Catalyst for producing tetramethylpiperidinol and preparation method thereof
By preparing a composite support and loading copper and rare earth metals, the problems of low activity, poor selectivity and poor stability of existing catalysts were solved, and the efficient production of tetramethylpiperidinol was achieved, which is suitable for industrial application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-11
- Publication Date
- 2026-03-03
AI Technical Summary
Existing catalysts suffer from low catalytic activity, poor selectivity, complex preparation process, high production cost, and poor stability in the preparation of tetramethylpiperidinol. In particular, the active components of the catalyst tend to agglomerate and have weak interaction with the support, resulting in low yield of tetramethylpiperidinol and hindering industrial production.
A composite support was prepared using chitosan, tetraethyl orthosilicate, magnesium gluconate, aminotrimethylenephosphonic acid, and yttrium nitrate. Copper and rare earth metals were loaded onto the support through plasma treatment to form an organic-inorganic hybrid network, which enhanced the activity and stability of the catalyst and improved its binding with the metal components.
The catalyst achieved a product yield of 99.47-99.65% after 336 hours of continuous operation and 98.18-98.97% after 504 hours of continuous operation. It also maintained a high yield after multiple cycles, which significantly improved the stability and selectivity of the catalyst and reduced production costs.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst technology, specifically relating to a catalyst for the production of tetramethylpiperidinol and its preparation method. Background Technology
[0002] Tetramethylpiperidinol, chemically named 2,2,6,6-tetramethyl-4-piperidinol, is a very important fine chemical intermediate. It is a white crystalline powder at room temperature, soluble in organic solvents such as acetone, ethanol, and chloroform, slightly soluble in water, and hygroscopic. The piperidine ring and hindered amine structure in the tetramethylpiperidinol molecular structure make it a core raw material for synthesizing hindered amine light stabilizers. Hindered amine light stabilizers are among the most effective light stabilizers currently available. They are a class of organic amine compounds with steric hindrance effects and are widely used in polymer materials such as rubber, plastics, coatings, and synthetic fibers. They effectively inhibit aging, yellowing, and degradation caused by ultraviolet light irradiation, significantly extending the service life of products. Therefore, the efficient synthesis of tetramethylpiperbutanol is of great research significance.
[0003] Currently, industrial methods for preparing tetramethylpiperidinol include catalytic hydrogenation, chemical reduction, electrochemical reduction, and bio-enzymatic catalysis. Catalytic hydrogenation has become the mainstream process due to its advantages such as low raw material cost, no by-product pollution, green safety, and simple operation. Specifically, it uses triacetone amine as a raw material, which undergoes an addition reaction with hydrogen under the action of a catalyst. The C=O bond on the piperidine ring is reduced to a C-OH bond to generate tetramethylpiperidinol.
[0004] The core of triacetone amine catalysis lies in the catalyst, and the existing catalysts mainly include the following types: Raney nickel catalyst: It was the most commonly used catalyst in the early days. It is made from nickel-aluminum alloy as raw material. Aluminum is dissolved by concentrated alkali solution to obtain Raney nickel with a porous structure. However, it is extremely flammable in air and is highly dangerous during storage, transportation and use. It is prone to decomposition during use, which leads to catalyst loss and reactor blockage. In addition, it is easy to cause over-hydrogenation, which in turn causes side reactions and ultimately affects the selectivity and yield of tetramethylpiperbutanol. Alumina-based Cu catalysts: These are typically produced using a co-precipitation method, where copper nitrate and aluminum nitrate are dissolved in deionized water, and sodium carbonate solution is added to adjust the pH to 7.0-8.0, generating Cu(OH)2-Al(OH)3 precipitate. After washing and calcination, a Cu / Al2O3 catalyst is obtained. However, the active sites are poorly dispersed, and Cu particles tend to agglomerate, leading to reduced hydrogenation activity and decreased conversion of triacetone amine. Furthermore, the interaction between Cu and the Al2O3 support is weak, and Cu particles are prone to detachment during the reaction, resulting in poor continuous use performance of the catalyst. Cu-Ru bimetallic doped titanium-silicon composite oxide catalysts: These are typically prepared using a sol-gel method, in which tetrabutyl titanate, tetraethyl orthosilicate, copper nitrate, and ruthenium nitrate are dissolved in ethanol, and hydrochloric acid is added to adjust the pH to form a sol. After aging, drying, calcination, and reduction, Cu-Ru / TiO2-SiO2 catalysts are obtained. The preparation process is relatively complex, and the use of the precious metal Ru greatly increases the production cost, which is not conducive to industrial production. During the reaction, the reactants do not come into contact with the reaction sites, which reduces the selectivity of tetramethylpiperbutanol.
