Preparation method and application of pd-ni single-atom alloy catalyst for synthesizing bis-dmapa

Abstract

The present application relates to the field of fine chemical industry, in particular to a kind of supported Pd-Ni monatomic alloy catalyst and method for synthesizing N,N,N',N'-tetramethyl dipropylene triamine using the same.The Pd-Ni monatomic alloy catalyst of the present application is a supported catalyst, which is prepared from metal salt and oxide carrier (as catalyst support).The metal salt is composed of palladium salt and nickel salt.The weight ratio of the sum of nickel and palladium to the oxide carrier is 1% to 40%, and the weight of palladium is less than or equal to 0.01% of the weight of the oxide carrier.The present application also provides a method for synthesizing N,N,N',N'-tetramethyl dipropylene triamine using the Pd-Ni monatomic alloy catalyst.The catalyst of the present application is used to prepare N,N,N',N'-tetramethyl dipropylene triamine, which has the advantages of simple operation, mild reaction conditions, high selectivity and high yield.

Description

Technical Field

[0001] This invention relates to the field of fine chemicals, specifically to a supported Pd-Ni single-atom alloy catalyst and its method for synthesizing N,N,N',N'-tetramethyldipropylenetriamine. Background Technology

[0002] N,N,N',N'-Tetramethyldipropylenetriamine, abbreviated as bis-DMAPA, has the molecular formula C2. 10 H 25 N3 is a colorless to yellow liquid with an ammonia odor, readily soluble in organic solvents such as alcohols, ethers, and acetone. Bis-DMAPA is chemically reactive, and its structure is shown in Formula 1:

[0003]

[0004] Currently, the main industrial production route uses DMAPN (dimethylaminopropionitrile) or DMAPA (dimethylaminopropanediamine) as a single raw material or a mixture of both, and catalytically couples them under high temperature and high pressure to obtain the product bis-DMAPA. Since the secondary amino group of the bis-DMAPA obtained from the reaction readily reacts with the raw material, thereby producing tris(dimethylaminopropyl)amine (Tris-DMAPA), the selectivity control of the reaction is very important. Patent US2002128513A1 reports a bis-DMAPA selectivity of up to 62% achieved using DMAPN as a feedstock in a fixed-bed reactor with a hydrogen pressure of 0.6–3.5 MPa, a temperature of 50–500 °C, and a 0.5 wt% Rh / γ-Al₂O₃ catalyst. Similarly, BASF patent US2003013873A1 reports a bis-DMAPA yield of only 52% in a fixed-bed tubular reactor using DMAPA as a feedstock and a Cu, Ni, Co multimetallic catalyst supported on an Al₂O₃ support at a reaction temperature of 120–160 °C and a hydrogen pressure of 1–3 MPa. Likewise, in patent US2008161611A1, BASF uses reactive distillation with DMAPA and hydrogen as feedstocks and a Pd / ZrO₂ catalyst with a noble metal content of at least 0.1 wt%. This reaction achieves a conversion rate of less than 50%, produces numerous byproducts, and involves a complex process. CN 106866428 reports the synthesis of bis-DMAPA in a batch reactor using DMAPN and DMAPA as raw materials and a bimetallic nanocatalyst (one of the metals being a noble metal such as Pd, Pt, or Ru) under reaction conditions of 0.1-20 MPa and 80-400 °C, with a selectivity of up to 90%. CN106866428A reports the synthesis of bis-DMAPA in a high-pressure reactor using dimethylaminopropionitrile (DMAPN) and dimethylaminopropanediamine (DMAPA) as raw materials and noble metals and / or non-noble metals as nanocatalysts, at a reaction temperature of 110-200 °C and a pressure of 1-4 MPa, with a selectivity of up to 90%.

