Cu-based multimetallic catalysts, methods of making, and use in the amination of diacid / dimethyl ester compounds to produce diamines

Abstract

The present application relates to Cu-based multimetallic catalyst and preparation method and application in the preparation of binary amine by the amination of binary acid / dimethyl ester compound; the catalyst is Cu 0 -Cu⁺‑M X , M is one or more metal elements selected from one or more of Zn, Al, Cu 0 Coexist with Cu⁺ in the form of bivalent state; the catalyst preparation method is simple, the raw material is cheap, and the catalyst can be reused, and after 5 cycles, the catalytic performance remains stable, and the conversion rate and yield decrease less than 5%; it is suitable for one-pot reduction amination reaction of binary acid and dimethyl ester, and high-efficiency conversion is realized under mild conditions, and the product yield and selectivity are significantly higher than those of traditional single-metal catalyst. The product is directly subjected to GC-MS and FID qualitative and quantitative analysis; the product yield is high, the yield of nonanediamine and decanediamine reaches 99.9%, and the problem of difficult reaction selectivity control, many side reactions and complex product distribution in the prior art is solved.

Description

Technical Field

[0001] This invention belongs to the field of industrial catalysis and bioenergy conversion technology, specifically relating to a Cu-based multimetallic catalyst and its preparation method, and its application in the amination of diamines from dicarboxylic acid / dimethyl ester compounds. Background Technology

[0002] Linear aliphatic diamines (such as hexamethylenediamine, nonanediamine, and decanediamine) are important basic raw materials in organic chemicals, widely used in polyamides, polyurethanes, surfactants, and pharmaceutical intermediates. Currently, industrial production primarily utilizes the petrochemical-based hydrocyanation process. This process typically uses olefins or nitrile compounds as raw materials, undergoing multiple reactions including hydrocyanation, hydrogenation, and amination to obtain the target product. While this route is technologically mature and produces high-purity products, it has gradually revealed significant shortcomings in terms of safety, economy, and sustainability.

[0003] Currently, linear aliphatic diamines (such as hexamethylenediamine, nonanediamine, and decanediamine) are mainly prepared through a petrochemical-based hydrocyanation process. First, existing processes rely on non-renewable fossil resources, and the hydrocyanation process generates highly toxic byproducts. Traditional hydrocyanation methods using olefins as raw materials require hydrogen cyanide or its precursors, a process with high toxicity and significant environmental risks. This not only imposes strict safety requirements but also contradicts the current strategic direction of green and low-carbon development. Second, existing diamine synthesis routes involve numerous steps, high energy consumption, and large equipment investments. They typically require multiple steps, including amidation, carbon chain extension, hydrogenation, and amination, with significantly different reaction conditions at each step. Intermediates also need to be separated and purified, resulting in low atom economy, high energy consumption, and complex processes, hindering large-scale production. Third, reaction selectivity is difficult to control, with numerous side reactions and complex product distribution. In reductive amination processes using diacids or dimethyl esters as substrates, some hydrogenation intermediates (such as aldehydes or alcohols) are prone to etherification, condensation, or over-hydrogenation, thereby reducing the selectivity of the target diamine. Existing catalytic systems struggle to effectively control the hydrogenation and amination reaction pathways. Furthermore, most catalysts exhibit insufficient activity under mild conditions. While traditional transition metal catalysts such as Ni and Co possess some hydrogenation activity, their reaction rates are limited at low temperatures, while high temperatures easily lead to metal particle agglomeration and sintering, resulting in activity degradation. Simultaneously, the competitive adsorption of ammonia molecules on the metal surface inhibits the amination reaction, further reducing catalytic efficiency.

[0004] In recent years, Cu-based catalysts have attracted attention due to their abundant resources, low cost, and strong hydrogenation selectivity. 0Cu catalysts can effectively activate hydrogen for carbonyl hydrogenation, and the electrophilic nature of the Cu⁺ center is beneficial for the amination step. However, traditional Cu catalysts readily form [Cu(NH₃)₄]²⁺ complexes under ammonia or methylamine atmospheres, leading to the deactivation of active centers. Simultaneously, metallic copper is prone to sintering and agglomeration under high-temperature reducing conditions, affecting catalytic lifetime. Therefore, achieving a balance between activity, selectivity, and stability in Cu systems has become a key challenge limiting the application of such catalysts in one-pot reductive amination reactions. To address this issue, the electronic structure and dispersion of Cu can be adjusted by introducing a second metal or modifying the support, such as in multi-metal systems like Cu-Zn and Cu-Al. Other metals such as M (Zn, Al) can modulate the redox properties of Cu and improve metal-support interface interactions, thereby enhancing the catalyst's resistance to ammonia deactivation and its cycling stability.

