A rare earth metal oxide modified ruthenium-based catalyst, a preparation method and application thereof

Abstract

The application discloses a rare earth metal oxide modified ruthenium-based catalyst and a preparation method and application thereof, an active component of the catalyst is Ru, an auxiliary agent is CeO2 nanomaterial, a carrier is graphite carbon, and the Ru and the CeO2 nanomaterial are both loaded on the carrier. The Ru-based catalyst (RuCe x / GC) modified by rare earth CeO2 nanoclusters is synthesized by an impregnation method, the Ru exists in the form of single atoms and nanoclusters, and the two synergistically promote nitrogen activation. Compared with a traditional CeO2 carrier loaded single atom or nanocluster catalyst, the Ru-based catalyst exhibits excellent ammonia synthesis performance and long-period catalytic stability under mild conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalyst material preparation, in particular to a rare earth metal oxide modified Ru-based catalyst and a preparation method and application thereof. BACKGROUND

[0002] Ammonia is an important chemical product, which is widely used for preparing chemical fertilizer, nitric acid, ammonia water, explosive and other products. About 80% of ammonia is used for chemical fertilizer production, which is crucial for food security. At the same time, due to the high hydrogen content (17.7wt%) and high energy density (3kWh kg -1 ), ammonia is considered as an ideal hydrogen energy carrier because of its easy storage and transportation.

[0003] At present, the ammonia industry mainly synthesizes ammonia through the Haber-Bosch process, and the Fe-based catalyst used has a low cost, but the synthesis conditions are harsh, and ammonia needs to be synthesized at high temperature (490-500℃) and high pressure (10-30 MPa), and the energy consumption per ton of ammonia is as high as about 1.52 tons of standard coal. Compared with traditional iron-based catalysts, Ru-based catalysts are considered to be the second generation of ammonia synthesis catalysts because they exhibit good ammonia synthesis performance at low temperature and low pressure (Bielawa H., et al. The Ammonia-Synthesis Catalyst of the Next Generation: Barium-Promoted Oxide-Supported Ruthenium [J]. Angew. Chem. Int. Ed, 2001, 40(6): 1061-1063). However, the ammonia synthesis activity of pure Ru metal is poor, and a suitable carrier or additive needs to be added to promote its activation of N2, thereby improving the ammonia synthesis performance. Rare earth metal oxides are a common carrier, and studies have shown that rare earth oxides such as CeO2, SmO2, etc. supported Ru metal catalysts have relatively good ammonia synthesis performance (Zhang X., et al. Synergizing Surface Hydride Species and Ru Clusters on Sm2O3 for Efficient Ammonia Synthesis [J]. ACS Catal. 2022, 12, 2178-2190; Lin B., et al. Ru surface density effect on ammonia synthesis activity and hydrogen poisoning of ceria-supported Ru catalysts [J]. Chin. J. Catal. 2021, 42, 1712-1723). Moreover, after reduction at high temperature, rare earth oxides are easy to generate oxygen vacancies, which in turn transfer electrons to Ru metal, acting as an electronic additive. However, the price of rare earth oxides is relatively high, and catalysts with rare earth oxides as carriers are difficult to be mechanically formed, so it greatly limits their large-scale application in ammonia synthesis. SUMMARY

[0004] To improve the above technical problems, the present application provides a ruthenium-based catalyst, the active component of the catalyst is Ru, the additive is CeO2 nanomaterial, and the carrier is graphite carbon, and the Ru and CeO2 nanomaterial are both loaded on the carrier.

[0005] According to an embodiment of the present application, the Ru is combined with the CeO2 nanomaterial and supported on the carrier, and the combination means that the Ru and the CeO2 are in contact with each other, rather than being distributed independently.

[0006] According to an embodiment of the present application, the Ru in the Ru-based catalyst exists in the form of Ru monatomic and / or Ru nanocluster. Preferably, the Ru monatomic and the Ru nanocluster coexist.