[0005] The methods for synthesizing bis-DMAPA reported in the aforementioned literature mostly use a mixture of dimethylaminopropanediamine (DMAPA) and dimethylaminopropionitrile (DMAPN) as raw materials, and dimethylaminopropanediamine needs to be prepared in advance (DMAPA needs to be prepared from DMAPN). These methods generally suffer from expensive catalysts, harsh reaction conditions, and the need for further improvement in product selectivity. In contrast, most US patents use noble metal catalysts in the process of synthesizing bis-DMAPA from dimethylaminopropanediamine (DMAPA), but these methods suffer from problems such as high noble metal loading, complex reaction process, and low reaction yield. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for preparing a catalyst for the synthesis of bis-DMAPA and its application. This invention first prepares a Pd-Ni single-atom alloy catalyst, and then, using DMAPA as a raw material, catalytically self-couples it in a fixed-bed reactor to synthesize bis-DMAPA. This reaction system exhibits high activity and good selectivity.

[0007] To solve the above technical problems, the present invention provides a Pd-Ni single-atom alloy catalyst (Pd is dispersed on Ni at the single-atom level) for the synthesis of N,N,N',N'-tetramethyldipropylenetriamine: the Pd-Ni single-atom alloy catalyst is a supported catalyst, which is prepared by a metal salt and an oxide support (as catalyst support), wherein the metal salt is composed of palladium salt and nickel salt;

[0008] The sum of the weights of nickel and palladium: oxide carrier = 1% to 40% by weight, and the weight of palladium ≤ 0.01% of the weight of oxide carrier.

[0009] As an improvement to the Pd-Ni single-atom alloy catalyst of the present invention for the synthesis of N,N,N',N'-tetramethyldipropylenetriamine:

[0010] The palladium content is 0.005% to 0.01% of the weight of the oxide support;

[0011] The nickel content is 1% to 8% of the weight of the oxide carrier.

[0012] This invention also provides a method for preparing the above-mentioned Pd-Ni single-atom alloy catalyst, comprising the following steps:

[0013] 1) A water-soluble metal salt is mixed with water to obtain a mixed metal salt solution; the water-soluble metal salt is composed of a water-soluble palladium salt and a water-soluble nickel salt; the weight ratio of water-soluble metal salt to water is (250±100):1000.

[0014] The oxide support used as a catalyst is dispersed in water at a weight ratio of (1000±300):2000. The mixture is ultrasonically stirred until the oxide support is completely dispersed. Then, a mixed metal salt solution is added. The weight ratio of the sum of the weights of nickel and palladium to the weight of the oxide support is 1% to 40%, and the weight of palladium is ≤0.01% of the weight of the oxide support.

[0015] 2) Place the mixture obtained in step 1) under a light source (xenon lamp light source) for irradiation and stirring for 3-24 hours. Then, freeze-dry the irradiated liquid under vacuum to obtain a catalyst precursor for bis-DMAPA synthesis. Then, calcine the precursor at 400-550℃ for 1-6 hours (calcine in a muffle furnace, for example, calcine at 450℃ for 3 hours) to obtain a Pd-Ni single-atom alloy catalyst.

[0016] 3) Activation of supported catalysts:

[0017] The Pd-Ni single-atom alloy catalyst obtained in step 2) is placed in a bed (the bed of a fixed-bed reactor), hydrogen is introduced, and it is activated at 100-500℃ (for example, around 400℃), with the activation pressure controlled at 0.1-0.3 MPa. After activation (until no water flows out, the activation time is about 1-9 hours), hydrogen is introduced to cool it down (to about room temperature) to obtain the activated supported Pd-Ni single-atom alloy catalyst (catalyst for the synthesis of N,N,N',N'-tetramethyldipropylenetriamine).

[0018] As an improvement to the preparation method of the Pd-Ni single-atom alloy catalyst of the present invention: the oxide support is composed of an oxide support one (belonging to semiconductor oxide) with visible light response capability and an oxide support two without visible light response capability.

[0019] The weight ratio of oxide carrier one to oxide carrier two is 1:0.3 to 10 (preferably 1:0.3 to 3, more preferably 1:1).

