Preparation method of supported shape-preserving nanometal catalyst, product and application thereof

Abstract

The application discloses a preparation method of a supported shape-preserving nanometal catalyst, which comprises the following steps: 1) preparing a metal nanocrystal dispersion liquid; 2) mixing a carrier with a solvent, then mixing the carrier with the metal nanocrystal dispersion liquid prepared in the step 1), and obtaining an intermediate product after filtration, washing and drying; the carrier is selected from reducible metal oxides or a mixture of reducible metal oxides and inert supports; and 3) sequentially performing oxidation atmosphere calcination, reduction atmosphere calcination and passivation treatment on the intermediate product. The application discloses the preparation method of the supported shape-preserving nanometal catalyst, and the prepared nanometal catalyst has a low proportion of edge and corner atoms, high catalytic selectivity, activity and stability, and can be widely applied in the selective hydrogenation reaction of alkyne compounds.

Description

Technical Field

[0001] This invention relates to the technical field of catalysts, and more particularly to a method for preparing a supported conformal nano-metal catalyst, its products, and applications. Background Technology

[0002] Selective hydrogenation of alkynes and hydroformylation of alkenes are important chemical processes for producing bulk and fine chemicals. For example, selective hydrogenation of alkynes is a key process in the production of fine chemicals such as vitamins, fragrances, and flavorings. Hydroformylation of alkenes is one of the largest homogeneous industrial reaction processes currently in operation, and is an important method for producing oxygen-containing chemicals and controlling carbon chain length.

[0003] Currently, most catalysts used for the selective hydrogenation of alkynes sacrifice activity to improve selectivity, with selectivity for olefin products generally not exceeding 95%. The most typical example is the Lindlar catalyst commonly used in industrial production. Further improving selectivity is extremely difficult and generally leads to a sharp decline in activity. For every percentage point increase in selectivity, the catalyst often sacrifices more than 20% of its activity. Wang et al. (J. Catal. 2017, 350, 13-20) found that the corner sites of Pd particles are the main cause of over-hydrogenation of alkynes. Based on this theory, they prepared a flat, nano-Pd-supported catalyst with a low corner site ratio by utilizing the strong interaction between the Pd metal salt precursor and the oxygen vacancies on the support during the reduction process. The reaction activity was significantly improved, but the selectivity remained at around 95%.

[0004] The hydroformylation of olefins is generally a homogeneous catalytic process using organometallic complex catalysts, with metal Rh being the most common industrial application. Homogeneous organometallic complex catalysts possess well-defined active center structures, exhibiting high catalytic activity, chemoselectivity, and regioselectivity. After the reaction, the catalyst is separated from the product by distillation. However, organometallic complex catalysts suffer from poor thermal stability. When the product has a high boiling point, high-temperature distillation can cause catalyst decomposition or polymerization, leading to deactivation and hindering catalyst recovery and recycling. Therefore, there is an urgent need to develop highly efficient heterogeneous supported Rh metal catalysts. However, conventional supported Rh nanoparticles readily form soluble carbonyl Rh species under syngas conditions, facing severe Rh loss and rapid catalyst deactivation, while also exhibiting certain olefin hydrogenation side reactions. The inventors' team discovered that Rh loss actually occurs at the corner sites of Rh metal nanoparticles. Therefore, theoretically, the corner-site targeted passivation strategy developed by the inventors' team in the early stages (CN201811010568.6; Green Chem., 2019, 21, 4143-4151) can suppress Rh loss, thereby improving catalyst stability. Furthermore, passivation of corner Rh atoms can also suppress olefin hydrogenation side reactions and improve reaction selectivity. However, direct reduction of supported metal precursor salts often results in irregularly shaped polyhedral or spherical metal nanoparticles. When the particle size of these irregular polyhedral or spherical metal nanoparticles is small, the proportion of corner sites is high, meaning that a considerable proportion of Rh metal atoms will be passivated and not effectively utilized, leading to low catalytic activity.

