Catalytic synthesis process of alpha-pyrrolidone

Abstract

The invention belongs to the field of organic chemical synthesis, and relates to a catalytic synthesis process of alpha-pyrrolidone, which comprises the following steps: S1, mixing gamma-butyrolactone with ammonia water, preheating, and introducing into a reactor filled with a catalyst; the catalyst comprises an alumina skeleton with a pore network, an inner core grown in the pore of the alumina skeleton, and mesoporous silica loaded with magnesium oxide. The inner core is mesoporous zirconium oxide loaded with phosphotungstic acid, and mesoporous silicon dioxide loaded with magnesium oxide is positioned on the surface of an aluminum oxide framework. S2, gamma-butyrolactone and ammonia water are subjected to a reaction at the temperature of 190-220 DEG C and under the pressure of 1.5-2.0 MPa, and a crude product is obtained; s3, the crude product is concentrated and rectified, and alpha-pyrrolidone is obtained. The catalytic synthesis process disclosed by the invention makes remarkable progress in the aspects of reducing energy consumption, relieving equipment burden, improving catalyst recoverability and the like, and has a good industrial application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of organic chemical synthesis, and particularly relates to a catalytic synthesis process of α-pyrrolidone. Background Art

[0002] α-Pyrrolidone, also known as 2-pyrrolidone, is a nitrogen-containing five-membered cyclic lactam compound with the molecular formula C4H7NO. It is a colorless and transparent liquid at room temperature, has strong polarity and hygroscopicity, and can be miscible with water and a variety of organic solvents.

[0003] As an important chemical intermediate, α-pyrrolidone is widely used in the fields of medicine, pesticides, and polymer materials. In the pharmaceutical field, α-pyrrolidone is not only a key synthetic raw material for antiviral drugs such as lopinavir and sedative piracetam, but also used for solubilizing poorly soluble drugs due to its excellent solubility. In the pesticide industry, α-pyrrolidone participates in the synthesis process of triazole fungicides such as cyproconazole. In the field of polymer materials, through ring-opening polymerization reaction, α-pyrrolidone can be used to prepare biodegradable nylon-4 fibers, and can also be used as an additive in lithium-ion battery electrolytes to improve their performance. In addition, α-pyrrolidone is widely used as an industrial solvent, liquid crystal cleaning agent, and polar solvent in organic synthesis reactions.

[0004] In the prior art, the industrial production of α-pyrrolidone mainly relies on the catalytic amination reaction between γ-butyrolactone and ammonia. This reaction is usually carried out at a high temperature of 250-280°C, and acidic substances are generally used as catalysts. However, this process still has the following problems in actual application:

[0005] First, the catalytic amination reaction between γ-butyrolactone and ammonia needs to be carried out at a relatively high temperature, resulting in high energy consumption and high requirements for the heat resistance and corrosion resistance of equipment.

[0006] Second, most of the existing processes use liquid acids as catalysts. Although they show certain catalytic activity, these catalysts are difficult to effectively separate from the reaction system and cannot be recycled, significantly reducing the process economy.

[0007] Therefore, it is necessary to provide a catalytic synthesis process of α-pyrrolidone with lower energy consumption, lower equipment requirements, and lower cost. Summary of the Invention

[0008] (I) Technical Problems to be Solved

[0009] In view of the above technical problems, in order to solve the problems of high energy consumption, high equipment requirements, and difficult recovery of catalysts in the catalytic synthesis process of α-pyrrolidone existing in the prior art, the present invention provides a catalytic synthesis process of α-pyrrolidone.

[0010] (2) Technical Solution

[0011] To achieve the above object, the main technical solutions adopted by the present invention include:

[0012] The present invention provides a catalytic synthesis process of α-pyrrolidone, comprising the following steps:

[0013] S1: Mix γ-butyrolactone with ammonia water, and after preheating treatment, introduce it into a reactor filled with a catalyst; the catalyst includes an alumina skeleton with a pore network, a core growing in the pores of the alumina skeleton, and mesoporous silica loaded with magnesium oxide; the core is mesoporous zirconia loaded with phosphotungstic acid, and the mesoporous silica loaded with magnesium oxide is located on the surface of the alumina skeleton;

[0014] S2: React γ-butyrolactone with ammonia water at 190 - 220 °C and 1.5 - 2.0 MPa to obtain a crude product;

[0015] S3: Concentrate the crude product, and then perform rectification treatment to obtain α-pyrrolidone.

