Dehydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention relates to a dehydrogenation catalyst and a preparation method and application thereof.The dehydrogenation catalyst comprises an L-type molecular sieve and active components loaded on the L-type molecular sieve, the active components comprise VIII family metal elements, rare earth metal elements and halogen, and the content of alkali metal in the dehydrogenation catalyst is 5-20% by weight. The dehydrogenation catalyst provided by the invention has relatively high selectivity and stability, can better exert a dehydrogenation function when being used for a dehydrogenation reaction of a liquid organic hydrogen storage medium, and prevents a naphthenic medium from ring opening and cracking reactions in the dehydrogenation process.

Description

Technical Field

[0001] This disclosure relates to the field of hydrogen energy technology, and more specifically, to a dehydrogenation catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a high-quality renewable and clean energy carrier, possesses advantages such as being clean, zero-carbon, pollution-free, having a high energy density per unit mass (33 kW·h / kg), wide availability, and diverse applications, thus showing broad application prospects. However, hydrogen has a low density (0.0899 kg / m³). 3 Hydrogen has a very low volumetric energy density (0.0033 kW·h / L), resulting in low efficiency for conventional hydrogen storage and transportation. Furthermore, hydrogen has a wide explosion limit, posing a certain degree of danger, which has long kept transportation costs high, severely restricting the development and utilization of hydrogen energy. Developing safe, efficient, economical, and convenient storage and transportation technologies is a crucial prerequisite for the widespread application of hydrogen energy.

[0003] Liquid organic hydrogen storage utilizes reversible hydrogenation / dehydrogenation reactions between unsaturated hydrocarbons (such as benzene, toluene, and naphthalene) and their corresponding saturated hydrocarbons (such as cyclohexane, methylcyclohexane, and decahydronaphthalene) and hydrogen to achieve hydrogen energy storage and release. Compared with other hydrogen storage technologies, liquid organic hydrogen storage has advantages such as low medium cost, high hydrogen density, large hydrogen storage capacity, easy transportation, high safety, convenient operation, and recyclability. It is suitable for long-distance hydrogen energy transportation, hydrogen storage at hydrogen refueling stations, renewable energy storage, and can also serve as a hydrogen source solution for hydrogen fuel cell vehicles.

[0004] Int. J. Hydrogen Energ. 2006, 31(10), 1348-1356. A catalyst and its preparation method were reported, using γ-Al2O3 as a support to support Pt and K to prepare the catalyst for the dehydrogenation reaction of methylcyclohexane. The catalyst showed good activity for the dehydrogenation reaction of methylcyclohexane. However, the article mainly focused on the reaction of methylcyclohexane under low temperature, low pressure and high hydrogen-to-oil ratio conditions, and could not be extended to other conditions. At the same time, it did not consider the problem of long-term coking stability decline caused by the acidity of Al2O3 support.

[0005] CN107537560A discloses a dehydrogenation catalyst, prepared by supporting platinum on modified MCM-41, for the dehydrogenation reaction of organic liquid hydrogen storage materials. The organic liquid hydrogen storage materials are selected from methylcyclohexane, cyclohexane, tetrahydronaphthalene, decahydronaphthalene, etc. However, MCM-41 molecular sieve is a pure silicon molecular sieve, which is inherently weakly acidic. While suppressing coking, the dispersibility and activity of Pt metal do not show significant advantages. Furthermore, the traditional Al2O3 support is too acidic, resulting in severe coking on the catalyst surface.

[0006] CN110882703A discloses a cycloalkane dehydrogenation catalyst containing alkaline earth metals and its preparation method, using Pt as the active metal component, Sn as the promoter component, and an alumina support containing alkaline earth metals, sulfur, and titanium. This catalyst is used in the dehydrogenation of cyclohexane to benzene, but suffers from problems such as low cyclohexane conversion, low catalyst stability, high coking, and frequent regeneration.

[0007] Liquid organic hydrogen storage media need to release stored hydrogen through a dehydrogenation reaction under the action of a dehydrogenation catalyst. Commonly used dehydrogenation catalysts include a support and an active component. Catalysts with noble metals as the active component have high dehydrogenation activity and good selectivity. However, for applications such as hydrogen refueling stations or hydrogen fuel cell vehicles, the hydrogen storage medium is generally required to be recycled multiple times. The hydrogenation process has a low temperature and fewer side reactions, with minimal impact on the medium; however, the dehydrogenation process requires a high reaction temperature and is prone to side reactions such as cracking and carbon deposition. These side reactions in the dehydrogenation process have a significant negative impact on the recycling of the hydrogen storage medium. After cycloalkane media undergo ring-opening to form alkanes, they cannot undergo further ring-forming and dehydrogenation under both hydrogenation and dehydrogenation reaction conditions. This results in a significant decrease in the hydrogen storage density of the medium after repeated hydrogen charging and discharging. At the same time, the ring-opening and cracking side reactions also lead to an increase in the hydrocarbon content in the hydrogen products, which can easily cause deactivation of the hydrogen fuel cell electrode catalyst, thus also hindering downstream applications of the dehydrogenation process. Currently, there is a lack of publicly disclosed effective methods for suppressing side reactions in the cycloalkane dehydrogenation process. Summary of the Invention

[0008] The purpose of this disclosure is to provide a dehydrogenation catalyst, its preparation method, and its application. This dehydrogenation catalyst has high selectivity and stability. When used in the dehydrogenation reaction of liquid organic hydrogen storage media, it can better perform the dehydrogenation function and prevent ring-opening and cracking reactions of cycloalkane media during the dehydrogenation process.

