3,3'-Dichlorobenzidine synthesis

Yield:-

Reaction Conditions:

with hydrogenchloride in water at 5 - 75;Large scale;

Steps:

e Indexing: Add 5000 kg of pre-prepared 25% hydrochloric acid solution into the indexing kettle 8 through the metering device, and then add 1500 kg of the 2,2’-dichlorohydroazobenzene obtained in the previous step through the metering device.The reaction temperature is controlled at 5-75°C. After 15 to 20 hours, the 2,2'-hydroazobenzene is completely converted into 3,3'-dichlorobenzidine hydrochloride and the reaction is completed;During the indexing period, the temperature is gradually increased by stepwise control: specifically, open the 2,2'-dichlorohydroazobenzene high-position tank pipeline valve to drip into the indexing kettle. The rate of dripping depends on the temperature in the kettle. The jacket of the kettle is always open with cooling water. During the dripping process, the reaction temperature is controlled not to exceed 30. After the dripping is completed, the heat preservation reaction is carried out in stages; the first stage, after the addition of 2,2'-dichlorohydroazobenzene Keep at the temperature not exceeding 40 (about 35) for 1 hour; the second stage, keep at 40-50 for 2 hours; the third stage, keep at 50-60 for 2 hours; the fourth stage, at 60-75 Keep it for 4 hours.f. Separation: solid-liquid separation using centrifuge 9 (can also be replaced by filter press) to obtain the finished product 3,3'-dichlorobenzidine hydrochloride and dilute hydrochloric acid. The finished product is packaged and sold, and the dilute hydrochloric acid enters the dilute acid storage tank 14 for recycling, and is used as the dilute acid added to the indexing tank 8.

References:

CN113548972,2021,A Location in patent:Paragraph 0026-0028