Preparation method of iron-based catalyst, iron-based catalyst and application thereof

Abstract

The application discloses a preparation method of an iron-based catalyst, the iron-based catalyst and application of the iron-based catalyst. The preparation method mainly comprises three steps: firstly, a mixed solution of an iron-based precursor and an organic template agent with uniform distribution is prepared by means of stable temperature and autogenous pressure in a solvothermal process; subsequently, a weak alkaline precipitant without alkali metal is added into the mixed solution under heating to prepare an iron-based precipitate; finally, a honeycomb-shaped iron-based catalyst for ortho-para hydrogen conversion is prepared through steps of cleaning, drying, calcining, granulating, re-cleaning and activation. By adding the organic template agent, the pore structure of the catalyst is effectively improved without affecting the crystal type of the catalyst, and the performance of the catalyst is improved; and the weak alkaline precipitant without alkali metal is adopted, so that the controllability of the preparation process of the catalyst is enhanced, the influence of impurities such as alkali metal ions on the performance of the catalyst is effectively avoided, and the method has a simple process and high practical potential.

Description

Technical Field

[0001] This invention belongs to the technical field of catalysts, specifically relating to a honeycomb-shaped iron-based catalyst for the conversion of n- and secondary hydrogen, its preparation method, and its application. Background Technology

[0002] At room temperature, hydrogen gas consists of approximately 75% orthohydrogen and approximately 25% secondary hydrogen. As the temperature decreases, orthohydrogen, with its high-energy ground state, spontaneously converts to secondary hydrogen, which has a lower energy state. However, this process is extremely slow, and the heat released during this conversion easily causes hydrogen volatilization, leading to hydrogen loss. Therefore, rapid and efficient conversion of orthohydrogen to secondary hydrogen is a crucial step in achieving stable liquid hydrogen storage. Studies have shown that catalytic conversion using catalysts is an essential pathway to achieve rapid conversion and efficient liquefaction of orthohydrogen and secondary hydrogen. Among numerous catalysts for orthohydrogen and secondary hydrogen conversion, iron-based catalysts have attracted widespread attention due to their high activity and good safety performance. However, their dense structure and high SO4 content... 2- Cl - Anions and Na + K + Impurities such as alkali metal ions affect the high efficiency of traditional iron-based catalysts for n-parahydrogen conversion. Considering the crucial role of n-parahydrogen conversion in liquid hydrogen storage and transportation, the development of a new generation of high-performance iron-based catalysts for n-parahydrogen conversion is of great significance to the development of the hydrogen energy industry.

[0003] Currently, iron-based catalysts for the n-parahydrogen conversion are mainly prepared by adding a strong alkali to a soluble iron salt solution, as described in Chinese Patent CN113797928A. However, catalysts prepared by this method often suffer from high levels of impurities such as alkali metals, affecting their performance. Furthermore, the resulting catalysts tend to have a dense morphology, impacting the exposure of active sites within the catalyst matrix and the contact efficiency between reactants and the catalyst. To improve the pore structure of the catalyst, Chinese Patent CN112844443A describes loading active materials onto the surface of ordered mesoporous molecular sieves and activated carbon, followed by high-temperature calcination to obtain a supported n-parahydrogen conversion catalyst. However, the limited specific surface area of ​​the support results in a limited loading of active materials and an insufficient number of active sites, affecting catalyst performance. Additionally, this method suffers from limitations such as the high cost of mesoporous materials. Therefore, finding an iron-based catalyst for n-parahydrogen conversion with low alkali metal content, easily controllable pore structure, and a large number of active sites, along with a simple preparation process and practical potential, is particularly important.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a method for preparing iron-based catalysts. By using an organic compound with suitable molecular size and good hydrothermal stability as a template agent, the relative ratio of iron-based precursor to organic template agent is controlled to effectively improve the pore structure of the catalyst. By using a weakly alkaline precipitant that does not contain alkali metal ions, combined with precise control of temperature and pH during the sedimentation process, the influence of impurities such as alkali metal ions on catalyst performance is effectively avoided. Furthermore, by controlling parameters such as aging, activation, stirring, drying, and cleaning, the crystal type, specific surface area, and particle size of the catalyst are controlled, thereby comprehensively improving the catalytic and mechanical properties of the catalyst.

[0006] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0007] A method for preparing an iron-based catalyst includes the following steps:

[0008] (1) The iron salt precursor and the organic template agent are placed in a solvent, stirred and dissolved, and a mixed solution of iron ions and organic template agent is obtained by solvothermal reaction;

[0009] (2) While stirring under controlled temperature, add a precipitant free of alkali metal ions dropwise to the mixed solution and continue stirring to obtain an iron-based precipitate suspension;

[0010] (3) The iron-based precipitate suspension was aged, filtered and washed to obtain the iron-based precipitate;

[0011] (4) The iron-based precipitate is dried, roasted, crushed, washed and activated to obtain an iron-based catalyst.

[0012] Furthermore, the organic template agent is selected from one or a combination of several of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, didodecyldimethylammonium chloride, and didodecyldimethylammonium bromide.

[0013] Preferably, the organic template agent is hexadecyltrimethylammonium bromide.

[0014] Furthermore, the molar ratio of the iron salt precursor to the organic template agent is (1-10):1, preferably (5-8):1, and more preferably 7:1.

[0015] Preferably, the iron salt precursor is selected from one or a combination of several of ferric nitrate, ferric chloride, ferric sulfate, and ferric acetylacetone, and more preferably ferric nitrate.

[0016] Among the above schemes, the molecular size of the organic template agent is more suitable as a template agent for the n- and secondary hydrogen iron-based catalyst, and it has better hydrothermal stability. Under hydrothermal conditions, the interaction with the iron-based precursor is stronger. In particular, the catalyst prepared using hexadecyltrimethylammonium bromide as an organic template agent has more suitable pore size and bulk density, more uniform distribution, and is more conducive to the n- and secondary hydrogen conversion reaction.

[0017] Furthermore, during the process of iron-based precipitates undergoing crystal transformation through calcination in air, the organic template agent can be removed by high-temperature calcination without additional removal treatment, making the removal method simple and convenient.

[0018] Due to NO3 - It can be eliminated by roasting and decomposing in air without any further removal treatment. Therefore, the present invention preferably uses ferric nitrate as an iron-based precursor.

[0019] Through multiple experiments, it was found that when the relative content of iron-based precursor is too high, the specific surface area of ​​the catalyst is too small; when the relative content of organic template agent is too high, the mechanical strength of the catalyst is too low, and it is easy to break in practical applications; when the molar ratio of iron salt precursor to organic template agent is in the range of (1~10):1, especially when it is 7:1, the pore structure and mechanical strength of the catalyst are both within a reasonable range, and the catalyst performance is the best.

[0020] Furthermore, the solvent in step (1) is a mixture of water and isopropanol, with a molar ratio of water to isopropanol of (1-10):1, preferably (1-3):1, and more preferably 3:2.