[0016] For the catalytic synthesis process of α-pyrrolidone as described above, preferably, in step S1, the molar ratio of γ-butyrolactone to ammonia in ammonia water is 1:1.5 - 1:2;

[0017] Preheat the mixture of γ-butyrolactone and ammonia water to 160 - 180 °C, and then make the mixture of γ-butyrolactone and ammonia water enter the reactor at a liquid hourly space velocity of 0.8 - 1.5 h -1 -1.

[0018] For the catalytic synthesis process of α-pyrrolidone as described above, preferably, the reactor in step S1 is a fixed-bed continuous flow reactor, the catalyst is filled in the reactor in the form of a fixed bed, and γ-butyrolactone and ammonia water flow through the fixed bed from top to bottom or from bottom to top.

[0019] For the catalytic synthesis process of α-pyrrolidone as described above, preferably, the pore diameter of the pores of the alumina skeleton is 60 - 80 μm, and the porosity of the alumina skeleton is 65 - 75%.

[0020] For the catalytic synthesis process of α-pyrrolidone as described above, preferably, the preparation method of the catalyst in step S1 includes the following steps:

[0021] A1: Mix alumina powder with resin to obtain a mixture, perform 3D printing on the mixture to obtain a precursor, heat-treat the precursor to remove the resin, and then perform sintering treatment to obtain an alumina skeleton with a pore network;

[0022] A2: Immerse the alumina framework into a mixed solution of ZrOCl2 and citric acid, conduct vacuum treatment, then take out the alumina framework filled with the mixed solution in the pore network from the mixed solution, conduct heat treatment, and then conduct calcination treatment to obtain an alumina framework with mesoporous zirconia grown in the pores;

[0023] A3: Coat the surface of the alumina framework with mesoporous zirconia grown in the pores with cetyltrimethylammonium bromide solution. After drying, immerse the alumina framework into an acetonitrile solution of phosphotungstic acid, conduct vacuum treatment, take it out and rinse the surface of the alumina framework with acetonitrile, and then conduct heat treatment to obtain an alumina framework with a core;

[0024] A4: Immerse the alumina framework with a core into a polystyrene microsphere suspension, conduct vacuum treatment, then dropwise coat a solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid on the surface of the alumina framework. After drying treatment, conduct extraction treatment with an ethanol aqueous solution, and then spin-coat an aqueous solution containing magnesium nitrate and polyvinylpyrrolidone on the surface of the alumina framework. After heating and drying, conduct calcination treatment to obtain the catalyst.

[0025] For the catalytic synthesis process of α-pyrrolidone as described above, preferably, in step A1, the mass ratio of the alumina powder to the resin is (70 - 80):(20 - 30), the resin is a photocurable resin, the mixture is printed by a photocurable 3D printer, the particle size of the alumina powder is 0.5 - 1.5 μm, the heat treatment temperature is 500 - 600 °C, the heat treatment duration is 1 - 2 h, the calcination temperature is 1300 - 1500 °C, and the calcination duration is 3 - 5 h.

[0026] For the catalytic synthesis process of α-pyrrolidone as described above, preferably, in step A2, in the mixed solution of ZrOCl2 and citric acid, the concentration of ZrOCl2 is 0.3 - 0.5 mol / L, the molar ratio of citric acid to Zr 4+ is 1:1 - 1:2, the solvent is water, the heating temperature is 80 - 90 °C, the heating duration is 3 - 5 h, the calcination temperature is 300 - 400 °C, and the calcination duration is 3 - 5 h.

[0027] For the catalytic synthesis process of α-pyrrolidone as described above, preferably, in step A3, the concentration of phosphotungstic acid in acetonitrile is 0.1 - 0.2 mol / L, the acetonitrile solution of phosphotungstic acid also contains 0.1 - 0.2 wt% of 18-crown-6 ether, the heat treatment temperature is 150 - 170 °C, and the duration is 2 - 3 h.

[0028] The catalytic synthesis process of α-pyrrolidone as described above. Preferably, in step A4, the diameter of the polystyrene microspheres is 200-300 nm. In the solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid, the volume ratio of ethanol to water is 5:1-6:1, the volume concentration of tetraethyl orthosilicate is 5-8%, the mass ratio of F127 is 1-2%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.01-0.05;

[0029] Aqueous solution containing magnesium nitrate and polyvinylpyrrolidone is spin-coated on the surface of the alumina framework, heated and dried, and then calcined at 300-350 °C for 2-4 h.

[0030] The catalytic synthesis process of α-pyrrolidone as described above. Preferably, in step S2, the reaction duration is 2-4 h.

