Synthesis method of dicyclohexylamine

Abstract

According to the synthesis method of dicyclohexylamine provided by the invention, cyclohexylamine is introduced into a reactor filled with a copper-based catalyst, and cyclohexylamine is subjected to a deamination condensation reaction under the conditions of 0-0.2 MPa and 220-280 DEG C to be converted into a target product dicyclohexylamine. Through the synthesis method, the yield of dicyclohexylamine is greater than 65% in terms of cyclohexylamine. The synthesis method is high in selectivity and few in side reaction, the copper-based catalyst is not prone to inactivation and can be continuously used after being regenerated for multiple times, and continuous production of dicyclohexylamine 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 dicyclohexylamine. Background Art

[0002] Dicyclohexylamine (DCHA, chemical formula C 12 H 23 Dicyclohexylamine (DCH) is an industrially valuable organic compound that is a colorless, transparent, oily liquid at room temperature. As a key organic synthesis intermediate, DCH is widely used as an insecticide, acid gas absorbent, and steel rust inhibitor.

[0003] Currently, dicyclohexylamine is commonly produced in conjunction with cyclohexylamine both domestically and internationally. The core process is the catalytic hydrogenation of aniline. This process uses aniline as the raw material and produces cyclohexylamine through hydrogenation over a catalyst (such as a nickel-, platinum-, or copper-based catalyst), with dicyclohexylamine produced as a byproduct.

[0004] Although the catalytic hydrogenation of aniline has achieved large-scale production of dicyclohexylamine, the existing process of catalytic hydrogenation of aniline to produce dicyclohexylamine has core problems such as low selectivity, complex by-products, and difficulty in separation and purification. Summary of the Invention

[0005] To address the problems in the background art, this application provides a method for synthesizing dicyclohexylamine. Cyclohexylamine is introduced into a reactor filled with a copper-based catalyst, where it undergoes a deamination condensation reaction at 0-0.2 MPa and 220-280°C, converting the cyclohexylamine into the target product, dicyclohexylamine. The reaction is catalyzed by a non-precious metal copper-based catalyst, which has a mature and inexpensive preparation process. The catalytic reaction occurs at a relatively low temperature, resulting in a high yield of the target product.

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

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

[0008] Cyclohexylamine is introduced into a reactor filled with a copper-based catalyst, and a deamination condensation reaction is carried out on the cyclohexylamine under the conditions of 0-0.2 MPa and 220-280° C. to convert the cyclohexylamine into the target product dicyclohexylamine.

[0009] Optionally, the feed liquid space velocity of the cyclohexylamine is 0.2 to 1.0 h -1 .

[0010] Optionally, water and hydrogen are introduced into the reactor so that the deamination condensation reaction is carried out in an environment containing water vapor and hydrogen;

[0011] The feed space velocity of the hydrogen is 25 to 200 h -1 ; The water feed space velocity is 0.01~0.33h -1 .

[0012] Optionally, the cyclohexylamine, the water, and the hydrogen are preheated in a preheater and then introduced into the reactor for reaction;

[0013] The preheating temperature is 190-220°C.

[0014] Optionally, 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 ZnO, MgO, CaO, MnO, Cr2O3, CrO3, and BaO.

[0015] 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%.

[0016] Optionally, before introducing cyclohexylamine into the reactor filled with the copper-based catalyst, the method further comprises: performing an activation treatment on the copper-based catalyst, comprising:

[0017] A mixed gas of H2 and N2 is introduced into the reactor and activated at 100°C to 300°C for 1h to 50h.

[0018] 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 .

[0019] 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;

[0020] The feed space velocity of the regeneration gas is 50h -1 ~1000h -1 ;

[0021] The regeneration gas is air, or nitrogen containing oxygen, wherein the volume proportion of oxygen in the nitrogen containing oxygen is 20% to 50%;

[0022] 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.

