Preparation method of monatomic ruthenium-based catalyst and application of monatomic ruthenium-based catalyst in hydrogen production through ammonia decomposition

Abstract

The invention belongs to the technical field of catalyst preparation, and particularly relates to a preparation method of a monatomic ruthenium-based catalyst and application of the monatomic ruthenium-based catalyst in hydrogen production through ammonia decomposition. According to the method, an atom capture method is adopted, ruthenium precursor powder and the oxide carrier are subjected to high-temperature treatment in the oxygen-containing atmosphere, Ru species volatilized in the high-temperature oxidizing atmosphere are captured through the oxide carrier, anchoring of Ru atoms is achieved, the stability of Ru on the surface of the carrier is effectively improved, and the atom utilization rate of precious metal is increased. The monatomic Ru-based catalyst prepared by the invention has high reaction activity in the reaction of catalyzing ammonia decomposition to produce hydrogen, the preparation method is simple, the stability is high, and the monatomic Ru-based catalyst has a wide application prospect in the field of ammonia decomposition to produce hydrogen.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and in particular relates to a method for preparing a single-atom ruthenium-based catalyst and its application in hydrogen production by decomposing ammonia. Background Art

[0002] Hydrogen is considered to be one of the most ideal clean energy sources, but the development of the hydrogen energy industry in the world is still facing major bottlenecks such as cross-regional, high safety, low cost, and large-scale storage and transportation difficulties. The liquefaction temperature of hydrogen at normal pressure is -253°C, and the liquefaction energy consumption is very high. The storage and transportation density of gaseous hydrogen is very low. A 40t hydrogen transport truck (20MPa) can only transport about 250kg of hydrogen, and the economic transportation radius of hydrogen is less than 200 kilometers. Ammonia is an efficient hydrogen storage medium with a hydrogen mass fraction of 17.6%. Ammonia can be liquefied at -33°C at normal pressure or 1MPa at room temperature. The storage and transportation technology, infrastructure, and transportation standards of liquid ammonia are very mature. It can be transported by road, water, and long-distance pipelines, and the transportation cost is low (the cost of road transportation is only 1% of hydrogen, and the cost of water and pipeline transportation is only 1‰ of hydrogen). Liquid ammonia, as an efficient storage and transportation medium for hydrogen, can increase the economic transportation radius of hydrogen from 150 to 200 kilometers to more than thousands of kilometers. Using ammonia as a hydrogen carrier and producing hydrogen through ammonia decomposition can achieve the safe storage and transportation of hydrogen. Therefore, ammonia decomposition to produce hydrogen is of great significance for the realization of the "hydrogen-ammonia" fusion development.

[0003] The ammonia decomposition reaction to produce hydrogen is a highly endothermic reaction. As shown in formula (1), low pressure and high temperature are conducive to the reaction. According to thermodynamic calculations, the equilibrium conversion rate of ammonia decomposition can reach 99% at normal pressure and temperature of 400°C. However, when no catalyst is used, the actual conversion rate of ammonia decomposition reaction at normal pressure and 700°C is less than 10%. Therefore, a highly active catalyst is required to achieve efficient decomposition of ammonia.

[0004] 2NH 3 = N 2 + 3H 2 , ΔH = 92.5 kJ mol -1 (1)

[0005] At present, supported Ru-based catalysts are recognized to have the highest catalytic ammonia decomposition activity. However, Ru, as a precious metal, has a high cost. High Ru content increases the cost of the catalyst, limiting its wide application. In conventional Ru-based catalysts, metallic Ru mostly exists in the form of particles. Catalytic reactions usually occur at the surface interface of the metal, and the atoms inside it cannot be effectively utilized, resulting in waste. In addition, the active component structure and properties of Ru particle catalysts are not uniform, resulting in low ammonia decomposition activity. In order to reduce the cost of the catalyst, it is necessary to improve the atomic utilization rate and intrinsic reaction activity of the precious metal. Therefore, the preparation of efficient Ru-based metal catalysts is of great significance.

