Activated carbon supported ruthenium catalyst for ammonia synthesis and preparation method thereof

Abstract

The invention discloses an activated carbon supported ruthenium catalyst for ammonia synthesis and a preparation method thereof. The catalyst is prepared by taking heat-treated activated carbon as a carrier, ruthenium metal as an active component and barium, silicon and cerium as auxiliaries. The preparation method of the catalyst comprises the following steps: firstly, carrying out heat treatment on activated carbon in an inert atmosphere and carrying out oxidation treatment in oxygen-containing mixed gas to obtain a heat-treated activated carbon carrier, drying, dipping in a carbonaceous organic matter aqueous solution, and carrying out oxidation treatment in a nitric acid atmosphere; then dipping and introducing barium nitrate and a ruthenium precursor solution, carrying out high-temperature treatment in an inert atmosphere, then adsorbing a silanol ammonia water solution, introducing a silicon component, finally dipping in a cerium nitrate water solution, and reducing to obtain the activated carbon supported ruthenium catalyst. Compared with the heat-treated activated carbon supported ruthenium catalyst prepared by the existing method, the catalyst prepared by the invention has higher ammonia synthesis activity and better application prospect.

Description

Technical Field

[0001] This invention belongs to the field of ammonia synthesis catalyst preparation technology, specifically relating to an activated carbon supported ruthenium catalyst for ammonia synthesis and its preparation method. Background Technology

[0002] Hydrogen has high costs due to its low volumetric energy density, requiring high-pressure storage and transportation at 35-70 MPa. Furthermore, hydrogen is flammable, explosive, and inherently unsafe. Therefore, to achieve large-scale application of hydrogen energy, it is urgent to overcome the bottlenecks of difficult hydrogen storage and transportation and its inherent safety, and to develop safe, mature, and efficient specialized hydrogen storage and transportation technologies and related industrial chains.

[0003] Ammonia offers a viable solution to overcome the bottlenecks in the hydrogen energy industry. Ammonia (NH3) is a bulk raw material, and its use as a hydrogen storage medium has significant advantages: First, high energy density: 1 L of liquid NH3 = 4.5 L of high-pressure hydrogen (35.0 MPa) = 1200 L of hydrogen at room temperature and pressure; Second, easy liquefaction and transportation: NH3 can be stored and transported in liquid form by pressurizing it to 1.0 MPa. A single liquid ammonia tanker can carry up to 30 tons of NH3 (containing approximately 5.29 tons of hydrogen), which is about 15 times higher than that of a long-tube trailer (carrying approximately 350 kg of hydrogen); Third, carbon-free energy storage: "Ammonia-hydrogen" energy storage can achieve seasonal, long-distance, and "carbon-free" energy storage; Fourth, high safety: NH3 is non-flammable, and its pungent odor serves as a reliable alarm signal. Therefore, developing NH3 as a hydrogen storage medium holds promise for solving the problems of high-pressure hydrogen storage and transportation and weak safety.

[0004] As is well known, ammonia synthesis has a history of over a century. The production, storage, transportation, and use of NH3, derived from fossil resources, have formed a complete industrial chain, standards, and safety regulations. Current industrial ammonia synthesis mainly employs Fe-based catalysts, the Haber-Bosch process, and operates under high temperature and high pressure conditions (480-510 °C). o The reaction is carried out at C (15.0-30.0 MPa). There is an urgent need to develop and design novel catalysts that can efficiently synthesize ammonia under mild conditions. Summary of the Invention

[0005] This invention proposes an activated carbon-supported ruthenium catalyst for ammonia synthesis and its preparation method. The catalyst has excellent ammonia synthesis activity and good application prospects.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An activated carbon-supported ruthenium catalyst for ammonia synthesis comprises heat-treated activated carbon as a support, ruthenium metal as the active component, and barium, silicon, and cerium as auxiliary agents; wherein the mass ratio of ruthenium to activated carbon is 0.01:1-0.10:1, the mass ratio of barium to activated carbon is 0.01:1-0.12:1, the mass ratio of silicon to activated carbon is 0.005:1-0.03:1, and the mass ratio of cerium to activated carbon is 0.005:1-0.05:1.

