CN109666032B - Preparation method of pyromellitic anhydride - Google Patents
Preparation method of pyromellitic anhydride Download PDFInfo
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- CN109666032B CN109666032B CN201811511452.0A CN201811511452A CN109666032B CN 109666032 B CN109666032 B CN 109666032B CN 201811511452 A CN201811511452 A CN 201811511452A CN 109666032 B CN109666032 B CN 109666032B
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- 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
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Abstract
The invention discloses a preparation method of pyromellitic dianhydride, which comprises the following steps: (1) pseudocumene reacts with dichloroethane for 0.5 to 5 hours in an organic solvent under the catalytic action of aluminum trichloride or ferric trichloride to generate 2,2 ', 4,4 ', 5,5 ' -hexamethyl diphenylethane; hydrolyzing and removing the solvent to obtain a crude product of 2,2 ', 4,4 ', 5,5 ' -hexamethyl diphenylethane; (2) heating and gasifying the crude product of 2,2 ', 4,4 ', 5,5 ' -hexamethyl diphenylethane, and collecting the product to obtain pyromellitic dianhydride under the action of a catalyst and through air oxidation at the reaction temperature of 350-500 ℃. The preparation method of pyromellitic dianhydride disclosed by the invention has the advantages of product selectivity of over 90%, good yield, low cost and industrial production.
Description
Technical Field
The invention relates to the technical field of organic compound synthesis, in particular to a preparation method of pyromellitic dianhydride.
Background
Pyromellitic anhydride is an important organic chemical raw material, 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.
The pyromellitic dianhydride has more production methods, and has various production processes even if the same raw material is adopted due to different raw materials and different selected process routes. At present, the technological routes developed at home and abroad mainly include heavy aromatic hydrocarbon separation and purification, partial trimethylbenzene alkylation, tetramethylbenzene isomerization and the like. As the pseudocumene is the main component of the reformed aromatic hydrocarbon, is cheap and easy to obtain, and is taken as the raw material mostly. The pseudocumene is obtained by further oxidizing a product obtained by an alkylation reaction with methanol, propylene or the like or a carbonylation reaction with CO. Also produced by the xylene chloromethylation reaction process.
The methanol alkylation of pseudocumene is the main process for preparing durene. Chennan, Lijie et al (Tianjin chemical, 2007,21(3), 42) report that the selectivity is only 48.73% when molecular sieve is used as catalyst. After improvements of li rui jiang, lingchu lei et al [ fine petrochemical, 2009,26(1),64 ], the selectivity can reach 85%, but the conversion rate is only 24.2%. The invention patent (CN105457669) of the Han Yinhen and the Han' bin et al uses an improved HZSM-5 catalyst, the selectivity reaches 90-99.9%, but the yield is only 7-11%. Japanese patent JP03215438(1991) reports that the selectivity can be increased to 99%, but the conversion is only 13%. The method for alkylating the pseudocumene methanol has the defects of non-ideal selectivity and conversion rate, high-temperature and high-pressure reaction, high equipment investment and strict process requirement.
The raw materials used in the pseudocumene-propylene alkylation process and the carbon monoxide carbonylation process are gases, so the production requirement is high and the raw materials are inconvenient to use.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method of pyromellitic dianhydride, which achieves the purposes of simplicity, convenience, easy operation, low cost, high selectivity and high conversion rate.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a preparation method of pyromellitic anhydride comprises the following steps:
(1) pseudocumene (I) reacts with dichloroethane for 0.5 to 5 hours in an organic solvent under the catalytic action of aluminum trichloride or ferric trichloride to generate 2,2 ', 4,4 ', 5,5 ' -hexamethyl diphenylethane (II); hydrolyzing and removing the solvent to obtain a crude product of 2,2 ', 4,4 ', 5,5 ' -hexamethyl diphenylethane (II);
(2) heating and gasifying the crude product of 2,2 ', 4,4 ', 5,5 ' -hexamethyl diphenylethane (II), and carrying out air oxidation under the action of a catalyst at the reaction temperature of 350-.
The reaction formula is as follows:
in the scheme, the organic solvent in the step (1) is one or a mixture of dichloroethane, cyclohexane, chlorobenzene, dichlorobenzene and o-dichlorobenzene.
In the scheme, the reaction ratio in the step (1) is as follows: the molar ratio of the pseudocumene to the aluminum trichloride or the ferric trichloride is 1: 0.05-1.5; the volume ratio of the pseudocumene to the organic solvent is 1: 1.5-5.
In the scheme, the reaction temperature in the step (1) is 0-80 ℃; the reaction pressure was normal pressure.
Preferably, the reaction temperature of step (1) is 0 to 50 ℃.
In the above embodiment, the catalyst in the step (2) is a vanadium-based catalyst.
In the scheme, the air oxidation in the step (2) has the feeding space velocity of 3000--1The concentration of 2,2 ', 4,4 ', 5,5 ' -hexamethyl-diphenylethane in air is 5-40g/m3。
Through the technical scheme, the reaction mechanism of the preparation method of pyromellitic dianhydride provided by the invention is as follows:
as can be seen from the reaction formula, as the generated chloroethyl positive ion and aluminum trichloride form a compound, the volume of the carbonium ion is increased, steric hindrance is formed, and compared with common Friedel-crafts alkylation, the method is more favorable for attack by selecting a position with small steric hindrance; the trimethylphenethyl cation formed in the second step is also very large in volume and is also favorable for attacking a position with small steric hindrance. The first step is slow reaction, the second step is fast reaction, and the hexamethyl diphenylethane has larger steric hindrance and can not continue to react, so that the final result improves the selectivity of the product. Therefore, the preparation method of pyromellitic dianhydride disclosed by the invention is simple to operate, convenient to control at normal temperature and normal pressure, low in cost, high in conversion rate and suitable for large-scale production.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below.