[0005] In summary, the development of a Cu 0 A Cu-based multimetallic catalyst with a Cu⁺ synergistic active center, maintaining high catalytic performance even under the coexistence of hydrogen and ammonia, and enabling the use of biomass-derived dicarboxylic acids or dimethyl esters as substrates, avoiding the use of fossil fuels and highly toxic hydrocyanide; a one-pot coupling of hydrogenation and amination reactions, significantly reducing energy consumption and equipment costs; Cu 0 / Cu⁺ synergistically regulates the reaction pathway, suppresses side reactions, and improves the selectivity of diamines; multi-metal synergy and carrier regulation prevent metal aggregation and improve resistance to ammonia poisoning; the reaction conditions are mild, the safety is high, and the product purity is high, which is in line with the development direction of green amination chemistry and sustainable manufacturing. Summary of the Invention

[0006] This invention proposes a Cu 0 A multi-metal Cu-based catalyst with a Cu⁺ synergistic active center was applied to the one-pot reductive amination reaction of dicarboxylic acids and dimethyl esters, achieving the goal of efficient and selective preparation of linear diamines.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A Cu-based multimetallic catalyst, using Cu 0 -Cu⁺-Mx represents a catalyst where M is one or more metallic elements selected from Zn and Al, and x represents the corresponding valence. The molar ratio of Cu to other metals M is 1:0.3~1. Cu is the main active component, accounting for 20~50 wt% of the total metal mass fraction of the catalyst. Cu in the catalyst is mainly composed of Cu⁺-Mx. 0 Cu exists in a dual-valent form coexisting with Cu⁺. 0 / Cu + Cu species account for 60%–80% of the total Cu species, of which Cu + The proportion is between 20% and 30%.

[0009] The preparation method of the Cu-based multimetallic catalyst of the present invention includes the following steps:

[0010] 1) Weigh out copper nitrate trihydrate and other metal sources, dissolve them in deionized water, and mix thoroughly;

[0011] 2) At room temperature, a precipitant is added dropwise under stirring to form a coprecipitate precursor that coexists with a solid-liquid mixture;

[0012] 3) The precursor was co-precipitated by vacuum filtration to obtain a black colloid, which was then washed with deionized water until neutral and dried.

[0013] 4) Subsequently, the precursor was calcined at 400-600℃ in a nitrogen atmosphere to obtain the oxidized precursor;

[0014] 5) The obtained oxidized precursor was placed in a 5% H2 / N2 mixture and reduced at 250-350 °C to obtain the catalyst.

[0015] In the preparation method of the Cu-based multimetallic catalyst, other metal sources can be selected from alumina, zinc oxide, or their complexes.

[0016] In the preparation method of the Cu-based multimetallic catalyst, in step 2, a mixed alkaline solution containing 0.001 mol / L Na2CO3 and 0.002 mol / L NaOH is added dropwise under stirring conditions of 450-550 rpm, and the pH value is controlled at 9.0 ± 0.1; after co-precipitation, stirring is continued for 0.5-1.5 h, and the mixture is allowed to stand for aging for 10-14 h.

[0017] In the preparation method of the Cu-based multimetallic catalyst, the calcination time in step 4 is 2-4 h;

[0018] In the preparation method of the Cu-based multimetallic catalyst, in step 5, the reducing atmosphere is a 5% hydrogen / nitrogen mixed gas, and the reduction time is 2-4 h.

[0019] The application of the Cu-based multimetallic catalyst of the present invention in the one-pot reductive amination reaction of dicarboxylic acids and dimethyl esters to produce diamines includes the following steps:

[0020] a) After thoroughly mixing the catalyst, reaction substrate, ammonia source and reaction solvent, add them to a high-pressure reactor, seal it, replace the air in the reactor with hydrogen, and then fill with ammonia to 1 MPa, and then fill with hydrogen to 4.8-5.3 MPa.

[0021] b) Heat the reactor to 220-250 °C and start stirring. The reaction time is 15-25 h. After the reaction is completed, stop stirring, cool to room temperature, then depressurize and open the reactor to separate the liquid products and catalyst.

[0022] The reaction substrate is a dicarboxylic acid or its dimethyl ester compound, including but not limited to dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimecrolate, dimethyl octanoate, dimethyl azelaate, dimethyl sebacate, and corresponding dicarboxylic acids such as butyric acid, glutaric acid, adipic acid, pimecrolate, octanoic acid, etc.; the ammonia source is ammonia gas.

[0023] The solvent used in the application reaction is dioxane.

[0024] The mass ratio of the catalyst to the substrate is 1:0.5-1.5.

[0025] The specific explanation is as follows:

[0026] In the Cu-based multimetal catalyst of the present invention, Cu is in the form of Cu 0 Cu exists in a dual-valent form coexisting with Cu⁺. 0 / Cu + Cu species account for 60%–80% of the total Cu species, of which Cu + It accounts for 20% to 30% and is used to promote the synergistic process of reduction hydrogenation and amination reactions.

[0027] The reaction equation is as follows:

[0028]

[0029] This invention employs a method that involves performing multiple reaction steps simultaneously in a single reaction vessel (one-pot reactor) without separating or purifying intermediate products, ultimately directly generating the target product. The specific details are as follows:

[0030] In this invention, the catalyst and liquid product after reaction are separated by filtration, and the liquid product is directly subjected to qualitative and quantitative analysis by GC-MS and FID. Since the catalyst has strong activity and the product yield is high, no further purification is required to meet the target requirements. This also solves the problems of difficult reaction selectivity control, numerous side reactions and complex product distribution in the prior art.

