Catalyst for preparing diamine from lactam in one step as well as preparation method and application of catalyst

Abstract

The invention provides a catalyst for one-step preparation of diamine from lactam and a preparation method and application of the catalyst. A catalyst carrier is sequentially subjected to sensitization treatment operation in the step S1, activation treatment operation in the step S2 so as to enable the catalyst carrier to load active metal, complexing treatment operation in the step S3, reduction treatment operation in the step S4 and acid treatment operation in the step S5; the catalyst can be coupled with an ammoniation reaction for preparing diamine from lactam and an aminonitrile hydrogenation reaction, so that the diamine is produced through one-step reaction of lactam, and the production process is greatly simplified.

Description

Technical Field

[0001] The present application relates to the technical field of catalyst preparation, and in particular to a catalyst for preparing diamine from lactam in one step, and a preparation method and application thereof. Background Art

[0002] Nylon 66 salt is the raw material for producing nylon 66 fiber and engineering plastics. It is widely used in the production of rubber products such as airbags and rubber conveyor belts. It can also replace metal materials to make mechanical accessories, machine casings, and blades of automobile engines. It can also be used to produce parts of electrical equipment, medical equipment, sports goods, daily necessities and food packaging. At present, the global total production capacity of PA66 has exceeded 3.5 million tons / year. If it is predicted at a growth rate of 3%, the global PA66 production capacity will exceed 4.7 million tons / year by 2030. In recent years, foreign nylon industry giants have reduced their production capacity and continuously transferred their nylon 66 business to Asia, especially the Chinese market. In 2017, the domestic nylon 66 chip production capacity was 505,000 tons and the output was 283,000 tons. The compound growth rate of output in the past three years was above 15%. In 2017, the apparent consumption of domestic nylon chips was 478,000 tons, and the import dependence was 40%. my country's nylon 66 and its intermediates still have huge development potential.

[0003] Hexamethylenediamine is the core key intermediate in the nylon 66 industry chain. The internationally used industrial production methods of hexamethylenediamine mainly include the adiponitrile method, acrylonitrile method, adipic acid method, caprolactam method, etc.

[0004] The adiponitrile method is mainly carried out by catalytic hydrogenation. The chemical reaction is as follows:

[0005]

[0006] In the 1970s, DuPont of the United States developed the direct hydrocyanation of butadiene based on the cyanochlorination of butadiene, and established the first production unit in Texas and achieved industrialization. The direct hydrocyanation of butadiene is to react two molecules of HCN with butadiene in the presence of a catalyst. The catalyst is composed of zero-valent nickel and a phosphorus-containing ligand. However, in the actual chemical reaction process, it is mainly divided into three steps: primary hydrocyanation, isomerization and secondary hydrocyanation.

[0007] The actual chemical reaction process includes three stages: the formation of pentenenitrile, isomerization reaction, and preparation of adiponitrile. Under certain temperature and pressure conditions, butadiene and hydrocyanic acid first undergo a primary cyanation reaction in the presence of a catalyst, mainly producing 3-pentenenitrile (3-PN) and 2-methyl-3-butene (2M3BN). 2-methyl-3-butene is isomerized to 3-pentenenitrile under the action of a catalyst. 3-Pentenenitrile is further isomerized to produce 4-pentene (4-PN), a precursor of adiponitrile, under the action of a catalyst. 4-Pentene further undergoes a secondary cyanation reaction with HCN to produce adiponitrile. Byproducts such as ESN (ethylsuccinonitrile), MGNMGN (3-methylglutaronitrile), and 2-PN (2-pentanenitrile) are also produced during the reaction. At present, the technical focus is on the direct hydrocyanation of butadiene (one-step method).

[0008] The production cost of this method is low. Since the raw materials and intermediates are catalytically reacted under gaseous conditions, the equipment is easy to control automatically. However, the production process must be carried out under high temperature and high pressure conditions, and a large amount of highly toxic HCN raw materials are required. Once a leak occurs, the consequences are very serious. Therefore, the direct hydrocyanation of butadiene has extremely high requirements for production equipment, operation, and management. The production site must be far away from residential areas, and a strict prevention and toxic gas leakage treatment mechanism must be established.

[0009] The acrylonitrile method uses an electrolytic process. In the 1960s, Monsanto Company of the United States took the lead in successfully developing this process and gradually improved it from a diaphragm electrolysis method to a diaphragm-free electrolysis method. The electrolytic dimerization of acrylonitrile to produce adiponitrile uses propylene as raw material, first converts it into acrylonitrile with oxygen, ammonia and a catalyst, and then electrolytically reduces acrylonitrile to adiponitrile. Among them, the diaphragm electrolysis method is divided into a solution method and an emulsion method. Monsanto Company first adopted the solution method, and later Asahi Kasei Company of Japan improved it to an emulsion method based on Monsanto Company; the diaphragm-free electrolysis method is a direct electrosynthesis process, using emulsion as the electrolyte. Considering that acrylonitrile does not participate in the anode reaction, the diaphragm is cancelled. This process is represented by the Belgian United Chemical Company. The diaphragm-free electrolysis method developed by BASF uses a special capillary gap electrolytic cell, which is composed of multiple overlapping graphite plates, and a diaphragm-free electrolysis device is established. Acrylonitrile electrochemical cathode hydrogenation undergoes polymerization and dimerization stages and is quantitatively converted into adiponitrile.

[0010] The mechanism of cathode hydrogenation dimerization of acrylonitrile to produce adiponitrile is as follows: first, an acrylonitrile molecule combines with two electrons and a proton, and the generated anion interacts with the second acrylonitrile molecule, and then the dimerized anion reacts with the hydrogen ion to produce adiponitrile. The dimerization process of acrylonitrile depends on the cathode material, using tetraethylammonium hydroxide + potassium phosphate as the electrolyte, and graphite, Pb, Cd, Ni, and Hg as the cathode material. The yield of adiponitrile can reach 81.0% to 99.6%.

[0011] Compared with the chemical method, the advantages of the electrochemical method are: electrochemical synthesis uses electrons as reducing agents or oxidizing agents, and electrons are equivalent to clean reaction reagents. Therefore, in addition to raw materials and products, the reaction system usually does not contain other reagents, and the final product is easy to separate and purify. In addition, the electrode potential is used to control the reaction process, which can significantly improve the selectivity of the target reaction. Therefore, the reaction product has high purity, few by-products, and can greatly reduce environmental pollution. Moreover, electrochemical synthesis is generally carried out at room temperature and pressure, the reaction conditions are relatively mild, and the material requirements for the equipment are not high. In the production process of acrylonitrile electrolytic dimerization to synthesize adiponitrile, the source of raw materials is relatively wide. The improved membrane-free electrolysis method has the characteristics of high product quality, low energy consumption, and high yield. It is a process widely used in the world. However, due to the current high market price of raw material acrylonitrile, the production scale is generally small, and there is basically no profit margin. It is expected that this process will be gradually eliminated.