[0021] Preferably, the mass ratio of the iron-based precursor to the mixed solvent is 1:(1-10), more preferably 1:(2-4), and even more preferably 1:3.

[0022] Preferably, the stirring and dissolving process is carried out at a temperature of 0 to 100°C for 1 to 10 hours, and more preferably at a temperature of 30°C for 5 hours.

[0023] Preferably, the solvothermal reaction is carried out at a temperature of 50–200°C for 1–20 h, more preferably at a temperature of 90–150°C for 8–12 h, and even more preferably at a temperature of 120°C for 10 h.

[0024] In the above scheme, specifically, in step (1), the iron salt precursor and the organic template agent are dissolved in a mixed solvent of water and isopropanol, stirred at a certain temperature for a period of time, and then transferred to a hydrothermal reactor lined with polytetrafluoroethylene. The mixture is kept at a certain temperature for a period of time to prepare a mixed solution in which iron ions and the organic template agent are uniformly distributed.

[0025] Because the iron-based precursor has high solubility in water and the organic template agent has high solubility in isopropanol solution, and because water and isopropanol are miscible, a mixed solvent of water and isopropanol was chosen as the solvent for dissolving the iron-based precursor and the organic template agent. Through multiple experiments, it was found that when the molar ratio of water to isopropanol is (1–10):1, especially 3:2, combined with the aforementioned defined molar ratio of iron salt precursor to organic template agent, the mass ratio of iron-based precursor to mixed solvent, and appropriate stirring temperature and time, the iron-based precursor and organic template agent achieve sufficient contact, resulting in the best solubility and dispersion uniformity in the solvent. This is beneficial for the organic template agent to improve the pore structure and mechanical properties of the catalyst, and also has a positive impact on the particle size and specific surface area control of the subsequent iron-based precipitate.

[0026] To further improve the solubility and dispersion uniformity of iron-based precursors and organic templates in a mixed solvent of water and isopropanol, a hydrothermal reactor containing the mixed solvent of iron-based precursors and organic templates was placed in an oven for a solvothermal reaction. Utilizing the strong dissolving power of the mixed solvent of water and isopropanol, and taking advantage of the suitable and stable temperature and the self-generated pressure of the mixed solvent during the solvothermal process, the solubility of iron-based precursors and organic templates in the mixed solvent of water and isopropanol was improved, and the iron ions and organic templates were uniformly distributed in the mixed solvent. Multiple experiments revealed that the solvothermal temperature was 50–200℃, the reaction time was 1–20 h, and especially the solvothermal temperature was 120℃ with a reaction time of 10 h, resulting in the best solubility and dispersion uniformity of iron ions and organic templates.

[0027] Furthermore, in step (2), the controlled temperature is 0 to 100°C, preferably 60 to 80°C, and more preferably 70°C.

[0028] Preferably, the stirring time is 1 to 10 hours, more preferably 1 to 3 hours, and even more preferably 2 hours.

[0029] Preferably, the stirring rate is 100-1000 r / min, more preferably 300-600 r / min, and even more preferably 500 r / min.

[0030] Preferably, the precipitant that does not contain alkali metal ions is selected from one or a combination of several of ammonia, ammonium bicarbonate, ammonium carbonate, and urea, preferably ammonia, and more preferably 0.5 mol / L ammonia.

[0031] Preferably, a precipitant free of alkali metal ions is added to the mixed solution until the pH of the solution is 8 to 13, more preferably 10 to 12, and even more preferably 11.

[0032] In the above solutions, the methods for controlling temperature are all within the protection scope of this application. The preferred method is water bath temperature control, which is adjustable, controllable, stable, and easy to operate.

[0033] Specifically, the mixed solution prepared in step (1) is transferred to a water bath at a certain temperature and stirred continuously for a period of time. Then, under stirring conditions, a weak alkaline precipitant without alkali metal ions is added dropwise until the acidity or alkalinity of the solution reaches a certain pH value. After stirring for a period of time, an iron-based precipitate suspension is obtained.

[0034] By adding a weakly alkaline precipitant free of alkali metal ions dropwise under water bath and stirring conditions, and by precisely controlling the environmental conditions during the formation of iron-based precipitates, a uniform iron-based suspension was prepared.

[0035] Since alkali metal ions have a significant impact on catalyst performance, this invention uses a weakly alkaline precipitant that does not contain alkali metal ions. Moreover, when using ammonia or other weakly alkaline substances as precipitants, the relatively weak alkalinity is beneficial for more precise control of the acidity and alkalinity of the solution, thereby controlling the sedimentation rate of iron ions and the particle size of the iron-based precipitate after sedimentation. After multiple experiments, it was found that using 0.5 mol / L ammonia as a precipitant resulted in the most suitable sedimentation rate of iron ions and the particle size of the iron-based precipitate after sedimentation.

[0036] Since temperature, stirring rate, and solution pH value affect the contact effect between iron ions and precipitant, and thus affect the physical structure of iron-based precipitate, after multiple experiments, it was found that the sedimentation rate of iron ions and the particle size of iron-based precipitate after sedimentation are most suitable when the solution temperature is 70℃, the stirring rate is 500r / min, and the solution pH value is 10-12.

[0037] Furthermore, in step (3), the aging is carried out at a temperature of 0 to 100°C for 10 to 30 hours, preferably at a temperature of 40 to 70°C for 15 to 30 hours, and more preferably at a temperature of 50°C for 24 hours.

[0038] Preferably, the cleaning solvent is a mixture of ethanol and water, with a mass ratio of ethanol to water of 1:(1-10), more preferably 1:(1-5), and even more preferably 1:3.

[0039] Preferably, the temperature of the mixed solvent of ethanol and water is 0 to 100°C, more preferably 50 to 80°C, and even more preferably 60°C.

[0040] In the above scheme, specifically, the iron-based precipitate suspension obtained in step (2) is transferred to an oven at a certain temperature and aged for a period of time. After aging, the iron-based precipitate is filtered out and washed with a mixed solvent of ethanol and water at least three times.

[0041] By aging the iron-based precipitate suspension in an oven and controlling the aging temperature and time, the nucleation rate of the iron-based precipitate can be regulated, thereby controlling the specific surface area of ​​the catalyst. After multiple experiments, it was found that the specific surface area of ​​the catalyst is most suitable when the aging temperature is 50℃ and the aging time is 24h.

[0042] A heated mixture of water and ethanol can effectively remove NO3 from transition metal-based precipitates. - Cl - and SO4 2- Anionic impurities were found to be minimal in the catalyst after washing with a mixed solvent of ethanol and water at a mass ratio of 1:3 and a temperature of 60°C. This method yielded iron-based precipitates with low impurity content and uniform physical properties.

[0043] Furthermore, in step (4), the drying is performed at a temperature of 80–200°C for 1–20 hours, preferably at a temperature of 90–150°C for 10–20 hours, and more preferably at a temperature of 120°C for 12 hours.

[0044] Preferably, the calcination is carried out at a temperature of 200-600°C for 1-10 hours, more preferably at a temperature of 300-500°C for 2-6 hours, and even more preferably at a temperature of 400°C for 5 hours.

