CN112387276A - Supported ruthenium cluster catalyst for ammonia synthesis and preparation method and application thereof - Google Patents
Supported ruthenium cluster catalyst for ammonia synthesis and preparation method and application thereof Download PDFInfo
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
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- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
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- C01C1/04—Preparation of ammonia by synthesis in the gas phase
- C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst
- C01C1/0411—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst characterised by the catalyst
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Abstract
The application discloses a supported ruthenium cluster catalyst for ammonia synthesis and a preparation method and application thereof, belonging to the technical field of preparation of ammonia synthesis catalysts. The supported ruthenium cluster catalyst for ammonia synthesis comprises a carrier and an active component, wherein the carrier comprises rare earth oxide, the active component comprises ruthenium in a cluster form, and the loading amount of the active component is 0.1-10% of the mass of the rare earth oxide carrier. The preparation method comprises the following steps: the supported ruthenium cluster catalyst for ammonia synthesis is prepared by taking rare earth hydroxide as a carrier precursor and adopting a precipitation deposition method. The supported ruthenium cluster catalyst for ammonia synthesis can be used for ammonia synthesis catalytic reaction, and has the advantages of low noble metal loading, high catalytic activity and high catalytic stability. The preparation method has the advantages of easily available raw materials, low cost, simple and safe preparation process and easy realization of industrial production.
Description
Technical Field
The application belongs to the technical field of preparation of ammonia synthesis catalysts, and particularly relates to a supported ruthenium cluster catalyst for ammonia synthesis and a preparation method and application thereof.
Background
Ammonia is one of chemical products with the largest yield in the world, is mainly used for producing chemical fertilizers, nitric acid, ammonium salts, sodium carbonate and other products, and plays an important role in global economy. China is the biggest synthetic ammonia producing country in the world, and compared with the advanced level in the world, the synthetic ammonia industry has the defects of high energy consumption and cost and the like. Currently based on HaberThe industrial synthetic ammonia of the Bosch process is widely applied to a molten iron catalyst, the activity of the molten iron catalyst is low, and the molten iron catalyst needs to be used under the conditions of high temperature (400-500 ℃) and high pressure (10-30 MPa). At present, the industrial ammonia synthesis process has high energy consumption which accounts for 1 percent of the total annual energy consumption of the world, and CO2The annual emission is huge. In recent years, the sustainable development and energy-saving emission-reducing policies of the society become stricter, and higher requirements and challenges are provided for the synthetic ammonia industry in China.
The key to reducing the energy consumption and cost of the synthetic ammonia industry is to develop a synthetic ammonia catalyst with high activity and high stability under relatively mild reaction conditions as much as possible. Compared with the traditional molten iron ammonia synthesis catalyst, the ruthenium-based ammonia synthesis catalyst has the advantages of high activity, mild reaction conditions, low energy consumption, insensitivity to water, carbon oxides, ammonia concentration and the like, can greatly reduce the production cost, and is considered as an ideal second-generation ammonia synthesis catalyst behind an iron catalyst. Currently, the KAAP process developed by oil companies in the united kingdom and Kellogg in the united states based on activated carbon supported ruthenium ammonia synthesis catalysts has been industrialized. However, under the reaction conditions of ammonia synthesis, the graphitized carbon carrier is easy to generate methanation reaction to cause the deactivation and loss of the catalyst, so that the wide application of the active carbon-loaded ruthenium catalyst for ammonia synthesis is limited.
The development of a novel ruthenium-based ammonia synthesis catalyst with high activity and high stability under relatively mild conditions has important significance. The rare earth oxide has excellent optical, electrical, magnetic and other properties. The rare earth oxide supported ruthenium catalyst prepared by Aika et al has good catalytic activity for ammonia synthesis, but is easily deactivated under the reaction conditions of ammonia synthesis (Journal of Catalysis,1996,162(1), 138-142). Bin Hu et al prepared cerium oxide supported ruthenium catalysts with different morphologies, but the synthetic ammonia activity was lower (Catalysis Science & Technology,2017,7(1), 191-199). Sato et al reported that a praseodymium oxide supported ruthenium catalyst for ammonia synthesis showed good activity and stability (Chemical Science,2017,8(1), 674-679); the lanthanum-cerium composite oxide supported ruthenium catalyst reported by Sato et al shows very high catalytic activity for ammonia synthesis after high-temperature pre-reduction treatment (Chemical Science,2018,9(8),2230-2237), but the ruthenium precursors adopted by the catalyst system are all dodecacarbonyl triruthenium, which is expensive, so that the application of the catalyst is greatly limited.
Compared with the conventional supported nanoparticle catalyst, the sub-nanocluster (with the size of 0.2-1.0 nm) catalyst has the advantages of high metal dispersion degree, small size, high metal utilization rate and the like, is expected to reduce the consumption of noble metals and reduce the cost, has stronger interaction between metal cluster particles and a carrier, and can greatly modulate the catalytic activity or selectivity of the cluster catalyst.
Therefore, the oxide-supported ruthenium cluster ammonia synthesis catalyst which is low in development cost, simple in preparation process, high in activity and high in stability under relatively mild reaction conditions (250-400 ℃) has important significance for promoting the development of ammonia synthesis technology. So far, ruthenium cluster supported oxide catalysts for ammonia synthesis have been reported. The preparation of the ruthenium oxide-supported synthetic ammonia catalyst with high catalytic activity and stability at low cost is to be further developed.
Disclosure of Invention
According to one aspect of the application, a supported ruthenium cluster catalyst for ammonia synthesis is provided, the catalyst can be used as a high-efficiency ammonia synthesis catalyst under relatively mild reaction conditions (250-400 ℃), and not only has the catalytic activity of the ammonia synthesis catalyst which is obviously higher than that of an oxide supported ruthenium nanoparticle catalyst, but also has very high stability, and the catalytic activity of the catalyst is kept stable in an online continuous test for 350 hours.
Thus, the present application provides a supported ruthenium cluster catalyst for ammonia synthesis reactions.