[0020] As a further improvement to the preparation method of the Pd-Ni single-atom alloy catalyst of the present invention:

[0021] The oxide support is at least one (i.e., one or more) selected from TiO2, ZnO, Ga2O3, Cu2O, Fe2O3, WO3, SnO2, Ta2O5, BiVO4, and Bi2WO6.

[0022] The oxide support is at least one (i.e., one or more) selected from Al2O3, MgO, CeO2, ZrO2, MnO2, and K2O.

[0023] As a further improvement to the preparation method of the Pd-Ni single-atom alloy catalyst of the present invention:

[0024] The palladium salt is palladium nitrate; the nickel salt is nickel nitrate.

[0025] As a further improvement to the preparation method of the Pd-Ni single-atom alloy catalyst of the present invention, the vacuum freeze-drying in step 2) is as follows:

[0026] The light-exposed liquid is first frozen at -40 to -10°C for 0.5 to 12 hours to solidify it. Then, the solid is freeze-dried under vacuum for 3 to 24 hours (0.001 to 0.1 MPa vacuum, -40 to -10°C).

[0027] This invention also provides a method for synthesizing N,N,N',N'-tetramethyldipropylenetriamine using a Pd-Ni single-atom alloy catalyst, comprising:

[0028] An activated catalyst (Pd-Ni single-atom alloy catalyst) is placed in the bed of the reaction bed (fixed-bed reaction device);

[0029] First, dimethylaminopropanediamine (DMAPA) used as a raw material is vaporized (e.g., at approximately 200°C) to obtain a vaporized product; then, the vaporized product is passed into a bed packed with an activated catalyst at a volume hourly space velocity of 0.05–0.5 h⁻¹. -1 The reaction pressure is 0.1–1 MPa (achieved by adjusting with hydrogen, preferably 0.2–0.5 MPa), and the reaction temperature is 220–300 °C.

[0030] The reaction product was condensed in a condenser (and the liquid phase obtained from the condensation was collected) to obtain the catalytic coupling product N,N,N',N'-tetramethyldipropylenetriamine.

[0031] Volumetric hourly space velocity of DMAPA = Volumetric flow rate of DMAPA after gasification (L / h) / Volume of supported catalyst (L).

[0032] This invention relates to a method for the fixed-bed coupling catalytic synthesis of N,N,N',N'-tetramethyldipropylenetriamine using a Pd-Ni single-atom alloy catalyst.

[0033] The synthetic equation for N,N,N',N'-tetramethyldipropylenetriamine of the present invention is as follows:

[0034]

[0035] In this invention: a Pd-Ni single-atom alloy catalyst is used; oxide support one and oxide support two need to be mixed during use; the catalyst needs to be dispersed by photo-deposition; the fixed-bed reactor consists of three reaction zones to achieve the best reaction effect.

[0036] This invention has the following advantages over existing catalytic systems:

[0037] 1. Unlike routes using dimethylaminopropionitrile (DMAPN) and dimethylaminopropanediamine (DMAPA) as raw materials, this invention directly uses DMAPA as a raw material and employs a self-made supported Pd-Ni single-atom alloy catalyst to efficiently synthesize N,N,N',N'-tetramethyldisproportiontriamine (bis-DMAPA) with a selectivity of over 95% and a yield of 90% or higher (e.g., up to 95% or higher). The catalyst exhibits high activity and is easily recyclable. The process employs room-temperature photodispersion and hydrogen activation steps. The preparation steps are simple, require a small amount of precious metals, and have industrial application value.

[0038] 2. In the catalyst of the present invention, the amount of palladium is significantly reduced, thereby significantly reducing the catalyst cost.

[0039] Furthermore, existing technologies involve Pd nanoparticles supported on the surface of a support, while the present invention is a Pd-Ni single-atom alloy catalyst.

