A boron nitride-anchored diatomic catalyst, and methods of making and using the same

Abstract

The present application relates to the technical field of catalyst preparation, and discloses a boron nitride-anchored diatomic catalyst and a preparation method and application thereof, and the preparation comprises the following steps: step 1, mixing silica, a boron precursor and a nitrogen precursor, and then performing in-situ pyrolysis reaction to obtain a boron nitride material coated on the surface of silica; step 2, mixing the material and a noble metal dimer precursor in an organic solvent to obtain a product, and then performing centrifugation, washing and drying to obtain a solid powder; and step 3, grinding the solid powder and then performing ozone oxidation treatment to obtain the diatomic catalyst. According to the pyrolysis-coordination anchoring method, a boron nitride coating layer is constructed on the surface of silica, and a noble metal diatomic is precisely loaded, so that the carrier is stabilized, the active site is precisely controlled, and a synergistic catalysis process of the dry reforming of methane and carbon dioxide is realized. When the catalyst is applied to the dry reforming of methane and carbon dioxide, the utilization rate of the noble metal can be improved, and excellent catalytic activity and long-term stability can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, and particularly relates to a boron nitride-anchored diatomic catalyst and a preparation method and application thereof. BACKGROUND

[0002] With the continuous growth of global energy demand and the increasingly serious environmental problems, it is of great significance to develop efficient methane carbon dioxide dry reforming technology. This reaction can convert two greenhouse gases (CH4 and CO2) into synthesis gas (H2 / CO), realizing resource utilization. The metal oxide supported nickel-based catalyst widely used in industry has the advantage of low price, but nickel particles are prone to sintering and carbon deposition during the reaction, resulting in a decrease in catalyst stability. Noble metal catalysts have high low-temperature catalytic activity and stability, but their high price limits their widespread application.

[0003] Compared with traditional nanocatalysts, single-atom catalysts (SACs) have the advantages of relatively uniform active sites, 100% atomic utilization efficiency, and controllable coordination environment, and many other advantages, which can reduce the cost by reducing the noble metal loading and further improve the activity of nanocatalysts.

[0004] CN115532272A discloses a preparation method and application of a NiY rare earth single-atom alloy nanocatalyst, which realizes high conversion rate of the methane dry reforming reaction under relatively mild conditions. Using nickel nitrate and yttrium nitrate as precursors and cerium oxide as a carrier, a highly dispersed and stable supported NiY single-atom alloy catalyst is obtained by a urea deposition precipitation method and further reduction. Studies have shown that Y atoms are dispersed at the atomic level on the surface of the carrier and the metal, and the catalyst has enhanced dual-active-site synergistic catalysis. When applied to the methane dry reforming reaction, it exhibits good catalytic performance and stability, thereby effectively solving the problems of high-temperature sintering and carbon deposition during the reaction, and providing a new method for efficient conversion of methane and carbon dioxide.

[0005] However, the development of SACs in the methane dry reforming reaction still faces challenges: on the one hand, due to the high surface energy of single atoms, they are unstable at high temperatures and tend to agglomerate into larger particles, resulting in reduced catalytic efficiency or carbon deposition, and even catalyst deactivation and inability to continue use. Therefore, although SACs have high atomic efficiency, the overall catalytic stability is not satisfactory. On the other hand, SACs are isolated active sites, usually containing a central metal atom and surrounding non-metal atoms such as O, C or N. It is worth noting that the methane dry reforming reaction usually requires the co-adsorption and activation of both CH4 and CO2 on the catalyst surface, which poses special requirements for the design of the active sites of the catalyst. Traditional single-atom catalysts, due to their isolated active sites, are difficult to achieve the co-adsorption and activation of both reactants, which is an important factor limiting their catalytic performance.

[0006] Double-atom catalysts (DACs) have a wide application prospect in energy conversion due to their unique synergistic and regulatory mechanisms. The special structure of double atoms can improve the metal loading, optimize the adsorption configuration of reactants, change the reaction pathway, and reduce the free energy of the rate-determining step. Especially for reactions with co-adsorption mechanism of reactant molecules, double-atom catalysts can effectively improve the activity and stability of the catalyst. Among them, double-atom catalysts have received extensive attention due to their high catalytic performance, but their general synthesis is to mix metal salts with carrier precursors by mechanical stirring, which has a large randomness.

