A barium-doped carbon-supported iron nanoparticle material, a preparation method thereof and application thereof in catalyzing ammonia pyrolysis to produce hydrogen
By dispersing iron ions in phenolic resin and preparing barium-doped carbon-supported iron nanoparticles, the problem of high cost of precious metal catalysts is solved, and efficient performance and stability of hydrogen production from ammonia pyrolysis are achieved, making it suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN UNIV OF TECH
- Filing Date
- 2023-12-26
- Publication Date
- 2026-06-26
AI Technical Summary
In the existing technology, precious metal-based catalysts are expensive and have low abundance in the process of ammonia decomposition to produce hydrogen, making it difficult to apply them on a large scale. In addition, the existing non-precious metal catalysts have insufficient catalytic activity and stability.
Iron-based carbon materials were formed by uniformly dispersing iron ions in phenolic resin and carbonizing them. Then, barium-doped carbon-supported iron nanoparticles were prepared by doping with barium salt solution, freeze-drying and calcination. The iron nanoparticles were uniformly distributed, and the barium element regulated the electronic structure to improve catalytic activity.
The prepared barium-doped carbon-supported iron nanoparticles achieved a catalytic ammonia conversion efficiency of over 90% at 550℃ and a space velocity of 6000 h⁻¹. The process was low-cost, simple, and environmentally friendly, making it suitable for large-scale production.
Smart Images
Figure CN117816177B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst technology containing iron-based metals, specifically relating to a barium-doped carbon-supported iron nanoparticle material, its preparation method, and its application in catalytic ammonia pyrolysis for hydrogen production. Background Technology
[0002] The use of fossil fuels has propelled human civilization, but it has also inevitably brought about environmental pollution and other problems. Social development has made clean energy increasingly important. Hydrogen is one of the most promising energy carriers, boasting a high enthalpy of combustion (142 MJ / kg) and zero carbon emissions. However, due to its low volumetric energy density and high risk, developing an efficient and convenient transport medium remains a pressing need, which has become a bottleneck for its large-scale industrial application. Currently, storing hydrogen by liquefying it under low temperature or high pressure requires extremely high energy. To address these issues, ammonia (NH3) is considered a promising alternative to hydrogen. On the one hand, ammonia has a high hydrogen content (~17.7 wt%) and mild liquefaction conditions, liquefying at approximately -25°C and about 3 atmospheres. On the other hand, ammonia decomposes into only hydrogen and nitrogen under appropriate catalysts, which is beneficial for subsequent separation and purification. Among various catalysts, noble metal-based catalysts, especially ruthenium-based catalysts, exhibit excellent catalytic performance for ammonia decomposition, but their high price and low abundance limit their large-scale application. Therefore, developing non-precious metal catalysts for ammonia decomposition with high activity and high stability is an urgent task. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a barium-doped carbon-supported iron nanoparticle material, its preparation method and its application in catalytic ammonia pyrolysis for hydrogen production. The barium-doped carbon-supported iron nanoparticle material has iron nanoparticles uniformly distributed on its surface and inside, exhibits high catalytic ammonia decomposition efficiency, and is prepared using non-precious metals as raw materials, thus having a price advantage.
[0004] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:
[0005] A barium-doped carbon-supported iron nanoparticle material is provided, which is obtained by mixing an iron-based carbon material obtained by uniformly dispersing organic iron in phenolic resin and then carbonizing it with a barium salt solution, followed by freeze-drying and calcination. The barium-doped carbon-supported iron nanoparticle material has iron nanoparticles uniformly distributed on its surface and inside, and barium elements are uniformly dispersed on the surface of the barium-doped carbon-supported iron nanoparticle material.
[0006] According to the above scheme, the carbon in the barium-doped carbon-supported iron nanoparticle material is amorphous carbon.
[0007] According to the above scheme, the iron nanoparticles have a particle size of 3-4 nm.
[0008] According to the above scheme, the iron content and barium content in the barium-doped carbon-supported iron nanoparticle material are 3-8% by mass and 3-8% by mass.
[0009] This invention also includes a method for preparing the above-mentioned barium-doped carbon-supported iron nanoparticle material, the specific steps of which are as follows:
[0010] 1) Add organic iron and phenolic resin to an organic solvent, heat to dissolve and obtain a uniform iron-phenolic resin mixed solution, then dry to remove the organic solvent to obtain iron-phenolic resin.
[0011] 2) The iron-phenolic resin obtained in step 1) is carbonized in an inert atmosphere to obtain iron-based carbon material, which is then ground into powder. The obtained iron-based carbon material is then mixed with barium salt solution. After the mixture is homogeneous, it is freeze-dried and then calcined in a reducing atmosphere to obtain barium-doped carbon-supported iron nanoparticle material.
