A catalytic synthesis process for α-pyrrolidone

Abstract

The present invention belongs to the field of organic chemical synthesis and relates to a catalytic synthesis process for α-pyrrolidone, comprising the following steps: S1: γ-butyrolactone is mixed with ammonia water and preheated and then passed 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: γ-butyrolactone is reacted with ammonia water at 190-220°C and 1.5-2.0MPa to obtain a crude product. S3: The crude product is concentrated and distilled to obtain α-pyrrolidone. The catalytic synthesis process of the present invention has made significant progress in reducing energy consumption, alleviating equipment burden, and improving catalyst recyclability, and has good industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of organic chemical synthesis, and in particular to a catalytic synthesis process of alpha-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, transparent liquid at room temperature. It has strong polarity and hygroscopicity and is miscible with water and various organic solvents.

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

[0004] In existing technologies, the industrial production of α-pyrrolidone primarily relies on the catalytic amination reaction between γ-butyrolactone and ammonia. This reaction is typically carried out at high temperatures of 250-280°C, and an acidic substance is generally used as a catalyst. However, this process still has the following problems in practical 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 and corrosion resistance of the equipment.

[0006] Second, most existing processes use liquid acid as a catalyst. Although it exhibits certain catalytic activity, this type of catalyst is difficult to effectively separate from the reaction system and cannot be recycled, which significantly reduces the process economy.

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

[0008] (1) Technical issues to be resolved

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

[0010] (2) Technical solution

[0011] In order to achieve the above objectives, the main technical solutions adopted by the present invention include:

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

[0013] S1: γ-butyrolactone is mixed with ammonia water, and after preheating, the mixture is introduced into a reactor filled with a catalyst; the catalyst comprises an alumina skeleton having 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;

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

[0015] S3: The crude product is concentrated and then distilled to obtain α-pyrrolidone.

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

[0017] Preheat the mixture of γ-butyrolactone and ammonia water to 160-180℃, then allow the mixture of γ-butyrolactone and ammonia water to stand for 0.8-1.5h. -1 The liquid hourly space velocity enters the reactor.

[0018] In 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 aqueous ammonia flow through the fixed bed from top to bottom or from bottom to top.

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

[0020] In the above-mentioned catalytic synthesis process of α-pyrrolidone, preferably, in step S1, the preparation method of the catalyst comprises the following steps:

[0021] A1: Alumina powder is mixed with resin to obtain a mixture, the mixture is 3D printed to obtain a precursor, the precursor is heated to remove the resin, and then sintered to obtain an alumina skeleton with a pore network;

[0022] A2: Immersing the alumina skeleton in a mixed solution of ZrOCl2 and citric acid, vacuum treating the alumina skeleton, then removing the alumina skeleton with the mixed solution in its pore network from the mixed solution, heating the alumina skeleton, and then calcining the alumina skeleton to obtain an alumina skeleton with mesoporous zirconia growing in its pores;

[0023] A3: Coating the surface of the alumina skeleton with mesoporous zirconia grown in the pores with a cetyltrimethylammonium bromide solution, drying, immersing the alumina skeleton in an acetonitrile solution of phosphotungstic acid, vacuum treating, and then removing and rinsing the surface of the alumina skeleton with acetonitrile. The alumina skeleton is then heated to obtain an alumina skeleton with a core.

[0024] A4: Immerse the alumina skeleton with an inner core in a polystyrene microsphere suspension and perform vacuum treatment. Then, a solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid is drop-coated on the surface of the alumina skeleton. After drying, the solution is extracted with an ethanol-water solution. Then, an aqueous solution containing magnesium nitrate and polyvinyl pyrrolidone is spin-coated on the surface of the alumina skeleton. After heating and drying, the solution is calcined to obtain a catalyst.

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

[0026] In 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, and the concentration of citric acid and ZrOCl2 is 0.3-0.5 mol / L. 4+ The molar ratio is 1:1-1:2, the solvent is water, the heating temperature is 80-90°C, the heating time is 3-5h, the calcination temperature is 300-400°C, and the calcination time is 3-5h.