[0007] CN105268466A discloses a preparation method of a mesoporous molecular sieve catalyst doped with Cu-Ni double atoms. The Cu-Ni double-atom mesoporous molecular sieve catalyst is prepared by ionothermal synthesis. The Cu-Ni double-atom mesoporous molecular sieve catalyst synthesized by the ionothermal synthesis method has high reaction activity and good stability in the carbon dioxide ethanol reaction pot, but still has insufficient effect on the methane dry reforming reaction catalytic process.

[0008] Therefore, there is an urgent need to develop a new catalyst system by designing a carrier structure with stable immobilization effect and developing a preparation method for precisely controlling double-atom active sites to prepare a double-atom catalyst with excellent methane dry reforming reaction performance. SUMMARY

[0009] The present application aims to solve the problems of easy sintering and carbon deposition of noble metal single-atom catalysts and the difficulty in preparing double-atom catalysts in the existing methane carbon dioxide dry reforming reaction, and provides a preparation method of a noble metal double-atom catalyst loaded on a boron nitride coated silica surface. The catalyst has excellent sintering resistance and carbon deposition resistance, high catalytic activity and good stability.

[0010] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is:

[0011] A preparation method of a boron nitride-anchored diatomic catalyst, comprising the steps of:

[0012] Step 1, mixing a nitrogen precursor, a boron precursor and silicon dioxide, and then pyrolyzing in situ to obtain a silicon dioxide surface-coated boron nitride material;

[0013] Step 2, mixing the silicon dioxide surface-coated boron nitride material and a noble metal dimer precursor in an organic solvent to obtain a product, and then centrifuging, washing and drying to obtain a solid powder;

[0014] Step 3, grinding the solid powder and then performing ozone oxidation treatment to obtain the diatomic catalyst.

[0015] The present application realizes the carrier stabilization, active site precise control and the synergistic catalysis process of the dry reforming reaction of methane and carbon dioxide by constructing a boron nitride coating layer on the surface of silicon dioxide and precisely loading noble metal diatomic through pyrolysis-coordination anchoring. The core-shell structure with silicon dioxide as the core and boron nitride as the shell is used as the carrier, the noble metal dimer is anchored through coordination, and the stable diatomic catalyst is obtained through ozone treatment. The catalyst can effectively inhibit the sintering of noble metal and reduce the formation of carbon deposition. Among them, the boron nitride shell layer provides stable anchoring sites, and the diatomic molecules activate methane and carbon dioxide molecules at the same time through synergistic effect, and then efficiently catalyze the reforming reaction. The catalyst applied to the dry reforming reaction of methane and carbon dioxide can not only improve the utilization rate of noble metal, but also obtain excellent catalytic activity and long-term stability.

[0016] The boron precursor includes one or more of boric acid, triethyl borate or polyborosilazane;

[0017] The nitrogen precursor includes one or more of urea, melamine or dicyandiamide;

[0018] The above-mentioned boron source and nitrogen source can form active substances in pyrolysis, and finally generate a boron nitride coating layer.

[0019] The noble metal dimer precursor includes one of dichloro(1,5-cyclooctadiene)rhodium(I) dimer, dichloro(pentamethylcyclopentadienyl)iridium(III) dimer, dichloro(p-methylisopropylphenyl)ruthenium(II) dimer, bis(acetylacetone)dicarbonyl iridium(I) dimer, acetylacetone platinum dimer, and dicarbonyl(acetylacetone)ruthenium(II) dimer;

[0020] The organic solvent includes one or more of tetrahydrofuran, acetone, N,N-dimethylformamide, acetonitrile and 1,4-dioxane.

[0021] The mass ratio of the silicon dioxide, the boron precursor and the nitrogen precursor is 1:1:1 to 1:1:5.

[0022] The mass ratio of the noble metal and the silicon dioxide surface-coated boron nitride material in the noble metal dimer precursor is 1:100-1:500;

[0023] The mass ratio of the organic solvent and the silicon dioxide surface-coated boron nitride material is 100:1-500:1.

