阅读说明：本技术 一种氰乙酸连续生产的方法 (Method for continuously producing cyanoacetic acid ) 是由 李娟� 张影 张国栋 宋香哲 王立新 赵欢 李晓俊 李成果 于 2020-07-27 设计创作，主要内容包括：本发明提供了一种氰乙酸连续生产的方法,属于氰乙酸生产技术领域,以乙二腈和乙酸为反应原料,以酸酐类物质为催化剂,通过氰化反应制备得到氰乙酸。本发明提供的氰乙酸连续生产的方法,解决了现有技术中生产的氰乙酸产品中含有杂质,导致产出率低,且会产生大量废水,造成环境污染的问题。(The invention provides a method for continuously producing cyanoacetic acid, belonging to the technical field of cyanoacetic acid production. The method for continuously producing cyanoacetic acid provided by the invention solves the problems that the cyanoacetic acid product produced in the prior art contains impurities, so that the yield is low, a large amount of waste water is generated, and the environment is polluted.)

1. A method for continuously producing cyanoacetic acid is characterized in that ethanedinitrile and acetic acid are used as reaction raw materials, acid anhydride substances are used as catalysts, and the cyanoacetic acid is prepared through a cyaniding reaction.

2. The method for continuously producing cyanoacetic acid according to claim 1, wherein the reaction temperature of the cyanation reaction is 100 to 120 ℃ and the reaction time is 23 to 25 hours.

3. A process for the continuous production of cyanoacetic acid as claimed in claim 1, wherein the acetic acid is preheated to 60 to 80 ℃ before the reaction.

4. A process for the continuous production of cyanoacetic acid according to claim 1, wherein the molar ratio of ethanedinitrile to acetic acid is from 0.8 to 1: 1.

5. a process for the continuous production of cyanoacetic acid as in claim 1, wherein the catalyst is acetic anhydride.

6. A method for the continuous production of cyanoacetic acid as in claim 1, wherein the amount of the catalyst added is 0.5 to 1% by mass of acetic acid.

7. A process for the continuous production of cyanoacetic acid according to claim 1, wherein the process for the preparation of ethanedinitrile comprises the steps of: and introducing high-purity nitrogen into the coke at the temperature of 600-800 ℃ to obtain ethanedinitrile.

8. The method for continuously producing cyanoacetic acid according to claim 1, wherein the high-purity nitrogen gas is introduced at a rate of 200 to 300 kg/h.

9. The method for continuously producing cyanoacetic acid according to claim 1, comprising the steps of:

s001, arranging a coke layer for heating in the first reactor, and introducing high-purity nitrogen into the first reactor, wherein the high-purity nitrogen passes through the coke layer to prepare ethanedinitrile gas;

s002, introducing acetic acid in the first storage tank into a heater for preheating, then introducing the preheated acetic acid into a second reactor, and simultaneously introducing the ethanedinitrile gas and the acid anhydride substances into the second reactor for reaction to obtain a reaction solution containing cyanoacetic acid;

s003, introducing the reaction liquid containing cyanoacetic acid into an evaporator, and distilling off acetic acid and hydrogen cyanide in the reaction liquid under a negative pressure state to obtain a pure cyanoacetic acid product;

s004, introducing the mixed gas of acetic acid and hydrogen cyanide separated by the evaporator into a condenser, introducing the condensed acetic acid into a recovery tank, introducing the uncondensed hydrogen cyanide gas into an absorption tank, and absorbing the uncondensed hydrogen cyanide gas by liquid caustic soda to generate sodium cyanide;

and S005, introducing the acetic acid in the recovery tank into the first storage tank for recycling.

10. The method of claim 9, wherein the degree of vacuum of the evaporator in S003 is 5 to 10 kpa.

Technical Field

The invention belongs to the technical field of cyanoacetic acid production, and particularly relates to a continuous production method of cyanoacetic acid.

