Dehydrogenation catalyst for preparing aza-aromatic rings, preparation method therefor and use thereof

Abstract

Provided are a dehydrogenation catalyst for preparing aza-aromatic rings, a preparation method therefor, and a use thereof, belonging to the technical field of catalyst preparation. The dehydrogenation catalyst comprises a carrier having specific physical parameters, a first active metal component Pd, at least one of a second active metal component selected from Re, Sn or Ir, and a P-containing active promoter. The provided dehydrogenation catalyst can be used for dehydrogenation reactions with raw material compounds containing aza-aromatic rings, directly obtaining aza-aromatic rings, with a raw material conversion rate of over 99%, an aza-aromatic ring product selectivity of over 99% and a yield of 98-99%, and the dehydrogenation catalyst has a service life of 5500 h or more. The dehydrogenation catalyst can be used to prepare aza-aromatic rings having different numbers of carbon atoms, particularly for dehydrogenating aza-aromatic byproducts in the production process of hexamethylenediamine to prepare aza-aromatic rings, thereby turning waste oil raw materials into valuable products, and converting them into high-value fine chemicals.

Description

Dehydrogenation catalyst for preparing nitrogen heteroaromatic ring and preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, in particular to a dehydrogenation catalyst for preparing nitrogen heteroaromatic ring and a preparation method and application thereof. BACKGROUND

[0002] Nitrogen heteroaromatic ring is an important chemical product, and is also a key intermediate for preparing various high-value-added pesticides and pharmaceutical products such as fungicides, herbicides, fragrances, and vitamins. 3-methylpyridine is a core raw material for producing nicotinamide and nicotinic acid (vitamin B3). Nicotinic acid is one of the indispensable vitamins for humans and animals, participates in the oxidation-reduction process of tissues, has the functions of promoting cell metabolism and expanding blood vessels, and can promote the growth and development of humans and animals. 3-methylpyridine as a starting material can also be used to synthesize dozens of high-value-added and patented pesticides, such as fluazifop-butyl, fluazifop-p-butyl, difenoxuron, ribonucleic acid, and ribonucleic acid. In addition, pyrrole and alkylpyrrole, as well as other nitrogen heteroaromatic substances, are important pharmaceutical intermediates for producing pyrrole antibiotics and anti-HIV drugs, and have been widely used in clinical treatment. At the same time, pyrrole and alkylpyrrole can also be used to synthesize pyrrole sulfonylurea herbicides and pyrrole pyrimidine alcohol fungicides.

[0003] Hexamethylenediamine is an important raw material for producing nylon materials. In the process of producing hexamethylenediamine by hydrogenation of adiponitrile, various nitrogen-containing heterocyclic compounds with similar molecular structures and similar boiling points, including 3-ethylpyrrolidine and 3-methylpiperidine, are by-produced. The normal boiling points of 3-ethylpyrrolidine and 3-methylpiperidine differ by less than 5°C, and only 10-15% of 3-ethylpyrrolidine and 85-90% of 3-methylpiperidine mixture can be obtained by conventional rectification separation, which cannot be separated into pure products for sale, and can only be incinerated in the form of waste oil. If the nitrogen-containing heterocyclic compounds by-produced in the production process of hexamethylenediamine, such as 3-ethylpyrrolidine and / or 3-methylpiperidine, can be used as raw materials to undergo dehydrogenation reaction by a dehydrogenation catalyst, 3-ethylpyrrole and / or 3-methylpyridine products can be obtained. The normal boiling points of 3-ethylpyrrole and 3-methylpyridine differ by 20°C, and high-purity products can be obtained by conventional rectification. This process can not only solve the problem of by-product separation and operation difficulty in the production process of hexamethylenediamine, but also can turn waste into treasure by converting the by-products into fine chemicals which are easy to purify by rectification and have high added value, which is very beneficial to the quality improvement and efficiency increase of industrial production. Therefore, the dehydrogenation catalyst is particularly important for the dehydrogenation reaction.

[0004] However, the existing production processes of nitrogen heteroaromatic ring all have defects such as long process route, low atom economy, harsh reaction conditions, high equipment investment and energy consumption.

[0005] The current industrial production process of 3-methylpyridine, a nitrogen heterocyclic compound, is the aldehyde ammonia oxidation method, that is, using acetaldehyde, formaldehyde and ammonia as raw materials, and converting them into pyridine through catalyst ZSM-5 molecular sieve or SiO2-Al2O3-Bi2O3, while producing 3-methylpyridine as a byproduct, with a yield of about 30%. The raw materials used in this reaction are cheap and easy to obtain, and it can be produced continuously on a large scale, which is the mainstream process for the industrial production of 3-methylpyridine at present. However, with the continuous challenge of the sales and production ban of paraquat, a downstream product of pyridine, in many countries in the world, more than 20 countries and regions including the European Union, China, Brazil and the United States have banned the production and sale of paraquat. This has led to a significant decline in the operating rate of the above-mentioned pyridine production device using this process. In addition, from the perspective of production process, (1) the selectivity of 3-methylpyridine in the aldehyde ammonia oxidation method is only 30% besides producing pyridine, and the ratio of the two is difficult to increase. This leads to the production of 3-methylpyridine being always affected by the production of pyridine, and it is difficult to increase the production capacity of 3-methylpyridine alone to meet the continuous growth of the downstream market demand; (2) the aldehyde ammonia oxidation method needs to be matched with a synthetic ammonia device, which has high energy consumption and huge carbon dioxide emissions, and does not conform to the national "double carbon" policy and the development trend of green chemical industry; (3) the aldehyde ammonia oxidation method also produces a variety of byproducts including 4-methylpyridine, 2-methylpyridine, 2,6-dimethylpyridine and bipyridine, which are difficult to separate by rectification and have complex purification process. Especially, about 1% of 4-methylpyridine byproduct is almost impossible to effectively separate and purify. This will have a very adverse effect on the quality and purity of downstream vitamin and other pharmaceutical intermediates.

[0006] The production process of pyrrole is to use butynediol produced from acetaldehyde and formaldehyde as raw material to react with ammonia gas at high temperature and high pressure (more than 10 MPa) to produce pyrrole. The reaction conditions are harsh and the equipment investment is high.

[0007] The current published processes for preparing (alkyl)pyrrole by dehydrogenation of (alkyl)pyrrolidine and preparing (alkyl)piperidine by dehydrogenation of (alkyl)piperidine include the following:

[0008] Patent US6162928A discloses that 0.5% Pd-0.5% Pt / ZrO2 catalyst is used to catalyze the dehydrogenation of pyrrolidine to prepare pyrrole at 230-240℃. However, from the published examples, the conversion rate of the raw material decreased from 96.3% to 91.0% after the catalyst ran for only 34h.

[0009] Patent CN1903842A reports that Pd / SiO2 catalyst is used to catalyze the dehydrogenation of 3-methylpiperidine to prepare 3-methylpyridine, but the yield of 3-methylpyridine is only about 90%, and the long-term operation of the catalyst is not disclosed.

[0010] Patent US5714610A discloses a two-step reaction to convert 2-methylpentanediamine into 3-methylpyridine by cyclization and dehydrogenation. First, 2-methylpentanediamine is cyclized into 3-methylpiperidine with hydrogen-type molecular sieve as the cyclization catalyst; then 3-methylpiperidine is dehydrogenated into 3-methylpyridine with Pd supported as the dehydrogenation catalyst. The two catalysts can be loaded into the same reactor or two reactors in series to realize continuous preparation of 3-methylpyridine. However, according to the information disclosed in the patent: (1) when 2-methylpentanediamine and 3-methylpiperidine are used as raw materials to evaluate the performance of the two catalysts respectively, the yield of the two-step reaction can reach 99%, but the dehydrogenation catalyst has a service life of only 300 hours; (2) when 2-methylpentanediamine is used as raw material and passed through the same reactor loaded with cyclization catalyst and dehydrogenation catalyst, the yield of 3-methylpyridine is 97%, and 2.9% of 3-methylpiperidine has not been dehydrogenated and converted, which needs to be purified by rectification; (3) when 2-methylpentanediamine is used as raw material and passed through two reactors in series loaded with cyclization catalyst and dehydrogenation catalyst respectively, the yield of 3-methylpiperidine can reach 99.7%, but the process evaluation time is only 71 hours. In addition, when the purity of the raw material decreases, the yield of 3-methylpyridine will decrease to different degrees under the above three process conditions, and the activity of the catalyst decreases rapidly. At the same time, in order to make the yield of dehydrogenation reaction reach 99%, the loading of Pd needs to be higher than 3wt%, which greatly increases the cost in industrial production due to the high market price of noble metal palladium.

[0011] Patent CN101384525B discloses a method for preparing 3-methylpyridine by dehydrogenating 3-methylpiperidine under oxygen-containing conditions. By adding a certain proportion of air or oxygen into the feed stream, the stability and service life of the dehydrogenation catalyst Pd / ZrO2 can be improved without affecting the reaction hot spot temperature. Moreover, with the increase of oxygen content, the degree of deactivation of the dehydrogenation catalyst gradually decreases. However, the patent only provides a 5-hour catalyst evaluation result, and it is still unknown whether this dehydrogenation method can maintain the activity of the catalyst for a long time in industrial production.

[0012] Patent CN102164895A discloses a method for converting 2-methylpentanediamine or 3-methylpiperidine into 3-methylpyridine with Pd / Al2O3 as catalyst and hydrogen as carrier gas. However, in this preparation method, when no solvent is used, Pd / Al2O3 quickly deactivates; when water or alcohol is used as solvent, the activity of the catalyst can be maintained for more than 300 hours, but the product still contains 3-4% of 3-methylpiperidine, which needs to be purified by rectification, and the reaction space velocity is low. In addition, the addition of water or alcohol also requires the design of separation and purification equipment, and the low reaction space velocity inhibits the release of production capacity, thereby increasing the production cost.

