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Method for preparing 1,2,4,5-benzene tetra-acid and 1,2,4,5-benzene tetra-anhydride

A technology of pyromellitic anhydride and pyromellitic acid, applied in the preparation of 1, can solve the problems of reduced oxidation catalyst activity and reduced oxidation efficiency

Inactive Publication Date: 2004-08-04
MITSUBISHI GAS CHEM CO INC
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  • Summary
  • Abstract
  • Description
  • Claims
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Problems solved by technology

If the separated liquid is reused as a partial oxidation reaction solvent, the activity of the oxidation catalyst will be reduced due to excessive dilution, thereby reducing the oxidation efficiency

Method used

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  • Method for preparing 1,2,4,5-benzene tetra-acid and 1,2,4,5-benzene tetra-anhydride

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Embodiment 1

[0019] according to figure 1 In the preparation process shown, 1,2,4,5-pyrellitic acid is prepared according to the following steps.

[0020] After liquid phase oxidation of TBAL, followed by precipitation, wet crude crystals of pyromellitic acid (purity 58% by weight) were obtained. The wet crude crystals and water were fed into the recrystallization step at feed rates of 1 part by weight and 1.2 parts by weight, respectively, so that the crude crystals were redissolved in water at 120° C. and 0.2 MPa. Then, the solution was cooled to 40° C. for recrystallization. Solid-liquid separation was performed on the recrystallized slurry to obtain pure pyromellitic acid crystals, which were then rinsed with 0.8 parts by weight / hour of water. Thus, 2.1 parts by weight of a recrystallization mother liquor containing 4.6% by weight of pyromellitic acid and 0.006% by weight of manganese can be obtained per hour. After concentration, the recrystallization mother liquor was continuously...

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Abstract

In a method of producing pyromellitic acid by liquid-phase oxidizing 2,4,5-trimethylbenzaldehyde in a water solvent with molecular oxygen, a recrystallization mother liquor separated in a recrystallization step is recycled to the oxidation step after a part of the water solvent is removed. With this method, the loss of pyromellitic acid and the oxidation catalyst can be minimized and the burden of discharging the waste water is reduced without lowering the efficiency of the liquid-phase oxidation reaction.

Description

technical field [0001] The present invention relates to the preparation of 1, 2, 4, 5- pyromellitic acid and 1, 2, 4, 5- pyromellitic anhydride. These compounds can be used in various fields, for example, in the preparation of various resins such as polyimide used as electronic materials, especially in the preparation of plasticizers and epoxy curing agents. Background technique [0002] Japanese Patent Application Laid-Open No. 56-26839 discloses a liquid-phase oxidation of 2,4,5-trimethylbenzaldehyde (hereinafter referred to as "TBAL") in the presence of a catalyst comprising a bromine compound and a heavy metal by means of air. A method for preparing 1,2,4,5-pyrellitic acid. Japanese Patent Application Laid-Open No. 58-121244 proposes to reduce the oxidation rate by separating the aqueous oxidation solution into crude crystals of pyromellitic acid and mother liquor, and then recycling the separated mother liquor into the oxidation reactor. Catalyst cost. Crude crystals...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07D307/89C07C51/265C07C51/43C07C51/56C07C63/307C07C63/313
CPCC07C51/265C07C51/56C07C51/43C07C63/313
Inventor 熊野达之安达盛治小川博史
Owner MITSUBISHI GAS CHEM CO INC
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