[0007] The preparation method of the activated carbon-supported ruthenium catalyst includes the following steps: 1) The activated carbon is heat-treated in an inert atmosphere and then cooled, and then oxidized in an oxygen-containing mixed gas to obtain a heat-treated activated carbon carrier. 2) The heat-treated activated carbon prepared in step 1) is impregnated with an aqueous solution of carbonaceous organic matter and introduced into the organic matter, then dried and subjected to oxidation treatment; 3) Immerse the sample obtained in step 2) in barium nitrate solution and dry it; 4) Impregnate the sample obtained in step 3) with an alcoholic solution containing ruthenium precursor and then dry it; 5) The sample obtained in step 4) is subjected to high-temperature treatment in an inert atmosphere; 6) The sample obtained in step 5) is adsorbed with silanol ammonia solution and introduced into the silicon component; 7) The sample obtained in step 6) is impregnated with cerium nitrate aqueous solution, dried and then reduced to obtain ruthenium catalyst supported on activated carbon.

[0008] Further, the inert atmosphere mentioned in step 1) is one or more of Group 0 gases and nitrogen; the heat treatment temperature is 1600-2000 ℃ and the time is 1-8 hours; the oxygen-containing mixed gas is a mixture of one or more of air, oxygen, carbon dioxide and water vapor providing oxygen components, and one or more of nitrogen and Group 0 gases, wherein the oxygen content in the mixed gas is 5-50 vol%; the oxidation treatment temperature is 300-600 ℃ and the time is 3-15 hours.

[0009] Further, the carbon-containing organic matter mentioned in step 2) is any one of glucose, melamine, and polyvinylpyrrolidone, and the mass ratio of the organic matter to the heat-treated activated carbon is 0.2:1-1:1; the oxidation treatment is carried out in a nitric acid atmosphere, with a treatment temperature of 80-200 ℃ and a time of 1-5 hours; the specific operation of the oxidation treatment includes: one or more gases from group 0 gas and nitrogen gas are used to treat the substrate through nitric acid gas carried by the nitric acid solution, with a treatment temperature of 80-200 ℃ and a time of 1-5 hours.

[0010] Further, in step 4), the solute of the ruthenium precursor alcohol solution is one of ruthenium nitrate, ruthenium chloride, ruthenium acetate, and potassium ruthenate, and the solvent is any one of methanol, ethanol, propanol, or a mixture of methanol and water, wherein the volume ratio of alcohol in the solvent is greater than or equal to 50%.

[0011] Further, in step 5), the inert atmosphere is one or more of nitrogen and group 0 gases; the high-temperature treatment temperature is 500-1200 ℃ and the time is 0.5-10 hours.

[0012] Further, the silanol ammonia solution in step 6) is composed of a silicon-containing substance, either tetraethyl or tetrabutyl silicate, ammonia, or an alcohol, either methanol or ethanol, wherein the molar ratio of the silicon-containing compound to the ammonium ion in the ammonia is 0.02:1-0.1:1; and the volume ratio of the alcohol to the ammonia is 1:1-1:4.

[0013] Further, the reduction in step 7) involves treatment in a hydrogen-containing gas at 200-600 °C for 0.2-20 hours, wherein the hydrogen-containing gas is a mixture of hydrogen and nitrogen or group 0 gases.

