CN117683039A - Method for producing pyromellitic anhydride by pyromellitic acid dehydration process - Google Patents
Method for producing pyromellitic anhydride by pyromellitic acid dehydration process Download PDFInfo
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- CN117683039A CN117683039A CN202211080516.2A CN202211080516A CN117683039A CN 117683039 A CN117683039 A CN 117683039A CN 202211080516 A CN202211080516 A CN 202211080516A CN 117683039 A CN117683039 A CN 117683039A
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- CYIDZMCFTVVTJO-UHFFFAOYSA-N pyromellitic acid Chemical compound OC(=O)C1=CC(C(O)=O)=C(C(O)=O)C=C1C(O)=O CYIDZMCFTVVTJO-UHFFFAOYSA-N 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 24
- 230000018044 dehydration Effects 0.000 title claims abstract description 18
- 238000006297 dehydration reaction Methods 0.000 title claims abstract description 18
- ANSXAPJVJOKRDJ-UHFFFAOYSA-N furo[3,4-f][2]benzofuran-1,3,5,7-tetrone Chemical compound C1=C2C(=O)OC(=O)C2=CC2=C1C(=O)OC2=O ANSXAPJVJOKRDJ-UHFFFAOYSA-N 0.000 title claims abstract description 18
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 5
- USIUVYZYUHIAEV-UHFFFAOYSA-N diphenyl ether Chemical compound C=1C=CC=CC=1OC1=CC=CC=C1 USIUVYZYUHIAEV-UHFFFAOYSA-N 0.000 claims abstract description 50
- 238000010438 heat treatment Methods 0.000 claims abstract description 48
- 239000000203 mixture Substances 0.000 claims abstract description 29
- 238000001816 cooling Methods 0.000 claims abstract description 20
- YJTKZCDBKVTVBY-UHFFFAOYSA-N 1,3-Diphenylbenzene Chemical group C1=CC=CC=C1C1=CC=CC(C=2C=CC=CC=2)=C1 YJTKZCDBKVTVBY-UHFFFAOYSA-N 0.000 claims abstract description 19
- 239000003960 organic solvent Substances 0.000 claims abstract description 12
- 238000002425 crystallisation Methods 0.000 claims abstract description 11
- 230000008025 crystallization Effects 0.000 claims abstract description 11
- 239000011259 mixed solution Substances 0.000 claims description 26
- 239000000126 substance Substances 0.000 claims description 3
- 239000002178 crystalline material Substances 0.000 claims 1
- VLDPXPPHXDGHEW-UHFFFAOYSA-N 1-chloro-2-dichlorophosphoryloxybenzene Chemical compound ClC1=CC=CC=C1OP(Cl)(Cl)=O VLDPXPPHXDGHEW-UHFFFAOYSA-N 0.000 abstract description 58
- 239000002904 solvent Substances 0.000 abstract description 5
- 230000015572 biosynthetic process Effects 0.000 abstract description 2
- 150000002894 organic compounds Chemical class 0.000 abstract description 2
- 238000003786 synthesis reaction Methods 0.000 abstract description 2
- WFDIJRYMOXRFFG-UHFFFAOYSA-N Acetic anhydride Chemical compound CC(=O)OC(C)=O WFDIJRYMOXRFFG-UHFFFAOYSA-N 0.000 description 39
- 239000000706 filtrate Substances 0.000 description 21
- 239000013078 crystal Substances 0.000 description 20
- 239000000047 product Substances 0.000 description 20
- 239000007787 solid Substances 0.000 description 20
- 239000002198 insoluble material Substances 0.000 description 11
- 230000000717 retained effect Effects 0.000 description 11
- 238000003756 stirring Methods 0.000 description 11
- 238000001914 filtration Methods 0.000 description 10
- 238000005406 washing Methods 0.000 description 10
- 238000001291 vacuum drying Methods 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 6
- 239000000243 solution Substances 0.000 description 5
- SQNZJJAZBFDUTD-UHFFFAOYSA-N durene Chemical compound CC1=CC(C)=C(C)C=C1C SQNZJJAZBFDUTD-UHFFFAOYSA-N 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- HNTLCLLUPYGURB-UHFFFAOYSA-N [2-(carboxymethyl)-4,5-dimethylphenyl]methanetricarboxylic acid Chemical compound C=1(C(C(=O)O)(C(=O)O)C(=O)O)C(CC(=O)O)=CC(C)=C(C)C1 HNTLCLLUPYGURB-UHFFFAOYSA-N 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 239000004642 Polyimide Substances 0.000 description 1
- GTDPSWPPOUPBNX-UHFFFAOYSA-N ac1mqpva Chemical compound CC12C(=O)OC(=O)C1(C)C1(C)C2(C)C(=O)OC1=O GTDPSWPPOUPBNX-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 239000010985 leather Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004811 liquid chromatography Methods 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229920001225 polyester resin Polymers 0.000 description 1
- 239000004645 polyester resin Substances 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 239000012808 vapor phase Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D493/00—Heterocyclic compounds containing oxygen atoms as the only ring hetero atoms in the condensed system