[0024] The in-situ pyrolysis reaction temperature is 1000-1200℃, the time is 30-180 min, and the inert gas (nitrogen or argon) environment is used, and the inert gas flow is 20-100 mL·min -1 .

[0025] The mixing in step 2 is carried out at room temperature, and the mixing time is 12-60h.

[0026] After centrifugation in step 2, the organic solvent and methanol are used for washing, and the centrifugation is performed 3-5 times. The drying temperature is 40-100℃, and the time is 6-24h.

[0027] The ozone concentration range during the ozone oxidation treatment is 20-500 ppm; the treatment temperature is at room temperature, and the treatment time is 20-200 min.

[0028] The application also provides a boron nitride-anchored diatomic catalyst prepared by the preparation method. The noble metal diatomic catalyst is a pair of diatomic catalysts dispersed in a monodisperse form on the silicon dioxide surface-coated boron nitride material, and the metals have a synergistic regulation mechanism, which promotes the occurrence of the methane dry reforming reaction.

[0029] The application also provides the application of the diatomic catalyst in catalyzing the methane carbon dioxide dry reforming reaction.

[0030] The process conditions of the methane carbon dioxide dry reforming reaction include: the reaction gas is a mixed gas of one or more of methane, carbon dioxide and nitrogen, the total speed of the reaction gas is 45-210 mL·min -1 ; the reaction temperature is 500-900℃; the reaction time is 0.5-2h; and the volume space velocity of the diatomic catalyst is 54000-252000 mL·g -1 ·h -1 .

[0031] Compared with the prior art, the application has the following beneficial effects:

[0032] (1) The noble metal diatomic catalyst of the application breaks through the loading limit and inherent activity limit of the monatomic catalyst through the synergistic effect of the diatomic catalyst, and the diatomic structure of the catalyst is relatively uniform, which not only significantly improves the catalytic activity, but also is beneficial to the clear structure-activity relationship.

[0033] (2) The preparation method of the precious metal diatomic catalyst has a simple process, and the prepared catalyst has excellent universality and anti-interference ability;

[0034] (3) The precious metal diatomic catalyst applied to the dry reforming of methane and carbon dioxide to synthesize synthesis gas can effectively avoid excessive coupling of C-C bonds, greatly improve the catalytic activity, stability and anti-coking ability, and reduce the application cost of the precious metal catalyst, which is a sustainable development path. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The infrared spectrum curves of the original silicon dioxide SiO2, boron nitride BN, the prepared silicon dioxide surface coated boron nitride material SiO2@BN, the ruthenium dimer precursor and the silicon dioxide surface coated boron nitride material loaded with the ruthenium diatomic catalyst Ru2 / SiO2@BN in Example 1.

[0036] Figure 2 The transmission electron microscope image of the precious metal diatomic catalyst Ru2 / SiO2@BN prepared by loading the silicon dioxide surface coated boron nitride in Example 1.

[0037] Figure 3 The spherical aberration correction transmission electron microscope image of the precious metal diatomic catalyst Ru2 / SiO2@BN prepared by loading the silicon dioxide surface coated boron nitride in Example 1, Figure 3 a in the middle, Figure 3 b in the middle, Figure 3 c in the middle are respectively selected from different regions of the catalyst surface having a typical diatomic pair, and the diatomic pair is marked with a red square. Figure 3 d in the middle is a statistical distribution of the Ru-Ru distance in the Ru diatomic based on the images of a-c.

[0038] Figure 4 The X-ray photoelectron spectrogram of the precious metal diatomic catalyst Ru2 / SiO2@BN prepared by loading the silicon dioxide surface coated boron nitride in Example 1.

[0039] Figure 5 The change of the conversion rate of methane and carbon dioxide with the reaction temperature of the precious metal diatomic catalyst Ru2 / SiO2@BN prepared by loading the silicon dioxide surface coated boron nitride in Example 1.

[0040] Figure 6 The methane conversion rate temperature data of the precious metal diatomic catalyst prepared by loading the silicon dioxide surface coated boron nitride in Examples 1-5. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. Any modification or equivalent replacement made by those skilled in the art based on the technical solutions of the present application without departing from the spirit and scope of the present application should be covered within the protection scope of the present application.

[0042] The reagents used in the embodiments of the present application can be purchased by marketable means, except for special provisions.