[0027] In 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 further contains 0.1-0.2 wt% of 18-crown-6 ether, and the heating temperature is 150-170° C. for 2-3 h.

[0028] In the catalytic synthesis process of α-pyrrolidone as described above, preferably, in step A4, the diameter of the polystyrene microspheres is 200-300 nm, and 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 proportion of F127 is 1-2%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.01-0.05;

[0029] An aqueous solution containing magnesium nitrate and polyvinyl pyrrolidone is spin-coated on the surface of the alumina skeleton, heated and dried, and then calcined at 300-350° C. for 2-4 hours.

[0030] In the above-mentioned catalytic synthesis process of α-pyrrolidone, preferably, in step S2, the reaction time is 2-4 hours.

[0031] (3) Beneficial effects

[0032] First, the catalyst of the present invention features a core of mesoporous zirconium oxide loaded with phosphotungstic acid, a porous alumina framework, and a surface layer of mesoporous silica loaded with magnesium oxide. This significantly improves the efficiency of the amination reaction between γ-butyrolactone and ammonia. Under the action of this catalyst, the amination reaction of γ-butyrolactone with ammonia proceeds smoothly under relatively low temperatures and pressures of 190-220°C and 1.5-2.0 MPa, significantly lowering the reaction temperature compared to the high temperatures of 250-280°C required by traditional processes. This effectively reduces heat energy consumption and improves energy efficiency.

[0033] Second, the significantly lower reaction temperature and the use of a solid catalyst instead of a traditional liquid acid catalyst prevent damage to equipment caused by highly corrosive substances. This reduces the need for high-temperature, high-pressure, and corrosion-resistant equipment, prolongs equipment life, improves process safety and operability, and facilitates continuous, automated production. Furthermore, the catalyst of the present invention can be recycled multiple times without significant degradation in catalytic performance, significantly improving catalyst utilization and reducing production costs.

[0034] Third, the present invention promotes the main reaction by setting strong acid sites of phosphotungstic acid inside the catalyst, and introduces weakly basic magnesium oxide in the outer layer to regulate the local microenvironment, forming an acid-base synergistic catalytic mechanism. On the one hand, the alkaline component can neutralize the NH4 generated during the reaction. + On the other hand, the alkaline sites can also promote the deprotonation of intermediates, improve the selectivity of the reaction path, and make the reaction more inclined to the target product. DETAILED DESCRIPTION

[0035] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below in conjunction with specific embodiments.

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

[0037] S1: γ-butyrolactone is mixed with ammonia water, and after preheating, it is introduced 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: reacting γ-butyrolactone with aqueous ammonia at 190-220° C. and 1.5-2.0 MPa to obtain a crude product.

[0039] S3: The crude product is concentrated and then distilled to obtain α-pyrrolidone.

[0040] The catalyst of the present invention features a core of mesoporous zirconium oxide loaded with phosphotungstic acid, a porous alumina framework, and a surface layer of mesoporous silica loaded with magnesium oxide. This catalyst significantly improves the efficiency of the amination reaction between γ-butyrolactone and ammonia. Under the action of this catalyst, the amination reaction of γ-butyrolactone and ammonia proceeds smoothly under relatively low temperatures and pressures of 190-220°C and 1.5-2.0 MPa. This significantly lowers the reaction temperature compared to the high temperatures of 250-280°C required by traditional processes, effectively reducing heat energy consumption and improving energy efficiency.

[0041] The significantly lower reaction temperature and the use of a solid catalyst in place of a traditional liquid acid catalyst prevent damage to equipment caused by highly corrosive substances, thereby reducing the requirements for high-temperature, high-pressure, and corrosion-resistant equipment, extending equipment life, and improving process safety and operability, thereby facilitating continuous, automated production. Furthermore, the catalyst of the present invention can be recycled multiple times without significant degradation in catalytic performance, significantly improving catalyst utilization and reducing production costs.

