Dehydrogenation catalyst for preparing aza-aromatic ring as well as preparation method and application of dehydrogenation catalyst

Abstract

The invention provides a dehydrogenation catalyst for preparing an aza-aromatic ring as well as a preparation method and application of the dehydrogenation catalyst, and belongs to the technical field of catalyst preparation. The dehydrogenation catalyst comprises a carrier with specific physical parameters, a first active metal component Pd, at least one of a second active metal component Re, Sn or Ir, and a P-containing active auxiliary agent. The dehydrogenation catalyst provided by the invention can be used for a dehydrogenation reaction of a nitrogen-containing heterocyclic compound as a raw material, the aza-aromatic ring can be directly obtained, the conversion rate of the raw material is 99% or above, the selectivity of the aza-aromatic ring product is 99% or above, the yield is 98-99%, and the service life of the dehydrogenation catalyst can reach 5500 h or above. The dehydrogenation catalyst can be used for preparing various nitrogen heteroaromatic rings with different carbon atom numbers, and is particularly used for preparing the nitrogen heteroaromatic rings by dehydrogenation of nitrogen-containing heterocyclic ring byproducts in the hexamethylenediamine production process, waste oil raw materials can be turned into wealth, and the waste oil raw materials are converted into fine chemicals with high additional value.

Description

Technical Field

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

[0002] Azoaromatic rings are an important class of chemical products and are also key intermediates for the preparation of a variety of high-value-added pesticides and pharmaceutical products such as fungicides, herbicides, flavors and fragrances, and vitamins. Azoaromatic ring substances such as 3-methylpyridine are the core raw materials for the production of nicotinamide and nicotinic acid (vitamin B3). Nicotinic acid is one of the indispensable vitamins in humans and animals. It participates in the redox process of tissues, has the function of promoting cell metabolism and dilating blood vessels, and can promote the growth and development of humans and animals. Using 3-methylpyridine as the starting material, dozens of high-value-added, patented pesticides can also be synthesized, such as fluazifop-butyl, fluazifop-butyl, fluazifop-butyl, nicotinamide, and pyrisulfuron. In addition, azoaromatic ring substances such as pyrrole and alkylpyrrole are important pharmaceutical intermediates for the production of 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-based sulfonylurea herbicides, pyrrole-based pyrimidine alcohol fungicides, etc.

[0003] Hexamethylenediamine is an important raw material for producing nylon materials. In the process of producing hexamethylenediamine by hydrogenating adiponitrile, a variety of nitrogen-containing heterocyclic compounds with similar molecular structures and similar boiling points, including 3-ethylpyrrolidine and 3-methylpiperidine, are produced as byproducts. Among them, the atmospheric boiling points of 3-ethylpyrrolidine and 3-methylpiperidine differ by less than 5°C. Only 10-15% of 3-ethylpyrrolidine and 85-90% of 3-methylpiperidine mixture can be obtained through conventional distillation separation, and the corresponding pure products cannot be separated for sale. In the end, they can only be incinerated in the form of waste oil. If the nitrogen-containing heterocyclic compounds such as 3-ethylpyrrolidine and / or 3-methylpiperidine produced as byproducts in the production of hexamethylenediamine can be used as raw materials for dehydrogenation reaction through a dehydrogenation catalyst, 3-ethylpyrrole and / or 3-methylpyridine products can be obtained. The atmospheric boiling points of 3-ethylpyrrole and 3-methylpyridine differ by 20°C, and high-purity products can be obtained through conventional distillation. On the one hand, this process can solve the problem of by-product separation and operation difficulties in the production of hexamethylenediamine, and on the other hand, it can turn the above by-products into valuables, and transform them into fine chemicals with high added value that are easy to distill and purify through dehydrogenation reaction, which is very beneficial for improving the quality and efficiency of industrial production. Therefore, dehydrogenation catalysts are particularly important for dehydrogenation reactions.

[0004] However, the existing nitrogen-aromatic ring production processes all have the disadvantages of long process routes, low atom economy, harsh reaction conditions, and high equipment investment and energy consumption.

[0005] At present, the industrial production process of nitrogen heteroaromatic substances 3-methylpyridine is the aldehyde ammonia oxidation method, that is, acetaldehyde, formaldehyde and ammonia are used as raw materials, and converted into pyridine through the catalyst ZSM-5 molecular sieve or SiO2-Al2O3-Bi2O3, while 3-methylpyridine is produced as a by-product, with a yield of about 30%. The raw materials used in this reaction are cheap and easy to obtain, and can be continuously produced on a large scale. It is currently the mainstream process for preparing 3-methylpyridine in industry. However, this process faces continuous challenges as paraquat, a downstream product of pyridine, is subject to sales and production bans in various countries around the world. Currently, 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 equipment using this process. In addition, from the perspective of production technology, (1) in addition to producing pyridine, the selectivity of 3-methylpyridine in the aldehyde ammonia oxidation method is only 30%, and the ratio of the two is difficult to increase. This results in the production of 3-methylpyridine always being affected by the production of pyridine, and it is impossible to increase the production capacity of 3-methylpyridine alone, making it difficult to meet the continued growth of downstream market demand; (2) The aldehyde ammonia oxidation method requires a supporting ammonia synthesis device, which has high energy consumption and huge carbon dioxide emissions, and is not in line with the national "dual carbon" policy and the development trend of green chemical industry; (3) The aldehyde ammonia oxidation method also produces a variety of by-products including 4-methylpyridine, 2-methylpyridine, 2,6-dimethylpyridine and bipyridine, which are difficult to separate by distillation and have complex purification processes. In particular, the 1% by-product 4-methylpyridine is almost impossible to effectively purify and separate. This will have a very adverse impact on the quality and purity of downstream vitamins and other pharmaceutical intermediates.

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

[0007] The currently disclosed 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 the use of 0.5% Pd-0.5% Pt / ZrO2 catalyst to catalyze the dehydrogenation of pyrrolidine to prepare pyrrole at 230-240° C. However, according to the disclosed examples, the conversion rate of the raw material decreased from 96.3% to 91.0% after the catalyst was operated for only 34 hours.

[0009] Patent CN1903842A reports the use of Pd / SiO2 catalyst 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 through cyclization reaction and dehydrogenation reaction. First, 2-methylpentanediamine is cyclized to generate 3-methylpiperidine using hydrogen molecular sieve as cyclization catalyst; then 3-methylpiperidine is dehydrogenated to generate 3-methylpyridine using supported Pd as dehydrogenation catalyst. The two catalysts can be loaded into the same reactor in sections, or loaded into two reactors respectively, and the continuous preparation of 3-methylpyridine can be achieved in a series or non-series manner. However, according to the information disclosed in the patent: (1) when 2-methylpentanediamine and 3-methylpiperidine are used as raw materials and the performance of the two catalysts is evaluated respectively, the yield of the two-step reaction can reach 99%, but the life of the dehydrogenation catalyst is only 300 hours; (2) when 2-methylpentanediamine is used as raw material and passed through the same reactor loaded with a cyclization catalyst and a dehydrogenation catalyst, the yield of 3-methylpyridine is 97%, and 2.9% of 3-methylpiperidine is not dehydrogenated and needs to be distilled and purified; (3) when 2-methylpentanediamine is used as raw material and passed through two series reactors loaded with a cyclization catalyst and a dehydrogenation catalyst, 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 varying degrees under the above three process conditions, and the catalyst activity decreases rapidly. At the same time, in order to achieve a dehydrogenation reaction yield of 99% in the preparation method, the Pd loading amount needs to be higher than 3wt%. Due to the high market price of the precious metal palladium, the cost in industrial production is greatly increased.

[0011] Patent CN101384525B discloses a method for preparing 3-methylpyridine by dehydrogenating 3-methylpiperidine under oxygen-containing conditions. That is, by adding a certain proportion of air or oxygen into the feed stream, the stability and life of the dehydrogenation catalyst Pd / ZrO2 can be improved without affecting the reaction hot spot temperature. Moreover, as the oxygen content increases, the deactivation degree 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 the conversion of 2-methylpentanediamine or 3-methylpiperidine into 3-methylpyridine using Pd / Al2O3 as a catalyst and hydrogen as a carrier gas. However, in this preparation method, when no solvent is used, Pd / Al2O3 is quickly deactivated. When water or alcohol is used as a solvent, the activity of the catalyst can be maintained for more than 300 hours, but the product still contains 3-4% 3-methylpiperidine, which requires rectification and purification, 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 production costs.

[0013] Patent CN102548655A discloses that a loaded Pd catalyst is used to catalyze the dehydrogenation reaction of 3-methylpiperidine to prepare 3-methylpyridine, and the catalyst life can reach 300 days. However, the Pd loading in the catalyst used in the patent is very high (5-10%), which will cause the cost of the catalyst to be too high, which is not conducive to the control of industrial production costs.