[0043] Example 1

[0044] a. A balance is used to weigh 0.93 g of urea, 0.31 g of boric acid and 0.31 g of nano-silicon dioxide, which are mixed and then placed in a ceramic boat; the ceramic boat loaded with the mixture is placed in the reaction zone of a tube furnace, and the tube furnace is sealed by connecting the two ends of the tube furnace with air tubes, respectively; 100 mL·min -1 of gas flow is introduced into the tube furnace for 10 min, and the air in the tube furnace is exhausted at normal pressure; the flow of inert gas is adjusted to 40 mL·min -1 , the tube furnace is started, the temperature of the reaction zone of the tube furnace is raised to 1100℃, and the temperature is kept at 1100℃ for 60 min; the tube furnace is turned off, the flow of inert gas in the tube furnace is kept at 40 mL·min -1 , and the tube furnace is naturally cooled to room temperature; then the ceramic boat is taken out, and a silicon dioxide surface coated with boron nitride material is obtained;

[0045] b. 7.6 mg of ruthenium precursor (dichloro(p-methylisopropylphenyl) ruthenium (II) dimer) and 500 mg of silicon dioxide surface coated with boron nitride material are dissolved in 50 g of N,N-dimethylformamide, and after continuous stirring at room temperature for about 24 hours, centrifugation is performed and the supernatant is discarded; the obtained precipitate is washed with N,N-dimethylformamide and methanol, and then transferred to an oven at 60℃ for drying for 12 h, and the solid powder is fully ground;

[0046] c. A balance is used to weigh 50 mg of the above solid powder and uniformly disperse it in a quartz reaction boat; the quartz boat loaded with the catalyst is placed in a reactor, 200 ppm ozone mixed gas (prepared by high-purity oxygen through an ozone generator) is introduced at room temperature for 30 min, and the flow of ozone mixed gas is 50 mL·min -1 ; the ozone introduction is stopped, and high-purity nitrogen gas is switched to purge for 1 h to remove residual ozone; then the quartz boat is taken out and washed with anhydrous ethanol solution and ultrapure water for 3 times, the precipitate is collected by centrifugation, and dried at 60℃ under vacuum conditions for 6 hours to obtain a stable ruthenium diatomic catalyst.

[0047] The catalyst experiment test analysis is as follows:

[0048] The microstructure of the ruthenium bimetallic catalyst supported on the prepared silicon dioxide surface coated boron nitride material in Example 1 was observed, and the catalyst was characterized by infrared spectroscopy, transmission electron microscopy, spherical aberration electron microscopy, and X-ray photoelectron spectroscopy, as shown in Figures 1-4 .

[0049] Figure 1 The infrared spectroscopy curves of the original silicon dioxide SiO2, boron nitride BN, the prepared silicon dioxide surface coated boron nitride material SiO2@BN, the ruthenium dimer precursor, and the ruthenium bimetallic catalyst Ru2 / SiO2@BN supported on the prepared silicon dioxide surface coated boron nitride material in Example 1 are shown. It can be seen that the boron nitride is successfully coated on the surface of the silicon dioxide, and the ligand is successfully removed after the ruthenium dimer precursor is supported on the surface of the silicon dioxide surface coated boron nitride material.

[0050] Figure 2 The transmission electron microscopy graph of the ruthenium bimetallic catalyst supported on the prepared silicon dioxide surface coated boron nitride material in Example 1 is shown. It can be seen that the boron nitride is uniformly coated on the surface of the silicon dioxide, and the ruthenium is successfully supported on the surface of the silicon dioxide surface coated boron nitride material.

[0051] Figure 3 The spherical aberration corrected transmission electron microscopy graph of the noble metal bimetallic catalyst supported on the prepared silicon dioxide surface coated boron nitride material in Example 1 is shown. Figure 3 a, Figure 3 b, Figure 3 c in the figure are different regions selected from the surface of the catalyst having typical bimetallic pairs, and the bimetallic pairs are marked with red boxes. Figure 3 d in the figure is the statistical distribution of the Ru-Ru distance in the Ru bimetallic pair based on the images a-c. It can be seen that most of the ruthenium atoms are supported on the surface of the silicon dioxide surface coated boron nitride material in the form of bimetallic pairs, and the distance between the paired metal atoms is about 0.31 nm.