[0031] This invention modulates the electronic structure and redox balance of Cu species by introducing Zn, Al, or other transition metal additives into a Cu-based system, thereby enabling Cu... 0 The / Cu⁺ interface remains dynamically reversible during the reaction, thereby constructing a stable Cu. 0 -Cu + -M x (M represents other metals) Synergistic active centers. The introduction of auxiliary metals can regulate the electron density and valence distribution of Cu's d orbitals through electron donor-acceptor effects and structural confinement, thereby inhibiting Cu... 0 Excessive oxidation or Cu +Irreversible reduction, maintaining Cu 0 / Cu + Controllable ratio of dual valence states, Cu 0 / Cu + Cu species account for 60%–80% of the total Cu species, of which Cu + The proportion is between 20% and 30%. This redox equilibrium is usually achieved under moderate reducing atmosphere (H2 / NH3) and medium temperature conditions (such as 220-250 °C).

[0032] Based on this, the synergistic active center can simultaneously promote hydrogenation and amination reactions: Cu 0 The site facilitates the dissociation and activation of H2, Cu + and other metals M x The site enhances the adsorption and amination coupling of carbonyl or hydroxyl substrates with NH3 molecules, thereby achieving highly efficient synergistic multi-step reactions in a single reactor. The regulation of the auxiliary metal can also improve the dispersibility and anti-sintering properties of the Cu component, enabling the catalyst to maintain high activity and structural stability in a hydrogen-ammonia coexisting system.

[0033] The significant advantages of this invention are:

[0034] 1. The Cu-based multimetallic catalyst of the present invention is constructed by Cu 0 The dual active centers of Cu⁺ enable synergistic promotion of hydrogenation and amination processes. 0 / Cu + Cu species account for 60%–80% of the total Cu species, of which Cu + With a content of 20% to 30%, it can maintain high activity and high selectivity under the condition of coexistence of hydrogen and ammonia.

[0035] 2. The catalyst of this invention is suitable for the one-pot reductive amination reaction of dicarboxylic acids and dimethyl esters, and can achieve efficient conversion under mild conditions. The product yield and selectivity are significantly higher than those of traditional single metal catalysts.

[0036] 3. The catalyst preparation method is simple, the raw materials are inexpensive, and it can be reused. After 5 cycles, the catalytic performance remains stable, with both the conversion rate and yield decreasing by less than 5%.

[0037] 4. This system avoids the intermediate separation process in traditional multi-step reactions, and has the advantages of simplified process, low energy consumption and green sustainability. Attached Figure Description

[0038] Figure 1 Transmission electron microscopy (TEM) image of the catalyst described in Example 1 of this invention.

[0039] The lattice fringe spacings are 0.128, 0.179, 0.209, 0.243 and 0.260 nm, respectively, corresponding to the (2 20), (2 0 0) and (1 1 1) crystal planes of Cu, the (1 1 1) plane of Cu2O and the (1 0 1) plane of ZnO.

[0040] Figure 2 X-ray photoelectron spectroscopy (XPS) spectra of the catalysts described in Examples 1 and 15 of this invention

[0041] in: Figure 2 a and Figure 2 b shows that Al and Zn mainly exist in oxidized forms, corresponding to Al₂O₃ and ZnO, respectively; meanwhile, Figure 2 In the spectrum of Cu in c, in addition to the CuO peak, there is also a significant Cu peak. 0 With Cu + Characteristic peak, Cu 0 / Cu + They account for 60%–80% of the total Cu species, among which Figure 2 d shows Cu + A proportion of 20% to 30% indicates that copper species in this catalyst exhibit multivalent coexistence, which is conducive to the formation of Cu. 0 / Cu⁺ Synergistic Active Center.

[0042] Figure 3 X-ray photoelectron spectroscopy (ICP) spectra of the catalysts described in Examples 1 and 15 of this invention

[0043] in: Figure 3 Column 1 shows that the Cu loading in the sample before and after the reaction was 39.3% and 38.4%, respectively. Figure 3 Column 2 shows that the Zn loadings were 20.2% and 21.4%, respectively; Figure 3 Column 3 shows that the loading of Zn element is 20.2% and 21.4%, respectively. The content of each metal remains basically the same before and after the reaction, indicating that each metal component has good structural stability. Detailed Implementation

[0044] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0045] Example 1

[0046] 1. Weigh 2.42 g of copper nitrate trihydrate, 1.49 g of zinc nitrate hexahydrate and 1.88 g of aluminum nitrate nonahydrate, and dissolve them in 100 mL of deionized water to form a mixed solution with a total metal salt concentration of 0.20 mol / L.

[0047] 2. At room temperature, with stirring (500 rpm), slowly add a mixed alkaline solution containing 0.001 mol / L Na2CO3 and 0.002 mol / L NaOH, controlling the pH value at 8.9. After co-precipitation, continue stirring for 0.5 h, and then allow to stand for 10 h for aging.

