Catalyst for deep dehydrogenation of naphthenic hydrocarbon-based hydrogen storage agent and method for preparing the same

Abstract

This invention provides a catalyst for deep dehydrogenation of cycloalkane hydrogen storage agents and its preparation method. The catalyst comprises a support and a metal active component supported on the support. The support is η-Al₂O₃, and the metal active component is Pt and M, where M is one or more metals selected from Groups VIII, IB, and IIB of the periodic table. The weight ratio of the metal active component to the support is 0.03:99.97 to 0.3:99.7, and the weight ratio of Pt to M in the metal active component is 10:1 to 120:1. The catalyst preparation method of this invention is simple, the Pt loading in the catalyst is low, and the catalyst raw materials and preparation costs are low. The cycloalkane hydrogen storage agent exhibits high dehydrogenation degree on the catalyst of this invention. The catalyst of this invention has good deep dehydrogenation stability.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy storage, specifically relating to a catalyst for the deep dehydrogenation process of cycloalkane hydrogen storage agents and its preparation method. Background Technology

[0002] Hydrogen, as a clean and renewable energy source, is becoming increasingly attractive in energy storage and fuel cell applications. Furthermore, hydrogen is widely used as a feedstock in industries such as petroleum refining, food, pharmaceuticals, and chemical production. Currently, hydrogen production technologies based on fossil fuels have been optimized, while those based on clean and renewable energy sources such as hydropower, wind power, solar power, biomass energy, waste streams, and geothermal resources are also developing rapidly. Hydrogen can serve as a future alternative to fossil fuels. However, hydrogen is highly flammable and explosive, and hydrogen storage and transportation are currently the technological bottleneck in the hydrogen energy industry chain, hindering the development of a hydrogen energy economy.

[0003] Organic liquid hydrogen storage technology, represented by cycloalkanes such as cyclohexane and decahydronaphthalene, stores and transports hydrogen in liquid form. This technology can make the most of existing oil and gas storage and transportation infrastructure, reduce storage and transportation costs, and enable energy storage and transportation for longer periods and over wider areas. Therefore, it has a very broad application prospect.

[0004] Organic liquid hydrogen storage technology achieves hydrogen storage through the catalytic hydrogenation and dehydrogenation cycle of aromatic cyclic hydrocarbons. The gas produced during the dehydrogenation reaction does not contain byproducts such as CO that are toxic to the catalyst, nor does it emit CO2. The hydrogen storage agent can be reused, and it also has excellent hydrogen mass density (typically 5-10%) and volume density (typically 45-70 g / L).

[0005] However, currently developed industrial dehydrogenation catalysts are generally used in selective dehydrogenation processes, such as the industrialized dehydrogenation of ethylbenzene to styrene and propane to propylene. These catalysts, to prevent deactivation due to carbon buildup caused by deep dehydrogenation, do not possess deep dehydrogenation capabilities. In contrast, the dehydrogenation process of cycloalkane hydrogen storage agents requires the complete removal of all available hydrogen to achieve efficient recycling of the storage agent. Therefore, the catalyst must possess deep dehydrogenation capabilities. This leads to the requirement of precious metals as the active component in most cycloalkane hydrogen storage agent dehydrogenation processes, resulting in high costs due to the large amount of precious metals used. Furthermore, while maintaining deep dehydrogenation activity, catalysts often suffer from deactivation due to carbon buildup and other factors, exhibiting poor stability. This is a major obstacle to the industrial application of cycloalkane hydrogen storage agent dehydrogenation processes.

[0006] Chinese invention patent application CN115106120A discloses a dehydrogenation catalyst, comprising a noble metal, an auxiliary metal, and a support, wherein the weight content of the noble metal is 0.3-5.0%, and the catalyst with the best performance has a stable operating time of up to 40 hours.

[0007] Chinese invention patent application CN113908880A discloses a dehydrogenation catalyst, its preparation method, and its application. The dehydrogenation catalyst includes a support and an active component supported on the support, wherein the support is a Na-type ZSM-5 molecular sieve, and the active component is the noble metal Pt. The mass content of the active component in the dehydrogenation catalyst is 0.05-0.3%. This application reduces the content of the active noble metal Pt in the catalyst, saving catalyst preparation costs. This catalyst has an ultra-long service life in the dehydrogenation of n-dodecane to prepare dodecyl monoolefin, and can also improve the selectivity of dodecyl monoolefin. However, the application system of this catalyst is a selective dehydrogenation reaction process and is not suitable for deep dehydrogenation processes.

[0008] Therefore, there is an urgent need in this field to develop Pt-based catalysts with low Pt loading, high dehydrogenation degree, and high stability for use in deep dehydrogenation processes catalyzed by cycloalkane hydrogen storage agents. Summary of the Invention

[0009] The purpose of this invention is to provide a Pt-based catalyst with low Pt loading and high stability for use in deep dehydrogenation processes of cycloalkanes.

[0010] In a first aspect, the present invention provides a catalyst for a dehydrogenation process, the catalyst comprising a support and a metal active component supported on the support, the support being η-Al₂O₃, the metal active component being Pt and M, wherein M is one or more metals selected from Group VIII, Group IB and Group IIB of the periodic table, the weight ratio of the metal active component to the support being 0.03:99.97 to 0.3:99.7, and the weight ratio of Pt to M in the metal active component being 10:1 to 120:1.

[0011] In one or more embodiments, the weight ratio of Pt to M in the metal active component is 15:1 to 110:1.

