A continuous preparation method and application of a core-shell Cu-based catalyst

Abstract

This invention discloses a continuous preparation method and application of a core-shell Cu-based catalyst. The method utilizes membrane dispersion microreactor technology, precisely controlling the solution pH and total flow rate to uniformly coat the metal core with SiO2 at a moderate condensation rate, forming a core-shell structure with uniform particle size and regular morphology. This structure provides abundant active sites and enhances the catalyst's hydrogenation activity. Simultaneously, the mutual doping of Cu and Ni creates a synergistic effect; the introduction of Ni significantly improves the catalyst's ability to dissociate H2 to generate activated hydrogen, promoting the adsorption and activation hydrogenation of the imine intermediate. The catalyst prepared by this invention exhibits excellent catalytic activity and stability in the reductive amination of 2,2,6,6-tetramethyl-4-piperidinone and n-butylamine to N-butyl-2,2,6,6-tetramethyl-4-piperidinamine.

Description

Technical Field

[0001] This invention relates to a continuous preparation method and application of a core-shell Cu-based catalyst, particularly to a method and catalyst for the preparation of N-butyl-2,2,6,6-tetramethyl-4-piperidinone and n-butylamine via reductive amination catalyzed by a multi-active component catalyst. Background Technology

[0002] Ultraviolet rays in sunlight can trigger photo-oxidation reactions in polymer materials, leading to molecular chain breakage, cross-linking, or degradation, causing discoloration, embrittlement, and shortened lifespan. Hindered amine light stabilizers (HALS) interrupt the photo-oxidation chain reaction through mechanisms such as capturing free radicals via the "Denison cycle," decomposing hydrogen peroxide, and quenching singlet oxygen, and have become the dominant type of polymer additive. N-Butyl-2,2,6,6-Tetramethyl-4-piperidinamine (TMPBA) is not only a highly efficient polymerization inhibitor for olefin monomer polymerization but also a key intermediate in the synthesis of high-performance hindered amine light stabilizers such as HALS 119 and HALS 2020. The n-butyl group introduced into its molecule endows the target light stabilizer with stronger lipophilicity and better polymer compatibility, making it widely used in the light stabilization treatment of polymer materials such as plastics, coatings and inks, rubber, and synthetic fibers. In addition, TMPBA also has important application value in the fine chemical fields of pharmaceuticals, pesticides, dyes, and food packaging.

[0003] Currently, N-butyl-2,2,6,6-tetramethyl-4-piperidinone is mainly prepared industrially via a one-step reductive amination of 2,2,6,6-tetramethyl-4-piperidinone and n-butylamine. Among these, Cu-based catalysts have attracted much attention due to their high selectivity for hydrogenation of the C=N bond and their low cost. Chen Ligong et al. (Catalysis Letters, 2011, 141(11): 1703-1708.) used Cr and La-doped Cu catalysts. 20 Cr5La5 / γ-Al2O3 catalyzed the reductive amination of TAA with n-butylamine to prepare TMPBA, with a TMPBA yield of 94%. Tang Tiandi et al. (CN115970736A) designed a copper-based catalyst CuNi@MMS, which was prepared by impregnation of lysine-modified active copper-nickel metal onto microporous crystals (MMS), and used it to catalyze the reductive amination of TAA with n-butylamine to prepare TMPBA with a yield of 97.7%. Ke Youbin et al. (CN119080678A) prepared a Co 2+ / Ni 2+A catalyst with a framework and porous structure formed by coordination with 2-methylimidazole, coated with CuLaCa nanomaterials, was applied to the catalytic reduction amination of TAA and n-butylamine to prepare TMPBA with a yield of 97.6%. Catalyst preparation often requires the introduction of highly toxic metal promoters such as Cr and Ba to improve catalytic activity, or the enhancement of performance through complex support modification, resulting in a lengthy preparation process.

