A production process for tetramethylpiperidinone and a method for preparing its catalyst

Abstract

This invention provides a production process for tetramethylpiperidinone and a method for preparing its catalyst, belonging to the technical field of tetramethylpiperidinone. The catalyst preparation method includes preparing a composite sol, preparing catalyst precursor powder, post-treatment, and calcination. The preparation of the catalyst precursor powder involves adding cerium nitrate and zirconium nitrate to deionized water, adding tartaric acid and stirring until homogeneous, then adding the mixture to the composite sol at a controlled addition rate of 1.5-2.0 g / min and a pH value of 8.8-9.2. After addition, the mixture is kept at 55-60℃ for 4.0 h, washed, and freeze-dried to obtain the catalyst precursor powder. The tetramethylpiperidinone obtained using the production process of this invention has high yield and purity, and a long catalyst lifespan.

Description

Technical Field

[0001] This invention belongs to the field of tetramethylpiperidone technology, specifically relating to a production process of tetramethylpiperidone and a method for preparing its catalyst. Background Technology

[0002] Tetramethylpiperidinone, also known as 2,2,6,6-tetramethylpiperidinone, has a rigid piperidine ring and hindered amine groups in its molecular structure. In the fine chemical industry, tetramethylpiperidinone is a core intermediate for the synthesis of hindered amine light stabilizers. Hindered amine light stabilizers, as highly efficient polymer anti-aging additives, can effectively prevent the degradation of polymer materials under the influence of environmental factors such as light, oxygen, and heat, significantly extending the service life of polymer products such as plastics, rubber, coatings, and fibers. They are widely used in industries such as plastic products and building materials. In the pharmaceutical field, tetramethylpiperidinone can be used as an intermediate for the synthesis of various drugs. Its piperidine ring structure can be modified to introduce different functional groups, thereby synthesizing drug molecules with antibacterial, anti-inflammatory, and antiviral biological activities. In the field of organic synthesis, tetramethylpiperidinone can act as a catalyst or ligand to participate in various organic reactions, such as oxidation, reduction, and addition reactions, promoting the efficient synthesis of complex organic compounds.

[0003] Currently, the industrial production of tetramethylpiperidone usually uses acetone and ammonia as raw materials. However, the direct reactivity of acetone and ammonia is very low. Even under high temperature and pressure, the main products are simple intermediates such as imine and enamine. It is difficult to efficiently and directionally carry out multi-molecular continuous condensation, cyclization and dehydration reactions, which makes it impossible to form the complex tetramethylpiperidone ring in the end. Therefore, catalysts that can activate reactant molecules are particularly important.

[0004] Catalysts mainly activate the carbonyl group of acetone by providing suitable acidic sites, promote the dehydration step, and lower the reaction energy barrier at each step, enabling the reaction to proceed efficiently under milder conditions. Existing technologies for catalyst preparation generally employ impregnation, mechanical blending, and co-precipitation methods. Among them, the impregnation method involves impregnating the surface of a support with a metal salt solution, followed by drying and calcination to obtain a catalyst. However, this method has poor controllability, the metal particles are prone to agglomeration during the preparation process, the interaction between the metal particles and the support is weak, the catalytic activity is unstable, and the active components are easily lost. Under the high temperature conditions of the reaction, they are prone to volatilization and migration, which leads to rapid decay of the catalyst's acidity and severely shortens the catalyst's lifespan. Mechanical blending involves directly physically grinding and mixing metal oxides and supports, followed by molding and calcination. Its drawback is that the active components and supports are only in physical contact, resulting in uneven mixing of catalyst components and poor homogeneity. This reduces the effective catalytic active centers, leading to low selectivity of the target reaction and easy generation of byproducts. The coprecipitation method involves mixing a metal salt solution containing catalytically active components (such as aluminum or silicon) with a precipitant (such as ammonia or ammonium carbonate) to generate hydroxide or carbonate precipitates, which are then dried and calcined to obtain an oxide catalyst. However, the catalysts obtained by this method have poor stability and short catalytic lifespan.

