Porous carbon coated ruthenium-based ammonia decomposition hydrogen production catalyst as well as preparation method and application thereof

Abstract

The invention discloses a porous carbon coated ruthenium-based ammonia decomposition hydrogen production catalyst and a preparation method and application thereof in the technical field of thermocatalytic ammonia decomposition hydrogen production, a catalytic material comprises an active component, a carrier material and a substrate material, the active component is Ru, the carrier material is a rare earth metal oxide CeOx, and the substrate material is a porous carbon coated ruthenium-based ammonia decomposition hydrogen production catalyst. The substrate material is a nitrogen-doped porous carbon material, and the mass fraction of the active component is 3wt.%. A catalytic material carrier precursor is prepared by adopting a hydrothermal method, active components are dispersed and anchored on the carrier precursor by adopting an impregnation method to prepare the catalytic material precursor, then the catalytic material precursor is placed in an inert atmosphere to be roasted, and finally the low-ruthenium-content efficient catalytic material for the ammonia decomposition reaction is prepared. The prepared catalytic material has the advantages of high activity, high dispersity and low precious metal content, the ammonia decomposition rate can reach 80.97% at the temperature of 350 DEG C, the wide industrial application panorama is achieved, and blue drawings of ammonia-hydrogen green circular economy can be achieved.

Description

Technical Field

[0001] The present invention relates to a catalyst for the technical field of thermal catalytic ammonia decomposition to produce hydrogen, and in particular to a porous carbon-coated ruthenium-based ammonia decomposition to produce hydrogen catalyst with low Ru loading, high activity at low temperature, and a preparation method and application thereof. Background Art

[0002] As an energy source, hydrogen has the outstanding advantages of abundant sources, high energy density, and clean and pollution-free. Therefore, in the context of dual carbon, the development and utilization of hydrogen has received unprecedented attention. However, hydrogen has a low density and is easy to burn, so the storage and transportation costs are high, and there are safety risks, which have long affected the utilization of hydrogen energy. Ammonia is a good hydrogen carrier, which helps to promote the large-scale application of green hydrogen. The hydrogen content of ammonia is as high as 17.6%, and compared with hydrogen, ammonia can be liquefied at low pressure, thus effectively solving the problem of hydrogen storage and transportation. Ammonia can be completely decomposed to prepare high-purity hydrogen for hydrogen refueling stations and fuel cells, and it can also be partially decomposed to obtain ammonia-hydrogen mixed gas to solve the problems of low combustion speed and high ignition energy of pure ammonia, thereby realizing the energy application of ammonia in multiple ways. Therefore, ammonia decomposition to produce hydrogen has been regarded as a very promising way to produce carbon-free hydrogen.

[0003] From a thermodynamic point of view, ammonia decomposition is an endothermic entropy-increasing reaction with a high reaction energy barrier. Therefore, promoting the development of efficient ammonia decomposition hydrogen production catalytic materials is an effective way to reduce reaction energy consumption and improve safety of use. Existing commercial ammonia decomposition hydrogen production catalytic materials have problems such as high operating temperature, high material cost, and short service life, which leads to high energy consumption, poor safety, and low economy in practical applications, which seriously limits the advantages of ammonia-hydrogen energy. Therefore, it is of great significance to develop low-temperature, high-efficiency, and low-cost ammonia decomposition hydrogen production catalytic materials.

[0004] With the continuous advancement of the dual-carbon strategic goals and the continuous improvement of carbon emission requirements, the field of ammonia decomposition and hydrogen production has received more and more attention and importance. The catalytic system composed of ruthenium as the active element and metal oxide as the carrier is currently the most outstanding catalytic performance and the most fruitful research results. Patent CN 117861651 A discloses a method for preparing a high-activity and high-stability ammonia decomposition catalytic material with γ-Al2O3 as the carrier and Ru as the active component. By adjusting the roasting atmosphere, roasting conditions, and alkali metal types, it provides a solution for high-temperature sintering agglomeration and low-temperature activity. Patent CN118237041A discloses a method for preparing a high-efficiency ammonia decomposition and hydrogen production ruthenium-based catalytic material with a composite oxide Co-Al-LDOs as a carrier. By accurately controlling the molar ratio of raw materials and the ratio of solution, the catalytic efficiency of the catalytic material at 450°C is increased to 68.94%. Patent CN118122321A uses a microwave-assisted method to synthesize Ru / CeO2 ammonia decomposition catalytic material in one step, thereby improving the activity and stability of the catalytic material and shortening the preparation cycle.

