Method for preparing 2,4-toluene dichloride

Abstract

The invention relates to a process for preparing 2, 4-dichlorotoluene by using p-chlorotoluene, chlorine as raw material for synthesizing 2, 4-dichlorotoluene through catalyzed chloridization, which comprises the steps of synthesizing, alkaline cleaning, rectifying, the synthesizing reaction temperature is between 35-45 deg. C, the alkaline cleaning agent for washing synthetic reaction product in the alkaline cleaning step is sodium carbonate crystal containing crystal water. The invention increases the yield of 2, 4-dichlorotoluene and improves the chlorine distribution status during reaction.

Description

technical field [0001] The invention relates to a production method of 2,4-dichlorotoluene. Background technique [0002] 2,4-Dichlorotoluene is an important chemical raw material, it is a colorless transparent liquid, and its structural formula is CI- Mainly used in organic synthesis, pharmaceutical and dye industries. At present, the main production routes at home and abroad are: [0003] 1. Use p-chlorotoluene and chlorine gas as raw materials, and synthesize it in a batch kettle in the presence of Lewis acid. The method has low selectivity to 2,4-dichlorotoluene in industrial production, and has many by-products, acid waste water, and large catalyst consumption. [0004] 2. Obtained by the isomerization of dichlorotoluene, and the isomerized product is separated by its medium-pore molecular sieve. The production cost of this method is relatively high, and industrial production is difficult. [0005] 3. Using 3-chloro-p-toluidine as raw material, carry out heavy chl...

AI Technical Summary

Problems solved by technology

The synthesis reaction temperature of this method is between 55-65 ° C, and the way of introducing chlorine gas into p-chlorotoluene is an inlet pipe. Due to the high reaction temperature and uneven distribution of chlorine gas, polychlorides in the reaction product The content is high, the reaction yield is only about 70%, and the utilization rate of chlorine gas is only about 80%.

Although the synthesis reaction is carried out under stirring, because the stirring speed is about 60 rpm, the reaction liquid is easy to form a vortex phenomenon, which reduces the residence time of chlorine gas, and the reaction time is as long as more than 20 hours, which increases the energy consumption of the system

Simultaneously, the alkaline cleaning method of the process is carried out in an alkaline cleaning tank. The alkaline cleaning agent used to wash hydrogen chloride in the synthetic reaction product is a sodium hydroxide solution. The material after the alkaline cleaning has free water to exist, so that the layering of the material is not obvious. It is not conducive to the separation of reaction products and sodium chloride, so that the waste liquid containing toxic and harmful substances is directly discharged, which seriously pollutes the environment; in addition, the rectification of this method is carried out in a rectification tower, and the packing selected for the rectification tower is BX type Net wave packing, its film-forming effect is not good, and its rectification yield is only about 85%

To sum up, this method has long reaction time, many by-products, high energy consumption, and the discharge of three wastes is difficult to meet the standards. Improving the process conditions to increase the yield and reduce environmental pollution is the expectation of the manufacturer and the purification of the natural environment.

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