[0006] Single-atom catalysts are metals dispersed on the surface of a carrier in the form of single atoms. They have the highest dispersion and the highest atomic utilization efficiency, and show high activity in many chemical reactions such as CO oxidation, PROX reaction, hydrogen evolution reaction (HER), and oxygen evolution reaction (OER). On the surface of single-atom catalysts, the active components are dispersed on the surface of the carrier in the form of atoms, so that the active components and reactants can fully contact, and the active site structure of the catalyst is uniform, which greatly improves the atomic utilization efficiency of the active components. Therefore, selecting a suitable carrier to prepare atomically dispersed Ru-based catalysts for ammonia decomposition reactions is expected to improve the utilization rate of the precious metal Ru.

[0007] At present, the methods for preparing single-atom catalysts with oxides as carriers mainly include adsorption method, precipitation method, etc. These methods mainly use the interaction between metal and adsorption sites on the carrier surface in an aqueous system for preparation. However, the above methods need to be operated in an aqueous phase, the process is complicated, and a large amount of wastewater is generated, which is difficult to meet the needs of practical applications. Therefore, it is urgent to develop a simple method to prepare oxide-supported Ru single-atom catalysts, which is of great significance for improving the utilization rate of precious metal Ru, reducing the cost of catalysts, and improving the performance of ammonia decomposition reactions. Summary of the invention

[0008] In view of the problem of complicated preparation process of single-atom ruthenium-based ammonia decomposition catalyst, the present invention provides a preparation method and application of a single-atom ruthenium-based ammonia decomposition catalyst. The preparation method is not only simple to operate, but also the prepared catalyst exhibits excellent performance in the ammonia decomposition reaction.

[0009] In order to achieve the above object, the technical solution of the present invention is as follows:

[0010] In one aspect, the present invention provides a method for preparing a single-atom ruthenium-based ammonia decomposition catalyst, wherein the preparation method is one of the following two methods:

[0011] Method 1:

[0012] The method comprises the following steps:

[0013] (1) Spread the ruthenium precursor powder in a hanging basket with a sand core, place the granulated oxide support particles on the ruthenium precursor powder, and place the hanging basket in a quartz tube;

[0014] (2) introducing oxygen-containing gas into a quartz tube and calcining at 400 to 1000° C. for 1 to 12 hours;

[0015] (3) separating the calcined oxide support particles from the ruthenium precursor powder, washing, drying in an oven, grinding into powder, and then performing a reduction treatment to obtain the ruthenium-based ammonia decomposition catalyst;

[0016] Method 2:

[0017] 1) placing the oxide carrier powder and the ruthenium precursor powder into two hanging baskets with sand cores respectively, with the oxide carrier powder placed above the ruthenium precursor powder, and placing the two hanging baskets in a quartz tube;

[0018] 2) introducing oxygen-containing gas into a quartz tube and calcining at 400-1000° C. for 1-12 hours;

[0019] 3) pouring out the powder and performing a reduction treatment to obtain the ruthenium-based ammonia decomposition catalyst.

[0020] In the above technical solution, further, the ruthenium precursor is selected from RuO 2 、RuO 4 At least one of;

[0021] The oxide support is selected from Al 2 O 3 、ZrO 2 、CeO 2 , and at least one of MgO.

[0022] In the above technical solution, further, the oxygen-containing gas is a mixture of oxygen and nitrogen, wherein the volume fraction of oxygen is 10-90%, and the flow rate of the oxygen-containing gas is 50-200 ml / min;

[0023] In the above technical solution, further, the mass ratio of the ruthenium precursor to the oxide carrier is 1:1 to 3:1.

[0024] In the above technical solution, further, the roasting temperature is 500-900° C., and the roasting time is 2-10 hours.

[0025] In the above technical solution, further, in method 1, the drying temperature is 80 to 120° C., and the drying time is 2 to 12 hours.