[0031] (III) Beneficial effects

[0032] First, the catalyst of the present invention uses mesoporous zirconia loaded with phosphotungstic acid as the core and an alumina framework with a porous structure. The surface has mesoporous silica loaded with magnesium oxide, significantly improving the amination reaction efficiency between γ-butyrolactone and ammonia. Under the action of this catalyst, the amination reaction between γ-butyrolactone and ammonia can proceed smoothly under relatively low temperature and low pressure conditions of 190-220 °C and 1.5-2.0 MPa. Compared with the high temperature conditions of 250-280 °C required by the traditional process, the reaction temperature is significantly reduced, effectively reducing heat energy consumption and improving energy utilization efficiency.

[0033] Second, due to the significant reduction of the reaction temperature in the present invention and the use of a solid catalyst to replace the traditional liquid acid catalyst, damage to equipment caused by strong corrosive substances is avoided, thereby reducing the requirements for high temperature, high pressure, and corrosion-resistant equipment, extending the service life of the equipment, improving the safety and operability of the process, and facilitating continuous and automated production. In addition, the catalyst of the present invention can be recycled multiple times with no obvious decrease in catalytic performance, significantly improving the catalyst utilization rate and reducing production costs.

[0034] Third, the present invention promotes the main reaction by setting strong acidic sites of phosphotungstic acid inside the catalyst and introducing weak basic magnesium oxide in the outer layer to regulate the local microenvironment, forming an acid-base synergistic catalysis mechanism. On the one hand, the basic component can neutralize acidic by-products such as NH4 + generated during the reaction, preventing side reactions caused by local over-acidity. On the other hand, the basic sites can also promote the deprotonation of intermediates, improving the selectivity of the reaction path and making the reaction more tend to the direction of the target product. Specific embodiments

[0035] For a better explanation and understanding of the present invention, the present invention will be described in detail below in conjunction with specific embodiments.

[0036] The present invention provides a catalytic synthesis process of α-pyrrolidone, comprising the following steps:

[0037] S1: Mix γ-butyrolactone with ammonia water, and after preheating treatment, introduce it into a reactor filled with a catalyst; the catalyst includes an alumina skeleton with a pore network, a core grown in the pores of the alumina skeleton, and mesoporous silica loaded with magnesium oxide; the core is mesoporous zirconia loaded with phosphotungstic acid, and the mesoporous silica loaded with magnesium oxide is located on the surface of the alumina skeleton.

[0038] S2: React γ-butyrolactone with ammonia water at 190 - 220 °C and 1.5 - 2.0 MPa to obtain a crude product.

[0039] S3: Concentrate the crude product, and then perform rectification treatment to obtain α-pyrrolidone.

[0040] The catalyst of the present invention uses mesoporous zirconia loaded with phosphotungstic acid as the core and an alumina skeleton with a porous structure, and has mesoporous silica loaded with magnesium oxide on the surface, significantly improving the amination reaction efficiency between γ-butyrolactone and ammonia water. Under the action of this catalyst, the amination reaction between γ-butyrolactone and ammonia water can proceed smoothly under relatively low temperature and low pressure conditions of 190 - 220 °C and 1.5 - 2.0 MPa, significantly reducing the reaction temperature compared with the traditional process that requires a high temperature condition of 250 - 280 °C, thereby effectively reducing heat energy consumption and improving energy utilization efficiency.

[0041] Due to the significant reduction of the reaction temperature of the present invention and the use of a solid catalyst to replace the traditional liquid acid catalyst, damage to equipment caused by strongly corrosive substances is avoided, thereby reducing the requirements for high-temperature, high-pressure and corrosion-resistant equipment, extending the service life of the equipment, enhancing the safety and operability of the process, and facilitating continuous and automated production. In addition, the catalyst of the present invention can be recycled multiple times without significant decline in catalytic performance, significantly improving the catalyst utilization rate and reducing production costs.

[0042] The present invention promotes the main reaction by setting strong acidic sites of phosphotungstic acid inside the catalyst, and introduces weak basic magnesium oxide in the outer layer to regulate the local microenvironment, forming an acid-base synergistic catalysis mechanism. On the one hand, the basic component can neutralize NH4 generated during the reaction +Acidic by-products, etc., to prevent side reactions caused by local over-acidity. On the other hand, the basic sites can also promote the deprotonation of intermediates, improve the selectivity of the reaction path, and make the reaction more tend to the direction of the target product. During the amination reaction of γ-butyrolactone and ammonia, there is a process of proton transfer or deprotonation. The basic sites can provide additional proton-accepting ability, accelerate the deprotonation steps of certain key intermediates, thereby reducing the reaction activation energy, increasing the reaction rate, and guiding the reaction to be more inclined to the direction of the target product. Specifically, the basic sites can help stabilize reaction intermediates, such as 1-hydroxybutyramide, etc., making it easier to convert into products. In addition, the presence of the basic component can also reduce the over-acidification of the catalyst and extend the service life of the catalyst.