[0013] Patent CN102548655A discloses a Pd catalyst supported catalyst catalyzes 3-methyl piperidine dehydrogenation reaction to prepare 3-methyl pyridine, and the catalyst life can reach 300 days. But the catalyst used in this patent has a high Pd loading (5-10%), which will cause the cost of the catalyst to be too high, and it is not conducive to the control of the cost of industrial production.

[0014] The preparation of nitrogen-containing aromatic ring products by dehydrogenation reaction of nitrogen-containing heterocyclic compounds has higher yield and higher atom economy compared with other processes, but the prior art also has the technical defects of high noble metal loading and easy deactivation of the catalyst. The present inventors have found that, compared with ordinary cycloalkanes such as cyclohexane or methylcyclohexane, the dehydrogenation reaction of heterocyclic alkane compounds with nitrogen atoms has the following technical difficulties: (1) the thermal stability of the raw material and the product is poor, which causes the catalyst to be more prone to coking and carbon deposition: cyclohexane or methylcyclohexane can maintain high thermal stability at 400°C high temperature, so the deactivation of such ordinary cycloalkane dehydrogenation catalyst is usually high-temperature carbon deposition, but this process is usually relatively long, so the life of such cycloalkane dehydrogenation catalyst is usually 1-2 years. The heterocyclic alkane compounds with nitrogen atoms (for example, 3-methyl piperidine or 3-ethyl pyrrolidine) are more active, and their thermal stability is poor, and they will undergo side reactions such as oxidation, dimerization, and trimerization at temperatures higher than 150°C; and their dehydrogenation products 3-methyl pyridine or 3-ethyl pyrrole will slowly undergo demethylation, dimerization, and other side reactions at temperatures above 250°C. The above-mentioned side reaction products are small molecules or oligomers containing nitrogen, which are extremely prone to coking and carbon deposition of the dehydrogenation catalyst, thus making the dehydrogenation catalyst for such raw materials usually have a shorter life (usually only a few tens to a few hundred hours), and a higher noble metal loading is needed to delay the deactivation process. (2) The raw material and product containing nitrogen heteroatoms have strong complexation ability with noble metals, which will affect the catalyst activity and cause the loss of noble metals: compared with ordinary cycloalkanes containing only carbon and hydrogen elements, nitrogen-containing heterocyclic compounds usually have strong complexation ability with Pd, Pt, Rh, or Ru noble metals, such as pyridine or pyrrole products. Especially in the case where the interaction between the noble metal and the support is not strong, some nitrogen-containing oligomers such as bipyridine by-products will complex with the noble metal, which on the one hand will destroy the dehydrogenation catalytic activity of the zero-valent noble metal, and on the other hand will cause the noble metal to dissolve into the product in the form of a complex, thus causing the slow loss of the noble metal, which is unacceptable for industrial catalyst use.

[0015] To overcome the limitations of the prior art and the technical difficulties of dehydrogenation of the above-mentioned nitrogen-containing heterocyclic compounds, the following problems need to be solved: (1) from the perspective of acceptable industrial cost, develop a production process for preparing high-value nitrogen heteroaromatic ring by dehydrogenation of by-product nitrogen-containing heterocyclic compounds in the production process of hexanediamine and supporting catalyst technology, and realize high reaction yield; (2) by improving the interaction between the active metal and the carrier of the catalyst and optimizing the distribution of the active metal in the catalyst, the catalytic activity of the catalyst can be maintained for a long time, and the use cost of the catalyst can be reduced; (3) improve production efficiency and maximize technical competitiveness. SUMMARY

[0016] To solve the above technical problems, the present application provides a dehydrogenation catalyst for preparing nitrogen heteroaromatic ring and its preparation method and application.

[0017] In one aspect, the present application provides a dehydrogenation catalyst for preparing nitrogen heteroaromatic ring: including a carrier, a first active metal component, a second active metal component and an active additive component.

[0018] The specific surface area of the carrier is 150-400 m2 / g, the pore volume is 0.6-1.5 cm3 / g, and the saturated water absorption rate is not less than 100%;

[0019] The first active metal component includes Pd;

[0020] The second active metal component includes one or more of Re, Sn or Ir;

[0021] The active additive component is a P-containing active additive.

[0022] Compared with conventional carriers, the carrier of the dehydrogenation catalyst of the present application has a larger specific surface area, pore volume and higher saturated water absorption rate, indicating that such a carrier has more levels of micropore structure. The dehydrogenation catalyst prepared with such a carrier can shorten the distance of the raw material (such as 3-methylpiperidine) to the active site of the catalyst, and the product (such as 3-methylpyridine) can be quickly desorbed from the active site, thereby reducing the occurrence of side reactions and the formation of coking.

[0023] The dehydrogenation catalyst prepared by the carrier of the application has a uniform distribution of the first active metal component Pd on the catalyst, rather than the eggshell distribution of the conventional supported catalyst. The more hierarchical pore structure of the carrier of the application ensures the uniform dispersion of the first active metal component Pd on the surface and inside of the catalyst, thereby improving the dispersion of the active metal. This is extremely beneficial to the gas-solid reaction such as the dehydrogenation of 3-methylpiperidine to prepare 3-methylpyridine, because the vaporized 3-methylpiperidine can not only react on the surface of the dehydrogenation catalyst, but also enter the hierarchical pore structure inside the catalyst to react at the active metal sites inside the catalyst. This type of active metal distribution can not only improve the processing capacity of the catalyst, but also delay the long-term high-temperature aggregation of the active metal, thereby prolonging the service life of the catalyst.

[0024] The dehydrogenation catalyst of the application introduces one or more of the second active metal components Re, Sn or Ir to inhibit the aggregation of the first active metal component. The introduction of the second active metal component (taking Re as an example) induces the first active metal Pd to be in a more reduced state or a stable metal state, while Re is usually in a higher oxidation state ReO x , which can act as an electronic modifier and form a ReO x layer around the Pd active site, thereby isolating the Pd active site into small metal clusters or even single metal sites, and further inhibiting the aggregation of the first active metal of the catalyst and the rapid deactivation of the catalyst under the condition of reducing the loading of the first active metal.

[0025] The active assistant of the dehydrogenation catalyst of the application is a P-containing active assistant. By doping P atoms into the alumina carrier, the effective P species tends to form Al-O-P species with the unsaturated coordinated Al sites and replace the weakly adsorbed hydroxyl groups in the carrier. After loading the active metal, the P-OH group promotes the formation of P-O-Pd bond, thereby forming a stronger interaction with the Pd species. The strong interaction between the P-modified carrier and the Pd nanoparticles leads to the suitable electronic structure of the Pd nanoparticles and more low-coordinated Pd sites, so that the catalyst shows more excellent dehydrogenation catalytic activity. More importantly, the stronger interaction between Pd and the carrier can effectively delay the high-temperature aggregation of Pd and prolong the service life of the catalyst. At the same time, it can also inhibit the coordination complexing ability of the nitrogen-containing oligomers with Pd metal, thereby avoiding the loss of noble metal, which is crucial for the industrial application and cost control of the catalyst.

[0026] Further, the carrier is pretreated with an alkaline compound.

[0027] The carrier is pretreated by an alkaline compound to make the ratio of basic center to acidic center of the carrier greater than 2:1. According to the research of the inventor, the heterocyclic alkane compound with nitrogen atom (for example, 3-methylpiperidine) has poor thermal stability, and side reactions such as oxidation, dimerization and trimerization occur at a temperature higher than 150℃. When the catalyst is treated by the alkaline compound, the acidic sites on the carrier of the catalyst are eliminated, which can avoid the polymerization reaction catalyzed by the acidic sites during the catalytic dehydrogenation of 3-methylpiperidine to some extent, and further effectively inhibit the coking and carbon deposition on the surface of the dehydrogenation catalyst, thereby prolonging the service life of the dehydrogenation catalyst.

[0028] In summary, the dehydrogenation catalyst of the present application has more levels of micropore structure and uniform active metal distribution mode, has better active metal dispersion, thereby delaying the long-term high-temperature aggregation of the active metal; in addition, the P-doped catalyst can promote the stronger interaction between Pd and the carrier, further effectively delay the high-temperature aggregation of Pd, prolong the service life of the catalyst, and effectively inhibit the complex coordination ability of the nitrogen-containing oligomer with Pd metal, thereby avoiding the loss of noble metal. The second active metal component can act as a modifier to induce the first active metal Pd to be in a more reduced state or a stable metal state, while the second active metal component has a higher oxidation state, which isolates the Pd active sites into small metal clusters or even single metal sites, further improves the Pd dispersion, and inhibits the aggregation of Pd and the rapid deactivation of the catalyst. After the alkaline pretreatment of the catalyst, the acidic sites on the carrier of the catalyst are eliminated, which can avoid the polymerization reaction catalyzed by the acidic sites to some extent during the catalytic dehydrogenation, effectively inhibits the coking and carbon deposition on the surface of the dehydrogenation catalyst, and thereby prolongs the service life of the dehydrogenation catalyst.

[0029] Further, the specific surface area of the carrier is 200-350m 2 / g, the pore volume is 0.8-1.3cm 3 / g, and the saturated water absorption rate is 120-150%, the carrier is preferably an aluminum-containing carrier, and further preferably at least one of alumina, an aluminum-containing molecular sieve or alumina-silica, wherein the alumina content in the aluminum-containing carrier alumina-silica is 60-100wt%, and the silica content is 0-40wt%. The present application provides data related to the parameters of the carrier.

[0030] Further, the molar ratio of the first active metal component to the second active metal component is (0.2-5):1, preferably (0.8-3):1;

[0031] Preferably, the mass ratio of the first active metal component to the carrier is (0.001-0.05):1, preferably (0.003-0.02):1; and / or, the mass ratio of the second active metal component to the carrier is (0.005-0.05):1, preferably (0.008-0.03):1.

