CN-121990928-A - Purification method of high-purity p-phenylenediamine

CN121990928ACN 121990928 ACN121990928 ACN 121990928ACN-121990928-A

Abstract

The invention relates to the technical field of p-phenylenediamine purification, in particular to a purification method of high-purity p-phenylenediamine. The purification method comprises the steps of S1, mixing a p-phenylenediamine crude product with water, stirring at a high temperature to form a uniform solution, S2, cooling and crystallizing the solution to obtain crystals and crystallization mother liquor, S3, heating and melting the crystals to obtain a molten liquid, and S4, rectifying the molten liquid to obtain the high-purity p-phenylenediamine and rectification residual liquid. The purification method only uses water as a solvent, is simple, avoids the problems of high cost, environmental protection and potential safety hazard of using an organic solvent in the traditional method, can realize the high purity requirement of a crystallized product by precisely controlling the adding amount of the solvent water, does not need high-precision temperature control equipment in the traditional method, is easy to realize automation and is suitable for industrial production.

Inventors

LIU YUHENG
LAI JU
WANG JIANHUI
ZHANG JINKAI
NING PING
DENG BIQIANG
ZHANG PING
WANG JINGJING

Assignees

四川北方红光特种化工有限公司

Dates

Publication Date: 20260508
Application Date: 20251223

Claims (10)

1. A method for purifying high-purity p-phenylenediamine is characterized by comprising the step of recrystallizing with water as a solvent.
2. The purification method according to claim 1, characterized by the specific steps of: S1, adding water into the crude p-phenylenediamine product, mixing, and stirring at a high temperature to form a uniform solution; s2, cooling and crystallizing the solution to obtain crystals and crystallization mother liquor; s3, heating and melting the crystals to obtain a molten liquid; and S4, rectifying the melt to obtain the high-purity p-phenylenediamine and rectification residual liquid.
3. The method according to claim 2, wherein in the step S1, the preparation method of the crude phenylenediamine is a catalytic hydrogenation reduction method.
4. The method according to claim 2, wherein in the step S1, the weight ratio of the crude p-phenylenediamine to water is 1:3.5.
5. The method according to claim 2, wherein the high temperature is 90 ℃.
6. The method according to claim 2, wherein in step S2, the cooling crystallization is performed by a plate-type static crystallizer.
7. The method according to claim 2, wherein in step S2, the temperature-reduced crystallization is performed at a temperature of 25 ℃.
8. The method according to claim 2, wherein in step S3, the temperature of the elevated melting is 90 ℃.
9. The method according to claim 2, wherein in step S4, the rectification includes dehydration and decoloration.
10. The purification method according to claim 2, further comprising the steps of: s5, recovering the crystallization mother liquor and the rectification raffinate, and preparing the crude p-phenylenediamine.

Description

Purification method of high-purity p-phenylenediamine Technical Field The invention relates to the technical field of p-phenylenediamine purification, in particular to a purification method of high-purity p-phenylenediamine. Background Para-aramid fiber, the school name poly-paraphenylene terephthalamide fiber, abbreviated as PPTA, is also known as aramid 1414 in China. As a representative of high-performance organic fibers, para-aramid is known as a strategic material of great specific strength, specific modulus, heat resistance and impact resistance. One of the key monomer raw materials for producing para-aramid is high purity, polymeric grade p-phenylenediamine. The p-phenylenediamine is usually obtained by catalytic hydrogenation reduction of dinitrobenzene and continuous rectification of a plurality of towers, and has the general purity of 99.5% -99.7%, while the polymer-grade p-phenylenediamine (the purity is more than or equal to 99.9%) required by para-aramid has higher quality requirements, and has the general purity of more than 99.9%, and specific harmful impurities, particularly isomers (m-phenylenediamine and o-phenylenediamine) and moisture are strictly controlled. However, the preparation of polymeric p-phenylenediamine is very difficult, and it is necessary to separate the isomeric impurities (mainly meta-and ortho-phenylenediamines) having nearly identical chemical structures and very close physical properties with very high efficiency, by increasing the purity from 99.5% to more than 99.9%. Therefore, the p-phenylenediamine purification method which is simple in process, low in cost, environment-friendly and suitable for industrial production is developed, and has important practical significance. In the prior art, there are a melt crystallization method and a solution crystallization method. The method has the defects that the method needs higher temperature control precision and longer operation time, has low production efficiency, takes crude p-phenylenediamine as a raw material, takes NMP and ionic liquid choline acetate as organic solvents, performs cooling under the stirring condition to separate out crystals, performs solid-liquid separation and washing under the crystallization final temperature condition, and then performs drying to obtain p-phenylenediamine crystals, and has the defects that the organic solvents NMP are used, the skin, eyes and respiratory tract are irritated, the long-term contact needs to be protected, the cost of the organic solvents is high, and the subsequent three-waste treatment process is complex. In view of the above, there is a need for a purification technology for high-purity polymeric p-phenylenediamine that is easy to operate, has high production efficiency, is low in cost, and is safer and more environmentally friendly. Disclosure of Invention The invention aims to overcome the defects of the prior art and provide a purification method of high-purity p-phenylenediamine, which at least takes a crude product of the p-phenylenediamine as a raw material to prepare a high-purity polymer-grade p-phenylenediamine product with the purity of more than 99.9 percent, and the method is easy to operate, high in production efficiency, low in cost, safe and environment-friendly. The invention aims at realizing the following technical scheme: A process for purifying high-purity p-phenylenediamine includes recrystallizing in water. In some embodiments, the purification method comprises the following specific steps: S1, adding water into the crude p-phenylenediamine product, mixing, and stirring at a high temperature to form a uniform solution; s2, cooling and crystallizing the solution to obtain crystals and crystallization mother liquor; s3, heating and melting the crystals to obtain a molten liquid; and S4, rectifying the melt to obtain the high-purity p-phenylenediamine and rectification residual liquid. In some examples, in step S1, the method for preparing the crude phenylenediamine is a catalytic hydrogenation reduction process. In some examples, the catalytic hydrogenation reduction method comprises the steps of taking dinitrobenzene as a raw material, reducing nitro groups of the dinitrobenzene into amino groups in the presence of hydrogen, a solvent and a catalyst to obtain a diaminobenzene mixture, and rectifying and separating the diaminobenzene mixture to obtain the crude p-phenylenediamine product. The diaminobenzene mixture comprises paraphenylene diamine, m-phenylene diamine, o-phenylene diamine and other isomerised byproducts and other trace impurities, wherein the m-phenylene diamine is the largest component, generally accounts for about 85 percent, the o-dinitrobenzene accounts for about 12 percent, the p-phenylene diamine is the lowest but the highest in value, and the m-phenylene diamine accounts for about 3 percent. The solvent is methanol or ethanol, and the catalyst is skeletal nickel or palladium carbon. Illustratively, the rectification is