A secondary carbinolamine and a method for its preparation

Abstract

This invention discloses a secondary carbon primary amine and its preparation method, relating to the field of chemical synthesis technology. The method includes the following steps: using 10-12 carbon fatty acids as raw materials, a fatty acid ketation reaction is carried out under the action of a composite catalyst to obtain a secondary carbon ketone; the composite catalyst is obtained by mixing a ZrO2-M catalyst and supported Pt-Pd metal nanoparticles at a mass ratio of 1:1.2-3.0, where M in ZrO2-M is a rare earth element; the secondary carbon ketone is prepared into a secondary carbon ketone solution using a solvent, and a nitrogen-doped activated carbon-supported ruthenium catalyst is added to obtain a suspension; the suspension is subjected to an amination reaction with ammonia under a hydrogen atmosphere to obtain a secondary carbon primary amine. This invention uses a composite catalyst system to catalyze the fatty acid ketation reaction, and its synergistic effect significantly improves the conversion efficiency and selectivity of fatty acids to secondary carbon ketones, achieving highly selective generation of the secondary carbon primary amine N1923, overcoming the defects of low conversion rate and poor selectivity in traditional routes, and significantly improving the yield of the target product.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a secondary carbon primary amine and its preparation method. Background Technology

[0002] Secondary carbon primary amine (N1923) is an important weakly basic amine extractant in the metallurgical industry. Its molecular structure features unique coordination characteristics between the secondary carbon groups and primary amine functional groups. As a core material in metal extraction, N1923 demonstrates an irreplaceable role in rare earth separation and precious metal recovery processes due to its precise ion selectivity and high complexing ability. In organic synthesis, this compound, as a multifunctional catalyst or auxiliary agent, significantly enhances the rate and regioselectivity of carbonyl addition and condensation reactions by regulating reaction pathways, and has become a key component in the preparation of fine chemicals.

[0003] Despite its significant application value, the industrial production of secondary amine N1923 still faces major technical bottlenecks. Traditional synthesis processes generally employ multi-stage amination-alkylation tandem reactions, requiring high temperature and pressure conditions and multiple purification steps, resulting in complex processes and excessive energy consumption. More importantly, according to the literature [J Catal. 2020, 391:123], the conversion rate of traditional processes is ≤40%, and the product purity fluctuates between 85-90%. This is mainly due to the uncontrollable formation of secondary amine isomers during the reaction and the accumulation of byproducts caused by catalyst deactivation. Furthermore, the use of precious metal catalysts not only increases production costs by more than 30%, but their residues also negatively impact the extraction performance of the final product.

[0004] It is worth noting that 10-12 carbon fatty acids, as a bulk petrochemical byproduct, have significant advantages such as suitable carbon chain length, controllable branched structure, and a cost that is only 1 / 5 of that of traditional raw materials. However, there are still key scientific challenges in achieving the efficient conversion of fatty acid raw materials into target amine compounds, especially the need to overcome technical barriers such as low carbon chain activation efficiency, poor amination selectivity, and weak compatibility of reaction systems. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to achieve efficient synthesis of secondary primary amines from 10-12 carbon fatty acids.

[0006] To address the above problems, the present invention proposes the following technical solution:

[0007] This invention provides a method for preparing secondary carbon primary amines, comprising the following steps:

[0008] S1. Using 10-12 carbon fatty acids as raw materials, a fatty acid ketation reaction is carried out under a composite catalyst atmosphere to obtain secondary carbon ketones; the composite catalyst comprises: a) a ZrO2-M catalyst supported on mesoporous silica, where M is a rare earth element; b) a Pt-Pd bimetallic nanoparticle catalyst supported on γ-alumina; the mass ratio of the two is 1:1.2-3.0.

[0009] S2. Prepare a solution of secondary carbon ketone with a concentration of 0.6-1.2 mol / L using a solvent, and add nitrogen-doped activated carbon supported ruthenium catalyst to obtain a suspension.

[0010] S3. The suspension obtained in step S2 is subjected to an amination reaction with ammonia under a hydrogen atmosphere to obtain a secondary primary amine.

[0011] A further technical solution is that, in the ZrO2-M catalyst, the loading of ZrO2-M is 10-18 wt%; in the Pt-Pd bimetallic nanoparticle catalyst, the loading of Pt-Pd metal nanoparticles is 2-6 wt%.