[0005] It is evident that in the existing production process of tetramethylpiperidinone, the catalyst has low catalytic activity, weak bonding between the active component and the support, poor catalyst stability, poor product yield and purity, and short catalytic life. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a production process for tetramethylpiperidinone and a method for preparing its catalyst. The catalyst exhibits high catalytic activity, strong bonding between the active component and the support, excellent stability, long catalytic lifetime, and high yield and purity of tetramethylpiperidinone.

[0007] To address the aforementioned technical problems, the present invention adopts the following technical solution: A process for producing tetramethylpiperidinone involves loading a catalyst into a fixed-bed packed tubular reactor with a diameter of 60-80 mm and a length of 2.5-3.0 m. The catalyst is then packed into the reactor tubes to a height of 1.8-2.0 m. Acetone is preheated to 120-130°C for vaporization, and liquid ammonia is heated to 84-88°C via a vaporizer for vaporization. The molar ratio of liquid ammonia to acetone is 3-5:1. After vaporization, the liquid ammonia and vaporized acetone are mixed, and nitrogen gas is introduced to control the volume fraction of acetone at 10-15%, resulting in a mixed feedstock. This mixed feedstock is then subjected to a process involving 0.7-1.0 h... -1 The catalyst is introduced into a fixed-bed tubular reactor, and the reaction temperature is controlled at 270-290℃ and the reaction pressure is 0.5-0.7MPa. The reaction product is collected by condensation and purified to obtain tetramethylpiperidinone. The catalyst preparation method includes the steps of preparing composite sol, preparing catalyst precursor powder, post-treatment and calcination. The steps for preparing the composite sol are as follows: aluminum isopropoxide is added to anhydrous ethanol, the temperature is raised to 58-62℃, deionized water and concentrated nitric acid solution are added, stirring is continued for 1.6-2.0h, tetraethyl orthosilicate solution is added, the temperature is raised to 64-68℃, and ultrasonic dispersion is performed with an ultrasonic power of 150W, an ultrasonic frequency of 32-38kHz, and an ultrasonic time of 1.5-2.0h to obtain the composite sol; The mass ratio of aluminum isopropoxide, anhydrous ethanol, deionized water, concentrated nitric acid solution, and tetraethyl orthosilicate solution is 20-24:50-60:7.0-7.5:0.2-0.3:17-23. The concentrated nitric acid solution has a mass concentration of 60-65%; The tetraethyl orthosilicate solution is prepared by stirring tetraethyl orthosilicate and anhydrous ethanol evenly; the mass ratio of tetraethyl orthosilicate to anhydrous ethanol is 7-8:10-15. The steps for preparing the catalyst precursor powder are as follows: Cerium nitrate and zirconium nitrate are added to deionized water, tartaric acid is added, and after stirring evenly, the mixture is added to the composite sol. The addition rate is controlled at 1.5-2.0 g / min, and the stirring speed is controlled at 120-140 rpm. The pH value is 8.8-9.2. After the addition is complete, the temperature is raised to 55-60℃ and kept at that temperature for 4.0 h. The mixture is then naturally cooled to room temperature, washed, and freeze-dried at -43 to -40℃ for 7-8 h. Then, the vacuum degree is controlled at 10-15 Pa, the temperature is raised to 25-27℃, and the mixture is dried for 24-26 h to obtain the catalyst precursor powder. The mass ratio of cerium nitrate, zirconium nitrate, tartaric acid, and composite sol is 6-8:4-5:50:2.0-2.5:95-100. The post-processing steps are as follows: ammonium dihydrogen phosphate is added to deionized water, ammonium molybdate and citric acid are added, and the mixture is stirred evenly to obtain an impregnation solution; catalyst precursor powder is added to the impregnation solution, and the mixture is stirred at 28-32℃ and 300-350rpm for 3.0-3.5h, filtered and dried to obtain calcined powder; The mass ratio of ammonium dihydrogen phosphate, deionized water, ammonium molybdate, and citric acid is 4.5-5.0:90:0.3-0.6:3.5-4.0. The mass ratio of the catalyst to the impregnation solution is 10:90-100; The calcination step is as follows: the calcined powder is placed in a muffle furnace for calcination, the temperature is increased to 200-210℃ at a rate of 1.0-1.3℃ / min, and held for 1.5-2.0h; then the temperature is increased to 380-400℃ at a rate of 2.0-2.5℃ / min, and held for 2.0-2.5h; then the temperature is increased to 600-610℃ at a rate of 2.8-3.2℃ / min, and held for 3.8-4.3h; and then cooled to room temperature in the furnace to obtain the catalyst.

