阅读说明：本技术 一种选择性合成n-烷基氨基丙酸盐溶液的方法 (Method for selectively synthesizing N-alkyl amino propionate solution ) 是由 周华 彭波 谭颖 于 2020-07-29 设计创作，主要内容包括：本发明属于有机合成技术领域,具体公开了一种选择性合成N-烷基氨基丙酸盐溶液的方法,以烷基伯胺和丙烯酸酯为原料,通过将丙烯酸酯滴加至过量烷基伯胺中搅拌反应,使得反应向生成N-烷基氨基丙酸酯的方向进行,再加入碱金属氢氧化物水溶液将N-烷基氨基丙酸酯转化为N-烷基氨基丙酸盐,过量的烷基伯胺采用有机溶剂萃取除去,实现N-烷基氨基丙酸盐的选择性合成。本发明可得到高纯度的N-烷基氨基丙酸盐,杂质含量能降到5%以下；而且不需要高温高压和复杂的结晶纯化步骤,简便易行；使用到的原料和溶剂都可以回收再次利用,非常节能环保。(The invention belongs to the technical field of organic synthesis, and particularly discloses a method for selectively synthesizing N-alkyl amino propionate solution, which comprises the steps of taking alkyl primary amine and acrylic ester as raw materials, dropwise adding acrylic ester into excessive alkyl primary amine, stirring for reaction, enabling the reaction to be carried out in the direction of generating N-alkyl amino propionate, adding an alkali metal hydroxide aqueous solution to convert N-alkyl amino propionate into N-alkyl amino propionate, and removing excessive alkyl primary amine by adopting an organic solvent for extraction, so as to realize the selective synthesis of the N-alkyl amino propionate. The invention can obtain high-purity N-alkyl amino propionate, and the impurity content can be reduced to below 5 percent; and does not need high temperature and high pressure and complicated crystallization purification steps, thus being simple and easy to operate; the used raw materials and the solvent can be recycled, so that the energy is saved and the environment is protected.)

1. A method for selectively synthesizing a solution of N-alkyl amino propionic acid salts, characterized in that: the method comprises the following steps:

s1: taking alkyl primary amine and acrylic ester as raw materials, dropwise adding 1 molar equivalent of acrylic ester into liquid 1.5-5 molar equivalents of alkyl primary amine, reacting for 5-48 hours at the temperature of 10-100 ℃, and stirring in the whole process;

s2: adding 1.0-2.0 molar equivalent of 0.5-2.0 mol/L alkali metal hydroxide aqueous solution into the reaction solution, and reacting at 10-100 ℃ for 10-48 hours;

s3: adding pure water with the mass 5-20 times that of the primary alkyl amine into the reaction solution, and then extracting for 1-5 times by using an organic solvent with the mass 1-10 times that of the primary alkyl amine;

s4: collecting the organic layer to recover the organic solvent and the alkyl primary amine raw material; the obtained aqueous solution is subjected to reduced pressure distillation at the temperature of 30-80 ℃ and the pressure of 0-0.03 MPa until the weight content of the N-alkyl amino propionate is 10-40%.

2. The process for the selective synthesis of solutions of N-alkylaminopropionic acids according to claim 1, characterized in that: the acrylate refers to a molecular formula of CH₂Compounds of formula i = CHCOOR1 wherein R1 denotes methyl, ethyl or propyl.

3. The process for the selective synthesis of solutions of N-alkylaminopropionates according to claim 1 or 2, characterized in that: the alkyl primary amine refers to the molecular formula of RNH₂Wherein R denotes an alkane group consisting of from 6 to 24 carbon atoms.

4. The process for the selective synthesis of solutions of N-alkylaminopropionic acids according to claim 1, characterized in that: the organic solvent is esters, alkanes, ethers or halogenated alkanes.

5. The process for the selective synthesis of solutions of N-alkylaminopropionic acids according to claim 1, characterized in that: in step S1, 1 molar equivalent of acrylate is added dropwise to 2 to 3 molar equivalents of liquid primary alkylamine, and the mixture is reacted at a temperature of 20 to 40 ℃ for 15 to 24 hours.

6. The process for the selective synthesis of solutions of N-alkylaminopropionates according to claim 1 or 5, characterized in that: in the step S1, the dropping speed of the acrylic ester is controlled to be 1-5 hours, and the stirring speed is 50-200 r/min.

