Non-supported catalysts, processes for their preparation and use, and methods for the hydrogenation and dehydrogenation of nitrogen-containing heterocycles

Abstract

The application relates to the field of organic liquid hydrogen storage, discloses a non-supported catalyst and a preparation method and application thereof, and a hydrogenation and dehydrogenation method of nitrogen-containing heterocyclic organic matter; the catalyst comprises Ni and Mo; the molar ratio of Mo to Ni is 0.2-5:1 in terms of elements; the Ni is located on the surface of a Mo-rich micro area, and the average grain size of the Ni is 1-200 nm. The non-supported catalyst provided by the application has bidirectional catalytic functions of hydrogenation and dehydrogenation, has relatively high hydrogenation activity and relatively high dehydrogenation activity, and the hydrogenation and dehydrogenation activity is close to that of noble metal and far higher than that of a conventional non-noble metal catalyst.

Description

Technical Field

[0001] This invention relates to the field of organic liquid hydrogen storage, specifically to an unsupported catalyst, its preparation method and application, and methods for hydrogenation and dehydrogenation of nitrogen-containing heterocyclic organic compounds. Background Technology

[0002] Hydrogen, as a renewable energy source, is not only highly energy-efficient but also produces almost no waste. Developing hydrogen energy is expected to become an important way to improve energy efficiency, reduce oil consumption, improve the ecological environment, and ensure energy security. The development of sustainable and efficient large-scale hydrogen production technology has become an urgent need in the hydrogen energy era.

[0003] Hydrogen exists in a gaseous state under normal conditions and is flammable, explosive, and easily diffused. Therefore, in practical applications, the safety, efficiency, and leak-free storage and transportation of hydrogen must be prioritized, which presents significant challenges. Thus, the utilization of hydrogen energy requires addressing the storage and transportation issues of hydrogen.

[0004] Achieving large-scale, efficient hydrogen storage and transportation is crucial for realizing the multi-scenario application of hydrogen. Currently, the main storage and transportation methods are gaseous storage and transportation, liquid storage and transportation, and chemical hydrogen storage. Gaseous and liquid hydrogen storage and transportation are based on physical methods. The former requires high airtightness and pressure resistance of the tank materials and suffers from low hydrogen transportation efficiency. Conventional 20MPa long-tube trailers only transport hydrogen with a density of about 1%, and can only transport hydrogen over short distances, while long-distance hydrogen transportation is costly. The latter requires high insulation of materials, has high equipment costs, suffers from significant liquid hydrogen evaporation losses in long-distance hydrogen transportation scenarios, and has high hydrogen liquefaction costs. Gaseous hydrogen storage tanks are widely used in vehicles, and cryogenic liquid hydrogen is widely used in the aerospace field, but civilian chemical hydrogen storage technology is still in the research and development stage.

[0005] Chemical hydrogen storage utilizes the ability of a storage medium to react with hydrogen under certain conditions to form stable compounds, and then releases hydrogen by altering these conditions. It mainly includes organic liquid hydrogen storage, liquid ammonia hydrogen storage, coordination hydride hydrogen storage, inorganic hydrogen storage, and methanol hydrogen storage. Organic liquid hydrogen storage technology is considered the most promising chemical hydrogen storage technology due to its advantages such as readily available raw materials, good compatibility of hydrogen absorption and desorption product transportation equipment with traditional oil and gas transportation systems, low transportation costs, and no need for large-scale investment. It is also believed to avoid wasting existing oil and gas resources in future energy transitions. The main organic liquid hydrogen carriers are aromatic compounds, among which heterocyclic aromatic compounds are widely studied due to their advantages such as high absorption and desorption reaction temperatures and easy separation of hydrogen and organic products.

[0006] CN111569901A discloses a method for preparing and applying a non-precious metal and precious metal bimetallic catalyst for hydrogenation and dehydrogenation of organic hydrogen storage materials. The method involves mixing a solution of metal oxides (alumina, silicon oxide, tin oxide, molybdenum oxide, cerium oxide), graphene and molecular sieve supports (MCM-41, HY), and a mixture of non-precious metal precursors (Ni, Cu, Mg, Fe) or precious metal precursors (Pt, Pd, Rh, Ru, Au) using an impregnation method. The mixture is then thoroughly stirred, dried, calcined, and reduced to obtain a catalyst for hydrogen storage and dehydrogenation on an organic support. Under the action of the catalyst, hydrogenation of the liquid organic hydrogen storage support yields a hydrogenated organic liquid, which is then dehydrogenated to obtain a liquid organic hydrogen storage support. This catalyst exhibits advantages such as high catalytic activity, good stability, and low cost in hydrogen storage reactions using organic hydrogen storage materials.

[0007] CN110841630A provides a hydrogenation and dehydrogenation catalyst for organic hydrogen storage materials, comprising an active component and a support. The active component is selected from one or more combinations of platinum, lead, rhodium, ruthenium, gold, and palladium, and the support is selected from one or more combinations of metal oxides, molecular sieves, and porous materials. The catalyst achieves a conversion rate of up to 98% for ethylcarbazole and a selectivity of up to 98% for dodecylhydroethylcarbazole. In the dehydrogenation reaction of organic hydrogen storage materials, the catalyst of this invention achieves a conversion rate of up to 91% for dodecylhydroethylcarbazole and a selectivity of up to 89% for ethylcarbazole.

[0008] In summary, there are few reports on bidirectional catalysts involving simultaneous dehydrogenation and hydrogenation of organic liquids in the existing technology. In order to obtain high hydrogenation / dehydrogenation activity, most catalysts use precious metal catalysts. However, this undoubtedly increases the cost of chemical hydrogen storage significantly. There are no publicly reported bidirectional catalysts without precious metals in the existing technology. Summary of the Invention

[0009] The purpose of this invention is to overcome the problems of high cost, insufficient catalytic activity, poor product selectivity, and difficulty in simultaneously possessing dehydrogenation and hydrogenation functions in existing organic liquid hydrogen storage catalysts. This invention provides a non-supported catalyst, its preparation method, and its application, as well as a method for hydrogenation and dehydrogenation of nitrogen-containing heterocyclic organic compounds. The non-supported catalyst has bidirectional catalytic function of hydrogenation / dehydrogenation and exhibits good selectivity for the complete hydrogenation products and complete dehydrogenation products of nitrogen-containing heterocyclic organic compounds.

[0010] To achieve the above objectives, the first aspect of the present invention provides an unsupported catalyst comprising Ni and Mo; wherein, elementally, the molar ratio of Mo to Ni is 0.2-5:1; the Ni is located on the surface of the Mo-enriched microregion, and the average grain size of Ni is 1-200 nm.