[0004] Therefore, by optimizing the catalyst preparation process and constructing a Cu-based multimetal synergistic system, the H2 dissociation activation ability is enhanced, side reactions caused by excessive hydrogenation are suppressed, and the unity of high activity and high selectivity of the catalyst is improved, so as to achieve efficient preparation of N-butyl-2,2,6,6-tetramethyl-4-piperidinone and n-butylamine by reductive amination. Summary of the Invention

[0005] The purpose of this invention is to address the limitations of current technologies by providing a continuous preparation and application of core-shell Cu-based catalysts. This method utilizes membrane dispersion microreactor technology to achieve refined catalyst nanoparticles, narrowed particle size distribution, and high dispersion of active metals, enabling continuous preparation of nanoscale catalysts while significantly shortening the preparation cycle and making the process more green and efficient. The catalyst prepared in this invention exhibits excellent catalytic activity and stability in the reductive amination of 2,2,6,6-tetramethyl-4-piperidinone and n-butylamine to prepare N-butyl-2,2,6,6-tetramethyl-4-piperidinamine, with a 2,2,6,6-tetramethyl-4-piperidinone conversion rate as high as 99.8% and an N-butyl-2,2,6,6-tetramethyl-4-piperidinamine yield of 98.2%.

[0006] The technical solution of this invention is as follows: A continuous preparation method for a core-shell Cu catalyst, comprising the following steps: A metal salt solution and a Na₂CO₃ solution are fed into a feed pump at a flow rate ratio of 1:0.5-1.5, and then introduced into a first membrane dispersion microreactor at a temperature of 20-40°C. After mixing, the mixture is held in a residence tube for 1-3 minutes to form a turbid liquid. This turbid liquid is then mixed with a NaSiO₃ solution at a flow rate ratio of 1:0.4-1.5 in a three-way valve, and then fed into a second membrane dispersion microreactor with sulfuric acid at a flow rate ratio of 1:0.2-1.5. The pH of the solution is controlled to 8-10 by adjusting the sulfuric acid flow rate. After mixing, the mixture is held in a residence tube for 10-20 minutes to form a precipitate. The precipitate is centrifuged and washed until the pH is neutral, dried, ground, and then reduced at 400-600°C for 2-4 hours in a hydrogen atmosphere to obtain a Cu-based catalyst. The metal salt solution contains Cu(NO3)2·3H2O and Ni(NO3)2·6H2O. The concentration of Cu(NO3)2·3H2O in the solution is 0.1-0.35 M, and the concentration of Ni(NO3)2·6H2O is 0-0.08 M. When the material value is 0, it means that the substance is not added. The concentration of the Na2CO3 solution is 0.20-0.75M; The concentration of the NaSiO3 solution was 0.01-0.08 M; The concentration of sulfuric acid is 0.05-0.30 M; In the membrane dispersion microreactor, the stainless steel microfiltration membrane has a pore size of 0.5-5 μm, a diameter of 6.5-100 mm, and a thickness of 1-5 mm; the residence tube is made of polytetrafluoroethylene, with an inner diameter of 1.5-2.5 mm and a length of 0.5-100 m.

[0007] The flow rate of the metal salt solution is 1-15 mL / min.

[0008] The concentration of Cu(NO3)2·3H2O is 0.15 M, and the concentration of Ni(NO3)2·6H2O is 0.05 M; The concentration of the Na₂CO₃ solution is 0.45 M; the concentration of the NaSiO₃ solution is 0.04 M. The concentration of sulfuric acid is 0.1 M; the preferred flow rate of the metal salt solution is 5 mL / min.

[0009] The core-shell catalyst comprises an active metal core and a support shell, wherein the support shell is silica, the active metal core is a main metal M1 or a main metal M1 and a co-metal M2; the molar ratio of the active component to the support is 1:0.1-0.5; the molar ratio of the main metal M1 to the co-metal M2 is 1:0.1-0.4. The main metal M1 is Cu; the auxiliary metal M2 is Ni; The average particle size of the catalyst is 4.97-12.63 nm.

[0010] The catalyst prepared by the method is used in the catalytic reduction amination of 2,2,6,6-tetramethyl-4-piperidinone (TAA) with n-butylamine to prepare N-butyl-2,2,6,6-tetramethyl-4-piperidinamine (TMPBA), and includes the following steps: 2,2,6,6-Tetramethyl-4-piperidinone (TAA), n-butylamine and Cu-based catalyst were added to a batch high-pressure reactor. The air in the reactor was replaced with N2, and then replaced with H2. The reaction was carried out at 80-120 °C for 1-8 h to undergo reductive amination to obtain N-butyl-2,2,6,6-tetramethyl-4-piperidinamine (TMPBA). The mass ratio of 2,2,6,6-tetramethyl-4-piperidinone to catalyst is 100-10:1; the molar ratio of TAA to n-butylamine is 1:1-5; and the hydrogen pressure is 0.5-2.0 MPa.

