Metal oxide loaded monatomic Ru catalyst as well as preparation method and application thereof

Abstract

The invention relates to a metal oxide loaded monatomic Ru catalyst and a preparation method and application thereof, the preparation method comprises the following steps: mixing salt of metal M with a grinding aid, and then carrying out ball milling to obtain a metal oxide precursor; calcining the metal oxide precursor to obtain a metal oxide MOx; and dissolving the metal oxide MOx in deionized water, adding a ruthenium source and 6-aminocaproic acid under oil bath heating, mixing, adding sodium borohydride, continuously stirring until the reaction is completed, and then washing and drying to obtain the metal oxide loaded monatomic Ru catalyst Ru SAs / MOx. According to the method, the 6-aminocaproic acid is used for assisting the NaBH4 reduction method, monatomic-scale Ru is constructed on the surface of the metal oxide, high-temperature reducing gas calcination is not needed, the method is simple and rapid, the requirements for equipment and raw materials are low, the economic effect is high, Ru is evenly dispersed on the surface of the oxide carrier and does not form clusters, and a large amount of Ru monatomic loaded oxide carriers can be rapidly prepared.

Description

Technical Field

[0001] The present invention relates to the field of thermal catalysis technology, and in particular to a metal oxide-supported single-atom Ru catalyst and a preparation method and application thereof. Background Art

[0002] Ammonia synthesis is the backbone of the chemical industry and has a milestone significance for the world's population growth and economic development. Ammonia is not only a raw material widely used in fertilizer production and basic chemical manufacturing, but also plays an important role in energy storage and practical application as an energy carrier. Traditional ammonia synthesis is usually based on the Haber-Bosch process, which consumes a lot of energy and has a great impact on the environment. Therefore, the development of efficient ammonia synthesis catalysts under low temperature and low pressure conditions is the current development trend of ammonia synthesis research.

[0003] Fe-based catalysts require high temperature and high pressure reaction conditions, while Ru can significantly reduce the operating conditions of the ammonia synthesis process (reaction temperature ≤ 400°C, reaction pressure ≤ 10MPa), achieving the goal of energy conservation and emission reduction. In recent years, single-atom catalysts have become the research frontier in the field of catalysis due to their unique atomic-level dispersibility and high atomic utilization. In the ammonia synthesis reaction, single-atom catalysts have potential advantages and can achieve precise control of catalytic active centers, thereby improving reaction activity and selectivity. This type of catalyst combines the surface acid-base properties of metal oxides and the excellent performance of ruthenium single-atom active sites, providing an efficient reaction pathway for ammonia synthesis.

[0004] In addition, the selection and surface structure of metal oxide supports have a significant impact on the dispersion and stability of single atoms, which is directly related to the overall performance of the catalyst. Studies have shown that metal oxide supports such as CeO2, TiO2, MgO, etc. can achieve uniform dispersion and stable loading of single atoms by adjusting the electronic structure and surface properties of the support, which can further optimize the performance of ammonia synthesis catalysts. This type of catalyst has broad application prospects in ammonia synthesis and is expected to have an important impact in the fields of energy conversion, environmental protection and agriculture.

[0005] The current Ru single atom synthesis methods include impregnation, electrodeposition, co-precipitation, step-by-step reduction, high-temperature pyrolysis, etc. The impregnation method has strict requirements on the carrier and requires the selection of a suitable precursor. In addition, whether a single atom can be formed and the loading amount are greatly affected by the impregnation solution; the electrodeposition method is limited by the equipment cost and is significantly affected by the deposition conditions, and may form clusters; the biggest problem with the co-precipitation method is that Ru will be buried in the catalyst body, and the yield is low, which is not suitable for carriers with large specific surface areas; the step-by-step reduction method has a complex preparation process, a low loading rate, and is prone to clustering; the high-temperature pyrolysis method requires high temperature conditions, which may lead to uneven distribution of the catalyst and poor activity. Summary of the invention

[0006] Based on this, in view of the shortcomings of the existing Ru single-atom synthesis method, the purpose of the present invention is to provide a metal oxide-supported single-atom Ru catalyst and its preparation method and application, so as to synthesize the metal oxide-supported single-atom Ru catalyst in a simple way. The metal oxide-supported single-atom Ru catalyst of the present invention is used as a catalyst for thermal catalytic synthesis of ammonia, and can achieve high efficiency, low energy consumption and low pollution in the synthesis of ammonia under mild conditions.