The supported ruthenium cluster catalyst for ammonia synthesis is characterized by comprising a carrier and an active component;
wherein the support comprises a rare earth oxide;
the active component comprises ruthenium in the form of clusters;
the loading capacity of the active component ruthenium cluster is 0.1-10% of the mass of the rare earth oxide carrier.
In the present application, the term "ruthenium in clusters" means ruthenium present in the form of sub-nanometer scale metal clusters, sometimes also referred to herein as "ruthenium clusters", both having the same meaning.
Optionally, the ruthenium in cluster form, i.e. the size of the ruthenium cluster, is 0.1-1.5 nm.
Preferably, the ruthenium in the form of clusters, i.e. the size of the ruthenium clusters, is 0.2-1.0 nm.
The characteristics of a scanning transmission electron microscope, Element distribution (HAADF STEM and Element Mapping), X-ray absorption fine structure spectrum (XAFS) and the like prove that ruthenium is distributed on the surface of the rare earth oxide carrier in a cluster form.
Optionally, the rare earth element in the rare earth oxide is selected from at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.
Optionally, the supported ruthenium cluster catalyst for ammonia synthesis consists of the support and the active component.
Optionally, the support is comprised of the rare earth oxide.
Optionally, the active component is comprised of ruthenium in the form of clusters.
Optionally, the loading amount of the ruthenium in the cluster form is 0.1-10% of the mass of the rare earth oxide carrier, wherein the mass of the active component is calculated by the mass of the active element, and the mass of the carrier is calculated by the mass of the rare earth oxide generated by decomposing the rare earth hydroxide carrier precursor.
According to another aspect of the present application, there is provided a method for preparing the supported ruthenium cluster catalyst for ammonia synthesis, which requires raw materials such as rare earth hydroxide, ruthenium salt, urea and the like, all of which are large commercial products and are low in cost; in addition, the preparation process of the method is simple and safe to operate, and industrial production is easy to realize.
Thus, the present application provides an efficient preparation method of a negative type ruthenium-supported cluster catalyst for ammonia synthesis reaction.
The preparation method of the supported ruthenium cluster catalyst for ammonia synthesis is characterized by comprising the following steps:
the supported ruthenium cluster catalyst for ammonia synthesis is prepared by taking rare earth hydroxide as a carrier precursor and adopting a precipitation deposition method.
Optionally, the method comprises:
(1) adding a precipitator into the solution containing the rare earth hydroxide and the ruthenium precursor, and reacting to obtain a catalyst precursor;
(2) and reducing the catalyst precursor to obtain the supported ruthenium cluster catalyst for ammonia synthesis.
Optionally, the solvent in the solution containing the rare earth hydroxide and the ruthenium precursor is water.
Optionally, in step (1), adding a rare earth hydroxide to the solution of the ruthenium precursor to obtain the solution containing the rare earth hydroxide and the ruthenium precursor.
Optionally, the conditions of the reaction include: the reaction temperature is 40-180 ℃; the reaction time is 1-36 hours.
Optionally, the upper limit of the reaction temperature is selected from 180 ℃, 170 ℃, 160 ℃, 150 ℃, 140 ℃, 130 ℃, 120 ℃, 110 ℃, 100 ℃, 90 ℃, 80 ℃, 70 ℃, 60 ℃ or 50 ℃; the lower limit is selected from 40 deg.C, 50 deg.C, 60 deg.C, 70 deg.C, 80 deg.C, 90 deg.C, 100 deg.C, 110 deg.C, 120 deg.C, 130 deg.C, 140 deg.C, 150 deg.C, 160 deg.C or 170 deg.C.
Alternatively, the upper limit of the reaction time is selected from 36 hours, 32 hours, 28.5 hours, 24 hours, 20 hours, 18 hours, 16 hours, 14 hours, 12 hours, 10 hours, 9 hours, 8 hours, 6 hours, 4 hours, or 2 hours; the lower limit is selected from 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 9 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 24 hours, 28.5 hours, 32 hours, or 36 hours.
Alternatively, the reaction is carried out under stirring conditions.
Optionally, the reaction is carried out under reflux conditions.
Optionally, the reaction conditions may further include: standing or stirring at room temperature for reaction for 1-24 hours.
Optionally, the material obtained after the reaction is filtered, washed and dried.
Optionally, the drying temperature is 40-200 ℃; the drying time is 1-60 hours.
Optionally, the reducing conditions comprise: under a reducing atmosphere; the reduction temperature is 300-800 ℃; the reduction time is 1-12 hours.
Optionally, the upper limit of the reduction temperature is selected from 800 ℃, 750 ℃, 700 ℃, 650 ℃, 600 ℃, 550 ℃, 500 ℃, 450 ℃, 400 ℃ or 350 ℃; the lower limit is selected from 300 deg.C, 350 deg.C, 400 deg.C, 450 deg.C, 500 deg.C, 550 deg.C, 600 deg.C, 650 deg.C, 700 deg.C or 750 deg.C.
Alternatively, the upper limit of the reduction time is selected from 12 hours, 10 hours, 8 hours, 6 hours, 4 hours, or 2 hours; the lower limit is selected from 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, or 10 hours.
Optionally, the reducing atmosphere is hydrogen, a mixed gas of hydrogen and argon, or a mixed gas of hydrogen and nitrogen, wherein the volume percentage of hydrogen in the mixed gas is more than or equal to 5%.
Optionally, the volume percentage of hydrogen in the mixed gas is more than or equal to 5% and less than 100%.
Optionally, the ruthenium precursor is selected from at least one of ruthenium salts.
Optionally, the ruthenium salt is selected from at least one of ruthenium chloride, ruthenium nitrosyl nitrate, ruthenium acetylacetonate, and potassium ruthenate.
Optionally, the rare earth element in the rare earth hydroxide corresponds to the rare earth element in the rare earth oxide.
Optionally, the rare earth hydroxide is selected from at least one of scandium hydroxide, yttrium hydroxide, lanthanum hydroxide, cerium hydroxide, praseodymium hydroxide, neodymium hydroxide, samarium hydroxide, europium hydroxide, gadolinium hydroxide, terbium hydroxide, dysprosium hydroxide, holmium hydroxide, erbium hydroxide, thulium hydroxide, ytterbium hydroxide, and lutetium hydroxide.