[0012] A further technical solution is that, in step S1, the mass ratio of raw material to composite catalyst is 20:1.1 to 1.5.

[0013] A further technical solution is that, in the Pt-Pd bimetallic nanoparticle catalyst, the molar ratio of Pt to Pd is 1:0.1 to 0.3; and in the ZrO2-M catalyst, the molar ratio of Zr to M is 1:0.1 to 0.3.

[0014] A further technical solution is that, in step S2, the mass fraction of the nitrogen-doped activated carbon supported ruthenium catalyst added to the system is 8-15%, and the loading amount of the nitrogen-doped activated carbon supported ruthenium catalyst is 18-25 wt%.

[0015] A further technical solution is that the preparation method of the Pt-Pd bimetallic nanoparticle catalyst is as follows:

[0016] γ-alumina was impregnated in a mixed solution containing chloroplatinic acid and palladium chloride, sonicated for 25-35 min, and then stirred at room temperature for 10-14 h. After filtration, the solid product was dried at 75-85 °C and then reduced at 280-320 °C for 2-4 h in a hydrogen atmosphere to obtain a supported Pt-Pd bimetallic nanoparticle catalyst.

[0017] A further technical solution is that the preparation method of the nitrogen-doped activated carbon supported ruthenium catalyst is as follows:

[0018] Activated carbon was soaked in an aqueous solution containing urea, ultrasonically treated for 15-25 minutes, stirred and evaporated at 75-85℃, and then calcined at 780-820℃ for 2-4 hours in a nitrogen atmosphere to obtain nitrogen-doped activated carbon.

[0019] Ruthenium trichloride was dissolved in deionized water, and nitrogen-doped activated carbon was added. The mixture was ultrasonically dispersed for 25-35 min and stirred at room temperature for 20-28 h. The sample was then filtered, washed, dried at 90-110 °C for 10-14 h, and finally reduced at 380-420 °C for 1-3 h in a hydrogen atmosphere to obtain a supported ruthenium catalyst.

[0020] A further technical solution is that, before step S1, the 10-12 carbon fatty acid raw material is further refined by heating the 10-12 carbon fatty acid to 150-200℃ under a low pressure environment of 0.1-0.5 kPa.

[0021] A further technical solution is that the 10-12 carbon fatty acids include decanoic acid, undecanoic acid, and lauric acid.

[0022] The present invention also provides a secondary carbon primary amine, which is prepared from 10-12 carbon fatty acids using the above-described preparation method for secondary carbon primary amines.

[0023] Compared with the prior art, the technical effects achieved by the present invention include:

[0024] The present invention provides a method for preparing secondary amines, employing an innovative composite catalyst system (ZrO2-M / Pt-Pd noble metal nanoparticles) to catalyze the ketation reaction of fatty acids. This synergistic effect significantly improves the conversion efficiency and selectivity of fatty acids to secondary ketones. In the subsequent amination reaction, a nitrogen-doped activated carbon-supported ruthenium catalyst is used to promote the reductive amination of secondary ketones with ammonia / hydrogen, achieving highly selective generation of the secondary amine N1923. The dual-catalyst system of this method exhibits significant synergistic effects, overcoming the shortcomings of low conversion and poor selectivity in traditional pathways. Examples show a product yield of 80-82%, an improvement of more than 5% compared to the comparative example.

[0025] Furthermore, this method uses widely available and inexpensive 10-12 carbon fatty acids as direct raw materials, abandoning the traditional multi-step complex synthetic route. Secondary primary amine N1923 can be efficiently prepared through a two-step core reaction of ketation and amination, greatly simplifying the process. The catalyst system reduces the total amount of precious metals (Pt-Pd) and adopts a supported design, improving catalyst utilization and reducing costs. More importantly, the highly selective catalysis significantly inhibits the formation of byproducts, reducing the difficulty of subsequent separation and purification and the burden of waste treatment, while avoiding the use of harmful reagents in traditional methods, making the overall process more environmentally friendly.