Background

Cyanoacetic acid is an organic synthesis intermediate, is mainly used for synthesizing cyanoacetic acid esters, and is an important raw material for producing pesticides and medicines. In the prior art, chloroacetic acid, sodium carbonate and sodium cyanide are generally used as raw materials, and cyanoacetic acid is synthesized through the processes of neutralization, cyanidation, acidification, dehydration and the like. However, the method for preparing cyanoacetic acid is complex in steps, the prepared product contains a large amount of sodium chloride impurities, the cyanoacetic acid is easy to decompose due to high temperature in the dehydration process, the yield is low, and a large amount of wastewater is generated in the dehydration process to cause environmental pollution.

Disclosure of Invention

The invention aims to provide a method for continuously producing cyanoacetic acid, which aims to solve the problems that the production yield is low, a large amount of waste water is generated and the environment is polluted because the cyanoacetic acid product produced in the prior art contains impurities.

In order to achieve the purpose, the invention adopts the technical scheme that: the cyanoacetic acid is prepared by taking ethanedinitrile and acetic acid as reaction raw materials and acid anhydride substances as catalysts through a cyaniding reaction.

Preferably, the reaction temperature of the cyanidation reaction is 100-120 ℃, and the reaction time is 23-25 hours.

Preferably, the acetic acid is preheated to 60-80 ℃ before the reaction.

Preferably, the molar ratio of the ethanedinitrile to the acetic acid is 0.8-1: 1.

preferably, the catalyst is acetic anhydride.

Preferably, the adding amount of the catalyst is 0.5-1 per mill of the mass of the acetic acid.

Preferably, the preparation method of ethanedinitrile comprises the following steps: and introducing high-purity nitrogen into the coke at the temperature of 600-800 ℃ to obtain ethanedinitrile.

Preferably, the introducing speed of the high-purity nitrogen is 200-300 kg/h.

Preferably, the continuous production method of cyanoacetic acid specifically comprises the following steps:

s001, arranging a coke layer for heating in the first reactor, and introducing high-purity nitrogen into the first reactor, wherein the high-purity nitrogen passes through the coke layer to prepare ethanedinitrile gas;

s002, introducing acetic acid in the first storage tank into a heater for preheating, then introducing the preheated acetic acid into a second reactor, and simultaneously introducing the ethanedinitrile gas and the acid anhydride substances into the second reactor for reaction to obtain a reaction solution containing cyanoacetic acid;

s003, introducing the reaction liquid containing cyanoacetic acid into an evaporator, and distilling off acetic acid and hydrogen cyanide in the reaction liquid under a negative pressure state to obtain a pure cyanoacetic acid product;

s004, introducing the mixed gas of acetic acid and hydrogen cyanide separated by the evaporator into a condenser, introducing the condensed acetic acid into a recovery tank, introducing the uncondensed hydrogen cyanide gas into an absorption tank, and absorbing the uncondensed hydrogen cyanide gas by liquid caustic soda to generate sodium cyanide;

and S005, introducing the acetic acid in the recovery tank into the first storage tank for recycling.

Preferably, the vacuum degree of the evaporator in the S003 is 5-10 kpa.

The method for continuously producing cyanoacetic acid has the beneficial effects that: compared with the prior art, the method has the advantages that ethanedinitrile gas and acetic acid are used as raw materials, acid anhydride is used as a catalyst, the cyanoacetic acid is prepared at a lower reaction temperature without high pressure in one step, reaction steps are simplified, the reaction time is shortened, the yield of a large amount of sodium chloride and acid water in the traditional process is avoided, the repeated compression process is avoided, the produced cyanoacetic acid product does not contain sodium chloride, the yield of the cyanoacetic acid is improved, the yield can reach more than 97%, and the purity can reach more than 98.5%.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed for the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a method for continuously producing cyanoacetic acid according to an embodiment of the present invention.

