A metal-supported dehydrogenation catalyst based on an organic liquid hydrogen support, its preparation method and application

Abstract

This invention relates to the field of hydrogen energy storage and transportation technology, specifically disclosing a metal-supported dehydrogenation catalyst based on an organic liquid hydrogen support, its preparation method, and its application. The organic liquid hydrogen support is one or more of the polycyclic aromatic hydrocarbon organic liquid hydrogen supports benzyltoluene, dibenzylbenzene, dibenzyltoluene, and dibenzylethylbenzene. The dehydrogenation catalyst is a supported metal catalyst, comprising a catalyst support, an active metal component, and an additive; wherein the catalyst support is γ-Al₂O₃, the active component includes Pt, Pd, or Ni, and the additive is one or more of elemental Ti, W, Mo, V, or their oxides. This dehydrogenation catalyst exhibits high activity, requires a low loading of the effective active component, has high dispersion, and good stability; when used for dehydrogenation of organic liquid hydrogen storage materials, it can effectively improve dehydrogenation efficiency and significantly extend catalyst lifetime.

Description

Technical Field

[0001] This invention relates to the field of hydrogen energy storage and transportation technology, specifically to a metal-supported dehydrogenation catalyst based on an organic liquid hydrogen carrier, its preparation method, and its application in dehydrogenation reactions. Background Technology

[0002] The existing high-pressure hydrogen storage and tanker truck transportation method cannot meet the needs of large-scale utilization and transportation of green hydrogen energy.

[0003] Organic liquid hydrogen carriers offer advantages such as high hydrogen storage efficiency, safe storage and transportation, and low storage costs, making them considered the most promising hydrogen storage technology for safe, efficient, and large-scale cross-regional hydrogen transportation. Existing technology CN114497630A discloses an organic liquid material for hydrogen storage, a catalytic hydrogen storage system, and a hydrogen storage method. The organic liquid material is a mixture of benzyltoluene-based and naphthalene-based organic liquid hydrogen carriers. The catalytic hydrogen storage system includes the organic liquid material for hydrogen storage and a hydrogen storage reaction catalyst, which is a supported metal catalyst comprising a catalyst support and an active metal component. However, the specific surface area of ​​the support used in this catalyst is generally only around 200 m². 2 Below a certain value (e.g.), the specific surface area is slightly smaller, which is not conducive to the dispersion of active components. CN111889094B discloses a dehydrogenation catalyst for producing hydrogen from an organic hydrogen storage compound. This dehydrogenation catalyst has better dehydrogenation activity and selectivity. However, this catalyst incorporates an auxiliary agent into the catalyst support, with the auxiliary agent content accounting for about 20% of the total support mass, resulting in excessive auxiliary agent usage. CN114436208A discloses a catalytic hydrogen supply system based on an organic liquid and its hydrogen supply method. The catalytic hydrogen supply system includes an organic liquid hydrogen supply material and a hydrogen supply reaction catalyst. The organic liquid hydrogen supply material is composed of a fully hydrogenated benzyltoluene-based and a decahydronaphthalene-based organic liquid hydrogen support. The hydrogen supply reaction catalyst is a supported metal catalyst, containing a catalyst support and an active metal component. However, the active metal content used in this catalyst is 5-30% by mass, resulting in high catalyst cost.

[0004] The aforementioned patents have achieved some success in dehydrogenation reactions based on organic liquid hydrogen storage systems. However, the preparation of dehydrogenation catalysts utilizes common hydrothermal and impregnation methods, resulting in the use of large amounts of reducing agents and additives. Furthermore, this preparation method easily leads to the aggregation of metal active components after reduction, making it difficult to uniformly disperse them in the active component support. This reduces the effectiveness of the active components in the catalyst system, generating a large amount of ineffective active components and affecting the porosity of the support. This results in waste of the catalyst's active metal component raw materials and, more importantly, leads to high dehydrogenation temperatures and slow dehydrogenation rates after hydrogen storage, increasing costs. Therefore, it is necessary to develop highly active dehydrogenation catalysts to reduce dehydrogenation temperatures and increase dehydrogenation rates. Summary of the Invention

[0005] To overcome the problems of existing organic liquid hydrogen carrier dehydrogenation catalysts having easy accumulation and poor dispersion of active components, and relatively low content of effective active components, which leads to high dehydrogenation temperature and slow dehydrogenation rate after hydrogen storage on existing organic liquid hydrogen carriers, this invention provides a metal-supported dehydrogenation catalyst based on an organic liquid hydrogen carrier, its preparation method, and its dehydrogenation application in organic liquid hydrogen carriers.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] The first objective of this invention is to provide a metal-supported dehydrogenation catalyst based on an organic liquid hydrogen support, comprising the following components by mass percentage:

[0008] (a) Support, using γ-Al2O3 with a content of 88.0%~98.5wt%;

[0009] (b) The active component is selected from at least one of Pt, Pd, and Ni, at a concentration of 0.5% to 5.0 wt%.

