Supported ruthenium nanocluster catalyst as well as preparation method and application thereof

Abstract

The invention discloses a supported ruthenium nanocluster catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalyst preparation. The supported ruthenium nanocluster catalyst comprises an oxide carrier and an active component ruthenium, the oxide carrier comprises one or more of titanium oxide, cerium oxide, aluminum oxide and silicon oxide, and the loading amount of the active component ruthenium is 0.5-5%. The supported ruthenium nanocluster catalyst is prepared by adopting a microwave-assisted coprecipitation-atmosphere induced dispersion method, the catalyst shows excellent activity, selectivity and stability in propane oxidative dehydrogenation reaction, the catalyst preparation process is simple and safe, green and energy-saving, the raw materials are cheap and easy to obtain, the preparation cost is low, and scale enlargement is easy to realize.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst preparation, and particularly relates to a supported ruthenium catalyst for propane oxidative dehydrogenation, a preparation method thereof, and an application thereof. Background Art

[0002] As an important chemical raw material, propylene is widely used in the fields of fine chemicals, pharmaceuticals, polymers, etc., and is mainly used for the production of polypropylene, propylene oxide, acrylonitrile, acrylic acid, etc. At present, the main sources of propylene in the market are through the cracking of naphtha and the direct dehydrogenation of propane. However, these methods are technically complex, require high reaction temperatures, and consume a large amount of energy. Propane oxidative dehydrogenation is an exothermic reaction, with a low reaction temperature, a simple reaction process, and in an oxidative atmosphere, the catalyst avoids carbon deposition, which is beneficial to the long-term use of the catalyst. In contrast, propane oxidative dehydrogenation has better market development prospects.

[0003] To date, various transition metal oxides such as vanadium (ACS Catal. 5, 5787–5793 (2015)), molybdenum (J. Mol. Catal. A, 2014, 392, 315), and chromium (Journal of Catalysis, 2017, 356:197-205) have good catalytic performance for propane oxidative dehydrogenation (ODHP) due to their unique chemical coordination and reducibility. In 2016, Grant et al. found that hexagonal boron nitride (h-BN) had amazing activity with a conversion rate of 14% and a propylene selectivity of 79% in the production of propylene by propane oxidative dehydrogenation (Science 354.6319 (2016):1570-1573). However, due to the excessive generation of CO x products during the dehydrogenation process, the propylene yield still does not reach an economically viable level. Therefore, further exploring excellent catalysts for propane oxidative dehydrogenation to propylene remains a huge challenge.

[0004] In recent years, due to the special energy transfer and conversion mode of microwaves, as a special green heating method, it has been widely used in the field of catalyst preparation. For example, Patent CN102658207A successfully prepared a highly dispersed Pd catalyst using microwave reaction technology. However, a large amount of organotin solvent was introduced in the catalyst preparation process, and a large number of by-products had great damage to the environment, restricting the development of this method; Patent CN105268433A also successfully prepared a series of highly dispersed platinum group series catalysts using microwave heating method. However, a large amount of alcohol reducing agents and polymer protecting agents were introduced in this method, making the preparation process complex and increasing the production cost input, resulting in the difficulty of industrializing this scheme. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, such as complex preparation process, extensive use of organic solvents, and low metal dispersion, the present invention successfully prepares a series of ruthenium nanocluster catalysts supported on different carriers through a microwave-assisted co-precipitation and atmosphere induction method. These catalysts exhibit excellent propane oxidative dehydrogenation activity and selectivity at atmospheric pressure and relatively low temperatures (200 - 450 °C), and also have high stability. The discovery of this technology has important value for the design of highly efficient propane oxidative dehydrogenation catalysts and may also be applicable to reactions such as methanol to olefins, methane reforming, and water gas shift.

[0006] In the first aspect of the present invention, a supported ruthenium nanocluster catalyst is provided, which includes an oxide carrier and an active component ruthenium. The oxide carrier includes one or more of titanium oxide, cerium oxide, alumina, silica, etc. The loading amount of the active component ruthenium is 0.5 - 5%.