[0048] 3. The black colloid was obtained by suction filtration, then washed with deionized water until neutral, and dried at 80 °C for 12 h.

[0049] 4. Subsequently, the precursor was calcined at 500 °C for 2 h in a nitrogen atmosphere to obtain the oxidized precursor.

[0050] 5. Finally, the obtained precursor was placed in a 5% H2 / N2 mixture and reduced at 300 °C for 4 h to obtain the catalyst.

[0051] Figure 1 The images shown are transmission electron microscope (TEM) images of the sample described in Example 1. The lattice fringe spacings are 0.128, 0.179, 0.209, 0.243, and 0.260 nm, corresponding to the (2 2 0), (2 0 0), and (1 1 1) crystal planes of Cu, the (1 1 1) plane of Cu2O, and the (1 0 1) plane of ZnO. This indicates that the catalyst exists in a multi-metallic alloy state.

[0052] Example 2

[0053] 1. Weigh 1.61 g of copper nitrate trihydrate (Cu(NO3)2·3H2O), 1.98 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 2.5 g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O), and dissolve them in 100 mL of deionized water to form a mixed solution with a total metal salt concentration of 0.20 mol / L.

[0054] 2. At room temperature, with stirring (450 rpm), slowly add a mixed alkaline solution containing 0.001 mol / L Na2CO3 and 0.002 mol / L NaOH, controlling the pH value at 9. After co-precipitation, continue stirring for 1 h, and then allow to stand for 12 h for aging.

[0055] 3. The black colloid was obtained by suction filtration, then washed with deionized water until neutral, and dried at 80 °C for 12 h.

[0056] 4. Subsequently, the precursor was calcined at 400 °C for 3 h in a nitrogen atmosphere to obtain the oxidized precursor.

[0057] 5. Finally, the obtained precursor was placed in a 5% H2 / N2 mixture and reduced at 250 °C for 4 h to obtain the catalyst.

[0058] Example 3

[0059] 1. Weigh 2.90 g of copper nitrate trihydrate (Cu(NO3)2·3H2O), 1.19 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 1.5 g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O), and dissolve them in 100 mL of deionized water to form a mixed solution with a total metal salt concentration of 0.20 mol / L.

[0060] 2. At room temperature, with stirring (500 rpm), slowly add a mixed alkaline solution containing 0.001 mol / L Na2CO3 and 0.002 mol / L NaOH, controlling the pH value at 9.1. After co-precipitation, continue stirring for 1.5 h, and then allow to stand for 14 h for aging.

[0061] 3. The black colloid was obtained by suction filtration, then washed with deionized water until neutral, and dried at 80 °C for 12 h.

[0062] 4. Subsequently, the precursor was calcined at 600 °C for 4 h in a nitrogen atmosphere to obtain the oxidized precursor.

[0063] 5. Finally, the obtained precursor was placed in a 5% H2 / N2 mixture and reduced at 350 °C for 4 h to obtain the catalyst.

[0064] Example 4

[0065] 1. Weigh 2.42 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) and 2.97 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O), and dissolve them in 100 mL of deionized water to form a mixed solution with a total metal salt concentration of 0.20 mol / L.

[0066] 2. At room temperature, with stirring (550 rpm), slowly add a mixed alkaline solution containing 0.001 mol / L Na2CO3 and 0.002 mol / L NaOH, controlling the pH value at 9.0 ± 0.1. After co-precipitation, continue stirring for 1 h, and then allow to stand for 12 h for aging.

[0067] 3. The black colloid was obtained by suction filtration, then washed with deionized water until neutral, and dried at 80 °C for 12 h.

[0068] 4. Subsequently, the precursor was calcined at 500 °C for 3 h in a nitrogen atmosphere to obtain the oxidized precursor.

[0069] 5. Finally, the obtained precursor was placed in a 5% H2 / N2 mixture and reduced at 300 °C for 4 h to obtain the catalyst.

[0070] Example 5

[0071] 1. Weigh 2.42 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) and 3.75 g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O), and dissolve them in 100 mL of deionized water to form a mixed solution with a total metal salt concentration of 0.20 mol / L.

[0072] 2. At room temperature, with stirring (500 rpm), slowly add a mixed alkaline solution containing 0.001 mol / L Na2CO3 and 0.002 mol / L NaOH, controlling the pH value at 9.0 ± 0.1. After co-precipitation, continue stirring for 1 h, and then allow to stand for 12 h for aging.

[0073] 3. The black colloid was obtained by suction filtration, then washed with deionized water until neutral, and dried at 80 °C for 12 h.

[0074] 4. Subsequently, the precursor was calcined at 500 °C for 3 h in a nitrogen atmosphere to obtain the oxidized precursor.

[0075] 5. Finally, the obtained precursor was placed in a 5% H2 / N2 mixture and reduced at 300 °C for 4 h to obtain the catalyst.

