Process for the synthesis of higher fatty amines from fatty alcohol amines

Abstract

The application discloses a method for synthesizing higher aliphatic amines from aliphatic alcohol amination. The method uses hydrogen as a hydrogen source and ammonia as a nitrogen source, and selects a ruthenium-loaded nitrogen-doped carbon nanotube and a ruthenium-loaded rod-shaped cerium oxide catalyst to catalyze a reaction, so as to prepare higher aliphatic amines through amination. In the preparation of the catalyst, the catalytic performance is improved through the "anchoring-electron" double effect: the specific structure formed by nitrogen doping effectively anchors the ruthenium nanoparticles, and the metal dispersion is significantly improved; the rod-shaped cerium oxide preferentially exposes specific crystal faces, and then the metal-support interaction is enhanced, and the metal dispersion is greatly improved. The application has high catalytic activity, primary amine selectivity and total amine (primary amine and secondary amine) yield, and has the advantages of simple process, mild conditions, high atom economy and good application prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing n-dodecylamine by the reductive amination reaction of lauryl alcohol and ammonia, belonging to the field of chemical synthesis. Background Technology

[0002] Higher fatty amines generally refer to primary, secondary, and tertiary fatty amines with a carbon chain length of 8 or more. These higher fatty amines are high-value-added derivative chemicals in industry. They can be further processed through ethoxylation, quaternization, and other chemical processes to produce quaternary ammonium salts, betaine, tertiary amine oxides, ether amines, and primary amine acetates, which are cationic, amphoteric, and nonionic surfactants with special physicochemical properties. These are widely used in light industry, textiles, building materials, mining, and other sectors, as well as in daily life, and are important products and intermediates in the fine chemical industry. The production processes of fatty amines are diverse, with significant differences in raw materials and reaction routes. They are mainly divided into amination and dehydration processes using natural fatty acids as raw materials, stepwise addition amination processes using olefins and hydrogen cyanide as raw materials, haloalkanes with amine substitution processes, and reductive amination processes using fatty alcohols as raw materials. The first three synthesis processes have a series of problems such as harsh reaction conditions, complex processes, high equipment requirements, and environmental pollution. In contrast, the one-step amination synthesis technology using fatty alcohols as raw materials has advantages such as low cost, wide availability of raw materials, environmental friendliness, and mild conditions, and is considered one of the most promising synthetic amine processes.

[0003] With the development of petrochemical and biomass chemical industries, fatty alcohols have become increasingly abundant and inexpensive. Direct reductive amination using fatty alcohols as raw materials produces only water as a byproduct, exhibiting high atom economy and conforming to green chemistry principles, thus attracting widespread attention. The reductive amination of alcohols follows a tandem mechanism of "dehydrogenation-imineation-hydrogenation": the alcohol first undergoes dehydrogenation on a catalyst to form an aldehyde, the aldehyde condenses with ammonia to form an imine, and the imine is then hydrogenated to form a primary amine. The key to this process lies in the development of highly efficient catalysts. In recent years, there has been considerable research on amination processes using aldehydes and ketones as substrates: 1) Heterogeneous noble metal catalysts, such as the graphene-supported ruthenium catalyst developed in patent CN202010449693.8, which achieves a near 100% benzylamine yield in the reductive amination of benzaldehyde. (2) Heterogeneous, non-precious metal catalysts, such as the hollow layered double hydroxide-supported nickel catalyst disclosed in patent CN202110919247.3, achieve a furfural amination yield of over 95% at 80℃ and 2MPa hydrogen. However, aldehydes and ketones are intermediates in the reductive amination of alcohols, and their sources are scarce, their prices are high, and they are prone to excessive alkylation side reactions, limiting their industrial application. Therefore, the process of producing fatty amines by the reductive amination of fatty alcohols has become a core focus of the industry.

