Catalyst for dehydrogenation of organic liquid hydrogen storage material and preparation method thereof

Abstract

The invention discloses a catalyst for dehydrogenation of an organic liquid hydrogen storage material and a preparation method of the catalyst, and relates to the technical field of dehydrogenation catalysts. The catalyst for dehydrogenation of the organic liquid hydrogen storage material is prepared from the following components in percentage by mass: 0.5 to 5 percent of platinum zirconium oxide, 1 to 7 percent of transition metal, 0.5 to 5 percent of lanthanide metal and the balance of zirconium diboride whisker-graphene composite carrier, the transition metal comprises at least one of cobalt and nickel; the lanthanide metal comprises at least two of lanthanum, cerium, neodymium, yttrium, scandium and europium. Through the synergistic effect of all the components, the catalyst has high catalytic stability in the dehydrogenation reaction of the organic liquid hydrogen storage material, can still keep a good catalytic effect in multiple reactions, and is basically not prone to inactivation.

Description

Technical Field

[0001] The present application relates to the technical field of dehydrogenation catalysts, and particularly relates to a catalyst for dehydrogenation of organic liquid hydrogen storage materials and a preparation method thereof. Background Art

[0002] Liquid Organic Hydrogen Carrier (LOHC) technology is a hydrogen storage and transportation technology. It "encapsulates" hydrogen through chemical reactions in liquid organic compounds to achieve high-density storage, transportation, and release of hydrogen. Usually, methylcyclohexane, cyclohexane, tetralin, decalin, perhydro-N-ethylcarbazole, perhydrocarbazole, etc. are used as organic liquid hydrogen storage materials, and hydrogen energy storage is achieved through catalytic hydrogenation and dehydrogenation reversible reactions. This process is reversible, and the reactants and products can be recycled, with a relatively high hydrogen storage capacity. The hydrogenation process of organic liquid hydrogen storage materials is relatively simple and the technology is relatively mature, but the dehydrogenation process is a strongly endothermic and highly reversible reaction. Currently, among common dehydrogenation catalysts, noble metal components are mainly used as dehydrogenation active components, and γ-Al 2 O 3 is used as the carrier of the active component. However, during the dehydrogenation process, the noble metal active components are prone to aggregation, resulting in an increase in size. Moreover, due to the weak acidity on the surface of γ-Al 2 O 3 , carbon deposition is easily generated after the catalytic reaction starts, leading to rapid coking and deactivation of the catalyst. Based on this, the present application proposes a catalyst for dehydrogenation of organic liquid hydrogen storage materials and a preparation method thereof. Summary of the Invention

[0003] The main purpose of the present application is to provide a catalyst for dehydrogenation of organic liquid hydrogen storage materials and a preparation method thereof, aiming to solve the technical problem that existing dehydrogenation catalysts are prone to deactivation.

[0004] To achieve the above object, the present application proposes a catalyst for dehydrogenation of organic liquid hydrogen storage materials, which includes the following components by mass percentage:

[0005] Platinum zirconium oxide 0.5% - 5%, transition metal 1% - 7%, lanthanide metal 0.5% - 5%, and zirconium diboride whisker-graphene composite carrier as the balance;

[0006] The transition metal includes at least one of cobalt and nickel;

[0007] The lanthanide metal includes at least two of lanthanum, cerium, neodymium, yttrium, scandium, and europium.

[0008] Optionally, the chemical formula of the platinum zirconium oxide is Pt x Zr y O 2-δ ;

[0009] Among them, the value range of x is 1 ≤ x ≤ 1.2, the value range of y is 0.1 ≤ y ≤ 0.8, and δ is the content of oxygen vacancies.

[0010] Optionally, the preparation steps of the platinum zirconium oxide include:

[0011] Dissolve the soluble compound of platinum and the soluble compound of zirconium in water, carry out hydrothermal reaction at 150°C - 240°C for 8h - 12h, and then obtain the intermediate product after centrifugation, washing with water, and drying;

[0012] Heat the intermediate product in an air atmosphere at a heating rate of 4°C·min -1 -5°C·min -1 to 400°C - 600°C, carry out solid-phase reaction for 3h - 5h, and then obtain the platinum zirconium oxide.

[0013] Optionally, the preparation steps of the zirconium diboride whisker-graphene composite support include:

[0014] Modify the original graphene to obtain modified graphene;

[0015] Ultrasonically disperse the modified graphene in water at an ultrasonic frequency of 50kHz - 90kHz for 0.8h - 2.5h to obtain a modified graphene dispersion;

[0016] Add zirconium diboride whiskers to the modified graphene dispersion, carry out ball milling and mixing to obtain a mixed slurry;

[0017] Add a reducing agent to the mixed slurry, and then carry out hydrothermal reaction at 120°C - 200°C under a pressure of 0.3Mpa - 0.7Mpa in a closed environment for 10h - 16h, and then obtain the zirconium diboride whisker-graphene composite support after centrifugation, washing, and drying;

[0018] Among them, the reducing agent is one of ethylene glycol, formaldehyde, and acetic acid.