[0005] Therefore, how to simply and controllably further reduce the proportion of corner atoms on the surface of metal nanoparticles, thereby further improving the selectivity and / or activity of the catalyst, is a challenge in the preparation of this type of catalyst. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, this invention discloses a method for preparing supported conformal nano-metal catalysts. The prepared nano-metal catalysts possess low atomic ratios at corner sites, high catalytic selectivity, high catalytic activity, and stability, and are expected to be widely used in selective hydrogenation and hydroformylation reactions.

[0007] The specific technical solution is as follows:

[0008] A method for preparing a supported conformal nano-metal catalyst, comprising:

[0009] 1) Preparation of metal nanocrystal dispersion;

[0010] 2) After mixing the carrier with the solvent, it is then mixed with the metal nanocrystal dispersion prepared in step 1). After filtration, washing and drying, an intermediate product is obtained.

[0011] The carrier is selected from reducible metal oxides, or a mixture of reducible metal oxides and inert supports;

[0012] The inert support is selected from non-reducing oxides and / or carbides;

[0013] When the carrier is selected from a mixture of reducible metal oxide and inert support, after mixing the carrier with the solvent, the pH value of the mixture needs to be adjusted first so that only the isoelectric point of the surface of the reducible oxide component in the carrier is opposite to the isoelectric point of the surface of the metal nanocrystal in the metal nanocrystal dispersion, and then it is mixed with the metal nanocrystal dispersion.

[0014] 3) The intermediate product is subjected to calcination in an oxidizing atmosphere, calcination in a reducing atmosphere, and passivation treatment in sequence.

[0015] The preparation method disclosed in this invention uses regularly shaped metal nanocrystals instead of commonly used metal salts as the precursor of the active component. The nanocrystal oxide particles are re-fragmented and dispersed by calcination in a high-temperature oxidizing atmosphere. Then, calcination and reduction are carried out in a reducing atmosphere. By utilizing the shape-preserving effect of metal nanocrystals and the strong metal-support interaction, regularly shaped flat polyhedral metal nanoparticles with a particle size of about 1-7 nm are loaded on the surface of the support. The metal nanoparticles with this specific morphology and particle size have a small proportion of edge and corner atoms. The prepared supported shape-preserving nano-metal catalyst has excellent catalytic performance, especially in the selective hydrogenation of alkynes and the hydroformylation of olefins, which have both ultra-high conversion rate, selectivity and cycle stability.

[0016] Choosing metal nanocrystals as a metal precursor allows for the inheritance of regular morphology and size to the final nanoparticles during subsequent loading and calcination processes. This avoids the formation of rough ellipsoidal or flat droplet-shaped metal nanoparticles with a high proportion of edge and corner atoms, which is often found when using metal salts as precursors due to surface thermodynamic factors. This shape-preserving effect endows the prepared catalyst with excellent selectivity for hydrogenation and hydroformylation.

[0017] By selecting reducible metal oxides or reducible metal oxide composite inert supports as carriers, the strong metal-oxide interactions can be utilized during subsequent loading and calcination to stabilize and redisperse metal oxide nanocrystals, reducing particle size and improving metal dispersion and catalyst stability. Simultaneously, the strong metal-oxide interactions can also regulate the morphology of the dispersed metal oxide nanocrystals, transforming them from aspect ratios close to 1 into regularly shaped, flattened nanocrystals. This reduces the proportion of edge and bulk atoms in the nanomaterials during subsequent reduction, increases the exposure ratio of planar atoms, and enhances the carrier's control over the electronic structure of the regularly shaped, flattened nanomaterials. Furthermore, the strong interactions between the metal-oxide carriers can target and cover the edge and corner sites of the nanomaterials using surface energy differences, further regulating the types of active sites on the nanomaterial surface and inhibiting the loss and growth of active components due to migration, thus improving catalyst stability. This targeted covering effect endows the prepared catalyst with excellent hydroformylation stability.