[0040] 3. Thanks to the synergistic effect between Pd-Ni atoms, the catalyst prepared by this invention can efficiently perform catalytic self-coupling with extremely low noble metal palladium loading, and the catalyst can be recycled, greatly reducing operating and production costs.

[0041] 4. The catalyst and method for preparing N,N,N',N'-tetramethyldipropylenetriamine provided by this invention are simple to operate, have mild reaction conditions, high selectivity, and high yield. Attached Figure Description

[0042] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0043] Figure 1 This is a schematic diagram of a fixed bed device;

[0044] Figure 2 This is the mass spectrum of N,N,N',N'-tetramethyldipropylenetriamine, the product. Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0046] Device Example 1 Figure 1 A fixed-bed continuous production apparatus for the synthesis of bis-DMAPA is presented, including a feedstock tank 1 for dimethylaminopropanediamine (DMAPA), a metering pump 5, a hydrogen cylinder 7, a vaporization chamber 12, a fixed-bed reactor 13 (a catalytic reaction bed filled with three sections of packing material), a condenser 16, and a crude product collection tank 19. The supported catalyst is packed into the three sections of the fixed-bed reactor 13.

[0047] The raw material tank 1 is equipped with a feed valve 2 and a discharge valve 4; the function of the discharge valve 4 is to facilitate the discharge of residual liquid from the raw material tank 1 when the device is not in use.

[0048] The raw material tank 1 is connected to the inlet of the vaporization chamber 12 through a pipeline equipped with a shut-off valve 3, a metering pump 5 and a ball valve 6; the outlet of the vaporization chamber 12 is connected to the top of the fixed bed reactor 13; a pressure gauge and a thermometer are installed on the vaporization chamber 12, and a thermometer is installed in each of the three bed sections of the fixed bed reactor 13.

[0049] The hydrogen cylinder 7 is connected to the inlet of the vaporization chamber 12 via a pressure reducing valve 8, a ball valve 9, and a pipeline with a flow meter 21.

[0050] The N2 bypass is connected to the pipeline with flow meter 21 via a pipeline with shut-off valve 11 and check valve 10; that is, the N2 bypass is connected before the hydrogen flow meter 21.

[0051] The bottom of the fixed-bed reactor 13 is equipped with a discharge valve 14 and a discharge ball valve 15; the discharge ball valve 15 is connected to the condenser 16. The liquid phase outlet of the condenser 16 is connected to the crude product collection tank 19 through a pipeline equipped with a ball valve 18, and the gas phase outlet of the condenser 16 is connected to the gas phase outlet of the crude product collection tank 19 to form a total gas phase outlet. The gas phase is collected and treated through the total gas phase outlet and then discharged into the air.

[0052] Note: The discharge valve 14 is generally only used for emergency discharge when flooding occurs in the fixed bed reactor 13.

[0053] The condenser 16 is equipped with a discharge valve 17, and the crude product collection tank 19 is equipped with a discharge valve 20. The function of the discharge valve 17 on the condenser 16 is to discharge the unstable reaction liquid in the early stage of the reaction.

[0054] The fixed-bed reactor 13 described in the following embodiment is a stainless steel tube with an inner diameter of 30 mm, an outer diameter of 36 mm, and a height of 2400 mm. The first bed section is 600 mm high, the second bed section is 800 mm high, and the third bed section is 800 mm high. Each adjacent catalyst bed section is filled with 100 mm of inert packing material (quartz sand). The advantage of dividing the catalyst into three sections is that the temperature of each section can be effectively adjusted to achieve optimal temperature conditions.

[0055] The height of vaporization chamber 12 is approximately 150mm.

[0056] Example 1: A method for synthesizing N,N,N',N'-tetramethyldipropylenetriamine, comprising the following steps:

[0057] 1. Catalyst preparation: The following steps are performed sequentially.