[0076] Example 6

[0077] Oxalic acid / dimethyl ester reductive amination reaction

[0078] a) Add 0.1 g of the catalyst obtained according to Example 1 and 10 mL of dioxane solution containing 0.1 g of oxalic acid / dimethyl ester and 0.1 g of n-dodecane to a high-temperature and high-pressure reactor;

[0079] b) Replace the air in the reactor with hydrogen three times, then fill the reactor with ammonia until the initial pressure is 1 MPa, then fill the reactor with hydrogen until the initial pressure is 5 MPa, heat to 240 ℃, stir at 500 r / min, and react for 20 h.

[0080] c) After the reaction is complete, stop stirring and cool to room temperature. Then, release the pressure and open the vessel to separate the liquid product and catalyst. Use mass spectrometry-gas chromatography to perform qualitative and quantitative analysis on the liquid product and calculate the substrate conversion rate and the yield of amination product.

[0081] The reaction results are shown in Tables 1 and 2.

[0082] Table 1. Results of catalytic conversion of oxalic acid in Example 1

[0083] Substrate Conversion rate (%) Ethylenediamine yield (%) oxalic acid 99.9 78.2

[0084] Table 2. Results of the catalytic conversion of dimethyl oxalate in Example 1

[0085] Substrate Conversion rate (%) Methylethylenediamine yield (%) Dimethyl oxalate 99.9 91.0

[0086] Example 7

[0087] Malonic acid / dimethyl ester reductive amination reaction

[0088] a) Add 0.1 g of the catalyst obtained according to Example 2 and 10 mL of dioxane solution containing 0.1 g of malonic acid / dimethyl ester and 0.1 g of n-dodecane to a high-temperature and high-pressure reactor;

[0089] b) Replace the air in the reactor with hydrogen three times, then fill the reactor with ammonia until the initial pressure is 1 MPa, then fill the reactor with hydrogen until the initial pressure is 5 MPa, heat to 240 ℃, stir at 500 r / min, and react for 20 h.

[0090] c) After the reaction is complete, stop stirring and cool to room temperature. Then, release the pressure and open the vessel to separate the liquid product and catalyst. Use mass spectrometry-gas chromatography to perform qualitative and quantitative analysis on the liquid product and calculate the substrate conversion rate and the yield of amination product.

[0091] The reaction results are shown in Tables 3 and 4.

[0092] Table 3. Results of catalytic conversion of malonic acid in Example 2

[0093] Substrate Conversion rate (%) Azacyclopropane yield (%) malonic acid 56.2 25.6

[0094] Table 4. Results of catalytic conversion of dimethyl malonate in Example 2

[0095] Substrate Conversion rate (%) Methylazacyclopropane yield (%) Dimethyl malonate 64.3 32.5

[0096] Example 8

[0097] Succinic acid / dimethyl ester reductive amination reaction

[0098] a) Add 0.1 g of the catalyst obtained according to Example 3 and 10 mL of dioxane solution containing 0.1 g of succinic acid / dimethyl ester and 0.1 g of n-dodecane to a high-temperature and high-pressure reactor;

[0099] b) Replace the air in the reactor with hydrogen three times, then fill the reactor with ammonia until the initial pressure is 1 MPa, then fill the reactor with hydrogen until the initial pressure is 5 MPa, heat to 240 ℃, stir at 500 r / min, and react for 20 h.

[0100] c) After the reaction is complete, stop stirring and cool to room temperature. Then, release the pressure and open the vessel to separate the liquid product and catalyst. Use mass spectrometry-gas chromatography to perform qualitative and quantitative analysis on the liquid product and calculate the substrate conversion rate and the yield of amination product.

[0101] The reaction results are shown in Tables 5 and 6.

[0102] Table 5. Results of catalytic conversion of succinic acid in Example 3

[0103] Substrate Conversion rate (%) Azacyclobutane yield (%) Succinic acid 99.9 32.6

[0104] Table 6. Results of catalytic conversion of dimethyl succinate in Example 3

[0105] Substrate Conversion rate (%) Yield of methylazacyclobutane (%) Dimethyl succinate 99.9 36.5

[0106] Example 9

[0107] Glutaric acid / dimethyl ester reductive amination reaction

[0108] a) Add 0.1 g of the catalyst obtained according to Example 4 and 10 mL of dioxane solution containing 0.1 g of glutaric acid / dimethyl ester and 0.1 g of n-dodecane to a high-temperature and high-pressure reactor;

[0109] b) Replace the air in the reactor with hydrogen three times, then fill the reactor with ammonia until the initial pressure is 1 MPa, then fill the reactor with hydrogen until the initial pressure is 5 MPa, heat to 240 ℃, stir at 500 r / min, and react for 20 h.

[0110] c) After the reaction is complete, stop stirring and cool to room temperature. Then, release the pressure and open the vessel to separate the liquid product and catalyst. Use mass spectrometry-gas chromatography to perform qualitative and quantitative analysis on the liquid product and calculate the substrate conversion rate and the yield of amination product.

[0111] The reaction results are shown in Tables 7 and 8.