[0018] Comparative experiments revealed that the traditional impregnation method, which involves mixing the support with a metal salt precursor, adjusting the isoelectric point of the mixture, and finally calcining and reducing, produces supported nano-metal catalysts with spherical or ellipsoidal metal nanoparticles. Further catalytic performance testing showed that the catalyst prepared by this traditional process exhibited significantly lower conversion rates, selectivity, and recyclability stability in the selective hydrogenation of alkynes and the hydroformylation of olefins compared to the catalyst prepared in this invention.

[0019] In this invention, the preparation of the metal nanocrystal dispersion in step 1) is well known to those skilled in the art, and can be referred to the method in the paper Chem. Mater. 1998, 10, 594-600.

[0020] Preferred:

[0021] The metal nanocrystal dispersion contains one or more of Ru, Rh, Pd, Os, Ir, and Pt; more preferably, it contains one or more of Ru, Rh, Pd, and Pt.

[0022] The metal nanocrystals are regular polyhedral in shape, with an average size of 2-7 nm and a particle aspect ratio of 0.9-1.0; more preferably, the average size of the metal nanocrystals is 2-5 nm.

[0023] The solvent in the metal nanocrystal dispersion is selected from one or more of methanol, ethanol, isopropanol, acetone, butanone, acetonitrile, formamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and dioxane.

[0024] The concentration of the metal nanocrystal dispersion is 1–50 mg / mL; more preferably 1–10 mg / mL.

[0025] In step 2):

[0026] The reducible metal oxide is selected from one or more of cerium oxide, titanium oxide, zirconium oxide, indium oxide, tungsten oxide, molybdenum oxide, manganese oxide, cobalt oxide, iron oxide, nickel oxide, and vanadium oxide.

[0027] The non-reducing oxide is selected from one or more of silicon oxide, aluminum oxide, and magnesium oxide;

[0028] The carbide is selected from silicon carbide;

[0029] When the carrier is selected from a mixture of reducible metal oxide and inert support, the mass ratio of reducible metal oxide to inert support is 1:(2-20).

[0030] The carrier is insoluble in the solvent, and the mixture formed after mixing with the solvent is a suspension.

[0031] The solvent is selected from water or an aqueous solution of polar organic molecules, wherein the mass ratio of water to polar organic molecules in the aqueous solution of polar organic molecules is 1:(0.01~1).

[0032] The polar organic molecule is selected from one or more of methanol, ethanol, isopropanol, acetone, butanone, acetonitrile, dimethyl carbonate, formamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and dioxane.

[0033] Preferred:

[0034] The specific surface area of ​​the carrier is greater than 20m². 2 / g; further preferably 50-200m 2 / g.

[0035] The mass-to-volume ratio of the carrier to the solvent is 1:(5-600)g / mL; more preferably 1:(200-400)g / mL.

[0036] The mass ratio of the reducible metal oxide in the carrier to the metal nanocrystals in the metal nanocrystal dispersion is (5-1000):1; more preferably (20-300):1.

[0037] When the support is selected only from reducible metal oxides, it is only necessary to disperse the support in a solvent and then mix it with the metal nanocrystal dispersion prepared in step 1).

[0038] When the support is selected only from a mixture of reducible metal oxide and inert support, before adding the metal nanocrystal dispersion, the pH value of the mixture of support and solvent is adjusted so that only the isoelectric point of the surface of the reducible metal oxide component in the support is opposite to the isoelectric point of the surface of the metal nanocrystal in the dispersion. This ensures that the metal nanocrystal selectively adheres to the surface of the reducible oxide component, preparing for the preservation of the morphology and size of the metal nanoparticles in the subsequent calcination and reduction steps.

[0039] To ensure that the morphology and size of metal nanocrystals meet the requirements of relevant catalytic reactions after oxidation and reduction calcination, further restrictions need to be placed on their respective process conditions.

[0040] Preferred:

[0041] The calcination is carried out in an oxidizing atmosphere with an oxygen content of 10-100 vol%, a calcination temperature of 350-700℃, a calcination time of 4-48 h, and a gas flow rate of 1-200 mL / min.