[0007] To achieve the above object, the present invention adopts the following technical solutions: The present invention first provides a method for preparing a metal oxide-supported single-atom Ru catalyst, which comprises the following steps: S1. The salt of metal M is mixed with a grinding aid and then ball-milled to obtain a metal oxide precursor; the metal oxide precursor is calcined to obtain a metal oxide MO. x ; S2. The metal oxide MO obtained in step S1 x Dissolve in deionized water, add ruthenium source and 6-aminocaproic acid under oil bath heating, add sodium borohydride after mixing, continue stirring until the reaction is complete, then wash and dry to obtain metal oxide supported single atom Ru catalyst Ru SAs / MO x .

[0008] The present invention first adopts a ball milling method to prepare a metal oxide carrier. The operation method is simple, easy to operate, and can be prepared in large quantities. Then, a 6-aminocaproic acid (AHA)-assisted NaBH4 reduction method is used to construct single-atom-level Ru on the surface of the metal oxide. No high-temperature reducing gas calcination is required, and the method is simple and fast. The AHA-assisted NaBH4 reduction method is simple to prepare Ru single atoms, has low requirements on equipment and raw materials, and has high economic benefits. Ru is evenly dispersed on the surface of the oxide carrier without forming clusters, and Ru single-atom-loaded oxide carriers can be quickly and massively prepared.

[0009] As a further improvement of the above scheme of the present invention, in step S1, the metal M is one of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Hf, Mo, W, Re, Mg, Ca, Sr, Ba, Sn, Pb, Bi, La, Ce, Nd, and Sm; And / or, in step S1, the salt of metal M is nitrate or ammonium salt of metal M.

[0010] As a further improvement of the above scheme of the present invention, in step S1, the grinding aid is (NH4)2CO3 or NH4HCO3.

[0011] As a further improvement of the above scheme of the present invention, in step S1, the molar ratio of the metal salt to the grinding aid is 1:0.1-10; And / or, the ball-to-material ratio of the ball mill is 1-60:1, the rotation speed of the ball mill is 200-600 rpm, and the ball milling time is 1-40 h.

[0012] As a further improvement of the above scheme of the present invention, in step S1, the calcination is carried out at 300-800°C for 2-24h, and the heating rate is 2-10°C / min.

[0013] As a further improvement of the above scheme of the present invention, in step S2, the ruthenium source is ruthenium acetate (C6H9O6Ru), triruthenium dodecacarbonyl (C 12 O 12 Ru3), ruthenium trichloride hydrate (RuCl3·xH2O), trinitronitrosylruthenium (N4O 10 Ru) one; And / or, in step S2, the metal oxide MO x , the mass ratio of the ruthenium source is 1:0.01-0.1; And / or, in step S2, the mass ratio of the ruthenium source, the 6-aminocaproic acid, and the sodium borohydride is 1:0.1-10:0.1-20; And / or, in step S2, the temperature of the oil bath is 50-120° C., and the oil bath time is 1-10 h.

[0014] The present invention also provides a metal oxide-supported single-atom Ru catalyst, which is prepared by the above-mentioned preparation method.

[0015] The present invention also provides an application of a metal oxide-supported single-atom Ru catalyst prepared by the above-mentioned preparation method in thermal catalytic ammonia synthesis.

[0016] As a further improvement of the above scheme of the present invention, it includes the following steps: filling the metal oxide-supported single-atom Ru catalyst in a quartz reaction tube, introducing a mixed gas of N2 and H2, and heating for reaction.

[0017] As a further improvement of the above solution of the present invention, the metal oxide-supported single-atom Ru catalyst is in powder or granular form; and / or, the molar ratio of N2 to H2 in the mixed gas is 1:0.5-5, and the flow rate of the mixed gas is 20-300 mL / min; And / or, the reaction temperature is 100-500° C. and the pressure is 0.1-5 MPa.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention first adopts a ball milling method to prepare a metal oxide precursor, and then calcines it. This operation method is simple and easy to operate, and can prepare metal oxide carriers in large quantities; then, a 6-aminocaproic acid (AHA)-assisted NaBH4 reduction method is used to construct single-atom-level Ru on the surface of the metal oxide. No high-temperature reducing gas calcination is required. The method is simple and fast, has low requirements on equipment and raw materials, and has high economic benefits. Ru is evenly dispersed on the surface of the oxide carrier without forming clusters, and single-atom Ru loaded on the oxide can be prepared quickly and in large quantities.

