A catalyst for synthesizing N,N-bis(3-aminopropyl)methylamine, and its preparation method and application

Abstract

The present invention relates to a catalyst for synthesizing N, N-bis (3-aminopropyl) methylamine and its preparation method and application. Catalyst preparation step: a first and a second water-soluble metal salt are mixed with water to obtain a mixed bimetallic salt solution; a carbon-based substrate and an equal amount of nano-TiO2 are dispersed in water as a catalyst load, ultrasonic stirring is performed until the dispersion is complete, and then a corresponding amount of mixed bimetallic salt solution is added; the mixed bimetallic salt solution is placed under a xenon lamp light source to irradiate and stir the reaction, the mixed bimetallic salt solution after the above illumination is frozen into a solid, and finally the solid is subjected to vacuum freeze drying to finally obtain the catalyst for synthesizing N, N-bis (3-aminopropyl) methylamine. The catalyst obtained by the present invention simplifies the facilities and operations of the synthesis production process of N, N-bis (3-aminopropyl) methylamine, and has the characteristics of high activity and good selectivity. The catalyst preparation method has the characteristics of wide source of raw materials, simple operation, and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical engineering, and in particular to a catalyst for synthesizing N,N-bis(3-aminopropyl)methylamine, and a preparation method and application thereof. Background Art

[0002] N,N-bis(3-aminopropyl)methylamine (BAPMA), its structural formula is shown in the figure below:

[0003]

[0004] BAPMA is an important fine organic chemical intermediate widely used in the pharmaceutical, pesticide, dye, petrochemical, semiconductor manufacturing, and polymer industries. As a key precursor to pentamethyldipropylenetriamine, BAPMA is commonly used in the production of reverse osmosis nanofiltration membranes, epoxy resin curing accelerators, Schiff bases and their complexes, pharmaceutical synthesis intermediates, and printing and dyeing wastewater treatment.

[0005] At present, N,N-bis(3-aminopropyl)methylamine is mainly obtained by catalytic hydrogenation of N,N-bis(cyanoethyl)methylamine. Catalysts with different active centers have different catalytic hydrogenation reduction processes for cyano groups, as well as catalytic activity and selectivity.

[0006] Industrial-scale nitrile hydrogenation mostly uses suspended catalysts such as Raney nickel and Raney cobalt. Hirano et al. (Manufacturing method of nitrile compound and catalytic converter null for production:, JP Patent No. 3156734 (P3156734) B2 [P]. 2001.) used a nickel-cobalt bimetallic catalyst to hydrogenate N,N-bis(cyanoethyl)methylamine. The reaction conditions were mild (80°C, 4.5 MPa, 3.9 h), and a yield of 93% was achieved. However, the selectivity of the reaction was poor over this catalyst, with the formation of various byproducts.

[0007] Eidamshaus et al. used a ZrO2-supported Ru catalyst as a fixed-bed catalyst (METHOD FOR HYDROGENATING NITRILES IN THE PRESENCE OF A RUTHENIUM CATALYST CARRIED ON ZrO2:, US20190169112[P].2019.) to hydrogenate N,N-bis(cyanoethyl)methylamine at 100°C and 140 bar. Although the reaction achieved a conversion of 99%, the reaction conditions were harsh, resulting in poor selectivity, a maximum product yield of 92%, and a high metal loading of 15 wt%, leading to high costs.

[0008] Reports on the one-step synthesis of N,N-bis(3-aminopropyl)methylamine are relatively rare. Chen et al. used Raney nickel as a cyanohydrogenation catalyst (An efficient synthesis of n,n,n',n',n"-pentamethyldipropylenetriamine) to synthesize N,N-bis(cyanoethyl)methylamine in a single step in an autoclave using acrylonitrile and methylamine as raw materials. Amination was performed in methanol solvent at room temperature for 4 hours, followed by hydrogenation under alkaline reaction conditions at 90°C and 2 MPa. The final yield of N,N-bis(3-aminopropyl)methylamine reached 85%. However, in this process, the Raney nickel catalyst only catalyzed the hydrogenation process, resulting in a long overall reaction time and low efficiency.

[0009] In summary, the numerous reported N,N-bis(3-aminopropyl)methylamine production routes mostly utilize nitrile as a raw material and are obtained through hydrogenation. These routes suffer from poor selectivity, harsh conditions, high costs, and low efficiency, and are difficult to achieve continuous production. Therefore, developing a technology that can synthesize N,N-bis(3-aminopropyl)methylamine in one step has become an urgent issue to be addressed in this field. Summary of the Invention

[0010] The primary purpose of the present invention is to provide a method for preparing a catalyst for synthesizing N,N-bis(3-aminopropyl)methylamine. The catalyst obtained by the preparation method simplifies the facilities and operations of the N,N-bis(3-aminopropyl)methylamine synthesis production process and has the characteristics of high activity and good selectivity in the synthesis reaction of N,N-bis(3-aminopropyl)methylamine. In addition, the catalyst preparation method has the characteristics of a wide source of raw materials, simple operation, low cost, etc.