[0012] In one or more embodiments, M is one or more selected from Ni, Cu, Co, Fe, Pd, and Zn.

[0013] In one or more embodiments, the weight ratio of the metal active component to the carrier is 0.05:99.95 to 0.25:99.75.

[0014] In one or more embodiments, the carrier is a flower-like η-Al2O3.

[0015] In one or more embodiments, the powder bulk density of the carrier is 0.1 ± 0.05 g / mL.

[0016] In one or more embodiments, the average pore size of the carrier is 20 ± 5 nm.

[0017] In one or more embodiments, the average dispersion of the metal active component on the support is 70-95%.

[0018] A second aspect of the present invention provides a method for preparing η-Al2O3, comprising the steps of:

[0019] (1) Dissolve Al2(SO4)3 and urea in water to obtain a reaction solution. The mass ratio of Al2(SO4)3 to urea is 0.3:1 to 2:1.

[0020] (2) The reaction solution is subjected to a hydrothermal reaction at 100-140°C for 5-24 hours, and then reacted at 150-200°C for 2-18 hours.

[0021] (3) After the reaction in step (2) is completed, the reaction solution is cooled and filtered to obtain a solid. The solid is then washed until it is neutral.

[0022] (4) Calcine the solid obtained in step (3) at 400-800℃ for 3-18h and then cool it to obtain η-Al2O3.

[0023] In one or more embodiments, in step (1), the mass ratio of water to Al2(SO4)3 is 0.5:1 to 2.5:1.

[0024] In one or more embodiments, the solid is first dried at 70–130°C for 3–18 hours before calcination.

[0025] A third aspect of the present invention provides a method for preparing the catalyst described in the first aspect of the present invention, the method comprising: loading the metal active component onto the support using a simultaneous impregnation method.

[0026] In one or more embodiments, the simultaneous impregnation method includes the steps of:

[0027] (a) Prepare an aqueous solution of chloroplatinic acid with a Pt mass content of 0.05% to 0.2% and an aqueous solution of metal salt with a M mass content of 0.01% to 0.05%; mix the aqueous solution of chloroplatinic acid and the aqueous solution of metal salt at a Pt to M mass ratio of 10:1 to 120:1, add ethylene glycol to obtain a mixed solution;

[0028] (b) Mix the mixture and the carrier, wherein the mass ratio of the mixture to the carrier is 0.3:1 to 3:1;

[0029] (c) The volumetric hourly space velocity (VHSV) is 5000–7000 h⁻¹. -1Nitrogen gas is calcined at 400–800℃ for 2–18 hours;

[0030] (d) Use at 200–400°C with a volumetric hourly space velocity of 5000–7000 h⁻¹ -1 The catalyst is obtained by reducing a hydrogen-nitrogen mixture and then cooling it.

[0031] In one or more embodiments, in step (a), the amount of ethylene glycol added is 1% to 5% of the sum of the mass of the aqueous chloroplatinic acid solution and the aqueous metal salt solution.

[0032] In one or more embodiments, in step (b), the mass ratio of the mixture to the carrier is 0.5:1 to 2.5:1.

[0033] In one or more embodiments, in step (c), the sample is first dried at 100–150°C for 2–18 hours before calcination.

[0034] In one or more embodiments, in step (d), the reduction reaction is carried out for 2 to 10 hours.

[0035] In one or more embodiments, in step (d), the volume fraction of hydrogen in the hydrogen-nitrogen mixture is 2% to 20%.

[0036] In one or more embodiments, in step (d), the cooling is achieved by introducing a volumetric hourly space velocity (VHSV) of 5000–7000 h⁻¹. -1 Nitrogen gas is used.

[0037] In one or more embodiments, the metal salt is selected from one or more of nitrates, halogen salts, and water-soluble acetates.

[0038] In one or more embodiments, the metal salt is selected from one or more nitrates and halogen salts.

[0039] A fourth aspect of the present invention provides the application of the catalyst described in the first aspect of the present invention in the dehydrogenation process of a hydrogen storage agent, wherein the hydrogen storage agent is a cycloalkane-based hydrogen storage agent.

[0040] In one or more embodiments, the hydrogen storage agent is selected from one or more of cyclohexane, methylcyclohexane, decahydronaphthalene, and perhydrodibenzyltoluene.

[0041] A fifth aspect of the present invention provides a method for dehydrogenating a cycloalkane-based hydrogen storage agent, comprising the steps of:

[0042] A cycloalkane-based hydrogen storage agent is passed into a reactor containing the catalyst described in the first aspect of this invention to carry out a dehydrogenation reaction.

[0043] In one or more embodiments, the reaction pressure is ≤0.5MPa.

[0044] In one or more embodiments, the reaction temperature is 200–500°C.

[0045] In one or more embodiments, the liquid hourly space velocity (LHSV) of the cycloalkane-based hydrogen storage agent in the reactor is 0.1–10 h⁻¹. -1 . Attached Figure Description

[0046] Figure 1 These are X-ray diffraction phase spectra of η-Al2O3 and γ-Al2O3 supports. The "*" marks the characteristic peaks of η-Al2O3 that distinguish it from the commonly used catalyst support γ-Al2O3.

[0047] Figure 2 This is a pore size distribution diagram of the η-Al2O3 support.