[0042] Further optimization:

[0043] Calcination in the oxidizing atmosphere:

[0044] When the calcination temperature is 350–450℃, the oxygen content in the oxidizing atmosphere is 30–70 vol%.

[0045] When the calcination temperature is 450–600℃, the oxygen content in the oxidizing atmosphere is 20–50 vol%.

[0046] When the calcination temperature is 600–700℃, the oxygen content in the oxidizing atmosphere is 10–20 vol%.

[0047] Experiments have shown that when oxidative calcination is carried out, and the calcination temperature and oxygen content in the oxidizing atmosphere meet the above requirements, the prepared catalyst has more optimized size and aspect ratio, giving the prepared catalyst better conversion rate, selectivity and cycle stability.

[0048] Preferred:

[0049] The calcination is carried out in a reducing atmosphere, wherein the content of reducing gas in the reducing atmosphere is 1-100%, the calcination temperature is 25-500℃, the calcination time is 0.1-3.0h, and the gas flow rate is 5-200mL / min.

[0050] The reducing gas is selected from hydrogen and / or carbon monoxide.

[0051] Further preferably, the reducing atmosphere contains 10-100% hydrogen or carbon monoxide, the gas flow rate is 10-20 mL / min, the calcination temperature is 100-300℃, the calcination time is 1-3 h, and the heating rate is 1-10℃ / min.

[0052] Because flat metal nanoparticles have high surface energy, they are more easily oxidized by air compared to conventional spherical metal nanoparticles. Therefore, this invention employs a two-step passivation process:

[0053] The first step, passivation, uses an oxidizing atmosphere with an oxygen content of (0.1–2.0)%, a gas flow rate of (1–20) mL / min, a passivation temperature of -20–50℃, and a time of 1–6 h.

[0054] The second step is passivation, which uses an oxidizing atmosphere with an oxygen content of (2-10)%, a gas flow rate of (1-5) mL / min, a passivation temperature of -20-35℃, and a time of 4-12 h.

[0055] Experiments have shown that if a one-step micro-oxygen passivation treatment is used, the content of high-oxidation-state nano-metal species in the prepared catalyst increases significantly, while the catalytic activity decreases significantly.

[0056] The present invention also discloses a supported conformal nano-metal catalyst prepared according to the method, comprising a support and nano-metal uniformly supported on the support;

[0057] When the carrier is selected from reducible metal oxides, the nano-metals are uniformly distributed on the surface of the carrier; at an appropriate reduction temperature, some types of reducible metal oxides can selectively cover the edges and corners of the nano-metals.

[0058] When the carrier is selected from a mixture of reducible metal oxide and inert support, the reducible metal oxide is uniformly distributed on the surface of the inert support.

[0059] Specifically, it is selected from one or more of Pd / CeO2, Pd / TiO2, Pd / CeO2 / Al2O3, Rh / TiO2, Pt / MoO3 / SiC, Ru / Co3O4 / Al2O3, and Rh / In2O3 / MgO.

[0060] Preferred:

[0061] In the supported conformal nano-metal catalyst, the nano-metal particles have a particle size of 1-7 nm, are regular flat polyhedral in shape, and have an aspect ratio of no more than 0.85.

[0062] The mass fraction of the nano-metal particles is 0.1% to 10% based on the total mass of the catalyst.

[0063] Further preferred, the particle size of the nano-metal particles is 1–5 nm;

[0064] The mass fraction of the nano-metal particles is 0.3% to 5.0% based on the total mass of the catalyst.

[0065] The present invention also discloses the application of the supported conformal nano-metal catalyst in catalytic hydrogenation reactions.

[0066] Experiments have shown that the catalyst disclosed in this invention has universal applicability in catalytic hydrogenation reactions, especially for the selective hydrogenation of alkyne compounds.