[0014] The preparation of nitrogen-containing aromatic ring products by dehydrogenation of nitrogen-containing heterocyclic compounds has higher yield and higher atom economy than other processes, but the prior art also has technical defects such as high precious metal loading and easy deactivation of catalysts. The inventors have found that compared with ordinary cycloalkanes such as cyclohexane or methylcyclohexane, the dehydrogenation reaction of heterocycloalkanes with nitrogen atoms has the following technical difficulties: (1) The thermal stability of raw materials and products is poor, causing the catalyst to be more prone to coking and carbon deposition: Cyclohexane or methylcyclohexane can still maintain a high thermal stability at a high temperature of 400°C, so the deactivation of such ordinary cycloalkane dehydrogenation catalysts is often high-temperature carbon deposition, but this process is usually relatively long, so the life of such cycloalkane dehydrogenation catalysts is usually 1 to 2 years. However, heterocyclic alkane compounds with nitrogen atoms (such as 3-methylpiperidine or 3-ethylpyrrolidine) are more active and have poor thermal stability. At temperatures above 150°C, side reactions such as oxidation, dimerization, and trimerization will occur; and their dehydrogenation products 3-methylpyridine or 3-ethylpyrrole will slowly undergo side reactions such as demethylation and dimerization at temperatures above 250°C. The above side reaction products are all small molecules or oligomers containing nitrogen, which can easily cause coking and carbon deposition of the dehydrogenation catalyst. Therefore, the life of the dehydrogenation catalyst used for such raw materials is often short (generally only tens to hundreds of hours), and a higher loading of precious metals is required to delay the deactivation process. (2) Raw materials and products containing nitrogen heteroatoms have strong complexing and coordination capabilities with precious metals, which will affect the catalyst activity and cause the loss of precious metals in the catalyst: Compared with ordinary cycloalkanes that only contain carbon and hydrogen elements, nitrogen-containing heterocyclic compounds usually have strong complexing and coordination capabilities with precious metals such as Pd, Pt, Rh or Ru, such as pyridine or pyrrole products. Especially when the interaction between the noble metal of the catalyst and the carrier is not strong, some nitrogen-containing oligomers such as bipyridine by-products will complex with the noble metal, which will, on the one hand, destroy the dehydrogenation catalytic activity of the zero-valent noble metal, and on the other hand, cause the noble metal to dissolve into the product in the form of a complex, thereby causing a slow loss of the noble metal, which is unacceptable for the use of industrial catalysts.

[0015] In order to overcome the limitations of the existing technology and the technical difficulties in the dehydrogenation of the above-mentioned nitrogen-containing heterocyclic compounds, it is necessary to focus on solving the following problems: (1) Develop a production process and supporting catalyst technology for the dehydrogenation of nitrogen-containing heterocyclic compounds produced as by-products in the production of hexamethylenediamine to prepare high-value-added nitrogen heteroaromatic rings from the perspective of acceptable industrial costs, so as to achieve a higher reaction yield; (2) Maintain the catalytic activity of the catalyst for a long time and reduce the cost of using the catalyst by improving the interaction between the active metal of the catalyst and the carrier and optimizing the distribution of the active metal in the catalyst; (3) Improve production efficiency and maximize the competitiveness of the technology. Summary of the invention

[0016] In order to solve the above technical problems, the present invention provides a dehydrogenation catalyst for preparing nitrogen heteroaromatic rings and a preparation method and application thereof.

[0017] In one aspect, the present invention provides a dehydrogenation catalyst for preparing nitrogen heteroaromatic rings, comprising a carrier, a first active metal component, a second active metal component and an active auxiliary component.

[0018] The carrier has a specific surface area of ​​150 to 400 m2 / g, a pore volume of 0.6 to 1.5 cm3 / g, and a saturated water absorption rate of 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 auxiliary component is a P-containing active auxiliary.

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

[0023] The dehydrogenation catalyst prepared with the carrier of the present invention has a uniform distribution of the first active metal component Pd in ​​the catalyst, rather than the eggshell distribution of the conventional supported catalyst. The multi-level microporous structure of the carrier of the present invention can ensure that the first active metal component Pd is uniformly dispersed on the catalyst surface and inside the catalyst, thereby improving the dispersion of the active metal. This is very conducive to the gas-solid reaction of preparing 3-methylpyridine by dehydrogenation of 3-methylpiperidine, because 3-methylpiperidine can not only react on the dehydrogenation catalyst surface after vaporization, but also enter the internal multi-level microporous structure of the catalyst, and react at the active metal site inside the catalyst. This type of active metal distribution mode can improve the processing capacity of the catalyst on the one hand, and can delay the long-term high temperature aggregation of the active metal on the other hand, thereby extending the service life of the catalyst.

[0024] The dehydrogenation catalyst of the present invention introduces one or more of the second active metal components Re, Sn or Ir to inhibit the agglomeration of the first active metal component. The introduction of the second active metal component (for example, Re) 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 electron modifier to form ReO around the Pd active site x layer, thereby isolating the Pd active sites into tiny metal clusters or even single metal sites, thereby partially suppressing the aggregation of the first active metal of the catalyst and the rapid deactivation of the catalyst while reducing the first active metal loading.

[0025] The dehydrogenation catalyst active promoter of the present invention is a P-containing active promoter. By doping P atoms into a carrier such as an alumina carrier, effective P species are more inclined to form Al-OP species with unsaturated coordinated Al sites in the carrier and replace weakly adsorbed hydroxyl groups. After the active metal is loaded, the P-OH group promotes the formation of PO-Pd bonds, thereby forming a more solid interaction with the Pd species. The strong interaction between the P-modified carrier and the Pd nanoparticles leads to a suitable electronic structure of the Pd nanoparticles and more low-coordinated Pd sites, so that the catalyst shows a 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 extend the service life of the catalyst. At the same time, the coordination and complexing ability of nitrogen-containing oligomers and Pd metals can also be suppressed, thereby avoiding the loss of precious metals, which is crucial for the industrial application and cost control of the catalyst.

[0026] Further, the support is pretreated with a basic compound.

[0027] The carrier is pretreated with an alkaline compound so that the ratio of the alkaline center to the acidic center of the carrier is greater than 2:1. According to the research of the inventors, heterocyclic alkane compounds with nitrogen atoms (taking 3-methylpiperidine as an example) have poor thermal stability, and side reactions such as oxidation, dimerization, and trimerization will occur at temperatures above 150°C. When the catalyst is treated with an alkaline compound, the acidic sites on the catalyst carrier are eliminated, which can avoid the polymerization reaction catalyzed by the acidic sites during the catalytic dehydrogenation of 3-methylpiperidine to a certain extent, and can effectively inhibit the coking and carbon deposition on the surface of the dehydrogenation catalyst, thereby extending the service life of the dehydrogenation catalyst.

[0028] In summary, the dehydrogenation catalyst of the present invention has a more multi-level microporous structure and a uniform active metal distribution mode, and has a better active metal dispersion, thereby delaying the long-term high-temperature aggregation of active metals; in addition, the P-doped catalyst can promote a stronger interaction between Pd and the carrier, further effectively delaying the high-temperature aggregation of Pd and extending the service life of the catalyst, while effectively inhibiting the complexing and coordination ability of nitrogen-containing oligomers and Pd metals, thereby avoiding the loss of precious metals. The second active metal component can be used as a modifier to induce the first active metal Pd to be in a more reduced state or a stable metal state, while the higher oxidation state of the second active metal component isolates the Pd active site into small metal clusters or even single metal sites, further improving the Pd dispersion, and inhibiting the aggregation of Pd and the rapid deactivation of the catalyst. In addition, after the catalyst is alkaline pretreated, the acidic sites on the catalyst carrier are eliminated, which can avoid the polymerization reaction catalyzed by the acidic sites during catalytic dehydrogenation to a certain extent, effectively inhibiting the coking and carbon deposition on the surface of the dehydrogenation catalyst, thereby extending the service life of the dehydrogenation catalyst.

[0029] Furthermore, the specific surface area of ​​the carrier is 200 to 350 m 2 / g, 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 more preferably at least one of aluminum oxide, aluminum-containing molecular sieve or aluminum oxide-silicon oxide, wherein the aluminum oxide content in the aluminum-containing carrier aluminum oxide-silicon oxide is 60-100wt%, and the silicon oxide content is 0-40wt%. The embodiment of the present invention provides data on the parameters related to 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 auxiliary component to the carrier is (0.01-0.05):1, preferably (0.02-0.04):1.

[0033] Further, the phosphorus source of the P-containing active agent is selected from one or more of ammonium phosphate, monoammonium hydrogen phosphate, diammonium hydrogen 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, monoammonium hydrogen phosphate or diammonium dihydrogen phosphate;

[0034] And / or, the Pd source of the first active metal is one or more of Pd hydrochloride, nitrate, acetate or ammonium salt, preferably one or more of palladium chloride, palladium nitrate, tetraamine palladium nitrate or dichlorotetraaminepalladium;

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

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

[0037]

[0038] Among them, R 1 , R 2 , R 3 and R 4 is selected from H and C1-C4 alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, preferably methyl, ethyl and n-propyl, X - is an anion selected from OH - 、HCO3 - and CO3 2- , preferably OH - After pretreatment, the N-containing compound will be burned off in the subsequent calcination process, which can avoid the introduction of other metal elements and affect the performance of the catalyst.