Optionally, the ratio of the ruthenium in cluster form to the rare earth hydroxide support precursor satisfies: the loading amount of the cluster type ruthenium is 0.1-10% of the mass of the carrier; wherein the mass of the active component is calculated by the mass of active element ruthenium, and the mass of the carrier is calculated by the mass of rare earth oxide generated by decomposing the rare earth hydroxide carrier precursor.
Optionally, the precipitant is added under stirring.
Optionally, the precipitant is selected from at least one of urea, ammonia, potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate.
Preferably, the precipitating agent is urea.
Optionally, the molar ratio of the precipitant to the ruthenium precursor is 10: 1-500: 1, wherein the mole number of the precipitant is calculated as the mole number of the precipitant itself, and the mole number of the ruthenium precursor is calculated as the mole number of the ruthenium element in the ruthenium precursor.
Optionally, the upper limit of the molar ratio of the precipitant to the ruthenium precursor is selected from 500:1, 450:1, 400:1, 380:1, 360:1, 340:1, 320:1, 300:1, 280:1, 260:1, 240:1, 220:1, 200:1, 180:1, 160:1, 140:1, 120:1, 100:1, 90:1, 80:1, 70:1, 60:1, 50:1, 40:1, 30:1, or 20: 1; the lower limit is selected from the group consisting of 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, 120:1, 140:1, 160:1, 180:1, 200:1, 220:1, 240:1, 260:1, 280:1, 300:1, 320:1, 340:1, 360:1, 380:1, 400:1, or 450:1, wherein the moles of the precipitating agent are calculated as the moles of the precipitating agent itself and the moles of the ruthenium precursor are calculated as the moles of ruthenium element in the ruthenium precursor.
Preferably, the molar ratio of the urea to the ruthenium element in the ruthenium precursor is 10: 1-500: 1.
Optionally, the method comprises:
(a) preparing a catalyst precursor: adding rare earth hydroxide into a ruthenium salt aqueous solution, adding a precipitator into the ruthenium salt aqueous solution containing the rare earth hydroxide under stirring, and reacting at 40-180 ℃ for 1-36 hours to obtain a catalyst precursor;
(b) reduction of a catalyst precursor: and reducing the catalyst precursor for 1-12 hours at 300-800 ℃ in a reducing atmosphere to obtain the supported ruthenium cluster catalyst for ammonia synthesis.
In one embodiment, the method comprises the steps of:
(a1) preparing a catalyst precursor: adding rare earth hydroxide into a ruthenium salt aqueous solution, adding a precipitator into the ruthenium salt aqueous solution containing the rare earth hydroxide under stirring, stirring and reacting for 1-36 hours at 40-180 ℃, and then standing or stirring for 1-24 hours at room temperature to obtain a catalyst precursor;
(b1) reduction of a catalyst precursor: and reducing the catalyst precursor for 1-12 hours at 300-800 ℃ in a reducing atmosphere to obtain the supported ruthenium cluster catalyst for ammonia synthesis.
According to still another aspect of the present application, there is provided a use of at least one of the supported ruthenium cluster catalyst for ammonia synthesis described above, the supported ruthenium cluster catalyst for ammonia synthesis prepared according to the above method, in a catalytic reaction for ammonia synthesis.
Optionally, the method for catalytic reaction of synthesis ammonia comprises: and (2) heating the supported ruthenium cluster catalyst for ammonia synthesis to 300-800 ℃ at a speed of 1-5 ℃/min in a reducing atmosphere containing hydrogen, reducing at the temperature for 1-12 hours, cooling to a reaction temperature of 250-400 ℃, and carrying out a synthetic ammonia catalytic reaction in a mixed atmosphere of nitrogen and hydrogen to obtain an ammonia product.
Optionally, the volume ratio of nitrogen to hydrogen in the mixed atmosphere is 1: 3-3: 1; the space velocity of the reaction gas is 1000-50000 mL/gcatH; the reaction pressure is 0.1-5.0 MPa.
In one embodiment, the supported ruthenium cluster catalyst for ammonia synthesis is heated to 300-800 ℃ at a speed of 1-5 ℃/min in a reducing atmosphere containing hydrogen, reduced at the temperature for 1-12 hours, then reduced to a reaction temperature of 250-400 ℃ in the reducing atmosphere, and the atmosphere is switched to a nitrogen-hydrogen mixed gas, so that an ammonia product can be obtained.
The supported ruthenium cluster ammonia synthesis catalyst for ammonia synthesis has high catalytic activity, good stability and wide application prospect. Compared with the prior art, the supported ruthenium cluster catalyst for ammonia synthesis and the preparation method thereof provided by the application can produce the following beneficial effects:
1) the supported ruthenium cluster catalyst for ammonia synthesis provided by the application has high catalytic activity, has high ammonia synthesis activity under low load, and can remarkably improve the ammonia synthesis activity and greatly improve the ammonia synthesis reaction efficiency compared with the conventional supported ruthenium nanoparticle catalyst.
2) The supported ruthenium cluster catalyst for ammonia synthesis provided by the application has high catalytic stability, and has high activity by dispersing and fixing the high-dispersion ruthenium cluster through the rare earth hydroxide, and good long-term stability under the reaction condition of ammonia synthesis, and the activity of the catalyst is not obviously changed after 350-hour stability test.
3) According to the preparation method of the supported ruthenium cluster catalyst for ammonia synthesis, the required raw materials such as rare earth hydroxide, ruthenium salt, urea and the like are large commercial products, and the cost is low.
4) The preparation method of the supported ruthenium cluster catalyst for ammonia synthesis has the advantages of simple and safe operation and the like, and is easy to realize industrial production.
Drawings
FIG. 1 is a graph showing the reaction activity of the catalysts of examples 1 to 4 of the present application and comparative example 1 with temperature, under the following reaction conditions: the temperature is 250-400 ℃, the reaction pressure is 1.0MPa, and the reaction space velocity is 24000mL/gcat·h。
FIG. 2 shows 5 wt% Ru clusterings/Sm in example 1 of the present application2O3Catalyst at 1.0MPa, 24000mL/gcatH and 400 ℃ reaction conditions.