[0007] In the second aspect of the present invention, a preparation method of a supported ruthenium nanocluster catalyst is provided, which includes the following steps: (1) Mix a ruthenium precursor solution and a carrier precursor solution, then add a dispersant and a pH regulator, react in a microwave reaction kettle, and wash and centrifuge the precipitated product to obtain a wet filter cake; (2) Reduce the wet filter cake obtained in step (1) in a microwave reaction tube under a reducing atmosphere, and reduce and disperse it by microwave induction to obtain a ruthenium cluster catalyst; The reducing atmosphere includes a reducing gas, an oxygen-containing gas, and a balance gas.

[0008] The reducing gas includes one or more of CO, CH4, NH3, H2, etc., and the volume fraction is 80 - 95%. The oxygen-containing gas includes one or more of H2O, CO, CH3OH, O2, HCHO, etc., and the volume fraction is 2 - 10%. The reducing gas and the oxygen-containing gas can be the same. The function of the oxygen-containing gas: Through the anchoring effect of oxygen, enhance the metal-support interaction and avoid the agglomeration and growth of metal Ru atoms during the high-temperature reduction process. The balance gas is an inert gas such as N2, Ar, etc., and the volume fraction of the balance gas is 0 - 18%.

[0009] Optionally, the ruthenium precursor is selected from at least one of metal salts, such as ruthenium chloride, potassium ruthenate, ruthenium acetate, ruthenium nitrate, ruthenium carbonyl, etc. The amount of the ruthenium precursor is calculated based on the amount of substance of the metal element in the precursor.

[0010] Optionally, the carrier precursor includes sodium silicate and one or more of metal nitrates, chlorides, sulfates, acetates, etc.

[0011] Optionally, the dispersant is selected from at least one of polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, sodium hexadecyl benzene sulfonate, sodium dodecyl sulfate, methanol, ethanol, polyacrylamide, etc.

[0012] Optionally, the molar ratio of the dispersant to Ru atoms is 1:1 to 10:1.

[0013] Optionally, the pH regulator mainly includes acids and bases such as sulfuric acid, nitric acid, hydrochloric acid, potassium hydroxide, sodium carbonate, potassium bicarbonate, etc., and the pH adjustment range is between 7 and 9.

[0014] Optionally, the conditions for the microwave-assisted precipitation reaction include: the temperature is 150 - 250 °C, the reaction duration is 5 - 48 h, the reaction pressure is 0.1 - 2.0 MPa, and the microwave input power is 0.2 - 0.7 kW.

[0015] Optionally, the temperature for microwave-induced reduction and dispersion is 300 - 700 °C, the microwave input power is 0.8 - 2.0 kW, and the reaction pressure is normal pressure.

[0016] The microwave reaction kettle uses microwave as the energy input source, which can uniformly heat the reaction system at the molecular level, making the formed precipitate particles finer, the size more uniform, and the reaction more complete. The equipment is purchased from Beijing Xianghu Science and Technology Development Co., Ltd., and the model is Hydrocube XH-800SE.

[0017] The microwave reaction tube uses microwave as the energy input source, which can heat the catalyst filter cake more uniformly. In addition, it can also integrate the drying and roasting reduction processes, reducing the product waste caused by complex operation processes. The equipment is purchased from Qingdao Microwave Physical and Chemical Research Institute of Mikewei, and the model is HXO-RT60.

[0018] The third aspect of the present invention provides an application of the supported ruthenium nanocluster catalyst, and the supported ruthenium nanocluster catalyst is used for the oxidative dehydrogenation reaction of propane. The test method is as follows: The supported ruthenium nanocluster catalyst is placed in an atmosphere of propane:oxygen:nitrogen = 20:20:60 (volume ratio), and the space velocity is controlled at 4000 - 8000 h -1 , the reaction temperature is 200 - 450 °C, and the products are analyzed by gas chromatography for tracking.