[0019] The metal oxide supported single atom Ru synthesized in the present invention is used as a catalyst to achieve a good thermal catalytic ammonia synthesis effect, with mild reaction conditions and good activity maintenance. Ammonia synthesis can be effectively carried out under relatively low temperature and pressure conditions, with high reaction efficiency and good catalytic stability, thereby alleviating the disadvantages of high energy consumption and environmental pollution in the traditional Haber-Bosch process, and greatly broadening the research and application fields of the catalyst for thermal catalytic ammonia synthesis reaction under mild conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the X-ray diffraction spectrum of the metal oxide-supported single-atom Ru catalyst prepared in Examples 1-6 of the present invention; Figure 2 It is a transmission electron microscope photograph of the metal oxide-supported single-atom Ru catalyst prepared in Examples 1-6 of the present invention; Figure 3 The EXAFS spectrum of synchrotron radiation Ru of Ru SAs / CeO2 prepared in Example 1 of the present invention; Figure 4 EPR spectra of Ru SAs / CeO2 prepared in Example 1 of the present invention and Ru NCs / CeO2 prepared in Comparative Example 1; Figure 5 This is a schematic diagram of the thermal catalytic synthesis of ammonia by metal oxide-supported single-atom Ru catalyst in Examples 7-10 of the present invention; DETAILED DESCRIPTION For ease of understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0022] Example 1 This embodiment provides a metal oxide supported single atom Ru catalyst, the preparation method of which comprises the following steps: S1. Place 21.7 g of Ce(NO3)3·6H2O and 9.6 g of (NH4)2CO3 in the zirconia grinding jar of a planetary ball mill. The grinding balls are zirconia balls with a diameter of 3 mm, the ball-to-material ratio is 30:1, the ball milling speed is 400 rpm, and the ball milling time is 12 h. After the ball milling is completed, take out the material, place it in a muffle furnace, heat it to 500 ° C at a heating rate of 5 ° C / min, and keep it at 500 ° C for 3 h to obtain CeO2.

[0023] S2. Dissolve 2 g of CeO2 prepared in step S1 in 50 mL of deionized water, stir in a 90°C oil bath for 30 min, add 160 mg of AHA and 127 mg of RuCl3·xH2O, continue stirring for 30 min, then add 280 mg of NaBH4, and continue stirring for 180 min. After the reaction is complete, wash and dry to obtain Ru SAs / CeO2.

[0024] Figure 1 a is the X-ray diffraction spectrum of Ru SAs / CeO2 prepared in this example obtained by XRD characterization (XRD, Cu-Kα, λ=1.5406Å). Figure 1 a It can be seen that the CeO2 in the Ru SAs / CeO2 prepared in this example has good crystallinity, which corresponds to the standard card (PDF#81-0792). Since the content of single-atom Ru is very low and cannot be detected by the instrument, the characteristic peak of Ru is not shown in the X-ray diffraction spectrum.

[0025] Figure 2 a is a transmission electron microscope photo of the Ru SAs / CeO2 prepared in this example. Figure 2 As can be seen from a, CeO2 in the Ru SAs / CeO2 prepared in this example exhibits a rod-like structure. Since the loading state of Ru is single atom and the dispersion is good, the transmission imaging of Ru is not directly observed.

[0026] Figure 3 The EXAFS spectrum of Ru in the Ru SAs / CeO2 catalyst prepared in this example shows only Ru-O bonds but no Ru-Ru bonds, which proves that in the Ru SAs / CeO2 catalyst, Ru exists in the form of a single atom.

[0027] Comparative Example 1 This comparative example proposes a metal oxide supported Ru cluster catalyst, the preparation method of which comprises the following steps: S1. Place 21.7 g of Ce(NO3)3·6H2O and 9.6 g of (NH4)2CO3 in the zirconia grinding jar of a planetary ball mill. The grinding balls are zirconia balls with a diameter of 3 mm, the ball-to-material ratio is 30:1, the ball milling speed is 400 rpm, and the ball milling time is 12 h. After the ball milling is completed, take out the material, place it in a muffle furnace, heat it to 500 ° C at a heating rate of 5 ° C / min, and keep it at 500 ° C for 3 h to obtain CeO2.