[0043] Preferably, in the above step S1, the molar ratio of γ-butyrolactone to ammonia in ammonia water is 1:1.5 - 1:2, and the mass concentration of ammonia water can be 25 - 30%. Specifically, the mixture of γ-butyrolactone and ammonia water is preheated to 160 - 180 °C, and then the mixture of γ-butyrolactone and ammonia water enters the reactor at a liquid hourly space velocity of 0.8 - 1.5 h -1 ^-1. And the reactor in step S1 is a fixed-bed continuous flow reactor, and the catalyst is filled in the reactor in the form of a fixed bed, and γ-butyrolactone and ammonia water flow through the fixed bed from top to bottom or from bottom to top.

[0044] Preferably, the pore diameter of the pores in the alumina framework is 60 - 80 μm, and the porosity of the alumina framework is 65 - 75%.

[0045] Preferably, in step S1, the preparation method of the catalyst includes the following steps:

[0046] A1: Mix alumina powder with resin to obtain a mixture, perform 3D printing on the mixture to obtain a precursor, perform heat treatment on the precursor to remove the resin, and then perform sintering treatment to obtain an alumina framework with a pore network. By mixing alumina powder with a photocurable resin and using a photocurable 3D printer for printing, the alumina framework can have a rich pore structure, which is crucial for subsequent loading of other functional components. The purpose of the heat treatment is to remove the resin in the precursor. High-temperature sintering can enhance the bonding strength between alumina particles, and can also promote grain growth, forming a porous framework structure with high strength and high stability, providing an ideal carrier platform for subsequent loading of active components.

[0047] A2: Immerse the alumina skeleton in a mixed solution of ZrOCl2 and citric acid, conduct vacuum treatment, then take out the alumina skeleton filled with the mixed solution in the pore network from the mixed solution, conduct heat treatment, and then conduct calcination treatment to obtain an alumina skeleton with mesoporous zirconia grown in the pores. Vacuum treatment can accelerate the penetration of the solution into the pores of the alumina skeleton, ensuring uniform deposition of zirconia. Heating can promote the conversion of the precursor into zirconia gel, and calcination further removes residual organic matter and crystallizes zirconia to form mesoporous zirconia with a high specific surface area and good mechanical properties, providing a basis for the effective loading of phosphotungstic acid.

[0048] A3: Coat the surface of the alumina skeleton with mesoporous zirconia grown in the pores with cetyltrimethylammonium bromide solution. After drying, immerse the alumina skeleton in an acetonitrile solution of phosphotungstic acid, conduct vacuum treatment, take it out and rinse the surface of the alumina skeleton with acetonitrile, and then conduct heat treatment to obtain an alumina skeleton with a core. After the cetyltrimethylammonium bromide solution is coated on the surface of the alumina skeleton, it can form a physical barrier on the surface of the alumina skeleton, changing the wettability of the surface of the alumina skeleton, making it difficult for phosphotungstic acid to be effectively adsorbed on the outer surface of the alumina skeleton, realizing the loading of phosphotungstic acid only on the mesoporous zirconia in the internal pores of the skeleton and not depositing on the outer surface, thus ensuring the concentrated distribution of catalytic active sites. Heat treatment can promote solvent evaporation and make phosphotungstic acid firmly adhere to the surface of mesoporous zirconia, forming an efficient acidic catalytic center.

[0049] A4: Immerse the alumina skeleton with a core in a polystyrene microsphere suspension, conduct vacuum treatment, and then dropwise coat a solution containing F127 (Pluronic F127 template agent), tetraethyl orthosilicate (TEOS), ethanol, water, and hydrochloric acid on the surface of the alumina skeleton. After drying treatment, conduct extraction treatment with an ethanol aqueous solution, and then spin-coat an aqueous solution containing magnesium nitrate and polyvinylpyrrolidone on the surface of the alumina skeleton. After heating and drying, conduct calcination treatment to obtain a catalyst. The polystyrene microspheres act as physical blockers in the present invention. Their main function is to temporarily block the pore openings on the surface of the alumina skeleton to prevent the subsequent mesoporous silica precursor solution from infiltrating into the internal pores of the skeleton. The synergistic effect of F127, tetraethyl orthosilicate, and hydrochloric acid can generate a mesoporous silica layer that covers the surface of the alumina skeleton and provides a basis for the loading of magnesium oxide.