[0019] Optionally, the step of modifying the original graphene to obtain modified graphene includes:

[0020] Stir and mix the original graphene, concentrated sulfuric acid, potassium persulfate, and phosphorus pentoxide evenly, heat in an oil bath to 75°C - 85°C and keep warm for 4.5h - 5.5h, then cool to room temperature, dilute with water, then carry out suction filtration and wash until the pH is 6.8 - 7.2, and dry at room temperature for 45h - 50h to obtain pretreated graphene;

[0021] Add the pretreated graphene into concentrated sulfuric acid, then add potassium permanganate, stir in an ice bath for 0.8 h - 1.2 h, react at 45°C - 55°C for 8 h - 72 h, place it in ice water, add hydrogen peroxide and continuously stir. When it turns bright yellow, let it stand for 45 h - 50 h, discard the supernatant, obtain the lower-layer precipitate, wash the lower-layer precipitate with deionized water and hydrochloric acid respectively until the pH is 6.8 - 7.2, and dry it at room temperature for 45 h - 50 h to obtain modified graphene.

[0022] The present application also provides a method for preparing a catalyst for dehydrogenation of an organic liquid hydrogen storage material, comprising the following steps:

[0023] Disperse platinum zirconium oxide in an organic solvent to obtain an active component dispersion;

[0024] Mix the precursors of transition metals and the precursors of lanthanide metals and dissolve them in water, then add a ligand and stir, and then add the active component dispersion. After mixing evenly, obtain a mixed dispersion;

[0025] Immerse the zirconium diboride whisker-graphene composite support in the mixed dispersion, perform rotary evaporation, and then obtain the finished catalyst after calcination.

[0026] Optionally, the step of dispersing platinum zirconium oxide in an organic solvent to obtain an active component dispersion includes:

[0027] Ultrasonically disperse platinum zirconium oxide in an organic solvent at 35°C - 50°C, with an ultrasonic frequency of 20 kHz - 40 kHz and an ultrasonic time of 10 min - 40 min to obtain an active component dispersion;

[0028] The organic solvent is one of isopropanol, propanol, ethanol, and butanol.

[0029] Optionally, the ligand includes pyridine and a phosphorus ligand.

[0030] Optionally, in the step of performing rotary evaporation, the rotation speed is 20 rpm - 100 rpm, the evaporation temperature is 60°C - 90°C, the evaporation time is 20 min - 90 min, and at the same time, evacuate to a vacuum degree of -0.05 MPa - 0.05 MPa.

[0031] Optionally, in the step of calcination, the calcination temperature is 400°C - 600°C and the calcination time is 1.5 h - 5 h.

[0032] The present application has at least the following beneficial effects:

[0033] The dehydrogenation catalyst of the present application uses platinum zirconium oxide as the main active ingredient, transition metals cobalt, nickel, and lanthanide metals lanthanum, cerium, neodymium, yttrium, scandium, and europium as co-active ingredients, and selects zirconium diboride whisker-graphene composite support. Platinum zirconium oxide provides high catalytic activity with platinum and catalytic support with zirconium. After zirconium is oxidized, it has good thermal stability, certain acidic properties, and good dispersibility. Compared with platinum oxide, in the dehydrogenation reaction process at high temperature, the stability of the catalytic ability of the platinum zirconium oxide of the present application will not be restricted by the electronic structure of platinum itself, can maintain the stability of the catalyst structure, reduce the agglomeration of platinum, and has high dispersibility, can be evenly distributed in the catalyst support, further reduce the agglomeration or accumulation of platinum, and avoid the decrease in catalytic activity caused by the increase in the size of platinum, thereby improving the durability and catalytic activity of the catalyst. Then, by using the synergistic effect between platinum zirconium oxide and transition metals and lanthanide metals, the hydrogen atoms in the organic liquid hydrogen storage material are further efficiently promoted to detach, and the reaction activity of the catalyst in the dehydrogenation reaction is improved. Using zirconium diboride whisker-graphene as the support, it has a large specific surface area and pore structure, can provide a wider reaction site, accelerate the catalytic reaction, and load more metal active ingredients, effectively disperse the catalytically active metal (such as platinum, etc.) and prevent its agglomeration. At the same time, zirconium diboride whiskers provide high mechanical support and stability on the surface of graphene, so that the composite support has good structural stability at high temperature, and can reduce the problems of carbon deposition deactivation and poisoning of the catalyst. Through the synergistic effect of platinum zirconium oxide, transition metals, lanthanide metals, and zirconium diboride whisker-graphene composite support, the catalyst of the present application has high catalytic stability in the dehydrogenation reaction of organic liquid hydrogen storage materials, can still maintain good catalytic effects in multiple reactions, and is basically not easy to deactivate. Detailed Embodiments

[0034] Next, the technical solutions of the present application will be clearly and completely described in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the protection scope of the present application.

[0035] In view of the technical problems existing in the above-mentioned prior art, the embodiments of the present application provide a catalyst for dehydrogenating organic liquid hydrogen storage materials, which includes the following components by mass percentage:

[0036] Platinum zirconium oxide 0.5%-5%, transition metal 1%-7%, lanthanide metal 0.5%-5%, and the balance is zirconium diboride whisker-graphene composite support;

[0037] The transition metal includes at least one of cobalt and nickel;

[0038] The lanthanide metals include at least two of lanthanum, cerium, neodymium, yttrium, scandium, and europium.