[0010] (c) Additives, selected from 0.5 to 7.0 wt% of at least one of the elements or oxides of Ti, W, Mo, and V;

[0011] In the above technical solution, the carrier is prepared by the sol-gel method.

[0012] In the above technical solution, the average particle size of the γ-Al2O3 is 60~150 mesh.

[0013] In the above technical solution, the specific surface area of ​​the metal-supported dehydrogenation catalyst based on an organic liquid hydrogen support is 300~500 m². 2 / g.

[0014] A second objective of this invention is to provide a method for preparing the above-mentioned metal-supported dehydrogenation catalyst based on an organic liquid hydrogen support, comprising the following steps:

[0015] Preparation of the support: The organoaluminum compound and the template agent were dispersed in an organic solvent, hydrolyzed with acid, allowed to stand for 24 h, dried at 110 °C, calcined at 550 °C, and the support γ-Al2O3 was obtained after washing, drying and calcination.

[0016] Preferably, the organoaluminum compound is aluminum isopropoxide; the template agent is one of hexadecyltrimethylammonium bromide (CTAB), citric acid, and ascorbic acid; the organic solvent is one of isopropanol, propanol, ethanol, and butanol; and the acid is nitric acid or hydrochloric acid.

[0017] Preferably, the molar ratio of aluminum isopropoxide, template agent, and acid is 20:1:4.

[0018] Preparation of a mixed dispersion system of active component precursor and auxiliary agent precursor: The auxiliary agent precursor and the auxiliary agent complex are prepared into a complex solution. The complex solution is mixed with the active component precursor and reacted. The precipitate formed by the reaction is filtered, washed and dried to prepare a suspension or solution, thus obtaining the mixed dispersion system of active component precursor and auxiliary agent precursor.

[0019] Preferably, the complex of the additive is bipyridine, pyridine, or indole; when the additive is Ti, the precursor is one or more of tetraethyl titanate, titanium nitrate, and titanium sulfate; when the additive is W, the precursor is one or more of tungsten chloride, ammonium tungstate, and copper tungstate; when the additive is Mo, the precursor is one or more of molybdenum nitrate, molybdenum sulfate, and molybdenum acetylacetonate; and when the additive is V, the precursor is one or more of vanadium nitrate, vanadium sulfate, and vanadium acetylacetonate.

[0020] Preferably, when the active component is Pt, its precursor is one or more of chloroplatinic acid hydrate, platinum ammonium nitrate, and platinum acetylacetonate; when the active component is Pd, its precursor is one or more of palladium acetate, palladium nitrate, and palladium acetylacetonate; when the active component is Ni, its precursor is one or more of nickel nitrate, nickel sulfate, and nickel acetylacetonate.

[0021] Preparation of metal-supported dehydrogenation catalyst: The catalyst support γ-Al2O3 prepared above is fully impregnated in the mixed dispersion system of the active component precursor and the auxiliary agent precursor prepared above to form a mixture. The mixture is heat-treated in Ar at 200~600℃, calcined in air at 200~650℃, and reduced in hydrogen at 200~650℃. The active metal component is fixed in a reduced state and the auxiliary agent is fixed in an oxidized state on the surface of the catalyst support to obtain the dehydrogenation reaction catalyst.

[0022] Preferably, the molar ratio of the auxiliaries, auxiliary complexes, active components and γ-Al2O3 is 1:3:1:63.

[0023] The third objective of this invention is to disclose the application of the above-mentioned metal-supported dehydrogenation catalyst based on organic liquid hydrogen carrier in the dehydrogenation reaction of organic liquid hydrogen storage materials. The target of the dehydrogenation reaction is a liquid organic hydrogen storage material, which is a mixed system formed by one or more of benzyltoluene, dibenzylbenzene, dibenzyltoluene, and dibenzylethylbenzene.