FIG. 3 shows 5 wt% Ru clusterings/Sm in example 1 of the present application2O3The catalyst was scanned by a transmission electron microscope and the distribution of elements (O element at the upper right; Ru element at the lower left; Sm element at the lower right).
FIG. 4 shows 5 wt% of Ru NPs/Sm in comparative example 1 of the present application2O3-1 catalyst scanning transmission electron microscope and element distribution image (upper right: O element; lower left: Ru element; lower right: Sm element).
Detailed Description
As previously described, the present application relates to a supported ruthenium cluster catalyst for ammonia synthesis and a method for preparing the same. The supported ruthenium cluster catalyst for ammonia synthesis is prepared by taking ruthenium as an active component and rare earth hydroxide as a carrier precursor through a precipitation deposition method. Compared with the existing ammonia synthesis catalyst system, the supported ruthenium cluster catalyst for ammonia synthesis prepared by the method has higher ammonia synthesis catalytic activity and stability, can effectively reduce the energy consumption in the ammonia synthesis process, and has good application prospect.
Unless otherwise indicated, all numbers such as active ingredients, temperature and time, gas conversion, etc. appearing in the specification and claims of this application are to be understood as being absolutely exact, and certain experimental errors in the measured values are inevitable due to standard deviation of the measurement technique.
The present application will be described in detail with reference to examples, but the present application is not limited to these examples.
Unless otherwise specified, the raw materials and reagents in the examples of the present application were all purchased commercially.
In the embodiment of the application, the synthetic ammonia reaction is carried out on a fixed bed micro reaction device, a stainless steel reactor is adopted, and a temperature control thermocouple is arranged on the outer wall of the reactor. The components of the reaction gas are analyzed on line by a conductivity meter, the reaction tail gas is introduced into the dilute sulfuric acid solution, the conductivity change of the solution is tracked by the conductivity meter, and finally the ammonia generation rate is deduced and calculated according to the change of the conductivity.
The presence form of Ru in the catalyst sample was observed and the size was measured by scanning transmission electron microscopy (model: JEM-ARM200F, available from JEOL, Japan) and the state of element distribution in the catalyst sample was measured.
Example 1
0.0628g of ruthenium nitrosyl nitrate is dissolved in 60mL of water, 0.4g of samarium hydroxide is added to the aqueous solution of ruthenium nitrosyl nitrate under stirring, 2.36g of urea is added to the suspension after uniform stirring, and the mixed solution is refluxed and reacted for 6 hours under stirring at 90 ℃. After the reaction, the reaction mixture was filtered, and the product was washed with deionized water until the filtrate was neutral, and then dried at 60 ℃ for 24 hours. The product is reduced for 2 hours at 400 ℃ by hydrogen after being dried to obtain the samarium oxide supported ruthenium cluster catalyst (5 wt% Ru clusters/Sm) with 5 wt% ruthenium load2O3)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusters/Sm2O3Ru in the catalyst is distributed in a sub-nanocluster state. The scanning transmission electron microscope and the element distribution characterization results are shown in FIG. 3.
And (3) carrying out synthetic ammonia reaction activity evaluation on the prepared samarium oxide supported ruthenium cluster catalyst in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at a speed of 5 ℃/min under a nitrogen-hydrogen mixed atmosphere with a volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to a reaction temperature (250-400 ℃). Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH, the reaction activity of the ammonia synthesis reaction is 508 to 32214 mu mol/g at different temperatures within the temperature range of 250 to 400 DEG CcatH. The variation of the reaction activity of the catalyst with temperature is shown in figure 1.
Example 2
0.03768g of ruthenium nitrosyl nitrate is dissolved in 60mL of water, 0.4g of samarium hydroxide is added into the ruthenium nitrosyl nitrate aqueous solution under stirring, 1.416g of urea is added into the suspension after uniform stirring, and the mixed solution is refluxed and reacted for 10 hours under stirring at 70 ℃. After the reaction was completed, filtration was carried out, and the product was washed with deionized water until the filtrate was neutral, and then dried at 70 ℃ for 24 hours. The product was dried and then treated with H having a hydrogen content of 5 vol.%2Reducing the/Ar mixed gas for 2 hours at 500 ℃ to obtain the samarium oxide supported ruthenium cluster catalyst (3 wt% Ru clusters/Sm) with the ruthenium load of 3 wt%2O3)。
Scanning transmission electron microscope and element distribution tableThe characterization result shows that the above 3 wt% Ru clusters/Sm2O3Ru in the catalyst is distributed in a sub-nanocluster state. And (3) carrying out synthetic ammonia reaction activity evaluation on the prepared samarium oxide supported ruthenium cluster catalyst in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at a speed of 5 ℃/min under a nitrogen-hydrogen mixed atmosphere with a volume ratio of 1:3, reducing for 5 hours at the temperature, and cooling to a reaction temperature (250-400 ℃). Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH, the reaction activity of the ammonia synthesis reaction is 122-19110 mu mol/g at different temperatures within the temperature range of 250-400 DEG CcatH. The variation of the reaction activity of the catalyst with temperature is shown in figure 1.
Example 3
0.0314g ruthenium nitrosyl nitrate is dissolved in 60mL water, 1.0g samarium hydroxide is added to the ruthenium nitrosyl nitrate aqueous solution under stirring, 1.18g urea is added to the suspension after uniform stirring, and the mixture is refluxed for 12 hours at 100 ℃ under stirring. After the reaction was completed, filtration was carried out, and the product was washed with deionized water until the filtrate was neutral, and then dried at 120 ℃ for 8 hours. The product was dried and then treated with H having a hydrogen content of 50 vol.%2Reducing the/Ar mixed gas for 4 hours at 500 ℃ to obtain the samarium oxide supported ruthenium cluster catalyst (1 wt% Ru clusters/Sm) with the ruthenium load of 1 wt%2O3)。
The results of scanning transmission electron microscope and element distribution characterization show that the 1 wt% Ru clusterics/Sm is2O3Ru in the catalyst is distributed in a sub-nanocluster state. And (3) carrying out synthetic ammonia reaction activity evaluation on the prepared samarium oxide supported ruthenium cluster catalyst in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at a speed of 5 ℃/min under a nitrogen-hydrogen mixed atmosphere with a volume ratio of 1:3, reducing for 2 hours at the temperature, and cooling to a reaction temperature (250-400 ℃). Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH, the reaction activity of the ammonia synthesis reaction is 29 to 7956 mu mol/g at different temperatures within the temperature range of 250 to 400 DEG CcatH. The variation of the reaction activity of the catalyst with temperature is shown in figure 1.