[0004] Existing technologies have reported catalysts for alcohol amination. For example, patent CN201711292866.4 discloses a nickel-cobalt catalyst for the amination of isopropanol to prepare 1,2-propanediamine, and investigates the effects of promoters such as Ru, Rh, and Pd; patent CN201711292887.6 reports a composite metal oxide catalyst with Ni, Co, or Cu as the main active component and Fe, Zn, La, Pd, Pt, etc. as co-active components, supported by titanium oxide, zirconium oxide, alumina, or molecular sieves; patent CN105457653A discloses a mixed metal oxide catalyst for the amination of diethylene glycol, with nickel oxide or copper oxide as the main active component. However, the above patents all use lower aliphatic alcohols or alcohols containing other functional groups as substrates, while research on the direct amination of higher aliphatic alcohols is limited. Therefore, it is necessary to develop a catalyst and process for the synthesis of higher aliphatic amines. Summary of the Invention

[0005] The purpose of this invention is to address the gaps and deficiencies in current technologies by providing a method for synthesizing higher fatty amines through the amination of fatty alcohols. This method uses hydrogen as the hydrogen source and ammonia as the nitrogen source, employing nitrogen-doped carbon nanotube-supported ruthenium and rod-shaped cerium oxide-supported ruthenium catalysts to catalyze the reaction, preparing higher fatty amines via an amination reaction. This invention exhibits high catalytic activity and primary amine selectivity, is simple, operates under mild conditions, and boasts high atom economy, showing promising application prospects.

[0006] The technical solution of the present invention is as follows: A method for synthesizing higher fatty amines by amination of fatty alcohols, wherein the method is any one of the following two methods: Method 1 includes the following steps: In a high-pressure batch reactor, fatty alcohol, nitrogen-doped carbon nanotube supported ruthenium catalyst or rod-shaped cerium oxide supported ruthenium catalyst and organic solvent are added. After being replaced with an inert gas, ammonia and hydrogen are introduced, and the temperature is raised to the reaction temperature to carry out a reduction amination reaction to obtain n-dodecylamine and didodecylamine. The reaction temperature was 160–250 °C, the hydrogen pressure was 0.2–1.0 MPa, the ammonia pressure was 0.2–0.8 MPa, and the reaction time was 3–24 hours; the catalyst mass was 20–80% of the lauryl alcohol mass. Preferably, the reaction temperature is 170~220 ℃; the hydrogen pressure is 0.3~0.6 MPa and the ammonia pressure is 0.4~0.6 MPa; the reaction time is 8~15 hours; and the catalyst mass is 40~60% of the fatty alcohol mass.

[0007] The organic solvent is tert-amyl alcohol or n-decane, and the mass ratio of solvent to fatty alcohol is 0.2~80:1.

[0008] Preferably, the mass ratio of solvent to lauryl alcohol is 40~60:1.

[0009] Alternatively, Method 2 includes the following steps: In a fixed-bed reactor, a mixture of a certain concentration of fatty alcohol organic solvent solution, ammonia, and hydrogen is introduced into a fixed-bed reactor loaded with nitrogen-doped carbon nanotube supported ruthenium catalyst or rod-shaped cerium oxide supported ruthenium catalyst, and a reductive amination reaction is carried out at 160~250 °C to obtain n-dodecylamine and didodecylamine. The molar ratio of ammonia to fatty alcohol is 20–40:1, the molar ratio of hydrogen to fatty alcohol is 5–40:1, and the mass hourly space velocity (HHSV) is 2–12 h⁻¹. -1 The reaction system pressure is 1~4 MPa; Preferably, the reaction temperature is 190–210 °C, the ammonia:ethanol molar ratio is 20–30, the hydrogen:ethanol molar ratio is 5–15, and the mass hourly space velocity is 3–6 h⁻¹. -1 The system pressure is 2~3 MPa.

[0010] The organic solvent is tert-amyl alcohol or n-decane, and the mass ratio of solvent to fatty alcohol is 0.2~80:1.

[0011] Preferably, the mass ratio of solvent to fatty alcohol is 0.2 to 10:1.

[0012] The fatty alcohol mentioned is lauryl alcohol, n-decyl alcohol, or n-tetradecyl alcohol; The nitrogen-doped carbon nanotube supported ruthenium catalyst or rod-shaped cerium oxide supported ruthenium catalyst consists of an active component and a support; wherein the active component is Ru metal with a loading of 0.5~2 wt%; and the support is nitrogen-doped carbon nanotube or rod-shaped cerium oxide, wherein the nitrogen doping amount of the nitrogen-doped carbon nanotube is 2~10 at.

[0013] The catalyst has a mesh size of 10-160 mesh.

[0014] Preferably, the catalyst has a mesh size of 20-80.