[0008] This invention uses acetone and liquid ammonia as reactants. Catalysis by a catalyst leads to a ketone-amine condensation-intramolecular cyclization reaction, yielding tetramethylpiperidinone. Specifically, the catalyst is prepared by first hydrolyzing aluminum isopropoxide, then adding tetraethyl orthosilicate, which, under condensation, forms a composite sol network, providing abundant anchoring sites for subsequent loading of active components. Cerium nitrate and zirconium nitrate are then used as the cerium source and zirconium nitrate as the zirconium source, introducing and fixing cerium and zirconium as active components onto the silica-alumina framework. Tartaric acid acts as a chelating agent, ensuring uniform dispersion of cerium and zirconium ions in the gel. Under alkaline conditions, the tartaric acid complex gradually decomposes, and cerium and zirconium co-precipitate and bond in situ with the composite gel. After aging, the precipitation is more complete and the structure more stable. Combined with freeze-drying, water molecules directly sublimate, avoiding pore collapse and particle aggregation, thus preserving the catalyst's high specific surface area and porous network. The catalyst precursor powder with uniformly dispersed cerium and zirconium active components was obtained. During the impregnation process, ammonium dihydrogen phosphate, as an acidity regulator and stabilizer, can form POX bonds with aluminum, silicon, cerium, and zirconium on the support surface after calcination and decomposition, providing stable acidic sites and thus improving the selectivity of tetramethylpiperidone. Ammonium molybdate, as an auxiliary component, can improve the stability of the catalyst after calcination. Citric acid, as a chelating agent and dispersant, ensures the uniformity of impregnation, thereby obtaining the catalyst. The catalyst uses alumina and silica as a composite support, whose porous structure provides channels for reactant diffusion. Zirconia-cerium oxide provides redox capabilities. Combined with the impregnation process of the impregnation solution, uniform dispersion of each component, strong interfacial bonding, and abundant hierarchical channels are achieved, which enhances its resistance to carbon deposition, effectively promotes the reaction, extends the service life of the catalyst, and makes it suitable for continuous production.

[0009] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. Using the production process of this invention, the yield is 93.2-93.8%, and the purity is 99.54-99.65%; 2. The catalyst prepared by the method of the present invention has excellent stability, long service life, continuous operation for 1200 hours, and a yield of 91.1-92.5% of tetramethylpiperidinone with a purity of 98.34-98.85%. Detailed Implementation