[0023] Optionally, based on cyclohexylamine, the yield of dicyclohexylamine is greater than 65%.

[0024] Compared with the existing technology, this application has the following advantages:

[0025] The method for synthesizing dicyclohexylamine provided in the present application has the following advantages: first, cyclohexylamine is used as a raw material, which is readily available and inexpensive, resulting in low production costs and less waste causing environmental pollution during the reaction process; second, a non-precious metal copper-based catalyst is used as a 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 dicyclohexylamine is relatively high, and the yield of dicyclohexylamine, calculated on the basis of cyclohexylamine, is greater than 65%; in a reactor containing the copper-based catalyst, a deamination condensation reaction of cyclohexylamine occurs under conditions of 0-0.2 MPa and 220-280° C. The copper-based catalyst is not easily deactivated and can be continuously used after multiple regenerations; 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

[0026] 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.

[0027] Figure 1 A schematic diagram of the synthesis system of dicyclohexylamine provided in an embodiment of the present application is shown;

[0028] Figure 2 The composition characterization diagram of the product obtained by the synthesis method provided in the examples of the present application is shown;

[0029] Figure 3 The gas chromatographic analysis diagram of the product provided in the examples of the present application is shown.

[0030] Reference numerals:

[0031] 1-Mixer, 2-Preheater, 3-Reactor, 4-Separator, 5-Product tank, 6-Ammonia adsorption tank, 7-Plunger pump. DETAILED DESCRIPTION

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Dicyclohexylamine (DCHA, chemical formula C 12 H 23 Dicyclohexylamine (DHC) is an organic compound of significant industrial value. It is a colorless, transparent, oily liquid at room temperature, exhibiting strong alkalinity and good compatibility with organic solvents. As a key organic synthesis intermediate, the secondary amine groups in its molecular structure lend it to a wide range of applications in pharmaceuticals, pesticides, and materials. In the pharmaceutical field, it can be used to synthesize the antihypertensive drug sedrinimide and anti-tumor drugs; in agriculture, it serves as an active ingredient in insecticides; and in industrial protection, it serves as an acid gas absorbent and a highly effective rust inhibitor for steel equipment, playing a particularly important role in the corrosion protection of steel equipment used in oil and natural gas extraction. With the advancement of fine chemicals and materials science, the demand for high-purity DHC continues to grow, but its efficient preparation technology remains challenging.

[0037] Currently, dicyclohexylamine is commonly produced in conjunction with cyclohexylamine both domestically and internationally. The core process is the catalytic hydrogenation of aniline. This process uses aniline as the raw material and produces cyclohexylamine through hydrogenation over a catalyst (such as a nickel-, platinum-, or copper-based catalyst), with dicyclohexylamine produced as a byproduct. Specifically, aniline is first hydrogenated under high temperature and pressure (typically 150-250°C and 3-10 MPa) in a hydrogen atmosphere to produce cyclohexylamine. Some of the cyclohexylamine then condenses with aniline or itself and undergoes hydrogenation to produce dicyclohexylamine. By adjusting the reaction temperature, pressure, catalyst composition, and material ratio (such as the molar ratio of aniline to hydrogen), the ratio of cyclohexylamine to dicyclohexylamine can be controlled within a certain range. Under standard production conditions, without careful adjustment of reaction parameters, the byproduct rate of dicyclohexylamine is approximately 10%. This process has become the mainstream route for the industrial production of dicyclohexylamine due to the widespread availability of the raw material aniline and its relatively simple process.

[0038] Although the catalytic hydrogenation of aniline has achieved large-scale production of dicyclohexylamine, its technical bottlenecks have significantly restricted the improvement of product purity and the control of production costs:

[0039] Complex side reactions lead to difficulty in product separation: During the hydrogenation process, aniline and the intermediate product cyclohexylamine are prone to various side reactions or secondary reactions, generating monocyclic impurities such as N-cyclohexylaniline, cyclohexanol, and cyclohexane, as well as high-boiling-point polymers such as aniline-cyclohexylamine trimers and polymers. These impurities have similar physical and chemical properties to dicyclohexylamine, making them difficult to efficiently separate using conventional distillation or extraction methods. This results in high energy consumption and low yields in subsequent purification processes.