[0015] The preparation method of the nitrogen-doped carbon nanotube supported ruthenium catalyst includes the following steps: (1) Disperse nitrogen-doped carbon nanotube carriers in deionized water and sonicate for 10-60 minutes; 0.2~2.0g of nitrogen-doped carbon nanotubes are added to every 20 ml of deionized water; (2) Dissolve anhydrous ruthenium trichloride in deionized water to prepare an impregnation solution, and slowly add it dropwise to the carrier dispersion while mechanically stirring for 5 to 24 hours; add 0.01 to 0.05 g of ruthenium trichloride per 1 g of nitrogen-doped carbon nanotubes; (3) Dissolve sodium borohydride in deionized water and slowly add it dropwise to the above mixture, and continue stirring for 2 to 16 hours; wherein the molar ratio of sodium borohydride to ruthenium is 1:1 to 40:1; (4) Filter and wash until neutral, dry under vacuum at 40~120 ℃ for 10~48 hours, and grind to obtain catalyst.

[0016] Preferably, the molar ratio of reducing agent to ruthenium is 5~20:1, the mechanical stirring time is 10~18 hours, the reduction time is 4~8 hours, the drying temperature is 60~80 ℃, and the drying time is 12~24 hours.

[0017] The preparation method of the rod-shaped cerium oxide supported ruthenium catalyst includes the following steps: (1) Dissolve the cerium precursor in deionized water, add morphology modifier, stir and mix evenly, then transfer to a hydrothermal reactor and hydrothermally treat at 80~180 ℃ for 12~48 hours. After cooling, centrifuge to separate the precipitate, wash with deionized water and ethanol until neutral, dry at 80~120 ℃ for 10~48 hours, and then calcine at 400~700 ℃ for 2~6 hours to obtain nanorod-shaped cerium oxide support; The morphology modifier is one or a mixture of sodium hydroxide, urea and ammonium carbonate, and the molar ratio of cerium precursor to morphology modifier is 1:1 to 1:100; preferably, the morphology modifier is one or both of sodium hydroxide and urea, and the molar ratio of cerium precursor to morphology modifier is 1:5 to 1:50.

[0018] 0.2-1.0g of cerium precursor was added to every 20 ml of deionized water; (2) The nanorod-shaped cerium oxide support obtained in step (1) is dried at 80~120 °C for 10~48 hours, and its saturated water absorption is measured; (3) Dissolve the ruthenium precursor in deionized water to prepare an impregnation solution. The volume of the impregnation solution is equal to the saturated water absorption of the carrier. Add the impregnation solution drop by drop to the carrier while stirring until the surface of the carrier is completely wetted. The ruthenium precursor is anhydrous ruthenium trichloride; the concentration of ruthenium in the impregnation solution is calculated based on the target loading, and the ruthenium loading is 0.5~2 wt%; (4) The impregnated catalyst is aged at room temperature for 6-48 hours, and then dried at 80-120 °C for 10-48 hours. Preferably, the aging time is 8-20 hours; (5) The dried catalyst is calcined in a nitrogen or air atmosphere at a temperature of 400-800 °C, a heating rate of 2-10 °C / min, and a calcination time of 2-8 hours. Preferably, the calcination temperature is 550-650 °C and the calcination time is 3-6 hours. (6) The calcined catalyst is reduced in a hydrogen atmosphere at a temperature of 200-350 °C, a heating rate of 2-10 °C / min, a reduction time of 2-5 hours, and a hydrogen flow rate of 20-50 mL / min. After the reduction is completed, the temperature is lowered to room temperature and 1% O2 / Ar mixed gas is introduced for passivation for 30-60 minutes to obtain rod-shaped cerium oxide supported ruthenium catalyst.

[0019] The essential features of this invention are: 1. Synergistic effect of nitrogen doping on the support and subsequent reducing agent: The catalytic performance is improved through the "anchoring-electron" dual effect: The functional groups such as pyridine nitrogen and pyrrole nitrogen formed by nitrogen doping effectively anchor the ruthenium nanoparticles, enhance the electron density on the active metal surface of the catalyst, and significantly improve the metal dispersion; and the addition of a specific reducing agent avoids the loss of functional groups such as pyridine nitrogen and pyrrole nitrogen, while maintaining the high dispersion of ruthenium nanoparticles, significantly improving the intrinsic catalytic activity of lauryl alcohol and reducing the reaction activation energy.