[0042] The present invention sets strong acid sites of phosphotungstic acid inside the catalyst to promote the main reaction, and introduces weakly basic magnesium oxide in the outer layer to regulate the local microenvironment, forming an acid-base synergistic catalytic mechanism. On the one hand, the alkaline component can neutralize the NH4 generated during the reaction. +On the other hand, the alkaline sites can also promote the deprotonation of intermediates, improve the selectivity of the reaction path, and make the reaction more inclined to the target product. During the amination reaction of γ-butyrolactone and ammonia, there is a proton transfer or deprotonation process. The alkaline sites can provide additional proton acceptance capacity, accelerate the deprotonation step of certain key intermediates, thereby reducing the reaction activation energy, increasing the reaction rate, and guiding the reaction to proceed more in the direction of the target product. Specifically, the alkaline sites can help stabilize reaction intermediates, such as 1-hydroxybutanamide, making it easier to convert them into products. In addition, the presence of alkaline components 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 the ammonia water is 1:1.5-1:2, and the mass concentration of the 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 is stirred for 0.8-1.5 hours. -1 The reactor in step S1 is a fixed-bed continuous flow reactor, in which 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 size of the pores of the alumina skeleton is 60-80 μm, and the porosity of the alumina skeleton is 65-75%.

[0045] Preferably, in step S1, the method for preparing the catalyst comprises the following steps:

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

[0047] A2: The alumina skeleton is immersed in a mixed solution of ZrOCl2 and citric acid and vacuum treated. The alumina skeleton with the mixed solution in its pore network is then removed from the mixed solution, heated, and then calcined to obtain an alumina skeleton with mesoporous zirconia growing within its pores. The vacuum treatment accelerates the penetration of the solution into the pores of the alumina skeleton, ensuring uniform deposition of zirconia. Heating promotes the conversion of the precursor into zirconia gel, while calcination further removes residual organic matter and crystallizes the zirconia, forming mesoporous zirconia with a high specific surface area and good mechanical properties, providing a foundation for the effective loading of phosphotungstic acid.

[0048] A3: The surface of an alumina skeleton with mesoporous zirconia grown within its pores is coated with a solution of hexadecyltrimethylammonium bromide. After drying, the alumina skeleton is immersed in an acetonitrile solution of phosphotungstic acid and vacuum-treated. After removal, the surface of the alumina skeleton is rinsed with acetonitrile and then heat-treated to obtain an alumina skeleton with an inner core. The hexadecyltrimethylammonium bromide solution, applied to the surface of the alumina skeleton, forms a physical barrier, altering the wettability of the alumina skeleton surface. This makes it difficult for phosphotungstic acid to effectively adsorb on the outer surface of the alumina skeleton. This ensures that the phosphotungstic acid is only loaded on the mesoporous zirconia within the pores of the skeleton, rather than deposited on the outer surface, thereby ensuring a concentrated distribution of catalytically active sites. The heat treatment promotes solvent evaporation and allows the phosphotungstic acid to firmly adhere to the surface of the mesoporous zirconia, forming highly efficient acidic catalytic centers.

[0049] A4: An alumina skeleton with a core is immersed in a suspension of polystyrene microspheres and vacuum-treated. A solution containing F127 (Pluronic F127 template), tetraethyl orthosilicate (TEOS), ethanol, water, and hydrochloric acid is then drop-coated on the surface of the alumina skeleton. After drying, the solution is extracted with an ethanol-water solution. An aqueous solution containing magnesium nitrate and polyvinyl pyrrolidone is then spin-coated on the surface of the alumina skeleton. After heating and drying, the solution is calcined to obtain a catalyst. The polystyrene microspheres serve as a physical barrier in this invention, their primary function being to temporarily block the pores on the surface of the alumina skeleton to prevent the subsequent mesoporous silica precursor solution from penetrating into the pores within 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 foundation for the loading of magnesium oxide.

[0050] Preferably, in the above step A1, the mass ratio of alumina powder to resin is (70-80): (20-30), the resin is a light-curing resin, and the mixture is printed by a light-curing 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 time is 1-2 hours, the calcination temperature is 1300-1500°C, and the calcination time is 3-5 hours.

[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 concentration of citric acid and ZrOCl2 is 0.3-0.5 mol / L. 4+ The molar ratio is 1:1-1:2, the solvent is water, the heating temperature is 80-90°C, the heating time is 3-5h, the calcination temperature is 300-400°C, and the calcination time is 3-5h.

