Method for recovering terephthalic acid from coloured terephthalic acid residue by complexation-crystallization

A terephthalic acid and complexing technology, which is applied in the field of recovering terephthalic acid from colored terephthalic acid residues by complex crystallization, can solve problems such as affecting the chromaticity and quality of products, and reduce the discharge of solid wastes. , the effect of protecting the environment and reducing production costs

Inactive Publication Date: 2008-11-12
SHAOXING YUANDONG PETROCHEM +1
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  • Abstract
  • Description
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  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The impurities in the colored terephthalic acid residue can be divided into two categories: one is the impurities that are easy to remove such as benzoic acid, p-toluic acid, p-carboxybenzaldehyde , isophthalic acid, phthalic acid, trimellitic acid, etc. Although the content of such impurities is relatively high, it is easy to remove through the reaction and crystallization process in the process; the other is colored fluorenone, anthraquinone carboxy Acid impurities, although the concentration of such impurities is usually very low (<50ppm), they still seriously affect the color quality of the product at very low concentrations (<1ppm)

Method used

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  • Method for recovering terephthalic acid from coloured terephthalic acid residue by complexation-crystallization
  • Method for recovering terephthalic acid from coloured terephthalic acid residue by complexation-crystallization

Examples

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Effect test

Embodiment 1

[0031] The TA residue treated in this example comes from the CTA mother liquor impurity removal system, and its main components are: TA (90.15wt%), 4-CBA (4.05wt%), PT (2.44wt%), BA (1.21wt%), IPA (0.75wt%), other components about 1.40wt%, the color index b value of the TA residue is 17.0.

[0032] Put the dry 100.0g colored terephthalic acid solid residue into the complex crystallizer, add 400.0g N, N-dimethylacetamide (DMA), stir and mix; the mixture is in the complex crystallizer at 70°C, After staying for 20 minutes, white TA complex crystals were formed, and the mother liquor also changed from transparent and colorless to yellow. After filtering and washing with a saturated TA complex crystal solution, a white TA complex crystal solid was finally obtained, weighing 117.8 g.

[0033]Using gas chromatography to analyze the mass fraction of solvent DMA in the TA complex crystallization, the mass fraction of DMA is 49.4%, that is, the molecular ratio of DMA and TA is 1.86:1,...

Embodiment 2

[0035] The treatment of the TA residue was carried out in a similar manner to Example 1. However, the complexing solvent used in this example is an equal mass of N,N-dimethylformamide (DMF), and 102.0 g of DMF complexing crystalline solids of TA were obtained. The mass fraction of solvent DMF in the DMF complex crystal of TA analyzed by gas chromatography is 46.0%, that is, the molecular ratio of DMF and TA is 1.94:1, that is, one TA molecule in the TA complex crystal is combined with about 2 DMF molecular. The crystallization of the complex was vacuum-dried at 120°C to remove the DMF solvent to obtain a TA solid. The impurity content and chromaticity index recovered from TA were analyzed. The relevant analysis data results are compared in Table 1.

Embodiment 3

[0037] The treatment of the TA residue was carried out in a similar manner to Example 1. However, the complex solvent used in this example is an equal mass of N-methylpyrrolidone (NMP), and 88.7 g of NMP complex crystalline solids of TA were obtained. The mass fraction of solvent NMP in the NMP complex crystal of TA analyzed by gas chromatography is 54.2%, that is, the molecular ratio of NMP and TA is 1.98:1, that is, there are about 2 TA molecules combined in the TA complex crystal. NMP molecule. The complex crystallization was vacuum-dried at 120°C to obtain TA solid, and the impurity content and chromaticity index recovered from TA were analyzed, and the relevant analysis data results were compared in Table 1.

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Abstract

The invention discloses a method for reclaiming terephthalic acid from colored terephthalic acid residue by adopting complex crystallization. The method is as follows: firstly, the terephthalic acid residue and complex crystallization solvent are mixed in a complex crystallizer, then the temperature is controlled to be between 10 and 120 DEG C to ensure that a pure terephthalic acid product is precipitated in the form of solvent complex crystallization, and colored impurities are enriched in solution. The method can effectively remove the colored impurities in the terephthalic acid residue, and the reclaimed terephthalic acid product has higher color quality. The method can effectively reduce the discharge of solid waste during the production process of PTA, protect the environment, can also reduce the consumption of raw materials and production cost, and improve the economic benefit.

Description

technical field [0001] The invention relates to a method for recovering terephthalic acid from colored terephthalic acid residues, in particular to a method for recovering terephthalic acid from colored terephthalic acid residues by complex crystallization. Background technique [0002] Purified terephthalic acid (PTA) is an important raw material for the production of polyester fibers and polyester materials, and is mainly produced by air-liquid phase catalytic oxidation of p-xylene (PX). In the production process of purified terephthalic acid (PTA), the chromaticity index is one of the key indicators of PTA product quality, and the control of PTA product chromaticity (such as b value) is closely related to the removal of colored impurities. During the operation of the PTA unit, due to the limited ability of the refining process to treat colored impurities, the quality of the crude terephthalic acid (CTA) product in the de-refining unit must be strictly controlled. In orde...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C63/26C07C51/42
Inventor 成有为郭霞谢刚徐海波王丽军李希李玲
Owner SHAOXING YUANDONG PETROCHEM
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