Synthesis method of N-cyclohexylaniline

Abstract

According to the synthesis method of N-cyclohexylaniline provided by the invention, aniline and a cyclohexyl derivative are taken as raw materials and are introduced into a reactor filled with a copper-based catalyst, so that the aniline and the cyclohexyl derivative are subjected to a condensation reaction under the conditions of 0-0.2 MPa and 200-260 DEG C, and the target product N-cyclohexylaniline is obtained through conversion. According to the synthetic method, the yield of the N-cyclohexylaniline is greater than 68% in terms of aniline. The synthesis method is high in selectivity and few in side reaction, the copper-based catalyst is not prone to inactivation, the copper-based catalyst can be continuously used after being regenerated for multiple times, and continuous production of N-cyclohexylaniline is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of organic synthesis, and in particular to a method for synthesizing N-cyclohexylaniline. Background Art

[0002] N-Cyclohexylaniline, as an organic amine compound with both aromatic and alicyclic structures, has unique application potential in the field of fine chemicals.

[0003] Currently available N-cyclohexylaniline synthesis technologies mainly focus on specific functional group conversion reactions. For example, diaryl ether compounds (such as phenylcyclohexyl ether) are used as substrates to achieve the synthesis of N-cyclohexylaniline compounds.

[0004] Although relevant patented technologies have verified the feasibility of synthesizing N-cyclohexylaniline, its industrial application still faces problems such as high costs for solvent recovery and waste treatment, and insufficient reaction selectivity. Summary of the Invention

[0005] In response to the problems existing in the background technology, the present application provides a method for synthesizing N-cyclohexylaniline, wherein aniline and a cyclohexyl derivative are introduced as raw materials into a reactor filled with a copper-based catalyst, and the aniline and the cyclohexyl derivative undergo a condensation reaction under the conditions of 0-0.2 MPa and 200°C-260°C to convert them into the target product N-cyclohexylaniline; a non-precious metal copper-based catalyst is used as the reaction catalyst, the catalyst preparation process is mature, the price is low, the catalytic reaction occurs at a relatively low temperature, and the yield of the target product is high.

[0006] The specific content of the invention is as follows:

[0007] The present application provides a method for synthesizing N-cyclohexylaniline, which specifically comprises the following steps:

[0008] Aniline and a cyclohexyl derivative are introduced as raw materials into a reactor filled with a copper-based catalyst, and the aniline and the cyclohexyl derivative undergo a condensation reaction under the conditions of 0-0.2 MPa and 200-260° C. to convert them into the target product N-cyclohexylaniline;

[0009] The cyclohexyl derivative is selected from one of cyclohexylamine, cyclohexanone and cyclohexanol; the molar ratio of the aniline to the cyclohexyl derivative is 1:0.4 to 1:2.

[0010] Optionally, the feed liquid space velocity of the raw material is 0.2 to 1.0 h -1 .

[0011] Optionally, water and hydrogen are introduced into the reactor so that the condensation reaction is carried out in an environment containing water vapor and hydrogen;

[0012] The feed space velocity of hydrogen is 25~300h -1 ; The water feed space velocity is 0.01~0.33h -1 .

[0013] Optionally, the aniline, the cyclohexyl derivative, the water, and the hydrogen are preheated in a preheater and then introduced into the reactor for reaction;

[0014] The preheating temperature is 190-220°C.

[0015] Optionally, the copper-based catalyst comprises a carrier, CuO and a promoter metal, the carrier being selected from one or more of Al2O3, SiO2, and carbon black, and the promoter metal being selected from one or more of Ce2O3, CeO2, MgO, CaO, MnO, Cr2O3, CrO3, and BaO.

[0016] Optionally, in the copper-based catalyst, the mass fraction of the carrier is 25wt% to 60wt%, the mass fraction of the Cu element is 20wt% to 50wt%, and the mass fraction of the metal in the auxiliary metal is 20wt% to 25wt%.

[0017] Optionally, before introducing aniline and cyclohexyl derivatives as raw materials into a reactor filled with a copper-based catalyst, the method further comprises: activating the copper-based catalyst, comprising:

[0018] A mixed gas of H2 and N2 is introduced into the reactor and activated at 100°C to 300°C for 1h to 50h.

[0019] Optionally, the volume proportion of hydrogen in the mixed gas is 1% to 20%, and the feed space velocity of the mixed gas is 100h -1 ~1000h -1 .

[0020] Optionally, when the copper-based catalyst is deactivated or its activity decreases, a regeneration gas is introduced into the reactor to perform in-situ regeneration treatment on the copper-based catalyst;

[0021] The feed space velocity of the regeneration gas is 50h -1 ~1000h -1 ;

[0022] The regeneration gas is air, or nitrogen containing oxygen, wherein the volume proportion of oxygen in the nitrogen containing oxygen is 20% to 50%;

[0023] The temperature of the regeneration treatment is 200° C. to 400° C., the heating rate is 10° C. / h to 20° C. / h, and the treatment time is 2h to 20h.

[0024] Optionally, based on aniline, the yield of the N-cyclohexylaniline is greater than or equal to 68%.

[0025] Compared with the existing technology, this application has the following advantages:

[0026] The present application provides a method for synthesizing N-cyclohexylaniline. First, aniline and cyclohexyl derivatives are used as raw materials. Both are readily available and inexpensive, resulting in low production costs and little waste causing environmental pollution during the reaction. Second, a non-precious metal copper-based catalyst is used as a reaction catalyst. The catalyst preparation process is mature and inexpensive. Catalysis occurs at a relatively low temperature, resulting in a high yield of the target product. The yield of N-cyclohexylaniline, calculated as aniline, is greater than or equal to 68%. In a reactor containing the copper-based catalyst, a condensation reaction occurs between aniline and the cyclohexyl derivative under conditions of 0-0.2 MPa and 200° C.-260° C. The copper-based catalyst is not easily deactivated and can be regenerated multiple times for continuous use. Thus, using the copper-based catalyst and the reactor, the synthesis method exhibits the advantages of high selectivity, simple by-products, continuous production, high production efficiency, and long-term stable output. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 A schematic diagram of the synthesis system of N-cyclohexylaniline provided in the examples of the present application is shown;

[0029] Figure 2 A schematic diagram of a synthesis system of N-cyclohexylaniline provided in another embodiment of the present application is shown;

[0030] Figure 3 The composition characterization diagram of the product obtained by the synthesis method provided in Example 1 of the present application is shown;

[0031] Figure 4 The composition characterization diagram of the product obtained by the synthesis method provided in Example 2 of the present application is shown;

[0032] Figure 5 The composition characterization diagram of the product obtained by the synthesis method provided in Example 3 of the present application is shown;

[0033] Figure 6 The gas chromatographic analysis diagram of the product provided in the examples of the present application is shown.

