A catalyst, its preparation method and application

Abstract

The application provides a catalyst and a preparation method and application thereof, relates to the technical field of catalysts, and comprises the following steps: (1) dispersing carbon nanospheres in a solvent, then adding tetrabutyl titanate and an ethanol aqueous solution, uniformly mixing, obtaining titanium dioxide coated carbon nanospheres, and through calcination, obtaining titanium dioxide hollow spheres; (2) dispersing the titanium dioxide hollow spheres in a solvent, adding silica nanoparticles, uniformly mixing, obtaining silica coated hollow spheres, and through calcination, obtaining a carrier; (3) immersing the carrier in a mixed solution containing chloroplatinic acid and nickel nitrate, obtaining a precursor solution; after the precursor solution is sequentially subjected to filtration, drying and a reduction reaction, the catalyst is obtained; and the mass ratio of Pt to Ni in the mixed solution is (1-2):(1-2). The catalyst provided by the scheme can reduce the cracking temperature in the cracking process of polysilane, further shorten the reaction time, and has low catalyst cost and good stability.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a catalyst, its preparation method, and its application. Background Technology

[0002] Ceramic precursors are crucial for the preparation of continuous ceramic fibers, and their properties play a decisive role in the quality of the ceramic fibers. Currently, in industry, ceramic precursors are mainly prepared through the cracking reaction of polysilanes under the action of a catalyst, and the performance of the catalyst has a vital impact on the reaction efficiency and the quality of the product.

[0003] While traditional single catalysts exhibit some activity in the preparation of ceramic precursors from polysilane pyrolysis, their high cost significantly increases production costs, limiting their large-scale application. Furthermore, achieving acceptable reaction rates and product yields often requires high reaction temperatures when using single catalysts, leading to high energy consumption and potential side reactions that reduce product quality. Moreover, traditional catalysts are prone to carbon buildup during the reaction, resulting in rapid deactivation and short lifespan. Additionally, traditional catalysts struggle to rapidly promote polysilane pyrolysis at lower temperatures, resulting in long reaction times, low production efficiency, and consequently, lower product yields and quality.

[0004] Chinese patent CN102585235A discloses a catalytic synthesis method for polycarbosilane precursors, which prepares polycarbosilanes by adding metal oxides (such as alumina, titanium oxide) or composite oxides of silicon oxide and metal oxides (such as aluminum silicate, titanium silicate, or aluminum silicate). However, the reaction still requires a temperature of 460°C, and the yield is only 61.7%. Therefore, there is an urgent need for a catalyst, its preparation method, and its application. Summary of the Invention

[0005] This invention provides a catalyst, its preparation method, and its application. The catalyst can reduce the pyrolysis temperature and further shorten the reaction time during the pyrolysis of polysilanes. Moreover, the catalyst has low cost and good stability.

[0006] In a first aspect, embodiments of the present invention provide a method for preparing a catalyst, comprising:

[0007] (1) Disperse carbon nanospheres in a solvent, then add tetrabutyl titanate and an aqueous ethanol solution and mix well to obtain titanium dioxide-coated carbon nanospheres; and calcine the titanium dioxide-coated carbon nanospheres to obtain hollow titanium dioxide spheres.

[0008] (2) Disperse the titanium dioxide hollow spheres in the solvent and add silica nanoparticles to mix evenly to obtain silica-coated hollow spheres; and calcine the silica-coated hollow spheres to obtain a carrier;

[0009] (3) The carrier is immersed in a mixed solution containing chloroplatinic acid and nickel nitrate to obtain a precursor solution; the precursor solution is filtered, dried and reduced in sequence to obtain the catalyst; wherein the mass ratio of Pt to Ni in the mixed solution is (1~2):(1~2).

[0010] Preferably, the carbon nanospheres have a particle size of 80~120 nm.

[0011] Preferably, the particle size of the silica nanoparticles is 10~30nm.

[0012] Preferably, in step (1), the mixing temperature is 50~70℃; the calcination temperature is 400~600℃, and the time is 2~3h.

[0013] Preferably, in step (2), the mixing is performed by ultrasonic treatment, the power density of the ultrasonic treatment is 300~500w; the calcination temperature is 400~600℃, and the time is 4~6h.

[0014] Preferably, the ratio of the carbon nanospheres to the tetrabutyl titanate is 100 mg: (8 mL to 10 mL).

[0015] Preferably, the mass ratio of the hollow titanium dioxide spheres to the silicon dioxide nanoparticles is (1~10):(1~10).

[0016] Preferably, the mass ratio of Pt to Ni in the mixed solution is 2:1.

[0017] Preferably, in step (3), the reduction reaction is carried out at 400~500℃ for 1~2h in a hydrogen atmosphere; the hydrogen atmosphere includes a mixture of hydrogen and argon or a mixture of hydrogen and nitrogen, and the volume fraction of hydrogen in the mixture is 20~30%.

[0018] In a second aspect, embodiments of the present invention provide a catalyst prepared by any of the preparation methods of the first aspect described above. The catalyst comprises, from the inside out, hollow titanium dioxide spheres, a silicon dioxide intermediate layer, and an active outer layer; the mass ratio of the hollow titanium dioxide spheres to the silicon dioxide intermediate layer is (1~10):(1~10); the active outer layer comprises Pt and Ni.

[0019] Preferably, the active outer layer accounts for 1 wt% to 2 wt% of the catalyst.

[0020] Preferably, the mass ratio of the hollow titanium dioxide spheres to the silicon dioxide intermediate layer is 5:1.

[0021] Thirdly, the present invention also provides an application of the catalyst described in the second aspect above, wherein the catalyst is used to prepare ceramic precursors from polysilanes by pyrolysis.

[0022] Preferably, the amount of catalyst used is 0.5wt% to 1wt% of the amount of polysilane used.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] (1) The catalyst of the present invention is a TiO2-SiO2 bioxide support with a hollow structure and active components loaded on its surface. This hollow core-shell nanostructure has better mass transfer and charge separation efficiency, larger surface area, and a three-dimensional heterogeneous structure than the same weight of bulk form, thus improving the catalyst's reactivity and efficiency. Among them, SiO2, as a composite material of TiO2 hollow spheres, further improves the thermal stability, mechanical strength, and surface area of ​​TiO2 hollow spheres. On the other hand, the synergistic effect between Pt-Ni bimetal optimizes the catalytic ability of the reactants. Thus, the hollow TiO2-SiO2 bioxide support and Pt-Ni bimetal work together to enable polysilane to rapidly decompose at a temperature lower than that required by traditional platinum-based catalysts, greatly shortening the reaction time and improving production efficiency.