[0032] Preferably, the mass ratio of the active promoter component to the carrier is (0.01-0.05):1, preferably (0.02-0.04):1.

[0033] Further, the P source of the P-containing active promoter is one or more of ammonium phosphate, monobasic ammonium phosphate, dibasic ammonium phosphate, trialkylammonium phosphate, dialkylammonium monohydrogen phosphate or alkylammonium dihydrogen phosphate, wherein the alkyl group in trialkylammonium phosphate, dialkylammonium monohydrogen phosphate or alkylammonium dihydrogen phosphate is selected from C1-C6 alkyl, preferably ammonium phosphate, monobasic ammonium phosphate or dibasic ammonium phosphate.

[0034] Further, the Pd source of the first active metal is one or more of hydrochloride, nitrate, acetate or ammonium salt of Pd, preferably one or more of palladium chloride, palladium nitrate, tetraammine palladium nitrate or dichlorotetraamine palladium.

[0035] Further, the metal source of the second active metal is one or more of acid, hydrochloride, nitrate, acetate or ammonium salt of the corresponding active metal component, preferably one or more of perrhenic acid, stannous chloride, ammonium perrhenate, chloroiridic acid hexahydrate.

[0036] Further, the basic compound is a N-containing compound of the following general formula (I) or (II):

[0037] wherein R 1 , R 2 , R 3 and R 4 are selected from H and C1-C4 alkyl, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, preferably methyl, ethyl and n-propyl, X - is an anion selected from OH - , HCO3 - and CO3 2- , preferably OH - . The N-containing compound is burned off during the subsequent calcination after the pre-treatment, which avoids the introduction of other metal elements and the influence on the performance of the catalyst.

[0038] Illustratively, the basic compound is tetraethylammonium hydroxide, tetramethylammonium hydroxide, triethylamine or tripropylamine.

[0039] Preferably, the mass ratio of the basic compound to the carrier is (0.1-5):1, preferably (0.5-2):1.

[0040] In another aspect, the present application also provides a preparation method for preparing a dehydrogenation catalyst for nitrogen heteroaromatic ring, the preparation method for the dehydrogenation catalyst comprising the following steps:

[0041] Step (1): impregnating the carrier with a P-containing active assistant precursor dissolved in a solvent after the P-containing active assistant precursor is dissolved in the solvent, and then preparing a P-doped carrier by drying and calcining;

[0042] Step (2): impregnating the P-doped carrier obtained in step (1) with a basic compound dissolved in a solvent, and then preparing a P-doped carrier treated with a base by post-treatment;

[0043] Step (3): impregnating the P-doped carrier treated with a base obtained in step (2) with a first active metal component dissolved in a solvent, and then preparing a carrier containing the first active metal component by drying and calcining;

[0044] Step (4): impregnating the carrier containing the first active metal component obtained in step (3) with a second active metal component dissolved in a solvent, and then preparing a dehydrogenation catalyst by drying and calcining.

[0045] Exemplarily, the preparation method for the dehydrogenation catalyst comprises the following steps:

[0046] Step (1): taking a solvent with a volume equal to the saturated absorption amount of the carrier to be impregnated, dissolving a P-containing active assistant in the solvent to prepare a homogeneous solution with a mass concentration of 5-30 wt%, dispersing the carrier in the solution to impregnate the carrier with the solution, and then preparing a P-doped carrier by drying at 80-150°C and calcining at 200-250°C;

[0047] Step (2): dissolving a basic compound in a solvent to prepare a homogeneous solution with a mass concentration of 10-30 wt%, dispersing the P-doped carrier obtained in step (1) in the solution, and then slowly stirring at 20-40°C for 1-2 h. Then, the carrier is filtered out, dried at 80-150°C, and calcined at 300-500°C;

[0048] Step (3): taking a solvent with a volume equal to the saturated absorption amount of the carrier to be impregnated, dissolving a first active metal component in the solvent to prepare a homogeneous solution with a mass concentration of 10-25 wt%, dispersing the carrier obtained in step (2) in the solution to impregnate the carrier with the solution, and then obtaining a carrier containing the first active metal component by drying at 80-150°C and calcining at 300-500°C;

[0049] Step (4): Take the same volume of solvent as the saturated absorption amount of the carrier to be impregnated, dissolve the second active metal component in the solvent to prepare a homogeneous solution with a mass concentration of 10-25wt%, and disperse the carrier containing the first active metal component obtained in step (3) in the solution to impregnate the carrier with the solution. After drying at 80-150°C and calcining at 300-500°C, a dehydrogenation catalyst is prepared.

[0050] Further, the solvent in steps (1)-(4) is one or more of water, ethanol or ammonia, preferably water or ammonia;

[0051] In another aspect, the present application also provides a dehydrogenation catalyst for use in the dehydrogenation of a nitrogen-containing heterocyclic compound to prepare a nitrogen-containing heteroaromatic ring.

[0052] The nitrogen-containing heterocyclic compound is a monocyclic or polycyclic hydrocarbon having one or more nitrogen atoms, wherein one or more hydrogen atoms can be substituted by the same or different groups, and at least one ring can undergo a dehydrogenation reaction, preferably one or more of pyrrolidine, alkylpyrrolidine, piperidine, alkylpiperidine, tetrahydroquinoline or alkyltetrahydroquinoline, and further preferably one or more of pyrrolidine, alkylpyrrolidine, piperidine, alkylpiperidine. Among them, alkylpyrrolidine is a compound in which at least one hydrogen atom on the pyrrolidine ring is substituted by an alkyl group, alkylpiperidine is a compound in which at least one hydrogen atom on the piperidine ring is substituted by an alkyl group, and alkyltetrahydroquinoline is a compound in which the hydrogen atom on the nitrogen atom of the tetrahydroquinoline molecule is substituted by an alkyl group.

[0053] Further, the dehydrogenation preparation is carried out under the condition that at least one of hydrogen, nitrogen and ammonia is a carrier gas, the reaction temperature is 200-300°C, the reaction pressure is 0-0.1 MPa, the mass space velocity of the nitrogen-containing heterocyclic compound is 0.5-2 h -1 .

[0054] The dehydrogenation preparation can be carried out by batch method or continuous method. In the continuous method, the raw material is continuously and stably fed into the reactor, and the product is continuously discharged during the reaction. This method can achieve efficient and rapid production, which helps to improve production efficiency and yield. Because the residence time of the reactant in the reactor is relatively short, and the reaction conditions can be stably controlled, the occurrence of side reactions can be minimized, and the purity and yield of the product can be improved. In contrast, the batch method of dehydrogenation reaction requires the raw material to be added into the reactor at one time, and the reaction is carried out under certain temperature, pressure and time conditions. When the reaction is completed, the feed needs to be stopped and the product needs to be discharged. The production efficiency of this method is relatively low, and each reaction needs to be prepared and adjusted again, which increases the production cost and time, so the continuous method is preferred. The reactor for dehydrogenation preparation is selected from a loop reactor, a fixed bed reactor, a reaction kettle or a fluidized bed reactor, preferably a loop reactor or a fixed bed reactor.

[0055] An exemplary method for preparing nitrogen heterocyclic compounds by dehydrogenation to prepare nitrogen heteroaromatic rings: The dehydrogenation catalyst is filled into a dehydrogenation reactor equipped with a heating and insulation device (a fixed bed reactor), the reactor has a pipe diameter of 39 mm, a pipe length of 2000 mm, and a catalyst filling height of 200 mm. Before the reaction, the reactor is purged with nitrogen three times. Before the reaction starts, hydrogen is introduced from the top of the reactor controlled by a gas flow meter, the temperature of the reactor is gradually increased, and finally the dehydrogenation catalyst is activated and reduced in a hydrogen atmosphere at 280-290℃ for 6h. After the reaction starts, the raw material nitrogen heterocyclic compound is pumped into a preheater by a plunger pump through a pipeline with heat tracing, the preheating temperature is 150℃, and the pipeline heat tracing temperature is 150℃. The raw material is mixed with hydrogen carrier gas (350sccm) and introduced into the fixed bed reactor from the top of the reactor. The bed temperature is controlled at 260℃, the system pressure is controlled at 0.02MPa, and the residence time is controlled by the mass space velocity of the raw material. The equipment is continuously operated for 72h, and the reaction liquid is taken out from the bottom of the reactor, and the product mixture is obtained after multi-stage cooling.

[0056] In another aspect, the application also provides a dehydrogenation catalyst for dehydrogenation of nitrogen heterocyclic by-products in the production of hexamethylene diamine to prepare nitrogen heteroaromatic rings.

[0057] The nitrogen heterocyclic compound raw material used in the application can come from nitrogen heterocyclic by-products in the production of hexamethylene diamine. Through the dehydrogenation process, the raw materials including 3-ethylpyrrolidine and / or 3-methylpiperidine, which are difficult to purify by rectification, are converted into 3-ethylpyrrole and / or 3-methylpyridine products with high purity, wherein the mass fraction of 3-methylpiperidine is 85-99.9% and / or the mass fraction of 3-ethylpyrrolidine is 5-12%.

[0058] Compared with the prior art, the application has the following advantages:

[0059] (1) The dehydrogenation catalyst of the application has a long service life and high activity, and can realize long-period continuous and stable operation.

[0060] (2) The dehydrogenation catalyst of the application can be used to prepare nitrogen heteroaromatic rings with different numbers of carbon atoms.

[0061] (3) The dehydrogenation catalyst of the application can realize continuous dehydrogenation reaction, directly obtain nitrogen heteroaromatic rings, has a raw material nitrogen heterocyclic compound conversion rate of more than 99%, a product nitrogen heteroaromatic ring selectivity of more than 99%, and a yield of 98-99%, has low separation difficulty of the reaction product, obvious separation energy saving advantage, high production efficiency, and is suitable for industrial production.