[0020] 2. Morphology regulation steps of cerium oxide: Morphology regulation significantly affects the exposed crystal faces and oxygen vacancy concentration of cerium oxide. Among them, rod-shaped cerium oxide preferentially exposes the (110) and (100) high-energy crystal faces, which have the highest oxygen vacancy concentration and the strongest metal-support interaction, promoting the reduction of Ru species to highly active Ru. 0 This improves the catalyst's activity in the amination of lauryl alcohol to produce n-dodecylamine and didodecylamine.

[0021] The beneficial effects of this invention are: (1) This invention provides two optional process routes for the preparation of dodecylamine by the reductive amination of lauryl alcohol: a batch reactor process and a fixed-bed continuous reaction process, which can be flexibly selected according to the production scale. Both processes use hydrogen as the hydrogen source and ammonia as the nitrogen source, with water as the only byproduct. They are highly atom-economical and environmentally friendly.

[0022] (2) Both processes of this invention use heterogeneous catalysts, which are easy to separate and recover, avoiding the problems of difficult separation and high cost of homogeneous catalysts. Compared with the traditional two-step fatty acid nitrification-hydrogenation method (high energy consumption and long process) and halohydrocarbon ammonolysis method (severe waste salt pollution), the process conditions of this invention are mild (200 ℃, 0.3~3.0 MPa), do not require high temperature and high pressure, have good safety, and low equipment investment.

[0023] (3) The catalyst preparation method provided by this invention is simple and the raw materials are readily available. The nitrogen-doped carbon nanotube support can be commercially available or prepared by simple pyrolysis; the cerium oxide nanorods are synthesized in one step by hydrothermal method without the need to add expensive template agents. Compared with traditional amination catalysts that require doping with multiple noble metals (such as Pt and Pd), the catalyst of this invention has a single active component (Ru only) and a low loading (1.5 wt%), high metal utilization efficiency, and the noble metals can be recycled, resulting in significant cost advantages.

[0024] The catalyst prepared in this invention exhibits advantages such as good dispersion of the active ruthenium component, small ruthenium particle size, low ruthenium agglomeration, and suitable interaction between ruthenium and the support. This allows the catalyst to achieve a lauryl alcohol conversion of 99%, a lauryl amine selectivity of up to 80%, and a total amine yield of up to 93.9% within a reaction temperature range of 150–300 °C. Furthermore, the catalyst preparation process is simple and low-cost. Its evaluation has been applied in both batch reactors and continuous phase fixed-bed reactors, demonstrating comprehensive research and a wide range of applications.

[0025] In summary, this invention achieves comprehensive advantages in the preparation of dodecylamine by the reductive amination of lauryl alcohol, including high conversion rate, high selectivity, high stability, low cost, and environmental friendliness, and has broad prospects for industrial application. Attached Figure Description

[0026] Figure 1 The X-ray diffraction (XRD) patterns of the two catalysts in Examples 1 and 7 show that no characteristic peaks of Ru metal were observed, indicating that Ru metal is highly dispersed.

[0027] Figure 2 The images show transmission electron microscopy (TEM) images of the nitrogen-doped carbon nanotube catalyst obtained in Example 1. In the images, 2a is the bright-field image of the Ru / NCNT catalyst, 2b is the dark-field image of the Ru / NCNT catalyst, 2c is the mapping image of N in the Ru / NCNT catalyst, and 2d is the mapping image of Ru in the Ru / NCNT catalyst. The TEM images show that ruthenium metal is well dispersed on the nitrogen-doped carbon nanotubes.

[0028] Figure 3 The images show TEM images of the rod-shaped cerium oxide-supported ruthenium catalyst in Example 7. 3a is a bright-field image of the Ru / CeO2-R catalyst, 3b is a dark-field image of the Ru / CeO2-R catalyst, 3c is a mapping image of Ce in the Ru / CeO2-R catalyst, and 3d is a mapping image of Ru in the Ru / CeO2-R catalyst. The TEM images show that ruthenium metal is well dispersed on the rod-shaped cerium oxide support.

[0029] Figure 4The N2 isotherm adsorption-desorption curves and pore size distribution diagrams of the two catalysts prepared in Examples 1 and 7 are shown, where 4a is the N2 isotherm adsorption-desorption curve of the catalyst. Figure 4 b is the pore size distribution diagram of the catalyst.

[0030] Figure 5 This is a stability evaluation graph for the Ru / NCNT catalyst in Example 6. The catalyst maintained good activity even after multiple uses, indicating good catalyst stability. Detailed Implementation

[0031] To better understand the above-mentioned objectives, features, and advantages of the present invention, the invention will be further described below with reference to embodiments. It should be noted that the embodiments are intended to explain the present invention, but the present invention is not limited to these embodiments.

