阅读说明：本技术 一种乙醛肟的分离提纯方法 (Method for separating and purifying acetaldoxime ) 是由 孟祥� 尹天长 娄瑞娟 赵会娟 张敏生 曹亚林 杨克明 于 2019-10-24 设计创作，主要内容包括：本发明公开了一种乙醛肟的分离提纯方法,涉及肟的分离提纯技术领域。包括以下步骤：1)将环己酮肟和乙醛进行肟交换反应制备得到的乙醛肟反应液,用碱中和,中和后控制乙醛肟反应液pH＝7；2)乙醛肟反应液中加入甲苯,减压精馏,分离乙醛肟和环己酮,分别得到乙醛肟甲苯混合液和环己酮；3)将得到的乙醛肟甲苯混合液加入萃取剂水,采用连续萃取工艺分离甲苯和乙醛肟,分别得到乙醛肟水溶液和甲苯；4)减压精馏乙醛肟水溶液,得到乙醛肟产品。本发明方法操作简单,乙醛肟纯度和收率高,无废液产生,是乙醛肟生产分离提纯的一种环境友好的绿色工艺路线。(The invention discloses a method for separating and purifying acetaldoxime, and relates to the technical field of oxime separation and purification. The method comprises the following steps: 1) performing oxime exchange reaction on cyclohexanone oxime and acetaldehyde to prepare an acetaldoxime reaction solution, neutralizing with alkali, and controlling the pH value of the acetaldoxime reaction solution to be 7 after neutralization; 2) adding toluene into the acetaldoxime reaction solution, carrying out reduced pressure rectification, and separating acetaldoxime and cyclohexanone to obtain acetaldoxime toluene mixed solution and cyclohexanone respectively; 3) adding the obtained acetaldoxime toluene mixed solution into extractant water, and separating toluene and acetaldoxime by adopting a continuous extraction process to respectively obtain an acetaldoxime aqueous solution and toluene; 4) and (3) rectifying the acetaldoxime aqueous solution under reduced pressure to obtain an acetaldoxime product. The method has the advantages of simple operation, high acetaldoxime purity and yield and no waste liquid, and is an environment-friendly green process route for producing, separating and purifying acetaldoxime.)

1. The method for separating and purifying the acetaldoxime is characterized by comprising the following steps of:

1) performing oxime exchange reaction on cyclohexanone oxime and acetaldehyde to prepare an acetaldoxime reaction solution, neutralizing with alkali, and controlling the pH value of the acetaldoxime reaction solution to be 7 after neutralization;

2) adding toluene into the acetaldoxime reaction solution, carrying out reduced pressure rectification, and separating acetaldoxime and cyclohexanone to obtain acetaldoxime toluene mixed solution and cyclohexanone respectively;

3) adding the obtained acetaldoxime toluene mixed solution into extractant water, and separating toluene and acetaldoxime by adopting a continuous extraction process to respectively obtain an acetaldoxime aqueous solution and toluene;

4) and (3) rectifying the acetaldoxime aqueous solution under reduced pressure to obtain an acetaldoxime product.

2. The method for separating and purifying aldoxime according to claim 1, which comprises the following steps: in the step 1), the reaction for preparing the acetaldehyde oxime by performing an oxime exchange process on the cyclohexanone oxime and the acetaldehyde comprises the following steps: adding cyclohexanone oxime and acid, dropwise adding anhydrous acetaldehyde at 4-10 ℃, continuously stirring and reacting for 1-2h at normal temperature and normal pressure after the dropwise adding of the anhydrous acetaldehyde is finished, obtaining an acetaldoxime reaction solution, and neutralizing with alkali.

3. The method for separating and purifying aldoxime according to claim 2, which comprises the following steps: in the step 1), in the reaction for preparing the acetaldehyde oxime by performing an oxime exchange process on cyclohexanone oxime and acetaldehyde: acetaldehyde: cyclohexanone oxime: the molar ratio of the acid is 1-1.6:1: 0.01.

4. The method for separating and purifying aldoxime according to claim 2, which comprises the following steps: in the step 1), the acid is sulfuric acid with the mass concentration of 40-70%, and the alkali used for neutralizing the reaction liquid is NaOH solid.

5. The method for separating and purifying aldoxime according to claim 1, which comprises the following steps: in the step 2), the molar ratio of the toluene to the acetaldoxime is 1:1-10: 1.

6. The method for separating and purifying aldoxime according to claim 1, which comprises the following steps: in the step 2), carrying out vacuum rectification, and collecting fractions with the vacuum degree of 0.06-0.065Mpa and the temperature of 66-71 ℃ to obtain the acetaldoxime toluene mixed solution.