[0012] The adipic acid method mainly involves adipic acid and ammonia being aminated and dehydrated to generate adiponitrile, and then adiponitrile is hydrogenated to finally obtain hexamethylenediamine. The chemical reaction is as follows:

[0013]

[0014] In the late 1960s, the French Rhone-Poulenc Company developed a production process for synthesizing adiponitrile by catalytic amination of adipic acid (ADA), and the industrialized production was carried out by: Lattic Chemical Plant, BASF Company and China Liaohua No. 4 Plant. Currently, the representative production processes are mainly liquid phase method and gas phase method. The liquid phase method has a long history, but the product quality is poor and the yield is relatively low (84% to 93%). The gas phase method is divided into Monsanto method and BASF method. The product yield and quality have been significantly improved compared with the liquid phase method, and the yield can reach 92% to 96%.

[0015] The reaction process is: first, adipic acid reacts with ammonia to remove one molecule of water to generate amine, and then continues to dehydrate to generate adiponitrile. Since the two-step dehydration reaction is a reversible reaction, it is necessary to add excess ammonia to move the reaction in the positive direction. In order to obtain a higher yield of adipic acid, the molar ratio of ammonia to adipic acid is generally greater than 5, and the water generated in the reaction process needs to be discharged in time. According to different process routes, it is divided into liquid phase method and gas phase method. The liquid phase method is to add a catalyst to adipic acid at 200-300°C for ammonia dehydration. The generated reaction product undergoes dehydration, removal of heavy components, chemical treatment and vacuum distillation to finally obtain pure adiponitrile. The gas phase method is to add boron phosphate as a catalyst to adipic acid at 300-350°C for reaction. However, since adipic acid decomposes when it is gasified, the product selectivity is low, only about 80%.

[0016] The caprolactam process mainly involves the reaction of caprolactam and ammonia under the action of a catalyst, using the gas phase principle to produce 6-aminocapronitrile. 6-aminocapronitrile is then hydrogenated to obtain hexamethylenediamine. The chemical reaction is as follows:

[0017]

[0018] In the process of preparing 6-aminocapronitrile, the reaction temperature needs to be kept above 350°C, and the yield can reach almost above 95%. Compared with the butadiene method and the adipic acid method, the caprolactam method has the advantages of short process, low raw material toxicity, low equipment cost, and high product yield, but the preparation of hexamethylenediamine from caprolactam requires two steps. The first step is the reaction of caprolactam with ammonia to generate aminocapronitrile. The active phase of the reaction is metal phosphate, and the reaction requires a higher temperature; the second step is the reaction of aminocapronitrile with hydrogen to generate hexamethylenediamine. The active phase of the reaction is a metal element, and the reaction requires a lower temperature and a higher pressure. The reaction conditions required for these two reactions are different and harsh, which is not conducive to industrial production. Summary of the invention

[0019] In view of this, the present application provides a method for preparing a catalyst for preparing hexamethylenediamine from caprolactam in one step and the application of the catalyst, which solves the technical problem that the prior art method for preparing hexamethylenediamine from caprolactam requires two steps and the reaction conditions of the two steps are harsh.

[0020] According to the first aspect of the present application, the present application provides a method for preparing a catalyst for converting lactam into diamine in one step, the preparation method comprising: sequentially performing a sensitization treatment operation in step S1, an activation treatment operation in step S2 to load the catalyst carrier with active metals, a complexation treatment operation in step S3, a reduction treatment operation in step S4, and an acid treatment operation in step S5, and then washing, drying and calcining the catalyst to obtain the catalyst.

[0021] In one embodiment, step S1, preparing a sensitizing solution, dissolving a tin salt and an acid in water to prepare a sensitizing solution, and then placing a catalyst carrier in the sensitizing solution, stirring until the catalyst carrier is completely immersed, and then taking out the catalyst carrier to remove water; preferably, dissolving a tin salt and an acid in water to prepare a sensitizing solution;

[0022] And / or, step S2, preparing an activation solution, then placing the catalyst support obtained in step S1 in the activation solution, stirring until the catalyst support is completely impregnated, then taking out the catalyst support and removing moisture; preferably, the palladium salt is dissolved in water to prepare the activation solution;

[0023] And / or, step S3, preparing a complex metal salt solution, placing the catalyst support obtained in step S2 in the metal salt solution; preferably, the metal salt and the complexing agent are dissolved in water to prepare the metal salt solution;

[0024] Step S4, preparing a reducing solution, adding the reducing solution to the metal salt solution in step S3 until the reaction is completed, and after the reaction is completed, taking out the obtained solid for washing and drying; preferably, the reducing agent is dissolved in water to prepare the reducing solution,

[0025] Step S5, preparing a phosphoric acid solution, placing the solid dried in step S4 in the phosphoric acid solution for treatment, taking out the treated solid, washing, drying and calcining it to obtain the catalyst; preferably, phosphoric acid is dissolved in water to prepare a phosphoric acid solution.

[0026] In one embodiment, in step S1, the catalyst carrier is one or more of γ-Al2O3, fumed silica, ZSM-5 molecular sieve, Y-molecular sieve, SBA-15 molecular sieve, S-1 molecular sieve, and the mass ratio of the sensitizing solution to the catalyst carrier is 5 to 50.

[0027] In one embodiment, in step S1, the tin salt is SnCl2, and the mass concentration of the tin salt in the sensitizing solution is 1% to 10%;

[0028] And / or, the acid is one of sulfuric acid and hydrochloric acid, and the mass concentration of the acid in the sensitizing solution is 0.5% to 5%.

[0029] In one embodiment, in step S2, the palladium salt is one of palladium chloride, palladium nitrate, palladium sulfate, and palladium acetate, and the mass concentration of the palladium salt is 0.05% to 0.5%; and / or, the mass ratio of the activation solution to the catalyst carrier is 5 to 50.

[0030] In one embodiment, in step S3, the cation of the metal salt is Co 2+ 、Ni 2+ , Cu 2+ 、Ce 3+ 、Zr 4+ One or more of the following, the anion of the metal salt is Cl - 、NO 3- , acetate, citrate or more, and the mass concentration of the metal salt in the complex metal salt solution is 1% to 8%.

