A dehydrogenation catalyst, a method for preparing the same, and use thereof

Abstract

The application discloses a dehydrogenation catalyst and a preparation method and application thereof, and relates to the technical field of catalyst synthesis. The dehydrogenation catalyst comprises an alumina carrier, a metal oxide and platinum, the metal oxide is in a nano-dispersed form on the surface of the alumina carrier, the platinum is loaded on the surface of the metal oxide, and the metal oxide is at least one selected from magnesium oxide, iron oxide and copper oxide. The dehydrogenation catalyst, the preparation method and the application thereof can reduce the platinum consumption, inhibit carbon deposition and platinum sintering, improve the conversion rate and selectivity when being used for dehydrogenation of perhydrodibenzyltoluene, and reduce the generation of methane by-products.

Description

Technical Field

[0001] This application relates to the field of catalyst synthesis technology, and in particular to a dehydrogenation catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a clean energy carrier, is key to achieving energy transition. However, the safe and efficient storage and transportation of hydrogen is a bottleneck restricting the development of the hydrogen energy industry. Organic liquid hydrogen storage technology, due to its advantages such as high hydrogen storage density, safety and reliability, and reusability, is considered one of the most promising technologies for realizing large-scale hydrogen energy storage and transportation.

[0003] Dibenzyltoluene is a common hydrogen storage carrier, and perhydrodibenzyltoluene has a high hydrogen storage density. However, perhydrodibenzyltoluene has a stable molecular structure and a high dehydrogenation temperature, resulting in problems such as slow hydrogen release rate and easy catalyst deactivation.

[0004] Currently, the dehydrogenation of perhydrodibenzyltoluene mainly uses Pt / Al2O3 catalysts. However, Pt / Al2O3 catalysts have problems such as high precious metal content, easy carbon deposition on the Al2O3 surface, and easy sintering and deactivation of Pt particles at high temperatures. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems. The purpose of this application is to provide a dehydrogenation catalyst, its preparation method and application, to reduce the amount of platinum used, inhibit carbon deposition and platinum sintering, and improve the conversion rate and selectivity when used for the dehydrogenation of perhydrodibenzyltoluene, while reducing the generation of methane byproducts.

[0006] In a first aspect, this application provides a dehydrogenation catalyst comprising: an alumina support, a metal oxide, and platinum, wherein the metal oxide exists in a nano-dispersion form on the surface of the alumina support, and platinum is supported on the surface of the metal oxide, wherein the metal oxide is selected from at least one of magnesium oxide, iron oxide, and copper oxide.

[0007] Secondly, this application also provides a method for preparing a dehydrogenation catalyst, comprising: Under stirring conditions, the pH of the alumina carrier dispersion was adjusted to alkaline, and then a metal salt solution was added. After the reaction, the mixture was filtered and dried to obtain the modified carrier. Under acidic conditions, the platinum precursor solution was contacted with the modified support, and after the reaction was complete, the mixture was filtered and dried to obtain the catalyst precursor. The catalyst precursor is calcined and reduced to obtain the dehydrogenation catalyst.

[0008] Thirdly, this application also provides the application of the dehydrogenation catalyst of the first aspect or the dehydrogenation catalyst prepared by the method of the second aspect in a dehydrogenation reaction, characterized in that the dehydrogenation reaction is a perhydrodibenzyltoluene dehydrogenation reaction.

[0009] Compared with the prior art, in one or more technical solutions provided in this application, firstly, the pH of the alumina support dispersion is adjusted to alkaline, and then a metal salt solution is added. Metal ions undergo in-situ hydrolysis and precipitation on the surface of the alumina support, generating a metal hydroxide precursor that is uniformly attached. After subsequent filtration and drying, a modified support loaded with the metal hydroxide precursor is obtained. Secondly, under acidic conditions, the surface hydroxyl groups of the metal hydroxide precursor on the modified support undergo protonation to form positively charged active sites. These sites can generate strong electrostatic attraction and coordination complexation with the dissociated platinum precursor anions, causing the platinum precursor to selectively adsorb onto the surface of the metal hydroxide precursor rather than binding to the alumina support, thus obtaining a catalyst precursor. This achieves high dispersion and uniform loading of the platinum active component, significantly improving the utilization efficiency of platinum metal and effectively reducing the amount of precious metal platinum used. Finally, the obtained catalyst precursor is calcined. During the calcination process, the metal hydroxide precursor dehydrates and decomposes, transforming into a metal oxide (at least one of magnesium oxide, iron oxide, and copper oxide) that is nano-dispersed on the surface of alumina. Since there are a large number of strongly acidic sites on the surface of alumina support, the introduced metal oxide can effectively modulate the acidic sites on the surface of alumina, neutralize and passivate the strongly acidic sites on the surface of alumina, and inhibit the cracking and coking pathway in the dehydrogenation reaction, thereby reducing the formation of carbon deposits from the source.