[0011] A second aspect of this invention provides a method for preparing an unsupported catalyst, comprising the following steps:

[0012] (1) The nickel source, molybdenum source and solvent are mixed in a first mixture to obtain a first mixture;

[0013] The molar ratio of molybdenum source (calculated as Mo) to nickel source (calculated as Ni) is 0.2-5:1.

[0014] (2) The first mixture and the alkaline solution are mixed a second time to obtain a second mixture;

[0015] (3) The second mixture and the alcohol are mixed for a third time to obtain a third mixture;

[0016] (4) The third mixture is heated to obtain catalyst precursor powder;

[0017] (5) The catalyst precursor powder is contacted with a hydrogen-containing atmosphere to obtain the unsupported catalyst.

[0018] A third aspect of the present invention provides an unsupported catalyst prepared by the above preparation method.

[0019] The fourth aspect of the present invention provides the application of the unsupported catalyst described in the first or third aspect in organic liquid hydrogen storage.

[0020] The fifth aspect of the present invention provides a method for hydrogenating a nitrogen-containing heterocyclic organic compound, comprising: contacting the nitrogen-containing heterocyclic organic compound with a hydrogenation catalyst under hydrogenation reaction conditions;

[0021] Wherein, the hydrogenation catalyst is the unsupported catalyst described in the first or third aspect above;

[0022] Preferably, the nitrogen-containing heterocyclic organic compound is selected from at least one of indole, quinoline, isoquinoline, N-alkylcarbazole, and alkyl-substituted carbazole on a benzene ring;

[0023] Preferably, the alkyl-substituted carbazole on the benzene ring is 2-methylcarbazole and / or 3-methylcarbazole;

[0024] Preferably, the N-alkylcarbazole is N-methylcarbazole and / or N-ethylcarbazole.

[0025] The sixth aspect of the present invention provides a method for dehydrogenation of nitrogen-containing heterocyclic organic compounds, comprising: contacting the hydrogenation product of the nitrogen-containing heterocyclic organic compound with a dehydrogenation catalyst under dehydrogenation reaction conditions to carry out a dehydrogenation reaction to obtain hydrogen gas;

[0026] The dehydrogenation catalyst is the unsupported catalyst described in the first or third aspect above;

[0027] Preferably, the hydrogenation product of the nitrogen-containing heterocyclic organic compound is the hydrogenation product of N-ethylcarbazole.

[0028] The beneficial effects obtained by the present invention through the above technical solution are as follows:

[0029] (1) The unsupported catalyst provided by the present invention has a dual catalytic function of hydrogenation / dehydrogenation. It has both high hydrogenation activity and high dehydrogenation activity, and its hydrogenation and dehydrogenation activities are close to those of noble metals and far higher than those of conventional non-noble metal catalysts.

[0030] (2) The method for preparing the unsupported catalyst provided by the present invention can control the ratio and distribution position of Mo / Ni, so that Ni is dispersed in the form of dots and / or clusters on the surface of the Mo-enriched micro-region, thereby making the prepared catalyst have excellent hydrogenation / dehydrogenation performance.

[0031] (3) The hydrogenation and dehydrogenation method for nitrogen-containing heterocyclic organic compounds provided by the present invention can realize the dehydrogenation and hydrogenation of organic liquids through a two-way catalyst that does not contain precious metals, which greatly reduces the raw material cost of organic liquid hydrogen storage and is conducive to further improving the efficiency of organic liquid hydrogen storage. Attached Figure Description

[0032] Figure 1 This is a TEM image of catalyst A1 from Example 1;

[0033] Figure 2 This is a TEM image of catalyst A4 from Example 4;

[0034] Figure 3 The N-ethylcarbazole hydrogenation product and the dehydrogenation product of the hydrogenation product from catalyst A1 in Example 1 are... 1 HNMR spectrum;

[0035] Figure 4 This is a comparison of the X-ray diffraction patterns of catalyst A1 before and after the reaction in Example 1. Detailed Implementation

[0036] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0037] In this invention, the term "room temperature" refers to 25±5°C.

[0038] The first aspect of the present invention provides an unsupported catalyst comprising Ni and Mo; wherein, by elemental calculation, the molar ratio of Mo to Ni is 0.2-5:1; the Ni is located on the surface of the Mo-enriched microregion, and the average grain size of Ni is 1-200 nm.

[0039] In this invention, "Ni located on the surface of the Mo-enriched microregion" can be understood as Mo enrichment forming a matrix, with Ni dispersed on the surface of the matrix. Compared to the prior art where Ni is supported on a Mo-containing support, the interaction between Ni and Mo is stronger in this invention. The unsupported catalyst provided by this invention has bidirectional catalytic function of hydrogenation / dehydrogenation, exhibiting both high hydrogenation activity and high dehydrogenation activity. Furthermore, its hydrogenation and dehydrogenation activities are close to those of noble metals and far exceed those of conventional non-noble metal catalysts.

[0040] According to the present invention, preferably, the molar ratio of Mo to Ni is 0.8-2:1, more preferably 0.8-1.2:1; for example, it can be a typical but not limiting ratio such as 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, etc.

[0041] The inventors of this invention have discovered that Mo and Ni in a specific ratio can produce a better synergistic effect, which is more conducive to improving the hydrogenation / dehydrogenation performance of the catalyst and has better selectivity for the full hydrogenation products of nitrogen-containing heterocyclic organic compounds and the full dehydrogenation products of their full hydrogenation products.

[0042] In this invention, the content of each component in the catalyst is determined by ICP.

[0043] According to the present invention, preferably, the catalyst is in the form of blocks, granules, or rods, and more preferably rods. It is understood that the shape of the catalyst being blocky, granular, or rod-shaped indicates that the shape of the Mo-enriched microregions is blocky, granular, or rod-shaped, and Ni is located on the surface of the Mo-enriched microregions.

[0044] According to the present invention, preferably, the catalyst is rod-shaped, and the aspect ratio of the catalyst is 1-100:1, more preferably 4-10:1; under the above preferred conditions, it is beneficial to improve the performance of the catalyst.

[0045] In this invention, the term "aspect ratio" is a conventional definition in the art, referring to the ratio of the longest diameter passing through the interior of a particle to the longest diameter perpendicular to it. For rod-shaped particles, it is the ratio of their length to the maximum diameter perpendicular to their length. In this invention, "diameter" refers to the maximum diameter.

[0046] According to the present invention, when the catalyst is rod-shaped, preferably, the length of the catalyst is 1-10 μm, more preferably 2-5 μm; and the diameter is 0.1-1 μm, more preferably 0.2-0.5 μm.