[0031] And / or, in step S3, the complexing agent is ammonia, the mass concentration of ammonia in the complexing metal salt solution is 1% to 15%, and the mass ratio of the complexing metal salt solution to the catalyst carrier is 5 to 20.

[0032] In one embodiment, in step S4, the reducing agent is one of NaBH4, LiBH4, and NaH2PO2, the mass concentration of the reducing agent in the reducing solution is 1-10%, and the mass ratio of the reducing agent to the metal salt solution is 0.2-5.

[0033] In one embodiment, in step S4, the reducing liquid is added as follows: first, the complex metal salt solution is stirred, and the reducing liquid is gradually added to the complex metal salt solution; as the reducing liquid is added, a chemical reaction occurs and a large number of bubbles are released; when bubbles are no longer generated, the reaction ends to obtain the solid; after the reaction, the obtained solid is taken out and washed to neutrality, and the washed neutral solid is dried in an inert gas flow; wherein, the drying temperature of step S4 is 100°C to 200°C, and the drying time in step S4 is 4h to 12h.

[0034] In one embodiment, in step S5, the solid treated in step S4 is taken out and washed to neutrality, and the washed neutral solid is dried in an inert gas flow, and then calcined in an inert gas flow after drying; wherein the drying temperature of step S5 is 30° C. to 100° C., and the drying time of step S5 is 20 min to 300 min;

[0035] And / or, the calcination temperature of step S5 is 400° C. to 800° C., and the calcination time of step S5 is 4 h to 12 h;

[0036] And / or, the mass concentration of phosphoric acid in the phosphoric acid solution is 2-15%.

[0037] According to the second aspect of the present application, the present application provides a catalyst for one-step preparation of diamine from lactam, wherein the catalyst is prepared by the preparation method described above.

[0038] According to the third aspect of the present application, the present application provides a one-step synthesis method of lactam to diamine, the above-mentioned catalyst is placed in a fixed bed reactor device and hydrogen is introduced, the catalyst is heated for pretreatment, after the pretreatment is completed, the fixed bed reactor is heated to the reaction temperature, ammonia and hydrogen are introduced, and lactam is added to react to obtain the diamine.

[0039] Preferably, the lactam comprises caprolactam; and the diamine comprises hexamethylenediamine.

[0040] In one embodiment, the pretreatment temperature is 200° C. to 500° C.;

[0041] And / or, the pretreatment pressure is 0.5MPa to 3MPa;

[0042] And / or, the pretreatment time is 30 min to 300 min;

[0043] And / or, during the pretreatment, the flow rate of hydrogen introduced into the catalyst is 10-100 ml / min;

[0044] And / or, the volume flow ratio of ammonia to hydrogen is 5 to 100;

[0045] And / or, the reaction temperature is 250-400°C;

[0046] And / or, the reaction pressure is 0.5-2.5 MPa;

[0047] And / or, the reaction space velocity of the caprolactam is 1.0 to 4.0 h -1 .

[0048] The present application provides a catalyst for converting lactam into diamine in one step, and a preparation method and application thereof. The catalyst carrier is subjected to a sensitization treatment operation, an activation treatment operation to load the catalyst carrier with an active metal, a complexation treatment operation, a reduction treatment operation and an acid treatment operation in sequence, and then washed, dried and calcined to obtain the catalyst. The present application adopts a specific step treatment sequence to make the catalyst first form a deposition center, and then improve the stability of the metal loaded on the surface of the catalyst carrier through complexation, and then adjust the density of the surface complexed metal, and then perform an acid treatment to prevent excessive reaction, thereby achieving the purpose of converting lactam into diamine in one step. The catalyst is activated by hydrogen before the reaction to form a coexistence of metal-metal phosphate dual active phases, wherein the metal phosphate is an active phase for the reaction of lactam with ammonia to generate aminonitriles, and the metal is an active phase for the reaction of aminonitriles with hydrogen to generate diamines, and the two active phases coexist. In the process of preparing diamines using the catalyst, the lactam amination reaction and the aminonitrile hydrogenation reaction can be coupled to realize the one-step reaction of lactam to produce diamines, which greatly simplifies the production process, the single-pass conversion rate of lactam is greater than 99.58%, and the selectivity of diamine is greater than 94.01%. DETAILED DESCRIPTION

[0049] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0050] Example 1

[0051] Step S1, dissolving SnCl2 and hydrochloric acid in water to prepare a sensitizing solution, wherein the mass concentration of tin salt in the sensitizing solution is 2%, and the mass concentration of hydrochloric acid in the sensitizing solution is 2.5%. Add 1 kg of fumed silicon oxide into the sensitizing solution and stir until it is completely impregnated, wherein the mass ratio of the sensitizing solution to the fumed silicon oxide is 10, and then take out the fumed silicon oxide and drain the water;

[0052] Step S2, dissolving palladium chloride in water to prepare an activation solution, wherein the concentration of palladium chloride in the activation solution is 0.1%, adding the sensitized fumed silicon oxide into the activation solution, wherein the mass ratio of the activation solution to the fumed silicon oxide is 10, stirring until the immersion is complete, then taking out the fumed silicon oxide and draining the water;

[0053] Step S3, dissolving nickel chloride in water to prepare a nickel chloride solution with a mass concentration of 8%, introducing ammonia as a complexing agent, and continuously stirring the metal salt solution while adding it. A precipitate is first generated in the metal salt solution, and the precipitate gradually disappears with the addition of ammonia. The mass concentration of ammonia is 5%. Adding the activated fumed silicon oxide to the nickel chloride solution, the mass ratio of the nickel chloride solution to the fumed silicon oxide is 10, and stirring to form a uniform suspension.

[0054] Step S4, dissolving NaH2PO2 in water to prepare a reducing agent solution, the mass concentration of the reducing agent in the reducing agent solution is 5%, gradually adding 5 kg of the reducing solution to the metal salt solution, the mass ratio of the reducing agent to the nickel chloride solution is 1, stirring continuously until no bubbles emerge to obtain a solid, taking out the solid, washing it to neutrality, and drying it at 100°C in a nitrogen flow for 10 hours.

[0055] Step S5, prepare a phosphoric acid solution with a mass concentration of 5%, heat the phosphoric acid solution to 60°C, add the solid dried in step S4 to the phosphoric acid solution, stir for 90 minutes, take out the solid, wash it to neutrality, dry it at 100°C for 10 hours in a nitrogen flow, and then calcine it at 500°C for 4 hours to obtain a catalyst for preparing hexamethylenediamine from caprolactam in one step.

