CN114618481A - Synthetic ammonia catalyst, preparation method and application thereof - Google Patents

Synthetic ammonia catalyst, preparation method and application thereof Download PDF

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Publication number
CN114618481A
CN114618481A CN202011455933.1A CN202011455933A CN114618481A CN 114618481 A CN114618481 A CN 114618481A CN 202011455933 A CN202011455933 A CN 202011455933A CN 114618481 A CN114618481 A CN 114618481A
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catalyst
ruthenium
active component
reaction
gas
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冯吉
柳林
陈萍
王杰敏
鞠晓花
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Dalian Institute of Chemical Physics of CAS
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Dalian Institute of Chemical Physics of CAS
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • 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
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/46—Ruthenium, rhodium, osmium or iridium
    • B01J23/462—Ruthenium
    • B01J35/393—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/031—Precipitation
    • B01J37/035—Precipitation on carriers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/16—Reducing
    • B01J37/18—Reducing with gases containing free hydrogen
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C1/00—Ammonia; Compounds thereof
    • C01C1/02—Preparation, purification or separation of ammonia
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Abstract

The application discloses a synthetic ammonia catalyst, a preparation method and application thereof, wherein the catalyst comprises a carrier and an active component; the active component is loaded on the carrier; the support comprises zirconia; the active component comprises a metal; the metal is selected from ruthenium; the active component is present in the form of clusters. The catalyst can be used as a synthetic ammonia catalyst under relatively mild conditions (250-400 ℃), has obviously higher activity than a zirconia-supported ruthenium nanoparticle catalyst, and also has quite high stability.

Description

Synthetic ammonia catalyst and preparation method and application thereof
Technical Field
The application relates to a synthetic ammonia catalyst, a preparation method and application thereof, and belongs to the technical field of synthetic ammonia catalyst preparation.
Background
Ammonia is one of the chemical products with the largest output in the world, is mainly used for producing chemical fertilizers, nitric acid, ammonium salts, sodium carbonate and other products, and has important application in the aspects of chemical fertilizers, plastics, medicines, explosives, metallurgy, environmental protection and the like. The development of society and the growth of population have led to an increasing demand for industrial chemicals related to ammonia, and the synthetic ammonia industry has an increasing status in national economy. At present, the synthesis ammonia process based on the Harbor-Bosch process is widely applied to a molten iron catalyst and needs to be used under the conditions of high temperature (400-. China is the biggest country for producing synthetic ammonia in the world, compared with the advanced level in the world, the synthetic ammonia industry has the defects of high energy consumption cost, large CO2 emission and the like, in recent years, the sustainable development and energy-saving emission-reduction policies of the society are becoming stricter, and the synthetic ammonia industry in China urgently needs to solve the problems of high energy consumption and high cost.
The technical innovation of the synthetic ammonia catalyst is the key for reducing the industrial energy consumption cost. Compared with a molten iron catalyst, the ruthenium-based ammonia synthesis catalyst has the advantages of high reaction activity, relatively mild reaction conditions, low energy consumption, long service life and the like. In 1992, the successful development of the KAAP process based on graphitized carbon-supported ruthenium catalysts (Ru/C) was considered to be an important breakthrough in the ammonia synthesis industry. However, under the condition of industrial ammonia synthesis, the graphitized carbon carrier can generate methanation reaction to cause catalyst deactivation, thereby limiting the wide application of the Ru/C catalyst. The development of a novel ruthenium-based catalyst with high activity and stability under mild conditions is very important for the development of the ammonia synthesis industry. The catalytic activity of the supported Ru-based catalyst is closely related to the particle size and dispersion degree of Ru particles, the interaction of metal carriers and other factors. The oxide-loaded Ru nanoparticle catalyst has the characteristics of large specific surface area, many active sites, good stability and the like, and is a synthetic ammonia catalyst system with better comprehensive performance at present.
