Method for purifying crude 2,6-naphthalic acid

A naphthalene dicarboxylic acid and naphthalene dicarboxylic acid slurry technology, applied in the separation/purification of carboxylic acid compounds, bulk chemical production, organic chemistry, etc., can solve a large number of solid absorbents and solvents, separation difficulties, and insufficient optimization of operating conditions, etc. problems, to achieve the effect of reducing the amount of solvent circulation, simplifying the process, and reducing energy consumption of the system

Inactive Publication Date: 2018-03-27
CHINA PETROLEUM & CHEM CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, this method requires a large amount of solid absorbent and solvent, and, along with the crystallization of all monoalkali metal salts, salts generated from impurities such as NA or FNA also crystallize out, thus causing separation difficulties
In addition, alkali metals remain in the crystals of 2,6-NDCA, thereby deteriorating the chromaticity at the time of polymerization, and causing disadvantages in terms of crystal size and yield
[0012] The above refining methods all use relatively complicated processes and expensive solvents, or use water as the solvent but the solubility of 2,6-NDCA is low due to insufficient operating conditions, and the solvent circulation is large and energy consumption is high

Method used

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  • Method for purifying crude 2,6-naphthalic acid
  • Method for purifying crude 2,6-naphthalic acid

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0034]The crude 2,6-NDCA has a purity of 90%, using supercritical water and acetic acid as a solvent, wherein the acetic acid content is 15%, the concentration of the slurry produced by the crude 2,6-NDCA in the mixing step is 18%, and dissolved The temperature in tank A is maintained at 410°C and 45MPa, and the dissolved slurry passes through the crystallization units in sequence. Each crystallization process lasts for 60 minutes. Four crystallization units in series are used to carry out the process. In the case of four crystallization units B in series , set their temperature and pressure as: set their temperature and pressure as: 350°C and 20MPa in the first crystallization unit, 285°C and 9MPa in the second crystallization unit C, and 285°C and 9MPa in the third crystallization unit 245°C and 5MPa, 200°C and 3.5MPa in the fourth crystallization unit, after crystallization, the product (3) and mother liquor (4) are obtained through the solid-liquid separation unit C, and th...

Embodiment 2

[0039] The crude 2,6-NDCA has a purity of 90%, using supercritical water and isopropanol as a solvent, wherein the content of isopropanol is 20%, and the concentration of the slurry produced by the crude 2,6-NDCA in the mixing step is 10%, the temperature in the dissolution tank A is maintained at 385°C and 28MPa, and the dissolved slurry passes through the crystallization units in sequence, and each crystallization process lasts for 60 minutes. The process is carried out by using 3 crystallization units B connected in series. When the units are connected in series, set their temperature and pressure as: 315°C and 15MPa in the first crystallization unit, 280°C and 9MPa in the second crystallization unit, and 315°C and 9MPa in the third crystallization unit 230°C and 3MPa in the crystallization unit, after crystallization, the product and mother liquor are obtained through the solid-liquid separation unit C, part of the mother liquor is discharged from the system (6), and part o...

Embodiment 3

[0043] The purity of 2,6-NDCA is 98.5%, using supercritical water, the concentration of the slurry produced in the mixing step of crude 2,6-NDCA is 18%, the temperature in the dissolution tank A is maintained at 430°C, 45MPa, and dissolved The final slurry passes through the crystallization unit successively, and each crystallization process lasts 60 minutes. Use 5 crystallization units in series to carry out the process. In the case of 5 crystallization units B in series, their temperature and pressure are respectively set as : Set their temperature and pressure as: 370°C and 25MPa in the first crystallization unit, 300°C and 12MPa in the second crystallization unit, 245°C and 5MPa in the third crystallization unit, 200°C and 200°C in the fourth crystallization unit 3.5MPa. After crystallization, the product (3) and mother liquor (4) are obtained through the solid-liquid separation unit C. The ratio of the mother liquor (6) discharged from the system to the mother liquor (5) r...

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Abstract

The invention provides a method for purifying crude 2,6-naphthalic acid. The method comprises the following steps: mixing crude 2,6-naphthalic acid with water to form crude 2,6-naphthalic acid slurryand carrying out heating to a supercritical state with a temperature of 375 to 450 DEG C and a pressure of 22 to 60 MPa for dissolving; subjecting 2,6-naphthalic acid dissolved in the supercritical state to cooling and crystallization; and subjecting the 2,6-naphthalic acid slurry having undergone cooling and crystallization to solid-liquid separation so as to obtain a 2,6-naphthalic acid product.The method provided by the invention overcomes the problems of low solubility of 2,6-naphthalic acid in solvents, great slurry circulation volume and high energy consumption in the prior art.

Description

technical field [0001] The invention relates to a method for purifying crude 2,6-naphthalene dicarboxylic acid. Background technique [0002] Polyethylene terephthalate (PET), an industrial polyester material, is widely used in the manufacture of polyester fibers, bottles and film products due to its excellent performance and affordable price, covering chemical fiber, packaging, electronic appliances, medical Health, construction, auto parts and other fields. Although engineering plastic grade PET is resistant to organic solvents and has good weather resistance. But the disadvantages are slow crystallization rate, difficult molding process, high molding temperature, long production cycle and poor impact performance. Commonly found in mineral water bottles, carbonated beverage bottles, etc., it is easily deformed when the temperature reaches 70°C, and substances harmful to the human body are dissolved. After 10 months of use, No. 1 plastic (PET) may release the carcinogen ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C51/42C07C51/43C07C63/38
CPCC07C51/42C07C51/43C07C63/38Y02P20/54
Inventor 王清立陈亮钟思青顾军民
Owner CHINA PETROLEUM & CHEM CORP
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