[0007] According to an embodiment of the present application, the size of the Ru nanocluster is less than 2.5 nm.

[0008] According to an embodiment of the present application, the CeO2 nanomaterial in the Ru-based catalyst exists in the form of CeO2 nanocluster. Preferably, the size of the CeO2 nanocluster is less than 3 nm.

[0009] According to an embodiment of the present application, the loading of the active component is 0.1-4 wt% of the Ru-based catalyst by metal element, and exemplary values are 0.1 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3 wt%, 3.5 wt% or 4 wt%.

[0010] According to an embodiment of the present application, the loading of Ce in the CeO2 nanomaterial is 0.1-16 wt% of the Ru-based catalyst by metal element, and preferably 0.2-12 wt%, and exemplary values are 0.2 wt%, 0.5 wt%, 1.0 wt%, 1.7 wt%, 2.0 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 8 wt%, 10 wt% or 12 wt%.

[0011] According to an embodiment of the present application, the mass ratio of the Ru to Ce in the CeO2 nanomaterial is 1:(0.5-4) by metal element, and exemplary values are 1:0.5, 1:1, 1:2, 1:4.

[0012] The present application also provides a preparation method of the above Ru-based catalyst, comprising the following steps:

[0013] (1) dissolving a ruthenium precursor and a cerium precursor in water to obtain a solution;

[0014] (2) immersing a carrier in the solution obtained in step (1);

[0015] (3) reducing the product obtained in step (2) by calcination to obtain the Ru-based catalyst.

[0016] According to an embodiment of the present application, in step (1), the ruthenium precursor is one or more of ruthenium trichloride, ammonium hexachlororuthenate, ruthenium acetate, ruthenium nitrosyl nitrate, ruthenium acetylacetonate, and triruthenium dodecacarbonyl; preferably, the ruthenium precursor is ruthenium nitrosyl nitrate.

[0017] According to an embodiment of the present application, in step (1), the cerium precursor is one or more of cerium nitrate hexahydrate and cerium nitrate ammonia.

[0018] According to an embodiment of the present application, in step (1), the mass ratio of Ce in the cerium precursor to Ru in the ruthenium precursor is 0.5-4:1, and examples include 0.5:1, 1:1, 2:1, and 4:1.

[0019] In step (1) of the present application, the content of water is not particularly limited, and each raw material can be partially or completely dissolved.

[0020] According to an embodiment of the present application, in step (2), the mass of the active component in the ruthenium precursor is 0.1-4.0 wt% of the Ru-based catalyst, and examples include 0.1 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3 wt%, 3.3 wt%, 3.5 wt%, or 4.0 wt%.

[0021] According to an embodiment of the present application, in step (2), the solution obtained in step (1) is gradually added dropwise to the carrier.

[0022] According to an embodiment of the present application, in step (2), ultrasonic dispersion can be used; the time for ultrasonic dispersion is 5-60 min, preferably 10-30 min, for example, 15 min, and the temperature for ultrasonic is room temperature.

[0023] According to an embodiment of the present application, in step (2), after ultrasonic treatment, the product can be allowed to stand, so that the solution and the graphite carbon are fully mixed; the standing time is, for example, 0.5-24 h.

[0024] According to an embodiment of the present application, in step (2), the carrier is immersed in the solution obtained in step (1), and then dried in an oven after ultrasonic treatment.

[0025] In step (2) of the present application, the immersion can be total immersion of the carrier in the solution or partial immersion of the carrier in the solution.

[0026] According to an embodiment of the present application, in step (3), before calcination, the mixture can be dried. For example, the drying is vacuum drying, and further, the temperature for drying is 50-80°C, and the time for drying is 8-24 h.

[0027] According to the embodiment of the present application, in step (3), the roasting reduction is performed under a reducing atmosphere. Preferably, the reducing atmosphere is selected from a mixture of hydrogen and an inert gas. The inert gas is, for example, nitrogen, argon or helium, etc. For example, in the reducing atmosphere, the volume fraction of hydrogen is 5-25%, exemplarily 10%.