[0025] (2) The catalyst of the present invention adopts a Pt-Ni bimetallic system. Compared with the traditional single catalyst, it reduces the amount of precious metals while ensuring catalytic performance, thereby significantly reducing the cost of the catalyst. At the same time, the active outer layer is obtained by impregnation method, which further reduces the cost of large-scale production of ceramic precursors.

[0026] (3) In this invention, the hollow TiO2-SiO2 double oxide support also has excellent thermal stability and anti-carbon deposition performance, which effectively inhibits the carbon deposition phenomenon of the catalyst during the polysilane cracking process, maintains the activity of the catalyst, and further ensures that the cracking reaction can continue to proceed efficiently, thereby improving the final yield of the product. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The following is the concept of the present invention, which provides a method for preparing a catalyst, comprising:

[0029] (1) Disperse carbon nanospheres in a solvent, then add tetrabutyl titanate and an aqueous ethanol solution and mix well to obtain titanium dioxide-coated carbon nanospheres; and calcine the titanium dioxide-coated carbon nanospheres to obtain hollow titanium dioxide spheres.

[0030] (2) Disperse titanium dioxide hollow spheres in a solvent and add silica nanoparticles to mix them to obtain silica-coated hollow spheres; then calcine the silica-coated hollow spheres to obtain a carrier;

[0031] (3) The support is immersed in a mixed solution containing chloroplatinic acid and nickel nitrate to obtain a precursor solution; the precursor solution is filtered, dried and reduced in sequence to obtain a catalyst; wherein the mass ratio of Pt to Ni in the mixed solution is (1~2):(1~2).

[0032] For (1~2): (1~2), it can be any value from 1:2 to 2:1, for example, it can be 1:1, 1:1.5, 1:2, 1.5:1, 1.5:2, 2:1.5 or 2:1.

[0033] The catalyst provided by this invention is a hollow TiO2-SiO2 bioxide support with active components loaded on its surface. This hollow core-shell nanostructure exhibits better mass transfer and charge separation efficiency, a larger surface area, and a three-dimensional heterogeneous structure compared to bulk forms of the same weight, thus improving the catalyst's reactivity and efficiency. SiO2, as a composite material for the hollow TiO2 spheres, further enhances the thermal stability, mechanical strength, and surface area of ​​the TiO2 hollow spheres. Furthermore, the synergistic effect between the Pt-Ni bimetal optimizes the catalytic activity towards the reactants. Thus, the combined action of the hollow TiO2-SiO2 bioxide support and the Pt-Ni bimetal enables rapid decomposition of polysilanes at temperatures lower than those required by traditional platinum-based catalysts, significantly shortening the reaction time and improving production efficiency.

[0034] In this invention, the hollow TiO2-SiO2 double oxide support also has excellent thermal stability and anti-carbon deposition properties, which effectively inhibits the carbon deposition phenomenon of the catalyst during the polysilane cracking process, maintains the activity of the catalyst, and further ensures that the cracking reaction can continue to proceed efficiently, thereby improving the final yield of the ceramic precursor.

[0035] In this invention, the process of preparing ceramic precursors by polysilane pyrolysis includes a multi-step reaction of Si-H bond activation, C-Si bond breaking and chain rearrangement. By limiting the ratio of Pt and Ni in the mixed solution during impregnation in step (3), the loading of Pt and Ni on the active outer layer of the catalyst can be further determined, thereby achieving synergy of the multi-step reaction. If the mass ratio of Pt to Ni in the mixed solution is less than 1:2, and the amount of Ni is too large, there will be too much Ni on the active outer layer of the catalyst. The C atoms generated by the pyrolysis of polysilane will be adsorbed on the Ni surface, causing excessive adsorption and affecting chain rearrangement. At the same time, carbon deposition will also cause the metal active sites to be obscured, resulting in a decrease in catalytic efficiency. Moreover, Ni has a strong ability to break C-Si bonds. Too much Ni may cause excessive breaking of C-Si bonds to generate small molecule byproducts, reducing the yield and purity of the ceramic precursor. If the mass ratio of Pt to Ni in the mixed solution is greater than 2:1, insufficient Ni will result in too little Ni in the active outer layer of the catalyst, leading to insufficient active sites for C-Si bond breaking and reduced production efficiency. Conversely, a relatively high amount of Pt will result in excessive Pt cost without a significant improvement in catalytic performance. Furthermore, a relatively high Pt content may cause activated Si-H bonds to form Si-Si bonds through self-coupling due to the lack of C-Si breaking fragments, which severely degrades the mechanical strength of the ceramic precursor. Therefore, this invention achieves functional synergy between Pt and Ni by controlling the mass ratio, ensuring effective C-Si bond breaking while avoiding excessive breaking and carbon deposition, thus guaranteeing the yield, purity, and thermal stability of the ceramic precursor. Compared to traditional single catalysts, this invention reduces the amount of precious metals used while maintaining catalytic performance, thereby significantly lowering catalyst costs and meeting industrial application requirements.

[0036] In a preferred embodiment, the carbon nanospheres have a particle size of 80-120 nm (e.g., 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm or 120 nm).

[0037] In this invention, the hollow size of titanium dioxide hollow spheres is controlled by controlling the particle size of carbon nanospheres. This avoids the hollow size from being too large, which could lead to the collapse of the hollow structure or the overly dispersed distribution of active sites, while also preventing the raw material diffusion from being hindered and affecting production efficiency if the hollow size is too small.

[0038] In a preferred embodiment, the particle size of the silica nanoparticles is 10-30 nm (e.g., 10 nm, 15 nm, 20 nm, 25 nm or 30 nm).

[0039] In this invention, experiments have confirmed that if the silica nanoparticles are smaller than 10 nm, the pores of the intermediate layer formed by the accumulation of silica nanoparticles are too narrow and the specific surface area is too high, which increases the mass transfer resistance and thus reduces the catalytic efficiency. At the same time, the high hydroxyl density on the surface of the intermediate layer leads to an imbalance between hydrophilicity and hydrophobicity, affecting the catalytic performance. If the silica nanoparticles are larger than 30 nm, the pores of the intermediate layer formed by the accumulation of silica nanoparticles are too wide and the specific surface area is low, resulting in uneven mass transfer and insufficient loading of active sites. At the same time, the weak interparticle bonding leads to a loose intermediate layer structure, resulting in insufficient thermal stability of the catalyst, and thus the prepared catalyst has poor performance.