[0052] Figure 4 The X-ray photoelectron spectroscopy graph of the ruthenium in the ruthenium dimer precursor and the ruthenium bimetallic catalyst supported on the prepared silicon dioxide surface coated boron nitride material in Example 1 is shown. It can be seen that the ratio of Ru &+ and Ru 2+ in the ruthenium bimetallic catalyst supported on the prepared silicon dioxide surface coated boron nitride material is 0.76.

[0053] The catalyst performance evaluation is as follows:

[0054] The catalyst is in a fixed bed mode using a gas chromatography detection system. 50 mg of catalyst with a particle size of 40-60 mesh and 0.5 g of silicon carbide are placed in a fixed bed quartz tube reactor for catalyst performance testing. The reaction atmosphere is a mixture of CH4, CO2 and N2, the flow rates of CH4 and CO2 are both 25 mL / min, and the flow rate of N2 is 75 mL / min. The baseline is run at room temperature, then switched to N2 to warm up to the target temperature, and finally switched to the reaction gas. The activity test temperature range is 550-700°C.

[0055] Figure 5 The conversion rates of methane and carbon dioxide of the noble metal diatomic catalyst prepared by coating boron nitride on the surface of the silica prepared in Example 1 vary with the reaction temperature. The results show that the conversion rate of CH4 reaches 72% at 650°C, and the conversion rate of CO2 can reach 79%.

[0056] Example 2

[0057] a. The boron nitride-coated silica material is prepared according to the scheme of Example 1;

[0058] b. 6.0 mg of rhodium precursor (dichloro(1,5-cyclooctadiene)rhodium(I) dimer) and 500 mg of boron nitride-coated silica material are dissolved in 50 g of N,N-dimethylformamide. After continuous stirring for about 24 hours, centrifugation is performed and the supernatant is discarded. The obtained precipitate is washed with N,N-dimethylformamide and methanol, then transferred to an oven at 60°C for drying for 12 h, and the solid powder is thoroughly ground;

[0059] c. The stable rhodium diatomic catalyst is obtained according to the scheme of Example 1.

[0060] The above catalyst performance evaluation: the catalyst is tested for methane carbon dioxide dry reforming reaction performance according to the scheme of Example 1. The activity test temperature range is 550-700°C. The results show that the conversion rate of CH4 finally stabilizes at 62% at 650°C, and the conversion rate of CO2 can reach 69%.

[0061] Example 3

[0062] a. The boron nitride-coated silica material is prepared according to the scheme of Example 1;

[0063] b. 5.2 mg of iridium precursor (dichloro(pentamethylcyclopentadienyl)iridium(III) dimer) and 500 mg of boron nitride-coated silica material are dissolved in 50 g of N,N-dimethylformamide. After continuous stirring for about 24 hours, centrifugation is performed and the supernatant is discarded. The obtained precipitate is washed with N,N-dimethylformamide and methanol, then transferred to an oven at 60°C for drying for 12 h, and the solid powder is thoroughly ground;

[0064] c. Stable platinum diatomic catalyst was obtained following the procedure of Example 1.

[0065] The catalyst performance evaluation: The catalyst was tested for the dry reforming of methane to synthesis gas following the procedure of Example 1. The activity test temperature range was 550-700 °C. The results showed that the CH4conversion rate was stabilized at 32% and the CO2conversion rate was up to 40% at 650 °C.

[0066] Example 4

[0067] a. The silica surface coated boron nitride material was prepared following the procedure of Example 1.

[0068] b. 5.0 mg of platinum precursor (platinum acetylacetonate dimer) and 500 mg of the silica surface coated boron nitride material were dissolved in 50 g of N,N-dimethylformamide. After continuous stirring for about 24 hours, the supernatant was discarded by centrifugation and the obtained precipitate was washed with N,N-dimethylformamide and methanol, then transferred to an oven at 60 °C for drying for 12 h, and the solid powder was thoroughly ground;

[0069] c. Stable platinum diatomic catalyst was obtained following the procedure of Example 1.