[0062] (4) The dehydrogenation catalyst can be used for preparing nitrogen heterocyclic ring by dehydrogenating nitrogen-containing heterocyclic byproducts in the production process of hexanediamine, waste oil raw materials can be turned into treasure, converted into fine chemicals with high added value, the resource utilization rate of raw materials and the high added value conversion of the production process are maximized, the production cost is effectively reduced, the economic benefits are maximized, and the competitiveness of the entire product industry chain is enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0063] The preferred embodiments of the present application will be described below in conjunction with the accompanying drawings, so as to further understand the technical solutions of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0064] Fig. 1 shows a TEM transmission electron microscope image of the dehydrogenation catalyst A of the present application;

[0065] Fig. 2 shows a cross-sectional view of the dehydrogenation catalyst A in Catalyst Preparation Example 1 of the present application;

[0066] Fig. 3 shows a cross-sectional view of the dehydrogenation catalyst G in Catalyst Preparation Comparative Example 1 of the present application;

[0067] Fig. 4 shows a life observation graph of different dehydrogenation catalysts catalyzing 3-methylpiperidine to prepare 3-methylpyridine. DETAILED DESCRIPTION

[0068] The preferred embodiments of the present application will be described below in conjunction with the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application, and are not intended to limit the protection scope of the present application. Those skilled in the art can make adjustments as needed to adapt to specific application occasions.

[0069] Unless defined, the technical terms used in the following examples have the same meaning as generally understood by those skilled in the art to which the present application belongs. The test reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods, unless otherwise specified, are conventional methods.

[0070] The present application will be described in detail below in conjunction with the examples and drawings.

[0071] Preparation of dehydrogenation catalyst

[0072] Catalyst Preparation Example 1: Preparation of dehydrogenation catalyst A (0.8% Pd-2.5% Re / γ-Al2O3)

[0073] The dehydrogenation catalyst A uses γ-Al2O3 carrier with a specific surface area of 350 m 2 / g, a pore volume of 1.1 cm 3 / g, and a saturated water absorption rate of 125%.

[0074] The preparation method of the dehydrogenation catalyst A comprises the following steps:

[0075] (1) 17.03 g of diammonium hydrogen phosphate (P content is 4 g) was dissolved in 125 g of desalted water to form a clear solution, and then the above-mentioned 100 g of γ-Al2O3 carrier was dispersed in the solution for sufficient impregnation for 24 h, and then dried at 120°C for 8 h and calcined at 250°C for 12 h to prepare a P-doped γ-Al2O3 carrier (P content is 4%).

[0076] (2) The P-doped carrier obtained in step (1) was dispersed in 500 g of 35 wt% aqueous solution of tetraethylammonium hydroxide, and slowly stirred at 40°C for 2 h. Then the carrier was filtered out, dried at 120°C for 8 h and calcined at 300°C for 12 h. According to the NH3 / CO2-TPD determination, the ratio of basic center to acidic center of the carrier after alkali pretreatment is 3:1.

[0077] (3) 1.73 g of palladium nitrate was dissolved in 125 g of desalted water to form a clear solution, and then the carrier obtained in step (2) was dispersed in the Pd-containing solution for sufficient impregnation for 24 h, and then dried at 120°C for 8 h and calcined at 450°C for 12 h to prepare a carrier containing Pd component.

[0078] (4) 3.37 g of perrhenic acid was dissolved in 125 g of desalted water to form a clear solution, and then the carrier containing Pd component obtained in step (3) was dispersed in the perrhenic acid solution for sufficient impregnation for 24 h, and then dried at 120°C for 8 h and calcined at 450°C for 12 h to prepare the dehydrogenation catalyst A (0.8% Pd-2.5% Re / γ-Al2O3), wherein the percentage of 0.8% Pd-2.5% Re / γ-Al2O3 refers to the mass fraction, and the percentage reference is the carrier, i.e. the carrier is 1.

[0079] The dehydrogenation catalyst A was tested by carbon monoxide pulse titration method, and the metal dispersion of Pd was 35%. FIG. 1 shows the transmission electron microscope (TEM) image of the dehydrogenation catalyst A after reduction at 280°C under hydrogen atmosphere for 6 h. According to the TEM, the particle size of the active metal Pd in the catalyst A is between 2-3 nm, so the dehydrogenation catalyst of the present application has higher catalytic efficiency, and can slow down the aggregation of Pd metal during the reaction, thereby prolonging the life of the catalyst. FIG. 2 shows the cross-sectional view of the dehydrogenation catalyst A after reduction at 280°C under hydrogen atmosphere for 6 h, and the first active metal Pd is uniformly distributed.

[0080] Catalyst preparation example 2: preparation of dehydrogenation catalyst B (1% Pd-3% Sn / Al2O3)

[0081] The dehydrogenation catalyst B uses a carrier with a specific surface area of 400 m 2 / g and a pore volume of 1.3 cm 3Al2O3 support having a specific surface area of 280 m

[0082] The method for preparing the dehydrogenation catalyst B includes the following steps:

[0083] (1) 9.28 g of diammonium hydrogen phosphate (P content 2.17 g) was dissolved in 150 g of deionized water to form a clear solution, and 100 g of the Al2O3 support was dispersed in the solution for sufficient impregnation for 24 h, and then dried at 120°C for 8 h and calcined at 250°C for 12 h to obtain a P-doped Al2O3 support.

[0084] (2) The P-doped support obtained in step (1) was dispersed in 350 g of 35 wt% aqueous tetramethylammonium hydroxide solution and slowly stirred at 40°C for 2 h. Then the support was filtered out and dried at 120°C for 8 h and calcined at 300°C for 12 h. The ratio of basic sites to acidic sites of the support after alkali pretreatment was 2:1, as determined by NH3 / CO2-TPD.

[0085] (3) 2.165 g of palladium nitrate was dissolved in 150 g of deionized water to form a clear solution, and the support obtained in step (2) was dispersed in the Pd-containing solution for sufficient impregnation for 24 h, and then dried at 120°C for 8 h and calcined at 350°C for 8 h to obtain a Pd-containing component-loaded support.

[0086] (4) 4.79 g of stannous chloride was dissolved in 150 g of deionized water to form a clear solution, and the Pd-containing component-loaded support obtained in step (3) was dispersed in the stannous chloride solution for sufficient impregnation for 24 h, and then dried at 120°C for 8 h and calcined at 500°C for 10 h to obtain the dehydrogenation catalyst B (1% Pd-3% Sn / Al2O3).

[0087] Catalyst Preparation Example 3: Preparation of Dehydrogenation Catalyst C (0.5% Pd-1.2% Re / Al2O3)

[0088] The dehydrogenation catalyst C used an Al2O3 support having a specific surface area of 280 m 2 / g, a pore volume of 0.95 cm 3 / g, and a saturated water absorption of 135%.

[0089] The method for preparing the dehydrogenation catalyst C includes the following steps:

[0090] (1) 21.3 g of diammonium hydrogen phosphate (P content 5 g) was dissolved in 135 g of deionized water to form a clear solution, and 100 g of the Al2O3 support was dispersed in the solution for sufficient impregnation for 24 h, and then dried at 120°C for 8 h and calcined at 250°C for 12 h to obtain a P-doped Al2O3 support.

[0091] (2) The P-doped support obtained in step (1) was dispersed in 400 g of a 50 wt% triethylamine ethanol solution and slowly stirred at 40°C for 2 h. The support was then filtered off and dried at 120°C for 8 h and calcined at 300°C for 12 h. The ratio of basic sites to acid sites of the support after base pre-treatment was 4:1 as determined by NH3 / CO2-TPD.

[0092] (3) 1.09 g of tetraammine palladium nitrate was dissolved in 135 g of deionized water to form a clear solution. The support obtained in step (2) was dispersed in the Pd solution to allow sufficient impregnation for 24 h. The Pd component-containing support was prepared by drying at 120°C for 8 h and calcining at 450°C for 10 h.

[0093] (4) 1.73 g of ammonium perrhenate was dissolved in 135 g of deionized water to form a clear solution. The Pd component-containing support obtained in step (3) was dispersed in the ammonium perrhenate solution to allow sufficient impregnation for 24 h. The dehydrogenation catalyst C (0.5% Pd-1.2% Re / Al2O3) was prepared by drying at 120°C for 8 h and calcining at 450°C for 12 h.

[0094] Catalyst Preparation Example 4: Preparation of Dehydrogenation Catalyst D (2% Pd-1% Ir / Al2O3-SiO2)

[0095] The dehydrogenation catalyst D used an Al2O3-SiO2 support having a specific surface area of 320 m 2 / g, a pore volume of 1.26 cm 3 / g, and a saturated water absorption of 120%, wherein the Al2O3 content in the Al2O3-SiO2 support was 75%.

[0096] The method for preparing the dehydrogenation catalyst D included the following steps:

[0097] (1) 17.03 g of diammonium hydrogen phosphate (P content: 4 g) was dissolved in 120 g of deionized water to form a clear solution. The above 100 g of Al2O3-SiO2 support was dispersed in the solution to allow sufficient impregnation for 24 h. The P-doped Al2O3-SiO2 support was prepared by drying at 120°C for 8 h and calcining at 250°C for 12 h.

[0098] (2) The P-doped support obtained in step (1) was dispersed in 400 g of a 40 wt% tripropylamine ethanol aqueous solution and slowly stirred at 40°C for 2 h. The support was then filtered off and dried at 120°C for 8 h and calcined at 300°C for 12 h. The ratio of basic sites to acid sites of the support after base pre-treatment was 3:1 as determined by NH3 / CO2-TPD.

