CN112358419B

CN112358419B - Synthesis process of 3, 4-dichlorophenyl isocyanate

Info

Publication number: CN112358419B
Application number: CN202011330789.9A
Authority: CN
Inventors: 夏晨东; 陈国全; 陈映波; 林玮; 陈海芳; 叶朝侯
Original assignee: Upchem China Co ltd
Current assignee: Upchem China Co ltd
Priority date: 2020-11-24
Filing date: 2020-11-24
Publication date: 2023-04-07
Anticipated expiration: 2040-11-24
Also published as: CN112358419A

Abstract

The application discloses a synthesis process of 3, 4-dichlorophenyl isocyanate, which comprises the step of adding 3, 4-dichloroaniline and a solvent into a reaction kettle to obtain a 3, 4-dichloroaniline solution. Simultaneously adding solid phosgene into a reaction kettle, and heating to dissolve; when the temperature of the reaction kettle reaches 60-100 ℃, controlling the dropping speed by a DCS control system to begin to drop 3, 4-dichloroaniline solution in the S1, so that 3, 4-dichloroaniline and solid phosgene generate 3, 4-dichloroaniline hydrochloride and 3, 4-dichloromethyl amino acyl chloride in a solvent medium; removing hydrogen chloride from the 3, 4-dichlorobenzylaminoyl chloride obtained in the step S3 to obtain 3, 4-dichlorophenyl isocyanate, and after the dropwise addition is finished, carrying out reflux heat preservation for 1-3h; the acid-containing solvent is removed under normal pressure and recovered for reuse, and the concentrated solution is transferred to a rectifying still for rectification to obtain the product 3, 4-dichlorophenyl isocyanate. Green chemicals are used as production raw materials, and potential safety hazards caused by phosgene leakage are reduced. The general chemical solid phosgene is adopted to replace virulent phosgene to serve as an acylation reagent, and a green degradable ester solvent is adopted as a reaction medium.

Description

Synthesis process of 3, 4-dichlorophenyl isocyanate

Technical Field

The invention belongs to the technical field of preparation of 3, 4-dichlorophenyl isocyanate, and particularly relates to a synthesis process of 3, 4-dichlorophenyl isocyanate.

Background

The 3, 4-dichlorophenyl isocyanate is an important intermediate of medicines, pesticides and high molecular materials, is mainly used for synthesizing urea herbicides, pesticides and other pesticides, synthesizing some medical intermediates, and derivatives prepared by reacting the intermediates with alcohol and amine, and can also be used for identifying compounds. The synthesis of 3, 4-dichlorophenyl isocyanate can be carried out by reacting 3, 4-dichloroaniline with phosgene in inert solvent toluene at low temperature and high temperature in two stages, such as Chinese patent CN107235860A. Chinese patents CN101781236A and CN102617407A all mention the target object obtained by low-temperature light-passing and then slow light-passing of 3,4-dichloroaniline. These methods all use phosgene as acylation reagent, and adopt low-temperature and high-temperature two-stage method with long period. Meanwhile, in order to improve the reaction effect, the excessive phosgene is required to be discharged to a tail gas system, so that the phosgene is wasted, and potential safety hazards caused by phosgene leakage exist.

Disclosure of Invention

The invention aims to provide a synthesis process of 3, 4-dichlorophenyl isocyanate, which takes green chemicals as production raw materials and reduces the potential safety hazard caused by phosgene leakage. The general chemical solid phosgene is adopted to replace virulent phosgene to serve as an acylation reagent, and a green degradable ester solvent is adopted as a reaction medium.

In order to solve the technical problems, the invention adopts the following technical scheme:

a synthesis process of 3, 4-dichlorophenyl isocyanate comprises the following steps:

s1, adding 3, 4-dichloroaniline and a solvent into a reaction kettle to obtain a 3, 4-dichloroaniline solution.

S2, simultaneously adding solid phosgene into the reaction kettle, and heating to dissolve;

s3, controlling the dropping speed by a DCS (distributed control System) control system to start dropping the 3, 4-dichloroaniline solution in the S1 when the temperature of the reaction kettle reaches 60-100 ℃, so that 3, 4-dichloroaniline hydrochloride and 3, 4-dichlorobenzyl amino acyl chloride are generated by the 3, 4-dichloroaniline and solid phosgene in a solvent medium;

s4, removing hydrogen chloride from the 3, 4-dichlorobenzyl amino acyl chloride obtained in the S3 to obtain 3, 4-dichlorophenyl isocyanate, and after the dropwise addition is finished, carrying out reflux and heat preservation for 1-3h;

s5, removing the acid-containing solvent at normal pressure, recycling and applying mechanically, transferring the concentrated solution to a rectifying still, and rectifying to obtain the product 3, 4-dichlorophenyl isocyanate.

Preferably, in S1, the mass ratio of the 3, 4-dichloroaniline to the solvent is 1.

Preferably, in S1, the mass ratio of 3, 4-dichloroaniline to solvent is 1.

Preferably, in S2, the mass ratio of the solid phosgene to the solvent is 1:2.0 to 4.0.