[0039] Illustratively, the basic compound is tetraethylammonium hydroxide, tetramethylammonium hydroxide, triethylamine or tripropylamine.

[0040] Preferably, the mass ratio of the alkaline compound to the carrier is (0.1-5):1, preferably (0.5-2):1.

[0041] On the other hand, the present invention also provides a method for preparing a nitrogen heteroaromatic ring dehydrogenation catalyst, and the preparation method of the dehydrogenation catalyst comprises the following steps:

[0042] Step (1): dissolving a P-containing active agent precursor in a solvent and then adding the solvent to a carrier for impregnation, and obtaining a P-doped carrier after drying and calcining;

[0043] Step (2): dissolving an alkaline compound in a solvent and then adding the solvent to the P-doped carrier obtained in step (1), followed by post-treatment to obtain an alkali-treated P-doped carrier;

[0044] Step (3): dissolving the first active metal component in a solvent and then adding the solvent to the alkali-treated P-doped carrier obtained in step (2) for impregnation, and obtaining a carrier containing the first active metal component after drying and calcining;

[0045] Step (4): dissolving the second active metal component in a solvent and then adding the solvent to the carrier containing the first active metal component obtained in step (3) for impregnation, and obtaining a dehydrogenation catalyst after drying and calcining.

[0046] Exemplarily, the method for preparing a dehydrogenation catalyst comprises the following steps:

[0047] Step (1): taking a solvent of a volume equal to the saturated absorption amount of the carrier to be impregnated, dissolving the P-containing active agent in the solvent to prepare a homogeneous solution with a mass concentration of 5 to 30 wt%, dispersing the carrier in the solution so that the solution is fully impregnated on the carrier, drying at 80 to 150° C. and calcining at 200 to 250° C. to obtain a P-doped carrier;

[0048] Step (2): dissolving the alkaline 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 slowly stirring at 20-40° C. for 1-2 hours. Then filtering out the carrier, drying at 80-150° C. and calcining at 300-500° C.;

[0049] Step (3): taking a solvent of a volume equal to the saturated absorption capacity of the carrier to be impregnated, dissolving the first active metal component in the solvent to prepare a homogeneous solution with a mass concentration of 10 to 25 wt%, dispersing the carrier obtained in step (2) in the solution so that the solution is fully impregnated on the carrier, drying at 80 to 150° C. and calcining at 300 to 500° C. to obtain a carrier containing the first active metal component;

[0050] Step (4): Take a solvent of a volume equal to the saturated absorption capacity 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 to 25 wt%, disperse the carrier containing the first active metal component obtained in step (3) in the solution so that the solution is fully impregnated on the carrier, and obtain a dehydrogenation catalyst after drying at 80 to 150° C. and calcining at 300 to 500° C.

[0051] Furthermore, the solvent in steps (1) to (4) is one or more of water, ethanol or ammonia, preferably water or ammonia;

[0052] On the other hand, the present invention also provides an application of a dehydrogenation catalyst in the dehydrogenation of nitrogen-containing heterocyclic compounds to prepare nitrogen heteroaromatic rings.

[0053] The nitrogen-containing heterocyclic compound is a monocyclic or polycyclic hydrocarbon having one or more nitrogen atoms, wherein one or more hydrogen atoms may 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 and alkylpiperidine. Among them, alkylpyrrolidine is a compound in which at least one hydrogen atom on the pyrrolidine ring is replaced by an alkyl group, alkylpiperidine is a compound in which at least one hydrogen atom on the piperidine ring is replaced by an alkyl group, and alkyltetrahydroquinoline is a compound in which the hydrogen atom on the nitrogen atom in the tetrahydroquinoline molecule is replaced by an alkyl group.

[0054] Furthermore, the dehydrogenation preparation is carried out under the condition that at least one of hydrogen, nitrogen and ammonia is used as a carrier gas, the reaction temperature is 200-300° C., the reaction pressure is 0-0.1 MPa, and the mass space velocity of the nitrogen-containing heterocyclic compound is 0.5-2 h -1 .

[0055] Dehydrogenation preparation can be performed by an intermittent process or a continuous process. In the continuous dehydrogenation reaction, the raw materials are added to the reactor in a continuous and stable manner, and the product is continuously discharged during the reaction. This method can achieve efficient and rapid production, which helps to improve production efficiency and output. Since the residence time of the reaction materials 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 intermittent dehydrogenation reaction requires the raw materials to be added to the reactor at one time and reacted under certain temperature, pressure and time conditions. After the reaction is completed, it is necessary to stop feeding and discharge the product. The production efficiency of this method is relatively low, and each reaction requires re-preparation and adjustment of the reaction conditions, which increases production costs and time, so it is preferably a continuous method. The reactor for dehydrogenation preparation is selected from a loop reactor, a fixed bed reactor, a reactor or a fluidized bed reactor, preferably a loop reactor or a fixed bed reactor.

[0056] Exemplary, a method for preparing nitrogen heteroaromatic rings by dehydrogenation of nitrogen-containing heterocyclic compounds: the dehydrogenation catalyst is filled into a dehydrogenation reactor (fixed bed reactor) equipped with a heating and heat preservation device, the reactor diameter is 39mm, the tube length is 2000mm, and the catalyst filling height is 200mm. Before the reaction, the reactor is purged three times with nitrogen. Before the reaction starts, hydrogen is introduced from the top of the reactor controlled by a gas flow meter, and the reactor temperature is gradually increased, and finally the dehydrogenation catalyst is activated and reduced at 280-290°C in a hydrogen atmosphere for 6h. After the reaction starts, the raw nitrogen heterocyclic compound is pumped into the preheater by a plunger pump through a pipeline heating, the preheating temperature is 150°C, and the pipeline heating temperature is 150°C. The raw material is mixed with a hydrogen carrier gas (350sccm) and introduced into a fixed bed reactor from the top of the reactor. The reaction bed temperature is controlled at 260°C, the system pressure is controlled at 0.02MPa, and the residence time is controlled by the raw material mass space velocity. The equipment was operated continuously for 72 hours, and the reaction liquid was taken out from the bottom of the reactor and the product mixture was obtained after multi-stage cooling.

[0057] On the other hand, the present invention also provides an application of a dehydrogenation catalyst in the dehydrogenation of nitrogen-containing heterocyclic byproducts in the production process of hexamethylenediamine to prepare nitrogen heteroaromatic rings.

[0058] The nitrogen-containing heterocyclic compound raw material used in the present invention can come from the nitrogen-containing heterocyclic by-products in the production process of hexamethylenediamine. The raw materials that are difficult to purify by distillation, including 3-ethylpyrrolidine and / or 3-methylpiperidine, are converted into high-purity 3-ethylpyrrole and / or 3-methylpyridine products by simple distillation through a dehydrogenation process, wherein the mass fraction of 3-methylpiperidine is 85-99.9% and / or the mass fraction of 3-ethylpyrrolidine is 5-12%.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) The dehydrogenation catalyst of the present invention has a long service life and high activity, and can achieve long-term continuous and stable operation.

[0061] (2) The dehydrogenation catalyst of the present invention can be used to prepare a variety of nitrogen heteroaromatic rings with different numbers of carbon atoms.

[0062] (3) The dehydrogenation catalyst of the present invention can realize the continuous dehydrogenation reaction and directly obtain nitrogen heteroaromatic rings. The conversion rate of the raw material nitrogen heterocyclic compound is more than 99%, the selectivity of the product nitrogen heteroaromatic ring is more than 99%, and the yield is 98-99%. The separation difficulty of the reaction product is low, the separation energy consumption advantage is obvious, the production efficiency is high, and it is suitable for industrial production.

[0063] (4) The dehydrogenation catalyst of the present invention can be used for the dehydrogenation of nitrogen-containing heterocyclic byproducts in the production process of hexamethylenediamine to prepare nitrogen heteroaromatic rings, which can turn waste oil raw materials into high-value-added fine chemicals, maximize the resource utilization of raw materials and the high-value-added conversion of the production process, effectively reduce production costs, maximize its economic benefits, and enhance the competitiveness of the entire product industry chain. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings to further understand the technical solution of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations of the present invention. In the accompanying drawings:

[0065] Figure 1 The TEM transmission electron microscope image of the dehydrogenation catalyst A of the present invention is shown;

[0066] Figure 2 A cross-sectional view of the dehydrogenation catalyst A in Catalyst Preparation Example 1 of the present invention is shown;

[0067] Figure 3 A cross-sectional view of the dehydrogenation catalyst G in comparative example 1 of the catalyst preparation of the present invention is shown;

[0068] Figure 4 A graph showing the life span of different dehydrogenation catalysts catalyzing the dehydrogenation of 3-methylpiperidine to prepare 3-methylpyridine. DETAILED DESCRIPTION

[0069] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0070] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0071] The present invention will be described in detail below with reference to the embodiments and the accompanying drawings.