[0010] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0011] Example 1 A process for producing tetramethylpiperidinone involves loading a catalyst into a fixed-bed packed tubular reactor (80 mm diameter, 3.0 m long). The catalyst is then packed into the reactor tubes to a height of 2.0 m. Acetone is preheated to 130°C for vaporization, and liquid ammonia is heated to 88°C via a vaporizer for vaporization. The molar ratio of liquid ammonia to acetone is 5:1. After vaporization, the liquid ammonia and vaporized acetone are mixed, and nitrogen gas is introduced to control the volume fraction of acetone at 15%, resulting in a mixed feedstock. This mixed feedstock is then subjected to a 1.0 h⁻¹ process. -1 The catalyst was introduced into a fixed-bed tubular reactor, and the reaction temperature was controlled at 290℃ and the reaction pressure at 0.7MPa. The reaction product was collected by condensation and purified to obtain tetramethylpiperidinone. The catalyst preparation method includes the steps of preparing composite sol, preparing catalyst precursor powder, post-treatment and calcination. The steps for preparing the composite sol are as follows: 24g of aluminum isopropoxide is added to 60g of anhydrous ethanol, the temperature is raised to 62℃, 7.5g of deionized water and 0.2g of concentrated nitric acid solution are added, and stirring is continued for 2.0h. Then, 23g of tetraethyl orthosilicate solution is added, the temperature is raised to 68℃, and ultrasonic dispersion is performed. The ultrasonic power is 150W, the ultrasonic frequency is 38kHz, and the ultrasonic time is 2.0h to obtain the composite sol. The concentrated nitric acid solution has a mass concentration of 65%. The tetraethyl orthosilicate solution is prepared by adding 8.0g of tetraethyl orthosilicate to 15g of anhydrous ethanol and stirring until homogeneous. The steps for preparing the catalyst precursor powder are as follows: 8g of cerium nitrate and 5g of zirconium nitrate are added to 50g of deionized water, 2.5g of tartaric acid is added, and after stirring evenly, it is added to 100g of composite sol. The addition rate is controlled at 2.0g / min, and the stirring speed is controlled at 140rpm. The pH value is 9.2. After the addition is completed, the temperature is raised to 60℃ and kept at that temperature for 4.0h. After naturally cooling to room temperature, it is washed and then freeze-dried at -40℃ for 8h. Then, the vacuum degree is controlled at 15Pa, the temperature is raised to 26℃, and it is dried for 26h to obtain the catalyst precursor powder. The post-processing steps are as follows: 5.0g of ammonium dihydrogen phosphate is added to 90g of deionized water, 0.6g of ammonium molybdate and 4.0g of citric acid are added, and the mixture is stirred evenly to obtain an impregnation solution; 10g of catalyst precursor powder is added to 100g of impregnation solution, and the mixture is stirred at 32℃ and 350rpm for 3.5h, filtered and dried to obtain calcined powder; The calcination step is as follows: the calcined powder is placed in a muffle furnace for calcination, the temperature is increased to 210°C at a rate of 1.3°C / min and held for 2.0 h, then the temperature is increased to 400°C at a rate of 2.5°C / min and held for 2.5 h, then the temperature is increased to 610°C at a rate of 3.2°C / min and held for 4.3 h, and then cooled to room temperature with the furnace to obtain the catalyst.