[0005] As can be seen from the above, the catalysts used in the existing catalytic method for preparing tetramethylpiperidinol have the following defects: 1. The catalyst has low activity and poor selectivity, resulting in a low yield of tetramethylpiperbutanol; 2. The preparation process of catalysts is complex, the production cost is high, and the safety is low, which is not conducive to industrial production; 3. The catalyst has poor stability, the active components are prone to agglomeration, the interaction between the catalyst and the support is weak, and the components are easy to detach, which seriously reduces the cycle life. Summary of the Invention
[0006] To address the technical problems existing in the prior art, this invention provides a catalyst for the production of tetramethylpiperidinol and its preparation method. The catalyst has high catalytic activity, low production cost, simple process, strong interaction between the active component and the support, can effectively improve the yield of tetramethylpiperidinol, has excellent recycling performance, and is beneficial for industrial production.
[0007] To address the aforementioned technical problems, the present invention adopts the following technical solution: A method for preparing a catalyst for the production of tetramethylpiperidinol includes the steps of preparing a composite support, pretreatment of the composite support, impregnation, and reduction, as detailed below: 1. Preparation of composite carriers (1) Preparation of composite gel Add chitosan to the acetic acid solution and stir at room temperature for 40-50 min. Add tetraethyl orthosilicate, magnesium gluconate, aminotrimethylene phosphonic acid and yttrium nitrate, and stir at 300-320 rpm for 70-80 min. After stirring, reduce the stirring speed to 200-210 rpm and continue stirring for 40-50 min. Add 20-23 wt% ammonia solution and adjust the pH to 7.2-7.6 to obtain the composite gel. The degree of deacetylation of the chitosan is 92-96%, and the molecular weight is 82-90 kDa; The mass ratio of the acetic acid solution, chitosan, tetraethyl orthosilicate, magnesium gluconate, aminotrimethylenephosphonic acid, and yttrium nitrate is 200:2.0-2.5:3.8-4.0:1.0-1.2:0.20-0.25:0.40-0.46. The acetic acid solution has a mass concentration of 2.0-2.5%; (2) Post-gel treatment The composite gel was cured at 60-64℃ for 20-24h and then freeze-dried. The temperature was then decreased to -42 to -37℃ at a rate of 8-10℃ / min and held for 1.5-2.0h. Then, the vacuum degree was controlled at 35-45Pa, and the temperature was increased to -25 to -22℃ at a rate of 2.0-2.5℃ / h and held for 20-24h. Next, the vacuum degree was controlled at 15-20Pa, and the temperature was increased to 25-27℃ at a rate of 2.5-3.0℃ / h and held for 6-8h. Finally, the temperature was increased to 680-700℃ at a rate of 2.0-2.5℃ / min and held for 2.8-3.0h. The temperature was then decreased to 280-310℃ at a rate of 4.0-5.0℃ / min and allowed to cool naturally to room temperature to obtain the composite carrier.
[0008] 2. Pretreatment of composite carrier 20g of the composite carrier was placed in a plasma apparatus and purged with nitrogen gas at a flow rate of 28-32 mL / min for 25-30 min. Then, ammonia and water vapor were introduced, with the ammonia flow rate controlled at 16-20 mL / min and the water vapor flow rate at 8-10 mL / min. The plasma power supply was turned on with a discharge power of 210-230 W and a temperature of 26-30℃ for 45-55 min. The electrode spacing was 16-20 mm. The plasma power supply was then turned off, and nitrogen gas was introduced again for 26-30 min at a flow rate of 15-20 mL / min. After cooling and drying, the pretreated composite carrier was obtained.
