A potassium-modified cobalt-molybdenum nitride catalyst, a preparation method and application thereof

Abstract

The application discloses a potassium-modified cobalt-molybdenum nitride catalyst and a preparation method and application thereof. The application provides a cobalt-molybdenum bimetallic nitride ammonia decomposition catalyst, a precursor is obtained by mixing a cobalt nitrate solution and an ammonium molybdate solution and then reacting, the precursor is stirred with a potassium carbonate solution, dried, and then calcined in an ammonia gas environment to obtain the potassium-modified cobalt-molybdenum nitride catalyst. The non-noble metal catalyst is prepared by the potassium modification method, can efficiently catalyze and promote solar energy ammonia decomposition to produce hydrogen under low-temperature conditions, the ammonia decomposition conversion rate can reach more than 87% under the reaction conditions of 500 DEG C and 0.1 MPa, can efficiently catalyze ammonia decomposition to produce hydrogen under low-temperature conditions, and has great industrial application significance.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a potassium-modified cobalt-molybdenum nitride catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a high-energy-density clean energy source, plays a vital role in addressing the energy crisis, global warming, and environmental pollution. However, stringent storage and transportation conditions severely hinder its application. Ammonia (NH3), due to its high hydrogen content and convenient transportation and storage conditions, is considered a promising renewable hydrogen (H2) carrier. Solar ammonia decomposition offers a green and sustainable pathway for releasing hydrogen from ammonia; however, traditional solar ammonia decomposition typically requires operating temperatures above 550°C and expensive and complex concentrating equipment. Therefore, developing a low-temperature, highly efficient catalyst to promote ammonia decomposition is crucial for the large-scale application of solar ammonia decomposition for hydrogen production.

[0003] Currently, ruthenium-based catalysts are considered to be the most active ammonia decomposition catalysts at low temperatures, typically achieving high ammonia decomposition conversion rates at 500℃. However, the scarcity and high cost of ruthenium hinder its commercial-scale application. Non-precious metal transition metals such as Ni, Co, Mo, and Fe are considered to be alternatives to ruthenium-based catalysts. Among them, nickel-based catalysts have the highest activity, but they suffer from problems such as easy sintering and poor stability, making it difficult to meet the requirements of solar ammonia decomposition under low-temperature conditions.

[0004] Currently, non-noble metal dual-transition metal catalysts have become a research hotspot. The synergistic effect of dual transition metals can exhibit excellent ammonia decomposition activity, but their performance remains poor at low temperatures. Meanwhile, studies have shown that alkali metal modification can effectively promote the catalytic activity of ammonia decomposition catalysts, but the interaction between different alkali metals and catalysts still requires further investigation.

[0005] In summary, exploring the synergistic effect of dual transition metals, screening for the optimal dual transition metal catalyst, and improving its low-temperature ammonia decomposition activity by modifying it with an appropriate ratio of alkali metals are new ideas for constructing novel solar ammonia decomposition catalysts. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a potassium-modified cobalt-molybdenum nitride catalyst, its preparation method, and its application in the catalytic decomposition of ammonia to produce hydrogen. This invention provides a cobalt-molybdenum bimetallic nitride ammonia decomposition catalyst with excellent performance, and based on the principle of alkali metal modification, a potassium-modified cobalt-molybdenum nitride catalyst was prepared. x -Co3Mo3N non-precious metal nitride catalyst further improves the catalyst's ammonia decomposition activity, enabling it to efficiently catalyze the decomposition of ammonia to produce hydrogen under low-temperature conditions.

[0007] This invention provides a method for preparing a potassium-modified cobalt-molybdenum nitride catalyst, which specifically includes the following steps:

[0008] 1) After mixing cobalt nitrate solution and ammonium molybdate solution, the mixture was reacted at 80℃ for 12 hours. After the reaction was completed, the mixture was cooled to room temperature and filtered. The filter residue was washed with water, dried, and ground to obtain precursor CoMoO4 powder.

[0009] 2) Add potassium carbonate solution to the precursor CoMoO4 powder from step 1), dry completely at 80°C with stirring, and then calcine in an ammonia atmosphere to obtain potassium-modified cobalt-molybdenum nitride catalyst K. x -Co3Mo3N.