[0028] S2. Dissolve 2 g of CeO2 prepared in step S1 in 50 mL of deionized water, stir with a magnetic stirrer for 30 min, add 127 mg of RuCl3·xH2O, continue stirring for 30 min, then add 3 mL of NaBH4 solution (concentration of 80 mg / mL) dropwise, and continue stirring for 120 min. After the reaction is completed, wash and dry to obtain Ru NCs / CeO2.

[0029] Figure 4 The EPR spectra of Ru SAs / CeO2 prepared in Example 1 and Ru NCs / CeO2 prepared in Comparative Example 1 are shown in Table 1. Figure 4 It can be seen that six equivalent peaks are shown in the Ru SAs / CeO2 catalyst, indicating that the interaction between Ru single atoms and CeO2 support is stronger than that between Ru clusters.

[0030] Example 2 This embodiment provides a metal oxide supported single atom Ru catalyst, the preparation method of which comprises the following steps: S1. Place 25.1g of Mn(NO3)2·4H2O and 14.4g of (NH4)2CO3 in the zirconia grinding jar of a planetary ball mill. The grinding balls are zirconia balls with a diameter of 3mm, the ball-to-material ratio is 20:1, the ball milling speed is 500rpm, and the ball milling time is 10h. After the ball milling is completed, take out the material, place it in a muffle furnace, heat it to 700℃ at a heating rate of 2℃ / min, and keep it at 700℃ for 4h to obtain MnO2.

[0031] S2. Dissolve 2 g of MnO2 obtained in step S1 in 50 mL of deionized water, stir in a 90°C oil bath for 30 min, add 762 mg of AHA and 381 mg of RuCl3·xH2O, continue stirring for 30 min, then add 762 mg of NaBH4, and continue stirring for 120 min. After the reaction is completed, wash and dry to obtain Ru SAs / MnO2.

[0032] Figure 1 b is the X-ray diffraction spectrum of Ru SAs / MnO2 prepared in this example obtained by XRD characterization (XRD, Cu-Kα, λ=1.5406Å). Figure 1 b It can be seen that the MnO2 in the Ru SAs / MnO2 prepared in this example has good crystallinity, which corresponds to the standard card (PDF#24-0735). Since the content of single-atom Ru is very low and cannot be detected by the instrument, the characteristic peak of Ru is not shown in the X-ray diffraction spectrum.

[0033] Figure 2 b is a transmission electron microscope photo of the Ru SAs / MnO2 prepared in this example. Figure 2 b It can be seen that the MnO2 in the Ru SAs / MnO2 prepared in this example presents a flake structure. Since the loading state of Ru is single atom and the dispersion is good, the transmission imaging of Ru is not directly observed.

[0034] Example 3 This embodiment provides a metal oxide supported single atom Ru catalyst, the preparation method of which comprises the following steps: S1. 29.1g of Co(NO3)2·6H2O and 31.622g of NH4HCO3 were placed in the zirconia grinding jar of a planetary ball mill. The grinding balls used were zirconia balls with a diameter of 3mm, the ball-to-material ratio was 40:1, the ball milling speed was 400 rpm, and the ball milling time was 22 h. After the ball milling was completed, the material was taken out and placed in a muffle furnace. The temperature was raised to 600℃ at a heating rate of 3℃ / min, and kept at 600℃ for 6 h to obtain Co3O4.

[0035] S2. Dissolve 2 g of Co3O4 obtained in step S1 in 50 mL of deionized water, stir in a 90°C oil bath for 30 min, add 556 mg of AHA and 278 mg of C2H4O2Ru, continue stirring for 30 min, then add 834 mg of NaBH4, and continue stirring for 120 min. After the reaction is completed, wash and dry to obtain Ru SAs / Co3O4.

[0036] Figure 1 c is the X-ray diffraction spectrum of Ru SAs / Co3O4 prepared in this example obtained by XRD characterization (XRD, Cu-Kα, λ=1.5406Å). Figure 1 c It can be seen that the Co3O4 in the Ru SAs / Co3O4 prepared in this example has good crystallinity, which corresponds to the standard card (PDF#43-1003). Since the content of single-atom Ru is very low and cannot be detected by the instrument, the characteristic peak of Ru is not shown in the X-ray diffraction spectrum.