[0040] The problem of low dicyclohexylamine selectivity: In the existing process, dicyclohexylamine mainly exists as a by-product. Even if the reaction conditions are optimized, its maximum selectivity is still less than 30%. A large amount of raw material aniline is converted into cyclohexylamine or other impurities other than the target product, resulting in insufficient raw material utilization and increasing the material cost of industrial production.

[0041] Issues with catalyst stability and lifespan: Polymers generated by side reactions are easily adsorbed on the catalyst surface, leading to blockage of active sites and accelerated catalyst deactivation. This forces frequent replacement or regeneration of catalysts during the production process, further increasing equipment maintenance costs and downtime.

[0042] Environmental and safety risks: High-temperature and high-pressure reaction conditions place stringent demands on equipment sealing, leading to a high risk of hydrogen leakage. Furthermore, nitrogen-containing organic wastewater and waste gas generated during by-product treatment require additional investment in environmental treatment facilities, exacerbating the environmental burden of industrial production.

[0043] In summary, the existing process of catalytic hydrogenation of aniline to produce dicyclohexylamine has core problems such as low selectivity, complex by-products, and difficulty in separation and purification. It is urgent to develop a new preparation method that can inhibit side reactions, improve the selectivity of the target product dicyclohexylamine, and simplify the separation process.

[0044] In view of the problems of low process selectivity, complex by-products, and difficulty in separation and purification in the production of dicyclohexylamine in the related art, the present application provides a method for synthesizing dicyclohexylamine, which specifically comprises the following steps:

[0045] Cyclohexylamine is introduced into a reactor filled with a copper-based catalyst, and a deamination condensation reaction is carried out on the cyclohexylamine under the conditions of 0-0.2 MPa and 220-280° C. to convert the cyclohexylamine into the target product dicyclohexylamine.

[0046] It should be noted that the above-mentioned reactor may be a fixed bed reactor, and the embodiments of the present application are all demonstrated by taking a fixed bed reactor as an example.

[0047] It should be noted that the pressure of the deamination condensation reaction of cyclohexylamine is 0-0.2 MPa. For example, the reaction pressure can be 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, 0.20 MPa, or any two of them. When the reaction pressure is 0 MPa, the catalyst is in a normal pressure state in the reactor to carry out the catalytic reaction. By controlling the pressure of the deamination condensation of cyclohexylamine to 0-0.2 MPa, the reaction efficiency of the deamination condensation of cyclohexylamine is improved, which is beneficial to balancing the selectivity and yield of dicyclohexylamine, while avoiding catalyst deactivation and keeping the catalyst stable.

[0048] It should be noted that the temperature for the deamination condensation reaction of cyclohexylamine is 220-280° C. For example, the reaction temperature may be in the range of one or any two of 220° C., 230° C., 240° C., 250° C., 260° C., 270° C., and 280° C. By controlling the temperature for the deamination condensation of cyclohexylamine at 220-280° C., the deamination condensation of cyclohexylamine is facilitated to proceed toward the main reaction of producing dicyclohexylamine, effectively avoiding side reactions and achieving higher selectivity.

[0049] It should also be noted that the deamination condensation of cyclohexylamine in the presence of a copper-based catalyst can be carried out in two steps: first, cyclohexylamine is dehydrogenated under the action of a copper catalyst to generate cyclohexylimine (C6H 11N=CH2), followed by a nucleophilic addition-deamination reaction between the imine and another molecule of cyclohexylamine to produce dicyclohexylamine. The deamination condensation reaction of cyclohexylamine over a copper-based catalyst is a cascade of dehydrogenation-nucleophilic addition-deamination. Copper promotes the reaction by providing dehydrogenation active sites and acid-base centers.