[0010] Based on this, the metal oxide in this application can form an interfacial anchoring effect with platinum, effectively inhibiting the surface migration and diffusion of platinum grains, significantly improving the thermal stability of platinum particles, preventing agglomeration and sintering of platinum particles under high-temperature dehydrogenation conditions, and avoiding irreversible loss of active sites. Simultaneously, the metal oxide itself possesses suitable dehydrogenation activity and electronic regulation capabilities, which can optimize the electronic structure of the platinum surface, lower the reaction energy barrier for the dehydrogenation of perhydrodibenzyltoluene, and promote the activation and breaking of carbon-hydrogen bonds, thereby improving the dehydrogenation reaction rate and conversion. Therefore, this application achieves high conversion and high selectivity with low platinum loading during the dehydrogenation reaction, reducing the generation of methane byproducts. Attached Figure Description

[0011] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating the preparation process of the dehydrogenation catalyst provided in the embodiments of this application. Detailed Implementation

[0012] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0013] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise expressly specified. "Several" means one or more, unless otherwise expressly specified.

[0014] In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0015] It should be noted that, in this application, the terms "exemplary" or "for example" are used to indicate that something is being described as an example, illustration, or illustration. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0016] In this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0017] Hydrogen energy, as a potential alternative fuel and energy carrier, has garnered widespread attention globally. While significant progress has been made in the development of the hydrogen energy industry both domestically and internationally, the current lack of safety and efficiency in hydrogen storage and transportation technologies has led to overcapacity at the upstream end of the industry chain and insufficient supply at the downstream end, severely hindering the overall development of the hydrogen energy industry. Therefore, storing hydrogen in a low-cost and safe manner is a critical issue that urgently needs to be addressed. Organic liquid hydrogen storage technology, due to its advantages such as high hydrogen storage capacity, recyclability, cleanliness, low cost, and high safety, is considered one of the most promising technologies for achieving large-scale hydrogen energy storage and transportation in the future.

[0018] Dibenzyltoluene, as a common hydrogen storage carrier, has shown promising application prospects. Germany uses dibenzyltoluene as a hydrogen storage carrier, achieving a hydrogen supply capacity of 500 kg / d. However, its fully hydrogenated product (perhydrodibenzyltoluene) has a more stable molecular structure, a higher dehydrogenation temperature (270℃~320℃), and a slower hydrogen release rate, limiting the large-scale application of organic liquid hydrogen storage technology. Therefore, developing a high-temperature resistant, low-cost perhydrodibenzyltoluene dehydrogenation catalyst is crucial.

[0019] Currently, the dehydrogenation of perhydrodibenzyltoluene mainly employs Pt / Al2O3 catalysts. The noble metal Pt exhibits excellent activation ability for CH bonds and is non-toxic and environmentally friendly, while the Al2O3 support offers advantages such as good thermal stability, large specific surface area, suitable mechanical strength, high thermal conductivity, and competitive price, making it widely used as a catalyst support. However, the Al2O3 support can shift the reaction towards a cracking pathway, generating light byproducts such as methane and ethane. Pt-based catalysts not only require a high amount of noble metal but also generally face the problem of decreased activity due to metal particle sintering and coke deposition during high-temperature reactions.

[0020] To address the aforementioned issues, this application provides a dehydrogenation catalyst, its preparation method, and its application. By introducing a metal oxide under alkaline conditions to modulate the acidity of the Al2O3 support and by selectively confining platinum under acidic conditions, the amount of platinum used is reduced while effectively inhibiting carbon deposition and platinum particle sintering, thus achieving high activity and ultra-long-term stability in the dehydrogenation reaction of perhydrodibenzyltoluene.

[0021] This application provides a dehydrogenation catalyst comprising: an alumina support, a metal oxide, and platinum. The metal oxide exists in a nano-dispersion form on the surface of the alumina support, and platinum is supported on the surface of the metal oxide. The metal oxide is selected from at least one of magnesium oxide, iron oxide, and copper oxide.

[0022] The dehydrogenation catalyst described in this application uses alumina as a support, with at least one metal oxide selected from magnesium oxide, iron oxide, and copper oxide uniformly distributed in a nano-dispersion morphology on the surface of the alumina support. This allows the metal oxides to effectively modulate the strong acid sites on the alumina support surface, suppressing cracking side reactions and reducing carbon deposition caused by coke at its source. Simultaneously, platinum is selectively loaded onto the metal oxide surface rather than directly attached to the alumina support. The nano-dispersed metal oxides have a large specific surface area and high dispersion, providing abundant and uniform attachment sites for platinum. Platinum loaded onto the metal oxide surface utilizes the interfacial interaction between the metal oxide and platinum to constrain platinum grain growth and aggregation, maintaining a highly dispersed state of the platinum active component and fully exposing the active sites, significantly improving the utilization efficiency of platinum metal and effectively reducing the amount of precious metal platinum used. Therefore, this application can achieve high conversion and high selectivity with low platinum loading during the dehydrogenation reaction, reducing the generation of methane byproducts.

[0023] Meanwhile, the aforementioned alumina support can provide a stable framework and support with a high specific surface area, enabling the metal oxide, platinum and alumina to form a regular microstructure match, thereby giving full play to the synergistic catalytic effect among the components and providing a good structural basis and active environment for the dehydrogenation reaction.