In the figure: 1. a first reactor; 2. a heater; 3. a second reactor; 4. a first storage tank; 5. a second storage tank; 6. a third storage tank; 7. a recovery tank; 8. an absorption tank; 9. an evaporator; 10. a condenser; 11. a valve; 12. and (6) a liquid pump.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to FIG. 1, a method for continuously producing cyanoacetic acid according to the present invention will now be described. A method for continuously producing cyanoacetic acid takes ethanedinitrile and acetic acid as reaction raw materials, takes acid anhydride substances as catalysts, and prepares the cyanoacetic acid through cyanidation reaction.

Compared with the prior art, the method for continuously producing the cyanoacetic acid provided by the invention has the advantages that the ethanedinitrile gas and the acetic acid are used as raw materials, the acid anhydride is used as a catalyst, the cyanoacetic acid is prepared at a lower reaction temperature without high pressure in one step, the reaction steps are simplified, the reaction time is shortened, the yield of a large amount of sodium chloride and acid water in the traditional process is avoided, the repeated compression process is avoided, the produced cyanoacetic acid product does not contain sodium chloride, the yield of the cyanoacetic acid is improved, the yield can reach more than 97%, and the purity can reach more than 98.5%.

As a specific implementation manner of the embodiment of the invention, the reaction temperature of the cyanidation reaction is 100-120 ℃, and the reaction time is 23-25 hours.

The method can ensure that ethanedinitrile and acetic acid fully react within the range of 100-120 ℃, and the cyanoacetic acid yield obtained within the temperature range is highest.

As a specific implementation manner of the embodiment of the invention, the acetic acid is preheated to 60-80 ℃ before the reaction.

Acetic acid is preheated and then undergoes a cyanidation reaction with ethanedinitrile gas to prepare cyanoacetic acid and hydrogen cyanide gas. The preheated acetic acid and ethanedinitrile gas react more fully, and the yield of cyanoacetic acid is improved.

As a specific implementation manner of the embodiment of the invention, the molar ratio of ethanedinitrile to acetic acid is 0.8-1: 1.

the molar ratio of ethanedinitrile to acetic acid is 0.8-1: 1, the ethanedinitrile and the acetic acid can be fully reacted, and raw material waste is avoided.

As a specific implementation of the embodiment of the invention, the catalyst is acetic anhydride.

Acetic anhydride is added as a catalyst, so that the ethanedinitrile gas and the acetic acid are subjected to cyanidation reaction fully and quickly.

As a specific implementation manner of the embodiment of the invention, the adding amount of the catalyst is 0.5-1 per mill of the mass of the acetic acid.

The addition of the catalyst in the amount can improve the reaction rate to the maximum extent, and meanwhile, the waste is not caused.

As a specific embodiment of the present invention, a method for preparing ethanedinitrile comprises the steps of: and introducing high-purity nitrogen into the coke at the temperature of 600-800 ℃ to obtain ethanedinitrile.

High purity nitrogen having a nitrogen value content of 99.9%.

High purity nitrogen gas and hot coke produce ethanedinitrile gas at high temperatures. The nitrogen is stable in property and low in cost, and does not generate danger. The method for preparing the ethanedinitrile gas by reacting the nitrogen with the coke layer has low cost, reduces the production cost, does not generate harmful substances or danger in the reaction, and improves the safety coefficient in production.

As a specific implementation manner of the embodiment of the invention, the high-purity nitrogen is introduced at a speed of 200-300 kg/h.

The nitrogen can be fully reacted with the coke by controlling the introduction speed of the nitrogen, so that the waste of the nitrogen caused by too fast introduction of the nitrogen is avoided, and the cyanoacetic acid yield is not influenced slowly by the introduction of the nitrogen.