[0019] The supported ruthenium nanocluster catalyst of the present invention has the advantages of high activity, good stability and low cost. Compared with the prior art, the beneficial effects of the catalyst provided by the present invention include: 1. The supported ruthenium nanocluster catalyst provided by the present invention has high selectivity under atmospheric pressure and quite high stability. Compared with the traditional propane direct dehydrogenation reaction, the carbon deposition situation is greatly reduced; at the same time, through the optimization of the catalyst conditions, the deep oxidation of the product is reduced, and the content of CO in the tail gas is reduced. x in the content; 2. The catalyst provided by the present invention can achieve a propane conversion rate of up to 23.4%, a propylene selectivity of 62%, and a propylene yield of 14.5% at 200 - 450 °C, greatly reducing the production energy consumption and the difficulty of product separation. 3. The preparation method of the supported ruthenium nanocluster catalyst provided by the present invention uses raw materials such as carrier precursor salts, ruthenium salts, and dispersants, etc., which are bulk chemicals and have low costs. 4. The preparation method of the supported ruthenium nanocluster catalyst provided by the present invention has the advantages of simple and safe preparation process, energy conservation and environmental protection, and easy scale-up. Description of the Drawings

[0020] Figure 1 is the XAFS near-edge absorption (a) and extended-edge absorption (b) spectra of the catalyst in Example 1; Figure 2 is the high-angle annular dark-field image and elemental EDX-Mapping image of the catalyst in Example 1; Figure 3 is the propane oxidative dehydrogenation stability test result of the catalysts in Example 1 and Comparative Examples 1 - 3; Figure 4 is the high-resolution transmission electron microscope images of Example 1 (a) and Comparative Examples 1 (b), 2 (c), 3 (d). Detailed Embodiments

[0021] Unless otherwise specified, all numbers appearing in the specification and claims of the present invention, such as loadings, temperatures, times, conversion rates, etc., should not be understood as absolute exact values. Due to the standard deviation of the measurement technology, there will inevitably be certain experimental errors in the measured values.

[0022] The present invention will be described in detail below with reference to the embodiments, but is not limited to the described embodiments.

[0023] All catalysts are tested in an atmospheric pressure fixed-bed reactor. The bed temperature is controlled by a thermocouple. The raw material gas composition is propane: oxygen: nitrogen (volume ratio) = 20:20:60 atmosphere, 0.5 g of catalyst, and the space velocity is controlled at 4000 - 8000 h -1The reaction temperature was 200 - 450 °C, and the products were analyzed by gas chromatography for tracking. The propane conversion rate was obtained by combining the propane content before and after the reaction, and the selectivity was obtained based on the propylene content in the tail gas. The product yield was obtained by multiplying the two values.

[0024] The high-angle annular dark-field images of the samples were observed using a spherical aberration-corrected electron microscope of the ThermoFisher model from the United States, and it was equipped with an EDX-Mapping image acquisition function.

[0025] The noble metal loading was tested and completed by an inductively coupled plasma instrument.

[0026] X-ray near-edge absorption spectroscopy was collected at the BL14W1 beamline of the Shanghai Synchrotron Radiation Facility. The sample was the sample before the reaction, and the reference samples were Ru foil and RuO2 provided by the Shanghai Synchrotron Radiation Facility.

[0027] The Ru metal dispersion was obtained by testing using the CO chemisorption method. Before the test, the catalyst was reduced at 300 °C in 10% (volume fraction) H2 / Ar for 2 h, and the reducing gas was purged with Ar. At 50 °C, 10% (volume fraction) CO / Ar was introduced, and the number of Ru atoms exposed on the surface was obtained based on the consumed CO gas amount. Assuming the Ru:CO atomic ratio was 1:1, the Ru metal dispersion was then obtained by combining the loading data.

[0028] The existence form and size of the metal in the catalyst samples were observed using a transmission electron microscope (model: JEOL 2100X, purchased from JEOL Ltd., Japan).

[0029] The microwave hydrothermal reaction was carried out in a microwave reaction furnace purchased from Beijing Xianghu Science and Technology Development Co., Ltd., with the model of Hydrocube XH-800SE. The maximum power used did not exceed 2 kW, and the maximum temperature did not exceed 600 °C.

[0030] The microwave reaction tube was from Qingdao Microwave Physical and Chemical Research Institute, with the model of HXO-RT60, and the input power was adjustable from 0.2 - 2 kW.

