Continuous preparation of m-toluidine

A technology of m-cresol and cresol, which is applied in the field of continuous preparation of m-cresol, can solve the problems of hindering m-cresol reaction system, large amount of three wastes, long reaction cycle, etc. Low, shorten the effect of the reaction cycle

Inactive Publication Date: 2005-05-18
王林
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Problems solved by technology

The viscous tar-like substance formed by the side reaction floats on the surface of the reaction liquid, which hinders m-cresol from being taken out of the reaction system with distillation, making the reaction cycle longer
In addition, the amount of sulfuric acid used in the above reaction is large, and the amount of three wastes to be treated is also large.

Method used

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  • Continuous preparation of m-toluidine
  • Continuous preparation of m-toluidine

Examples

Experimental program
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Effect test

Embodiment 1

[0016] Embodiment 1: The diazonium salt solution of m-toluidine is prepared alternately according to conventional method with more than two reaction kettles at 0-10°C. Referring to accompanying drawing, in the reactor of 500L, add the sulfuric acid 281kg of 20wt%, then add 25kg m-toluidine, keep reaction temperature 0~10 ℃ under agitation, add the solution that 17.5kg sodium nitrite is dissolved in 35kg water and pass heavy Nitriding reaction to prepare m-toluidine diazonium salt solution.

[0017] In the 500L hydrolysis reactor, add 300L of 30wt% sulfuric acid, at 105~110 ​​℃, the m-toluidine diazonium salt solution that above-mentioned making is continuously added in the hydrolysis reactor; The water vapor is continuously taken out by distillation, and at the same time, the dilute sulfuric acid and tar-like by-products with m-cresol are continuously overflowed from the upper overflow port of the reactor.

[0018] Separation of waste sulfuric acid and tar-like substances con...

Embodiment 2

[0021] Embodiment 2: m-toluidine diazotization is the same as embodiment 1; adopt the sulfuric acid of 50wt% to carry out hydrolysis reaction, and hydrolysis reaction temperature is 110~150 ℃; Phenol <0.02 g / L). The crude m-cresol was recovered by eluting with methanol. The waste sulfuric acid is used as raw material to prepare m-toluidine diazonium salt solution after being adsorbed by resin. The organic substances adsorbed on the resin are eluted with water vapor. 24.04kg of crude m-cresol with a content of 95-97wt% was obtained. The crude m-cresol was rectified to obtain 21.69 kg of finished m-cresol with a content ≥ 99.5%, and the yield was 85.96%.

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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...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07C37/05C07C39/07
Inventor 刘仁培王林
Owner 王林
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