[0050] Preferably, in the above step A1, the mass ratio of the alumina powder to the resin is (70 - 80):(20 - 30), the resin is a photocurable resin, the mixture is printed by a photocurable 3D printer, the particle size of the alumina powder is 0.5 - 1.5 μm, the heating temperature of the precursor is 500 - 600 °C, the heating duration is 1 - 2 h, the calcination temperature is 1300 - 1500 °C, and the calcination duration is 3 - 5 h.

[0051] Preferably, in the above step A2, in the mixed solution of ZrOCl2 and citric acid, the concentration of ZrOCl2 is 0.3 - 0.5 mol / L, and the molar ratio of citric acid to Zr 4+ is 1:1 - 1:2, the solvent is water, the heating temperature is 80 - 90 °C, the heating duration is 3 - 5 h, the calcination temperature is 300 - 400 °C, and the calcination duration is 3 - 5 h.

[0052] Preferably, in the above step A3, the concentration of phosphotungstic acid in acetonitrile is 0.1 - 0.2 mol / L. The acetonitrile solution of phosphotungstic acid also contains 0.1 - 0.2 wt% of 18 - crown - 6 ether, and 18 - crown - 6 ether can promote the dissolution of phosphotungstic acid. The temperature of the heat treatment is 150 - 170 °C, and the duration is 2 - 3 h.

[0053] Preferably, in the above step A4, the diameter of the polystyrene microspheres is 200 - 300 nm. In the solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid, the volume ratio of ethanol to water is 5:1 - 6:1, the volume concentration of tetraethyl orthosilicate is 5 - 8%, the mass fraction of F127 is 1 - 2%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.01 - 0.05;

[0054] Aqueous solution containing magnesium nitrate and polyvinylpyrrolidone is spin - coated on the surface of the alumina framework, heated and dried, and then calcined at 300 - 350 °C for 2 - 4 h.

[0055] Further preferably, in the above step S2, the reaction duration is 2 - 4 h.

[0056] To further clarify the solution of the present invention and its technical progressiveness, the following is described in combination with specific examples and technical effects.

[0057] Example 1

[0058] This example provides a catalytic synthesis process of α - pyrrolidone, including the following steps:

[0059] S1: Mix γ - butyrolactone with ammonia water. The molar ratio of γ - butyrolactone to ammonia in the ammonia water is 1:1.8, the mass concentration of the ammonia water is 27%. After the mixture is pre - heated to 170 °C, it is fed into the reactor filled with the catalyst at a liquid hourly space velocity of 1 h -1 The reactor is a fixed - bed continuous - flow reactor, and the catalyst is filled in the reactor in the form of a fixed bed. γ - Butyrolactone and ammonia water flow through the fixed bed from top to bottom.

[0060] The preparation method of the catalyst includes the following steps:

[0061] A1: Mix alumina powder and photocurable resin in a mass ratio of 75:25 to obtain a mixture. The particle size of the alumina powder is 1 μm. Print the mixture using a photocurable 3D printer to obtain a precursor. Heat the precursor to 550 °C, hold for 1.5 h, and then calcine at 1400 °C for 4 h to obtain an alumina framework with a pore network. After testing, the pore diameter of the pores in the alumina framework of this example is 74 μm, and the porosity is 71%.

[0062] A2: Immerse the alumina framework in an aqueous mixed solution of ZrOCl2 and citric acid. The concentration of ZrOCl2 is 0.4 mol / L, and the molar ratio of citric acid to Zr 4+ is 1:1.5. After vacuum treatment, take out the alumina framework filled with the mixed solution in the pore network from the mixed solution, heat to 85 °C, hold for 4 h, and then calcine at 350 °C for 4 h to obtain an alumina framework with mesoporous zirconia grown in the pores.

[0063] A3: Coat the surface of the alumina framework with mesoporous zirconia grown in the pores with cetyltrimethylammonium bromide solution. After drying, immerse the alumina framework in an acetonitrile solution of phosphotungstic acid, perform vacuum treatment, take it out and rinse the surface of the alumina framework with acetonitrile, and then perform heat treatment to obtain an alumina framework with a core. Among them, the concentration of phosphotungstic acid in acetonitrile is 0.15 mol / L, the acetonitrile solution of phosphotungstic acid also contains 0.15 wt% of 18-crown-6 ether, and the temperature of the heat treatment is 160 °C and the duration is 2.5 h.