[0011] In order to achieve the above-mentioned purpose of the invention, the technical solutions adopted by the present invention are as follows:

[0012] A method for preparing a catalyst for synthesizing N,N-bis(3-aminopropyl)methylamine, the method comprising the following steps:

[0013] 1) mixing a first water-soluble metal salt, a second water-soluble metal salt, and water to obtain a mixed bimetallic salt solution; the first water-soluble metal salt is one or more of sodium nitrate, potassium nitrate, and magnesium nitrate, and the second water-soluble metal salt is one or more of nickel nitrate, zinc nitrate, and chromium nitrate;

[0014] 2) dispersing a carbon-based substrate and an equal amount of nano-TiO2 as a catalyst load in water, stirring ultrasonically until the dispersion is complete, and then adding a corresponding amount of a mixed double metal salt solution, wherein the mass ratio of metal to catalyst load in the mixed double metal salt solution is 0.5 to 5.0 wt%;

[0015] 3) placing the mixed bimetallic salt solution under a xenon lamp light source and stirring for 3 to 6 hours at a current of 10 to 20 A, freezing the mixed bimetallic salt solution after illumination into a solid, and finally freeze-drying the solid under a vacuum degree of 0.001 to 0.01 MPa and conditions of -60 to -50°C to obtain a composite bimetallic single atom catalyst, i.e., the catalyst for synthesizing N,N-bis(3-aminopropyl)methylamine.

[0016] Preferred solution: The carbon-based substrate is one or more of graphene, graphene oxide, carbon nanotubes, C3N4, and nitrogen-doped graphene.

[0017] Optimal solution: The freezing time of the mixed bimetallic salt solution after illumination is 2 to 4 hours, and the vacuum freeze-drying time of the solid is 23 to 25 hours.

[0018] The second object of the present invention is to provide a catalyst for synthesizing N,N-bis(3-aminopropyl)methylamine obtained based on the above preparation method.

[0019] The third object of the present invention is to provide an application of the above catalyst for preparing N,N-bis(3-aminopropyl)methylamine, and the application method is as follows:

[0020] A composite bimetallic single-atom catalyst and raw materials, acrylonitrile and methylamine, are added to an autoclave, wherein the mass ratio of the composite bimetallic single-atom catalyst to the raw materials, acrylonitrile and methylamine, is 1 to 5 wt %. The inner cavity of the autoclave is gas-displaced with nitrogen, and then the reaction is stirred at a reaction temperature of 80 to 100° C. and a reaction pressure of 0.5 to 2.0 MPa for 1.5 to 2.5 hours. Hydrogen is then introduced, and the reaction is stirred at 130 to 160° C. for 1.5 to 2.5 hours while maintaining a pressure of 1.5 to 3 MPa. After the reaction is completed, the autoclave is opened, a solvent is added to dissolve the reaction product, and the reaction product is filtered to obtain the product, N,N-bis(3-aminopropyl)methylamine.

[0021] Preferred solution: the stirring reaction time is 2h.

[0022] The technical effects achieved by the present invention are as follows:

[0023] 1) The preparation principle of the composite bimetallic single-atom catalyst of the present invention is: during the process of preparing the catalyst by the photodeposition method, when the photosensitive material is irradiated with ultraviolet light, it generates easily mobile and highly active electron-hole pairs. The photogenerated carrier pairs can freely migrate in the crystal lattice to the lattice surface or other reaction sites, forming free holes and free electrons, and are immediately captured by surface species, causing various redox reactions, anchoring different metal atoms on the carrier, and forming a composite bimetallic single-atom catalyst. The role of each step in the catalyst preparation process is as follows: different types of metal salts are precursors of different active centers; TiO2 and C3N4 serve as photosensitive materials to generate electron holes under light; the addition of a carbon-based carrier with a large specific surface area, special morphology and structure can provide a loading surface, which is conducive to dispersion, while separating electrons and preventing rapid recombination of electron holes; the role of the vacuum freeze-drying step is to remove moisture in the system at low temperature while retaining the stable structure inside the catalyst; the influence of its corresponding technical parameters on the successful preparation of the catalyst is: the mass ratio of metal to carrier is controlled at 0.5-5.0wt%, too high will form agglomerates, and too low will result in insufficient activity; the illumination time is controlled at 3-6h, too low will not cause metal reduction, and too high will affect the carrier structure; sodium salt, potassium salt, magnesium salt, nickel salt, zinc salt, and chromium salt are selected as the metal salts as active centers for amination reaction and hydrogenation reaction, respectively. Key technical points include: the mass ratio of the metal to the carrier controls the metal's dispersion on the carrier surface; the illumination duration influences the metal's reduced valence; and the choice of metal salt influences the type of active center, allowing the active sites in the previous step to serve as co-catalysts in the subsequent step, improving hydrogenation selectivity. Overall, the successful preparation of this catalyst ensures the one-step synthesis of N,N-bis(3-aminopropyl)methylamine.