[0072] Preparation of dehydrogenation catalyst

[0073] Catalyst Preparation Example 1 : Preparation of dehydrogenation catalyst A (0.8% Pd-2.5% Re / γ-Al2O3)

[0074] The specific surface area of ​​dehydrogenation catalyst A is 350m 2 / g, pore volume is 1.1cm3 / g, and a γ-Al2O3 carrier with a saturated water absorption rate of 125%.

[0075] The preparation method of dehydrogenation catalyst A comprises the following steps:

[0076] (1) 17.03 g of diammonium hydrogen phosphate (P content: 4 g) was dissolved in 125 g of desalted water to completely dissolve into a clear solution. 100 g of the γ-Al2O3 carrier was dispersed in the solution and fully immersed for 24 h. The carrier was dried at 120°C for 8 h and calcined at 250°C for 12 h to obtain a P-doped γ-Al2O3 carrier (P content: 4%).

[0077] (2) The P-doped carrier obtained in step (1) was dispersed in 500 g of a 35 wt% tetraethylammonium hydroxide aqueous solution and slowly stirred at 40° C. for 2 h. The carrier was then filtered out, dried at 120° C. for 8 h, and calcined at 300° C. for 12 h. The ratio of the basic center to the acidic center of the carrier after alkali pretreatment was 3:1 as determined by NH3 / CO2-TPD.

[0078] (3) 1.73 g of palladium nitrate was dissolved in 125 g of desalted water to completely dissolve into a clear solution. The carrier obtained in step (2) was dispersed in the Pd-containing solution and fully immersed for 24 h. The carrier was dried at 120° C. for 8 h and calcined at 450° C. for 12 h to obtain a carrier containing a Pd component.

[0079] (4) 3.37 g of perrhenic acid was dissolved in 125 g of desalted water to completely dissolve the solution into a clear solution. The Pd-containing carrier obtained in step (3) was dispersed in the perrhenic acid solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 450° C. for 12 h, a dehydrogenation catalyst A (0.8% Pd-2.5% Re / γ-Al2O3) was obtained. The percentage of 0.8% Pd-2.5% Re / γ-Al2O3 refers to the mass fraction, and the percentage is referenced to the carrier, that is, the carrier is 1.

[0080] The metal dispersion of Pd in ​​the dehydrogenation catalyst A was tested by carbon monoxide pulse titration method and was found to be 35%. Figure 1 The figure shows a transmission electron microscope (TEM) image of dehydrogenation catalyst A after reduction at 280°C for 6 hours in a hydrogen atmosphere. According to TEM, the particle size of the active metal Pd in ​​catalyst A is between 2 and 3 nm. Therefore, the dehydrogenation catalyst of the present invention has a higher catalytic efficiency and can slow down the aggregation of Pd metal during the reaction, thereby extending the life of the catalyst. Figure 2 Shown is a cross-sectional view of the dehydrogenation catalyst A after reduction at 280° C. for 6 hours in a hydrogen atmosphere, in which the first active metal Pd is evenly distributed.

[0081] Catalyst Preparation Example 2: Preparation of dehydrogenation catalyst B (1% Pd-3% Sn / Al2O3)

[0082] The specific surface area of ​​dehydrogenation catalyst B is 400m 2 / g, pore volume is 1.3cm 3 / g and an Al2O3 carrier with a saturated water absorption rate of 150%.

[0083] The preparation method of the dehydrogenation catalyst B comprises the following steps:

[0084] (1) 9.28 g of diammonium hydrogen phosphate (P content: 2.17 g) was dissolved in 150 g of desalted water to completely dissolve into a clear solution. 100 g of the Al2O3 carrier was dispersed in the solution and fully immersed for 24 h. The carrier was dried at 120°C for 8 h and calcined at 250°C for 12 h to obtain a P-doped Al2O3 carrier.

[0085] (2) The P-doped carrier obtained in step (1) was dispersed in 350 g of a 35 wt% tetramethylammonium hydroxide aqueous solution and slowly stirred at 40° C. for 2 h. The carrier was then filtered out, dried at 120° C. for 8 h, and calcined at 300° C. for 12 h. The ratio of the basic center to the acidic center of the carrier after alkali pretreatment was 2:1 as determined by NH3 / CO2-TPD.

[0086] (3) 2.165 g of palladium nitrate was dissolved in 150 g of desalted water to completely dissolve into a clear solution. The carrier obtained in step (2) was dispersed in the Pd-containing solution and fully immersed for 24 h. The carrier was dried at 120° C. for 8 h and calcined at 350° C. for 8 h to obtain a carrier containing a Pd component.

[0087] (4) 4.79 g of stannous chloride was dissolved in 150 g of desalted water to completely dissolve into a clear solution. The Pd-containing carrier obtained in step (3) was dispersed in the stannous chloride solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 500° C. for 10 h, a dehydrogenation catalyst B (1% Pd-3% Sn / Al2O3) was obtained.

[0088] Catalyst Preparation Example 3 : Preparation of dehydrogenation catalyst C (0.5% Pd-1.2% Re / Al2O3)

[0089] The specific surface area of ​​dehydrogenation catalyst C is 280m 2 / g, pore volume is 0.95cm 3 / g and an Al2O3 carrier with a saturated water absorption rate of 135%.

[0090] The preparation method of the dehydrogenation catalyst C comprises the following steps:

[0091] (1) Take 21.3 g of diammonium hydrogen phosphate (P content: 5 g) and dissolve it in 135 g of desalted water to make it completely dissolved into a clear solution. Disperse the above-mentioned 100 g of Al2O3 carrier in the solution and soak it for 24 h. After drying at 120°C for 8 h and calcining at 250°C for 12 h, a P-doped Al2O3 carrier is obtained.

[0092] (2) The P-doped carrier obtained in step (1) was dispersed in 400 g of 50 wt% triethylamine ethanol solution and slowly stirred at 40° C. for 2 h. The carrier was then filtered out, dried at 120° C. for 8 h, and calcined at 300° C. for 12 h. The ratio of the basic center to the acidic center of the carrier after alkali pretreatment was 4:1 as determined by NH3 / CO2-TPD.

[0093] (3) 1.09 g of tetraaminopalladium nitrate was dissolved in 135 g of desalted water to completely dissolve into a clear solution. The support obtained in step (2) was dispersed in the Pd-containing solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 450° C. for 10 h, a support containing a Pd component was obtained.

[0094] (4) 1.73 g of ammonium perrhenate was dissolved in 135 g of desalted water to completely dissolve it into a clear solution. The Pd-containing carrier obtained in step (3) was dispersed in the ammonium perrhenate solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 450° C. for 12 h, a dehydrogenation catalyst C (0.5% Pd-1.2% Re / Al2O3) was obtained.

[0095] Catalyst Preparation Example 4 :Preparation of dehydrogenation catalyst D (2% Pd-1% Ir / Al2O3-SiO2)

[0096] Dehydrogenation catalyst D has a specific surface area of ​​320m 2 / g, pore volume is 1.26cm 3 / g and an Al2O3-SiO2 carrier with a saturated water absorption rate of 120%, wherein the Al2O3 content in the Al2O3-SiO2 carrier is 75%.

[0097] The preparation method of the dehydrogenation catalyst D comprises the following steps:

[0098] (1) Take 17.03 g of diammonium hydrogen phosphate (P content is 4 g) and dissolve it in 120 g of desalted water to make it completely dissolved into a clear solution. Disperse the above-mentioned 100 g of Al2O3-SiO2 carrier in the solution and soak it fully for 24 hours. After drying at 120°C for 8 hours and calcining at 250°C for 12 hours, a P-doped Al2O3-SiO2 carrier is obtained.

[0099] (2) The P-doped carrier obtained in step (1) was dispersed in 400 g of 40 wt% tripropylamine ethanol aqueous solution and slowly stirred at 40° C. for 2 h. The carrier was then filtered out, dried at 120° C. for 8 h, and calcined at 300° C. for 12 h. The ratio of the basic center to the acidic center of the carrier after alkali pretreatment was 3:1 as determined by NH3 / CO2-TPD.

[0100] (3) 4.33 g of palladium nitrate was dissolved in 120 g of desalted water to completely dissolve into a clear solution. The carrier obtained in step (2) was dispersed in the Pd-containing solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 400° C. for 6 h, a carrier containing a Pd component was obtained.

[0101] (4) 2.12 g of chloroiridic acid hexahydrate was dissolved in 120 g of desalted water to completely dissolve into a clear solution. The Pd-containing carrier obtained in step (3) was dispersed in the chloroiridic acid solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 500° C. for 8 h, a dehydrogenation catalyst D (2% Pd-1% Ir / Al2O3-SiO2) was obtained.

[0102] Catalyst Preparation Example 5 : Preparation of dehydrogenation catalyst E (1.5% Pd-4.2% Sn / Al2O3-SiO2)

[0103] The specific surface area of ​​dehydrogenation catalyst E is 250m 2 / g, pore volume is 1.13cm 3 / g and an Al2O3-SiO2 carrier with a saturated water absorption rate of 130%, wherein the Al2O3 content in the Al2O3-SiO2 carrier is 60%.