[0099] (3) Dissolve 4.33 g of palladium nitrate in 120 g of deionized water to obtain a clear solution. Disperse the support obtained in step (2) in the Pd-containing solution to impregnate the support for 24 h. Dry the impregnated support at 120°C for 8 h and calcine at 400°C for 6 h to obtain the Pd component-containing support.

[0100] (4) Dissolve 2.12 g of chloroiridic acid hexahydrate in 120 g of deionized water to obtain a clear solution. Disperse the Pd component-containing support obtained in step (3) in the chloroiridic acid solution to impregnate the support for 24 h. Dry the impregnated support at 120°C for 8 h and calcine at 500°C for 8 h to obtain the dehydrogenation catalyst D (2% Pd-1% Ir / Al2O3-SiO2).

[0101] Catalyst Preparation Example 5: Preparation of Dehydrogenation Catalyst E (1.5% Pd-4.2% Sn / Al2O3-SiO2)

[0102] The dehydrogenation catalyst E uses an Al2O3-SiO2 support having a specific surface area of 250 m2 / g, a pore volume of 1.13 cm3 / g, and a saturated water absorption of 130%, wherein the Al2O3 content in the Al2O3-SiO2 support is 60%. 2 3 The dehydrogenation catalyst E uses an Al2O3-SiO2 support having a specific surface area of 250 m2 / g, a pore volume of 1.13 cm3 / g, and a saturated water absorption of 130%, wherein the Al2O3 content in the Al2O3-SiO2 support is 60%.

[0103] The method for preparing the dehydrogenation catalyst E includes the following steps:

[0104] (1) Dissolve 15.39 g of ammonium phosphate (P content: 3.2 g) in 130 g of deionized water to obtain a clear solution. Disperse the above 100 g of Al2O3-SiO2 support in the solution to impregnate the support for 24 h. Dry the impregnated support at 120°C for 8 h and calcine at 250°C for 12 h to obtain the P-doped Al2O3-SiO2 support.

[0105] (2) Disperse the P-doped support obtained in step (1) in 500 g of 35 wt% aqueous tetraethylammonium carbonate solution and slowly stir at 40°C for 2 h. Then filter out the support and dry at 120°C for 8 h and calcine at 300°C for 12 h. The ratio of basic sites to acidic sites of the support after the alkali pretreatment is 2.6:1, as determined by NH3 / CO2-TPD.

[0106] (3) Dissolve 2.5 g of palladium chloride in 130 g of deionized water to obtain a clear solution. Disperse the support obtained in step (2) in the Pd-containing solution to impregnate the support for 24 h. Dry the impregnated support at 120°C for 8 h and calcine at 500°C for 3 h to obtain the Pd component-containing support.

[0107] ​(4) 6.71 g of stannous chloride was dissolved in 130 g of deionized water to form a clear solution. The Pd component-containing support obtained in step (3) was dispersed in the stannous chloride solution to allow sufficient impregnation for 24 h. After drying at 120°C for 8 h and calcination at 400°C for 8 h, dehydrogenation catalyst E (1.5% Pd-4.2% Sn / Al2O3-SiO2) was prepared.

[0108] Catalyst Preparation Example 6: Preparation of Dehydrogenation Catalyst F (3% Pd-4.2% Re / Al2O3-SiO2)

[0109] Dehydrogenation catalyst F was prepared using an Al2O3-SiO2 support having a specific surface area of 375 m2 / g, a pore volume of 1.08 cm3 / g, and a saturated water absorption of 105%, wherein the Al2O3 content in the Al2O3-SiO2 support was 90%. 2 3 Dehydrogenation catalyst F was prepared using an Al2O3-SiO2 support having a specific surface area of 375 m2 / g, a pore volume of 1.08 cm3 / g, and a saturated water absorption of 105%, wherein the Al2O3 content in the Al2O3-SiO2 support was 90%.

[0110] The method for preparing dehydrogenation catalyst F included the following steps:

[0111] (1) 12.78 g of diammonium hydrogen phosphate (P content: 3 g) was dissolved in 105 g of deionized water to form a clear solution. The above 100 g of Al2O3-SiO2 support was dispersed in the solution to allow sufficient impregnation for 24 h. After drying at 120°C for 8 h and calcination at 250°C for 12 h, a P-doped Al2O3-SiO2 support was prepared.

[0112] (2) The P-doped support obtained in step (1) was dispersed in 500 g of a 20 wt% aqueous solution of tetraethylammonium hydroxide and slowly stirred at 40°C for 2 h. Then, the support was filtered and dried at 120°C for 8 h and calcined at 300°C for 12 h. According to the NH3 / CO2-TPD measurement, the ratio of basic sites to acidic sites of the support after alkali pretreatment was 4:1.

[0113] (3) 6.92 g of dichlorotetraammine palladium was dissolved in 105 g of deionized water to form a clear solution. The support obtained in step (2) was dispersed in the Pd-containing solution to allow sufficient impregnation for 24 h. After drying at 120°C for 8 h and calcination at 450°C for 5 h, a Pd component-containing support was prepared.

[0114] (4) 5.67 g of perrhenic acid was dissolved in 105 g of deionized water to form a clear solution. The Pd component-containing support obtained in step (3) was dispersed in the perrhenic acid solution to allow sufficient impregnation for 24 h. After drying at 120°C for 8 h and calcination at 400°C for 12 h, dehydrogenation catalyst F (3% Pd-4.2% Re / Al2O3-SiO2) was prepared.

[0115] The specific preparation parameters and control conditions of dehydrogenation catalysts A to F are shown in Table 1. ​

[0116] Preparation of a dehydrogenation catalyst comparative example

[0117] Catalyst preparation comparative example 1 : Preparation of a dehydrogenation catalyst G (0.8% Pd-2.5% Re / γ-Al2O3) using a low saturated water absorption carrier

[0118] The dehydrogenation catalyst G used a γ-Al2O3 carrier with a specific surface area of 350 m 2 / g, a pore volume of 0.9 cm 3 / g, and a saturated water absorption of 65%, instead of the γ-Al2O3 carrier with a specific surface area of 350 m 2 / g, a pore volume of 1.1 cm 3 / g, and a saturated water absorption of 125% used in the dehydrogenation catalyst A, and the other parameters and control conditions of the dehydrogenation catalyst A in the catalyst preparation example 1 were the same.

[0119] The dehydrogenation catalyst G was tested by the carbon monoxide pulse titration method and the metal dispersion of Pd was 24%. Figure 3 shows the cross-sectional view of the dehydrogenation catalyst G after reduction at 280°C for 6 h in a hydrogen atmosphere, and the first active metal Pd was distributed in the form of an eggshell.

[0120] Catalyst preparation comparative example 2: Preparation of a dehydrogenation catalyst H (0.8% Pd-2.5% Re / γ-Al2O3) without alkali pretreatment of the carrier

[0121] The dehydrogenation catalyst H omitted step (2) in the preparation steps of the dehydrogenation catalyst A, i.e., the γ-Al2O3 carrier was not pretreated with alkali, and the other parameters and control conditions of the dehydrogenation catalyst A in the catalyst preparation example 1 were the same.

[0122] The ratio of basic centers to acidic centers of the carrier was 0.8:1, as determined by NH3 / CO2-TPD.

[0123] Catalyst preparation comparative example 3: Preparation of a dehydrogenation catalyst I (0.8% Pd / γ-Al2O3) without adding a second metal active component

[0124] The dehydrogenation catalyst I omitted step (4) in the preparation steps of the dehydrogenation catalyst A, i.e., the second metal active component was not added, and the other parameters and control conditions of the dehydrogenation catalyst A in the catalyst preparation example 1 were the same.

[0125] Catalyst preparation comparative example 4: Preparation of a dehydrogenation catalyst J (2.5% Re / γ-Al2O3) without adding a first metal active component

[0126] Dehydrogenation catalyst J was prepared in the same manner as dehydrogenation catalyst A of catalyst preparation example 1 except that step (3) was omitted, i.e. the first metal active component was not added.

[0127] Catalyst preparation comparative example 5: Preparation of dehydrogenation catalyst K (0.8% Pd-2.5% Re / γ-Al2θ3) without doping with the active promoter component P

[0128] Dehydrogenation catalyst K was prepared in the same manner as dehydrogenation catalyst A of catalyst preparation example 1 except that step (1) was omitted, i.e. the active promoter component P was not doped.

[0129] Catalyst preparation comparative example 6: Preparation of dehydrogenation catalyst L (0.8% Pd-2.5% Re / γ-Al2θ3) using a low specific surface area support

[0130] Dehydrogenation catalyst L was prepared in the same manner as dehydrogenation catalyst A of catalyst preparation example 1 except that a γ-Al2θ3 support having a specific surface area of 138 m 2 / g, a pore volume of 1.05 cm 3 / g and a saturated water absorption of 122% was used instead of the γ-Al2θ3 support having a saturated water absorption of 125%, a specific surface area of 350 m 2 / g and a pore volume of 1.1 cm 3 / g used in dehydrogenation catalyst A.

[0131] Catalyst preparation comparative example 7: Preparation of dehydrogenation catalyst M (0.8% Pd-2.5% Re / γ-Al2θ3) using a low pore volume support

[0132] Dehydrogenation catalyst M was prepared in the same manner as dehydrogenation catalyst A of catalyst preparation example 1 except that a γ-Al2θ3 support having a saturated water absorption of 120%, a specific surface area of 343 m 2 / g and a pore volume of 0.53 cm 3 / g was used instead of the γ-Al2θ3 support having a specific surface area of 350 m 2 / g, a pore volume of 1.1 cm 3 / g and a saturated water absorption of 125% used in dehydrogenation catalyst A.