Example 4
0.0157g of ruthenium nitrosyl nitrate is dissolved in 60mL of water, 1.0g of samarium hydroxide is added into the ruthenium nitrosyl nitrate aqueous solution under stirring, 0.59g of urea is added into the suspension after uniform stirring, and the mixed solution is refluxed and reacted for 6 hours under stirring at 150 ℃. After the reaction, the reaction mixture was filtered, and the product was washed with deionized water until the filtrate was neutral, and then dried at 60 ℃ for 12 hours. The product was dried and then treated with H having a hydrogen content of 5 vol.%2/N2Reducing the mixed gas for 2 hours at 450 ℃ to obtain the samarium oxide supported ruthenium cluster catalyst (0.5 wt% Ru clusters/Sm) with the ruthenium load of 0.5 wt%2O3)。
The results of a scanning transmission electron microscope and element distribution characterization show that the 0.5 wt% Ru clusterics/Sm2O3Ru in the catalyst is distributed in a sub-nanocluster state. And (3) carrying out synthetic ammonia reaction activity evaluation on the prepared samarium oxide supported ruthenium cluster catalyst in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at a speed of 5 ℃/min under a nitrogen-hydrogen mixed atmosphere with a volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to a reaction temperature (250-400 ℃). Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH, the reaction activity of the ammonia synthesis reaction is 146-5160 mu mol/g at different temperatures within the temperature range of 250-400 DEG CcatH. The variation of the reaction activity of the catalyst with temperature is shown in figure 1.
Example 5
0.157g of ruthenium nitrosyl nitrate is dissolved in 60mL of water, 1.0g of lanthanum hydroxide is added into the aqueous solution of ruthenium nitrosyl nitrate under stirring, 5.9g of urea is added into the suspension after uniform stirring, and the mixed solution is refluxed and reacted for 12 hours under stirring at 60 ℃. After the reaction, the reaction mixture was filtered, and the product was washed with deionized water until the filtrate was neutral, and then dried at 120 ℃ for 12 hours. The product was dried and then treated with H having a hydrogen content of 10 vol.%2/N2Reducing the mixed gas at 600 ℃ for 4 hours to obtain the lanthanum oxide supported ruthenium cluster catalyst (5 wt% Ru clusters/La) with the ruthenium load of 5 wt%2O3)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusters/La2O3Ru in the catalyst is distributed in a sub-nanocluster state. The obtained lanthanum oxide supported ruthenium cluster catalyst is subjected to ammonia synthesis reaction activity evaluation in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH at 400 ℃ the activity of the reaction for synthesizing ammonia is 32136. mu. mol/gcat·h。
Example 6
0.157g of ruthenium nitrosyl nitrate is dissolved in 60mL of water, 1.0g of cerium hydroxide is added to the aqueous solution of ruthenium nitrosyl nitrate under stirring, 5.9g of urea is added to the suspension after uniform stirring, and the mixed solution is refluxed and reacted for 9 hours at 80 ℃ under stirring. After the reaction was completed, filtration was carried out, and the product was washed with deionized water until the filtrate was neutral, and then dried at 90 ℃ for 8 hours. The product was dried and then treated with H having a hydrogen content of 80 vol.%2/N2Reducing the mixed gas at 500 ℃ for 2 hours to obtain the cerium oxide supported ruthenium cluster catalyst (5 wt% Ru clusters/CeO) with 5 wt% of ruthenium load2)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusters/CeO2Ru in the catalyst is distributed in a sub-nanocluster state. The activity of the synthesis ammonia reaction of the prepared cerium oxide supported ruthenium cluster catalyst is evaluated in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH reaction Activity for Ammonia Synthesis at 400 ℃ of 24725. mu. mol/gcat·h。
Example 7
Dissolving 0.314g of ruthenium nitrosyl nitrate in 60mL of water, adding 2.0g of praseodymium hydroxide into the aqueous solution of ruthenium nitrosyl nitrate under stirring, and stirringAfter homogenization, 11.8g of urea was added to the suspension, and the mixture was refluxed at 90 ℃ for 9 hours with stirring. After the reaction was completed, filtration was carried out, and the product was washed with deionized water until the filtrate was neutral, and then dried at 110 ℃ for 10 hours. The product was dried and then treated with H having a hydrogen content of 5 vol.%2/N2Reducing the mixed gas for 4 hours at 300 ℃ to obtain the praseodymium oxide supported ruthenium cluster catalyst (5 wt% Ru clusters/Pr) with the ruthenium loading of 5 wt%2O3)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusters/Pr2O3Ru in the catalyst is distributed in a sub-nanocluster state. The prepared praseodymium oxide-supported ruthenium cluster catalyst was subjected to evaluation of the activity of the ammonia synthesis reaction in an ammonia synthesis apparatus. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH reaction Activity for Ammonia Synthesis at 400 ℃ of 27222. mu. mol/gcat·h。
Example 8
0.314g of ruthenium nitrosyl nitrate is dissolved in 60mL of water, 2.0g of neodymium hydroxide is added into the aqueous solution of ruthenium nitrosyl nitrate under stirring, 11.8g of urea is added into the suspension after uniform stirring, and the mixed solution is refluxed and reacted for 10 hours under stirring at 100 ℃. After the reaction, the reaction mixture was filtered, and the product was washed with deionized water until the filtrate was neutral, and then dried at 80 ℃ for 6 hours. The product was dried and then treated with H having a hydrogen content of 50 vol.%2/N2Reducing the mixed gas at 400 ℃ for 2 hours to obtain the neodymium oxide supported ruthenium cluster catalyst (5 wt% Ru clusters/Nd) with the ruthenium load of 5 wt%2O3)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusters/Nd2O3Ru in the catalyst is distributed in a sub-nanocluster state. The obtained neodymium oxide-supported ruthenium cluster catalyst was subjected to evaluation of ammonia synthesis reaction activity in an ammonia synthesis apparatus. The catalyst is placed in N2/H2Volume ratio of 13, heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere, reducing for 10 hours at the temperature, and cooling to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH at 400 ℃ the activity of the reaction for the synthesis of ammonia is 28314. mu. mol/gcat·h。