[0056] The catalyst obtained in step S5 was placed in a fixed bed reactor and hydrogen was introduced. The mass of the added catalyst was 100 g, the flow rate of the introduced hydrogen was 2 L / min, and the fixed bed reactor was heated to 300° C. and pretreated for 300 min.

[0057] After the pretreatment, the catalyst was evaluated. The fixed bed reactor was heated to 320°C and the reaction gas was introduced. The gas composition was a mixture of ammonia and hydrogen. The volume flow ratio of ammonia to hydrogen was 20. The reaction pressure was maintained at 1 MPa. Caprolactam was introduced. The reaction space velocity of caprolactam was 2.1 h -1 .

[0058] According to the analysis, the single-pass conversion rate of caprolactam is 99.98%, and the selectivity of hexamethylenediamine is 95.23%.

[0059] Example 2

[0060] Step S1, dissolving SnCl2 and hydrochloric acid in water to prepare a sensitizing solution, wherein the mass concentration of tin salt in the sensitizing solution is 1%, and the mass concentration of hydrochloric acid in the sensitizing solution is 0.5%. Adding 1 kg of γ-Al2O3 into the sensitizing solution and stirring until the sensitizing solution is completely impregnated, wherein the mass ratio of the sensitizing solution to γ-Al2O3 is 5, and then taking out the γ-Al2O3 and draining the water;

[0061] Step S2, dissolving palladium nitrate in water to prepare an activation solution, wherein the concentration of palladium chloride in the activation solution is 0.05%, adding the sensitized γ-Al2O3 to the activation solution, wherein the mass ratio of the activation solution to the γ-Al2O3 is 5, stirring until the immersion is complete, then taking out the γ-Al2O3 and draining the water;

[0062] Step S3, dissolving cobalt nitrate in water to prepare a cobalt nitrate solution with a mass concentration of 1%, introducing ammonia as a complexing agent, and continuously stirring the cobalt nitrate solution while adding, a precipitate is first generated in the solution, and the precipitate gradually disappears with the addition of ammonia, and the mass concentration of ammonia is 1%. Adding the activated γ-Al2O3 to the cobalt nitrate solution, the mass ratio of the cobalt nitrate solution to the γ-Al2O3 is 20, and stirring to form a uniform suspension.

[0063] Step S4, dissolving NaBH4 in water to prepare a reducing agent solution, wherein the mass concentration of the reducing agent in the reducing agent solution is 1%. The reducing agent solution is gradually added to the cobalt nitrate solution, wherein the mass ratio of the reducing agent to the cobalt nitrate solution is 5, and the solution is continuously stirred until no more bubbles emerge to obtain a solid, and the solid is taken out, washed to neutrality, and dried at 100° C. for 12 hours in a nitrogen stream.

[0064] Step S5, prepare a phosphoric acid solution with a mass concentration of 2%, heat the phosphoric acid solution to 30°C, add the solid dried in step S4 to the phosphoric acid solution, and stir for 300 minutes. Take out the catalyst, wash it to neutrality, dry it at 100°C for 10 hours in a nitrogen flow, and then calcine it at 400°C for 12 hours to obtain a catalyst for preparing hexamethylenediamine from caprolactam in one step.

[0065] The catalyst obtained in step S5 was placed in a fixed bed reactor and hydrogen was introduced. The mass of the added catalyst was 100 g, the flow rate of the introduced hydrogen was 10 L / min, and the fixed bed reactor was heated to 500° C. and pretreated for 30 minutes.

[0066] After the pretreatment, the catalyst was evaluated. The fixed bed reactor was heated to 250°C and the reaction gas was introduced. The gas composition was a mixture of ammonia and hydrogen. The volume flow ratio of ammonia to hydrogen was 100. The reaction pressure was maintained at 2.5 MPa. Caprolactam was introduced. The reaction space velocity of caprolactam was 0.5 h -1 .

[0067] According to the analysis, the single-pass conversion rate of caprolactam is 99.82%, and the selectivity of hexamethylenediamine is 94.31%.

[0068] Example 3

[0069] Step S1, dissolving SnCl2 and hydrochloric acid in water to prepare a sensitizing solution, wherein the mass concentration of tin salt in the sensitizing solution is 10%, and the mass concentration of hydrochloric acid in the sensitizing solution is 5%. Add 1 kg of ZSM-5 molecular sieve into the sensitizing solution and stir until it is completely impregnated, wherein the mass ratio of the sensitizing solution to the catalyst carrier is 50, and then take out the ZSM-5 molecular sieve and drain the water;

[0070] Step S2, dissolving palladium acetate in water to prepare an activation solution, wherein the concentration of palladium acetate in the activation solution is 0.5%, adding the sensitized ZSM-5 molecular sieve into the activation solution, wherein the mass ratio of the activation solution to the ZSM-5 molecular sieve is 50, stirring until the immersion is complete, then taking out the ZSM-5 molecular sieve and draining the water;

[0071] Step S3, dissolving cupric acetate in water to prepare a metal salt solution with a mass concentration of 8%, introducing ammonia as a complexing agent, and continuously stirring the cupric acetate solution while adding it. A precipitate is first generated in the solution, and the precipitate gradually disappears with the addition of ammonia. The mass concentration of ammonia is 15%. The activated ZSM-5 molecular sieve is added to the cupric acetate solution, the mass ratio of the cupric acetate solution to the ZSM-5 molecular sieve is 5, and stirred into a uniform suspension.

[0072] Step S4, dissolving NaBH4 in water to prepare a reducing agent solution, wherein the mass concentration of the reducing agent in the reducing agent solution is 10%. The reducing agent solution is gradually added to the copper acetate solution, wherein the mass ratio of the reducing agent to the copper acetate solution is 5, and the solution is continuously stirred until no more bubbles emerge to obtain a solid, and the solid is taken out, washed to neutrality, and dried at 200° C. for 4 hours in a nitrogen stream.

[0073] Step S5, preparing a phosphoric acid solution with a mass concentration of 15%, heating the phosphoric acid solution to 100° C., adding the solid dried in step S4 to the phosphoric acid solution, stirring for 20 minutes, taking out the solid, washing it to neutrality, drying it at 120° C. in a nitrogen flow for 6 hours, and then calcining it at 800° C. for 4 hours to obtain a one-step catalyst for preparing hexamethylenediamine from caprolactam.

[0074] The catalyst obtained in step S5 was placed in a fixed bed reactor and hydrogen was introduced. The mass of the added catalyst was 100 g, the flow rate of the introduced hydrogen was 1 L / min, and the fixed bed reactor was heated to 200° C. and pretreated for 300 min.

