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Preparation method of ultralow-metal ion content pyromellitic dianhydride

A technology of pyromellitic dianhydride and metal ions, applied in the field of preparation of pyromellitic dianhydride, can solve the problems of heavy vinegar smell, large corrosion of solvent equipment, large environmental protection problems, etc., and achieves the effect of broad development prospects

Inactive Publication Date: 2013-01-30
DONGYING ZHONGJIE CHEM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] Many domestic production plants also use acetic anhydride / acetic acid mixture to purify pyromellitic dianhydride. The advantage of this method is that the cost is low, but it is a big environmental protection problem, and the vinegar smell is too strong. In addition, the solvent is also corrosive to the equipment. From the perspective of product purity It can't meet the needs of the microelectronics industry

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0020] A mixed gas of 1,2,4,5-tetramethylbenzene and air with a purity of 96-97% by weight, the concentration of 1,2,4,5-tetramethylbenzene in the mixed gas is 1-5 mol%, At 400°C, enter a stainless steel tubular reactor with an inner diameter of 25mm and a length of 2500mm at a speed of 4500m / min. The airflow flows from bottom to top. The tubular reactor is filled with an oxidation catalyst of 650g. The catalyst composition is vanadium pentoxide 33wt %, 63% by weight of titanium dioxide, 3% by weight of sodium oxide and 1% by weight of phosphorus pentoxide, the catalyst is carried on silicon carbide spheres, and the weight of the catalyst is 13% by weight of the carrier. The mixed gas of 1,2,4,5-tetramethylbenzene and air is catalyzed and oxidized through the catalyst layer, and then pyromellitic acid is first converted into crude pyromellitic anhydride at 425°C, and the mixed gas passes through the heat exchanger Cooling; the temperature of the cooled stream drops to 300°C, a...

Embodiment 2

[0022] In addition to the catalyst weight composition is vanadium pentoxide 32% by weight, titanium dioxide 62% by weight, sodium oxide 1% by weight, and phosphorus pentoxide 5% by weight, the oxidation reaction temperature is 426 ° C, and the temperature of the stream cooled by the heat exchanger is 250 °C °C, adsorbent molecular sieve 5A: silica is equal to 2:80 (weight ratio), the weight of silica gel G is 3% by weight of the total weight of molecular sieve 5A and silica, and the filling height of adsorbent is 300mm. When the crude pyromellitic dianhydride is collected, the temperature is 180°C, and the crude pyromellitic dianhydride is recrystallized with a mixed solvent of petroleum ether and dimethylacetamide, and the mixing weight ratio of petroleum ether and dimethylacetamide solvent is 50 : 50, corresponding to 1,2,4,5-tetramethylbenzene, except that the yield of purified pyromellitic dianhydride is 42%, other operating processes and product quality indicators are the ...

Embodiment 3

[0024] In addition to the weight of the catalyst, the composition is 30% by weight of vanadium pentoxide, 64% by weight of titanium dioxide, 5% by weight of sodium oxide and 1% by weight of phosphorus pentoxide. The oxidation reaction temperature is 380°C, and the temperature of the stream cooled by the heat exchanger is 350°C. , adsorbent molecular sieve 3A: silica is equal to 20:98 (weight ratio), the weight of silica gel G is 5% by weight of the total weight of molecular sieve 3A and silica, the adsorbent filling height is 400mm, and the The stream temperature is 220°C, and the crude pyromellitic dianhydride is recrystallized with a mixed solvent of butanone and dimethylformamide. The mixing ratio of the two solvents is 40:60, corresponding to 1,2,4,5-tetramethyl Benzene, the yield of pure pyromellitic dianhydride is 40%, other operation process, product quality index and embodiment 1 are identical.

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Abstract

The invention provides a preparation method of ultralow-metal ion content pyromellitic dianhydride, which comprises the following steps of: taking 1, 2, 4, 5-tetramethylbenzene of which the purity is 96-97 weight% as raw material, oxidizing by air, taking metal oxide which consists of vanadium, titanium, sodium and phosphorus as oxidation catalyst, reacting under the temperature of 380-420 DEG C, cooling by a heat exchanger, absorbing by adsorbent which consists of molecular sieves 3A, 4A and 5A and silicon dioxide under the temperature of 250-350 DEG C, removing harmful organic matters and metal ions, collecting crude pyromellitic dianhydride gathered by a first gathering machine, and recrystallizing, filtering and drying by low-boiling point low-toxicity solvent such as mixed solvent of acetone and butanone to obtain fine pyromellitic dianhydride, wherein the melting point of the fine pyromellitic dianhydride is 286-287.5 DEG C, the yield of the fine pyromellitic dianhydride is 40-45%, the product is crystalloid grain, the grain size of the pyromellitic dianhydride is 300-1000mm, and each content of the contained metal irons is less than 1ppm, i.e., iron, aluminum, nickel, manganese, tin, zinc, potassium, sodium, cobalt, chromium, copper and calcium.

Description

1. Technical field [0001] The present invention relates to a preparation method of pyromellitic dianhydride, more precisely the present invention relates to a method for preparing pyromellitic dianhydride from 1,2,4,5-tetramethylbenzene. 2. Background technology [0002] Pyromellitic dianhydride is an important raw material used in the chemical industry, electrical electronics and national defense industries. It can be used as a curing agent for epoxy resin coatings, adhesives and molding compounds; it can be used to prepare polyester paints, polyimide films, molds, etc. Plastics and wire enamels, especially polyimide films, have the largest number of raw materials. Now pyromellitic dianhydride is a bulk product in the world, the world's production capacity is close to 70,000 tons, and the scale of production equipment in general production plants has reached the level of thousands of tons. [0003] In order to prepare high-purity pyromellitic dianhydride for use in the mic...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07D493/04
Inventor 朱裕龙项志度王福博宋庆伟刘继库孙学磊孙学芳
Owner DONGYING ZHONGJIE CHEM
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