[0032] The nitrogen-doped carbon nanotubes mentioned are known materials, such as the nitrogen-doped multi-walled carbon nanotubes (item number JCMT-98-40-20-N) from Nanjing Jicang Nanotechnology Co., Ltd.; but are not limited to this.

[0033] Example 1: 1 g of nitrogen-doped carbon nanotube support was dispersed in 20 ml of deionized water to obtain a support mixture. Separately, 0.0308 g (0.148 mmol) of anhydrous ruthenium trichloride was weighed and dissolved in 20 ml of deionized water, sonicated for 15 min to ensure uniform dissolution, and then added dropwise to the support mixture. The mixture was mechanically stirred and impregnated for 15 h. After impregnation, 0.0578 g (1.528 mmol) of sodium borohydride was weighed and dissolved in 20 ml of deionized water to obtain a reducing agent. Freshly prepared reducing agent was added dropwise to the stirred mixture, and mechanically stirred for reduction for 6 h. Finally, the mixture was filtered, washed five times with deionized water, and the resulting solid catalyst was dried in a vacuum drying oven at 60 °C for 12 h. After grinding, a Ru / NCNT catalyst with a mesh size of 60-80 mesh and a loading of 1.5 wt.% was obtained.

[0034] In a batch reactor, 0.41 g lauryl alcohol, 0.2 g of 60-80 mesh catalyst, and 20 g of tert-amyl alcohol were added to a 100 ml polytetrafluoroethylene liner. After sealing, the reactor was purged three times with nitrogen inert gas to displace the air. Then, 0.40 MPa ammonia and 0.30 MPa hydrogen were introduced, and the reactor was heated to 200 °C for 3 h at a rotation speed of 800 rpm. After the reaction, the temperature was rapidly reduced, and the reaction liquid was collected by filtration. The catalyst performance evaluation results are shown in Table 1.

[0035] Example 2: The reaction was basically the same as in Example 1, except that the reaction time was 12 h. The catalyst performance evaluation results are shown in Table 1.

[0036] Example 3: The reaction was essentially the same as in Example 1, except that the reaction temperature was 190 °C. The catalyst performance evaluation results are shown in Table 1.

[0037] Example 4: The reaction was essentially the same as in Example 1, except that the reaction temperature was 210 °C. The catalyst performance evaluation results are shown in Table 1.

[0038] Example 5: The reaction was basically the same as in Example 1, except that the reaction time was 13 h and the hydrogen partial pressure was adjusted to 0.50 MPa. The catalyst performance evaluation results are shown in Table 1.

[0039] Example 6: The reaction was essentially the same as in Example 1, except that the reaction time was 13 h and the hydrogen partial pressure was adjusted to 1.0 MPa. The catalyst performance evaluation results are shown in Table 1. After each reaction, the suspension was filtered and washed, repeatedly cleaned with solvent, and then the cleaned and dried catalyst was added to the reactor for a new round of reaction. This process was repeated four times. The catalyst stability results are as follows: Figure 5 As shown.

[0040] Example 7: First, 2.61 g (6.011 mmol) of cerium nitrate hexahydrate and 28.8 g (0.72 mol) of sodium hydroxide were dissolved in 20 mL and 100 mL of deionized water, respectively. After mixing the two solutions, the mixture was stirred at room temperature for 30 min to obtain a purple slurry. The slurry was transferred to a 150 mL stainless steel autoclave lined with polytetrafluoroethylene and hydrothermally treated at 100 °C for 24 h. After the reaction was completed, the precipitate was collected after being washed several times with deionized water and ethanol. The product was dried at 80 °C for 24 h and then calcined in a muffle furnace at 600 °C for 5 h to obtain a yellow powdery product, which is the nanorod-shaped cerium oxide (CeO2-R). The obtained nanorod-shaped cerium oxide support was dried at 80–120 °C for 10–48 h, and its saturated water absorption was determined to be 1.2 mL / g.