[0112] Table 7. Results of catalytic conversion of glutaric acid in Example 4

[0113] Substrate Conversion rate (%) Azacyclopentane yield (%) glutaric acid 99.9 35.6

[0114] Table 8. Results of catalytic conversion of dimethyl glutarate in Example 4

[0115] Substrate Conversion rate (%) Yield of methylazacyclopentane (%) Dimethyl glutarate 99.9 44.2

[0116] Example 10

[0117] adipic acid / dimethyl ester reductive amination reaction

[0118] a) Add 0.1 g of the catalyst obtained according to Example 5 and 10 mL of dioxane solution containing 0.1 g of adipic acid / dimethyl ester and 0.1 g of n-dodecane to a high-temperature and high-pressure reactor;

[0119] b) Replace the air in the reactor with hydrogen three times, then fill the reactor with ammonia until the initial pressure is 1 MPa, then fill the reactor with hydrogen until the initial pressure is 5 MPa, heat to 240 ℃, stir at 500 r / min, and react for 20 h.

[0120] c) After the reaction is complete, stop stirring and cool to room temperature. Then, release the pressure and open the vessel to separate the liquid product and catalyst. Use mass spectrometry-gas chromatography to perform qualitative and quantitative analysis on the liquid product and calculate the substrate conversion rate and the yield of amination product.

[0121] The reaction results are shown in Tables 9 and 10.

[0122] Table 9. Results of catalytic conversion of adipic acid in Example 5

[0123] Substrate Conversion rate (%) Azacyclohexane yield (%) adipic acid 89.9 37.8

[0124] Table 10. Results of catalytic conversion of dimethyl adipic acid in Example 5

[0125] Substrate Conversion rate (%) Yield of methylazacyclohexane (%) dimethyl adipic acid 85.2 38.5

[0126] Example 11

[0127] pimelic acid / dimethyl ester reductive amination reaction

[0128] a) Add 0.1 g of the catalyst obtained according to Example 1 and 10 mL of dioxane solution containing 0.05 g of pimelic acid / dimethyl ester and 0.1 g of n-dodecane to a high-temperature and high-pressure reactor;

[0129] b) Replace the air in the reactor with hydrogen three times, then fill the reactor with ammonia until the initial pressure is 1 MPa, then fill the reactor with hydrogen until the initial pressure is 5.3 MPa, raise the temperature to 250 ℃, stir at 500 r / min, and react for 25 h.

[0130] c) After the reaction is complete, stop stirring and cool to room temperature. Then, release the pressure and open the vessel to separate the liquid product and catalyst. Use mass spectrometry-gas chromatography to perform qualitative and quantitative analysis on the liquid product and calculate the substrate conversion rate and the yield of amination product.

[0131] The reaction results are shown in Tables 11 and 12.

[0132] Table 11. Results of catalytic conversion of pimelic acid in Example 11

[0133] Substrate Conversion rate (%) Heptanediamine yield (%) pimelic acid 99.9 98.8

[0134] Table 12. Results of catalytic conversion of dimethyl pimecrolate in Example 1

[0135] Substrate Conversion rate (%) Methylheptane diamine yield (%) Dimethyl pimecronate 99.9 97.6

[0136] Example 12

[0137] Succinic acid / dimethyl ester reductive amination reaction

[0138] a) Add 0.1 g of the catalyst obtained according to Example 1 and 10 mL of dioxane solution containing 0.15 g of octanoic acid / dimethyl ester and 0.1 g of n-dodecane to a high-temperature and high-pressure reactor;

[0139] b) Replace the air in the reactor with hydrogen three times, then fill the reactor with ammonia until the initial pressure is 1 MPa, then fill the reactor with hydrogen until the initial pressure is 4.8 MPa, raise the temperature to 220 ℃, stir at 500 r / min, and react for 15 h.

[0140] c) After the reaction is complete, stop stirring and cool to room temperature. Then, release the pressure and open the vessel to separate the liquid product and catalyst. Use mass spectrometry-gas chromatography to perform qualitative and quantitative analysis on the liquid product and calculate the substrate conversion rate and the yield of amination product.

[0141] The reaction results are shown in Tables 13 and 14.

[0142] Table 13. Results of catalytic conversion of octanoic acid in Example 1

[0143] Substrate Conversion rate (%) Octanediamine yield (%) Oleic acid 90.2 97.5

[0144] Table 14. Results of catalytic conversion of dimethyl octanoate in Example 1

[0145] Substrate Conversion rate (%) Methyloctanediamine yield (%) dimethyl octanoate 94.5 98.0

[0146] Example 13

[0147] Azelaic acid / dimethyl ester reductive amination reaction

[0148] a) Add 0.1 g of the catalyst obtained according to Example 1 and 10 mL of a dioxane solution containing 0.1 g of azelaic acid / dimethyl ester and 0.1 g of n-dodecane to a high-temperature and high-pressure reactor;

[0149] b) Replace the air in the reactor with hydrogen three times, then fill the reactor with ammonia until the initial pressure is 1 MPa, then fill the reactor with hydrogen until the initial pressure is 5 MPa, heat to 240 ℃, stir at 500 r / min, and react for 20 h.