[0045] Preferably, the solution used for rewashing is ultrapure water at 0–100°C, more preferably at 50–80°C, and even more preferably at 60°C.

[0046] Preferably, the activation is performed at a temperature of 50–200°C for 10–30 hours, more preferably at a temperature of 150–190°C for 20–25 hours, and even more preferably at a temperature of 180°C for 24 hours.

[0047] In the above scheme, specifically, the iron-based precipitate that has been cleaned in step (3) is placed in an oven at a certain temperature and dried for a period of time, then transferred to a muffle furnace and calcined at a certain temperature for a period of time, and then crushed into particles of a specific mesh size; the particles of a specific mesh size are washed with ultrapure water at a specific temperature and then transferred to an oven at a certain temperature and activated for a period of time to obtain an iron-based catalyst.

[0048] The transformation of the crystal form of iron-based species and the removal of organic template agents are completed through drying and calcination. Subsequently, iron-based particles with uniform particle size are prepared by crushing and sieving. Among them, the drying temperature and time affect the evaporation rate of free water, which in turn affects the specific surface area of ​​the catalyst. After multiple experiments, it was found that the evaporation rate of free water and the specific surface area of ​​the catalyst are most suitable when the drying temperature is 120℃ and the drying time is 12h.

[0049] When the block catalyst is crushed into granules, catalyst powder will adhere to the surface of the catalyst particles. Since the attached powder will block the pores of the catalyst, it is necessary to wash it with warm water in order to reduce the impact of the catalyst powder on the catalyst. After multiple experiments, it was found that the water temperature is 60℃ and the washing is three times is the most suitable.

[0050] Cleaned catalyst particles retain residual free water, and the surface catalyst undergoes a change in crystal type due to cleaning. To eliminate the impact of free water and the change in surface catalyst crystal type on the catalyst, further activation of the catalyst particles is necessary. Through activation treatment, by controlling the activation temperature and time, the free water content in the catalyst matrix can be effectively reduced, and the bulk density of the catalyst can be increased. This allows for a larger amount of catalyst to be packed into the fixed space inside the reactor, thereby improving catalyst performance. After multiple experiments, it was found that an activation temperature of 180℃ and an activation time of 24 hours are the most suitable.

[0051] An iron-based catalyst is prepared by the method described above. The iron-based catalyst is honeycomb-shaped and has a mesh size of 10 to 100 mesh, preferably 30 to 80 mesh.

[0052] In the above schemes, catalyst particle size that is too large will reduce the number of exposed active sites, thus affecting catalyst performance; catalyst particle size that is too small will cause greater resistance to the reactant gas in the reaction tube, thus increasing the gas resistance, reaction pressure, and energy consumption. Multiple experiments have shown that when the catalyst particle size is 10–100 mesh, especially 30–80 mesh, the number of exposed active sites is sufficient, and the gas resistance is within a reasonable range, without increasing reaction energy consumption.

[0053] Furthermore, the pore size of the iron-based catalyst is 10-50 nm, preferably 36 nm.

[0054] Preferably, the specific surface area of ​​the iron-based catalyst is 250–350 cm². 2 / g, preferably 315.2cm 2 / g.

[0055] In the above schemes, the iron-based catalyst prepared by the present invention has suitable pore size and specific surface area, which can expose more active sites, increase the loading of active materials, and improve the performance of the catalyst.

[0056] An application of an iron-based catalyst, as described above, is demonstrated in the conversion of n- and secondary hydrogen, at a volume hourly space velocity (VHSV) of 600 min⁻¹. -1 At that time, the positive hydrogen conversion rate was higher than 48%.

[0057] In the above schemes, the iron-based catalyst prepared by the present invention is suitable for devices such as hydrogen liquefaction equipment, liquid hydrogen storage tanks and secondary hydrogen generators, and is used for the conversion of ortho- and para-hydrogen to improve conversion efficiency.

[0058] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0059] 1. This invention uses organic materials with suitable molecular size and good hydrothermal stability as template agents. By changing the relative ratio between the iron-based precursor and the template agent, the pore structure of the catalyst can be effectively controlled without affecting the mechanical strength of the catalyst. More importantly, during the crystal transformation process of the iron-based precipitate in air, the organic template agent can be removed by means of the high-temperature calcination environment. Finally, without leaving any impurities, the pore structure of the catalyst can be effectively improved, the number of active sites of the catalyst can be increased, and the performance of the catalyst can be enhanced.

[0060] 2. This invention places a mixed solution containing iron ions and a template agent in a hydrothermal reactor. By utilizing the constant high temperature of the solvothermal environment and the self-generated pressure inside the reactor, the dispersion and uniformity of iron ions and the template agent in the mixed solution are improved. Combined with the precise control of reaction conditions such as temperature and pH during the subsequent sedimentation process, the internal pore structure of the catalyst is effectively improved.

[0061] 3. This invention effectively avoids the problem of alkali metal ions affecting catalyst performance in traditional n- and para-hydrogen catalysts by using a precipitant that does not contain alkali metal ions and has a weak alkalinity. At the same time, by utilizing the weak alkalinity of the precipitant, it effectively avoids the problem of excessively rapid changes in solution pH caused by the strong base used in the preparation of traditional n- and para-hydrogen catalysts. This achieves the purpose of precisely controlling the solution pH during the sedimentation process and effectively controlling the crystal type and particle size of the catalyst.

[0062] 4. This invention effectively removes NO3 from iron-based precipitates by using a mixed solvent of heated water and ethanol to wash them. - Impurities such as anions and alkali metal ions are effectively eliminated, thus reducing the impact of impurities on catalyst performance.

[0063] 5. This invention reduces the impact of powder generated during the pulverization process on the catalyst structure and performance by crushing and sieving block catalysts and combining them with the subsequent activation process, making the prepared catalyst particles more suitable for the actual application environment of devices such as hydrogen liquefaction equipment, liquid hydrogen storage tanks and secondary hydrogen generators.

[0064] 6. The preparation process of this invention is simple, has low requirements for equipment performance, and has great practical potential.

[0065] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0066] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings:

[0067] Figure 1 These are scanning electron microscope (SEM) images of the catalyst in different embodiments of the present invention;

[0068] Figure 2 These are specific surface area (BET) test graphs of the catalyst in different embodiments of the present invention;

[0069] Figure 3 These are X-ray diffraction (XRD) patterns of the catalyst in different embodiments of the present invention;

[0070] Figure 4 These are H2-TPR (H2-TPR) diagrams of the catalyst in different embodiments of the present invention;

[0071] Figure 5 These are performance test diagrams of the catalyst in different embodiments of the present invention.

[0072] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0073] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below with reference to some embodiments. Those skilled in the art will understand that the following embodiments are only used to explain the technical principles of this invention and are not intended to limit the scope of protection of this invention. For example, although this application describes the steps of the method of this invention in a specific order, these orders are not restrictive. Those skilled in the art can perform the steps in different orders without departing from the basic principles of this invention.