[0024] 2) The effect of the composite bimetallic single-atom catalyst prepared by the present invention on the synthesis of N,N-bis(3-aminopropyl)methylamine is as follows: it simplifies the facilities and operations of the synthesis production process of N,N-bis(3-aminopropyl)methylamine. The traditional production process requires two sets of production equipment, and the amination and hydrogenation operations are separated, which makes the equipment and operations complicated. In the present invention, only one reactor is used, and the amination and hydrogenation are carried out successively, without the need to separate the intermediate products, thus reducing the equipment and intermediate operation steps. The composite bimetallic single-atom catalyst has the characteristics of high activity and good selectivity for the synthesis of N,N-bis(3-aminopropyl)methylamine. The traditional operation uses Raney nickel or precious metal catalysts for hydrogenation, which has no effect on the amination reaction. The catalyst of the present invention has a promoting effect on amination and hydrogenation at the same time, with a yield higher than 94.1% and a selectivity higher than 96.2%. In addition, the catalyst preparation method has the characteristics of wide raw material sources, simple operation, low cost, etc. Transition metal salts and carbon-based carriers are cheaper and easier to obtain than precious metals. The price of commonly used precious metal catalysts in industrialization is 1.5 times that of the transition metal in the present invention. In addition, the metal utilization rate of the present invention (nearly 100%) is much higher than that of traditional catalysts. Traditional industrial catalysts require complex operations such as high-temperature roasting, while the catalyst of the present invention is completed at room temperature and normal pressure, and is simple to operate.

[0025] 3) The catalytic principle of the present invention for preparing and synthesizing N,N-bis(3-aminopropyl)methylamine using a composite bimetallic single-atom catalyst is as follows: acrylonitrile and methylamine undergo a Michael addition reaction at the active site of the sodium atom of the catalyst, acrylonitrile forms transitional hydrogen bonds with the active hydrogens on the cyano and amino groups, and the lone pair of electrons on the nitrogen nucleophilically attacks the carbon atom at the β position, resulting in conjugate addition and rearrangement to form an intermediate containing a cyano group; this intermediate further undergoes a hydrogenation reaction at the active site of the nickel atom of the catalyst to produce an amine. The functions of each step in the synthesis process of N,N-bis(3-aminopropyl)methylamine of the present invention are as follows: nitrogen replacement is to exhaust the air in the reactor to prevent oxidation of the product or danger; amination reaction occurs during "reaction temperature of 80-100° C., reaction pressure of 0.5-2.0 MPa, stirring reaction for 1.5-2.5 hours", "hydrogenation reaction occurs during "introducing hydrogen, maintaining pressure of 1.5-3 MPa, stirring reaction at 130-160° C. for 1.5-2.5 hours", and "adding solvent to dissolve the reaction product and filtering" to separate the product to obtain a product with higher purity; the corresponding technical parameters are for the successful synthesis of N,N-bis(3-aminopropyl)methylamine. The effects of (-aminopropyl)methylamine are: if the reaction temperature is too low, the reaction activity is insufficient, while if it is too high, the deamination of the reaction intermediate is accelerated and by-products increase; if the catalyst dosage is too low, the active sites are insufficient, while if the catalyst dosage is too high, the cost increases and causes waste; the reaction pressure affects the reaction effect; high hydrogen pressure can increase the reaction speed, but too high a pressure has little effect on the rate of increase and may even be operationally dangerous. The key technical points are: the temperature during the reaction affects the activity and selectivity, with the optimal temperatures being 80-100°C and 130-160°C; the appropriate mass ratio of catalyst dosage to reactants is 1-5wt%; and the appropriate reaction pressure during hydrogenation is 1.5-3MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a SEM image of the catalyst Na-GO-Ni of the present invention;

[0027] Figure 2 This is the XRD spectrum of the catalyst Na-GO-Ni of the present invention.

[0028] from Figure 1 It can be seen that the graphene oxide carrier is wrinkled and the preparation process has no obvious effect on its morphology; the surface of the substrate is white with photosensitive titanium dioxide particles of varying sizes; no obvious metal Na and Ni aggregates or particles are seen, indicating that the metal has good atomic-level dispersion.

[0029] from Figure 2 It can be seen that after comparing with the X-ray diffraction standard card, only the characteristic peaks of the photosensitizer titanium dioxide were observed, while the characteristic peaks of Na and Ni crystals were not observed, indicating that there are no Na and Ni nanocrystals in the catalyst, further verifying its high metal dispersion. DETAILED DESCRIPTION

[0030] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to the following examples. It should be understood that the following text is only used to describe one or more specific embodiments of the present invention and does not strictly limit the scope of protection of the present invention.