[0104] The preparation method of the dehydrogenation catalyst E comprises the following steps:

[0105] (1) Take 15.39 g of ammonium phosphate (P content is 3.2 g) and dissolve it in 130 g of desalted water to make it completely dissolved into a clear solution. Disperse the above-mentioned 100 g of Al2O3-SiO2 carrier in the solution and soak it fully for 24 hours. After drying at 120°C for 8 hours and calcining at 250°C for 12 hours, a P-doped Al2O3-SiO2 carrier is obtained.

[0106] (2) The P-doped carrier obtained in step (1) was dispersed in 500 g of a 35 wt% tetraethylammonium carbonate aqueous solution and slowly stirred at 40° C. for 2 h. The carrier was then filtered out, dried at 120° C. for 8 h, and calcined at 300° C. for 12 h. The ratio of the basic center to the acidic center of the carrier after alkali pretreatment was 2.6:1 as determined by NH3 / CO2-TPD.

[0107] (3) 2.5 g of palladium chloride was dissolved in 130 g of desalted water to completely dissolve into a clear solution. The carrier obtained in step (2) was dispersed in the Pd-containing solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 500° C. for 3 h, a carrier containing a Pd component was obtained.

[0108] (4) 6.71 g of stannous chloride was dissolved in 130 g of desalted water to completely dissolve into a clear solution. The Pd-containing carrier obtained in step (3) was dispersed in the stannous chloride solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 400° C. for 8 h, a dehydrogenation catalyst E (1.5% Pd-4.2% Sn / Al2O3-SiO2) was obtained.

[0109] Catalyst Preparation Example 6 : Preparation of dehydrogenation catalyst F (3% Pd-4.2% Re / Al2O3-SiO2)

[0110] Dehydrogenation catalyst F has a specific surface area of ​​375m 2 / g, pore volume is 1.08cm 3 / g and an Al2O3-SiO2 carrier with a saturated water absorption rate of 105%, wherein the Al2O3 content in the Al2O3-SiO2 carrier is 90%.

[0111] The preparation method of the dehydrogenation catalyst F comprises the following steps:

[0112] (1) Take 12.78 g of diammonium hydrogen phosphate (P content is 3 g) and dissolve it in 105 g of desalted water to make it completely dissolved into a clear solution. Disperse the above-mentioned 100 g of Al2O3-SiO2 carrier in the solution and soak it fully for 24 hours. After drying at 120°C for 8 hours and calcining at 250°C for 12 hours, a P-doped Al2O3-SiO2 carrier is obtained.

[0113] (2) The P-doped carrier obtained in step (1) was dispersed in 500 g of a 20 wt% tetraethylammonium hydroxide aqueous solution and slowly stirred at 40° C. for 2 h. The carrier was then filtered out, dried at 120° C. for 8 h, and calcined at 300° C. for 12 h. The ratio of the basic center to the acidic center of the carrier after alkali pretreatment was 4:1 as determined by NH3 / CO2-TPD.

[0114] (3) 6.92 g of dichlorotetraamminepalladium was dissolved in 105 g of desalted water to completely dissolve into a clear solution. The support obtained in step (2) was dispersed in the Pd-containing solution and fully immersed for 24 h. The support was dried at 120° C. for 8 h and calcined at 450° C. for 5 h to obtain a support containing a Pd component.

[0115] (4) 5.67 g of perrhenic acid was dissolved in 105 g of desalted water to completely dissolve the solution into a clear solution. The Pd-containing carrier obtained in step (3) was dispersed in the perrhenic acid solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 400° C. for 12 h, a dehydrogenation catalyst F (3% Pd-4.2% Re / Al2O3-SiO2) was obtained.

[0116] The specific preparation parameters and control conditions of dehydrogenation catalysts A to F are shown in Table 1.

[0117] Preparation of Dehydrogenation Catalyst Comparative Example

[0118] Catalyst Preparation Comparative Example 1 :Preparation of dehydrogenation catalyst G (0.8% Pd-2.5% Re / γ-Al2O3) with low saturated water absorption carrier

[0119] Dehydrogenation catalyst G has a specific surface area of ​​350m 2 / g, pore volume is 0.9cm 3 / g, and the γ-Al2O3 carrier with a saturated water absorption rate of 65% was used instead of the dehydrogenation catalyst A with a specific surface area of ​​350m 2 / g, pore volume is 1.1cm 3 / g, and a γ-Al2O3 carrier with a saturated water absorption rate of 125%, other parameters and control conditions of the dehydrogenation catalyst A in Catalyst Preparation Comparative Example 1 are the same as those in Catalyst Preparation Example 1.

[0120] The metal dispersion of Pd in ​​the dehydrogenation catalyst G was 24% as measured by carbon monoxide pulse titration. Figure 3 Shown is a cross-sectional view of the dehydrogenation catalyst G after reduction at 280°C for 6 hours in a hydrogen atmosphere, in which the first active metal Pd is distributed in an eggshell shape.

[0121] Catalyst Preparation Comparative Example 2 : Preparation of dehydrogenation catalyst H (0.8% Pd-2.5% Re / γ-Al2O3) without alkali pretreatment of the carrier

[0122] Dehydrogenation Catalyst H Except that step (2) is omitted in the preparation steps of Dehydrogenation Catalyst A, that is, no base is used to pretreat the γ-Al2O3 carrier, the other parameters and control conditions of Dehydrogenation Catalyst A in Catalyst Preparation Example 2 are the same as those in Catalyst Preparation Example 1.

[0123] The ratio of the basic center to the acidic center of the carrier was 0.8:1 as determined by NH3 / CO2-TPD.

[0124] Catalyst Preparation Comparative Example 3 : Preparation of dehydrogenation catalyst I (0.8% Pd / γ-Al2O3) without adding the second metal active component

[0125] Dehydrogenation Catalyst I Except that step (4) is omitted in the preparation steps of Dehydrogenation Catalyst A, that is, no second metal active component is added, the other parameters and control conditions of Dehydrogenation Catalyst A in Catalyst Preparation Example 3 are the same as those in Catalyst Preparation Example 1.

[0126] Catalyst Preparation Comparative Example 4 : Preparation of dehydrogenation catalyst J (2.5% Re / γ-Al2O3) without adding the first metal active component

[0127] Dehydrogenation Catalyst J Except that step (3) is omitted in the preparation steps of Dehydrogenation Catalyst A, that is, the first metal active component is not added, the other parameters and control conditions of Dehydrogenation Catalyst A in Catalyst Preparation Example 4 are the same as those in Catalyst Preparation Example 1.

[0128] Catalyst Preparation Comparative Example 5 : Preparation of dehydrogenation catalyst K (0.8% Pd-2.5% Re / γ-Al2O3) without doping with active auxiliary component P

[0129] Dehydrogenation Catalyst K Except that step (1) is omitted in the preparation process of Dehydrogenation Catalyst A, that is, the active auxiliary component P is not doped, the other parameters and control conditions of Dehydrogenation Catalyst A in Catalyst Preparation Example 5 are the same as those in Catalyst Preparation Example 1.

[0130] Catalyst Preparation Comparative Example 6 :Preparation of dehydrogenation catalyst L (0.8% Pd-2.5% Re / γ-Al2O3) with low specific surface area support

[0131] Dehydrogenation catalyst L has a specific surface area of ​​138m 2 / g, pore volume is 1.05cm 3 / g, and the saturated water absorption rate is 122%, and the γ-Al2O3 carrier used in the dehydrogenation catalyst A has a saturated water absorption rate of 125% and a specific surface area of ​​350m 2 / g, pore volume is 1.1cm 3 / gγ-Al2O3 carrier, the parameters and control conditions of the dehydrogenation catalyst A in the catalyst preparation comparative example 6 are the same as those in the catalyst preparation example 1.

[0132] Catalyst Preparation Comparative Example 7 :Preparation of dehydrogenation catalyst M (0.8% Pd-2.5% Re / γ-Al2O3) with low pore volume support

[0133] The dehydrogenation catalyst M has a saturated water absorption rate of 120% and a specific surface area of ​​343m 2 / g, pore volume is 0.53cm 3 / g of γ-Al2O3 carrier instead of the one used in dehydrogenation catalyst A with a specific surface area of ​​350m 2 / g, pore volume is 1.1cm 3 / g, and a γ-Al2O3 carrier with a saturated water absorption rate of 125%, other parameters and control conditions of the dehydrogenation catalyst A in Catalyst Preparation Comparative Example 7 are the same as those in Catalyst Preparation Example 1.

[0134] Catalyst Preparation Comparative Example 8 :Preparation of dehydrogenation catalyst N (0.8% Pd-2.5% Re / γ-Al2O3)

[0135] The carrier, preparation parameters and control conditions used in the preparation of dehydrogenation catalyst N are exactly the same as those used in the dehydrogenation catalyst A in Catalyst Preparation Example 1. The only difference is the preparation steps, that is, step (1) in Catalyst Preparation Example 1 is placed after step (4). The specific steps are:

[0136] (1) The γ-Al2O3 carrier in Catalyst Preparation Example 1 was dispersed in 500 g of a 35 wt% tetraethylammonium hydroxide aqueous solution and slowly stirred at 40°C for 2 h. The carrier was then filtered out, dried at 120°C for 8 h, and calcined at 300°C for 12 h. The ratio of the basic center to the acidic center of the carrier after alkali pretreatment was 3:1 as determined by NH3 / CO2-TPD.