[0009] To achieve the above objectives, the first aspect of this disclosure provides a dehydrogenation catalyst comprising an L-type molecular sieve and an active component supported on the L-type molecular sieve, wherein the active component comprises a Group VIII metal element, a rare earth metal element, and a halogen, and the content of an alkali metal in the dehydrogenation catalyst is 5-20% by weight.

[0010] Optionally, the silicon-to-aluminum molar ratio of the dehydrogenation catalyst is 2.5-3.5, preferably 2.7-3.0; the relative crystallinity is 90-100%, preferably 95-100%; the average particle size is 300-2000 nm, preferably 500-1000 nm; and the specific surface area is 80-150 m². 2 / g, preferably 100~120m 2 / g; pore volume is 0.01~0.1cm 3 / g, preferably 0.03~0.06cm 3 / g.

[0011] Optionally, based on the total weight of the dehydrogenation catalyst, the content of group VIII metal elements in the dehydrogenation catalyst is 0.2-1.5 wt%, preferably 0.5-1.0 wt%; the content of rare earth metal elements is 0.1-3.0 wt%, preferably 0.1-1.0 wt%; and the content of halogens is 0.5-1.5 wt%, preferably 0.5-1.0 wt%.

[0012] Optionally, the weight ratio of Group VIII metal elements to rare earth metal elements in the dehydrogenation catalyst is (0.1~6):1, preferably (0.1~2):1; the weight ratio of Group VIII metal elements to halogens is (0.5~2):1, preferably (1~2):1.

[0013] Optionally, the group VIII metal element is selected from one or more of Pt, Ru, or Rh, preferably Pt; the rare earth metal element is selected from one or more of La, Ce, and Pr, preferably La and / or Ce; the halogen is selected from one or more of F, Cl, Br, and I, preferably F and / or Cl. The alkali metal is selected from one or more of Na, K, Rb and Cs, preferably Na and / or K.

[0014] The second aspect of this disclosure provides a method for preparing the dehydrogenation catalyst described in the first aspect of this disclosure, the method comprising: contacting an impregnation solution containing a group III metal compound, a rare earth compound, a halide and a solvent with an L-type molecular sieve for impregnation treatment; drying, calcining and reducing the impregnated solid material; wherein the alkali metal content in the L-type molecular sieve is 5-20% by weight.

[0015] Optionally, relative to 1g of the L-type molecular sieve, the impregnation solution contains 0.2-1.5% by weight of Group VIII metal compounds (based on metal elements), 0.1-3.0% by weight of rare earth compounds (based on metal elements), and 0.5-1.5% by weight of halides (based on halogens). Optionally, the Group VIII metal compound is selected from one or more of chloroplatinic acid, tetraammonium dichloroplatinate, ammonium chloroplatinate, platinum trichloride, platinum tetrachloride hydrate, dicarbonyl platinum dichloride, dinitrodiaminoplatinum, and sodium tetranitroplatinate, preferably chloroplatinic acid; The rare earth compound is selected from one or more of cerium nitrate, lanthanum nitrate and praseodymium nitrate, preferably cerium nitrate and / or lanthanum nitrate; The halide is selected from one or more of hydrochloric acid, hydrofluoric acid, potassium chloride, potassium fluoride, sodium chloride and sodium fluoride, preferably potassium chloride and / or potassium fluoride; The alkali metal is selected from one or more of Na, K, Rb and Cs, preferably Na and / or K.

[0016] Optionally, the L-shaped molecular sieve has a silica-alumina molar ratio of 2.5 to 3.5, preferably 2.7 to 3.0; a relative crystallinity of 90 to 100%, preferably 95 to 100%; an average particle size of 300 to 2000 nm, preferably 500 to 1000 nm; and a pore volume of 0.01 to 0.1 cm³. 3 / g, preferably 0.03~0.06cm 3 / g.

[0017] Optionally, the impregnation temperature is 20~80℃ and the time is 3~12h; the drying temperature is 70~150℃ and the time is 3~48h; the calcination temperature is 300~550℃ and the time is 2~12h; and the reduction temperature is 400~520℃ and the time is 2~12h.

[0018] Optionally, the impregnation process includes: first impregnating the L-type molecular sieve with an impregnation solution containing the rare earth compound, and then impregnating the resulting intermediate with an impregnation solution containing the group VIII metal compound and the halide.