[0028] According to the embodiment of the present application, in step (3), the roasting temperature is 100-600℃, the heating rate during roasting is 2-8℃ / min, preferably 3-6℃ / min; the roasting time is 1-8h, preferably 2-6h. For example, the roasting temperature is 100℃, 200℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃ or 600℃.

[0029] Preferably, the roasting process is: first roasting at 100-300℃ for 1-3h, and then roasting at 300-600℃ for 1-5h. Exemplarily, first maintaining at 100℃ for 1h, and then maintaining at 500℃ for 1h after continuously increasing the temperature.

[0030] According to the embodiment of the present application, in step (3), after the roasting is completed, the product can also be subjected to passivation treatment; the passivation is performed in a tube furnace, for example, after the reducing atmosphere is closed, one end of the tube furnace is opened for passivation for 10min.

[0031] The present application also provides the use of the above-mentioned Ru catalyst in the catalytic synthesis of ammonia, preferably as a catalyst for synthesizing ammonia, preferably as a catalyst for synthesizing ammonia under low temperature and low pressure conditions.

[0032] The present application also provides a catalyst for synthesizing ammonia, which contains at least the above-mentioned Ru-based catalyst.

[0033] The present application also provides a method for synthesizing ammonia, which uses the above-mentioned Ru-based catalyst.

[0034] According to the embodiment of the present application, the temperature for synthesizing ammonia is 300-400℃, exemplarily 300℃, 350℃, 370℃, 380℃ or 400℃; the pressure for synthesizing ammonia is 0.5-5MPa, exemplarily 1MPa.

[0035] The present application has the following beneficial effects:

[0036] 1、The present application synthesizes the Ru-based catalyst (RuCe xThe Ru is in the form of single atoms and / or nanoclusters, and in particular in the form of single atoms and nanoclusters, both of which synergistically promote nitrogen activation. Compared with a traditional CeO2 carrier loaded single atom or nanocluster catalyst, the Ru-based catalyst of the present application exhibits excellent ammonia synthesis performance and long-period catalytic stability under mild conditions.

[0037] 2. The Ru catalyst of the present application has a higher ammonia synthesis performance than a traditional CeO2 carrier loaded Ru catalyst, because the CeO2 promoter in the Ru catalyst is in the form of nanoclusters. The CeO2 nanoclusters can effectively stabilize Ru single atoms and nanoclusters, and transfer electrons to Ru sites, promoting nitrogen activation and ammonia synthesis reactions.

[0038] 3. The Ru catalyst of the present application has an excellent ammonia synthesis reaction rate and good thermal stability compared with traditional Ru-based and Fe-based catalysts. The Ru catalyst preparation method provided by the present application is relatively simple, and the catalyst is easy to shape, which is conducive to industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 TEM and particle size statistics of the catalysts obtained in Examples 1 and 2.

[0040] Figure 2 Spherical aberration electron microscope image of the RuCe2 / GC catalyst of Example 2.

[0041] Figure 3 Ammonia synthesis performance of the RuCe x / GC catalyst of Examples 1 and 2.

[0042] Figure 4 Activation energy graph of the catalysts obtained in Examples 1 and 2.

[0043] Figure 5 Thermal stability graph of the RuCe2 / GC catalyst of Example 2 at 400°C. DETAILED DESCRIPTION

[0044] The technical solutions of the present application will be described in further detail below in conjunction with specific examples. It should be understood that the following examples are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology implemented based on the above description of the present application is encompassed within the scope of the present application.

[0045] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0046] Example 1

[0047] Preparation of the RuCe 0.5 / GC catalyst

[0048] (1) Take 1 g of graphite carbon (GC), dissolve 3.17 mL of ruthenium nitrosyl nitrate (12 mg Ru / mL) and 0.06 g of Ce(NO3)3·6H2O in 10 mL of deionized water to make a solution. The solution is added dropwise to the GC and mixed thoroughly. Then the wet sample is treated with ultrasound for 15 minutes and dried in an oven at 60°C.