[0024] In the dehydrogenation catalytic reaction, the above-mentioned organic liquid material after hydrogenation is used as the target for dehydrogenation. Under the conditions of reaction temperature of 200~400℃ and reaction system pressure of 0.1~10.0MPa, the target for dehydrogenation is brought into contact with the above-mentioned supported metal dehydrogenation catalyst to achieve the dehydrogenation reaction.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The metal-supported dehydrogenation catalyst based on an organic liquid hydrogen support proposed in this invention includes a support, an active component, and a metal promoter. The support is γ-Al2O3, and the active component is a metal. The metal promoter can form a complex, resulting in a catalyst system with a large specific surface area, high dispersion of active metal, and low required active metal loading. When used in the dehydrogenation reaction of organic liquid hydrogen storage materials, it exhibits high activity, high stability, and long lifespan.

[0027] The method for preparing a metal-supported dehydrogenation catalyst based on an organic liquid hydrogen support proposed in this invention utilizes the sol-gel method to prepare the catalyst support, which improves the thermal stability and heat resistance of alumina and increases the specific surface area of ​​the alumina support to twice that of commercial supports, thus facilitating the dispersion of the active components within the support. Pre-treating the promoters and precursors of the active components into complexes ensures strong interaction between the active components and promoters during subsequent heat treatment, improving the dispersion of the active components and further enhancing the catalytic activity of the catalyst. The increased dispersion of the active components further reduces the required amount of precious metal active components, thereby lowering raw material costs.

[0028] The metal-supported dehydrogenation catalyst based on an organic liquid hydrogen support proposed in this invention exhibits a mass space velocity (MSV) of 0.6 h⁻¹ during fixed-bed dehydrogenation catalysis. -1 Under atmospheric pressure and a reaction temperature of 250℃, the dehydrogenation rate can reach 90%, and the activity does not decrease significantly after 150 hours of continuous use. The reaction temperature of the dehydrogenation catalyst is reduced, the service life is significantly improved, and the energy consumption of the dehydrogenation process is greatly reduced. Attached Figure Description

[0029] Figure 1 This is a diagram showing the experimental results of continuous dehydrogenation of the catalyst of this invention;

[0030] Figure 2 The results are TEM characterizations of the catalyst of this invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] The present invention will now be described in further detail with reference to the accompanying drawings:

[0034] All reagents used in the following examples are commercially available reagents.

[0035] Example 1

[0036] A catalyst support for a metal-based dehydrogenation catalyst was prepared using the sol-gel method. Aluminum isopropoxide, CTAB, isopropanol, and nitric acid were reacted in a molar ratio of 1:0.05:6:0.2. Specifically, 12.01 g of aluminum isopropoxide and 1.07 g of CTAB were dissolved in 21.20 g of isopropanol, and after stirring, 21.92 g of a 3.4% nitric acid aqueous solution was added for hydrolysis. After standing for 24 h, the solution was dried at 110 °C, calcined at 550 °C, washed, and dried to obtain a γ-Al₂O₃ support. 3 g of the γ-Al₂O₃ support was obtained by sieving through a 60–150 mesh sieve.

[0037] A mixed precursor of the active component and promoter for supported metal dehydrogenation catalyst was prepared by a precursor pretreatment method, wherein the molar ratio of promoter, promoter complex and active component was 1:3:1. Specifically, 0.16 g of tungsten chloride and 0.19 g of bipyridine were dissolved in 60 mL of ethanol and stirred for 12 h. Then, 40 mL of 0.6% (w / w) chloroplatinic acid hexahydrate ethanol solution was added. The precipitate was filtered, washed and dried at 40 °C, and dispersed in water to obtain a suspension or solution of the mixed precursor.

[0038] To prepare a metal-supported dehydrogenation catalyst for an organic liquid hydrogen support, a solution or suspension of a mixed precursor was mixed with 2 g of γ-Al₂O₃ support, impregnated for 8 h, and dried at 60 °C. The dried powder was pretreated at 450 °C for 5 h in an Ar atmosphere, then pretreated at 400 °C for 5 h in an air atmosphere, and finally reduced in an H₂ atmosphere for 3 h. After cooling to room temperature, a WPt / Al₂O₃ catalyst was obtained, wherein the support was γ-Al₂O₃, the active component was Pt, and the promoter was WO₃.

[0039] Example 2

[0040] A catalyst support for a metal-based dehydrogenation catalyst was prepared using the sol-gel method. 12.01 g of aluminum isopropoxide and 0.56 g of citric acid were dissolved in 21.20 g of propanol. After stirring, 21.6 g of a 2% hydrochloric acid aqueous solution was added for hydrolysis. The molar ratio of aluminum isopropoxide, citric acid, propanol, and hydrochloric acid was 1:0.05:6:0.2. After standing for 24 h, the solution was dried at 110 °C, calcined at 550 °C, washed, dried, and sieved through a 60–150 mesh sieve to obtain 3 g of γ-Al₂O₃ support.