- C07D493/02—Heterocyclic compounds containing oxygen atoms as the only ring hetero atoms in the condensed system in which the condensed system contains two hetero rings
- C07D493/04—Ortho-condensed systems
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Heterocyclic Carbon Compounds Containing A Hetero Ring Having Oxygen Or Sulfur (AREA)
Abstract
The invention provides a method for producing pyromellitic anhydride by a pyromellitic acid dehydration process, and belongs to the technical field of organic compound synthesis. The method comprises the following steps: (1) Dissolving pyromellitic acid in an organic solvent, and heating and dehydrating; (2) cooling and crystallizing, and separating to obtain pyromellitic dianhydride; the organic solvent comprises diphenyl ether and hydrogenated terphenyl. The invention adopts the mixture of diphenyl ether and hydrogenated terphenyl, expands the low-temperature operation window, obtains better PMDA yield and PMDA purity than the method which singly adopts diphenyl ether or hydrogenated terphenyl as solvent, and solves the problems of easy system viscosity, narrow temperature operation window, inconvenient operation and the like in the low-temperature crystallization in the prior art.
Description
Technical Field
The invention relates to a method for refining pyromellitic anhydride by dehydrating pyromellitic acid, belonging to the technical field of organic compound synthesis.
Background
Pyromellitic anhydride (PMDA) is an important organic chemical raw material, and is mainly used for producing polyimide, epoxy resin, polyester resin, plasticizer and the like, and can also be used as an adhesive, a surfactant, a metal corrosion inhibitor, a leather tanning agent, a high-temperature lubricant, fuel and the like.
At present, the technological process of pyromellitic dianhydride is mainly divided into two types, namely gas-phase oxidation and liquid-phase oxidation. The gas phase oxidation mainly uses durene as raw material and V 2 O 5 As a catalyst, the pyromellitic dianhydride is directly produced by high-temperature gas-phase oxidation. Although the vapor phase method can generate pyromellitic dianhydride in one step, the cycle conversion rate is low, the product has more impurities, the pyromellitic dianhydride can be used as an intermediate after hydrolysis and purification, the reaction process temperature is too high, and the energy consumption is high. The liquid phase method is to oxidize durene in acetic acid solvent to produce durene tetracarboxylic acid with Co-Mn-Br catalyst system, and then to dewater and refine durene tetracarboxylic dianhydride with high reaction temperature.
When the pyromellitic anhydride is refined by adopting a pyromellitic acid dehydration process in the prior art, the solvent is diphenyl ether alone, so that the problems that the system is sticky, even the diphenyl ether is crystallized and the like are easily caused during low-temperature crystallization, the temperature operation window of the low-temperature crystallization is narrow, and the operation is inconvenient; or acetic anhydride and pyromellitic acid are mixed, heated and dehydrated, but the consumption of the acetic anhydride is overlarge, the acetic anhydride is difficult to recycle, and the cost is overlarge.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for refining pyromellitic anhydride by dehydrating pyromellitic acid, which has good PMDA yield and PMDA purity.
According to one aspect of the present invention, there is provided a method for producing pyromellitic anhydride by dehydration of pyromellitic acid, the method comprising:
(1) Heating and dehydrating a mixed solution containing pyromellitic acid and an organic solvent to obtain a mixture;
(2) Cooling and crystallizing the mixture, and separating to obtain a crystalline substance containing pyromellitic anhydride;
the organic solvent comprises diphenyl ether and hydrogenated terphenyl.
Optionally, the mass ratio of hydrogenated terphenyl to diphenyl ether in the organic solvent is 4-15.
In the above technical solution, as a non-limiting example, the mass ratio of hydrogenated terphenyl to diphenyl ether in the organic solvent is 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or any value between any two points.
Optionally, the mass ratio of pyromellitic acid to the organic solvent in the mixed solution is 0.1-0.4.