[0024] In a preferred embodiment, the aforementioned metal oxide is magnesium oxide. Compared to iron oxide and copper oxide, magnesium oxide has moderate alkalinity, stronger thermal stability, and better compatibility with alumina supports. It can efficiently passivate strong acid sites on the support, significantly inhibit carbon deposition during the dehydrogenation process, and form a stronger interfacial anchoring and electronic regulation effect with platinum, effectively inhibiting the high-temperature sintering and agglomeration of platinum particles, so that the catalyst still has excellent dehydrogenation conversion rate under low platinum loading conditions.

[0025] In one feasible embodiment, the total weight percentage of the aforementioned dehydrogenation catalyst is 100%, wherein the platinum content in the dehydrogenation catalyst is 0.3% to 0.8% by mass, and the metal oxide content is 0.5% to 5% by mass. This application, by limiting the ratio of platinum content in the catalyst to 0.3% to 0.8% and the metal oxide content to 0.5% to 5% by mass, achieves optimal nano-dispersion of the metal oxide on the alumina support surface while ensuring low platinum doping. This effectively modulates the surface properties of the support, providing suitable interfacial anchoring points for platinum, without causing pore blockage or specific surface area loss. Simultaneously, the platinum loading is within the optimal low-dosage range, improving platinum atom utilization. This significantly reduces catalyst preparation costs while maintaining smaller grain size and higher dispersion of platinum, thus enhancing the catalyst's dehydrogenation activity and structural stability.

[0026] In a preferred embodiment, the platinum content in the above-mentioned dehydrogenation catalyst is 0.4% to 0.6% by mass, and the metal oxide content is 1% to 3% by mass.

[0027] In one feasible manner, embodiments of this application provide a method for preparing a dehydrogenation catalyst. Figure 1 A flowchart illustrating a method for preparing a dehydrogenation catalyst according to an embodiment of this application is shown. Figure 1 As shown, the preparation method of the dehydrogenation catalyst in this application includes: Step 101: Under stirring conditions, adjust the pH of the alumina carrier dispersion to alkaline, then add the metal salt solution, and after the reaction, filter and dry to obtain the modified carrier.

[0028] For example, the above-mentioned method of adjusting the pH of the alumina carrier dispersion to alkaline under stirring conditions, then adding a metal salt solution, reacting, filtering, and drying to obtain the modified carrier specifically includes: First, adjusting the pH of the alumina carrier dispersion to 9-10 using an alkaline substance under stirring conditions to obtain an alkaline alumina carrier dispersion. Next, under stirring conditions, slowly adding a metal salt solution to the alkaline alumina carrier dispersion, reacting fully, and then filtering, washing, and drying to obtain the modified carrier. The alkaline substance can be selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonia water, preferably ammonia water.

[0029] For example, the pH of the alumina carrier dispersion can be adjusted to 9-10 using ammonia water, and the mixture can be stirred continuously for 0.5-2 hours to obtain a uniform and stable alkaline alumina carrier dispersion. Under vigorous stirring conditions of 600-800 rpm, a metal salt solution is slowly added to the alkaline alumina carrier dispersion, with the addition completed within 30-35 minutes. After the addition is complete, the mixture is stirred at a constant temperature for 1-1.5 hours to allow the reaction to proceed. After the reaction is complete, the mixture is filtered and washed multiple times with deionized water to remove unreacted metal ions and residual ammonium salt impurities from the surface. The resulting solid filter cake is then dried overnight at 60-65°C to obtain a modified carrier with a uniformly loaded metal hydroxide precursor. The mass concentration of the ammonia water used in this process is 10%-25%.

[0030] This application employs ammonia water to adjust the pH of the alumina support dispersion to a weakly alkaline range of 9-10 under stirring conditions. Then, a metal salt solution is slowly added dropwise to initiate the reaction. On one hand, the constant weakly alkaline system allows metal salt ions to slowly hydrolyze and precipitate in situ on the alumina support surface, generating metal hydroxide precursors. This avoids the problems of particle agglomeration and uneven particle size caused by the instantaneous rapid precipitation of metal ions under strong alkaline conditions. On the other hand, maintaining stirring throughout the process ensures that the alumina support is fully dispersed and free from agglomeration, allowing metal ions to fully contact and directionally deposit with the hydroxyl groups on the alumina surface, achieving uniform modification of the alumina surface sites. Furthermore, the method of adjusting the alkali first and then slowly adding the metal salt ensures a mild and controllable reaction process. After subsequent filtration, washing, and drying, the resulting modified support exhibits a regular morphology and uniform component distribution. The entire reaction is conducted under mild conditions, without damaging the original pore structure and framework integrity of the alumina support.

[0031] Building upon this foundation, this step modifies the alumina support, effectively neutralizing and weakening the strongly acidic sites on its surface, thus reducing the overall surface acid strength. The strong acidity of the alumina support is a major contributing factor to hydrocarbon cracking side reactions during dehydrogenation. Modification inhibits unnecessary cracking side reactions at their source, significantly reducing the formation of light byproducts such as methane. Simultaneously, it weakens the carbon deposition-inducing effect of acidity, slowing down the deposition rate of coke on the catalyst surface during the reaction. This prevents excessive carbon buildup from covering active sites and clogging support pores, ensuring unobstructed pores and effective exposure of active sites. Consequently, it improves the catalyst's resistance to carbon deposition, allowing the catalytic reaction to proceed steadily and continuously, extending the catalyst's lifespan and long-term operational stability.