[0031] 1. Preparation Example of Composite Bimetallic Single Atom Catalyst

[0032] In the following catalyst notation, graphene is represented by G, graphene oxide is represented by GO, graphitic carbon nitride is represented by C3N4, nitrogen-doped graphene is represented by NG, and carbon nanotubes are represented by C. The vacuum degree of the vacuum freeze dryer is 0.001 to 0.01 MPa, and the temperature is -60 to -50°C.

[0033] Preparation Example 1: The preparation process of the composite bimetallic single-atom catalyst Na-G-Ni is as follows:

[0034] 1) Mix and disperse 1.85 mg of a first water-soluble metal salt, sodium nitrate, 2.48 mg of a second water-soluble metal salt, nickel nitrate, and 10 ml of deionized water to obtain a mixed bimetallic salt solution;

[0035] 2) Add 50 mg of graphene substrate and 50 mg of nano-TiO2 as catalyst loading to 20 ml of deionized water, stir ultrasonically until fully dispersed, and then add the mixed bimetallic salt solution, maintaining the mass ratio of metal to catalyst loading in the mixed bimetallic salt solution = 1.0 wt%;

[0036] 3) The mixed solution was placed under a xenon lamp light source and stirred for 3 hours at a current of 10 A. The irradiated solution was placed in a refrigerator and frozen for 4 hours until the solution became solid. Finally, it was placed in a vacuum dryer and dried for 24 hours to obtain a composite bimetallic single-atom catalyst Na-G-Ni with a metal content of 1.0 wt%.

[0037] Preparation Example 2: The preparation process of the composite bimetallic single atom catalyst Mg-G-Zn is as follows:

[0038] 1) Mix and disperse 5.34 mg of a first water-soluble metal salt, magnesium nitrate, 1.46 mg of a second water-soluble metal salt, zinc nitrate hexahydrate, and 10 ml of deionized water to obtain a mixed bimetallic salt solution;

[0039] 2) Add 50 mg of graphene substrate and 50 mg of nano-TiO2 as catalyst loading to 20 ml of deionized water, stir ultrasonically until fully dispersed, and then add a mixed bimetallic salt aqueous solution, maintaining a mass ratio of metal:catalyst loading in the mixed bimetallic salt solution = 1.0 wt%;

[0040] 3) The mixed solution was placed under a xenon lamp light source and stirred for 3 hours at a current of 10 A. The irradiated solution was placed in a refrigerator and frozen for 4 hours until the solution became solid. Finally, it was placed in a vacuum dryer and dried for 24 hours to obtain a composite bimetallic single-atom catalyst Mg-G-Zn with a metal content of 1.0 wt%.

[0041] Preparation Example 3: The preparation process of the composite bimetallic single atom catalyst KG-Cr is as follows:

[0042] 1) Mix and disperse 1.29 mg of a first water-soluble metal salt, potassium nitrate, 3.85 mg of a second water-soluble metal salt, chromium nitrate nonahydrate, and 10 ml of deionized water to obtain a mixed bimetallic salt solution;

[0043] 2) Add 50 mg of graphene substrate and 50 mg of nano-TiO2 as catalyst loading to 20 ml of deionized water, stir ultrasonically until fully dispersed, and then add a mixed bimetallic salt aqueous solution, maintaining a mass ratio of metal:catalyst loading in the mixed bimetallic salt solution = 1.0 wt%;

[0044] 3) The mixed solution was placed under a xenon lamp light source and stirred for 3 hours at a current of 10 A. The irradiated solution was placed in a refrigerator and frozen for 4 hours until the solution became solid. Finally, it was placed in a vacuum dryer and dried for 24 hours to obtain a composite bimetallic single atom catalyst KG-Cr with a metal content of 1.0 wt%.

[0045] Preparation Example 4: The preparation process of the composite bimetallic single atom catalyst Na-GO-Cr is as follows:

[0046] 1) 20 mg of a first water-soluble metal salt, sodium nitrate, 3.85 mg of a second water-soluble metal salt, chromium nitrate nonahydrate, and 10 ml of deionized water were mixed and dispersed uniformly to obtain a mixed bimetallic salt solution;

[0047] 2) Add 50 mg of graphene oxide substrate and an equal amount of nano-TiO2 as a catalyst load to 20 ml of deionized water, stir ultrasonically until completely dispersed, and then add the corresponding amount of mixed bimetallic salt aqueous solution, maintaining the mass ratio of metal to catalyst load in the mixed bimetallic salt solution = 1.0 wt%;

[0048] 3) The mixed solution was placed under a xenon lamp light source and stirred for 3 hours at a current of 10 A. The irradiated solution was placed in a refrigerator and frozen for 4 hours until the solution became solid. Finally, it was placed in a vacuum dryer and dried for 24 hours to obtain a composite bimetallic single-atom catalyst Na-GO-Cr with a metal content of 1.0 wt%.