[0026] The method for preparing secondary primary amines provided by this invention overcomes the core defects of existing secondary primary amine N1923 synthesis processes, such as cumbersome steps, low yield, high cost, numerous byproducts, and serious environmental pollution. This method achieves efficient and highly selective conversion using inexpensive fatty acids as raw materials, providing a practical and feasible technical solution for the large-scale, green industrial production of secondary primary amine N1923. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is an overall process flow diagram of the secondary carbon primary amine preparation method provided in Example 1 of the present invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0031] It should also be understood that the terminology used in this specification of embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. As used in this specification of embodiments of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0032] This invention provides a method for preparing secondary primary amines, comprising the following steps:

[0033] S1. Using 10-12 carbon fatty acids as raw materials, fatty acid ketation reaction is carried out under the action of a composite catalyst to obtain secondary carbon ketones; the composite catalyst comprises: a) a ZrO2-M catalyst supported on mesoporous silica, where M is a rare earth element; b) a Pt-Pd bimetallic nanoparticle catalyst supported on γ-alumina; the mass ratio of the two is 1:1.2-3.0.

[0034] S2. Prepare a solution of secondary carbon ketone with a concentration of 0.6-1.2 mol / L using a solvent, and add nitrogen-doped activated carbon supported ruthenium catalyst to obtain a suspension.

[0035] S3. The suspension obtained in step S2 is subjected to an amination reaction with ammonia under a hydrogen atmosphere to obtain a secondary primary amine.

[0036] In some embodiments, the loading of ZrO2-M in the ZrO2-M catalyst is 10-18 wt%, for example 12 wt%, 15 wt%, or 18 wt%; and the loading of Pt-Pd metal nanoparticles in the Pt-Pd bimetallic nanoparticle catalyst is 2-6 wt%, for example 2 wt%, 5 wt%, or 6 wt%.

[0037] In some embodiments, the molar ratio of Pt to Pd in ​​the supported Pt-Pd bimetallic nanoparticle catalyst is 1:0.1 to 0.3, and the support is γ-alumina.

[0038] In some embodiments, the Pt-Pd bimetallic nanoparticle catalyst is prepared as follows:

[0039] Weigh 4-6 g of γ-alumina and immerse it in 80-120 mL of a mixed solution containing 0.4-0.6 g of chloroplatinic acid (H₂PtCl₅) and 0.2-0.4 g of palladium chloride (PdCl₂) in an ethanol-water solution (ethanol:water volume ratio 1:1). Sonicate the solution for 25-35 min, then stir at room temperature for 10-14 h. Filter the solution, dry the solid product at 75-85 °C, and then reduce it in a hydrogen atmosphere at 280-320 °C for 2-4 h to obtain supported Pt-Pd bimetallic nanoparticles.

[0040] In some embodiments, the molar ratio of Zr to M in the ZrO2-M catalyst is 1:0.1 to 0.3, and the support is mesoporous silica. In this embodiment, M is cerium.

[0041] The composite catalyst system employed in this invention enhances the performance of the ketation reaction through the synergistic effect between its components. This composite catalyst fully utilizes the high dispersibility of the mesoporous silica support to disperse the active components (including Ce-modified zirconium oxide and Pt-Pd bimetallic nanoparticles), significantly increasing the number of contactable active sites with fatty acid raw material molecules. Furthermore, the introduction of Ce optimizes the acid-base properties of zirconium oxide, giving its surface both acidic sites required for activating fatty acid carboxyl groups and basic sites required for promoting decarboxylation. This inherent acid-base synergistic effect significantly lowers the reaction energy barrier. Simultaneously, the bimetallic structure formed by Pt and Pd preferentially catalyzes the reaction pathway for the formation of the target secondary ketone through electronic effects, effectively suppressing side reactions.

[0042] Compared to traditional catalysts, the composite catalyst system used in this invention can drive the efficient conversion of fatty acids to secondary ketones under milder conditions, resulting in a simpler and more efficient reaction process. The highly selective catalytic effect not only directly improves the yield of the target intermediate secondary ketone, but more importantly, it significantly reduces the formation of byproducts. This simplifies subsequent separation and purification steps and reduces the overall environmental impact of the process. Therefore, the core advantage of this composite catalyst lies in its ability to fundamentally overcome the key bottlenecks of poor selectivity and low efficiency in traditional fatty acid ketation processes through the synergistic effect between its components, laying a solid foundation for the subsequent amination preparation of high-purity secondary amine N1923.

