阅读说明：本技术 一种聚α-羟基丙烯酸的制备方法 (Preparation method of poly alpha-hydroxy acrylic acid ) 是由 周响 程终发 申义驰 陆久田 于 2020-06-01 设计创作，主要内容包括：本发明公开了一种聚α-羟基丙烯酸的制备方法,具体是以丙酮酸为原料,以无水乙醇为溶剂,在催化剂环境下,通过管式反应器合成反应,再经过滤,蒸馏,水洗等处理,得聚α-羟基丙烯酸水溶液。本发明采用丙酮酸替代二氯代丙酸为原料,不仅价格低廉,降低成本,且原料本身相对安全稳定,毒副作用小；生产过程中避免了氯气等卤素的使用,生产安全系数提高；所用溶剂和催化剂均可回收再用,同时无盐酸等废酸产生,绿色环保。(The invention discloses a preparation method of poly alpha-hydroxy acrylic acid, which particularly takes pyruvic acid as a raw material and absolute ethyl alcohol as a solvent, and obtains a poly alpha-hydroxy acrylic acid aqueous solution through a tubular reactor synthesis reaction, filtration, distillation, water washing and other treatments under the environment of a catalyst. The invention adopts pyruvic acid to replace dichloropropionic acid as raw material, which not only has low price and reduced cost, but also has relatively safe and stable raw material and small toxic and side effect; the use of halogens such as chlorine and the like is avoided in the production process, and the production safety coefficient is improved; the used solvent and catalyst can be recycled, and meanwhile, no waste acid such as hydrochloric acid is generated, so that the method is green and environment-friendly.)

1. A method for preparing poly alpha-hydroxyacrylic acid, which is characterized by comprising the following steps:

(1) uniformly premixing pyruvic acid, absolute ethyl alcohol and sodium peroxide, and heating to 75-78 ℃;

(2) fixing a set of catalyst carriers in a tubular reactor every 0.5-1 m, enabling the mixed solution to pass through the tubular reactor and a heating tubular reactor at a constant speed, after 4-6 hours, enabling the mixed solution to flow out of the tubular reactor, filtering, and distilling to separate pyruvic acid and ethanol to obtain a crude poly alpha-hydroxyacrylic acid product;

(3) washing the crude poly alpha-hydroxy acrylic acid with water to obtain poly alpha-hydroxy acrylic acid aqueous solution.

2. The method according to claim 1, wherein the molar ratio of the pyruvic acid to the absolute ethyl alcohol in the step (1) is 1: 1-2; the molar ratio of the sodium peroxide to the pyruvic acid is 0-0.1: 1.

3. The method of claim 1, wherein the pyruvic acid is previously treated with an inorganic base to form pyruvate.

4. The method according to claim 1, wherein the tubular reactor in the step (2) has a diameter of 5 to 10cm and a total length of 50 to 150 m.

5. The process of claim 1, wherein the catalyst support in step (2) consists of two parts, a sodium ethoxide support and a metallocene catalyst support.

6. The method according to claim 1 or 5, wherein the carrier supporting material in the step (2) is mesoporous molecular sieve SBA-15, and the sodium ethoxide and the supporting material are fixed by a physical mode; the metallocene catalyst and the load material are fixedly connected through a cocatalyst.

7. The process of claim 6, wherein the metallocene catalyst has a central metal of iron, titanium or zirconium and a cocatalyst of alkylaluminoxane.

8. The method according to claim 5, wherein the catalyst carriers are of a grid structure, each carrier has a cross section equivalent to that of the tubular reactor, has a thickness of 1-2 cm, and is alternately connected for 3-5 times.

9. The method according to claim 1, wherein the distillation in the step (2) adopts negative pressure distillation, and the negative pressure range is-0.1 MPa to-0.07 MPa.

10. The method of claim 1, wherein the fractionated pyruvic acid and ethanol of step (2) are reused for production.

Technical Field

The invention relates to the technical field of fine chemicals, in particular to a preparation method of poly alpha-hydroxyacrylic acid.