7. The process for the selective synthesis of solutions of N-alkylaminopropionic acids according to claim 1, characterized in that: in step S2, 1.0 to 1.2 molar equivalents of an alkali metal hydroxide aqueous solution having a concentration of 0.8 to 1.2 mol/liter is added to the reaction solution, and the reaction is carried out at a temperature of 20 to 60 ℃ for 15 to 24 hours.

8. The process for the selective synthesis of solutions of N-alkylaminopropionates according to claim 1 or 7, characterized in that: in step S2, the alkali metal hydroxide aqueous solution is a sodium hydroxide solution or a potassium hydroxide solution.

9. The process for the selective synthesis of solutions of N-alkylaminopropionic acids according to claim 1, characterized in that: in the step S3, pure water with the mass 10-15 times that of the primary alkylamine is added into the reaction solution, and then an organic solvent S1 with the mass 3-5 times that of the primary alkylamine is used for extraction for 2-4 times.

10. The process for the selective synthesis of solutions of N-alkylaminopropionic acids according to claim 1, characterized in that: in step S4, the obtained aqueous solution is distilled under reduced pressure at 45-65 ℃ and 0-0.03 MPa until the weight content of N-alkyl amino propionate is 10-20%.

Technical Field

The invention belongs to the technical field of organic synthesis, and particularly relates to a method for selectively synthesizing an N-alkyl amino propionate solution.

Background

N-alkyl aminopropionates and N-alkyl aminopropionates are two very useful classes of surfactants, widely used as cleaning agents, emulsifiers, flotation agents, and plating additives, among others. The synthesis of these two compounds is basically obtained by the conversion of aliphatic amines and α, β -unsaturated acids, nitriles or esters under certain conditions, but the reaction products are mixed with N-alkyl aminopropionates and N-alkyl aminopropionates, which are required to be selectively prepared in high purity due to the difference in their hydrophilic and lipophilic properties and the wide use in household detergents and cosmetics.

U.S. Pat. No. 4,000,691,691 discloses the preparation of N-alkyl aminopropionic acids/esters by reacting aliphatic amines with acrylic esters. The excess of acrylic ester in the reaction is 10-30%, raising the reaction temperature to 60-120 ℃ is advantageous for obtaining the maximum proportion of N-alkylaminopropionic acid/ester/salt, but this method, besides the unavoidable di-acrylic ester addition product, also gives the N-alkylaminopropionamide, an acrylic ester aminolysis by-product. U.S. Pat. No. 5,5922909 describes a method of adjusting the ratio of N-alkylaminopropionate to N-alkylaminopropionate by controlling the pH of the reaction, but the adjustment range is not so large that an absolute advantage cannot be obtained. Therefore, it is difficult to obtain N-alkyl aminopropionates singly by the conventional synthetic methods.

Disclosure of Invention

In order to solve the problems, the invention provides a method for selectively synthesizing N-alkyl amino propionate solution, which can obtain high-purity N-alkyl amino propionate and has simple process.

In order to achieve the purpose, the invention adopts the following specific technical scheme:

a process for the selective synthesis of a solution of N-alkylaminopropionic acid salts comprising the steps of:

s1: taking alkyl primary amine and acrylic ester as raw materials, dropwise adding 1 molar equivalent of acrylic ester into liquid 1.5-5 molar equivalents of alkyl primary amine, reacting for 5-48 hours at the temperature of 10-100 ℃, and stirring in the whole process;

s2: adding 1.0-2.0 molar equivalent of 0.5-2.0 mol/L alkali metal hydroxide aqueous solution into the reaction solution, and reacting at 10-100 ℃ for 10-48 hours;

s3: adding pure water with the mass 5-20 times that of the primary alkyl amine into the reaction solution, and then extracting for 1-5 times by using an organic solvent with the mass 1-10 times that of the primary alkyl amine;

s4: collecting the organic layer to recover the organic solvent and the alkyl primary amine raw material; distilling the obtained aqueous solution under reduced pressure at the temperature of 30-80 ℃ and the pressure of 0-0.03 MPa until the weight content of the N-alkyl amino propionate is 10-40 percent;

note: the molar equivalents are a relative term, and in the present invention specifically refer to the acrylates: alkyl primary amine: the molar ratio of alkali metal hydroxide is 1: (1.5-5): (1.0-2.0).

Preferably, the acrylate refers to the formula CH₂Compounds of formula i = CHCOOR1 wherein R1 denotes methyl, ethyl or propyl.