Zirconium dioxide has the properties of high temperature resistance, wear resistance, corrosion resistance and the like, and is widely applied as a refractory material and special ceramics. The zirconium dioxide is a P-type oxide semiconductor, oxygen vacancies are easily generated on the surface, and the zirconium dioxide has unique physical and chemical properties of weak acid, weak alkalinity, oxidation-reduction property, abundant surface defects and the like. In recent years, the ruthenium nanoparticle catalyst loaded by zirconia is also applied to ammonia synthesis, but the activity of the catalyst is poor and is far lower than that of the Cs-Ru/MgO catalyst commonly used at present. The size of the ruthenium metal particles is an important factor affecting their catalytic performance. Compared with the nano-particle catalyst, the sub-nanocluster (generally, particles smaller than 1nm are clusters) has the characteristics of small size, high metal dispersity and the like, can expose more surface active sites, generates more coordinated unsaturated metal centers, and reduces the catalyst cost. Meanwhile, the metal cluster particles and the carrier have strong interaction, so that the activity and the stability of the catalyst can be effectively improved. However, the zirconia-supported ruthenium cluster ammonia synthesis catalyst has not been reported so far, and needs to be further developed.
Disclosure of Invention
According to one aspect of the present application, there is provided a synthetic ammonia catalyst comprising a support and an active component; the active component is loaded on the carrier; the support comprises zirconia; the active component comprises a metal; the metal is selected from ruthenium; the active component is present in the form of clusters. The catalyst can be used as a synthetic ammonia catalyst under relatively mild conditions (250-400 ℃), has obviously higher activity than a zirconia-supported ruthenium nanoparticle catalyst, and also has quite high stability. The zirconium oxide loaded ruthenium cluster synthetic ammonia catalyst prepared by the invention has higher activity and stability, and the preparation process is simple, the raw materials are cheap and easy to obtain, the preparation cost is lower, and the large-scale preparation is easy to realize.
According to a first aspect of the present application, there is provided a catalyst comprising a support and an active component; the active component is loaded on the carrier;
the support comprises zirconia;
the active component comprises a metal; the metal is selected from ruthenium;
the active component is present in the form of clusters.
Optionally, the size of the cluster is 0.2-1.0 nm.
Alternatively, the upper size limit of the clusters is independently selected from 1nm, 0.8nm, 0.6nm, 0.4nm, and the lower limit is independently selected from 0.2nm, 0.8nm, 0.6nm, 0.4 nm.
Optionally, the mass of the active component is 0.1-10% of the mass of the carrier;
the mass of the active component is calculated by the mass of metallic ruthenium.
According to a second aspect of the present application, there is also provided a method of preparing the above catalyst, the method comprising:
(1) loading a mixture containing a precipitator, zirconium oxide and a ruthenium source to obtain an intermediate product;
(2) and reducing the intermediate product in a hydrogen-containing atmosphere to obtain the catalyst.
Optionally, the ruthenium source is selected from ruthenium salts.
Optionally, the ruthenium salt is selected from at least one of ruthenium chloride, ruthenium nitrosyl nitrate, ruthenium acetylacetonate, ammonium chlororuthenate, sodium ruthenate, and potassium ruthenate.
Optionally, the precipitant is selected from at least one of ammonia water, urea, potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate.
Optionally, the molar ratio of the precipitant to the ruthenium source is 10:1 to 400: 1;
the moles of the precipitating agent are calculated as the moles of the precipitating agent itself and the moles of the ruthenium source are calculated as the moles of the metallic ruthenium.
Optionally, the upper limit of the molar ratio of the precipitant to the ruthenium source is independently selected from 10: 1. 30: 1. 50: 1. 70: 1. 100, and (2) a step of: 1. 150: 1. 200: 1. 250: 1. 300, and (2) 300: 1. 350: 1, the lower limit is independently selected from 400: 1. 30: 1. 50: 1. 70: 1. 100: 1. 150: 1. 200: 1. 250: 1. 300: 1. 350: 1.
optionally, in the step (1), the load condition is: the temperature is 25-100 ℃; the time is 1-48 h;
in the step (2), the reduction conditions are as follows: the temperature is 300-600 ℃; the time is 1-24 h.
Optionally, the upper temperature limit of the loading is independently selected from 100 ℃, 80 ℃, 60 ℃, 40 ℃, and the lower temperature limit is independently selected from 25 ℃, 80 ℃, 60 ℃, 40 ℃.
Optionally, the upper time limit of the load is independently selected from 24h, 20h, 16h, 12h, 8h, 4h, and the lower limit is independently selected from 1h, 20h, 16h, 12h, 8h, 4 h.
Preferably, the atmosphere comprises a hydrogen-argon mixture or a nitrogen-hydrogen mixture, wherein the volume percentage of hydrogen in the mixture is greater than 5%.
Alternatively, the upper temperature limit of the reduction is independently selected from 600 ℃, 500 ℃, 400 ℃, and the lower temperature limit is independently selected from 300 ℃, 500 ℃, 400 ℃.