[0137] (2) 1.73 g of palladium nitrate was dissolved in 125 g of desalted water to completely dissolve into a clear solution. The carrier obtained in step (1) was dispersed in the Pd-containing solution and fully immersed for 24 h. The carrier was dried at 120° C. for 8 h and calcined at 450° C. for 12 h to obtain a carrier containing a Pd component.

[0138] (3) 3.37 g of perrhenic acid was dissolved in 125 g of desalted water to completely dissolve into a clear solution. The Pd-containing carrier obtained in step (2) was dispersed in the perrhenic acid solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 450° C. for 12 h, a carrier containing two active metal components, Pd and Re, was obtained.

[0139] (4) 17.03 g of diammonium hydrogen phosphate (P content: 4 g) was dissolved in 125 g of desalted water to completely dissolve into a clear solution. The support containing two active metal components, Pd and Re, obtained in step (3) was dispersed in the solution and fully immersed for 24 h. After drying at 120° C. for 8 h and calcining at 250° C. for 12 h, a dehydrogenation catalyst N (containing 4% P) was obtained.

[0140] Catalyst Preparation Comparative Example 9: Preparation of dehydrogenation catalyst Q (0.8% Pd-2.5% Re / γ-Al2O3)

[0141] The carrier, preparation parameters and control conditions used in the preparation of dehydrogenation catalyst Q are exactly the same as those used in the dehydrogenation catalyst A in Catalyst Preparation Example 1. Only the preparation steps are different, that is, step (3) and step (4) in the dehydrogenation catalyst A in Example 1 are swapped. The specific steps are:

[0142] (1) 17.03 g of diammonium hydrogen phosphate (P content: 4 g) was dissolved in 125 g of desalted water to completely dissolve into a clear solution. The γ-Al2O3 carrier was dispersed in the solution and fully immersed for 24 h. The carrier was dried at 120°C for 8 h and calcined at 250°C for 12 h to obtain a P-doped γ-Al2O3 carrier (P content: 4%).

[0143] (2) The P-doped carrier obtained in step (1) was dispersed in 500 g of a 35 wt% tetraethylammonium hydroxide aqueous solution and slowly stirred at 40° C. for 2 h. The carrier was then filtered out, dried at 120° C. for 8 h, and calcined at 300° C. for 12 h. The ratio of the basic center to the acidic center of the carrier after alkali pretreatment was 3:1 as determined by NH3 / CO2-TPD.

[0144] (3) 3.37 g of perrhenic acid was dissolved in 125 g of desalted water to completely dissolve into a clear solution. The carrier obtained in step (2) was dispersed in the perrhenic acid solution and fully immersed for 24 h. The carrier was dried at 120° C. for 8 h and calcined at 450° C. for 12 h to obtain a carrier containing a Re component.

[0145] (4) 1.73 g of palladium nitrate was dissolved in 125 g of desalted water to completely dissolve into a clear solution. The Re-containing component carrier obtained in step (3) was dispersed in the Pd-containing solution and fully immersed for 24 h. The dehydrogenation catalyst Q was obtained after drying at 120° C. for 8 h and calcining at 450° C. for 12 h.

[0146] The preparation parameters and control conditions of the above dehydrogenation catalyst comparative examples are shown in Table 1.

[0147] Table 1 Preparation of dehydrogenation catalyst

[0148]

[0149]

[0150]

[0151]

[0152] Evaluation of dehydrogenation catalyst activity

[0153] In the following examples, gas chromatography was used to analyze the components in the reaction system, and the calibration normalization method was used for quantification, which can be carried out with reference to the prior art, and on this basis, the conversion rate of the reactants, the selectivity and yield of the products were calculated. The gas chromatography analysis conditions are as follows:

[0154] Chromatographic column: Agilent DB-Wax (specifications: 30m×0.32mm×0.25mm); inlet temperature: 300℃; split ratio: 30:1; column flow rate: 1.5mL / min; column temperature: 100℃0.5min; heating program: 15℃ / min to 300℃, hold for 8min; detector temperature: 300℃, hydrogen flow rate: 35mL / min, air flow rate: 350mL / min.

[0155] Example 1

[0156] 100g of dehydrogenation catalyst A was filled into a dehydrogenation reactor (fixed bed reactor) equipped with a heating and heat preservation device. The reactor diameter was 39mm, the tube length was 2000mm, and the catalyst filling 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 controlled by a gas flowmeter, and the reactor temperature was gradually increased, and finally the dehydrogenation catalyst A was activated and reduced at 280-290°C in a hydrogen atmosphere for 6h. After the reaction started, the raw material 3-methylpiperidine was pumped into the preheater by a plunger pump through a pipeline heating pump, the preheating temperature was 150°C, and the pipeline heating temperature was 150°C. The raw material was mixed with a hydrogen carrier gas (350sccm) and introduced into the fixed bed reactor from the top of the reactor in parallel. The reaction bed temperature was controlled at 260°C, the system pressure was controlled at 0.02MPa, and the residence time was controlled by the raw material mass space velocity, that is, controlled at 1.5 grams of raw material / gram of catalytically active metal / hour. The equipment was operated continuously for 72 hours, and the reaction liquid was taken from the bottom of the reactor and cooled in multiple stages to obtain a product mixture. After gas chromatography detection and quantitative analysis by calibration normalization method, 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%.

[0157] Embodiments 2 to 6

[0158] 100g of dehydrogenation catalyst B~F are respectively filled into a dehydrogenation reactor (fixed bed reactor) equipped with a heating and heat preservation device. The reactor diameter is 39mm, the tube length is 2000mm, and the catalyst filling height is 200mm. Before the reaction, the reactor is purged three times with nitrogen. Before the reaction starts, hydrogen is introduced from the top of the reactor controlled by a gas flow meter, and the reactor temperature is gradually increased, and finally the dehydrogenation catalysts B~F are activated and reduced at 280~290℃ in a hydrogen atmosphere for 6~24h. After the reaction starts, the raw material 3-methylpiperidine is pumped into the preheater by a plunger pump through a pipeline heating, the preheating temperature is 150~200℃, and the pipeline heating temperature is 150℃. The raw material and the carrier gas are mixed and introduced into the fixed bed reactor from the top of the reactor in parallel. The reaction bed temperature is controlled at 230~280℃, the system pressure is controlled at 0~0.1MPa, and the residence time is controlled by the raw material mass space velocity, that is, controlled at 0.5~2.0g raw material / g catalytic active metal / hour. The equipment was operated continuously for 100 hours, and the reaction liquid was taken from the bottom of the reactor and the product mixture was obtained after multi-stage cooling. After gas chromatography detection and quantitative analysis by calibration and normalization method, the reaction results were shown in Table 2.

[0159] Comparative Examples 1-9

[0160] 100g of dehydrogenation catalyst G~Q were respectively filled into a dehydrogenation reactor (fixed bed reactor) equipped with a heating and heat preservation device. The reactor diameter was 39mm, the tube length was 2000mm, and the catalyst filling 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 controlled by a gas flowmeter, and the reactor temperature was gradually increased, and finally the dehydrogenation catalyst A was activated and reduced at 280-290°C in a hydrogen atmosphere for 6h. After the reaction started, the raw material 3-methylpiperidine was pumped into the preheater by a plunger pump through a pipeline heating, the preheating temperature was 150°C, and the pipeline heating temperature was 150°C. The raw material was mixed with a hydrogen carrier gas (350sccm) and introduced into the fixed bed reactor from the top of the reactor in parallel. The reaction bed temperature was controlled at 260°C, the system pressure was controlled at 0.02MPa, and the residence time was controlled by the raw material mass space velocity, that is, controlled at 1.5 grams of raw material / gram of catalytically active metal / hour. The equipment was operated continuously for 72 hours, and the reaction liquid was taken from the bottom of the reactor and the product mixture was obtained after multi-stage cooling. After gas chromatography detection and quantitative analysis by calibration and normalization method, the reaction results were shown in Table 2.

[0161] Table 2 Evaluation of dehydrogenation catalyst activity

[0162]

[0163] Dehydrogenation catalyst life evaluation

[0164] Example 7

[0165] 100g of dehydrogenation catalyst A was filled into a dehydrogenation reactor (fixed bed reactor) equipped with a heating and heat preservation device. The reactor diameter was 39mm, the tube length was 2000mm, and the catalyst filling 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 controlled by a gas flowmeter, and the reactor temperature was gradually increased, and finally the dehydrogenation catalyst A was activated and reduced at 280-290°C in a hydrogen atmosphere for 6h. After the reaction started, the raw material 3-methylpiperidine was pumped into the preheater by a plunger pump through a pipeline heating pump, the preheating temperature was 150°C, and the pipeline heating temperature was 150°C. The raw material was mixed with a hydrogen carrier gas (350sccm) and introduced into the fixed bed reactor from the top of the reactor in parallel. The reaction bed temperature was controlled at 260°C, the system pressure was controlled at 0.02MPa, and the residence time was controlled by the raw material mass space velocity, that is, controlled at 1.5 grams of raw material / gram of catalytically active metal / hour. The equipment was operated continuously, and the reaction liquid was collected from the bottom of the reactor every 120 hours. After multi-stage cooling, the product mixture was obtained. After gas chromatography detection and quantitative analysis by calibration and normalization method, the reaction results were shown in Figure 4 .