[0049] Preparation Example 5: The preparation process of the composite bimetallic single-atom catalyst Na-C3N4-Zn is as follows:

[0050] 1) uniformly dispersing 1.85 mg of a first water-soluble metal salt, sodium nitrate, 20 mg of a second water-soluble metal salt, zinc nitrate, and 10 ml of deionized water to obtain a mixed bimetallic salt solution;

[0051] 2) Add 100 mg of graphite-like carbon nitride material C3N4 as a catalyst load to 20 ml of deionized water, stir ultrasonically until fully dispersed, and then add a mixed double metal salt aqueous solution, maintaining a mass ratio of metal to catalyst load in the mixed double metal salt solution = 1.0 wt%;

[0052] 3) The mixed solution was placed under a xenon lamp light source and stirred for 3 hours at a current of 10 A. The irradiated solution was placed in a refrigerator and frozen for 4 hours until the solution became solid. Finally, it was placed in a vacuum dryer and dried for 23 hours to obtain a composite bimetallic single-atom catalyst Na-GO-Zn with a metal content of 1.0 wt%.

[0053] Preparation Example 6: The preparation process of the composite bimetallic single-atom catalyst Na-NG-Ni is as follows:

[0054] 1) Mix and disperse 9.25 mg of a first water-soluble metal salt, sodium nitrate, 7.30 mg of a second water-soluble metal salt, zinc nitrate, and 10 ml of deionized water to obtain a mixed bimetallic salt solution;

[0055] 2) Add 50 mg of nitrogen-doped graphene NG and 50 mg of nano-TiO2 as catalyst loading to 20 ml of deionized water, stir ultrasonically until fully dispersed, and then add a mixed bimetallic salt aqueous solution, maintaining a mass ratio of metal:catalyst loading in the mixed bimetallic salt solution = 5.0 wt%;

[0056] 3) The mixed solution was placed under a xenon lamp light source and stirred for 3 hours at a current of 10 A. The irradiated solution was placed in a refrigerator and frozen for 4 hours until the solution became solid. Finally, it was placed in a vacuum dryer and dried for 24 hours to obtain a composite bimetallic single-atom catalyst Na-NG-Ni with a metal content of 5.0 wt%.

[0057] Preparation Example 7: The preparation process of the composite bimetallic single-atom catalyst Na-G-Ni is as follows:

[0058] 1) Mix and disperse 0.92 mg of a first water-soluble metal salt, sodium nitrate, 1.24 mg of a second water-soluble metal salt, nickel nitrate, and 5 ml of deionized water to obtain a mixed bimetallic salt solution;

[0059] 2) Add 50 mg of graphene substrate and 50 mg of nano-TiO2 as catalyst loading to 20 ml of deionized water, stir ultrasonically until fully dispersed, and then add the mixed bimetallic salt solution, maintaining the mass ratio of metal to catalyst loading in the mixed bimetallic salt solution at 0.5 wt%;

[0060] 3) The mixed solution was placed under a xenon lamp light source and stirred for 6 hours at a current of 20 A. The irradiated solution was placed in a refrigerator and frozen for 2 hours until the solution became solid. Finally, it was placed in a vacuum dryer and dried for 24 hours to obtain a composite bimetallic single-atom catalyst Na-G-Ni with a metal content of 0.5 wt%.

[0061] Preparation Example 8: The preparation process of the composite bimetallic single-atom catalyst Mg-G-Zn is as follows:

[0062] 1) Mix and disperse 5.34 mg of a first water-soluble metal salt, magnesium nitrate, 1.46 mg of a second water-soluble metal salt, zinc nitrate hexahydrate, and 10 ml of deionized water to obtain a mixed bimetallic salt solution;

[0063] 2) Add 50 mg of graphene substrate and 50 mg of nano-TiO2 as catalyst loading to 20 ml of deionized water, stir ultrasonically until fully dispersed, and then add a mixed bimetallic salt aqueous solution, maintaining a mass ratio of metal:catalyst loading in the mixed bimetallic salt solution = 1.0 wt%;

[0064] 3) The mixed solution was placed under a xenon lamp light source and stirred for 4 hours at a current of 15 A. The irradiated solution was placed in a refrigerator and frozen for 3 hours until the solution became solid. Finally, it was placed in a vacuum dryer and dried for 24 hours to obtain a composite bimetallic single-atom catalyst Mg-G-Zn with a metal content of 1.0 wt%.

[0065] Preparation Example 9: The preparation process of the composite bimetallic single atom catalyst KC-Cr is as follows:

[0066] 1) Mix and disperse 1.29 mg of a first water-soluble metal salt, potassium nitrate, 3.85 mg of a second water-soluble metal salt, chromium nitrate nonahydrate, and 10 ml of deionized water to obtain a mixed bimetallic salt solution;

[0067] 2) Add 50 mg of carbon nanotube substrate and 50 mg of nano-TiO2 as catalyst loading to 20 ml of deionized water, stir ultrasonically until fully dispersed, and then add a mixed bimetallic salt aqueous solution, maintaining a mass ratio of metal:catalyst loading in the mixed bimetallic salt solution = 1.0 wt%;

[0068] 3) The mixed solution was placed under a xenon lamp light source and stirred for 3 hours at a current of 10 A. The irradiated solution was placed in a refrigerator and frozen for 4 hours until the solution became solid. Finally, it was placed in a vacuum dryer and dried for 24 hours to obtain a composite bimetallic single-atom catalyst KC-Cr with a metal content of 1.0 wt%.