[0050] In this embodiment, first, cyclohexylamine is used as a raw material, which is readily available and inexpensive, resulting in low production costs and less waste causing environmental pollution during the reaction process. Second, a non-precious metal copper-based catalyst is used as a 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, dicyclohexylamine, is relatively high. Calculated on the basis of cyclohexylamine, the yield of dicyclohexylamine is greater than 65%. In a reactor containing a copper-based catalyst, a deamination condensation reaction of cyclohexylamine occurs under conditions of 0 to 0.2 MPa and 220 to 280° C. The copper-based catalyst is not easily deactivated and can be continuously used after being regenerated multiple times. Thus, using a copper-based catalyst and a reactor, the synthesis method exhibits the advantages of high selectivity, simple by-products, and can achieve continuous production, high production efficiency, and long-term stable output.

[0051] In some embodiments, the feed liquid space velocity of cyclohexylamine is 0.2 to 1.0 h -1 .

[0052] It should be noted that the liquid space velocity refers to the volume of liquid feed passing through a unit volume of catalyst per unit time (unit: h -1 ). The space velocity directly determines the residence time of cyclohexylamine molecules in the catalyst bed.

[0053] It should be noted that the feed liquid space velocity of cyclohexylamine is 0.2~1.0h -1 For example, the feed liquid space velocity of cyclohexylamine can be 0.2h -1 , 0.3h -1 , 0.4h -1 , 0.5h -1 , 0.8h -1 , 1.0h -1 For example, when the feed liquid space velocity of cyclohexylamine is less than 0.2h -1 If cyclohexylamine stays on the surface of the copper-based catalyst for too long, the generated dicyclohexylamine may undergo further side reactions (such as polycondensation to generate tricyclohexylamine or larger molecular products), resulting in a decrease in selectivity and accelerated carbon deposition and deactivation of the catalyst. When the feed liquid space velocity of cyclohexylamine is greater than 1.0h -1 The residence time of cyclohexylamine on the surface of the copper-based catalyst is too short, and the cyclohexylamine molecules do not fully contact the active sites of the catalyst, resulting in a decrease in the conversion rate of cyclohexylamine and a decrease in the yield of the target product dicyclohexylamine.

[0054] In the present embodiment, the feed liquid space velocity of cyclohexylamine raw material is controlled at 0.2~1.0h -1 , which helps to maximize the yield and selectivity of dicyclohexylamine while inhibiting side reactions; prolong the service life of copper-based catalysts, reduce carbon deposition and sintering risks; optimize the economic efficiency of reactor operation and reduce energy consumption.

[0055] In some embodiments, water and hydrogen are introduced into the reactor so that the deamination condensation reaction is carried out in an environment containing water vapor and hydrogen;

[0056] The feed space velocity of the hydrogen is 25 to 200 h -1 ; The water feed space velocity is 0.01~0.33h -1 .

[0057] It should be noted that hydrogen is introduced into the reactor at a certain flow rate, carrying the cyclohexylamine raw material with it to carry out a catalytic reaction. The gaseous raw material reacts on the solid copper-based catalyst bed. After the reaction is completed, the reaction product is 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.

[0058] It should be noted that the feed space velocity of hydrogen is 25 to 200 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 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; copper-based catalysts need to be in the form of metallic copper (Cu 0 ) or low-valent copper (such as Cu + ) exists in the form of its active sites are sensitive to the reducing environment. When the feed space velocity of hydrogen is maintained at 25-200h -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 dicyclohexylamine.

[0059] 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 deamination condensation of cyclohexylamine is an exothermic reaction, and local overheating can easily trigger side reactions (such as carbon deposition and polymerization condensation). After water is introduced, the water evaporates into water vapor, which absorbs heat. This can effectively reduce the peak reaction temperature, prevent catalyst sintering or deactivation due to high temperature, and protect the catalyst. At the same time, water vapor can flush the catalyst surface and reduce the adsorption residence time of carbon deposit precursors. At the same time, water vapor reacts with carbon deposits to form a water-gas reaction, directly removing some of the carbon deposits and extending the life of the catalyst.