In the above technical solution, as a non-limiting example, the mass ratio of pyromellitic acid to the organic solvent is 0.15, 0.2, 0.25, 0.3, 0.35, or any value between any two points.
Optionally, the temperature of the heating dehydration is 150-270 ℃.
In the above technical scheme, the temperature of the heating dehydration is 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃, 250 ℃, 260 ℃ or any value between any two points, by way of non-limiting example.
Optionally, the time of the heating dehydration is 1-6 h.
In the above technical solution, as a non-limiting example, the time of the heating and dehydrating is 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, or any value between any two points.
Optionally, the heated dewatering is divided into a first stage heated dewatering and a second stage heated dewatering.
Optionally, the temperature of the first stage of heating dehydration is 150-210 ℃ and the time is 1-3 h.
Optionally, the temperature of the second stage of heating dehydration is 220-270 ℃ and the time is 1-3 h.
In the above technical solution, as a non-limiting example, the first stage of heating and dehydrating time is 1.5h, 2h, 2.5h, 3h, or any value between any two points; the temperature of the first stage heating dehydration is 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃ or any value between any two points;
the time of the second section of heating dehydration is 1.5h, 2h, 2.5h and 3h, or any value between any two points; the temperature of the second stage of the heating dehydration is 220 ℃, 230 ℃, 240 ℃, 250 ℃, 260 ℃, 265 ℃ or any value between any two points.
Optionally, the temperature of the cooling crystallization is 5-35 ℃.
In the above technical scheme, the temperature of the cooling crystallization is, by way of non-limiting example, 10 ℃, 12 ℃, 15 ℃, 18 ℃, 20 ℃, 22 ℃, 25 ℃, 30 ℃, or any value between any two points of the above.
Optionally, the cooling crystallization time is 2-10 h.
In the above technical solution, as a non-limiting example, the cooling crystallization time is 3h, 4h, 5h, 6h, 7h, 8h, 9h, or any value between any two points.
Optionally, the purity of pyromellitic acid is 80wt.% to 100wt.%.
The yield of pyromellitic anhydride described herein is greater than 90.0mol.%, preferably greater than 95.0mol.%; the purity of pyromellitic anhydride in the crystalline substance is more than 91.0%; preferably 99.8%.
The invention has the following beneficial effects:
in the prior art, diphenyl ether is used as a solvent, but when the diphenyl ether is singly used, the system is easy to be thick and even the diphenyl ether is easy to crystallize at low temperature, the temperature operation window of the low temperature crystallization is narrow, and the operation is inconvenient. The invention adopts the mixture of diphenyl ether and hydrogenated terphenyl, expands the low-temperature operation window, and obtains better PMDA yield and PMDA purity than the method which adopts diphenyl ether or hydrogenated terphenyl as solvent.
Detailed Description
The invention is further illustrated below in connection with specific examples, which are not to be construed as limiting the invention in any way.
In the present application,
y (yield, mol%) = (C Pyromellitic dianhydride (powder) -C Pyromellitic dianhydride (primary) )/C Pyromellitic acid (original)
C Pyromellitic dianhydride (powder) : the content of pyromellitic dianhydride at the end of the reaction and mol;
C pyromellitic acidDianhydride (junior) : the content of pyromellitic dianhydride at the beginning of the reaction and mol;
C pyromellitic acid (original) : and the content of pyromellitic acid and mol are carried out at the beginning of the reaction.
The purity parameter of pyromellitic dianhydride is measured by liquid chromatography (GC 780) to compare the integral area S with the pyromellitic dianhydride standard (99.9 wt%;
purity% (test sample) /S (pyromellitic dianhydride standard sample) 。
Example 1
100g of pyromellitic acid (90 wt.%) and 50g of diphenyl ether are stirred uniformly, and 400g of hydrogenated terphenyl is added to obtain a mixed solution. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And heating the filtrate to 240 ℃, keeping the temperature for 2 hours, cooling to 30 ℃, standing for 6 hours to generate solid crystals, filtering the solid crystals, washing twice with acetic anhydride, and vacuum drying at 60 ℃ for 3 hours to obtain the pyromellitic dianhydride (PMDA) product. The pyromellitic dianhydride (PMDA) product yield was 96.6 mol% with a purity of 99.8%.
For comparison, the experimental results are presented in Table 1.