[0064] A4: Immerse the alumina framework with a core in a polystyrene microsphere suspension. The diameter of the polystyrene microspheres is 250 m, perform vacuum treatment, and then dropwise coat a solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid on the surface of the alumina framework. After drying, perform extraction treatment with an ethanol aqueous solution, and then spin-coat an aqueous solution containing magnesium nitrate and polyvinylpyrrolidone on the surface of the alumina framework. After heating and drying, calcine at 320 °C for 3 h to obtain a catalyst. In this step, in the solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid, the volume ratio of ethanol to water is 5.5:1, the volume concentration of tetraethyl orthosilicate is 6%, the mass fraction of F127 is 1.5%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.03.

[0065] S2: React γ-butyrolactone with ammonia at 200 °C and 1.8 MPa for 3 h to obtain a crude product.

[0066] S3: Concentrate the crude product and then perform rectification treatment to obtain α-pyrrolidone.

[0067] Example 2

[0068] This embodiment provides a catalytic synthesis process of α-pyrrolidone, which includes the following steps:

[0069] S1: Mix γ-butyrolactone with ammonia water. The molar ratio of γ-butyrolactone to ammonia in ammonia water is 1:1.5, and the mass concentration of ammonia water is 25%. After the mixture is preheated to 160 °C, it is fed into a reactor filled with a catalyst at a liquid hourly space velocity of 0.8 h -1 . The reactor is a fixed-bed continuous flow reactor, and the catalyst is filled in the reactor in the form of a fixed bed. γ-Butyrolactone and ammonia water flow through the fixed bed from top to bottom.

[0070] The preparation method of the catalyst includes the following steps:

[0071] A1: Mix alumina powder with a photocurable resin in a mass ratio of 80:20 to obtain a mixture. The particle size of the alumina powder is 0.5 μm. The mixture is printed by a photocurable 3D printer to obtain a precursor. The precursor is heated to 500 °C, held for 1 h, and then calcined at 1300 °C for 3 h to obtain an alumina skeleton with a pore network. After testing, the pore diameter of the pores in the alumina skeleton of this embodiment is 60 μm, and the porosity is 65%.

[0072] A2: Immerse the alumina skeleton in a mixed aqueous solution of ZrOCl2 and citric acid. The concentration of ZrOCl2 is 0.3 mol / L, and the molar ratio of citric acid to Zr 4+ is 1:1. After vacuum treatment, the alumina skeleton filled with the mixed solution in the pore network is taken out from the mixed solution, heated to 80 °C, held for 3 h, and then calcined at 300 °C for 3 h to obtain an alumina skeleton with mesoporous zirconia grown in the pores.

[0073] A3: Coat the surface of the alumina skeleton with mesoporous zirconia grown in the pores with a cetyltrimethylammonium bromide solution. After drying, immerse the alumina skeleton in an acetonitrile solution of phosphotungstic acid, perform vacuum treatment, take it out and rinse the surface of the alumina skeleton with acetonitrile, and then perform heat treatment to obtain an alumina skeleton with a core. Among them, the concentration of phosphotungstic acid in acetonitrile is 0.1 mol / L, and the acetonitrile solution of phosphotungstic acid also contains 0.1 wt% of 18-crown-6 ether. The temperature of the heat treatment is 150 °C, and the duration is 2 h.

[0074] A4: Immerse an alumina skeleton with a core in a polystyrene microsphere suspension. The diameter of the polystyrene microspheres is 200 nm. Conduct a vacuum treatment. Then, dropwise coat a solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid on the surface of the alumina skeleton. After drying, conduct an extraction treatment with an ethanol aqueous solution. Then, spin-coat an aqueous solution containing magnesium nitrate and polyvinylpyrrolidone on the surface of the alumina skeleton. After heating and drying, calcine at 300 °C for 2 h to obtain a catalyst. In this step, in the solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid, the volume ratio of ethanol to water is 5:1, the volume concentration of tetraethyl orthosilicate is 5%, the mass ratio of F127 is 1%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.01.

[0075] S2: React γ-butyrolactone with ammonia water at 190 °C and 2.0 MPa for 4 h to obtain a crude product.

[0076] S3: Concentrate the crude product and then conduct a rectification treatment to obtain α-pyrrolidone.

[0077] Example 3

[0078] This example provides a catalytic synthesis process for α-pyrrolidone, including the following steps:

[0079] S1: Mix γ-butyrolactone with ammonia water. The molar ratio of γ-butyrolactone to ammonia in the ammonia water is 1:2, and the mass concentration of the ammonia water is 30%. After preheating the mixture to 180 °C, feed it into a reactor filled with a catalyst at a liquid hourly space velocity of 1.5 h -1 The reactor is a fixed-bed continuous flow reactor, and the catalyst is filled in the reactor in a fixed-bed form. γ-Butyrolactone and ammonia water flow through the fixed bed from top to bottom.