[0040] It should be noted that the particle size of carbon nanospheres and silica nanoparticles refers to the median particle size, also known as D50.

[0041] In a preferred embodiment, in step (1), the mixing temperature is 50~70℃ (e.g., 50℃, 55℃, 60℃, 65℃ or 70℃); the calcination temperature is 400~600℃ (e.g., 400℃, 450℃, 500℃, 550℃ or 600℃); and the time is 2~3h (e.g., 2h, 2.5h or 3h).

[0042] It should be noted that the volume ratio of anhydrous ethanol to water in the ethanol-water solution is (3~5):1 (for example, it can be 3:1, 3.5:1, 4:1, 4.5:1 or 5:1).

[0043] Specifically, carbon nanospheres are dispersed in a solvent (anhydrous ethanol) and ultrasonically dispersed uniformly. Then, while magnetically stirring, tetrabutyl titanate (TBOT) is slowly added dropwise at a rate of 2-4 mL / min (e.g., 2 mL / min, 2.5 mL / min, 3 mL / min, 3.5 mL / min, or 4 mL / min). Next, an aqueous ethanol solution is added dropwise to the above solution at a rate of 1-3 mL / min (e.g., 1 mL / min, 1.5 mL / min, 2 mL / min, 2.5 mL / min, or 3 mL / min). The mixture is then stirred at 250 rpm / min for 3 h at 50-70 °C to allow TBOT to adsorb onto the surface of the carbon nanospheres and hydrolyze. The volume ratio of the aqueous ethanol solution to TBOT is (6-8):1 (e.g., 6:1, 6.5:1, 7:1, 7.5:1, or 8:1). After the reaction is complete, the solution is filtered and dried to obtain titanium dioxide-coated carbon nanospheres. Titanium dioxide-coated carbon nanospheres were placed in a muffle furnace and calcined at 400-600℃ for 2-3 hours to remove the core layer of the carbon nanospheres, resulting in hollow titanium dioxide spheres.

[0044] In this invention, by controlling the dropping rate of tetrabutyl titanate, the dropping rate of the ethanol-water solution, the amount of ethanol-water solution used, and the volume ratio of water in the ethanol-water solution, it is possible to avoid a sudden increase in local TBOT concentration when the dropping rate of tetrabutyl titanate is too fast, which would cause the concentration to far exceed the adsorption capacity of the carbon nanospheres. Unadsorbed TBOT would then directly hydrolyze and aggregate in the solution, forming large-diameter TiO2 particles. Simultaneously, it avoids situations where the dropping rate of the ethanol-water solution is too fast or the water content in the system is too high, resulting in excessively rapid hydrolysis of TBOT and the hydrolysis products (Ti(OH)4) not having enough time to adhere to the carbon nanosphere surface, thus self-aggregating into large-diameter TiO2 particles. It also avoids situations where the dropping rate of the ethanol-water solution is too slow or the water content in the system is too low, resulting in incomplete hydrolysis of TBOT, discontinuous TiO2 coating, and subsequent calcination easily forming broken particles, leading to uneven particle size and affecting catalyst performance.

[0045] In this invention, by limiting the relevant parameters in the preparation process of titanium dioxide-coated carbon nanospheres, the titanium dioxide coated on the carbon nanospheres has an excellent specific surface area and exposes more catalytic active sites, thereby improving catalytic efficiency. This avoids the problem that excessively small titanium dioxide size can lead to an excessively strong quantum size effect, increasing the probability of electron-hole recombination, and also avoids the problem that excessively small titanium dioxide size can easily lead to agglomeration and a sharp drop in specific surface area.

[0046] In a preferred embodiment, the ratio of carbon nanospheres to tetrabutyl titanate is 100 mg: (8 mL to 10 mL) (for example, it can be 100 mg: 8 mL, 100 mg: 8.5 mL, 100 mg: 9 mL, 100 mg: 9.5 mL or 100 mg: 10 mL).

[0047] In this invention, experiments have confirmed that if the amount of tetrabutyl titanate is too high, it will cause TiO2 to self-aggregate and form large-diameter particles, affecting catalytic performance. If the amount of tetrabutyl titanate is too low, it will cause the TiO2 coating layer to be discontinuous, and subsequent calcination will easily form broken particles, resulting in uneven particle size and affecting catalyst performance.

[0048] In a preferred embodiment, in step (2), the mixing is performed by ultrasonic treatment, the power density of which is 300~500W (e.g., 300W, 350W, 400W, 450W or 500W); the calcination temperature is 400~600℃ (e.g., 400℃, 450℃, 500℃, 550℃ or 600℃), and the time is 4~6h (e.g., 4h, 4.5h, 5h, 5.5h or 6h).

[0049] In this invention, in order to ensure that the silica nanoparticles can be uniformly coated on the surface of the titanium dioxide hollow spheres and to avoid damaging the hollow structure of the titanium dioxide hollow spheres, the ultrasonic processing power density is limited to 300~500w.

[0050] In a preferred embodiment, the mass ratio of titanium dioxide hollow spheres to silicon dioxide nanoparticles is (1~10):(1~10) (for example, it can be 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 2:3, 2:5, 2:7, 2:9, 3:1, 3:2, 3:4, 3:8, 4:1, 4:3, 4:7, 4:9, 5:1, 5:2, 5:3, 5:9, 6:1, 6:9, 7:1, 7:9, 8:1, 8:9, 9:1 or 10:1).

[0051] In a more preferred embodiment, the mass ratio of Pt to Ni in the mixed solution is 2:1.

[0052] In a preferred embodiment, in step (3), the reduction reaction is carried out in a hydrogen atmosphere at 400-500°C (e.g., 400°C, 420°C, 450°C, 480°C or 500°C) for 1-2 hours (e.g., 1 hour, 1.5 hours or 2 hours); the hydrogen atmosphere includes a mixture of hydrogen and argon or a mixture of hydrogen and nitrogen, and the volume fraction of hydrogen in the mixture is 20-30% (e.g., 20%, 22%, 25%, 28% or 30%).

[0053] In this invention, the active outer layer is obtained by impregnation, which further reduces the cost of large-scale production of ceramic precursors.

[0054] The present invention also provides a catalyst comprising, from the inside out, hollow titanium dioxide spheres, a silica intermediate layer and an active outer layer; the mass ratio of the hollow titanium dioxide spheres to the silica intermediate layer is (1~10):(1~10); the active outer layer comprises Pt and Ni.