Alternatively, the upper time limit of the reduction is independently selected from 24h, 20h, 16h, 12h, 8h, 4h, and the lower time limit is independently selected from 1h, 20h, 16h, 12h, 8h, 4 h.
Optionally, the method comprises:
a) preparing a catalyst precursor: adding zirconium oxide into a ruthenium salt solution, adding a precipitator under the stirring condition, and heating and reacting for 1-48h at a certain temperature to obtain a catalyst precursor;
b) reduction of a catalyst precursor: and reducing the catalyst precursor for 1-24h at the temperature of 300-600 ℃ in a reducing atmosphere to obtain the used ammonia synthesis catalyst.
Optionally, the upper limit of the reduction temperature is selected from 350 ℃, 400 ℃, 450 ℃, 500 ℃, 550 ℃ and 600 ℃; the lower limit is selected from 300 deg.C, 350 deg.C, 400 deg.C, 450 deg.C, 500 deg.C, 550 deg.C.
Optionally, the upper limit of the reduction time is selected from 2h, 4h, 8h, 12h and 24 h; the lower limit is selected from 2h, 4h, 8h, 12h and 24 h.
Optionally, the solvent containing the support and the ruthenium precursor solution is water.
Optionally, in step a), the carrier is added to the ruthenium precursor solution to obtain the solution containing the carrier and the ruthenium precursor.
Alternatively, the reaction is carried out with stirring.
Optionally, the material obtained after the reaction is filtered, washed and dried.
Optionally, the drying temperature is 40-200 ℃.
According to a third aspect of the present application, there is provided a method of producing ammonia gas, the method comprising:
reacting raw material gas containing nitrogen and hydrogen in the presence of a catalyst to obtain ammonia gas;
the catalyst is at least one selected from the group consisting of the above-mentioned catalysts and the catalysts prepared according to the above-mentioned methods.
Optionally, the method comprises: loading ruthenium cluster catalyst in reducing atmosphere containing hydrogen at 1-5 deg.C for min-1Heating to 600 ℃ at 300 ℃, reducing to 400 ℃ at 250 ℃ after 1-24h of reduction treatment, and carrying out catalytic reaction of synthetic ammonia in the mixed atmosphere of nitrogen and hydrogen to obtain an ammonia product.
Optionally, the volume ratio of the nitrogen to the hydrogen in the feed gas is 1: 3-3: 1.
Optionally, the reaction conditions are: the reaction temperature is 300-600 ℃; the gas space velocity of the raw material gas is 1000--1h-1(ii) a The reaction pressure is 0.1-5.0 MPa.
Optionally, the method for catalytic reaction of synthesis ammonia comprises: loading ruthenium cluster catalyst in reducing atmosphere containing hydrogen at 1-5 deg.C for min-1Heating to 600 ℃ at 300 ℃, reducing to 400 ℃ at 250 ℃ after 1-24h of reduction treatment, and carrying out catalytic reaction of synthetic ammonia in the mixed atmosphere of nitrogen and hydrogen to obtain an ammonia product.
Characteristics of a high-angle annular dark field Scanning Transmission Electron Microscope (STEM), an X-ray absorption fine structure spectrum (EXAFS) and the like indicate that ruthenium is dispersed on the surface of the zirconia carrier in a highly dispersed cluster form.
The application provides a preparation method of supported ruthenium clusters for ammonia synthesis reaction, raw materials required by the method, such as zirconium oxide carriers, ruthenium salts and precipitating agents, such as ammonia water, sodium hydroxide and the like, are bulk commercial chemicals, and the cost is low; in addition, the method has simple and safe preparation process and is easy to realize large-scale preparation.
Thus, the present application provides an efficient preparation method of a supported ruthenium cluster catalyst for ammonia synthesis.
The beneficial effects that this application can produce include:
compared with the conventional zirconia-supported ruthenium nanoparticle catalyst, the ruthenium cluster-supported zirconia synthetic ammonia catalyst provided by the application has higher activity.
2 the zirconia-loaded ruthenium nanocluster catalyst for ammonia synthesis provided by the application has good stability, and the activity is not obviously changed in a 150-hour test.
3 the preparation method of the zirconia-supported ruthenium nanocluster catalyst provided by the application has the advantages that the required raw materials such as zirconia, ruthenium salt, a precipitator and the like are bulk chemicals, and the cost is low.
