A method for preparing amine compounds by reductive amination of alcohols

Abstract

This invention proposes a method for efficiently catalyzing the reductive amination of alcohols to prepare high-value amines using an alloy catalyst with 100% atom utilization of precious metals. In this catalyst, the precious metal is in a monolayer atomic dispersion form, achieving 100% atom utilization. Compared to existing research and patents, the catalyst preparation method of this invention is simple, significantly improves the utilization rate of precious metals, has lower catalyst costs, and operates under milder reaction conditions, resulting in considerable yields of primary amines. The method of this invention is suitable for batch reactors, the reaction process is environmentally friendly, and the catalyst has good renewability. The catalyst prepared by this invention exhibits good applicability to various types of alcohol substrates. The technical solution of this invention provides a route for the efficient synthesis of high-value primary amines from inexpensive alcohols, with excellent prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of catalytic conversion of alcohols, and describes a method for efficiently catalyzing the reductive amination of alcohols to prepare high-value amines using an alloy catalyst with 100% atom utilization of a precious metal. Background Technology

[0002] Amines are an important class of chemical intermediates used in the synthesis of pharmaceuticals, agrochemicals, biomolecules, organic dyes, fabric softeners, and polymers. Among amine compounds, primary amines have attracted the most attention due to their greatest derivatization potential. In recent years, methods for preparing primary amines, such as the hydrogenation and reduction of nitro compounds and the reductive amination of aldehydes and ketones, have been developed (Chem. Soc. Rev., 2020, 49, 6273-6328). In addition, the direct amination of alcohols is also a promising method for synthesizing primary amines because alcohols are less expensive and less toxic than other substrates, and the byproduct of the reaction is water. This means that alcohol amination is economically and environmentally advantageous and meets the requirements of energy conservation and environmental protection. The amination of alcohols to produce primary amines generally proceeds through the following process: (1) dehydrogenation of the alcohol to produce the corresponding aldehyde or ketone, which is the rate-determining step of the entire reaction; (2) reaction of the aldehyde or ketone with ammonia to produce a primary imine; (3) combination of the imine with the hydrogen removed from the alcohol, followed by hydrogenation to produce a primary amine. In this process, the primary amine formed can also attack aldehydes or ketones to form secondary imines, which can then be hydrogenated to form secondary amines. Since primary amines have more electrons than ammonia, they are more likely to attack carbonyl groups; therefore, this is the main side reaction in the entire process. Simultaneously, the secondary imines formed by the attack of primary amines on aldehydes or ketones can also undergo transimineation with ammonia to regenerate primary imines. Therefore, for catalysts used in the direct amination of alcohols to primary amines, appropriate transimineation and hydrogenation activities are beneficial for obtaining highly selective primary amines. Currently, catalysts for the amination of alcohols to primary amines mostly use metals as active centers, which have problems such as high catalyst preparation costs, susceptibility to poisoning, low selectivity for primary amines, and harsh reaction conditions (ACS Catal., 2019, 9, 5986-5997; ACS Sustain. Chem. Eng., 2020, 8, 9962-9967; Appl. Catal. B, 2021, 286, 119942; ACS Catal., 2019, 9, 2931-2939; Chinese Patent CN 201710200098.9; Chinese Patent CN 202111417421.0). In recent years, the introduction of the single-atom concept has sparked widespread interest in catalysts with 100% metal atom utilization. Compared to metal nanoparticle catalysts, which sacrifice some metal sites, catalysts with 100% metal atom utilization can effectively reduce catalyst costs. Furthermore, their unique electronic structure and coordination environment significantly influence the reaction process and product selectivity (Nat. Rev. Chem., 2018, 2, 65-81; J. Am. Chem. Soc., 2019, 141, 14515-14519). This holds promise for addressing issues such as catalyst poisoning and low selectivity during the amination of alcohols. Therefore, developing highly efficient catalysts with 100% metal utilization is of great significance for the amination of alcohols to prepare primary amines. Summary of the Invention

[0003] This invention proposes a method for preparing an alloy catalyst with 100% atom utilization of precious metals and achieving efficient reduction amination of alcohols to primary amines under mild conditions. The precious metal atoms in the catalyst are not stacked on the catalyst surface, but are in a monolayer atomic dispersion form, achieving 100% atom utilization. This significantly reduces the amount of precious metals used, resulting in low catalyst cost. Furthermore, the catalyst exhibits excellent selectivity and renewability, and shows good substrate applicability in various types of alcohol substrates, demonstrating broad application prospects.

[0004] A method for efficiently catalyzing the reductive amination of alcohols to primary amines under mild conditions using an alloy catalyst with 100% atom utilization of precious metals.

[0005] The steps are as follows:

[0006] Preparation of the support: The support was prepared using a hydrothermal method. 10-30 g of urea was dissolved in 20-60 mL of deionized water until fully dissolved. 5-20 g of zirconium precursor (one or both of ZrO(NO3)2·H2O and ZrOCl2·8H2O) was dissolved in 10-40 mL of deionized water until fully dissolved, then slowly added to the urea solution. The mixture was stirred in a water bath at 25-50℃ for 0.5-5 h. The solution was transferred to a 100 mL hydrothermal reactor and heated in an oven at 120-180℃ for 10-20 h to crystallize under autogenous pressure. After washing and centrifugation several times, the sample was dried in an oven at 80-120℃ for 8-12 h. The dried sample was ground into powder with a size between 100-300 mesh and calcined in air at 400-600℃ for 2-6 h to obtain the ZrO2 support.

[0007] Catalyst Preparation: The catalyst was prepared using an equal-volume co-impregnation method: Precursor solutions of two metal components, M1 (M1 = Co, Ni) and M2 (M2 = Pt, Ru, Pd, Rh), were impregnated in equal volumes onto 1-5 g of ZrO2 support. The total loading of metals M1 and M2 was 1-10 wt%, preferably 5-10 wt%, and the molar ratio of M1 to M2 was between 60-10, preferably 30-20. The prepared catalyst was first dried in an oven at 80-120℃ for 6-12 h, then calcined in air at 200-600℃ for 2-6 h, preferably at 400-500℃ for 3-4 h. Subsequently, it was reduced in hydrogen at 300-500℃ for 1-5 h, preferably at 300-400℃ for 2-3 h, finally yielding a monolayer atomically dispersed catalyst M1M2 / ZrO2 with 100% atomic utilization.