[0047] In this invention, the length and diameter of the catalyst are obtained by transmission electron microscopy (TEM). The specific testing method includes: taking 10 photographs at 50k magnification, statistically analyzing the length and diameter of the catalyst particles within the field of view, and calculating their average value.

[0048] According to the present invention, preferably, Mo in the catalyst exists at least partially in the form of oxide, and Ni in the catalyst exists at least partially in the form of elemental Ni. The present invention does not particularly limit the amount of elemental Ni present; the presence of even a portion of elemental Ni can effectively improve the hydrogenation and dehydrogenation performance of the catalyst. XRD testing confirms the presence of elemental nickel in the catalyst. The presence of elemental nickel allows the catalyst to better promote hydrogenation and dehydrogenation, thereby increasing the hydrogenation / dehydrogenation rate.

[0049] Preferably, the XRD pattern of the catalyst exhibits strong diffraction peaks of elemental Ni and nickel oxide at 2θ values ​​of 37°, 44°, 51°, 62°, and 76°. It should be noted that a deviation of ±2° in these peak positions is permissible and falls within the scope of this invention. The XRD pattern also shows that Mo exhibits higher amorphous characteristics compared to Ni, indicating a higher degree of disorder in its elemental distribution region.

[0050] XRD tests were performed using a Bruker X-ray diffractometer.

[0051] According to the present invention, preferably, the average grain size of Ni is 20-100 nm, more preferably 60-100 nm.

[0052] In this invention, the average grain size of Ni is obtained by transmission electron microscopy. The specific testing method includes taking 10 photos at 50k magnification, counting the longest diameter of all Ni grains in the field of view, and calculating their average value.

[0053] Preferably, the catalyst has a specific surface area of ​​100-300 cm². 2 / g, preferably 120-200cm 2 / g.

[0054] In this invention, the specific surface area is measured by the BET method of nitrogen physical adsorption determination.

[0055] A second aspect of this invention provides a method for preparing an unsupported catalyst, comprising the following steps:

[0056] (1) The nickel source, molybdenum source and solvent are mixed in a first mixture to obtain a first mixture;

[0057] The molar ratio of molybdenum source (calculated as Mo) to nickel source (calculated as Ni) is 0.2-5:1.

[0058] (2) The first mixture and the alkaline solution are mixed a second time to obtain a second mixture;

[0059] (3) The second mixture and the alcohol are mixed for a third time to obtain a third mixture;

[0060] (4) The third mixture is heated to obtain catalyst precursor powder;

[0061] (5) The catalyst precursor powder is contacted with a hydrogen-containing atmosphere to obtain the unsupported catalyst.

[0062] In this invention, the above preparation method can control the ratio and distribution of Mo / Ni, so that Ni is dispersed in the form of dots and / or clusters on the surface of the Mo-enriched micro-regions, thereby making the prepared catalyst have excellent hydrogenation / dehydrogenation performance.

[0063] According to the present invention, preferably, the molar ratio of molybdenum source (calculated as Mo) to nickel source (calculated as Ni) is 0.8-2:1, more preferably 0.8-1.2:1. By controlling a specific Mo / Ni ratio, better synergistic effects can be achieved, metal distribution can be optimized, and the performance of the catalyst can be improved.

[0064] In this invention, there is no special limitation on the amount of solvent used, as long as the dispersion of each component can be achieved. Preferably, the total mass concentration of nickel source and molybdenum source in the first mixture is 0.005-5 g / mL, and more preferably 0.01-1 g / mL.

[0065] In this invention, the selection range for the specific types of nickel and molybdenum sources is relatively wide, and they can be selected from any conventional substances well known to those skilled in the art. Preferably, the nickel source is selected from at least one of nickel chloride, nickel nitrate, nickel sulfate, nickel phosphate, nickel fluoroborate, nickel acetate, nickel acetylacetone, nickel aminosulfonate, and nickel citrate.

[0066] Preferably, the molybdenum source is selected from at least one of molybdic acid, phosphomolybdic acid, ammonium molybdate, and molybdenum chloride.

[0067] In this invention, the specific compounds selected for the nickel source and molybdenum source may also contain water of crystallization, which is well known to those skilled in the art and will not be described in detail here.

[0068] In this invention, the solvent can be selected from a wide range of options; preferably, the solvent is water.

[0069] To facilitate mixing, a co-solvent is preferably added to the first mixture; the co-solvent can be a conventional choice in the art and will not be described in detail here.

[0070] In this invention, the first mixing can be carried out using conventional methods in the art, such as mixing under stirring conditions, as long as the components are mixed uniformly. Preferably, the temperature of the first mixing is 10-50°C, more preferably 15-40°C.

[0071] In this invention, the alkaline solution can be an alkaline compound or an aqueous solution containing an alkaline compound; preferably, the alkaline solution is an aqueous solution containing an alkaline compound.

[0072] According to the present invention, the range of alkaline compounds is relatively wide. Preferably, the alkaline compound is an organic base and / or an inorganic base, and more preferably selected from at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, ethylenediamine and isopropylamine; more preferably, ammonia.

[0073] According to the present invention, preferably, the concentration of the alkaline compound in the alkaline solution is 0.2-5 mol / L, more preferably 1-4 mol / L.

[0074] According to the present invention, preferably, the volume ratio of the first mixture to the alkaline solution is 1-10:1, more preferably 1-5:1; within the above-mentioned preferred dosage range, it is beneficial to improve the activity of the catalyst.

[0075] According to the present invention, preferably, the temperature of the second mixing is 20-100°C, more preferably 30-50°C.

[0076] According to the present invention, preferably, the alcohol is a C2-C3 water-soluble alcohol, more preferably at least one selected from ethanol, ethylene glycol, n-propanol, isopropanol, and propylene glycol. More preferably, it is a water-soluble diol, more preferably ethylene glycol and / or propylene glycol; most preferably, it is ethylene glycol. Using the above-described preferred embodiments is beneficial for improving the activity of the catalyst.

[0077] According to a preferred embodiment of the present invention, the basic compound is ammonia and the alcohol is ethylene glycol. In the above preferred case, the synergistic effect of ammonia and ethylene glycol can further optimize the distribution of Ni on the surface of the Mo-enriched micro-region and improve the hydrogenation / dehydrogenation performance of the catalyst.

[0078] According to the present invention, preferably, the volume ratio of the second mixture to the alcohol is 0.1-1:1, more preferably 0.2-0.5:1. Adopting the above-mentioned preferred embodiments is beneficial for improving activity.