[0005] In summary, a lot of basic research has been carried out on catalytic materials for hydrogen production from ammonia decomposition, and certain research results have been achieved. However, existing catalytic materials still have problems such as cumbersome preparation procedures, high energy and reagent consumption in the preparation process, and insufficient catalytic activity and chemical stability of catalytic materials, which restrict their application in practical scenarios. Therefore, it is urgent to develop and design a new type of efficient and stable catalytic material for hydrogen production from ammonia decomposition through innovative preparation methods. Summary of the invention

[0006] The purpose of the present invention is to solve the above-mentioned problems existing in practical application scenarios, and to provide a ruthenium-based ammonia decomposition hydrogen production catalyst coated with porous carbon and its preparation method and application, so as to simplify the preparation process of ammonia decomposition hydrogen production catalytic materials, and meet the requirements of low temperature and high efficiency, stable structure and low loading, so as to improve the catalytic efficiency of the ammonia decomposition reaction.

[0007] The present invention is achieved through the following technical solutions:

[0008] The present invention provides a porous carbon-coated ruthenium-based ammonia decomposition hydrogen production catalyst, which has a core-shell structure, wherein the core layer comprises an active component and a carrier material, the active component is ruthenium, and the carrier material is cerium oxide; and the shell layer material is a nitrogen-doped porous carbon material.

[0009] Furthermore, in the present invention, the particle size of the catalyst is 40-60 mesh.

[0010] The present invention also provides a method for preparing a ruthenium-based ammonia decomposition hydrogen production catalyst coated with porous carbon, comprising the following steps:

[0011] S1: Place the surfactant, cerium salt and organic acid ligand in a mixed solvent in a certain proportion step by step, stirring each step until they are evenly dispersed before adding new substances;

[0012] S2: heating the mixed solution for a period of time, centrifuging, washing, and drying to obtain a carrier precursor powder;

[0013] S3: re-dispersing the carrier precursor powder uniformly in the solvent, adding a certain amount of ruthenium precursor to the carrier solution, and sequentially performing ultrasonic, stirring, washing, and drying operations to obtain a catalytic material precursor;

[0014] S4: heat-treating the catalyst material precursor under a suitable atmosphere;

[0015] S5: After naturally cooling to room temperature, grinding, tableting and screening are performed in sequence to obtain a ruthenium-based ammonia decomposition hydrogen production catalytic material.

[0016] Furthermore, in the above step S1, the mixed solvent is a mixed solvent containing ethanol and an organic solvent to dissolve the raw materials; the surfactant is polyvinyl pyrrolidone (PVP), the cerium salt is cerium nitrate hexahydrate (CeNO3·6H2O), and the organic acid ligand is 1,3,5-trimethylbenzenecarboxylic acid (H3-BTC).

[0017] Furthermore, in the above step S2, the heating method is a hydrothermal method, the uniformly mixed solution is transferred to a sealed autoclave, heated to 80°C, and maintained for 24 hours to obtain a carrier precursor; the washing operation refers to multiple washings with ethanol and DMF; and the drying treatment temperature is 70°C.

[0018] Furthermore, in the above step S3, the dispersing solvent is ethanol; the Ru precursor is Ru3(CO) 12 , Ru(NO)(NO3)3, Ru(acac)3, RuCl3; the mass fraction of the active component Ru is 3wt% with the mass of the carrier after calcination as the reference standard; the washing treatment refers to washing with ethanol and deionized water for multiple times; the stirring time is 12 hours; the drying temperature is 80°C and the drying time is 24 hours.

[0019] Furthermore, in step S4, the appropriate atmosphere for the heat treatment is an inert gas, and the preferred gas type is argon; the heat treatment conditions are slowly heated to 300°C and maintained for 1 hour, and then heated to 550°C and maintained for 3 hours.

[0020] The present invention also provides an application of the catalyst, wherein the catalyst is used for decomposing ammonia to produce hydrogen.

[0021] Furthermore, in the application of the above catalyst, the catalyst is loaded into a quartz tube of an ammonia decomposition hydrogen production reaction device, and is activated at high temperature under NH3 atmosphere and then subjected to a programmed temperature test.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] The present invention makes full use of the characteristics of MOF materials, such as high order, high specific surface area, and adjustable pore properties, and improves the dispersion of the active component ruthenium through spatial confinement and electron transfer effects, and improves the extranuclear electronic properties of Ru, thereby increasing the reaction sites and intrinsic activity of the catalyst. Furthermore, the present invention uses cerium oxide materials with highly variable valence states and abundant oxygen vacancies as catalyst carriers, and since the cerium element is used as a MOF skeleton node, it can be closely combined with ruthenium after heat treatment.