[0039] The dehydrogenation catalyst of the present application uses platinum zirconium oxide as the main active component, transition metals cobalt, nickel, and lanthanide metals lanthanum, cerium, neodymium, yttrium, scandium, and europium as co-active components, and selects zirconium diboride whisker-graphene composite support. Platinum zirconium oxide provides high catalytic activity with platinum and catalytic support with zirconium. After zirconium is oxidized, it has good thermal stability, certain acidic properties, and good dispersibility. Compared with platinum oxide, during the dehydrogenation reaction at high temperature, the stability of the catalytic ability of the platinum zirconium oxide of the present application will not be restricted by the electronic structure of platinum itself, can maintain the stability of the catalyst structure, reduce the agglomeration of platinum, and has high dispersibility, can be evenly distributed in the catalyst support, further reduce the agglomeration or accumulation of platinum, and avoid the decrease in catalytic activity caused by the increase in the size of platinum, thereby improving the durability and catalytic activity of the catalyst. Then, by using the synergistic effect between platinum zirconium oxide and transition metals and lanthanide metals, the hydrogen atoms in the organic liquid hydrogen storage material are further efficiently promoted to detach, and the reaction activity of the catalyst in the dehydrogenation reaction is improved. Using zirconium diboride whisker-graphene as the support, it has a large specific surface area and pore structure, can provide more extensive reaction sites, accelerate the catalytic reaction, and load more metal active components, effectively disperse catalytically active metals (such as platinum, etc.) and prevent their agglomeration. At the same time, zirconium diboride whiskers provide high mechanical support and stability on the surface of graphene, making the composite support have good structural stability at high temperature, and can reduce the problems of carbon deposition deactivation and poisoning of the catalyst. Through the synergistic effect of platinum zirconium oxide, transition metals, lanthanide metals, and zirconium diboride whisker-graphene composite support, the catalyst of the present application has high catalytic stability in the dehydrogenation reaction of organic liquid hydrogen storage materials, can still maintain good catalytic effects in multiple reactions, and is basically not easily deactivated.

[0040] As an implementable manner of the present application, the chemical formula of the platinum zirconium oxide is Pt x Zr y O 2-δ ;

[0041] wherein, the value range of x is 1≤x≤1.2, the value range of y is 0.1≤y≤0.8, and δ is the content of oxygen vacancies.

[0042] As an implementable manner of the present application, the preparation steps of the platinum zirconium oxide include:

[0043] Dissolve the soluble compound of platinum and the soluble compound of zirconium in water, carry out hydrothermal reaction at 150°C - 240°C, the reaction time is 8h - 12h, and then obtain the intermediate product after centrifugation, washing, and drying;

[0044] Heat the intermediate product in an air atmosphere at a heating rate of 4 °C·min -1 -5 °C·min -1 to 400 °C - 600 °C and carry out a solid-phase reaction for 3 h - 5 h to obtain the platinum-zirconium oxide.

[0045] Since platinum has excellent catalytic activity in dehydrogenation reactions and can be used as the main metal active component in dehydrogenation catalysts, but platinum is prone to aggregation, resulting in an increase in size. Therefore, in this application, platinum-zirconium oxide is prepared by compounding platinum with zirconium to control the size of platinum. Since zirconium has certain acidic properties and good thermal stability after oxidation, it can effectively provide catalytic support, and during the high-temperature dehydrogenation reaction process, it can maintain the stability of the catalyst structure, thereby reducing the agglomeration of platinum and avoiding the decrease in catalytic activity caused by the increase in the size of platinum. Moreover, after platinum and zirconium are compounded, compared with platinum as a single active component, platinum-zirconium oxide has higher dispersibility, and the stability of the catalytic ability is not restricted by the electronic structure of platinum itself, enabling it to be evenly distributed in the catalyst carrier, reducing the agglomeration or accumulation of platinum, thereby improving the durability and catalytic activity of the catalyst, and enabling the catalyst of this application to maintain stable catalytic performance for a long time.

[0046] As an implementable mode of this application, the preparation steps of the zirconium diboride whisker-graphene composite carrier include:

[0047] Modify the original graphene to obtain modified graphene;

[0048] Ultrasonically disperse the modified graphene in water at an ultrasonic frequency of 50 kHz - 90 kHz for an ultrasonic time of 0.8 h - 2.5 h to obtain a modified graphene dispersion;

[0049] Add zirconium diboride whiskers to the modified graphene dispersion and carry out ball milling and mixing to obtain a mixed slurry;

[0050] Add a reducing agent to the mixed slurry, and then carry out a hydrothermal reaction at 120 °C - 200 °C and a pressure of 0.3 Mpa - 0.7 Mpa in a closed environment for 10 h - 16 h. After centrifugation, washing, and drying, the zirconium diboride whisker-graphene composite carrier is obtained;

[0051] Among them, the reducing agent is one of ethylene glycol, formaldehyde, and acetic acid.