[0009] 3. Impregnation The pretreated composite carrier was placed in a copper nitrate solution and subjected to ultrasonic oscillation for 50-60 min, with an ultrasonic power of 380-420 W and an ultrasonic frequency of 45-50 kHz. After ultrasonication, it was washed and placed in a rare earth mixture for further ultrasonic oscillation for 50-60 min. Then, it was stirred at 120-150 rpm for 50-60 min. After filtration and drying, the impregnated composite carrier was obtained. The mass ratio of the pretreated composite carrier, copper nitrate solution, and rare earth mixture is 5.0:45-50:35-40; The copper nitrate solution is a mixture of deionized water, copper nitrate, and disodium ethylenediaminetetraacetate, wherein the mass ratio of deionized water, copper nitrate, and disodium ethylenediaminetetraacetate is 100:2.3-2.6:2.8-3.0. The rare earth mixture is obtained by mixing deionized water, nickel nitrate, cerium nitrate and citric acid, and adjusting the pH to 5.7-6.0 with 10-15wt% ammonia solution. The mass ratio of the deionized water, nickel nitrate, cerium nitrate and citric acid is 100:0.8-1.2:0.3-0.5:1.4-1.7.
[0010] 4. Restore The impregnated composite support is heated to 540-550℃ at a rate of 2.0-2.5℃ / min under a hydrogen atmosphere, held at that temperature for 30-40min, and then naturally cooled to room temperature to obtain the catalyst.
[0011] A catalyst for the production of tetramethylpiperidinol was prepared using the aforementioned method.
[0012] The catalyst of this invention is prepared by first preparing a catalyst support, then impregnating and loading a metal active component onto the support, followed by reduction. Chitosan is introduced during the catalyst support preparation step, which determines the macroporous and mesoporous structure of the catalyst support. Tetraethyl orthosilicate is then combined with it; the Si-OH groups generated from its hydrolysis bind to the hydroxyl and amino groups of chitosan through electrostatic interactions and hydrogen bonds, forming an organic-inorganic hybrid network. This improves the high thermal stability and abundant silanol groups of the catalyst support. Magnesium gluconate binds to the chitosan chains, subsequently enhancing its binding affinity to triacetone amine, thereby promoting the forward catalytic reaction. The phosphonic acid groups in aminotrimethylenephosphonic acid strongly complex with metal ions. Amino acids provide a nitrogen source, thereby enhancing the binding affinity with metal components. Yttrium nitrate acts as a stabilizer, improving catalyst stability and effectively extending catalyst lifespan. Plasma treatment of the composite support then increases the surface active sites, laying the foundation for subsequent metal loading. In the impregnation step, copper, as the main active center, works synergistically with nickel and cerium to effectively improve the selectivity of the hydrogenation reaction, enhance catalytic activity, and improve reaction stability. This accelerates the reaction efficiency in the hydrogenation step, prevents the shedding and migration of metal active components during catalyst recycling and regeneration, ensures catalyst stability, and effectively extends catalyst lifespan.
[0013] Compared with the prior art, the present invention achieves the following beneficial effects: 1. The catalyst prepared by this invention is used to produce tetramethylpiperidinol, with a product yield of 99.47-99.65% after 336 hours of continuous operation and 98.18-98.97% after 504 hours of continuous operation; 2. The catalyst prepared in this invention was placed in a 5.0 wt% sodium hydroxide solution and soaked at room temperature for 12 h. After soaking, it was washed and dried, and then the temperature was increased to 150 °C at a rate of 5.0 °C / min and kept at that temperature for 12 h. This treatment was considered as one cycle. After 10 cycles of treatment, it was used again to produce tetramethylpiperidinol. The product yield was 94.89-96.26% after 336 h of continuous operation and 93.47-95.11% after 504 h of continuous operation. Detailed Implementation
[0014] 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.
[0015] Example 1 1. Preparation of composite carriers (1) Preparation of composite gel Add 2.5g of chitosan to 200g of 2.5wt% acetic acid solution and stir at room temperature for 50min. Then add 4.0g of tetraethyl orthosilicate, 1.0g of magnesium gluconate, 0.25g of aminotrimethylenephosphonic acid and 0.46g of yttrium nitrate. Stir at 320rpm for 80min. After stirring, reduce the stirring speed to 210rpm and continue stirring for 50min. Add 23wt% ammonia solution and adjust the pH to 7.6 to obtain a composite gel. The degree of deacetylation of the chitosan is 96%, and the molecular weight is 90 kDa; (2) Post-gel treatment The composite gel was cured at 64℃ for 20 h and then freeze-dried. The temperature was decreased to -37℃ at a rate of 10℃ / min and held for 1.5 h. Then, the vacuum was controlled at 45 Pa and the temperature was increased to -22℃ at a rate of 2.5℃ / h and held for 24 h. Next, the vacuum was controlled at 20 Pa and the temperature was increased to 27℃ at a rate of 3.0℃ / h and held for 8 h. Finally, the temperature was increased to 700℃ at a rate of 2.5℃ / min and held for 3.0 h. The temperature was then decreased to 310℃ at a rate of 5.0℃ / min and allowed to cool naturally to room temperature to obtain the composite carrier.