[0008] The performance evaluation of the reductive amination of alcohols to prepare primary amines was carried out in a batch high-pressure autoclave reactor. The substrates included alcohols with different functional groups and structures, such as octanol, phenethyl alcohol, butanol, cyclohexanol, and p-fluorophenylethyl alcohol. The reaction conditions were as follows: substrate concentration 1-10 wt%, preferably 1-5 wt%; reaction temperature 140-180℃, preferably 140-160℃; ammonia pressure 0.4-1 MPa, preferably 0.6-1 MPa; hydrogen pressure 0.1-1 MPa, preferably 0.3-0.5 MPa; reaction time 0.5-5 h, preferably 1-2 h; alkyl-substituted derivatives of benzene were used as solvents, such as toluene, xylene, and trimethylbenzene, preferably p-xylene; n-dodecane was used as an internal standard. The total liquid charge was less than 1 / 3 of the reactor volume.

[0009] This invention utilizes an alloy catalyst with 100% atom utilization of precious metals to efficiently catalyze the reductive amination of alcohols to prepare high-value amines. In this catalyst, the precious metals are in a monolayer atomic dispersion form, achieving 100% atom utilization. Compared to existing research and patents, the catalyst preparation method of this invention is simple, significantly improves the utilization rate of precious metals, has lower catalyst costs, and operates under milder reaction conditions, resulting in considerable yields of primary amines. The method of this invention is suitable for batch reactors, the reaction process is environmentally friendly, and the catalyst has good renewability. The catalyst prepared by this invention exhibits good applicability to various types of alcohol substrates. The technical solution of this invention provides a route for the efficient synthesis of high-value primary amines from inexpensive alcohols, with excellent prospects for industrial application.

[0010] Advantages of this invention:

[0011] (1) The catalyst proposed in this invention has good dispersibility, wherein a high content of metal M1 is dispersed on the surface of the support, and a low loading of metal M2 is distributed on the surface of metal M1 in the form of a single layer of atomic dispersion, forming a surface alloy morphology. The atomic utilization rate of metal M2 reaches 100%, and all active sites are exposed on the catalyst surface, realizing the efficient catalytic reduction and amination of alcohol compounds to prepare primary amines. The catalyst preparation is simple, the reaction conditions are mild, and the selectivity of primary amines is high, which is in line with the concept of green environmental protection.

[0012] (2) Compared with the single metal M1 / ZrO2 catalyst, the addition of metal M2 significantly improved the substrate conversion and primary amine selectivity, and the two metals formed an alloy, which improved the stability of the catalyst.

[0013] (3) Compared with existing literature and patents, the amount of precious metal M2 used is greatly reduced, the reaction conditions are milder, the primary amine yield is higher, the substrate applicability of the catalyst is better, and it has industrial application prospects. Attached Figure Description

[0014] Figure 1 : Monolayer atomically dispersed 5Co 30 Transmission electron microscopy (TEM) image of Ru1 / ZrO2 alloy catalyst (a), and corresponding elemental surface scan (bd);

[0015] Figure 2 : Monolayer atomically dispersed 5Co 30 Transmission electron microscopy (TEM) image of the Ru1 / ZrO2 alloy catalyst (a), and elemental line scan image of the catalyst on Co particles (b).

[0016] Figure 3 XPS characterization of Ru signal before and after Ar etching; 5Co monolayer atomic dispersion before and after Ar etching. 30 XPS spectrum of elemental Ru on Ru1 / ZrO2 alloy catalyst;

[0017] Figure 4 : Monolayer atomically dispersed 5Co 30 Stability test of octanol reductive amination to octylamine catalyzed by Ru1 / ZrO2 alloy catalyst. Reaction conditions: 0.06 g octanol, 3 g p-xylene, 0.05 g n-dodecane (internal standard), 0.05 g 5Co 30 The reaction conditions were Ru1 / ZrO2, reaction temperature 160℃, ammonia pressure 0.7 MPa, hydrogen pressure 0.3 MPa, reaction time 1.5 h, and rotation speed 500 rpm / min. Each example corresponds from left to right to the conversion rate of a, the selectivity of b, and the selectivity of c.

[0018] Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0020] Example 1: Preparation of ZrO2 support

[0021] 22g of urea was dissolved in 40mL of deionized water and stirred at 600rpm / min. 13g of ZrO(NO3)2·H2O was dissolved in 30mL of deionized water, sonicated for 10 minutes, and then slowly added to the urea solution. The mixture was stirred at 700rpm / min for 0.5h in a 25℃ water bath. The solution was transferred to a 100mL hydrothermal reactor, sealed, and heated in an oven at 180℃ for 20h to crystallize under autogenous pressure. After washing and centrifugation, the sample was dried in an oven at 110℃ for 12h. The dried sample was ground into a uniform powder of 100-300 mesh and calcined in a muffle furnace at 400℃ for 4h at a heating rate of 5℃ / min. The resulting solid powder is the prepared ZrO2 support.

[0022] Example 2: Preparation of single-metal catalyst M1 / ZrO2

[0023] Taking the preparation of the single-metal catalyst 5Co / ZrO2 as an example: an appropriate amount of cobalt nitrate solution was impregnated onto the ZrO2 support obtained in Example 1 by equal volume, and the loading of the active component Co in the catalyst was 5 wt%. The catalyst was dried in an oven at 80 °C for 12 h, then calcined at 400 °C for 3 h in an air atmosphere, and then reduced at 350 °C for 2 h in a hydrogen atmosphere. After cooling to room temperature, it was passivated for 12 h in an atmosphere of 1% O2 / He (volume fraction). The resulting catalyst is denoted as 5Co / ZrO2.

[0024] Example 3: Preparation of single-metal catalyst M2 / ZrO2

[0025] Taking the preparation of the single-metal catalyst 0.3Ru / ZrO2 as an example: an appropriate amount of ruthenium chloride solution was impregnated onto the ZrO2 support obtained in Example 1 by equal volume, and the loading of the active component Ru in the catalyst was 0.3wt%. The catalyst was dried in an oven at 80℃ for 12h, then calcined at 400℃ for 3h in air atmosphere, and finally reduced at 350℃ for 2h in hydrogen atmosphere. After cooling to room temperature, it was passivated for 12h in an atmosphere of 1% O2 / He (volume fraction). The resulting catalyst was denoted as 0.3Ru / ZrO2.