[0055] For (1~10): (1~10), it can be any value from 1:10 to 10:1, for example, it can be 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 2:3, 2:5, 2:7, 2:9, 3:1, 3:2, 3:4, 3:8, 4:1, 4:3, 4:7, 4:9, 5:1, 5:2, 5:3, 5:9, 6:1, 6:9, 7:1, 7:9, 8:1, 8:9, 9:1 or 10:1.

[0056] In this invention, experiments have confirmed that if the mass ratio of hollow titanium dioxide spheres to the silicon dioxide interlayer is greater than 10:1, grain sintering is likely to occur at 200-400℃, leading to the collapse of the hollow structure of the support. This results in a longer mass transfer path and a significant reduction in catalytic efficiency. Secondly, since SiO2 is located between the active outer layer and TiO2, it can inhibit the agglomeration of Pt-Ni bimetallic particles through spatial confinement. If the proportion of TiO2 is too high, the thickness of SiO2 becomes thinner or even locally absent, failing to effectively encapsulate TiO2. This causes the bimetallic particles to easily agglomerate at high temperatures, leading to a sharp decline in catalytic activity. If the mass ratio of hollow titanium dioxide spheres to the silicon dioxide interlayer is less than 1:10, the amount of hollow titanium dioxide spheres is too small, resulting in insufficient acidic sites and difficulty in effectively weakening the Si-C bond. This leads to an increase in the activation energy, requiring a higher reaction temperature or a longer reaction time, thus reducing catalytic efficiency.

[0057] In a preferred embodiment, the active outer layer accounts for 1 wt% to 2 wt% of the catalyst (e.g., it can be 1 wt%, 1.2 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.8 wt% or 2 wt%).

[0058] In this embodiment of the invention, the composition of the active outer layer is limited to 1wt%~2wt%, which can ensure high catalytic efficiency and high yield during polysilane pyrolysis, reduce pyrolysis temperature and shorten reaction time, avoid low efficiency when the amount of the active outer layer is too small, and avoid production cost due to excessive amount of the active outer layer.

[0059] In a more preferred embodiment, the mass ratio of the titanium dioxide hollow spheres to the silicon dioxide interlayer is 5:1.

[0060] The present invention also provides an application of a catalyst, which is used to prepare ceramic precursors from polysilanes via a cracking reaction.

[0061] In a preferred embodiment, the amount of catalyst used is 0.5wt% to 1wt% of the amount of polysilane (e.g., it can be 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, or 1wt%).

[0062] In this invention, the above-mentioned catalyst is used in the process of preparing ceramic precursors from polysilane, which not only reduces the pyrolysis temperature to 400°C, but also further shortens the reaction time and improves the yield of ceramic precursors.

[0063] Unless otherwise specified, the raw materials used in this invention can be commercially available products or synthesized using existing methods.

[0064] In this invention, the use of "and / or" between multiple technical features indicates that these technical features are connected by an "and / or" relationship, meaning that it can be any one of these technical features, or any combination of two or more of these technical features.

[0065] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0066] In the following examples and comparative examples, chloroplatinic acid is chloroplatinic acid hexahydrate H2PtCl6·6H2O; nickel nitrate is nickel nitrate hexahydrate Ni(NO3)2·6H2O.

[0067] Example 1

[0068] A method for preparing a catalyst:

[0069] (1) 100 mg of carbon nanospheres (particle size 100 nm) were dispersed in 100 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h. After stirring magnetically for 1 h, 9 mL of tetrabutyl titanate (TBOT) was added dropwise at a rate of 3 mL / min while stirring. Then, 54 mL of ethanol aqueous solution (composed of 9 mL of water and 45 mL of anhydrous ethanol) was added dropwise to the above system at a rate of 2 mL / min. Then, at 60 °C and 250 rpm, TBOT was adsorbed on the surface of the carbon nanospheres and hydrolyzed to obtain a mixed liquid system containing titanium dioxide-coated carbon nanospheres. The mixed liquid system was filtered and dried at 80 °C to obtain titanium dioxide-coated carbon nanospheres. The titanium dioxide-coated carbon nanospheres were placed in a muffle furnace and calcined at 600 °C for 3 h to remove the core layer of the carbon spheres to obtain hollow titanium dioxide spheres.

[0070] (2) Take 0.1g of the titanium dioxide hollow spheres obtained in step (1) and disperse them in 50mL of anhydrous ethanol and sonicate them at a power density of 500w for 30min; then, add 0.1g of silica nanoparticles (particle size of 20nm) to the system and continue to sonicate for 30min to mix them. Then, stir the above mixed solution at 250rpm for 1.5h at 60℃, filter and dry (dry at 100℃ for 2h) to obtain silica-coated hollow spheres; place the silica-coated hollow spheres in a muffle furnace and calcine at 500℃ for 5h to form a complex hollow TiO2-SiO2 double oxide carrier;

[0071] (3) Take 1g of the complexed hollow TiO2-SiO2 bioxide support obtained in step (2) and disperse it in deionized water. Then, add a mixed solution containing chloroplatinic acid and nickel nitrate (where the mass ratio of Pt to Ni is 1:1) to the above dispersion. Stir at room temperature (25℃) for 1h to obtain a precursor solution. Filter and dry the precursor solution to obtain a precursor. Place the precursor in a hydrogen atmosphere (a mixture of 20% hydrogen and 80% nitrogen) at 400℃ for 1h to convert the precursor into metallic Pt and Ni and load it on the support in step (2) to obtain a catalyst. The catalyst, from the inside out, consists of hollow titanium dioxide spheres, a silica intermediate layer, and an active outer layer; the mass ratio of the hollow titanium dioxide spheres to the silica intermediate layer is 1:1; the active outer layer is composed of Pt and Ni; the active outer layer accounts for approximately 1wt% of the catalyst.

[0072] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 400℃ and kept at 400℃ for 5h. After the reaction was completed, the product of polydimethylsilane, liquid polysilane (LPS), was obtained by cooling to room temperature.

[0073] Example 2

[0074] Example 2 is basically the same as Example 1, except that the mass ratio of the titanium dioxide hollow spheres to the silicon dioxide intermediate layer is 1:5.

[0075] Specifically, in step (2), 0.1g of the titanium dioxide hollow spheres obtained in step (1) are dispersed in 50mL of anhydrous ethanol and ultrasonically treated at a power density of 500W for 30min; then, 0.5g of silica nanoparticles (particle size of 20nm) are added to the system and ultrasonically mixed for another 30min. The above mixed solution is then stirred at 250rpm for 1.5h at 60℃, filtered, and dried (dried at 100℃ for 2h) to obtain silica-coated hollow spheres; the silica-coated hollow spheres are then placed in a muffle furnace and calcined at 500℃ for 5h to form a complexed hollow TiO2-SiO2 double oxide carrier.