[0058] 1.1) Mix and disperse 250g of nickel nitrate (containing 80g of nickel), 0.2g of palladium nitrate (containing 0.1g of palladium) and 1000ml of deionized water to obtain a mixed metal salt solution;

[0059] 1.2) Add 500g of Al2O3 and 500g of nano-TiO2 as catalyst support (i.e., carrier) to another 2000ml of deionized water, and stir ultrasonically until completely dispersed; then add the mixed metal salt solution obtained in step 1.1) above to obtain a mixed solution;

[0060] 1.3) The mixture obtained in step 1.2) was irradiated and stirred under a xenon lamp source with a current of 10A for 3 hours. The irradiated solution was then placed in a freezing device and frozen at -40 to -20°C for about 4 hours until it became solid. Finally, it was placed in a vacuum dryer and dried for 24 hours (vacuum degree of 0.1 MPa, temperature of -40 to -20°C), and then calcined at 450°C for 3 hours to obtain Ni8-Pd with a Ni content of 8wt%. 0.01 @Al2O3-TiO2 single-atom alloy catalyst.

[0061] illustrate:

[0062] Ni8 represents: Nickel / catalyst loading = 80g / 1000g = 8%, Pd 0.01 Example: Palladium / catalyst loading = 0.1 / 1000 = 0.01%, and the same applies below.

[0063] Xenon lamp illumination enables metal to be deposited on the surface of a carrier, achieving single-atom dispersion.

[0064] 2. Catalyst activation:

[0065] 2.1) The Ni8-Pd obtained in step 1.3) 0.01 The Al2O3-TiO2 single-atom alloy catalyst is loaded into the three sections of the fixed-bed reactor 13. With the shut-off valve 11 open, N2 supplied by the N2 bypass enters the fixed-bed reactor 13 through the shut-off valve 11, check valve 10, and a pipeline with a flow meter 21, and is finally discharged from the gas phase outlet of the condenser 16; that is, an appropriate amount of N2 is introduced to replace the air in the fixed-bed reactor 13 and the pipeline.

[0066] 2.2) After the nitrogen purging is completed, close the shut-off valve 11. Then, heat the gas to 120°C and 400°C respectively using the heating jackets attached to the vaporization chamber 12 and the fixed-bed reactor 13. Open the discharge valve 14.

[0067] The H2 supplied by hydrogen cylinder 7 enters the fixed-bed reactor 13 through pressure reducing valve 8, ball valve 9, and pipeline with flow meter 21. The H2 then reacts with the supported catalyst (Ni8-Pd). 0.01 The catalyst (Al2O3-TiO2 single-atom alloy catalyst) is activated by fully opening ball valve 9 and adjusting H2 via pressure reducing valve 8 to control the pressure in fixed-bed reactor 13 to 0.3 MPa. H2 is ultimately discharged from the gas phase outlet of condenser 16. After no water flows out, hydrogen is continuously passed through discharge valve 14 for 30 minutes to cool the catalyst (to room temperature), and then discharge valve 14 is closed. This completes the catalyst activation, yielding the activated catalyst.

[0068] 3. Feeding and discharging:

[0069] After catalyst activation, the pressure in the fixed-bed reactor 13 is kept stable at 0.3 MPa. The temperature of the vaporization chamber 12 is maintained at 200℃ by adjusting the corresponding jacket heating power, and the heating temperature of the fixed-bed reactor 13 is maintained at 230℃. The shut-off valve 3 is opened, the feed pump 5 for dimethylaminopropyldiamine is turned on, and the feed rate of dimethylaminopropyldiamine is maintained at 150 ml / h by adjusting the ball valve 6. The pressure reducing valve 8 and the ball valve 9 for hydrogen are opened, so that dimethylaminopropyldiamine and hydrogen can pass evenly through the catalyst bed for amination reaction. The H2 flow rate is adjusted by the flow meter 21 and the pressure reducing valve 8, and finally discharged from the gas phase outlet of the condenser 16.