[0034] Reference numerals:

[0035] 1-Mixer, 2-Preheater, 3-Reactor, 4-Separator, 5-Product tank, 6-Ammonia adsorption tank, 7-Plunger pump. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its application or use. Based on the embodiments in the present application, any product that is identical or similar to the present application and is derived by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts falls within the scope of protection of the present application. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work fall within the scope of protection of the present application.

[0037] Where specific experimental steps or conditions are not specified in the examples, the conventional experimental steps or conditions described in the prior art in this field may be used. The reagents and other instruments used, for which the manufacturer is not specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely schematic illustrations of the embodiments of the present application and are not necessarily drawn to scale. Identical reference numerals in the figures represent identical or similar parts, and their repeated descriptions will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0038] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the description of this application.

[0039] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0040] N-Cyclohexylaniline, an organic amine compound with both aromatic and alicyclic structures, has unique application potential in the field of fine chemicals. The bicyclic skeleton in its molecular structure confers excellent chemical stability and reactivity, making it a key raw material for the preparation of pharmaceutical intermediates (such as precursors for the synthesis of targeted drugs), pesticide intermediates (such as new herbicide synergists), and polymer material additives (such as high-performance resin curing agents). Although the market size of this compound is limited by the demand of specific downstream fields, its properties as a high-value-added fine chemical intermediate make the development of efficient synthesis methods of great industrial value. It is worth noting that in the mainstream industrial process of cyclohexylamine preparation by catalytic hydrogenation of aniline, N-cyclohexylaniline is only produced as a trace by-product, making it difficult to achieve large-scale production through by-product recovery. At present, there is still a lack of systematic research on the dedicated industrial synthesis method for this compound, and there is an urgent need to break through the existing technical bottleneck.

[0041] Currently disclosed N-cyclohexylaniline synthesis technologies mainly focus on specific functional group conversion reactions. For example, Dutch patent NL6410986 proposes using a nitrohalogenated benzene compound (such as p-nitrochlorobenzene) as a starting material, catalytically reducing it with hydrogen in the presence of a solvent (such as methanol or ethanol), and then simultaneously reducing the nitro group and the haloalkyl group by regulating the reaction temperature, pressure, and catalyst parameters (such as palladium carbon or Raney nickel) to generate a mixed product containing N-cyclohexylaniline, and finally separating the target product by distillation or column chromatography. Chinese patent CN109053463B uses a diaryl ether compound (such as phenylcyclohexyl ether) as a substrate, introduces a reducing agent (such as sodium borohydride or zinc powder) into an ammonia system, and realizes the synthesis of N-cyclohexylaniline compounds through a series process of ether bond cleavage and amination reaction. The above method is based on the reductive amination of nitro compounds and the aminolysis reaction of ether compounds, respectively, and provides a differentiated technical route for the synthesis of N-cyclohexylaniline.

[0042] Although the relevant patent technology has verified the feasibility of the synthesis of N-cyclohexylaniline, it still has significant deficiencies in its industrial application. First, the nitrohalobenzene raw materials relied on by the relevant methods are toxic and the synthesis steps are cumbersome. The hydrogen halide by-products generated during the reaction are easy to corrode the equipment. At the same time, the separation of the mixed products requires a large amount of solvent, resulting in low atom economy and high environmental pressure. Or the diaryl ether compound raw materials used in the relevant methods are relatively expensive, and the large-scale use of reducing agents increases the process safety risk. The reaction conditions (such as strong alkalinity or high temperature) have harsh requirements on the equipment, making it difficult to achieve continuous production. In addition, none of the above methods solve the following core problems:

[0043] (1) Lack of green solvent system, high cost of solvent recovery and waste disposal;

[0044] (2) Insufficient reaction selectivity, resulting in low yield of target product (usually less than 60%) due to the formation of by-products;

[0045] (3) The operating procedures are complex and it is difficult to meet the industrialization requirements for “convenience” and “efficiency”.

[0046] Therefore, there is an urgent need to develop a green chemistry-oriented method for synthesizing N-cyclohexylaniline with readily available raw materials, mild reaction conditions, simple separation, and high atom economy.

[0047] In view of the problems of low process selectivity and complex by-products in the production of N-cyclohexylaniline in the related art, the present application provides a method for synthesizing N-cyclohexylaniline, which specifically comprises the following steps:

[0048] Aniline and a cyclohexyl derivative are introduced as raw materials into a reactor filled with a copper-based catalyst, and the aniline and the cyclohexyl derivative undergo a condensation reaction under the conditions of 0-0.2 MPa and 200-260° C. to convert them into the target product N-cyclohexylaniline;

[0049] The cyclohexyl derivative is selected from one of cyclohexylamine, cyclohexanone and cyclohexanol; the molar ratio of the aniline to the cyclohexyl derivative is 1:0.4 to 1:2.

[0050] It should be noted that the above-mentioned reactor is a fixed bed reactor, and the embodiments of the present application are demonstrated using a fixed bed reactor as an example.

[0051] It should be noted that aniline and cyclohexylamine undergo a deamination condensation reaction under the conditions of a copper-based catalyst, 0-0.2 MPa, and 200°C-260°C to produce N-cyclohexylaniline; aniline and cyclohexanone undergo a dehydration condensation reaction under the conditions of a copper-based catalyst, 0-0.2 MPa, and 200°C-260°C to produce N-cyclohexylaniline; aniline and cyclohexanol undergo a dehydration condensation reaction under the conditions of a copper-based catalyst, 0-0.2 MPa, and 200°C-260°C to produce N-cyclohexylaniline.