[0070] The catalyst performance evaluation: The catalyst was tested for the dry reforming of methane to synthesis gas following the procedure of Example 1. The activity test temperature range was 550-700 °C. The results showed that the CH4conversion rate was stabilized at 32% and the CO2conversion rate was up to 40% at 650 °C.

[0071] Example 5

[0072] a. The silica surface coated boron nitride material was prepared following the procedure of Example 1.

[0073] b. 6.4 mg of ruthenium precursor (dichloro(acetylacetonate)ruthenium(II) dimer) and 500 mg of the silica surface coated boron nitride material were dissolved in 50 g of N,N-dimethylformamide. After continuous stirring for about 24 hours, the supernatant was discarded by centrifugation and the obtained precipitate was washed with N,N-dimethylformamide and methanol, then transferred to an oven at 60 °C for drying for 12 h, and the solid powder was thoroughly ground;

[0074] c. Stable ruthenium diatomic catalyst was obtained following the procedure of Example 1.

[0075] The catalyst performance evaluation:

[0076] The catalyst was tested for dry methane carbon dioxide reforming reaction performance according to the scheme of Example 1. The activity test temperature range was 550-700℃. The results showed that CH4conversion rate was finally stabilized at 49% and CO2conversion rate could reach 60% at 650℃.

[0077] Comparative Example 1

[0078] a. The boron nitride coated silica material was prepared according to the scheme of Example 1;

[0079] b. 200mg of the boron nitride coated silica material was dispersed in 50mL of deionized water, oscillated in an ultrasonic cleaner, and stirred with a glass rod in a beaker. Then, the Ir precursor (IrCl3) was dissolved in water to prepare a solution with a concentration of 12mmol / L, and then 0.44mL of the solution was added dropwise into the above deionized water containing the carrier material using a micropipette; after continuous stirring for about 12 hours, the product was centrifuged, the supernatant was discarded, and then transferred to a 60℃ oven for drying for 12h. Subsequently, the prepared powder was treated at 150℃ for 2 hours under a nitrogen atmosphere to obtain a boron nitride coated silica supported monatomic catalyst.

[0080] The catalyst performance evaluation: the catalyst was tested for dry methane carbon dioxide reforming reaction performance according to the scheme of Example 1. The activity test temperature range was 550-700℃. The results showed that CH4conversion rate was finally stabilized at 28% and CO2conversion rate could reach 37% at 650℃.

[0081] Comparative Example 2

[0082] a. 200mg of the silica material was dispersed in 50mL of deionized water, oscillated in an ultrasonic cleaner, and stirred with a glass rod in a beaker. Then, the Ir precursor (IrCl3) was dissolved in water to prepare a solution with a concentration of 12mmol / L, and then 0.44mL of the solution was added dropwise into the above deionized water containing the carrier material using a micropipette; after continuous stirring for about 12 hours, the product was centrifuged, the supernatant was discarded, and then transferred to a 60℃ oven for drying for 12h. Subsequently, the prepared powder was treated at 150℃ for 2 hours under a nitrogen atmosphere to obtain a silica supported monatomic catalyst.

[0083] The catalyst performance evaluation: the catalyst was tested for dry methane carbon dioxide reforming reaction performance according to the scheme of Example 1. The activity test temperature range was 550-700℃. The results showed that CH4conversion rate was finally stabilized at 28% and CO2conversion rate could reach 37% at 650℃.

[0084] Comparative Example 3

[0085] a. The same procedure as Example 1 was used, but without adding the silica, to produce a boron nitride material;

[0086] b. 200 mg of the boron nitride material was dispersed in 50 mL of deionized water, and was oscillated in an ultrasonic cleaner and stirred in a beaker with a glass rod. Subsequently, an Ir precursor (IrCl3) was dissolved in water to prepare a solution with a concentration of 12 mmol / L, and then 0.44 mL of the solution was added dropwise into the deionized water containing the carrier material using a micropipette; after continuous stirring for about 12 hours, the product was centrifuged, the supernatant was discarded, and then was transferred to an oven at 60°C for drying for 12 h. Subsequently, the prepared powder was treated at 150°C for 2 hours under a nitrogen atmosphere to obtain a boron nitride supported monatomic catalyst.