[0014] Significant advantages of this invention: This invention provides an activated carbon-supported ruthenium catalyst for ammonia synthesis and its preparation method. The catalyst is prepared by first heat-treating activated carbon in an inert atmosphere and then oxidizing it in an oxygen-containing mixed gas to obtain a heat-treated activated carbon support. After drying, the support is impregnated with an aqueous solution of carbonaceous organic matter and oxidized in a nitric acid atmosphere. Subsequently, a solution of barium nitrate and ruthenium precursors is impregnated and subjected to high-temperature treatment in an inert atmosphere. Then, a silicon component is introduced by adsorbing a silanol ammonia solution. Finally, the catalyst is impregnated with a cerium nitrate aqueous solution and reduced to obtain the activated carbon-supported ruthenium catalyst. Compared with existing technologies, This invention promotes the concentration of a large amount of Ba elements around Ru elements in the catalyst by impregnating the support with carbon organic matter and oxidizing it in a nitric acid atmosphere, changing the impregnation order of Ba and Ru, and high-temperature heat treatment. This facilitates the transfer and reaction of reactants, especially hydrogen species, in Ru metal and Ba promoters. Therefore, the prepared activated carbon supported ruthenium catalyst has excellent ammonia synthesis performance. Attached Figure Description

[0015] Figure 1 In the middle (ab), the TEM and HRTEM images of 1Ce-2Si-9Ru-9Ba / C-PVP are respectively (inset: ruthenium metal particle size distribution). (cd) are 1Ce-2Si-(9Ru-9Ba / C-PVP) H TEM and HRTEM images (inset: ruthenium metal particle size distribution), (f) is 1Ce-2Si-(9Ru-9Ba / C-PVP) HEDS plots of Ru and Ba (yellow: Ru, green: Ba).

[0016] Figure 2 The image shows a comparison of the color changes of the mixture of catalyst and WO3 obtained in Example 1 and Comparative Example 1 when hydrogen-treated at 60 °C for different times. Detailed Implementation

[0017] An activated carbon-supported ruthenium catalyst for ammonia synthesis and its preparation method, comprising the following steps: 1) The activated carbon is heat-treated in an inert atmosphere and then cooled, and then oxidized in an oxygen-containing mixed gas to obtain a heat-treated activated carbon carrier. 2) The heat-treated activated carbon prepared in step 1) is impregnated with an aqueous solution of carbonaceous organic matter and introduced into the organic matter, then dried and subjected to oxidation treatment; 3) Immerse the sample obtained in step 2) in barium nitrate solution and dry it; 4) Impregnate the sample obtained in step 3) with an alcoholic solution containing ruthenium precursor and then dry it; 5) The sample obtained in step 4) is subjected to high-temperature treatment in an inert atmosphere; 6) The sample obtained in step 5) is adsorbed with silanol ammonia solution and introduced into the silicon component; 7) The sample obtained in step 6) is impregnated with cerium nitrate aqueous solution, dried and then reduced to obtain ruthenium catalyst supported on activated carbon.

[0018] In step 1), the inert atmosphere is one or more of Group 0 gases and nitrogen; the heat treatment temperature is 1600-2000 ℃ and the time is 1-8 hours; the oxygen-containing mixed gas is a mixture of one or more of air, oxygen, carbon dioxide and water vapor providing the oxygen-containing component, and one or more of nitrogen and Group 0 gases, wherein the oxygen content in the mixed gas is 5-50 vol%; the oxidation treatment temperature is 300-600 ℃ and the time is 3-15 hours.

[0019] The carbon-containing organic matter mentioned in step 2) is any one of glucose, melamine, and polyvinylpyrrolidone, and the mass ratio of the organic matter to the heat-treated activated carbon is 0.2:1-1:1; the oxidation treatment atmosphere is one or more of group 0 gases and nitrogen, which are nitric acid-containing gases generated by nitric acid solution, and the treatment temperature is 80-200 ℃ and the time is 1-5 hours.

[0020] The solute of the ruthenium precursor solution mentioned in step 4) is one of ruthenium nitrate, ruthenium chloride, ruthenium acetate, and potassium ruthenate, and the solvent is any one of methanol, ethanol, propanol, or a mixture of methanol and water, wherein the volume ratio of alcohol in the solvent is greater than or equal to 50%.