[0048] Figure 3 The flower cluster-shaped Pt prepared in Example 4 0.2 -Pd 0.002 Transmission electron microscopy images of the η-Al2O3 catalyst show that the material with a flower-like morphology is the η-Al2O3 support, and the many small black dots distributed on the petals of the η-Al2O3 support are Pt-Pd nanoparticles. Detailed Implementation

[0049] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as embodiments) can be combined with each other to form preferred technical solutions.

[0050] In this article, cycloalkane hydrogen storage agents include, but are not limited to, cyclohexane, methylcyclohexane, decahydronaphthalene, and perhydrodibenzyltoluene. The structural formulas, molecular weights, boiling points, hydrogen mass densities, and volume densities of these substances are shown in Table 1. They all have a cycloalkane structure, are liquids at room temperature, and have a high hydrogen content, enabling the release and storage of hydrogen through catalytic dehydrogenation and hydrogenation processes.

[0051] Table 1: Molecular structure and physicochemical properties of representative cycloalkane hydrogen storage agents

[0052]

[0053] In this paper, the catalyst support is flower-like η-Al2O3, which is η-phase active alumina with a flower-like morphology, a powder bulk density of 0.1±0.05 g / mL, and an average pore size of 20±5 nm.

[0054] In this article, the "degree of dehydrogenation" of a hydrogen storage agent is defined as the percentage of actual hydrogen removed to the theoretical hydrogen content, serving as an indicator of the dehydrogenation extent (depth) of the agent. The closer the degree of dehydrogenation is to 100%, the better the catalyst's deep dehydrogenation activity. For example, the partial dehydrogenation product of decahydronaphthalene is tetrahydronaphthalene, while the deep dehydrogenation product is naphthalene; whereas the partial dehydrogenation products of dodecahydroethylcarbazole include octahydroethylcarbazole and tetrahydroethylcarbazole, with ethylcarbazole being the deep dehydrogenation product.

[0055] In this article, "space velocity" refers to the volume or mass of gas or liquid processed per unit volume or mass of catalyst per unit time under specified conditions, with units of m³. 3 / (m 3 The catalyst·h) or g / (g catalyst·h) can be simplified to h -1 "Liquid volume hourly space velocity" refers to the volume of liquid processed by a unit volume of catalyst per unit time. In this invention, the liquid volume hourly space velocity of the catalyst used for deep dehydrogenation of cycloalkane hydrogen storage agents refers to the volume of liquid hydrogen storage agent processed (flowing through) by a unit volume of catalyst per unit time.

[0056] This paper uses gas chromatography to analyze hydrogen content, for example, but not limited to, using a PerkinElmer Clarus 580 gas chromatograph with a TDX column, high-purity nitrogen as the carrier gas, and a thermal conductivity detector to detect and analyze the hydrogen content in the reactor outlet gas.

[0057] X-ray diffraction phase patterns can be determined using an X-ray diffractometer (e.g., Rigaku Max2550VB / PC, Japan). The International Data Center for Diffraction of η-Al₂O₃ is designated PDF#04-0875.

[0058] The pore size distribution can be analyzed using the principle of low-temperature physical adsorption-desorption of N2, employing a fully automated physical adsorption instrument such as the ASAP2020 from Micromeritics, USA, to obtain the pore size distribution map and calculate the average pore size value. The powder bulk density can be measured according to the national standard GB / T 16913.3-1997, "Determination of Bulk Density of Powder / Powder Substances".

[0059] Transmission electron microscope images can be taken using the JEM-2010 high-resolution transmission electron microscope from JOEL Corporation of Japan.

[0060] The average dispersion of the metal active component on the support can be determined using conventional CO pulse adsorption methods, such as the ChemiSorb 2720 chemisorption analyzer from Micromeritics, USA. A large average dispersion indicates that the metal active component has a small particle size and a large active surface area, which is beneficial for improving catalytic activity.

[0061] The mass ratios of Pt-M to η-Al2O3 and the mass ratio of Pt to M were determined by inductively coupled plasma atomic emission spectrometry (ICP-OES) using a PerkinElmer Optima 8300 instrument.

[0062] The Pt-M / η-Al2O3 catalyst of the present invention

[0063] The low Pt loading catalyst of the present invention is composed of η-Al2O3 as a support and a metal active component (Pt-M) (written as: Pt-M / η-Al2O3).

[0064] The Pt-M / η-Al2O3 catalyst of the present invention comprises a support and a metallic active component supported on the support, wherein the support is η-phase alumina η-Al2O3, and the metallic active component is Pt and M, wherein M is a metal from Group VIII, IB, or IIB of the periodic table. M can be one or more of Ni, Cu, Co, Fe, Pd, or Zn. Preferably, M can be Ni, Pd, Fe, or Zn. The weight ratio of Pt to M can be 10:1 to 120:1, for example 30:1 to 90:1, 40:1 to 80:1. Preferably, the weight ratio of Pt to M can be 15:1 to 110:1. In some embodiments, the weight ratio of Pt to M can be 20:1 to 100:1. The weight ratio of Pt-M to η-Al2O3 can be 0.03:99.97 to 0.3:99.7. Preferably, the weight ratio of Pt-M to η-Al2O3 can be 0.05:99.95 to 0.25:99.75.

[0065] The support is a flower-like cluster of η-Al₂O₃, where η-Al₂O₃ is the η-phase active alumina. The powder bulk density of the support can be 0.1 ± 0.05 g / mL. The average pore size of the support can be 20 ± 5 nm. The average dispersion of the metal active component on the support can be 70–95%, for example, 75–90%.