[0031] Example 1

[0032] Dissolve 0.17 g of ruthenium nitrosyl nitrate in 10 mL of water. Then, dissolve 4.34 g of Ce(NO3)3·6H2O in 10 mL of water. After mixing the two evenly, add 2 mL of polyethylene glycol solution, and gradually add 3.8 g of 1 mol / L K2CO3 solution to adjust the pH of the mixed solution between 7 and 8. Conduct a precipitation reaction in a 50 mL microwave reaction kettle, control the reaction temperature at about 150 °C, the microwave input power at 0.4 kW, and the pressure at about 0.2 MPa. Then, maintain for 12 h. After thoroughly washing and filtering the obtained precipitate to get a filter cake, reduce it in a microwave reaction tube under the conditions of 500 °C in 10% CO / 80% H2 / Ar for 2 h with a microwave input power of 1.3 kW to obtain a 3 wt. % Ru / CeO2 catalyst.

[0033] Figure 1 X-ray near-edge absorption results show that the Ru state in the above 3 wt. % Ru / CeO2 catalyst is close to the oxidized state, indicating its highly unsaturated coordination state.

[0034] Figure 2 High-angle annular dark-field imaging shows that the Ru catalyst obtained by microwave-assisted precipitation-atmosphere-induced dispersion method is in an obvious highly dispersed nanocluster state, and no obvious particles are observed. The measured Ru dispersion reaches 96%.

[0035] Then, evaluate the reaction performance of the prepared catalyst. At normal pressure, a temperature of 300 °C, and a space velocity of 4000 h -1 Under these conditions, the propane conversion rate is 23.4%, the propylene selectivity is 62%, and the propylene yield is 14.5%.

[0036] Example 2

[0037] Dissolve 0.04 g of ruthenium chloride in 10 mL of water. Then, take 2.3 mL of TiCl4 and dissolve it in 10 mL of water. After mixing the two evenly, add 4.2 g of polyvinylpyrrolidone, and gradually add 2.7 g of Na2CO3 to adjust the pH of the mixed solution between 8 and 9. Conduct a precipitation reaction in a 50 mL microwave reaction kettle, control the reaction temperature at about 200 °C, the microwave input power at 0.6 kW, and the pressure at about 0.1 MPa. Then, maintain for 24 h. After thoroughly washing and filtering the obtained precipitate to get a filter cake, reduce it in a microwave reaction tube under the conditions of 300 °C in 95% CH4 / 2% H2O / Ar for 2 h with a microwave input power of 0.8 kW to obtain a 0.5 wt. % Ru / TiO2 catalyst.

[0038] Then, evaluate the reaction performance of the prepared catalyst. At normal pressure, a temperature of 300 °C, and a space velocity of 4000 h -1Under the conditions, the propane conversion rate was measured to be 16.7%, the propylene selectivity was 48%, and the propylene yield was 8.0%.

[0039] Example 3

[0040] Dissolve 0.52 g of potassium ruthenate in 10 mL of water. Then, dissolve 3.33 g of Al2(SO4)3 in 10 mL of water. After mixing the two evenly, add 1.2 g of polyacrylamide, and gradually add 2.3 g of NaOH dropwise to adjust the pH of the mixed solution between 8 and 9. Carry out a precipitation reaction in a 50 mL microwave reaction kettle, control the reaction temperature at about 250 °C, the microwave input power at 0.7 kW, and the pressure at about 2.0 MPa. Then, maintain for 8 h. After thoroughly washing and filtering the obtained precipitate to get a filter cake, then pass 85% NH3 / 2% O2 / N2 into the microwave reaction tube and reduce it at 600 °C for 2 h with a microwave input power of 1.6 kW to obtain a 5 wt.% Ru / Al2O3 catalyst.

[0041] After that, evaluate the reaction performance of the prepared catalyst. Under the conditions of normal pressure, a temperature of 300 °C, and a space velocity of 4000 h -1 Under the conditions, the propane conversion rate was measured to be 34.7%, the propylene selectivity was 38%, and the propylene yield was 13.2%.

