A kind of preparation technology of p-phenylenediamine

Abstract

The invention discloses a preparation process of p-phenylenediamine. The p-phenylenediamine uses p-nitroaniline and hydrogen as raw materials, methanol as a solvent, and a Raney Ni catalyst for reduction reaction, adding The p-phenylenediamine crystal grains are used as crystal seeds, and the crystallization is carried out through repeated heating and cooling processes, and the crystals are separated and dried to obtain the p-phenylenediamine, so that the crystallization of p-phenylenediamine presents multiple cycles of precipitation With dissolution, multiple recrystallizations are produced, which improves the purity of p-phenylenediamine while reducing its purification time, and also forms more uniform crystals.

Description

technical field [0001] The present invention relates to the technical field of production of p-phenylenediamine, in particular to a preparation process of p-phenylenediamine. Background technique [0002] P-phenylenediamine is an important organic chemical raw material, mainly used in the production of dyes, rubber antioxidants, etc. The traditional production method of p-phenylenediamine is to use p-nitrochlorobenzene as raw material, react with ammonia water (or ammonia gas) under high temperature and high pressure to prepare p-nitroaniline, and p-nitroaniline is then reduced by alkali sulfide or iron powder to produce p-nitroaniline The crude product of p-phenylenediamine is finally purified by recrystallization to obtain high-purity p-phenylenediamine. The biggest defect of this process is that there is a lot of industrial wastewater, and the reduction of iron powder produces a large amount of iron sludge, which seriously pollutes the environment. In addition, the proce...

AI Technical Summary

Problems solved by technology

The biggest defect of this process is that there is a lot of industrial wastewater, and the reduction of iron powder produces a large amount of iron sludge, which seriously pollutes the environment. In addition, the process generally adopts low-temperature sedimentation for separation during purification, that is, the reacted solution is cooled to separate out p-phenylenediamine. The crystals are then dried. Traditional cooling precipitation generally relies on continuous cooling to gradually precipitate crystals. Although this method can obtain relatively pure crystals, it lasts for a long time, and is affected by the chemical properties of p-phenylenediamine. In this long crystallization process, the loss is also large