[0075] After the pretreatment, the catalyst was evaluated, the fixed bed reactor was heated to 400°C, the reaction gas was introduced, the gas composition was a mixture of ammonia and hydrogen, the volume flow ratio of ammonia to hydrogen was 5, the reaction pressure was maintained at 0.5MPa, caprolactam was introduced, and the reaction space velocity of caprolactam was 4.0h -1 .

[0076] According to the analysis, the single-pass conversion rate of caprolactam is 99.77%, and the selectivity of hexamethylenediamine is 94.01%.

[0077] Example 4

[0078] Step S1, dissolving SnCl2 and hydrochloric acid in water to prepare a sensitizing solution, wherein the mass concentration of tin salt in the sensitizing solution is 7.5%, and the mass concentration of hydrochloric acid in the sensitizing solution is 3%. Add 1 kg of Y molecular sieve into the sensitizing solution and stir until it is completely immersed, wherein the mass ratio of the sensitizing solution to the Y molecular sieve is 30, and then take out the Y molecular sieve and drain the water;

[0079] Step S2, dissolving palladium sulfate in water to prepare an activation solution, wherein the concentration of palladium sulfate in the activator is 0.3%, adding the sensitized Y molecular sieve into the activation solution, wherein the mass ratio of the activation solution to the Y molecular sieve is 30, stirring until the immersion is complete, then taking out the Y molecular sieve and draining the water;

[0080] Step S3, dissolving cerium citrate in water to prepare a metal salt solution with a mass concentration of 6%, introducing ammonia, and continuously stirring the cerium citrate solution while introducing ammonia, a precipitate is first generated in the cerium citrate solution, and the precipitate gradually disappears with the addition of ammonia, and the mass concentration of ammonia is 10%. Adding the activated Y molecular sieve to the cerium citrate solution, the mass ratio of the cerium citrate solution to the Y molecular sieve is 10, and stirring to form a uniform suspension.

[0081] Step S4, dissolving LiBH4 in water to prepare a reducing agent solution, wherein the mass concentration of the reducing agent in the reducing solution is 7.5%. The reducing agent solution is gradually added to the cerium citrate solution, wherein the mass ratio of the reducing agent to the cerium citrate solution is 5, and the solution is continuously stirred until no more bubbles are emitted to obtain a solid, and the solid is taken out, washed to neutrality, and dried at 150° C. for 8 hours in a nitrogen stream.

[0082] Step S5, prepare a phosphoric acid solution with a mass concentration of 8%, heat the phosphoric acid solution to 80°C, add the solid dried in step S4 to the phosphoric acid solution, stir for 60 minutes, take out the solid, wash it to neutrality, dry it at 120°C for 6 hours in a nitrogen flow, and then calcine it at 600°C for 6 hours to obtain a one-step catalyst for preparing hexamethylenediamine from caprolactam.

[0083] The catalyst obtained in step S5 was placed in a fixed bed reactor and hydrogen was introduced. The mass of the added catalyst was 100 g, the flow rate of the introduced hydrogen was 8 L / min, and the fixed bed reactor was heated to 400° C. and pretreated for 80 minutes.

[0084] After the pretreatment, the catalyst was evaluated. The fixed bed reactor was heated to 360°C and the reaction gas was introduced. The gas composition was a mixture of ammonia and hydrogen. The volume flow ratio of ammonia to hydrogen was 75. The reaction pressure was maintained at 1.5 MPa. Caprolactam was introduced and the reaction space velocity of caprolactam was 3.0 h -1 .

[0085] According to the analysis, the single-pass conversion rate of caprolactam is 99.58%, and the selectivity of hexamethylenediamine is 95.09%.

[0086] Example 5

[0087] Step S1, dissolving SnCl2 and hydrochloric acid in water to prepare a sensitizing solution, wherein the mass concentration of tin salt in the sensitizing solution is 2.5%, and the mass concentration of hydrochloric acid in the sensitizing solution is 1.5%. Add 1 kg of SBA-15 molecular sieve into the sensitizing solution and stir until it is completely impregnated, wherein the mass ratio of the sensitizing solution to the SBA-15 molecular sieve is 10, and then take out the SBA-15 molecular sieve and drain the water;

[0088] Step S2, dissolving palladium chloride in water to prepare an activation solution, wherein the concentration of palladium chloride in the activation solution is 0.1%, adding the sensitized SBA-15 molecular sieve into the activation solution, wherein the mass ratio of the activation solution to the SBA-15 molecular sieve is 10, stirring until the immersion is complete, then taking out the SBA-15 molecular sieve and draining the water;

[0089] Step S3, dissolving zirconium nitrate in water to prepare a metal salt solution with a mass concentration of 2.5%, introducing ammonia, and continuously stirring the zirconium nitrate solution while introducing ammonia, a precipitate is first generated in the zirconium nitrate solution, and the precipitate gradually disappears with the addition of ammonia, and the mass concentration of ammonia is 5%. Adding the activated SBA-15 molecular sieve to the zirconium nitrate solution, the mass ratio of the zirconium nitrate solution to the SBA-15 molecular sieve is 8, and stirring to form a uniform suspension.

[0090] Step S4, dissolving NaH2PO2 in water to prepare a reducing agent solution, wherein the mass concentration of the reducing agent in the reducing agent solution is 2.5%. The reducing agent solution is gradually added to the zirconium nitrate solution, wherein the mass ratio of the reducing agent to the zirconium nitrate solution is 1, and the solution is continuously stirred until no more bubbles are emitted to obtain a solid, and the solid is taken out, washed to neutrality, and dried at a temperature of 120° C. in a nitrogen stream for 8 hours.

[0091] Step S5, prepare a phosphoric acid solution with a mass concentration of 4%, heat the phosphoric acid solution to 50°C, add the solid dried in step S4 to the phosphoric acid solution, and stir for 180 minutes. After the treatment, take out the solid, wash it to neutrality, dry it at 120°C for 6 hours in a nitrogen flow, and then calcine it at 450°C for 8 hours. A catalyst for the one-step preparation of hexamethylenediamine from caprolactam is obtained.

[0092] The solid obtained in step S5 was placed in a fixed bed reactor and hydrogen was introduced. The mass of the added catalyst was 100 g, the flow rate of the introduced hydrogen was 2.5 L / min, and the fixed bed reactor was heated to 280° C. and pretreated for 240 min.