[0052] It should be noted that the pressure of the condensation reaction between aniline and the cyclohexyl derivative is 0 to 0.2 MPa. For example, the reaction pressure can be in the range of one or any two of 0 MPa, 0.01 MPa, 0.03 MPa, 0.05 MPa, 0.08 MPa, 0.10 MPa, 0.12 MPa, 0.15 MPa, 0.17 MPa, and 0.20 MPa. When the reaction pressure is 0 MPa, the catalyst is in a state of normal pressure in the reactor to carry out the catalytic reaction. By controlling the pressure of the condensation reaction between aniline and the cyclohexyl derivative to 0 to 0.2 MPa, the efficiency of the condensation reaction is improved, which is beneficial to balancing the selectivity and yield of N-cyclohexylaniline, while avoiding catalyst deactivation and maintaining the catalyst stability.

[0053] It should be noted that the condensation reaction temperature of aniline and the cyclohexyl derivative is 200-260° C. For example, the reaction temperature may be in the range of one or any two of 200° C., 210° C., 220° C., 230° C., 240° C., 250° C., and 260° C. By controlling the condensation reaction temperature of aniline and the cyclohexyl derivative to be 200-260° C., the condensation reaction of aniline and the cyclohexyl derivative is facilitated to proceed toward the main reaction of condensing to form N-cyclohexylaniline, effectively avoiding side reactions and achieving higher selectivity.

[0054] It should be noted that the molar ratio of aniline to the cyclohexyl derivative is 1:0.4 to 1:2. For example, the molar ratio can be in the range of one or any two of 1:0.4, 1:0.5:1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.7, and 1:2. Controlling the molar ratio of aniline to the cyclohexyl derivative within the range of 1:0.4 to 1:2 can improve the selectivity of the condensation reaction to produce N-cyclohexylaniline, suppress side reactions, and improve raw material utilization.

[0055] In this embodiment, first, aniline and cyclohexyl derivatives are used as raw materials. Both are easily available and inexpensive, with low production costs and less waste causing environmental pollution during the reaction process. Secondly, a non-precious metal copper-based catalyst is used as the reaction catalyst. The catalyst preparation process is mature, the price is low, catalysis occurs at a lower temperature, and the yield of the target product is high. Calculated on the basis of aniline, the yield of N-cyclohexylaniline is greater than or equal to 68%. In the reactor of the copper-based catalyst, the molar ratio of aniline and cyclohexyl derivative is controlled at 1:0.4 to 1:2, and a condensation reaction occurs under the conditions of 0 to 0.2 MPa and 200° C. to 260° C. The copper-based catalyst is not easily deactivated and can be continuously used after multiple regenerations. Thus, using a copper-based catalyst and a reactor, the synthesis method exhibits the advantages of high selectivity, simple by-products, continuous production, high production efficiency, and long-term stable output.

[0056] In some embodiments, the feed liquid space velocity of the raw material is 0.2 to 1.0 h -1 .

[0057] It should be noted that the feed liquid space velocity of aniline and cyclohexyl derivative raw materials is 0.2~1.0h -1 For example, the feed liquid space velocity of the raw material can be 0.2h -1 , 0.3h -1 , 0.4h -1 , 0.5h -1 , 0.8h -1 , 1.0h -1 The range of values ​​for one or both of .

[0058] In this embodiment, the feed liquid space velocity of aniline and cyclohexyl derivative raw materials is controlled at 0.2~1.0h -1 , that is, controlling the residence time of aniline and cyclohexyl derivative raw materials on the surface of the copper-based catalyst, helps to maximize the yield and selectivity of N-cyclohexylaniline, improve the conversion rate of aniline, and inhibit side reactions; extend the service life of the copper-based catalyst, reduce the risk of carbon deposition and sintering; optimize the economy of reactor operation, reduce energy consumption, and provide support for continuous production.

[0059] In some embodiments, water and hydrogen are introduced into the reactor so that the condensation reaction is carried out in an environment containing water vapor and hydrogen;

[0060] The feed space velocity of hydrogen is 25~300h -1 ; The water feed space velocity is 0.01~0.33h -1 .

[0061] It should be noted that hydrogen is introduced into the reactor at a specific flow rate, carrying the raw materials with it to carry out the catalytic reaction. The gaseous raw materials react on the solid copper-based catalyst bed. After the reaction is completed, the reaction products are condensed in a separator (condenser) and converted from a gaseous state to a partially liquid product. The liquid product flows into a product tank, and the gas can be returned to the hydrogen inlet pipeline for recycling.

[0062] It should be noted that the feed space velocity of hydrogen is 25 to 300 h -1 For example, the feed space velocity of hydrogen can be 25h -1 , 30h -1 40h -1 , 50h -1 , 80h -1 、100h -1 , 150h -1 , 200h -1 , 250h -1 , 300h-1 For example, when the feed space velocity of hydrogen is less than 25h -1 The catalyst may gradually deactivate, resulting in a decrease in conversion rate; the copper-based catalyst needs to exist in the form of low-reduction copper in the reaction, and its active site is sensitive to the reducing environment. When the feed space velocity of hydrogen is maintained at 25-300h -1 The appropriate space velocity can create a reducing atmosphere, continuously reduce copper species that may be oxidized, ensure the stability of catalyst activity, and at the same time, the copper-based catalyst inhibits the formation of carbon deposits and improves the selectivity of N-cyclohexylaniline.

[0063] It should be noted that the feed space velocity of water is 0.01~0.33h -1 For example, the feed space velocity of water can be 0.01h -1 , 0.02h -1 , 0.03h -1 , 0.05h -1 , 0.08h -1 , 0.10h -1 , 0.15h -1 , 0.20h -1 , 0.25h -1 , 0.30h -1 , 0.33h -1 The condensation reaction between aniline and cyclohexyl derivatives is an exothermic reaction, and local overheating can easily trigger side reactions (such as carbon deposition and polymerization). When water is introduced, the water evaporates into water vapor, which absorbs heat. This effectively reduces the peak reaction temperature, prevents catalyst sintering or deactivation due to high temperatures, and protects the catalyst. Simultaneously, the water vapor flushes the catalyst surface, reducing the adsorption residence time of carbon deposit precursors. Furthermore, the water vapor reacts with carbon deposits to form a water-gas reaction, directly removing some of the carbon deposits and extending the catalyst life.