[0066] Preparation method of catalyst of the present invention

[0067] This invention provides a method for preparing a Pt-M / η-Al2O3 catalyst. The Pt-M / η-Al2O3 catalyst is prepared by a hydrothermal method combined with a simultaneous impregnation method. Specifically, η-Al2O3 is prepared using a hydrothermal method, and the active metal component is loaded onto a support using a simultaneous impregnation method. The method for preparing η-Al2O3 includes the following steps:

[0068] (1) Dissolve Al2(SO4)3 and urea in water to obtain a reaction solution. The mass ratio of Al2(SO4)3 to urea is 0.3 to 2:1.

[0069] (2) After reacting the reaction solution at 100-140°C for 5-24 hours, react it at 150-200°C for 2-18 hours.

[0070] (3) After the reaction in step (2) is completed, the reaction solution is cooled and filtered to obtain a solid. The solid is then washed until it is neutral.

[0071] (4) Calcine the solid obtained in step (3) at 400-800℃ for 3-18h and cool it to obtain η-Al2O3; preferably, the solid is dried at 70-130℃ for 3-18h before calcination.

[0072] In step (1), the mass ratio of Al2(SO4)3 to urea is 0.3–2:1, for example, 0.5–1.5:1 or 1–1.2:1. In some embodiments, Al2(SO4)3 is Al2(SO4)3·18H2O. The mass ratio of water to Al2(SO4)3 is 0.5–2.5:1, for example, 1–2:1.

[0073] In step (2), the reaction solution is reacted at 100–140°C for 5–24 hours, and then at 150–200°C for 2–18 hours. In some embodiments, the reaction solution is reacted at 100–140°C for 5–24 hours, and then at 160–190°C for 5–12 hours.

[0074] In step (3), the reaction solution after the reaction in step (2) is cooled and filtered to obtain a white solid. The white solid is washed until neutral. Preferably, the white solid is washed several times alternately with anhydrous ethanol and deionized water until the filtrate is neutral.

[0075] In step (4), the solid obtained in step (3) can be calcined at 400–800°C for 3–18 hours. Preferably, the solid obtained in step (3) can be calcined at 500–700°C for 5–12 hours. Preferably, the solid can be dried at 70–130°C for 3–18 hours before calcination. In some embodiments, the solid is vacuum dried at 90–120°C for 5–12 hours, and then calcined at 400–800°C for 3–18 hours.

[0076] The method for preparing Pt-M / η-Al2O3 catalyst includes the following steps:

[0077] (a) Prepare an aqueous solution of chloroplatinic acid with a Pt mass content of 0.05% to 0.2% and an aqueous solution of a metal salt with a M mass content of 0.01% to 0.05%; mix the aqueous solution of chloroplatinic acid and the aqueous solution of metal salt at a Pt to M mass ratio of 10:1 to 120:1, add ethylene glycol to obtain a mixture; preferably, the amount of ethylene glycol added is 1% to 5% of the sum of the mass of the aqueous solution of chloroplatinic acid and the aqueous solution of metal salt;

[0078] (b) The mixture is added to η-Al2O3, and the mass ratio of the mixture to η-Al2O3 is 0.3 to 3; preferably, the mass ratio of the mixture to the η-Al2O3 sample is 0.5 to 2.5.

[0079] (c) The volumetric hourly space velocity (VHSV) is 5000–7000 h⁻¹. -1 Nitrogen gas is calcined at 400–800°C for 2–18 hours; preferably, it is dried at 100–150°C for 2–18 hours before calcination.

[0080] (d) Use at 200–400°C with a volumetric hourly space velocity of 5000–7000 h⁻¹ -1 A hydrogen-nitrogen mixture is reduced, and after cooling, a Pt-M / η-Al2O3 catalyst is obtained; preferably, the reaction is carried out for 2 to 10 hours; preferably, the volume fraction of hydrogen in the hydrogen-nitrogen mixture is 2 to 20%; preferably, the cooling is achieved by introducing a volume hourly space velocity (VHSV) of 5000 to 7000 h⁻¹. -1 Nitrogen gas is used.

[0081] In step (a), the mass content of Pt in the chloroplatinic acid aqueous solution can be 0.05% to 0.2%. Preferably, the mass content of Pt in the chloroplatinic acid aqueous solution can be 0.1% to 0.15%. The mass content of metal M in the metal salt aqueous solution can be 0.01% to 0.05%, for example, 0.02% to 0.04%. The chloroplatinic acid aqueous solution and the metal salt aqueous solution can be mixed at a mass ratio of Pt to metal M of 10:1 to 120:1, for example, 15:1 to 110:1, 30:1 to 90:1. Preferably, the chloroplatinic acid aqueous solution and the metal salt aqueous solution can be mixed at a mass ratio of Pt to metal M of 20:1 to 100:1. Ethylene glycol is added to the mixture of chloroplatinic acid aqueous solution and metal salt aqueous solution, and the amount of ethylene glycol added can be 1% to 5% of the sum of the mass of the chloroplatinic acid aqueous solution and the metal salt aqueous solution, for example, 2% to 4%. The metal salt can be selected from one or more of nitrates, halogen salts, and water-soluble acetates. Preferably, the metal salt is selected from nitrates or halogen salts. In some embodiments, the metal salt may be selected from one or more of palladium chloride, zinc chloride, ferric chloride, nickel nitrate, copper nitrate, cobalt nitrate, and nickel acetate.

