Continuous preparation of m-toluidine

Abstract

The invention relates to a method for continuously preparing m-cresol. The m-toluidine diazonium salt is continuously added to dilute sulfuric acid of 25 to 64 wt%, and the concentration of sulfuric acid in the reactor is controlled at 25 to 64 wt%, and the reaction temperature is 106 ~150°C to obtain m-cresol. The invention has the following advantages: not only the production cost is low, but also the finished product yield of m-cresol with a content ≥ 99.5% is above 84%, which is about 10% higher than that of the discontinuous preparation method. The reaction volume is small, and the volume of the hydrolysis reactor is only 2 / 5 of the intermittent production, which not only reduces investment, but also saves energy consumption and reduces operating costs. The invention can be carried out without solvent, saves the trouble of separating and recovering the solvent, and greatly reduces material consumption. The waste sulfuric acid produced by the hydrolysis reaction can be recycled as a raw material for the preparation of m-toluidine diazonium salt after being treated by the macroporous adsorption resin, which solves the problem of a large amount of waste acid discharge in the intermittent hydrolysis reaction.

Description

technical field

[0001] The invention relates to a method for continuously preparing m-cresol, which belongs to the field of fine chemicals. Background technique

[0002] The conversion from m-toluidine to m-cresol through diazotization and hydrolysis reactions is currently generally carried out in a discontinuous production method. In this method, sodium nitrite, sulfuric acid, and m-toluidine are used for diazotization reaction at low temperature to generate a diazonium salt solution of m-toluidine, and then the m-toluidine diazonium salt solution is added to boiling dilute sulfuric acid for hydrolysis reaction. The m-cresol produced by the reaction is distilled out with water vapor, and the m-cresol left in the reaction kettle and the m-cresol evaporated are obtained by solvent extraction and then distilled off the solvent. This method is discontinuous and batch production, requires a very large equipment volume, uses a large amount of solvent, and generally has a low yie...

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