[0010] Furthermore, the present invention further specifies that the concentration of cobalt nitrate (Co(NO3)2·6H2O, relative molecular mass 291) solution is 0.4 mol / L, the concentration of ammonium molybdate ((NH4)2MoO4, relative molecular mass 196) is 0.4 mol / L, and the concentration of potassium carbonate (K2CO3, relative molecular mass 138) solution is 0.00116-0.116 mol / L, wherein the molar ratio of Co to Mo elements is 1:1.

[0011] Furthermore, the present invention also specifies that the precursor CoMoO4 powder is screened through a filter to obtain a particle size of less than 40 micrometers.

[0012] Furthermore, the present invention also specifies that the formula for calculating the mass of potassium carbonate fed in step 2), based on the molar number of Mo, is as follows:

[0013]

[0014] In this process, the number of moles of Mo remains constant from the precursor to the catalyst. In the catalyst, the ratio of potassium to mole of mole is x:3. The number of moles of potassium is calculated based on the number of moles of Mo. The number of moles of potassium carbonate is half that of potassium. The mass of potassium carbonate is then calculated.

[0015] Furthermore, the present invention also specifies that the potassium-modified cobalt-molybdenum nitride catalyst K in step 2) x The molar ratio of potassium ions in potassium carbonate to molybdenum ions in ammonium molybdate in Co3Mo3N is 0.005-0.5:1, preferably 0.01-0.1:1, and most preferably 0.05:1; that is, x = 0.015-1.5, preferably 0.03-0.3, and most preferably 0.15.

[0016] Furthermore, the present invention also specifies that the calcination temperature in step 2) is gradually increased from room temperature to 785°C, and the total calcination time is 12 hours. The gradual increase in temperature is specifically as follows: from room temperature to 357°C at 5°C / min, then to 450°C at 0.5°C / min, and finally to 785°C at 2.1°C / min, so as to completely ammonify the precursor.

[0017] Furthermore, the present invention also specifies a potassium-modified cobalt-molybdenum nitride catalyst obtained by a specific preparation method, with the structural formula K. x -Co3Mo3N, where x represents the molar proportion of potassium in the metal element in the catalyst, x = 0.015-1.5.

[0018] Furthermore, the present invention also specifies the application of the obtained potassium-modified cobalt-molybdenum nitride catalyst in the solar ammonia decomposition hydrogen production reaction; the potassium-modified cobalt-molybdenum nitride catalyst is added to a quartz reaction tube, wrapped with heat insulation material, placed under a solar simulator, and reacted under sealed conditions with ammonia gas, the reaction temperature is 350-500℃, and the ammonia gas pressure is 0.1MPa.

[0019] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0020] 1) This invention designs a cobalt-molybdenum bimetallic nitride ammonia decomposition catalyst, which, based on the principle of alkali metal modification, obtains K through potassium modification. x A non-precious metal catalyst, Co3Mo3N, was developed to efficiently catalyze the solar-powered ammonia decomposition for hydrogen production at low temperatures. The catalyst precursor is formed using ammonium molybdate and cobalt nitrate, both non-precious metal salts. This precursor is then mixed with potassium carbonate and calcined to form a potassium-modified cobalt-molybdenum nitride catalyst. This catalyst exhibits high catalytic activity, enabling ammonia decomposition at 350℃ and 0.1 MPa, with a conversion rate reaching 100% at 550℃ and 0.1 MPa. Compared to other non-precious metal catalysts reported in the literature, which typically require reaction temperatures above 800℃ to achieve similar catalytic effects, this catalyst demonstrates high efficiency at low temperatures, making it significant for industrial applications.

[0021] 2) The present invention employs staged heating during calcination, which allows for a more complete ammoniation reaction;

[0022] 3) Through experimental comparison of the effects of different potassium compound promoters (K2CO3, KOH, KNO3) on improving the ammonia decomposition activity of Co3Mo3N, this invention found that the promoting effect of K2CO3 is significantly better than that of KOH and KNO3. Therefore, using K2CO3 as a promoter in the preparation process of this invention is more in line with the requirements of economy, environmental protection and practicality. Attached Figure Description

[0023] Figure 1 The graph shows the ammonia decomposition conversion rate of the catalysts in Examples 1-4, 5-8, 9-12, 13-16, 17-20, and 21-24 of this invention.