Preferably, in S2, the mass ratio of the solid phosgene to the solvent is 1:3.0.

preferably, the molar ratio of the 3, 4-dichloroaniline to the solid phosgene in S2 is 1.

Preferably, the molar ratio of 3, 4-dichloroaniline to solid phosgene in S2 is 1.

Preferably, the solvent is ethyl acetate, butyl acetate or sec-butyl acetate.

Preferably, the solid phosgene is bis (trichloromethyl) carbonate.

Preferably, in S5, the yield of the product 3, 4-dichlorophenyl isocyanate is 94%, and the product content is more than or equal to 99.0%.

The invention has the following beneficial effects:

1. the solid phosgene is bis (trichloromethyl) carbonate, is used as a substitute of phosgene and diphosgene, and has the characteristics of safety, economy, convenient use, no pollution, accurate reaction metering and the like.

2. The green and environment-friendly esters are used as solvents, so that the investment of toxic and harmful substances is reduced from the source. Meanwhile, the temperature is easy to control, the reaction efficiency is high, and the yield and the quality of the product are ensured at a higher level.

3. The one-step method is adopted for synthesis, the synthesis period is shortened, the efficiency is improved, and the energy consumption is saved, because the reaction efficiency of the 3, 4-dichloroaniline and the solid phosgene is high at 60-100 ℃, the product mainly takes the unstable intermediate product 3, 4-dichlorobenzyl amino acyl chloride as the main material, and simultaneously, a small amount of 3, 4-dichloroaniline hydrochloride can efficiently react with the solid phosgene to generate the 3, 4-dichlorobenzyl amino acyl chloride at the temperature, so the reaction period is shortened, and the reaction efficiency is improved.

4. A DCS automatic control system is adopted in the process, so that the metering, temperature control and dropping speed of materials are more accurate, and the reaction conditions are more stable.

Detailed Description

In order to facilitate a better understanding of the invention, the following examples are given to illustrate, but not to limit the scope of the invention.

Example 1

Firstly, uniformly mixing 3, 4-dichloroaniline and a solvent in a mixing kettle according to a mass ratio of 1. Simultaneously adding bis (trichloromethyl) carbonate and a solvent into a reaction kettle according to a mass ratio of 1: and 3, heating to dissolve. The molar ratio of 3, 4-dichloroaniline to bis (trichloromethyl) carbonate was 1. When the temperature of the reaction kettle reaches 80 ℃, a DCS control system controls the dripping speed to begin to drip 3, 4-dichloroaniline solution, so that 3, 4-dichloroaniline and solid phosgene generate a small amount of 3, 4-dichloroaniline hydrochloride and unstable intermediate product 3, 4-dichloromethyl amino acyl chloride in a solvent medium, and the 3, 4-dichloromethyl amino acyl chloride is subjected to hydrogen chloride removal to obtain 3, 4-dichlorophenyl isocyanate. The dropwise adding reaction time is 1.3h, and after the dropwise adding is finished, the reflux and heat preservation are carried out for 2h. The acid-containing solvent is removed under normal pressure and recovered for reuse, and the concentrated solution is transferred to a rectifying still. Rectifying to obtain the product 3, 4-dichlorophenyl isocyanate with yield of 94% and product content not less than 99.0%, and burning the residue.

Example 2

Uniformly mixing 3, 4-dichloroaniline and a solvent in a mixing kettle according to a mass ratio of 1. Simultaneously adding bis (trichloromethyl) carbonate and a solvent into a reaction kettle according to a mass ratio of 1:4.0, heating to dissolve. The molar ratio of 3, 4-dichloroaniline to bis (trichloromethyl) carbonate was 1. And (3) controlling the dropping speed by a DCS (distributed control system) control system to start dropping a 3, 4-dichloroaniline solution so that a small amount of 3, 4-dichloroaniline hydrochloride and an unstable intermediate product, namely 3, 4-dichlorobenzyl amino acyl chloride are generated by the 3, 4-dichloroaniline and solid phosgene in a solvent medium, and removing hydrogen chloride from the 3, 4-dichlorobenzyl amino acyl chloride to obtain the 3, 4-dichlorophenyl isocyanate. The dropwise adding reaction time is 0.5h, and after the dropwise adding is finished, the reflux and heat preservation are carried out for 3h. The acid-containing solvent is removed under normal pressure and recovered for reuse, and the concentrated solution is transferred to a rectifying still. Rectifying to obtain the product 3, 4-dichlorophenyl isocyanate with yield of 94% and product content not less than 99.0%, and burning the residue.

