CN-122010770-A - Method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride

Abstract

The invention belongs to the technical field of oxadiazon intermediate preparation, and particularly discloses a method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride. The invention respectively pre-cools the 2, 4-dichloro-5-isopropoxy benzene diazonium salt solution and stannous chloride aqueous solution, and then introduces the pre-cooled solution into a micro-channel reactor for mixing, and reacts to obtain the 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride. The invention strengthens the mixing effect of diazonium salt and reducing agent stannous chloride by utilizing micro-reaction technology, improves the reaction speed, improves the mass transfer and heat transfer effects, solves the problems of poor heat transfer and mass transfer effects, low production efficiency, uncontrollable reaction process and large amount of diazonium salt aggregation existing in the existing intermittent reaction, and solves the problems of high cost and poor stability existing in the existing continuous reaction.

Inventors

• LIU DONG
• WANG HANDE
• An Tingwang
• HE HUAYANG
• ZHOU CHUAN
• WANG KE
• WEI WEI
• LI SHULONG

Assignees

• 沈阳化工研究院有限公司

Dates

Publication Date

20260512

Application Date

20260331

Claims (6)

1. 1. A method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride, which is characterized by comprising the following steps: Pre-cooling a2, 4-dichloro-5-isopropoxy benzene diazonium salt solution and a stannous chloride aqueous solution respectively, introducing the pre-cooled solution into a microchannel reactor for mixing, and reacting to obtain the 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride.
2. 2. The method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride according to claim 1, wherein the mass fraction of 2, 4-dichloro-5-isopropoxy phenyldiazonium chloride in the 2, 4-dichloro-5-isopropoxy phenyldiazonium chloride solution is 10-13%; the mass fraction of stannous chloride in the stannous chloride aqueous solution is 30-40%.
3. 3. The method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride according to claim 2, wherein the molar ratio of 2, 4-dichloro-5-isopropoxy phenyldiazonium chloride to stannous chloride in the microchannel reactor is 1:2-2.6.
4. 4. A method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride according to any one of claims 1 to 3, wherein the temperature of the 2, 4-dichloro-5-isopropoxy phenyldiazonium chloride solution and the temperature of the stannous chloride aqueous solution after precooling are independently-10 to 0 ℃.
5. 5. The method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride according to claim 4, wherein the reaction pressure is 0.3-0.5 mpa and the reaction temperature is 0-15 ℃; the residence time of the reaction in the microchannel reactor is 0.5-1 s.
6. 6. The method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride according to claim 5, wherein the inner channel of the microchannel reactor has an overall diameter of 0.4-0.6 mm, the length of the inner channel is 20-50 mm, the inner channel is in a zigzag shape, and the channel diameter of the discharge port is 3-5 mm.

Description

Method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride Technical Field The invention relates to the technical field of oxadiazon intermediate preparation, in particular to a method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride. Background Oxadiazon is a nitrogen-containing heterocyclic herbicide. Under the illumination condition, the herbicide can show excellent weeding effect. It is widely used in fields of rice, soybean, cotton, sugarcane and other crops, and in orchards for preventing and killing annual gramineae and broadleaf weeds such as barnyard grass, moleplant seed and the like. The structural formula is as follows: The synthetic process of oxadiazon is complex, the industrial synthetic route mainly takes 2, 4-dichloro-phenol as raw material, and is obtained through 10 steps of reactions of esterification, nitration, hydrolysis, etherification, reduction, diazotization, reduction, alkalization, acylation and cyclization, wherein 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride obtained through diazotization and reduction reactions by taking 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride as raw material is a key intermediate for synthesizing oxadiazon. Chinese patent applications CN120757464A and CN1169423A describe the use of sulfite as a reducing agent for reducing diazonium salt, but diazonium salt is an acidic system, sulfite is an alkaline system, side reaction easily occurs when the PH is controlled improperly to generate asphaltic byproducts, so that the yield is reduced, and concentrated hydrochloric acid is required to carry out reflux reaction to obtain phenylhydrazine hydrochloride, so that the operation is complex and the production efficiency is low. The method for producing the common reduced diazonium salt comprises the steps of reducing stannous chloride by using a reducing agent under an acidic condition, controlling the dropping speed to control the reaction temperature to be 0-10 ℃, concentrating and recovering the reacted stannous chloride, wherein the reaction steps are as follows: The reduction reaction of the diazonium salt and the stannous chloride is a second-level fast reaction, the heat release amount is large, when the stirring efficiency is low and the mass transfer effect is insufficient to disperse the generated phenylhydrazine hydrochloride, the active diazonium salt can be wrapped in the generated phenylhydrazine hydrochloride to generate a plurality of side reactions, the color of the generated phenylhydrazine hydrochloride is darker, the viscosity becomes larger, the mass transfer process is further hindered, the purity and the content are finally low, the product selectivity and the yield are poor, and the production yield of the batch process is about 80 percent, so the mass transfer effect of the kettle type reaction can directly influence the reaction selectivity. Meanwhile, the intermittent reaction needs to control the dropping speed to control the reaction temperature, the reaction temperature is too high, and the yield of the reduction reaction can be reduced. Therefore, the intermittent kettle type process has poor heat and mass transfer effects, so that the production yield is reduced, the production efficiency is low, the reaction process is uncontrollable, and a great amount of diazonium salt is accumulated to have potential safety hazards. Chinese patent CN107663161B discloses a continuous synthesis process of phenylhydrazine hydrochloride, which can continuously prepare phenylhydrazine hydrochloride, but the residence time is in the order of minutes, the production cost is high, and the generated phenylhydrazine hydrochloride is mostly solid, which is highly likely to block the channel, and affects the stability of long-time operation of the device. In order to solve the problems, the invention provides a method for producing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride by utilizing a microchannel technology to carry out continuous reduction reaction. The mass transfer process of the reduction reaction is reinforced by a micro-channel technology, so that phenylhydrazine hydrochloride solid is dispersed more uniformly, the particle size of phenylhydrazine hydrochloride particles is reduced, the viscosity of the reduced slurry is reduced, the reaction channel is prevented from being blocked, and meanwhile, the reaction can be controlled to improve the selectivity and the yield of the product. Disclosure of Invention In view of the above, the invention provides a method for continuously preparing 2, 4-dichloro-5-isopropoxy phenylhydrazine hydrochloride, which solves the problems of poor heat and mass transfer effect, low production efficiency, uncontrollable reaction process and aggregation of a large amount of diazonium salt in the existing intermittent reaction, and the problems of high cost and poor stability in the existing continuous reaction. In