[0019] Optionally, the method for preparing the L-type molecular sieve includes: (1) A mixture gel is prepared by mixing silicon source, aluminum source, alkali source and water, wherein the molar ratio of each substance in the mixture gel is M2O:Al2O3:SiO2:H2O=(1.5~3.0):1:(5~9):(80~150), wherein M is selected from one or more of Na, K, Rb and Cs, preferably Na and / or K; (2) The mixture gel is subjected to hydrothermal crystallization treatment, and the product after hydrothermal crystallization is subjected to solid-liquid separation to obtain the L-type molecular sieve; the hydrothermal crystallization temperature is 150~200℃ and the time is 24~96h.

[0020] The third aspect of this disclosure provides the application of the dehydrogenation catalyst described in the first aspect of this disclosure in the dehydrogenation reaction of a liquid organic hydrogen storage medium.

[0021] Optionally, the application includes: under dehydrogenation reaction conditions, contacting the dehydrogenation catalyst described in the first aspect of this disclosure with a liquid organic hydrogen storage medium to carry out a dehydrogenation reaction; The conditions for the dehydrogenation reaction include: a temperature of 320~380℃, a pressure of 0.1~1.5MPa, and a feed mass hourly space velocity of 2.0~8.0h. -1 The hydrogen / hydrocarbon volume ratio is 600~1200.

[0022] Optionally, the liquid organic hydrogen storage medium is cyclohexane or methylcyclohexane, more preferably cyclohexane.

[0023] Through the above technical solutions, this disclosure provides a dehydrogenation catalyst, its preparation method, and its application. The dehydrogenation catalyst provided by this disclosure uses an L-shaped molecular sieve with a suitable pore structure as a support, which is beneficial for improving the adsorption and desorption rates of liquid organic hydrogen storage media and increasing their diffusion rate. Furthermore, loading Group VIII metal elements, rare earth metal elements, and halogens as active components onto the L-shaped molecular sieve effectively enhances the interaction between the L-shaped molecular sieve and the active components, thereby improving the selectivity and stability of the dehydrogenation catalyst. When used in the dehydrogenation reaction of liquid organic hydrogen storage media, it can better exert its dehydrogenation function. In addition, the dehydrogenation catalyst of this disclosure also contains a specific amount of alkali metal, which has a certain pore confinement effect, preventing ring-opening and cracking reactions in cycloalkane media during dehydrogenation and reducing the amount of carbon deposited on the catalyst.

[0024] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0025] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0026] The first aspect of this disclosure provides a dehydrogenation catalyst comprising an L-type molecular sieve and an active component supported on the L-type molecular sieve, wherein the active component comprises a Group VIII metal element, a rare earth metal element, and a halogen; the content of the alkali metal in the dehydrogenation catalyst is 5-20% by weight.

[0027] The dehydrogenation catalyst disclosed herein uses an L-shaped molecular sieve with a suitable pore structure as a support, which is beneficial for improving the adsorption and desorption rates of liquid organic hydrogen storage media and increasing their diffusion rate. Furthermore, loading Group VIII metal elements, rare earth metal elements, and halogens as active components onto the L-shaped molecular sieve effectively enhances the interaction between the L-shaped molecular sieve and the active components, thereby improving the selectivity and stability of the dehydrogenation catalyst. When used in the dehydrogenation reaction of liquid organic hydrogen storage media, it can better perform its dehydrogenation function. In addition, the dehydrogenation catalyst of this disclosure also contains a specific amount of alkali metal, which has a certain pore confinement effect, preventing ring-opening and cracking reactions in cycloalkane media during dehydrogenation and reducing the amount of carbon deposited on the catalyst.

[0028] In one embodiment of this disclosure, the alkali metal content in the dehydrogenation catalyst is 12-18% by weight. In the above embodiment, it is beneficial to prevent ring-opening and cracking reactions of the cycloalkane medium during dehydrogenation, and to reduce the amount of carbon deposits on the catalyst.

[0029] In one embodiment of this disclosure, the silicon-to-aluminum molar ratio of the dehydrogenation catalyst is 2.5-3.5, preferably 2.7-3.0; the relative crystallinity is 90-100%, preferably 95-100%; the average particle size is 300-2000 nm, preferably 500-1000 nm; and the specific surface area is 80-150 m². 2 / g, preferably 100~120m 2 / g; pore volume is 0.01~0.1cm 3 / g, preferably 0.03~0.06cm 3 / g. In the above embodiments, the dehydrogenation catalyst has a large specific surface area and a suitable pore structure, which is beneficial to improving the adsorption and desorption rates of the liquid organic hydrogen storage medium and further improving the dehydrogenation performance.

[0030] In one embodiment of this disclosure, based on the total weight of the dehydrogenation catalyst, the content of group VIII metal elements in the dehydrogenation catalyst is 0.2-1.5 wt%, preferably 0.5-1.0 wt%; the content of rare earth metal elements is 0.1-3.0 wt%, preferably 0.1-1.0 wt%; and the content of halogens is 0.5-1.5 wt%, preferably 0.5-1.0 wt%.

