: in the step (1), the reflux temperature is 65 ℃, and the weight ratio of acetone to acetonitrile in the mixed solvent is 3: 1; the weight ratio of the crude anhydride to the mixed solvent is 1: 8.
3. The method according to claim 1, wherein the pyromellitic dianhydride is selected from the group consisting of: in the step (3), the content of ozone in the air is 2-4vt%, the continuous introducing time is 20-40min, and the air flow per hour is 60-80 times of the volume of the mixed solvent.
4. The method according to claim 3, wherein the step of refining pyromellitic dianhydride comprises the steps of: the content of ozone in the air is 3vt%, the continuous introducing time is 30min, and the ventilation volume per hour is 70 times of the volume of the mixed solvent.
5. The method according to claim 1, wherein the pyromellitic dianhydride is selected from the group consisting of: in the step (4), 1/3-4/5 times of the weight of the mixed solvent is removed by atmospheric distillation.
6. The method according to claim 5, wherein the step of refining pyromellitic dianhydride comprises the steps of: 2/3 times by weight of the mixed solvent was distilled off.
7. The method according to claim 1, wherein the pyromellitic dianhydride is selected from the group consisting of: in the step (5), the crystallization temperature is 15-25 ℃, the stirring speed is 30-300r/min, and the cooling speed is 0.35-1 ℃/min.
8. The method according to claim 7, wherein the step of refining pyromellitic dianhydride comprises the steps of: in the step (5), the crystallization temperature is 20 ℃, the stirring speed is 135r/min, and the cooling speed is 0.7 ℃.
9. The method according to claim 1, wherein the pyromellitic dianhydride is selected from the group consisting of: in the step (6), a vacuum filtration dryer is adopted for drying, the vacuum degree is 0.08-0.09MPa, and the drying temperature is 75-85 ℃.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210756691.2A CN114853775B (en) | 2022-06-30 | 2022-06-30 | Method for refining pyromellitic dianhydride |
| PCT/CN2022/122123 WO2024000879A1 (en) | 2022-06-30 | 2022-09-28 | Method for refining pyromellitic dianhydride |
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| CN202210756691.2A CN114853775B (en) | 2022-06-30 | 2022-06-30 | Method for refining pyromellitic dianhydride |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113583016A (en) * | 2021-09-01 | 2021-11-02 | 潍坊弘润新材料有限公司 | Method for improving purity of crude pyromellitic dianhydride, device and application thereof |
| WO2024000879A1 (en) * | 2022-06-30 | 2024-01-04 | 江苏正丹化学工业股份有限公司 | Method for refining pyromellitic dianhydride |
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| GB1066148A (en) * | 1965-03-24 | 1967-04-19 | Gelsenberg Benzin Ag | Purification of pyromellitic dianhydride |
| GB1280562A (en) * | 1969-06-13 | 1972-07-05 | Veba Chemie Ag | Process for the purification of pyromellitic acid dianhydride |
| JPS48437U (en) * | 1971-05-29 | 1973-01-06 | ||
| SU268408A1 (en) * | 1968-08-19 | 1976-01-25 | The method of purification of pyromellitic dianhydride | |
| JPH0578367A (en) * | 1991-09-18 | 1993-03-30 | Nippon Steel Chem Co Ltd | Production of high-purity pyromellitic anhydride |
| JPH05331103A (en) * | 1992-05-27 | 1993-12-14 | Kawasaki Steel Corp | Purification of pyromellitic anhydride |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114853775B (en) * | 2022-06-30 | 2023-05-30 | 江苏正丹化学工业股份有限公司 | Method for refining pyromellitic dianhydride |
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- 2022-09-28 WO PCT/CN2022/122123 patent/WO2024000879A1/en unknown
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113583016A (en) * | 2021-09-01 | 2021-11-02 | 潍坊弘润新材料有限公司 | Method for improving purity of crude pyromellitic dianhydride, device and application thereof |
| WO2024000879A1 (en) * | 2022-06-30 | 2024-01-04 | 江苏正丹化学工业股份有限公司 | Method for refining pyromellitic dianhydride |
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| WO2024000879A1 (en) | 2024-01-04 |
| CN114853775B (en) | 2023-05-30 |
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