[0021] Step 5) The inert atmosphere is one or more of nitrogen and group 0 gases; the high-temperature treatment temperature is 500-1200 ℃ and the time is 0.5-10 hours.

[0022] Step 6) The silanol ammonia solution is composed of a silicon-containing substance, either tetraethyl or tetrabutyl silicate, ammonia, or an alcohol, either methanol or ethanol, wherein the molar ratio of the silicon-containing compound to the ammonium ion in the ammonia is 0.02:1-0.1:1; and the volume ratio of the alcohol to the ammonia is 1:1-1:4.

[0023] Step 7) The reduction is performed by treating the gas in a hydrogen-containing gas at 200-600 °C for 0.2-20 hours. The hydrogen-containing gas is a mixture of hydrogen and nitrogen or group 0 gases.

[0024] Example 1: 1) Activated carbon was heat-treated in argon (1000 mL / min) at 1900 °C for 4 hours, then cooled to room temperature, and then oxidized and expanded in a mixture of water vapor and nitrogen (300 mL / min) with an oxygen content of 45 vol% at 450 °C for 10 hours to obtain heat-treated activated carbon carrier. 2) The obtained heat-treated activated carbon carrier was impregnated with polyvinylpyrrolidone aqueous solution, with a mass ratio of polyvinylpyrrolidone to heat-treated activated carbon of 0.5:1. After drying, the activated carbon sample containing polyvinylpyrrolidone was treated with 68wt% concentrated nitric acid solution under nitrogen gas at a rate of 200 mL / min for 4 hours at a temperature of 180 °C. 3) The sample obtained in step 2) is impregnated with barium nitrate solution and dried, with a mass ratio of barium to heat-treated activated carbon of 0.09:1; 4) The sample obtained in step 3) is impregnated with a ruthenium nitrate methanol aqueous solution, wherein the volume ratio of methanol to water is 60% and the mass ratio of ruthenium to heat-treated activated carbon is 0.09:1; 5) Treat the sample obtained in step 4) with nitrogen at 1000 °C for 6 hours; 6) Adsorb the sample obtained in step 5) into a silanol ammonia solution composed of tetraethyl silicate, ammonia and ethanol, wherein the theoretical mass ratio of silicon in tetraethyl silicate to heat-treated activated carbon is 0.02:1, the molar ratio of tetraethyl silicate to ammonium in the silanol ammonia solution is 0.1:1, and the volume ratio of ethanol to ammonia is 1:4. 7) The sample obtained in step 6) is impregnated with an aqueous solution of cerium nitrate, with a mass ratio of cerium to heat-treated activated carbon of 0.01:1. After drying, it is treated in pure hydrogen at 500 °C for 10 hours to obtain the activated carbon-supported ruthenium catalyst 1Ce-2Si-(9Ru-9Ba / C-PVP). H .

[0025] Example 2: 1) Activated carbon was heat-treated in argon (1000 mL / min) at 1700 °C for 8 hours, then cooled to room temperature, and then oxidized and expanded in a mixture of water vapor and nitrogen (300 mL / min) with an oxygen content of 20 vol% at 400 °C for 15 hours to obtain heat-treated activated carbon carrier. 2) The obtained heat-treated activated carbon carrier was impregnated with melamine aqueous solution, the mass ratio of melamine to heat-treated activated carbon was 0.8:1, and after drying, the above activated carbon sample containing melamine was treated with 68wt% concentrated nitric acid solution in argon gas at 200 mL / min for 5 hours at 100 ℃. 3) The sample obtained in step 2) is impregnated with barium nitrate solution and dried, with a mass ratio of barium to heat-treated activated carbon of 0.06:1; 4) Impregnate the sample obtained in step 3) with a ruthenium nitrate ethanol aqueous solution, wherein the volume ratio of ethanol to water is 80% and the mass ratio of ruthenium to heat-treated activated carbon is 0.07:1. 5) Treat the sample obtained in step 4) with nitrogen at 800 °C for 10 hours; 6) Adsorb the sample obtained in step 5) into a silanol ammonia solution composed of tetrabutyl silicate, ammonia and ethanol, wherein the theoretical mass ratio of silicon in tetrabutyl silicate to heat-treated activated carbon is 0.03:1, the molar ratio of tetrabutyl silicate to ammonium in the silanol ammonia solution is 0.05:1, and the volume ratio of methanol to ammonia is 1:2. 7) The sample obtained in step 6) was impregnated with an aqueous solution of cerium nitrate, with a mass ratio of cerium to heat-treated activated carbon of 0.04:1. After drying, it was treated in pure hydrogen at 500 °C for 10 hours to obtain the activated carbon-supported ruthenium catalyst 4Ce-3Si-(7Ru-6Ba / C-Mel). H .