[0032] The aforementioned metal salt solution is selected from at least one of magnesium salt solution, iron salt solution, and copper salt solution. The magnesium salt solution can be magnesium nitrate solution, the iron salt solution can be ferric nitrate solution, and the copper salt solution can be copper nitrate solution. The preferred metal salt solution is magnesium nitrate solution. Magnesium nitrate, ferric nitrate, or copper nitrate are selected as the metal salt precursor. The anion is nitrate ion, which is easily decomposed and removed during high-temperature subsequent treatment and will not remain on the surface of the modified carrier to cause pore blockage or enrichment of acidic impurities.

[0033] The mass concentration of the aforementioned metal salt solution is 0.5% to 5%, preferably 1% to 3%. This ensures sufficient metal ions, allowing for the formation of a uniform and complete nano-metal oxide modified layer on the alumina support surface after subsequent calcination. This effectively passivates strong acid sites on the support and provides sufficient platinum anchoring points. Simultaneously, it avoids excessive concentration leading to localized enrichment of metal ions, preventing grain agglomeration and blockage of support pores. The concentration range of this application allows for a moderate rate of metal ion hydrolysis and nucleation, resulting in good grain dispersion. This balances the integrity of the support pore structure, the modification effect, and the subsequent loading and dispersion effect of the platinum component.

[0034] The above-mentioned metal salt solution with a mass concentration of 0.5wt%~5% was slowly added to the alkaline alumina carrier dispersion. The temperature of the system was controlled at room temperature of 25℃~35℃ throughout the entire dropping and constant temperature stirring process. The temperature was mild and controllable, avoiding abnormal growth of metal hydroxide precursor grains caused by excessive temperature, and also preventing excessively low temperature from causing slow hydrolysis nucleation rate and uneven loading.

[0035] Step 102: Under acidic conditions, the platinum precursor solution is contacted with the modified support, and after sufficient reaction, it is filtered and dried to obtain the catalyst precursor.

[0036] For example, the above-mentioned process of contacting the platinum precursor solution with the modified support under acidic conditions, reacting fully, filtering and drying to obtain the catalyst precursor specifically includes: first, uniformly dispersing the modified support in water to obtain a modified support dispersion; then, adjusting the pH of the modified support dispersion to 3-4 using an acidic substance to obtain an acidic modified support dispersion; next, adding the platinum precursor solution to the acidic modified support dispersion, stirring to allow for a full reaction, and then filtering, washing, and drying to obtain the catalyst precursor. The platinum precursor can be chloroplatinic acid.

[0037] In some examples, the acidic substance is dilute hydrochloric acid, with a mass concentration of 5% to 10%. Dilute hydrochloric acid can gently adjust the system pH to maintain a stable level of 3 to 4, offering strong acidity control, avoiding excessive corrosion of the modified carrier structure, and preventing the introduction of difficult-to-remove impurity ions. The platinum precursor selected is chloroplatinic acid, which has good water solubility and a high degree of dissociation. In weakly acidic systems, it readily forms platinum complex anions, which can be adsorbed onto the surface of the metal hydroxide precursor via electrostatic interactions, improving the selective loading and uniform dispersion of platinum.

[0038] For example, firstly, the modified support obtained in step 101 is dispersed in deionized water and sonicated for 30 minutes to ensure thorough and uniform dispersion, resulting in a modified support dispersion. Then, the pH of the modified support dispersion is adjusted to 3 using hydrochloric acid to obtain an acidic modified support dispersion. Next, a chloroplatinic acid solution is added to the acidic modified support dispersion, and the mixture is stirred continuously for 2 hours. Under this acidic environment, the active sites abundant on the surface of the modified support (such as surface hydroxyl groups and metal defect sites) undergo protonation, forming positively charged adsorption centers that can react with [PtCl6] dissociated from chloroplatinic acid. 2- Anions form a strong electrostatic adsorption effect, while the alumina support, although also positively charged due to protonation at this pH, does not exhibit strong adsorption for [PtCl6]. 2-The adsorption capacity of the product is much weaker than that of the active components introduced on the surface of the modified support, thereby achieving selective adsorption of the chloroplatinic acid precursor on the active sites on the surface of the modified support. After the reaction, the filter cake is repeatedly washed with deionized water until no chloride ions are detected in the washing liquid (no white precipitate is detected by silver nitrate solution) to remove unadsorbed free chloroplatinic acid and impurity ions. Then the filter cake is placed in an oven at 100~110℃ and dried for 8~12h to obtain the catalyst precursor.

[0039] The mass concentration of the chloroplatinic acid solution is 0.3% to 0.8%, preferably 0.4% to 0.6%. This concentration range ensures that a sufficient amount of platinum precursor is uniformly adsorbed on the surface of the metal hydroxide precursor to achieve the target loading, while avoiding excessive concentration that could lead to localized platinum ion enrichment and particle agglomeration. Simultaneously, a moderate concentration allows for a gradual adsorption rate of platinum complex anions, further improving platinum dispersion and active site utilization, and also prevents insufficient loading and decreased catalytic activity due to excessively low concentration.