[0067] Tests showed that the catalytic performance was excellent when the following alkyne compounds were used as substrates: 2-methyl-3-butyn-2-ol, 3,7-dimethyl-1-octyyn-3-ol, 3,7-dimethyl-6-octen-1-yntyyn-3-ol, 3,7,11-trimethyl-1-dodecyn-3-ol, 3,7,11-trimethyl-6-dodecen-1-yntyyn-3-ol, 3,7,11-trimethyl-6,10-dodecadien-1-yntyyn-3-ol, and 3,7,11,15-tetramethyl-1-hexadecyn-3-ol. 3-Methyl-1-(2,6,6-trimethyl-1-cyclohexen-1-yl)-1-penten-4-yn-3-ol, Probolon, Norethindrone, Diphenylacetylene, 4-Heptyne, 1,4-Butynediol, 6-hydroxy-3-(3-hydroxy-3-methylpent-4-en-1-yn-1-yl)-2,4,4-trimethylcyclohexen-2-en-1-one, 3-hexyn-1-ol, 3,6-dimethyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,7-octadien-4-yn-1,6-diol, Mifepristone.

[0068] Preferably, the support is selected from a mixture of reducible metal oxides and inert supports. Experiments have shown that the catalyst prepared using the above-mentioned composite support has superior catalytic performance.

[0069] Further preferably, the catalyst is selected from supported conformal nano-Pd catalysts.

[0070] The present invention also discloses the application of the supported conformal nano-metal catalyst in the catalytic hydroformylation reaction.

[0071] Experiments have shown that the catalyst disclosed in this invention is also universally applicable in catalytic hydroformylation reactions, especially for the hydroformylation of olefin compounds.

[0072] Tests have shown that the catalyst exhibits excellent catalytic performance when the following olefin compounds are used as substrates: ethylene, isobutylene, acrylamide, 1,1-stilbene, vinyl acetate, 1,4-butenediol diacetate, 3,4-butenediol diacetate, cyclopentene, cyclohexene, cyclooctene, and dicyclopentadiene.

[0073] Preferably, the catalyst is selected from supported conformal nano-Rh catalysts. Experiments have shown that in the supported conformal nano-Rh catalysts prepared by the method of the present invention, the surface of Rh nanoparticles is partially coated with reducible metal oxide species in the support, which can prevent the dissolution of Rh metal and further stabilize the catalyst.

[0074] Further preferred, it is selected from Rh / TiO2 and Rh / In2O3 / MgO; more preferably, it is Rh / TiO2.

[0075] Compared with the prior art, the present invention has the following beneficial effects:

[0076] This invention uses regularly shaped metal nanocrystals instead of commonly used metal salts as the precursor of the active component. It selects reducible metal oxides or reducible metal oxide composite inert supports as carriers, and utilizes the strong metal-oxide interaction to break down, reconstruct, and redisperse the metal oxide nanocrystals by controlling the calcination process in oxidizing and reducing atmospheres. This further reduces the particle size of the nano-metals, achieves flattening, and improves the dispersion of the nano-metals and the stability of the catalyst.

[0077] The nano-metal catalyst prepared by this invention has a low proportion of side-corner atoms, high catalytic selectivity, high catalytic activity and stability, and is expected to be widely used in selective hydrogenation and hydroformylation reactions. Attached Figure Description

[0078] Figure 1 X-ray diffraction pattern of the cerium dioxide-supported conformal nano-Pd metal catalyst prepared in Example 1;

[0079] Figure 2 The image shows a transmission electron microscope (TEM) image of the cerium dioxide-supported conformal nano-Pd metal catalyst prepared in Example 1. Further magnified images of the catalyst and its particle size distribution are provided in the smaller images.

[0080] Figure 3 Transmission electron microscopy (TEM) images of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Comparative Example 1 are shown, with further magnified images of the catalyst and its particle size distribution provided in the smaller images.

[0081] Figure 4The image shows a transmission electron microscope (TEM) image of the catalyst prepared in Comparative Example 4, with further magnified images of the catalyst and its particle size distribution shown in the smaller figures. Detailed Implementation

[0082] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to embodiments and accompanying drawings. However, it should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0083] Unless otherwise specified, all test materials and reagents used in the following embodiments are commercially available. Where specific techniques or conditions are not specified in the embodiments, they can be performed according to the techniques or conditions described in the literature in this field or according to the product instructions.