[0026] Example 3: 1) Activated carbon was heat-treated in argon (1000 mL / min) at 1800 °C for 3 hours, then cooled to room temperature, and then oxidized and expanded in a mixture of water vapor and nitrogen (300 mL / min) with an oxygen content of 35 vol% at 350 °C for 12 hours to obtain heat-treated activated carbon carrier. 2) The obtained heat-treated graphitized activated carbon carrier was impregnated with a glucose aqueous solution, with a glucose to heat-treated activated carbon mass ratio of 0.3:1. After drying, the activated carbon sample containing glucose was treated with 68wt% concentrated nitric acid solution under nitrogen gas at a rate of 200 mL / min for 4 hours at a temperature of 180 °C. 3) The sample obtained in step 2) is impregnated with barium nitrate solution and dried, with a mass ratio of barium to heat-treated activated carbon of 0.04:1; 4) Impregnate the sample obtained in step 3) with a ruthenium nitrate methanol aqueous solution, wherein the volume ratio of methanol to water is 60% and the mass ratio of ruthenium to heat-treated activated carbon is 0.04:1; 5) Treat the sample obtained in step 4) with nitrogen at 1100 °C for 3 hours; 6) Adsorb the sample obtained in step 5) into a silanol ammonia solution composed of tetraethyl silicate, ammonia and ethanol, wherein the theoretical mass ratio of silicon in tetraethyl silicate to heat-treated activated carbon is 0.01:1, the molar ratio of tetraethyl silicate to ammonium in the silanol ammonia solution is 0.06:1, and the volume ratio of ethanol to ammonia is 1:3. 7) The sample obtained in step 6) was impregnated with an aqueous solution of cerium nitrate, with a mass ratio of cerium to heat-treated activated carbon of 0.03:1. After drying, it was treated in pure hydrogen at 450 °C for 8 hours to obtain the activated carbon-supported ruthenium catalyst 3Ce-1Si-(4Ru-4Ba / C-Glu). H .

[0027] Comparative Example 1: 1) Activated carbon was heat-treated in argon (1000 mL / min) at 1900 °C for 4 hours, then cooled to room temperature, and then oxidized and expanded in a mixture of water vapor and nitrogen (300 mL / min) with an oxygen content of 45 vol% at 450 °C for 10 hours to obtain heat-treated activated carbon carrier. 2) The obtained heat-treated activated carbon carrier was impregnated with polyvinylpyrrolidone aqueous solution, with a mass ratio of polyvinylpyrrolidone to heat-treated activated carbon of 0.5:1. After drying, the activated carbon sample containing polyvinylpyrrolidone was treated with 68wt% concentrated nitric acid solution under nitrogen gas at a rate of 200 mL / min for 4 hours at a temperature of 180 °C. 3) The sample obtained in step 2) is impregnated with barium nitrate solution and dried, with a mass ratio of barium to heat-treated activated carbon of 0.09:1; 4) The sample obtained in step 3) is impregnated with a ruthenium nitrate methanol aqueous solution, wherein the volume ratio of methanol to water is 60% and the mass ratio of ruthenium to heat-treated activated carbon is 0.09:1; 5) Adsorb the sample obtained in step 4) into a silanol ammonia solution composed of tetraethyl silicate, ammonia and ethanol, wherein the theoretical mass ratio of silicon in tetraethyl silicate to heat-treated activated carbon is 0.02:1, the molar ratio of tetraethyl silicate to ammonium in the silanol ammonia solution is 0.1:1, and the volume ratio of ethanol to ammonia is 1:4. 6) The sample obtained in step 5) is impregnated with an aqueous solution of cerium nitrate, with a mass ratio of cerium to heat-treated activated carbon of 0.01:1. After drying, it is treated in pure hydrogen at 500 °C for 10 hours to obtain the activated carbon-supported ruthenium catalyst 1Ce-2Si-9Ru-9Ba / C-PVP.