[0012] According to the above scheme, the organic iron in step 1) is one of ferric acetylacetonate, ferric phthalocyanine, ferrocene, and ferric citrate. More preferably, the organic iron is ferric acetylacetonate.
[0013] According to the above scheme, the phenolic resin in step 1) is one of ordinary phenolic resin, water-soluble phenolic resin, or a mixture of both.
[0014] According to the above scheme, the organic solvent in step 1) is one or a mixture of several of ethanol, isopropanol, acetone, and N,N-dimethylformamide.
[0015] According to the above scheme, the mass ratio of phenolic resin to organic iron in step 1) is 5 to 10:1.
[0016] According to the above scheme, the mass-to-volume ratio of phenolic resin to organic solvent in step 1) is 0.1–0.3 g / mL.
[0017] According to the above scheme, the heating and melting temperature in step 1) is 25-50℃.
[0018] According to the above scheme, step 2) uses one of nitrogen, helium, or argon as the inert atmosphere.
[0019] According to the above scheme, the carbonization process conditions for step 2) are: heat treatment at 800-1300℃ for 0.5-3 hours.
[0020] According to the above scheme, the barium salt solution in step 2) is an aqueous solution of barium salt with a concentration of 0.01 to 0.05 g / mL, and the barium salt is one or more of barium nitrate, barium chloride, and barium sulfate.
[0021] According to the above scheme, in step 2), the molar ratio of iron in the iron-based carbon material to barium in the barium salt solution is 1:1 to 2.
[0022] According to the above scheme, the reducing atmosphere in step 2) is one of the following: a mixture of hydrogen and argon (where hydrogen accounts for 8-12 vol%), a mixture of ammonia and argon (where ammonia accounts for 8-12 vol%), or a mixture of carbon monoxide and argon (where carbon monoxide accounts for 8-12 vol%).
[0023] According to the above scheme, the process conditions for calcination in step 2) are: heating at 400-700℃ for 1-2.5 hours.
[0024] The present invention also includes the application of the above-mentioned barium-doped carbon-supported iron nanoparticles in the catalytic ammonia pyrolysis for hydrogen production.
[0025] The specific application method is as follows: Barium-doped carbon-supported iron nanoparticles are placed in a fluidized bed reactor as a catalyst. Argon gas is purged for 30 minutes to remove impurities adhering to the catalyst. Then, the temperature is increased to 300–400°C at a rate of 5°C / min and held for 1 hour to activate the catalyst. After activation, pure ammonia gas is introduced at 400–600°C and a pure ammonia gas space velocity of 3000–10000 h⁻¹. -1 Catalytic decomposition of ammonia.
[0026] This invention prepares iron-based carbon materials by uniformly dispersing non-precious metal iron ions in phenolic resin, immobilizing the iron ions using the phenolic resin polymer framework, and then performing high-temperature carbonization. The phenolic resin is directly carbonized to become the carbon support, and the previously added organic iron aggregates into nanoparticles that are uniformly distributed on the carbon support to maximize active sites. Then, barium-doped carbon-supported iron nanoparticles are obtained through doping with barium salt solution, freeze-drying, and calcination. The Ba doping affects the d-band electron structure of the Fe nanoclusters, adjusts the NH bond desorption energy, and improves its catalytic activity. This allows the prepared barium-doped carbon-supported iron nanoparticles to function as a catalyst for ammonia pyrolysis hydrogen production at 550°C and a space velocity of 6000 h⁻¹. -1 Under certain conditions, the catalytic ammonia conversion efficiency reaches over 90%.
[0027] The beneficial effects of this invention are as follows: 1. The barium-doped carbon-supported iron nanoparticle material provided by this invention has good catalytic performance for hydrogen production from ammonia pyrolysis, at 550℃ and a space velocity of 6000h⁻¹. -1Under suitable conditions, the catalytic ammonia conversion efficiency reaches over 90%, and the cost is low, showing promising prospects for industrial application. 2. This invention utilizes an organic iron-phenolic resin precursor for one-step carbonization to form an iron-based catalyst. Uniform distribution of active sites can be achieved without the use of any surfactants or dispersants. The preparation method is simple, easy to operate, and has good repeatability. The entire reaction process is non-toxic, environmentally friendly, and easy for large-scale production. Attached Figure Description
[0028] Figure 1 This is the XPS full spectrum of the barium-doped carbon-supported iron nanoparticle material prepared in Example 1 of this invention;
[0029] Figure 2 This is a TEM image of the barium-doped carbon-supported iron nanoparticle material prepared in Example 1;
[0030] Figure 3 This is a particle size distribution diagram of the barium-doped carbon-supported iron nanoparticle material prepared in Example 1;
[0031] Figure 4 This is a mapping image of the barium-doped carbon-supported iron nanoparticle material prepared in Example 1;
[0032] Figure 5 The graph shows a comparison of the ammonia pyrolysis conversion efficiency of the barium-doped carbon-supported iron nanoparticles prepared in Examples 1-3 at different temperatures.