[0040] This step first involves fully dispersing the modified support in water to eliminate particle agglomeration, ensuring thorough and uniform contact between the support and the platinum precursor. Then, the pH of the system is adjusted to a weakly acidic environment of 3-4 using an acidic substance. Utilizing the surface charge difference between the metal hydroxide and alumina on the modified support surface at this acidity, the platinum precursor selectively adsorbs onto the metal hydroxide surface, making it less likely to adhere to the alumina support. This achieves both targeted anchoring and high dispersion of platinum, preventing disordered agglomeration and accumulation. Furthermore, the acid-base interface strengthens the adsorption and binding force between the platinum precursor and the metal hydroxide, effectively reducing the possibility of platinum particle migration, agglomeration, and growth during subsequent processing. This, in turn, effectively inhibits the occurrence of cracking side reactions during catalysis, reducing the generation of light byproducts such as methane. Simultaneously, it weakens the carbon deposition-induced effect caused by the strongly acidic sites on the alumina support, delaying carbon deposition and pore blockage on the catalyst surface, alleviating the problem of active site deactivation due to coverage, and improving the structural stability and operational life of the catalyst in long-cycle dehydrogenation reactions.

[0041] Step 103: The catalyst precursor is calcined and reduced to obtain the dehydrogenation catalyst.

[0042] For example, the above-described calcination and reduction of the catalyst precursor to obtain a dehydrogenation catalyst specifically includes: first, calcining the catalyst precursor at 300°C to 400°C for 2 to 5 hours in an air atmosphere to obtain a calcined product. Then, reducing the calcined product at 400°C to 600°C for 1 to 4 hours in a hydrogen atmosphere to obtain the dehydrogenation catalyst.

[0043] For example, the dried catalyst precursor is placed in a muffle furnace and calcined at a constant temperature of 300℃~400℃ for 2h~5h in air atmosphere to remove residual moisture, organic matter, and chloride ions, causing the residual chloroplatinic acid to decompose into platinum oxide. The calcined product is then transferred to a tube furnace and reduced at a constant temperature of 400℃~600℃ for 1h~4h in pure hydrogen atmosphere to reduce platinum oxide to the active component of metallic platinum, ultimately obtaining the perhydrodibenzyltoluene dehydrogenation catalyst.

[0044] This step begins with medium-temperature calcination at 300℃~400℃ in air, which allows for the complete dehydration and decomposition of the metal hydroxides on the modified support surface, transforming them into nano-dispersed magnesium oxide, iron oxide, or copper oxide metal oxides. Simultaneously, it fully decomposes the platinum precursor to remove chloride ions, organic matter, and residual moisture, solidifying the support's pore structure and further stabilizing the surface modification sites. Next, a reduction treatment at 400℃~600℃ in a hydrogen atmosphere reduces platinum oxide to highly active platinum particles. The in-situ formed metal oxides establish a strong metal-support interaction with the platinum components, effectively anchoring the platinum grains and inhibiting their migration, agglomeration, and sintering growth during the high-temperature reaction. This process preserves the complete pore structure and suitable surface acidity of the alumina while achieving a highly dispersed and stable loading of the active metal.

[0045] The above-mentioned calcination and reduction temperature range is mild and controllable, which can ensure that the platinum component is fully reduced and the grain size is small and uniform, without damaging the pore structure of the support and the morphology of the surface metal oxide modified layer. This effectively maintains the high dispersion of the active component and endows the catalyst with excellent dehydrogenation activity, thermal stability and anti-sintering performance.

[0046] For example, the preferred calcination temperature in the air atmosphere is 320℃~360℃, and the preferred calcination time is 2h~3h. The preferred reduction temperature in the hydrogen atmosphere is 450℃~500℃, and the preferred reduction time is 1.5h~2.5h.

[0047] In an alternative embodiment, before contacting the metal salt solution with the alumina support under alkaline conditions, the method further includes: firstly, pre-calcining boehmite at 400℃~600℃ for 3 to 4 hours to obtain the alumina support. Subsequently, the alumina support is dispersed in deionized water and sonicated for 30 minutes to obtain a uniform and stable alumina support dispersion.

[0048] This application first pre-calcines boehmite to remove the water of crystallization and volatile impurities from the precursor, transforming it into a γ-alumina support with a stable crystalline phase and well-developed pore structure. Simultaneously, it can regulate the specific surface area, pore volume, and pore size distribution of the alumina support, improving its skeletal strength and thermal stability, and preventing pore collapse and structural collapse during subsequent loading of metal hydroxide precursors, platinum components, and high-temperature calcination and reduction. Subsequently, the obtained γ-alumina support is ultrasonically dispersed. Utilizing the cavitation effect and mechanical vibration of ultrasound, the agglomeration and adhesion between support particles are broken down, allowing alumina particles to be fully dispersed in deionized water, forming a uniformly concentrated and evenly dispersed alumina support dispersion. The alumina support obtained through the above treatment has moderate surface acidity and alkalinity and abundant surface defect sites, which is conducive to the uniform nucleation and loading of metal ions and provides sufficient anchoring points for subsequent platinum active components.