[0074] It should be noted that:

[0075] Elemental content was tested using an ICP-AES instrument (Shimadzu ICPS-7500); scanning electron microscopy (SEM) characterization was performed using a JEM-2010F instrument to analyze the catalyst surface morphology; specific surface area (BET) was measured using a Quantachrome Autosorb-iQ fully automated specific surface area and pore size distribution analyzer, with N2 adsorption-desorption curves determined in a liquid nitrogen atmosphere, specific surface area calculated according to the BET equation, and pore structure data deduced from the BJH model; X-ray diffraction (XRD) characterization was performed using a Gigaku XRD-6000 diffractometer, with a scanning speed of 10° / min and a scanning range of 10°–90°; H2 temperature-programmed reduction (H2-TPR) was performed using a Micromeritics ChemisSorb2720 instrument with a thermal conductivity detector (TCD), with a test range of 25–900℃.

[0076] (1) Test method for catalyst mechanical strength: First, the particle diameter of each catalyst was measured using vernier calipers, and the cross-sectional area was calculated. Second, the catalyst was placed vertically in a mechanical strength tester, and the maximum pressure value that each catalyst could withstand was measured. Finally, the maximum pressure value that each catalyst could withstand was calculated by combining the cross-sectional area of ​​each catalyst and the maximum pressure it could withstand. Each catalyst was tested twenty times, and the two maximum values ​​and two minimum values ​​were removed. The average value of the remaining sixteen tests was taken as the mechanical strength test value of the catalyst.

[0077] (2) Method for testing the bulk density of the catalyst: First, weigh a certain amount of catalyst using a balance. Place the weighed catalyst into a suitable clean graduated cylinder and secure the cylinder to the base of the tap density meter using clips. Second, turn on the power switch of the tap density meter, set the vibration frequency, and begin vibration. After vibration, record the reading on the graduated cylinder as the volume of the catalyst. Finally, calculate the bulk density of the catalyst by combining its weight and volume. Each catalyst is tested ten times; the maximum and minimum values ​​are removed, and the average of the remaining eight tests is taken as the bulk density test value for that catalyst.

[0078] (3) Catalyst activity testing method: Weigh 10g of catalyst at liquid nitrogen temperature, fill the catalyst into a test tube, immerse the test tube containing the catalyst in liquid nitrogen, and maintain this for a period of time to ensure that the entire catalyst bed is at liquid nitrogen temperature. Based on the amount of catalyst, introduce the corresponding amount of hydrogen gas. The hydrogen reaction gas contains 75% positive hydrogen and 25% secondary hydrogen. During the test, the volume hourly space velocity (VHSV) of the hydrogen reaction gas is 50–1200 min⁻¹. -1 At this point, some of the positive hydrogen is converted into secondary hydrogen under the action of the catalyst. The performance of the catalyst is calculated by testing the concentration of secondary hydrogen at the outlet of the reaction tube.

[0079] Example 1

[0080] (1) Ferric nitrate and hexadecyltrimethylammonium bromide were dissolved in a mixed solvent of water and isopropanol and stirred at 30°C for 5 hours to form a mixed solution. The molar ratio of ferric nitrate to hexadecyltrimethylammonium bromide was 7:1, the molar ratio of water to isopropanol was 3:2, and the mass ratio of ferric nitrate to the mixed solvent was 1:3.

[0081] (2) Transfer the mixed solution in step (1) into a polytetrafluoroethylene-lined hydrothermal reactor and place it in an oven at 120°C for 10 hours. When the temperature drops to room temperature, take out the mixture in the hydrothermal reactor to obtain a mixed solution that has undergone a solvothermal reaction.

[0082] (3) Place the mixed solution after the solvothermal reaction in a water bath at 70°C and stir at 500 r / min for 2 h. Then, add 0.5 mol / L ammonia water dropwise to the continuously stirred mixed solution until the pH of the mixed solution is 11. After the addition is completed, continue stirring for 2 h to obtain the mixed solution after sedimentation.

[0083] (4) Transfer the settled mixed solution to a water bath at 50°C, stop stirring, and age for 24 hours. Then, remove the iron-based precipitate and wash it three times with a mixed solvent of water and ethanol at 60°C to obtain the washed iron-based precipitate. The mass ratio of ethanol to water in the mixed solvent is 1:3.

[0084] (5) The cleaned iron-based precipitate was placed in an oven at 120°C and dried for 12 hours. After drying, it was transferred to a muffle furnace at 400°C and calcined for 5 hours. After calcination, the block catalyst was crushed into particles of 30-80 mesh.

[0085] (6) The crushed particles were washed with ultrapure water at 60°C. After washing three times, the particles were transferred to an oven at 180°C for activation for 24 hours to obtain a honeycomb iron-based catalyst for the conversion of positive and negative hydrogen.

[0086] Experimental Example 1

[0087] Based on Example 1, the use of the template agent was omitted or the type of template agent was changed, while other conditions remained unchanged, resulting in Example 2, Comparative Example 1, and Comparative Example 2. The prepared catalysts were then tested, and the test results are shown in Table 1.

[0088] Table 1

[0089]

[0090]

[0091] As can be seen from Table 1, when the volumetric hourly space velocity is 600 min... -1 In Examples 1 and 2, the catalysts prepared using the organic template agent of this application achieved a positive hydrogen conversion rate exceeding 42%, significantly higher than the catalytic performance of the catalyst prepared without a template agent in Comparative Example 1. This is because the molecular size of the organic template agent is more suitable for use as a template agent in the secondary hydrogen-iron catalyst, and it possesses better hydrothermal stability. Under hydrothermal conditions, it can generate stronger van der Waals forces with the iron-based precursor, effectively improving the pore structure of the catalyst. In particular, the catalyst prepared in Example 1 using hexadecyltrimethylammonium bromide as the organic template agent has suitable specific surface area, pore size, and bulk density, which is more conducive to exposing more active sites. This facilitates the contact between the reactant gas and the active sites during the secondary hydrogen conversion reaction, enhancing catalyst performance, and achieving a positive hydrogen conversion rate of 48.17%. Furthermore, while ensuring suitable specific surface area, pore size, and bulk density, the mechanical strength is also within a reasonable range, enabling it to withstand harsh environmental conditions, ensuring smooth catalytic reaction, and extending service life.