[0031] In one embodiment, the weight ratio of Group VIII metal elements to rare earth metal elements in the dehydrogenation catalyst is (0.1~6):1, preferably (0.1~2):1; the weight ratio of Group VIII metal elements to halogens is (0.5~2):1, preferably (1~2):1. In the above embodiment, by selecting the preferred proportions of active components, the interaction between the active components and the L-type molecular sieve can be further improved, thereby enhancing the selectivity and stability of the dehydrogenation catalyst.

[0032] In one embodiment of this disclosure, the Group VIII metal element is selected from one or more of Pt, Ru, or Rh, preferably Pt; the rare earth metal element is selected from one or more of La, Ce, and Pr, preferably La and / or Ce; the halogen is selected from one or more of F, Cl, Br, and I, preferably F and / or Cl; the alkali metal is selected from one or more of Na, K, Rb, and Cs, preferably Na and / or K. In the above embodiment, the dehydrogenation catalyst has a certain alkali metal, which can better exert the pore confinement effect of the dehydrogenation catalyst, prevent ring-opening and cracking side reactions in the cycloalkane medium during dehydrogenation, and reduce carbon deposition.

[0033] The second aspect of this disclosure provides a method for preparing the dehydrogenation catalyst described in the first aspect of this disclosure. The method includes: contacting an impregnation solution containing a Group VIII metal compound, a rare earth compound, a halide, and a solvent with an L-type molecular sieve for impregnation treatment; drying, calcining, and reducing the impregnated solid material; wherein the alkali metal content in the L-type molecular sieve is 5-20% by weight, preferably 12-18% by weight. The L-type molecular sieve of this disclosure has an alkali metal framework, which has a certain pore confinement effect, preventing ring opening and cracking of cycloalkane media during dehydrogenation and reducing carbon deposition.

[0034] In one embodiment of this disclosure, relative to 1g of the L-type molecular sieve, the impregnation solution contains 0.2-1.5% by weight of Group VIII metal compounds (based on metal element), 0.1-3.0% by weight of rare earth compounds (based on metal element), and 0.5-1.5% by weight of halides (based on halogen). Specifically, the Group VIII metal compounds are selected from one or more of chloroplatinic acid, tetraammonium dichloroplatinate, ammonium chloroplatinate, platinum trichloride, platinum tetrachloride hydrate, dicarbonyl platinum dichloride, dinitrodiaminoplatinum, and sodium tetranitroplatinate, preferably tetraammonium dichloroplatinate; the rare earth compounds are selected from one or more of cerium nitrate, lanthanum nitrate, and praseodymium nitrate, preferably cerium nitrate and / or lanthanum nitrate; the halides are selected from one or more of hydrochloric acid, hydrofluoric acid, potassium chloride, potassium fluoride, sodium chloride, and sodium fluoride, preferably potassium chloride and / or potassium fluoride; the alkali metals are selected from one or more of Na, K, Rb, and Cs, preferably Na and / or K.

[0035] In one embodiment of this disclosure, the L-shaped molecular sieve has a silica-alumina molar ratio of 2.5 to 3.5, preferably 2.7 to 3.0; a relative crystallinity of 90 to 100%, preferably 95 to 100%; an average particle size of 300 to 2000 nm, preferably 500 to 1000 nm; and a pore volume of 0.01 to 0.1 cm³. 3 / g, preferably 0.03~0.06cm 3 / g; In the above embodiments, the L-type molecular sieve is a porous molecular sieve with a suitable pore structure, which includes micropores with a pore size of less than 2 nm, mesopores with a pore size of 2~50 nm, and macropores with a pore size of greater than 50 nm, wherein the mesopores with a pore size in the range of 10~50 nm contain a large amount, and their pore volume is 0.01 cm³. 3 The material has a microporous structure with a pore size of over / g, accounting for 50-70% of the pore volume of L-type molecular sieves. The pore size of the microporous structure of this material matches the molecular size of the cycloalkane medium. The mesoporous structure is conducive to the adsorption and desorption of the cycloalkane medium, thereby improving the selectivity of the dehydrogenation catalyst.

[0036] In one embodiment of this disclosure, the impregnation process can be performed in steps, comprising: first impregnating the L-shaped molecular sieve with an impregnation solution containing the rare earth compound, and then impregnating the resulting intermediate with an impregnation solution containing the group VIII metal compound and a halide. Optionally, a drying and calcination step may be included between the two impregnation steps, i.e., the intermediate undergoes drying and calcination before the second impregnation step.

[0037] In one embodiment of this disclosure, the immersion treatment is carried out at a temperature of 20-80°C for 3-12 hours.

[0038] In one embodiment of this disclosure, the drying temperature is 70~150°C and the time is 3~48h.

[0039] In one embodiment of this disclosure, the calcination temperature is 300~550℃ and the time is 2~12h.

[0040] In one embodiment of this disclosure, the reduction temperature is 400~520℃ and the time is 2~12h.

[0041] In one embodiment, the method for preparing the L-type molecular sieve includes: (1) A mixture gel is prepared by mixing silicon source, aluminum source, alkali source and water, wherein the molar ratio of each substance in the mixture gel is M2O:Al2O3:SiO2:H2O=(1.5~3.0):1:(5~9):(80~150), wherein M is selected from one or more of Na, K, Rb and Cs, preferably Na and / or K; (2) The mixture gel is subjected to hydrothermal crystallization treatment, and the product after hydrothermal crystallization is subjected to solid-liquid separation to obtain the L-type molecular sieve; the hydrothermal crystallization temperature is 150~200℃ and the time is 24~96h.