[0016] 2. Pretreatment of composite carrier The composite carrier was placed in a plasma device and purged with nitrogen gas at a flow rate of 32 mL / min for 30 min. Then, a mixture of ammonia and water vapor was introduced at a flow rate of 20 mL / min and 10 mL / min. The plasma power supply was turned on with a discharge power of 230 W, a temperature of 30 °C, and a treatment time of 55 min. The electrode spacing was 20 mm. The plasma power supply was then turned off, and nitrogen gas was introduced for another 30 min at a flow rate of 20 mL / min. After cooling and drying, the pretreated composite carrier was obtained.
[0017] 3. Impregnation 5.0g of pretreated composite carrier was placed in 50g of copper nitrate solution and subjected to ultrasonic oscillation for 60min, with an ultrasonic power of 420W and an ultrasonic frequency of 50kHz. After ultrasonication, the carrier was washed and placed in 40g of rare earth mixture and subjected to ultrasonic oscillation for another 60min. Then, the carrier was stirred at 150rpm for 60min. After filtration and drying, the impregnated composite carrier was obtained. The copper nitrate solution is a mixture of deionized water, copper nitrate, and disodium ethylenediaminetetraacetate, wherein the mass ratio of deionized water, copper nitrate, and disodium ethylenediaminetetraacetate is 100:2.6:3.0. The rare earth mixture is obtained by mixing deionized water, nickel nitrate, cerium nitrate and citric acid, and adjusting the pH to 6.0 with 15wt% ammonia solution. The mass ratio of the deionized water, nickel nitrate, cerium nitrate and citric acid is 100:1.2:0.5:1.7.
[0018] 4. Restore The impregnated composite support was heated to 550°C at a rate of 2.5°C / min under a hydrogen atmosphere, held at that temperature for 40 min, and then naturally cooled to room temperature to obtain the catalyst.
[0019] Example 2 1. Preparation of composite carriers (1) Preparation of composite gel Add 2.2g of chitosan to 200g of 2.3wt% acetic acid solution and stir at room temperature for 45min. Then add 3.9g of tetraethyl orthosilicate, 1.2g of magnesium gluconate, 0.23g of aminotrimethylenephosphonic acid and 0.43g of yttrium nitrate, and stir at 310rpm for 75min. After stirring, reduce the stirring speed to 210rpm and continue stirring for 45min. Add 22wt% ammonia solution and adjust the pH to 7.5 to obtain a composite gel. The degree of deacetylation of the chitosan is 94%, and the molecular weight is 85 kDa; (2) Post-gel treatment The composite gel was cured at 62℃ for 22h and then freeze-dried. The temperature was decreased to -4037℃ at a rate of 9℃ / min and held for 1.8h. Then, the vacuum was controlled at 40Pa and the temperature was increased to -24℃ at a rate of 2.3℃ / h and held for 22h. Next, the vacuum was controlled at 18Pa and the temperature was increased to 26℃ at a rate of 2.8℃ / h and held for 7h. Finally, the temperature was increased to 690℃ at a rate of 2.3℃ / min and held for 3.0h. The temperature was then decreased to 300℃ at a rate of 4.5℃ / min and allowed to cool naturally to room temperature to obtain the composite carrier.
[0020] 2. Pretreatment of composite carrier The composite carrier was placed in a plasma device and purged with nitrogen gas at a flow rate of 30 mL / min for 28 min. Then, a mixture of ammonia and water vapor was introduced at a flow rate of 18 mL / min and 10 mL / min. The plasma power supply was turned on with a discharge power of 220 W, a temperature of 28 °C, and a treatment time of 50 min. The electrode spacing was 18 mm. The plasma power supply was then turned off, and nitrogen gas was introduced again for 28 min at a flow rate of 18 mL / min. After cooling and drying, the pretreated composite carrier was obtained.
