Preparation method of 2-pyrrolidone

Abstract

The invention provides a preparation method of 2-pyrrolidone, which comprises the following steps: by taking gamma-butyrolactone and liquid ammonia as raw materials, premixing to generate 4-hydroxybutyramide, then removing excessive liquid ammonia, and then dehydrating the 4-hydroxybutyramide to synthesize the 2-pyrrolidone. According to the method disclosed by the invention, the 2-pyrrolidone is synthesized by firstly deaminating and then dehydrating, so that the contents of light and heavy components are effectively reduced, and the yield can reach 95% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and in particular to a method for preparing 2-pyrrolidone. Background Art

[0002] Pyrrolidone is an excellent organic solvent and important intermediate. It is widely used in medicine, dyes, inks, coatings, textiles, papermaking, etc. It is used to prepare N-vinylpyrrolidone, aminobutyric acid, etc.

[0003] Currently, the industrial production of 2-pyrrolidone typically employs the amination of 1,4-butyrolactone (GBL, i.e., γ-butyrolactone) method, using zeolite, mesoporous silica, or solid superacids as catalysts and employing fixed-bed catalysis to prepare 2-pyrrolidone. This process requires high equipment investment, faces difficulties in separating the product from the catalyst, and presents high costs associated with the catalyst itself, resulting in high costs for large-scale industrial production.

[0004] Patent CN202110991933.1 uses a vertical wound tubular reactor to continuously prepare pyrrolidone and its derivatives using water as a solvent; Patent CN202210217376.2 uses a microchannel reactor to continuously prepare pyrrolidone and its derivatives using 25% industrial ammonia water; Patent CN02817318.X continuously prepares 2-pyrrolidone by reacting in the liquid phase in the presence of water. Although all of the above patents use continuous production methods, they all use water as a solvent, which has problems such as reaction coking, a large number of hydrolysis impurities, and low yield. Therefore, the existing technology needs further development. Summary of the Invention

[0005] In view of the various deficiencies of the prior art and in order to solve the above problems, a method for preparing 2-pyrrolidone is proposed, and the following technical solutions are provided: A method for preparing 2-pyrrolidone comprises the following steps: using gamma-butyrolactone and liquid ammonia as raw materials, premixing to generate 4-hydroxybutyramide, removing excess liquid ammonia, and then dehydrating the 4-hydroxybutyramide to synthesize 2-pyrrolidone.

[0006] Furthermore, the time for premixing to generate 4-hydroxybutyramide is 10-20 minutes, the pressure is 7.0-9.0 MPa, and the temperature is room temperature.

[0007] Furthermore, the time for premixing to generate 4-hydroxybutyramide is 15 minutes and the pressure is 8.0 MPa.

[0008] Furthermore, the dehydration synthesis of 2-pyrrolidone takes 10-60 minutes, the temperature is 240-300° C., and the pressure is 7.0-9.0 MPa.

[0009] Furthermore, the dehydration synthesis of 2-pyrrolidone takes 30 minutes at a temperature of 270° C. and a pressure of 9.0 MPa.

[0010] Furthermore, the molar ratio of γ-butyrolactone to liquid ammonia is 1:(2-4).

[0011] Furthermore, after premixing to generate 4-hydroxybutyramide, the mixture is decompressed and enters a flash tank to remove part of the ammonia, and then the remaining ammonia is removed by distillation in a deamination tower.

[0012] Furthermore, the mixer is filled with inert gas to 7.0-9.0 MPa, γ-butyrolactone and liquid ammonia are added to the mixer, mixed in the mixer for 10-20 minutes, and then excess liquid ammonia is removed before entering the pipeline reactor. The reaction temperature is increased to 240-300° C., the inert gas is filled to a pressure of 7.0-9.0 MPa, and the mixture is reacted for 10-60 minutes to obtain 2-pyrrolidone.

[0013] Furthermore, the inert gas is one or a mixture of nitrogen, argon, and helium.

[0014] Furthermore, the process of removing excess liquid ammonia is as follows: the 4-hydroxybutyramide reaction liquid is decompressed and enters a flash tank to remove most of the ammonia, and then distilled in a deamination tower to remove trace ammonia; the removed ammonia is condensed and pressurized into liquid ammonia and then recycled.

[0015] Furthermore, 4-hydroxybutyramide is dehydrated and then post-treated, and the post-treatment includes light removal, heavy removal, and crystallization.