[0024] Figure 2(a) shows the ammonia decomposition conversion rate of catalysts in Examples 1-4, 9-12, 25-28, and 33-36 of the present invention;

[0025] Figure 2(b) shows the ammonia decomposition conversion rate of catalysts in Examples 1-4, 13-16, 29-32, and 41-44 of the present invention.

[0026] Figure 2(c) shows the ammonia decomposition conversion rate of catalysts in Examples 1-4, 17-20, 33-36, and 45-48 of the present invention;

[0027] Figure 3 The XRD patterns are of the catalysts in Examples 1-4, 5-8, 9-12, 13-16, 17-20, and 21-24 of this invention.

[0028] Figure 4 XPS images of the catalysts in Examples 13-16 of this invention;

[0029] Figure 5 These are SEM images of the catalysts in Examples 13-16 of this invention. Detailed Implementation

[0030] The following examples illustrate the content of the present invention, but the scope of protection of the present invention is not limited thereto:

[0031] Unless otherwise specified, the equipment, reagents, processes, parameters, etc. involved in this invention are all conventional equipment, reagents, processes, parameters, etc., and no further examples are provided. All ranges listed in this invention include all point values ​​within that range. The terms "approximately," "about," or "around" used in this invention refer to a range or value within ±20%.

[0032] In this invention, "room temperature" refers to the normal ambient temperature, which can be 10 to 30°C.

[0033] Examples 1-4

[0034] 7.84 g (0.04 mol) of ammonium molybdate and 11.64 g (0.04 mol) of cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was separated by high-speed centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol, and then dried in a drying oven at 80 °C for 10 h. After drying, the precipitate was ground to obtain precursor powder (CoMoO4). Particles with a diameter of less than 40 μm were screened through a filter. The precursor powder was then subjected to high-temperature nitriding in a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at a rate of 5 °C / min, then to 450 °C at a rate of 0.5 °C / min, and finally to 785 °C at a rate of 2.1 °C / min. The temperature was maintained at this temperature for 5 h, and then cooled to room temperature in an ammonia atmosphere to obtain the cobalt-molybdenum nitride catalyst. Particles with a diameter of less than 20 μm were screened through a filter. The catalyst was labeled as Co3Mo3N.

[0035] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted. 0.3g of Co3Mo3N catalyst was added to a quartz reaction tube, which was then sealed and wrapped with insulating material (except for the catalyst storage section) to ensure stable temperature inside the quartz tube during the reaction. The wrapped quartz reaction tube was then placed under a solar simulator (a combination of a concentrator and a xenon lamp). The xenon lamp was turned on to irradiate the catalyst storage section not covered by insulating material, and ammonia gas was introduced into the quartz reaction tube at a flow rate of 30ml / min (GHSV = 6000ml). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 1-4.

[0036] Examples 5-8

[0037] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0038] The mass of potassium carbonate is calculated using the following formula:

[0039]

[0040] 0.0032 g of potassium carbonate was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium carbonate solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at a rate of 5 °C / min, then to 450 °C at a rate of 0.5 °C / min, and finally to 785 °C at a rate of 2.1 °C / min. This temperature was maintained for 5 hours, and then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.005. The catalyst was labeled K. 0.015 -Co3Mo3N(K2CO3).

[0041] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.015 -Co3Mo3N(K2CO3) catalyst was sealed, and the quartz reaction tube (except for the catalyst storage section) was wrapped with insulating material to ensure stable temperature inside the quartz tube during the reaction. The wrapped quartz reaction tube was then placed under a solar simulator (the solar simulator is a combination of a condenser and a xenon lamp). The xenon lamp was turned on to irradiate the catalyst storage section not wrapped with insulating material, and ammonia gas was introduced into the quartz reaction tube at a flow rate of 30 ml / min (GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 6-8.

[0042] Examples 9-12

[0043] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0044] The mass of potassium carbonate is calculated using the following formula:

[0045]

[0046] 0.0063 g of potassium carbonate was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium carbonate solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at a rate of 5 °C / min, then to 450 °C at a rate of 0.5 °C / min, and finally to 785 °C at a rate of 2.1 °C / min. This temperature was maintained for 5 hours, and then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.01. The catalyst was labeled K. 0.03 -Co3Mo3N(K2CO3).