[0084] Example 1: Calcination of 2nm Pd / CeO2 at -500℃ and reduction at -200℃

[0085] 1) Dissolve 2g of polyvinylpyrrolidone (PVP, Mw = 58000) and 60mg of PdCl2 in 30mL of ethanol. Stir at room temperature for 10min, then heat to 165℃ and reflux under argon for 30min. After cooling to room temperature, add 150mL of acetone to precipitate Pd particles. Wash three times with acetone by centrifugation and disperse in 36mg of ethanol to obtain a PVP-stabilized Pd nanocrystal dispersion (Pd mass concentration 1mg / mL), which is then ready for use. Transmission electron microscopy characterization results show that the Pd nanocrystals in the dispersion have a regular spherical polyhedral morphology with an aspect ratio of approximately 0.91; the size is uniform, with an average size of 2.9nm.

[0086] 2) Disperse commercial cerium dioxide in 10 mL of water, add Pd nanocrystal dispersion dropwise until the theoretical loading mass fraction of Pd is 0.5%, stir at room temperature for 4 h, then filter and dry.

[0087] 3) The obtained solid was calcined in a tube furnace at 500℃ for 8 hours, then naturally cooled to room temperature with an air flow rate of 20 mL / min and a heating rate of 5℃ / min. It was then switched to a hydrogen atmosphere and calcined at 200℃ for 2 hours, followed by natural cooling to room temperature with an air flow rate of 40 mL / min and a heating rate of 5℃ / min. Next, it was passedivated at room temperature for 1 hour with nitrogen gas containing 0.1 vol% oxygen at a gas flow rate of 10 mL / min. Finally, it was passedivated at room temperature for 6 hours with nitrogen gas containing 5 vol% oxygen at a gas flow rate of 2 mL / min, thus obtaining the cerium dioxide-supported conformal nano-Pd metal catalyst.

[0088] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the cerium dioxide-supported conformal nano-Pd metal catalyst prepared in this embodiment was 0.52%, which is basically consistent with the theoretical Pd loading mentioned above.

[0089] X-ray diffraction tests were performed on the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in this embodiment. The results are shown in the figure. Figure 1 .Depend on Figure 1 It is evident that no characteristic diffraction peaks at 40.1° and 46.7° were observed belonging to Pd metal, indicating that the average particle size of Pd nanoparticles is less than 4 nm.

[0090] The conformal Pd nano-metal catalyst prepared in this embodiment was further subjected to transmission electron microscopy (TEM) testing. Magnified images of the catalyst and its particle size distribution are shown in the inset images. The results are presented in the figures below. Figure 2 .Depend on Figure 2 As can be seen, Pd nanoparticles are uniformly dispersed on the surface of a commercial cerium dioxide support, with an extremely narrow particle size distribution, an average particle size of about 2.2 nm, and an aspect ratio of 0.75.

[0091] Comparative Example 1

[0092] The preparation process is basically the same as in Example 1, except that in step 3), the calcination temperature during calcination in an oxidizing atmosphere is reduced from 500°C to 300°C.

[0093] Atomic emission spectroscopy analysis showed that the actual Pd loading mass fraction in the supported catalyst prepared in this comparative example was 0.52%, which is basically consistent with the theoretical Pd loading.

[0094] X-ray diffraction results showed that no characteristic diffraction peaks at 40.1° and 46.7° were observed at the catalyst, indicating that the average particle size of Pd nanoparticles is less than 4 nm.