[0042] In one embodiment of this disclosure, the silicon source is selected from one or more of silica sol, silicon dioxide, and silicic acid, preferably silica sol; the SiO2 content in the silica sol is 20-45% by weight; the aluminum source is selected from aluminum hydroxide and / or sodium aluminate; the alkali source is selected from inorganic alkali, and the inorganic alkali is selected from one or more of sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, preferably sodium hydroxide and / or potassium hydroxide.

[0043] The third aspect of this disclosure provides the application of the dehydrogenation catalyst described in the first aspect of this disclosure in the dehydrogenation reaction of a liquid organic hydrogen storage medium.

[0044] In one embodiment of this disclosure, the application includes: contacting the dehydrogenation catalyst with a liquid organic hydrogen storage medium to carry out a dehydrogenation reaction under dehydrogenation reaction conditions; the dehydrogenation reaction conditions include: a temperature of 320~380℃, a pressure of 0.1~1.5MPa, and a feed mass hourly space velocity of 2.0~8.0h. -1 The hydrogen / hydrocarbon volume ratio is 600~1200.

[0045] In one embodiment of this disclosure, the liquid organic hydrogen storage medium is cyclohexane or methylcyclohexane, preferably cyclohexane.

[0046] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0047] Unless otherwise specified, all raw materials used in the following embodiments are commercially available products.

[0048] In the following embodiments, the specific testing methods are as follows: The chemical composition of the molecular sieve and catalyst was determined using a Rigaku Electric Co., Ltd. 3013 X-ray fluorescence spectrometer. The silicon-to-aluminum ratio of the molecular sieve and catalyst was calculated. The tungsten target was used, the excitation voltage was 40 kV, and the excitation current was 50 mA. The specific surface area, average pore size, and pore volume of the molecular sieve and catalyst were calculated using a BET testing system. The instrument was an ASAP2400 specific surface area analyzer manufactured by Micromeritics Instruments. The specific surface area of ​​the sample was calculated using the BET (Brunauer-Emmett-Teller) equation. The volume of N2 adsorbed by the sample at a relative pressure (p / p0) of 0.98 was measured and converted to liquid nitrogen volume, which is the total pore volume.

[0049] The microstructure of the molecular sieve and catalyst was analyzed using a Tecnai G2 F20 S-TWIN field emission transmission electron microscope (TEM) from FEI (USA) at an accelerating voltage of 200 kV. Before analysis, the samples were finely ground, ultrasonically dispersed in anhydrous ethanol, and then dropped onto a copper grid supporting a carbon film for observation.

[0050] The conversion rate of cyclohexane and the selectivity of benzene were determined by gas chromatography. An Agilent 7697B gas chromatograph was used for the test, equipped with a flame ionization detector (FID) and a capillary column (CBP-W12-100).

[0051] Example 1 L-type molecular sieves were prepared using the following steps: (1) Dissolve 60g Al(OH)3 (aluminum source, mass fraction of 99%) and 125g KOH (alkali source, mass fraction of 95%) in 365mL of deionized water and heat to dissolve to obtain aluminum sol; stir and add the aluminum sol to 916g silica sol (silicon source, mass fraction of 25.6%, calculated as SiO2), stir for 0.5h to obtain a mixture gel, the molar ratio of each substance in the mixture gel is K2O:Al2O3:SiO2:H2O=2.8:1:10.3:154; (2) The mixture gel was transferred into a reaction vessel and subjected to hydrothermal crystallization treatment at 170°C for 72 h. Then it was cooled to 40°C. The product was separated into solid and mother liquor. The solid was washed with deionized water until the pH of the washing liquid was 8. Then it was dried at 120°C for 10 h to obtain molecular sieve powder. The powder was pressed into tablets under a pressure of 8~25 MPa and crushed to a particle size of 20~40 mesh to obtain L-type molecular sieve, denoted as ZT-1. Its physicochemical properties are shown in Table 1. The dehydrogenation catalyst was prepared using the following steps: S1. Take 50g of the ZT-1 prepared above as a carrier, and prepare an impregnation solution with cerium nitrate, so that the content of cerium nitrate in the impregnation solution, calculated as Ce, is 0.2% by weight (relative to the weight of the L-type molecular sieve). Pour ZT-1 and the impregnation solution into a 500mL flask (the liquid / solid volume ratio of the impregnation solution to ZT-1 is 1.5), and impregnate in a rotary vacuum evaporator at 25℃, 0.02MPa, and a rotational speed of 0.03m / s for 3h. Dry the solid under reduced pressure at 70℃, dry at 120℃ for 12h, and calcine in dry air at 350℃ and a gas / agent volume ratio of 700 for 4h to obtain an L-type molecular sieve containing Ce, denoted as ZT-1-Ce.