[0026] Example 4: Bimetallic catalyst M 1x M 2y Preparation of ZrO2

[0027] With bimetallic catalyst 5Co 30 Taking the preparation of Ru1 / ZrO2 as an example: Equal volumes of cobalt nitrate and ruthenium chloride solutions were impregnated onto the ZrO2 support obtained in Example 1. The total loading of the active components Co and Ru in the catalyst was 5 wt%, with the subscript indicating the molar ratio of the elements (i.e., the molar ratio of Co:Ru was 30:1). The catalyst was dried in an oven at 80°C for 12 h, then calcined at 400°C for 3 h in air, and then reduced at 350°C for 2 h in hydrogen atmosphere. After cooling to room temperature, it was passivated for 12 h in an atmosphere of 1% O2 / He (1% O2 volume fraction in the mixed gas). The resulting catalyst is denoted as 5Co. 30 Ru1 / ZrO2. (In the following examples, the numbers preceding the elements represent the total mass fraction of the two metals, and the subscripts of the metal elements represent the molar ratio, i.e., the molar ratio of Co:Ru is 30:1.) Because the atomic number of Zr is greater than that of Co, the particle distribution cannot be directly observed from the transmission electron microscope image; the distribution of Co can only be determined through elemental surface scanning results. Figure 1The elemental surface scan results of the catalyst show that Co is uniformly distributed on the catalyst (support) surface, and the particle size of Co is between 10-20 nm. The distribution of Ru is more uniform, and the particle size is less than 1 nm. Figure 2 It is 5Co 30 High-resolution electron microscopy images of the catalyst on Ru1 / ZrO2 and elemental line scans on Co particles clearly show that as the signal intensity of Co increases, the signal of Ru also increases, indicating that Ru is more concentrated on the surface of Co particles and can form alloys with Co. Figure 3 It uses XPS detection method to detect 5Co 30 The surface Ru distribution of Ru1 / ZrO2 was analyzed using Ar etching technology to obtain catalyst surface information at different depths. When the Ar etching depth (0.3 nm) was greater than the diameter of one Ru atom (0.27 nm), the Ru element signal was no longer detectable compared to before etching, while the Co element signal was still very obvious before and after etching, indicating that the Co particle height on the catalyst exceeded 0.3 nm and was distributed in a particle form on the support. The Ru signal became undetectable after being etched to a depth exceeding its atomic diameter, proving that Ru atoms were not stacked on the catalyst surface but were dispersed in a monolayer atomic form (with a height of one Ru atom). Therefore, when the etching depth was between 1 and 2 Ru atom diameters, all the Ru elements on the catalyst were etched away, thus the Ru signal was undetectable. At this point, the utilization rate of Ru atoms reached 100%, greatly improving the utilization of the precious metal.

[0028] The preparation processes and conditions of Examples 5-7 and Comparative Example 1 in Table 1 are the same as those of Example 2. The difference is that the amount of cobalt nitrate used in Examples 5-7 and Comparative Example 1 is 1 / 5, 3 / 5, 2 and 1 / 10 of the mass of cobalt nitrate used in Example 2, respectively. In Examples 5-7, the surface scanning results of electron microscopy show that the metallic Co on the catalyst is uniformly dispersed on the support, and the particle size ranges are 1-5 nm, 4-10 nm and 15-40 nm, respectively.

[0029] The reaction conditions for the preparation of octylamine by the amination of octanol using different catalysts in Examples 2, 5-7, and Comparative Example 1 were consistent (only the catalysts changed, i.e., different types of catalysts were used). Taking the catalyst prepared in Example 2 as an example, the reaction conditions were: 0.06 g octanol, 3 g p-xylene, 0.05 g internal standard n-dodecane, 0.05 g 5Co / ZrO2, reaction temperature 160℃, ammonia pressure 0.7 MPa, hydrogen pressure 0.3 MPa, reaction time 1.5 h, rotation speed 500 rpm / min, and the reaction was carried out in a batch reactor with a total volume of 50 ml. After the reaction was completed, the reaction solution was centrifuged, and the supernatant was collected for gas chromatography and mass spectrometry analysis. As can be seen from the results in Table 1, the conversion rate of octanol increased with the increase of Co content, and the product octylamine showed good selectivity. However, the overall conversion rate of octanol was low, so the yield of octylamine was low.

[0030] The catalyst preparation processes and conditions in Examples 8-10 and Comparative Example 2 were the same as in Example 3, except that the amount of ruthenium chloride used in Examples 8-10 and Comparative Example 2 was 1 / 6, 1 / 3, 5 / 3, and 10 / 3 of the mass of ruthenium chloride used in Example 3, respectively. Electron microscopy surface scanning results also showed that Ru was uniformly dispersed on the catalyst. The Ru particles in Examples 8-10 had a particle size of less than 1 nm, while the Ru particles in Comparative Example 2 had a particle size range of 1-3 nm. The reaction conditions for the catalytic amination of octanol to octylamine in Examples 3, 8-10, and Comparative Example 2 were the same as in Example 2, except that the catalyst type changed (i.e., a different type of catalyst was used). The analysis method for the reaction results was the same as in Example 2. Table 1 shows that as the Ru content increased, the conversion rate of octanol also increased continuously (in Example 8, the substrate conversion rate was too low to be detected due to the low Ru content), while maintaining good selectivity for octylamine.

[0031] Comparative Example 3 employed a stepwise impregnation method. First, Co / ZrO2 was prepared by equal-volume impregnation. The catalyst was dried in an oven at 80°C for 12 h, followed by calcination at 400°C for 3 h in air. The resulting catalyst (as a support) was then further impregnated in a ruthenium chloride precursor solution by equal volume, followed by drying in an oven at 80°C for 12 h, calcination at 400°C for 3 h in air, and reduction at 350°C for 2 h in a hydrogen atmosphere. After cooling to room temperature, it was passivated for 12 h in a 1% O2 / He (volume fraction) atmosphere (the total loading of the two metals remained at 5 wt% of the support, while maintaining a Co:Ru molar ratio of 30:1), ultimately yielding 5Co. 30The reaction conditions for the amination of octanol to octylamine in Example 4 and Comparative Example 3 were the same as in Example 2, except for the catalyst type (i.e., different catalysts were used). The results show that in Example 4, the conversion of octanol reached over 90%, the selectivity of octylamine was around 85%, and the yield of octylamine exceeded 75%. In Comparative Example 3, the yield of octanol decreased compared to Example 4, indicating that the co-impregnation method is more conducive to the interaction between the two metals, thus resulting in better catalytic performance. Notably, the octanol conversion and yield in Example 4 were significantly higher than the sum of those in Examples 2 and 3, demonstrating a significant interaction between Co and Ru, thereby achieving efficient amination of octanol to octylamine.