[0024] The present invention adopts a hydrothermal method to prepare a Ce-based MOF material as a carrier precursor, adopts an impregnation method to disperse Ru in the pores of the MOF material, and finally adopts an inert gas step-by-step calcination to obtain a low-temperature, high-efficiency, low-ruthenium content ammonia decomposition hydrogen production catalytic material. In particular, Ru3(CO) 12 The ammonia decomposition catalyst prepared for the Ru precursor showed the best catalytic activity. The test results showed that the NH3 decomposition rate reached 87.8% at 350°C and 98.6% at 400°C. The active component prepared by this preparation method has good dispersibility, the carrier material has a large specific surface area, and performs well in the ammonia decomposition hydrogen production reaction. It is a low-temperature, high-efficiency, low-ruthenium content ammonia decomposition hydrogen production catalytic material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A curve diagram showing the ammonia decomposition rate of the catalysts prepared in Examples 1, 2, 3 and 4 of the present invention in the ammonia decomposition hydrogen production reaction;

[0026] Figure 2 This is a curve diagram of the ammonia decomposition rate of the catalysts prepared in Example 1 of the present invention and Comparative Examples 1 and 2 in the ammonia decomposition hydrogen production reaction. DETAILED DESCRIPTION

[0027] In order to make the technical solution of the present invention clearer and easier to understand, the present invention will be described in detail below in conjunction with specific examples. It should be emphasized that these examples are only used to illustrate the embodiments of the present invention and do not constitute a limitation on the scope of protection of the present invention. In the following examples, for steps that do not specify the operating conditions, they should be performed according to the conventional conditions well known to those skilled in the art, or according to the instructions of the relevant products. As for the chemical reagents that do not specify the specific manufacturers in the examples, they should all be understood as general chemicals that meet national quality standards, and these chemicals can be obtained through conventional market channels.

[0028] Hydrothermal preparation process:

[0029] Take equal volumes of ethanol and N,N-dimethylformamide (DMF), stir until uniformly mixed, then add polyvinyl pyrrolidone (PVP), 0.05mol / L cerium nitrate hexahydrate (CeNO3·6H2O) and 0.1mol / L 1,3,5-trimethylbenzene carboxylic acid (H3-BTC) in sequence. Transfer the uniformly mixed solution to a sealed autoclave, heat to 80°C, and keep it for 24 hours. After cooling naturally to room temperature, wash it repeatedly with ethanol and DMF for several times, and dry it at 70°C for 24 hours to obtain a carrier precursor (Ce-BTC) powder.

[0030] Example 1

[0031] The support precursor (Ce-BTC) powder prepared by hydrothermal method was redispersed in ethanol solution, and a certain amount of Ru3(CO) 12 Dissolved in the mixed solution. After stirring at a speed of 500r / min for 12 hours, it was repeatedly washed with ethanol and deionized water several times and dried at 80°C for 24 hours. The obtained powder was placed in a tubular furnace and argon was introduced for heat treatment. During the heat treatment process, it was heated from room temperature to 300°C at a heating rate of 10°C / min and maintained at 300°C for 1 hour, and then continued to rise to 550°C at a heating rate of 10°C / min and maintained for 3 hours. After returning to room temperature, a mixture with a certain powder-to-particle ratio was obtained, and the Ru3(CO)12 / CeOx@PCN catalytic material was finally obtained by tableting.

[0032] Example 2

[0033] The carrier precursor (Ce-BTC) powder prepared by the hydrothermal method was re-dispersed in an ethanol solution, and a certain amount of Ru(NO)(NO3)3 was weighed and dissolved in the mixed solution. After stirring at a speed of 500r / min for 12 hours, it was repeatedly washed with ethanol and deionized water several times and dried at 80°C for 24 hours. The obtained powder was placed in a tubular furnace and argon was introduced for heat treatment. During the heat treatment process, the temperature was heated from room temperature to 300°C at a heating rate of 10°C / min, and maintained at 300°C for 1 hour, and then continued to rise to 550°C at a heating rate of 10°C / min and maintained for 3 hours. After returning to room temperature, a mixture with a certain powder-to-particle ratio was obtained, and Ru(NO)(NO3)3 / CeO was finally obtained by tableting. x @PCN catalytic material.