Example 2
100g of pyromellitic acid (90 wt.%) and 50g of diphenyl ether are stirred uniformly, and 400g of hydrogenated terphenyl is added to obtain a mixed solution. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And heating the filtrate to 240 ℃, keeping the temperature for 2 hours, cooling to 20 ℃, standing for 6 hours to generate solid crystals, filtering the solid crystals, washing twice with acetic anhydride, and vacuum drying at 60 ℃ for 3 hours to obtain the pyromellitic dianhydride (PMDA) product. The yield of pyromellitic dianhydride (PMDA) was 90.5 mol% and the purity was 91.2% for comparison and the experimental results are shown in table 1.
Example 3
100g of pyromellitic acid (90 wt.%) and 40g of diphenyl ether are stirred uniformly, and 410g of hydrogenated terphenyl is added to obtain a mixed solution. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And heating the filtrate to 240 ℃, keeping the temperature for 2 hours, cooling to 30 ℃, standing for 6 hours to generate solid crystals, filtering the solid crystals, washing twice with acetic anhydride, and vacuum drying at 60 ℃ for 3 hours to obtain the pyromellitic dianhydride (PMDA) product. The pyromellitic dianhydride (PMDA) product yield was 94.4 mol% with a purity of 95.7%.
For comparison, the experimental results are presented in Table 1.
Example 4
100g of pyromellitic acid (90 wt.%) and 70g of diphenyl ether are stirred uniformly, and 380g of hydrogenated terphenyl is added to obtain a mixed solution. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And heating the filtrate to 240 ℃, keeping the temperature for 2 hours, cooling to 30 ℃, standing for 6 hours to generate solid crystals, filtering the solid crystals, washing twice with acetic anhydride, and vacuum drying at 60 ℃ for 3 hours to obtain the pyromellitic dianhydride (PMDA) product. The pyromellitic dianhydride (PMDA) product yield was 92.5 mol% with a purity of 91.9%.
For comparison, the experimental results are presented in Table 1.
Example 5
100g of pyromellitic acid (90 wt.%) and 50g of diphenyl ether are stirred uniformly, and 400g of hydrogenated terphenyl is added to obtain a mixed solution. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And keeping the temperature for 2 hours, cooling to 30 ℃, standing for 6 hours to generate solid crystals, filtering the solid crystals, washing twice with acetic anhydride, and drying in vacuum at 60 ℃ for 3 hours to obtain the pyromellitic dianhydride (PMDA) product. The pyromellitic dianhydride (PMDA) product yield was 82.3 mol% with a purity of 90.6%.
For comparison, the experimental results are presented in Table 1.
Example 6
100g of pyromellitic acid (90 wt.%) and 50g of diphenyl ether are stirred uniformly, and 400g of hydrogenated terphenyl is added to obtain a mixed solution. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And heating the filtrate to 260 ℃, keeping the temperature for 2 hours, cooling to 30 ℃, standing for 6 hours to generate solid crystals, filtering the solid crystals, washing twice with acetic anhydride, and vacuum drying at 60 ℃ for 3 hours to obtain the pyromellitic dianhydride (PMDA) product. The pyromellitic dianhydride (PMDA) product yield was 95.2 mol% with a purity of 98.9%.
Example 7
100g of pyromellitic acid (90 wt.%) and 70g of diphenyl ether are stirred uniformly, 560g of hydrogenated terphenyl is added, and a mixed solution is obtained. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And heating the filtrate to 240 ℃, keeping the temperature for 2 hours, cooling to 30 ℃, standing for 6 hours to generate solid crystals, filtering the solid crystals, washing twice with acetic anhydride, and vacuum drying at 60 ℃ for 3 hours to obtain the pyromellitic dianhydride (PMDA) product. The pyromellitic dianhydride (PMDA) product yield was 95.0 mol% with a purity of 97.7%.
For comparison, the experimental results are presented in Table 1.
Example 8
100g of pyromellitic acid (90 wt.%) and 30g of diphenyl ether are stirred uniformly, 240g of hydrogenated terphenyl is added, and a mixed solution is obtained. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And heating the filtrate to 240 ℃, keeping the temperature for 2 hours, cooling to 30 ℃, standing for 6 hours to generate solid crystals, filtering the solid crystals, washing twice with acetic anhydride, and vacuum drying at 60 ℃ for 3 hours to obtain the pyromellitic dianhydride (PMDA) product. The pyromellitic dianhydride (PMDA) product yield was 90.3 mol% with a purity of 94.1%.
For comparison, the experimental results are presented in Table 1.