4 the preparation method of the zirconia-loaded ruthenium nanocluster catalyst has the advantages of simple and safe preparation process and the like, and is easy to realize large-scale preparation.
Drawings
FIG. 1 shows 5% Ru clusterings/ZrO from example 12High angle annular dark field scanning transmission electron micrographs of the catalyst.
FIG. 2 shows 5% Ru clusterings/ZrO in example 12X-ray absorption fine structure diagram of catalyst.
FIG. 3 is a graph showing 5% of Ru NPs/ZrO in comparative example 12Transmission electron micrograph of catalyst.
FIG. 4 shows 5% Ru clusterings/ZrO in example 12Catalyst under the pressure of 1MPa and the space velocity of 24000mL g- 1h-1And stability test results of the reaction for synthesizing ammonia under the reaction conditions of the temperature of 425 ℃.
Detailed Description
As previously mentioned, the present application relates to a supported ruthenium cluster catalyst for ammonia synthesis, a method for preparing the same, and applications thereof. The catalyst takes zirconia as a carrier, and the ammonia synthesis supported ruthenium cluster catalyst is prepared by adopting a precipitation deposition method. Compared with the existing ruthenium-based catalyst system, the zirconium oxide loaded ruthenium cluster catalyst prepared by the invention has higher catalytic activity and stability. Has good application prospect.
Unless otherwise indicated, all numbers such as loading, temperature, time, conversion, etc. appearing in the specification and claims of this application are to be understood as not being absolutely exact, and certain experimental errors may be inevitable with regard to the measured values due to the standard deviation of the measurement technique.
The present application is described in detail below with reference to examples, but not limited to the examples.
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, the components of reaction gas are analyzed by a conductivity meter, reaction tail gas is introduced into dilute sulfuric acid solution, the conductivity meter is used for tracking the change of the conductivity, and finally the generation rate of ammonia is deduced and calculated according to the conductivity parameter.
The conductivity tester is a METTLLER TOLEDO instrument produced by seven stars and has the model of S230-K-CN. The model of a spherical aberration correction transmission electron microscope is JEOL-JEM2100F, the model of a high-resolution transmission electron microscope is JEM-2100, an X-ray absorption spectrum is tested at a BL14W1 line station of a Shanghai synchrotron radiation light source (SSRF), a signal mode is a transmission mode, and data fitting is completed through FEFF9 software.
The active ingredient contents described in the examples refer to the mass of active ingredient as a percentage of the mass of support, e.g. 5 wt% Ru clusters/ZrO in example 12Indicating that the mass of ruthenium was 5 wt% of the mass of the support.
Example 1
Dissolving 0.0784g of ruthenium nitrosyl nitrate in 50mL of water, adding 0.5g of zirconium oxide into a solution containing a ruthenium precursor under stirring, adding 3g of urea into the suspension after uniformly stirring, stirring the mixed solution under an oil bath at 80 ℃ for reacting for 8 hours, filtering after the reaction is finished, washing the product with deionized water until the solution is neutral, and then drying in an oven at 60 ℃. Drying the product, reducing for 2h at 450 ℃ in a hydrogen atmosphere to obtain the zirconium oxide loaded ruthenium cluster catalyst (5 wt% Ru clusters/ZrO) with 5% ruthenium load2)。
FIG. 1 shows 5% Ru clusterings/ZrO from example 12High-angle annular dark-field scanning transmission electron microscope image (four images are a) Ru clusters/ZrO of catalyst2b) An oxygen element imaging schematic diagram c) a zirconium element imaging schematic diagram d) a ruthenium element imaging schematic diagram), and the high-resolution transmission electron microscope characterization result of FIG. 1 shows that the 5% Ru clusters/ZrO2CatalysisThe Ru in the agent is in a highly dispersed state, approximately 0.1-2nm in size, with no significant nanoparticles. FIG. 2 shows 5% Ru clusterings/ZrO in example 12X-ray absorption microstructure of the catalyst, FIG. 2X-ray absorption microstructure Spectroscopy (EXAFS) results show 5% Ru clusters/ZrO2Ru in the catalyst in the oxidic staten+Mainly, the Ru species are dispersed on the surface of the carrier in the form of clusters, and have strong interaction with the carrier through Ru-O bonds.
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature was raised to 400 ℃. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (1).