[0064] In this embodiment, water and hydrogen are introduced into the reactor so that the condensation reaction is carried out in an environment containing water vapor and hydrogen; water and hydrogen do not participate in the condensation reaction of aniline and cyclohexyl derivative to form N-cyclohexylaniline, and the feed space velocity of hydrogen is controlled at 25 to 200 h / min. -1 ; The water feed space velocity is controlled at 0~0.33h -1 , which is beneficial to protecting the catalyst, maintaining the copper-based catalyst in a reduced state through hydrogen, and inhibiting carbon deposition and overheating deactivation of the copper-based catalyst through water; thereby balancing the conversion rate and selectivity; the simultaneous introduction of water and hydrogen can avoid the risks caused by local overheating or accumulation of by-products.

[0065] In some embodiments, the aniline, the cyclohexyl derivative, the water, and the hydrogen are preheated in a preheater and then introduced into the reactor for reaction;

[0066] The preheating temperature is 190-220°C.

[0067] It should be noted that the preheating temperature is 190-220°C. For example, the preheating temperature in the preheater can be in the range of one or any two of 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, and 220°C.

[0068] It should be noted that the preheating temperature of the preheater is a key parameter to ensure efficient and stable reaction. The raw materials of aniline and cyclohexyl derivatives are liquids, and the temperature is low at room temperature. The cold liquid has a greater impact on the copper-based catalyst. The liquid raw materials may condense on the catalyst surface, dilute the reactant concentration around the active site, and even cause the pores between the catalyst particles to be clogged. Therefore, before the reaction, the raw materials and other auxiliary substances (water, hydrogen) are preheated to become gas, so that the condensation reaction is carried out under gas-solid reaction conditions. When the raw materials are preheated to gas and preheated to close to the reaction temperature, the solid copper-based catalyst also reaches a certain temperature accordingly. The temperature difference is small, and the impact on the copper-based catalyst is small, which can protect the copper-based catalyst, make the condensation reaction more complete, the reaction effect is good, and extend the service life of the copper-based catalyst.

[0069] It should also be noted that the activity of copper-based catalysts is highly dependent on temperature. At low temperatures, the surface adsorption capacity and electron transfer efficiency of copper atoms are insufficient. The preheater heats aniline, cyclohexyl derivatives, water, and hydrogen to the activation temperature of the copper-based catalyst, 190-220°C, to form active adsorption centers on the copper surface, promoting the condensation reaction of aniline and cyclohexyl derivatives. In specific implementation, Figure 1 As shown, aniline (raw material 1) and cyclohexyl derivatives (raw material 2, applicable to cyclohexanone and cyclohexanol) are transported to the reaction mixer 1 by a plunger pump 7, and water and hydrogen are introduced into the mixer 1 for premixing at the same time. The mixed system is introduced into the preheater 2 and preheated to a certain temperature. The hydrogen entering the preheater 2 carries the vaporized aniline and cyclohexyl derivatives at a certain flow rate and enters the reactor 3 for catalytic reaction. The hydrogen flow rate is controlled by a mass flow meter and enters the preheater 2 through a one-way valve. Afterwards, the mixed gaseous raw materials react on the solid copper-based catalyst bed. The reaction product is condensed by the condenser and converted from a gaseous state to a partially liquid product. The gas can be returned to the hydrogen inlet pipeline for recycling, and the liquid product flows into the product tank 5 through the separator 4. As shown Figure 2 As shown, when aniline (raw material 1) and cyclohexyl derivative (raw material 2, applicable to cyclohexylamine) undergo deamination condensation, the process is the same as the above process, except that the ammonia generated by the condensation of aniline and cyclohexylamine can be adsorbed by the ammonia adsorption tank 6.

[0070] In this embodiment, the preheating temperature of the aniline, cyclohexyl derivative, water, and hydrogen is controlled at 190-220°C by a preheater. This is to create suitable starting conditions for the condensation reaction of aniline and the cyclohexyl derivative. Excessively low preheating temperatures slow the reaction rate, while excessively high preheating temperatures accelerate side reactions and may cause catalyst sintering due to overheating (copper particle agglomeration and reduction in active surface area). Controlling the preheating temperature at 190-220°C helps extend the catalyst's service life while balancing aniline conversion and N-cyclohexylaniline selectivity.

[0071] In some embodiments, the copper-based catalyst comprises a carrier, CuO and a promoter metal, wherein the carrier is selected from one or more of Al2O3, SiO2, and carbon black, and the promoter metal is selected from one or more of Ce2O3, CeO2, MgO, CaO, MnO, Cr2O3, CrO3, and BaO.

[0072] It should be noted that the support in copper-based catalysts can support the active components, regulate interfacial interactions, and optimize mass and heat transfer. In the examples of this application, the support is selected from one or more of Al2O3, SiO2, and carbon black to suppress deep side reactions and improve the selectivity of N-cyclohexylaniline in the condensation reaction of aniline and cyclohexyl derivatives.

[0073] It should be noted that the copper-based catalyst needs to be activated before use, and the copper oxide (active component) is reduced to low-reduction copper so that CuO can provide active sites for the condensation reaction of aniline and cyclohexyl derivatives.

[0074] It should be noted that the auxiliary metal in the copper-based catalyst is selected from one or more of Ce2O3, CeO2, MgO, CaO, MnO, Cr2O3, CrO3, and BaO, which can optimize the structure of the active component, regulate selectivity, and enhance resistance to deactivation. Specifically, Ce2O3 and CeO2 can inhibit copper sintering, promote dispersion, and increase the density of active sites. At the same time, Ce2O3 and CeO2 have oxygen storage and release capabilities, can oxidize surface carbon to CO or CO2, reduce carbon accumulation, extend catalyst life, and improve selectivity for N-cyclohexylaniline; MgO and CaO can neutralize acidic sites on the support surface, improving selectivity; MnO, Cr2O3, and CrO3 can both improve copper dispersion and accelerate electron transfer, thereby increasing reaction rate.