Example 9
Dissolving 0.314g of ruthenium nitrosyl nitrate in 60mL of water, adding 2.0g of gadolinium hydroxide into the ruthenium nitrosyl nitrate aqueous solution under stirring, adding 11.8g of urea into the suspension after uniformly stirring, and carrying out reflux reaction on the mixed solution for 6 hours at 120 ℃ under stirring. After the reaction, the reaction mixture was filtered, and the product was washed with deionized water until the filtrate was neutral, and then dried at 60 ℃ for 24 hours. The product is reduced for 4 hours at 600 ℃ by hydrogen after being dried to obtain the gadolinium oxide loaded ruthenium cluster catalyst (5 wt% Ru clusters/Gd) with 5 wt% ruthenium load2O3)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusterics/Gd2O3Ru in the catalyst is distributed in a sub-nanocluster state. And (3) carrying out ammonia synthesis reaction activity evaluation on the prepared gadolinium oxide supported ruthenium cluster catalyst in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH at 400 ℃ the activity of the ammonia synthesis reaction was 27144. mu. mol/gcat·h。
Example 10
0.314g of ruthenium nitrosyl nitrate is dissolved in 60mL of water, 2.0g of scandium hydroxide is added to the aqueous solution of ruthenium nitrosyl nitrate under stirring, 11.8g of urea is added to the suspension after uniform stirring, and the mixture is refluxed for 8 hours at 70 ℃ under stirring. After the reaction, the reaction mixture was filtered, and the product was washed with deionized water until the filtrate was neutral, and then dried at 80 ℃ for 12 hours. The product was dried and then treated with H having a hydrogen content of 5 vol.%2Reducing the/Ar mixed gas at 400 ℃ for 6 hours to obtain scandium oxide loaded ruthenium cluster with 5 wt% of ruthenium loadCatalyst (5 wt% Ru clusters/Sc2O3)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusters/Sc2O3Ru in the catalyst is distributed in a sub-nanocluster state. And (3) carrying out ammonia synthesis reaction activity evaluation on the prepared scandium oxide supported ruthenium cluster catalyst in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH reaction activity of 24136. mu. mol/g of ammonia at 400 ℃cat·h。
Example 11
0.314g of ruthenium nitrosyl nitrate is dissolved in 60mL of water, 2.0g of yttrium hydroxide is added into the aqueous solution of ruthenium nitrosyl nitrate under stirring, 11.8g of urea is added into the suspension after uniform stirring, and the mixed solution is refluxed and reacted for 12 hours under stirring at 110 ℃. After the reaction, the reaction mixture was filtered, and the product was washed with deionized water until the filtrate was neutral, and then dried at 120 ℃ for 12 hours. The product was dried and then treated with H having a hydrogen content of 20 vol.%2Reducing the/Ar mixed gas at 500 ℃ for 2 hours to obtain the yttrium oxide supported ruthenium cluster catalyst (5 wt% Ru clusters/Y) with the ruthenium load of 5 wt%2O3)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusters/Y2O3Ru in the catalyst is distributed in a sub-nanocluster state. The prepared yttrium oxide supported ruthenium cluster catalyst is subjected to ammonia synthesis reaction activity evaluation in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH, ammonia synthesis activity 23698. mu. mol/g at 400 ℃cat·h。
Example 12
0.205g of ruthenium chloride was dissolved in60mL of water, 2.0g of lanthanum hydroxide was added to the aqueous ruthenium chloride solution under stirring, 20.0g of urea was added to the suspension after stirring uniformly, and the mixture was refluxed at 70 ℃ for 8 hours under stirring. After the reaction, the reaction mixture was filtered, and the product was washed with deionized water until the filtrate was neutral, and then dried at 80 ℃ for 8 hours. The product was dried and then treated with H having a hydrogen content of 30 vol.%2Reducing the/Ar mixed gas at 600 ℃ for 4 hours to obtain the lanthanum oxide supported ruthenium cluster catalyst with the ruthenium load of 5 wt% (5 wt% Ru clusters/La)2O3)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusters/La2O3Ru in the catalyst is distributed in a sub-nanocluster state. The obtained lanthanum oxide supported ruthenium cluster catalyst is subjected to ammonia synthesis reaction activity evaluation in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH reaction Activity for Ammonia Synthesis at 400 ℃ of 27653. mu. mol/gcat·h。
Example 13
0.394g of ruthenium acetylacetonate is dissolved in 60mL of water, 2.0g of cerium hydroxide is added to the aqueous solution of ruthenium acetylacetonate with stirring, 5.0g of urea is added to the suspension after uniform stirring, and the mixture is refluxed at 90 ℃ for 12 hours with stirring. After the reaction, the reaction mixture was filtered, and the product was washed with deionized water until the filtrate was neutral, and then dried at 100 ℃ for 10 hours. The product was dried and then treated with H having a hydrogen content of 60 vol.%2Reducing the/Ar mixed gas at 600 ℃ for 4 hours to obtain the cerium oxide supported ruthenium cluster catalyst (5 wt% Ru clusters/CeO) with 5 wt% of ruthenium load2)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusters/CeO2Ru in the catalyst is distributed in a sub-nanocluster state. The activity of the synthesis ammonia reaction of the prepared cerium oxide supported ruthenium cluster catalyst is evaluated in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH activity of 23152. mu. mol/g at 400 ℃ for ammonia synthesiscat·h。