Comparative example 1
100g of pyromellitic acid (90 wt.%) was added with 450g of hydrogenated terphenyl to obtain a mixed solution. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And heating the filtrate to 240 ℃, keeping the temperature for 2 hours, cooling to 30 ℃, standing for 6 hours to generate solid crystals, filtering the solid crystals, washing twice with acetic anhydride, and vacuum drying at 60 ℃ for 3 hours to obtain the pyromellitic dianhydride (PMDA) product. The pyromellitic dianhydride (PMDA) product yield was 40.1 mol% with a purity of 64.3%.
For comparison, the experimental results are presented in Table 1.
Comparative example 2
100g of pyromellitic acid (90 wt.%) and 450g of diphenyl ether are uniformly stirred to obtain a mixed solution. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And heating the filtrate to 240 ℃, keeping the temperature for 2 hours, cooling to 30 ℃, standing for 6 hours to generate solid crystals, filtering the solid crystals, washing twice with acetic anhydride, and vacuum drying at 60 ℃ for 3 hours to obtain the pyromellitic dianhydride (PMDA) product. The pyromellitic dianhydride (PMDA) product yield was 80.4 mol% with a purity of 83.9%.
For comparison, the experimental results are presented in Table 1.
Comparative example 3
100g of pyromellitic acid (90 wt.%) and 450g of diphenyl ether are uniformly stirred to obtain a mixed solution. And then heating the mixed solution to 200 ℃ with continuous stirring at a heating rate of 10 ℃/min at 30 ℃ for 2 hours to obtain a mixture. The insoluble material in the mixture was then filtered off while hot, and the filtrate was retained. And heating the filtrate to 240 ℃, keeping the temperature for 2 hours, cooling to 20 ℃, and gradually thickening the liquid mixture until solidification, so that the crystallization operation can not be completed.
For comparison, the experimental results are presented in Table 1.
Table 1.
Any numerical value recited in this disclosure includes all values incremented by one unit from the lowest value to the highest value if there is only a two unit interval between any lowest value and any highest value. For example, if the amount of one component, or the value of a process variable such as temperature, pressure, time, etc., is stated to be 50-90, it is meant in this specification that values such as 51-89, 52-88 … …, and 69-71, and 70-71 are specifically recited. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 units may be considered as appropriate. This is only a few examples of the specific designations. In a similar manner, all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be disclosed in this application.
It should be noted that the above-described embodiments are only for explaining the present invention and do not constitute any limitation of the present invention. The invention has been described with reference to exemplary embodiments, but it is understood that the words which have been used are words of description and illustration, rather than words of limitation. Modifications may be made to the invention as defined in the appended claims, and the invention may be modified without departing from the scope and spirit of the invention. Although the invention is described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, as the invention extends to all other means and applications which perform the same function.
Claims (10)
1. A method for producing pyromellitic anhydride by dehydration of pyromellitic acid, the method comprising:
(1) Heating and dehydrating a mixed solution containing pyromellitic acid and an organic solvent to obtain a mixture;
(2) Cooling and crystallizing the mixture, and separating to obtain a crystalline substance containing pyromellitic anhydride;
the organic solvent comprises diphenyl ether and hydrogenated terphenyl.
2. The method according to claim 1, wherein the mass ratio of hydrogenated terphenyl to diphenyl ether in the organic solvent is 4 to 15.
3. The method according to claim 1 or 2, wherein the mass ratio of pyromellitic acid to the organic solvent in the mixed solution is 0.1 to 0.4.
4. A method according to any one of claims 1 to 3, wherein the temperature of the heated dehydration is 150 to 270 ℃;
and/or the time of the heating dehydration is 1-6 h.
5. The method of claim 4, wherein the heated dewatering is divided into a first stage heated dewatering and a second stage heated dewatering.
6. The method according to claim 5, wherein the first stage of heating dehydration is carried out at a temperature of 150-210 ℃ for a time of 1-3 hours;
and/or the temperature of the second section of heating dehydration is 220-270 ℃ and the time is 1-3 h.
7. The method according to any one of claims 1 to 6, wherein the temperature of the cooling crystallization is 5 to 35 ℃.
8. The method of claim 7, wherein the cooling crystallization time is 2 to 10 hours.
9. The method according to any one of claims 1-8, wherein the purity of pyromellitic acid is 80wt.% to 100wt.%.
10. The process according to any one of claims 1 to 9, characterized in that the yield of pyromellitic anhydride is greater than 90.0mol.%, preferably greater than 95.0mol.%; the purity of pyromellitic anhydride in the crystalline material is greater than 91.0 wt%; preferably 99.8% by weight.
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