[0060] In this embodiment, water and hydrogen are introduced into the reactor so that the deamination condensation reaction is carried out in an environment containing water vapor and hydrogen; water and hydrogen do not participate in the deamination condensation reaction of cyclohexylamine to produce dicyclohexylamine, and the feed space velocity of hydrogen is controlled at 25 to 200 h / min. -1 ; The water feed space velocity is controlled at 0.01~0.33h -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.

[0061] In some embodiments, the cyclohexylamine, the water, and the hydrogen are preheated in a preheater and then introduced into the reactor for reaction;

[0062] The preheating temperature is 190-220°C.

[0063] 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.

[0064] It should be noted that the preheating temperature of the preheater is a key parameter to ensure efficient and stable reaction. The cyclohexylamine raw material is liquid, and the temperature is low at room temperature. The cold liquid has a greater impact on the copper-based catalyst. The liquid cyclohexylamine 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 material cyclohexylamine and other auxiliary substances (water, hydrogen) are preheated to become gas, so that the cyclohexylamine deamination condensation reaction is carried out under gas-solid reaction conditions. When the raw material is 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 deamination condensation reaction more complete, the reaction effect is good, and extend the service life of the copper-based catalyst.

[0065] 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 cyclohexylamine, water, and hydrogen to the activation temperature of the copper-based catalyst, 190-220°C, to form active adsorption centers on the copper surface, thereby promoting the deamination condensation reaction of cyclohexylamine.

[0066] When implementing it specifically, Figure 1 As shown, cyclohexylamine is transported to a reaction mixer 1 by a plunger pump 7, and water and hydrogen are introduced simultaneously for premixing in the mixer 1. The mixed system is introduced into a preheater 2 and preheated to a certain temperature. The hydrogen entering the preheater 2 carries the vaporized cyclohexylamine 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 in a condenser and converted from a gaseous state to a partially liquid product. The gas can be returned to the hydrogen inlet pipeline for recycling. The liquid product flows into the product tank 5 through a separator 4, and the generated ammonia is adsorbed by the ammonia adsorption tank 6.

[0067] In this embodiment, the preheating temperature of cyclohexylamine, water, and hydrogen is controlled at 190-220°C by a preheater. The core function is to create suitable starting conditions for the deamination condensation reaction of cyclohexylamine. If the preheating temperature is too low, the reaction rate will be slow. If the preheating temperature is too high, side reactions will be accelerated and the catalyst may be sintered due to overheating (copper particles agglomerate and the active surface area is reduced). Controlling the preheating temperature at 190-220°C is beneficial to extending the service life of the catalyst and taking into account both the conversion rate of cyclohexylamine and the selectivity of dicyclohexylamine.

[0068] 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 ZnO, MgO, CaO, MnO, Cr2O3, CrO3, and BaO.

[0069] It should be noted that the support in a copper-based catalyst 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 dicyclohexylamine selectivity in the cyclohexylamine deamination condensation reaction.

[0070] It should be noted that the copper-based catalyst needs to be activated before use to reduce copper oxide (active component) to reduced copper so that CuO can provide active sites for the deamination condensation reaction of cyclohexylamine.

[0071] It should be noted that the additive metal in the copper-based catalyst is selected from one or more of ZnO, MgO, CaO, MnO, Cr2O3, CrO3, and BaO. This can optimize the structure of the active component, regulate selectivity, and enhance resistance to deactivation. Specifically, ZnO can inhibit copper sintering, promote dispersion, and increase the density of active sites; MgO and CaO can neutralize acidic sites on the support surface, improving selectivity; and MnO, Cr2O3, and CrO3 can improve copper dispersion, accelerate electron transfer, and increase the rate of the dehydrogenation-condensation reaction.