[0076] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 420℃ and kept at 420℃ for 4.5h. After the reaction was completed, the product of polydimethylsilane, liquid polysilane (LPS), was obtained by cooling to room temperature.

[0077] Example 3

[0078] Example 3 is basically the same as Example 1, except that the mass ratio of the titanium dioxide hollow spheres to the silicon dioxide intermediate layer is 1:10.

[0079] Specifically, 0.1g of the titanium dioxide hollow spheres obtained in step (1) were dispersed in 50mL of anhydrous ethanol and ultrasonically treated at a power density of 500W for 30min. Then, 1g of silica nanoparticles (particle size of 20nm) were added to the system and ultrasonically treated for another 30min to mix them. The mixture was then stirred at 250rpm for 1.5h at 60℃, filtered, and dried (drying at 100℃ for 2h) to obtain silica-coated hollow spheres. The silica-coated hollow spheres were then placed in a muffle furnace and calcined at 500℃ for 5h to form a complexed hollow TiO2-SiO2 double oxide carrier.

[0080] Example 4

[0081] Example 4 is basically the same as Example 1, except that the mass ratio of the titanium dioxide hollow spheres to the silicon dioxide intermediate layer is 5:1.

[0082] Specifically, in step (2), 0.5g of the titanium dioxide hollow spheres obtained in step (1) are dispersed in 50mL of anhydrous ethanol and ultrasonically treated at a power density of 500W for 30min; then, 0.1g of silica nanoparticles (particle size of 20nm) are added to the system and ultrasonically mixed for another 30min. The above mixed solution is then stirred at 250rpm for 1.5h at 60℃, filtered, and dried (drying at 100℃ for 2h) to obtain silica-coated hollow spheres; the silica-coated hollow spheres are then placed in a muffle furnace and calcined at 500℃ for 5h to form a complex hollow TiO2-SiO2 double oxide carrier.

[0083] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 380℃ and kept at 380℃ for 5.5h. After the reaction was completed, the product of polydimethylsilane, liquid polysilane (LPS), was obtained by cooling to room temperature.

[0084] Example 5

[0085] Example 5 is basically the same as Example 1, except that the mass ratio of the titanium dioxide hollow spheres to the silicon dioxide intermediate layer is 10:1.

[0086] Specifically, in step (2), 1g of the titanium dioxide hollow spheres obtained in step (1) are dispersed in 50mL of anhydrous ethanol and ultrasonically treated at a power density of 500W for 30min; then, 0.1g of silica nanoparticles (particle size of 20nm) are added to the system and ultrasonically mixed for another 30min. The above mixed solution is then stirred at 250rpm for 1.5h at 60℃, filtered, and dried (dried at 100℃ for 2h) to obtain silica-coated hollow spheres; the silica-coated hollow spheres are then placed in a muffle furnace and calcined at 500℃ for 5h to form a complex hollow TiO2-SiO2 double oxide carrier.

[0087] Example 6

[0088] Example 6 is basically the same as Example 4, except that the mass ratio of Pt to Ni in the mixed solution is 1:2.

[0089] Specifically, in step (3), 1g of the complexed hollow TiO2-SiO2 bioxide support obtained in step (2) is dispersed in deionized water, and then a mixed solution containing chloroplatinic acid and nickel nitrate (where the mass ratio of Pt to Ni is 1:2) is added to the above dispersion. The mixture is stirred at room temperature (25°C) for 1h to obtain a precursor solution; the precursor solution is filtered and dried sequentially to obtain a precursor; the precursor is placed in a hydrogen atmosphere (a mixture of 20% hydrogen and 80% nitrogen) at 400°C for 1h to convert the precursor into metallic Pt and Ni and load it on the support in step (2) to obtain a catalyst. The catalyst, from the inside out, consists of hollow titanium dioxide spheres, a silica intermediate layer, and an active outer layer; the mass ratio of the hollow titanium dioxide spheres to the silica intermediate layer is 1:1; the active outer layer is composed of Pt and Ni; the active outer layer accounts for approximately 1wt% of the catalyst.

[0090] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 420℃ and kept at 420℃ for 5h. After the reaction was completed, the product of the cracking of polydimethylsilane, liquid polysilane (LPS), was obtained.

[0091] Example 7

[0092] Example 7 is basically the same as Example 4, except that the mass ratio of Pt to Ni in the mixed solution is 2:1.

[0093] Specifically, in step (3), 1g of the complexed hollow TiO2-SiO2 bioxide support obtained in step (2) is dispersed in deionized water, and then a mixed solution containing chloroplatinic acid and nickel nitrate (where the mass ratio of Pt to Ni is 2:1) is added to the above dispersion. The mixture is stirred at room temperature (25°C) for 1h to obtain a precursor solution; the precursor solution is filtered and dried sequentially to obtain a precursor; the precursor is placed in a hydrogen atmosphere (a mixture of 20% hydrogen and 80% nitrogen) at 400°C for 1h to convert the precursor into metallic Pt and Ni and load it on the support in step (2) to obtain a catalyst. The catalyst, from the inside out, consists of hollow titanium dioxide spheres, a silica intermediate layer, and an active outer layer; the mass ratio of the hollow titanium dioxide spheres to the silica intermediate layer is 1:1; the active outer layer is composed of Pt and Ni; the active outer layer accounts for approximately 1wt% of the catalyst.

[0094] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 380℃ and kept at 380℃ for 5h. After the reaction was completed, the product of polydimethylsilane, liquid polysilane (LPS), was obtained by cooling to room temperature.

[0095] Example 8

[0096] Example 8 is basically the same as Example 1, except that the preparation method of the catalyst is different;

[0097] Specifically, (1) 100 mg of carbon nanospheres (particle size 120 nm) were dispersed in 100 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h. After stirring magnetically for 1 h, 8 mL of tetrabutyl titanate (TBOT) was added dropwise at a rate of 2 mL / min while stirring. Then, 54 mL of ethanol aqueous solution (composed of 9 mL of water and 45 mL of anhydrous ethanol) was added dropwise to the above system at a rate of 1 mL / min. Then, at 70 °C and 250 rpm, TBOT was adsorbed on the surface of the carbon nanospheres and hydrolyzed to obtain a mixed liquid system containing titanium dioxide-coated carbon nanospheres. The mixed liquid system was filtered and dried at 80 °C to obtain titanium dioxide-coated carbon nanospheres. The titanium dioxide-coated carbon nanospheres were placed in a muffle furnace and calcined at 400 °C for 3 h to remove the core layer of the carbon spheres to obtain hollow titanium dioxide spheres.