[0079] In this invention, preferably, the third mixing is carried out under stirring conditions, preferably, the stirring rate is 100-1500 rpm.

[0080] Preferably, the temperature of the third mixing is 20-100℃, more preferably 30-80℃.

[0081] According to the present invention, preferably, the conditions for the heating reaction include: a reaction temperature of not less than 90°C, preferably 100-150°C, and a reaction time of 0.5-5h, preferably 1-4h.

[0082] Preferably, step (4) further includes: performing solid-liquid separation, washing and drying on the product of the heated reaction to obtain the catalyst precursor powder.

[0083] In this invention, the solid-liquid separation, washing, and drying can be carried out using conventional operating methods in the art, and this invention does not have any special limitations on them.

[0084] Preferably, the washing solution is selected from water and / or ethanol. More preferably, the washing solution is water and ethanol, with a volume ratio of water to ethanol of 1-6:6-1.

[0085] Preferably, the drying temperature is 60-100℃, more preferably 70-80℃; the drying time is 6-24h, more preferably 10-12h.

[0086] Preferably, step (4) does not include a roasting process.

[0087] According to the present invention, preferably, the hydrogen-containing atmosphere is hydrogen or a mixture of hydrogen and an inert gas; for example, a mixture of hydrogen and argon.

[0088] Preferably, the hydrogen volume fraction in the hydrogen-containing atmosphere is 10-100%, and the gas volume is measured under standard conditions.

[0089] Preferably, the contact conditions include: a contact temperature of not less than 350°C, preferably 400-550°C, more preferably 450-500°C; a contact time of 0.5-5 hours, preferably 1-4 hours; and a hydrogen-containing atmosphere pressure of 0.01-1 MPa, preferably 0.02-0.5 MPa, more preferably 0.05-0.2 MPa.

[0090] In this invention, in order to ensure uniform crystal growth, preferably, the contact includes: heating the catalyst precursor powder to the contact temperature at a heating rate of 2-10°C / min under a hydrogen-containing atmosphere.

[0091] In this invention, the contact can be performed in a conventional apparatus in the art, such as a tubular furnace.

[0092] Preferably, before the contact, the method further includes: replacing the air in the device with an inert gas; there is no special limitation on the amount of inert gas used, as long as it can replace the air in the device.

[0093] Preferably, the preparation method further includes: after the contact, cooling the contact product to no higher than 50°C in the presence of an inert gas to obtain the unsupported catalyst. By adopting the above preferred embodiments, crystal breakage can be avoided, which is beneficial to improving the hydrogenation / dehydrogenation performance of the catalyst.

[0094] A third aspect of the present invention provides an unsupported catalyst prepared by the above preparation method.

[0095] The fourth aspect of the present invention provides the application of the unsupported catalysts described in the first and third aspects in organic liquid hydrogen storage.

[0096] The fifth aspect of the present invention provides a method for hydrogenating a nitrogen-containing heterocyclic organic compound, comprising: contacting the nitrogen-containing heterocyclic organic compound with hydrogen gas under hydrogenation reaction conditions and in the presence of a hydrogenation catalyst;

[0097] The hydrogenation catalyst is the unsupported catalyst described in the first or third aspect.

[0098] Preferably, the hydrogenation reaction conditions include: a reaction temperature of 50-200℃, more preferably 130-200℃; and a weight hourly space velocity (WHSV) of 0.5-50 h⁻¹ for nitrogen-containing heterocyclic organic compounds. -1 Preferably 1-30h -1 The reaction pressure is 2-10 MPa, preferably 5-8 MPa.

[0099] In this invention, the selection range of the nitrogen-containing heterocyclic organic compounds is relatively wide, and they can be selected from any nitrogen-containing heterocyclic organic compounds capable of hydrogen storage. Preferably, the nitrogen-containing heterocyclic organic compounds are selected from at least one of indole, quinoline, isoquinoline, N-alkylcarbazole, and alkyl-substituted carbazoles on the benzene ring.

[0100] In this invention, the alkyl-substituted carbazole on the benzene ring refers to a carbazole compound having an alkyl substitution on the benzene ring. Preferably, the alkyl-substituted carbazole on the benzene ring is 2-methylcarbazole and / or 3-methylcarbazole.

[0101] Preferably, the N-alkylcarbazole is N-methylcarbazole and / or N-ethylcarbazole.

[0102] The sixth aspect of the present invention provides a method for dehydrogenating nitrogen-containing heterocyclic organic compounds, comprising: contacting the hydrogenation product of the nitrogen-containing heterocyclic organic compound with a dehydrogenation catalyst under dehydrogenation reaction conditions to carry out a dehydrogenation reaction to obtain hydrogen gas; wherein the dehydrogenation catalyst is the unsupported catalyst described in the first aspect or the third aspect.

[0103] Preferably, the dehydrogenation reaction conditions include: a reaction temperature of 50-250℃, more preferably 100-150℃; and a weight hourly space velocity (WHSV) of 0.5-50 h⁻¹ for the hydrogenation products of nitrogen-containing heterocyclic organic compounds. -1 Preferably 1-30h -1 The reaction pressure is 0.1-2 MPa, preferably 1-1.5 MPa.

[0104] In this invention, the selection range of the nitrogen-containing heterocyclic organic compounds is the same as that in the above-mentioned hydrogenation reaction, and will not be repeated here.

[0105] According to the present invention, the hydrogenation product of the nitrogen-containing heterocyclic organic compound can be a partially hydrogenated product or a fully hydrogenated product. For example, the nitrogen-containing heterocyclic organic compound is N-ethylcarbazole. It is understood that, depending on the degree of hydrogenation, the hydrogenation product of N-ethylcarbazole can be one or more of tetrahydro-N-ethylcarbazole, octahydro-N-ethylcarbazole, and dodecahydro-N-ethylcarbazole, or a mixture thereof.

[0106] Preferably, the contact is carried out under hydrogen-exposed or non-hydrogen-exposed conditions; preferably, the contact is carried out under hydrogen-exposed conditions, with a hydrogen volume hourly space velocity of 0.5-2 h⁻¹. -1 Preferably 1-1.5h -1 .

[0107] This invention also provides a method for continuous hydrogenation / dehydrogenation of nitrogen-containing heterocyclic organic compounds, comprising:

[0108] S1. Under hydrogenation reaction conditions, in the presence of a first catalyst, nitrogen-containing heterocyclic organic compounds are contacted with hydrogen-containing gas to undergo hydrogenation, thereby obtaining hydrogenation products of nitrogen-containing heterocyclic organic compounds.

