Preparation method of 2,5-diaminotoluene sulfate

Abstract

The invention provides a preparation method of 2,5-diaminotoluene sulfate, which mainly relates to effective separation of reaction products 2,5-diaminotoluene and o-toluidine and removal technique of o-toluidine in a 2,5-diaminotoluene sulfate product. The method comprises the following steps: by using 2-aminoazotoluene as the raw material, carrying out reducing metallic iron, zinc or other azo bond rupture reduction one-step reaction or distilling off the byproduct o-toluidine and filtering out the metal sludge, carrying out alkaline extraction, adsorbing and decolorizing to trace amounts of OT, and reacting with sulfuric acid to obtain the high-quality 2,5-TDAS, wherein the yield is 70-86%; or distilling off the byproduct o-toluidine, filtering out the metal sludge, adding sulfuric acid into the filtrate, filtering, taking out the 2,5-TDAS crude product, and repeatedly adsorbing and decolorizing with acidic / alkaline activated carbon to remove the OT in the product, wherein the total yield is 65-76%. The product 2,5-TDAS is preferably used in cosmetics due to high quality and low toxicity, and the o-toluidine content is less than 10 ppm. The alkaline extraction and activated carbon adsorption and decolorization techniques can lower the energy consumption, enhance the productivity and greatly reduce the wastewater amount.

Description

technical field [0001] The invention relates to the field of chemical engineering, in particular to a preparation method of 2,5-diaminotoluene sulfate. It is mainly the effective separation of the reaction product 2,5-diaminotoluene and o-toluidine and the removal technology of o-toluidine in the 2,5-diaminotoluene sulfate product. Background technique [0002] 2,5-diaminotoluene (2,5-TDA) is an aromatic hydrocarbon substance containing para-diamino groups in its molecular structure. In addition to replacing p-phenylenediamine as a hair dye, it can also be used for linear polyamides, polyamides, etc. New material fields such as imine and polyurethane. Its structure is as shown in formula (I): [0003] [0004] From the appearance of 2,5-TDA substance at the beginning of the 20th century to the 1980s, there were few reports on its synthesis and application due to its narrow application range and low demand. Since the 1990s, with the rise of beauty salons around the worl...

AI Technical Summary

Problems solved by technology

One of the inventors of this patent has disclosed a kind of synthetic method of 2,5-diaminotoluene and sulfate thereof in patent CN101450904, but does not have relevant its removal carcinogen o-toluidine (o-toluidine ( OT), to make it reach the OT content below 10ppm currently demanded in the international market, the hydrogenation of the RaneyNi and Pd / C catalysts used, the reduction of hydrazine hydrate and metal reduction under acidic conditions, the operation is all from the perspective of recycling OT, When the oil droplets in the distillate basically disappear, stop the steam distillation (it takes about 4 hours), that is, the filtrate is repeatedly decolorized by activated carbon and absorbs impurities, then added sulfuric acid to form a salt, cooled and filtered, washed with water, and dried to obtain 2,5-TDAS product The bench-scale technique does not involve the removal of OT in the product

In addition, there are no other documents and related patents that have reported about the removal of harmful substances such as OT to meet the requirements and standards of the cosmetics market.

The method adopted in the industry is to use activated carbon for about 18-20 hours after a long time of steam distillation (usually about 5 times) to obtain a product with an OT content of about 500ppm 2,5- TDAS, there is still a big gap compared to market requirements, and the loss of each decolorized product is about 1-2%, and the loss rate is large

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