[0042] Example 4

[0043] Dissolve 0.23 g of ruthenium acetate in 10 mL of water. Then, dissolve 3.5 g of La(CH3COO)3 in 10 mL of water. After mixing the two evenly, add 5.3 mL of sodium hexadecylbenzenesulfonate solution, and gradually add 6.4 g of NH3·H2O dropwise to adjust the pH of the mixed solution between 7 and 8. Carry out a precipitation reaction in a 50 mL microwave reaction kettle, control the reaction temperature at about 180 °C, the microwave input power at 0.5 kW, and the pressure at about 0.4 MPa. Then, maintain for 12 h. After thoroughly washing and filtering the obtained precipitate to get a filter cake, then pass 90% H2 / 5% CH3OH / N2 into the microwave reaction tube and reduce it at 400 °C for 2 h with a microwave input power of 1 kW to obtain a 3 wt.% Ru / La2O3 catalyst.

[0044] After that, evaluate the reaction performance of the prepared catalyst. Under the conditions of normal pressure, a temperature of 300 °C, and a space velocity of 4000 h -1 Under the conditions, the propane conversion rate was measured to be 24.4%, the propylene selectivity was 43%, and the propylene yield was 10.5%.

[0045] Example 5

[0046] Dissolve 0.24 g of ruthenium carbonyl in 10 mL of tetrahydrofuran solution. Then, dissolve 2.14 g of Na2SiO3·5H2O in 10 mL of water. After mixing the two evenly, add 2 mL of methanol solution, and gradually add 5.9 g of 20% H2SO4 dropwise to adjust the pH of the mixed solution between 8 and 9. Carry out the precipitation reaction in a 50 mL microwave reaction kettle, control the reaction temperature at about 150 °C, the microwave input power at 0.4 kW, and the pressure at about 0.3 MPa. Then maintain for 18 h. After thoroughly washing and filtering the obtained precipitate to get a filter cake, then reduce it in a microwave reaction tube under the conditions of 700 °C in 95% H2 / 4% HCHO / N2 for 2 h, with a microwave input power of 2 kW, to obtain a 3 wt. % Ru / SiO2 catalyst.

[0047] After that, evaluate the reaction performance of the prepared catalyst. At atmospheric pressure, a temperature of 300 °C, and a space velocity of 4000 h -1 Under these conditions, the propane conversion rate is measured to be 19.4%, the propylene selectivity is 29.8%, and the propylene yield is 5.8%.

[0048] Example 6

[0049] Dissolve 0.17 g of ruthenium nitrosyl nitrate in 10 mL of aqueous solution. Then, dissolve 3.89 g of Sm2(SO4)3·8H2O in 10 mL of water. After mixing the two evenly, add 3 mL of polyvinyl alcohol solution, and gradually add 6.7 g of NaHCO3 dropwise to adjust the pH of the mixed solution between 8 and 9. Carry out the precipitation reaction in a 50 mL microwave reaction kettle, control the reaction temperature at about 110 °C, the microwave input power at 0.2 kW, and the pressure at about 0.2 MPa. Then maintain for 19 h. After thoroughly washing and filtering the obtained precipitate to get a filter cake, then reduce it in a microwave reaction tube under the conditions of 300 °C in 95% CO / 3% H2O / N2 for 2 h, with a microwave input power of 0.8 kW, to obtain a 3 wt. % Ru / Sm2O3 catalyst.

[0050] After that, evaluate the reaction performance of the prepared catalyst. At atmospheric pressure, a temperature of 300 °C, and a space velocity of 4000 h -1 Under these conditions, the propane conversion rate is measured to be 21.4%, the propylene selectivity is 51.8%, and the propylene yield is 11.1%.

[0051] Example 7

[0052] Dissolve 0.17 g of ruthenium nitrosyl nitrate in 10 mL of aqueous solution. Then, dissolve 2.17 g of La(NO3)3·6H2O and 2.23 g of Ce(NO3)3·6H2O in 10 mL of water. After mixing them evenly, add 4.8 mL of polyvinyl alcohol solution, and gradually add 9.6 g of potassium bicarbonate to adjust the pH of the mixed solution between 8 and 9. Conduct a precipitation reaction in a 50 mL microwave reaction kettle, control the reaction temperature at about 180 °C, the microwave input power at 0.5 kW, and the pressure at about 1.0 MPa. Then, maintain for 18 h. After thoroughly washing and suction filtering the obtained precipitate to get a filter cake, reduce it in a microwave reaction tube under the conditions of 80% CH4 / 2% H2O / N2 at 500 °C for 2 h with a microwave input power of 1 kW to obtain 3 wt. % Ru / LaCeO x catalyst.