Background

Poly-alpha-hydroxy acrylic acid is used as a novel important industrial raw material and widely applied to industries such as paper making industry, paint, graphite, dyeing auxiliary agents and the like, and the structural hydroxyl and carboxyl groups of the poly-alpha-hydroxy acrylic acid provide excellent chemical characteristics and can be used for preparing auxiliary agents such as chelating agents, plasticizers, coupling agents and the like.

Japanese patent CN1260270C proposes a method for preparing an aqueous solution of poly-alpha-hydroxyacrylate. In particular, a polylactone compound of poly-alpha-hydroxy acrylic acid and alkali are subjected to hydrolysis reaction to generate a poly-alpha-hydroxy acrylic acid salt aqueous solution. The method does not involve monomer synthesis and cannot meet the requirement of industrial production. DE2061584 proposes a process for obtaining poly-alpha-hydroxyacrylic acids by polymerization of monomeric alpha-haloacrylic acids in the presence of organic solvents and free-radically active catalysts. The alpha-halogenated acrylic acid for polymerization by the method is difficult to exist in a pure form, and is usually reacted by using dihalopropionic acid, the dihalopropionic acid is expensive, and a large amount of halogen simple substances are consumed in the self-manufacturing process to generate a large amount of acid, so that the process risk coefficient is large, the environmental protection cost is high, and the method is not favorable for industrial popularization.

In order to overcome the defects of the problems, the invention provides a method for preparing poly alpha-hydroxy acrylic acid aqueous solution by using acrylic acid as a monomer.

Disclosure of Invention

The invention provides a preparation method of poly alpha-hydroxyacrylic acid, which replaces dihalogenated propionic acid with pyruvic acid, reduces cost, is safe and environment-friendly, and mainly comprises the following steps:

(1) premixing a certain amount of pyruvic acid, absolute ethyl alcohol and sodium peroxide uniformly, and heating to 75-78 ℃;

(2) fixing a set of catalyst carriers in a tubular reactor every 0.5-1 m, enabling the mixed solution to pass through the tubular reactor at a constant speed according to a certain flow, heating the outer wall of the tubular reactor through steam, enabling the mixed solution to flow out of the tubular reactor after 4-6 hours, filtering, and distilling under negative pressure to separate pyruvic acid and ethanol to obtain a crude poly alpha-hydroxyacrylic acid product;

(3) washing the crude poly alpha-hydroxy acrylic acid to obtain poly alpha-hydroxy acrylic acid aqueous solution with the mass fraction of about 25%;

(4) the fractionated pyruvic acid and ethanol are reused for production.

Wherein the molar ratio of the pyruvic acid to the absolute ethyl alcohol in the step (1) is 1: 1-2, and the molar ratio of the sodium peroxide to the pyruvic acid is 0-0.1:1, preferably 0.05 to 0.08: 1.

wherein, the pyruvic acid is treated by inorganic alkali such as sodium hydroxide to form pyruvate.

Wherein, in the step (2), the diameter of the tubular reactor is 5-10 cm, the total length is 50-150 m, and preferably 70-100 m.

The catalyst carrier in the step (2) consists of a sodium ethoxide carrier and a metallocene catalyst carrier, both of which are of a leaky net structure, the section of each carrier is equivalent to that of the tubular reactor, the thickness of each carrier is 1-2 cm, and the carriers are alternately connected for 3-5 times.

The carrier load material is mesoporous molecular sieve SBA-15, sodium ethoxide and the load material are fixed in a physical mode, the metallocene catalyst and the load material are fixedly connected through a cocatalyst, the central metal of the metallocene catalyst can be iron, titanium, zirconium and the like, and the cocatalyst can be alkylaluminoxane and the like.

Wherein, the flow rate of the mixed liquid entering the tubular reactor in the step (2) is determined by the inner diameter of the tubular reactor and the time of flowing through the tubular reactor.

Wherein the negative pressure range in the step (2) is-0.1 MPa to-0.07 MPa.

The related chemical formula is:

。

the beneficial effects of the invention are as follows:

the invention adopts pyruvic acid to replace dichloropropionic acid as raw material, which not only has low price and reduced cost, but also has relatively safe and stable raw material and small toxic and side effect; the use of halogens such as chlorine and the like is avoided in the production process, and the production safety coefficient is improved; the used solvent and catalyst can be recycled, and meanwhile, no waste acid such as hydrochloric acid is generated, so that the method is green and environment-friendly.