[0011] The essential features of this invention are: This invention employs membrane dispersion microreactor technology, utilizing a microporous membrane driven by pressure difference to cut the dispersed phase into micron-sized droplets, achieving rapid and uniform mixing of the two phases, enhancing the mass transfer process, promoting high dispersion of active metals, and regulating the catalyst structure to possess a high specific surface area and suitable pore size distribution. This provides sufficient active sites for the adsorption and activation of reactants, thereby significantly improving the hydrogenation activity of the catalyst. Simultaneously, this preparation method is simple, significantly shortens the catalyst preparation cycle, and allows for continuous production of integrally formed catalyst precursors, possessing potential for large-scale application.

[0012] This invention constructs a core-shell structured silica-coated Cu-Ni bimetallic heterogeneous catalyst. By precisely controlling the solution pH and total flow rate, SiO2 is uniformly coated onto the metal core at a moderate condensation rate, forming a core-shell structure with uniform particle size and regular morphology. This structure provides abundant active sites and enhances the catalyst's hydrogenation activity. Simultaneously, the mutual doping of Cu and Ni creates a synergistic effect. The introduction of Ni significantly improves the catalyst's ability to dissociate H2 to generate activated hydrogen, promoting the adsorption and activation hydrogenation of imine intermediates. This overcomes the bottleneck of insufficient activity in single Cu-based catalysts, achieving a balance between high catalyst activity and high selectivity.

[0013] The beneficial effects of this invention are as follows: This invention provides a method for the efficient preparation of N-butyl-2,2,6,6-tetramethyl-4-piperidinone (TAA) and n-butylamine via reductive amination. Using a non-precious metal heterogeneous solid catalyst, under optimized conditions of a reaction temperature of 110 °C, an H₂ pressure of 1.4 MPa, a reaction time of 3 h, and a catalyst dosage of 3% of the TAA mass, the TAA conversion reaches 99.8%, and the TMPBA yield reaches 98.2%. Furthermore, the catalyst maintains good catalytic performance after 5 cycles, exhibiting excellent stability.

[0014] This invention replaces traditional precious metals and highly toxic additives (such as Cr, Ba, etc.) with non-precious metals, resulting in low raw material costs, a green and simple preparation process, and environmental friendliness. The use of membrane dispersion microreactors enables continuous catalyst preparation with high metal dispersion, showing promising prospects for industrial applications. Attached Figure Description

[0015] Figure 1TEM image of the 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-500 catalyst obtained in Example 8; Figure 2 TEM images of the catalysts in Examples 9, 8, and 12; wherein, Figure 2 In the image, 'a' represents the TEM image of the catalyst 8.2-20-7.5Cu-2.5Ni@SiO2-0.2-500 obtained in Example 9. Figure 2 In the image, b represents the TEM image of the catalyst 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-500 obtained in Example 8. Figure 2 In the image, c represents the TEM image of the catalyst 9.8-20-7.5Cu-2.5Ni@SiO2-0.2-500 obtained in Example 12. Detailed Implementation

[0016] The synthetic route of this invention is shown in the figure below:

[0017] The technical features of this invention will be further illustrated below with examples.

[0018] The membrane dispersion microreactor is a known device. The specific details used in the following embodiments are as follows: the stainless steel microfiltration membrane has a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm; the retention tube is made of polytetrafluoroethylene (PTFE) with an inner diameter of 2 mm. The first membrane dispersion microreactor has a 3 m long inlet tube to ensure complete metal salt precipitation; the second membrane dispersion microreactor has a 50 m long inlet tube to ensure complete hydrolysis of sodium silicate to form a silica-coated metal core structure. However, this is not a limitation.