[0026] In the above technical solution, further, the atmosphere of the reduction treatment is ammonia and / or hydrogen, and the volume space velocity is 100 to 3600h -1 ;

[0027] The temperature rise rate of the reduction treatment is 1-10°C / min, the reduction treatment temperature is 200-600°C, and the reduction treatment time is 1-48h.

[0028] Another aspect of the present invention provides a catalyst obtained by the above preparation method, wherein the catalyst has Ru as an active component, and Ru is distributed on the surface of the carrier in the form of a single atom; the active component accounts for 0.01-1% of the mass percentage of the catalyst.

[0029] The present invention also provides an application of the catalyst in producing hydrogen by decomposing ammonia.

[0030] In the above technical solution, further, the reaction space velocity of the ammonia decomposition is 200 to 60000 ml / g·h.

[0031] In the above technical solution, further, the reaction temperature of the ammonia decomposition is 300-900°C.

[0032] The active component of the catalyst of the present invention is metal Ru, and Ru atoms are uniformly dispersed in the form of single atoms on the surface of the carrier. The preparation method of the catalyst of the present invention is an atom capture method, in which the ruthenium precursor powder and the carrier are treated at high temperature in an oxygen-containing atmosphere, and the oxide carrier is used to capture the volatilized Ru species in the high-temperature oxidizing atmosphere to achieve the anchoring of Ru atoms, effectively improve the stability of Ru on the surface of the carrier, and improve the atomic utilization rate of the precious metal. The single-atom Ru-based catalyst prepared by the present invention has high reaction activity in the catalytic ammonia decomposition hydrogen production reaction, and the preparation method is simple and the stability is high, and it has broad application prospects in the field of ammonia decomposition hydrogen production.

[0033] The beneficial effects of the present invention are:

[0034] 1) The single-atom ruthenium-based ammonia decomposition catalyst provided by the present invention can realize hydrogen production by decomposing ammonia at a relatively low temperature, thereby improving the utilization rate of the precious metal Ru and reducing the cost of the catalyst.

[0035] 2) The single-atom ruthenium-based ammonia decomposition catalyst provided by the present invention directly utilizes the interaction between the solid phase carrier and the metal to realize the preparation of the single-atom catalyst. The preparation method is simple and easy to scale up production.

[0036] 3) The ruthenium-based ammonia decomposition catalyst provided by the present invention, and its preparation method and application, have the advantages of low ammonia decomposition reaction temperature, high ammonia space velocity, and high ammonia conversion rate. The catalyst prepared according to the method provided by the present invention has lower cost and higher performance than the current nickel-based catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of the device used in the preparation method of the present invention;

[0038] Figure 2 High-resolution transmission electron microscopy and EDS mapping images of the catalyst prepared in Example 4. DETAILED DESCRIPTION

[0039] The technical details of the present invention are described in detail by the following examples. It should be noted that the examples cited are only used to further illustrate the technical features of the present invention, rather than to limit the present invention. Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained through commercial channels or prepared according to conventional methods well known to those skilled in the art.

[0040] Example 1

[0041] (1) Weigh 2g RuO 2 The powder was spread in a hanging basket with a sand core, and 1g of 20-40 mesh MgO particles after granulation were placed in the RuO 2 Above the powder, place the basket in the quartz tube;

[0042] (2) Pass O into the quartz tube 2 The volume fraction of O is 10% 2 and N 2 The mixed gas was calcined at 600 °C for 2 h with a flow rate of 100 ml / min.

[0043] (3) The calcined oxide support particles were separated from the ruthenium oxide powder, washed with anhydrous ethanol, ultrasonicated several times, and then dried in an oven at 120°C for 4 hours and ground into powder. Subsequently, the powder was reduced with hydrogen at a temperature of 300°C, a heating rate of 5°C / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 100h / min. -1 , the pressure was normal pressure, the reduction time was 4 h, and the catalyst was obtained, recorded as 0.01% Ru / MgO-particles.

