Method of crystallization

A crystallization and crystal technology, applied in the field of separation process of pure terephthalic acid crystals, can solve problems such as filter blockage

Inactive Publication Date: 2004-01-28
MITSUBISHI GAS CHEM CO INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In addition, it was found that the pressure filtration method chosen as the separation method would cause severe clogging of the filter, requiring frequent cleaning of the filter at short intervals

Method used

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Examples

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Embodiment 1

[0052] In a plant for the production of pure terephthalic acid by catalytic hydrotreating of a solution of crude terephthalic acid obtained from the liquid-phase oxidation of p-xylene in water, the figure 1 The device shown in the system diagram performs crystallization operation on the first mother liquor product obtained by the mother liquor replacement method.

[0053] The first mother liquor product obtained by the mother liquor replacement method is sent to the crystallization vessel 1 through the first mother liquor product feed pipe 4 at 145° C., and the operation is performed according to the system diagram. The amount of the first mother liquid product supplied to the crystallization vessel 1 is 100 parts of water and 0.3 parts of terephthalic acid partially present in crystals. Almost all other impurities are soluble in water.

[0054] In the crystallization vessel 1, the temperature of the first mother liquid product is lowered to 100° C. through flash vaporization...

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Abstract

A method of crystallization which comprises feeding to a crystallization vessel either a solution of terephthalic acid or a slurry solution in which part of terephthalic acid has been precipitated, crystallizing the terephthalic acid in the vessel to obtain a slurry comprising crystals and the solvent, and discharging the slurry, wherein the slurry discharged from the crystallization vessel is introduced into a liquid cyclone through a tangential-direction inlet, and the slurry component constituting a descending turning flow and flowing out through the lower outlet of the cyclone is returned to the crystallization vessel, while the slurry component overflowing through the upper outlet of the cyclone is discharged. Thus, crystals having a large particle diameter can be obtained. Furthermore, no crystal deposition or accumulation within the crystallization vessel occurs, and the crystallization operation can be stably conducted for long.

Description

technical field [0001] The invention relates to a crystallization method. The slurry of terephthalic acid is sent into a crystallization container, wherein the terephthalic acid is precipitated, and the slurry including crystals and solvent (mother liquor) is discharged. More specifically, the present invention is useful in the separation process of pure terephthalic acid crystals and the like. Background technique [0002] The production method of pure terephthalic acid is to oxidize p-xylene with molecular oxygen in liquid phase, dissolve the crude product of terephthalic acid in hot water, and contact it with a catalyst of Group VIII of the Periodic Table of Elements in the presence of hydrogen. Crude aqueous terephthalic acid is subjected to catalytic hydrotreatment. This production process has been developed over many years in industrial scale installations with production operational capabilities. [0003] In this method, usually, the hydrogenation reaction solution ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01D9/00C07C51/265C07C51/43
CPCC07C51/265C07C51/43B01D9/0059C07C63/26B01D9/02
Inventor 大越二三夫古屋贵久
Owner MITSUBISHI GAS CHEM CO INC
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