[0032] The preparation method of the support in Comparative Example 4 differs from that in Example 1. The difference lies in the fact that the support in Comparative Example 4 was directly heated to 400°C in a muffle furnace with 13g of ZrO(NO3)2·H2O precursor at a heating rate of 5°C / min, and then calcined at 400°C for 4 hours. The resulting powder is the ZrO2 support in Comparative Example 4. The method (process and conditions) for impregnating the metal is the same as in Example 4. The support in Comparative Example 5 is a commercially available ZrO2 support, without any treatment. The impregnation process and conditions are the same as in Example 4. The catalytic effects in Comparative Examples 4-5 are all decreased to varying degrees compared to Example 4, demonstrating that the support prepared in Example 1 is more conducive to obtaining a catalyst with better catalytic performance.

[0033] Table 1. Performance of CoRu / ZrO2 series catalysts in catalyzing the reductive amination of octanol to octylamine

[0034]

[0035] Table 1. Reaction conditions: 0.06 g octanol, 3 g p-xylene, 0.05 g n-dodecane (internal standard), 0.05 g catalyst, reaction temperature 160 °C, ammonia pressure 0.7 MPa, hydrogen pressure 0.3 MPa, reaction time 1.5 h, rotation speed 500 rpm / min. The reaction was carried out in a batch reactor with a total volume of 50 ml.

[0036] The previous results show that the conversion rate of octanol and the yield of octylamine increase significantly when both metals are present. Therefore, we further investigated the effect of different metal molar ratios on the amination of octanol to octylamine. The catalyst preparation processes in Examples 11-13 and Comparative Examples 6-8 are similar to those in Example 4, except that the mass contents of cobalt nitrate and ruthenium chloride in the equal-volume impregnation solution are different. In Examples 11-13 and Comparative Examples 6-8, the amounts of cobalt nitrate and ruthenium chloride must satisfy the requirement that the total loading of Co and Ru is 5 wt%, and the molar ratios of Co:Ru are 98.5:1.5, 20:1, 10:1, 1:1, 1:5, and 1:10, respectively. Electron microscopy results confirm that Co is uniformly dispersed on the catalysts of Examples 11-13 (the average particle size of Co is 15 nm, 12 nm, and 9 nm). The high loading of Co provides a substrate for Ru dispersion, contributing to the high dispersion of Ru, with particle sizes all less than 1 nm. In Comparative Example 6, the catalysts had consistent content of both metals, and some metal particles with a diameter range of 1-5 nm were observed, making it difficult to distinguish which metal served as the substrate. In Comparative Examples 6-7, the catalysts had a higher Ru content, resulting in metal particles with a diameter range of 2-8 nm forming on the catalyst surface. The reaction conditions for the catalysts in Examples 11-14 and Comparative Examples 6-7 were consistent with those in Example 4. The results in Table 2 show that when the molar ratio of Co to Ru changed, the conversion rate of octanol and the yield of octylamine differed significantly. When Co or Ru was dominant in the catalyst, the conversion rate of octanol and the selectivity of octylamine were both considerable, proving that both metals were active sites. The octanol conversion rate in Example 14 was low, indicating that poor metal dispersion was detrimental to the reaction. Although the reaction results in Comparative Examples 7-8 were also good, the high content of noble metals increased the catalyst preparation cost, so catalysts with a higher non-noble metal Co loading were preferred. The reaction activity in Example 11 was slightly lower than that in Example 4, possibly because the excessively high Co content covered Ru, resulting in the coverage of some active sites. Combining the results in Tables 1 and 2, within our selected metal loading range, an appropriate metal molar ratio will form a bimetallic alloy. Co can provide a suitable substrate for Ru to form a highly dispersed monolayer. Through the interaction between the two metals, octanol can be efficiently catalyzed to form octylamine. The suitable Co / Ru molar ratio is between 60 and 10, preferably between 30 and 20.

[0037] Table 2. Performance of CoRu / ZrO2 series catalysts with different Co / Ru molar ratios in catalyzing the reductive amination of octanol to octylamine.

[0038]

[0039]

[0040] Table 2. Reaction conditions: 0.06 g octanol, 3 g p-xylene, 0.05 g n-dodecane (internal standard), 0.05 g catalyst, reaction temperature 160 °C, ammonia pressure 0.7 MPa, hydrogen pressure 0.3 MPa, reaction time 1.5 h, rotation speed 500 rpm / min. The reaction was carried out in a batch reactor with a total volume of 50 ml.

[0041] The catalyst preparation processes and reaction conditions in Examples 14-17 and Comparative Example 9 in Table 3 are consistent with those in Example 4, except for the total metal loading of Co and Ru. In the catalyst preparation stages of Examples 14-17 and Comparative Example 9, the mass amounts of cobalt nitrate and ruthenium chloride are 1 / 5, 3 / 5, 7 / 5, 2, and 1 / 10 of those in Example 4, respectively. Electron microscopy results show that in Examples 14-16, the particle sizes of Co on the catalyst range from 1-4 nm, 5-9 nm, and 16-23 nm, respectively, and they are uniformly distributed on the support surface. Ru is more concentrated on the Co nanoparticles, with particle sizes all less than 1 nm. In Example 17, Ru has a small amount of aggregation on the Co particles, with Ru particle sizes ranging from 1-3 nm, and Co particle sizes ranging from 20-30 nm. The results in Table 3 show that the conversion rate of octanol increases with increasing total metal loading. However, when the total loading exceeds 5 wt%, the increase in octanol conversion slows down, while the yield of octylamine remains above 75%. Furthermore, the selectivity of octylamine decreases with increasing total loading. The suitable range for total metal loading is 1-10 wt%, preferably 5-10 wt%.