[0016] Beneficial effects: Compared with the prior art method of first dehydrating and then deaminating, the present invention synthesizes 2-pyrrolidone by first deaminating and then dehydrating, thereby reducing the types of impurities in the reactants, eliminating the generation of impurities such as 1,4-butanediol, acrylonitrile, and butyrolactam, and reducing the probability of 2-pyrrolidone polymerization. The yield can reach more than 95%.

[0017] 2. The present invention uses inert gas as the pressure gas, which effectively reduces the amount of nitrogen-containing wastewater to be treated during the production process.

[0018] 3. The process of the present invention is simple, low in cost, and suitable for industrial-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the preparation principle of 2-pyrrolidone of the present invention. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by ordinary technicians in this field without making any creative work should fall within the scope of protection of this application.

[0021] According to an embodiment of the present invention, a method for preparing 2-pyrrolidone is provided, and the preparation method is as follows: using γ-butyrolactone and liquid ammonia as raw materials, premixing to generate 4-hydroxybutyramide, removing excess liquid ammonia, and then dehydrating 4-hydroxybutyramide to synthesize 2-pyrrolidone. The present invention first deaminates and then dehydrates to synthesize 2-pyrrolidone, which reduces the types of impurities in the reactants, and does not generate impurities such as 1,4-butanediol, acrylonitrile, and butyrolactam, thereby reducing the probability of 2-pyrrolidone polymerization, and the yield can reach more than 95%. The preparation principle of 2-pyrrolidone is as follows Figure 1 shown.

[0022] The premixing process to generate 4-hydroxybutyramide takes 10-20 minutes at a pressure of 7.0-9.0 MPa and room temperature. The dehydration process to synthesize 2-pyrrolidone takes 10-60 minutes at a temperature of 240-300°C and a pressure of 7.0-9.0 MPa. The reaction temperature and pressure must be strictly controlled during the reaction. Excessively low temperature and pressure will result in a lack of reaction and a large amount of residual raw materials. Excessively high temperature and pressure will cause the raw materials and products to polymerize, resulting in a low yield.

[0023] Excess liquid ammonia is recovered in a deammonification tower and recycled. Rectification is used for light ammonia removal, while thin-film evaporation is preferred for heavy ammonia removal. Plate crystallizers are preferred for crystallization. The excess liquid ammonia removal process involves depressurizing the 4-hydroxybutyramide reaction liquid into a flash tank to remove most ammonia, followed by rectification in a deammonification tower to remove trace amounts. The removed ammonia is condensed and pressurized into liquid ammonia for recycling.

[0024] Example 1 The mixer was filled with inert nitrogen gas to 8.0 MPa, and γ-butyrolactone was mixed at a rate of 5.6 g / min and liquid ammonia at a rate of 2.22 g / min in the mixer at room temperature for 15 minutes. After removing excess liquid ammonia, the mixture entered the pipeline reactor. The reaction temperature was increased to 240°C, and the inert nitrogen gas was filled to a pressure of 7.5 MPa. The reactants stayed in the reaction stage for 30 minutes. The reaction products were collected and passed through a distillation tower to remove light substances and a thin film evaporator to remove heavy substances, and then crystallized to obtain 2-pyrrolidone. After gas chromatography, the purity of 2-pyrrolidone was 99.6% and the yield was 95.5%.

[0025] Example 2 The mixer was filled with inert argon gas to 8.0 MPa, and γ-butyrolactone was mixed at a rate of 5.6 g / min and liquid ammonia at a rate of 4.43 g / min in the mixer at room temperature for 15 minutes. After removing excess liquid ammonia, the mixture entered the pipeline reactor. The reaction temperature was increased to 240°C, and the inert argon gas was filled to a pressure of 7.5 MPa. The reactants stayed in the reaction stage for 30 minutes. The reaction products were collected and then passed through a distillation tower to remove light substances and a thin film evaporator to remove heavy substances, and then crystallized to obtain 2-pyrrolidone. After gas chromatography, the purity of 2-pyrrolidone was 99.5% and the yield was 97.48%.