[0109] Preferably, the hydrogenation reaction conditions include: a reaction temperature of 50-200℃, more preferably 130-200℃; and a weight hourly space velocity (WHSV) of 0.5-50 h⁻¹ for nitrogen-containing heterocyclic organic compounds. -1 Preferably 1-30h -1 The hydrogen pressure is 2-10 MPa, preferably 5-8 MPa.

[0110] S2. Under dehydrogenation reaction conditions, the hydrogenation product of the nitrogen-containing heterocyclic organic compound is contacted with a second catalyst to carry out a dehydrogenation reaction to obtain hydrogen gas;

[0111] Preferably, the dehydrogenation reaction conditions include: a reaction temperature of 50-250℃, more preferably 100-150℃; and a weight hourly space velocity (WHSV) of 0.5-50 h⁻¹ for the hydrogenation products of nitrogen-containing heterocyclic organic compounds. -1 Preferably 1-30h -1 The reaction pressure is 0.1-2 MPa, preferably 1-1.5 MPa.

[0112] Wherein, the first catalyst and the second catalyst are each independently selected from the unsupported catalysts described in the first aspect or the third aspect.

[0113] Preferably, the nitrogen-containing heterocyclic organic compound is selected from at least one of indole, quinoline, isoquinoline, N-alkylcarbazole, and alkyl-substituted carbazole on a benzene ring, more preferably at least one of 2-methylcarbazole, 3-methylcarbazole, N-methylcarbazole, and N-ethylcarbazole, and more preferably N-ethylcarbazole.

[0114] The present invention will be described in detail below through embodiments.

[0115] In the examples and comparative examples, all raw materials used were commercially available and had a purity >99%; the purity of hydrogen and argon was ≥99.999%, and the purity of hydrogen and argon was obtained by mass spectrometry analysis.

[0116] In each example and comparative example, the content of each component in the catalyst was determined by ICP.

[0117] XRD tests were performed using a Bruker X-ray diffractometer.

[0118] The specific surface area of ​​the catalyst was determined by the BET method using nitrogen physical adsorption.

[0119] The composition of the hydrogenation product and the dehydrogenation product of N-ethylcarbazole are both composed of... 1 H NMR determination.

[0120] Example 1

[0121] (1) According to the stoichiometric ratio of Mo / Ni 1:1, a certain amount of nickel nitrate hexahydrate and ammonium heptamolybdate tetrahydrate were weighed using an electronic balance. The total mass was 10 grams. 25 mL of deionized water was added to obtain the first mixture. The first mixing temperature was 40 °C.

[0122] (2) Then add 10 mL of 2 mol / L dilute ammonia water and carry out the second mixing at 50 °C. After a clear solution is formed, the second mixture is obtained.

[0123] (3) Add 250 mL of ethylene glycol to the second mixture and stir evenly with a magnetic stirrer at 50 °C to obtain the third mixture. The stirring speed is 300 rpm. Transfer the third mixture to a round-bottom flask and keep stirring. React at a constant temperature of 120 °C in an oil bath for 1 h. After the liquid in the flask turns into a suspension, filter to obtain the precursor powder of the catalyst composition. Wash the separated precursor powder three times with deionized water and ethanol at a volume ratio of 1:1. Dry at 60 °C for 12 h to obtain the catalyst precursor.

[0124] The 1g catalyst precursor was loaded into a quartz tube furnace in a small porcelain boat, and Ar was first passed through it at room temperature for 30 min, followed by Ar and H2 flow rates of 50 mL / min. -1 and 30 mL·min -1 In a mixed atmosphere at 10℃·min -1 The temperature was increased to 450℃ at a rate of 0.1 MPa, and held at this temperature for 2 hours. Then, the H2 flow was stopped, and Ar was continued to flow until the temperature of the tube furnace dropped below 50℃, yielding the unsupported catalyst Al. The physicochemical data are shown in Table 1.

[0125] TEM image of A1 as follows Figure 1 As shown, the catalyst has a rod-like morphology, with a length of 2 μm, a diameter of 0.5 μm, and an aspect ratio of 4:1. Ni is distributed in dots or clusters on the surface of the Mo-enriched microregions. XRD patterns are shown below. Figure 4 As shown in the XRD pattern, distinct diffraction peaks are observed at 2θ values ​​of 37°, 44°, 51°, 62°, and 76°. Specifically, the peaks at 37° and 62° represent nickel oxide, while those at 44°, 51°, and 76° represent elemental nickel, confirming the presence of both nickel oxide and elemental nickel in the catalyst, with the Ni component existing as elemental Ni. Furthermore, the XRD pattern reveals that Mo exhibits a higher degree of amorphous characteristics compared to Ni, indicating a higher degree of disorder in its elemental distribution region.

[0126] Example 2

[0127] (1) According to the Mo / Ni stoichiometric ratio of 0.8:1, a certain amount of nickel nitrate hexahydrate and ammonium heptamolybdate tetrahydrate were weighed using an electronic balance. The total mass was 10 grams. 25 mL of deionized water was added to obtain the first mixture. The first mixing temperature was 50℃.

[0128] (2) Then add 10 mL of 4 mol / L dilute ammonia water and carry out the second mixing at 50 °C. After a clear solution is formed, the second mixture is obtained.

[0129] (3) Add 250 mL of ethylene glycol to the second mixture and stir it evenly with a magnetic stirrer at 50 °C to obtain the third mixture. The stirring speed is 300 rpm. Transfer the third mixture to a round bottom flask and keep stirring. React at a constant temperature of 120 °C in an oil bath for 30 min. After the liquid in the flask turns into a suspension, filter to obtain the precursor powder of the catalyst composition. Wash the obtained precursor powder three times with deionized water and ethanol at a volume ratio of 1:1. Dry it at 60 °C for 12 h to obtain the catalyst precursor.

[0130] The 1g catalyst precursor was loaded into a quartz tube furnace in a small porcelain boat, and Ar was first passed through it at room temperature for 30 min, followed by Ar and H2 flow rates of 50 mL / min. -1 and 30 mL·min -1 In a mixed atmosphere at 10℃·min -1 The temperature was increased to 450℃ at a rate of 0.5 MPa, and the temperature was maintained for 2 hours. Then, the H2 was stopped, and Ar was continued to be introduced until the temperature of the tube furnace dropped to below 50℃, thus obtaining the unsupported catalyst A2.

[0131] TEM images show that the catalyst has a rod-like morphology, with a length of 3 μm, a diameter of 0.5 μm, and an aspect ratio of 6:1. Ni is distributed in dots or clusters on the surface of the Mo-enriched microregions.