[0098] (2) Take 0.5g of titanium dioxide hollow spheres obtained in step (1) and disperse them in 50mL of anhydrous ethanol and sonicate them at a power density of 300w for 30min; then, add 0.1g of silica nanoparticles (particle size of 30nm) to the system and continue to sonicate for 30min to mix them. Then, stir the above mixed solution at 250rpm for 1.5h at 60℃, filter and dry (dry at 100℃ for 2h) to obtain silica-coated hollow spheres; place the silica-coated hollow spheres in a muffle furnace and calcine at 600℃ for 5h to form a complex hollow TiO2-SiO2 double oxide carrier;

[0099] (3) Take 1g of the complexed hollow TiO2-SiO2 double oxide support obtained in step (2) and disperse it in deionized water. Then add a mixed solution containing chloroplatinic acid and nickel nitrate (where the mass ratio of Pt to Ni is 1:1) to the above dispersion. Stir at room temperature (25℃) for 1h to obtain a precursor solution. Filter and dry the precursor solution to obtain a precursor. Place the precursor in a hydrogen atmosphere (a mixture of 30% hydrogen and 70% nitrogen) at 400℃ for 2h to convert the precursor into metallic Pt and Ni and load it on the support in step (2) to obtain a catalyst.

[0100] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 400℃ and kept at 400℃ for 5h. After the reaction was completed, the product of polydimethylsilane, liquid polysilane (LPS), was obtained by cooling to room temperature.

[0101] Example 9

[0102] Example 9 is basically the same as Example 1, except that the preparation method of the catalyst is different;

[0103] Specifically, (1) 100 mg of carbon nanospheres (particle size 80 nm) were dispersed in 100 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h. After stirring magnetically for 1 h, 10 mL of tetrabutyl titanate (TBOT) was added dropwise at a rate of 4 mL / min while stirring. Then, 54 mL of ethanol aqueous solution (composed of 9 mL of water and 45 mL of anhydrous ethanol) was added dropwise to the above system at a rate of 3 mL / min. Then, at 50 °C and 250 rpm, TBOT was adsorbed onto the surface of the carbon nanospheres and hydrolyzed to obtain a mixed liquid system containing titanium dioxide-coated carbon nanospheres. The mixed liquid system was filtered and dried at 80 °C to obtain titanium dioxide-coated carbon nanospheres. The titanium dioxide-coated carbon nanospheres were placed in a muffle furnace and calcined at 500 °C for 3 h to remove the core layer of the carbon spheres to obtain hollow titanium dioxide spheres.

[0104] (2) Take 0.5g of titanium dioxide hollow spheres obtained in step (1) and disperse them in 50mL of anhydrous ethanol and sonicate them at a power density of 500w for 30min; then, add 0.1g of silica nanoparticles (particle size of 10nm) to the system and continue to sonicate for 30min to mix them. Then, stir the above mixed solution at 250rpm for 1.5h at 60℃, filter and dry (dry at 100℃ for 2h) to obtain silica-coated hollow spheres; and place the silica-coated hollow spheres in a muffle furnace and calcine at 400℃ for 6h to form a complex hollow TiO2-SiO2 double oxide carrier;

[0105] (3) Take 1g of the complexed hollow TiO2-SiO2 double oxide support obtained in step (2) and disperse it in deionized water. Then add a mixed solution containing chloroplatinic acid and nickel nitrate (where the mass ratio of Pt to Ni is 1:1) to the above dispersion. Stir at room temperature (25℃) for 1h to obtain a precursor solution. Filter and dry the precursor solution to obtain a precursor. Place the precursor in a hydrogen atmosphere (a mixture of 20% hydrogen and 80% argon) at 500℃ for 1h to convert the precursor into metallic Pt and Ni and load it on the support in step (2) to obtain a catalyst.

[0106] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 400℃ and kept at 400℃ for 5h. After the reaction was completed, the product of polydimethylsilane, liquid polysilane (LPS), was obtained by cooling to room temperature.

[0107] Comparative Example 1

[0108] The atmospheric pressure pyrolysis system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. The temperature was then raised to 480℃ and kept at 480℃ for 8 hours. After the reaction was completed, the product of PDMS pyrolysis, liquid polysilane (LPS), was obtained.

[0109] Comparative Example 2

[0110] The atmospheric pressure pyrolysis system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated three times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of B(CF)3 was added, and then the temperature was raised to 460℃ and kept at 460℃ for 7h. After the reaction was completed, the product of PDMS pyrolysis, liquid polysilane (LPS), was obtained.

[0111] Comparative Example 3

[0112] A Pt catalyst is a Pt-coated SiO2 nanosphere support.

[0113] Preparation method of Pt catalyst: 1g of SiO2 nanospheres were dispersed in 20mL of deionized water, and then 0.069g of chloroplatinic acid was added to the solution. After stirring at room temperature (25℃) for 1h, the nanospheres were removed and dried to obtain the precursor. The precursor was then placed in a hydrogen atmosphere (a mixture of 20% hydrogen and 80% nitrogen) at 400℃ for 1h to convert the precursor into metallic Pt, which was then supported on a SiO2 support to obtain the SiO2 / Pt catalyst.

[0114] Application of Pt catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane was added to the reaction device of the system and stirred. 5g of the above-mentioned Pt catalyst was added, and then the temperature was raised to 420℃ and kept at 420℃ for 7h. After the reaction was completed, the product of polydimethylsilane was cooled to room temperature to obtain liquid polysilane (LPS), which is the cracking product of polydimethylsilane.

[0115] Comparative Example 4

[0116] Comparative Example 4 is basically the same as Example 1, except that the catalyst does not contain an active outer layer, that is, the complexed hollow TiO2-SiO2 double oxide support obtained in step (2) is used as the catalyst.

[0117] Specifically, a catalyst comprises, from the inside out, hollow titanium dioxide spheres and a silicon dioxide intermediate layer; the mass ratio of the hollow titanium dioxide spheres to the silicon dioxide intermediate layer is 1:1.