[0034] Example 3

[0035] The carrier precursor (Ce-BTC) powder prepared by the hydrothermal method was re-dispersed in an ethanol solution, and a certain amount of Ru(acac)3 was weighed and dissolved in the mixed solution. After stirring at a speed of 500r / min for 12 hours, it was repeatedly washed with ethanol and deionized water several times and dried at 80°C for 24 hours. The obtained powder was placed in a tubular furnace and argon was introduced for heat treatment. During the heat treatment process, the temperature was heated from room temperature to 300°C at a rate of 10°C / min, and maintained at 300°C for 1 hour, and then continued to rise to 550°C at a rate of 10°C / min and maintained for 3 hours. After returning to room temperature, a mixture with a certain powder-to-particle ratio was obtained, and Ru(acac)3 / CeO was finally obtained by tableting. x @PCN catalytic material.

[0036] Example 4

[0037] The carrier precursor (Ce-BTC) powder prepared by the hydrothermal method was re-dispersed in an ethanol solution, and a certain amount of RuCl3 was weighed and dissolved in the mixed solution. After stirring at a speed of 500r / min for 12 hours, it was repeatedly washed with ethanol and deionized water several times and dried at 80°C for 24 hours. The obtained powder was placed in a tubular furnace and argon was introduced for heat treatment. During the heat treatment process, the temperature was heated from room temperature to 300°C at a heating rate of 10°C / min, and maintained at 300°C for 1 hour, and then continued to rise to 550°C at a heating rate of 10°C / min and maintained for 3 hours. After returning to room temperature, a mixture with a certain powder-particle ratio was obtained, and RuCl3 / CeO was finally obtained by tableting. x @PCN catalytic material.

[0038] Comparative Example 1

[0039] The support precursor (Ce-BTC) powder prepared by hydrothermal method was redispersed in ethanol solution, and a certain amount of Ru3(CO) 12 Dissolved in the mixed solution. After stirring at a speed of 500r / min for 12 hours, it was repeatedly washed with ethanol and deionized water several times and dried at 80°C for 24 hours. The obtained powder was placed in a muffle furnace for air calcination. The calcination procedure was to heat from room temperature to 300°C at a heating rate of 10°C / min, and maintain at 300°C for 1 hour, and then continue to heat to 550°C at a heating rate of 10°C / min and maintain for 3 hours. After returning to room temperature, a mixture with a certain powder-to-particle ratio was obtained, and Ru3(CO) was finally obtained by tableting. 12 / CeO2 catalytic material.

[0040] Comparative Example 2

[0041] Weigh a certain amount of graphite powder and ultrasonically disperse it in ethanol solution for 1 hour. Then weigh a certain amount of Ru3(CO) 12 Dissolved in the mixed solution. After stirring at a speed of 500r / min for 12 hours, it was repeatedly washed with ethanol and deionized water several times and dried at 80°C for 24 hours. The obtained powder was placed in a tubular furnace and argon was introduced for heat treatment. During the heat treatment process, it was heated from room temperature to 300°C at a heating rate of 10°C / min and maintained at 300°C for 1 hour, and then continued to heat up to 550°C at a heating rate of 10°C / min and maintained for 3 hours. After returning to room temperature, a mixture with a certain powder-to-particle ratio was obtained, and Ru3(CO) was finally obtained by tableting. 12 / CNTs catalytic materials.

[0042] Application Example 1

[0043] In order to better illustrate the catalytic effect of the present invention, a test bench test system was built to test the catalytic activity of the ammonia decomposition catalytic materials prepared in Examples 1-4 and Comparative Examples 1-2. The test process is as follows:

[0044] Take 0.5g of the catalyst (40-60 mesh) into the quartz glass tube of the tube furnace, and introduce 16mL / min of NH3 to ensure that the experimental space velocity is 2,000mL·h -1 ·g cat -1 The experimental examples were pre-treated at 550°C.

[0045] Furthermore, the pretreatment duration is 1 hour.

[0046] After pretreatment, the temperature was raised uniformly from 250°C again and stayed at the test temperature until it stabilized, and then the data was recorded. The NH3 decomposition rate results of the catalyst at temperatures of 250°C, 300°C, 350°C, 400°C, 450°C, 500°C and 550°C are shown in Table 1.

[0047] Table 1 Activity evaluation results of examples and comparative examples

[0048]

[0049]

[0050] The activity test results of samples in Examples 1, 2, 3 and 4 of the present invention are as follows Figure 1 As shown in the figure, different types of ruthenium precursors with the same content have a significant effect on the catalytic ammonia decomposition activity of Ru-based catalysts, among which Ru3(CO) 12 >Ru(NO)(NO3)3>Ru(acac)3>RuCl3. The strong attraction of chloride ions to electrons and the electron donation of carbonyl ligands adjust the electronic structure of Ru, which is considered to be the reason for this result.