[0049] The preferred calcination temperature for the above-mentioned boehmite is 450℃~550℃, and the preferred calcination time is 3h.

[0050] In one feasible manner, before pre-calcining the pseudoboehmite at 400℃~600℃ for 3 to 4 hours to obtain the alumina carrier, the preparation method further includes: pre-treating the industrial pseudoboehmite.

[0051] The above pretreatment includes conventional pretreatment such as cleaning, drying and grinding. Specifically, it includes: first, adding industrial boehmite to deionized water, heating to above 50°C and stirring to clean it, removing residual soluble alkali metal impurities, inorganic salts and dust impurities from the raw material, and then filtering, drying, grinding and passing through a mesh sieve to obtain boehmite powder with uniform particle size and low impurity content.

[0052] In one feasible embodiment, this application also provides the application of a dehydrogenation catalyst in a dehydrogenation reaction, which is a perhydrodibenzyltoluene dehydrogenation reaction.

[0053] For example, the process conditions for the above-mentioned dehydrogenation reaction of perhydrodibenzyltoluene include: First, screening a dehydrogenation catalyst with a particle size of 20-40 mesh and loading it into a fixed-bed reactor. Then, the reactor is heated to a reaction temperature of 320℃-350℃, hydrogen is continuously introduced, the hydrogen-to-oil ratio is controlled at 1:1, and the hydrogen flow rate is stably maintained at 8.0 mL / min. After the reaction system has been kept at a constant temperature and flow rate for 30 min, perhydrodibenzyltoluene feedstock is introduced for reaction, and the volume hourly space velocity is controlled at 0.5-3 h⁻¹. -1 Samples were taken every 2 hours to screen and determine the optimal reaction conditions. Finally, the hydrogen production volume was measured using a bubble flow meter and the feed conversion rate was calculated. The purity of the hydrogen gas and the composition of the organic components were analyzed using a gas chromatograph equipped with a flame ionization detector.

[0054] As can be seen from the above, the dehydrogenation catalyst, its preparation method, and its application in this application, through support pretreatment, metal oxide modification, selective loading of platinum active components, and calcination reduction, allow metal hydroxides to be uniformly dispersed and attached to the surface of an alumina support under weakly alkaline conditions. This rationally modulates the surface acidity of the alumina support and establishes uniform active anchoring sites. Furthermore, by utilizing the surface charge difference under weakly acidic conditions, platinum components are selectively adsorbed onto the metal hydroxide surface, effectively inhibiting the migration and aggregation of active metals and grain growth. Simultaneously, metal modification weakens the strong acidity of the support surface, fundamentally inhibiting the occurrence of cracking side reactions, reducing the generation of light byproducts, alleviating carbon deposition problems during the reaction process, and preventing the active sites from being covered and the support channels from being blocked, significantly improving the reaction stability and service life of the catalyst. The overall preparation process is mild, simple, and controllable, making it easy to scale up industrially. When applied to the dehydrogenation reaction of perhydrodibenzyltoluene, the obtained catalyst exhibits good dehydrogenation conversion effect, strong anti-carbon deposition ability, and excellent long-term operating performance, demonstrating good practical value and promising prospects in the field of organic liquid hydrogen storage, dehydrogenation, and hydrogen production.

[0055] To verify the effectiveness of the dehydrogenation catalyst provided in the embodiments of this application, this application uses a comparison of embodiments and comparative examples for demonstration.

[0056] Example 1 Example 1 of this application provides a method for preparing a platinum-supported perhydrodibenzyltoluene dehydrogenation catalyst, comprising the following steps: Step 1, Modified Carrier: Industrial pseudoboehmite was pretreated, and then calcined at 600℃ for 4 hours in air at a heating rate of 3℃ / min. The calcined alumina carrier was dispersed in water and sonicated for 30 minutes. The pH of the system was adjusted to 9-10 with ammonia and stirred continuously for 2 hours. Under vigorous stirring, a 3wt% magnesium nitrate solution was slowly added. After the addition was completed within 30 minutes, the mixture was kept warm and stirred for 1 hour. After filtration and drying at 60℃ overnight, the modified carrier was obtained.

[0057] The second step is the catalyst precursor: the dried modified support is redispersed in water, sonicated for 30 min, the pH of the system is adjusted to 3 with hydrochloric acid, a 0.5 wt% chloroplatinic acid solution is added, the mixture is stirred at a constant temperature for 2 h, filtered, and dried overnight at 60 °C to obtain the catalyst precursor.

[0058] The third step is the dehydrogenation catalyst: the obtained catalyst precursor is calcined in air at 300°C for 4 hours, and then reduced in hydrogen at 500°C for 2 hours to obtain a perhydrodibenzyltoluene dehydrogenation catalyst with platinum nanoparticles supported on magnesium-modified alumina.

[0059] Example 2 Example 2 of this application provides a method for preparing a platinum-supported perhydrodibenzyltoluene dehydrogenation catalyst on an iron-modified alumina support, comprising the following steps: Step 1, Modified Carrier: Industrial pseudoboehmite was pretreated, and then calcined at 600℃ for 4 hours in air at a heating rate of 3℃ / min. The calcined alumina carrier was dispersed in water and sonicated for 30 minutes. The pH of the system was adjusted to 9-10 with ammonia and stirred continuously for 2 hours. Under vigorous stirring, a 3wt% ferric nitrate solution was slowly added. After the addition was completed within 30 minutes, the mixture was kept warm and stirred for 1 hour. After filtration and drying at 60℃ overnight, the modified carrier was obtained.