[0044] The catalyst prepared in Example 1 was used in the reaction conditions of ammonia decomposition to produce hydrogen: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400-500°C, space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0045] Example 2

[0046] (1) Weigh 2g RuO 4 The powder was spread in a hanging basket with a sand core, and 1g of 20-40 mesh MgO particles after granulation were placed in the RuO 4 Above the powder, place the basket in the quartz tube;

[0047] (2) Pass O into the quartz tube 2 The volume fraction of O is 20% 2 and N 2 The mixed gas was calcined at 700 °C for 4 h with a flow rate of 100 ml / min.

[0048] (3) The calcined oxide support particles were separated from the ruthenium oxide powder, washed with anhydrous ethanol, ultrasonicated several times, and then dried in an oven at 80°C for 12 hours and ground into powder. Subsequently, the powder was reduced with hydrogen at a temperature of 200°C, a heating rate of 10°C / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 1000 h / min. -1 , the pressure was normal pressure, the reduction time was 48 h, and the catalyst was obtained, which was recorded as 0.1% Ru / MgO-particles.

[0049] The catalyst prepared in Example 2 was used in the reaction conditions of ammonia decomposition to produce hydrogen: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400-500°C, space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0050] Example 3

[0051] (1) Weigh 2g RuO 2 The powder was spread in a hanging basket with a sand core, and 1g of 20-40 mesh MgO particles after granulation were placed in the RuO 2 Above the powder, place the basket in the quartz tube;

[0052] (2) Pass O into the quartz tube 2 The volume fraction of O is 30% 2 and N 2 The mixed gas was calcined at 800 °C for 2 h with a flow rate of 200 ml / min.

[0053] (3) The calcined oxide support particles were separated from the ruthenium oxide powder, washed with anhydrous ethanol, ultrasonicated several times, dried in an oven at 120°C for 2 h, and ground into powder. Subsequently, the powder was reduced with hydrogen at a temperature of 600°C, a heating rate of 10°C / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 3600 h / min. -1 , the pressure was normal pressure, the reduction time was 1 h, and the catalyst was obtained, which was recorded as 0.3% Ru / MgO-particles.

[0054] The catalyst prepared in Example 3 was used in the reaction conditions of ammonia decomposition to produce hydrogen: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400-500°C, space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0055] Example 4

[0056] (1) Weigh 2g RuO 2 The powder was spread in a hanging basket with a sand core, and 1g of 20-40 mesh MgO particles after granulation were placed in the RuO 2 Above the powder, place the basket in the quartz tube;

[0057] (2) Pass O into the quartz tube 2 The volume fraction of O is 50% 2 and N 2 The mixed gas was calcined at 900 °C for 10 h with a flow rate of 200 ml / min.

[0058] (3) The calcined oxide support particles were separated from the ruthenium oxide powder, washed with anhydrous ethanol, ultrasonicated several times, dried in an oven at 120°C for 12 hours, and ground into powder. Subsequently, the powder was reduced with hydrogen at a temperature of 300°C, a heating rate of 5°C / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 3600 h / min. -1 , the pressure was normal pressure, the reduction time was 4 h, and the catalyst was obtained, recorded as 0.5% Ru / MgO-particles.

[0059] The catalyst prepared in Example 4 was used in the reaction conditions of ammonia decomposition to produce hydrogen: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400-500°C, and the reaction performance under different space velocities was tested. The reaction results are shown in Table 1.

[0060] The high-resolution transmission electron microscopy image and EDS mapping image of the catalyst material in Example 4 are as follows: Figure 2 As shown in the figure, the MgO carrier presents a crystal plane spacing of 0.21nm, which belongs to the (200) crystal plane of MgO. From the EDS mapping, it can be seen that Ru is evenly dispersed on the surface of MgO, indicating that Ru has a good dispersion. In the high-resolution electron microscopy image, it can be seen that single Ru atoms are distributed on the MgO carrier, further indicating the successful preparation of the single-atom Ru catalyst.