[0019] Example 1: Preparation of 9.8-20-Cu@SiO2-0.2-500 Solution A is prepared by dissolving 0.02 mol Cu(NO3)2·3H2O in 100 mL of deionized water; solution B is prepared by dissolving 0.045 mol Na2CO3 in 100 mL of deionized water; solution C is prepared by dissolving 0.004 mol NaSiO3·9H2O in 100 mL of deionized water; and solution D is prepared by adding 0.01 mol sulfuric acid to 100 mL of deionized water. Solutions A and B are fed into a feed pump at the same flow rate of 5 mL / min and kept at 30 °C in the first membrane dispersion microreactor. After mixing and settling in the tube for 2 min, a turbid liquid is formed. Simultaneously, solution A is mixed with solution C (5 mL / min) at a flow rate of 10 mL / min in a three-way valve, and then mixed with solution D (5 mL / min) in the second membrane dispersion microreactor. The pH of the solution is controlled at 9.8. After mixing and settling in the tube for 8 min, a precipitate is formed. The precipitate is washed by centrifugation until the pH is neutral and then dried in an oven at 80 °C for 4 min. The precursor was dried and ground to obtain the catalyst precursor, which was then reduced in a tube furnace at 500℃ under H2 atmosphere for 3 h to obtain the catalyst 9.8-20-Cu@SiO2-0.2-500.

[0020] Example 2: Preparation of 9.8-20-9Cu-Ni@SiO2-0.2-500 Solution A is prepared by dissolving 0.018 mol Cu(NO3)2·3H2O and 0.002 mol Ni(NO3)2·6H2O in 100 mL of deionized water; solution B is prepared by dissolving 0.045 mol Na2CO3 in 100 mL of deionized water; solution C is prepared by dissolving 0.004 mol NaSiO3·9H2O in 100 mL of deionized water; and solution D is prepared by adding 0.01 mol sulfuric acid to 100 mL of deionized water. Solutions A and B are fed into a feed pump at the same flow rate of 5 mL / min and kept at 30 °C in the first membrane dispersion microreactor. After mixing and settling in the tube for 2 min, a turbid liquid is formed. Simultaneously, solution A is mixed with solution C (5 mL / min) at a flow rate of 10 mL / min in a three-way valve, and then mixed with solution D (5 mL / min) in the second membrane dispersion microreactor. The pH of the solution is controlled at 9.8, and the mixture is held in the tube for 8 min. After min, a precipitate was formed; the precipitate was washed by centrifugation until the pH was neutral, dried in an oven at 80 ℃ for 4 h, ground to obtain the catalyst precursor, and then reduced in a tube furnace at 500 ℃ under H2 atmosphere for 3 h to obtain the catalyst 9.8-20-9Cu-Ni@SiO2-0.2-500.

[0021] Examples 3-7: Preparation of 9.8-20-9Cu-Fe@SiO2-0.2-500, 9.8-20-9Cu-Co@SiO2-0.2-500, 9.8-20-9Cu-Ce@SiO2-0.2-500, 9.8-20-9Cu-La@SiO2-0.2-500, and 9.8-20-9Cu-Zr@SiO2-0.2-500 The other steps are the same as in Example 2, except that 0.002 mol Ni(NO3)2·6H2O is replaced with 0.002 mol Fe(NO3)2·9H2O, 0.002 mol Co(NO3)2·6H2O, 0.002 mol Ce(NO3)2·6H2O, 0.002 mol La(NO3)3·6H2O, and 0.002 mol Zr(NO3)4·5H2O, respectively. Ultimately, five different materials were obtained: 9.8-20-9Cu-Fe@SiO2-0.2-500, 9.8-20-9Cu-Co@SiO2-0.2-500, 9.8-20-9Cu-Ce@SiO2-0.2-500, 9.8-20-9Cu-La@SiO2-0.2-500, and 9.8-20-9Cu-Zr@SiO2-0.2-500 catalysts.

[0022] The catalyst is represented by AB-xM1-yM2@SiO2-ab, where A represents the solution pH value, B represents the total flow rate, M1 represents the main metal, M2 represents the auxiliary metal, x and y represent the proportion of M1 and M2 in the total metal molar amount in the catalyst, a represents the ratio of sodium silicate to the total metal molar amount, and b represents the catalyst reduction temperature.

