Refining and purifying method of dodecanedioic acid

Abstract

The invention relates to a refining and purifying method of dodecanedioic acid. The method is characterized in that the moisture content of a crude dodecane material is controlled to be lower than orequal to 1.0 wt% and the content of an acetic acid solvent is higher than or equal to 95.0wt%; three-section gradient cooling is adopted in a crystallization process, and inducing seed crystals are added after second-section cooling to induce crystallization; crystallized filter cakes are firstly eluted with acetic acid, then eluted with water and subjected to centrifugal filtration; then, the filter cakes are washed with water at the environment temperature; the acetic acid solvent produced in the refining process is completely recovered with an azeotropic distillation method to be recycled;a washing solution and mother liquor produced in the refining process are completely recovered and recycled. The refining and purifying method of dodecanedioic acid has high product yield, lower refining cost and high purity. The refined and purified dodecanedioic acid has the total acid content of 99.90%, the monomer acid content of 99.45%, the total nitrogen of 6 ppm, the iron ion content of 0.5ppm, the ash content lower than or equal to 10 ppm, the moisture content lower than or equal to 0.10% and the comprehensive yield of purification of 98.64%. All quality technical indexes meet the user requirement.

Description

technical field [0001] The invention relates to a method for refining and purifying dodecanedioic acid. It belongs to the purification treatment of acyclic dicarboxylic acids with 12 carbon atoms. Background technique [0002] Dodecanedioic Acid (Dodecanedioic Acid) is also known as Lauric Acid. It is an industrial product developed earlier among long-chain dibasic acids. It is mainly used in the synthesis of polymer materials, spices, medicines, etc. Among them, it is one of the most important uses to synthesize long carbon chain nylon (also known as polyamide resin) engineering plastics through polycondensation reaction between polycondensation monomer and diamine. [0003] Nylon is a class of polymer compounds containing amide groups (-NHCO-) ​​in the main chain of the molecule. Because the molecular structure of nylon contains a large number of amide groups, and the end of the macromolecule is an amino or carboxyl group, it is a kind of crystalline polymer with stron...

AI Technical Summary

Problems solved by technology

The removal of impurities increases the difficulty

Simultaneously, also reduced the purification yield of dodecanedioic acid

[0013] 2. Cooling natural crystallization method, the crystallization mother liquor remaining in the decolorized filter cake has not been replaced, that is, washing with high temperature water, when a large amount of water contacts the crystallization mother liquor remaining in the filter cake, due to the influence of water on the solubility of acetic acid , so that the dissolved impurities in the mother liquor are precipitated instantly, and the residues in the filter cake are difficult to remove in the subsequent process

[0014] 3. Washing with high temperature water only speeds up the washing speed, and cannot wash away more impurities than washing at normal temperature. The purification effect is minimal, and it consumes heat energy, which increases the amount of wastewater discharged.

[0016] Due to the above deficiencies in the prior art, the total acid content and monoacid content of the refined dodecanedioic acid product are not high enough to meet the stringent requirements of the long-chain nylon or bio-based polyamide fiber industry for the purity of dodecanedioic acid products requirements

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