[0052] The mass ratio of zirconium diboride whiskers to modified graphene is (0.1 - 0.4):1.

[0053] In this application, zirconium diboride whisker - graphene composite is used as the carrier of the dehydrogenation catalyst. Graphene itself has excellent electrical conductivity, surface activity and a relatively high specific surface area. Moreover, the two - dimensional structure of graphene can provide a wider range of reaction sites, which can accelerate the catalytic reaction. Zirconium diboride whiskers have high hardness and excellent thermal stability, making the composite carrier have good stability in high - temperature environments, which is beneficial to the high - temperature dehydrogenation process in organic liquid hydrogen storage reactions. And zirconium diboride whiskers, as part of the composite carrier, provide a high degree of mechanical support and stability on the surface of graphene, can effectively disperse catalytically active metals (such as platinum, etc.) and prevent their agglomeration. At the same time, the enhanced structural stability of the composite carrier enables the catalyst to still maintain good catalytic performance in multiple reactions, reducing the problems of catalyst carbon deposition deactivation and poisoning. In addition, the zirconium diboride whisker - graphene composite carrier of this application also has a relatively large specific surface area and pore structure, enabling it to load more metal active components and facilitating the effective adsorption and reaction of organic liquid hydrogen storage materials on the catalyst surface, thereby improving the efficiency of the dehydrogenation reaction.

[0054] As an implementable mode of this application, the step of modifying the original graphene to obtain modified graphene includes:

[0055] After stirring and mixing the original graphene, concentrated sulfuric acid, potassium persulfate and phosphorus pentoxide evenly, heat it in an oil bath to 75 °C - 85 °C and keep it warm for 4.5 h - 5.5 h, then cool it to room temperature. After adding water for dilution, filter it by suction and wash it until the pH is 6.8 - 7.2, and dry it at room temperature for 45 h - 50 h to obtain pretreated graphene;

[0056] Add the pretreated graphene into concentrated sulfuric acid, then add potassium permanganate, stir it in an ice bath for 0.8 h - 1.2 h, and react at 45 °C - 55 °C for 8 h - 72 h. Then place it in ice water and continuously stir it while adding hydrogen peroxide. When it turns bright yellow, let it stand for 45 h - 50 h, discard the supernatant, and obtain the lower - layer precipitate. Wash the lower - layer precipitate with deionized water and hydrochloric acid respectively until the pH is 6.8 - 7.2, and dry it at room temperature for 45 h - 50 h to obtain modified graphene.

[0057] Specifically, pristine graphene is a two-dimensional material composed of layers of carbon atom units that was initially discovered and untreated. In this application, inorganic strong protonic acids are used to modify pristine graphene, which disrupts the conjugated structure on the surface of pristine graphene. The obtained modified graphene has a wrinkled lamellar structure on its surface and contains abundant oxygen-containing functional groups, enabling it to have good dispersibility in an aqueous solution. This improves the problem of easy agglomeration between pristine graphenes, thereby enhancing the contact area with zirconium diboride whiskers. Moreover, when the modified graphene is compounded with zirconium diboride whiskers, these oxygen functional groups can form covalent bonds with the surface of zirconium diboride or enhance their interfacial binding force through electrostatic interactions, thus improving the stability and uniformity of the composite support. This enhanced interfacial binding property helps to improve the catalytic performance of catalytically active metals (such as platinum, etc.) during the dehydrogenation process.

[0058] The embodiments of this application also provide a preparation method for a catalyst used for dehydrogenation of organic liquid hydrogen storage materials, including the following steps:

[0059] S10. Disperse platinum zirconium oxide in an organic solvent to obtain an active component dispersion liquid.

[0060] Specifically, ultrasonically disperse platinum zirconium oxide in an organic solvent at 35°C - 50°C, with an ultrasonic frequency of 20 kHz - 40 kHz and an ultrasonic time of 10 min - 40 min to obtain an active component dispersion liquid;

[0061] The organic solvent is one of isopropanol, propanol, ethanol, and butanol.

[0062] S20. Mix the precursors of transition metals and the precursors of lanthanide metals and dissolve them in water. Then, add a ligand and stir, and then add the active component dispersion liquid. After mixing evenly, obtain a mixed dispersion liquid.

[0063] Among them, when the transition metal is Co, its precursor is CoSO 4 ·7H 2 O; when the transition metal is Ni, its precursor is Ni(NO 3 ) 2 or Ni(CH 3 COO) 2 ;

[0064] When the lanthanide metal is La, its precursor is La(CH 3 COO) 3 ·4H 2 O; when the lanthanide metal is Ce, its precursor is Ce(CH 3 COO) 3 ; when the lanthanide metal is Nd, its precursor is Nd(NO 3 ) 3 ·6H2 O; When the lanthanide metal is Y, its precursor is Y(NO 3 ) 3 ·6H 2 O; When the lanthanide metal is Sc, its precursor is Sc 2 (C 2 O 4 ) 3 ; When the lanthanide metal is Eu, its precursor is Eu(NO 3 ) 3 。

[0065] As an implementable mode of the present application, the ligand includes pyridine and a phosphorus ligand; the phosphorus ligand includes one of phosphine, trimethylphosphine, and triphenylphosphine.