[0012] Example 2 A process for producing tetramethylpiperidinone involves loading a catalyst into a fixed-bed packed tubular reactor (60 mm diameter, 2.5 m length), filling the reactor tubes to a height of 1.8 m, preheating acetone to 120°C for vaporization, and vaporizing liquid ammonia to 84°C via a vaporizer. The molar ratio of liquid ammonia to acetone is 3:1. After vaporization, the liquid ammonia and vaporized acetone are mixed, and nitrogen gas is introduced to control the volume fraction of acetone at 10%, resulting in a mixed feedstock. The mixed feedstock is then subjected to a 0.7 h⁻¹ process. -1 The catalyst was introduced into a fixed-bed tubular reactor, and the reaction temperature was controlled at 270℃ and the reaction pressure at 0.5MPa. The reaction product was collected by condensation and purified to obtain tetramethylpiperidinone. The catalyst preparation method includes the steps of preparing composite sol, preparing catalyst precursor powder, post-treatment and calcination. The steps for preparing the composite sol are as follows: 20g of aluminum isopropoxide is added to 50g of anhydrous ethanol, the temperature is raised to 58℃, 7.0g of deionized water and 0.2g of concentrated nitric acid solution are added, and stirring is continued for 1.6h. Then, 17g of tetraethyl orthosilicate solution is added, the temperature is raised to 64℃, and ultrasonic dispersion is performed. The ultrasonic power is 140W, the ultrasonic frequency is 32kHz, and the ultrasonic time is 1.5h to obtain the composite sol. The concentrated nitric acid solution has a mass concentration of 60%. The tetraethyl orthosilicate solution is prepared by adding 7.0g of tetraethyl orthosilicate to 10g of anhydrous ethanol and stirring until homogeneous. The steps for preparing the catalyst precursor powder are as follows: 6g of cerium nitrate and 4g of zirconium nitrate are added to 50g of deionized water, 2.0g of tartaric acid is added, and after stirring evenly, it is added to 95g of composite sol. The addition rate is controlled at 1.5g / min, and the stirring speed is controlled at 120rpm. The pH value is 8.8. After the addition is completed, the temperature is raised to 55℃ and kept at that temperature for 3.8h. After naturally cooling to room temperature, it is washed and then freeze-dried at -43℃ for 7h. Then, the vacuum degree is controlled at 10Pa, the temperature is raised to 25℃, and it is dried for 24h to obtain the catalyst precursor powder. The post-processing steps are as follows: 4.5g of ammonium dihydrogen phosphate is added to 90g of deionized water, 0.3g of ammonium molybdate and 3.5g of citric acid are added, and the mixture is stirred evenly to obtain an impregnation solution; 10g of catalyst precursor powder is added to 90g of impregnation solution, and the mixture is stirred at 28℃ and 300rpm for 3.0h, filtered and dried to obtain calcined powder; The calcination step is as follows: the calcined powder is placed in a muffle furnace for calcination, the temperature is increased to 200°C at a rate of 1.0°C / min and held for 1.5 hours, then the temperature is increased to 380°C at a rate of 2.0°C / min and held for 2.0 hours, then the temperature is increased to 600°C at a rate of 2.8°C / min and held for 3.8 hours, and then cooled to room temperature with the furnace to obtain the catalyst.

[0013] Example 3 A process for producing tetramethylpiperidinone involves loading a catalyst into a fixed-bed packed tubular reactor (70 mm diameter, 2.8 m long). The catalyst is then packed into the reactor tubes to a height of 2.0 m. Acetone is preheated to 125°C and vaporized. Liquid ammonia is heated to 86°C via a vaporizer and vaporized. The molar ratio of liquid ammonia to acetone is 4:1. After vaporization, the liquid ammonia and vaporized acetone are mixed, and nitrogen gas is introduced to control the volume fraction of acetone at 12%, resulting in a mixed feedstock. This mixed feedstock is then subjected to a 0.8 h⁻¹ process. -1 The catalyst was introduced into a fixed-bed tubular reactor, and the reaction temperature was controlled at 280℃ and the reaction pressure at 0.6MPa. The reaction product was collected by condensation and purified to obtain tetramethylpiperidinone. The catalyst preparation method includes the steps of preparing composite sol, preparing catalyst precursor powder, post-treatment and calcination. The steps for preparing the composite sol are as follows: 22g of aluminum isopropoxide is added to 55g of anhydrous ethanol, the temperature is raised to 60℃, 7.3g of deionized water and 0.3g of concentrated nitric acid solution are added, and stirring is continued for 1.8h. Then, 20g of tetraethyl orthosilicate solution is added, the temperature is raised to 66℃, and ultrasonic dispersion is performed. The ultrasonic power is 145W, the ultrasonic frequency is 36kHz, and the ultrasonic time is 1.8h to obtain the composite sol. The concentrated nitric acid solution has a mass concentration of 63%. The tetraethyl orthosilicate solution is prepared by adding 7.5g of tetraethyl orthosilicate to 12g of anhydrous ethanol and stirring until homogeneous. The steps for preparing the catalyst precursor powder are as follows: 7g of cerium nitrate and 5g of zirconium nitrate are added to 50g of deionized water, 2.3g of tartaric acid is added, and after stirring evenly, it is added to 98g of composite sol. The addition rate is controlled at 1.7g / min, and the stirring speed is controlled at 130rpm. The pH value is 9.0. After the addition is completed, the temperature is raised to 57℃ and kept at that temperature for 4.0h. After naturally cooling to room temperature, it is washed and then freeze-dried at -42℃ for 8h. Then, the vacuum degree is controlled at 13Pa, the temperature is raised to 27℃, and it is dried for 25h to obtain the catalyst precursor powder. The post-processing steps are as follows: 4.7g of ammonium dihydrogen phosphate is added to 90g of deionized water, 0.5g of ammonium molybdate and 3.8g of citric acid are added, and the mixture is stirred evenly to obtain an impregnation solution; 10g of catalyst precursor powder is added to 95g of impregnation solution, and the mixture is stirred at 30℃ and 320rpm for 3.3h, filtered and dried to obtain calcined powder; The calcination step is as follows: the calcined powder is placed in a muffle furnace for calcination, the temperature is increased to 205°C at a rate of 1.2°C / min and held for 1.8 hours, then the temperature is increased to 390°C at a rate of 2.3°C / min and held for 2.3 hours, then the temperature is increased to 605°C at a rate of 3.0°C / min and held for 4.0 hours, and then cooled to room temperature with the furnace to obtain the catalyst.