[0080] The preparation method of the catalyst includes the following steps:

[0081] A1: Mix alumina powder with a photocurable resin at a mass ratio of 70:30 to obtain a mixture. The particle size of the alumina powder is 1.5 μm. Print the mixture with a photocurable 3D printer to obtain a precursor. Heat the precursor to 600 °C, hold for 2 h, and then calcine at 1500 °C for 5 h to obtain an alumina skeleton with a pore network. After testing, the pore diameter of the pores in the alumina skeleton of this example is 80 μm, and the porosity is 75%.

[0082] A2: Immerse the alumina skeleton in a mixed aqueous solution of ZrOCl2 and citric acid. The concentration of ZrOCl2 is 0.5 mol / L, and the citric acid and Zr 4+The molar ratio is 1:2. After vacuum treatment, the alumina framework filled with the mixed solution in the pore network is taken out from the mixed solution, heated to 90 °C, held for 5 h, and then calcined at 400 °C for 5 h to obtain an alumina framework with mesoporous zirconia grown in the pores.

[0083] A3: Cetyltrimethylammonium bromide solution is coated on the surface of the alumina framework with mesoporous zirconia grown in the pores. After drying, the alumina framework is immersed in an acetonitrile solution of phosphotungstic acid, vacuum treatment is carried out, and after taking out, the surface of the alumina framework is rinsed with acetonitrile, and then heat treatment is carried out to obtain an alumina framework with a core. Among them, the concentration of phosphotungstic acid in acetonitrile is 0.2 mol / L, and the acetonitrile solution of phosphotungstic acid also contains 0.2 wt% of 18-crown-6 ether. The temperature of the heat treatment is 170 °C and the duration is 3 h.

[0084] A4: The alumina framework with a core is immersed in a polystyrene microsphere suspension. The diameter of the polystyrene microspheres is 300 nm. Vacuum treatment is carried out, and then a solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid is drop-coated on the surface of the alumina framework. After drying treatment, extraction treatment is carried out with an ethanol aqueous solution. Then, an aqueous solution containing magnesium nitrate and polyvinylpyrrolidone is spin-coated on the surface of the alumina framework. After heating and drying, it is calcined at 350 °C for 4 h to obtain a catalyst. In this step, in the solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid, the volume ratio of ethanol to water is 6:1, the volume concentration of tetraethyl orthosilicate is 8%, the mass fraction of F127 is 2%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.05.

[0085] S2: γ-Butyrolactone and ammonia water are reacted at 220 °C and 1.5 MPa for 2 h to obtain a crude product.

[0086] S3: The crude product is concentrated and then rectified to obtain α-pyrrolidone.

[0087] Comparative Example 1

[0088] This comparative example provides a catalytic synthesis process of α-pyrrolidone, which is different from Example 1 in that mesoporous silica and magnesium oxide are not loaded on the catalyst surface.

[0089] After testing, in the crude products prepared in Examples 1-3 and Comparative Example 1, the contents of residual γ-butyrolactone are 0.004 wt%, 0.005 wt%, 0.006 wt%, and 0.09 wt% respectively, and the contents of the intermediate 1-hydroxybutyramide are 0.002 wt%, 0.006 wt%, 0.003 wt%, and 0.1 wt% respectively.

[0090] After the crude products prepared in Examples 1-3 and Comparative Example 1 were concentrated and rectified, the yields of α-pyrrolidone obtained were 99%, 98.1%, 98.4% and 96.2% respectively, and the purities were 99.8%, 99.7%, 99.6% and 99.3% respectively. Moreover, the catalysts in Examples 1-3 could be stably used for more than 1000 h, and the performance of the catalyst in Comparative Example 1 decreased significantly after 300-400 h of use.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A catalytic synthesis process of α-pyrrolidone, characterized in that, It includes the following steps: S1: Mix γ-butyrolactone with ammonia water, and after preheating, introduce it into a reactor filled with a catalyst; the catalyst includes an alumina skeleton with a pore network, a core grown in the pores of the alumina skeleton, and mesoporous silica loaded with magnesium oxide; the core is mesoporous zirconia loaded with phosphotungstic acid, and the mesoporous silica loaded with magnesium oxide is located on the surface of the alumina skeleton; S2: React γ-butyrolactone with ammonia water at 190-220 °C and 1.5-2.0 MPa to obtain a crude product; S3: Concentrate the crude product, and then perform rectification treatment to obtain α-pyrrolidone.