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

[0053] Preferably, in step A4 above, the diameter of the polystyrene microspheres is 200-300 nm, and 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 proportion of F127 is 1-2%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.01-0.05;

[0054] An aqueous solution containing magnesium nitrate and polyvinyl pyrrolidone is spin-coated on the surface of the alumina skeleton, heated and dried, and then calcined at 300-350° C. for 2-4 hours.

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

[0056] In order to further clarify the solution of the present invention and its technical advancement, the following description is made in conjunction with specific embodiments and technical effects.

[0057] Example 1

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

[0059] S1: Mix γ-butyrolactone with ammonia water. The molar ratio of γ-butyrolactone to ammonia in ammonia water is 1:1.8. The mass concentration of ammonia water is 27%. After preheating the mixture to 170℃, heat it for 1 hour. -1 The catalyst is fed into a reactor filled with catalyst at a liquid hourly space velocity of 1000 rpm. The reactor is a fixed-bed continuous flow reactor, in which 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.

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

[0061] A1: Alumina powder and a photocurable resin were mixed in a mass ratio of 75:25 to obtain a mixture. The alumina powder had a particle size of 1 μm. The mixture was printed using a photocurable 3D printer to obtain a precursor. The precursor was heated to 550°C, held for 1.5 hours, and then calcined at 1400°C for 4 hours to obtain an alumina skeleton with a pore network. Testing showed that the pores of the alumina skeleton in this example had a pore diameter of 74 μm and a porosity of 71%.

[0062] A2: Immerse the alumina skeleton in a mixed aqueous solution of ZrOCl2 and citric acid, the concentration of ZrOCl2 is 0.4 mol / L, and the concentration of citric acid and Zr 4+ The molar ratio is 1:1.5. After vacuum treatment, the alumina skeleton filled with the mixed solution in the pore network is taken out from the mixed solution, heated to 85°C, kept warm for 4 hours, and then calcined at 350°C for 4 hours to obtain an alumina skeleton with mesoporous zirconia growing in the pores.

[0063] A3: The surface of an alumina framework with mesoporous zirconia grown within the pores is coated with a hexadecyltrimethylammonium bromide solution. After drying, the alumina framework is immersed in an acetonitrile solution of phosphotungstic acid and vacuum-treated. After removal, the surface of the alumina framework is rinsed with acetonitrile and then heat-treated to obtain an alumina framework with a core. The concentration of phosphotungstic acid in acetonitrile is 0.15 mol / L, and the acetonitrile solution also contains 0.15 wt% 18-crown-6 ether. The heating temperature is 160°C and the duration is 2.5 hours.

[0064] A4: Immerse the alumina skeleton with a core in a suspension of polystyrene microspheres with a diameter of 250 μm and perform vacuum treatment. Then, a solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid is drop-coated on the surface of the alumina skeleton. After drying, the solution is extracted with an ethanol-water solution. Then, an aqueous solution containing magnesium nitrate and polyvinyl pyrrolidone is spin-coated on the surface of the alumina skeleton. After heating and drying, the solution is calcined at 320°C for 3 hours to obtain a catalyst. In this step, the volume ratio of ethanol to water in the solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid is 5.5:1, the volume concentration of tetraethyl orthosilicate is 6%, the mass proportion of F127 is 1.5%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.03.

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

[0066] S3: The crude product is concentrated and then distilled to obtain α-pyrrolidone.

[0067] Example 2

[0068] This embodiment provides a catalytic synthesis process of α-pyrrolidone, comprising 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. The mass concentration of ammonia water is 25%. After preheating the mixture to 160℃, heat it for 0.8h. -1 The catalyst is fed into a reactor filled with catalyst at a liquid hourly space velocity of 1000 rpm. The reactor is a fixed-bed continuous flow reactor, in which 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.