[0092] from Figure 1 The SEM images revealed that the catalysts prepared in Examples 1 and 2 both exhibited a porous honeycomb morphology with uniform pore size distribution, which is beneficial for the loading and uniformity of the active material. Figure 2 The BET plot shows that the catalyst prepared in Example 1 has a specific surface area of ​​315.2 cm². 2 / g, the catalyst prepared in Example 2 has a specific surface area of ​​288.4 cm². 2 / g; via Figure 3 The XRD patterns show that the catalysts prepared in Examples 1 and 2 have characteristic peaks corresponding to α-Fe2O3 at diffraction peak positions of 24.15°, 33.15°, 35.61°, 40.86°, 49.46°, 54.07°, 62.43°, and 64.02°, namely (012), (104), (110), (113), (024), (116), (214), and (300). Apart from these, no other impurity peaks are observed, indicating that the catalysts prepared in Examples 1 and 2 are mainly composed of α-Fe2O3. Figure 4The H2-TPR chromatograms show that the catalysts prepared in Examples 1 and 2 both exhibit a hydrogen consumption peak in the high-temperature region and a peak in the low-temperature region. Literature review indicates that the hydrogen consumption peak in the low-temperature region is attributed to the conversion of α-Fe2O3 to Fe3O4, while the hydrogen consumption peak in the high-temperature region is attributed to the reduction of Fe3O4 to FeO and the subsequent reduction of FeO to α-Fe. In Example 1, the hydrogen consumption peaks in the low-temperature and high-temperature regions are located at 436℃ and 662℃, respectively, while in Example 2, the peaks are located at 402℃ and 615℃, respectively. The higher reduction temperatures indicate that the catalyst prepared using the organic template agent has a more stable crystal structure and better high-temperature tolerance. Figure 5 As shown in the performance test graphs of the catalysts, the catalysts prepared in Examples 1 and 2 have good catalytic ability for the reaction of n- and secondary hydrogens, when the volume hourly space velocity is 600 min⁻¹. -1 At that time, the positive hydrogen conversion rate and the secondary hydrogen content at the device outlet of the catalyst prepared in Example 1 were 48.17% and 36.56%, respectively, and the positive hydrogen conversion rate and the secondary hydrogen content at the device outlet of the catalyst prepared in Example 2 were 42.35% and 35.16%, respectively.

[0093] In Comparative Example 1, because no organic template agent was used, the surface of the prepared catalyst was relatively dense, which reduced the number of exposed active sites and the loading of active species. Furthermore, the active species were prone to agglomeration, which significantly reduced the catalytic performance.

[0094] In Comparative Example 2, the catalyst prepared using a carbon template agent has a pore size that is too large, resulting in a bulk density and mechanical strength that are much lower than those in Examples 1 and 2. This would lead to a smaller mass of catalyst placed in a fixed space within the reactor, significantly reducing catalytic performance and efficiency, and also narrowing the applicable range.

[0095] It should be noted that the carbon template agent used in Comparative Document 2 is at least one of activated carbon, coal-based carbon, wood-based carbon, fruit shell carbon, and coconut shell carbon.

[0096] In addition, elemental analysis of the catalysts prepared in Examples 1 and 2 and Comparative Examples 1 and 2 revealed that the content of alkali metal ions or anions was 0, therefore there was no adverse effect of alkali metal ions or anions on the performance of the catalysts.

[0097] Experiment Example 2

[0098] Based on Example 1, the type of iron salt precursor or the molar ratio of iron salt precursor to organic template agent was changed, while other conditions remained unchanged, to obtain Examples 3-5 and Comparative Examples 3-4. The prepared catalysts were tested, and the test results are shown in Table 2.

[0099] Table 2

[0100]

[0101] As shown in Table 2, when the relative content of the organic template agent increases, the specific surface area of ​​the catalyst increases, while its bulk density and mechanical strength decrease. This reduces the amount of catalyst packed in the fixed space within the reactor, thus lowering catalytic performance. Conversely, when the relative content of the organic template agent decreases, although the bulk density and mechanical strength of the catalyst increase, the specific surface area decreases, reducing the number of exposed active sites and further lowering catalytic performance. When the molar ratio of the iron salt precursor to the organic template agent is within the scope of protection of this application, as in Examples 1, 3-5, especially Example 1, the specific surface area, bulk density, and mechanical strength of the prepared catalyst are all within a suitable range, resulting in good catalytic performance.

[0102] When the iron salt precursor is ferric nitrate, due to NO3 - Anions can be eliminated by calcination in air, followed by washing with a mixture of heated water and ethanol, resulting in a catalyst that is essentially free of anions, thus avoiding the negative impact of anions on catalytic performance. When the iron salt precursor is changed from ferric nitrate to ferric chloride, washing with a mixture of heated water and ethanol further reduces the content of anionic impurities in the catalyst, resulting in a catalyst with certain catalytic performance. However, the presence of chloride ions also affects catalyst performance; therefore, ferric nitrate is the preferred iron salt precursor.

[0103] Among them, from Figure 1 SEM images revealed that the catalyst prepared in Example 3 exhibited a porous honeycomb morphology on its surface; through... Figure 2 As shown in the BET plot, the catalyst prepared in Example 3 has a specific surface area of ​​332.6 cm². 2 / g; via Figure 3 The XRD pattern shows that the catalyst prepared in Example 3 has characteristic peaks corresponding to α-Fe2O3 at diffraction peak positions of 24.15°, 33.15°, 35.61°, 40.86°, 49.46°, 54.07°, 62.43°, and 64.02°, namely (012), (104), (110), (113), (024), (116), (214), and (300). Apart from these, no other impurity peaks are observed, indicating that the catalyst prepared in Example 3 is mainly composed of α-Fe2O3. Figure 4 The H2-TPR chromatogram shows that the catalyst prepared in Example 3 exhibits a hydrogen consumption peak in both the high-temperature and low-temperature regions. Literature review indicates that the hydrogen consumption peak in the low-temperature region corresponds to the conversion of α-Fe2O3 to Fe3O4, while the hydrogen consumption peak in the high-temperature region corresponds to the reduction of Fe3O4 to FeO and subsequent reduction of FeO to α-Fe. The hydrogen consumption peaks in the low-temperature and high-temperature regions are located at 421℃ and 648℃, respectively. Figure 5 As shown in the catalyst performance test graph, the catalyst prepared in Example 3 has good catalytic ability for the reaction of n- and secondary hydrogens, wherein the volume hourly space velocity (VHSV) is 600 min⁻¹. -1 At that time, the positive hydrogen conversion rate and the secondary hydrogen content at the unit outlet were 44.91% and 35.78%, respectively.

[0104] The catalyst prepared in Example 4 was tested, and elemental analysis revealed that the content of alkali metal ions or anions was 0; from Figure 1 SEM images revealed that the catalyst prepared in Example 4 exhibited a honeycomb morphology with fewer pores, which was denser than that in Example 1; through... Figure 2 As shown in the BET plot, the catalyst prepared in Example 4 has a specific surface area of ​​293.7 cm². 2 / g; via Figure 3 The XRD pattern shows that the catalyst prepared in Example 4 has characteristic peaks corresponding to α-Fe2O3 at diffraction peak positions of 24.15°, 33.15°, 35.61°, 40.86°, 49.46°, 54.07°, 62.43°, and 64.02°, namely (012), (104), (110), (113), (024), (116), (214), and (300). Apart from these, no other impurity peaks are observed, indicating that the catalyst prepared in Example 4 is mainly composed of α-Fe2O3. Figure 4 The H2-TPR chromatogram shows that the catalyst prepared in Example 4 exhibits a hydrogen consumption peak in both the high-temperature and low-temperature regions. Literature review indicates that the hydrogen consumption peak in the low-temperature region is attributed to the conversion of α-Fe2O3 to Fe3O4, while the hydrogen consumption peak in the high-temperature region is attributed to the reduction of Fe3O4 to FeO and subsequent reduction of FeO to α-Fe. The hydrogen consumption peaks in the low-temperature and high-temperature regions are located at 403℃ and 619℃, respectively. Figure 5 As shown in the performance test graph of the catalyst, the catalyst prepared in Example 4 has good catalytic ability for the reaction of n- and secondary hydrogens, wherein the volume hourly space velocity (VHSV) is 600 min⁻¹. -1 At that time, the positive hydrogen conversion rate and the secondary hydrogen content at the unit outlet were 41.53% and 34.49%, respectively.