[0070] Therefore, dimethylaminopropanediamine (DMAPA), used as a raw material, is vaporized in vaporization chamber 12 to obtain a vaporized product. The vaporized product then enters a bed packed with activated catalyst for an amination reaction, with a volume hourly space velocity of 0.1 h⁻¹. -1 The reaction pressure was 0.3 MPa and the reaction temperature was 230℃.

[0071] Volumetric space velocity = Volumetric flow rate after DMAPA gasification (L / h) / Volume of supported catalyst (L).

[0072] The amination product generated in the fixed-bed reactor 13 is discharged through the discharge ball valve 15 and cooled to 40°C by the condenser 16. The material separates into gas and liquid phases. The liquid phase enters the crude product collection tank 19, and the gas phase is discharged after conventional treatment. Gas chromatography analysis of the liquid in the crude product collection tank 19 (sampled through the discharge valve 20) shows that the conversion rate of dimethylaminopropanediamine is 99%, and the yield of N,N,N',N'-tetramethyldisproportiontriamine is 98.5%.

[0073] The liquid in crude product collection tank 19 is purified by vacuum distillation to obtain the product bis-DMAPA. Specifically, firstly, atmospheric distillation is performed, and the fraction collected at 132-134°C is DMAPA. Then, vacuum distillation is performed, and the fraction collected at 128-131°C under 0.03 bar pressure is bis-DMAPA.

[0074] Examples 2 to 13 were obtained by changing the content of the following metals (palladium and nickel) and the type of carrier in Example 1, while keeping the rest the same as in Example 1. Specific data are shown in Table 1.

[0075] Table 1

[0076]

[0077] illustrate:

[0078] Using "Ni8-Pd" from Example 2 0.005 Taking "@Al2O3-TiO2" as an example, in step 1.1) of Example 1, "0.2g palladium nitrate (containing 0.1g palladium)" is changed to "0.1g palladium nitrate (containing 0.05g palladium)"; the rest is the same as step 1 of Example 1, thereby obtaining Ni8-Pd. 0.005 @Al2O3-TiO2; Subsequent steps are the same as in Example 1.

[0079] Using "Ni6-Pd" from Example 5 0.01 Taking "@Al2O3-TiO2" as an example, in step 1.1) of Example 1, "250g nickel nitrate (containing 80g nickel)" is changed to "187.5g nickel nitrate (containing 60g nickel)", and the rest is the same as step 1 of Example 1, thereby obtaining Ni6-Pd. 0.01 @Al2O3-TiO2; Subsequent steps are the same as in Example 1.

[0080] Using "Ni8-Pd" from Example 9 0.01 Taking "@CeO2-ZnO" as an example, in step 1.2) of Example 1, "500g Al2O3 and 500g nano TiO2" are replaced with "500g CeO2 and 500g ZnO", while the rest is the same as step 1 of Example 1, thus obtaining Ni8-Pd. 0.01 @CeO2-ZnO; Subsequent steps are the same as in Example 1.

[0081] Additionally: Among the oxide supports mentioned in Table 1 above, TiO2, MgO, Fe2O3, CeO2, and Al2O3 are nanoscale, i.e., with a particle size of 0.01–50 nm; the particle size of the remaining oxide supports is 0.1–200 μm.

[0082] Examples 14 to 25 were obtained by changing the volumetric flow rate of dimethylaminopropyldiamine in step 3 of Example 1 (and thus changing the volume hourly space velocity), catalytic reaction temperature, pressure, etc., while the rest were the same as in Example 1; the specific data are shown in Table 2.

[0083] Table 2

[0084]

[0085] Example 26: In Example 1, step 1.1), the palladium nitrate was replaced with another water-soluble palladium salt, such as palladium acetate, palladium chloride, or potassium chloropalladate, while the effective amount of palladium remained unchanged at 0.1 g. The water-soluble nickel nitrate in Example 1, step 1.1) was replaced with, for example, nickel acetate, nickel chloride, or nickel acetylacetonate, while the effective amount of nickel remained unchanged at 80 g. The rest was the same as in Example 1. The yield of the resulting product was not significantly different from that of Example 1.