Preferably, the alkyl primary amine is represented by the formula RNH₂Wherein R denotes an alkane group consisting of from 6 to 24 carbon atoms.

Preferably, the organic solvent is an ester, an alkane, an ether or a halogenated alkane. Wherein: esters such as ethyl acetate, butyl acetate, etc., alkanes such as n-hexane, petroleum ether, etc., ethers such as diethyl ether, methyl t-butyl ether, etc., halogenated alkanes such as methylene chloride, chloroform, etc.

Preferably, in step S1, 1 molar equivalent of acrylate is added dropwise to 2 to 3 molar equivalents of liquid primary alkylamine, and the mixture is reacted at 20 to 40 ℃ for 15 to 24 hours.

Preferably, in step S1, the dropping speed of the acrylic ester is controlled to be 1-5 hours, and the stirring speed is 50-200 rpm.

Preferably, in step S2, 1.0 to 1.2 molar equivalents of an aqueous alkali metal hydroxide solution having a concentration of 0.8 to 1.2 mol/liter is added to the reaction solution, and the reaction is carried out at a temperature of 20 to 60 ℃ for 15 to 24 hours.

Preferably, in step S2, the alkali metal hydroxide aqueous solution is a sodium hydroxide solution or a potassium hydroxide solution.

Preferably, in step S3, pure water in an amount 10 to 15 times the mass of the primary alkylamine is added to the reaction solution, and then the mixture is extracted 2 to 4 times with an organic solvent S1 in an amount 3 to 5 times the mass of the primary alkylamine.

Preferably, in step S4, the obtained aqueous solution is distilled under reduced pressure at 45-65 ℃ and 0-0.03 MPa until the weight content of N-alkyl amino propionate is 10-20%.

According to the method, alkyl primary amine and acrylic ester are used as raw materials, the acrylic ester and excessive alkyl primary amine react to generate N-alkyl amino propionate, then alkali metal hydroxide aqueous solution is added to convert the N-alkyl amino propionate into N-alkyl amino propionate, the excessive alkyl primary amine is removed by adopting organic solvent extraction, and the selective synthesis of the N-alkyl amino propionate is realized.

The invention has the following beneficial effects:

1. the acrylic ester is dripped into excessive alkyl primary amine, and the reaction direction is controlled by combining stirring, so that the generation of N-alkyl amino dipropionate is reduced, and the purity is improved. Specifically, the acrylic ester is dripped to react with excessive alkyl primary amine, so that the aggregation of the acrylic ester can be avoided, the N-alkyl amino propionate obtained by the reaction can be quickly transferred by stirring, and the N-alkyl amino propionate is prevented from contacting with the acrylic ester to generate the N-alkyl amino dipropionate.

2. The addition of aqueous alkali metal hydroxide solution converts the N-alkyl amino propionate into N-alkyl amino propionate, and simultaneously, the reaction of the acrylate and the alkyl primary amine is more thorough, thereby improving the conversion rate (the N-alkyl amino propionate is rapidly transferred from an organic phase to the aqueous alkali metal hydroxide solution while the aqueous alkali metal hydroxide solution is added, so that the residual raw materials in the organic phase can be continuously reacted). More optimally, the alkali metal hydroxide is strong alkaline sodium hydroxide or potassium hydroxide, so that the hydrolysis speed can be accelerated, and the conversion efficiency can be improved.

3. The yield of N-alkyl amino propionate is improved by adding pure water for extraction. The reaction solution is divided into an alkyl primary amine organic layer and an alkali metal hydroxide solution layer after the hydrolysis process, and the product has strong hydrophilicity but also has hydrophobic groups, so that the two layers are distributed, and the method has the advantages that pure water with the mass 5-20 times of that of the alkyl primary amine is added and then the organic solvent is added for extraction, so that the product is basically separated from the organic layer, the entrainment of the organic reagent is reduced, the yield is effectively improved, and the purity of the product is not influenced; and the product is diluted after the pure water is added, so that the concentration of the product is reduced, and the extraction loss can be effectively reduced.

4. The invention can obtain high-purity N-alkyl amino propionate, and the impurity content can be reduced to below 5 percent; and does not need high temperature and high pressure and complicated crystallization purification steps, thus being simple and easy to operate; the used raw materials and the solvent can be recycled, so that the energy is saved and the environment is protected.

Detailed Description

The present invention will be further described with reference to the following specific examples.