Technology for separating and purifying 2,4-diaminotoluene and 2,6-diaminotoluene by derivatization crystallization process

Abstract

The invention provides a technology for separating and purifying 2,4-diaminotoluene and 2,6-diaminotoluene by a derivatization crystallization process. The technology adopts TDA as a raw material and comprises the following steps of: performing rectification degumming treatment and dissolving in distilled water; adjusting the pH to 6-6.5, adding sodium chloride and performing a catalysis reaction; crystallizing and separating to obtain a crude product of 2,6-diaminotoluene; performing sectional rectification to obtain a pure product of 2,6-diaminotoluene; adjusting the pH of the mother liquid obtained after separating the 2,6-diaminotoluene to 10-12; adding sodium hydrosulfite and performing a catalysis reaction; crystallizing and separating to obtain a crude product of 2,4-diaminotoluene; performing sectional rectification to obtain a pure product of 2,4-diaminotoluene. According to the technology provided by the invention, a derivatization crystallization process is adopted for separation and purification so that the 2,4-diaminotoluene and 2,6-diaminotoluene in TDA (Toluene Diammonium) are completely separated, the utilization rate of the raw materials is over 99%, and the main content of the product is over 99%.

Description

technical field [0001] The invention belongs to the field of chemical products, and relates to a process for separating and purifying 2, 4-diaminotoluene 2, 6-diaminotoluene by TDA, in particular to a process for separating and purifying 2, 4-diaminotoluene by derivatization crystallization method Toluene 2,6-diaminotoluene process. Background technique [0002] Both 2,4-diaminotoluene (2,4-TDA) and 2,6-diaminotoluene (2,6-TDA) are important raw materials for organic synthesis, among which, 2,4-diaminotoluene is not only the It is also an important raw material for the production of toluene diisocyanate (TDI). 2,6-diaminotoluene is an important pharmaceutical intermediate. The method for industrially synthesizing TDA is usually to first nitrate toluene to obtain mixed dinitrotoluene, and then obtain meta-position mixed dinitrotoluene after rectification and separation to remove the ortho-position dinitrotoluene isomers, and then reduce to obtain mixed TDA, wherein Contain...

AI Technical Summary

Problems solved by technology

Domestic manufacturers of 2,4-diaminotoluene mostly use 2,4-dinitrotoluene to reduce 2,4-diaminotoluene with iron powder under acidic conditions to produce 2,4-diaminotoluene. During the production process, a large amount of acidic wastewater, waste residue, causing serious environmental pollution, therefore, the process of producing 2,4-diaminotoluene with this method is gradually being eliminated

In addition, very few domestic manufacturers use double-effect process distillation to produce 2,4-diaminotoluene by high-vacuum distillation of TDA at high temperature, but this process has disadvantages such as low recovery rate and large waste of raw materials.

At the same time, after extracting 2,4-diaminotoluene, a large amount of mixture of 2,4-diaminotoluene and 2,6-diaminotoluene will remain. The content of the two components in the mixture is about 50% each. Purification produces a large amount of waste residue, and the environmental pollution is also very serious

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