[0150] c) After the reaction is complete, stop stirring and cool to room temperature. Then, release the pressure and open the vessel to separate the liquid product and catalyst. Use mass spectrometry-gas chromatography to perform qualitative and quantitative analysis on the liquid product and calculate the substrate conversion rate and the yield of amination product.

[0151] The reaction results are shown in Tables 15 and 16.

[0152] Table 15. Results of Catalytic Conversion of Azelaic Acid in Example 1

[0153] Substrate Conversion rate (%) Nonadiamine yield (%) azelaic acid 99.9 99.9

[0154] Table 16. Results of catalytic conversion of dimethyl azelaate in Example 1

[0155] Substrate Conversion rate (%) Nonadiamine yield (%) Dimethyl azelaate 99.9 99.9

[0156] Example 14

[0157] Sebacic acid / dimethyl ester reductive amination reaction

[0158] a) Add 0.1 g of the catalyst obtained according to Example 1 and 10 mL of a dioxane solution containing 0.1 g of sebacic acid / dimethyl ester and 0.1 g of n-dodecane to a high-temperature and high-pressure reactor;

[0159] b) Replace the air in the reactor with hydrogen three times, then fill the reactor with ammonia until the initial pressure is 1 MPa, then fill the reactor with hydrogen until the initial pressure is 5 MPa, heat to 240 ℃, stir at 500 r / min, and react for 20 h.

[0160] c) After the reaction is complete, stop stirring and cool to room temperature. Then, release the pressure and open the vessel to separate the liquid product and catalyst. Use mass spectrometry-gas chromatography to perform qualitative and quantitative analysis on the liquid product and calculate the substrate conversion rate and the yield of amination product.

[0161] The reaction results are shown in Tables 17 and 18.

[0162] Table 17. Results of Cu2Zn1Al1-catalyzed conversion of sebacic acid

[0163] Substrate Conversion rate (%) Sebacdiamine yield (%) sebacic acid 99.9 99.9

[0164] Table 18. Results of Cu2Zn1Al1-catalyzed conversion of dimethyl sebacate

[0165] Substrate Conversion rate (%) Sebacdiamine yield (%) Dimethyl sebacate 99.9 99.9

[0166] Example 15

[0167] Cyclic stability test of catalyst for the reduction amination reaction of dimethyl azelaate

[0168] The catalyst after the reaction in Example 13 was filtered and separated, washed multiple times with ethanol, and dried under vacuum to obtain the catalyst after one cycle. This catalyst was used for the reductive amination reaction of dimethyl azelate, under the same operating conditions as in Example 13. The operation was repeated four times, and the activity data of the catalyst after four cycles were measured. The reaction results are shown in Table 19.

[0169] Table 19. Stability test results of Cu2Zn1Al catalytic conversion of dimethyl azelate

[0170] Substrate catalyst Conversion rate (%) Nonadiamine yield (%) Dimethyl azelaate Fresh Example 1 99.9 99.9 Dimethyl azelaate Example 1 of 1-time recycling 99.9 98.5 Dimethyl azelaate Example 1 of two-stage recycling 99.9 98.2 Dimethyl azelaate Example 1 of 3-time recycling 99.9 97.3 Dimethyl azelaate Example 1 of 4-time recycling 99.9 95.8

[0171] The results in Table 19 show that the catalyst maintained stable catalytic activity after multiple cycles, and the substrate conversion rate and product yield decreased by less than 5%, indicating that the catalyst has good cycle stability. Figure 2 The X-ray photoelectron spectroscopy (XPS) results are for the samples from Examples 1 and 15. Figure 2 As can be seen from a and b, Al and Zn mainly exist in their oxidized forms, corresponding to Al₂O₃ and ZnO, respectively; meanwhile, Figure 2 In the spectrum of Cu in c, in addition to the CuO peak, there is also a significant Cu peak. 0 With Cu + Characteristic peak, Cu 0 / Cu + They account for 60%–80% of the total Cu species, among which Figure 2 d shows Cu + A proportion of 20% to 30% indicates that copper species in this catalyst exhibit multivalent coexistence, which is conducive to the formation of Cu. 0 / Cu⁺ Synergistic Active Center. Figure 3 The results are from inductively coupled plasma mass spectrometry (ICP) analysis of the samples from Examples 1 and 15. Figure 3 Column 1 shows that the Cu loading in the sample before and after the reaction was 39.3% and 38.4%, respectively. Figure 3 Column 2 shows that the Zn loadings were 20.2% and 21.4%, respectively; Figure 3 Column 3 shows that the loading of Zn element is 20.2% and 21.4%, respectively. The content of each metal remains basically the same before and after the reaction, indicating that each metal component has good structural stability.