[0087] The catalyst performance evaluation: the catalyst was tested for the dry reforming of methane and carbon dioxide according to the procedure of Example 1. The activity test temperature range was 550-700°C. The results showed that the CH4conversion rate was finally stabilized at 12% and the CO2conversion rate was up to 21% at 650°C. It can be seen that the catalyst without silica and the carrier core has insufficient catalytic performance and stability.

[0088] As can be seen from the examples, the silica surface coated with boron nitride and loaded with a noble metal double-atom catalyst according to the present application has good activity in the dry reforming of methane and carbon dioxide. In addition, Figure 6 The change of the CH4conversion rate with the reaction time for the silica surface coated with boron nitride and loaded with a noble metal double-atom catalyst prepared in Examples 1-5. The results showed that the above examples all maintained stable catalytic activity in the 50 h stability test, and the catalytic properties were stable.

[0089] The above is only a few examples of the present application, and does not limit the present application in any form. Although the present application is disclosed with preferred examples, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the disclosed technical content without departing from the scope of the technical solution of the present application, and such changes or modifications are equivalent to equivalent embodiments, and are within the scope of the technical solution.

Claims

1. A method for preparing a boron nitride-anchored diatomic catalyst, characterized in that, Including the following steps: Step 1: After mixing nitrogen precursor, boron precursor and silicon dioxide, the mixture undergoes in-situ pyrolysis reaction to obtain a silicon dioxide surface coated with boron nitride material. Step 2: The boron nitride material coated on the surface of silica and the noble metal dimer precursor are mixed in an organic solvent to obtain a solid powder after centrifugation, washing and drying. Step 3: The solid powder is ground and then subjected to ozone oxidation treatment to obtain the diatomic catalyst; The noble metal dimer precursor includes one of the following: dichloro(1,5-cyclooctadiene)rhodium(I) dimer, dichloro(pentamethylcyclopentadienyl)iridium(III) dimer, dichloro(p-methylisopropylphenyl)ruthenium(II) dimer, and acetylacetone platinum dimer.

2. The method for preparing the boron nitride-anchored diatomic catalyst according to claim 1, characterized in that, The boron precursor includes one or more of boric acid, triethyl borate, or polyborosilicate; And / or, the nitrogen precursor includes one or more of urea, melamine, or dicyandiamide; And / or, the organic solvent includes one or more of tetrahydrofuran, acetone, N,N-dimethylformamide, acetonitrile, and 1,4-dioxane.

3. The method for preparing the boron nitride-anchored diatomic catalyst according to claim 1, characterized in that, The mass ratio of silicon dioxide, boron precursor, and nitrogen precursor is 1:1:1 to 1:1:

5.

4. The method for preparing the boron nitride-anchored diatomic catalyst according to claim 1, characterized in that, The mass ratio of the noble metal and the boron nitride material coated on the surface of silicon dioxide in the noble metal dimer precursor is 1:100~1:500; And / or, the mass ratio of the organic solvent to the boron nitride material coated on the silica surface is 100:1 to 500:

1.

5. The method for preparing the boron nitride-anchored diatomic catalyst according to claim 1, characterized in that, The in-situ pyrolysis reaction is carried out at a temperature of 1000~1200℃ for 30~180 min in an inert gas environment.

6. The method for preparing the boron nitride-anchored diatomic catalyst according to claim 1, characterized in that, In step 2, the mixing is carried out at room temperature for 12 to 60 hours.

7. The method for preparing the boron nitride-anchored diatomic catalyst according to claim 1, characterized in that, The ozone concentration range during the ozone oxidation treatment is 20~500 ppm; the treatment temperature is room temperature; and the treatment time is 20~200 min.

8. A boron nitride-anchored diatomic catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the diatomic catalyst according to claim 8 in the catalytic dry reforming reaction of methane and carbon dioxide.

10. The application according to claim 9, characterized in that, The process conditions for the methane-carbon dioxide dry reforming reaction include: the reaction gas is a mixture of methane, carbon dioxide, and nitrogen, and the total reaction gas velocity is 45~210 mL·min. -1 The reaction temperature is 500~900℃; the reaction time is 0.5~2h; and the volume hourly space velocity of the diatomic catalyst is 54000~252000mL·g. -1 ·h -1 .

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