[0047] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.03 -Co3Mo3N(K2CO3) catalyst was sealed, and the quartz reaction tube (except for the catalyst storage section) was wrapped with insulating material to ensure stable temperature inside the quartz tube during the reaction. The wrapped quartz reaction tube was then placed under a solar simulator (the solar simulator is a combination of a condenser and a xenon lamp). The xenon lamp was turned on to irradiate the catalyst storage section not wrapped with insulating material, and ammonia gas was introduced into the quartz reaction tube at a flow rate of 30 ml / min (GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in serial numbers 9-12 in Table 1.

[0048] Examples 13-16

[0049] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0050] The mass of potassium carbonate is calculated using the following formula:

[0051]

[0052] 0.032 g of potassium carbonate was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium carbonate solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at a rate of 5 °C / min, then to 450 °C at a rate of 0.5 °C / min, and finally to 785 °C at a rate of 2.1 °C / min. This temperature was maintained for 5 hours, and then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.05. The catalyst was labeled K. 0.15 -Co3Mo3N(K2CO3).

[0053] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.15 -Co3Mo3N(K2CO3) catalyst was sealed, and the quartz reaction tube (except for the catalyst storage section) was wrapped with insulating material to ensure stable temperature inside the quartz tube during the reaction. The wrapped quartz reaction tube was then placed under a solar simulator (the solar simulator is a combination of a condenser and a xenon lamp). The xenon lamp was turned on to irradiate the catalyst storage section not wrapped with insulating material, and ammonia gas was introduced into the quartz reaction tube at a flow rate of 30 ml / min (GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is brought to 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 13-16.

[0054] Examples 17-20

[0055] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0056] The mass of potassium carbonate is calculated using the following formula:

[0057]

[0058] 0.063 g of potassium carbonate was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium carbonate solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at 5 °C / min, then to 450 °C at 0.5 °C / min, and finally to 785 °C at 2.1 °C / min, and held at this temperature for 5 h. The mixture was then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.1. The catalyst was labeled K. 0.3 -Co3Mo3N(K2CO3).

[0059] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.3 -Co3Mo3N(K2CO3) catalyst was sealed, and the quartz reaction tube (except for the catalyst storage section) was wrapped with insulating material to ensure stable temperature inside the quartz tube during the reaction. The wrapped quartz reaction tube was then placed under a solar simulator (the solar simulator is a combination of a condenser and a xenon lamp). The xenon lamp was turned on to irradiate the catalyst storage section not wrapped with insulating material, and ammonia gas was introduced into the quartz reaction tube at a flow rate of 30 ml / min (GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 17-20.

[0060] Examples 21-24

[0061] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0062] The mass of potassium carbonate is calculated using the following formula:

[0063]

[0064] 0.32 g of potassium carbonate was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium carbonate solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at a rate of 5 °C / min, then to 450 °C at a rate of 0.5 °C / min, and finally to 785 °C at a rate of 2.1 °C / min. This temperature was maintained for 5 hours, and then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.5. The catalyst was labeled K. 1.5 -Co3Mo3N(K2CO3).

[0065] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.3 -Co3Mo3N(K2CO3) catalyst was sealed, and the quartz reaction tube (except for the catalyst storage section) was wrapped with insulating material to ensure stable temperature inside the quartz tube during the reaction. The wrapped quartz reaction tube was then placed under a solar simulator (the solar simulator is a combination of a condenser and a xenon lamp). The xenon lamp was turned on to irradiate the catalyst storage section not wrapped with insulating material, and ammonia gas was introduced into the quartz reaction tube at a flow rate of 30 ml / min (GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 21-24.

[0066] Examples 25-28

[0067] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0068] The mass of potassium hydroxide is calculated using the following formula:

[0069]

[0070] 0.0051 g of potassium hydroxide was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium hydroxide solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at a rate of 5 °C / min, then to 450 °C at a rate of 0.5 °C / min, and finally to 785 °C at a rate of 2.1 °C / min. This temperature was maintained for 5 hours, and then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.01. The catalyst was labeled K. 0.03 -Co3Mo3N(KOH).