Example 2
Dissolving 0.047g of ruthenium nitrosyl nitrate in 50mL of water, adding 0.5g of zirconium oxide into a solution containing a ruthenium precursor under stirring, adding 1.8g of urea into the suspension after uniform stirring, stirring the mixed solution under an oil bath at 80 ℃ for reaction for 8h, filtering after the reaction is finished, washing the product with deionized water until the solution is neutral, and drying in an oven at 60 ℃. The product is reduced for 2h at 450 ℃ in a hydrogen atmosphere after being dried to obtain the zirconia-loaded ruthenium cluster catalyst (3 wt% Ru clusters/ZrO) with 3% ruthenium load2) And approximately 0.1-2nm in size.
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature was raised to 450 ℃. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (1).
Example 3
Dissolving 0.016g of ruthenium nitrosyl nitrate in 50mL of water, adding 0.5g of zirconium oxide into a solution containing a ruthenium precursor under stirring, adding 0.6g of urea into the suspension after uniform stirring, stirring the mixed solution under an oil bath at 80 ℃ for reaction for 8h, filtering after the reaction is finished, washing the product with deionized water until the solution is neutral, and then carrying out the reaction at 60 DEG CAnd (5) drying in an oven. Drying the product, reducing for 2h at 450 ℃ in a hydrogen atmosphere to obtain the zirconia-supported ruthenium cluster catalyst (1 wt% Ru clusters/ZrO) with the ruthenium load of 1%2) And approximately 0.1-2nm in size.
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature was raised to 500 ℃. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (1).
Example 4
0.1568g of ruthenium nitrosyl nitrate is dissolved in 50mL of water, 0.5g of zirconium oxide is added into a solution containing a ruthenium precursor under stirring, 6g of urea is added into the suspension after uniform stirring, the mixed solution is stirred and reacted for 8 hours under an oil bath at 80 ℃, after the reaction is finished, the solution is filtered, the product is washed by deionized water until the solution is neutral, and then the product is dried in an oven at 60 ℃. Drying the product, reducing for 2h at 450 ℃ in a hydrogen atmosphere to obtain the zirconia-supported ruthenium cluster catalyst (10 wt% Ru clusters/ZrO) with the ruthenium load of 10%2) And approximately 0.1-2nm in size.
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature was raised to 600 ℃. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (1).
Example 5
Dissolving 0.103g of ruthenium chloride in 50mL of water, adding 0.5g of zirconium oxide into a solution containing a ruthenium precursor under stirring, adding 3g of urea into the suspension after uniform stirring, stirring the mixed solution under an oil bath at 80 ℃ for reaction for 8 hours, filtering after the reaction is finished, washing the product with deionized water until the solution is neutral, and drying in an oven at 60 ℃. Drying the product, reducing for 2h at 450 ℃ in a hydrogen atmosphere to obtain the zirconium oxide loaded ruthenium cluster catalyst (5 wt% Ru clusters/ZrO) with 5% ruthenium load2) And approximately 0.1-2nm in size.
The prepared catalyst is subjected to reaction performance evaluation in an ammonia synthesis device, and the catalyst is placed in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 at 5 ℃ for min-1The temperature was raised to 400 ℃. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (1).
Example 6
Dissolving 0.197g of ruthenium acetylacetonate in 50mL of water, adding 0.5g of zirconium oxide into a solution containing a ruthenium precursor under stirring, adding 3g of urea into the suspension after uniformly stirring, stirring the mixed solution under an oil bath at 80 ℃ for reacting for 8 hours, filtering after the reaction is finished, washing a product with deionized water until the solution is neutral, and drying in an oven at 60 ℃. Drying the product, reducing for 2h at 450 ℃ in a hydrogen atmosphere to obtain the zirconium oxide loaded ruthenium cluster catalyst (5 wt% Ru clusters/ZrO) with 5% ruthenium load2) And approximately 0.1-2nm in size.
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature was raised to 400 ℃. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (1).
Example 7
Dissolving 0.129g of potassium ruthenate in 50mL of water, adding 0.5g of zirconium oxide into a solution containing a ruthenium precursor under stirring, adding 3g of urea into the suspension after uniform stirring, stirring the mixed solution under an oil bath at 80 ℃ for reaction for 8h, filtering after the reaction is finished, washing the product with deionized water until the solution is neutral, and drying in an oven at 60 ℃. Drying the product, reducing for 2h at 450 ℃ in a hydrogen atmosphere to obtain the zirconium oxide loaded ruthenium cluster catalyst (5 wt% Ru clusters/ZrO) with 5% ruthenium load2) And approximately 0.1-2nm in size.