[0082] In step (b), the mixture prepared in step (1) is added to η-Al2O3. The mass ratio of the mixture to η-Al2O3 can be 0.3 to 3, for example, 0.8 to 2 or 1 to 1.5. Preferably, the mass ratio of the mixture to η-Al2O3 can be 0.5 to 2.5.

[0083] In step (c), the volumetric hourly space velocity is 5000–7000 h⁻¹. -1Nitrogen gas is calcined at 400–800°C for 2–18 hours, for example, at 500–700°C for 4–12 hours. Preferably, the volume hourly space velocity (VHSV) during calcination is 5500–6500 h⁻¹. -1 Nitrogen gas. Preferably, the sample is dried at 100–150°C for 2–18 hours before calcination, for example, at 110–130°C for 5–12 hours.

[0084] In step (d), a volumetric hourly space velocity (VHSV) of 5000–7000 h⁻¹ can be used at 200–400 °C. -1 The hydrogen-nitrogen mixture is used for reduction. Preferably, the volume hourly space velocity (VHSV) of the hydrogen-nitrogen mixture is 5500–6500 h⁻¹. -1 After cooling, a Pt-M / η-Al₂O₃ catalyst is obtained. Preferably, the reaction proceeds for 2–10 h, for example, 5–8 h. The volume fraction of hydrogen in the hydrogen-nitrogen mixture can be 2–20%, for example, 5–15%, 7–10%. In some embodiments, cooling is achieved by introducing a volume hourly space velocity (VHSV) of 5000–7000 h⁻¹. -1 The process is carried out using nitrogen gas, for example, at a volume hourly space velocity of 5500–6500 h⁻¹. -1 Nitrogen gas.

[0085] Methods for deep dehydrogenation of cycloalkanes as hydrogen storage agents

[0086] Includes the following steps:

[0087] The hydrogen storage agent is introduced into a reactor containing a Pt-M / η-Al₂O₃ catalyst. Preferably, the reactor is a fixed-bed reactor. In some embodiments, the Pt-M / η-Al₂O₃ catalyst is placed in the fixed-bed reactor. The fixed-bed reactor may be equipped with a preheater. The preheater can heat the hydrogen storage agent and catalyst to a specified temperature, such as 200–500°C or 300–400°C, before the catalytic dehydrogenation reaction proceeds. In some embodiments, a volume hourly space velocity (VHSV) of 5000–7000 h⁻¹ is introduced into the reactor. -1 Nitrogen gas, for example, 5500–6500 h -1 Nitrogen gas is used. The pressure of the reaction system can be 0.1–0.5 MPa, for example, 0.2–0.4 MPa. In some embodiments, the hydrogen storage agent can be metered into the feed inlet line of the reactor. The liquid hourly space velocity (LHSV) of the catalyst in the reactor is 0.1–10 h⁻¹. -1 For example, 1 to 5 hours -1 .

[0088] The advantages of this invention include:

[0089] (1) The catalyst preparation method of the present invention is simple, the Pt loading in the catalyst is low, and the catalyst raw materials and preparation costs are low. Since the support is prepared by conventional hydrothermal method and the active component is loaded by mature impregnation method, the whole preparation process is simple and mild, the amount of precious metal used is very small, and the price of other raw materials is low, making it easy for the catalyst to be industrialized and applied.

[0090] (2) The cycloalkane hydrogen storage agent exhibits high dehydrogenation degree on the Pt-M / η-Al2O3 catalyst of this invention. The catalyst uses a small amount of noble metal, resulting in high dispersion of the active components. Simultaneously, the addition of trace amounts of elements located in VIII, IB, and IIB as a second metal provides excellent synergistic catalytic effect. This enhances the dehydrogenation activity of the noble metal active components and significantly weakens the adsorption inhibition effect of deep dehydrogenation products on the noble metal active sites, leading to the conversion of some dehydrogenation products into deep dehydrogenation products. This significantly improves the deep dehydrogenation efficiency of the cycloalkane hydrogen storage agent.

[0091] (3) The Pt-M / η-Al2O3 catalyst exhibits good stability in deep dehydrogenation. The catalyst uses flower-like η-Al2O3 as a support. On one hand, the flower-like support has an open pore structure with an average pore size (20±5 nm) significantly larger than commercial activated alumina (generally less than 10 nm, such as the average pore size of 8.6 nm for commercial YH-SAC type activated alumina). Therefore, it is highly conducive to the rapid escape and transfer of hydrogen and dehydrogenation products, not only promoting the forward dehydrogenation equilibrium but also preventing catalyst coking and deactivation caused by the accumulation of deep dehydrogenation products. On the other hand, η-Al2O3 has weaker surface acidity than commonly used γ-Al2O3, and strong surface acidity is the main cause of coking of deep dehydrogenation products. In summary, the Pt-M / η-Al2O3 catalyst provided by this invention can maintain good stability in the deep dehydrogenation process of cycloalkane hydrogen storage agents.

[0092] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Percentages and parts are by weight unless otherwise stated.

[0093] In the examples, the average dispersion of the metal active component on the support was determined using a CO pulse adsorption method on a ChemiSorb 2720 chemisorption analyzer manufactured by Micromeritics, USA.

[0094] In this embodiment, the pore size distribution of the sample was analyzed using the N2 low-temperature physical adsorption-desorption principle and the ASAP2020 fully automated physical adsorption instrument from Micromeritics, USA, to obtain a pore size distribution map and calculate the average pore size value.