[0061] Example 5

[0062] (1) Weigh 2g RuO 2 The powder was spread in a hanging basket with a sand core, and 1g of 20-40 mesh MgO particles after granulation were placed in the RuO 2 Above the powder, place the basket in the quartz tube;

[0063] (2) Pass O into the quartz tube 2 The volume fraction is 90% O 2 and N 2 The mixed gas was calcined at 900 °C for 10 h with a flow rate of 200 ml / min.

[0064] (3) The calcined oxide support particles were separated from the ruthenium oxide powder, washed with anhydrous ethanol, ultrasonicated several times, and then dried in an oven at 80°C for 2 h and ground into powder. Subsequently, the powder was reduced with hydrogen at a temperature of 300°C, a heating rate of 5°C / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 1000 h / min. -1 , the pressure was normal pressure, and the reduction time was 4 h. The catalyst was obtained and was recorded as 1.0% Ru / MgO-particles.

[0065] The catalyst prepared in Example 5 was used in the reaction conditions of ammonia decomposition to produce hydrogen: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400-500°C, space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0066] Example 6

[0067] (1) Weigh 2g RuO 2 Spread the powder flat in a hanging basket with a sand core, put 1g of MgO powder in another hanging basket with a sand core, place it above the ruthenium precursor powder, and place both hanging baskets in a quartz tube;

[0068] (2) Pass O into the quartz tube 2 The volume fraction of O is 50% 2 and N 2 The mixed gas was calcined at 900 °C for 10 h with a flow rate of 200 ml / min.

[0069] (3) The calcined oxide support particles were separated from the ruthenium oxide powder, washed with anhydrous ethanol, ultrasonicated several times, dried in an oven at 120°C for 12 hours, and ground into powder. Subsequently, the powder was reduced with hydrogen at a temperature of 300°C, a heating rate of 5°C / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 3600 h / min. -1 , the pressure was normal pressure, the reduction time was 4 h, and the catalyst was obtained, recorded as 0.5% Ru / MgO-powder.

[0070] The catalyst prepared in Example 6 was used in the reaction conditions of ammonia decomposition to produce hydrogen: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400-500°C, space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0071] Example 7

[0072] (1) Weigh 2g RuO 4 The powder was spread flat in a hanging basket with a sand core, and 1g Al 2 O 3 The powder is placed in another hanging basket with a sand core, which is placed above the ruthenium precursor powder, and both hanging baskets are placed in a quartz tube;

[0073] (2) Pass O into the quartz tube 2 The volume fraction of O is 50% 2 and N 2 The mixed gas was calcined at 900 °C for 10 h with a flow rate of 200 ml / min.

[0074] (3) The calcined oxide support particles were separated from the ruthenium oxide powder, washed with anhydrous ethanol, ultrasonicated several times, dried in an oven at 120°C for 12 hours, and ground into powder. Subsequently, the powder was reduced with hydrogen at a temperature of 300°C, a heating rate of 5°C / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 3600 h / min. -1 , the pressure is normal pressure, and the reduction time is 4h. The catalyst is obtained and is recorded as 0.5%Ru / Al 2 O 3 -powder.

[0075] The catalyst prepared in Example 7 was used in the reaction conditions of ammonia decomposition to produce hydrogen: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400-500°C, space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0076] Example 8

[0077] (1) Weigh 2g RuO 2 The powder was spread flat in a hanging basket with a sand core, and 1g ZrO 2 The powder is placed in another hanging basket with a sand core, which is placed above the ruthenium precursor powder, and both hanging baskets are placed in a quartz tube;

[0078] (2) Pass O into the quartz tube 2 The volume fraction of O is 50% 2 and N 2 The mixed gas was calcined at 900 °C for 10 h with a flow rate of 200 ml / min.

[0079] (3) The calcined oxide support particles were separated from the ruthenium oxide powder, washed with anhydrous ethanol, ultrasonicated several times, dried in an oven at 120°C for 12 hours, and ground into powder. Subsequently, the powder was reduced with hydrogen at a temperature of 300°C, a heating rate of 5°C / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 3600 h / min. -1 , the pressure was normal pressure, the reduction time was 4 h, and the catalyst was obtained, which was recorded as 0.5%Ru / ZrO 2 -powder.