[0014] Comparative Example 3-1 Based on Example 3, the following changes were made: In the catalyst preparation method, in the step of preparing catalyst precursor powder, zirconium nitrate is replaced by cerium nitrate in an equal amount; The post-processing steps are omitted; the catalyst precursor powder is directly calcined. The rest of the operations are exactly the same.

[0015] Performance testing The purity and yield of tetramethylpiperidone obtained in Examples 1-3 and Comparative Example 3-1 are as follows:

[0016] The processes of Examples 1-3 and Comparative Example 3-1 were run continuously for 1200 hours, and the yield and purity of tetramethylpiperidone were tested respectively. The results are as follows:

[0017] Comparative Example 3-1 omits the post-processing steps, lacks the regulation of components such as ammonium dihydrogen phosphate and ammonium molybdate, and lacks the synergistic effect of zirconium, which weakens the stability of the catalyst, resulting in poorer pores and dispersibility, leading to a decrease in the specific surface area of ​​the catalyst, ultimately resulting in an increase in by-products and a decrease in the selectivity of tetramethylpiperidone. As a result, after continuous operation for a long time, the thermal stability of the catalyst is weakened, and the structure is prone to collapse under high temperature conditions, which leads to a significant decrease in product yield and purity.

[0018] Unless otherwise specified, all proportions mentioned in this invention are mass proportions, and all percentages are mass percentages.

[0019] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for producing tetramethylpiperidinone, characterized in that, The acetone and liquid ammonia are vaporized respectively, mixed with nitrogen, and then obtained as a mixed raw material. The mixed raw material is introduced into a fixed bed tubular reactor with a catalyst at a reaction temperature of 270-290°C and a reaction pressure of 0.5-0.7 MPa, and then obtained as tetramethylpiperidone. -1 The acetone and liquid ammonia are vaporized respectively, mixed with nitrogen, and then obtained as a mixed raw material. The mixed raw material is introduced into a fixed bed tubular reactor with a catalyst at a reaction temperature of 270-290°C and a reaction pressure of 0.5-0.7 MPa, and then obtained as tetramethylpiperidone. The method for preparing the catalyst includes the steps of preparing a composite sol, preparing catalyst precursor powder, post-treatment, and calcination. The steps for preparing the catalyst precursor powder are as follows: cerium nitrate and zirconium nitrate are added to deionized water, tartaric acid is added and stirred evenly, and then added to the composite sol. The addition rate is controlled at 1.5-2.0 g / min, and the pH value is 8.8-9.