[0075] In this embodiment, the copper-based catalyst, the support, copper oxide (active component), and promoter metal work synergistically to determine the catalyst's activity, selectivity, and stability. When the support is selected from one or more of Al2O3, SiO2, and carbon black; and the promoter metal is selected from one or more of Ce2O3, CeO2, MgO, CaO, MnO, Cr2O3, CrO3, and BaO, along with the copper oxide active component, the copper-based catalyst achieves high activity, high selectivity, and long life in the condensation reaction of aniline and cyclohexyl derivatives.

[0076] In some embodiments, in the copper-based catalyst, the mass fraction of the carrier is 25wt% to 60wt%, the mass fraction of Cu element is 20wt% to 50wt%, and the mass fraction of the metal in the auxiliary metal is 20wt% to 25wt%.

[0077] It should be noted that in the copper-based catalyst, the weight percentage of the carrier is 25wt% to 60wt%. For example, the weight percentage of the carrier can be in the range of one or any two of 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, and 60wt%. The weight percentage of the carrier is controlled within the range of 25wt% to 60wt% to optimize the specific surface area, pore volume, and chemical interactions of the carrier, while balancing dispersibility and mass transfer efficiency.

[0078] It should be noted that the Cu content of the copper-based catalyst is 20 wt% to 50 wt%. For example, the Cu content can be in the range of 20 wt%, 25 wt%, 30 wt%, 40 wt%, or 50 wt%, or any two of these. Controlling the Cu content between 20 wt% and 50 wt% balances the active site density and sintering resistance, achieving optimal activity and stability for the copper-based catalyst.

[0079] It should be noted that in the copper-based catalyst, the weight percentage of the metal in the promoter metal is 20wt% to 25wt%. For example, the weight percentage of the metal in the promoter metal can be in the range of one or any two of 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, and 25wt%. The weight percentage of the metal in the promoter metal is 20wt% to 25wt%, which allows for precise control of the electronic structure, acidity and alkalinity, or resistance to deactivation.

[0080] In this embodiment, by controlling the mass proportion of the carrier to 25wt% to 60wt%, the mass proportion of the Cu element to 20wt% to 50wt%, and the mass proportion of the metal in the auxiliary metal to 20wt% to 25wt%, the aniline conversion rate, the N-cyclohexylaniline selectivity, and the service life of the copper-based catalyst can be achieved to peak values.

[0081] In some embodiments, before introducing aniline and cyclohexyl derivatives as raw materials into a reactor filled with a copper-based catalyst, the method further comprises: activating the copper-based catalyst, comprising:

[0082] A mixed gas of H2 and N2 is introduced into the reactor and activated at 100°C to 300°C for 1h to 50h.

[0083] It should be noted that the activation temperature of the copper-based catalyst is 100°C to 300°C. For example, the activation temperature can be in the range of 100°C, 150°C, 200°C, 250°C, 300°C, or any two of them. The copper-based catalyst is usually in the form of copper oxide (CuO). By controlling the activation temperature at 100°C to 300°C, copper oxide can be converted into catalytically active metallic copper (Cu 0 ) or low-valent copper (such as Cu + ), increase the active surface area and improve stability to avoid sintering.

[0084] It should be noted that the activation treatment time for the copper-based catalyst is 1 to 50 hours. For example, the activation treatment time can be within the range of one or any two of 1 hour, 5 hours, 8 hours, 10 hours, 15 hours, 20 hours, 30 hours, 40 hours, and 50 hours. Controlling the activation time within 1 to 50 hours can ensure that the reduction reaction proceeds fully and promotes uniform reduction within the catalyst.

[0085] In this embodiment, by controlling the activation temperature of the copper-based catalyst within a range of 100°C to 300°C and the activation time within a range of 1 hour to 50 hours, the degree of copper reduction, particle size, and interaction with the carrier / additive can be regulated to optimize the activity, selectivity, and stability of the catalyst, thereby ensuring that the copper-based catalyst performs optimally in the condensation reaction of aniline and cyclohexyl derivatives while avoiding activity attenuation or shortened life.

[0086] In some embodiments, the volume proportion of hydrogen in the mixed gas is 1% to 20%, and the feed space velocity of the mixed gas is 100h -1 ~1000h -1 .

[0087] It should be noted that the volume proportion of hydrogen in the mixed gas is 1% to 20%. For example, the volume proportion of hydrogen can be one or any two of 1%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, and 20%.

[0088] It should be noted that the feed space velocity of the mixed gas is 100h -1 ~1000h -1 For example, the feed space velocity may be 100 h-1 , 200h -1 , 500h -1 , 700h -1 , 900h -1 、1000h -1 The range of values ​​for one or both of .

[0089] In this embodiment, nitrogen containing hydrogen is used for reduction. Hydrogen has high selectivity and strong reducing ability, which can effectively reduce the catalyst and increase its activity. At the same time, hydrogen is environmentally friendly and does not produce harmful by-products. However, pure hydrogen cannot be used for reduction. Catalyst reduction is a highly exothermic reaction. Excessive hydrogen concentration will release significant heat, and high temperature will affect the catalyst structure, affecting the catalyst activity and life. Therefore, the volume proportion of hydrogen in the mixed gas is controlled at 1% to 20%, and the feed space velocity is 100h -1 ~1000h -1 .

[0090] In some embodiments, when the copper-based catalyst is deactivated or its activity decreases, a regeneration gas is introduced into the reactor to perform in-situ regeneration of the copper-based catalyst;

[0091] The feed space velocity of the regeneration gas is 50h -1 ~1000h -1 ;

[0092] The regeneration gas is air, or nitrogen containing oxygen, wherein the volume proportion of oxygen in the nitrogen containing oxygen is 20% to 50%;

[0093] The temperature of the regeneration treatment is 200° C. to 400° C., the heating rate is 10° C. / h to 20° C. / h, and the treatment time is 2h to 20h.