[0133] Catalyst preparation comparative example 8: Preparation of dehydrogenation catalyst N (0.8% Pd-2.5% Re / γ-Al2θ3)

[0134] Dehydrogenation catalyst N was prepared using the same support and preparation parameters and control conditions as for dehydrogenation catalyst A in Catalyst Preparation Example 1, except that the preparation steps were different, i.e. step (1) in Catalyst Preparation Example 1 was placed after step (4). The specific steps were as follows:

[0135] (1) The γ-Al2O3 support in Catalyst Preparation Example 1 was dispersed in 500 g of a 35 wt% aqueous solution of tetraethylammonium hydroxide and slowly stirred at 40°C for 2 h. The support was then filtered off, dried at 120°C for 8 h and calcined at 300°C for 12 h. After the alkali pretreatment, the ratio of basic sites to acidic sites on the support was 3:1, as determined by NH3 / CO2-TPD.

[0136] (2) 1.73 g of palladium nitrate was dissolved in 125 g of deionized water to form a clear solution. The support obtained in step (1) was dispersed in the Pd solution and impregnated for 24 h. The Pd component-containing support was then dried at 120°C for 8 h and calcined at 450°C for 12 h to obtain the Pd component-containing support.

[0137] (3) 3.37 g of perrhenic acid was dissolved in 125 g of deionized water to form a clear solution. The Pd component-containing support obtained in step (2) was dispersed in the perrhenic acid solution and impregnated for 24 h. The Pd and Re active metal component-containing support was then dried at 120°C for 8 h and calcined at 450°C for 12 h to obtain the Pd and Re active metal component-containing support.

[0138] (4) 17.03 g of diammonium hydrogen phosphate (P content 4 g) was dissolved in 125 g of deionized water to form a clear solution. The Pd and Re active metal component-containing support obtained in step (3) was dispersed in the solution and impregnated for 24 h. The dehydrogenation catalyst N (P content 4%) was then dried at 120°C for 8 h and calcined at 250°C for 12 h.

[0139] Catalyst Preparation Comparative Example 9: Preparation of dehydrogenation catalyst Q (0.8% Pd-2.5% Re / γ-Al2O3)

[0140] Dehydrogenation catalyst Q was prepared using the same support and preparation parameters and control conditions as for dehydrogenation catalyst A in Catalyst Preparation Example 1, except that the preparation steps were different, i.e. step (3) and step (4) in Catalyst Preparation Example 1 were interchanged. The specific steps were as follows:

[0141] (1) 17.03 g of diammonium hydrogen phosphate (P content 4 g) was dissolved in 125 g of deionized water to form a clear solution. The γ-Al2O3 support was dispersed in the solution and impregnated for 24 h. The P-doped γ-Al2O3 support (P content 4%) was then dried at 120°C for 8 h and calcined at 250°C for 12 h.

[0142] (2) The P-doped support obtained in step (1) was dispersed in 500 g of 35 wt% aqueous tetraethylammonium hydroxide solution and slowly stirred at 40 °C for 2 h. The support was then filtered off, dried at 120 °C for 8 h and calcined at 300 °C for 12 h. The ratio of basic sites to acidic sites of the support after alkali pretreatment was 3:1, as determined by NH3 / CO2-TPD.

[0143] (3) 3.37 g of perrhenic acid was dissolved in 125 g of deionized water to form a clear solution. The support obtained in step (2) was dispersed in the perrhenic acid solution for sufficient impregnation for 24 h. The Re component-containing support was prepared by drying at 120 °C for 8 h and calcining at 450 °C for 12 h.

[0144] (4) 1.73 g of palladium nitrate was dissolved in 125 g of deionized water to form a clear solution. The Re component-containing support obtained in step (3) was dispersed in the Pd-containing solution for sufficient impregnation for 24 h. The dehydrogenation catalyst Q was prepared by drying at 120 °C for 8 h and calcining at 450 °C for 12 h.

[0145] The preparation parameters and control conditions of the above dehydrogenation catalyst comparative examples are shown in Table 1.

[0146] Table 1 Preparation of dehydrogenation catalyst

[0147] Evaluation of dehydrogenation catalyst activity

[0148] In the following examples, gas chromatography was used for analysis of each component in the reaction system, and quantitative correction normalization method was used for quantification, which can be carried out according to the prior art. On this basis, the conversion rate of reactants, the selectivity and yield of products were calculated. The gas chromatography analysis conditions are as follows:

[0149] Chromatographic column: Agilent DB-Wax (specification: 30 m x 0.32 mm x 0.25 mm); injection port temperature: 300 °C; split ratio: 30:1; column flow rate: 1.5 mL / min; column temperature: 100 °C for 0.5 min; temperature rising program: 15 °C / min to 300 °C, holding for 8 min; detector temperature: 300 °C, hydrogen flow rate: 35 mL / min, air flow rate: 350 mL / min.

[0150] Example 1

[0151] A dehydrogenation reactor (fixed bed reactor) was charged with 100 g of dehydrogenation catalyst A, which was equipped with a heating and insulation device. The reactor had a tube diameter of 39 mm, a tube length of 2000 mm, and a catalyst filling height of 200 mm. Before the reaction, the reactor was purged with nitrogen three times. Before the reaction started, hydrogen was introduced from the top of the reactor, and the reactor temperature was gradually increased until the dehydrogenation catalyst A was activated and reduced in a hydrogen atmosphere at 280-290°C for 6 h. After the reaction started, the raw material 3-methylpiperidine was pumped into a preheater by a plunger pump through a line with heating, and the preheating temperature was 150°C, and the line heating temperature was 150°C. After the raw material was mixed with the hydrogen carrier gas (350 sccm), it was introduced into the fixed bed reactor from the top of the reactor. The reaction bed temperature was controlled at 260°C, the system pressure was controlled at 0.02 MPa, and the residence time was controlled by the mass space velocity of the raw material, i.e., controlled at 1.5 g of raw material / g of catalytically active metal / hour. The equipment was continuously operated for 72 h, and the reaction liquid was taken out from the bottom of the reactor and cooled through multiple stages to obtain a product mixture. After detection by gas chromatography and quantification by correction normalization, the conversion rate of the raw material 3-methylpiperidine was 99.8%, the selectivity of the product 3-methylpyridine was 99.5%, and the yield was 99.3%.

[0152] Examples 2-6

[0153] A dehydrogenation reactor (fixed bed reactor) was charged with 100 g of dehydrogenation catalyst B-F, respectively, which was equipped with a heating and insulation device. The reactor had a tube diameter of 39 mm, a tube length of 2000 mm, and a catalyst filling height of 200 mm. Before the reaction, the reactor was purged with nitrogen three times. Before the reaction started, hydrogen was introduced from the top of the reactor, and the reactor temperature was gradually increased until the dehydrogenation catalyst B-F was activated and reduced in a hydrogen atmosphere at 280-290°C for 6-24 h. After the reaction started, the raw material 3-methylpiperidine was pumped into a preheater by a plunger pump through a line with heating, and the preheating temperature was 150-200°C, and the line heating temperature was 150°C. After the raw material was mixed with the carrier gas, it was introduced into the fixed bed reactor from the top of the reactor. The reaction bed temperature was controlled at 230-280°C, the system pressure was controlled at 0-0.1 MPa, and the residence time was controlled by the mass space velocity of the raw material, i.e., controlled at 0.5-2.0 g of raw material / g of catalytically active metal / hour. The equipment was continuously operated for 100 h, and the reaction liquid was taken out from the bottom of the reactor and cooled through multiple stages to obtain a product mixture. After detection by gas chromatography and quantification by correction normalization, the reaction results are shown in Table 2.

[0154] Comparative Examples 1-9

[0155] A 100 g of dehydrogenation catalyst G to Q was filled into a dehydrogenation reactor (a fixed bed reactor) equipped with a heating and heat preservation device, the reactor had a tube diameter of 39 mm, a tube length of 2000 mm, and a catalyst filling height of 200 mm. Before the reaction, the reactor was purged with nitrogen three times. Before the reaction started, hydrogen was introduced from the top of the reactor controlled by a gas flow meter, the reactor temperature was gradually increased, and finally the dehydrogenation catalyst A was activated and reduced in a hydrogen atmosphere at 280 to 290°C for 6 h. After the reaction started, the raw material 3-methylpiperidine was pumped into a preheater by a plunger pump through a line with heat tracing, the preheating temperature was 150°C, and the line heat tracing temperature was 150°C. After the raw material was mixed with hydrogen carrier gas (350 sccm), it was introduced into the fixed bed reactor from the top of the reactor in parallel flow. The reaction bed temperature was controlled at 260°C, the system pressure was controlled at 0.02 MPa, and the residence time was controlled by the mass space velocity of the raw material, i.e. controlled at 1.5 grams of raw material per gram of catalytically active metal per hour. The equipment was continuously operated for 72 h, the reaction liquid was taken out from the bottom of the reactor, and the product mixture was obtained after multi-stage cooling. After detection by gas chromatography and quantification by correction normalization method, the reaction results are shown in Table 2.

[0156] Table 2 Dehydrogenation catalyst activity evaluation

[0157] Dehydrogenation catalyst life evaluation

[0158] Example 7

[0159] A 100 g of dehydrogenation catalyst A was filled into a dehydrogenation reactor (a fixed bed reactor) equipped with a heating and heat preservation device, the reactor had a tube diameter of 39 mm, a tube length of 2000 mm, and a catalyst filling height of 200 mm. Before the reaction, the reactor was purged with nitrogen three times. Before the reaction started, hydrogen was introduced from the top of the reactor controlled by a gas flow meter, the reactor temperature was gradually increased, and finally the dehydrogenation catalyst A was activated and reduced in a hydrogen atmosphere at 280 to 290°C for 6 h. After the reaction started, the raw material 3-methylpiperidine was pumped into a preheater by a plunger pump through a line with heat tracing, the preheating temperature was 150°C, and the line heat tracing temperature was 150°C. After the raw material was mixed with hydrogen carrier gas (350 sccm), it was introduced into the fixed bed reactor from the top of the reactor in parallel flow. The reaction bed temperature was controlled at 260°C, the system pressure was controlled at 0.02 MPa, and the residence time was controlled by the mass space velocity of the raw material, i.e. controlled at 1.5 grams of raw material per gram of catalytically active metal per hour. The equipment was continuously operated, and every 120 h, the reaction liquid was taken out from the bottom of the reactor, and the product mixture was obtained after multi-stage cooling. After detection by gas chromatography and quantification by correction normalization method, the reaction results are shown in Figure 4.