[0095] In the examples, the bulk density of the powder was measured according to the national standard GB / T 16913.3-1997, "Method for Determination of Bulk Density of Powder / Powder Components".

[0096] In this embodiment, gas chromatography was used to analyze the hydrogen content. A Clarus 580 gas chromatograph from PerkinElmer, USA, with a TDX column and high-purity nitrogen as the carrier gas, was used to detect and analyze the hydrogen content in the reactor outlet gas.

[0097] In this embodiment, the X-ray diffraction phase pattern was determined using an X-ray diffractometer (Rigaku, Japan, Max2550VB / PC).

[0098] In this embodiment, the transmission electron microscope images were taken using a JEM-2010 high-resolution transmission electron microscope from JOEL Corporation of Japan.

[0099] In the examples, the mass ratio of Pt-M to η-Al2O3 and the mass ratio of Pt to M were determined by inductively coupled plasma optical emission spectrometry (ICP-OES instrument of PerkinElmer Optima 8300, USA).

[0100] Example 1 (Pt) 0.1 -Ni 0.005 Preparation of / η-Al2O3 catalyst)

[0101] Preparation of flower-like η-Al₂O₃ by hydrothermal method: 66.6 g of Al₂(SO₄)₃·18H₂O and 66.6 g of urea were dissolved in deionized water at a mass ratio of 1:1. The solution was stirred at room temperature to obtain a transparent solution, which was then transferred to a hydrothermal reactor and reacted at 120 °C for 12 h, followed by a reaction at 180 °C for 6 h. After the reaction, the hydrothermal reactor was cooled to room temperature and opened. The reaction product was filtered to obtain a white precipitate. The white precipitate was washed several times alternately with anhydrous ethanol and deionized water until the filtrate was neutral. The white precipitate was then vacuum dried at 100 °C for 6 h, and then transferred to a muffle furnace and calcined at 600 °C for 6 h. After cooling, flower-like η-Al₂O₃ was obtained. The X-ray diffraction phase pattern of the flower-like η-Al₂O₃ is shown below. Figure 1 As shown, the pore size distribution of the flower-like η-Al2O3 is as follows: Figure 2As shown, the powder bulk density of the flower-like η-Al2O3 is 0.11 g / mL, and the average pore size is 22 nm.

[0102] Simultaneous impregnation method for preparing Pt 0.1 -Ni 0.005 / η-Al2O3 catalyst: Prepare 100 mL of chloroplatinic acid solution with a Pt weight content of 0.15% and 100 mL of nickel nitrate solution with a Ni weight content of 0.015% using deionized water. Mix the two solutions at a Pt to Ni weight ratio of 20:1, and add ethylene glycol at a weight of 2% of the mixture. Take 20 g of flower-like η-Al2O3, and add the above ethylene glycol-containing mixed solution dropwise to the η-Al2O3, with a mixed solution to η-Al2O3 weight ratio of 1:1. Stir well with a glass rod and let stand at room temperature for 4 h. Then dry in an oven at 120 °C for 6 h, and then transfer to a tube furnace with a volume hourly space velocity of 6000 h⁻¹. -1 Nitrogen gas was used and the temperature was raised to 600℃ for 6 hours, then the temperature was lowered to 300℃ and the volume hourly space velocity was switched to 6000 h⁻¹. -1 A hydrogen / nitrogen mixture with a hydrogen volume content of 10% was used for catalyst reduction and maintained for 4 hours, then switched to a volume hourly space velocity (VHSV) of 6000 h⁻¹. -1 The nitrogen gas was cooled to room temperature, and then the gas flow was stopped to obtain the Pt. 0.1 -Ni 0.005 The / η-Al2O3 catalyst has a Pt mass content of 0.1% and a Ni mass content of 0.005%, and the average dispersion of the active metal component is measured to be 86%.

[0103] Example 2 (Pt) 0.05 -Fe 0.001 Preparation of / η-Al2O3 catalyst)

[0104] Flower clusters of η-Al2O3 were prepared using the same steps as in Example 1.

[0105] Pt was then prepared using the simultaneous impregnation method. 0.05 -Fe 0.001 / η-Al2O3 catalyst: Prepare 100 mL of chloroplatinic acid solution with a Pt weight content of 0.1% and 100 mL of ferric chloride solution with a Fe weight content of 0.01% using deionized water. Mix the two solutions at a Pt to Fe weight ratio of 50:1, and add ethylene glycol at a weight of 2% of the mixture. Take 50 g of flower cluster η-Al2O3, and add the above ethylene glycol-containing mixed solution dropwise to the η-Al2O3, with a mixed solution to η-Al2O3 weight ratio of 0.6:1. Stir evenly with a glass rod and let stand at room temperature for 4 h. Then, perform drying, calcination, reduction, and cooling treatments as in Example 1 to obtain the Pt.0.05 -Fe 0.001 The / η-Al2O3 catalyst has a Pt mass content of 0.05% and an Fe mass content of 0.001%, and the average dispersion of the active metal component is measured to be 95%.

[0106] Example 3 (Pt) 0.15 -Zn 0.002 Preparation of / η-Al2O3 catalyst)

[0107] Flower clusters of η-Al2O3 were prepared using the same steps as in Example 1.