[0026] Example 3 The mixer was filled with inert helium gas to 8.0 MPa, and γ-butyrolactone was mixed at a rate of 5.6 g / min and liquid ammonia at a rate of 3.2 g / min in the mixer at room temperature for 15 minutes. After removing excess liquid ammonia, the mixture entered a pipeline reactor. The reaction temperature was increased to 300°C, and the inert helium gas was filled to a pressure of 8.5 MPa. The reactants stayed in the reaction stage for 10 minutes. The reaction products were collected and passed through a distillation tower to remove light substances and a thin film evaporator to remove heavy substances, and then crystallized to obtain 2-pyrrolidone. After gas chromatography, the purity of 2-pyrrolidone was 99.6% and the yield was 96.48%.

[0027] Example 4 The mixer was filled with inert helium gas to 7.5 MPa, and γ-butyrolactone was mixed at a rate of 5.6 g / min and liquid ammonia at a rate of 3.2 g / min in the mixer at room temperature for 10 minutes. After removing excess liquid ammonia, the mixture entered the pipeline reactor. The reaction temperature was increased to 270°C, and the inert helium gas was filled to a pressure of 9.0 MPa. The reactants stayed in the reaction stage for 10 minutes. The reaction products were collected and passed through a distillation tower to remove light substances and a thin film evaporator to remove heavy substances, and then crystallized to obtain 2-pyrrolidone. After gas chromatography, the purity of 2-pyrrolidone was 99.6%, and the yield was 96.38%.

[0028] Example 5 The mixer was filled with inert nitrogen gas to 9.0 MPa, and γ-butyrolactone was mixed at a rate of 5.6 g / min and liquid ammonia at a rate of 2.8 g / min in the mixer at room temperature for 15 minutes. After removing excess liquid ammonia, the mixture entered a pipeline reactor. The reaction temperature was increased to 240°C, and the inert nitrogen gas was filled to a pressure of 9.0 MPa. The reactants stayed in the reaction stage for 60 minutes. The reaction products were collected and then passed through a distillation tower to remove light substances and a thin film evaporator to remove heavy substances, and then crystallized to obtain 2-pyrrolidone. After gas chromatography, the purity of 2-pyrrolidone was 99.7% and the yield was 97.18%.

[0029] Comparative Example 1 The mixer was filled with inert nitrogen gas to 8.0 MPa, γ-butyrolactone was mixed at a rate of 5.6 g / min and liquid ammonia at a rate of 2.22 g / min in the mixer at room temperature for 15 minutes, and then entered into a pipeline reactor. The reaction temperature was increased to 260°C, and the inert nitrogen gas was filled to a pressure of 7.5 MPa. The reactants stayed in the reaction stage for 60 minutes. The reaction products were collected and deaminated in a deamination tower, de-light-phase was removed in a distillation tower, and de-heavy-phase was removed in a thin film evaporator. 2-pyrrolidone was crystallized. After gas chromatography detection, the purity of 2-pyrrolidone was 99.2%, and the yield was 75.68%.

[0030] Comparative Example 2 The mixer was filled with inert gas to 9.0 MPa, and γ-butyrolactone was mixed at a rate of 5.6 g / min and liquid ammonia at a rate of 4.22 g / min in the mixer at room temperature for 15 minutes and then entered into a pipeline reactor. The reaction temperature was increased to 270°C, and the inert gas nitrogen was filled to a pressure of 8.0 MPa. The reactants stayed in the reaction stage for 30 minutes. The reaction products were collected and deaminated in a deamination tower, de-light-phase was removed in a distillation tower, and de-heavy-phase was removed in a thin film evaporator. 2-pyrrolidone was then crystallized. After gas chromatography, the purity of 2-pyrrolidone was 99% and the yield was 68.68%.

[0031] Comparative Example 3 The mixer was filled with inert nitrogen gas to 9.0 MPa, and γ-butyrolactone was mixed at a rate of 5.6 g / min and liquid ammonia at a rate of 3.22 g / min in the mixer at room temperature for 15 minutes. After removing excess liquid ammonia, the mixture entered the pipeline reactor. The reaction temperature was raised to 330°C and the inert nitrogen pressure was filled to 9.5 MPa. The reactants stayed in the reaction stage for 45 minutes. The reaction products were collected and then removed by distillation tower and thin film evaporator. After removal of heavy phase, 2-pyrrolidone was crystallized. After gas chromatography, the purity of 2-pyrrolidone was 99.5%, and the yield was 88.48%. Comparative Example 4 The mixer was filled with inert nitrogen gas to 8.0 MPa, and γ-butyrolactone at a rate of 5.6 g / min, ammonia at a rate of 2.22 g / min, and water at a rate of 2.34 g / min were mixed in the mixer at room temperature for 15 minutes, and then excess ammonia was removed before entering the pipeline reactor. The reaction temperature was increased to 240°C, and the inert nitrogen gas was filled to a pressure of 7.5 MPa. The reactants stayed in the reaction stage for 30 minutes. The reaction products were collected and then passed through a distillation tower to remove light substances and a thin film evaporator to remove heavy substances, and then crystallized to obtain 2-pyrrolidone. After gas chromatography, the purity of 2-pyrrolidone was 99.5%, and the yield was 85.46%.