[0037] Figure 2 c is a transmission electron microscope photo of the Ru SAs / Co3O4 prepared in this example. Figure 2 c It can be seen that the Co3O4 in the Ru SAs / Co3O4 prepared in this embodiment presents a granular structure. Since the loading state of Ru is single atom and the dispersion is good, the transmission imaging of Ru is not directly observed.

[0038] Example 4 This embodiment provides a metal oxide supported single atom Ru catalyst, the preparation method of which comprises the following steps: S1. 29.07g of Ni(NO3)2·6H2O and 15.81g of NH4HCO3 were placed in the zirconia grinding jar of a planetary ball mill. The grinding balls used were zirconia balls with a diameter of 3mm, the ball-to-material ratio was 30:1, the ball milling speed was 600rpm, and the ball milling time was 14h. After the ball milling was completed, the material was taken out and placed in a muffle furnace. The temperature was raised to 800℃ at a heating rate of 5℃ / min, and kept at 800℃ for 5h to obtain NiO.

[0039] S2. Dissolve 2 g of NiO obtained in step S1 in 50 mL of deionized water, stir in a 90 ° C oil bath for 30 min, add 680 mg of AHA and 639 mg of C12O 12 Ru3, continued stirring for 30 min, then added 958.8 mg of NaBH4, and continued stirring for 120 min. After the reaction was completed, washed and dried to obtain Ru SAs / NiO.

[0040] Figure 1 d is the X-ray diffraction spectrum of Ru SAs / NiO prepared in this example obtained by XRD characterization (XRD, Cu-Kα, λ=1.5406Å). Figure 1 d It can be seen that the NiO in the Ru SAs / NiO prepared in this example has good crystallinity, which corresponds to the standard card (PDF#71-1179). Since the content of single-atom Ru is very low and cannot be detected by the instrument, the characteristic peak of Ru is not shown in the X-ray diffraction spectrum.

[0041] Figure 2 d is a transmission electron microscope photo of the Ru SAs / NiO prepared in this example. Figure 2 d It can be seen that the NiO in the Ru SAs / NiO prepared in this example presents a flake structure. Since the loading state of Ru is single atom and the dispersion is good, the transmission imaging of Ru is not directly observed.

[0042] Example 5 This embodiment provides a metal oxide supported single atom Ru catalyst, the preparation method of which comprises the following steps: S1. Place 39.5g of (NH4)2MoO4 and 14.4g of (NH4)2CO3 in a zirconia grinding jar of a planetary ball mill. The grinding balls are zirconia balls with a diameter of 3mm, the ball-to-material ratio is 30:1, the ball milling speed is 600 rpm, and the ball milling time is 20h. After the ball milling is completed, take out the material, place it in a muffle furnace, heat it to 800℃ at a heating rate of 5℃ / min, and keep it at 800℃ for 4h to obtain MoO3.

[0043] S2. Dissolve 2 g of MoO3 obtained in step S1 in 50 mL of deionized water, stir in an oil bath at 90 °C for 30 min, add 634 mg of AHA and 317 mg of N4O 10 After stirring for 30 min, 951 mg of NaBH4 was added and stirred for 120 min. After the reaction was completed, the mixture was washed and dried to obtain Ru SAs / MoO3.

[0044] Figure 1 e is the X-ray diffraction spectrum of Ru SAs / MoO3 prepared in this example obtained by XRD characterization (XRD, Cu-Kα, λ=1.5406Å). Figure 1 e It can be seen that the MoO3 in the Ru SAs / MoO3 prepared in this example has good crystallinity, which corresponds to the standard card (PDF#35-0609). Since the content of single-atom Ru is very low and cannot be detected by the instrument, the characteristic peak of Ru is not shown in the X-ray diffraction spectrum.

[0045] Figure 2 e is a transmission electron microscopy photograph of the Ru SAs / MoO3 prepared in this example. Figure 2 e It can be seen that the MoO3 in the Ru SAs / MoO3 prepared in this embodiment presents a rod-like structure. Since the loading state of Ru is single atom and the dispersion is good, the transmission imaging of Ru is not directly observed.