The invention provides a preparation method of pyromellitic dianhydride, which comprises the following specific embodiments:
example 1:
80g of dichloroethane is put into a reaction kettle, 36g of aluminum trichloride is added, the temperature is cooled to 0 ℃, 30g of pseudocumene is dropwise added under the controlled temperature, and the reaction is kept at 0 ℃ for 5 hours. 120g of cold water was added, stirred for 10 minutes, and the aqueous phase was separated. The solvent was distilled off to obtain 33g of crude 2,2 ', 4, 4', 5,5 '-hexamethyldiphenylethane having a 2, 2', 4,4 ', 5, 5' -hexamethyldiphenylethane content of 90.6%.
(Ⅱ)1H NMR(CDCl3)：δ2.19(s,18H),2.7(S,4H),6.9(S,4H)。
2,2 ', 4,4 ', 5,5 ' -hexamethyl diphenylethane crude product is mixed with air according to the proportion of 20g per cubic meter by a material melting device and a vaporizer according to the space velocity of 6000h-1Introducing the mixed gas into a container filled with commercial V2O5-TiO2-P2O5And (3) keeping the reaction temperature of a fixed bed reactor of the catalyst at 380 ℃, and collecting gas at the outlet of the reactor to obtain a crude pyromellitic dianhydride (III). The crude pyromellitic anhydride (III) is further refined and purified to obtain the finished pyromellitic anhydride (III). Yield: 82.3 percent.
(Ⅲ)1H NMR(DMSO)：δ8.61(s,2H)。
Example 2:
90g of o-dichlorobenzene and 14g of dichloroethane are put into a reaction kettle, 8g of ferric trichloride are added, the temperature is cooled to 10 ℃, 30g of pseudocumene is dropwise added at controlled temperature, and the reaction is kept at 10 ℃ for 1 hour. 100g of cold water was added, stirred for 10 minutes, and the aqueous phase was separated. The solvent was evaporated to give crude 2,2 ', 4,4 ', 5,5 ' -hexamethyldiphenylethane.
2,2 ', 4,4 ', 5,5 ' -hexamethyl diphenylethane is mixed with air according to the proportion of 20g per cubic meter by a material melting device and a vaporizer according to the space velocity of 3000h-1Introducing the mixed gas into a container filled with commercial V2O5-TiO2Fixed bed reactor for catalyst, maintaining reaction temperatureAnd collecting the gas at the outlet of the reactor at 500 ℃ to obtain a crude pyromellitic dianhydride (III). Further refining the crude pyromellitic anhydride (III) to obtain a finished pyromellitic anhydride (III).
Example 3:
80g of chlorobenzene and 15g of dichloroethane are put into a reaction kettle, 36g of aluminum trichloride is added, the temperature is cooled to 20 ℃, 30g of pseudocumene is dropwise added at controlled temperature, and the reaction is kept at 20-30 ℃ for 3 hours. 100g of cold water was added, stirred for 10 minutes, and the aqueous phase was separated. The solvent was evaporated to give crude 2,2 ', 4,4 ', 5,5 ' -hexamethyldiphenylethane.
2,2 ', 4,4 ', 5,5 ' -hexamethyl diphenylethane is mixed with air according to the proportion of 5g per cubic meter by a material melting device and a vaporizer according to the space velocity of 3000h-1Introducing the mixed gas into a container filled with commercial V2O5-P2O5-Al2O3And (3) keeping the reaction temperature of the fixed bed reactor of the catalyst at 450 ℃, and collecting gas at the outlet of the reactor to obtain a crude pyromellitic dianhydride (III). Further refining the crude pyromellitic anhydride (III) to obtain a finished pyromellitic anhydride (III).
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (1)
1. A preparation method of pyromellitic anhydride is characterized by comprising the following steps: putting 80g of dichloroethane into a reaction kettle, adding 36g of aluminum trichloride, cooling to 0 ℃, dropwise adding 30g of pseudocumene under controlled temperature, and keeping the temperature at 0 ℃ for reaction for 5 hours; adding 120g of cold water, stirring for 10 minutes, and separating out a water phase; the solvent was distilled off to obtain 33g of crude 2,2 ', 4,4 ', 5,5 ' -hexamethyldiphenylethane;
2,2 ', 4,4 ', 5,5 ' -hexamethyl diphenylethane crude product is passed throughThe material melting device and the carburetor are mixed with air according to the proportion of 20g per cubic meter and the air speed is 6000h-1Introducing the mixed gas into a container filled with commercial V2O5-TiO2-P2O5A fixed bed reactor of the catalyst keeps the reaction temperature at 380 ℃, and gas at the outlet of the reactor is collected to obtain a crude pyromellitic dianhydride product; the crude pyromellitic anhydride is further refined and purified to prepare the finished pyromellitic anhydride.
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| CN102000596A (en) * | 2010-11-15 | 2011-04-06 | 常熟市联邦化工有限公司 | Catalyst for preparing pyromellitic dianhydride from durene through gaseous catalytic oxidation and preparation method thereof |
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| CN1115321C (en) * | 1998-08-21 | 2003-07-23 | 黑龙江省石油化学研究院 | Production method of pyromellitic acid |
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| CN102000596A (en) * | 2010-11-15 | 2011-04-06 | 常熟市联邦化工有限公司 | Catalyst for preparing pyromellitic dianhydride from durene through gaseous catalytic oxidation and preparation method thereof |
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| 100t/a 均苯四甲酸二酐的技术开发;丁志平等;《化学工业与工程技术》;20030228;第24卷(第1期);第7-9页 * |
| 均四甲苯的制备及应用;伍川等，;《化工技术与开发》;20040630;第33卷(第3期);第24-28页 * |
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