[0023] Example 8: Preparation of 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-500 Solution A is prepared by dissolving 0.015 mol Cu(NO3)2·3H2O and 0.005 mol Ni(NO3)2·6H2O in 100 mL of deionized water; solution B is prepared by dissolving 0.045 mol Na2CO3 in 100 mL of deionized water; solution C is prepared by dissolving 0.004 mol NaSiO3·9H2O in 100 mL of deionized water; and solution D is prepared by adding 0.01 mol sulfuric acid to 100 mL of deionized water. Solutions A and B are fed into a feed pump at the same flow rate of 5 mL / min and kept at 30 °C in the first membrane dispersion microreactor. After mixing and settling in the tube for 2 min, a turbid liquid is formed. Simultaneously, solution A is mixed with solution C (5 mL / min) at a flow rate of 10 mL / min in a three-way valve, and then mixed with solution D (5 mL / min) in the second membrane dispersion microreactor. The pH of the solution is controlled at 9.0, and the mixture is held in the tube for 8 min. After min, a precipitate was formed; the precipitate was washed by centrifugation until the pH was neutral, dried in an oven at 80 ℃ for 4 h, and ground to obtain the catalyst precursor. Subsequently, it was reduced in a tube furnace at 500 ℃ under H2 atmosphere for 3 h to obtain the catalyst 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-500.

[0024] The morphology of the obtained catalyst is as follows Figure 1 As shown in the figure, the dark core Cu-Ni nanoparticles are partially or completely covered by the light-colored outer shell SiO2 carrier layer, and the metal particles are uniformly dispersed in the porous silicon-oxygen network.

[0025] Examples 9-12: Preparation of 8.2-20-7.5Cu-2.5Ni@SiO2-0.2-500, 8.6-20-7.5Cu-2.5Ni@SiO2-0.2-500, 9.4-20-7.5Cu-2.5Ni@SiO2-0.2-500, and 9.8-20-7.5Cu-2.5Ni@SiO2-0.2-500 The other steps are the same as in Example 8, except that the solution pH is controlled at 8.2, 8.6, 9.4, and 9.8, respectively. Ultimately, four different materials were obtained: 8.2-20-7.5Cu-2.5Ni@SiO2-0.2-500, 8.6-20-7.5Cu-2.5Ni@SiO2-0.2-500, 9.4-20-7.5Cu-2.5Ni@SiO2-0.2-500, and 9.8-20-7.5Cu-2.5Ni@SiO2-0.2-500 catalysts.

[0026] Figure 2 TEM images of the catalysts in Examples 9, 8, and 12, wherein Figure 2In the image, 'a' represents the TEM image of the catalyst 8.2-20-7.5Cu-2.5Ni@SiO2-0.2-500 obtained in Example 9. Figure 2 In the image, b represents the TEM image of the catalyst 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-500 obtained in Example 8. Figure 2 In the image, 'c' represents the TEM image of the catalyst 9.8-20-7.5Cu-2.5Ni@SiO2-0.2-500 obtained in Example 12. Figure 2 It can be seen that the structure of the dark metal core being covered by light-colored silica indicates that the catalysts all have obvious core-shell structure characteristics, with average particle sizes of 9.58 nm, 6.31 nm, and 7.35 nm, respectively.

[0027] Example 13: Preparation of 9.0-10-7.5Cu-2.5Ni@SiO2-0.2-500 Solution A is prepared by dissolving 0.015 mol Cu(NO3)2·3H2O and 0.005 mol Ni(NO3)2·6H2O in 100 mL of deionized water; solution B is prepared by dissolving 0.045 mol Na2CO3 in 100 mL of deionized water; solution C is prepared by dissolving 0.004 mol NaSiO3·9H2O in 100 mL of deionized water; and solution D is prepared by adding 0.01 mol sulfuric acid to 100 mL of deionized water. Solutions A and B are fed into a feed pump at the same flow rate of 2.5 mL / min and kept at 30 °C in the first membrane dispersion microreactor. After mixing and settling in the tube for 2 min, a turbid liquid is formed. Simultaneously, solution A is mixed with solution C (2.5 mL / min) at a flow rate of 5 mL / min in a three-way valve, and then mixed with solution D (2.5 mL / min) in the second membrane dispersion microreactor. The pH of the solution is controlled at 9.0, and the mixture is held in the tube for 8 min. After min, a precipitate was formed; the precipitate was washed by centrifugation until the pH was neutral, dried in an oven at 80 ℃ for 4 h, and ground to obtain the catalyst precursor. Subsequently, it was reduced in a tube furnace at 500 ℃ under H2 atmosphere for 3 h to obtain the catalyst 9.0-10-7.5Cu-2.5Ni@SiO2-0.2-500.