[0043] In some embodiments, the ZrO2-M catalyst is prepared as follows:

[0044] (1) Dissolve 8-12g of template agent (e.g., P123) in 350-450mL of hydrochloric acid solution (2M), stir until homogeneous, and then slowly add 18-22mL of tetraethyl orthosilicate (TEOS) dropwise under a 40℃ water bath. After the addition is complete, continue stirring for 22-26h to form a homogeneous sol. Transfer the sol to a hydrothermal reactor and crystallize at 100℃ for 46-50h. After filtration, washing, and drying, the product is calcined at 540-560℃ for 5-7h to obtain a mesoporous silica (mSiO2) support.

[0045] (2) Weigh 12-18g of zirconium oxychloride octahydrate (ZrOCl2·8H2O) and 0.8-1.2g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O), dissolve them in 80-120mL of deionized water, and stir to form a transparent solution. Add ammonia dropwise to adjust the pH of the solution to 9-10, and a precipitate will form. After aging the precipitate for 10-14h, filter and wash until neutral, dry at 90-110℃ for 10-14h, and finally calcine at 580-620℃ for 3-5h to obtain Ce-doped modified zirconium oxide (ZrO2-Ce).

[0046] (3) Add 8-12g of the prepared mesoporous silica support to a suspension containing 10-14g of ZrO2-Ce (180-220mL of deionized water), disperse ultrasonically for 25-35min, stir and evaporate the water, and dry at 110-130℃ for 5-7h to obtain the ZrO2-M catalyst.

[0047] The preparation method of the composite catalyst includes: mixing the above ZrO2-M catalyst with Pt-Pd bimetallic nanoparticle catalyst evenly to obtain the final novel composite catalyst.

[0048] In some embodiments, in step S1, the mass ratio of raw material to composite catalyst is 20:1.1 to 1.5.

[0049] In some embodiments, in step S2, the mass fraction of the nitrogen-doped activated carbon supported ruthenium catalyst added to the system is 8-15%, and the loading amount of the nitrogen-doped activated carbon supported ruthenium catalyst is 18-25 wt%.

[0050] In some embodiments, the nitrogen-doped activated carbon supported ruthenium catalyst is prepared as follows:

[0051] Take 8-12g of activated carbon and soak it in 80-120mL of aqueous solution containing 4-6g of urea. After ultrasonic treatment for 15-25min, stir and evaporate the water at 75-85℃. Then calcine the sample at 780-820℃ for 2-4h in a nitrogen atmosphere to obtain nitrogen-doped activated carbon.

[0052] Weigh 1.5-2.5 g of ruthenium trichloride (RuCl3) and dissolve it in 80-120 mL of deionized water. Add 8-12 g of nitrogen-doped activated carbon prepared above, and disperse the mixture ultrasonically for 25-35 min. Then stir at room temperature for 20-28 h. Subsequently, filter and wash the sample, dry it at 90-110 °C for 10-14 h, and finally reduce it in a hydrogen atmosphere at 380-420 °C for 1-3 h to obtain a nitrogen-doped activated carbon supported ruthenium catalyst.

[0053] In some embodiments, prior to step S1, the 10-12 carbon fatty acid raw material is further purified by heating it to 150-200°C under a low pressure environment of 0.1-0.5 kPa. The purity of the 10-12 carbon fatty acid raw material is ≥98%. Refining can effectively remove low-boiling-point impurities and moisture that may be present in the raw material, providing pure raw materials for subsequent reactions.

[0054] In some embodiments, the 10-12 carbon fatty acids include decanoic acid (C10-C2 ...). 10 H 20 O2), undecanoic acid (C11 H 22 O2) and lauric acid (C 12 H 24 O2).

[0055] The present invention also provides a secondary carbon primary amine, which is prepared from 10-12 carbon fatty acids using the above-described preparation method for secondary carbon primary amines.

[0056] Comparative Example 1

[0057] Comparative Example 1 provides a method for preparing a secondary carbon primary amine, comprising the following steps:

[0058] 1. Raw material pretreatment: Take 200g of 10-12 carbon fatty acids with a purity of 98.5%, of which decanoic acid accounts for 35%, undecanoic acid accounts for 33%, and lauric acid accounts for 32%. Place it in a 500mL vacuum distillation apparatus, heat to 170℃ under a pressure of 0.25kPa, and distill for 1.2h to obtain 194g of purified 10-12 carbon fatty acids.

[0059] 2. Fatty acid ketation reaction: 194g of refined fatty acids were added to a 1L reactor, along with 12g of a single catalyst, MnO. Nitrogen gas was introduced to replace the air at a flow rate of 70mL / min for 50min. The mixture was stirred at 450r / min and heated to 380℃ for 18hr. After the reaction was complete, gas chromatography analysis showed that the yield of secondary ketones was 85%.