[0042] Table 3. Co with different total metal loadings 30 Performance of Ru1 / ZrO2 catalyst in catalyzing the reductive amination of octanol to octylamine

[0043]

[0044]

[0045] Table 3. Reaction conditions: 0.06 g octanol, 3 g p-xylene, 0.05 g n-dodecane (internal standard), 0.05 g catalyst, reaction temperature 160 °C, ammonia pressure 0.7 MPa, hydrogen pressure 0.3 MPa, reaction time 1.5 h, rotation speed 500 rpm / min. The reaction was carried out in a batch reactor with a total volume of 50 ml.

[0046] Table 4 shows Examples 18-20, which investigated 5Co loading on different carriers. 30The Ru1 catalyst exhibits good performance in catalytic reduction and amination of octanol to octylamine. The catalyst preparation, reaction process, and conditions are consistent with those in Example 4, except that the catalyst supports used are SiO2, BN, and TiO2, respectively. As shown in Table 4, ZrO2 is the most suitable catalyst support.

[0047] Table 4. 5Co with different carriers 30 Performance of Ru1 catalyst in catalytic reduction amination of octanol to octylamine

[0048]

[0049] Table 4. Reaction conditions: 0.06 g octanol, 3 g p-xylene, 0.05 g n-dodecane (internal standard), 0.05 g catalyst, reaction temperature 160 °C, ammonia pressure 0.7 MPa, hydrogen pressure 0.3 MPa, reaction time 1.5 h, rotation speed 500 rpm / min. The reaction was carried out in a batch reactor with a total volume of 50 ml.

[0050] The effects of different noble metals on the reaction performance of octanol amination to octylamine were then investigated. The catalysts in Examples 21-23 and Comparative Example 10 were prepared using the same method (process and conditions) as in Example 4, except that the selected M2 metal precursors were chloroplatinic acid, rhodium chloride, palladium chloride, and iridium chloride, respectively. The total loading of Co and M2 metal was 5 wt%, with a molar ratio of 30:1. Electron microscopy results showed that the Co particles on the catalysts in Examples 21-23 and Comparative Example 10 were between 10-30 nm in size, and the noble metals were more concentrated on the surface of the Co particles in the form of a monolayer of atoms. As shown in Table 5, the conversion rate of octanol did not change significantly after the addition of different noble metals, indicating that the catalysts with different noble metals all had good dehydrogenation performance. The selectivity of octylamine showed a significant difference. Due to the appropriate imide conversion and hydrogenation capabilities of Ru, 5Co... 30 The Ru1 / ZrO2 reaction yielded the best results, achieving the highest primary amine selectivity. Meanwhile, the relatively low price of Ru helps reduce catalyst costs.

[0051] Table 5.5 Performance of CoM2 / ZrO2 catalyst in catalyzing the amination of octanol to octylamine

[0052]

[0053] Table 5. Reaction conditions: 0.06 g octanol, 3 g p-xylene, 0.05 g n-dodecane (internal standard), 0.05 g catalyst, reaction temperature 160 °C, ammonia pressure 0.7 MPa, hydrogen pressure 0.3 MPa, reaction time 1.5 h, rotation speed 500 rpm / min. The reaction was carried out in a batch reactor with a total volume of 50 ml.

[0054] After determining that Ru was the most suitable noble metal, the performance of catalysts with different non-noble metal substrates for the amination of octanol to octylamine was subsequently investigated. The catalyst preparation methods, reaction processes, and conditions for Examples 24 and Comparative Examples 11-13 were the same as in Example 4, except that the precursors for the non-noble metal M1 were nickel nitrate, copper nitrate, zinc nitrate, and iron nitrate, respectively, and the total loading of non-noble metal M1 and Ru was 5 wt%, with a molar ratio of 30:1. Electron microscopy results showed that the particle size of the non-noble metals on the catalysts of Examples 24 and Comparative Examples 11-13 was between 10-50 nm, and Ru was more concentratedly distributed on the surface of the non-noble metal particles in a monolayer atomic dispersion. The results in Table 6 show that the yield of octylamine was highest when Co was used as the substrate metal. For Ni in Example 24, its dehydrogenation ability was limited due to its difficulty in reduction, resulting in a slightly lower conversion rate of octanol. Overall, Co and Ni are more suitable non-noble metals.

[0055] Table 6.5 Performance of M1Ru1 / ZrO2 catalyst in catalyzing the preparation of octylamine from octanol.

[0056]

[0057]

[0058] Table 6. Reaction conditions: 0.06 g octanol, 3 g p-xylene, 0.05 g n-dodecane (internal standard), 0.05 g catalyst, reaction temperature 160 °C, ammonia pressure 0.7 MPa, hydrogen pressure 0.3 MPa, reaction time 1.5 h, rotation speed 500 rpm / min. The reaction was carried out in a batch reactor with a total volume of 50 ml.

[0059] The monolayer atomically dispersed 5Co prepared in this invention 30 The Ru1 / ZrO2 catalyst exhibited excellent performance in the amination of octanol to octylamine. Examples 25-29 further investigated the performance of this catalyst in the preparation of primary amines from other alcohol substrates. All catalysts were prepared from 5Co prepared in Example 4. 30 The Ru1 / ZrO2 catalyst, with reaction conditions differing from Example 4 above, lies in the substrate. The substrates for the different examples are shown in the second column of Table 7. As can be seen from the results in Table 7, for both aliphatic and aromatic alcohols, monolayer atomically dispersed 5Co... 30 Both Ru1 / ZrO2 catalysts can catalyze the efficient amination of alcohol substrates to prepare the corresponding primary amines, demonstrating strong substrate applicability and providing a foundation for practical production.

[0060] Table 7. Performance of Reductive Amination of Different Alcohols in the Preparation of Primary Amines

[0061] Example Substrate Conversion rate (%) Primary amine selectivity (%) Example 4 Octyl alcohol 90.9 84.1 Example 25 benzyl alcohol 85.3 79.5 Example 26 Cyclohexanol 86.2 93.4 Example 27 Butanol 82.5 82.4 Example 28 p-Fluorophenylethanol 98.2 78.0 Example 29 Isoamyl alcohol 74.0 79.5

[0062] Table 7 Reaction conditions: 0.06 g substrate, 3 g p-xylene, 0.05 g internal standard n-dodecane, 0.05 g 5Co 30 The reaction of Ru1 / ZrO2 was carried out at a temperature of 160℃, an ammonia pressure of 0.7 MPa, a hydrogen pressure of 0.3 MPa, a reaction time of 1.5 h, and a rotation speed of 500 rpm / min in a batch reactor with a total volume of 50 ml.