[0033] Figure 6 The image shows the durability test results of the barium-doped carbon-supported iron nanoparticle material prepared in Example 1 at 550°C for 120 hours.
[0034] Figure 7 This is a comparison of the ammonia pyrolysis conversion efficiency of the barium-doped carbon-supported iron nanoparticles prepared in Examples 1 and 4-5 at different temperatures;
[0035] Figure 8 The graph shows a comparison of the ammonia pyrolysis conversion efficiency of the ammonia pyrolysis hydrogen production catalysts prepared in Example 1 and Comparative Examples 1-2 at different temperatures. Detailed Implementation
[0036] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.
[0037] Example 1
[0038] A barium-doped carbon-supported iron nanoparticle material is prepared by the following steps:
[0039] 1) Add 4g of phenolic resin (Ron, BR grade) and 0.6g of acetylacetone iron to 20mL of anhydrous ethanol, heat and stir at 40℃ for 0.5h to obtain an iron-phenolic resin mixed solution. Dry the obtained iron-phenolic resin mixed solution in a forced-air drying oven at 70℃ for 18h to obtain iron-phenolic resin.
[0040] 2) The iron-phenolic resin obtained in step 1) was carbonized at 1100℃ for 2 hours under a nitrogen atmosphere to obtain an iron-based carbon material. The carbon material was ground into powder and then mixed with a barium salt solution (0.45g barium nitrate dissolved in 20mL water). The mixture was stirred for 6 hours until homogeneous, then freeze-dried and calcined at 600℃ for 2 hours in an H2 / Ar mixed gas (H2 content of 10 vol%) to obtain barium-doped carbon-supported iron nanoparticle material (Ba / Fe-PRC). The iron content in the product was 4.9203% by mass and the barium content was 4.3829% by mass.
[0041] The ammonia conversion catalytic efficiency of the barium-doped carbon-supported iron nanoparticles prepared in this embodiment as an ammonia pyrolysis hydrogen production catalyst was tested in a fixed-bed reactor. A mass flow meter was used to control the gas flow rate, and a gas chromatograph was used to detect and analyze the gas concentration. The reaction temperature was controlled by an automated temperature controller at 550°C, with a heating rate of 10 K / min and a pure ammonia gas hourly space velocity of 6000 h⁻¹. -1 The catalyst was loaded into a quartz tube and installed in the corresponding position of the detector. It was reduced at a constant temperature of 773 K and Ar gas at a flow rate of 10 mL / min for 2 h. Then, the temperature was lowered to 573 K and the catalyst was purged with ammonia gas to bring it down to room temperature. The temperature was then increased to the set temperature at a heating rate of 25 K / min and reacted for 1 h. The ammonia conversion catalytic efficiency of the ammonia pyrolysis hydrogen production catalyst in this embodiment at 550 °C was measured to be 95%. The ammonia conversion catalytic efficiency = (initial ammonia content - treated ammonia content) / initial ammonia content × 100%.
[0042] Figure 1 The image shows the XPS full spectrum of the barium-doped carbon-supported iron nanoparticle material prepared in this embodiment. As can be seen from the image, iron and barium were successfully doped into the amorphous carbon.
[0043] Figure 2 and Figure 3 The images show TEM images and particle size distribution of the barium-doped carbon-supported iron nanoparticle material prepared in Example 1. As can be seen from the images, the iron nanoparticles are uniformly distributed on the carbon support, and the particle size of the iron nanoparticles is uniformly distributed with a size of about 3 nm.
[0044] Figure 4The images show HAADF-TEM (left) and mapping (right) images of the barium-doped carbon-supported iron nanoparticle material prepared in this embodiment. It can be seen from the images that iron and barium are uniformly distributed on the carbon support after carbonization of phenolic resin.
[0045] Example 2
[0046] A barium-doped carbon-supported iron nanoparticle material is prepared in a manner that differs from that in Example 1 in that the barium salt solution used in step 2) is obtained by dissolving 0.3 g of barium nitrate in 20 mL of water.