[0028] Examples 14-16: Preparation of 9.0-15-7.5Cu-2.5Ni@SiO2-0.2-500, 9.0-25-7.5Cu-2.5Ni@SiO2-0.2-500, and 9.0-30-7.5Cu-2.5Ni@SiO2-0.2-500 The other steps are the same as in Example 12, except that the flow rates of the four feed solutions are controlled at 3.75 mL / min, 6.25 mL / min, and 7.5 mL / min, respectively (with no change in residence time). Finally, three different materials were obtained: 9.0-15-7.5Cu-2.5Ni@SiO2-0.2-500, 9.0-25-7.5Cu-2.5Ni@SiO2-0.2-500, and 9.0-30-7.5Cu-2.5Ni@SiO2-0.2-500 catalysts.

[0029] Example 17: Preparation of 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-400 Solution A is prepared by dissolving 0.015 mol Cu(NO3)2·3H2O and 0.005 mol Ni(NO3)2·6H2O in 100 mL of deionized water; solution B is prepared by dissolving 0.045 mol Na2CO3 in 100 mL of deionized water; solution C is prepared by dissolving 0.004 mol NaSiO3∙9H2O in 100 mL of deionized water; and solution D is prepared by adding 0.01 mol sulfuric acid to 100 mL of deionized water. Solutions A and B are fed into a feed pump at the same flow rate of 5 mL / min and kept at 30 °C in the first membrane dispersion microreactor. After mixing and settling in the tube for 2 min, a turbid liquid is formed. Simultaneously, solution A is mixed with solution C (5 mL / min) at a flow rate of 10 mL / min in a three-way valve, and then mixed with solution D (5 mL / min). The solution was fed into the second membrane dispersion microreactor at a rate of mL / min, and the pH of the solution was controlled at 9.0. After mixing and holding in the tube for 8 min, a precipitate was formed. The precipitate was washed by centrifugation until the pH was neutral, and then dried in an oven at 80 ℃ for 4 h. The precipitate was then ground to obtain the catalyst precursor, which was subsequently reduced in a tube furnace at 400 ℃ under H2 atmosphere for 3 h to obtain the catalyst 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-400.

[0030] Examples 18-20: Preparation of 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-450, 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-550, and 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-600 The other steps are the same as in Example 16, except that the reduction temperature in hydrogen is changed to 450 ℃, 550 ℃, and 600 ℃, respectively. Finally, three different materials were obtained: 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-450, 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-550, and 9.0-20-7.5Cu-2.5Ni@SiO2-0.2-600 catalysts.

[0031] Example 21: Reductive amination of 2,2,6,6-tetramethyl-4-piperidinone and n-butylamine The reaction was carried out in a batch high-pressure reactor, with 0.047 g of the catalyst prepared in Example 1, 0.9314 g (6 mmol) of 2,2,6,6-tetramethyl-4-piperidinone, and 1.3167 g (18 mmol) of n-butylamine added. Before the reaction, the reactor was purged five times with H2 to replace the gas. The reaction was carried out at 1 MPa H2 and 100 °C for 5 h. After the reaction was completed, the mixture was cooled to room temperature, and the filtered supernatant was quantitatively analyzed by gas chromatography using the internal standard method, with n-dodecyl alcohol as the internal standard. The gas phase temperature program was as follows: initial temperature 80 °C, hold for 1 min, then increase to 240 °C at a rate of 10 °C / min and hold for 20 min. The conversion of 2,2,6,6-tetramethyl-4-piperidinone reached 99.35%, and the yield of N-butyl-2,2,6,6-tetramethyl-4-piperidinamine reached 42.19%.

[0032] Example 22: Reductive amination of 2,2,6,6-tetramethyl-4-piperidinone and n-butylamine The reaction was carried out in a batch high-pressure reactor, with 0.047 g of the catalyst prepared in Examples 2-7, 0.9314 g (6 mmol) of 2,2,6,6-tetramethyl-4-piperidinone, and 1.3167 g (18 mmol) of n-butylamine added. Before the reaction, the reactor was purged five times with H2 to replace the gas. The reaction was carried out at 1 MPa H2 and 100 °C for 5 h. After the reaction was completed, the mixture was cooled to room temperature, and the filtered supernatant was quantitatively analyzed. The reaction results are shown in Table 1.

