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Process for producing high-purity terephthalic acid

A terephthalic acid, high-purity technology, applied in the field of preparing high-purity terephthalic acid, can solve the problems of reduction catalyst poisoning, activity reduction and the like

Active Publication Date: 2005-11-02
MITSUBISHI RAYON CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Carbon monoxide is a catalyst poison of the reduction catalyst used in this reduction step, as a result, the reduction catalyst is poisoned and its activity is reduced

Method used

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  • Process for producing high-purity terephthalic acid
  • Process for producing high-purity terephthalic acid

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0030] This example uses figure 1 The process shown is complete. Specifically, in the mixing tank 11, crude terephthalic acid containing 3,000 ppm of 4CBA and water were charged at 18 tons / hour to prepare a slurry C of 30% by weight of crude terephthalic acid. Pressurize the slurry C to a pressure of 8.9MPa, raise the temperature to 285°C through a multi-tubular heat exchanger 12 to dissolve terephthalic acid, and then inject the aqueous solution D of terephthalic acid into the hydrogenation reactor 13 middle. The hydrogenation reactor 13 had a column diameter of 1,260 mm and a height of 10 m, and 0.5% by weight of palladium attached to activated carbon was used as a reduction catalyst, and the amount of the catalyst charged was 6 tons. In this hydrogenation reactor 13, hydrogen gas was simultaneously injected to reduce the aforementioned aqueous solution D of terephthalic acid, and the resulting reduction treatment liquid E was crystallized in the subsequent crystallization...

Embodiment 2

[0035] use figure 2 The process shown performs a hydrogenation reaction. Specifically, the crude terephthalic acid A containing 3,000 ppm of 4CBA and water B were charged at 1.2 kg / hr in the metering tank 21 to prepare a slurry C of 20% by weight of the crude terephthalic acid. Pressurize the slurry C to a pressure of 7.9 MPa, raise the temperature to 280°C through the preheater 22, dissolve terephthalic acid in the dissolution tower 23, and then inject the aqueous solution D' of terephthalic acid into the hydrogenation reaction device 24. The hydrogenation reactor 24 had a column diameter of 15 mm and a height of 1,450 mm, and 0.5% by weight of palladium attached to activated carbon was used as a reduction catalyst, and the catalyst filling amount was 120 g. In this hydrogenation reactor 24, hydrogen gas is simultaneously injected to reduce the aforementioned aqueous solution of terephthalic acid. The obtained reduction treatment solution E' is temporarily stored in the r...

Embodiment 3

[0039] Operated under the same conditions as in the aforementioned Example 2, except that hydrogen / 4CBA was 3 (molar ratio), the ratio was the amount of hydrogen injected into the hydrogenation reactor 24 to the amount of 4CBA in the solution injected into the hydrogenation reactor 24 ratio.

[0040] Through this operation, the amount of carbon monoxide formed in the hydrogenation reactor was calculated as a ratio of carbon monoxide / 4CBA to 0.09 (molar ratio) relative to the amount of 4CBA in the solution injected into the hydrogenation reactor.

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PUM

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Abstract

The life of a reduction catalyst to be used in a reduction step where 4CBA is reduced with hydrogen to p-toluic acid is prolonged. The process for producing high-purity terephthalic acid is characterized in that, in the reduction step, the ratio of the amount of hydrogen to be fed to a hydrogenation reactor to the amount of 4CBA in a solution thereof to be fed to the reactor, hydrogen / 4CBA, is from 2 to 10 (by mole) and that the ratio of the amount of crude terephthalic acid to be treated in the reduction step to the amount of the reduction catalyst present in the hydrogenation reactor, [amount of terephthalic acid being treated (t / h)] / [amount of reduction catalyst (t)], is from 400 to 5,000 (1 / h).

Description

technical field [0001] The invention relates to a method for preparing high-purity terephthalic acid. Background technique [0002] Generally, the crude product of terephthalic acid obtained by oxidation of p-xylene contains relatively large amounts of various impurities represented by 4-carboxybenzaldehyde (hereinafter referred to as "4CBA"). Esters are used as raw materials. When purifying the terephthalic acid crude product, a method of separation and purification is adopted, the method comprises a dissolution step, a reduction step and a subsequent crystallization step, the dissolution step is to dissolve the terephthalic acid crude product in water, and the reduction step is The above-mentioned 4CBA in the solution obtained in the dissolving step is reduced to p-toluic acid with hydrogen gas, and the crystallization step is to crystallize by utilizing the different solubility of terephthalic acid and p-toluic acid in water. [0003] Currently, the decarboxylation of 4...

Claims

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Application Information

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IPC IPC(8): C07C51/487
CPCC07C51/487
Inventor 沼田元干矶贝隆行绪方知彦
Owner MITSUBISHI RAYON CO LTD
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