[0132] Example 3

[0133] Following the method in Example 1, except that the Mo / Ni stoichiometric ratio was 2:3, an unsupported catalyst was obtained, denoted as A3.

[0134] TEM images show that the catalyst has a rod-like morphology, with a length of 2.8 μm, a diameter of 0.4 μm, and an aspect ratio of 7:1. Ni is located on the surface of the Mo-enriched microregions. Physicochemical data are shown in Table 1.

[0135] Example 4

[0136] Following the method in Example 1, except that the Mo / Ni stoichiometric ratio was 1.5:1, an unsupported catalyst, denoted as A4, was obtained. TEM characterization showed that the catalyst had a particulate morphology, such as... Figure 2 As shown, Ni is located on the surface of the Mo-enriched microregion. Physicochemical data are shown in Table 1.

[0137] Example 5

[0138] Following the method of Example 1, except that an equal amount of isopropanol was used instead of ethylene glycol, the resulting catalyst was A5. TEM images showed that the catalyst had a bulk morphology, with Ni located on the surface of the Mo-enriched microregions. Physicochemical data are shown in Table 1.

[0139] Example 6

[0140] Following the method of Example 1, except that no alcohol was added, the resulting catalyst was designated A6, and its physicochemical data are shown in Table 1.

[0141] Comparative Example 1

[0142] According to the Mo / Ni stoichiometric ratio of 1:1, a certain amount of nickel nitrate hexahydrate and ammonium heptamolybdate tetrahydrate, with a total mass of 10 grams, were weighed using an electronic balance. 250 mL of deionized water was added, and the mixture was stirred evenly with a magnetic stirrer to obtain the first mixture. The stirring speed was 300 rpm, and the mixture was transferred to a round-bottom flask. Stirring was maintained, and the mixture was reacted at a constant temperature of 120 °C in an oil bath for 30 min. After the liquid in the flask turned into a suspension, it was filtered to obtain the precursor powder of the catalyst composition. The separated precursor powder was washed three times with deionized water and ethanol at a volume ratio of 1:1, and dried at 60 °C for 12 h to obtain the catalyst precursor.

[0143] 1g of catalyst precursor was loaded into a quartz tube furnace in a small porcelain boat. Ar was first passed through the furnace at room temperature for 30min, and then Ar and H2 flow rates were increased to 50mL·min. -1 and 30 mL·min -1 In a mixed atmosphere at 10℃·min -1 The temperature was increased to 450℃ at a rate of 0.5 MPa, and held at this temperature for 2 hours. Then, the H2 flow was stopped, and Ar was continued to flow until the temperature of the tube furnace dropped below 50℃, yielding catalyst DA1. The physicochemical data are shown in Table 1.

[0144] Comparative Example 2

[0145] (1) According to the stoichiometric ratio of Mo / Ni 1:1, a certain amount of nickel nitrate hexahydrate and ammonium heptamolybdate tetrahydrate were weighed using an electronic balance. The total mass was 10 grams. 25 mL of deionized water was added to obtain the first mixture. The first mixing temperature was 50 °C.

[0146] (2) Add 250 mL of ethylene glycol to the first mixture above and stir evenly at 60 °C to obtain the second mixture;

[0147] (3) Add 10 mL of 6 mol / L dilute ammonia to the second mixture, stir evenly with a magnetic stirrer at 60 °C to obtain the third mixture, transfer the third mixture to a round bottom flask, keep stirring, and react at a constant temperature of 120 °C in an oil bath for 30 min. After the liquid in the flask turns into a suspension, filter to obtain the precursor powder of the catalyst composition. Wash the separated precursor powder three times with deionized water and ethanol at a volume ratio of 1:6 to obtain the catalyst precursor.

[0148] (4) The catalyst precursor was loaded into a quartz tube furnace in a small porcelain boat, and Ar was first passed through it at room temperature for 30 min, and then Ar and H2 flow rates were set at 50 mL / min. -1 and 30 mL·min -1 In a mixed atmosphere at 10℃·min -1 The temperature was increased to 450℃ at a certain rate and held for 2 hours. The pressure of the hydrogen-containing atmosphere was 0.5 MPa. Then, the H2 supply was stopped, and Ar was continued to be introduced until the temperature of the tube furnace dropped below 50℃, yielding catalyst DA2. The physicochemical data are shown in Table 1.

[0149] Table 1

[0150]

[0151] Test case

[0152] The catalysts used in the above examples and comparative examples were used to conduct hydrogenation experiments on N-ethylcarbazole (NEC).

[0153] The hydrogenation reaction was carried out in a high-pressure reactor under the following conditions: reaction temperature 180℃, hydrogen pressure 7 MPa, reaction time 20 h, and N-ethylcarbazole (NEC) weight hourly space velocity (WHSV) 0.5 h⁻¹. -1 Record the pressure sensor count p as a function of time t, and then calculate the hydrogen uptake using formulas 1 and 2. Finally, obtain the curve showing how the hydrogen uptake of the reaction substrate changes over time.

[0154] Formula 1: n=ΔpV / RT, where T is the reaction temperature, Δp is the pressure change during the reaction, and V is the volume of the reactor cavity.

[0155] Formula 2: C = 100 × n × 2 / M

[0156] Where M is the mass of the substrate N-ethylcarbazole (NEC), and C is the amount of hydrogen absorbed by the catalyst. The composition of the products was determined by NMR after the reaction, and the Ct curve was corrected by combining the relative proportions of several products with the total amount of feedstock.

[0157] The content of NEC's hydrogen absorption products, tetrahydro-N-ethylcarbazole (4H-NEC), octahydro-N-ethylcarbazole (8H-NEC), and dodecahydro-N-ethylcarbazole (12H-NEC), can be determined by... 1 Peaks at specific positions in H NMR were identified, and the content of each product and the total hydrogen absorption of the NEC hydrogenation reaction were calculated based on the area ratio.

[0158] like Figure 3As shown, the chemical shifts of the H atoms attached to the benzene ring in NEC, 4H-NEC, 8H-NEC, and 12H-NEC are at positions ranging from 1.07 to 0.90 ppm. The chemical shifts of the H atoms on the methylene group attached to the N atom are different: NEC has a quartet of about 4.4 ppm, 4H-NEC has about 4.1 ppm, and 8H-NEC has about 3.7 ppm, while 12H-NEC has about 2.6 ppm.

[0159] The contents of each substance and the total hydrogen absorption in the hydrogenation reaction products of nitrogen-containing heterocyclic compounds were calculated according to Formula 3-5, and the results are shown in Table 2:

[0160] Formula 3: Product mole percentage = S n / (S1+S2+S3+S4), where n is 1-4.