[0063] Table 8 shows the conversion performance of octanol reductive amination to octylamine at different temperatures. The catalysts used in Examples 30-32 and Comparative Examples 14-16 were the same as those prepared in Example 4. The reaction temperatures of the different examples are shown in the second column of Table 8. The results in Table 8 show that the reaction temperature has a significant impact on the preparation of octylamine by octanol amination. When the temperature rises above 160°C, the conversion rate of octanol is above 90%. However, as the temperature continues to rise, the selectivity of octylamine decreases because hydrogenation reactions are more likely to occur at high temperatures, leading to the conversion of more secondary imines into secondary amines. When the temperature decreases, the conversion rate of octanol decreases, while the selectivity of octylamine increases because the energy required for octanol dehydrogenation is high, and lower temperatures are not conducive to the dehydrogenation reaction. Therefore, the reaction temperature for the efficient production of octylamine from octanol needs to be within a suitable temperature range (140-160°C).

[0064] Table 8. Conversion performance of octanol amination to prepare octylamine at different reaction temperatures

[0065]

[0066] Table 8 Reaction conditions: 0.06 g substrate, 3 g p-xylene, 0.05 g internal standard n-dodecane, 0.05 g 5Co 30 The reaction was carried out in a batch reactor with a total volume of 50 ml, using Ru1 / ZrO2, ammonia pressure of 0.7 MPa, hydrogen pressure of 0.3 MPa, reaction time of 1.5 h, and rotation speed of 500 rpm / min.

[0067] Ammonia pressure is crucial for the amination of octanol to octylamine. Examples 33-36 and Comparative Examples 17-18 in Table 8 investigated the effect of different ammonia pressures on the reaction results. The catalysts used in Examples 33-36 and Comparative Examples 17-18 were the same as those prepared in Example 4 above. The ammonia pressures for the reaction conditions differed, and the ammonia pressures for different examples are shown in the second column of Table 9. The results in Table 9 show that as the ammonia pressure decreases, the conversion of octanol decreases, and the selectivity of octylamine also decreases. At higher ammonia pressures (0.8 MPa, 1 MPa), the conversion of octanol decreases slightly, but a high yield of octylamine can still be maintained. The preferred ammonia pressure is (0.6-1 MPa).

[0068] Table 9. Effect of ammonia pressure on the conversion performance of octanol amination to octylamine

[0069]

[0070] Table 9 Reaction conditions: 0.06 g substrate, 3 g p-xylene, internal standard n-dodecane 0.05 g, 0.05 g 5Co 30 The reaction of Ru1 / ZrO2 was carried out at a temperature of 160℃, a hydrogen pressure of 0.3 MPa, a reaction time of 1.5 h, and a rotation speed of 500 rpm / min in a batch reactor with a total volume of 50 ml.

[0071] The preparation of octylamine by octanol amination can proceed via a "hydrogen transfer" mechanism, whereby the hydrogen removed from the alcohol can be used for subsequent hydrogenation of the primary imine. Therefore, theoretically, no additional hydrogen is required. However, in Examples 37-39 and Comparative Example 19, the hydrogen pressure was altered, significantly affecting the results of the octanol-to-octylamine preparation. Therefore, hydrogen pressure also significantly influences the reaction results. The catalysts and reaction conditions in Examples 37-39 and Comparative Example 19 were the same as in Example 4 above, the difference being the hydrogen pressure. The hydrogen pressures of the different examples are shown in Table 10. The results in Table 10 show that when the hydrogen pressure increases, the selectivity of octylamine decreases. This is because increasing the hydrogen pressure also increases the side reaction of secondary imine hydrogenation to secondary amine formation. Continuously increasing the hydrogen pressure inhibits the octanol dehydrogenation rate, thereby reducing the octanol conversion. When the hydrogen pressure decreases, both the octanol conversion and the octylamine selectivity decrease, indicating that external hydrogen can also promote the hydrogenation of primary imine to primary amine. Without external hydrogen, the conversion rate of octanol decreases significantly. This is because carbon deposits form on the catalyst surface during the reaction. External hydrogen can react with these carbon deposits to form substances such as methane, thus removing the carbon deposits and ensuring that the active sites of the catalyst are not covered. Therefore, an appropriate hydrogen pressure is crucial for obtaining high octanol conversion and octylamine selectivity; the preferred hydrogen pressure range is 0.3-0.5 MPa.

[0072] Table 10. Effect of hydrogen pressure on the conversion performance of octanol amination to octylamine

[0073]

[0074] Table 10 Reaction conditions: 0.06 g substrate, 3 g p-xylene, internal standard n-dodecane 0.05 g, 0.05 g 5Co 30 The reaction of Ru1 / ZrO2 was carried out at a temperature of 160℃, an ammonia pressure of 0.7 MPa, a reaction time of 1.5 h, and a rotation speed of 500 rpm / min in a batch reactor with a total volume of 50 ml.

[0075] The effects of catalyst calcination temperature on 5Co were investigated in Examples 40-43 of Table 11. 30 The effect of Ru1 / ZrO2 on the reaction performance of octanol to octylamine. The calcination temperature affects the interaction between the metal and the support, and has a significant impact on metal dispersion. The catalyst preparation process and reaction conditions in Examples 40-43 are the same as in Example 4 above, except for the calcination temperature of the catalyst. The calcination temperatures of the catalysts in Examples 40-43 are shown in the second column of Table 11. The results in Table 11 show that at lower calcination temperatures (200℃, 300℃), the conversion rate of octanol is less than 80%. At lower calcination temperatures, the interaction between the metal particles and the support is not conducive, and metal agglomeration is more likely to occur during subsequent reduction, thus reducing the substrate conversion rate. When the calcination temperature reaches 600℃, the excessively high calcination temperature is not conducive to the dispersion of Ru on Co particles, thus leading to a decrease in the octylamine yield. The preferred calcination temperature is 400-500℃.

[0076] Table 11. Effect of catalyst calcination temperature on the conversion performance of octanol amination to octylamine

[0077]

[0078] Table 11 Reaction conditions: 0.06 g substrate, 3 g p-xylene, internal standard n-dodecane 0.05 g, 0.05 g 5Co 30 The reaction of Ru1 / ZrO2 was carried out at a temperature of 160℃, an ammonia pressure of 0.7 MPa, a hydrogen pressure of 0.3 MPa, a reaction time of 1.5 h, and a rotation speed of 500 rpm / min in a batch reactor with a total volume of 50 ml.