[0047] The ammonia conversion catalytic efficiency of the product prepared in this example was tested using the method of Example 1. The ammonia conversion catalytic efficiency of the ammonia pyrolysis hydrogen production catalyst in this example at 550°C was measured to be 92%.
[0048] Example 3
[0049] A barium-doped carbon-supported iron nanoparticle material is prepared in a manner that differs from that in Example 1 in that the barium salt solution used in step 2) is obtained by dissolving 0.9 g of barium nitrate in 20 mL of water.
[0050] The ammonia conversion catalytic efficiency of the product prepared in this example was tested using the method of Example 1. The ammonia conversion catalytic efficiency of the ammonia pyrolysis hydrogen production catalyst in this example at 550°C was measured to be 93%.
[0051] Example 4
[0052] A barium-doped carbon-supported iron nanoparticle material is prepared in a manner that differs from that in Example 1 in that the iron-phenolic resin in step 2) is carbonized at a temperature of 900°C under a nitrogen atmosphere.
[0053] The ammonia conversion catalytic efficiency of the product prepared in this example was tested using the method of Example 1. The ammonia conversion catalytic efficiency of the ammonia pyrolysis hydrogen production catalyst in this example at 550°C was measured to be 91%.
[0054] Example 5
[0055] A barium-doped carbon-supported iron nanoparticle material is prepared in a manner that differs from that in Example 1 in that the iron-phenolic resin in step 2) is carbonized at a temperature of 1300°C under a nitrogen atmosphere.
[0056] The ammonia conversion catalytic efficiency of the product prepared in this example was tested using the method of Example 1. The ammonia conversion catalytic efficiency of the ammonia pyrolysis hydrogen production catalyst in this example at 550°C was measured to be 90%.
[0057] Figure 5This is a comparison of the ammonia pyrolysis conversion efficiency of the barium-doped carbon-supported iron nanoparticle materials prepared in Examples 1-3 of this invention at different temperatures. The test method was the same as in Example 1, only the reaction temperature was adjusted. The horizontal axis represents temperature (°C), and the vertical axis represents the ammonia conversion catalytic efficiency (NH3 Conversion, %). It can be seen that the ammonia conversion catalytic efficiency of the ammonia pyrolysis hydrogen production catalysts in Examples 1-3 is all above 90% at 550°C. However, in Example 2, only 0.3g of barium nitrate was added during the preparation process, which was too small and insufficient to regulate the electrons on the surface of the iron nanoparticles, thus reducing the catalytic efficiency. In Example 3, 0.9g of barium nitrate was added during the preparation process, which was excessive and covered the catalytic active centers, thus reducing the catalytic efficiency. In Example 1, 0.6g of barium nitrate was added, and the product prepared had the best catalytic performance in ammonia pyrolysis hydrogen production.
[0058] Figure 6 The image shows the durability test results of the product prepared in Example 1 for catalytic ammonia pyrolysis to produce hydrogen. The test method was the same as in Example 1, with the product reacting at 550°C for 120 hours. It can be seen that the product of Example 1 has good durability.
[0059] Figure 7 The graph shows the comparison of ammonia pyrolysis conversion efficiency of barium-doped carbon-supported iron nanoparticles prepared in Examples 1 and 4-5 of this invention at different temperatures. The horizontal axis represents temperature (°C), and the vertical axis represents ammonia conversion catalytic efficiency (NH3 Conversion, %). It can be seen that the sample in Example 4 was calcined at 900°C, which is lower than the temperature in Example 1. The phenolic resin was in a hardened state, and the dense surface resulted in incomplete carbonization, which reduced the catalytic activity. The sample in Example 5 was calcined at 1300°C, which is higher than the temperature in Example 1. Excessive calcination caused the iron nanoparticles to agglomerate into clumps, reducing the reactive centers and lowering the catalytic activity.
[0060] Comparative Example 1
[0061] A catalyst for hydrogen production by ammonia pyrolysis is prepared in a manner similar to that in Example 1, except that iron acetylacetone in step 1) is replaced with an equimolar amount of iron sulfate.
[0062] The ammonia conversion catalytic efficiency of the product prepared in this comparative example was tested using the method of Example 1. The ammonia conversion catalytic efficiency of the ammonia pyrolysis hydrogen production catalyst in this comparative example at 550°C was measured to be 88%.
[0063] Comparative Example 2
[0064] A catalyst for hydrogen production by ammonia pyrolysis is prepared in a manner similar to that in Example 1, except that iron acetylacetone in step 1) is replaced with an equimolar amount of ferric chloride.