[0033] Table 1. Effects of different auxiliary metals on the reaction

[0034] Example 23: Reductive amination of 2,2,6,6-tetramethyl-4-piperidinone and n-butylamine The reaction was carried out in a batch high-pressure reactor, with 0.028 g of the catalyst prepared in Examples 9, 10, 8, 11, and 12, 0.9314 g (6 mmol) of 2,2,6,6-tetramethyl-4-piperidinone, and 1.3167 g (18 mmol) of n-butylamine added. Before the reaction, the reactor was purged five times with H2 to replace the gas. The reaction was carried out at 1 MPa H2 and 100 °C for 3 h. After the reaction was completed, the mixture was cooled to room temperature, and the filtered supernatant was quantitatively analyzed. The reaction results are shown in Table 2.

[0035] Table 2 Effect of solution pH on the reaction

[0036] Example 24: Reductive amination of 2,2,6,6-tetramethyl-4-piperidinone and n-butylamine The reaction was carried out in a batch high-pressure reactor, with the addition of 0.028 g of the catalyst prepared in Examples 13-16, 0.9314 g (6 mmol) of 2,2,6,6-tetramethyl-4-piperidinone, and 1.3167 g (18 mmol) of n-butylamine. Before the reaction, the reactor was purged five times with H2 to replace the gas. The reaction was carried out at 1 MPa H2 and 100 °C for 3 h. After the reaction was completed, the mixture was cooled to room temperature, and the filtered supernatant was quantitatively analyzed. The reaction results are shown in Table 3.

[0037] Table 3 Effect of total feed flow rate on the reaction

[0038] Example 25: Reductive amination of 2,2,6,6-tetramethyl-4-piperidinone and n-butylamine The reaction was carried out in a batch high-pressure reactor, with the addition of 0.028 g of the catalyst prepared in Examples 17-20, 0.9314 g (6 mmol) of 2,2,6,6-tetramethyl-4-piperidinone, and 1.3167 g (18 mmol) of n-butylamine. Before the reaction, the reactor was purged five times with H2 to replace the gas. The reaction was carried out at 1 MPa H2 and 100 °C for 3 h. After the reaction was completed, the mixture was cooled to room temperature, and the filtered supernatant was quantitatively analyzed. The reaction results are shown in Table 4.

[0039] Table 4 Effect of reduction temperature on the reaction

[0040] Example 26: Reductive amination of 2,2,6,6-tetramethyl-4-piperidinone and n-butylamine The reaction was carried out in a batch high-pressure reactor, with 0.028 g of the catalyst prepared in Example 8, 0.9314 g (6 mmol) of 2,2,6,6-tetramethyl-4-piperidinone, and 0.6584 g (9 mmol) of n-butylamine added. Before the reaction, the reactor was purged five times with H2 to replace the gas. The reaction was carried out at 1.4 MPa H2 and 110 °C for 3 h. After the reaction was completed, the mixture was cooled to room temperature, and the filtered supernatant was quantitatively analyzed. The conversion of 2,2,6,6-tetramethyl-4-piperidinone reached 99.83%, and the yield of N-butyl-2,2,6,6-tetramethyl-4-piperidinamine reached 98.23%.

[0041] Example 27: Reductive amination of 2,2,6,6-tetramethyl-4-piperidinone and n-butylamine The reaction was carried out in a batch high-pressure reactor, with 0.028 g of the catalyst prepared in Example 8, 0.9314 g (6 mmol) of 2,2,6,6-tetramethyl-4-piperidinone, and 0.6584 g (9 mmol) of n-butylamine added. Before the reaction, the reactor was purged five times with H2 to replace the gas. The reaction was carried out at 1.2 MPa H2 and 100 °C for 2.5 h. After the reaction was completed, the mixture was cooled to room temperature, and the filtered supernatant was quantitatively analyzed. The conversion of 2,2,6,6-tetramethyl-4-piperidinone reached 99.60%, and the yield of N-butyl-2,2,6,6-tetramethyl-4-piperidinamine reached 81.89%.