2. After the addition is completed, the mixture is kept at 55-60℃ for 4.0 h, washed, and then freeze-dried to obtain the catalyst precursor powder. The post-processing steps are as follows: ammonium dihydrogen phosphate is added to deionized water, and ammonium molybdate and citric acid are added to obtain an impregnation solution; catalyst precursor powder is added to the impregnation solution and stirred for 3.0-3.5 hours to obtain calcined powder.

2. The production process of tetramethylpiperidinone according to claim 1, characterized in that, The catalyst is filled in a fixed bed packed tubular reactor with a pipe diameter of 60-80 mm and a pipe length of 2.5-3.0 m, and the catalyst is filled in the reactor column pipe with a filling height of 1.8-2.0 m. The acetone is preheated to 120-130 ℃ for vaporization, and the liquid ammonia is heated to 84-88 ℃ by a vaporizer for vaporization. The molar ratio of the liquid ammonia to the acetone is 3-5:

1. After vaporization, the liquid ammonia is mixed with the vaporized acetone, and then nitrogen is introduced to control the volume fraction of the acetone to 10-15%, so as to obtain the mixed raw material. The mixed raw material is introduced into the fixed bed tubular reactor at a flow rate of 0.7-1.0 h -1 The reaction temperature is controlled to be 270-290 ℃, and the reaction pressure is controlled to be 0.5-0.7 MPa. After the reaction product is collected by condensation, it is purified to obtain tetramethylpiperidone.

3. The production process of tetramethylpiperidone according to claim 1, characterized in that, The steps for preparing the composite sol are as follows: aluminum isopropoxide is added to anhydrous ethanol, the temperature is raised to 58-62℃, deionized water and concentrated nitric acid solution are added, stirring is continued for 1.6-2.0h, tetraethyl orthosilicate solution is added, the temperature is raised to 64-68℃, and ultrasonic dispersion is performed with an ultrasonic power of 150W, an ultrasonic frequency of 32-38kHz, and an ultrasonic time of 1.5-2.0h to obtain the composite sol; The mass ratio of aluminum isopropoxide, anhydrous ethanol, deionized water, concentrated nitric acid solution, and tetraethyl orthosilicate solution is 20-24:50-60:7.0-7.5:0.2-0.3:17-23. The concentrated nitric acid solution has a mass concentration of 60-65%; The tetraethyl orthosilicate solution is prepared by stirring tetraethyl orthosilicate and anhydrous ethanol evenly; the mass ratio of tetraethyl orthosilicate to anhydrous ethanol is 7-8:10-15.

4. The production process of tetramethylpiperidone according to claim 1, characterized in that, In the step of preparing the catalyst precursor powder, the mass ratio of cerium nitrate, zirconium nitrate, tartaric acid, and composite sol is 6-8:4-5:50:2.0-2.5:95-100. The freeze-drying process involves first freezing at -43 to -40°C for 7-8 hours, then controlling the vacuum degree at 10-15 Pa, raising the temperature to 25-27°C, and drying for 24-26 hours.

5. The production process of tetramethylpiperidone according to claim 1, characterized in that, In the post-processing step, the mass ratio of ammonium dihydrogen phosphate, deionized water, ammonium molybdate, and citric acid is 4.5-5.0:90:0.3-0.6:3.5-4.0; The mass ratio of the catalyst to the impregnation solution is 10:90-100.

6. The production process of tetramethylpiperidinone according to claim 1, characterized in that, The calcination step is as follows: the calcined powder is placed in a muffle furnace for calcination, the temperature is increased to 200-210℃ at a rate of 1.0-1.3℃ / min, and held for 1.5-2.0h; then the temperature is increased to 380-400℃ at a rate of 2.0-2.5℃ / min, and held for 2.0-2.5h; then the temperature is increased to 600-610℃ at a rate of 2.8-3.2℃ / min, and held for 3.8-4.3h; and then cooled to room temperature in the furnace to obtain the catalyst.

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