[0021] 3. Impregnation 5.0 g of pretreated composite carrier was placed in 48 g of copper nitrate solution and subjected to ultrasonic oscillation for 55 min, with an ultrasonic power of 400 W and an ultrasonic frequency of 47 kHz. After ultrasonication, the carrier was washed and placed in 37 g of rare earth mixture and subjected to ultrasonic oscillation for another 55 min. Then, the carrier was stirred at 130 rpm for 55 min. After filtration and drying, the impregnated composite carrier was obtained. The copper nitrate solution is a mixture of deionized water, copper nitrate, and disodium ethylenediaminetetraacetate, wherein the mass ratio of deionized water, copper nitrate, and disodium ethylenediaminetetraacetate is 100:2.4:2.9. The rare earth mixture is obtained by mixing deionized water, nickel nitrate, cerium nitrate and citric acid, and adjusting the pH to 5.8 with a 12wt% ammonia solution. The mass ratio of the deionized water, nickel nitrate, cerium nitrate and citric acid is 100:1.0:0.4:1.5.
[0022] 4. Restore The impregnated composite support was heated to 545°C at a rate of 2.3°C / min under a hydrogen atmosphere, held at that temperature for 35 min, and then naturally cooled to room temperature to obtain the catalyst.
[0023] Example 3 1. Preparation of composite carriers (1) Preparation of composite gel Add 2.0g of chitosan to 200g of 2.0wt% acetic acid solution and stir at room temperature for 40min. Then add 3.8g of tetraethyl orthosilicate, 1.0g of magnesium gluconate, 0.20g of aminotrimethylenephosphonic acid and 0.40g of yttrium nitrate, and stir at 300rpm for 70min. After stirring, reduce the stirring speed to 200rpm and continue stirring for 40min. Add 20-23wt% ammonia solution and adjust the pH to 7.2 to obtain a composite gel. The degree of deacetylation of the chitosan is 92%, and the molecular weight is 82 kDa; (2) Post-gel treatment The composite gel was cured at 60℃ for 24 hours and then freeze-dried. The temperature was decreased to -42℃ at a rate of 8℃ / min and held for 2.0 hours. Then, the vacuum degree was controlled at 35Pa and the temperature was increased to -25℃ at a rate of 2.0℃ / h and held for 20 hours. Next, the vacuum degree was controlled at 15Pa and the temperature was increased to 25℃ at a rate of 2.5℃ / h and held for 6 hours. Finally, the temperature was increased to 680℃ at a rate of 2.0℃ / min and held for 2.8 hours. The temperature was decreased to 280℃ at a rate of 4.0℃ / min and allowed to cool naturally to room temperature to obtain the composite carrier.
[0024] 2. Pretreatment of composite carrier The composite carrier was placed in a plasma device and purged with nitrogen gas at a flow rate of 28 mL / min for 25 min. Then, a mixture of ammonia and water vapor was introduced at a flow rate of 16 mL / min and 8 mL / min. The plasma power supply was turned on with a discharge power of 210 W and a temperature of 26 °C for 45 min. The electrode spacing was 16 mm. The plasma power supply was then turned off, and nitrogen gas was introduced for another 26 min at a flow rate of 15 mL / min. After cooling and drying, the pretreated composite carrier was obtained.
[0025] 3. Impregnation 5.0 g of pretreated composite carrier was placed in 45 g of copper nitrate solution and subjected to ultrasonic oscillation for 50 min at a power of 380 W and a frequency of 45 kHz. After ultrasonication, the carrier was washed and placed in 35 g of rare earth mixture and subjected to ultrasonic oscillation for another 50 min. Then the carrier was stirred at 120 rpm for 500 min. After filtration and drying, the impregnated composite carrier was obtained. The copper nitrate solution is a mixture of deionized water, copper nitrate, and disodium ethylenediaminetetraacetate, wherein the mass ratio of deionized water, copper nitrate, and disodium ethylenediaminetetraacetate is 100:2.36:2.8. The rare earth mixture is obtained by mixing deionized water, nickel nitrate, cerium nitrate and citric acid, and adjusting the pH to 5.7 with 10wt% ammonia solution. The mass ratio of the deionized water, nickel nitrate, cerium nitrate and citric acid is 100:0.8:0.3:1.4.