[0066] As a weak electron donor and a relatively strong π - acceptor, pyridine can regulate the electron density around the metal center. The phosphorus ligand can increase the electron density of the metal through the supply of its lone pair electrons. Through the coordination with the metal center, pyridine and the phosphorus ligand can change the electronic structure of the metal center, thereby improving the catalytic activity and selectivity of the metal. Moreover, the metal active component may undergo redox changes in the catalytic reaction, leading to oxidation or deposition on the metal surface, thus reducing the activity of the catalyst. However, pyridine and the phosphorus ligand can stabilize the metal center, reduce its oxidation or deactivation, and help maintain the stability and durability of the catalyst. At the same time, after the metal active component combines with the ligand, a stable complex can be formed, enabling the metal to be more evenly dispersed in the reaction medium, thereby enhancing the efficiency of the catalytic dehydrogenation reaction.

[0067] S30. Immerse the zirconium diboride whisker - graphene composite support in the mixed dispersion liquid, perform rotary evaporation, and then obtain the finished catalyst after calcination.

[0068] Specifically, in the step of performing rotary evaporation, the rotation speed is 20 rpm - 100 rpm, the evaporation temperature is 60 °C - 90 °C, the evaporation time is 20 min - 90 min, and at the same time, vacuum is pumped to a vacuum degree of -0.05 MPa - 0.05 MPa.

[0069] Specifically, the calcination temperature is 400 °C - 600 °C, and the calcination time is 1.5 h - 5 h.

[0070] The above - mentioned technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0071] Example 1

[0072] A catalyst for dehydrogenation of organic liquid hydrogen storage materials is prepared by the following steps:

[0073] According to the chemical formula of platinum zirconium oxide PtZr0.5 O 2-δ For the stoichiometric ratios of the elements in 0.5 , chloroplatinic acid and zirconium acetate tetrahydrate were weighed separately and dissolved in water. A hydrothermal reaction was carried out at 195 °C for 10 h. After centrifugation, washing with water, and drying, an intermediate product was obtained.

[0074] The intermediate product was heated to 500 °C at a heating rate of 5 °C·min -1 in an air atmosphere for a solid-phase reaction for 4 h to obtain platinum zirconium oxide.

[0075] 2 g of platinum zirconium oxide was ultrasonically dispersed in an ethanol solution with an ultrasonic frequency of 30 kHz and an ultrasonic time of 25 min to obtain an active component dispersion.

[0076] CoSO 4 ·7H 2 O 5 g and La(CH 3 COO) 3 ·4H 2 O 1.5 g, Ce(CH 3 COO) 3 1.5 g were mixed and dissolved in water. After adding a ligand and stirring, the active component dispersion was added. After mixing evenly, a mixed dispersion was obtained; among them, the ligand is a composition of pyridine and phosphine.

[0077] 1.5 g of pristine graphene, 50 mL of concentrated sulfuric acid, 0.5 g of potassium persulfate, and 0.2 g of phosphorus pentoxide were stirred and mixed evenly. After heating in an oil bath to 80 °C and holding for 5.0 h, it was cooled to room temperature. After diluting with 500 mL of ice water, it was filtered by suction and washed until the pH was 7.0. After drying at room temperature for 48 h, pretreated graphene was obtained.

[0078] The pretreated graphene was added to 120 mL of concentrated sulfuric acid, and then 1.8 g of potassium permanganate was added. It was stirred in an ice bath for 1.0 h and reacted at 50 °C for 48 h. Then it was placed in ice water, and 100 mL of hydrogen peroxide was added for continuous stirring. When it turned bright yellow, it was left standing for 48 h, and the supernatant was discarded to obtain the lower-layer precipitate. The lower-layer precipitate was washed separately with deionized water and hydrochloric acid until the pH was 7.0 and dried at room temperature for 48 h to obtain modified graphene.

[0079] 10 g of the modified graphene was ultrasonically dispersed in water with an ultrasonic frequency of 70 kHz and an ultrasonic time of 1.2 h to obtain a modified graphene dispersion.

[0080] Add 2 g of zirconium diboride whiskers to the modified graphene dispersion, and carry out ball milling and mixing to obtain a mixed slurry; add ethylene glycol to the mixed slurry, and then carry out hydrothermal reaction for 13 h in a sealed environment at 160 °C and a pressure of 0.5 Mpa. After centrifugation, washing, and drying, a zirconium diboride whisker-graphene composite support is obtained.

[0081] Immerse 90 g of the zirconium diboride whisker-graphene composite support in the mixed dispersion, carry out rotary evaporation, with a rotation speed of 60 rpm, an evaporation temperature of 75 °C, and an evaporation time of 55 min. At the same time, evacuate to a vacuum degree of 0 MPa, and then calcine at 500 °C for 3 h to obtain the finished catalyst.