[0094] It should be noted that the deactivation or reduced activity of the copper-based catalyst is achieved by monitoring the conversion rate of aniline. For example, when the reaction starts, the conversion rate of aniline is at a relatively high level. Based on this conversion rate, when the conversion rate decreases or significantly decreases, it can be determined that the activity of the copper-based catalyst is reduced or deactivated.

[0095] It should be noted that the feed space velocity of the regeneration gas is 50h -1 ~1000h -1 For example, the feed space velocity can be 50h -1 、100h -1 , 150h -1 , 200h -1 , 300h -1 , 500h -1 , 800h -1 、1000h -1The range of values ​​for one or both of .

[0096] It should be noted that the volume proportion of oxygen is 20% to 50%; for example, the volume proportion of oxygen can be one or any two of 20%, 25%, 30%, 35%, 40%, 50%, which can slow down the oxidation rate and avoid local overheating.

[0097] It should be noted that the regeneration temperature is 200°C to 400°C. For example, the regeneration temperature can be in the range of one or any two of 200°C, 220°C, 250°C, 280°C, 300°C, 330°C, 350°C, 370°C, and 400°C. During the reaction process, coke is easily deposited on the catalyst surface or other non-reactive substances are adsorbed, covering the active sites. A regeneration temperature of 200°C to 400°C can achieve oxidation and carbonization (air / oxygen) and hydrogen reduction to remove impurities and restore the active surface.

[0098] It should be noted that the heating rate is 10°C / h to 20°C / h. For example, it can be a range of one or any two of 10°C / h, 12°C / h, 14°C / h, 15°C / h, 17°C / h, 19°C / h, and 20°C / h to avoid local overheating causing "hot spots" and prevent copper particles from agglomerating due to thermal stress.

[0099] It should be noted that the processing time is 2 hours to 20 hours. For example, it can be a range of one or any two of 2 hours, 3 hours, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, and 20 hours to ensure complete combustion of carbon deposits.

[0100] In this embodiment, the regeneration and reduction treatment can restore the activity of the copper-based catalyst and extend its service life, so as to achieve the effect of continuously reacting and synthesizing N-cyclohexylaniline in the condensation reaction of aniline and cyclohexyl derivatives.

[0101] In some embodiments, the yield of N-cyclohexylaniline is greater than or equal to 68% based on aniline.

[0102] In this embodiment, the yield of N-cyclohexylaniline is greater than 68%, the product has high purity and good economic benefits.

[0103] In order to enable those skilled in the art to understand the present application more clearly, the synthesis method of N-cyclohexylaniline described in the present application is now described in detail through the following examples.

[0104] Example 1

[0105] (1) Activation of copper-based catalysts

[0106] A copper-based catalyst was prepared by using 45 wt% Al2O3 as a carrier, 30 wt% CuO as an active component, and 25 wt% Ce2O3 as an additive metal. The copper-based catalyst was loaded into a fixed bed reactor with a loading volume of 30 mL. A N2 mixed gas containing 5% H2 by volume was introduced at a feed space velocity of 200 h -1 , activated at 250°C for 12h.

[0107] (2) Synthesis of N-cyclohexylaniline

[0108] Aniline and cyclohexanol were transported to the reaction mixer with a plunger pump in a molar ratio of 1:1. The feed liquid space velocity of the above raw materials was 0.4h -1 , pump the water with a plunger pump at a rate of 0.05h -1 The air velocity of hydrogen is 50h -1 Aniline, cyclohexanol, water and hydrogen are transported to the preheater for preheating at a temperature of 200°C. The hydrogen entering the preheater is heated for 50 hours. -1 The flow rate entrains gaseous aniline and cyclohexanol into a reactor containing an activated copper-based catalyst. The mixed gas phase undergoes a dehydration condensation reaction in a solid catalyst bed at a reaction temperature of 230°C and a reaction pressure of 0.05 MPa to convert them into the target product, N-cyclohexylaniline.

[0109] The reaction products are condensed in a separator (condenser) and transformed from gaseous to partially liquid products. The liquid products flow into the product tank, and the gas can be returned to the hydrogen inlet pipeline for recycling.

[0110] Figure 3 The composition characterization diagram of the product obtained by the synthesis method provided in Example 1 of the present application is shown as follows: Figure 3 As shown, the synthetic product was characterized by gas chromatography-mass spectrometry (GC-MS). It can be seen from the GC-MS graph that the substance with a peak at 12.6 min is consistent with the standard spectrum of N-cyclohexylaniline, proving that the target product N-cyclohexylaniline was successfully prepared from aniline and cyclohexanol in this application.

[0111] Example 2

[0112] The difference between Example 2 and Example 1 is that:

[0113] The copper-based catalyst loading amount in the copper-based catalyst activation step (1) was adjusted to 20 mL;

[0114] The molar ratio of raw materials, aniline and cyclohexyl derivatives, reaction temperature, reaction pressure, feed liquid space velocity of raw materials, feed space velocity of hydrogen, feed space velocity of water, and preheating temperature in the synthesis step (2) of N-cyclohexylaniline were adjusted to 1:1.2 for aniline and cyclohexylamine, 240°C, 0.2 MPa, 0.3 h -1 、100h -1 , 0.1h -1 , 220℃.

[0115] The nitrogen generated by the condensation reaction is adsorbed by the nitrogen adsorption tank 6.

[0116] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0117] Figure 4 The composition characterization diagram of the product obtained by the synthesis method provided in Example 2 of the present application is shown as follows: Figure 4 As shown, the synthetic product was characterized by gas chromatography-mass spectrometry (GC-MS). It can be seen from the GC-MS graph that the substance with a peak at 12.5 min is consistent with the standard spectrum of N-cyclohexylaniline, proving that the target product N-cyclohexylaniline was successfully prepared from aniline and cyclohexylamine in this application.