[0026] 4. Restore The impregnated composite support was heated to 540°C at a rate of 2.0°C / min under a hydrogen atmosphere, held at that temperature for 30 min, and then naturally cooled to room temperature to obtain the catalyst.
[0027] Comparative Example 1 Based on Example 2, the following changes were made: In the step of preparing the composite carrier, in the step of preparing the composite gel, the components "chitosan and yttrium nitrate" are replaced with tetraethyl orthosilicate. The composite carrier pretreatment step is omitted. In the impregnation step, "pretreated composite carrier" is replaced with "composite carrier" in equal amounts. All other operations are the same.
[0028] Comparative Example 2 Based on Example 2, the following changes were made: In the step of preparing the composite carrier, in the step of preparing the composite gel, "magnesium gluconate and aminotrimethylene phosphonic acid" are replaced with tetraethyl orthosilicate in equal amounts; In the impregnation step, the operation step of "placing it in 37g of rare earth mixture and continuing ultrasonic oscillation for 55min" is omitted. All other operations are the same.
[0029] Application performance testing (1) Application method The catalysts prepared in Examples 1-3 and Comparative Examples 1-2 were used to produce tetramethylpiperidinol. Specifically, 3.0 g of catalyst was placed in a fixed-bed reactor, hydrogen was introduced, and the temperature was raised to 75°C for reaction. The hydrogen flow rate was controlled at 1 L / h, and the reaction pressure was 1.0 MPa. The reaction solution (isopropanol to triacetone amine molar ratio of 3:1) was added to the reactor at a flow rate of 12 mL / h to start the reaction. After the reaction stabilized, the reaction products were collected and analyzed by gas chromatography.
[0030] (2) Test results A. Recyclability The catalysts obtained in Examples 1-3 and Comparative Examples 1-2 were used to produce tetramethylpiperanol according to the above application method. The average product yield (%) after continuous operation for 336 h and 504 h was statistically analyzed, and the results are as follows:
[0031] B. Stability performance The catalysts prepared in Examples 1-3 and Comparative Examples 1-2 were respectively placed in a 5.0 wt% sodium hydroxide solution and soaked at room temperature for 12 h. After soaking, they were washed and dried, and then the temperature was increased to 150 °C at a rate of 5.0 °C / min and held for 12 h. This treatment constituted one cycle, and 10 cycles were performed consecutively. Tetramethylpiperidinol was then produced again according to the above application method. The average yield percentage of the product after continuous operation for 336 h and 504 h was calculated as follows:
[0032] In Comparative Example 1, chitosan and yttrium nitrate were omitted from the composite support preparation process and replaced with tetraethyl orthosilicate. This omitted the pore template effect of chitosan, resulting in a silica support with a single surface functional group and weak interaction with the active metal component. Furthermore, the plasma pretreatment step for the composite support was omitted, leaving insufficient sites on the support surface to anchor the metal. This resulted in a weak bond between the active metal and the support, making it prone to migration, detachment, and aggregation during the reaction. This reduced the catalyst activity, weakened catalytic performance, significantly decreased recyclability and stability, and shortened the service life.
[0033] In Comparative Example 2, magnesium gluconate and aminotrimethylene phosphonic acid were omitted in the preparation of the composite support. As a result, the anchoring sites with the metal active components were missing, the metal loading strength decreased, and the catalytic effect weakened. In the process of loading the metal, the loading of nickel and cerium was omitted, and the catalyst was left with only Cu as a single active center, which reduced the selectivity, cycle performance and stability, and overall performance.
[0034] Unless otherwise specified, all proportions mentioned in this invention are mass proportions, and all percentages are mass percentages.
[0035] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are 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 method for preparing a catalyst for the production of tetramethylpiperidinol, characterized in that, This includes steps such as preparation of the composite carrier, pretreatment of the composite carrier, impregnation, and reduction. The steps for preparing the composite carrier include preparing the composite gel and post-gel processing steps. The steps for preparing the composite gel are as follows: chitosan is added to an acetic acid solution and stirred at room temperature for 40-50 min; tetraethyl orthosilicate, magnesium gluconate, aminotrimethylenephosphonic acid, and yttrium nitrate are added; the mixture is stirred at 300-320 rpm for 70-80 min and then at 200-210 rpm for 40-50 min; the pH value is adjusted to 7.2-7.6 to obtain the composite gel. The pretreatment step of the composite carrier is as follows: the composite carrier is placed in a plasma device, nitrogen gas is introduced for purging, then ammonia gas and water vapor are introduced, and the plasma power supply is turned on to process and obtain the pretreated composite carrier. The impregnation step involves placing the pretreated composite carrier into a copper nitrate solution and subjecting it to ultrasonic oscillation. Then, the carrier is placed into a rare earth mixture and subjected to ultrasonic oscillation for 50-60 minutes, followed by stirring at 120-150 rpm for 50-60 minutes to obtain the impregnated composite carrier.