[0052] S2. Prepare an impregnation solution by mixing chloroplatinic acid and potassium chloride, ensuring that the content of chloroplatinic acid (calculated as Pt) in the impregnation solution is 1.0 wt% and the content of potassium chloride (calculated as Cl) is 1.0 wt% (both relative to the weight of the L-type molecular sieve). Pour ZT-1-Ce and the impregnation solution into a 500 mL flask (the liquid / solid volume ratio of the impregnation solution to ZT-1 is 1.5). Impregnate the solid in a rotary vacuum evaporator at 25 °C, 0.02 MPa, and a rotational speed of 0.03 m / s for 3 h. Dry the solid under reduced pressure at 70 °C, dry it at 120 °C for 12 h, calcine it in dry air at 350 °C and a gas / agent volume ratio of 700 for 4 h, and then reduce it with H2 at 480 °C and a gas / agent volume ratio of 500 for 4 h to obtain catalyst Cat-1. Its composition and structure are shown in Tables 2-3.

[0053] Example 2 Same as Example 1, except that in step S2, the content of chloroplatinic acid in the impregnation solution, calculated as Pt, is 0.5% by weight, and the catalyst Cat-2 is obtained, the composition and structure of which are shown in Tables 2-3.

[0054] Example 3 Same as Example 1, except that in step S1, the content of cerium nitrate (calculated as Ce) in the impregnation solution is 1.0% by weight, and the catalyst Cat-3 is obtained, the composition and structure of which are shown in Tables 2-3.

[0055] Example 4 Same as Example 1, except that in step S1, cerium nitrate is replaced with lanthanum nitrate, so that the content of lanthanum nitrate in the impregnation solution, calculated as La, is 0.2% by weight, and catalyst Cat-4 is obtained, the composition and structure of which are shown in Tables 2-3.

[0056] Example 5 Same as Example 1, except that in step (1), 3.45g Al(OH)3 (aluminum source, mass fraction of 99%) and 10.22g KOH (alkali source, mass fraction of 95%) were dissolved in 28.3mL of deionized water and heated to dissolve to obtain aluminum sol; the aluminum sol was added to 58.1g silica sol (silicon source, mass fraction of 25.6%, calculated as SiO2) by stirring and stirring for 0.5h to obtain a mixture gel, the molar ratio of each substance in the mixture gel is K2O:Al2O3:SiO2:H2O=3.6:1:11.2:183; an L-type molecular sieve was obtained, denoted as ZT-2, and its physicochemical properties are shown in Table 1; finally, the catalyst Cat-5 was obtained, and its composition and structure are shown in Tables 2-3.

[0057] Example 6 Same as in Example 1, except that in step (2), the mixture gel was transferred into the reactor and subjected to hydrothermal crystallization treatment at 170°C for 18 hours; an L-type molecular sieve was obtained, denoted as ZT-3, whose physicochemical properties are shown in Table 1; finally, the catalyst Cat-6 was obtained, whose composition and structure are shown in Tables 2-3.

[0058] Comparative Example 1 Same as Example 1, except that steps (1) to (2) are omitted, and the L-type molecular sieve in step S1 is replaced with the same weight of high-purity γ-Al2O3 support (SB powder) prepared by aluminum alkoxide hydrolysis. Chloroplatinic acid, potassium chloride, and hydrochloric acid are prepared into an impregnation solution, so that the content of chloroplatinic acid in the impregnation solution is 0.6% by weight (calculated as Pt), the content of potassium chloride in the impregnation solution is 0.1% by weight (calculated as K), and the content of hydrochloric acid in the impregnation solution is 1.0% by weight (all relative to the weight of alumina). Finally, the comparative catalyst DBCat-1 is obtained, and its composition and structure are shown in Tables 2 to 3.

[0059] Comparative Example 2 A 0.98 mol / L aluminum trichloride solution was prepared, and magnesium sulfate (calculated as 110% of the theoretical sulfur requirement) was added. Under stirring, the aluminum trichloride solution and ammonia solution were slowly added in parallel flow at a flow rate of 2.0 mL / min. Simultaneously, a solution containing a certain amount of titanium sulfate was titrated at a flow rate of 2.0 mL / min. The system temperature was controlled at 70℃, and the pH at 8–10. The mixture was then aged for 0.5 h and dried under vacuum at 50℃ for 60 h. After molding, the mixture was calcined at 700℃ for 6 h under a nitrogen atmosphere to obtain the alumina support Mg-Ti-S / γ-Al₂O₃.

[0060] An appropriate amount of tin tetrachloride was weighed and prepared into an aqueous solution to achieve a Sn content of 1.0 wt% in the catalyst. The catalyst was impregnated with alumina at 70℃ for 2 h, then vacuum dried at 120℃ for 2 h, and calcined at 650℃ for 4 h to obtain the catalyst precursor Mg-Ti-S-Sn / γ-Al2O3. An appropriate amount of chloroplatinic acid was then weighed and prepared into an aqueous solution to achieve a Pt content of 0.6 wt% in the catalyst. The chloroplatinic acid solution was impregnated using an equal-volume impregnation method at 70℃ under vacuum for 6 h, then vacuum dried at 120℃ for 2 h, and calcined at 550℃ for 4 h. The calcined sample was reduced with H2 at 530℃, 0.1 MPa, and a gas / agent volume ratio of 1000 for 4 h to obtain the comparative catalyst DBCat-2, the composition and structure of which are shown in Tables 2-3.