[0118] Example 3

[0119] The difference between Example 3 and Example 1 is that:

[0120] The copper-based catalyst loading amount in the copper-based catalyst activation step (1) was adjusted to 40 mL;

[0121] The molar ratio of raw materials, aniline and cyclohexyl derivatives, reaction temperature, reaction pressure, feed liquid space velocity of raw materials, feed space velocity of hydrogen, feed space velocity of water, and preheating temperature in the synthesis step (2) of N-cyclohexylaniline were adjusted to 1:0.8 for aniline and cyclohexanone, 220°C, 0 MPa, 0.2 h -1 , 25h -1 、0h -1 , 200℃.

[0122] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0123] Figure 5 The composition characterization diagram of the product obtained by the synthesis method provided in Example 3 of the present application is shown as follows: Figure 5 As shown, the synthetic product was characterized by gas chromatography-mass spectrometry (GC-MS). It can be seen from the GC-MS graph that the substance with a peak at 12.4 min is consistent with the standard spectrum of N-cyclohexylaniline, proving that the target product N-cyclohexylaniline was successfully prepared from aniline and cyclohexanone in this application.

[0124] Example 4

[0125] The difference between Example 4 and Example 1 is that:

[0126] In the activation step of the copper-based catalyst (1), the mass proportions of the carrier, CuO, and the auxiliary metal are adjusted to 60 wt%, 20 wt%, and 20 wt%, respectively, and the auxiliary metal is adjusted to CeO2.

[0127] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0128] Example 5

[0129] The difference between Example 5 and Example 1 is that:

[0130] In the activation step of the copper-based catalyst (1), the mass proportions of the carrier, CuO, and the auxiliary metal are adjusted to 25 wt%, 50 wt%, and 25 wt%, respectively.

[0131] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0132] Example 6

[0133] The difference between Example 6 and Example 1 is:

[0134] In the activation step of the copper-based catalyst (1), the carrier and the auxiliary metal are adjusted to SiO2 and MgO, respectively.

[0135] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0136] Example 7

[0137] The difference between Example 7 and Example 1 is that:

[0138] In the activation step of the copper-based catalyst (1), the promoter metal is adjusted to: 15 wt% Ce2O3, 10 wt% CaO.

[0139] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0140] Example 8

[0141] The difference between Example 8 and Example 1 is that:

[0142] In the activation step of the copper-based catalyst (1), the promoter metal is adjusted to: 15 wt% Ce2O3, 10 wt% MnO.

[0143] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0144] Example 9

[0145] The difference between Example 9 and Example 1 is that:

[0146] In the activation step of the copper-based catalyst (1), the volume ratio of H2, the feed space velocity of the mixed gas, the activation temperature, and the activation time were adjusted to 10%, 500 h, and 10% respectively. -1 , 150℃, 36h.

[0147] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0148] Example 10

[0149] The difference between Example 10 and Example 1 is that:

[0150] In the synthesis step (2) of N-cyclohexylaniline, the reaction temperature and preheating temperature were adjusted to 260° C. and 190° C., respectively.

[0151] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0152] Example 11

[0153] The difference between Example 11 and Example 1 is that:

[0154] In the synthesis step (2) of N-cyclohexylaniline, the reaction pressure, the feed liquid space velocity of the raw material, the feed space velocity of hydrogen, and the feed space velocity of water were adjusted to 0.10 MPa, 1.0 h -1 , 200h -1 , 0.30h -1 .

[0155] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0156] Examples 12-13

[0157] The difference between Examples 12 and 13 and Example 1 is that:

[0158] In the synthesis step (2) of N-cyclohexylaniline, the molar ratios of aniline and cyclohexanol were adjusted to 1:0.4 and 1:2.

[0159] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0160] The composition characterization diagrams of the products obtained by the synthesis methods provided in Examples 4 to 13 are similar to those in Example 1 and are not repeated here.

[0161] Example 14

[0162] The difference between Example 14 and Example 1 is that:

[0163] The promoter metal in the activation step of the copper-based catalyst (1) is adjusted to Cr2O3.

[0164] In the (2) synthesis step of N-cyclohexylaniline, the reaction temperature was adjusted to 200°C.

[0165] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0166] Examples 15-16

[0167] The difference between Examples 15 and 16 and Example 1 is that:

[0168] In the (2) N-cyclohexylaniline synthesis step, the reaction temperatures were adjusted to 210°C and 250°C, respectively.

[0169] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0170] Gas chromatography analysis

[0171] Take the liquid product in Example 1 and perform gas chromatography analysis. Figure 6 As shown, the product peaks are based on the size of the boiling point, and the one with a low boiling point peaks first. The specific results are as follows: at 1.5min, the first peak to peak is the dilution solvent peak, followed by cyclohexanol and aniline at 2.2min and 2.4min, respectively. The by-product dicyclohexylamine peaks at 5.1min, and the target product N-cyclohexylaniline peaks at the last 6.8min. According to the chromatogram, the by-product is represented by dicyclohexylamine, but there may actually be other component by-products, which are not detected in this application. The reaction result shows that the aniline conversion rate is 85%, and the yield of N-cyclohexylaniline is 75% (by-product dicyclohexylamine, 0.2%) based on aniline. It should be noted that the by-product is represented by dicyclohexylamine here, but there may actually be other by-products that are not detected.

[0172] The chromatograms of the liquid products of other examples are similar to the chromatogram of Example 1 and are not repeated here. The aniline conversion rate, N-cyclohexylaniline yield and by-products of each example are shown in Table 1.