[0105] The catalyst prepared in Example 5 was tested, and elemental analysis revealed that Cl... - The ion content was 1.31 at.%; from Figure 1 SEM images revealed that the catalyst prepared in Example 5 exhibited a porous honeycomb morphology on its surface; through... Figure 2 The BET plot shows that the catalyst prepared in Example 5 has a specific surface area of ​​309.6 cm². 2 / g; via Figure 3The XRD pattern shows that the catalyst prepared in Example 5 has characteristic peaks corresponding to α-Fe2O3 at diffraction peak positions of 24.15°, 33.15°, 35.61°, 40.86°, 49.46°, 54.07°, 62.43°, and 64.02°, namely (012), (104), (110), (113), (024), (116), (214), and (300). Apart from these, no other impurity peaks are observed, indicating that the catalyst prepared in Example 5 is mainly composed of α-Fe2O3. Figure 4 The H2-TPR chromatogram shows that the catalyst prepared in Example 5 exhibits a hydrogen consumption peak in both the high-temperature and low-temperature regions. Literature review indicates that the hydrogen consumption peak in the low-temperature region corresponds to the conversion of α-Fe2O3 to Fe3O4, while the hydrogen consumption peak in the high-temperature region corresponds to the reduction of Fe3O4 to FeO and subsequent reduction of FeO to α-Fe. The hydrogen consumption peaks in the low-temperature and high-temperature regions are located at 385℃ and 608℃, respectively. Figure 5 As shown in the performance test graph of the catalyst, the catalyst prepared in Example 5 has good catalytic ability for the reaction of n- and secondary hydrogens, wherein the volume hourly space velocity (VHSV) is 600 min⁻¹. -1 At that time, the positive hydrogen conversion rate and the secondary hydrogen content at the unit outlet were 31.92% and 32.66%, respectively. Performance test results show that Cl... - The presence of ions affects catalyst performance.

[0106] Experimental Example 3

[0107] Based on Example 1, the solvothermal process in step (2) was omitted, or the solvothermal temperature and time in step (2) were changed, while other conditions remained unchanged, resulting in Examples 6-8 and Comparative Examples 5-6. The prepared catalysts were then tested, and the test results are shown in Table 3.

[0108] Table 3

[0109]

[0110] As can be seen from Table 3, no solvothermal reaction process was involved in Comparative Example 5. The catalyst prepared in Comparative Example 5 was tested... Figure 1 SEM images revealed that the catalyst prepared in Comparative Example 5 had a denser surface morphology, reducing the number of exposed active sites and the loading of active species. Furthermore, the active species were prone to aggregation, significantly reducing catalytic performance. Figure 2 The BET plot shows that the catalyst prepared in Comparative Example 5 has a specific surface area of ​​269.3 cm². 2 / g; via Figure 3The XRD pattern shows that the catalyst prepared in Comparative Example 5 has characteristic peaks corresponding to α-Fe2O3 at diffraction positions of 24.15°, 33.15°, 35.61°, 40.86°, 49.46°, 54.07°, 62.43°, and 64.02°, namely (012), (104), (110), (113), (024), (116), (214), and (300). Apart from these, no other impurity peaks are observed, indicating that the catalyst prepared in Comparative Example 5 is mainly composed of α-Fe2O3. Figure 4 The H2-TPR chromatogram shows that the catalyst prepared in Comparative Example 5 exhibits a hydrogen consumption peak in both the high-temperature and low-temperature regions. Literature review indicates that the hydrogen consumption peak in the low-temperature region corresponds to the conversion of α-Fe2O3 to Fe3O4, while the hydrogen consumption peak in the high-temperature region corresponds to the reduction of Fe3O4 to FeO and subsequent reduction of FeO to α-Fe. The hydrogen consumption peaks in the low-temperature and high-temperature regions are located at 419℃ and 634℃, respectively. Figure 5 The performance test chart of the catalyst shows that when the volume hourly space velocity is 600 min... -1 At that time, the positive hydrogen conversion rate and the secondary hydrogen content at the unit outlet were 36.19% and 33.69%, respectively. Therefore, without the participation of a solvothermal reaction, the binding effect between the organic template agent and the iron salt precursor will be affected, thereby reducing the specific surface area and catalyst performance of the catalyst.

[0111] When the solvothermal reaction conditions are within the scope of protection of this application, such as in Examples 1, 6-8, the prepared catalysts exhibit good specific surface area, bulk density, and mechanical strength, and high catalytic performance. In particular, under the conditions of Example 1, the positive hydrogen conversion rate in the catalytic reaction reached 48.17%. However, when the solvothermal reaction temperature is low, the binding effect between the organic template agent and the iron salt precursor is poor, reducing the specific surface area and catalyst performance. When the solvothermal reaction temperature is high, the binding effect between the organic template agent and the iron salt precursor is improved, but the type of active sites of the catalyst is affected, thus affecting the catalyst performance.

[0112] Experiment Example 4

[0113] Based on Example 1, the aging temperature and aging time were changed while other conditions remained unchanged to obtain Examples 9-10 and Comparative Examples 7-10. The prepared catalysts were tested, and the test results are shown in Table 4.

[0114] Table 4

[0115]

[0116] As shown in Table 4, when the aging conditions are within the scope of protection of this application, such as in Examples 1, 9, and 10, the prepared catalysts exhibit good specific surface area, pore size, bulk density, and mechanical strength, resulting in high catalytic performance. However, increasing the aging temperature and shortening the aging time both affect the pore size of the catalyst, reduce its bulk density, decrease the amount of catalyst packed in a fixed volume within the reactor, and thus impact catalyst performance. Conversely, decreasing the aging temperature and extending the aging time reduce the specific surface area and pore size of the catalyst, decrease the number of exposed active sites, and affect catalyst performance. Multiple experiments revealed that an aging temperature of 50°C and an aging time of 24 hours are the optimal aging conditions.

[0117] In Comparative Example 10, no aging treatment was performed, and the prepared sample had a large specific surface area and pore size. However, the catalyst had a low bulk density, resulting in a small amount of catalyst that could be placed in the fixed space of the reactor, which in turn affected the overall performance of the catalyst.