[0046] Example 6 This embodiment provides a metal oxide supported single atom Ru catalyst, the preparation method of which comprises the following steps: S1. Place 29.1g of Bi(NO3)3·5H2O and 15.81g of NH4HCO3 in a zirconia grinding jar of a planetary ball mill. The grinding balls are zirconia balls with a diameter of 3mm, the ball-to-material ratio is 40:1, the ball milling speed is 400rpm, and the ball milling time is 12h. After the ball milling is completed, take out the material, place it in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and keep it at 600℃ for 6h to obtain Bi2O3.

[0047] S2. Dissolve 2 g of Bi2O3 obtained in step S1 in 50 mL of deionized water, stir in a 90°C oil bath for 30 min, add 398 mg of AHA and 199 mg of C2H4O2Ru, continue stirring for 30 min, add 597 mg of NaBH4, and continue stirring for 120 min. After the reaction is completed, wash and dry to obtain Ru SAs / Bi2O3.

[0048] Figure 1 f is the X-ray diffraction spectrum of Ru SAs / Bi2O3 prepared in this example obtained by XRD characterization (XRD, Cu-Kα, λ=1.5406Å). Figure 1 It can be seen from f that the Bi2O3 in the Ru SAs / Bi2O3 prepared in this example has good crystallinity, which corresponds to the standard card (PDF#27-0050). Since the content of single-atom Ru is very low and cannot be detected by the instrument, the characteristic peak of Ru is not shown in the X-ray diffraction spectrum.

[0049] Figure 2 f is a transmission electron microscope photo of the Ru SAs / Bi2O3 prepared in this example. Figure 2 As can be seen from f, the Bi2O3 in the Ru SAs / Bi2O3 prepared in this embodiment presents a flake structure. Since the loading state of Ru is single atom and the dispersion is good, the transmission imaging of Ru is not directly observed.

[0050] Example 7 This embodiment uses the metal oxide supported single-atom Ru catalyst Ru SAs / CeO2 obtained in step S2 of embodiment 1 for synthesizing ammonia, comprising the following steps: 500 mg of the Ru SAs / CeO2 obtained in step S2 of embodiment 1 is loaded into a quartz reaction tube of a fixed-bed reactor for synthesizing ammonia, the reaction temperature is fixed at 400°C, the reaction pressure is 3MPa, the reaction gas is a mixture of N2 and H2, the molar ratio of N2 to H2 is 1:3, the mixed gas flow rate is 80mL / min, after pre-activation for 3h, sampling is performed every 1h, and the generated ammonia is detected by colorimetric method. The principle of thermal catalytic synthesis of ammonia by the metal oxide supported single-atom Ru catalyst of this embodiment is as follows Figure 5 shown.

[0051] Comparative Example 2 This comparative example uses the CeO2 obtained in step S1 of Example 1 to synthesize ammonia, comprising the following steps: taking 500 mg of the prepared CeO2 obtained in step S1 of Example 1 and placing it in a quartz reaction tube of a fixed-bed reactor for synthesizing ammonia, fixing the reaction temperature at 400°C, the reaction pressure at 3 MPa, the reaction gas being a mixture of N2 and H2, the molar ratio of N2 to H2 being 1:3, the mixed gas flow rate being 80 mL / min, and after pre-activation for 3 hours, sampling every 1 hour and detecting the generated ammonia by a colorimetric method.

[0052] The test results of the catalytic reaction activity of synthetic ammonia of Example 7 and Comparative Example 2 are shown in Table 1.

[0053] Table 1 Test results of the catalytic reaction activity of synthetic ammonia in Example 7 and Comparative Example 2

[0054] It can be seen from the results in Table 1 that the metal oxide-supported single-atom Ru catalyst prepared in Example 1 has a very high ammonia synthesis reaction rate.

[0055] Example 8 This embodiment uses the metal oxide supported single-atom Ru catalyst Ru SAs / MnO2 obtained in step S2 of embodiment 2 for synthesizing ammonia, comprising the following steps: 500 mg of the Ru SAs / MnO2 obtained in step S2 of embodiment 2 is loaded into a quartz reaction tube of a fixed bed reactor for synthesizing ammonia, the reaction temperature is fixed at 400°C, the reaction pressure is 5MPa, the reaction gas is a mixture of N2 and H2, the molar ratio of N2 to H2 is 1:3, the mixed gas flow rate is 120mL / min, after pre-activation for 3h, sampling is performed every 1h, and the generated ammonia is detected by colorimetric method. The principle of thermal catalytic synthesis of ammonia by the metal oxide supported single-atom Ru catalyst of this embodiment is as follows Figure 5 shown.