[0028] Comparative Example 2: 1) Activated carbon was heat-treated in argon (1000 mL / min) at 1900 °C for 4 hours, then cooled to room temperature, and then oxidized and expanded in a mixture of water vapor and nitrogen (300 mL / min) with an oxygen content of 45 vol% at 450 °C for 10 hours to obtain heat-treated activated carbon carrier. 2) The obtained heat-treated activated carbon carrier was impregnated with polyvinylpyrrolidone aqueous solution, with a mass ratio of polyvinylpyrrolidone to heat-treated activated carbon of 0.5:1. After drying, the activated carbon sample containing polyvinylpyrrolidone was treated with 68wt% concentrated nitric acid solution under nitrogen gas at a rate of 200 mL / min for 4 hours at a temperature of 180 °C. 3) The sample obtained in step 2) is impregnated with barium nitrate solution and dried, with a mass ratio of barium to heat-treated activated carbon of 0.09:1; 4) The sample obtained in step 3) is impregnated with a ruthenium nitrate methanol aqueous solution, wherein the volume ratio of methanol to water is 60% and the mass ratio of ruthenium to heat-treated activated carbon is 0.09:1; 5) Treat the sample obtained in step 4) with nitrogen at 1000 °C for 6 hours; 6) Adsorb the sample obtained in step 5) into a silanol ammonia solution composed of tetraethyl silicate, ammonia and ethanol, wherein the theoretical mass ratio of silicon in tetraethyl silicate to heat-treated activated carbon is 0.02:1, the molar ratio of tetraethyl silicate to ammonium in the silanol ammonia solution is 0.1:1, and the volume ratio of ethanol to ammonia is 1:4. 7) The sample obtained in step 6) was treated in pure hydrogen at 500 °C for 10 hours to obtain the activated carbon supported ruthenium catalyst 2Si-(9Ru-9Ba / C-PVP). H .

[0029] Comparative Example 3: 1) Activated carbon was heat-treated in argon (1000 mL / min) at 1900 °C for 4 hours, then cooled to room temperature, and then oxidized and expanded in a mixture of water vapor and nitrogen (300 mL / min) with an oxygen content of 45 vol% at 450 °C for 10 hours to obtain heat-treated activated carbon carrier. 2) The sample obtained in step 1) is impregnated with barium nitrate solution and dried, with a mass ratio of barium to heat-treated activated carbon of 0.09:1; 3) The sample obtained in step 2) is impregnated with a ruthenium nitrate methanol aqueous solution, wherein the volume ratio of methanol to water is 60% and the mass ratio of ruthenium to heat-treated activated carbon is 0.09:1; 4) Treat the sample obtained in step 3) with nitrogen at 1000 °C for 6 hours; 5) Adsorb the sample obtained in step 4) into a silanol ammonia solution composed of tetraethyl silicate, ammonia and ethanol, wherein the theoretical mass ratio of silicon in tetraethyl silicate to heat-treated activated carbon is 0.02:1, the molar ratio of tetraethyl silicate to ammonium in the silanol ammonia solution is 0.1:1, and the volume ratio of ethanol to ammonia is 1:4. 6) The sample obtained in step 5) is impregnated with an aqueous solution of cerium nitrate, with a mass ratio of cerium to heat-treated activated carbon of 0.01:1. After drying, it is treated in pure hydrogen at 500 °C for 10 hours to obtain the activated carbon-supported ruthenium catalyst 1Ce-2Si-(9Ru-9Ba / C). H .