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

[0071] A1: Alumina powder and a photocurable resin were mixed in a mass ratio of 80:20 to obtain a mixture. The alumina powder had a particle size of 0.5 μm. The mixture was printed using a photocurable 3D printer to obtain a precursor. The precursor was heated to 500°C, held for 1 hour, and then calcined at 1300°C for 3 hours to obtain an alumina skeleton with a pore network. Testing showed that the pores of the alumina skeleton in this example had a pore diameter of 60 μm and a porosity of 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 concentration of citric acid and Zr 4+ The molar ratio of the mixed solution 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, kept warm for 3 hours, and then calcined at 300°C for 3 hours to obtain an alumina skeleton with mesoporous zirconia growing in the pores.

[0073] A3: The surface of the alumina skeleton with mesoporous zirconia grown in the pores is coated with a hexadecyltrimethylammonium bromide solution. After drying, the alumina skeleton is immersed in an acetonitrile solution of phosphotungstic acid and vacuum treated. After removal, the surface of the alumina skeleton is rinsed with acetonitrile and then heated to obtain an alumina skeleton with a core. The concentration of phosphotungstic acid in acetonitrile is 0.1 mol / L, and the acetonitrile solution of phosphotungstic acid also contains 0.1 wt% 18-crown-6 ether. The heating temperature is 150°C and the duration is 2 hours.

[0074] A4: An alumina skeleton with a core is immersed in a suspension of polystyrene microspheres with a diameter of 200 nm. The polystyrene microspheres are vacuum treated, and then a solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid is drop-coated on the surface of the alumina skeleton. After drying, the solution is extracted with an ethanol-water solution. Then, an aqueous solution containing magnesium nitrate and polyvinyl pyrrolidone is spin-coated on the surface of the alumina skeleton. The solution is heat-dried and calcined at 300°C for 2 hours to obtain a catalyst. In this step, the volume ratio of ethanol to water in the solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid 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: γ-butyrolactone and aqueous ammonia were reacted at 190° C. and 2.0 MPa for 4 h to obtain a crude product.

[0076] S3: The crude product is concentrated and then distilled to obtain α-pyrrolidone.

[0077] Example 3

[0078] This embodiment provides a catalytic synthesis process of α-pyrrolidone, comprising the following steps:

[0079] S1: Mix γ-butyrolactone with ammonia water. The molar ratio of γ-butyrolactone to ammonia in ammonia water is 1:2. The mass concentration of ammonia water is 30%. Preheat the mixture to 180℃ and heat for 1.5h. -1 The catalyst is fed into a reactor filled with catalyst at a liquid hourly space velocity of 1000 rpm. The reactor is a fixed-bed continuous flow reactor, in which 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.

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

[0081] A1: Alumina powder and a photocurable resin were mixed in a mass ratio of 70:30 to obtain a mixture. The alumina powder had a particle size of 1.5 μm. The mixture was printed using a photocurable 3D printer to obtain a precursor. The precursor was heated to 600°C, held for 2 hours, and then calcined at 1500°C for 5 hours to obtain an alumina skeleton with a pore network. Testing showed that the pores of the alumina skeleton in this example had a pore diameter of 80 μm and a porosity of 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 concentration of citric acid and Zr 4+The molar ratio of the mixed solution is 1:2. After vacuum treatment, the alumina skeleton filled with the mixed solution in the pore network is taken out from the mixed solution, heated to 90°C, kept warm for 5 hours, and then calcined at 400°C for 5 hours to obtain an alumina skeleton with mesoporous zirconia growing in the pores.

[0083] A3: The surface of an alumina skeleton with mesoporous zirconia grown within the pores is coated with a hexadecyltrimethylammonium bromide solution. After drying, the alumina skeleton is immersed in an acetonitrile solution of phosphotungstic acid and vacuum-treated. After removal, the surface of the alumina skeleton is rinsed with acetonitrile and then heat-treated to obtain an alumina skeleton with a core. The concentration of phosphotungstic acid in acetonitrile is 0.2 mol / L, and the acetonitrile solution also contains 0.2 wt% 18-crown-6 ether. The heating temperature is 170°C and the duration is 3 hours.