[0093] After the pretreatment, the catalyst was evaluated. The fixed bed reactor was heated to 320°C and the reaction gas was introduced. The gas composition was a mixture of ammonia and hydrogen. The volume flow ratio of ammonia to hydrogen was 25. The reaction pressure was maintained at 1.2 MPa. Caprolactam was introduced and the reaction space velocity of caprolactam was 1.8 h -1 .

[0094] According to the analysis, the single-pass conversion rate of caprolactam is 99.76%, and the selectivity of hexamethylenediamine is 95.52%.

[0095] Example 6

[0096] Step S1, dissolving SnCl2 and hydrochloric acid in water to prepare a sensitizing solution, wherein the mass concentration of tin salt in the sensitizing solution is 2.5%, and the mass concentration of hydrochloric acid in the sensitizing solution is 2.5%. Add 1 kg of S-1 molecular sieve into the sensitizing solution and stir until it is completely impregnated, wherein the mass ratio of the sensitizing solution to the S-1 molecular sieve is 20, and then take out the S-1 molecular sieve and drain the water;

[0097] Step S2, dissolving palladium chloride in water to prepare an activation solution, wherein the concentration of palladium chloride in the activation solution is 0.3%, adding the sensitized S-1 molecular sieve into the activation solution, wherein the mass ratio of the activation solution to the S-1 molecular sieve is 25, stirring until the immersion is complete, then taking out the S-1 molecular sieve and draining the water;

[0098] Step S3, dissolving nickel acetate in water to prepare a metal salt solution with a mass concentration of 3%, introducing ammonia, and continuously stirring the nickel acetate solution while introducing ammonia, a precipitate is first generated in the solution, and the precipitate gradually disappears with the addition of ammonia, and the mass concentration of ammonia is 5%. The activated S-1 molecular sieve is added to the nickel acetate solution, the mass ratio of the nickel acetate solution to the S-1 molecular sieve is 10, and stirred into a uniform suspension.

[0099] Step S4, dissolving NaBH4 in water to prepare a reducing agent solution, wherein the mass concentration of the reducing agent in the reducing agent solution is 3%. The reducing agent solution is gradually added to the nickel acetate solution, wherein the mass ratio of the reducing agent to the nickel acetate solution is 2, and the solution is continuously stirred until no more bubbles emerge to obtain a solid, and the solid is taken out, washed to neutrality, and dried at a temperature of 140° C. for 6 hours in a nitrogen stream.

[0100] Step S5, prepare a phosphoric acid solution with a mass concentration of 6%, heat the phosphoric acid solution to 80°C, add the solid dried in step S4 to the phosphoric acid solution, stir for 120 minutes, take out the solid, wash it to neutrality, dry it at 120°C in a nitrogen flow for 6 hours, and then calcine it at 550°C for 6 hours to obtain a one-step catalyst for preparing hexamethylenediamine from caprolactam.

[0101] The catalyst obtained in step S5 was placed in a fixed bed reactor and hydrogen was introduced. The mass of the added catalyst was 100 g, the flow rate of the introduced hydrogen was 5 L / min, and the fixed bed reactor was heated to 300° C. and pretreated for 240 min.

[0102] After the pretreatment, the catalyst was evaluated, the fixed bed reactor was heated to 360°C, the reaction gas was introduced, the gas composition was a mixture of ammonia and hydrogen, the volume flow ratio of ammonia to hydrogen was 50, the reaction pressure was maintained at 1.5 MPa, caprolactam was introduced, and the reaction space velocity of caprolactam was 1.5 h -1 .

[0103] According to the analysis, the single-pass conversion rate of caprolactam is 99.91%, and the selectivity of hexamethylenediamine is 96.44%.

[0104] Example 7

[0105] Step S1, dissolving SnCl2 and hydrochloric acid in water to prepare a sensitizing solution, wherein the mass concentration of tin salt in the sensitizing solution is 2.5%, and the mass concentration of hydrochloric acid in the sensitizing solution is 2.5%. Add 1 kg of S-1 molecular sieve into the sensitizing solution and stir until it is completely impregnated, wherein the mass ratio of the sensitizing solution to the S-1 molecular sieve is 20, and then take out the S-1 molecular sieve and drain the water;

[0106] Step S2, dissolving palladium chloride in water to prepare an activation solution, wherein the concentration of palladium chloride in the activation solution is 0.3%, adding the sensitized S-1 molecular sieve into the activation solution, wherein the mass ratio of the activation solution to the S-1 molecular sieve is 25, stirring until the immersion is complete, then taking out the S-1 molecular sieve and draining the water;

[0107] Step S3, dissolving nickel acetate in water to prepare a metal salt solution with a mass concentration of 3%, introducing ammonia, and continuously stirring the nickel acetate solution while introducing ammonia, a precipitate is first generated in the solution, and the precipitate gradually disappears with the addition of ammonia, and the mass concentration of ammonia is 5%. The activated S-1 molecular sieve is added to the nickel acetate solution, the mass ratio of the nickel acetate solution to the S-1 molecular sieve is 10, and stirred into a uniform suspension.

[0108] Step S4, dissolving NaBH4 in water to prepare a reducing agent solution, wherein the mass concentration of the reducing agent in the reducing agent solution is 3%. The reducing agent solution is gradually added to the nickel acetate solution, wherein the mass ratio of the reducing agent to the nickel acetate solution is 2, and the solution is continuously stirred until no more bubbles emerge to obtain a solid, and the solid is taken out, washed to neutrality, and dried at a temperature of 140° C. for 6 hours in a nitrogen stream.

[0109] Step S5, prepare a phosphoric acid solution with a mass concentration of 6%, heat the phosphoric acid solution to 80°C, add the solid dried in step S4 to the phosphoric acid solution, stir for 120 minutes, take out the solid, wash it to neutrality, dry it at 120°C in a nitrogen flow for 6 hours, and then calcine it at 550°C for 6 hours to obtain a one-step catalyst for preparing hexamethylenediamine from caprolactam.

[0110] The catalyst obtained in step S5 was placed in a fixed bed reactor and hydrogen was introduced. The mass of the added catalyst was 100 g, the flow rate of the introduced hydrogen was 5 L / min, and the fixed bed reactor was heated to 300° C. and pretreated for 240 min.

[0111] After the pretreatment, the catalyst was evaluated. The fixed bed reactor was heated to 360°C and the reaction gas was introduced. The gas composition was a mixture of ammonia and hydrogen. The volume flow ratio of ammonia to hydrogen was 50. The reaction pressure was maintained at 1.5 MPa. Lauryl lactam was introduced. The reaction space velocity of lauryl lactam was 1.5 h -1 .