[0108] Pt was then prepared using the simultaneous impregnation method. 0.15 -Zn 0.002 / η-Al2O3 catalyst: Prepare 100 mL of chloroplatinic acid solution with a Pt weight content of 0.075% and 100 mL of zinc chloride solution with a Zn weight content of 0.05% using deionized water. Mix the two solutions at a Pt to Zn weight ratio of 75:1, and add ethylene glycol at a weight ratio of 2% of the mixture. Take 100 g of flower-shaped η-Al2O3, and add the above ethylene glycol-containing mixed solution dropwise to the η-Al2O3, with a mixed solution to η-Al2O3 weight ratio of 2.1:1. Stir evenly with a glass rod and let stand at room temperature for 4 h. Then, perform drying, calcination, reduction, and cooling treatments as in Example 1 to obtain the Pt. 0.15 -Zn 0.002 The / η-Al2O3 catalyst has a Pt mass content of 0.15% and a Zn mass content of 0.002%, and the average dispersion of the active metal component is measured to be 78%.

[0109] Example 4 (Pt) 0.2 -Pd 0.002 Preparation of / η-Al2O3 catalyst)

[0110] Flower clusters of η-Al2O3 were prepared using the same steps as in Example 1.

[0111] Pt was then prepared using the simultaneous impregnation method. 0.2 -Pd 0.002 / η-Al2O3 catalyst: Prepare 100 mL of chloroplatinic acid solution with a Pt weight content of 0.2% and 100 mL of palladium chloride solution with a Pd weight content of 0.02% using deionized water. Mix the two solutions at a Pt:Pd weight ratio of 100:1, and add ethylene glycol at a weight ratio of 2% of the mixture. Take 100 g of flower-like η-Al2O3, and add the above ethylene glycol-containing mixed solution dropwise to the η-Al2O3, with a mixed solution:η-Al2O3 weight ratio of 1.1:1. Stir evenly with a glass rod and let stand at room temperature for 4 h. Then, perform drying, calcination, reduction, and cooling treatments as in Example 1 to obtain the Pt. 0.2 -Pd 0.002 The / η-Al2O3 catalyst has a Pt mass content of 0.2% and a Pd mass content of 0.002%, and the average dispersion of the active metal components is measured to be 75%.

[0112] Comparative Example 1 (Pt) 0.2 Preparation of / η-Al2O3 catalyst (compared with Example 4)

[0113] Flower clusters of η-Al2O3 were prepared using the same steps as in Example 4.

[0114] Pt was then prepared by impregnation. 0.2 / η-Al2O3 catalyst: Prepare 100 mL of chloroplatinic acid solution with a Pt content of 0.2% by weight using deionized water, and add ethylene glycol, with a weight of 2% of the aforementioned solution. Take 100 g of flower-shaped η-Al2O3, and add the above ethylene glycol-containing solution dropwise to the η-Al2O3, with a weight ratio of solution to η-Al2O3 of 1:1. Stir evenly with a glass rod and let stand at room temperature for 4 h. Then, perform drying, calcination, reduction, and cooling treatment using the same steps as in Example 4 to obtain the Pt. 0.2 / η-Al2O3 catalyst, in which the mass content of Pt is 0.2%.

[0115] Comparative Example 2 (Pt) 0.2 -Pd 0.2 Preparation of / η-Al2O3 catalyst (Pt:Pd mass ratio = 1:1, compared with Example 4)

[0116] Flower clusters of η-Al2O3 were prepared using the same steps as in Example 4.

[0117] Pt was then prepared using the simultaneous impregnation method. 0.2 -Pd 0.2 / η-Al2O3 catalyst: Prepare 100 mL of chloroplatinic acid solution with a Pt weight content of 0.2% and 100 mL of palladium chloride solution with a Pd weight content of 0.2% using deionized water. Mix the two solutions at a Pt to Pd weight ratio of 1:1, and add ethylene glycol at a weight ratio of 2% of the mixture. Take 100 g of flower-shaped η-Al2O3, and add the above ethylene glycol-containing mixed solution dropwise to the η-Al2O3, with a mixed solution to η-Al2O3 weight ratio of 2.1:1. Stir evenly with a glass rod and let stand at room temperature for 4 h. Then, perform drying, calcination, reduction, and cooling treatment using the same steps as in Example 4 to obtain the Pt. 0.2 -Pd 0.2 / η-Al2O3 catalyst, in which the mass content of Pt is 0.2% and the mass content of Pd is 0.2%.

[0118] Comparative Example 3 (Pt) 0.2 -Pd 0.002 (Preparation of γ-Al2O3 catalyst, compared with Example 4)

[0119] Commercial YH-SAC type activated alumina powder (γ-Al2O3, produced by Zibo Yinghe Chemical Co., Ltd.) with an average pore size of 8.6 nm was used as the carrier to replace the flower-like η-Al2O3 in Example 4. The remaining steps were the same as in Example 4.

[0120] Example 5 (Catalytic Dehydrogenation Reaction)

[0121] The catalysts prepared in Examples 1-4 and Comparative Examples 1-3 were placed in fixed-bed reactors equipped with preheaters, and a volume hourly space velocity (VHSV) of 6000 h⁻¹ was introduced. -1 Nitrogen gas is introduced, and then the preheater and fixed-bed reactor are heated to the required temperature and maintained at a stable temperature; the bed gas pressure is maintained at one atmosphere; then, liquid cycloalkane hydrogen storage agent is injected into the feed inlet line of the unit using a metering pump, flows through the preheater and enters the fixed-bed reactor, and the ratio of the liquid hydrogen storage agent flow rate to the volume of the catalyst bed in the reactor (liquid hourly space velocity) is 0.1–10 h⁻¹. -1 The nitrogen gas was then shut off, and the dehydrogenation reaction began. The flow rate of the gas at the reactor outlet was measured using a flow meter, and the hydrogen content in the gas at the reactor outlet was detected using a gas chromatograph. The degree of dehydrogenation of the hydrogen storage agent was calculated using the amount of hydrogen produced, and the stability of the catalyst was evaluated based on the change in the degree of dehydrogenation over time.