[0080] The catalyst prepared in Example 8 was used in the reaction conditions of ammonia decomposition to produce hydrogen: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400-500°C, space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0081] Example 9

[0082] (1) Weigh 2g RuO 2 The powder was spread flat in a hanging basket with a sand core, and 1g CeO 2 The powder is placed in another hanging basket with a sand core, which is placed above the ruthenium precursor powder, and both hanging baskets are placed in a quartz tube;

[0083] (2) Pass O into the quartz tube 2 The volume fraction of O is 50% 2 and N 2 The mixed gas was calcined at 900 °C for 10 h with a flow rate of 200 ml / min.

[0084] (3) The calcined oxide support particles were separated from the ruthenium oxide powder, washed with anhydrous ethanol, ultrasonicated several times, dried in an oven at 120°C for 12 hours, and ground into powder. Subsequently, the powder was reduced with hydrogen at a temperature of 300°C, a heating rate of 5°C / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 3600 h / min. -1 , the pressure was normal pressure, the reduction time was 4 h, and the catalyst was obtained, which was recorded as 0.5%Ru / CeO 2 -powder.

[0085] The catalyst prepared in Example 9 was used in the reaction conditions of ammonia decomposition to produce hydrogen: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400-500°C, space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0086] Comparative Example 1

[0087] Weigh 1.0g of MgO particle carrier and 2g of RuCl with a metal Ru concentration of 5mg / g. 3 The solution was added dropwise to the MgO carrier and mixed evenly, immersed at room temperature for 12 h, dried at 80 ° C for 12 h, calcined at 300 ° C in air atmosphere for 4 h, and then reduced with hydrogen at a temperature of 300 ° C, a heating rate of 5 ° C / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 2000 h -1 , the pressure was normal pressure, the reduction time was 1 h, and the catalyst was obtained, recorded as 0.5%Ru / MgO-IW.

[0088] The catalyst prepared in Comparative Example 1 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400-500°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0089] Comparative Example 2

[0090] Weigh 1.0g Al 2 O 3 Support, weigh 0.7469g Ni(NO 3 ) 2 Dissolve it in 2g of deionized water to prepare a mixed solution, and add it dropwise to the Al 2 O 3 The carrier is mixed evenly, impregnated at room temperature for 12 hours, dried at 80°C for 12 hours, and calcined at 300°C in air atmosphere for 4 hours, wherein the Ni mass content is 20%, and then it is reduced by hydrogen at a temperature of 600°C, a heating rate from room temperature to the reduction temperature of 5°C / min, and a volume space velocity of hydrogen of 2000h -1 , the pressure is normal pressure, and the reduction time is 1h. The catalyst is recorded as 20% Ni / Al 2 O 3 .

[0091] The catalyst prepared in Comparative Example 2 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 500°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0092] Result analysis:

[0093] As shown in Table 1, from the results of the ammonia decomposition reaction performance of Example 4 and Comparative Example 1, it can be seen that under the same Ru loading amount and the same carrier, the Ru / MgO prepared in Example 4 has a higher ammonia decomposition conversion rate at 400-500°C than the Ru / MgO prepared by the impregnation method (Comparative Example 1), indicating that the Ru / MgO prepared by the method of the present invention has a higher reaction activity in the ammonia decomposition reaction. 2 O 3 The Ru / MgO catalyst in Example 4 also has higher reaction activity than the catalyst.

[0094] In Examples 1-5, as the Ru loading increases, the ammonia decomposition conversion rate gradually increases, which is more obvious at a relatively low reaction temperature such as 400°C.

[0095] Comparing Example 4 with Example 6, the ammonia decomposition reaction activity of the Ru / MgO catalyst prepared by Method 1 or Method 2 is slightly different, and the ammonia decomposition conversion rate of the Ru / MgO catalyst prepared by Method 1 is slightly higher. However, the Ru / MgO catalyst prepared by the two methods both exhibit high ammonia decomposition reaction activity.