[0161] Formula 4: Total hydrogen absorption = (4S2 + 8S3 + 12S4)M1 / (S1 + S2 + S3 + S4), where M1 is the number of NEC moles.

[0162] Wherein S1 is the peak area at chemical shift 4.4 (NEC), S2 is the peak area at chemical shift 4.1 (4H-NEC), S3 is the peak area at chemical shift 3.7 (8H-NEC), and S4 (12H-NEC) is the peak area at chemical shift 2.6.

[0163] Table 2

[0164]

[0165] Dehydrogenation experiments were conducted on the N-ethylcarbazole (NEC) hydrogenation products using the catalysts in the above examples and comparative examples.

[0166] The hydrogenation product of N-ethylcarbazole (NEC) is the 12H-NEC product from the hydrogenation experiment in Example 1 above.

[0167] The reaction temperature was 150℃, the pressure was 1 MPa, the reaction time was 20 h, and the weight hourly space velocity (WHSV) of the hydrogenation product of N-ethylcarbazole (NEC) was 0.5 h⁻¹. -1 Record the instantaneous hydrogen release flow rate q as a function of time t. After hydrogen release is complete, integrate the instantaneous flow rate q with respect to time t to obtain the Qt curve showing the total hydrogen release flow rate Q as a function of time t. Calculate the molar percentage of each substance in the product according to Formula 3. Correct the total hydrogen release amount according to Formula 5, and the results are shown in Table 3.

[0168] Formula 5: Total hydrogen release = (12S2 + 8S3 + 4S4)M4 / (S1 + S2 + S3 + S4), where M4 is the number of moles of 12H-NEC.

[0169] The total hydrogen absorption represents the degree of hydrogen absorption under specific reaction conditions, with a theoretical maximum of 5.8 wt%, corresponding to the conversion of all N-ethylcarbazole to 12H-NEC; the total hydrogen release represents the degree of hydrogen release under specific conditions, with a theoretical maximum of 5.5 wt%, corresponding to the conversion of all 12H-NEC to N-ethylcarbazole.

[0170] Hydrogen release / absorption efficiency (%) = (total hydrogen release / M4) / (total hydrogen absorption / M1)×100%.

[0171] X-ray diffraction patterns of catalyst A1 before and after reaction in Example 1 are compared. Figure 4 As shown, the structure and composition of the catalyst before and after the reaction exhibit good stability.

[0172] Table 3

[0173] Example number Total hydrogen absorption (wt%) Total hydrogen release (wt%) Hydrogen absorption / desorption efficiency % Example 1 5.72 5.38 88.61 Example 2 5.64 4.51 75.33 Example 3 5.48 3.98 68.42 Example 4 5.98 3.89 61.28 Example 5 5.11 4.23 77.98 Example 6 4.68 5.12 103.07* Comparative Example 1 <0.1 <0.1 - Comparative Example 2 <0.1 <0.1 -

[0174] *The hydrogen absorption / desorption efficiency calculated in Example 6 exceeds 100%. This is because its hydrogen absorption effect is poor and the total hydrogen absorption is far from saturated. Therefore, the relative reference significance of the hydrogen absorption / desorption efficiency here is not great.

[0175] As can be seen from the results in Tables 2 and 3, the unsupported catalyst provided by this invention has a dual catalytic function of hydrogenation / dehydrogenation, exhibiting both high hydrogenation activity and high dehydrogenation activity. It can realize the dehydrogenation and hydrogenation of organic liquids, significantly reducing the raw material cost of organic liquid hydrogen storage, and at the same time, it is conducive to further improving the efficiency of organic liquid hydrogen storage.

[0176] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A non-supported catalyst, characterized in that, The catalyst comprises Ni and Mo; wherein, elementally, the molar ratio of Mo to Ni is 0.2-2:1; the Ni is located on the surface of the Mo-enriched microregion, and the average grain size of Ni is 20-100 nm; the catalyst is rod-shaped with an aspect ratio of 1-100:1; the length of the catalyst is 1-10 μm; the diameter of the catalyst is 0.1-1 μm; the Mo in the catalyst exists at least partially in the form of oxide, and the Ni in the catalyst exists at least partially in the form of elemental Ni; the specific surface area of ​​the catalyst is 100-300 cm². 2 / g.

2. The catalyst according to claim 1, wherein, The molar ratio of Mo to Ni is 0.8-2:

1.

3. The catalyst according to claim 2, wherein, The molar ratio of Mo to Ni is 0.8-1.2:

1.

4. The catalyst according to claim 1, wherein, The catalyst has an aspect ratio of 4-10:

1.

5. The catalyst according to claim 1, wherein, The catalyst has a length of 2-5 μm.

6. The catalyst according to claim 1, wherein, The catalyst has a diameter of 0.2-0.5 μm.

7. A method for preparing a non-supported catalyst according to any one of claims 1-6, characterized in that, Includes the following steps: (1) The nickel source, molybdenum source and solvent are mixed for the first time to obtain the first mixture; The molar ratio of molybdenum source (calculated as Mo) to nickel source (calculated as Ni) is 0.2-5:

1. (2) The first mixture and the alkaline solution are mixed a second time to obtain a second mixture; (3) The second mixture and the alcohol are mixed for a third time to obtain a third mixture; (4) The third mixture is heated to obtain catalyst precursor powder; (5) The catalyst precursor powder is contacted with a hydrogen-containing atmosphere to obtain the unsupported catalyst.

8. The preparation method according to claim 7, wherein, The molar ratio of molybdenum source (calculated as Mo) to nickel source (calculated as Ni) is 0.8-2:

1.

9. The preparation method according to claim 8, wherein, The molar ratio of molybdenum source (calculated as Mo) to nickel source (calculated as Ni) is 0.8-1.2:

1.

10. The preparation method according to claim 7, wherein, In the first mixture, the total mass concentration of nickel source and molybdenum source is 0.005-5 g / mL.

11. The preparation method according to claim 10, wherein, In the first mixture, the total mass concentration of nickel source and molybdenum source is 0.01-1 g / mL.

12. The preparation method according to claim 7, wherein, The nickel source is selected from at least one of nickel chloride, nickel nitrate, nickel sulfate, nickel phosphate, nickel fluoroborate, nickel acetate, nickel acetylacetone, nickel aminosulfonate, and nickel citrate.

13. The preparation method according to claim 7, wherein, The molybdenum source is selected from at least one of molybdic acid, phosphomolybdic acid, ammonium molybdate, and molybdenum chloride.