[0122] The conditions and results of each catalytic dehydrogenation reaction are listed in Table 2 below. It can be seen that the catalysts of Examples 1-4 exhibit high dehydrogenation degree and stability, demonstrating excellent catalytic dehydrogenation ability. Compared with the catalyst of Example 4, under the same reaction conditions, the catalysts of Comparative Examples 1-3 not only showed a significant decrease in dehydrogenation degree but also a marked deterioration in stability.

[0123] Table 2: Dehydrogenation reaction results of the catalysts prepared in Examples 1-4 and Comparative Examples 1-3

[0124]

Claims

1. A catalyst for a dehydrogenation process, characterized in that, The catalyst comprises a support and a metallic active component supported on the support, wherein the support is flower-shaped. -Al2O3, wherein the metal active component is Pt and M, where M is one or more metals selected from Ni, Fe, Pd and Zn, the weight ratio of the metal active component to the support is 0.03:99.97 to 0.3:99.7, and the weight ratio of Pt to M in the metal active component is 10:1 to 120:

1.

2. The catalyst according to claim 1, characterized in that, The weight ratio of Pt to M is 15:1 to 110:

1.

3. The catalyst according to claim 1, characterized in that, The weight ratio of the active metal component to the carrier is 0.05:99.95 to 0.25:99.

75.

4. The catalyst according to claim 1, characterized in that, The powder bulk density of the carrier is 0.

1. 0.05 g / mL; and / or, the average pore size of the support is 20 μm. 5 nm.

5. The catalyst according to claim 1, characterized in that, The average dispersion of the metal active component on the carrier is 70-95%.

6. A method for preparing a catalyst as described in any one of claims 1-5, characterized in that, The method includes loading the metal active component onto the carrier using a simultaneous impregnation method.

7. The method as described in claim 6, characterized in that, The simultaneous impregnation method includes the following steps: (a) Prepare an aqueous solution of chloroplatinic acid with a Pt mass content of 0.05%~0.2% and an aqueous solution of metal salt with a M mass content of 0.01%~0.05%; mix the aqueous solution of chloroplatinic acid and the aqueous solution of metal salt at a Pt to M mass ratio of 10:1~120:1, add ethylene glycol to obtain a mixed solution; (b) Mixing the mixture and the carrier, wherein the mass ratio of the mixture to the carrier is 0.3:1 to 3:1; (c) The volumetric hourly space velocity (VHSV) is 5000~7000 h⁻¹ -1 Nitrogen gas is calcined at 400~800℃ for 2~18 hours; (d) Use at 200~400℃ with a volumetric hourly space velocity of 5000~7000h -1 The catalyst is obtained by reducing a hydrogen-nitrogen mixture and then cooling it.

8. The method as described in claim 7, characterized in that, The metal salt is selected from one or more of nitrates, halogen salts, and water-soluble acetates.

9. The method as described in claim 7, characterized in that, The metal salt is selected from one or more of nitrates and halide salts.

10. The method as described in claim 7, characterized in that, In step (a), the amount of ethylene glycol added is 1% to 5% of the sum of the mass of the aqueous chloroplatinic acid solution and the aqueous metal salt solution.

11. The method as described in claim 7, characterized in that, In step (b), the mass ratio of the mixture to the carrier is 0.5:1 to 2.5:

1.

12. The method as described in claim 7, characterized in that, In step (c), the sample is first dried at 100~150℃ for 2~18h before calcination.

13. The method as described in claim 7, characterized in that, In step (d), the reduction reaction proceeds for 2 to 10 hours.

14. The method as described in claim 7, characterized in that, In step (d), the volume fraction of hydrogen in the hydrogen-nitrogen mixture is 2% to 20%.

15. The method as described in claim 7, characterized in that, In step (d), the cooling is achieved by introducing a volumetric space velocity of 5000~7000 h⁻¹. -1 Nitrogen gas is used.

16. The application of the catalyst according to any one of claims 1-5 in the dehydrogenation process of a hydrogen storage agent, wherein the hydrogen storage agent is a cycloalkane-based hydrogen storage agent.

17. The application as described in claim 16, characterized in that, The hydrogen storage agent is selected from one or more of cyclohexane, methylcyclohexane, decahydronaphthalene, and perhydrodibenzyltoluene.

18. A method for dehydrogenating cycloalkane hydrogen storage agents, characterized in that, Including the following steps: A cycloalkane-based hydrogen storage agent is passed into a reactor containing a catalyst according to any one of claims 1-5 to carry out a dehydrogenation reaction.

19. The method as described in claim 18, characterized in that, The reaction pressure is ≤0.5MPa.

20. The method as described in claim 18, characterized in that, The reaction temperature is 200~500℃.

21. The method as described in claim 18, characterized in that, The liquid hourly space velocity (LHSV) of the cycloalkane-based hydrogen storage agent in the reactor is 0.1–10 h⁻¹. -1 .

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