[0160] Comparative Example 10

[0161] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced with the dehydrogenation catalyst G in the catalyst preparation Comparative Example, and the reaction results are shown in Fig. 4.

[0162] Comparative Example 11

[0163] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced with the dehydrogenation catalyst H in the catalyst preparation Comparative Example, and the reaction results are shown in Fig. 4.

[0164] Comparative Example 12

[0165] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced with the dehydrogenation catalyst K in the catalyst preparation Comparative Example, and the reaction results are shown in Fig. 4.

[0166] Comparative Example 13

[0167] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced with the dehydrogenation catalyst L in the catalyst preparation Comparative Example, and the reaction results are shown in Fig. 4.

[0168] Comparative Example 14

[0169] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced with the dehydrogenation catalyst M in the catalyst preparation Comparative Example, and the reaction results are shown in Fig. 4.

[0170] Comparative Example 15

[0171] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced with the dehydrogenation catalyst N in the catalyst preparation Comparative Example, and the reaction results are shown in Fig. 4.

[0172] Comparative Example 16

[0173] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced with the dehydrogenation catalyst Q in the catalyst preparation Comparative Example, and the reaction results are shown in Fig. 4.

[0174] Table 2 summarizes the results of the preliminary evaluation of the activity of each dehydrogenation catalyst in Examples 1 to 6 and Comparative Examples 1 to 9, and Fig. 4 summarizes the results of the reaction during the long-term operation of each dehydrogenation catalyst in Example 7 and Comparative Examples 10 to 16.

[0175] From Table 2, it can be seen that in the process of preparing 3-methylpyridine by catalytic dehydrogenation of 3-methylpiperidine, the dehydrogenation catalysts A to F used in Examples 1 to 6 respectively can achieve conversion of more than 99%, selectivity of more than 99% and yield of more than 98%, which can meet the requirements of industrialization. On the basis of high conversion, selectivity and yield, the dehydrogenation catalysts A to F used in Examples 1 to 6 respectively can continuously operate for 5500 to 8000 hours, still maintaining good catalytic activity, and no catalyst deactivation occurs.

[0176] Further, the catalyst A and the catalyst were selected to prepare the comparative examples for dehydrogenation catalyst life evaluation, and the results are shown in Figure 4.

[0177] Compared with the dehydrogenation catalyst A, the dehydrogenation catalyst G prepared by using a conventional carrier with low saturated water absorption rate has the active metal Pd distributed in the form of eggshell on the surface of the catalyst (see Figure 3), and the dispersion degree of the active metal is obviously lower than that of the uniform distribution of the catalyst A. Moreover, the dehydrogenation reaction can only occur on the surface of the catalyst. During long-time operation, the active metal Pd is more likely to aggregate into larger metal particles, and once coking and carbon deposition occur on the surface of the catalyst, the catalyst will be rapidly deactivated. The dehydrogenation catalysts L and M prepared by using carriers with lower specific surface area or lower pore volume can only continuously catalyze for 2000 to 2500 hours, and then are rapidly deactivated. This also shows that the carrier must have high saturated water absorption rate, high specific surface area and high pore volume. Such a carrier has more levels of micropore structures, which can shorten the distance of the raw material such as 3-methylpiperidine from contacting the active sites of the catalyst, and the product such as 3-methylpyridine can be quickly desorbed from the active sites, thereby reducing the occurrence of side reactions and the formation of coking and carbon deposition. Meanwhile, the more levels of micropore structures and the ultra-high saturated water absorption rate of the carrier can ensure the uniform dispersion of the first active metal component Pd on the surface and inside of the catalyst, thereby improving the dispersion degree of the active metal, delaying the long-term high-temperature aggregation of the active metal, and prolonging the service life of the catalyst.

[0178] From Comparative Example 2 and Comparative Example 7, it can be seen that the service life of the dehydrogenation catalyst A is much longer than that of the dehydrogenation catalyst H, and the selectivity and yield of 3-methylpyridine in the product are higher, which shows that when the catalyst carrier is pretreated by an alkaline compound, the acid sites are eliminated, and the basic center is greater than the acid center. This can avoid the polymerization reaction catalyzed by the acid sites during the catalytic dehydrogenation of 3-methylpiperidine to some extent, which can effectively improve the selectivity of the reaction, and effectively inhibit the coking and carbon deposition on the surface of the dehydrogenation catalyst, thereby prolonging the service life of the dehydrogenation catalyst.

[0179] From Comparative Example 3 and Comparative Example 4, it can be seen that, compared with the dehydrogenation catalyst A, the initial activity of the dehydrogenation catalyst I loaded with only Pd is lower than that of catalyst A, and the conversion rate of the raw material is only about 89% after continuous operation for 100 h, and the catalytic activity thereof rapidly decreases within 1000 h; and the catalyst loaded with only Re is almost unable to complete the catalytic dehydrogenation reaction. This shows that the introduction of the second active metal component (for example, Re) induces Pd to be in a more reduced state or a stable metal state, and Re is usually in a higher oxidation state ReO x The ReO x layer can be formed around the Pd active sites, thereby isolating the Pd active sites into small metal clusters or even single metal sites, and thus the aggregation of Pd metal and the rapid deactivation of the catalyst can be effectively inhibited while reducing the loading of the first active metal.

[0180] From Comparative Example 5 and Comparative Example 12, it can be seen that, compared with the dehydrogenation catalyst A, the catalyst K has similar activity to catalyst A, but the catalytic activity of catalyst K begins to decrease after continuous operation for 2000 h, and the conversion rate of the raw material finally decreases to below 90% after 3300 h. The Pd content of catalyst K before and after the reaction is determined by ion chromatography ICP, and the results show that the average Pd content of catalyst K before the reaction is 8322 ppm, and the average Pd content thereof after operation for 3300 h is 7588 ppm, and the Pd loss rate is 8.8%. However, the Pd content of catalyst A before and after the reaction is determined by ion chromatography ICP, and the results show that the average Pd content of catalyst A before the reaction is 8169 ppm, and the average Pd content thereof after operation for 6000 h is 8126 ppm, and the Pd loss rate is less than 0.5%.

[0181] When step (1) in catalyst preparation example 1 was placed after step (4), i.e. using dehydrogenation catalyst N, the catalyst life was significantly higher than catalyst K, but lower than catalyst A. This indicates that, relative to dehydrogenation catalyst A, the last introduction of P active promoter, the unsaturated coordination of Al sites in the support and the substitution of weakly adsorbed hydroxyl groups have formed Al-O-H-Pd species with the first active metal, and the interaction force between Pd and the support in the species is lower than that in the Al-O-P-Pd species. Only by doping P atoms into the alumina support in advance, the effective P species can be more inclined to form Al-O-P species with the unsaturated coordination of Al sites in the support and the substitution of weakly adsorbed hydroxyl groups. After the active metal is loaded, the P-OH group promotes the formation of P-O-Pd bond, thereby forming a stronger interaction with the Pd species. This strong interaction leads to a suitable electronic structure of Pd nanoparticles and more low-coordination Pd sites, so that the catalyst shows more excellent dehydrogenation catalytic activity. More importantly, the stronger interaction between Pd and the support can effectively delay the high-temperature aggregation of Pd and prolong the service life of the catalyst. At the same time, it can also inhibit the coordination complexing ability of nitrogen-containing oligomers with Pd metal, thereby avoiding the loss of noble metal, which is crucial for the industrial application and cost control of the catalyst.

[0182] As can be seen from comparative example 9 and comparative example 16, when step (3) and step (4) in catalyst preparation example 1 are exchanged in order, i.e. using dehydrogenation catalyst Q, the catalyst life is significantly lower than catalyst A. It is speculated that the reason may be that the second active metal component Re loaded first may be transitionally dispersed on the surface of the support, and when the first active metal Pd is loaded later, Re may block or cover a part of the active metal sites of Pd, thereby affecting the activity and life of the catalyst.

[0183] Application of dehydrogenation catalyst in the preparation of nitrogen heterocyclic ring by dehydrogenation of nitrogen heterocyclic compound

[0184] Examples 8-12

[0185] A ~ E dehydrogenation catalysts were filled into a dehydrogenation reactor (fixed bed reactor) equipped with a heating and insulation device, the reactor tube diameter was 39 mm, the tube length was 2000 mm, and the catalyst filling height was 200 mm. Before the reaction, the reactor was purged with nitrogen three times. Before the reaction started, hydrogen was introduced from the top of the reactor controlled by a gas flow meter, and the reactor temperature was gradually increased, and finally the dehydrogenation catalyst A was activated and reduced in a hydrogen atmosphere at 280 ~ 290 ℃ for 6 h. After the reaction started, the nitrogen heterocyclic compound raw material was pumped into the preheater by the plunger pump through the pipeline heating, the preheating temperature was 180 ℃, and the pipeline heating temperature was 180 ℃. After the raw material was mixed with the carrier gas, it was introduced into the fixed bed reactor from the top of the reactor. The reaction bed temperature was controlled at 250 ~ 300 ℃, the system pressure was controlled at 0 ~ 0.05 MPa, and the residence time was controlled by the mass space velocity of the raw material, that is, controlled at 0.5 ~ 2.0 g of raw material / g of catalytically active metal / hour. The equipment was continuously operated for 1000 h, and the reaction liquid was taken out from the bottom of the reactor, and after multi-stage cooling, the product mixture was obtained. After detection by gas chromatography and quantitative correction by normalization method, the reaction results are shown in Table 3.