[0069] Preparation Example 10: The preparation process of the composite bimetallic single atom catalyst Na-GO-Ni is as follows:

[0070] 1) Mix and disperse 1.85 mg of a first water-soluble metal salt, sodium nitrate, 2.48 mg of a second water-soluble metal salt, nickel nitrate, and 10 ml of deionized water to obtain a mixed bimetallic salt solution;

[0071] 2) Add 50 mg of graphene oxide substrate and 50 mg of nano-TiO2 as catalyst loading to 20 ml of deionized water, stir ultrasonically until fully dispersed, and then add the mixed bimetallic salt solution, maintaining the mass ratio of metal to catalyst loading in the mixed bimetallic salt solution = 1.0 wt%;

[0072] 3) The mixed solution was irradiated with stirring under a xenon lamp light source for 3 hours at a current of 10 A. The irradiated solution was frozen in a refrigerator for 4 hours until the solution became solid. Finally, the solution was dried in a vacuum dryer for 24 hours to obtain a composite bimetallic single-atom catalyst Na-GO-Ni with a metal content of 1.0 wt%.

[0073] 2. Continuous Synthesis of N,N-Bis(3-aminopropyl)methylamine Example

[0074] The synthesis method uses acrylonitrile and methylamine as raw materials, and the synthesis reaction equation is as follows:

[0075]

[0076] The specific synthesis steps are as follows:

[0077] Example 1. 100 mg of a composite bimetallic single-atom catalyst Na-G-Ni with a metal content of 1.0 wt% and raw materials acrylonitrile and methylamine were added to an autoclave, with a catalyst to raw material mass ratio of 2%. The inner cavity of the autoclave was gas-displaced with nitrogen, and then stirred for reaction at a reaction temperature of 80°C and a reaction pressure of 0.5 MPa for 2 h. Hydrogen was then introduced, and the reaction was stirred for 2 h at 130°C while maintaining the pressure at 1.5 MPa. After the reaction, the autoclave was opened, a solvent was added to dissolve the reaction product, and the product was filtered to obtain the product N,N-bis(3-aminopropyl)methylamine with a yield of 94.1% and a selectivity of 96.2%.

[0078] Example 2: 100 mg of a composite bimetallic single-atom catalyst Mg-G-Zn with a metal content of 1.0 wt% and raw materials acrylonitrile and methylamine were added to an autoclave, with a catalyst to raw material mass ratio of 2%. The inner cavity of the autoclave was gas-displaced with nitrogen, and then stirred for reaction at a reaction temperature of 90°C and a reaction pressure of 0.5 MPa for 2 h. Hydrogen was then introduced, and the reaction was stirred for 2 h at 130°C while maintaining the pressure at 2.0 MPa. After the reaction, the autoclave was opened, a solvent was added to dissolve the reaction product, and the product was filtered to obtain N,N-bis(3-aminopropyl)methylamine in a yield of 95.3% and a selectivity of 98.6%.

[0079] Example 3. 100 mg of a composite bimetallic single-atom catalyst KG-Cr with a metal content of 1.0 wt% and raw materials acrylonitrile and methylamine were added to an autoclave at a catalyst to raw material mass ratio of 2%. The inner cavity of the autoclave was replaced with nitrogen, and then stirred for reaction at a reaction temperature of 100° C. and a reaction pressure of 0.5 MPa for 2 h. Hydrogen was then introduced, and the reaction was stirred for 2 h at 130° C. while maintaining the pressure at 2.5 MPa. After the reaction, the autoclave was opened, a solvent was added to dissolve the reaction product, and the product was filtered to obtain the product N,N-bis(3-aminopropyl)methylamine with a yield of 96.0% and a selectivity of 97.6%.

[0080] Example 4: 100 mg of a composite bimetallic single-atom catalyst Na-GO-Cr with a metal content of 1.0 wt% and raw materials acrylonitrile and methylamine were added to an autoclave at a catalyst to raw material mass ratio of 2%. The inner cavity of the autoclave was replaced with nitrogen, and then stirred for reaction at a reaction temperature of 85°C and a reaction pressure of 0.5 MPa for 2 h. Hydrogen was then introduced, and the reaction was stirred for 2 h at 140°C while maintaining the pressure at 2.0 MPa. After the reaction, the autoclave was opened, a solvent was added to dissolve the reaction product, and the product was filtered to obtain N,N-bis(3-aminopropyl)methylamine in a yield of 96.5% and a selectivity of 97.9%.