2. The method for preparing a catalyst for producing tetramethylpiperidinol according to claim 1, characterized in that, In the step of preparing the composite gel, the degree of deacetylation of the chitosan is 92-96%, and the molecular weight is 82-90 kDa; The mass ratio of the acetic acid solution, chitosan, tetraethyl orthosilicate, magnesium gluconate, aminotrimethylenephosphonic acid, and yttrium nitrate is 200:2.0-2.5:3.8-4.0:1.0-1.2:0.20-0.25:0.40-0.
46. The mass concentration of the acetic acid solution is 2.0-2.5%.
3. The method for preparing a catalyst for producing tetramethylpiperidinol according to claim 1, characterized in that, The post-gelling process involves curing the composite gel at 60-64℃ for 20-24 hours, followed by freeze-drying. The temperature is then decreased to -42 to -37℃ at a rate of 8-10℃ / min and held for 1.5-2.0 hours. Next, the vacuum is controlled at 35-45 Pa, and the temperature is increased to -25 to -22℃ at a rate of 2.0-2.5℃ / h and held for 20-24 hours. Then, the vacuum is controlled at 15-20 Pa, and the temperature is increased to 25-27℃ at a rate of 2.5-3.0℃ / h and held for 6-8 hours. Finally, the temperature is increased to 680-700℃ at a rate of 2.0-2.5℃ / min and held for 2.8-3.0 hours. The temperature is then decreased to 280-310℃ at a rate of 4.0-5.0℃ / min and allowed to cool naturally to room temperature to obtain the composite carrier.
4. The method for preparing a catalyst for producing tetramethylpiperidinol according to claim 1, characterized in that, The pretreatment steps for the composite carrier are as follows: 20g of the composite carrier is placed in a plasma device, and nitrogen gas is introduced for purging at a flow rate of 28-32 mL / min for 25-30 min. Then, ammonia and water vapor are introduced, with the ammonia flow rate controlled at 16-20 mL / min and the water vapor flow rate at 8-10 mL / min. The plasma power supply is turned on, with a discharge power of 210-230 W, a temperature of 26-30℃, a treatment time of 45-55 min, and an electrode spacing of 16-20 mm. The plasma power supply is then turned off, and nitrogen gas is introduced again for 26-30 min at a flow rate of 15-20 mL / min. After cooling and drying, the pretreated composite carrier is obtained.
5. The method for preparing a catalyst for producing tetramethylpiperidinol according to claim 1, characterized in that, In the impregnation step, the mass ratio of the pretreated composite carrier, copper nitrate solution, and rare earth mixture is 5.0:45-50:35-40.
6. The method for preparing a catalyst for producing tetramethylpiperidinol according to claim 5, characterized in that, The copper nitrate solution is a mixture of deionized water, copper nitrate, and disodium ethylenediaminetetraacetate, wherein the mass ratio of deionized water, copper nitrate, and disodium ethylenediaminetetraacetate is 100:2.3-2.6:2.8-3.
0. The rare earth mixture is obtained by mixing deionized water, nickel nitrate, cerium nitrate and citric acid, and adjusting the pH to 5.7-6.0 with 10-15wt% ammonia solution. The mass ratio of the deionized water, nickel nitrate, cerium nitrate and citric acid is 100:0.8-1.2:0.3-0.5:1.4-1.
7.
7. The method for preparing a catalyst for producing tetramethylpiperidinol according to claim 1, characterized in that, The reduction step involves heating the impregnated composite support to 540-550°C at a rate of 2.0-2.5°C / min under a hydrogen atmosphere, holding the temperature for 30-40 minutes, and then naturally cooling it to room temperature to obtain the catalyst.
8. A catalyst for the production of tetramethylpiperidinol prepared by the preparation method according to any one of claims 1-7.