[0049] (2) The sample obtained in step (1) is transferred to a tube furnace for reduction with 10% H2 / Ar (160 mL / min), with a heating rate of 5°C / min. First, it is kept at 100°C for 1 h, and then the temperature is increased to 500°C and kept for another 1 h.

[0050] (3) After the sample is reduced, it is cooled to room temperature, the end cover of the tube furnace is opened, and the catalyst is taken out after passivation for 10 min, obtaining the catalyst RuCe 0.5 / GC.

[0051] Example 2

[0052] Preparation of RuCe x / GC (x = 1-4) catalysts

[0053] (1) Take 1 g of graphite carbon (GC), dissolve 3.17 mL of ruthenium nitrosyl nitrate (12 mg Ru / mL) and 0.06 g of Ce(NO3)3·6H2O in 10 mL of deionized water to make a solution. The solution is added dropwise to the GC and mixed thoroughly. Then the wet sample is treated with ultrasound for 15 minutes and dried in an oven at 60°C.

[0054] (2) The sample obtained in step (1) is transferred to a tube furnace for reduction with 10% H2 / Ar (160 mL / min), with a heating rate of 5°C / min. First, it is kept at 100°C for 1 h, and then the temperature is increased to 500°C and kept for another 1 h.

[0055] (3) After the sample is reduced, it is cooled to room temperature, the end cover of the tube furnace is opened, and the catalyst is taken out after passivation for 10 min, obtaining the catalyst RuCe1 / GC, RuCe2 / GC, RuCe4 / GC in turn.

[0056] Example 3

[0057] Preparation of 0.1RuCe / GC catalyst

[0058] (1) Take 1 g of graphite carbon (GC), dissolve 0.09 mL of ruthenium nitrosyl nitrate (12 mg RuCe(NO3)3-6H2O (0.06 g) was dissolved in 10 ml of deionized water to make a solution. The solution was added dropwise to GC and mixed well. Then the wet sample was treated with ultrasound for 15 minutes and dried in an oven at 60°C.

[0059] (2) The sample obtained in step (1) was transferred to a tube furnace for reduction with 10% H2 / Ar (160 mL / min) at a heating rate of 5°C / min. First, it was kept at 100°C for 1 h, and then the temperature was increased to 500°C and kept for another 1 h.

[0060] (3) After the sample was reduced, it was cooled to room temperature, the end cover of the tube furnace was opened, and the catalyst was obtained after 10 min of passivation, which was 0.1 RuCe / GC.

[0061] Example 4

[0062] Preparation of xRuCe / GC (x = 1-4) catalysts

[0063] In Example 3, the ruthenium nitrosyl nitrate was replaced with 0.90 mL, 1.80 mL, and 3.60 mL, respectively, and the other preparation processes were the same as in Example 3, and the catalysts obtained were named 1RuCe / GC, 2RuCe / GC, and 4RuCe / GC, respectively.

[0064] Comparative Example 1

[0065] The difference between Comparative Example 1 and Example 1 is that 0.06 g of Ce(NO3)3-6H2O was not added in Comparative Example 1. The catalyst Ru / GC was prepared.

[0066] Comparative Example 2

[0067] Preparation of Ru1 / CeO2 catalyst

[0068] (1) 1 g of CeO2 support was taken, and 3.17 mL of ruthenium nitrosyl nitrate (12 mg Ru / mL) was dissolved in 10 ml of deionized water to make a solution. The solution was added dropwise to CeO2 and mixed well. Then the wet sample was treated with ultrasound for 15 minutes and dried in an oven at 60°C.

[0069] (2) The sample obtained in step (1) was transferred to a tube furnace for reduction with 10% H2 / Ar (160 mL / min) at a heating rate of 5°C / min. First, it was kept at 100°C for 1 h, and then the temperature was increased to 800°C and kept for another 1 h.