[0041] Ruthenium was loaded using an equal-volume impregnation method. 1 g of CeO2-R was weighed and placed in a beaker. 0.0308 g of anhydrous ruthenium trichloride was dissolved in 1.2 ml of deionized water and stirred until completely dissolved to obtain an impregnation solution. The impregnation solution was added dropwise to the CeO2-R powder until the powder surface was completely wetted. The powder was aged at room temperature for 12 hours, then dried in a forced-air drying oven at 80 °C for 12 hours. The dried solid was transferred to a tube furnace and calcined at 400 °C for 3 hours under a nitrogen atmosphere at a rate of 2 °C / min. After calcination, the atmosphere was switched to hydrogen (flow rate 30 mL / min), and the temperature was increased to 250 °C at a rate of 2 °C / min for 2 hours for reduction. After reduction, the powder was cooled to room temperature under a hydrogen atmosphere, then passivated for 40 minutes by introducing a 1% O2 / Ar mixed gas. After grinding, a catalyst with a mesh size of 60-80 mesh and a loading of 1.5 wt.% Ru / CeO2-R was obtained.

[0042] In a batch reactor, 0.41 g lauryl alcohol, 0.2 g of 60-80 mesh catalyst, and 20 g of tert-amyl alcohol were added to a 100 ml polytetrafluoroethylene liner. The reactor was purged three times with nitrogen inert gas to displace the air, and then purged with 0.40 MPa ammonia and 0.30 MPa hydrogen gas. The reactor was rotated at 800 rpm and heated to 200 °C for 3 h. After the reaction was completed, the temperature was rapidly reduced, and the reaction liquid was collected by filtration. The catalyst performance evaluation results are shown in Table 1.

[0043] Example 8: The reaction was basically the same as in Example 7, except that the catalyst loading was 0.05 g and the reaction time was 1 h. The catalyst performance evaluation results are shown in Table 1.

[0044] Example 9: The reaction was basically the same as in Example 7, except that the reaction time was 2 hours. The catalyst performance evaluation results are shown in Table 1.

[0045] Example 10: The process is basically the same as in Example 7, except that the catalyst particle size is 40-60 mesh. Furthermore, unlike Example 7 where lauryl alcohol amination is carried out in a batch reactor, Example 10 differs in that the amination of n-dodecylamine and didodecylamine is performed in a fixed-bed reactor. The specific process flow and parameters are as follows: In a fixed-bed reactor, 0.5 g of 40-60 mesh catalyst particles were placed in the isothermal section of the reactor. The bed was filled with 20-40 mesh quartz sand, and the two ends of the bed were fixed with quartz wool. The reactor feed pipe was insulated with a heating jacket, and a heat tracing cable was wrapped around the reaction pipe to the feed inlet to ensure stable material temperature. After loading, the airtightness of the reaction system was checked, and the air inside the reactor was replaced with inert gas to eliminate potential safety hazards. Before the reaction, the catalyst was reduced in situ: hydrogen was introduced at a flow rate of 30 ml / min, and the temperature was raised to 250 °C at a heating rate of 2 °C / min and held for 2 h. After reduction, the temperature was lowered to the target reaction temperature, and the system pressure was raised to the set value. Subsequently, liquid feedstock and liquid ammonia were vaporized and introduced into the reactor through a feed pump. The reaction was carried out under set conditions, and the products were collected periodically for analysis of catalyst activity and selectivity. The following examples are all the same.

[0046] The system pressure was 3.0 MPa, the molar ratio of ammonia:hydrogen:ethanol was 30:10:1, and the mass hourly space velocity was 3 h⁻¹. -1 The amination of lauryl alcohol was carried out at a reaction temperature of 200℃. The catalyst performance evaluation results are shown in Table 1.

[0047] All samples for evaluation were quantitatively analyzed using a gas chromatograph (GC-3240A) manufactured by Beijing Beifen Ruili Analytical Instrument Co., Ltd. The gas chromatograph used a flame ionization detector and a KB-5-amine column manufactured by Beijing Keruimai Technology Co., Ltd. with dimensions of 30 m × 0.32 mm × 1.00 μm.

[0048] To ensure the accuracy of the analytical results, the conversion and selectivity of the amination reaction were calculated using the internal standard method. Tridecane was used as the internal standard, and tert-amyl alcohol was used as the solvent. The correction factor ki was determined by preparing standard samples of lauryl alcohol, n-dodecylamine, dodecylonitrile, didodecylamine, undecane, and dodecane. The lauryl alcohol conversion C, the selectivity Si of each product, and the yield Yi were calculated using the following formulas: (1-1) % (1-2) (1-3) (1-4) in, The relative correction factors for each product and reactant are: This refers to the amount of internal standard added to the sample. The peak areas of each product and reactant in gas chromatography are given. The peak area of ​​the internal standard. (1-Dodecanol represents lauryl alcohol) is the amount of lauryl alcohol added. This refers to the amount of lauryl alcohol produced. The product represents the amount of each product. Where i represents undecane, dodecane, n-dodecylamine, dodecanoic acid, and didodecylamine. The correction factors using tridecane as an internal standard are as follows: lauryl alcohol: 1.1928; n-dodecylamine: 1.4164; didodecylamine: 0.9736; dodecanoic acid: 1.1605; undecane: 1.1992; dodecane: 1.4164.