[0096] Examples 6-9 all exhibited high ammonia decomposition reaction activity using Ru-based catalysts supported by different carriers, indicating that the method has good adaptability.

[0097] Comparing the ammonia decomposition reaction activity at different space velocities in Example 4, it can be seen that as the space velocity increases, the ammonia conversion rate at different temperatures decreases. Increasing the space velocity reduces the ammonia conversion rate, but increases the hydrogen yield per unit time, which can be applied to the reaction requirements at different space velocities.

[0098] In summary, the present invention adopts the atom capture method to prepare a Ru-based catalyst dispersed at the single-atom level, effectively improving the stability of Ru on the carrier surface, improving the atomic utilization rate of the precious metal, and reducing the cost of the catalyst. The prepared Ru single-atom catalyst has high reactivity in the ammonia decomposition reaction, and the preparation method is simple, and has broad application prospects in the field of ammonia decomposition and hydrogen production.

[0099] Table 1

[0100]

[0101]

[0102] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing a single-atom ruthenium-based ammonia decomposition catalyst, characterized in that: The preparation method is one of the following two methods: Method 1: The method comprises the following steps: (1) Spread the ruthenium precursor powder in a hanging basket with a sand core, place the granulated oxide support particles on the ruthenium precursor powder, and place the hanging basket in a quartz tube; (2) introducing oxygen-containing gas into a quartz tube and calcining at 400 to 1000° C. for 1 to 12 hours; (3) separating the calcined oxide support particles from the ruthenium precursor powder, washing, drying in an oven, grinding into powder, and then performing a reduction treatment to obtain the ruthenium-based ammonia decomposition catalyst; Method 2: 1) placing the oxide carrier powder and the ruthenium precursor powder into two hanging baskets with sand cores respectively, with the oxide carrier powder placed above the ruthenium precursor powder, and placing the two hanging baskets in a quartz tube; 2) introducing oxygen-containing gas into a quartz tube and calcining at 400-1000° C. for 1-12 hours; 3) pouring out the powder and performing a reduction treatment to obtain the ruthenium-based ammonia decomposition catalyst.

2. The preparation method according to claim 1, characterized in that: The ruthenium precursor is selected from at least one of RuO2 and RuO4; The oxide carrier is selected from at least one of Al2O3, ZrO2, CeO2, and MgO; The mass ratio of the ruthenium precursor to the oxide carrier is 1:1 to 3:

1.

3. The preparation method according to claim 1, characterized in that: The oxygen-containing gas is a mixed gas of oxygen and nitrogen, wherein the volume fraction of oxygen is 10-90%, and the flow rate of the oxygen-containing gas is 50-200 ml / min.

4. The preparation method according to claim 1, characterized in that: The calcination temperature is 500-900° C., and the calcination time is 2-10 hours.

5. The preparation method according to claim 1, characterized in that: In method 1, the drying temperature is 80-120° C., and the drying time is 2-12 hours.

6. The preparation method according to claim 1, characterized in that: The atmosphere of the reduction treatment is ammonia and / or hydrogen, and the volume space velocity is 100 to 3600 h -1 ; The temperature rise rate of the reduction treatment is 1-10°C / min, the reduction treatment temperature is 200-600°C, and the reduction treatment time is 1-48h.

7. A catalyst prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The catalyst uses Ru as an active component, and Ru is distributed on the surface of the carrier in the form of single atoms; the active component accounts for 0.01-1% of the mass percentage of the catalyst.

8. Use of the catalyst according to claim 7 in producing hydrogen by decomposing ammonia.

9. The use according to claim 8, characterized in that: The reaction space velocity of the ammonia decomposition is 200 to 60000 ml / g·h.

10. The use according to claim 9, characterized in that: The reaction temperature of the ammonia decomposition is 300-900°C.

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