[0118] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane was added to the reaction apparatus of the system and stirred. 5g of the above catalyst was added, and then the temperature was raised to 450℃ and kept at 450℃ for 8 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain the cracking product of polydimethylsilane, liquid polysilane (LPS).

[0119] Comparative Example 5

[0120] Comparative Example 5 is basically the same as Example 1, except that the active outer layer is Pt;

[0121] Specifically, a catalyst comprises, from the inside out, hollow titanium dioxide spheres, a silica intermediate layer, and an active outer layer; the mass ratio of the hollow titanium dioxide spheres to the silica intermediate layer is 1:1; the active outer layer is Pt; and the active outer layer accounts for 1 wt% of the catalyst.

[0122] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 420℃ and kept at 420℃ for 5h. After the reaction was completed, the product of the cracking of polydimethylsilane, liquid polysilane (LPS), was obtained.

[0123] Comparative Example 6

[0124] Comparative Example 6 is basically the same as Example 1, except that the active outer layer is Ni;

[0125] Specifically, a catalyst comprises, from the inside out, hollow titanium dioxide spheres, a silica intermediate layer, and an active outer layer; the mass ratio of the hollow titanium dioxide spheres to the silica intermediate layer is 1:1; the active outer layer is Ni; and the active outer layer accounts for 1 wt% of the catalyst.

[0126] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 420℃ and kept at 420℃ for 5h. After the reaction was completed, the product of the cracking of polydimethylsilane, liquid polysilane (LPS), was obtained.

[0127] Comparative Example 7

[0128] Comparative Example 7 is basically the same as Example 1, except that: the catalyst, from the inside out, includes a hollow silica sphere, a titanium dioxide intermediate layer and an active outer layer; the mass ratio of the hollow silica sphere to the titanium dioxide intermediate layer is 1:1; the active outer layer is composed of Pt and Ni; the active outer layer accounts for about 1 wt% of the catalyst.

[0129] Catalyst preparation methods:

[0130] (1) 100 mg of carbon nanospheres (particle size 100 nm) were dispersed in 100 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h. After stirring magnetically for 1 h, 9 mL of tetraethyl orthosilicate was slowly added dropwise while stirring. Then, 54 mL of ethanol aqueous solution (composed of 9 mL of water and 45 mL of anhydrous ethanol) was added dropwise to the above system. Then, at 60 °C and 250 rpm, tetraethyl orthosilicate was adsorbed onto the surface of the carbon nanospheres and hydrolyzed to obtain a mixed liquid system containing silica-coated carbon nanospheres. The mixed liquid system was filtered and dried at 80 °C to obtain silica-coated carbon nanospheres. The silica-coated carbon nanospheres were placed in a muffle furnace and calcined at 600 °C for 3 h to remove the core layer of the carbon spheres to obtain silica hollow spheres.

[0131] (2) Take 0.1g of the silica hollow spheres obtained in step (1) and disperse them in 50mL of anhydrous ethanol and sonicate them at a power density of 500w for 30min; then, add 0.1g of titanium dioxide nanoparticles (particle size of 20nm) to the system and continue to sonicate for 30min to mix them. Then, stir the above mixed solution at 250rpm for 1.5h at 60℃, filter and dry (dry at 100℃ for 2h) to obtain titanium dioxide coated hollow spheres; and place the titanium dioxide coated hollow spheres in a muffle furnace and calcine them at 500℃ for 5h to form a carrier;

[0132] (3) Take 1g of the support obtained in step (2) and disperse it in deionized water. Then add a mixed solution containing chloroplatinic acid and nickel nitrate (where the mass ratio of Pt to Ni is 1:1) to the above dispersion. Stir at room temperature (25℃) for 1h to obtain a precursor solution. Filter and dry the precursor solution to obtain a precursor. Place the precursor in a hydrogen atmosphere (a mixture of 20% hydrogen and 80% nitrogen) at 400℃ for 1h to convert the precursor into metallic Pt and Ni and load it on the support in step (2) to obtain a catalyst.

[0133] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 480℃ and kept at 480℃ for 5h. After the reaction was completed, the product of polydimethylsilane, liquid polysilane (LPS), was obtained by cooling to room temperature.

[0134] Comparative Example 8

[0135] Comparative Example 8 is basically the same as Example 1, except that the mass ratio of the titanium dioxide hollow spheres to the silicon dioxide intermediate layer is 1:11.

[0136] Specifically, in step (2), 0.1g of the titanium dioxide hollow spheres obtained in step (1) are dispersed in 50mL of anhydrous ethanol and ultrasonically treated at a power density of 500W for 30min; then, 1.1g of silica nanoparticles (particle size of 20nm) are added to the system and ultrasonically mixed for another 30min. The mixture is then stirred at 250rpm for 1.5h at 60℃, filtered, and dried (dried at 100℃ for 2h) to obtain silica-coated hollow spheres; the silica-coated hollow spheres are then placed in a muffle furnace and calcined at 500℃ for 5h to form a complexed hollow TiO2-SiO2 double oxide carrier.

[0137] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 460℃ and kept at 460℃ for 7h. After the reaction was completed, the product of polydimethylsilane, liquid polysilane (LPS), was obtained by cooling to room temperature.

[0138] Comparative Example 9

[0139] Comparative Example 9 is basically the same as Example 1, except that the mass ratio of the titanium dioxide hollow spheres to the silicon dioxide intermediate layer is 11:1.

[0140] Specifically, in step (2), 1.1g of the titanium dioxide hollow spheres obtained in step (1) are dispersed in 50mL of anhydrous ethanol and ultrasonically treated at a power density of 500W for 30min; then, 0.1g of silica nanoparticles (particle size of 20nm) are added to the system and ultrasonically mixed for another 30min. The above mixed solution is then stirred at 250rpm for 1.5h at 60℃, filtered, and dried (dried at 100℃ for 2h) to obtain silica-coated hollow spheres; the silica-coated hollow spheres are then placed in a muffle furnace and calcined at 500℃ for 5h to form a complex hollow TiO2-SiO2 double oxide carrier.

[0141] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 440℃ and kept at 440℃ for 6 hours. After the reaction was completed, the product of polydimethylsilane, liquid polysilane (LPS), was obtained by cooling to room temperature.

[0142] Comparative Example 10

[0143] Comparative Example 10 is basically the same as Example 1, except that the mass ratio of Pt to Ni in the mixed solution is 1:3.