[0086] Example 27-1: Compared to Example 1, in step 1.2), "500g Al2O3 and 500g nano TiO2" was replaced with "750g Al2O3 and 250g nano TiO2", while the rest was the same as step 1 of Example 1; subsequent steps were the same as in Example 1. The yield of the obtained product was approximately 88%.

[0087] Example 27-2: Compared to Example 1, in step 1.2), "500g Al2O3 and 500g nano TiO2" were replaced with "250g Al2O3 and 750g nano TiO2". The rest of the steps were the same as step 1 of Example 1, and subsequent steps were also the same as in Example 1. The yield of the obtained product was 92%.

[0088] Examples 28 and 1 present the results of normal reaction after initial catalyst activation. The reaction was then continued for 360 hours, and the yield of bis-DMAPA remained at 95%.

[0089] Comparative Example 1, compared to Example 1, omits the use of "250g nickel nitrate (containing 80g nickel)" in step 1.1), and replaces "500g Al2O3 and 500g TiO2" in step 1.2) with "1000g ZrO2". The rest is identical to step 1 of Example 1, thereby obtaining Pd. 0.01 @ZrO2; Subsequent steps are the same as in Example 1. The yield of the obtained product is 15%.

[0090] Comparative Example 2, compared to Example 1, omits the use of "250g nickel nitrate" in step 1.1), and replaces "0.2g palladium nitrate (containing 0.1g palladium)" with "approximately 2g palladium nitrate (containing 1g palladium)"; and replaces "500g Al2O3 and 500g TiO2" in step 1.2) with "1000g ZrO2". The rest remains the same as step 1 of Example 1, thereby obtaining Pd. 0.1 @ZrO2; Subsequent steps are the same as in Example 1. The yield of the obtained product is 32%.

[0091] Comparative Example 3-1: Compared to Example 1, in step 1.2), "500g Al2O3 and 500g TiO2" were replaced with "1000g Al2O3", while the rest remained the same as step 1 of Example 1, thereby obtaining Ni8-Pd. 0.01 @Al2O3; Subsequent steps were the same as in Example 1. The yield of the obtained product was 45%.

[0092] Comparative Example 3-2: Compared to Example 1, in step 1.2), "500g Al2O3 and 500g TiO2" were replaced with "1000g TiO2", while the rest remained the same as step 1 of Example 1, thereby obtaining Ni8-Pd. 0.01 @TiO2; Subsequent steps were the same as in Example 1. The yield of the obtained product was 61%.

[0093] Comparative Example 4-1: Compared to Example 1, step 1.1) is modified by replacing "nickel nitrate containing 80g of nickel" with "copper nitrate containing 80g of Cu". The rest is the same as step 1 of Example 1, thereby obtaining Cu8-Pd. 0.01 @Al2O3-TiO2; subsequent steps are the same as in Example 1. The yield of the obtained product is 28%.

[0094] Comparative Example 4-2: Compared to Example 1, step 1.1) is modified by replacing "nickel nitrate containing 80g of nickel" with "cobalt nitrate containing 80g of Co," while the rest remains the same as step 1 of Example 1, thereby obtaining Co8-Pd. 0.01 @Al2O3-TiO2; subsequent steps are the same as in Example 1. The yield of the obtained product is 68%.

[0095] Comparative Example 5: The inert packing material between two adjacent catalyst beds was removed, and the first, second, and third bed sections were merged into one, with a total height of 2200 mm. The rest remained the same as in Example 1. The resulting product yield was 82%.

[0096] Comparative Example 6: Step 1.3, "Irradiating and stirring the mixture obtained in step 1.2) for 3 hours under a xenon lamp light source," was omitted; otherwise, it was the same as Example 1. Due to the lack of photodeposition dispersion, the product yield was only 46%.