[0049] Example 11: It is basically the same as Example 10, except that the mass hourly space velocity is 4 h. -1 The catalyst performance evaluation results are shown in Table 1.

[0050] Example 12: The reaction was essentially the same as in Example 10, except that the reaction temperature was 210 °C. The catalyst performance evaluation results are shown in Table 1.

[0051] Table 1 Evaluation results of the catalyst used in the lauryl alcohol amination reaction

[0052] The present invention has been described in detail above with specific embodiments. Obviously, the described examples are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Matters not covered in this invention are common knowledge.

Claims

1. A method for synthesizing higher fatty amines by amination of fatty alcohols, characterized in that, This method can be any one of the following two methods: Method 1 includes the following steps: In a high-pressure batch reactor, fatty alcohol, nitrogen-doped carbon nanotube supported ruthenium catalyst or rod-shaped cerium oxide supported ruthenium catalyst and organic solvent are added. After being replaced with an inert gas, ammonia and hydrogen are introduced, and the temperature is raised to the reaction temperature to carry out a reduction amination reaction to obtain n-dodecylamine and didodecylamine. The reaction temperature is 160~250 ℃, the hydrogen pressure is 0.2~1.0 MPa, the ammonia pressure is 0.2~0.8 MPa, and the reaction time is 3~24 hours; the catalyst mass is 20~80% of the fatty alcohol mass. Alternatively, Method 2 includes the following steps: In a fixed-bed reactor, a mixture of a certain concentration of fatty alcohol organic solvent solution, ammonia, and hydrogen is introduced into a fixed-bed reactor loaded with nitrogen-doped carbon nanotube supported ruthenium catalyst or rod-shaped cerium oxide supported ruthenium catalyst, and a reductive amination reaction is carried out at 160~250 °C to obtain n-dodecylamine and didodecylamine. The molar ratio of ammonia to fatty alcohol is 20-40:1, the molar ratio of hydrogen to fatty alcohol is 5-40:1, the mass space velocity is 2-12 h -1 , and the reaction system pressure is 1-4 MPa. In both methods, the organic solvent is tert-amyl alcohol or n-decane, and the mass ratio of the solvent to the fatty alcohol is 0.2~80:

1.

2. The method for synthesizing higher fatty amines by amination of fatty alcohols as described in claim 1, characterized in that, The fatty alcohol mentioned is lauryl alcohol, n-decyl alcohol, or n-tetradecyl alcohol.

3. The method for synthesizing higher fatty amines by amination of fatty alcohols as described in claim 1, characterized in that, The nitrogen-doped carbon nanotube supported ruthenium catalyst or rod-shaped cerium oxide supported ruthenium catalyst is composed of an active component and a support; wherein the active component is Ru metal with a loading of 0.5~2 wt%; the support is nitrogen-doped carbon nanotubes or rod-shaped cerium oxide, wherein the nitrogen doping amount of the nitrogen-doped carbon nanotubes is 2~10 at%; and the catalyst has a mesh size of 10-160 mesh.

4. The method for synthesizing higher fatty amines by amination of fatty alcohols as described in claim 1, characterized in that, The catalyst has a mesh size of 20-80.

5. The method for synthesizing higher fatty amines by amination of fatty alcohols as described in claim 1, characterized in that, In Method 1, the reaction temperature is 170~220 ℃; the hydrogen pressure is 0.3~0.6 MPa and the ammonia pressure is 0.4~0.6 MPa; the reaction time is 8~15 hours; the catalyst mass is 40~60% of the fatty alcohol mass; and the solvent to fatty alcohol mass ratio is 0.2~10:

1.