[0056] Comparative Example 3 This embodiment uses the MnO2 obtained in step S1 of embodiment 2 to synthesize ammonia, comprising the following steps: 500 mg of the MnO2 obtained in step S1 of embodiment 2 is loaded into a quartz reaction tube of a fixed bed reactor for synthesizing ammonia, the reaction temperature is fixed at 400°C, the reaction pressure is 5 MPa, the reaction gas is a mixture of N2 and H2, the molar ratio of N2 to H2 is 1:3, the mixed gas flow rate is 120 mL / min, after pre-activation for 3 hours, sampling is performed every 1 hour, and the generated ammonia is detected by a colorimetric method.

[0057] The test results of the catalytic reaction activity of synthetic ammonia of Example 8 and Comparative Example 3 are shown in Table 2.

[0058] Table 2 Test results of the catalytic reaction activity of synthetic ammonia in Example 8 and Comparative Example 3

[0059] It can be seen from the results in Table 2 that the metal oxide-supported single-atom Ru catalyst prepared in Example 2 has a very high ammonia synthesis reaction rate.

[0060] Example 9 This embodiment uses the metal oxide supported single-atom Ru catalyst Ru SAs / Co3O4 obtained in step S2 of embodiment 3 for synthesizing ammonia, comprising the following steps: 500 mg of the Ru SAs / Co3O4 obtained in step S2 of embodiment 3 is loaded into a quartz reaction tube of a fixed bed reactor for synthesizing ammonia, the reaction temperature is fixed at 500°C, the reaction pressure is 4MPa, the reaction gas is a mixture of N2 and H2, the molar ratio of N2 to H2 is 1:3, the mixed gas flow rate is 120mL / min, after pre-activation for 3h, sampling is performed every 1h, and the generated ammonia is detected by colorimetric method. The principle of thermal catalytic synthesis of ammonia by the metal oxide supported single-atom Ru catalyst of this embodiment is as follows Figure 5 shown.

[0061] Comparative Example 4 This comparative example uses the Co3O4 obtained in step S1 of Example 3 to synthesize ammonia, comprising the following steps: 500 mg of the Co3O4 obtained in step S1 of Example 3 is loaded into a quartz reaction tube of a fixed-bed reactor for synthesizing ammonia, the reaction temperature is fixed at 500°C, the reaction pressure is 4 MPa, the reaction gas is a mixture of N2 and H2, the molar ratio of N2 to H2 is 1:3, the mixed gas flow rate is 120 mL / min, and after pre-activation for 3 hours, samples are taken every 1 hour, and the generated ammonia is detected by a colorimetric method.

[0062] The test results of the catalytic reaction activity of synthetic ammonia of Example 9 and Comparative Example 4 are shown in Table 3.

[0063] Table 3 Test results of the catalytic reaction activity of synthetic ammonia in Example 9 and Comparative Example 4

[0064] It can be seen from the results in Table 3 that the metal oxide-supported single-atom Ru catalyst prepared in Example 3 has a very high ammonia synthesis reaction rate.

[0065] Example 10 This embodiment uses the metal oxide supported single-atom Ru catalyst Ru SAs / MoO3 obtained in step S2 of embodiment 5 for synthesizing ammonia, comprising the following steps: 500 mg of the Ru SAs / MoO3 obtained in step S2 of embodiment 5 is loaded into a quartz reaction tube of a fixed bed reactor for synthesizing ammonia, the reaction temperature is fixed at 500°C, the reaction pressure is 4MPa, the reaction gas is a mixture of N2 and H2, the molar ratio of N2 to H2 is 2:3, the mixed gas flow rate is 120mL / min, after pre-activation for 3h, sampling is performed every 1h, and the generated ammonia is detected by colorimetric method. The principle of thermal catalytic synthesis of ammonia by the metal oxide supported single-atom Ru catalyst of this embodiment is as follows Figure 5 shown.