[0060] 3. Reductive amination reaction: The reaction solution containing the secondary carbon ketone was transferred to a high-pressure reactor, and 18g of 10% Ranny nickel catalyst was added. Isopropanol was added to prepare a solution with a secondary carbon ketone concentration of 0.9mol / L. Ammonia gas was introduced to a pressure of 2MPa, followed by hydrogen gas to a pressure of 5MPa. The reaction was carried out at 150℃ and a stirring speed of 550r / min for 6 hours.

[0061] 4. Product Separation and Purification: After the reaction, the catalyst was removed by cooling and filtration, and isopropanol was recovered by atmospheric distillation. The crude product was then distilled under reduced pressure at 0.02 kPa, and the fraction collected at 180-200℃ was used to obtain 148 g of secondary primary amine N1923, with a yield of 76% and a purity of 95.1%.

[0062] Comparative Example 2

[0063] Comparative Example 2 provides a method for preparing a secondary primary amine, comprising the following steps:

[0064] 1. Raw material pretreatment: Take 200g of 10-12 carbon fatty acids with a purity of 98.5%, of which decanoic acid accounts for 40%, undecanoic acid accounts for 31%, and lauric acid accounts for 29%. Place it in a 500mL vacuum distillation apparatus, heat to 170℃ under a pressure of 0.25kPa, and distill for 1.2h to obtain 195g of purified 10-12 carbon fatty acids.

[0065] 2. Fatty acid ketation reaction: 195g of refined fatty acids were added to a 1L reactor, along with 12g of a composite catalyst FeCl2-ZrO2-MnO2 (the catalyst was prepared by impregnation using γ-alumina as a support; the active components FeCl2, ZrO2, and MnO2 accounted for 20% of the catalyst mass, and the molar ratio of the three components was 1:2:1). Nitrogen gas was introduced to replace the air at a flow rate of 70mL / min for 50min. The temperature was raised to 300℃ at a stirring speed of 450r / min, and the reaction was carried out for 10hr. After the reaction was completed, gas chromatography analysis showed that the yield of secondary carbon ketones was 90%.

[0066] 3. Reductive amination reaction: The reaction solution containing the secondary carbon ketone was transferred to a high-pressure reactor, and 18g of 10% Ranny nickel catalyst was added. Isopropanol was added to prepare a solution with a secondary carbon ketone concentration of 0.9mol / L. Ammonia gas was introduced to a pressure of 2MPa, followed by hydrogen gas to a pressure of 5MPa. The reaction was carried out at 150℃ and a stirring speed of 550r / min for 6 hours.

[0067] 4. Product Separation and Purification: After the reaction, the catalyst was removed by cooling and filtration, and isopropanol was recovered by atmospheric distillation. The crude product was then distilled under reduced pressure at 0.02 kPa, and the fraction collected at 180-200℃ was used to obtain 152 g of secondary primary amine N1923, with a yield of 78% and a purity of 96.1%.

[0068] Example 1

[0069] 1. Raw material pretreatment: Take 200g of 10-12 carbon fatty acids with a purity of 98.8%, of which decanoic acid accounts for 45%, undecanoic acid accounts for 30%, and lauric acid accounts for 25%. Place it in a 500mL vacuum distillation apparatus, heat to 170℃ under a pressure of 0.25kPa, and distill for 1.2h to obtain 196g of purified 10-12 carbon fatty acids.

[0070] 2. Fatty acid ketation reaction: 196g of refined fatty acids were added to a 1L reactor, along with 12g of a novel composite catalyst (mSiO2 as support, ZrO2-Ce loading of 15wt%, and Pt-Pd bimetallic nanoparticles loaded on the mSiO2 support of 4wt%). Nitrogen gas was introduced to replace the air at a flow rate of 70mL / min for 50min. The mixture was stirred at 450r / min and heated to 280℃ for 4h. After the reaction, gas chromatography analysis showed that the yield of secondary ketones was 92%.

[0071] 3. Reductive amination reaction: The reaction solution containing the secondary carbon ketone was transferred to a high-pressure reactor, and 18 g of 10% (w / w) nitrogen-doped activated carbon-supported Ru catalyst was added. Isopropanol was added to prepare a solution with a secondary carbon ketone concentration of 0.9 mol / L. Ammonia gas was introduced to a pressure of 2 MPa, followed by hydrogen gas to a pressure of 5 MPa. The reaction was carried out at 150 °C and a stirring speed of 550 r / min for 3 h.