[0070] (3) After the sample was reduced, it was cooled to room temperature, the end cover of the tube furnace was opened, and the catalyst was obtained after 10 min of passivation, which was Ru1 / CeO2.

[0071] Comparative Example 3

[0072] Ru NP Preparation of / CeO2 catalyst

[0073] (1) Take 1g of CeO2 carrier and add 1.6mL of Ru colloidal particles (1.2mg) Ru Dissolve the sample ( / mL) in 10 mL of deionized water to prepare a solution. Add this solution dropwise to CeO2 and mix thoroughly. Then sonicate the wet sample for 15 minutes and dry it in an oven at 60°C.

[0074] (2) The sample obtained in step (1) was transferred to a tube furnace and reduced with 10% H2 / Ar (160 mL / min) at a heating rate of 5 °C / min. First, the temperature was kept at 100 °C for 1 h, and then the temperature was increased to 500 °C and kept for another 1 h.

[0075] (3) After sample reduction, cool to room temperature, open one end of the tube furnace, passivate for 10 minutes, and then remove the sample to obtain Ru catalyst. NP / CeO2.

[0076] Comparative Example 4

[0077] Preparation of Cs-Ru / MgO catalyst

[0078] Take 1g of commercial magnesium oxide in a beaker, immerse 3.17mL of Ru(NO)(NO3)3 onto the support, and dry under an infrared lamp to obtain sample A. Then, dissolve 0.073g of CsNO3 in 2mL of deionized water, immerse sample A on it, and dry under an infrared lamp. Finally, place the resulting solid powder in a tube furnace and reduce it under a 10% H2 / Ar atmosphere (160mL / min) with a heating rate of 2℃ / min. -1 Heating to 400℃ and calcining for 2 hours yielded Cs-Ru / MgO.

[0079] Application examples

[0080] Ammonia synthesis catalyst performance evaluation

[0081] Weigh 0.20 g of the catalyst from Examples 1-4 and Comparative Examples 1-4 above, with a gas hourly space velocity (GHSV) of 60,000 mL g. -1 h -1 The ammonia synthesis rate was determined using an ammonia synthesis catalyst performance evaluation device. The change in NH3 concentration in the outlet tail gas was determined by ion chromatography (Thermo Scientific, DIONEX, ICS-600). The composition of the reaction gas was 25 vol% N2 + 75 vol% H2. The ammonia synthesis rate of the catalyst was determined at 400℃ and 1–5 MPa.

[0082] Catalyst characterization and performance evaluation

[0083] Figure 1 TEM images of RuCe x / GC catalysts in Example 1 and 2, wherein, Figure 1 a is the TEM image of catalyst in Example 1, Figure 1 b-d are respectively TEM images of catalyst in RuCe1 / GC, RuCe2 / GC and RuCe4 / GC in Example 2. Wherein, RuCe 0.5 Ru in RuCe1 / GC and RuCe1 / GC catalysts is nanocluster, Ru in RuCe4 / GC catalyst is single atom, and RuCe2 / GC is coexistence of Ru nanocluster and single atom, from the figure, it can be seen that Ru nanocluster and / or Ru single atom are uniformly distributed on the graphite carbon carrier, and the particle size of Ru-based catalyst is about 1.3-2.3nm.

[0084] Figure 2 is the spherical aberration transmission electron microscopy image of RuCe2 / GC catalyst in Example 2, it can be seen that Ru is dispersed on CeO2, Ru exists in the form of single atom and nanocluster, and CeO2 exists in the form of nanocluster.