[0081] Example 5. 100 mg of a composite bimetallic single-atom catalyst Na-C3N4-Zn with a metal content of 1.0 wt% and raw materials acrylonitrile and methylamine were added to an autoclave, with a mass ratio of catalyst to raw materials of 2%. The inner cavity of the autoclave was replaced with nitrogen, and then the reaction was stirred at a reaction temperature of 80°C and a reaction pressure of 0.5 MPa for 2 h. Hydrogen was then introduced, and the reaction was stirred at 150°C for 2 h while maintaining the pressure at 2.0 MPa. After the reaction was completed, the autoclave was opened, a solvent was added to dissolve the reaction product, and the product was filtered to obtain the product N,N-bis(3-aminopropyl)methylamine with a yield of 94.4% and a selectivity of 96.9%.

[0082] Example 6. 100 mg of a composite bimetallic single-atom catalyst Na-NG-Ni with a metal content of 5.0 wt% and raw materials acrylonitrile and methylamine were added to an autoclave, with a mass ratio of catalyst to raw materials of 2%. The inner cavity of the autoclave was replaced with nitrogen, and then the reaction was stirred at a reaction temperature of 90°C and a reaction pressure of 0.5 MPa for 2 h. Hydrogen was then introduced, and the reaction was stirred at 160°C for 2 h while maintaining the pressure at 2.0 MPa. After the reaction was completed, the autoclave was opened, a solvent was added to dissolve the reaction product, and the product was filtered to obtain the product N,N-bis(3-aminopropyl)methylamine with a yield of 94.3% and a selectivity of 95.7%.

[0083] Example 7. 100 mg of a composite bimetallic single-atom catalyst Na-NG-Ni with a metal content of 5.0 wt% and raw materials acrylonitrile and methylamine were added to an autoclave, with a mass ratio of catalyst to raw materials of 2%. The inner cavity of the autoclave was replaced with nitrogen, and then the reaction was stirred at a reaction temperature of 95°C and a reaction pressure of 1.0 MPa for 2 h. Hydrogen was then introduced, and the reaction was stirred at 150°C for 2 h while maintaining the pressure at 2.0 MPa. After the reaction was completed, the autoclave was opened, a solvent was added to dissolve the reaction product, and the product was filtered to obtain the product N,N-bis(3-aminopropyl)methylamine with a yield of 95.0% and a selectivity of 97.7%.

[0084] Example 8. 100 mg of a composite bimetallic single-atom catalyst Na-NG-Ni with a metal content of 5.0 wt% and raw materials acrylonitrile and methylamine were added to an autoclave, with a mass ratio of catalyst to raw materials of 1%. The inner cavity of the autoclave was replaced with nitrogen, and then the reaction was stirred at a reaction temperature of 95°C and a reaction pressure of 0.5 MPa for 2 h. Hydrogen was then introduced, and the reaction was stirred at 150°C for 2 h while maintaining the pressure at 1.5 MPa. After the reaction was completed, the autoclave was opened, a solvent was added to dissolve the reaction product, and the product was filtered to obtain the product N,N-bis(3-aminopropyl)methylamine with a yield of 94.0% and a selectivity of 96.7%.

[0085] Example 9. 100 mg of a composite bimetallic single-atom catalyst Na-NG-Ni with a metal content of 5.0 wt% and raw materials acrylonitrile and methylamine were added to an autoclave, with a mass ratio of catalyst to raw materials of 5%. The inner cavity of the autoclave was replaced with nitrogen, and then the reaction was stirred at a reaction temperature of 95°C and a reaction pressure of 2.0 MPa for 2 h. Hydrogen was then introduced, and the reaction was stirred at 150°C for 2 h while maintaining the pressure at 3 MPa. After the reaction was completed, the autoclave was opened, a solvent was added to dissolve the reaction product, and the product was filtered to obtain the product N,N-bis(3-aminopropyl)methylamine with a yield of 94.5% and a selectivity of 96.5%.

[0086] Example 10. 100 mg of a composite bimetallic single-atom catalyst Na-GO-Ni having a metal content of 1.0 wt% and raw materials acrylonitrile and methylamine were added to an autoclave at a catalyst to raw material mass ratio of 2%. The inner cavity of the autoclave was replaced with nitrogen, and then stirred for reaction at a reaction temperature of 80°C and a reaction pressure of 0.5 MPa for 2 h. Hydrogen was then introduced, and the reaction was stirred for 2 h at 130°C while maintaining the pressure at 1.5 MPa. After the reaction, the autoclave was opened, a solvent was added to dissolve the reaction product, and the product was filtered to obtain the product N,N-bis(3-aminopropyl)methylamine with a yield of 95.1% and a selectivity of 96.5%.

[0087] The above are only some examples of the synthesis of N,N-bis(3-aminopropyl)methylamine. The composite bimetallic single-atom catalysts obtained in the preparation examples of the present invention can be effectively used to synthesize N,N-bis(3-aminopropyl)methylamine, and the yield and selectivity of N,N-bis(3-aminopropyl)methylamine can basically reach more than 95%.