2. The catalytic synthesis process of α-pyrrolidone according to claim 1, wherein In step S1, the molar ratio of γ-butyrolactone to ammonia in ammonia water is 1:1.5-1:2; Preheat the mixture of γ-butyrolactone and ammonia water to 160-180 °C, and then feed the mixture of γ-butyrolactone and ammonia water into the reactor at a liquid hourly space velocity of 0.8-1.5 h -1 .

3. The catalytic synthesis process of α-pyrrolidone according to claim 1, characterized in that, The reactor in step S1 is a fixed-bed continuous flow reactor, the catalyst is filled in the reactor in the form of a fixed bed, and γ-butyrolactone and ammonia water flow through the fixed bed from top to bottom or from bottom to top.

4. The catalytic synthesis process of α-pyrrolidone according to claim 1, characterized in that, The pore diameter of the pores of the alumina skeleton is 60-80 μm, and the porosity of the alumina skeleton is 65-75%; 5. The catalytic synthesis process of α-pyrrolidone according to claim 1, characterized in that, In step S1, the preparation method of the catalyst includes the following steps: A1: Mix alumina powder with resin to obtain a mixture, perform 3D printing on the mixture to obtain a precursor, heat-treat the precursor to remove the resin, and then perform sintering treatment to obtain an alumina skeleton with a pore network; A2: Immerse the alumina skeleton in a mixed solution of ZrOCl2 and citric acid, perform vacuum treatment, then take out the alumina skeleton filled with the mixed solution in the pore network from the mixed solution, perform heat treatment, and then perform calcination treatment to obtain an alumina skeleton with mesoporous zirconia grown in the pores; A3: Coat the surface of the alumina skeleton with mesoporous zirconia grown in the pores with cetyltrimethylammonium bromide solution, dry it, then immerse the alumina skeleton in an acetonitrile solution of phosphotungstic acid, perform vacuum treatment, take it out and rinse the surface of the alumina skeleton with acetonitrile, and then perform heat treatment to obtain an alumina skeleton with a core; A4: Immerse the alumina skeleton with a core in a polystyrene microsphere suspension, perform vacuum treatment, then dropwise coat a solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid on the surface of the alumina skeleton, perform drying treatment, then perform extraction treatment with an ethanol aqueous solution, and then spin-coat an aqueous solution containing magnesium nitrate and polyvinylpyrrolidone on the surface of the alumina skeleton, heat and dry it, and then perform calcination treatment to obtain the catalyst.

6. The catalytic synthesis process of α-pyrrolidone according to claim 5, characterized in that, In step A1, the mass ratio of alumina powder to resin is (70-80):(20-30), the resin is a photocurable resin, the mixture is printed by a photocurable 3D printer, the particle size of the alumina powder is 0.5-1.5 μm, the temperature of the heat treatment is 500-600 °C, the heating duration is 1-2 h, the calcination temperature is 1300-1500 °C, and the calcination duration is 3-5 h.

7. The catalytic synthesis process of α-pyrrolidone according to claim 5, wherein, In step A2, in the mixed solution of ZrOCl2 and citric acid, the concentration of ZrOCl2 is 0.3 - 0.5 mol / L, the molar ratio of citric acid to Zr 4+ is 1:1 - 1:2, the solvent is water, the heating temperature is 80 - 90 °C, the heating duration is 3 - 5 h, the calcination temperature is 300 - 400 °C, and the calcination duration is 3 - 5 h.

8. The catalytic synthesis process of α-pyrrolidone according to claim 5, characterized in that, In step A3, the concentration of phosphotungstic acid in acetonitrile is 0.1 - 0.2 mol / L, the acetonitrile solution of phosphotungstic acid further contains 0.1 - 0.2 wt% of 18-crown-6 ether, the temperature of the heat treatment is 150 - 170 °C, and the duration is 2 - 3 h.

9. The catalytic synthesis process of α-pyrrolidone according to claim 5, characterized in that, In step A4, the diameter of the polystyrene microspheres is 200 - 300 nm. In the solution containing F127, tetraethyl orthosilicate, ethanol, water and hydrochloric acid, the volume ratio of ethanol to water is 5:1 - 6:1, the volume concentration of tetraethyl orthosilicate is 5 - 8%, the mass ratio of F127 is 1 - 2%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.01 - 0.05; Aqueous solution containing magnesium nitrate and polyvinylpyrrolidone is spin-coated on the surface of the alumina framework, heated and dried, and then calcined at 300 - 350 °C for 2 - 4 h.

10. The catalytic synthesis process of α-pyrrolidone according to claim 1, characterized in that, In step S2, the reaction duration is 2 - 4 h.