[0186] Table 3 Reaction results of different nitrogen-containing heterocyclic compounds using dehydrogenation catalyst

[0187] As shown in Table 3, when the dehydrogenation catalyst prepared by the present application is used in the preparation of nitrogen heteroaromatic ring by dehydrogenation of nitrogen-containing heterocyclic compounds, the raw material conversion rate is more than 99%, the selectivity of nitrogen heteroaromatic ring product is more than 99%, and the yield is 98 ~ 99%, so the dehydrogenation catalyst of the present application has good reaction effect for the preparation of nitrogen heteroaromatic ring by dehydrogenation of nitrogen-containing heterocyclic compounds.

[0188] Dehydrogenation of nitrogen-containing heterocyclic byproduct in the production of hexamethylene diamine to prepare nitrogen heteroaromatic ring by dehydrogenation catalyst

[0189] Examples 13 ~ 14

[0190] 100g of dehydrogenation catalysts A and B were separately packed into a dehydrogenation reactor (fixed-bed reactor) equipped with a heating and insulation device. The reactor tube diameter was 39mm, the tube length was 2000mm, and the catalyst packing height was 200mm. Before the reaction, the reactor was purged three times with nitrogen. Before the reaction started, hydrogen was introduced from the top of the reactor under the control of a gas flow meter, gradually increasing the reactor temperature until dehydrogenation catalysts A and B were activated and reduced in a hydrogen atmosphere at 280-290℃ for 6 hours. After the reaction started, 3-methylpiperidine feedstock (purity after distillation purification is shown in Table 4) produced by hexamethylenediamine was pumped into the preheater via a plunger pump and a pipeline with heating tracing. The preheating temperature was 180℃, and the pipeline heating temperature was also 180℃. The feedstock and carrier gas were mixed and introduced into the fixed-bed reactor in parallel from the top of the reactor. The reaction bed temperature was controlled at 250–260℃, the system pressure at 0.03 MPa, and the residence time was controlled by the feed mass hourly space velocity (MHSV), i.e., 1.5 g feed / g catalytically active metal / hour. After 3000 hours of continuous operation, the reaction liquid was collected from the bottom of the reactor and subjected to multi-stage cooling to obtain a product mixture. The reaction results, obtained by gas chromatography and quantification using a calibration normalization method, are shown in Table 4.

[0191] Table 4. Results of the reaction of nitrogen-containing heterocyclic byproducts in the hexamethylenediamine production process using a dehydrogenation catalyst.

[0192] As shown in Table 4, when the dehydrogenation catalyst prepared by the present invention is used in the dehydrogenation of nitrogen-containing heterocyclic byproducts to prepare nitrogen-containing aromatic rings in the production process of hexamethylenediamine, the conversion rate of 3-methylpiperidine, the selectivity of 3-methylpyridine, and the selectivity of 3-ethylpyrrole are all above 99%. Therefore, the dehydrogenation catalyst of the present invention has a good reaction effect on the dehydrogenation of nitrogen-containing heterocyclic byproducts to prepare nitrogen-containing aromatic rings in the production process of hexamethylenediamine.

[0193] Industrial availability

[0194] According to the method of the present invention, nitrogen-containing heterocyclic compounds can be advantageously produced industrially. For example, 3-methylpyridine can be prepared by dehydrogenation reaction using 3-methylpiperidine as a raw material. 3-methylpyridine can be further used to produce nicotinic acid and nicotinamide, quizalofop-P-ethyl, quizalofop-P-ethyl, pyrifluquinazon, nicosulfuron, pyrifluquinazon, and other high-value-added pharmaceutical and pesticide intermediates.

[0195] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

A dehydrogenation catalyst for the preparation of azaheteroaromatic rings, characterized in that The dehydrogenation catalyst comprises a carrier, a first active metal component, a second active metal component and an active promoter component, the specific surface area of the carrier is 150-400 m 2 / g, the pore volume is 0.6-1.5 cm 3 / g, and the saturated water absorption is not less than 100%. The first active metal component comprises Pd; The second active metal component comprises one or more of Re, Sn or Ir; The active promoter component is a P-containing active promoter. A dehydrogenation catalyst for preparing a nitrogen heteroaromatic ring according to claim 1, wherein The carrier is pre-treated with a basic compound. A dehydrogenation catalyst for preparing a nitrogen heteroaromatic ring according to claim 1, wherein The specific surface area of the carrier is 200 to 350 m 2 The pore volume is 0.8 to 1.3 cm 3 The specific surface area of the carrier is 200 to 350 m The carrier is preferably an aluminium-containing carrier, further preferably at least one of alumina, an aluminium-containing molecular sieve or alumina-silica. A dehydrogenation catalyst for preparing a nitrogen heteroaromatic ring according to claim 1, wherein The molar ratio of the first active metal component to the second active metal component is (0.2-5):1, preferably (0.8-3):1; Preferably, the mass ratio of the first active metal component to the carrier is (0.001-0.05):1, preferably (0.003-0.02):1; and / or the mass ratio of the second active metal component to the carrier is (0.005-0.05):1, preferably (0.008-0.03):1; Preferably, the mass ratio of the active promoter component to the carrier is (0.01-0.05):1, preferably (0.02-0.04):

1. A dehydrogenation catalyst for preparing a nitrogen heteroaromatic ring according to claim 1, wherein The phosphorus source of the P-containing active promoter is one or more of ammonium phosphate, monohydrogen ammonium phosphate, dihydrogen ammonium phosphate, trialkylammonium phosphate, dialkylammonium monohydrogen phosphate or alkylammonium dihydrogen phosphate, wherein the alkyl group in trialkylammonium phosphate, dialkylammonium monohydrogen phosphate or alkylammonium dihydrogen phosphate is selected from C1-C6 alkyl, preferably ammonium phosphate, monohydrogen ammonium phosphate or dihydrogen ammonium phosphate; Preferably, the Pd source of the first active metal is one or more of hydrochloride, nitrate, acetate or ammonium salt of Pd, preferably one or more of palladium chloride, palladium nitrate, tetraammine palladium nitrate or dichlorotetraamine palladium; Preferably, the metal source of the second active metal is one or more of acid, hydrochloride, nitrate, acetate or ammonium salt of the corresponding active metal component, preferably one or more of perrhenic acid, stannous chloride, ammonium perrhenate, chloroiridic acid hexahydrate. The dehydrogenation catalyst for preparing a nitrogen heteroaromatic ring according to claim 2, wherein The basic compound is an N-containing compound of the following general formula (I) or (II): wherein R 1 , R 2 , R 3 and R 4 are selected from H and C1-C4 alkyl, X - is an anion selected from OH - , HCO3 - and CO3 2- ; Preferably, the mass ratio of the basic compound to the carrier is (0.1-5):1, preferably (0.5-2):

1. A production method for producing a catalyst for dehydrogenation of a nitrogen heteroaromatic ring as claimed in any one of claims 1 to 6, characterized in that, The preparation method of the dehydrogenation catalyst comprises the following steps: Step (1): dissolving the P-containing active promoter in a solvent and then adding the carrier for impregnation, and then drying and calcining to obtain a P-doped carrier; Step (2): dissolving the basic compound in a solvent and then adding the P-doped carrier obtained in step (1), and then post-treating to obtain a basic-treated P-doped carrier; Step (3): dissolving the first active metal component in a solvent and then adding the basic-treated P-doped carrier obtained in step (2) for impregnation, and then drying and calcining to obtain a carrier containing the first active metal component; Step (4): dissolving the second active metal component in a solvent and then adding the carrier containing the first active metal component obtained in step (3) for impregnation, and then drying and calcining to obtain a dehydrogenation catalyst. The preparation method of claim 7, wherein the preparation method of the dehydrogenation catalyst for nitrogen heteroaromatic ring is characterized in that, The solvent in steps (1)-(4) is one or more of water, ethanol or ammonia water, preferably water or ammonia water. Use of a dehydrogenation catalyst as claimed in any of claims 1 to 6 for the dehydrogenation of nitrogen heterocycles to nitrogen heteroaromatics, characterized in that The nitrogen-containing heterocyclic compound comprises a monocyclic or polycyclic hydrocarbon having one or more nitrogen atoms, wherein one or more hydrogen atoms can be substituted by the same or different groups, and at least one ring can undergo a dehydrogenation reaction, preferably one or more of pyrrolidine, alkylpyrrolidine, piperidine, alkylpiperidine, tetrahydroquinoline or alkyltetrahydroquinoline. The application of the dehydrogenation catalyst according to claim 9 in the preparation of nitrogen heterocyclic aromatic ring by dehydrogenation of nitrogen-containing heterocyclic compound, characterized in that, The dehydrogenation is carried out under the condition that at least one of hydrogen, nitrogen or ammonia is carrier gas, the reaction temperature is 200-300℃, the reaction pressure is 0-0.1MPa, the mass space velocity of the nitrogen-containing heterocyclic compound is 0.5-2h -1 . Use of a dehydrogenation catalyst as claimed in any of claims 1 to 6 for the production of nitrogen heteroaromatic rings from nitrogen heterocyclic by-products in the production of hexamethylenediamine, characterized in that The nitrogen-containing heterocyclic by-products include 3-methylpiperidine and / or 3- ethylpyrrolidine. Use of the dehydrogenation catalyst according to claim 11 for the production of nitrogen heteroaromatic rings from nitrogen heterocyclic by-products in the production of hexamethylenediamine, characterized in that, The mass fraction of the 3-methylpiperidine is 85-99.9% and / or the mass fraction of the 3- ethylpyrrolidine is 5-12%.

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