[0071] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.03 -Co3Mo3N(KOH) catalyst, after sealing, the quartz reaction tube (except for the catalyst storage section) was wrapped with insulating material to ensure stable temperature inside the quartz tube during the reaction. Then, the wrapped quartz reaction tube was placed under a solar simulator (the solar simulator is a combination of a condenser lens and a xenon lamp). The xenon lamp was turned on to irradiate the catalyst storage section that was not wrapped with insulating material, and ammonia gas was introduced into the quartz reaction tube at a flow rate of 30 ml / min (space velocity GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 25-28.

[0072] Examples 29-32

[0073] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0074] The mass of potassium hydroxide is calculated using the following formula:

[0075]

[0076] 0.026 g of potassium hydroxide was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium hydroxide solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at a rate of 5 °C / min, then to 450 °C at a rate of 0.5 °C / min, and finally to 785 °C at a rate of 2.1 °C / min. This temperature was maintained for 5 hours, and then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.05. The catalyst was labeled K. 0.15 -Co3Mo3N(KOH).

[0077] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.15 -Co3Mo3N(KOH) catalyst, after sealing, the quartz reaction tube (except for the catalyst storage section) was wrapped with insulating material to ensure stable temperature inside the quartz tube during the reaction. Then, the wrapped quartz reaction tube was placed under a solar simulator (the solar simulator is a combination of a condenser lens and a xenon lamp). The xenon lamp was turned on to irradiate the catalyst storage section that was not wrapped with insulating material, and ammonia gas was introduced into the quartz reaction tube at a flow rate of 30 ml / min (space velocity GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 29-32.

[0078] Examples 33-36

[0079] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0080] The mass of potassium hydroxide is calculated using the following formula:

[0081]

[0082] 0.051 g of potassium hydroxide was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium hydroxide solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at a rate of 5 °C / min, then to 450 °C at a rate of 0.5 °C / min, and finally to 785 °C at a rate of 2.1 °C / min. This temperature was maintained for 5 hours, and then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.1. The catalyst was labeled K. 0.3 -Co3Mo3N(KOH).

[0083] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.3 -Co3Mo3N(KOH) catalyst, after sealing, the quartz reaction tube (except for the catalyst storage section) was wrapped with insulating material to ensure stable temperature inside the quartz tube during the reaction. Then, the wrapped quartz reaction tube was placed under a solar simulator (the solar simulator is a combination of a condenser lens and a xenon lamp). The xenon lamp was turned on to irradiate the catalyst storage section that was not wrapped with insulating material, and ammonia gas was introduced into the quartz reaction tube at a flow rate of 30 ml / min (space velocity GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 33-36.

[0084] Examples 37-40

[0085] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0086] The mass of potassium nitrate is calculated using the following formula:

[0087]

[0088] 0.0092 g of potassium nitrate was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium nitrate solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at 5 °C / min, then to 450 °C at 0.5 °C / min, and finally to 785 °C at 2.1 °C / min, and held at this temperature for 5 h. The mixture was then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.01. The catalyst was labeled K. 0.03 -Co3Mo3N(KNO3).

[0089] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.03 -Co3Mo3N(KNO3) catalyst, after sealing, the quartz reaction tube (except for the catalyst storage section) is wrapped with heat-insulating material to ensure stable temperature inside the quartz tube during the reaction. Then, the wrapped quartz reaction tube is placed under a solar simulator (the solar simulator is a combination of a condenser lens and a xenon lamp). The xenon lamp is turned on to irradiate the catalyst storage section that is not wrapped with heat-insulating material, and ammonia gas is introduced into the quartz reaction tube at a flow rate of 30 ml / min (space velocity GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 37-40.

[0090] Examples 41-44

[0091] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0092] The mass of potassium nitrate is calculated using the following formula:

[0093]

[0094] 0.046 g of potassium nitrate was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium nitrate solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at a rate of 5 °C / min, then to 450 °C at a rate of 0.5 °C / min, and finally to 785 °C at a rate of 2.1 °C / min. This temperature was maintained for 5 hours, and then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.05. The catalyst was labeled K. 0.15 -Co3Mo3N(KNO3).