[0066] Comparative Example 5 This comparative example uses the MoO3 obtained in step S1 of Example 5 to synthesize ammonia, comprising the following steps: 500 mg of the MoO3 obtained in step S1 of Example 5 is loaded into a quartz reaction tube of a fixed-bed reactor for synthesizing ammonia, the reaction temperature is fixed at 500°C, the reaction pressure is 4 MPa, the reaction gas is a mixture of N2 and H2, the molar ratio of N2 to H2 is 2:3, the mixed gas flow rate is 120 mL / min, and after pre-activation for 3 hours, samples are taken every 1 hour, and the generated ammonia is detected by a colorimetric method.

[0067] The test results of the catalytic reaction activity of synthetic ammonia of Example 10 and Comparative Example 5 are shown in Table 4.

[0068] Table 4 Test results of the catalytic reaction activity of synthetic ammonia in Example 10 and Comparative Example 5

[0069] It can be seen from the results in Table 4 that the metal oxide-supported single-atom Ru catalyst prepared in Example 5 has a very high ammonia synthesis reaction rate.

[0070] In summary, the metal oxide-supported single-atom Ru catalyst of the present invention has good reaction activity, can reduce the energy consumption of the ammonia synthesis process, improve the efficiency of the ammonia synthesis reaction, and has good application prospects.

[0071] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a metal oxide-supported single-atom Ru catalyst, characterized in that: It includes the following steps: S1. The salt of metal M is mixed with a grinding aid and then ball-milled to obtain a metal oxide precursor; the metal oxide precursor is calcined to obtain a metal oxide MO. x ; S2. The metal oxide MO obtained in step S1 x Dissolve in deionized water, add ruthenium source and 6-aminocaproic acid under oil bath heating, add sodium borohydride after mixing, continue stirring until the reaction is complete, then wash and dry to obtain metal oxide supported single atom Ru catalyst Ru SAs / MO x .

2. The method for preparing the metal oxide supported single atom Ru catalyst according to claim 1, characterized in that: In step S1, the metal M is one of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Hf, Mo, W, Re, Mg, Ca, Sr, Ba, Sn, Pb, Bi, La, Ce, Nd, and Sm; And / or, in step S1, the salt of metal M is nitrate or ammonium salt of metal M.

3. The method for preparing the metal oxide supported single atom Ru catalyst according to claim 1, characterized in that: In step S1, the grinding aid is (NH4)2CO3 or NH4HCO3.

4. The method for preparing the metal oxide supported single atom Ru catalyst according to claim 1, characterized in that: In step S1, the molar ratio of the metal salt to the grinding aid is 1:0.1-10; And / or, the ball-to-material ratio of the ball mill is 1-60:1, the rotation speed of the ball mill is 200-600 rpm, and the ball milling time is 1-40 h.

5. The method for preparing the metal oxide supported single atom Ru catalyst according to claim 1, characterized in that: In step S1, the calcination is carried out at 300-800°C for 2-24h, with a heating rate of 2-10°C / min.

6. The method for preparing a metal oxide supported single atom Ru catalyst according to claim 1, characterized in that: In step S2, the ruthenium source is one of ruthenium acetate, triruthenium dodecacarbonyl, ruthenium trichloride hydrate, and trinitronitrosyl ruthenium; And / or, in step S2, the metal oxide MO x , the mass ratio of the ruthenium source is 1:0.01-0.1; And / or, in step S2, the mass ratio of the ruthenium source, the 6-aminocaproic acid, and the sodium borohydride is 1:0.1-10:0.1-20; And / or, in step S2, the temperature of the oil bath is 50-120° C., and the oil bath time is 1-10 h.

7. A metal oxide supported single atom Ru catalyst, characterized in that: The invention is prepared by the preparation method described in any one of claims 1 to 6.

8. Use of a metal oxide-supported single-atom Ru catalyst prepared by the preparation method according to any one of claims 1 to 6 in thermal catalytic ammonia synthesis.

9. The use according to claim 8, characterized in that: It includes the following steps: The metal oxide-supported single-atom Ru catalyst is loaded into a quartz reaction tube, a mixed gas of N2 and H2 is introduced, and the reaction is heated.

10. The use according to claim 9, characterized in that: The metal oxide-supported single-atom Ru catalyst is in powder or granular form; And / or, the molar ratio of N2 to H2 in the mixed gas is 1:0.5-5, and the flow rate of the mixed gas is 20-300 mL / min; And / or, the reaction temperature is 100-500° C. and the pressure is 0.1-5 MPa.

Images