[0118] Experimental Example 5

[0119] Based on Example 1, the drying temperature and drying time in step (4) were changed while other conditions remained unchanged to obtain Examples 11-12 and Comparative Examples 11-13. The prepared catalysts were tested, and the test results are shown in Table 5.

[0120] Table 5

[0121]

[0122] As shown in Table 5, when the drying conditions are within the scope of protection of this application, such as in Examples 1, 11, and 12, the prepared catalysts exhibit good specific surface area, pore size, bulk density, and mechanical strength, resulting in high catalytic performance. However, excessively low drying temperatures or short drying times will reduce the specific surface area and pore size of the catalyst due to residual free water, thereby affecting the number of exposed active sites and ultimately impacting catalyst performance. Excessively high drying temperatures or excessively long drying times will alter the crystal type of the catalyst, affecting its performance. Multiple experiments revealed that a drying temperature of 120°C and a drying time of 12 hours are the optimal drying conditions.

[0123] Experimental Example 6

[0124] Based on Example 1, only the type of precipitant was changed while other conditions remained the same, resulting in Example 13 and Comparative Example 14. The prepared catalysts were then tested, and the results are shown in Table 6.

[0125] Table 6

[0126]

[0127] As shown in Table 6, compared with the catalyst prepared using ammonia as a precipitant, the catalyst prepared using ammonium bicarbonate as a precipitant has a smaller specific surface area and fewer exposed active sites; it also has a lower bulk density, resulting in a smaller amount of catalyst placed in the fixed space inside the reactor, thus leading to a decrease in catalyst performance. The catalyst prepared using sodium hydroxide as a precipitant has a higher sodium ion content, which also affects catalyst performance.

[0128] Among them, the catalyst prepared in Example 13 was tested, and elemental analysis revealed that the content of alkali metal ions or anions was 0; from Figure 1 SEM images revealed that the catalyst prepared in Example 13 exhibited a porous honeycomb morphology on its surface; through Figure 2 As shown in the BET plot, the catalyst prepared in Example 13 has a specific surface area of ​​306.5 cm². 2 / g; via Figure 3 The XRD pattern shows that the catalyst prepared in Example 12 has characteristic peaks corresponding to α-Fe2O3 at diffraction peak positions of 24.15°, 33.15°, 35.61°, 40.86°, 49.46°, 54.07°, 62.43°, and 64.02°, namely (012), (104), (110), (113), (024), (116), (214), and (300). Apart from these, no other impurity peaks are observed, indicating that the catalyst prepared in Example 13 is mainly composed of α-Fe2O3. Figure 4 The H2-TPR chromatogram shows that the catalyst prepared in Example 13 exhibits a hydrogen consumption peak in both the high-temperature and low-temperature regions. Literature review indicates that the hydrogen consumption peak in the low-temperature region corresponds to the conversion of α-Fe2O3 to Fe3O4, while the hydrogen consumption peak in the high-temperature region corresponds to the reduction of Fe3O4 to FeO and subsequent reduction of FeO to α-Fe. The hydrogen consumption peaks in the low-temperature and high-temperature regions are located at 425℃ and 647℃, respectively. Figure 5 As shown in the performance test graph of the catalyst, the catalyst prepared in Example 13 has good catalytic ability for the reaction of n- and secondary hydrogens, wherein the volume hourly space velocity (VHSV) is 600 min⁻¹. -1 At that time, the positive hydrogen conversion rate and the secondary hydrogen content at the unit outlet were 34.75% and 33.34%, respectively.

[0129] The catalyst prepared in Comparative Example 14 was tested, and elemental analysis revealed that Na... + The ion content was 2.3 wt.%; from Figure 1 SEM images revealed that the catalyst prepared in Comparative Example 14 exhibited a porous honeycomb morphology on its surface; through... Figure 2 The BET plot shows that the catalyst prepared in Comparative Example 14 has a specific surface area of ​​318.4 cm². 2 / g; via Figure 3 The XRD pattern shows that the catalyst prepared in Comparative Example 14 has characteristic peaks corresponding to α-Fe2O3 at diffraction positions of 24.15°, 33.15°, 35.61°, 40.86°, 49.46°, 54.07°, 62.43°, and 64.02°, namely (012), (104), (110), (113), (024), (116), (214), and (300). Apart from these, no other impurity peaks are observed, indicating that the catalyst prepared in Comparative Example 14 is mainly composed of α-Fe2O3. Figure 4 The H2-TPR chromatogram shows that the catalyst prepared in Comparative Example 14 exhibits a hydrogen consumption peak in both the high-temperature and low-temperature regions. Literature review indicates that the hydrogen consumption peak in the low-temperature region corresponds to the conversion of α-Fe2O3 to Fe3O4, while the peak in the high-temperature region corresponds to the reduction of Fe3O4 to FeO and subsequent reduction of FeO to α-Fe. The hydrogen consumption peaks in the low-temperature and high-temperature regions are located at 382℃ and 604℃, respectively. Figure 5 The performance test results of the catalyst show that the catalyst prepared in Comparative Example 14 has good catalytic ability for the reaction of n- and secondary hydrogen, especially when the volume hourly space velocity is 600 min⁻¹. -1 At that time, the positive hydrogen conversion rate and the secondary hydrogen content at the unit outlet were 27.66% and 31.64%, respectively.

[0130] Experimental Example 7

[0131] Based on Example 1, the activation temperature and activation time were changed while other conditions remained unchanged to obtain Examples 14-17 and Comparative Examples 15-16. The prepared catalysts were tested, and the test results are shown in Table 7.

[0132] Table 7

[0133]

[0134]

[0135] As shown in Table 7, when the activation conditions are within the scope of protection of this application, such as in Examples 1, 14-17, the prepared catalysts have lower bulk density and less free water content in the catalyst matrix, resulting in higher catalytic performance. However, when the activation temperature is low or the activation time is short, the free water content in the catalyst matrix is ​​high, affecting the catalyst performance; when the activation temperature is high or the activation time is too long, the bulk density of the catalyst is low, resulting in a smaller amount of catalyst packed in the fixed space inside the reactor, thus affecting the catalyst performance. After multiple experiments, it was found that an activation temperature of 180℃ and an activation time of 24h are the optimal activation conditions.

[0136] In Comparative Example 16, no activation treatment was performed, resulting in a high free water content in the catalyst matrix, which affected the catalyst performance.

[0137] Experimental Example 8

[0138] This experiment tested the catalytic performance of the catalyst samples prepared in Examples 1-5, 13, and Comparative Examples 5 and 14. The test results are shown in Tables 8 and 9.

[0139] Table 8. Test results of positive hydrogen conversion rate at different space velocities.

[0140]

[0141] Table 9. Test results of secondary hydrogen content at the unit outlet.

[0142]

[0143]

[0144] As can be seen from Tables 8 and 9, when the airspeed is relatively low, at 50 min... -1 At the same time, the positive hydrogen conversion rate was 100%, and the secondary hydrogen content at the unit outlet was 49%. As the space velocity increased, the contact time between the reactant gas and the catalyst decreased, resulting in a significant decrease in both the positive hydrogen conversion rate and the secondary hydrogen content at the unit outlet under the action of different types of catalysts.