[0095] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.15 -Co3Mo3N(KNO3) catalyst, after sealing, the quartz reaction tube (except for the catalyst storage section) is wrapped with heat-insulating material to ensure stable temperature inside the quartz tube during the reaction. Then, the wrapped quartz reaction tube is placed under a solar simulator (the solar simulator is a combination of a condenser lens and a xenon lamp). The xenon lamp is turned on to irradiate the catalyst storage section that is not wrapped with heat-insulating material, and ammonia gas is introduced into the quartz reaction tube at a flow rate of 30 ml / min (space velocity GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 41-44.

[0096] Examples 45-48

[0097] 7.84 g (0.04 mol) ammonium molybdate and 11.64 g (0.04 mol) cobalt nitrate hexahydrate were dissolved in 100 ml of deionized water respectively. The two solutions were mixed and stirred, and reacted at 80 °C for 12 h. The resulting purple solid precipitate was obtained by centrifugation. The precipitate was washed three times with deionized water and once with anhydrous ethanol. It was then placed in a drying oven and dried at 80 °C for 10 h. After filtration, washing with water, drying, and grinding, the precursor powder (CoMoO4) was obtained. Particles with a diameter of less than 40 micrometers were screened through a filter.

[0098] The mass of potassium nitrate is calculated using the following formula:

[0099]

[0100] 0.092 g of potassium nitrate was dissolved in 20 ml of deionized water. Then, 2 g of precursor powder was added to the potassium nitrate solution. The mixture was dried completely at 80 °C to obtain a purple solid. After grinding, the solid was nitrided at high temperature under a pure ammonia atmosphere. The temperature was increased from room temperature to 357 °C at a rate of 5 °C / min, then to 450 °C at a rate of 0.5 °C / min, and finally to 785 °C at a rate of 2.1 °C / min. This temperature was maintained for 5 hours, and then cooled to room temperature under an ammonia atmosphere to obtain a potassium-modified cobalt-molybdenum nitride catalyst. Particles with a diameter less than 20 micrometers were screened using a filter. The molar ratio of potassium to molybdenum was 0.01. The catalyst was labeled K. 0.3 -Co3Mo3N(KNO3).

[0101] Subsequently, a solar-powered ammonia decomposition hydrogen production simulation experiment was conducted, in which 0.3 g K was added to a quartz reaction tube. 0.3 -Co3Mo3N(KNO3) catalyst, after sealing, the quartz reaction tube (except for the catalyst storage section) is wrapped with heat-insulating material to ensure stable temperature inside the quartz tube during the reaction. Then, the wrapped quartz reaction tube is placed under a solar simulator (the solar simulator is a combination of a condenser lens and a xenon lamp). The xenon lamp is turned on to irradiate the catalyst storage section that is not wrapped with heat-insulating material, and ammonia gas is introduced into the quartz reaction tube at a flow rate of 30 ml / min (space velocity GHSV = 6000 ml / min). NH3 / g cat / h), by adjusting the xenon lamp power, the temperature inside the quartz reaction tube is made to reach 350℃, 400℃, 450℃ and 500℃ respectively (measured by the temperature sensor). After the outlet flow controller reading stabilizes, the data is recorded. The ammonia conversion rate is calculated according to the formula ammonia conversion rate = (0.5 * outlet flow rate / inlet flow rate) * 100%. The results are listed in Table 1, serial numbers 45-48.

[0102] Table 1 Ammonia decomposition conversion rate in each example

[0103]

[0104]

[0105]

[0106]

[0107] As shown in Table 1, appropriate potassium modification improved the ammonia decomposition activity of the Co3Mo3N catalyst. Examples 9-12, 13-16, and 17-20 showed significant improvements, with Example 13-16 exhibiting the most significant improvement (K). 0.15The Co3Mo3N(K2CO3) catalyst exhibits the best catalytic activity at low temperatures. Furthermore, comparing the data from Examples 1-4 with those from Examples 21-24 reveals that excessive potassium modification inhibits the ammonia decomposition activity of the Co3Mo3N catalyst. This is because the excess potassium exists on the catalyst surface, covering the active sites.

[0108] As can be seen from the comparison of the example data in Table 1, potassium modification of Co3Mo3N catalyst with KOH and KNO3 also has a promoting effect. However, under the same molar amount of potassium modification (K:Mo = 0.01, 0.1), the promoting effect of KOH and KNO3 is not as obvious as that of K2CO3. Therefore, from the perspective of promoting effect and economy, K2CO3 is the optimal potassium modifier for Co3Mo3N compared with KOH and KNO3.