Example 3

Firstly, 3, 4-dichloroaniline and a solvent are uniformly mixed in a mixing kettle according to the mass ratio of 1. Simultaneously adding bis (trichloromethyl) carbonate and a solvent in a mass ratio of 1: and 2.0, heating to dissolve. The molar ratio of 3, 4-dichloroaniline to bis (trichloromethyl) carbonate was 1. And (3) controlling the dropping speed by a DCS (distributed control system) control system to start dropping a 3, 4-dichloroaniline solution so that a small amount of 3, 4-dichloroaniline hydrochloride and an unstable intermediate product, namely 3, 4-dichlorobenzyl amino acyl chloride are generated by the 3, 4-dichloroaniline and solid phosgene in a solvent medium, and removing hydrogen chloride from the 3, 4-dichlorobenzyl amino acyl chloride to obtain the 3, 4-dichlorophenyl isocyanate. The dropwise adding reaction time is 2.0h, and after the dropwise adding is finished, the reflux and heat preservation are carried out for 1h. The acid-containing solvent is removed under normal pressure and recovered for reuse, and the concentrated solution is transferred to a rectifying still. Rectifying to obtain the product 3, 4-dichlorophenyl isocyanate with yield of 94% and product content not less than 99.0%, and burning the residue

It can be understood that the DCS is a decentralized control system, and is a new generation of instrument control system based on a microprocessor and adopting a design principle of decentralized control function, centralized display operation, and consideration of both autonomous and comprehensive coordination.

Example 4

11.88g of bis (trichloromethyl) carbonate and 150ml of toluene were put into a 500ml four-necked flask equipped with a reflux apparatus cooled with-20 ℃ frozen ethanol, and dissolved by stirring. At 0-10 deg.C, within 45min, 150ml toluene solution dissolved with 100mmol arylamine is dropped into the above reaction solution, and then the temperature is raised and the reflux is carried out for 2-3 h until the reaction solution becomes clear. Then, dry nitrogen gas is introduced into the reaction solution under the reflux state, and the residual hydrogen chloride gas and a very small amount of phosgene are driven to a recovery bottle and a tail gas absorption bottle until the pH value of the tail gas is about 7. And cooling the reaction liquid to room temperature, slowly introducing 6.75g of dimethylamine gas while stirring, stopping the reaction after about 30min, filtering, and drying in vacuum to obtain a powdery crystalline product.

Based on the above embodiment, bis (trichloromethyl) carbonate is a solid at normal temperature, can be accurately weighed, is convenient to feed, and can be completely reacted generally only by a small amount of bis (trichloromethyl) carbonate.

The above description should not be taken as limiting the invention to the embodiments, but rather, as will be apparent to those skilled in the art to which the invention pertains, numerous simplifications or substitutions may be made without departing from the spirit of the invention, which shall be deemed to fall within the scope of the invention as defined by the claims appended hereto.

Claims

1. A synthesis process of 3, 4-dichlorophenyl isocyanate is characterized by comprising the following steps:

s1, adding 3, 4-dichloroaniline and a solvent into a reaction kettle to obtain a 3, 4-dichloroaniline solution;

s2, adding solid phosgene into the reaction kettle, and heating to dissolve;

s3, controlling the dropping speed to start dropping the 3, 4-dichloroaniline solution in the S1 by a DCS (distributed control system) control system when the temperature of the reaction kettle reaches 60-100 ℃, so that 3, 4-dichloroaniline hydrochloride and 3, 4-dichlorobenzyl amino acyl chloride are generated by the 3, 4-dichloroaniline and solid phosgene in a solvent medium, the dropping reaction time is 0.5-2.0 hours, and after the dropping is finished, carrying out reflux and heat preservation for 1-3 hours;

s4, removing hydrogen chloride from the 3, 4-dichlorobenzyl amino acyl chloride obtained in the S3 to obtain 3, 4-dichlorophenyl isocyanate;

s5, removing the acid-containing solvent at normal pressure, recovering and recycling, transferring the concentrated solution to a rectifying still, and rectifying to obtain a product 3, 4-dichlorophenyl isocyanate;

wherein the solid phosgene is bis (trichloromethyl) carbonate;

the solvent is ethyl acetate, butyl acetate or sec-butyl acetate.

2. The process for synthesizing 3, 4-dichlorophenyl isocyanate according to claim 1, wherein the mass ratio of 3, 4-dichloroaniline to solvent in S1 is 1.

3. The process for synthesizing 3, 4-dichlorophenyl isocyanate according to claim 2, wherein the mass ratio of 3, 4-dichloroaniline to solvent in S1 is 1.

4. The process for synthesizing 3, 4-dichlorophenyl isocyanate according to claim 1, wherein in S2, the mass ratio of the solid phosgene to the solvent is 1:2.0 to 4.0.

5. The process for synthesizing 3, 4-dichlorophenyl isocyanate according to claim 4, wherein in S2, the mass ratio of the solid phosgene to the solvent is 1:3.0.

6. the process for synthesizing 3, 4-dichlorophenyl isocyanate according to claim 1, wherein the molar ratio of 3, 4-dichloroaniline to phosgene solid in S2 is 1.

7. The process for synthesizing 3, 4-dichlorophenyl isocyanate according to claim 6, wherein the molar ratio of 3, 4-dichloroaniline to phosgene solid in S2 is 1.

8. The process for synthesizing 3, 4-dichlorophenyl isocyanate according to claim 1, wherein in S5, the yield of 3, 4-dichlorophenyl isocyanate is 94% and the content of 3, 4-dichlorophenyl isocyanate is not less than 99.0%.