[0053] After that, evaluate the reaction performance of the prepared catalyst. At atmospheric pressure, a temperature of 300 °C, and a space velocity of 4000 h -1 the propane conversion rate is measured to be 23.8%, the propylene selectivity is 49.6%, and the propylene yield is 11.8%.

[0054] Example 8

[0055] The preparation process is the same as that of Example 1, except that the propane oxidative dehydrogenation temperature is 200 °C. The propane conversion rate is measured to be 8.8%, the propylene selectivity is 74.6%, and the propylene yield is 6.6%.

[0056] Example 9

[0057] The preparation process is the same as that of Example 1, except that the tested propane oxidative dehydrogenation temperature is 450 °C. The propane conversion rate is measured to be 36.8%, the propylene selectivity is 53.2%, and the propylene yield is 19.6%.

[0058] Example 10

[0059] The preparation process is the same as that of Example 1, except that the reaction space velocity is 8000 h -1 , and then evaluate the reaction performance of the prepared catalyst. At atmospheric pressure and a temperature of 300 °C, the propane conversion rate is measured to be 16.9%, the propylene selectivity is 67.2%, and the propylene yield is 11.4%.

[0060] Comparative Example 1

[0061] All operations are exactly the same as those in Example 1, except that the induced precipitation is not carried out in a microwave reactor but in an ordinary hydrothermal kettle instead.

[0062] The prepared catalyst was evaluated for its reaction performance. At atmospheric pressure and a temperature of 300 °C, the propane conversion was measured to be 4.8%, the propylene selectivity was 23.8%, and the propylene yield was 1.1%. Compared with Example 1, the propylene yield of the reaction decreased significantly, indicating that the microwave-assisted coprecipitation process is beneficial to the nucleation of fine particles, thus obtaining highly dispersed Ru nanoclusters.

[0063] Comparative Example 2

[0064] All operations were exactly the same as those in Example 1, except that the induction dispersion process in the microwave reaction tube was replaced with a conventional fixed-bed reactor to remove the microwave effect.

[0065] The prepared catalyst was evaluated for its reaction performance. At atmospheric pressure and a temperature of 300 °C, the propane conversion was measured to be 2.8%, the propylene selectivity was 13.8%, and the propylene yield was 0.4%. Compared with Example 1, the propylene yield and the Ru metal dispersion decreased significantly, indicating that the microwave reduction process is beneficial to the uniform heating of the catalyst, and at the same time, reducing the catalyst while removing moisture may be more beneficial to the dispersion of Ru.

[0066] Comparative Example 3

[0067] All operations were exactly the same as those in Example 1, except that the induction dispersion gas in the microwave reaction tube removed CO and was changed to 80% H2 / Ar.

[0068] The prepared catalyst was evaluated for its reaction performance. At atmospheric pressure and a temperature of 300 °C, the propane conversion was measured to be 14.9%, the propylene selectivity was 11.8%, and the propylene yield was 1.8%. Compared with Example 1, the propylene yield and the Ru metal dispersion decreased significantly, indicating that the presence of oxygen-containing gas enhanced the metal-support interaction, avoided the agglomeration of Ru metal during the reduction process, and was beneficial to maintaining the Ru nanocluster state during the high-temperature reaction process.

[0069] Figure 4Comparing (a) with (b), the Ru nanoparticles obtained by microwave-assisted precipitation are smaller, indicating that the introduction of microwaves plays a crucial role in liquid-phase homogeneous nucleation. This may be related to the uniform heating method of microwaves. The absence of temperature difference results in a more uniform precipitation nucleation process and finer particles. Comparing (a) with (c), it is found that the growth of relatively severe Ru nanocluster species still occurs during the reduction process without microwaves. This may be related to the uniform heating of the wet filter cake by microwaves during the reduction process. When microwaves are not used and only heat conduction is relied on, it will lead to differences in the drying degree inside and outside the filter cake, further prolonging the reduction process and resulting in the growth of Ru nanoclusters. Comparing (a) with (d), it is found that when oxygen-containing gas is not added, the Ru nanoclusters grow significantly, the dispersion decreases, and the activity and selectivity also decrease to some extent. This shows that the presence of oxygen-containing gas during the reduction process increases the metal-support interaction and avoids the growth of Ru nanoclusters.