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature was raised to 400 ℃. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (1).
Comparative example 1
0.157g of ruthenium nitrosyl nitrate is weighed and dissolved in 3mL of deionized water, and 1g of zirconia carrier is added into the ruthenium nitrosyl nitrate solution for dipping after full dissolution. Dipping overnight, drying at 80 ℃ after the surface water is naturally evaporated, then roasting for 2h at 500 ℃ in argon, and then reducing the obtained product for 2h at 450 ℃ in hydrogen to obtain the zirconium oxide loaded ruthenium nano-particle catalyst (5 wt% Ru NPs/ZrO) prepared by dipping2)。
FIG. 3 is a graph showing 5% of Ru NPs/ZrO in comparative example 12Transmission electron microscopy of the catalyst, FIG. 3 shows that the above-mentioned 5% Ru NPs/ZrO2The size of Ru in the reduced catalyst is larger, and the Ru is dispersed on the surface of the zirconia carrier in the form of nano particles.
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature is increased to 450 ℃, and the temperature is reduced to 400 ℃ after 10 hours of reduction. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (1).
Comparative example 2
0.197g of ruthenium acetylacetonate was weighed and dissolved in 3mL of deionized water, and after sufficient dissolution, 1g of the zirconia support was added to the ruthenium nitrosylnitrate solution and impregnated. Dipping overnight, drying at 80 ℃ after the surface water is naturally evaporated, roasting for 2h at 500 ℃ in argon, reducing the obtained product for 2h at 450 ℃ in hydrogen, and obtaining the zirconium oxide loaded ruthenium nanoparticle catalyst (5 wt% RuNPs/ZrO) prepared by dipping2)。
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature is increased to 450 ℃, and the temperature is reduced to 400 ℃ after 10 hours of reduction. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (1).
Comparative example 3
0.103g of ruthenium chloride is weighed and dissolved in 3mL of deionized water, and 1g of zirconia carrier is added into the ruthenium nitrosyl nitrate solution for impregnation after the ruthenium chloride is fully dissolved. Dipping overnight, drying at 80 ℃ after the surface water is naturally evaporated, roasting for 2h at 500 ℃ in argon, reducing the obtained product for 2h at 450 ℃ in hydrogen, and obtaining the zirconium oxide loaded ruthenium nanoparticle catalyst (5 wt% RuNPs/ZrO) prepared by dipping2)。
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature is increased to 450 ℃, and the temperature is reduced to 400 ℃ after 10 hours of reduction. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (2).
Comparative example 4
Dissolving 0.0784g of ruthenium nitrosyl nitrate in 50mL of water, adding 0.5g of silicon oxide into a solution containing a ruthenium precursor under stirring, adding 3g of urea into the suspension after uniformly stirring, stirring the mixed solution under an oil bath at 80 ℃ for reacting for 8h, filtering after the reaction is finished, washing the product with deionized water until the solution is neutral, and then drying in an oven at 60 ℃. Drying the product, and then reducing for 2h at 450 ℃ in a hydrogen atmosphere to obtain the silicon oxide supported ruthenium catalyst (5 wt% Ru/SiO) with 5% ruthenium load2)。
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature is increased to 450 ℃, and the temperature is reduced to 400 ℃ after 10 hours of reduction. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (2).
Comparative example 5
Dissolving 0.0784g of ruthenium nitrosyl nitrate in 50mL of water, adding 0.5g of alumina into a solution containing a ruthenium precursor under stirring, adding 3g of urea into the suspension after uniform stirring, stirring the mixed solution under an oil bath at 80 ℃ for reaction for 8h, filtering after the reaction is finished, washing the product with deionized water until the solution is neutral,and then dried in an oven at 60 ℃. Drying the product, and then reducing for 2h at 450 ℃ in a hydrogen atmosphere to obtain the alumina supported ruthenium catalyst (5 wt% Ru/Al) with 5% ruthenium load2O3)。
The reaction performance of the prepared catalyst is evaluated in an ammonia synthesis device, and the catalyst is put in mixed gas with the volume ratio of nitrogen to hydrogen of 1:3 for 5 ℃ min-1The temperature is increased to 450 ℃, and the temperature is reduced to 400 ℃ after 10 hours of reduction. At a reaction pressure of 1MPa and a gas space velocity of 24000mL g-1h-1The reactivity was measured under the reaction conditions of (1).
