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High-pressure waste TA converting process of preparing DMT

A high-pressure, high-tech technology, which is applied in the field of preparation technology for the conversion and reuse of terephthalic acid to dimethyl terephthalate, can solve the problems of the conversion process of polluted waste and low recovery rate, and achieve pollution-free, High recovery rate and the effect of increasing the recovery rate

Inactive Publication Date: 2002-10-16
SINOPEC YIZHENG CHEM FIBER
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

These methods described still cannot effectively solve the problems of pollution in the conversion process, waste decomposition and low recovery rate, and solving such problems is the goal that the industry has been working hard for

Method used

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  • High-pressure waste TA converting process of preparing DMT
  • High-pressure waste TA converting process of preparing DMT

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0013] After the waste TA material is dried at 160°C, it is put into an autoclave, and 3 times the weight of methanol is added, and the temperature is raised for esterification. The pressure was controlled at 2.5 MPa (gauge pressure), the temperature was controlled at 230° C., and the esterification time was 15 hours. After the esterification process is completed, the pressure is gradually reduced to normal pressure, the esterification water is discharged, and excess methanol is recovered. Then gradually reduce the pressure to 50mmHg (absolute pressure), distill and recover the low boilers of fractions below 180°C, and then collect the fractions within 180-200°C as crude DMT to obtain: recovery of methanol, low boilers, and crude DMT and residue. Recovery of methanol, low boilers, crude DMT and fractional distillation to obtain: recycled methanol, by-products and product DMT.

Embodiment 2

[0015] After drying the waste TA material at 170°C, put it into an autoclave, add 3 times the weight of methanol and about 8% weight of crude DMT, and heat up to esterify. The pressure was controlled at 3.5 MPa (gauge pressure), the temperature was controlled at 215° C., and the esterification time was 16 hours. After the esterification process is completed, the pressure is gradually reduced to normal pressure, the esterification water is discharged, and excess methanol is recovered. Then gradually reduce the pressure to 50mmHg (absolute pressure), distill and recover the low boilers of fractions below 180°C, and then collect the fractions within 180-200°C as crude DMT to obtain: recovery of methanol, low boilers, and crude DMT and residue. Recovery of methanol, low boilers, crude DMT and fractional distillation to obtain: recycled methanol, by-products and product DMT.

Embodiment 3

[0017] After drying the waste TA material at 180°C, put it into an autoclave, add 3 times the weight of methanol and about 10% by weight of crude DMT, and heat up for esterification. The pressure was controlled at 3 MPa (gauge pressure), the temperature was controlled at 230° C., and the esterification time was 15 hours. After the esterification process is completed, the pressure is gradually reduced to normal pressure, the esterification water is discharged, and excess methanol is recovered. Then gradually reduce the pressure to 50mmHg (absolute pressure), distill and recover the low boilers of fractions below 180°C, and then collect the fractions within 180-200°C as crude DMT to obtain: recovery of methanol, low boilers, and crude DMT and residue. Recovery of methanol, low boilers, crude DMT and fractional distillation to obtain: recycled methanol, by-products and product DMT. The preparation of DMT in a 0.5-liter autoclave is completed intermittently in two steps. For eve...

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Abstract

The present invention relates to the conversion and utilization of chemical waste, and is especially the converting process of low-purity waste terephthalic acid to high-purity dimethyl terephthalateat high pressure. The waste terephthalic acid after being stoved is esterified with methanol at high pressure condition and the product is twice distilled to purity to obtain dimethyl terephthalate while recovering other organic ester. The esterification process has proper reaction condition, simple waste pre-treatment, no need of catalyst, and water washing of the intermediate product before direct fractionation, so that it has short process, high heat efficiency, less pollution, high recovery rate and high product purity.

Description

[0001] Involved areas: [0002] The invention relates to a conversion and utilization process of chemical waste, in particular to a production process for converting low-purity terephthalic acid (TA) into dimethyl terephthalate (DMT). Background technique: [0003] Purified terephthalic acid (PTA) is an important chemical product and one of the main raw materials for polyester (PET) production. In the industrial PTA production process, a large amount of terephthalic acid waste (waste TA) is often produced. As the world's PET production capacity continues to grow, the demand for PTA is increasing, and accordingly, the amount of waste TA is increasing. The impurity content of this waste is about 10%, and it cannot be directly applied to PET production, so the price is low, and there has been experience of free material. For this industrial waste, domestic existing utilization technology mainly contains: 1. Terephthalic acid residue produces dimethyl terephthalate (Jiangsu Chem...

Claims

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Application Information

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IPC IPC(8): C07C67/08C07C69/82
Inventor 纪祥高空
Owner SINOPEC YIZHENG CHEM FIBER
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