[0072] In this embodiment, the copper-based catalyst, the support, copper oxide (active component), and the 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 ZnO, 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 cyclohexylamine deamination condensation reaction.

[0073] 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%.

[0074] 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.

[0075] It should be noted that the mass percentage of the Cu element in the copper-based catalyst is 20 wt% to 50 wt%. For example, the mass percentage of the Cu element can be in the range of 20 wt%, 25 wt%, 30 wt%, 40 wt%, 50 wt%, or any two of these. When the mass percentage of the Cu element is controlled between 20 wt% and 50 wt%, balancing the active site density and sintering resistance, the activity and stability of the copper-based catalyst are optimized.

[0076] 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.

[0077] 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 cyclohexylamine conversion rate, dicyclohexylamine selectivity, and the service life of the copper-based catalyst can be achieved to peak values.

[0078] In some embodiments, before introducing cyclohexylamine into a reactor filled with a copper-based catalyst, the method further comprises: activating the copper-based catalyst, comprising:

[0079] A mixed gas of H2 and N2 is introduced into the reactor and activated at 100°C to 300°C for 1h to 50h.

[0080] 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.

[0081] 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.

[0082] In this embodiment, by controlling the activation temperature of the copper-based catalyst to 100°C to 300°C and the activation time to 1h to 50h, 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 deamination condensation reaction of cyclohexylamine while avoiding activity attenuation or shortened life.

[0083] 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 .

[0084] 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%.

[0085] 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 .

[0086] 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 .

[0087] 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;

[0088] The feed space velocity of the regeneration gas is 50h -1 ~1000h -1 ;

[0089] The regeneration gas is air, or nitrogen containing oxygen, wherein the volume proportion of oxygen in the nitrogen containing oxygen is 20% to 50%;

[0090] 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.

[0091] It should be noted that the deactivation or reduced activity of the copper-based catalyst is achieved by monitoring the conversion rate of cyclohexylamine. For example, when the reaction starts, the conversion rate of cyclohexylamine 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.

[0092] 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 -1 The range of values ​​for one or both of .

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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 dicyclohexylamine in the deamination condensation reaction of cyclohexylamine.

[0098] In some embodiments, the yield of dicyclohexylamine is greater than 65% based on cyclohexylamine.

[0099] In this embodiment, the yield of dicyclohexylamine is greater than 65%, the product purity is high, and the economic benefit is good.

[0100] In order to enable those skilled in the art to understand the present application more clearly, the synthesis method of dicyclohexylamine described in the present application is now described in detail through the following examples.

[0101] Example 1

[0102] (1) Activation of copper-based catalysts

[0103] A copper-based catalyst was prepared by using 45 wt% Al2O3 as a carrier, 30 wt% CuO as an active component, and 25 wt% ZnO as a metal promoter. The copper-based catalyst was loaded into a fixed bed reactor with a loading volume of 40 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.

[0104] (2) Synthesis of dicyclohexylamine

[0105] Cyclohexylamine was delivered to the reaction mixer by a plunger pump, and the feed liquid space velocity of cyclohexylamine was 0.2h -1 At the same time, hydrogen was introduced, and the feed space velocity of hydrogen was 50h -1 The cyclohexylamine 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. -1The flow rate entrains the gaseous cyclohexylamine into a reactor containing an activated copper-based catalyst. The mixed gas phase undergoes a deamination condensation reaction in a solid catalyst bed at a reaction temperature of 220°C and a reaction pressure of 0.05 MPa to convert it into the target product, dicyclohexylamine.

[0106] The reaction products are condensed in a separator (condenser) and transformed from gaseous state into partially liquid products. The liquid products flow into the product tank, and the gas can be returned to the hydrogen inlet pipeline for recycling. The nitrogen is adsorbed by the nitrogen adsorption tank.