[0030] Comparative Example 4: 1) Activated carbon was heat-treated in argon (1000 mL / min) at 1900 °C for 4 hours, then cooled to room temperature, and then oxidized and expanded in a mixture of water vapor and nitrogen (300 mL / min) with an oxygen content of 45 vol% at 450 °C for 10 hours to obtain heat-treated activated carbon carrier. 2) The sample obtained in step 1) is impregnated with barium nitrate solution and dried, with a mass ratio of barium to heat-treated activated carbon of 0.09:1; 3) The sample obtained in step 2) is impregnated with a ruthenium nitrate methanol aqueous solution, wherein the volume ratio of methanol to water is 60% and the mass ratio of ruthenium to heat-treated activated carbon is 0.09:1; 4) The sample obtained in step 3) was treated in pure hydrogen at 500 °C for 10 hours to obtain the activated carbon supported ruthenium catalyst 9Ru-9Ba / C.

[0031] As can be seen from the figure, a large amount of Ba elements in the catalyst reported in Example 1 are focused around Ru elements, which helps the transfer and reaction of reactants in Ru metal and Ba promoters.

[0032] WO3 is reduced by hydrogen to form blue H. x To address this, the catalyst and WO3 powder are mixed and then heat-treated in a hydrogen atmosphere to detect the transfer of hydrogen atoms from the catalyst surface to the WO3 powder and their reaction with it. Figure 2 The figures show a comparison of the color changes of mixtures of the catalysts obtained in Example 1 and Comparative Example 1 with WO3 (mass ratio 1:10) after hydrogen treatment at 60 °C for different times. As can be seen from the figures, the catalyst obtained in Example 1 changes color faster during hydrogen treatment. This indicates that hydrogen atoms on the Ru surface of the catalyst obtained in Example 1 have a faster migration ability to WO3, which is beneficial to improving the catalyst's ammonia synthesis activity.

[0033] The catalytic activity of the ammonia synthesis catalysts obtained in the examples and comparative examples was evaluated in a high-pressure activity testing apparatus. During the test, 0.3 g of catalyst was mixed with quartz sand and packed into the isothermal zone of the reactor. The reaction gas was a nitrogen-hydrogen mixture obtained from the high-temperature catalytic cracking of ammonia, with a hydrogen-nitrogen volume ratio of 3:1; the reaction conditions were: pressure 1 MPa, reaction temperature 400 °C, and reaction space velocity 3.6 × 10⁻⁶. 4 cm 3 g -1 h -1 The results of the catalytic activity determination are shown in Table 1.

[0034] Table 1 As can be seen from Table 1, under the same conditions, the ammonia synthesis rate of the activated carbon-supported ruthenium catalyst obtained in the examples is significantly higher than that of the catalyst obtained in the comparative examples, proving that it has good ammonia synthesis catalytic activity and has good application prospects.

[0035] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. An activated carbon supported ruthenium catalyst for the synthesis of ammonia, characterized in that: The catalyst is composed of heat-treated activated carbon as carrier, ruthenium metal as active component, and barium, silicon and cerium as additives; wherein the mass ratio of ruthenium to activated carbon is 0.01:1-0.10:1, the mass ratio of barium to activated carbon is 0.01:1-0.12:1, the mass ratio of silicon to activated carbon is 0.005:1-0.03:1, and the mass ratio of cerium to activated carbon is 0.005:1-0.05:

1.