[0172] In summary, this invention focuses on the construction of a Cu-based multimetallic catalyst and its application in the one-pot reductive amination reaction of dicarboxylic acids / dimethyl esters to diamines. In terms of application performance, this catalytic system exhibits significant catalytic advantages. From a reaction performance perspective, this catalyst can achieve highly efficient conversion of various dicarboxylic acids and their ester substrates under mild conditions (e.g., 240 °C, 4 MPa, 1 MPa, 20 h), with excellent substrate conversion and target diamine yield. Taking dimethyl azelaate as an example, its conversion rate reaches as high as 99.9%, and the yield of the target product, nonanediamine, reaches 99.9%, significantly better than the conversion performance of traditional Ru, Ni, or Co catalytic systems, which require higher temperatures (>250 °C). Regarding cycle stability, the catalyst maintains excellent activity and selectivity after multiple cycles, with substrate conversion and diamine yield decreasing by less than 5%, indicating that the catalyst has excellent structural stability and resistance to ammonia deactivation. Furthermore, the Cu proposed in this invention… 0 The synergistic effect of the / Cu⁺ dual-valent active center and the auxiliary metal can effectively promote the sequential coupling of hydrogenation and amination reactions, achieving a single-step, highly efficient conversion of diacids or dimethyl esters to diamines. Overall, this invention provides a Cu-based multimetallic catalyst that is simple to prepare, uses inexpensive raw materials, and exhibits excellent performance. It offers a new, energy-efficient, fewer-step, green, and sustainable pathway for the efficient synthesis of linear diamines from renewable or petroleum-derived diacids / dimethyl esters, possessing significant industrial application potential and broad prospects for wider application.

[0173] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.

Claims

1. A Cu-based polymetallic catalyst, characterized in that, With Cu 0 -Cu⁺-Mx represents a catalyst where M is one or more metallic elements selected from Zn and Al, and x represents the corresponding valence. The molar ratio of Cu to other metals M is 1:0.3~1. Cu is the main active component, accounting for 20~50 wt% of the total metal mass fraction of the catalyst. Cu in the catalyst is mainly composed of Cu⁺-Mx. 0 Cu exists in a dual-valent form coexisting with Cu⁺. 0 / Cu + Cu species account for 60%–80% of the total Cu species, of which Cu + The proportion is between 20% and 30%.

2. The method for preparing the Cu-based polymetallic catalyst of claim 1, characterized in that, Includes the following steps: 1) Weigh out copper nitrate trihydrate and other metal sources, dissolve them in deionized water, and mix thoroughly; 2) At room temperature, a precipitant is added dropwise under stirring to form a coprecipitate precursor that coexists with a solid-liquid mixture; 3) The coprecipitate precursor was obtained by vacuum filtration and a black colloid was obtained, which was then washed with deionized water until neutral and dried. 4) Subsequently, the precursor was calcined at 400-600℃ in a nitrogen atmosphere to obtain the oxidized precursor; 5) The obtained oxidized precursor was placed in a 5% H2 / N2 mixture and reduced at 250-350 °C to obtain the catalyst.

3. The method for preparing the Cu-based multimetallic catalyst as described in claim 2, characterized in that, Other metal sources are selected from aluminum oxide, zinc oxide, or their compounds.

4. The method for preparing the Cu-based multimetallic catalyst as described in claim 2, characterized in that, In step 2, a mixed alkaline solution containing 0.001 mol / L Na2CO3 and 0.002 mol / L NaOH is added dropwise under stirring conditions of 450-550 rpm, and the pH value is controlled at 9.0 ± 0.

1. After co-precipitation, stirring is continued for 0.5-1.5 h, and the mixture is allowed to stand for aging for 10-14 h.

5. The method for preparing the Cu-based polymetallic catalyst as described in claim 2, characterized in that, In step 4, the calcination time is 2-4 hours.

6. The method for preparing the Cu-based polymetallic catalyst as described in claim 2, characterized in that, In step 5, the reducing atmosphere is a 5% hydrogen / nitrogen mixture, and the reduction time is 2–4 hours.

7. The application of the Cu-based polymetallic catalyst of claim 1 in the one-pot reductive amination reaction of dicarboxylic acids and dimethyl esters to produce diamines, characterized in that, Includes the following steps: a) After thoroughly mixing the catalyst, reaction substrate, ammonia source and reaction solvent, add them to a high-pressure reactor, seal it, replace the air in the reactor with hydrogen, and then fill with ammonia to 1 MPa, and then fill with hydrogen to 4.8-5.3 MPa. b) Heat the reactor to 220-250 °C and start stirring. The reaction time is 15-25 h. After the reaction is completed, stop stirring, cool to room temperature, then depressurize and open the reactor to separate the liquid products and catalyst.

8. The application as described in claim 7, characterized in that, The reaction substrate is a dicarboxylic acid or its dimethyl ester compound, including but not limited to dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimecrolate, dimethyl octanoate, dimethyl azelaate, dimethyl sebacate, and corresponding dicarboxylic acids such as butyric acid, glutaric acid, adipic acid, pimecrolate, octanoic acid, etc.; the ammonia source is ammonia gas.

9. The application as described in claim 7, characterized in that, The reaction solvent used is dioxane.

10. The application as described in claim 7, characterized in that, The mass ratio of catalyst to substrate is 1:0.5-1.5.

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