14. The preparation method according to claim 7, wherein, The solvent is water.

15. The preparation method according to claim 7, wherein, The temperature of the first mixture is 10-50℃.

16. The preparation method according to claim 15, wherein, The temperature of the first mixture is 15-40℃.

17. The preparation method according to claim 7, wherein, The alkaline solution is an aqueous solution containing an alkaline compound.

18. The preparation method according to claim 17, wherein, The alkaline compound is an organic base and / or an inorganic base.

19. The preparation method according to claim 18, wherein, The alkaline compound is selected from at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, ethylenediamine, and isopropylamine.

20. The preparation method according to claim 17, wherein, The concentration of alkaline compounds in the alkaline solution is 0.2-5 mol / L.

21. The preparation method according to claim 7, wherein, The volume ratio of the first mixture to the alkali solution is 1-10:

1.

22. The preparation method according to claim 21, wherein, The volume ratio of the first mixture to the alkali solution is 1-5:

1.

23. The preparation method according to claim 7, wherein, The temperature of the second mixture is 20-100℃.

24. The preparation method according to claim 23, wherein, The temperature of the second mixture is 30-50℃.

25. The preparation method according to claim 7, wherein, The alcohol is a C2-C3 water-soluble alcohol.

26. The preparation method according to claim 25, wherein, The alcohol is at least one of ethanol, ethylene glycol, n-propanol, isopropanol, and propylene glycol.

27. The preparation method according to claim 26, wherein, The alcohol is ethylene glycol and / or propylene glycol.

28. The preparation method according to claim 7, wherein, The volume ratio of the second mixture to alcohol is 0.1-1:

1.

29. The preparation method according to claim 28, wherein, The volume ratio of the second mixture to alcohol is 0.2-0.5:

1.

30. The preparation method according to claim 7, wherein, The third mixing is carried out under stirring conditions, with a stirring rate of 100-1500 rpm.

31. The preparation method according to claim 7, wherein, The temperature of the third mixture is 20-100℃.

32. The preparation method according to claim 31, wherein, The temperature of the third mixture is 30-80℃.

33. The preparation method according to claim 7, wherein, The conditions for the heating reaction include: a reaction temperature of not less than 90°C and a reaction time of 0.5-5 hours.

34. The preparation method according to claim 33, wherein, The conditions for the heating reaction include: a reaction temperature of 100-150℃ and a reaction time of 1-4h.

35. The preparation method according to claim 7, wherein, Step (4) further includes: performing solid-liquid separation, washing and drying on the product of the heated reaction to obtain the catalyst precursor powder.

36. The preparation method according to claim 7, wherein, The hydrogen-containing atmosphere is hydrogen gas or a mixture of hydrogen gas and an inert gas.

37. The preparation method according to claim 36, wherein, The hydrogen volume fraction in the hydrogen-containing atmosphere is 10-100%, and the gas volume is measured under standard conditions.

38. The preparation method according to claim 7, wherein, The contact conditions include: a contact temperature not lower than 350°C; a contact time of 0.5-5 hours; a hydrogen-containing atmosphere pressure of 0.01-1 MPa; and a hydrogen volume hourly space velocity of 0.5-2 h⁻¹. -1 .

39. The preparation method according to claim 38, wherein, The contact conditions include: a contact temperature of 400-550℃; a contact time of 1-4 hours; and a hydrogen-containing atmosphere pressure of 0.02-0.5 MPa.

40. The preparation method according to claim 39, wherein, The contact conditions include: a contact temperature of 450-500℃ and a hydrogen-containing atmosphere pressure of 0.05-0.2MPa.

41. The application of the unsupported catalyst according to any one of claims 1-6 in organic liquid hydrogen storage.

42. A method for hydrogenating a nitrogen-containing heterocyclic organic compound, comprising: Under hydrogenation reaction conditions, in the presence of a hydrogenation catalyst, nitrogen-containing heterocyclic organic compounds are brought into contact with hydrogen gas; The hydrogenation catalyst is characterized in that it is an unsupported catalyst as described in any one of claims 1-6.

43. The method according to claim 42, wherein, The hydrogenation reaction conditions include: a reaction temperature of 50-200℃; and a weight hourly space velocity (WHSV) of 0.5-50 h⁻¹ for nitrogen-containing heterocyclic organic compounds. -1 The hydrogen pressure is 2-10 MPa.

44. The method according to claim 43, wherein, The hydrogenation reaction conditions include: a reaction temperature of 130-200℃; and a weight hourly space velocity of 1-30 h⁻¹ for nitrogen-containing heterocyclic organic compounds. -1 The hydrogen pressure is 5-8 MPa.

45. The method according to claim 42, wherein, The nitrogen-containing heterocyclic organic compound is selected from at least one of indole, quinoline, isoquinoline, N-alkylcarbazole, and alkyl-substituted carbazole on the benzene ring.

46. ​​The method according to claim 45, wherein, The alkyl-substituted carbazole on the benzene ring is 2-methylcarbazole and / or 3-methylcarbazole.

47. The method according to claim 45, wherein, The N-alkylcarbazole is N-methylcarbazole and / or N-ethylcarbazole.

48. A method for dehydrogenating nitrogen-containing heterocyclic organic compounds, comprising: Under dehydrogenation reaction conditions, the hydrogenation products of nitrogen-containing heterocyclic organic compounds are contacted with a dehydrogenation catalyst to carry out a dehydrogenation reaction to obtain hydrogen gas; The dehydrogenation catalyst is characterized in that it is an unsupported catalyst as described in any one of claims 1-6.

49. The method according to claim 48, wherein, The dehydrogenation reaction conditions include: a reaction temperature of 50-250℃, and a weight hourly space velocity (WHSV) of 0.5-50 h⁻¹ for the hydrogenation products of nitrogen-containing heterocyclic organic compounds. -1 The reaction pressure is 0.1-2 MPa; And / or, the contact is carried out under hydrogen-exposed or non-hydrogen-exposed conditions.

50. The method according to claim 48, wherein, The nitrogen-containing heterocyclic organic compound is selected from at least one of indole, quinoline, isoquinoline, N-alkylcarbazole, and alkyl-substituted carbazole on a benzene ring.

51. The method according to claim 50, wherein, The alkyl-substituted carbazole on the benzene ring is 2-methylcarbazole and / or 3-methylcarbazole.

52. The method according to claim 50, wherein, The N-alkylcarbazole is N-methylcarbazole and / or N-ethylcarbazole.

53. The method according to claim 48, wherein, The hydrogenation product of the nitrogen-containing heterocyclic organic compound is the hydrogenation product of N-ethylcarbazole.

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