Method for refining p-phenylene diamine

Abstract

The invention provides a refining method of p-phenylenediamine, which combines distillation and melting crystallization, uses the distillation product condensate to directly process melt crystallization for purification and processes fractional crystallization composed of one crystallization at least and one transpiration to obtain high-purity product. The invention combines distillation and melting crystallization to refine p-phenylenediamine and the invention can obtain high-purity and high-qaulity p-phenylenediamine product whose purity can reach 99.99-99.999% via controlling operation parameters, while the product quality can satisfy the quality demand of polymerization level product and the high-quality p-phenylenediamine can not be produced only by distillation. The refining method of p-phenylenediamine has the advantages of high product purity and flexible production set according to different standards, high yield of high-quality product and low cost, while the operation is processed without solvent to reduce pollution.

Description

(1) Technical field [0001] The invention relates to a method for refining p-phenylenediamine, in particular to a method for refining p-phenylenediamine used in the production of para-aramid fibers and imaging, etc., which require high quality. (2) Background technology [0002] P-phenylenediamine is a widely used intermediate, which can be used in the production of dyes, pigments, hair dyes, rubber anti-aging agents, para-aramid fibers, p-phenylenediisocyanate as a raw material for polyurethane production, etc. It is also commonly used to test iron and copper It is a sensitive reagent for gasoline polymerization inhibition and color photography coupling agent and other raw materials. [0003] Usually, p-phenylenediamine is obtained by reducing p-nitroaniline after amination of p-nitrochloroaniline. In order to obtain high-purity p-phenylenediamine raw materials, the p-phenylenediamine products obtained through reduction need to be purified and refined. The domestic traditio...

AI Technical Summary

Problems solved by technology

During the cooling process of p-phenylenediamine, the molecular mobility is hindered, and it is difficult to form its own crystal nucleus. In order to ensure the production capacity of the crystallization device, it is usually difficult to reach an equilibrium state for crystallization, which is controlled by heat transfer, mass transfer and crystallization kinetics. The crystal will inevitably produce occlusion phenomenon. The mother liquor containing impurities is occluded, mixed in the crystal, or adhered to the surface of the crystal, which makes the crystal purity decrease, deviate from the equilibrium composition, and the separation effect is significantly reduced.

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