[0082] Example 2

[0083] A catalyst for dehydrogenation of organic liquid hydrogen storage materials is prepared by the following steps:

[0084] According to the stoichiometric ratio of elements in the chemical formula PtZr 0.1 O 2-δ Weigh chloroplatinic acid and zirconium acetate tetrahydrate respectively and dissolve them in water, carry out hydrothermal reaction at 150 °C for 12 h, and then obtain an intermediate product after centrifugation, washing with water, and drying.

[0085] Heat the intermediate product in an air atmosphere at a heating rate of 4 °C·min -1 to 400 °C for solid-phase reaction for 5 h to obtain platinum zirconium oxide.

[0086] Disperse 5 g of platinum zirconium oxide in an ethanol solution by ultrasonic wave, with an ultrasonic frequency of 20 kHz and an ultrasonic time of 40 min to obtain an active component dispersion.

[0087] Mix 1 g of Ni(NO 3 ) 2 and 0.5 g of Y(NO 3 ) 3 ·6H 2 O and 0.5 g of Eu(NO 3 ) 3 in water, add a ligand and stir, then add the active component dispersion, and mix well to obtain a mixed dispersion; among them, the ligand is a composition of pyridine and trimethylphosphine.

[0088] Stir and mix 1.5 g of pristine graphene, 50 mL of concentrated sulfuric acid, 0.5 g of potassium persulfate, and 0.2 g of phosphorus pentoxide, heat in an oil bath to 75 °C and keep warm for 5.5 h, then cool to room temperature, dilute with 500 mL of ice water, then filter and wash until the pH is 6.8, and dry at room temperature for 50 h to obtain pretreated graphene.

[0089] Add the pretreated graphene into 120 mL of concentrated sulfuric acid, then add 1.8 g of potassium permanganate, stir in an ice bath for 1.2 h, react at 45 °C for 72 h, place it in ice water, add 100 mL of hydrogen peroxide and continue stirring. When it turns bright yellow, let it stand for 50 h, discard the supernatant, obtain the lower-layer precipitate, wash the lower-layer precipitate with deionized water and hydrochloric acid respectively until the pH is 6.8, and dry it at room temperature for 50 h to obtain modified graphene;

[0090] Disperse 10 g of the modified graphene in water by ultrasonic wave, with an ultrasonic frequency of 50 kHz and an ultrasonic time of 2.5 h to obtain a modified graphene dispersion;

[0091] Add 1 g of zirconium diboride whiskers into the modified graphene dispersion, and carry out ball milling and mixing to obtain a mixed slurry;

[0092] Add formaldehyde into the mixed slurry, and then carry out hydrothermal reaction in a closed environment at 120 °C and a pressure of 0.3 Mpa for 16 h. After centrifugation, washing and drying, zirconium diboride whisker-graphene composite support is obtained;

[0093] Immerse 93 g of zirconium diboride whisker-graphene composite support in the mixed dispersion, carry out rotary evaporation, with a rotary speed of 20 rpm, an evaporation temperature of 60 °C, and an evaporation time of 90 min. At the same time, evacuate to a vacuum degree of -0.05 Mpa, and then calcine at 400 °C for 5 h to obtain the finished catalyst.

[0094] Example 3

[0095] A catalyst for dehydrogenation of organic liquid hydrogen storage materials is prepared by the following steps:

[0096] According to the chemical stoichiometry of the elements in the chemical formula of platinum zirconium oxide Pt 1.2 Zr 0.8 O 2-δ Weigh chloroplatinic acid and zirconium acetate tetrahydrate respectively and dissolve them in water according to the chemical stoichiometry of the elements in the chemical formula of platinum zirconium oxide PtZrO. Carry out hydrothermal reaction at 240 °C for 8 h, and then obtain an intermediate product after centrifugation, water washing and drying;

[0097] Heat the intermediate product to 600 °C at a heating rate of 5 °C·min -1 in an air atmosphere for solid-phase reaction for 3 h to obtain platinum zirconium oxide;

[0098] Disperse 1 g of platinum zirconium oxide in an ethanol solution by ultrasonic wave, with an ultrasonic frequency of 240 kHz and an ultrasonic time of 10 min to obtain an active component dispersion;

[0099] Add CoSO 4 ·7H2 O 7 g, La(CH 3 COO) 3 ·4H 2 O 1.5 g, Nd(NO 3 ) 3 ·6H 2 O 1 g, Y(NO 3 ) 3 ·6H 2 O 2.5 g are mixed and dissolved in water. Then, a ligand is added and stirred, and then the active component dispersion is added. After mixing evenly, a mixed dispersion is obtained; wherein, the ligand is a composition of pyridine and triphenylphosphine;

[0100] 1.5 g of pristine graphene, 50 mL of concentrated sulfuric acid, 0.5 g of potassium persulfate, and 0.2 g of phosphorus pentoxide are stirred and mixed evenly. After heating in an oil bath to 85 °C and holding for 4.5 h, it is cooled to room temperature. After diluting with 500 mL of ice water, it is filtered with suction and washed until the pH is 7.2, and then dried at room temperature for 45 h to obtain pretreated graphene;