[0166] Comparative Example 10

[0167] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced by the dehydrogenation catalyst G in the catalyst preparation comparative example. The reaction results are shown in FIG. Figure 4 .

[0168] Comparative Example 11

[0169] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced by the dehydrogenation catalyst H in the catalyst preparation comparative example. The reaction results are shown in FIG. Figure 4 .

[0170] Comparative Example 12

[0171] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced by the dehydrogenation catalyst K in the catalyst preparation comparative example. The reaction results are shown in FIG. Figure 4 .

[0172] Comparative Example 13

[0173] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced by the dehydrogenation catalyst L in the catalyst preparation comparative example. The reaction results are shown in FIG. Figure 4 .

[0174] Comparative Example 14

[0175] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced by the dehydrogenation catalyst M in the catalyst preparation comparative example. The reaction results are shown in FIG. Figure 4 .

[0176] Comparative Example 15

[0177] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced by the dehydrogenation catalyst N in the catalyst preparation comparative example. The reaction results are shown in FIG. Figure 4 .

[0178] Comparative Example 16

[0179] The same operation was performed except that the dehydrogenation catalyst A used in Example 7 was replaced by the dehydrogenation catalyst Q in the catalyst preparation comparative example. The reaction results are shown in the attached Figure 4 .

[0180] Table 2 summarizes the initial evaluation results of the activity of each dehydrogenation catalyst in Examples 1 to 6 and Comparative Examples 1 to 9. Figure 4 The reaction results of the dehydrogenation catalysts in Example 7 and Comparative Examples 10 to 16 during long-term operation are summarized.

[0181] As shown in Table 2, in the process of preparing 3-methylpyridine by catalyzing the dehydrogenation reaction of 3-methylpiperidine by using dehydrogenation catalysts A to F in Examples 1 to 6, a conversion rate of more than 99%, a selectivity of more than 99% and a yield of more than 98% can be obtained, which can meet the requirements of industrial use. On the basis of having a high conversion rate, selectivity and yield, Examples 1 to 6 can respectively use dehydrogenation catalysts A to F to continuously operate for 5500 to 8000 hours, and still maintain good catalytic activity without the phenomenon of catalyst deactivation.

[0182] Further, catalyst A and catalyst preparation comparison were selected to evaluate the life of the dehydrogenation catalyst. The results are as follows: Figure 4 shown.

[0183] Compared with dehydrogenation catalyst A, dehydrogenation catalyst G prepared by using a conventional carrier with low saturated water absorption rate has an active metal Pd distributed in an eggshell shape on the catalyst surface (see Appendix Figure 3), this distribution form has a significantly lower active metal dispersion than the uniform distribution of catalyst A. Moreover, the dehydrogenation reaction can only be carried out on the surface of the catalyst. During long-term operation, the active metal Pd is more likely to aggregate into larger metal particles. At the same time, once coking and carbon deposition occurs on the catalyst surface, the catalyst will be rapidly deactivated. At the same time, the dehydrogenation catalysts L and M made of carriers with lower specific surface area or lower pore volume can only continuously catalyze for 2000 to 2500 hours, and then they will be rapidly deactivated. This also shows that the carrier has a high saturated water absorption rate, a high specific surface area and a pore volume. This type of carrier has a more multi-level microporous structure, which can shorten the distance for raw materials such as 3-methylpiperidine to contact the active sites of the catalyst, and products such as 3-methylpyridine can quickly desorb from the active sites, thereby reducing the occurrence of side reactions and the formation of coking and carbon deposition. At the same time, the more hierarchical microporous structure and ultra-high saturated water absorption rate of this type of carrier can ensure that the first active metal component Pd is evenly dispersed on the catalyst surface and inside the catalyst, thereby improving the dispersion of the active metal, delaying the long-term high-temperature aggregation of the active metal, and thus extending the service life of the catalyst.

[0184] From Comparative Examples 2 and 7, it can be seen that the life of dehydrogenation catalyst A is much longer than that of dehydrogenation catalyst H, and the selectivity and yield of 3-methylpyridine in the product are higher, indicating that when the catalyst support is pretreated with a basic compound, its acidic site is eliminated, and the basic center is larger than the acidic center. This avoids the occurrence of polymerization reactions catalyzed by acidic sites during the catalytic dehydrogenation of 3-methylpiperidine to a certain extent, which can effectively improve the selectivity of the reaction, and at the same time effectively inhibit the coking and carbon deposition on the surface of the dehydrogenation catalyst, thereby extending the service life of the dehydrogenation catalyst.

[0185] From Comparative Examples 3 and 4, it can be seen that compared with dehydrogenation catalyst A, the initial activity of dehydrogenation catalyst I loaded with only Pd is lower than that of catalyst A. After 100 hours of continuous operation, the conversion rate of the raw material is only about 89%, and its catalytic activity decreases rapidly within 1000 hours; while the catalyst loaded with only Re can hardly complete the catalytic dehydrogenation reaction. This shows that the introduction of the second active metal component (taking Re as an example) will induce 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 form ReO around the Pd active sites x layer, thereby isolating the Pd active sites into tiny metal clusters or even single metal sites, thereby effectively inhibiting the aggregation of Pd metal and the rapid deactivation of the catalyst while reducing the first active metal loading.

[0186] It can be seen from Comparative Examples 5 and 12 that compared to dehydrogenation catalyst A, catalyst K has an activity similar to that of catalyst A, but after 2000 hours of continuous operation, the catalytic activity of catalyst K begins to decline, and finally the conversion rate of the raw material drops to less than 90% after 3300 hours. The Pd content of catalyst K before and after the reaction was determined by ion chromatography ICP, and the results showed that the average Pd content of catalyst K before the reaction was 8322ppm, and after running for 3300 hours, the average Pd content was 7588ppm, and the Pd loss rate was 8.8%. However, the Pd content of catalyst A before and after the reaction was determined by ion chromatography ICP, and the results showed that the average Pd content of catalyst A before the reaction was 8169ppm, and after running for 6000 hours, the average Pd content was 8126ppm, and the Pd loss rate was less than 0.5%.

[0187] When step (1) in catalyst preparation example 1 is placed after step (4), that is, when dehydrogenation catalyst N is used, its catalyst life is significantly higher than that of catalyst K, but lower than that of catalyst A. This indicates that relative to dehydrogenation catalyst A, the P active agent is finally introduced, the unsaturated coordinated Al sites in the carrier and the weakly adsorbed hydroxyl groups have formed Al-OH-Pd species with the first active metal, and the interaction force between Pd and the carrier is lower than that between Pd and the Al-OP-Pd species. Only by doping P atoms into the alumina carrier in advance can the effective P species be more inclined to form Al-OP species with the unsaturated coordinated Al sites in the carrier and the weakly adsorbed hydroxyl groups. After the active metal is loaded, the P-OH group promotes the formation of the PO-Pd bond, thereby forming a stronger interaction with the Pd species. This strong interaction leads to a suitable electronic structure of the Pd nanoparticles and more low-coordinated Pd sites, so that the catalyst shows a better dehydrogenation catalytic activity. More importantly, the stronger interaction between Pd and the carrier can effectively delay the high-temperature aggregation of Pd and extend the service life of the catalyst. At the same time, it can also inhibit the coordination and complexing ability of nitrogen-containing oligomers with Pd metal, thereby avoiding the loss of precious metals, which is crucial for the industrial application and cost control of catalysts.

[0188] It can be seen from Comparative Examples 9 and 16 that when the order of step (3) and step (4) in Catalyst Preparation Example 1 is reversed, that is, when dehydrogenation catalyst Q is used, the catalyst life is significantly lower than that of catalyst A. It is speculated that the reason may be that the second active metal component Re loaded first may be excessively dispersed on the carrier surface, 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.