7. The method for separating and purifying aldoxime according to claim 1, which comprises the following steps: in the step 2), carrying out vacuum rectification, and collecting fractions with the vacuum degree of 0.06-0.065Mpa and the temperature of 83-90 ℃ to obtain cyclohexanone, wherein the purity of the cyclohexanone is more than or equal to 99%.

8. The method for separating and purifying aldoxime according to claim 1, which comprises the following steps: in the step 3), the molar ratio of water to acetaldoxime is 10:1-20: 1.

9. The method for separating and purifying aldoxime according to claim 1, which comprises the following steps: in the step 3), the toluene obtained by separation is directly recycled to the step 2).

10. The method for separating and purifying aldoxime according to claim 1, which comprises the following steps: in the step 4), carrying out reduced pressure rectification, and collecting fractions with the vacuum degree of-0.075 Mpa and the tower top temperature of 48-49 ℃ to obtain an acetaldoxime product with the acetaldoxime mass fraction of 50% and the purity of 99.9%; and (4) recycling the residual aqueous solution in the tower bottom into the step 3) as an extracting agent.

Technical Field

The invention relates to the technical field of oxime separation and purification, in particular to a method for separating and purifying acetaldoxime.

Background

The acetaldoxime is an organic intermediate, and is mainly used for synthesizing pesticide methomyl; meanwhile, the reagent is an important organic synthesis and analysis reagent, is mainly used as a reducing agent and a deoxidant, and has the advantages of low price, low toxicity, good deoxidization effect and the like. At present, the production process of the acetaldoxime mainly comprises the following steps: the production method adopts hydroxylamine hydrochloride or hydroxylamine sulfate to be directly oximated with acetaldehyde, and has the advantages of complex production process, high production cost, long reaction flow, byproduct generation and environmental friendliness; in the second process, acetaldehyde, ammonia and peroxide are directly subjected to an acetaldoxime synthesis reaction in an alcohol solvent in a proper catalyst, and the catalyst adopted in the process is expensive and complex to prepare; the third process adopts an oxime exchange method, and has the advantages of simple process, mild reaction conditions, environmental friendliness, high acetaldehyde conversion rate, high acetaldoxime selectivity and no by-product. A method for preparing acetaldoxime (patent No. CN104628597A) discloses a method for preparing acetaldoxime by ketoxime oxime exchange, which mainly adopts acetone oxime or butanone oxime as raw materials to synthesize acetaldoxime, and the production method of acetone oxime and butanone oxime mainly completes an ammoximation reaction under the action of a TS-1 catalyst. However, TS-1 is mainly designed for ammoximation research of cyclohexanone, and although TS-1 can be used for ammoximation research of other ketones, such as acetone and butanone, the conversion rate and selectivity are not the same as those of cyclohexanone. In recent years, along with the maturity of the TS-1 catalyst synthesis technology and the reduction of the cost, the production cost of the cyclohexanone oxime is also greatly reduced; moreover, the production scale of cyclohexanone oxime reaches the million ton grade, the raw material supply is sufficient, while the production scale of acetone oxime/butanone oxime is below ten thousand ton grade, the downstream production is greatly influenced by the raw material, and the market price is higher than that of cyclohexanone oxime.

The method for preparing the acetaldoxime by cyclohexanone oxime exchange has the advantages of high conversion rate of cyclohexanone oxime, good selectivity, clean process, good economy, good industrialization prospect, and great potential in developing environment-friendly processes and promoting sustainable development. But the acetaldoxime and the cyclohexanone are azeotropic, and qualified acetaldoxime and cyclohexanone products cannot be obtained by separation through a simple rectification operation.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for separating and purifying acetaldoxime, which has the advantages of simple operation, high acetaldoxime purity and yield and no waste liquid, and is an environment-friendly green process route for producing, separating and purifying acetaldoxime.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a method for separating and purifying acetaldoxime comprises the following steps:

1) performing oxime exchange reaction on cyclohexanone oxime and acetaldehyde to prepare an acetaldoxime reaction solution, neutralizing with alkali, and controlling the pH value of the acetaldoxime reaction solution to be 7 after neutralization;

2) adding toluene into the acetaldoxime reaction solution, carrying out reduced pressure rectification, and separating acetaldoxime and cyclohexanone to obtain acetaldoxime toluene mixed solution and cyclohexanone respectively;

3) adding the obtained acetaldoxime toluene mixed solution into extractant water, and separating toluene and acetaldoxime by adopting a continuous extraction process to respectively obtain an acetaldoxime aqueous solution and toluene;

4) and (3) rectifying the acetaldoxime aqueous solution under reduced pressure to obtain an acetaldoxime product.