[0101] The pretreated graphene is added to 120 mL of concentrated sulfuric acid, and then 1.8 g of potassium permanganate is added. It is stirred in an ice bath for 0.8 h and reacted at 55 °C for 8 h. Then, it is placed in ice water, and 100 mL of hydrogen peroxide is added for continuous stirring. When it turns bright yellow, it is left standing for 45 h, and the supernatant is discarded to obtain the lower-layer precipitate. The lower-layer precipitate is washed with deionized water and hydrochloric acid respectively until the pH is 7.2, and then dried at room temperature for 45 h to obtain modified graphene;

[0102] 10 g of the modified graphene is ultrasonically dispersed in water with an ultrasonic frequency of 90 kHz and an ultrasonic time of 0.8 h to obtain a modified graphene dispersion;

[0103] 4 g of zirconium diboride whiskers are added to the modified graphene dispersion, and ball milling is carried out for mixing to obtain a mixed slurry;

[0104] Acetic acid is added to the mixed slurry, and then hydrothermal reaction is carried out in a closed environment at 200 °C and a pressure of 0.7 MPa for 10 h. After centrifugation, washing, and drying, the zirconium diboride whisker-graphene composite support is obtained;

[0105] 87 g of the zirconium diboride whisker-graphene composite support is immersed in the mixed dispersion, and rotary evaporation is carried out with a rotary speed of 100 rpm, an evaporation temperature of 90 °C, and an evaporation time of 20 min. At the same time, vacuum is pumped to a vacuum degree of 0.05 MPa, and then calcination is carried out at 600 °C for 1.5 h to obtain the finished catalyst.

[0106] Comparative Example 1

[0107] Compared with Example 1, platinum zirconium oxide was replaced with PtO 2 , and the remaining steps remained unchanged.

[0108] Comparative Example 2

[0109] Compared with Example 1, the zirconium diboride whisker-graphene composite support was replaced with γ-Al 2 O 3 , and the remaining steps remained unchanged.

[0110] Comparative Example 3

[0111] Compared with Example 1, when preparing the zirconium diboride whisker-graphene composite support, zirconium diboride whiskers were not incorporated, and modified graphene was directly used as the support, and the remaining steps remained unchanged.

[0112] Experimental Example

[0113] Evaluate the dehydrogenation reaction performance of the catalysts prepared in the examples and comparative examples of the present application.

[0114] Using methylcyclohexane as a representative raw material for organic liquid hydrogen storage, after mixing 1.5 g of the catalyst to be tested with an appropriate amount of 20-mesh quartz sand, it was pressed and crushed into particles with a particle size of about 2 mm, filled in an isothermal fixed-bed reactor, and the filling amount was 10 mL. Before evaluation, the catalyst was reduced with hydrogen, and the reduction conditions were as follows: temperature 350 °C, pressure normal pressure, hydrogen flow rate 200 mL / min, reduction time 3 h; the evaluation conditions were: reaction temperature 350 °C, pressure normal pressure, and the reaction volume liquid hourly space velocity of the methylcyclohexane liquid was 1.5 h -1 , and the conversion rates of methylcyclohexane at 4 h and 80 h of the catalytic reaction were recorded respectively, and the results are shown in Table 1 below.

[0115] Table 1

[0116] Group Conversion rate at 4h (%) Conversion rate at 80h (%) Example 1 99.1 98.6 Example 2 98.5 98.0 Example 3 98.8 98.2 Comparative Example 1 97.5 95.8 Comparative Example 2 95.4 92.1 Comparative Example 3 96.8 93.7

[0117] As can be seen from Table 1, the conversion rate of methylcyclohexane of the catalyst prepared in the examples of the present application can reach more than 98.5% at 4 h. Even after 80 h of the catalytic reaction, the conversion rate of methylcyclohexane can still reach more than 98.0%, and still maintain a good catalytic effect, and the catalytic activity decreases insignificantly; while in Comparative Example 1, PtO 2 is used as the main active component, and the stability of its catalytic ability is easily restricted by the electronic structure of Pt itself and is prone to deactivation. After 80 h of the catalytic reaction, the catalytic ability decreases more significantly; in Comparative Example 2, conventional γ-Al 2 O 3 is used as the catalyst support. Since γ-Al 2 O 3 is prone to carbon deposition, and γ-Al 2 O3 The interaction with the metal active component is weak, resulting in a decline in its catalytic activity and durability; the carrier in Comparative Example 3 does not incorporate zirconium diboride whiskers, and the high hardness and excellent thermal stability of zirconium diboride whiskers can keep the carrier in good stability under high-temperature environments. Therefore, after 80 h of the catalytic reaction, the conversion rate of the catalyst in Comparative Example 3 for methylcyclohexane decreases significantly.

[0118] The above are only optional embodiments of the present application, and do not limit the patent scope of the present application accordingly. Any equivalent structural transformation made using the content of the specification of the present application under the inventive concept of the present application, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present application.

Claims

1. A catalyst for dehydrogenation of an organic liquid hydrogen storage material, characterized in that: Calculated by mass percentage, it includes the following components: 0.5%-5% of platinum zirconium oxide, 1%-7% of transition metal, 0.5%-5% of lanthanide metal and zirconium diboride whisker-graphene composite carrier as the balance; The transition metal includes at least one of cobalt and nickel; The lanthanide metal includes at least two of lanthanum, cerium, neodymium, yttrium, scandium and europium.