[0060] The second step is the catalyst precursor: the dried modified support is redispersed in water, sonicated for 30 min, the pH of the system is adjusted to 3 with hydrochloric acid, a 0.5 wt% chloroplatinic acid solution is added, the mixture is stirred at a constant temperature for 2 h, filtered, and dried overnight at 60 °C to obtain the catalyst precursor.

[0061] The third step is the dehydrogenation catalyst: the obtained catalyst precursor is calcined in air at 300°C for 4 hours, and then reduced in hydrogen at 500°C for 2 hours to obtain a perhydrodibenzyltoluene dehydrogenation catalyst with iron-modified alumina support and platinum nanoparticles.

[0062] Example 3 Example 3 of this application provides a method for preparing a platinum-supported perhydrodibenzyltoluene dehydrogenation catalyst on a copper-modified alumina support, comprising the following steps: Step 1, Modified Carrier: Industrial pseudoboehmite was pretreated, then calcined in air at a heating rate of 3℃ / min to 600℃ for 4h; the calcined alumina carrier was dispersed in water and sonicated for 30min, the pH of the system was adjusted to 9-10 with ammonia, and stirred for 2h; a 3wt% copper nitrate solution was added to the solution under vigorous stirring, and stirring was continued for 1h after the addition was completed within 30min, filtered, and dried overnight at 60℃ to obtain the modified carrier.

[0063] The second step is the catalyst precursor: the dried modified support is redispersed in water, sonicated for 30 min, the pH of the system is adjusted to 3 with hydrochloric acid, 0.5 wt% chloroplatinic acid solution is added, stirred for 2 h, filtered, and dried overnight at 60 °C to obtain the catalyst precursor.

[0064] The third step is the dehydrogenation catalyst: the obtained catalyst precursor is calcined at 300°C for 4 hours in air atmosphere, and then reduced at 500°C for 2 hours in hydrogen atmosphere to obtain a perhydrodibenzyltoluene dehydrogenation catalyst with platinum nanoparticles supported on a copper-modified alumina support.

[0065] Comparative Example 1 Comparative Example 1 of this application provides a method for preparing a platinum-supported perhydrodibenzyltoluene dehydrogenation catalyst with calcium-modified alumina. The difference from Example 1 is that calcium nitrate is used instead of magnesium nitrate for support modification, while the other preparation process conditions are the same as in Example 1.

[0066] Comparative Example 2 Comparative Example 2 of this application provides a method for preparing a platinum-supported perhydrodibenzyltoluene dehydrogenation catalyst with calcium-modified alumina. The preparation process and parameters are consistent with those of Example 1, except that zinc nitrate is used instead of magnesium nitrate as the modified precursor.

[0067] Comparative Example 3 Comparative Example 3 of this application provides a method for preparing a perhydrodibenzyltoluene dehydrogenation catalyst with platinum directly supported on an alumina support. Compared with Example 1, Comparative Example 3 omits the metal oxide modification step and directly loads the platinum component on the surface of the unmodified alumina support. The remaining calcination, loading, and reduction process conditions are consistent with those of Example 1.

[0068] In addition, samples of the dehydrogenation catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3 of this application were taken, and catalyst particles with a size of 20-40 mesh were sieved. 4 mL of each catalyst was then loaded into a fixed-bed reactor. After heating the reactor to a reaction temperature of 320°C, hydrogen gas was introduced, controlling the hydrogen-to-oil ratio at 1:1 and maintaining the hydrogen gas flow rate at 8.0 mL / min. Feeding began after the reaction system had stabilized for 30 min, with a volume hourly space velocity (VHSV) set at 0.5 h⁻¹. -1 After 5 hours of continuous reaction, the hydrogen production volume was measured using a bubble flow meter and the dehydrogenation conversion rate of the feedstock was calculated. Simultaneously, the purity of the product hydrogen was analyzed using a gas chromatograph equipped with a flame ionization detector. The reaction performance results for each group are shown in Table 1. Table 1: Test data of dehydrogenation catalyst

[0069] As can be seen from the table above, the dehydrogenation catalysts prepared in Examples 1 to 3 of this application are significantly better than those in Comparative Examples 1 to 3 in terms of conversion rate, selectivity and methane suppression.

[0070] Specifically, the catalyst in Example 1, using a magnesium-modified alumina support to support platinum, exhibited the best performance, with a conversion rate of 92.20%, a selectivity of 94.21%, and a methane content of only 30 ppm. Examples 2 (iron-modified) and 3 (copper-modified) also demonstrated good catalytic performance, with conversion rates of 91.37% and 88.49%, respectively, both higher than the 83.23% of Comparative Example 3 (unmodified).