[0107] Figure 2 The composition characterization diagram of the product obtained by the synthesis method provided in the embodiment of the present application is shown in FIG. Figure 2 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 8.0 min is consistent with the standard spectrum of dicyclohexylamine, proving that the target product dicyclohexylamine was successfully prepared in this application.

[0108] Example 2

[0109] The difference between Example 2 and Example 1 is that:

[0110] In the activation step of the copper-based catalyst (1), the copper-based catalyst loading amount was adjusted to 20 mL;

[0111] In the synthesis step (2) of dicyclohexylamine, cyclohexylamine is transported to a reaction mixer by a plunger pump, water is also pumped into the mixer by a plunger pump, and hydrogen is introduced at the same time. The cyclohexylamine, hydrogen and water are transported together to a preheater for preheating.

[0112] The reaction temperature, reaction pressure, feed liquid space velocity of cyclohexylamine, feed space velocity of hydrogen, feed space velocity of water, and preheating temperature were adjusted to 240 ° C, 0.2 MPa, 0.4 h -1 、100h -1 , 0.05h -1 , 220℃.

[0113] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0114] Example 3

[0115] The difference between Example 3 and Example 1 is that:

[0116] 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.

[0117] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0118] Example 4

[0119] The difference between Example 4 and Example 1 is that:

[0120] 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.

[0121] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0122] Example 5

[0123] The difference between Example 5 and Example 1 is that:

[0124] In the activation step of the copper-based catalyst (1), the carrier and the auxiliary metal are adjusted to SiO2 and MgO, respectively.

[0125] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0126] Example 6

[0127] The difference between Example 6 and Example 1 is:

[0128] In the activation step of the copper-based catalyst (1), the promoter metals are adjusted to: 15 wt% ZnO, 10 wt% CaO.

[0129] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0130] Example 7

[0131] The difference between Example 7 and Example 1 is that:

[0132] In the activation step of the copper-based catalyst (1), the promoter metals are adjusted to: 15 wt% ZnO, 10 wt% MnO.

[0133] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0134] Example 8

[0135] The difference between Example 8 and Example 1 is that:

[0136] 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.

[0137] The other steps and amounts used were the same as in Example 1 to obtain the target product.

[0138] Example 9

[0139] The difference between Example 9 and Example 2 is that:

[0140] In the synthesis step (2) of dicyclohexylamine, the reaction temperature and preheating temperature were adjusted to 280°C and 190°C, respectively.

[0141] The other steps and amounts were the same as those in Example 2 to obtain the target product.

[0142] Example 10

[0143] The difference between Example 10 and Example 2 is that:

[0144] In the synthesis step (2) of dicyclohexylamine, the reaction pressure, the feed liquid space velocity of cyclohexylamine, the feed space velocity of hydrogen, and the feed space velocity of water were adjusted to 0 MPa, 1.0 h -1 , 200h -1 , 0.30h -1 .

[0145] The other steps and amounts used were the same as those in Example 2 to obtain the target product. The compositional characterization diagrams of the products obtained by the synthesis methods provided in Examples 2 to 10 are similar to those in Example 1 and are not repeated here.

[0146] Example 11

[0147] The difference between Example 11 and Example 3 is that:

[0148] In the activation step of the copper-based catalyst (1), the mass proportions of the carrier and CuO were adjusted to 60 wt% and 40 wt%, respectively.

[0149] Gas chromatography analysis

[0150] Take the liquid product in Example 1 and perform gas chromatography analysis. Figure 3 As shown, the first peak to appear at 1.5 minutes is the dilution solvent peak, followed by cyclohexylamine at 2.2 minutes. The target product, dicyclohexylamine, appears at 5.2 minutes, and the last peak, N-cyclohexylaniline, the byproduct, appears at 6.6 minutes. The reaction results show that the conversion of cyclohexylamine is 80%, and the yield of dicyclohexylamine, calculated on the basis of cyclohexylamine, is 75% (byproduct, N-cyclohexylaniline, 0.5%).