[0109] Figure 1 The graph shows the ammonia decomposition conversion rate of the catalysts in Examples 1-4, 5-8, 9-12, 13-16, 17-20, and 21-24 of this invention. Figure 1 As can be seen from the above, the addition of an appropriate amount of potassium significantly improved the ammonia decomposition activity of the Co3Mo3N catalyst, as shown in Examples 13-16 (K). 0.15 -Co3Mo3N(K2CO3)) catalysts exhibit better catalytic activity at low temperatures.

[0110] As shown in Figures 2(a), 2(b), and 2(c), under the conditions of molar ratios K:Mo = 0.01, 0.05, and 0.1:1, K2CO3, KNO3, and KOH all have a promoting effect on the Co3Mo3N catalyst at temperatures of 350-500℃, and the order of their promoting effect is K2CO3 > KNO3 > KOH.

[0111] Figure 3 The XRD patterns of the catalysts in Examples 1-4, 5-8, 9-12, 13-16, 17-20, and 21-24 of this invention are shown below. Figure 3 As can be seen from the diffraction patterns of all K2CO3 modified catalysts, they are consistent with the pure phase of Co3Mo3N, indicating that no impurity phase was detected by XRD and that potassium is highly dispersed on the surface of Co3Mo3N.

[0112] Figure 4 XPS images of the catalysts in Examples 13-16 of this invention; Figure 5 These are SEM images of the catalysts in Examples 13-16 of this invention. Figure 4 As can be seen from this, potassium was successfully incorporated into Co3Mo3N. Figure 5 As can be seen from this, Examples 13-16 (K) 0.15The particle size of -Co3Mo3N(K2CO3) is about 10 μm, and potassium is uniformly distributed on the surface of Co3Mo3N.

Claims

1. The application of a potassium-modified cobalt-molybdenum nitride catalyst in a solar-powered ammonia decomposition hydrogen production reaction, wherein the preparation method of the potassium-modified cobalt-molybdenum nitride catalyst includes the following steps: 1) After mixing cobalt nitrate solution and ammonium molybdate solution, the mixture was reacted at 80℃ for 12 hours. After the reaction was completed, the mixture was cooled to room temperature and filtered. The filter residue was washed with water, dried, and ground to obtain precursor CoMoO4 powder. 2) Add potassium carbonate solution to the precursor CoMoO4 powder from step 1), dry completely at 80°C with stirring, and then calcine in an ammonia atmosphere to obtain potassium-modified cobalt-molybdenum nitride catalyst K. x -Co3Mo3N, wherein the molar ratio of potassium to molybdenum in the catalyst is x:3, and the potassium-modified cobalt-molybdenum nitride catalyst K x The molar ratio of potassium to molybdenum in -Co3Mo3N is 0.005-0.1:1, and x = 0.015-0.

3.

2. The application according to claim 1, characterized in that... The concentration of cobalt nitrate solution is 0.4 mol / L, the concentration of ammonium molybdate is 0.4 mol / L, and the concentration of potassium carbonate solution is 0.00116-0.116 mol / L, wherein the molar ratio of Co to Mo is 1:

1.

3. The application according to claim 1, characterized in that... The precursor CoMoO4 powder has a particle size of less than 40 micrometers.

4. The application according to claim 1, characterized in that... In step 2), the formula for calculating the mass of potassium carbonate feed, based on the number of moles of Mo, is as follows:

5. The application according to claim 1, characterized in that... In step 2), the calcination temperature is gradually increased from room temperature to 785℃, and the total calcination time is 12 hours. The gradual temperature increase is as follows: from room temperature to 357℃ at 5℃ / min, then to 450℃ at 0.5℃ / min, and finally to 785℃ at 2.1℃ / min, so as to completely ammonify the precursor.

6. The application according to claim 1, characterized in that... The solar ammonia decomposition hydrogen production process is as follows: potassium-modified cobalt-molybdenum nitride catalyst is added to a quartz reaction tube, wrapped with heat insulation material, placed under a solar simulator, and ammonia gas is introduced under sealed conditions to carry out the reaction. The reaction temperature is 350-500℃ and the ammonia gas pressure is 0.1MPa.

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