[0145] When the airspeed is 600 min -1 Based on the test results of the positive hydrogen conversion rate and the secondary hydrogen content at the device outlet prepared in each embodiment or comparative example, it was found that the catalyst performance was optimal in Example 1 when the organic template agent was hexadecyltrimethylammonium bromide, the iron-based precursor was ferric nitrate, the molar ratio of the iron-based precursor to the organic template agent was 7:1, the aging temperature was 50°C, the aging time was 24h, the drying temperature was 120°C, the drying time was 12h, and the precipitant was ammonia.

[0146] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing an iron-based catalyst, characterized in that, Includes the following steps: (1) The iron salt precursor and the organic template agent are placed in a solvent, stirred and dissolved, and a mixed solution of iron ions and organic template agent is obtained by solvothermal reaction; the organic template agent is selected from one or more of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, didodecyldimethylammonium chloride, and didodecyldimethylammonium bromide; the molar ratio of the iron salt precursor to the organic template agent is (1~10):1; (2) While stirring at a controlled temperature, a precipitant free of alkali metal ions is added dropwise to the mixed solution, and stirring is continued to obtain an iron-based precipitate suspension; the precipitant free of alkali metal ions is selected from one or a combination of several of ammonia, ammonium bicarbonate, ammonium carbonate, and urea. (3) The iron-based precipitate suspension was aged, filtered, and washed to obtain the iron-based precipitate; (4) The iron-based precipitate is dried, roasted, crushed, washed and activated to obtain an iron-based catalyst.

2. The method for preparing the iron-based catalyst according to claim 1, characterized in that, In step (1), the organic template agent is hexadecyltrimethylammonium bromide.

3. The method for preparing the iron-based catalyst according to claim 1, characterized in that, In step (1), the molar ratio of the iron salt precursor to the organic template agent is (5~8):

1.

4. The method for preparing the iron-based catalyst according to claim 1, characterized in that, In step (1), the iron salt precursor is selected from one or a combination of several of ferric nitrate, ferric chloride, ferric sulfate, and ferric acetylacetone.

5. The method for preparing the iron-based catalyst according to claim 4, characterized in that, The iron salt precursor is ferric nitrate.

6. The method for preparing the iron-based catalyst according to claim 1, characterized in that, The solvent in step (1) is a mixture of water and isopropanol, with a molar ratio of water to isopropanol of (1~10):

1.

7. The method for preparing the iron-based catalyst according to claim 6, characterized in that, The molar ratio of water to isopropanol is (1~3):

1.

8. The method for preparing the iron-based catalyst according to claim 6, characterized in that, The mass ratio of the iron-based precursor to the mixed solvent is 1:(1~10).

9. The method for preparing the iron-based catalyst according to claim 8, characterized in that, The mass ratio of the iron-based precursor to the mixed solvent is 1:(2~4).

10. The method for preparing the iron-based catalyst according to claim 1, characterized in that, In step (1), the solvothermal reaction is carried out at a temperature of 50~200℃ for 1~20h.

11. The method for preparing the iron-based catalyst according to claim 10, characterized in that, The solvothermal reaction is carried out at a temperature of 90~150℃ for 8~12 hours.

12. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (2), the controlled temperature is 0~100℃.

13. The method for preparing the iron-based catalyst according to claim 12, characterized in that, In step (2), the controlled temperature is 60~80℃.

14. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (2), the stirring time is 1 to 10 hours.

15. The method for preparing the iron-based catalyst according to claim 14, characterized in that, In step (2), the stirring time is 1 to 3 hours.

16. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (2), the stirring rate is 100~1000 r / min.

17. The method for preparing the iron-based catalyst according to claim 16, characterized in that, In step (2), the stirring rate is 300~600 r / min.

18. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (2), the precipitant that does not contain alkali metal ions is ammonia.

19. The method for preparing the iron-based catalyst according to claim 18, characterized in that, In step (2), the precipitant that does not contain alkali metal ions is 0.5 mol / L ammonia water.

20. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (2), a precipitant without alkali metal ions is added to the mixed solution until the pH of the solution is 8-13.

21. The method for preparing the iron-based catalyst according to claim 20, characterized in that, In step (2), a precipitant without alkali metal ions is added to the mixed solution until the pH of the solution is 10-12.

22. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (3), the aging process is carried out at a temperature of 0~100℃ for 10~30h.

23. The method for preparing the iron-based catalyst according to claim 22, characterized in that, In step (3), the aging process is carried out at a temperature of 40~70℃ for 15~30h.

24. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (3), the cleaning solvent is a mixture of ethanol and water, and the mass ratio of ethanol to water is 1:(1~10).

25. The method for preparing the iron-based catalyst according to claim 24, characterized in that, The mass ratio of ethanol to water is 1:(1~5).

26. The method for preparing the iron-based catalyst according to claim 24, characterized in that, The temperature range for a mixed solvent of ethanol and water is 0~100℃.

27. The method for preparing the iron-based catalyst according to claim 24, characterized in that, The temperature range for a mixed solvent of ethanol and water is 50~80℃.

28. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (4), the drying is carried out at a temperature of 80~200℃ for 1~20h.

29. The method for preparing the iron-based catalyst according to claim 28, characterized in that, In step (4), the drying is carried out at a temperature of 90~150℃ for 10~20h.

30. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (4), the roasting is carried out at a temperature of 200~600℃ for 1~10h.

31. The method for preparing the iron-based catalyst according to claim 30, characterized in that, In step (4), the roasting is carried out at a temperature of 300~500℃ for 2~6 hours.

32. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (4), the solution used for re-washing is ultrapure water at 0~100℃.

33. The method for preparing the iron-based catalyst according to claim 32, characterized in that, In step (4), the solution used for re-washing is at 50~80℃.

34. The method for preparing the iron-based catalyst according to any one of claims 1-11, characterized in that, In step (4), the activation is carried out at a temperature of 50~200℃ for 10~30h.

35. The method for preparing the iron-based catalyst according to claim 34, characterized in that, In step (4), the activation is performed at a temperature of 150~190℃ for 20~25h.

36. An iron-based catalyst, characterized in that, The iron-based catalyst is prepared by any one of the preparation methods of the iron-based catalyst as described in claims 1-35. The iron-based catalyst is honeycomb-shaped and has a mesh size of 10-100 mesh.

37. The iron-based catalyst according to claim 36, characterized in that, The mesh size of iron-based catalysts is 30-80 mesh.

38. The iron-based catalyst according to claim 36 or 37, characterized in that, The iron-based catalyst has a pore size of 10~50 nm.

39. The iron-based catalyst according to claim 36 or 37, characterized in that, The specific surface area of ​​the iron-based catalyst is 250~350 cm². 2 / g.

40. The application of an iron-based catalyst, characterized in that, The iron-based catalyst according to any one of claims 36-39 is applied to the conversion of n- and para-hydrogen.

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