2. The catalyst for dehydrogenation of organic liquid hydrogen storage materials according to claim 1, characterized in that: The chemical formula of the platinum zirconium oxide is Pt x Zr y O 2-δ ; Among them, the value range of x is 1≤x≤1.2, the value range of y is 0.1≤y≤0.8, and δ is the content of oxygen vacancies.

3. The catalyst for dehydrogenation of organic liquid hydrogen storage materials according to claim 2, characterized in that: The preparation steps of the platinum zirconium oxide include: The soluble compound of platinum and the soluble compound of zirconium are dissolved in water, and a hydrothermal reaction is carried out at 150°C-240°C for 8h-12h, and then the intermediate product is obtained after centrifugation, water washing and drying; The intermediate product was heated in air at 4 °C min -1 -5℃·min -1 The temperature is raised to 400° C.-600° C. at a heating rate of 3 h-5 h to carry out a solid phase reaction, thereby obtaining the platinum zirconium oxide.

4. The catalyst for dehydrogenation of organic liquid hydrogen storage materials according to claim 1, characterized in that: The steps for preparing the zirconium diboride whisker-graphene composite carrier include: Performing modification treatment on original graphene to obtain modified graphene; Ultrasonic dispersion of the modified graphene in water at an ultrasonic frequency of 50 kHz to 90 kHz and an ultrasonic time of 0.8 h to 2.5 h to obtain a modified graphene dispersion; adding zirconium diboride whiskers to the modified graphene dispersion, and performing ball milling to mix to obtain a mixed slurry; Adding a reducing agent to the mixed slurry, and then performing a hydrothermal reaction in a closed environment at 120° C.-200° C. and a pressure of 0.3 Mpa-0.7 Mpa for 10 h-16 h, and then centrifuging, washing, and drying to obtain the zirconium diboride whisker-graphene composite carrier; Wherein, the reducing agent is one of ethylene glycol, formaldehyde and acetic acid.

5. The catalyst for dehydrogenation of organic liquid hydrogen storage materials according to claim 4, characterized in that: The step of modifying the original graphene to obtain modified graphene comprises: The original graphene, concentrated sulfuric acid, potassium persulfate and phosphorus pentoxide were stirred and mixed, and then heated to 75°C-85°C in an oil bath and kept warm for 4.5h-5.5h, cooled to room temperature, diluted with water, filtered and washed to a pH of 6.8-7.2, and dried at room temperature for 45h-50h to obtain pretreated graphene; The pretreated graphene is added to concentrated sulfuric acid, and then potassium permanganate is added, and the mixture is stirred in an ice bath for 0.8h-1.2h, and reacted at 45°C-55°C for 8h-72h, and then placed in ice water, and hydrogen peroxide is added for continuous stirring. When a bright yellow color appears, the mixture is allowed to stand for 45h-50h, and the supernatant is discarded to obtain a lower precipitate. The lower precipitate is washed with deionized water and hydrochloric acid respectively until the pH value is 6.8-7.2, and dried at room temperature for 45h-50h to obtain modified graphene.

6. A method for preparing a catalyst for dehydrogenation of an organic liquid hydrogen storage material according to any one of claims 1 to 5, characterized in that: The following steps are involved: dispersing platinum zirconium oxide in an organic solvent to obtain an active component dispersion; The precursor of the transition metal and the precursor of the lanthanide metal are mixed and dissolved in water, the ligand is added and stirred, and then the active component dispersion is added and mixed to obtain a mixed dispersion; The zirconium diboride whisker-graphene composite carrier is immersed in the mixed dispersion, subjected to rotary evaporation, and then calcined to obtain a finished catalyst product.

7. The method for preparing a catalyst for dehydrogenation of an organic liquid hydrogen storage material according to claim 6, characterized in that: The step of dispersing platinum zirconium oxide in an organic solvent to obtain an active component dispersion comprises: Ultrasonic dispersion of platinum zirconium oxide in an organic solvent at 35° C.-50° C., with an ultrasonic frequency of 20 kHz-40 kHz and an ultrasonic time of 10 min-40 min, to obtain an active component dispersion; The organic solvent is one of isopropanol, propanol, ethanol and butanol.

8. The method for preparing a catalyst for dehydrogenation of an organic liquid hydrogen storage material according to claim 6, characterized in that: The ligand includes pyridine and a phosphorus ligand.

9. The method for preparing a catalyst for dehydrogenation of an organic liquid hydrogen storage material according to claim 6, characterized in that: In the step of rotary evaporation, the rotation speed is 20rpm-100rpm, the evaporation temperature is 60°C-90°C, the evaporation time is 20min-90min, and the vacuum is simultaneously evacuated to a vacuum degree of -0.05MPa-0.05MPa.

10. The method for preparing a catalyst for dehydrogenation of an organic liquid hydrogen storage material according to claim 6, characterized in that: In the calcination step, the calcination temperature is 400° C.-600° C., and the calcination time is 1.5 h-5 h.