[0072] 4. Product Separation and Purification: After the reaction was completed, the catalyst was removed by cooling and filtration, and isopropanol was recovered by atmospheric distillation. The crude product was then distilled under reduced pressure, and the fraction collected at 180-200℃ was obtained at 0.02 kPa to yield 160 g of secondary primary amine N1923, with a yield of 82% and a purity of 99.2%.

[0073] Example 2

[0074] 1. Raw material pretreatment: Take 250g of 10-12 carbon fatty acids with a purity of 99.2%, of which decanoic acid accounts for 38%, undecanoic acid accounts for 32%, and lauric acid accounts for 30%. In a vacuum distillation apparatus, distill at 165℃ for 1.3h under a pressure of 0.35kPa to obtain 245g of refined fatty acids.

[0075] 2. Fatty acid ketation reaction: 245g of refined fatty acids were added to a reaction vessel, along with 14g of a novel composite catalyst (mSiO2 as support, ZrO2-Ce loading 13wt%, Pt-Pd bimetallic nanoparticle loading 3wt%). Air was replaced with nitrogen at a flow rate of 80mL / min for 55min. The stirring speed was 550r / min, and the temperature was raised to 270℃ for 3.5h. The yield of secondary ketones was determined to be 90%.

[0076] 3. Reductive amination reaction: Transfer the reaction solution containing the secondary carbon ketone to an autoclave, add 22 g of nitrogen-doped activated carbon-supported Ru catalyst (11% by mass), and prepare an isopropanol solution with a secondary carbon ketone concentration of 0.8 mol / L. Purge with ammonia to a pressure of 1.8 MPa and with hydrogen to a pressure of 4.5 MPa. React at 160 °C and a stirring speed of 650 r / min for 3.5 h.

[0077] 4. Product separation and purification: Cooling and filtration were performed, and isopropanol was recovered by atmospheric distillation. The crude product was then distilled under reduced pressure. The fraction collected at 175-195℃ under a pressure of 0.015 kPa yielded 190 g of secondary primary amine N1923, with a yield of 80% and a purity of 98.8%.

[0078] It should be noted that the preparation process of the composite catalyst used in Examples 1 and 2 is as follows:

[0079] Preparation of mesoporous silica support: 10 g of template agent (P123) was dissolved in 400 mL of hydrochloric acid solution (2M). After stirring until homogeneous, 20 mL of tetraethyl orthosilicate (TEOS) was slowly added dropwise under a 40 °C water bath. After the addition was complete, stirring was continued for 25 h to form a homogeneous sol. The sol was transferred to a hydrothermal reactor and crystallized at 100 °C for 50 h. The product was filtered, washed, dried, and then calcined at 550 °C for 6 h to obtain the mesoporous silica (mSiO2) support.

[0080] Preparation of modified zirconium oxide (ZrO2-Ce): Weigh 10 g of zirconium oxychloride octahydrate (ZrOCl2·8H2O) and 1.0 g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O), dissolve them in 100 mL of deionized water, and stir to form a transparent solution. Add ammonia dropwise to adjust the pH of the solution to 9, and a precipitate will form. After aging the precipitate for 12 h, filter and wash until neutral, dry at 100 °C for 12 h, and finally calcine at 600 °C for 5 h to obtain Ce-doped modified zirconium oxide (ZrO2-Ce).

[0081] Pt-Pd bimetallic nanoparticle catalyst: 5g of γ-alumina was weighed and impregnated in a mixed solution (100mL, ethanol-water volume ratio 1:1) containing 0.5g of chloroplatinic acid (H2PtCl6) and 0.3g of palladium chloride (PdCl2). The solution was ultrasonically treated for 30min and then stirred at room temperature for 12h. Subsequently, the impregnated γ-alumina was dried at 80℃ and then reduced at 300℃ for 2h in a hydrogen atmosphere to obtain the Pt-Pd bimetallic nanoparticle catalyst.

[0082] Loading the active component onto the support: 10g of the prepared mesoporous silica support was added to a suspension containing 12g of ZrO2-Ce (200mL of deionized water), ultrasonically dispersed for 30min, stirred and evaporated to dryness, and dried at 120℃ for 6h; then it was mixed evenly with Pt-Pd bimetallic nanoparticle catalyst to obtain the final composite catalyst.