[0151] The chromatograms of the liquid products of other examples are similar to the chromatogram of Example 1 and are not repeated here. The conversion rate of cyclohexylamine, the yield of dicyclohexylamine and the by-products of each example are shown in Table 1.

[0152] Table 1

[0153]

[0154]

[0155]

[0156] As shown in Table 1, when comparing Examples 1 to 5, it can be seen that the copper-based catalyst carrier is Al2O3 embodiment (i.e., Example 1 to 4), the conversion rate of cyclohexylamine is all greater than 70%, and the yield of dicyclohexylamine is all greater than or equal to 65%, and the copper-based catalyst carrier is SiO2 embodiment (Example 5), the conversion rate of cyclohexylamine is all less than 70%, and the yield of dicyclohexylamine is all only 65%, therefore, the copper-based catalyst carrier is Al2O3 in the synthesis of dicyclohexylamine, to be better than the catalytic effect of carrier being SiO2. The conversion rate of cyclohexylamine and the yield of dicyclohexylamine that CuO accounts for higher (such as Example 1, 2) in the copper-based catalyst and is higher than the conversion rate of cyclohexylamine and the yield of dicyclohexylamine that CuO accounts for lower (such as Example 3) in the copper-based catalyst, therefore, the catalytic effect that CuO accounts for higher in the copper-based catalyst is better for the synthesis of dicyclohexylamine. In the process of synthesizing dicyclohexylamine, the catalytic effect of the copper-based catalyst is shown to be better than that of the case where no water is introduced (for example, in Example 1, the conversion rate of cyclohexylamine is 80%, and the yield of dicyclohexylamine is 75%) when water is introduced (for example, in Example 2, the conversion rate of cyclohexylamine is 75%, and the yield of dicyclohexylamine is 68%). In addition, when the feed space velocity of hydrogen reaches 200h -1 Although the conversion rate of cyclohexylamine can reach 80%, the proportion of byproduct N-cyclohexylaniline reaches 1.5%. At this time, the feed space velocity of hydrogen reduces the selectivity for dicyclohexylamine. In Example 11, when no auxiliary metal is added, the yield of dicyclohexylamine is extremely poor and contains multiple unidentified byproducts.

[0157] Regeneration of copper-based catalysts

[0158] The conversion rate of cyclohexylamine in each embodiment was monitored. When the conversion rate decreased or significantly decreased, it indicated that the activity of the copper-based catalyst in each embodiment was reduced or deactivated. At this time, the copper-based catalyst was subjected to in-situ regeneration treatment as follows:

[0159] 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 deamination condensation reaction of cyclohexylamine.

[0160] 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.

[0161] 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.

[0162] The above is a detailed introduction to the synthesis method of dicyclohexylamine 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 concept of the present application. At the same time, for those skilled in the art, according to the concept of the present application, there may be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present application.

Claims

1. A method for synthesizing dicyclohexylamine, characterized in that: The method comprises the following steps: Cyclohexylamine is introduced into a reactor filled with a copper-based catalyst, and a deamination condensation reaction is carried out on the cyclohexylamine under the conditions of 0-0.2 MPa and 220-280° C. to convert the cyclohexylamine into the target product dicyclohexylamine.

2. The synthesis method according to claim 1, wherein The feed liquid space velocity of the cyclohexylamine 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 deamination condensation reaction is carried out in an environment containing water vapor and hydrogen; The feed space velocity of the hydrogen is 25 to 200 h -1 ; The water feed space velocity is 0.01~0.33h -1 .

4. The synthesis method according to claim 3, characterized in that The cyclohexylamine, 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 ZnO, 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 introducing cyclohexylamine into the reactor filled with the 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 7, 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 cyclohexylamine, the yield of the dicyclohexylamine is greater than 65%.

Images