Preferably, in the step 1), the reaction of preparing the acetaldoxime by performing an oxime exchange process on cyclohexanone oxime and acetaldehyde comprises the following steps: adding cyclohexanone oxime and acid, dropwise adding anhydrous acetaldehyde at 4-10 ℃, continuously stirring and reacting for 1-2h at normal temperature and normal pressure after the dropwise adding of the anhydrous acetaldehyde is finished, obtaining an acetaldoxime reaction solution, and neutralizing with alkali.

Further preferably, in the step 1), in the reaction for preparing the acetaldoxime by performing an oxime exchange process on cyclohexanone oxime and acetaldehyde: acetaldehyde: cyclohexanone oxime: the molar ratio of the acid is 1-1.6:1: 0.01.

More preferably, in the step 1), the acid is 40-70% sulfuric acid by mass concentration, and the alkali used for neutralizing the reaction solution is NaOH solid. Because the sodium sulfate generated after the reaction of the sulfuric acid and the sodium hydroxide has the property of easy water absorption, the trace water in the reaction can be well eliminated, and the anhydrous condition in the rectification is fully ensured.

Preferably, in step 2), the molar ratio of toluene to acetaldoxime is 1:1 to 10: 1.

Further preferably, in step 2), the molar ratio of toluene to acetaldoxime is 4:1 to 8: 1.

Still more preferably, in step 2), the molar ratio of toluene to acetaldoxime is 4: 1.

Preferably, in the step 2), the mixture is rectified under reduced pressure, and fractions with the vacuum degree of 0.06-0.065Mpa and the temperature of 66-71 ℃ are collected to obtain the acetaldoxime toluene mixture.

Preferably, in the step 2), the mixture is rectified under reduced pressure, and the fraction with the vacuum degree of 0.06-0.065Mpa and the temperature of 66-71 ℃ is collected to obtain the acetaldehyde oxime toluene mixed solution with the content of 15-25% (Wt%).

Preferably, in the step 2), the distillation is carried out under reduced pressure, and fractions with the vacuum degree of 0.06-0.065Mpa and the temperature of 83-90 ℃ are collected to obtain cyclohexanone, wherein the purity of the cyclohexanone is more than or equal to 99%.

Preferably, in step 3), the molar ratio of water to acetaldoxime is 10:1 to 20: 1.

Further preferably, in step 3), the molar ratio of water to acetaldoxime is from 13:1 to 18: 1.

Still more preferably, in step 3), the molar ratio of water to acetaldoxime is 18: 1.

Preferably, in step 3), the toluene obtained by separation is directly recycled to step 2).

Preferably, in the step 4), carrying out reduced pressure rectification, collecting fractions with the vacuum degree of-0.075 Mpa and the tower top temperature of 48-49 ℃, and obtaining an acetaldoxime product with the mass fraction of 50% and the purity of 99.9%; and (4) recycling the residual aqueous solution in the tower bottom into the step 3) as an extracting agent.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in:

(1) the method for separating and purifying the acetaldoxime provided by the invention utilizes an organic solvent toluene to destroy an azeotropic system of the acetaldoxime and cyclohexanone under an anhydrous condition, so that a new azeotropic system toluene-acetaldoxime is formed, and the purpose of separating the acetaldoxime and the cyclohexanone is achieved;

(2) the method can obtain cyclohexanone (more than or equal to 99 percent) with higher purity in the rectification process, and can be sold again, thereby reducing the cost;

(3) and (3) continuously extracting the toluene-acetaldoxime mixed solution obtained by rectification to finally realize the separation of toluene and acetaldoxime. The solvent toluene and water adopted in the separation process can be recycled, so that the cost is reduced; the method is simple to operate, the acetaldoxime purity and the yield are high (the acetaldoxime purity is 99.9%, the yield can reach 97%), no waste liquid is generated in the separation and purification process, and the method is an environment-friendly green process route for producing, separating and purifying acetaldoxime.

Drawings

The invention is described in further detail below with reference to the drawings and the detailed description;

FIG. 1 is a schematic diagram of a process flow structure of a method for separating and purifying acetaldoxime of the present invention;

in the figure, 1, a rectifying tower I; 2. a cyclohexanone storage tank; 3. a toluene aldoxime mixed solution storage tank; 4. an extraction device; 5. an acetaldoxime aqueous solution buffer tank; 6. a rectifying tower II; 7. a condensing unit.

Detailed Description