[0083] As can be clearly seen from the above examples, the preparation method provided by this invention utilizes a novel composite catalyst system and uses 10-12 carbon fatty acids as raw materials to synthesize secondary carbon primary amine N1923 simply and efficiently. The reaction process is simple, and the yield and product purity are significantly improved compared to the comparative example. Furthermore, the 10-12 carbon fatty acid raw material is inexpensive, effectively reducing production costs and minimizing negative environmental impacts, thus opening up a promising new path for the industrial production of secondary carbon primary amine N1923.

[0084] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0085] The above description describes specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a secondary primary amine, characterized in that, Includes the following steps: S1. Using 10-12 carbon fatty acids as raw materials, a fatty acid ketation reaction is carried out under the action of a composite catalyst to obtain secondary carbon ketones; the composite catalyst comprises: a) a ZrO2-M catalyst supported on mesoporous silica, where M is cerium; b) a Pt-Pd bimetallic nanoparticle catalyst supported on γ-alumina; the mass ratio of the two is 1:1.2~3.

0. S2. Prepare a solution with a secondary carbon ketone concentration of 0.6-1.2 mol / L using a solvent, and add a nitrogen-doped activated carbon-supported ruthenium catalyst to obtain a suspension. S3. The suspension obtained in step S2 is subjected to an amination reaction with ammonia under a hydrogen atmosphere to obtain a secondary primary amine.

2. The method for preparing secondary primary amines according to claim 1, characterized in that, In the ZrO2-M catalyst, the loading of ZrO2-M is 10-18 wt%; in the Pt-Pd bimetallic nanoparticle catalyst, the loading of Pt-Pd metal nanoparticles is 2-6 wt%.

3. The method for preparing secondary primary amines according to claim 1, characterized in that, In step S1, the mass ratio of raw material to composite catalyst is 20:1.1~1.

5.

4. The method for preparing secondary primary amines according to claim 1, characterized in that, In the Pt-Pd bimetallic nanoparticle catalyst, the molar ratio of Pt to Pd is 1:0.1~0.3; in the ZrO2-M catalyst, the molar ratio of Zr to M is 1:0.1~0.

3.

5. The method for preparing secondary primary amines according to claim 1, characterized in that, In step S2, the mass fraction of the nitrogen-doped activated carbon supported ruthenium catalyst added to the system is 8-15%, and the loading amount of the nitrogen-doped activated carbon supported ruthenium catalyst is 18-25 wt%.

6. The method for preparing secondary primary amines according to claim 1, characterized in that, The preparation method of the Pt-Pd bimetallic nanoparticle catalyst is as follows: γ-alumina was impregnated in a mixed solution containing chloroplatinic acid and palladium chloride, sonicated for 25-35 min, and then stirred at room temperature for 10-14 h. After filtration, the solid product was dried at 75-85 °C and then reduced at 280-320 °C for 2-4 h in a hydrogen atmosphere to obtain a supported Pt-Pd bimetallic nanoparticle catalyst.

7. The method for preparing secondary primary amines according to claim 1, characterized in that, The preparation method of the nitrogen-doped activated carbon supported ruthenium catalyst is as follows: Activated carbon was soaked in an aqueous solution containing urea, ultrasonically treated for 15-25 min, and then the water was evaporated by stirring at 75-85℃. The sample was then calcined at 780-820℃ for 2-4 h in a nitrogen atmosphere to obtain nitrogen-doped activated carbon. Ruthenium trichloride was dissolved in deionized water, and nitrogen-doped activated carbon was added. The mixture was ultrasonically dispersed for 25-35 min and stirred at room temperature for 20-28 h. The sample was then filtered, washed, dried at 90-110 °C for 10-14 h, and finally reduced at 380-420 °C for 1-3 h in a hydrogen atmosphere to obtain a supported ruthenium catalyst.

8. The method for preparing secondary primary amines according to claim 1, characterized in that, Before step S1, the 10-12 carbon fatty acid raw material is further refined by heating it to 150-200°C under a low pressure environment of 0.1-0.5 kPa.

9. The method for preparing secondary primary amines according to claim 1, characterized in that, The 10-12 carbon fatty acids include decanoic acid, undecanoic acid, and lauric acid.

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