[0189] Application of dehydrogenation catalysts in the dehydrogenation of nitrogen-containing heterocyclic compounds to prepare nitrogen heteroaromatic rings

[0190] Embodiments 8 to 12

[0191] 100g of A-E dehydrogenation catalyst is filled into a dehydrogenation reactor (fixed bed reactor) equipped with a heating and heat preservation device. The reactor diameter is 39mm, the tube length is 2000mm, and the catalyst filling height is 200mm. Before the reaction, the reactor is purged three times with nitrogen. Before the reaction starts, hydrogen is introduced from the top of the reactor controlled by a gas flow meter, and the reactor temperature is gradually increased, and finally the dehydrogenation catalyst A is activated and reduced at 280-290°C in a hydrogen atmosphere for 6h. After the reaction starts, the nitrogen heterocyclic compound raw material is pumped into the preheater by a plunger pump through a pipeline heating pump, the preheating temperature is 180°C, and the pipeline heating temperature is 180°C. The raw material and the carrier gas are mixed and introduced into the fixed bed reactor from the top of the reactor in parallel. The reaction bed temperature is controlled at 250-300°C, the system pressure is controlled at 0-0.05MPa, and the residence time is controlled by the raw material mass space velocity, that is, controlled at 0.5-2.0 grams of raw material / gram of catalytically active metal / hour. The equipment was operated continuously for 1000 h, and the reaction liquid was collected from the bottom of the reactor, and the product mixture was obtained after multi-stage cooling. After gas chromatography detection and quantitative analysis by calibration and normalization method, the reaction results were shown in Table 3.

[0192] Table 3 Reaction results of different nitrogen-containing heterocyclic compounds using dehydrogenation catalysts

[0193]

[0194] As shown in Table 3, when the dehydrogenation catalyst prepared by the present invention is used in the dehydrogenation of nitrogen-containing heterocyclic compounds to prepare nitrogen heteroaromatic rings, the raw material conversion rate is more than 99%, the selectivity of nitrogen heteroaromatic ring products is more than 99%, and the yield is 98-99%. Therefore, the dehydrogenation catalyst of the present invention has a good reaction effect on the dehydrogenation of nitrogen-containing heterocyclic compounds to prepare nitrogen heteroaromatic rings.

[0195] Dehydrogenation catalyst for the dehydrogenation of nitrogen-containing heterocyclic byproducts in the production of hexamethylenediamine to produce nitrogen heteroaromatic rings

[0196] Embodiments 13-14

[0197] 100g of dehydrogenation catalyst A and B were respectively filled into a dehydrogenation reactor (fixed bed reactor) equipped with a heating and heat preservation device. The reactor diameter was 39mm, the tube length was 2000mm, and the catalyst filling 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 controlled by a gas flow meter, and the reactor temperature was gradually increased, and finally the dehydrogenation catalysts A and B were activated and reduced at 280-290°C in a hydrogen atmosphere for 6h. After the reaction started, the 3-methylpiperidine raw material (purity after distillation and purification is shown in Table 4) produced as a by-product of hexamethylenediamine was pumped into the preheater by a plunger pump through a pipeline heating temperature of 180°C and a pipeline heating temperature of 180°C. The raw material was mixed with the carrier gas and introduced into the fixed bed reactor from the top of the reactor in parallel. The temperature of the reaction bed was controlled at 250-260°C, the system pressure was controlled at 0.03 MPa, and the residence time was controlled by the raw material mass space velocity, that is, 1.5 g raw material / g catalytic active metal / hour. The equipment was continuously operated for 3000 h, and the reaction liquid was taken from the bottom of the reactor, and the product mixture was obtained after multi-stage cooling. After gas chromatography detection and quantitative analysis by calibration normalization method, the reaction results obtained are shown in Table 4.

[0198] Table 4 Nitrogen-containing heterocyclic byproducts in the production process of hexamethylenediamine using dehydrogenation catalyst reaction results

[0199]

[0200] 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 heteroaromatic rings in the production process of hexamethylenediamine, the 3-methylpiperidine conversion rate, 3-methylpyridine selectivity and 3-ethylpyrrole selectivity 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 heteroaromatic rings in the production process of hexamethylenediamine.

[0201] Industrial Applicability

[0202] According to the method of the present invention, nitrogen heteroaromatic compounds can be advantageously produced industrially. For example, 3-methylpiperidine can be used as a raw material to carry out a dehydrogenation reaction to prepare 3-methylpyridine. 3-methylpyridine can further produce high value-added pharmaceutical and pesticide intermediates such as nicotinic acid and nicotinamide, fluazifop-butyl, fluazifop-butyl, fluazifop-butyl, nicotinamide, and pyrisulfuron.

[0203] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle 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 these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A dehydrogenation catalyst for preparing nitrogen heteroaromatic rings, characterized in that The dehydrogenation catalyst comprises a carrier, a first active metal component, a second active metal component and an active auxiliary component, wherein the specific surface area of ​​the carrier is 150 to 400 m 2 / g, pore volume is 0.6~1.5cm 3 / g, and the saturated water absorption rate is not less than 100%; The first active metal component includes Pd; The second active metal component includes one or more of Re, Sn or Ir; The active auxiliary component is a P-containing active auxiliary.

2. A dehydrogenation catalyst for preparing nitrogen heteroaromatic rings according to claim 1, characterized in that: The support is pretreated with a basic compound.

3. A dehydrogenation catalyst for preparing nitrogen heteroaromatic rings according to claim 1, characterized in that: The specific surface area of ​​the carrier is 200 to 350 m 2 / g, 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 more preferably at least one of alumina, an aluminum-containing molecular sieve or alumina-silicon oxide.

4. A dehydrogenation catalyst for preparing nitrogen heteroaromatic rings according to claim 1, characterized in that: 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 auxiliary component to the carrier is (0.01-0.05):1, preferably (0.02-0.04):

1.

5. A dehydrogenation catalyst for preparing nitrogen heteroaromatic rings according to claim 1, characterized in that: The phosphorus source of the P-containing active agent is selected from one or more of ammonium phosphate, monoammonium hydrogen phosphate, diammonium dihydrogen 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, monoammonium hydrogen phosphate or diammonium dihydrogen phosphate; And / or, the Pd source of the first active metal is one or more of Pd hydrochloride, nitrate, acetate or ammonium salt, preferably one or more of palladium chloride, palladium nitrate, tetraamine palladium nitrate or dichlorotetraaminepalladium; And / or, the metal source of the second active metal comes from one or more of the acid, hydrochloride, nitrate, acetate or ammonium salt of the corresponding active metal component, preferably one or more of perrhenic acid, stannous chloride, ammonium perrhenate, and chloroiridic acid hexahydrate.

6. A dehydrogenation catalyst for preparing nitrogen heteroaromatic rings according to claim 2, characterized in that: The basic compound is a N-containing compound of the following general formula (I) or (II): Among them, R 1 , R 2 , R 3 and R 4 is selected from H and C1-C4 alkyl, X - is an anion selected from OH - 、HCO3 - and CO3 2- ; Preferably, the mass ratio of the alkaline compound to the carrier is (0.1-5):1, preferably (0.5-2):

1.

7. A method for preparing a nitrogen heteroaromatic ring dehydrogenation catalyst 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 a P-containing active agent in a solvent and then adding the solvent to a carrier for impregnation, followed by drying and calcining to obtain a P-doped carrier; Step (2): dissolving an alkaline compound in a solvent and then adding the solvent to the P-doped carrier obtained in step (1), followed by post-treatment to obtain an alkali-treated P-doped carrier; Step (3): dissolving the first active metal component in a solvent and then adding the solvent to the alkali-treated P-doped carrier obtained in step (2) for impregnation, and obtaining a carrier containing the first active metal component after drying and calcining; Step (4): dissolving the second active metal component in a solvent and then adding the solvent to the carrier containing the first active metal component obtained in step (3) for impregnation, and obtaining a dehydrogenation catalyst after drying and calcining.

8. The method for preparing a nitrogen heteroaromatic ring dehydrogenation catalyst according to claim 7, characterized in that: The solvent in steps (1) to (4) is one or more of water, ethanol or ammonia, preferably water or ammonia.

9. Use of the dehydrogenation catalyst according to any one of claims 1 to 6 in the dehydrogenation of nitrogen-containing heterocyclic compounds to prepare nitrogen heteroaromatic rings, characterized in that: The nitrogen-containing heterocyclic compound includes a monocyclic or polycyclic hydrocarbon having one or more nitrogen atoms, wherein one or more hydrogen atoms may be substituted by the same or different groups, and at least one ring is capable of undergoing a dehydrogenation reaction, preferably one or more of pyrrolidine, alkylpyrrolidine, piperidine, alkylpiperidine, tetrahydroquinoline or alkyltetrahydroquinoline.

10. Use of a dehydrogenation catalyst according to claim 9 in dehydrogenating nitrogen-containing heterocyclic compounds to prepare nitrogen heteroaromatic rings, characterized in that: The dehydrogenation preparation is carried out under the condition that at least one of hydrogen, nitrogen or ammonia is used as a carrier gas, the reaction temperature is 200-300° C., the reaction pressure is 0-0.1 MPa, and the mass space velocity of the nitrogen-containing heterocyclic compound is 0.5-2 h -1 .

11. Use of the dehydrogenation catalyst according to any one of claims 1 to 6 in the dehydrogenation of nitrogen-containing heterocyclic byproducts to prepare nitrogen heteroaromatic rings in the production process of hexamethylenediamine, characterized in that: The nitrogen-containing heterocyclic byproducts include 3-methylpiperidine and / or 3-ethylpyrrolidine.

12. Use of the dehydrogenation catalyst according to claim 11 in the dehydrogenation of nitrogen-containing heterocyclic byproducts to prepare nitrogen heteroaromatic rings in the production process 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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