[0097] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing N,N,N',N'-tetramethyldipropylenetriamine using a Pd-Ni single-atom alloy catalyst, characterized in that... include: An activated Pd-Ni single-atom alloy catalyst is placed in the bed of the reaction bed; First, dimethylaminopropanediamine, used as a raw material, is vaporized to obtain a vaporized product; then, the vaporized product is passed into a bed packed with an activated catalyst at a volume hourly space velocity of 0.05–0.5 h⁻¹. -1 The reaction pressure is 0.1~1 MPa, and the reaction temperature is 220~300℃; The reaction product was condensed in a condenser to obtain N,N,N',N'-tetramethyldipropylenetriamine; The Pd-Ni single-atom alloy catalyst is prepared by water-soluble metal salt and oxide support, wherein the water-soluble metal salt is composed of water-soluble palladium salt and water-soluble nickel salt; The sum of the weights of nickel and palladium: oxide support = 1%~40% by weight, and the weight of palladium ≤ 0.01% of the weight of oxide support; The Pd-Ni single-atom alloy catalyst was placed in a bed, hydrogen gas was introduced, and it was activated at 100–500 °C, with the activation pressure controlled at 0.1–0.3 MPa. After activation, hydrogen gas is passed through to cool the catalyst and obtain the activated Pd-Ni single-atom alloy catalyst.

2. The method for synthesizing N,N,N',N'-tetramethyldipropylenetriamine using a Pd-Ni single-atom alloy catalyst according to claim 1, characterized in that: The weight of palladium is 0.005% to 0.01% of the weight of the oxide support; The weight of nickel is 1% to 8% of the weight of the oxide carrier.

3. The method for synthesizing N,N,N',N'-tetramethyldipropylenetriamine using a Pd-Ni single-atom alloy catalyst according to claim 2, characterized in that: The oxide carrier is composed of an oxide carrier one with visible light response capability and an oxide carrier two without visible light response capability. The weight ratio of oxide carrier one to oxide carrier two is 1:0.3~10.

4. The method for synthesizing N,N,N',N'-tetramethyldipropylenetriamine using a Pd-Ni single-atom alloy catalyst according to claim 3, characterized in that: The oxide support is at least one of TiO2, ZnO, Ga2O3, Cu2O, Fe2O3, WO3, SnO2, Ta2O5, BiVO4, and Bi2WO6. The oxide support is at least one of Al2O3, MgO, CeO2, ZrO2, MnO2, and K2O.

5. The method for synthesizing N,N,N',N'-tetramethyldipropylenetriamine using a Pd-Ni single-atom alloy catalyst according to claim 4, characterized in that: The palladium salt is palladium nitrate; the nickel salt is nickel nitrate.

6. The method for synthesizing N,N,N',N'-tetramethyldipropylenetriamine using a Pd-Ni single-atom alloy catalyst according to any one of claims 1 to 5, characterized in that... The preparation method of Pd-Ni single-atom alloy catalyst is as follows: 1) Mix water-soluble metal salts with water to obtain a mixed metal salt solution; The oxide support used as a catalyst is dispersed in water and ultrasonically stirred until the oxide support is completely dispersed. Then, a mixed metal salt solution is added. 2) Place the mixture obtained in step 1) under a light source and stir for 3-24 hours. Then, freeze-dry the irradiated liquid under vacuum and calcine it at 400-550℃ for 1-6 hours to obtain the Pd-Ni single-atom alloy catalyst.

7. The method for synthesizing N,N,N',N'-tetramethyldipropylenetriamine using a Pd-Ni single-atom alloy catalyst according to claim 6, characterized in that... The vacuum freeze-drying in step 2) is as follows: The liquid exposed to light is first frozen at -40 to -10°C for 0.5 to 12 hours to solidify it, and then the solid is freeze-dried under vacuum for 3 to 24 hours.

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