Detailed Description

The present invention is described in detail below by way of examples, which are intended to be illustrative only and not to be construed as limiting the scope of the invention, and one skilled in the art will be able to make variations within the scope of the invention based on the disclosure herein, in reagents, catalysts and reaction process conditions. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

The pyruvic acid content is 98.0%;

the total length of the tubular reactor is 100m, and the diameter is 10 cm;

the catalyst carrier is a disc with the diameter of 10cm and the thickness of 1cm, and different catalysts are put into the respective carriers.

Example 1

The method comprises the following steps: adding 900kg of sodium pyruvate and 920kg of absolute ethyl alcohol into a mixing kettle in sequence, starting stirring and heating to 76 ℃, introducing the mixed reaction liquid into a tubular reactor at a constant speed according to the flow of 195L/h, heating the tubular reactor by heating jacket steam, placing a set of catalyst components every 1m in the tubular reactor, wherein each set of catalyst components consists of a metallocene catalyst carrier and a sodium ethoxide catalyst carrier alternately for 3 times;

step two: after 4.03h, the reaction solution begins to flow out of the tubular reactor, is filtered and injected into an external steaming kettle, ethanol and pyruvic acid are separated by distillation under the pressure of-0.07 MPa, and the residual components are diluted by 1900kg of pure water to obtain 2540kg of poly alpha-hydroxyacrylic acid aqueous solution with the mass fraction of 25.1%.

Step three: and (5) distilling the separated ethanol and pyruvic acid, and repeating the first step for recycling.

Wherein, the primary conversion rate of pyruvic acid is 72.4%, the chroma of the product is 13, the average molecular weight is 2296, and the viscosity is 2103.

Example 2

The method comprises the following steps: adding 900kg of sodium pyruvate and 460kg of absolute ethyl alcohol into a mixing kettle in sequence, starting stirring and heating to 78 ℃, introducing the mixed reaction liquid into a tubular reactor at a constant speed according to the flow of 131L/h, heating the tubular reactor by heating jacket steam, placing a set of catalyst components every 0.5m in the tubular reactor, wherein each set of catalyst components consists of a metallocene catalyst carrier and a sodium ethoxide catalyst carrier alternately for 5 times;

step two: after 6.0h, the reaction solution begins to flow out of the tubular reactor, the reaction solution is filtered and injected into an external steaming kettle, ethanol and pyruvic acid are separated by distillation under the pressure of-0.1 MPa, and 2486kg of poly alpha-hydroxyacrylic acid aqueous solution with the mass fraction of 25.5 percent is obtained after 1850kg of pure water is added to dilute the residual components.

Step three: and (5) distilling the separated ethanol and pyruvic acid, and repeating the first step for recycling.

Wherein, the primary conversion rate of pyruvic acid is 71.9%, the chroma of the product is 12, the average molecular weight is 2328, and the viscosity is 2135.

Example 3

The method comprises the following steps: adding 900kg of sodium pyruvate, 920kg of absolute ethyl alcohol and 46.8kg of sodium peroxide into a mixing kettle in sequence, starting stirring and heating to 76 ℃, introducing the mixed reaction liquid into a tubular reactor at a constant speed according to the flow of 195L/h, heating the tubular reactor by heating jacket steam, placing a set of catalyst components every 1m in the tubular reactor, wherein each set of catalyst components consists of a metallocene catalyst carrier and a sodium ethoxide catalyst carrier alternately for 3 times;

step two: after 4.03h, the reaction solution begins to flow out of the tubular reactor, is filtered and injected into an external steaming kettle, ethanol, water and pyruvic acid are separated by distillation under the pressure of-0.07 MPa, and the residual components are diluted by 1900kg of pure water to obtain 2540kg of poly alpha-hydroxyacrylic acid aqueous solution with the mass fraction of 25.1%.

Step three: and (5) distilling the separated ethanol and pyruvic acid, and repeating the first step for recycling.

Wherein, the primary conversion rate of pyruvic acid is 76.3%, the product chroma is 13, the average molecular weight is 2274, and the viscosity is 2097.