2. The method for preparing an activated carbon supported ruthenium catalyst for the synthesis of ammonia according to claim 1, characterized in that: The method comprises the following steps: 1) heat treating and cooling activated carbon in an inert atmosphere, and then performing oxidation treatment in an oxygen-containing mixed gas to obtain a heat-treated activated carbon carrier; 2) impregnating the heat-treated activated carbon prepared in step 1) with a carbon-containing organic matter aqueous solution to introduce the organic matter, drying, and then performing oxidation treatment; 3) impregnating the sample obtained in step 2) with a barium nitrate solution and drying; 4) impregnating the sample obtained in step 3) with a ruthenium precursor alcohol solution and drying; 5) performing high-temperature treatment on the sample obtained in step 4) in an inert atmosphere; 6) adsorbing a silicon alcohol ammonia aqueous solution to introduce a silicon component; 7) impregnating the sample obtained in step 6) with a cerium nitrate aqueous solution, drying, and then reducing to obtain an activated carbon-supported ruthenium catalyst.

3. The method for preparing an activated carbon supported ruthenium catalyst for the synthesis of ammonia according to claim 2, characterized in that: In step 1), the inert atmosphere is one or more of group 0 gases and nitrogen; the heat treatment temperature is 1600-2000 ℃, and the time is 1-8 hours; the oxygen-containing mixed gas is one or more of air, oxygen, carbon dioxide and water vapor to provide an oxygen-containing component, and is mixed with one or more of nitrogen and group 0 gases, wherein the oxygen content in the mixed gas is 5-50 vol%; the oxidation treatment temperature is 300-600 ℃, and the time is 3-15 hours.

4. The process for the preparation of an activated carbon supported ruthenium catalyst for the synthesis of ammonia according to claim 2, characterized in that: In step 2), the carbon-containing organic matter is any one of glucose, melamine and polyvinylpyrrolidone, and the mass ratio of the organic matter to the heat-treated activated carbon is 0.2:1-1:1; the oxidation treatment operation comprises: treating the substrate with nitric acid gas carried by one or more of group 0 gases and nitrogen gas through a nitric acid solution, and the treatment temperature is 80-200 ℃, and the time is 1-5 hours.

5. The method for preparing an activated carbon-supported ruthenium catalyst for ammonia synthesis according to claim 2, characterized in that: In step 4), the solute of the ruthenium precursor alcohol solution is one of ruthenium nitrate, ruthenium chloride, ruthenium acetate and potassium ruthenate, and the solvent is any one of methanol, ethanol and propanol or a mixture with water, and the volume ratio of alcohol in the solvent is greater than or equal to 50%.

6. The process for the preparation of an activated carbon supported ruthenium catalyst for the synthesis of ammonia as claimed in claim 2 wherein: In step 5), the inert atmosphere is one or more of nitrogen and group 0 gases; the high-temperature treatment temperature is 500-1200 ℃, and the time is 0.5-10 hours.

7. The method of claim 2, wherein the ruthenium catalyst is prepared by the following steps: (a) mixing ruthenium chloride with a reducing agent; (b) adding a carbon support to the mixture; (c) heating the mixture to a temperature of about 300°C to about 400°C; and (d) cooling the mixture to room temperature. In step 6), the silicon alcohol ammonia aqueous solution is composed of tetraethyl silicate or tetrabutyl silicate, ammonia and methanol or ethanol, wherein the molar ratio of tetraethyl silicate or tetrabutyl silicate to ammonium in the ammonia is 0.02:1-0.1:1; and the volume ratio of methanol or ethanol to ammonia is 1:1-1:

4.

8. The method for preparing an activated carbon-supported ruthenium catalyst for ammonia synthesis according to claim 2, characterized in that: In step 7), the reduction is performed in a hydrogen-containing gas at 200-600 ℃ for 0.2-20 hours, and the hydrogen-containing gas is a mixed gas of hydrogen and nitrogen or group 0 gas.

9. Application of the activated carbon-supported ruthenium catalyst according to claim 1 in synthesis of ammonia.

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