[0071] In comparison, the conversion rates of Comparative Example 1 (calcium modified) and Comparative Example 2 (zinc modified) were 73.59% and 73.23%, respectively, significantly lower than those of the embodiments in this application, indicating that the modification effects of magnesium, iron, and copper are superior to those of calcium and zinc. Although the conversion rate of Comparative Example 3 (unmodified) was slightly higher than that of Comparative Examples 1 and 2, its methane content was as high as 180 ppm, far exceeding that of the embodiments in this application, indicating that the acidity of the unmodified alumina carrier surface led to severe cracking side reactions.

[0072] The above results indicate that this application can effectively reduce the acidity of the support surface, suppress cracking side reactions, and reduce the generation of carbon deposits and methane by first precipitating metal hydroxide precursors in situ on the surface of an alumina support under alkaline conditions and then selectively loading platinum under acidic conditions. At the same time, it can achieve efficient dispersion and confined loading of platinum, and obtain excellent dehydrogenation activity and selectivity with low platinum content.

[0073] The above description is merely a specific embodiment of this application. Obviously, various modifications and combinations can be made without departing from the spirit and scope of this application. Accordingly, this specification and accompanying drawings are merely exemplary illustrations of this application as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and modifications of this application fall within the scope of the claims of this application and their equivalents, the intent of this application includes these modifications and modifications. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A dehydrogenation catalyst, characterized in that, include: The alumina carrier, a metal oxide, and platinum are provided, wherein the metal oxide exists in a nano-dispersion form on the surface of the alumina carrier, and the platinum is loaded on the surface of the metal oxide, wherein the metal oxide is selected from at least one of magnesium oxide, iron oxide, and copper oxide.

2. The dehydrogenation catalyst according to claim 1, characterized in that, Based on the total weight percentage of the dehydrogenation catalyst being 100%, the platinum content in the dehydrogenation catalyst is 0.3% to 0.8% by mass, and the metal oxide content is 0.5% to 5% by mass.

3. A method for preparing a dehydrogenation catalyst, characterized in that, include: Under stirring conditions, the pH of the alumina carrier dispersion was adjusted to alkaline, and then a metal salt solution was added. After the reaction, the mixture was filtered and dried to obtain the modified carrier. Under acidic conditions, the platinum precursor solution was contacted with the modified support, and after the reaction was complete, the mixture was filtered and dried to obtain the catalyst precursor. The catalyst precursor is calcined and reduced to obtain the dehydrogenation catalyst.

4. The method for preparing the dehydrogenation catalyst according to claim 3, characterized in that, The metal salt solution includes at least one of magnesium salt solution, iron salt solution and copper salt solution.

5. The method for preparing the dehydrogenation catalyst according to claim 3, characterized in that, Under stirring conditions, the pH of the alumina support dispersion is adjusted to alkaline, then a metal salt solution is added. After the reaction, the mixture is filtered and dried to obtain the modified support, comprising: Under stirring conditions, the pH of the alumina carrier dispersion is adjusted to 9-10 using an alkaline substance to obtain an alkaline alumina carrier dispersion. The metal salt solution is slowly added to the alkaline alumina carrier dispersion. After the reaction is complete, the mixture is filtered, washed, and dried to obtain the modified carrier.

6. The method for preparing the dehydrogenation catalyst according to claim 3, characterized in that, Under acidic conditions, the platinum precursor solution is contacted with the modified support, and after sufficient reaction, the mixture is filtered and dried to obtain the catalyst precursor, comprising: The modified carrier is uniformly dispersed in water to obtain a modified carrier dispersion. The pH of the modified carrier dispersion was adjusted to 3-4 using an acidic substance to obtain an acidic modified carrier dispersion. The platinum precursor solution was added to the acid-modified support dispersion, and after sufficient reaction, the mixture was filtered, washed, and dried to obtain the catalyst precursor.

7. The method for preparing the dehydrogenation catalyst according to claim 5, characterized in that, Before adjusting the pH of the alumina carrier dispersion to 9-10 using an alkaline substance under stirring conditions to obtain an alkaline alumina carrier dispersion, the method further includes: The pseudoboehmite was pre-calcined at 400℃~600℃ for 3 to 4 hours to obtain an alumina support; The alumina carrier was dispersed in water and subjected to ultrasonic treatment to obtain an alumina carrier dispersion.

8. The method for preparing the dehydrogenation catalyst according to claim 3, characterized in that, The process of calcining and reducing the catalyst precursor to obtain the dehydrogenation catalyst includes: The catalyst precursor was calcined at 300°C to 400°C for 2 to 5 hours in an air atmosphere to obtain the calcined product. The calcined product was reduced at 400°C to 600°C for 1 to 4 hours under a hydrogen atmosphere to obtain the dehydrogenation catalyst.

9. The application of a dehydrogenation catalyst according to any one of claims 1-2 or a dehydrogenation catalyst prepared by the method according to any one of claims 3-8 in a dehydrogenation reaction, characterized in that, The dehydrogenation reaction is a perhydrodibenzyltoluene dehydrogenation reaction.

10. The application according to claim 9, characterized in that, The conditions for the dehydrogenation reaction are: reaction temperature 320℃~350℃, volume hourly space velocity 0.5 h⁻¹. -1 ~3 h -1 The hydrogen-to-oil volume ratio is 0.5:1 to 2:1.

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