6. The method for synthesizing higher fatty amines by amination of fatty alcohols as described in claim 1, characterized in that, In Method 2, the reaction temperature is 190–210 °C, the ammonia:ethanol molar ratio is 20–30, the hydrogen:ethanol molar ratio is 5–15, and the mass hourly space velocity (HHSV) is 3–6 h⁻¹. -1 The system pressure is 2~3 MPa; the mass ratio of solvent to lauryl alcohol is 40~60:

1.

7. The method for synthesizing higher fatty amines by amination of fatty alcohols as described in claim 1, characterized in that, The preparation method of the nitrogen-doped carbon nanotube supported ruthenium catalyst includes the following steps: (1) Disperse nitrogen-doped carbon nanotube carriers in deionized water and sonicate for 10-60 minutes to obtain a carrier dispersion; 0.2~2.0g of nitrogen-doped carbon nanotubes are added to every 20 ml of deionized water; (2) Dissolve anhydrous ruthenium trichloride in deionized water to prepare an impregnation solution, add it dropwise to the carrier dispersion, and stir mechanically for 5 to 24 hours; add 0.01 to 0.05 g of ruthenium trichloride for every 1 g of nitrogen-doped carbon nanotubes; (3) Dissolve sodium borohydride in deionized water and slowly add it dropwise to the above mixture, and continue stirring for 2 to 16 hours; wherein the molar ratio of sodium borohydride to ruthenium is 1:1 to 40:1; (4) Filter and wash until neutral, dry under vacuum at 40~120 ℃ for 10~48 hours, and grind to obtain catalyst.

8. The method for synthesizing higher fatty amines by amination of fatty alcohols as described in claim 7, characterized in that, The molar ratio of reducing agent to ruthenium is 5~20:1, the mechanical stirring time is 10~18 hours, the reduction time is 4~8 hours, the drying temperature is 60~80 ℃, and the drying time is 12~24 hours.

9. The method for synthesizing higher fatty amines by amination of fatty alcohols as described in claim 1, characterized in that, The preparation method of the rod-shaped cerium oxide supported ruthenium catalyst includes the following steps: (1) Dissolve the cerium precursor in deionized water, add morphology modifier, stir and mix evenly, then transfer to a hydrothermal reactor and hydrothermally treat at 80~180 ℃ for 12~48 hours. After cooling, centrifuge to separate the precipitate, wash with deionized water and ethanol until neutral, dry at 80~120 ℃ for 10~48 hours, and then calcine at 400~700 ℃ for 2~6 hours to obtain nanorod-shaped cerium oxide support; The morphology modifier is one or a mixture of sodium hydroxide, urea and ammonium carbonate, and the molar ratio of cerium precursor to morphology modifier is 1:1 to 1:

100. 0.2-1.0g of cerium precursor was added to every 20 ml of deionized water; (2) The nanorod-shaped cerium oxide support obtained in step (1) is dried at 80~120 °C for 10~48 hours, and its saturated water absorption is measured; (3) Dissolve the ruthenium precursor in deionized water to prepare an impregnation solution. The volume of the impregnation solution is equal to the saturated water absorption of the carrier. Add the impregnation solution drop by drop to the carrier while stirring until the surface of the carrier is completely wetted. The ruthenium precursor is anhydrous ruthenium trichloride; the concentration of ruthenium in the impregnation solution is calculated based on the target loading, and the ruthenium loading is 0.5~2 wt%; (4) The impregnated catalyst is aged at room temperature for 6 to 48 hours, and then dried at 80 to 120 °C for 10 to 48 hours; (5) The dried catalyst is calcined in a nitrogen or air atmosphere at a temperature of 400-800 °C, a heating rate of 2-10 °C / min, and a calcination time of 2-8 hours. (6) The calcined catalyst is reduced under a hydrogen atmosphere at a temperature of 200-350 °C, a heating rate of 2-10 °C / min, a reduction time of 2-5 hours, and a hydrogen flow rate of 20-50 mL / min. After the reduction is completed, the temperature is lowered to room temperature and a 1% O2 / Ar mixed gas is introduced for passivation for 30-60 minutes to obtain a rod-shaped cerium oxide supported ruthenium catalyst.

10. The method for synthesizing higher fatty amines by amination of fatty alcohols as described in claim 9, characterized in that, In step (1), the morphology modifier is one or both of sodium hydroxide and urea, and the molar ratio of cerium precursor to morphology modifier is 1:5~1:50; in step (4), the aging time is 8~20 hours; in step (4), the calcination temperature is 550~650℃, and the calcination time is 3~6 hours.

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