[0144] Specifically, in step (3), 1g of the complexed hollow TiO2-SiO2 bioxide support obtained in step (2) is dispersed in deionized water, and then a mixed solution containing chloroplatinic acid and nickel nitrate (where the mass ratio of Pt to Ni is 1:3) is added to the above dispersion. The mixture is stirred at room temperature (25°C) for 1h to obtain a precursor solution; the precursor solution is filtered and dried sequentially to obtain a precursor; the precursor is placed in a hydrogen atmosphere (a mixture of 20% hydrogen and 80% nitrogen) at 400°C for 1h to convert the precursor into metallic Pt and Ni and load it on the support in step (2) to obtain a catalyst. The catalyst, from the inside out, consists of hollow titanium dioxide spheres, a silica intermediate layer, and an active outer layer; the mass ratio of the hollow titanium dioxide spheres to the silica intermediate layer is 1:1; the active outer layer is composed of Pt and Ni; the active outer layer accounts for approximately 1wt% of the catalyst.

[0145] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 420℃ and kept at 420℃ for 5h. After the reaction was completed, the product of the cracking of polydimethylsilane, liquid polysilane (LPS), was obtained.

[0146] Comparative Example 11

[0147] Comparative Example 11 is basically the same as Example 1, except that the mass ratio of Pt to Ni in the mixed solution is 3:1.

[0148] Specifically, in step (3), 1g of the complexed hollow TiO2-SiO2 bioxide support obtained in step (2) is dispersed in deionized water, and then a mixed solution containing chloroplatinic acid and nickel nitrate (where the mass ratio of Pt to Ni is 1:2) is added to the above dispersion. The mixture is stirred at room temperature (25°C) for 1h to obtain a precursor solution; the precursor solution is filtered and dried sequentially to obtain a precursor; the precursor is placed in a hydrogen atmosphere (a mixture of 20% hydrogen and 80% nitrogen) at 400°C for 1h to convert the precursor into metallic Pt and Ni and load it on the support in step (2) to obtain a catalyst. The catalyst, from the inside out, consists of hollow titanium dioxide spheres, a silica intermediate layer, and an active outer layer; the mass ratio of the hollow titanium dioxide spheres to the silica intermediate layer is 1:1; the active outer layer is composed of Pt and Ni; the active outer layer accounts for approximately 1wt% of the catalyst.

[0149] Application of the catalyst: The atmospheric pressure cracking system was evacuated and replaced with high-purity nitrogen gas, and this process was repeated 3 times. Under the protection of high-purity nitrogen gas, 1000g of polydimethylsilane (PDMS) was added to the reaction apparatus of the system and stirred. 5g of the above-mentioned catalyst was added, and then the temperature was raised to 420℃ and kept at 420℃ for 5h. After the reaction was completed, the product of the cracking of polydimethylsilane, liquid polysilane (LPS), was obtained.

[0150] In this invention, the catalysts used in each embodiment and comparative example are applied to the preparation of ceramic precursors by cracking polysilane, and the reaction temperature, reaction time and LPS yield of ceramic precursors in the cracking process are statistically analyzed. The data results are shown in Table 1.

[0151] Table 1

[0152]

[0153] As can be seen from the data in Table 1, the catalyst prepared in the embodiments of the present invention, compared with the traditional single metal supported catalyst and the catalyst in the comparative example, can reduce the pyrolysis temperature, shorten the reaction time, and significantly improve the yield of ceramic precursor in the reaction of polysilane pyrolysis to prepare ceramic precursor, showing good application prospects.

[0154] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a catalyst, characterized in that, include: (1) Disperse carbon nanospheres in a solvent, then add tetrabutyl titanate and an aqueous ethanol solution and mix well to obtain titanium dioxide-coated carbon nanospheres; and calcine the titanium dioxide-coated carbon nanospheres to obtain hollow titanium dioxide spheres. (2) Disperse the hollow titanium dioxide spheres in the solvent and add silica nanoparticles to mix evenly to obtain silica-coated hollow spheres; and calcine the silica-coated hollow spheres to obtain a carrier; the mass ratio of the hollow titanium dioxide spheres to the silica nanoparticles is (1~10):(1~10). (3) The carrier is immersed in a mixed solution containing chloroplatinic acid and nickel nitrate to obtain a precursor solution; the precursor solution is filtered, dried and reduced in sequence to obtain the catalyst; wherein the mass ratio of Pt to Ni in the mixed solution is (1~2):(1~2).

2. The preparation method according to claim 1, characterized in that, The carbon nanospheres have a particle size of 80~120nm.

3. The preparation method according to claim 1, characterized in that, The silica nanoparticles have a particle size of 10~30nm.

4. The preparation method according to claim 1, characterized in that, In step (1), the mixing temperature is 50~70℃; the calcination temperature is 400~600℃ and the time is 2~3h.

5. The preparation method according to claim 1, characterized in that, In step (2), the mixing is performed by ultrasonic treatment, the power density of the ultrasonic treatment is 300~500w; the calcination temperature is 400~600℃ and the time is 4~6h.

6. The preparation method according to claim 1, characterized in that, The ratio of the amount of carbon nanospheres to the amount of tetrabutyl titanate is 100 mg: (8 mL to 10 mL).

7. The preparation method according to claim 1, characterized in that, The mass ratio of Pt to Ni in the mixed solution is 2:

1.

8. The preparation method according to any one of claims 1 to 7, characterized in that, In step (3), the reduction reaction is carried out at 400-500°C for 1-2 hours in a hydrogen atmosphere; the hydrogen atmosphere includes a mixture of hydrogen and argon or a mixture of hydrogen and nitrogen, and the volume fraction of hydrogen in the mixture is 20-30%.

9. A catalyst prepared by any one of the preparation methods according to claims 1 to 8, characterized in that, From the inside out, it comprises hollow titanium dioxide spheres, a silicon dioxide intermediate layer, and an active outer layer; the mass ratio of the hollow titanium dioxide spheres to the silicon dioxide intermediate layer is (1~10):(1~10); the active outer layer comprises Pt and Ni.

10. The catalyst according to claim 9, characterized in that, The active outer layer accounts for 1 wt% to 2 wt% of the catalyst.

11. The catalyst according to claim 9, characterized in that, The mass ratio of the hollow titanium dioxide spheres to the silicon dioxide intermediate layer is 5:

1.

12. The application of a catalyst prepared by any of the methods described in claims 1 to 8, or a catalyst described in any of claims 9 to 11, characterized in that, The catalyst was used to prepare ceramic precursors from polysilanes via a pyrolysis reaction.

13. The application according to claim 12, characterized in that, The amount of catalyst used is 0.5wt% to 1wt% of the amount of polysilane used.

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