[0079] The effects of calcination time of the catalyst at 400 °C on 5Co were investigated in Examples 44-46 and Comparative Example 20 in Table 12. 30The effect of Ru1 / ZrO2 on the reaction performance of octanol to octylamine. The catalyst preparation process and reaction conditions in Examples 44-46 and Comparative Example 20 were the same as in Example 4, except for the calcination time of the catalyst. The calcination times of the catalysts in Examples 44-46 and Comparative Example 20 are shown in the second column of Table 12. The results in Table 12 show that both excessively long and short calcination times are detrimental to obtaining a high octylamine yield. The preferred calcination time is 3-4 hours.

[0080] Table 12. Effect of calcination time of catalyst at 400℃ on conversion performance of octanol amination to octylamine

[0081]

[0082] Table 12 Reaction conditions: 0.06 g substrate, 3 g p-xylene, internal standard n-dodecane 0.05 g, 0.05 g 5Co 30 The reaction of Ru1 / ZrO2 was carried out at a temperature of 160℃, an ammonia pressure of 0.7 MPa, a hydrogen pressure of 0.3 MPa, a reaction time of 1.5 h, and a rotation speed of 500 rpm / min in a batch reactor with a total volume of 50 ml.

[0083] The reduction temperature of the catalyst on 5Co was investigated in Examples 47-49 of Table 13 and Comparative Example 21. 30 The effect of Ru1 / ZrO2 catalysis on the reaction performance of octanol to octylamine. Changes in reduction temperature affect the valence state and dispersion of the metal, thus influencing the amination of octanol to octylamine. The catalyst preparation process and reaction conditions in Examples 47-49 and Comparative Example 21 were the same as in Example 4, except for the reduction temperature of the catalyst. The reduction temperatures in Examples 47-49 and Comparative Example 21 are shown in the second column of Table 13. The results in the table show that at lower reduction temperatures, the metal valence state deviates from zero, which is unfavorable for the dehydrogenation of octanol, thus affecting the octanol conversion and resulting in a lower conversion rate. Increasing the reduction temperature causes the metal to continue agglomerating, reducing the active sites on the catalyst and also causing a decrease in conversion rate. The preferred reduction temperature is 300-400℃.

[0084] Table 13. Effect of catalyst reduction temperature on the conversion performance of octanol amination to octylamine

[0085]

[0086] Table 13 Reaction conditions: 0.06 g substrate, 3 g p-xylene, internal standard n-dodecane 0.05 g, 0.05 g 5Co 30The reaction of Ru1 / ZrO2 was carried out at a temperature of 160℃, an ammonia pressure of 0.7 MPa, a hydrogen pressure of 0.3 MPa, a reaction time of 1.5 h, and a rotation speed of 500 rpm / min in a batch reactor with a total volume of 50 ml.

[0087] In Examples 50-53 of Table 14, the effect of reduction time of the catalyst at 350°C on 5Co was investigated. 30 The effect of Ru1 / ZrO2 on the reaction performance of octanol to octylamine. The catalyst preparation process and reaction conditions in Examples 50-53 were the same as in Example 4, except for the reduction time of the catalyst. The reduction times of the catalysts in Examples 50-53 are shown in the second column of Table 14. The results in the table show that when the reduction time is short, the degree of metal reduction is insufficient, affecting the octanol dehydrogenation process, thus resulting in a low conversion rate. Increasing the reduction time increases the degree of metal aggregation, reducing the active sites of the metal on the catalyst, which also leads to a decrease in conversion rate. The preferred reduction time is 2-3 hours.

[0088] Table 14. Effect of reduction time of catalyst at 350℃ on conversion performance of octanol amination to octylamine

[0089]

[0090] Table 14 Reaction conditions: 0.06 g substrate, 3 g p-xylene, internal standard n-dodecane 0.05 g, 0.05 g 5Co 30 The reaction of Ru1 / ZrO2 was carried out at a temperature of 160℃, an ammonia pressure of 0.7 MPa, a hydrogen pressure of 0.3 MPa, a reaction time of 1.5 h, and a rotation speed of 500 rpm / min in a batch reactor with a total volume of 50 ml.

[0091] Table 15 shows Examples 54-57, which investigated the effect of octanol concentration on the reaction performance for the preparation of octylamine. The catalyst and reaction conditions used in Examples 54-57 were the same as those in Example 4, except for the substrate concentration. The substrate concentrations in Examples 54-57 are shown in the second column of Table 15. The results show that the conversion rate of octanol gradually decreases with increasing substrate concentration. When the substrate concentration increases to 10 wt%, the yield of octylamine can still reach approximately 60%, indicating that the catalyst remains applicable over a wide range of substrate concentrations, which is beneficial for practical applications. The preferred range is 1-5 wt%.

[0092] Table 15. Effect of substrate concentration on the conversion performance of octanol amination to octylamine

[0093]

[0094] Table 15 Reaction conditions: 3g p-xylene, 0.05g internal standard n-dodecane, 0.05g 5Co 30 The reaction of Ru1 / ZrO2 was carried out at a temperature of 160℃, an ammonia pressure of 0.7 MPa, a hydrogen pressure of 0.3 MPa, a reaction time of 1.5 h, and a rotation speed of 500 rpm / min in a batch reactor with a total volume of 50 ml.

[0095] Table 16 shows the effects of the reaction solvent on the reaction performance of octanol to octylamine in Examples 58-59 and Comparative Example 22. The catalysts and reaction conditions used in Examples 58-59 and Comparative Example 22 were the same as those in Example 4, except for the reaction solvents. The solvents in Examples 58, 59, and Comparative Example 20 were toluene, mesitylene, and methanol, respectively. The results in Table 16 show that when the reaction solvent is a less polar alkyl-substituted benzene, both the substrate conversion and the selectivity for octylamine are quite good. However, when the solvent is changed to a highly polar methanol solution, the octanol conversion decreases significantly. Therefore, less polar solvents are more suitable for the amination of octanol to octylamine. Among the alkyl-substituted benzenes, p-xylene is preferred as the solvent.