[0085] Figure 3 Synthesis ammonia performance of RuCe x / GC catalysts in Example 1 and 2, wherein, Figure 3 a is the ammonia synthesis rate graph under different pressures at 400℃; Figure 3 b is the ammonia synthesis rate graph under 1MPa pressure and temperature of 300℃, 350℃, 370℃, 380℃ and 400℃ respectively; from Figure 3 It can be seen that when the mass ratio of Ru and Ce is 1:2, the ammonia synthesis rate of the catalyst is the highest. Under 400℃ and 1MPa, the ammonia synthesis rate of RuCe2 / GC reaches 24.9mmol g cat -1 h -1 Under 400℃ and 5MPa, the ammonia synthesis rate reaches 33.0mmol g cat -1 h -1 .

[0086] Figure 4 is the activation energy graph of the catalyst obtained in Example 1 and 2, according to Arrhenius formula, the activation energy of the catalyst is calculated as RuCe2 / GC(56.6kJ mol -1 )<RuCe / GC(74.1kJ mol -1 )<RuCe4 / GC(81.1kJ mol -1 )<RuCe 0.5 / GC (101.5 kJ mol -1 ), wherein the activation energy of the RuCe2 / HGC catalyst is the lowest at 56.6 kJ / mol, indicating that Ru coexists in the form of single atoms and nanoclusters is beneficial to the activation of N2 to generate NH3.

[0087] Figure 5 For the stability test of the RuCe2 / GC catalyst in Example 2, 25% N2-75% H2 mixed gas was used as the raw gas, and the test conditions were selected as a mass space velocity of 60,000 mL g -1 h -1 , a temperature of 400°C, and a pressure of 1 MPa. The test results show that the catalyst has a stable ammonia synthesis rate in 1000 h of reaction, and has good thermal stability.

[0088] Table 1 is the ammonia synthesis rate of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4. The specific test process of the ammonia synthesis rate is as follows: 0.20 g of each catalyst was weighed, the mass space velocity was 60,000 mL g -1 h -1 , and the ammonia synthesis rate was determined on a continuous flow micro fixed bed reactor, the change of NH3 concentration in the tail gas was determined by ion chromatography, and the reaction gas composition was 75% H2+25% N2 (volume ratio) mixed gas. At 400°C and 1 MPa, the ammonia synthesis reaction rate of different catalysts was measured.

[0089] As can be seen from the comparison of sequences 1-4, with the increase of Ce content, the ammonia synthesis rate of the catalyst first increases and then decreases. Among them, the RuCe 0.5 / GC and RuCe1 / GC catalysts have Ru in the form of nanoclusters, the RuCe4 / GC catalyst has Ru in the form of single atoms, and the RuCe2 / GC catalyst has Ru in the form of nanoclusters and single atoms, indicating that the coexistence of Ru nanoparticles and single atoms has higher ammonia synthesis performance.

[0090] As can be seen from the comparison of sequences 5-8, with the increase of Ru content from 1% to 4% and the Ce content remaining basically unchanged, the ammonia synthesis rate increases from 2.3 mmol g -1 h -1 to 30.5 mmol g -1 h -1 , indicating that Ru is the active center.

[0091] As can be seen from the comparison of sequences 3 and 9-11, the activity of the RuCe2 / GC catalyst with CeO2 as the additive is significantly higher than that of the Ru-based catalyst with CeO2 or GC as the carrier. At the same time, the ammonia synthesis activity of the RuCe2 / GC catalyst is respectively 2.3 times, 2.6 times and 2.8 times that of the Ru nanoparticles supported on CeO2 (Ru NPThe 2 times and 4 times of the ammonia synthesis rate of the CeO2-supported monatomic catalyst (Ru1 / CeO2) and the CeO2-supported Ru nanocluster catalyst (Ru2 / CeO2) further indicate that the Ru nanocluster and the monatomic catalyst have higher ammonia synthesis performance when coexisting.

[0092] As can be seen from the comparison of sequences 3 and 12, the RuCe2 / GC catalyst has significantly higher ammonia synthesis activity than the Cs-Ru / MgO catalyst.

[0093] Table 1. Ammonia synthesis rate of the catalysts in Examples 1-4 and Comparative Examples 1-4 at 400°C and 1 MPa

[0094]

[0095]

[0096] In Table 1, the Ru content refers to the content of Ru in the Ru-based catalyst; and the Ce content refers to the content of Ce in the Ru-based catalyst.