[0061] Comparative Example 3 Same as Example 1, except that steps (1) to (2) are omitted, and the L-type molecular sieve in step S1 is replaced with the same weight of high-purity γ-Al2O3 support (SB powder) prepared by aluminum alkoxide hydrolysis, and finally the comparative catalyst DBCat-3 is obtained, the composition and structure of which are shown in Tables 2 to 3.

[0062] Comparative Example 4 Same as Example 1, except that: ZT-1 obtained in step (2) was subjected to ion exchange with ammonium chloride solution (concentration of 0.2 mol / L) at a solid-liquid mass ratio of 1:10. The ion exchange temperature was 80℃ and the time was 12h until the K ion content was less than 3% by mass; then it was washed with deionized water until neutral, and then dried at 120℃ for 12h and calcined at 500℃ for 8h to obtain hydrogen-type molecular sieve, denoted as H-ZT-1. Its physicochemical properties are shown in Table 1; in step S1, ZT-1 was replaced with the same amount of H-ZT-1 to finally obtain the comparative catalyst DBCat-4. Its composition and structure are shown in Tables 2-3.

[0063] Table 1

[0064] Table 2

[0065] Table 3

[0066] Reaction Example 1 0.5 g of catalyst Cat-1 was loaded onto a microreactor, and the dehydrogenation performance of the catalyst was evaluated using cyclohexane as feedstock. The evaluation conditions were: temperatures of 320℃ and 380℃, pressure of 0.85 MPa, time of 192 h, and feed mass hourly space velocity of 4.0 h⁻¹. -1 The hydrogen / hydrocarbon volume ratio was 1000, and the dehydrogenation product was benzene. Samples were taken for analysis at regular intervals, and the evaluation results are shown in Table 4.

[0067] Reaction Examples 2-6 The reaction conditions were the same as in Example 1, except that the catalysts prepared in Examples 2-6 were used to carry out the dehydrogenation reaction with cyclohexane. The reaction results are shown in Table 4.

[0068] Reaction Comparative Examples 1-4 The reaction conditions were the same as in Example 1, except that the comparative catalysts prepared in Comparative Examples 1-4 were used to carry out the dehydrogenation reaction with cyclohexane. The reaction results are shown in Table 4.

[0069] Table 4

[0070] As shown in Table 4, when the dehydrogenation catalysts prepared in Examples 1-6 were used in the dehydrogenation reaction, the cyclohexane conversion rate reached 94.8%, and the benzene selectivity was greater than 96.5%. The cycloalkane media exhibited fewer ring-opening and cracking reactions during the dehydrogenation process. In contrast, when the comparative catalysts prepared in Comparative Examples 1-4 were used in the dehydrogenation reaction, the cyclohexane conversion rate was lower, the benzene selectivity was poorer, and the cycloalkane media exhibited more ring-opening and cracking reactions during the dehydrogenation process. This indicates that the dehydrogenation catalysts prepared in Examples 1-6 of this disclosure have excellent dehydrogenation performance and effectively prevent ring-opening and cracking reactions in the cycloalkane media during the dehydrogenation process.

[0071] By comparing Example 1 and Example 5, it can be seen that within the molar ratio range of each substance in the mixed gel disclosed herein, the prepared catalyst has a higher relative crystallinity, higher benzene selectivity, and a better inhibitory effect on ring-opening and cracking reactions of cycloalkane media during dehydrogenation.

[0072] By comparing Example 1 and Example 6, it can be seen that within the hydrothermal crystallization conditions disclosed herein, the catalyst prepared has a higher relative crystallinity, a higher cyclohexane conversion rate, a higher benzene selectivity, and a better inhibitory effect on ring-opening and cracking reactions of the cycloalkane medium during dehydrogenation.

[0073] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0074] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0075] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A dehydrogenation catalyst, characterized in that, The dehydrogenation catalyst comprises an L-type molecular sieve and an active component supported on the L-type molecular sieve. The active component comprises group VIII metal elements, rare earth metal elements, and halogens. The content of alkali metal in the dehydrogenation catalyst is 5-20% by weight.

2. The dehydrogenation catalyst according to claim 1, characterized in that, The dehydrogenation catalyst has a silicon-to-aluminum molar ratio of 2.5–3.5, preferably 2.7–3.0; a relative crystallinity of 90–100%, preferably 95–100%; an average particle size of 300–2000 nm, preferably 500–1000 nm; and a specific surface area of ​​80–150 m². 2 / g, preferably 100~120m 2 / g; pore volume is 0.01~0.1cm 3 / g, preferably 0.03~0.06cm 3 / g.