[0173] Table 1

[0174]

[0175]

[0176]

[0177] As shown in Table 1, compared with embodiment 1~6, it can be learned that the copper-based catalyst support is Al o embodiment (i.e. embodiment 1~5), the yield of N-cyclohexylaniline is all about 75%, and the copper-based catalyst support is SiO embodiment (embodiment 6), the yield of N-cyclohexylaniline is 76%, therefore, the copper-based catalyst support is Al o aspect the synthesis of N-cyclohexylaniline and carrier is SiO catalytic effect suitable. In the copper-based catalyst, CuO accounts for the yield of the N-cyclohexylaniline of higher (for example embodiment 1,5), is higher than the yield of the N-cyclohexylaniline of lower (for example embodiment 4) that CuO accounts for in the copper-based catalyst, therefore, in the copper-based catalyst, CuO accounts for the catalytic effect better for the synthesis of N-cyclohexylaniline. In the process of synthesizing N-cyclohexylaniline, the catalytic effect of copper-based catalyst shows that not passing water (for example embodiment 3, the conversion rate of aniline 90%) is slightly better than passing water (for example embodiment 1, 2, the conversion rate of aniline 85% or so). In addition, when the reaction temperature reaches 260 ℃, although the conversion rate of aniline can reach 83%, the proportion of by-product dicyclohexylamine reaches 0.5% at the same time. At this time, the selectivity of reaction temperature for N-cyclohexylaniline is reduced. When the temperature difference between preheating temperature and reaction temperature is less, for example, the temperature difference is 10 ℃ (embodiment 15), the aniline conversion rate is 90%. When the temperature difference between preheating temperature and reaction temperature is larger, for example, the temperature difference is greater than 30 ℃ (embodiment 10), the aniline conversion rate is only 83%. It can be seen that when the preheating temperature and reaction temperature temperature difference are smaller, it is more conducive to the copper-based catalyst to play catalytic performance in the process of synthesizing N-cyclohexylaniline. The feed liquid space velocity of raw material is maintained at 0.2~1.0h -1 , the conversion rate of aniline can be maintained at 85%, and the yield of N-cyclohexylaniline can be maintained at 75%. When the feed liquid space velocity of the raw material is 1.0h -1 When (Example 11), the yield of N-cyclohexylaniline is slightly reduced, it can be seen that the feed liquid space velocity of the raw material is 0.2~1.0h -1 It helps to maximize the yield and selectivity of N-cyclohexylaniline and improve the conversion rate of aniline.

[0178] Regeneration of copper-based catalysts

[0179] The conversion rate of aniline in each example was monitored. When the conversion rate decreased or significantly decreased, it indicated that the activity of the copper-based catalyst in each example was reduced or deactivated. In this case, the copper-based catalyst was subjected to in-situ regeneration treatment as follows:

[0180] A nitrogen regeneration gas containing 25% oxygen was introduced into the reactor filled with the copper-based catalyst at a feed space velocity of 200 h -1, heating to 280°C at a heating rate of 12°C / h, and performing in-situ regeneration treatment on the copper-based catalyst for 10 hours; the regenerated copper-based catalyst is further used to catalyze the condensation reaction of aniline and cyclohexyl derivatives.

[0181] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0182] For the sake of simplicity, the method embodiments are described as a series of action combinations. However, those skilled in the art should be aware that this application is not limited by the order of the actions described, because according to this application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in this specification are all preferred embodiments, and the actions and components involved are not necessarily required by this application.

[0183] The above is a detailed introduction to the synthesis method of N-cyclohexylaniline provided in the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only intended to help understand the method and core ideas of the present application. At the same time, for those skilled in the art, according to the ideas of the present application, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present application.

Claims

1. A method for synthesizing N-cyclohexylaniline, characterized in that: The method comprises the following steps: Aniline and a cyclohexyl derivative are introduced as raw materials into a reactor filled with a copper-based catalyst, and the aniline and the cyclohexyl derivative undergo a condensation reaction under the conditions of 0-0.2 MPa and 200-260° C. to convert them into the target product N-cyclohexylaniline; The cyclohexyl derivative is selected from one of cyclohexylamine, cyclohexanone and cyclohexanol; the molar ratio of the aniline to the cyclohexyl derivative is 1:0.4 to 1:

2.

2. The synthesis method according to claim 1, wherein The feed liquid space velocity of the raw material is 0.2~1.0h -1 .

3. The synthesis method according to claim 1, wherein The method further comprises: introducing water and hydrogen into the reactor so that the condensation reaction proceeds in an environment containing water vapor and hydrogen; The feed space velocity of hydrogen is 25~300h -1 ; The water feed space velocity is 0.01~0.33h -1 .

4. The synthesis method according to claim 3, characterized in that The aniline, the cyclohexyl derivative, the water, and the hydrogen are preheated in a preheater and then introduced into the reactor for reaction; The preheating temperature is 190-220°C.

5. The synthesis method according to claim 1, characterized in that The copper-based catalyst comprises a carrier, CuO and a promoter metal, wherein the carrier is selected from one or more of Al2O3, SiO2 and carbon black, and the promoter metal is selected from one or more of Ce2O3, CeO2, MgO, CaO, MnO, Cr2O3, CrO3 and BaO.

6. The synthesis method according to claim 5, characterized in that In terms of mass fraction, in the copper-based catalyst, the mass fraction of the carrier is 25wt% to 60wt%, the mass fraction of the Cu element is 20wt% to 50wt%, and the mass fraction of the metal in the auxiliary metal is 20wt% to 25wt%.

7. The synthesis method according to claim 1, characterized in that Before the aniline and cyclohexyl derivatives are introduced as raw materials into a reactor filled with a copper-based catalyst, the method further comprises: activating the copper-based catalyst, including: A mixed gas of H2 and N2 is introduced into the reactor and activated at 100°C to 300°C for 1h to 50h.

8. The synthesis method according to claim 8, characterized in that The volume proportion of hydrogen in the mixed gas is 1% to 20%, and the feed space velocity of the mixed gas is 100h -1 ~1000h -1 .

9. The synthesis method according to any one of claims 1 to 8, characterized in that When the copper-based catalyst is deactivated or its activity decreases, a regeneration gas is introduced into the reactor to perform in-situ regeneration treatment on the copper-based catalyst; The feed space velocity of the regeneration gas is 50h -1 ~1000h -1 ; The regeneration gas is air, or nitrogen containing oxygen, wherein the volume proportion of oxygen in the nitrogen containing oxygen is 20% to 50%; The temperature of the regeneration treatment is 200° C. to 400° C., the heating rate is 10° C. / h to 20° C. / h, and the treatment time is 2h to 20h.

10. The synthesis method according to claim 1, characterized in that Calculated on the basis of aniline, the yield of the N-cyclohexylaniline is greater than or equal to 68%.

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