Example 14
0.202g of potassium ruthenate was dissolved in 60mL of water, 2.0g of neodymium hydroxide was added to the aqueous solution of potassium ruthenate with stirring, 15.0g of urea was added to the suspension after stirring, and the mixture was refluxed at 120 ℃ for 6 hours with stirring. After the reaction was completed, filtration was carried out, and the product was washed with deionized water until the filtrate was neutral, and then dried at 90 ℃ for 12 hours. The product was dried and then treated with H having a hydrogen content of 15 vol.%2Reducing the mixed gas/Ar for 4 hours at 300 ℃ to obtain the neodymium oxide supported ruthenium cluster catalyst (5 wt% Ru clusters/Nd) with the ruthenium load of 5 wt%2O3)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru clusters/Nd2O3Ru in the catalyst is distributed in a sub-nanocluster state. And (3) carrying out ammonia synthesis reaction activity evaluation on the prepared gadolinium oxide supported ruthenium cluster catalyst in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH reaction Activity for Ammonia Synthesis at 400 ℃ of 25169. mu. mol/gcat·h。
Comparative example 1
0.157g of ruthenium nitrosylnitrate was weighed out and dissolved in 60mL of water, and after sufficient dissolution, 1.0g of samarium oxide (Sm) was added2O3) Adding into ruthenium nitrosyl nitrate water solution for dipping. After ultrasonic treatment for 10 minutes, drying for 12 hours at 80 ℃, roasting for 2 hours at 550 ℃ in argon, and then reducing the obtained product for 2 hours at 550 ℃ in hydrogen to obtain the impregnated samarium oxide supported ruthenium nanoparticle catalyst (5 wt% Ru NPs/Sm)2O3-1)。
The results of scanning transmission electron microscope and element distribution characterization show that the 5 wt% Ru NPs/Sm2O3-1 the Ru in the catalyst is distributed in the form of nanoparticles of larger size. The scanning transmission electron microscope and the element distribution characterization results are shown in FIG. 4.
And (3) carrying out synthetic ammonia reaction activity evaluation on the prepared samarium oxide supported ruthenium nanoparticle catalyst in an ammonia synthesis device. The catalyst is placed in N2/H2Heating to 500 ℃ at a speed of 5 ℃/min under a nitrogen-hydrogen mixed atmosphere with a volume ratio of 1:3, reducing for 10 hours at the temperature, and cooling to a reaction temperature (250-400 ℃). Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH, the reaction activity of the synthetic ammonia is 26 to 6614 mu mol/g at different temperatures within the temperature range of 250 to 400 DEG CcatH. The variation of the reaction activity of the catalyst with temperature is shown in figure 1.
Comparative example 2
0.157g of ruthenium nitrosyl nitrate was weighed and dissolved in 60mL of water, and after sufficient dissolution, 1.0g of samarium hydroxide was added to the aqueous solution of ruthenium nitrosyl nitrate to impregnate the solution. After 10 minutes of sonication, the mixture was dried at 80 ℃ for 12 hours, then calcined at 550 ℃ for 2 hours under argon, and subjected to hydrogen in the presence of 5 vol.% H2Reducing for 4 hours at 500 ℃ in/Ar mixed gas to obtain the ruthenium nanoparticle-loaded catalyst (5 wt% Ru NPs/Sm) prepared by an impregnation method and taking samarium hydroxide as a carrier precursor2O3-2)。
The obtained catalyst was subjected to evaluation of the activity of the ammonia synthesis reaction in an ammonia synthesis apparatus. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and then reducing to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH reaction activity of 14028. mu. mol/g of ammonia synthesis reaction at 400 ℃cat·h。
Comparative example 3
0.135g of ruthenium chloride was weighed out and dissolved in 60mL of water, and after sufficient dissolution, 1.0g of samarium oxide (Sm) was added2O3) Adding into ruthenium chloride aqueous solution for leachingAnd (5) soaking. After 10 minutes of sonication, drying at 80 ℃ for 12 hours, then calcining at 550 ℃ under argon for 2 hours, and subjecting the product to hydrogen with a hydrogen content of 50 vol.% H2Reducing the/Ar mixed gas for 4 hours at 550 ℃ to obtain the impregnated samarium oxide supported ruthenium nanoparticle catalyst (5 wt% Ru NPs/Sm)2O3-3)。
The obtained catalyst was subjected to evaluation of the activity of the ammonia synthesis reaction in an ammonia synthesis apparatus. The catalyst is placed in N2/H2Heating to 500 ℃ at the speed of 5 ℃/min under the nitrogen-hydrogen mixed atmosphere with the volume ratio of 1:3, reducing for 10 hours at the temperature, and then reducing to the reaction temperature of 400 ℃. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH the activity of the reaction for synthesizing ammonia at 400 ℃ is 1360. mu. mol/gcat·h。
As can be seen from FIG. 1, Ru clusterings/Sm were also present at 5 wt% ruthenium loading2O3The activity of the catalyst is far higher than that of Ru NPs/Sm2O3-1 activity of the catalyst. At 300 ℃, 5 wt% Ru clusters/Sm2O3Has an activity of 5 wt% Ru NPs/Sm2O3-about 21.7 times the activity of 1; 5 wt% Ru clusters/Sm at 350 deg.C2O3Has an activity of 5 wt% Ru NPs/Sm2O3-about 13 times the activity of 1; 0.5 wt% Ru clusters/Sm at the temperature of 300-375 DEG C2O3Catalytic activity of (3) and 5 wt% of Ru NPs/Sm2O3The catalytic activity of-1 is comparable. In addition, Table 1 shows that the catalysts of examples 1 to 14 and comparative examples 1 to 3 had a reaction temperature of 400 ℃, a reaction pressure of 1.0MPa, and a reaction gas space velocity of 24000mL/gcatH reaction activity of ammonia synthesis under conditions of reaction temperature. By comparison, the supported ruthenium cluster catalyst system for ammonia synthesis not only has high ammonia synthesis activity, but also can reduce the catalyst cost.