[0096] Table 16. Effect of reaction solvent on the conversion performance of octanol amination to octylamine

[0097]

[0098]

[0099] Table 16 Reaction conditions: 0.06 g substrate, 3 g solvent, internal standard n-dodecane 0.05 g, 0.05 g 5Co 30 The reaction of Ru1 / ZrO2 was carried out at a temperature of 160℃, an ammonia pressure of 0.7 MPa, a hydrogen pressure of 0.3 MPa, a reaction time of 1.5 h, and a rotation speed of 500 rpm / min in a batch reactor with a total volume of 50 ml.

[0100] Figure 4 It is a monolayer atomically dispersed 5Co 30Stability test of octylamine preparation by the catalytic reduction amination of octanol using Ru1 / ZrO2 alloy catalyst. The reaction procedure was as follows: 0.06 g substrate, 3 g p-xylene, 0.05 g internal standard n-dodecane, 0.05 g catalyst, reaction temperature 160 °C, ammonia pressure 0.7 MPa, hydrogen pressure 0.3 MPa, reaction time 1.5 h, rotation speed 500 rpm / min. After the reaction, the reaction solution was centrifuged, and the supernatant was collected for gas chromatography and mass spectrometry analysis. Examples 60 and 61 are activity tests of the recovered catalyst. The catalyst in Example 60 was obtained by washing and filtering the catalyst after the reaction in Example 4 with ethanol, and then drying it in an oven at 60 °C for 6 h. The remaining reaction conditions were the same as in Example 4. The catalyst in Example 61 was obtained by washing and filtering the catalyst after the reaction in Example 60 with ethanol, and then drying it in an oven at 60 °C for 6 h. The remaining reaction conditions were the same as in Example 4. Example 62 is an activity test of the regenerated catalyst. The catalyst in Example 62 was obtained by washing and filtering the catalyst from the reaction in Example 61 with ethanol, drying it in an oven at 80°C for 12 hours, calcining it at 400°C for 3 hours in air, and then reducing it at 350°C for 2 hours in hydrogen. After cooling to room temperature, it was passivated for 12 hours in an atmosphere of 1% O2 / He (volume fraction). The reaction results of the recovery and regeneration experiments are as follows. Figure 4 As shown in the figure, the conversion rate of octanol gradually decreased during the recovery experiment, while the conversion rate of octylamine slightly increased, resulting in an overall decrease in the yield of octylamine. The regeneration experiment restored the results to those of the first experiment. Thermogravimetric analysis revealed significant weight loss of the catalyst in the recovery experiment within the 200℃ and 300℃ range, indicating the presence of carbon deposits on the catalyst surface. Therefore, the decrease in activity during the recovery experiment is attributed to the carbon deposits covering the active sites of the catalyst. The reaction results of the regeneration experiment demonstrate that monolayer atomically dispersed 5Co... 30 Ru1 / ZrO2 alloy catalysts have good renewability.

Claims

1. A method for preparing amine compounds by reductive amination of alcohols, characterized in that: The catalyst used is M1M2 / ZrO2, where M1 is a non-noble metal and M2 is a noble metal. M1 is a metal Co supported on ZrO2 as a substrate; metal M2 is one of Ru, Rh, and Pd, and is distributed on the surface of metal M1 in the form of a monolayer atomic dispersion; the total loading of metals M1 and M2 in the catalyst is 1-10 wt%; the particle size of the nanoparticles formed by metal M1 is between 1-30 nm. Within the selected total loading range of metals M1 and M2, the molar ratio of M1 to M2 is between 60 and 10; the reaction temperature is 140-160 ℃. The support was prepared by a hydrothermal method, specifically as follows: a zirconium precursor solution was mixed with a urea solution, and the mixture was stirred in a water bath; the solution was transferred to a closed hydrothermal reactor and heated at 120-180 °C for 10-20 hours; after washing and centrifugation, the solid sample was dried in an oven at 80-120 °C for 8-12 hours; the dried sample was ground into powder with a size between 100-300 mesh and calcined at 400-600 °C for 2-6 hours in an air atmosphere to obtain the ZrO2 support; The catalyst is prepared by an equal-volume co-impregnation method. The specific process is as follows: the precursor solution containing active metals M1 and M2 is mixed according to the total loading and molar ratio of the metals and impregnated on the support ZrO2. The prepared catalyst is first dried in an oven at 80-120 ℃ for 6-12 h, and then calcined at 200-600 ℃ in air atmosphere for 2-6 h. Subsequently, the catalyst was reduced at 300-500 °C for 1-5 h in a hydrogen atmosphere, then cooled to 20-30 °C, and passivated at 0.5-2% O2 / He for 4-12 h to finally obtain the catalyst M1M2 / ZrO2.

2. The method according to claim 1, characterized in that: The total loading of metals M1 and M2 in the catalyst is 5-10 wt%; the nanoparticles formed by metal M1 have a particle size between 10-30 nm; and within the selected total loading range of metals M1 and M2, the molar ratio of M1 to M2 is between 30-20.

3. The method according to claim 1, characterized in that: Metal M1 is dispersed on the surface of the carrier to form particles; metal M2 forms an alloy with metal M1 on the surface of the metal M1 particles.

4. The method according to claim 1, characterized in that: The selected precursor solution of metal M1 is one or both of the corresponding metal nitrate or acetate. The selected precursor solution of metal M2 is one or both of the corresponding metal chloride or nitrate.

5. The method according to claim 1, characterized in that: The reaction was carried out in a batch high-pressure autoclave reactor, and the reaction process was as follows: the concentration of alcohol substrate was 1-10 wt%; the ammonia pressure was 0.4-1 MPa; the hydrogen pressure was 0.1-1 MPa; the reaction time was 0.5-5 h; and the alkyl-substituted derivative of benzene was used as the solvent.

6. The method according to claim 5, characterized in that: The reaction is carried out in an intermittent high-pressure autoclave reactor, and the reaction process is as follows: the concentration of alcohol substrate is 1-5 wt%; the ammonia pressure is 0.6-1 MPa; the hydrogen pressure is 0.3-0.5 MPa; the reaction time is 1-2 h; and the solvent is one or more of toluene, xylene, and trimethylbenzene.

7. The method according to claim 1 or 5, characterized in that: The reaction substrate is selected from one or more of octanol, phenylethanol, butanol, cyclohexanol, and p-fluorophenylethanol.

8. The method according to claim 1 or 5, characterized in that: n-Dodecane was used as an internal standard; the total liquid charge was less than or equal to 1 / 3 of the reactor volume.

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