Table 1 shows the space velocity of 24000mL g of catalyst at 400 ℃ under 1MPa for examples 1-7 and comparative examples 1-5-1h-1The activity of the ruthenium nanocluster catalyst loaded by zirconia is obviously higher than that of the ruthenium nanoparticle catalyst loaded by zirconia, silica and alumina on the premise of the same ruthenium loading amount.
TABLE 1 comparison of the activity of ammonia synthesis with different catalysts
Figure BDA0002828795010000111
Example 8 catalyst stability testing
The zirconia-supported ruthenium nanocluster catalyst of example 1 was subjected to a stability test in an ammonia synthesis plant and was subjected to a 5 ℃ min in a nitrogen-hydrogen mixed gas (volume ratio of 1:3)-1The temperature is increased to 450 ℃, then the temperature is reduced to 425 ℃, the reaction pressure is 1MPa, and the gas space velocity is 24000mL g-1h-1The stability was tested continuously for 150h under this condition.
5% Ru clusters/ZrO in example 12The catalyst-1 has higher stability (FIG. 4), the activity is not changed within 150h, and similar to the above results, the catalysts prepared in other examples all have higher stability.
Catalyst Activity test
The supported ruthenium cluster catalyst prepared in the above example was subjected to a test of ammonia synthesis reactivity under different reaction conditions in an ammonia synthesis apparatus. See table 2 for details.
TABLE 2 Ammonia synthesis reactivity of supported ruthenium cluster catalysts under different reaction conditions
Figure BDA0002828795010000121
As can be seen from Table 2, the zirconia-supported ruthenium nanocluster catalyst still has high activity under different reaction conditions, and realizes high-efficiency ammonia synthesis under relatively mild conditions (250 ℃ C. and 400 ℃ C.). Similar to the above results, the catalysts obtained in the other examples all had better catalytic activity.
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 synthetic ammonia catalyst, characterized in that the catalyst comprises a carrier and an active component; the active component is loaded on the carrier;
the support comprises zirconia;
the active component comprises a metal; the metal is selected from ruthenium;
the active component is present in the form of clusters.
2. The catalyst according to claim 1, wherein the cluster has a size of 0.2 to 1.0 nm.
3. The catalyst according to claim 1, wherein the mass of the active component is 0.1-10% of the mass of the carrier;
the mass of the active component is based on the mass of metallic ruthenium.
4. A process for preparing a catalyst as claimed in any one of claims 1 to 3, characterized in that it comprises:
(1) loading a mixture containing a precipitator, zirconium oxide and a ruthenium source to obtain an intermediate product;
(2) and reducing the intermediate product in a hydrogen-containing atmosphere to obtain the catalyst.
5. A method according to claim 4, wherein the ruthenium source is selected from ruthenium salts.
6. The method according to claim 5, wherein the ruthenium salt is at least one selected from the group consisting of ruthenium chloride, ruthenium nitrosylnitrate, ruthenium acetylacetonate, ammonium chlororuthenate, sodium ruthenate and potassium ruthenate.
7. The method according to claim 4, wherein the precipitant is at least one selected from the group consisting of ammonia water, urea, potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate.
8. The method according to claim 4, wherein the molar ratio of the precipitant to the ruthenium source is 10:1 to 400: 1;
the moles of the precipitating agent are calculated as the moles of the precipitating agent per se, and the moles of the ruthenium source are calculated as the moles of metallic ruthenium;
preferably, in the step (1), the load condition is: the temperature is 25-100 ℃; the time is 1-48 h;
in the step (2), the reduction conditions are as follows: the temperature is 300-600 ℃; the time is 1-24 h.
9. A method of producing ammonia gas, the method comprising:
reacting raw material gas containing nitrogen and hydrogen in the presence of a catalyst to obtain ammonia gas;
the catalyst is selected from at least one of the catalyst of any one of claims 1 to 3, the catalyst prepared by the method of any one of claims 4 to 8.
10. The method according to claim 9, wherein the volume ratio of the nitrogen gas to the hydrogen gas in the feed gas is 1: 3-3: 1;
preferably, the reaction conditions are: the reaction temperature is 300-600 ℃; the gas space velocity of the raw material gas is 1000--1h-1(ii) a The reaction pressure is 0.1-5.0 MPa.
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