[0041] A mixed precursor of active component and promoter for supported metal dehydrogenation catalyst was prepared by a precursor pretreatment method, wherein the molar ratio of promoter, promoter complex and active component was 1:3:1. Specifically, 0.17 g of molybdenum nitrate and 0.093 g of pyridine were dissolved in 60 mL of ethanol and stirred for 12 h. Then, 40 mL of 0.3% palladium nitrate ethanol solution was added. The precipitate was filtered, washed and dried at 40 °C and dispersed in water to obtain a suspension or solution of the mixed precursor.

[0042] To prepare a metal-supported dehydrogenation catalyst with an organic liquid hydrogen support, a solution or suspension of a mixed precursor was mixed with 2 g of γ-Al₂O₃ support, impregnated for 8 h, and dried at 60 °C. The dried powder was pretreated at 450 °C for 5 h in an Ar atmosphere, then pretreated at 400 °C for 5 h in an air atmosphere, and finally reduced in an H₂ atmosphere for 3 h. After cooling to room temperature, a MoPd / Al₂O₃ catalyst was obtained, wherein the support was γ-Al₂O₃, the active component was Pd, and the promoter was MoO₃.

[0043] Example 3

[0044] A catalyst support for a metal-based dehydrogenation catalyst was prepared using the sol-gel method. 12.01 g of aluminum isopropoxide and 0.52 g of ascorbic acid were dissolved in 26.12 g of butanol. After stirring, 21.6 g of a 2% hydrochloric acid aqueous solution was added for hydrolysis. The molar ratio of aluminum isopropoxide, ascorbic acid, butanol, and hydrochloric acid was 1:0.05:6:0.2. After standing for 24 h, the solution was dried at 110 °C, calcined at 550 °C, washed, dried, and sieved through a 60-150 mesh sieve to obtain 3 g of γ-Al₂O₃ support.

[0045] A mixed precursor of the active component and promoter for supported metal dehydrogenation catalyst was prepared by a precursor pretreatment method, wherein the molar ratio of promoter, promoter complex and active component was 1:3:1. Specifically, 0.09 g of tetraethyl titanate and 0.14 g of indole were dissolved in 60 mL of ethanol and stirred for 12 h. Then, 40 mL of 0.3% palladium nitrate ethanol solution was added. The precipitate was filtered, washed and dried at 40 °C, and dispersed in water to obtain a suspension or solution of the mixed precursor.

[0046] To prepare a metal-supported dehydrogenation catalyst with an organic liquid hydrogen support, a solution or suspension of a mixed precursor was mixed with 2 g of γ-Al₂O₃ support, impregnated for 8 h, and dried at 60 °C. The dried powder was pretreated at 450 °C for 5 h in an Ar atmosphere, then pretreated at 400 °C for 5 h in an air atmosphere, and finally reduced in an H₂ atmosphere for 3 h. After cooling to room temperature, a TiPd / Al₂O₃ catalyst was obtained, wherein the support was γ-Al₂O₃, the active component was Pd, and the promoter was TiO₂.

[0047] Example 1

[0048] 0.85g of the WPt / Al2O3 catalyst from Example 1 was placed in a fixed-bed reactor, purged with Ar, and heated to 270°C. Then, fully hydrogenated dibenzyltoluene was introduced at atmospheric pressure. The dehydrogenation rate reached 97%, significantly higher than the 80% dehydrogenation rate of the unmodified Pt / Al2O3 catalyst at 270°C, indicating a substantial improvement in catalytic activity. This is because the specific surface area of ​​the Al2O3 support prepared by the sol-gel method is significantly higher than that of commercially available Al2O3 supports (200m²). 2 / g increased to 300-500m 2 / g can improve the dispersion of the active component Pt, and the auxiliary element W forms a complex with Pt during the preparation process. The TEM characterization results of the catalyst are as follows: Figure 2 As shown, this further enhances the dispersion of Pt, and on the other hand, it is conducive to the formation of a WO3-Pt system with close contact between WO3 and Pt, which enhances the interaction during catalytic dehydrogenation and improves catalytic activity.

[0049] Example 2

[0050] 0.85g of the WPt / Al2O3 catalyst from Example 1 was placed in a fixed-bed reactor. After heating, a mixture of fully hydrogenated dibenzyltoluene and fully hydrogenated benzyltoluene in a 1:1 volume ratio was introduced. The temperature was 250°C and the pressure was 0.1 MPa. The dehydrogenation results were as follows: Figure 1 As shown, the dehydrogenation rate can still be maintained at 85% after 150 hours of continuous dehydrogenation. In contrast, the dehydrogenation rate of the unmodified Pt / Al2O3 catalyst decreased to 60% after 150 hours of continuous dehydrogenation at 270℃ and 0.1MPa, indicating a significant improvement in catalyst life.