[0112] The analysis showed that the single-pass conversion rate of laurolactam was 99.91%, and the selectivity of dodecanediamine was 96.44%.

[0113] Comparative Example 1

[0114] The preparation method of the catalyst in Comparative Example 1 adopts a method of mechanically mixing nickel and nickel phosphate;

[0115] In a nitrogen atmosphere, 80 g of Raney nickel was taken and mixed evenly with 20 g of nickel phosphate to obtain a catalyst for preparing hexamethylenediamine from caprolactam in one step.

[0116] The obtained catalyst was placed in a fixed bed reactor and hydrogen was introduced at a flow rate of 5 L / min. The fixed bed reactor was heated to 300° C. and pretreated for 240 min.

[0117] After the pretreatment, the catalyst was evaluated, the fixed bed reactor was heated to 360°C, the reaction gas was introduced, the gas composition was a mixture of ammonia and hydrogen, the volume flow ratio of ammonia to hydrogen was 50, the reaction pressure was maintained at 1.5 MPa, caprolactam was introduced, and the mass space velocity of caprolactam was 1.5 h -1 .

[0118] According to the analysis, the single-pass conversion rate of caprolactam is 27.51%, and the selectivity of hexamethylenediamine is 45.78%.

[0119] Comparative Example 2

[0120] The preparation method of the catalyst in Comparative Example 2 adopts the nickel-loaded impregnation method;

[0121] 1 kg of S-1 molecular sieve was placed in 3% nickel acetate, and after being fully impregnated, it was taken out, dried at 120°C for 4 hours, and then calcined at 550°C for 6 hours.

[0122] Prepare a phosphoric acid solution with a mass concentration of 6%, heat the phosphoric acid solution to 80°C, add the catalyst into the phosphoric acid solution, and stir for 120 minutes. After the treatment, take out the catalyst, wash it to neutrality, dry it at 120°C for 6 hours in a nitrogen flow, and then calcine it at 550°C for 6 hours. A catalyst for the one-step preparation of hexamethylenediamine from caprolactam is obtained.

[0123] The obtained catalyst was placed in a fixed bed reactor and hydrogen was introduced. The mass of the catalyst was 100 g and the flow rate of the introduced hydrogen was 5 L / min. The fixed bed reactor was heated to 300° C. and pretreated for 240 min.

[0124] After the pretreatment, the catalyst was evaluated, the fixed bed reactor was heated to 360°C, the reaction gas was introduced, the gas composition was a mixture of ammonia and hydrogen, the volume flow ratio of ammonia to hydrogen was 50, the reaction pressure was maintained at 1.5 MPa, caprolactam was introduced, and the reaction space velocity of caprolactam was 1.5 h -1 .

[0125] According to the analysis, the single-pass conversion rate of caprolactam is 41.63%, and the selectivity of hexamethylenediamine is 78.52%.

[0126] Comparative Example 3

[0127] The difference between Comparative Example 3 and Example 6 is that, in step S3, nickel acetate is dissolved in water to prepare a metal salt solution with a mass concentration of 3%, the activated S-1 molecular sieve is added to the metal salt solution, the mass ratio of the nickel acetate solution to the S-1 molecular sieve is 10, and the mixture is stirred into a uniform suspension.

[0128] According to the analysis, the single-pass conversion rate of caprolactam is 34.57%, and the selectivity of hexamethylenediamine is 85.41%.

[0129] Comparative Example 4

[0130] The difference between Comparative Example 4 and Example 6 is that the solid dried in step S4 is not subjected to phosphoric acid treatment;

[0131] According to the analysis, the single-pass conversion rate of caprolactam was 14.84%, and the selectivity of hexamethylenediamine was 0%.

[0132] Comparative Example 5

[0133] The difference between Comparative Example 5 and Example 6 is that, during the heat treatment in step S5, nitrogen protection is not used, and drying is performed in an air flow;

[0134] According to the analysis, the single-pass conversion rate of caprolactam is 79.62%, and the selectivity of hexamethylenediamine is 27.41%.

[0135] Comparative Example 6

[0136] The difference between Comparative Example 6 and Example 6 is that the catalyst obtained in step S5 is not subjected to reduction pretreatment before use;

[0137] According to the analysis, the single-pass conversion rate of caprolactam is 72.62%, and the selectivity of hexamethylenediamine is 90.09%.

[0138] Comparative Example 7

[0139] The difference between Comparative Example 7 and Example 6 is that the step of preparing the reducing solution in step S4 is advanced to before S3, and the activated molecular sieve is placed in the reducing solution and stirred into a suspension, and then the metal salt solution prepared in step S3 is gradually added to the reducing solution.

[0140] According to the analysis, the single-pass conversion rate of caprolactam is 57.12%, and the selectivity of hexamethylenediamine is 87.62%.

[0141] The following beneficial effects are achieved through the above-mentioned embodiments of the present application:

[0142] The preparation of diamines from lactams requires two-step reactions. The first step is the reaction of lactams with ammonia to form aminonitriles. The active phase of the reaction is metal phosphate, and the reaction requires a higher temperature. The second step is the reaction of aminonitriles with hydrogen to form diamines. The active phase of the reaction is a metal element, and the reaction requires a lower temperature and a higher pressure. The reaction conditions required for these two steps are different. Therefore, the reaction is carried out in two steps. The present application adopts a specific step processing sequence to allow the catalyst to first form a deposition center, and then improve the stability of the metal loaded on the surface of the catalyst carrier by complexation, and then adjust the density of the surface complexed metal, and then perform an acid treatment to prevent overreaction, thereby achieving the one-step conversion of lactam into diamines.

[0143] The present application first performs sensitization and activation treatment on the catalyst carrier, loads a small amount of Pd metal particles on the catalyst surface, forms a deposition center of the catalyst active phase, and ensures that the metal active phase can be selectively deposited on the catalyst carrier; then, by introducing a complexing agent, the metal cations are converted into metal complexes to improve the stability of the metal ions, and then a reducing agent is added to adjust the density of the surface complexed metal. The reduction reaction intensity of the reducing agent and the metal complex is moderate, and the generated hydrogen bubbles can be used as a dynamic template to make the generated metal phase present a loose and porous morphology; finally, the catalyst carrying the active metal phase is placed in phosphoric acid for acid treatment to prevent excessive reaction, and metal phosphate is generated on the metal surface. Since the metal phosphate is insoluble in water, the generated metal phosphate will adhere to the catalyst surface, preventing the reaction from proceeding further, thereby realizing the one-step conversion of lactam into diamine.