3. The dehydrogenation catalyst according to claim 1, characterized in that, Based on the total weight of the dehydrogenation catalyst, the content of group VIII metal elements in the dehydrogenation catalyst is 0.2~1.5 wt%, preferably 0.5~1.0 wt%; the content of rare earth metal elements is 0.1~3.0 wt%, preferably 0.1~1.0 wt%; and the content of halogens is 0.5~1.5 wt%, preferably 0.5~1.0 wt%.

4. The dehydrogenation catalyst according to claim 1, characterized in that, The weight ratio of Group VIII metal elements to rare earth metal elements in the dehydrogenation catalyst is (0.1~6):1, preferably (0.1~2):1; the weight ratio of Group VIII metal elements to halogens is (0.5~2):1, preferably (1~2):

1.

5. The dehydrogenation catalyst according to claim 1, characterized in that, The group VIII metal element is selected from one or more of Pt, Ru or Rh, preferably Pt; the rare earth metal element is selected from one or more of La, Ce and Pr, preferably La and / or Ce; the halogen is selected from one or more of F, Cl, Br and I, preferably F and / or Cl; The alkali metal is selected from one or more of Na, K, Rb and Cs, preferably Na and / or K.

6. A method for preparing the dehydrogenation catalyst according to any one of claims 1 to 5, characterized in that, The method includes: contacting an impregnation solution containing group VIII metal compounds, rare earth compounds, halides and solvents with an L-type molecular sieve for impregnation treatment; drying, calcining and reducing the impregnated solid material; wherein the alkali metal content in the L-type molecular sieve is 5-20% by weight.

7. The method according to claim 6, characterized in that, Relative to 1g of the L-type molecular sieve, the impregnation solution contains 0.2-1.5% by weight of Group VIII metal compounds (based on metal element), 0.1-3.0% by weight of rare earth compounds (based on metal element), and 0.5-1.5% by weight of halides (based on halogen). Optionally, the Group VIII metal compound is selected from one or more of chloroplatinic acid, tetraammonium dichloroplatinate, ammonium chloroplatinate, platinum trichloride, platinum tetrachloride hydrate, dicarbonyl platinum dichloride, dinitrodiaminoplatinum, and sodium tetranitroplatinate, preferably chloroplatinic acid; The rare earth compound is selected from one or more of cerium nitrate, lanthanum nitrate and praseodymium nitrate, preferably cerium nitrate and / or lanthanum nitrate; The halide is selected from one or more of hydrochloric acid, hydrofluoric acid, potassium chloride, potassium fluoride, sodium chloride and sodium fluoride, preferably potassium chloride and / or potassium fluoride; The alkali metal is selected from one or more of Na, K, Rb and Cs, preferably Na and / or K.

8. The method according to claim 6, characterized in that, The L-shaped molecular sieve has a silica-alumina molar ratio of 2.5–3.5, preferably 2.7–3.0; a relative crystallinity of 90–100%, preferably 95–100%; an average particle size of 300–2000 nm, preferably 500–1000 nm; and a pore volume of 0.01–0.1 cm³. 3 / g, preferably 0.03~0.06cm 3 / g.

9. The method according to claim 6, characterized in that, The impregnation treatment is carried out at a temperature of 20~80℃ for 3~12h; the drying treatment is carried out at a temperature of 70~150℃ for 3~48h; the calcination treatment is carried out at a temperature of 300~550℃ for 2~12h; and the reduction treatment is carried out at a temperature of 400~520℃ for 2~12h.

10. The method according to claim 6, characterized in that, The impregnation process includes: first impregnating the L-type molecular sieve with an impregnation solution containing the rare earth compound, and then impregnating the resulting intermediate with an impregnation solution containing the group VIII metal compound and the halide.

11. The method according to claim 6, characterized in that, The preparation method of the L-type molecular sieve includes: (1) A mixture gel is prepared by mixing silicon source, aluminum source, alkali source and water, wherein the molar ratio of each substance in the mixture gel is M2O:Al2O3:SiO2:H2O=(1.5~3.0):1:(5~9):(80~150), wherein M is selected from one or more of Na, K, Rb and Cs, preferably Na and / or K; (2) The mixture gel is subjected to hydrothermal crystallization treatment, and the product after hydrothermal crystallization is subjected to solid-liquid separation to obtain the L-type molecular sieve; the hydrothermal crystallization temperature is 150~200℃ and the time is 24~96h.

12. The application of the dehydrogenation catalyst according to any one of claims 1 to 5 in the dehydrogenation reaction of liquid organic hydrogen storage medium.

13. The application according to claim 12, characterized in that, The application includes: under dehydrogenation reaction conditions, contacting the dehydrogenation catalyst according to any one of claims 1 to 5 with a liquid organic hydrogen storage medium to carry out a dehydrogenation reaction; The conditions for the dehydrogenation reaction include: a temperature of 320~380℃, a pressure of 0.1~1.5MPa, and a feed mass hourly space velocity of 2.0~8.0h. -1 The hydrogen / hydrocarbon volume ratio is 600~1200.

14. The application according to claim 13, characterized in that, The liquid organic hydrogen storage medium is cyclohexane or methylcyclohexane, more preferably cyclohexane.

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