[0032] Comparative Example 5 The mixer was filled with inert nitrogen gas to 8.0 MPa, and γ-butyrolactone at a rate of 5.6 g / min, ammonia at a rate of 2.22 g / min, and water at a rate of 2.34 g / min were mixed in the mixer at room temperature for 15 minutes and then entered into a pipeline reactor. The reaction temperature was increased to 240°C, and the inert nitrogen gas was filled to a pressure of 7.5 MPa. The reactants stayed in the reaction stage for 30 minutes. The reaction products were collected and deaminated in a deamination tower, de-light-phase was removed in a distillation tower, and de-heavy-phase was removed in a thin film evaporator, and then crystallized to obtain 2-pyrrolidone. After gas chromatography detection, the purity of 2-pyrrolidone was 99.3%, and the yield was 76.58%.

[0033] As can be seen from the above examples and comparative examples, the present invention provides a new method for synthesizing 2-pyrrolidone with a yield of up to 97.48%. In particular, using inert gas to pressurize, first removing excess liquid ammonia and then dehydrating to synthesize 2-pyrrolidone can effectively reduce the formation of reactant impurities and improve the yield; temperature and pressure affect its conversion rate and impurity formation.

[0034] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing 2-pyrrolidone, characterized in that: The preparation method is as follows: γ-butyrolactone and liquid ammonia are used as raw materials, premixed to generate 4-hydroxybutyramide, and then excess liquid ammonia is removed and then dehydrated to synthesize 2-pyrrolidone.

2. The method for preparing 2-pyrrolidone according to claim 1, wherein The time for premixing to generate 4-hydroxybutyramide is 10-20 minutes, the pressure is 7.0-9.0 MPa, and the temperature is room temperature.

3. The method for preparing 2-pyrrolidone according to claim 1 or 2, wherein: The time for premixing to generate 4-hydroxybutyramide is 15 minutes and the pressure is 8.0 MPa.

4. The method for preparing 2-pyrrolidone according to claim 1, wherein The dehydration synthesis of 2-pyrrolidone takes 10-60 minutes, the temperature is 240-300° C., and the pressure is 7.0-9.0 MPa.

5. The method for preparing 2-pyrrolidone according to claim 1 or 4, wherein: The dehydration synthesis of 2-pyrrolidone takes 30 minutes at a temperature of 270° C. and a pressure of 9.0 MPa.

6. The method for preparing 2-pyrrolidone according to claim 1, wherein The molar ratio of the gamma-butyrolactone to the liquid ammonia is 1:(2-4).

7. The method for preparing 2-pyrrolidone according to claim 1, wherein: After premixing to generate 4-hydroxybutyramide, it is decompressed and enters a flash tank to remove part of the ammonia, and then the remaining ammonia is distilled in a deamination tower.

8. The method for preparing 2-pyrrolidone according to claim 1, wherein The mixer is filled with inert gas to 7.0-9.0 MPa, γ-butyrolactone and liquid ammonia are added to the mixer, mixed in the mixer for 10-20 minutes, and then excess liquid ammonia is removed before entering the pipeline reactor. The reaction temperature is increased to 240-300°C, the inert gas is filled to a pressure of 7.0-9.0 MPa, and the mixture is reacted for 10-60 minutes to obtain 2-pyrrolidone.

9. The method for preparing 2-pyrrolidone according to claim 8, wherein: The inert gas is nitrogen, argon, helium or a mixture of several of them.

10. The method for preparing 2-pyrrolidone according to claim 1, wherein: After the 4-hydroxybutyramide is dehydrated, a post-treatment is performed, and the post-treatment includes light removal, heavy removal, and crystallization.

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