[0051] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. Use of a metal supported dehydrogenation catalyst based on an organic liquid hydrogen carrier for the dehydrogenation of an organic liquid hydrogen storage material, characterized in that, The metal supported dehydrogenation catalyst based on organic liquid hydrogen carrier comprises the following components in mass percentage: (a) carrier, selected from 88.0%~98.5% of γ-Al2O3; (b) active component, selected from 0.5%~5.0% of at least one of Pt, Pd and Ni; (c) assistant, selected from 0.5~7.0% of at least one of oxides of Ti, W, Mo and V; The metal-supported dehydrogenation catalyst based on an organic liquid hydrogen carrier has a specific surface area of 300-500 m 2 / g; The preparation method of the metal supported dehydrogenation catalyst based on organic liquid hydrogen carrier comprises the following steps: Preparation of carrier: dispersing organic aluminum compound and template agent in organic solvent, adding acid hydrolysis, drying and calcining to obtain carrier γ-Al2O3, the organic aluminum compound used in the preparation of carrier is aluminum isopropoxide, the template agent is cetyltrimethylammonium bromide, citric acid or ascorbic acid, and the acid is nitric acid or hydrochloric acid; Preparation of mixed dispersion system of active component precursor and assistant precursor: configuring the complex of the precursor of the assistant and the complexing agent into a complex solution, mixing and reacting the complex solution with the precursor of the active component, and drying, filtering and washing the precipitate formed by the reaction to prepare a suspension or a solution, thereby obtaining the mixed dispersion system of the active component precursor and the assistant precursor; Preparation of dehydrogenation catalyst: fully impregnating the carrier γ-Al2O3 in the mixed dispersion system, drying and calcining, and then reducing in a hydrogen atmosphere to obtain the metal supported dehydrogenation catalyst based on organic liquid hydrogen carrier.

2. Use of the metal-supported dehydrogenation catalyst based on an organic liquid hydrogen carrier according to claim 1 for dehydrogenation of an organic liquid hydrogen storage material, characterized in that, The average particle size of the γ-Al2O3 is 60~150 mesh.

3. Use of the metal-supported dehydrogenation catalyst based on an organic liquid hydrogen carrier according to claim 1 for dehydrogenation of an organic liquid hydrogen storage material, characterized in that, The organic solvent used in the preparation of carrier is isopropyl alcohol, propyl alcohol, ethanol or butanol.

4. Use of the metal-supported dehydrogenation catalyst based on an organic liquid hydrogen carrier according to claim 1 for dehydrogenation of an organic liquid hydrogen storage material, characterized in that, The complex of the assistant is bipyridine, pyridine or indole.

5. Use of the metal-supported dehydrogenation catalyst based on an organic liquid hydrogen carrier according to claim 1 for dehydrogenation of an organic liquid hydrogen storage material, characterized in that: When the assistant is Ti, the precursor of the assistant is one or more of tetraethyl titanate, titanium nitrate and titanium sulfate; when the assistant is W, the precursor of the assistant is one or more of tungsten chloride, ammonium tungstate and copper tungstate; when the assistant is Mo, the precursor of the assistant is one or more of molybdenum nitrate, molybdenum sulfate and molybdenum acetylacetone; and when the assistant is V, the precursor of the assistant is one or more of vanadium nitrate, vanadium sulfate and vanadium acetylacetone.

6. Use of the metal-supported dehydrogenation catalyst based on an organic liquid hydrogen carrier according to claim 1 for dehydrogenation of an organic liquid hydrogen storage material, characterized in that, When the active component is Pt, the precursor of the active component is one or more of chloroplatinic acid hydrate, platinum ammonium nitrate and platinum acetylacetone; when the active component is Pd, the precursor of the active component is one or more of palladium acetate, palladium nitrate and palladium acetylacetone; and when the active component is Ni, the precursor of the active component is one or more of nickel nitrate, nickel sulfate and nickel acetylacetone.

7. Use of the metal-supported dehydrogenation catalyst based on an organic liquid hydrogen carrier according to claim 1 for dehydrogenation of an organic liquid hydrogen storage material, characterized in that, The organic liquid hydrogen storage material is selected from a mixed system formed by one or more of benzyl toluene, dibenzyl benzene, dibenzyl toluene and dibenzyl ethyl benzene.

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