Referring to fig. 1, a method for continuously producing cyanoacetic acid specifically includes the following steps:

s001, arranging a coke layer for heating in the first reactor 1, introducing high-purity nitrogen into the first reactor 1, and preparing ethanedinitrile gas from the high-purity nitrogen through the coke layer;

s002, introducing the acetic acid in the first storage tank 4 into a heater 2 for preheating, then introducing the preheated acetic acid into a second reactor 3, simultaneously introducing ethanedinitrile gas and acid anhydride substances into a second reactor 6, and reacting to obtain a reaction liquid containing cyanoacetic acid;

s003, introducing the reaction liquid containing cyanoacetic acid into an evaporator 9, and distilling off acetic acid and hydrogen cyanide in the reaction liquid under a negative pressure state to obtain a pure cyanoacetic acid product;

s004, introducing mixed gas of acetic acid and hydrogen cyanide separated by the evaporator 9 into a condenser 10, introducing the condensed acetic acid into a recovery tank 7, introducing uncondensed hydrogen cyanide gas into an absorption tank 8, and absorbing the uncondensed hydrogen cyanide gas by liquid caustic soda to generate sodium cyanide;

and S005, introducing the acetic acid in the recovery tank 7 into the first storage tank 4 for recycling.

The device for preparing cyanoacetic acid by the method comprises a first reactor 1, a first storage tank 4, a second storage tank 5, an evaporator 9, a third storage tank 6, a condenser 10, a recovery tank 7 and an absorption tank 8, wherein the first reactor 1 is used for preparing ethanedinitrile gas; the first storage tank 4 is used for storing acetic acid; a liquid inlet of the second reactor 3 is communicated with a liquid outlet of the first storage tank 4 through a pipeline, and a gas inlet of the second reactor 3 is communicated with a gas outlet of the first reactor 1 through a pipeline; a liquid inlet of the second storage tank 5 is communicated with a liquid outlet of the second reactor 3 through a pipeline and is used for storing reaction liquid; a liquid inlet of the evaporator 9 is communicated with a liquid outlet of the second storage tank 5 through a pipeline; a liquid inlet of the third storage tank 6 is communicated with a liquid outlet of the evaporator 9 through a pipeline and is used for storing cyanoacetic acid; the air inlet of the condenser 10 is communicated with the air outlet of the evaporator 9 through a pipeline; a liquid inlet of the recovery tank 7 is communicated with a liquid outlet of the condenser 10 through a pipeline, a liquid outlet of the recovery tank 7 is communicated with a liquid inlet of the first storage tank 4 through a pipeline, and the recovery tank 7 is used for storing acetic acid obtained by condensation; the air inlet of the absorption tank 8 is communicated with the air outlet of the condenser 10 through a pipeline.

Specifically, the pipeline through which the first reactor 1 is communicated with the second reactor 3 and the pipeline through which the first storage tank 4 is communicated with the first reactor 1 are both provided with valves 11. The flow of acetic acid and ethanedinitrile is controlled, and the yield of cyanoacetic acid is increased.

Specifically, a liquid pump 12 is arranged on a pipeline through which the first storage tank 4 is communicated with the second reactor 3, a liquid pump 12 is arranged on a pipeline through which the second storage tank 5 is communicated with the evaporator 9, and a liquid pump 12 is arranged on a pipeline through which the recovery tank 7 is communicated with the first storage tank 4. The provision of the liquid pump 12 enables the liquid to flow more smoothly through the device while avoiding the occurrence of liquid backflow.

Referring to fig. 1, as a specific implementation manner of the embodiment of the present invention, in S004, the vacuum degree of the evaporator 9 is 5 to 10 kpa.

The vacuum degree in the evaporator 9 is kept within the range of 5-10 kpa, and acetic acid and hydrogen cyanide can be separated to the maximum extent to obtain pure cyanoacetic acid.

Referring to fig. 1, a distributor is disposed in a first reactor 1 and below a coke layer.

High-purity nitrogen is introduced from the lower part of the first reactor 1, the high-purity nitrogen is uniformly dispersed in the first reactor 1 after passing through the distributor, and the dispersed high-purity nitrogen fully reacts with the coke layer, so that the reaction efficiency is improved.

Referring to fig. 1, an absorption tank 8 is connected to a vacuum system as a specific embodiment of the present invention.

The gas outlet of the absorption tank 8 is communicated with a vacuum system and used for discharging gas in the device, so that the evaporator 9 reacts under a vacuum condition, and the vacuum degree of the whole device is ensured.