[0084] A4: Immerse the alumina skeleton with a core in a suspension of polystyrene microspheres with a diameter of 300 nm. Vacuum treatment is then performed. A solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid is then drop-coated on the surface of the alumina skeleton. After drying, the solution is extracted with an ethanol-water solution. An aqueous solution containing magnesium nitrate and polyvinyl pyrrolidone is then spin-coated on the surface of the alumina skeleton. The solution is heat-dried and then calcined at 350°C for 4 hours to obtain a catalyst. In this step, the volume ratio of ethanol to water in the solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid is 6:1, the volume concentration of tetraethyl orthosilicate is 8%, the mass ratio of F127 is 2%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.05.

[0085] S2: γ-butyrolactone and aqueous ammonia were 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 distilled to obtain α-pyrrolidone.

[0087] Comparative Example 1

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

[0089] After testing, the contents of residual γ-butyrolactone in the crude products prepared in Examples 1-3 and Comparative Example 1 were 0.004 wt%, 0.005 wt%, 0.006 wt% and 0.09 wt%, respectively, and the contents of the intermediate 1-hydroxybutyramide were 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 distilled, 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. The catalysts of Examples 1-3 could be stably used for more than 1000 hours, while the performance of the catalyst in Comparative Example 1 decreased significantly after 300-400 hours 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A catalytic synthesis process for α-pyrrolidone, characterized in that: The steps include: S1: γ-butyrolactone is mixed with ammonia water, and after preheating, the mixture is introduced into a reactor filled with a catalyst; the catalyst comprises an alumina skeleton having 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: reacting γ-butyrolactone with aqueous ammonia at 190-220° C. and 1.5-2.0 MPa to obtain a crude product; S3: The crude product is concentrated and then distilled to obtain α-pyrrolidone.

2. The catalytic synthesis process of α-pyrrolidone according to claim 1, characterized in that: In step S1, the molar ratio of γ-butyrolactone to ammonia in aqueous ammonia is 1:1.5-1:2; Preheat the mixture of γ-butyrolactone and ammonia water to 160-180℃, then allow the mixture of γ-butyrolactone and ammonia water to stand for 0.8-1.5h. -1 The liquid hourly space velocity enters the reactor.

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 comprises the following steps: A1: Alumina powder is mixed with resin to obtain a mixture, the mixture is 3D printed to obtain a precursor, the precursor is heated to remove the resin, and then sintered to obtain an alumina skeleton with a pore network; A2: Immersing the alumina skeleton in a mixed solution of ZrOCl2 and citric acid, vacuum treating the alumina skeleton, then removing the alumina skeleton with the mixed solution in its pore network from the mixed solution, heating the alumina skeleton, and then calcining the alumina skeleton to obtain an alumina skeleton with mesoporous zirconia growing in its pores; A3: Coating the surface of the alumina skeleton with mesoporous zirconia grown in the pores with a cetyltrimethylammonium bromide solution, drying, immersing the alumina skeleton in an acetonitrile solution of phosphotungstic acid, vacuum treating, and then removing and rinsing the surface of the alumina skeleton with acetonitrile. The alumina skeleton is then heated to obtain an alumina skeleton with a core. A4: Immerse the alumina skeleton with an inner core in a polystyrene microsphere suspension and perform vacuum treatment. Then, a solution containing F127, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid is drop-coated on the surface of the alumina skeleton. After drying, the solution is extracted with an ethanol-water solution. Then, an aqueous solution containing magnesium nitrate and polyvinyl pyrrolidone is spin-coated on the surface of the alumina skeleton. After heating and drying, the solution is calcined to obtain a 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 light-curing resin, and the mixture is printed using a light-curing 3D printer. The particle size of the alumina powder is 0.5-1.5 μm, the heating temperature is 500-600°C, the heating time is 1-2 hours, and the calcination temperature is 1300-1500°C, and the calcination time is 3-5 hours.

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

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 also contains 0.1-0.2 wt% of 18-crown-6 ether, and the heating temperature is 150-170° C. for 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 proportion of F127 is 1-2%, and the molar ratio of hydrochloric acid to tetraethyl orthosilicate is 0.01-0.05; An aqueous solution containing magnesium nitrate and polyvinyl pyrrolidone is spin-coated on the surface of the alumina skeleton, heated and dried, and then calcined at 300-350° C. for 2-4 hours.

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