[0042] Matters not covered in this invention are common knowledge.

Claims

1. A continuous preparation method for a core-shell Cu catalyst, characterized in that, The method includes the following steps: A metal salt solution and a Na₂CO₃ solution are fed into a feed pump at a flow rate ratio of 1:0.5-1.5, and then introduced into a membrane dispersion microreactor at a temperature of 20-40 °C. After mixing, the mixture is held in a residence tube for 1-3 minutes to form a turbid liquid. This turbid liquid is then mixed with a NaSiO₃ solution at a flow rate of 1:0.4-1.5 in a three-way valve, and then fed into a second membrane dispersion microreactor with sulfuric acid at a flow rate ratio of 1:0.2-1.

5. The pH of the solution is controlled to 8-10 by adjusting the sulfuric acid flow rate. After mixing, the mixture is held in a residence tube for 10-20 minutes to form a precipitate. The precipitate is then centrifuged and washed until the pH is neutral. After drying and grinding, it is reduced at 400-600 °C for 2-4 hours in a hydrogen atmosphere to obtain a Cu-based catalyst. The metal salt solution contains Cu(NO3)2·3H2O and Ni(NO3)2·6H2O. The concentration of Cu(NO3)2·3H2O in the solution is 0.1-0.35 M, and the concentration of Ni(NO3)2·6H2O is 0-0.08 M. When the material value is 0, it means that the substance is not added. The concentration of the Na2CO3 solution is 0.20-0.75M; The concentration of the NaSiO3 solution was 0.01-0.08 M; The concentration of sulfuric acid is 0.05-0.30 M.

2. The continuous preparation method of the core-shell Cu catalyst as described in claim 1, characterized in that, In the membrane dispersion microreactor, the stainless steel microfiltration membrane has a pore size of 0.5-5 μm, a diameter of 6.5-100 mm, and a thickness of 1-5 mm; the residence tube is made of polytetrafluoroethylene, with an inner diameter of 1.5-2.5 mm and a length of 0.5-100 m.

3. The continuous preparation method of the core-shell Cu catalyst as described in claim 1, characterized in that, The flow rate of the metal salt solution is 1-15 ml / min.

4. The continuous preparation method of the core-shell Cu catalyst as described in claim 1, characterized in that, The concentration of Cu(NO3)2·3H2O is 0.15 M, and the concentration of Ni(NO3)2·6H2O is 0.05 M; The concentration of the Na₂CO₃ solution is 0.45 M; the concentration of the NaSiO₃ solution is 0.04 M. The concentration of sulfuric acid is 0.1 M; the flow rate of the metal salt solution is 5 mL / min.

5. The continuous preparation method of the core-shell Cu catalyst as described in claim 1, characterized in that, The core-shell catalyst comprises an active metal core and a support shell, wherein the support shell is silica, the active metal core is a main metal M1 or a main metal M1 and a co-metal M2; the molar ratio of the active component to the support is 1:0.1-0.5; the molar ratio of the main metal M1 to the co-metal M2 is 1:0.1-0.

4. The main metal M1 is Cu; the auxiliary metal M2 is Ni; and the average particle size of the catalyst is 4.97-12.63 nm.

6. The application of the core-shell Cu catalyst prepared by the method described in claim 1, characterized in that, It is used to catalyze the reductive amination of 2,2,6,6-tetramethyl-4-piperidinone (TAA) with n-butylamine to prepare N-butyl-2,2,6,6-tetramethyl-4-piperidinamine (TMPBA).

7. The application as described in claim 6, characterized in that, Includes the following steps: 2,2,6,6-Tetramethyl-4-piperidinone (TAA), n-butylamine and Cu-based catalyst were added to a batch high-pressure reactor. The air in the reactor was replaced with N2, and then replaced with H2. The reaction was carried out at 80-120 °C for 1-8 h to undergo reductive amination to obtain N-butyl-2,2,6,6-tetramethyl-4-piperidinamine (TMPBA). The mass ratio of 2,2,6,6-tetramethyl-4-piperidinone to catalyst is 100-10:1; the molar ratio of TAA to n-butylamine is 1:1-5; and the hydrogen pressure is 0.5-2.0 MPa.

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