A kind of synthetic method that improves yield of phenylenediamine

Abstract

The invention relates to a synthesis method for improving the yield of phenylenediamine. In the synthesis method, nitroaniline is used as a raw material, sodium sulfide is used as a reducing agent, a reduction reaction occurs at a high temperature, and a phenylenediamine solution is generated in a first reaction kettle. Sodium thiosulfate solution and sodium hydroxide solution; The material in the first reaction kettle is distilled under negative pressure under vacuum conditions, and the sodium thiosulfate solution is distilled under vacuum conditions; Continue to carry out negative pressure on the remaining materials in the first reaction kettle The phenylenediamine solution is distilled under vacuum conditions; the phenylenediamine solution is crystallized in the second reaction kettle to obtain the crude phenylenediamine; then the crude phenylenediamine is refined in the third reaction kettle After distillation, it can be sliced ​​and packaged. Wherein, the second reaction device comprises a still body, a still cover and a jacket. The synthesis method for improving the yield of phenylenediamine in the invention effectively reduces the cooling time in the crystallization process of the phenylenediamine, so that the yield of the phenylenediamine reaches more than 90%.

Description

technical field [0001] The invention relates to a synthesis method of phenylenediamine, which belongs to the field of fine chemicals, and specifically relates to a synthesis method for improving the yield of phenylenediamine. Background technique [0002] Phenylenediamine is a widely used organic chemical intermediate, including three isomers, namely m-phenylenediamine, o-phenylenediamine and p-phenylenediamine. P-phenylenediamine can be used to prepare azo dyes, polymers, fur dyes, rubber anti-aging agents and photo developers. In addition, p-phenylenediamine is also a sensitive reagent for testing iron and copper. [0003] The finished p-phenylenediamine products sold on the market mainly have two states of flakes and blocks. The flakes are formed by condensing and slicing p-phenylenediamine after rectification. Compared with bulk products, flaky phenylenediamine has a large contact area with air and fast heat dissipation, so the proportion of oxidized in the high tempera...

AI Technical Summary

Problems solved by technology

The existing process has the following disadvantages: the yield of the product is low, and the yield is less than 80%; a large amount of sulfide-containing red water is produced after the reduction reaction, which seriously pollutes the environment; it is difficult to adopt a rectification method for the reaction solution, and the yield lower

Existing reaction still has following shortcoming: traditional cooling method generally adopts larger volume crystallization still, passes into the mode of low temperature, saturated salt water (coolant) in the outer jacket to cool, but due to massive phenylenediamine The contact with air is only on the surface, and phenylenediamine has a high density and poor thermal conductivity, which leads to a very slow cooling rate of the liquid center of p-phenylenediamine, and its central part is easy to oxidize and blacken. Increased the difficulty of good product screening

[0005] To sum up, from the perspective of storage and use, block-shaped phenylenediamine products are more suitable for conventional use and storage, and have a longer shelf life. However, there are defects in the synthesis process and equipment of the prior art, resulting in poor quality products. low rate

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