[0051] Figure 2 The activity test curves of Example 1 and Comparative Examples 1 and 2 obtained by changing different carriers are shown in the figure. As shown in the figure, the activities of the examples obtained by different carrier treatment methods are different, among which Ru3(CO) 12 / CeO x @PCN>Ru3(CO) 12 / CeO2>Ru3(CO) 12 / CNTs. There is an interaction between the porous carbonaceous material prepared by MOF material as a sacrificial template and cerium oxide, which jointly promotes the catalytic performance of Ru-based catalysts.

[0052] Combining Table 1 and Figure 2It can be seen that the Ru3(CO) prepared by the present invention 12 / CeO x @PCN sample has higher catalytic ammonia decomposition activity than other examples, with NH3 decomposition rate reaching 80.97% at 350°C and 97.82% at 400°C, showing broad prospects for industrial application.

[0053] The above description is only a preferred embodiment of the present invention. Any equivalent changes and modifications made by any technician familiar with the profession within the scope of the patent application of the present invention also belong to the scope covered by the claims attached to the present invention.

Claims

1. A porous carbon-coated ruthenium-based ammonia decomposition hydrogen production catalyst, which has a core-shell structure, wherein the core layer includes an active component and a carrier material, characterized in that: The active component is ruthenium, the carrier material is cerium oxide, and the shell material is nitrogen-doped porous carbon material.

2. The porous carbon-coated ruthenium-based ammonia decomposition hydrogen production catalyst according to claim 1, characterized in that The particle size of the catalyst is 40-60 mesh.

3. A method for preparing the porous carbon-coated ruthenium-based ammonia decomposition hydrogen production catalyst as claimed in claims 1 and 2, characterized in that The following steps are involved: S1: Place the surfactant, cerium salt and organic acid ligand in a mixed solvent in a certain proportion step by step, stirring each step until they are evenly dispersed before adding new substances; S2: heating the mixed solution for a period of time, centrifuging, washing, and drying to obtain a carrier precursor powder; S3: re-dispersing the carrier precursor powder uniformly in the solvent, adding a certain amount of ruthenium precursor to the carrier solution, and sequentially performing ultrasonic, stirring, and drying operations to obtain a catalytic material precursor; S4: heat-treating the catalyst material precursor under a suitable atmosphere; S5: After naturally cooling to room temperature, grinding, tableting and screening are performed in sequence to obtain a ruthenium-based ammonia decomposition hydrogen production catalytic material.

4. The method for preparing the porous carbon-coated ruthenium-based ammonia decomposition hydrogen production catalyst according to claim 3, characterized in that In step S1, the mixed solvent is a mixed solvent containing ethanol and an organic solvent to dissolve the raw materials; the surfactant is polyvinyl pyrrolidone, the cerium salt is cerium nitrate hexahydrate, and the organic acid ligand is 1,3,5-trimethylbenzene.

5. The method for preparing the porous carbon-coated ruthenium-based ammonia decomposition hydrogen production catalyst according to claim 3, characterized in that In step S2, the heating method is a hydrothermal method, the mixed solution is transferred to a sealed autoclave, heated to 80°C, and maintained for 24 hours to obtain a carrier precursor.

6. The method for preparing the porous carbon-coated ruthenium-based ammonia decomposition hydrogen production catalyst according to claim 3, characterized in that In step S3, the dispersing solvent is ethanol; the Ru precursor is Ru3(CO) 12 , Ru(NO)(NO3)3, Ru(acac)3, RuCl3; the stirring time is 12 hours; the drying temperature is 80°C and the drying time is 24 hours.

7. The method for preparing the porous carbon-coated ruthenium-based ammonia decomposition hydrogen production catalyst according to claim 3, characterized in that In step S4, the appropriate atmosphere is an inert gas, and the preferred gas type is argon; the heat treatment condition is to slowly heat to 300°C and maintain for 1 hour, then heat to 550°C and maintain for 3 hours.

8. The method for preparing the porous carbon-coated ruthenium-based ammonia decomposition hydrogen production catalyst according to claim 3, characterized in that In step S5, the mass fraction of Ru in the ruthenium-based ammonia decomposition hydrogen production catalytic material is 3 wt.%.

9. Use of a catalytic material as claimed in any one of claims 1 to 3 or a catalytic material prepared by the method as claimed in any one of claims 4 to 8, characterized in that The catalytic material is used for decomposing ammonia to produce hydrogen.

10. Use of the catalytic material according to claim 9, characterized in that The catalytic material is loaded into a quartz tube of an ammonia decomposition hydrogen production reaction device, and is reduced at high temperature in a pure NH3 atmosphere before undergoing an ammonia decomposition hydrogen production reaction.

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