[0065] The ammonia conversion catalytic efficiency of the product prepared in this comparative example was tested using the method of Example 1. The ammonia conversion catalytic efficiency of the ammonia pyrolysis hydrogen production catalyst in this comparative example at 550°C was measured to be 86%.
[0066] Figure 8 This is a comparison graph of the ammonia pyrolysis hydrogen production catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention at different temperatures. The horizontal axis represents temperature (°C) and the vertical axis represents the ammonia conversion catalytic efficiency (NH3 Conversion, %). Comparative Examples 1 and 2 used ferric sulfate and ferric chloride as iron salts, and their catalytic efficiency was worse than that of Example 1.
Claims
1. A barium-doped carbon-supported iron nanoparticle material, characterized in that, The iron-based carbon material is obtained by uniformly dispersing organic iron in phenolic resin, carbonizing the resulting iron-phenolic resin at 800~1300℃ under an inert atmosphere, mixing it with a barium salt solution, freeze-drying it, and calcining it in a reducing atmosphere. The organic iron is one of acetylacetone iron, phthalocyanine iron, ferrocene, and ferric citrate. The molar ratio of iron to barium in the barium salt solution in the iron-based carbon material is 1:1~2. The barium-doped carbon-supported iron nanoparticle material has iron nanoparticles uniformly distributed on its surface and inside, with a particle size of 3-4 nm. Barium is uniformly dispersed on the surface of the barium-doped carbon-supported iron nanoparticle material. The mass percentage of iron in the barium-doped carbon-supported iron nanoparticle material is 3-8%, and the mass percentage of barium is 3-8%. The carbon in the barium-doped carbon-supported iron nanoparticle material is amorphous carbon.
2. A method for preparing barium-doped carbon-supported iron nanoparticles as described in claim 1, characterized in that, The specific steps are as follows: 1) Add organic iron and phenolic resin to an organic solvent, heat to dissolve and obtain a uniform iron-phenolic resin mixed solution, then dry to remove the organic solvent to obtain iron-phenolic resin. 2) The iron-phenolic resin obtained in step 1) is carbonized at 800~1300℃ under an inert atmosphere to obtain iron-based carbon material, which is then ground into powder. The obtained iron-based carbon material is then mixed with a barium salt solution. After the mixture is homogeneous, it is freeze-dried and then calcined in a reducing atmosphere to obtain barium-doped carbon-supported iron nanoparticle material. The organic iron is one of acetylacetone iron, phthalocyanine iron, ferrocene, and ferric citrate. The molar ratio of iron element in the iron-based carbon material to barium element in the barium salt solution is 1:1~2.
3. The method for preparing barium-doped carbon-supported iron nanoparticles according to claim 2, characterized in that, In step 1), the mass ratio of phenolic resin to organic iron is 5~10:
1.
4. The method for preparing barium-doped carbon-supported iron nanoparticles according to claim 2, characterized in that, The organic solvent in step 1) is one or a mixture of several of ethanol, isopropanol, acetone, and N,N-dimethylformamide; the mass-volume ratio of the phenolic resin to the organic solvent in step 1) is 0.1~0.3 g / mL.
5. The method for preparing barium-doped carbon-supported iron nanoparticles according to claim 2, characterized in that, Step 2) The carbonization process conditions are: heat treatment at 800~1300℃ for 0.5~3h; the barium salt solution in Step 2) is an aqueous solution of barium salt with a concentration of 0.01~0.05g / mL, and the barium salt is one or two of barium nitrate and barium chloride.
6. The method for preparing barium-doped carbon-supported iron nanoparticles according to claim 2, characterized in that, Step 2) The reducing atmosphere is one of the following: a mixture of hydrogen and argon, a mixture of ammonia and argon, or a mixture of carbon monoxide and argon; Step 2) The calcination process conditions are: heating at 400~700℃ for 1~2.5h.
7. The application of the barium-doped carbon-supported iron nanoparticle material according to claim 1 in the catalytic ammonia pyrolysis for hydrogen production.
8. The application of the barium-doped carbon-supported iron nanoparticle material according to claim 7 in the catalytic ammonia pyrolysis for hydrogen production, characterized in that, The specific application method is as follows: Barium-doped carbon-supported iron nanoparticles are placed in a fluidized bed reactor as a catalyst. Argon gas is purged for 30 minutes to remove impurities adhering to the catalyst. Then, the temperature is increased to 300-400℃ at a rate of 5℃ / min and held for 1 hour to activate the catalyst. After activation, pure ammonia gas is introduced at 400-600℃ with a pure ammonia gas space velocity of 3000-10000 h⁻¹. -1 Catalytic decomposition of ammonia.