[0070] Table 1 gives the comparative data of the propane oxidative dehydrogenation reaction performance and catalyst-related properties of the catalysts in Examples 1-10 and Comparative Examples 1-3. It can be found that compared with the comparative examples without microwave-assisted precipitation, microwave atmosphere-induced dispersion, and without adding oxygen-containing gas, all highly dispersed Ru catalysts exhibit better low-temperature propane oxidative dehydrogenation selectivity and propylene yield.

[0071] Table 1 Comparison of Physicochemical Properties of Different Catalysts

[0072] Example 11 Stability Test of Propane Oxidative Dehydrogenation Reaction The ruthenium nanocluster catalysts in Example 1 and Comparative Examples 1-3 above were subjected to a stability test in a fixed-bed reactor (reaction temperature 300 °C, pressure 0.1 MPa, 0.5 g catalyst, space velocity 4000 h -1 ), and the change of activity with reaction time was tested.

[0073] Compared with Comparative Examples 1-3, the 3 wt.% Ru / CeO2 catalyst in Example 1 has higher stability and propylene yield ( Figure 3 ).

[0074] The above are only several embodiments of the present invention and do not constitute any form of limitation to the present invention. Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the technical scope of the present invention, making some changes or modifications using the technical content disclosed above is equivalent to equivalent embodiments and all fall within the technical scope.

Claims

1. A supported ruthenium nanocluster catalyst, comprising an oxide support and an active component ruthenium. The oxide support includes one or more of titanium oxide, cerium oxide, aluminum oxide, and silicon oxide, and the loading of the active component ruthenium is 0.5 - 5%.

2. A method for preparing the supported ruthenium nanocluster catalyst according to claim 1, comprising the following steps: (1) Mix a ruthenium precursor solution and a support precursor solution, then add a dispersant and a pH regulator, react in a microwave reactor, and wash and centrifuge the precipitated product to obtain a wet filter cake. (2) Subject the wet filter cake obtained in step (1) to a reduction treatment in a microwave reaction tube under a reducing atmosphere, and reduce and disperse it by microwave induction to obtain a ruthenium cluster catalyst. The reducing atmosphere includes a reducing gas, an oxygen-containing gas, and a balance gas.

3. The preparation method according to claim 2, characterized in that, The reducing gas includes one or more of CO, CH4, NH3, H2, etc.; the oxygen-containing gas includes one or more of H2O, CO, CH3OH, O2, HCHO, etc.; the balance gas is an inert gas.

4. The preparation method according to claim 2, characterized in that, The volume fraction of the reducing gas is 80 - 95%, the volume fraction of the oxygen-containing gas is 2 - 10%, and the volume fraction of the balance gas is 0 - 18%.

5. The preparation method according to claim 2, characterized in that, The ruthenium precursor is selected from at least one of metal salts, preferably ruthenium chloride, potassium ruthenate, ruthenium acetate, ruthenium nitrate, ruthenium carbonyl, etc.; the support precursor includes sodium silicate and one or more of metal nitrates, chlorides, sulfates, acetates, etc.

6. The preparation method according to claim 2, characterized in that, The dispersant is selected from at least one of polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, sodium hexadecyl benzene sulfonate, sodium dodecyl sulfate, methanol, ethanol, polyacrylamide, etc.

7. The preparation method according to claim 2, characterized in that The molar ratio of the dispersant to Ru atoms is 1:1 - 10:

1.

8. The preparation method according to claim 2, wherein The temperature of the microwave-assisted precipitation reaction is 150 - 250 °C, and the microwave input power is 0.2 - 0.7 kW.

9. The preparation method according to claim 2, characterized in that, The temperature of microwave-induced reduction and dispersion is 300 - 700 °C, and the microwave input power is 0.8 - 2.0 kW.

10. An application of the supported ruthenium nanocluster catalyst according to claim 1 or the supported ruthenium nanocluster catalyst prepared by the preparation method according to any one of claims 2 - 9, wherein the supported ruthenium nanocluster catalyst is used for the oxidative dehydrogenation reaction of propane.

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