[0144] Among them, the catalyst is activated by hydrogen before the reaction to form a metal-metal phosphate dual active phase coexistence form, in which the metal element can provide free electrons, effectively increase the electron cloud density of the metal phosphate, reduce the dissociation temperature of the ammonia molecule on the catalyst surface, and reduce the temperature required for the reaction of lactam and ammonia. At the same time, due to the good conductivity of the metal element, the hydrogen cations formed after the dissociation of ammonia can be transferred to the metal element, inducing hydrogen to dissociate into hydrogen ions therein, reducing the hydrogen pressure required for the hydrogenation reaction, and the two active components interact with each other. In the process of using the catalyst to prepare diamines, the lactam amination reaction can be coupled with the aminonitrile hydrogenation reaction, and the two-step reaction can be combined into a one-step reaction, realizing the one-step reaction of lactam to produce diamines, which greatly simplifies the production process.

[0145] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a catalyst for converting lactam into diamine in one step, characterized in that: The preparation method comprises: The catalyst carrier is sequentially subjected to step S1 sensitization treatment operation, step S2 activation treatment operation to load active metal on the catalyst carrier, step S3 complexation treatment operation, step S4 reduction treatment operation and step S5 acid treatment operation, and then washed, dried and calcined to obtain the catalyst.

2. The preparation method according to claim 1, characterized in that: Step S1, preparing a sensitizing solution, placing a catalyst carrier in the sensitizing solution, taking out the catalyst carrier after complete immersion, and removing moisture; preferably, dissolving a tin salt and an acid in water to prepare a sensitizing solution; And / or, step S2, preparing an activation solution, placing the catalyst support obtained in step S1 in the activation solution, taking out the catalyst support after complete immersion, and removing moisture; preferably, dissolving palladium salt in water to prepare the activation solution, And / or, step S3, preparing a complex metal salt solution, placing the catalyst support obtained in step S2 in the complex metal salt solution; preferably, the metal salt and the complexing agent are dissolved in water to prepare the complex metal salt solution; And / or, step S4, preparing a reducing solution, adding the reducing solution to the complex metal salt solution of step S3 until the reaction is completed, taking out the obtained solid after the reaction is completed, washing and drying, preferably, the reducing agent is dissolved in water to prepare the reducing solution; And / or, step S5, dissolving phosphoric acid in water to prepare a phosphoric acid solution, placing the solid dried in step S4 in the phosphoric acid solution for treatment, taking out the treated solid, washing, drying and calcining to obtain the catalyst.

3. The preparation method according to claim 2, characterized in that: The catalyst carrier is one or more of γ-Al2O3, fumed silicon oxide, ZSM-5 molecular sieve, Y-molecular sieve, SBA-15 molecular sieve, S-1 molecular sieve, and the mass ratio of the sensitizing solution to the catalyst carrier is 5-50.

4. The preparation method according to claim 3, characterized in that: In the step S1, the tin salt is SnCl2, and the mass concentration of the tin salt in the sensitizing solution is 1% to 10%; And / or, the acid is one of sulfuric acid and hydrochloric acid, and the mass concentration of the acid in the sensitizing solution is 0.5% to 5%.

5. The preparation method according to claim 3, characterized in that: In step S2, the palladium salt is at least one of palladium chloride, palladium nitrate, palladium sulfate and palladium acetate, and the mass concentration of the palladium salt is 0.05% to 0.5%; and / or, the mass ratio of the activation solution to the catalyst carrier is 5 to 50.

6. The preparation method according to claim 2, characterized in that: In step S3, the cation in the complex metal salt solution is Co 2+ 、Ni 2+ , Cu 2+ 、Ce 3+ 、Zr 4+ One or more of the following, wherein the anion in the complex metal salt solution is Cl - 、NO 3- , acetate, citrate or more, wherein the mass concentration of the metal salt in the complex metal salt solution is 1% to 8%; And / or, in step S3, the complexing agent is ammonia, the mass concentration of ammonia in the complexing metal salt solution is 1% to 15%, and the mass ratio of the complexing metal salt solution to the catalyst carrier is 5 to 20.

7. The preparation method according to claim 2, characterized in that: In step S4, the reducing agent is at least one of NaBH4, LiBH4, and NaH2PO2, the mass concentration of the reducing agent in the reducing solution is 1-10%, and the mass ratio of the reducing agent to the metal salt solution is 0.2-5.

8. The preparation method according to claim 7, characterized in that: In the step S4, the reducing solution is added by first stirring the complex metal salt solution, and then gradually adding the reducing solution to the complex metal salt solution. After the reaction is completed, the obtained solid is taken out and cleaned to neutrality, and then dried in an inert gas flow; wherein, the drying temperature in the step S4 is 100°C to 200°C, and the drying time in the step S4 is 4h to 12h.

9. The preparation method according to claim 2, characterized in that: In the step S5, the solid treated in the step S4 is taken out and washed to neutrality, and then dried in an inert gas flow, and then calcined in an inert gas flow after drying; wherein the drying temperature of the step S5 is 30° C. to 100° C., and the drying time of the step S5 is 20 min to 300 min; And / or, the calcination temperature of step S5 is 400° C. to 800° C., and the calcination time of step S5 is 4 h to 12 h; And / or, the mass concentration of phosphoric acid in the phosphoric acid solution is 2-15%.

10. A catalyst for one-step preparation of diamine from lactam, characterized in that: The catalyst is prepared by the preparation method according to any one of claims 1 to 9.

11. A method for synthesizing diamine from lactam in one step, characterized in that: The catalyst according to claim 10 is placed in a fixed bed reactor and hydrogen is introduced, and the catalyst is subjected to heat pretreatment. After the pretreatment is completed, the fixed bed reactor is heated to a reaction temperature, ammonia, hydrogen and lactam are introduced and reacted to obtain the diamine.

12. The method for synthesizing diamine from lactam in one step according to claim 11, characterized in that: The lactam includes caprolactam; the diamine includes hexamethylenediamine; the pretreatment temperature is 200°C to 500°C; and / or, the pretreatment pressure is 0.5MPa to 3MPa; and / or, the pretreatment time is 30min to 300min; and / or, during the pretreatment, the flow rate of hydrogen introduced when 1g of catalyst is added is 10 to 100ml / min; And / or, the volume flow ratio of ammonia to hydrogen is 5 to 100; And / or, the reaction temperature is 250-400°C; And / or, the reaction pressure is 0.5-2.5 MPa; And / or, the reaction space velocity of the caprolactam is 1.0 to 4.0 h -1 .

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