[0088] Comparative Example 1-1: The following catalyst preparation conditions in Catalyst Preparation Example 1 were modified: the metal content was 10.0 wt %. Other preparation conditions remained unchanged, and the synthesis reaction process for N,N-bis(3-aminopropyl)methylamine was identical to that in Example 1. The yield of N,N-bis(3-aminopropyl)methylamine was 54.5%, and the selectivity was 65.2%.

[0089] Comparative Example 1-2: The following catalyst preparation conditions in Catalyst Preparation Example 1 were modified: activated carbon was used as the carbon-based substrate, and other preparation conditions remained unchanged. The synthesis reaction process for N,N-bis(3-aminopropyl)methylamine was identical to that of Example 1. The yield of N,N-bis(3-aminopropyl)methylamine was 44.5%, and the selectivity was 54.6%.

[0090] Comparative Example 2-1: The catalyst preparation was identical to that of Catalyst Preparation Example 1. The synthesis reaction process for N,N-bis(3-aminopropyl)methylamine was the same as that of Example 1, except that the reaction temperature of 80°C and the reaction pressure of 0.5 MPa in Example 1 were changed to 60°C, atmospheric pressure. All other reaction conditions remained unchanged. The yield of N,N-bis(3-aminopropyl)methylamine was 34.5%, and the selectivity was 40.2%.

[0091] Comparative Example 2-2: Catalyst preparation was identical to that of Catalyst Preparation Example 1. The synthesis reaction process for N,N-bis(3-aminopropyl)methylamine was the same as that of Example 1, except that the reaction conditions of "introducing hydrogen, maintaining a pressure of 2.0 MPa, and stirring the reaction at 150°C for 2 hours" in Example 1 were changed to "introducing hydrogen, maintaining a pressure of 0.5 MPa, and stirring the reaction at 100°C for 1 hour." All other reaction conditions remained unchanged. The yield of N,N-bis(3-aminopropyl)methylamine was 39.2%, and the selectivity was 46.5%.

[0092] The foregoing is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained herein shall, unless otherwise specified or limited, be implemented in accordance with conventional means in the art.

Claims

1. A method for preparing a catalyst for synthesizing N,N-bis(3-aminopropyl)methylamine, characterized in that The preparation method comprises the following steps: 1) mixing a first water-soluble metal salt, a second water-soluble metal salt, and water to obtain a mixed bimetallic salt solution; the first water-soluble metal salt is one or more of sodium nitrate, potassium nitrate, and magnesium nitrate, and the second water-soluble metal salt is one or more of nickel nitrate, zinc nitrate, and chromium nitrate; 2) dispersing a carbon-based substrate and an equal amount of nano-TiO2 as a catalyst load in water, stirring ultrasonically until the dispersion is complete, and then adding a corresponding amount of a mixed bimetallic salt solution, wherein the mass ratio of metal to catalyst load in the mixed bimetallic salt solution is 0.5wt% to 5.0wt%, and the carbon-based substrate is one or more of graphene, graphene oxide, carbon nanotubes, C3N4, and nitrogen-doped graphene; 3) placing the mixed bimetallic salt solution under a xenon lamp light source and stirring for a reaction of 3 to 6 hours at a current of 10 to 20 A, freezing the irradiated mixed bimetallic salt solution into a solid, and finally freeze-drying the solid under a vacuum degree of 0.001 to 0.01 MPa and conditions of -60 to -50°C to obtain a composite bimetallic single-atom catalyst, i.e., the catalyst for synthesizing N,N-bis(3-aminopropyl)methylamine, wherein the freezing time of the irradiated mixed bimetallic salt solution is 2 to 4 hours, and the vacuum freeze-drying time of the solid is 23 to 25 hours.

2. A catalyst for synthesizing N,N-bis(3-aminopropyl)methylamine obtained based on the preparation method according to claim 1.

3. Use of the catalyst according to claim 2 for preparing N,N-bis(3-aminopropyl)methylamine, characterized in that The application method is as follows: A composite bimetallic single-atom catalyst and raw materials, acrylonitrile and methylamine, are added to an autoclave, wherein the mass ratio of the composite bimetallic single-atom catalyst to the raw materials, acrylonitrile and methylamine, is 1wt% to 5wt%. The inner cavity of the autoclave is gas-displaced with nitrogen, and then the reaction is stirred at a reaction temperature of 80 to 100°C and a reaction pressure of 0.5 to 2.0 MPa for 1.5 to 2.5 hours. Hydrogen is then introduced, and the reaction is stirred at 130 to 160°C for 1.5 to 2.5 hours while maintaining a pressure of 1.5 to 3 MPa. After the reaction is completed, the autoclave is opened, a solvent is added to dissolve the reaction product, and the reaction product is filtered to obtain the product, N,N-bis(3-aminopropyl)methylamine.

4. The use according to claim 3, characterized in that: The stirring reaction time is 2h.

Images