[0097] The above has exemplarily described the embodiments of the present application. However, the protection scope of the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A Ru-based catalyst characterized in that, The active component of the catalyst is Ru, the assistant is CeO2 nanomaterial, and the carrier is graphite carbon, and the Ru and CeO2 nanomaterial are both loaded on the carrier; The Ru in the Ru-based catalyst coexists in the form of Ru single atom and Ru nanocluster; The size of the Ru nanocluster is less than 2.5 nm; The CeO2 nanomaterial in the Ru-based catalyst exists in the form of CeO2 nanocluster.

2. The Ru-based catalyst according to claim 1, characterized in that, The size of the CeO2 nanocluster is less than 3 nm.

3. The Ru-based catalyst of claim 1, wherein The loading amount of the Ru active component is 0.1-4 wt% of the weight of the Ru-based catalyst.

4. The Ru-based catalyst of claim 1, wherein The loading amount of Ce in the CeO2 nanomaterial is 0.1-16 wt% of the weight of the Ru-based catalyst in terms of metal elements.

5. The Ru-based catalyst of claim 1, wherein The mass ratio of the Ru to Ce in the CeO2 nanomaterial is 1:(0.5-4) in terms of metal elements.

6. Process for the preparation of a Ru-based catalyst according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: (1) dissolving a ruthenium precursor and a cerium precursor in water to obtain a solution; (2) immersing a carrier in the solution obtained in step (1); (3) reducing and calcining the product obtained in step (2) to obtain the Ru-based catalyst.

7. The method of claim 6, wherein, In step (1), the ruthenium precursor is one or more of ruthenium trichloride, ammonium hexachlororuthenate, ruthenium acetate, ruthenium nitrosyl nitrate, ruthenium acetylacetonate, and triruthenium dodecacarbonyl.

8. The method of claim 6, wherein, In step (1), the cerium precursor is one or more of cerium nitrate hexahydrate and cerium nitrate ammonia.

9. The method of claim 6, wherein, In step (1), the mass ratio of Ce in the cerium precursor to Ru in the ruthenium precursor is (0.5-4):1 in terms of metal elements.

10. The method of claim 6, wherein, In step (2), the mass of the active component in the ruthenium precursor is 0.1-4.0 wt% of the Ru-based catalyst.

11. The method of claim 6, wherein, In step (3), the reduction and calcination are carried out in a reducing atmosphere.

12. The method of claim 11, wherein, The reducing atmosphere is selected from a mixed gas of hydrogen and an inert gas, and the inert gas is nitrogen, argon, or helium.

13. The method of claim 12, wherein, In the reducing atmosphere, the volume fraction of hydrogen is 5-25%.

14. The method of claim 6, wherein, In step (3), the calcination temperature is 100-600℃, the temperature rising rate during calcination is 2-8℃ / min, and the calcination time is 1-8h.

15. The method of claim 14, wherein, The calcination process is: first calcination at 100-300℃ for 1-3h, and then calcination at 300-600℃ for 1-5h.

16. The Ru-based catalyst according to any one of claims 1-5 is used for catalyzing the synthesis of ammonia.

17. Use according to claim 16, characterized in that, The Ru-based catalyst is used as a catalyst for synthesizing ammonia.

18. The use according to claim 16, characterized in that, The Ru-based catalyst is used as a catalyst for synthesizing ammonia under low-temperature and low-pressure conditions.

19. A catalyst for the synthesis of ammonia, characterized in that At least the Ru-based catalyst according to any one of claims 1-5 is used.

20. A method of synthesizing ammonia, characterized by, The method uses the Ru-based catalyst according to any one of claims 1-5.

21. The method of claim 20, wherein, The temperature for synthesizing ammonia is 300-400℃, and the pressure for synthesizing ammonia is 0.5-5 MPa.

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