TABLE 1 comparison of the activity of ammonia synthesis with different catalysts and the reaction conditions for ammonia synthesis
Example 15 Supported ruthenium Cluster catalyst Synthesis Ammonia reaction stability test
The rare earth oxide-supported ruthenium cluster catalyst prepared in the above example was subjected to evaluation of stability of the synthesis ammonia reaction in an ammonia synthesis apparatus. The catalyst is placed in N2/H2Heating to 400 ℃ at a speed of 5 ℃/min under a nitrogen-hydrogen mixed atmosphere with a volume ratio of 1:3, and maintaining the constant temperature. Under the conditions that the reaction pressure is 1.0MPa and the space velocity of reaction gas is 24000mL/gcatH reaction temperature of 400 ℃ for 350 hours, 5 wt% Ru clusterings/Sm in example 12O3The results of the catalyst stability test are shown in FIG. 2.
As can be seen from FIG. 2, 5 wt% Ru clusterings/Sm in example 12O3The catalyst has very stable catalytic activity, and the activity is basically kept unchanged after 350 hours of reaction. The stability test results of the catalysts prepared in other examples are similar to those described above, and all have better stability.
In summary, the supported ruthenium cluster ammonia synthesis catalyst for ammonia synthesis has high catalytic activity, high stability and good application prospect.
Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.
Claims (10)
1. A supported ruthenium cluster catalyst for ammonia synthesis, comprising a support and an active component;
wherein the support comprises a rare earth oxide;
the active component comprises ruthenium in the form of clusters;
the loading amount of the active component is 0.1-10% of the mass of the rare earth oxide carrier.
2. The supported ruthenium cluster catalyst for ammonia synthesis according to claim 1, wherein the size of the ruthenium in cluster form is 0.2 to 1.0 nm;
preferably, the rare earth element in the rare earth oxide is selected from at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium;
preferably, the ratio of the active component cluster form ruthenium to the support is such that: the loading capacity of the active component ruthenium cluster is 0.1-10% of the mass of the rare earth oxide carrier; wherein the mass of the active component is calculated by the mass of the active element, and the mass of the carrier is calculated by the mass of the rare earth oxide generated by decomposing the rare earth hydroxide carrier precursor.
3. The method for producing a supported ruthenium cluster catalyst for ammonia synthesis according to claim 1 or 2, characterized by comprising:
the supported ruthenium cluster catalyst for ammonia synthesis is prepared by taking rare earth hydroxide as a carrier precursor and adopting a precipitation deposition method.
4. The method of claim 3, comprising:
(1) adding a precipitator into the solution containing the rare earth hydroxide and the ruthenium precursor, and reacting to obtain a catalyst precursor;
(2) and reducing the catalyst precursor to obtain the supported ruthenium cluster catalyst for ammonia synthesis.
5. The method according to claim 4, wherein the ruthenium precursor is selected from at least one of ruthenium salts;
preferably, the ruthenium salt is selected from at least one of ruthenium chloride, ruthenium nitrosyl nitrate, ruthenium acetylacetonate, and potassium ruthenate;
preferably, the rare earth hydroxide is selected from at least one of scandium hydroxide, yttrium hydroxide, lanthanum hydroxide, cerium hydroxide, praseodymium hydroxide, neodymium hydroxide, samarium hydroxide, europium hydroxide, gadolinium hydroxide, terbium hydroxide, dysprosium hydroxide, holmium hydroxide, erbium hydroxide, thulium hydroxide, ytterbium hydroxide and lutetium hydroxide;
preferably, the ratio of the ruthenium in the form of the active component cluster to the rare earth hydroxide support precursor satisfies: the loading amount of the cluster type ruthenium is 0.1-10% of the mass of the carrier; wherein the mass of the active component is calculated by the mass of active element ruthenium, and the mass of the carrier is calculated by the mass of rare earth oxide generated by decomposing the rare earth hydroxide carrier precursor.
6. The method of claim 4, wherein the precipitant is selected from at least one of urea, ammonia, potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate;
preferably, the molar ratio of the precipitant to the ruthenium precursor is 10: 1-500: 1, wherein the mole number of the precipitant is calculated as the mole number of the precipitant itself, and the mole number of the ruthenium precursor is calculated as the mole number of the ruthenium element in the ruthenium precursor.
7. The method of claim 4, wherein the reaction conditions comprise: the reaction temperature is 40-180 ℃; the reaction time is 1-36 hours;
the reduction conditions include: under a reducing atmosphere; the reduction temperature is 300-800 ℃; the reduction time is 1-12 hours;
preferably, the reducing atmosphere is hydrogen, a mixed gas of hydrogen and argon, or a mixed gas of hydrogen and nitrogen, wherein the volume percentage of hydrogen in the mixed gas is more than or equal to 5%.
8. The method according to any one of claims 3 to 7, comprising:
(a) preparing a catalyst precursor: adding rare earth hydroxide into a ruthenium salt aqueous solution, adding a precipitator into the ruthenium salt aqueous solution containing the rare earth hydroxide under stirring, and reacting at 40-180 ℃ for 1-36 hours to obtain a catalyst precursor;
(b) reduction of a catalyst precursor: and reducing the catalyst precursor for 1-12 hours at 300-800 ℃ in a reducing atmosphere to obtain the supported ruthenium cluster catalyst for ammonia synthesis.
9. Use of at least one of the supported ruthenium cluster catalyst for ammonia synthesis according to claim 1 or 2, the supported ruthenium cluster catalyst for ammonia synthesis prepared according to the process of any one of claims 3 to 8 in catalytic reactions for ammonia synthesis.
10. The application of claim 9, wherein the supported ruthenium cluster catalyst for ammonia synthesis is heated to 300-800 ℃ at a rate of 1-5 ℃/min in a reducing atmosphere containing hydrogen, reduced at the temperature for 1-12 hours, cooled to a reaction temperature of 250-400 ℃, and subjected to catalytic reaction of ammonia synthesis in a mixed atmosphere of nitrogen and hydrogen to obtain ammonia gas as a product;
preferably, the volume ratio of nitrogen to hydrogen in the mixed atmosphere is 1: 3-3: 1; the space velocity of the reaction gas is 1000-50000 mL/gcatH; the reaction pressure is 0.1-5.0 MPa.
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