[0095] Transmission electron microscopy (TEM) testing, such as Figure 3 As shown, the results indicate that Pd nanoparticles are uniformly dispersed on the surface of a commercial cerium dioxide support, with an extremely narrow particle size distribution, an average particle size of approximately 2.9 nm, and an aspect ratio of 0.86. Unlike Example 1, under calcination at 300°C, the particle size of the Pd nanoparticles in this catalyst did not change significantly compared to the particle size of the Pd nanocrystals in the dispersion; the morphology of the Pd nanoparticles in this catalyst showed a certain degree of flattening compared to the Pd nanocrystals in the dispersion, but this was not significant.

[0096] Comparative Example 2

[0097] The preparation process is basically the same as in Example 1, except that in step 3), the calcination time during calcination in an oxidizing atmosphere is reduced from 8 hours to 2 hours.

[0098] Atomic emission spectroscopy analysis showed that the actual Pd loading mass fraction in the supported catalyst prepared in this comparative example was 0.52%, which is basically consistent with the theoretical Pd loading.

[0099] X-ray diffraction results showed that no characteristic diffraction peaks at 40.1° and 46.7° were observed at the catalyst, indicating that the average particle size of Pd nanoparticles is less than 4 nm.

[0100] Transmission electron microscopy (TEM) results showed that Pd nanoparticles were uniformly dispersed on the surface of a commercial cerium dioxide support, with an extremely narrow particle size distribution, an average particle size of approximately 2.8 nm, and an aspect ratio of 0.87. Unlike Example 1, under the 2-hour calcination condition, due to the short calcination time, the particle size of the Pd nanoparticles in this catalyst did not have enough time to change significantly compared to the particle size of the Pd nanocrystals in the dispersion; the morphology of the Pd nanoparticles in this catalyst showed a certain degree of flattening compared to the Pd nanocrystals in the dispersion, but this was not significant.

[0101] Example 2: 2nm Pd / CeO2-10% O2-500℃ calcination-200℃ reduction

[0102] The preparation process is basically the same as in Example 1, except for step 3):

[0103] When calcining in an oxidizing atmosphere, the air atmosphere is replaced with a nitrogen atmosphere containing 10 vol% oxygen.

[0104] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the cerium dioxide-supported conformal nano-Pd metal catalyst prepared in this embodiment was 0.52%, which is basically consistent with the theoretical Pd loading.

[0105] X-ray diffraction results showed that no characteristic diffraction peaks at 40.1° and 46.7° were observed at the catalyst, indicating that the average particle size of Pd nanoparticles is less than 4 nm.

[0106] Transmission electron microscopy (TEM) results showed that Pd nanoparticles were uniformly dispersed on the surface of a commercial cerium dioxide support, with an average particle size of approximately 2.5 nm and an aspect ratio of 0.81. Compared to Example 1, under calcination conditions with 10% oxygen, the Pd nanoparticles in this catalyst exhibited a wider particle size distribution, larger particle size, and lower flattening due to the insufficient oxygen content.

[0107] Example 3: Calcination of 2nm Pd / CeO2 at -400℃ and reduction at -200℃

[0108] The preparation process is basically the same as in Example 1, except that in step 3), the calcination temperature during calcination in an oxidizing atmosphere is reduced from 500°C to 400°C.

[0109] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the CeO2-supported conformal nano-Pd metal catalyst prepared in this embodiment was 0.52%, which is basically consistent with the theoretical Pd loading mentioned above.

[0110] Transmission electron microscopy results show that the Pd nanoparticles of the prepared catalyst have an extremely narrow particle size distribution, with an average particle size of about 2.6 nm and an aspect ratio of 0.83.

[0111] Example 4: Calcination of 2nm Pd / CeO2 at -400℃ and reduction at -200℃

[0112] The preparation process is basically the same as in Example 1, except for step 3):

[0113] The calcination temperature during oxidizing atmosphere calcination was reduced from 500℃ to 400℃, and the air atmosphere was replaced with a nitrogen atmosphere with an oxygen content of 35 vol%.

[0114] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the CeO2-supported conformal nano-Pd metal catalyst prepared in this embodiment was 0.52%, which is basically consistent with the theoretical Pd loading mentioned above.

[0115] Transmission electron microscopy results showed that the Pd nanoparticles of the prepared catalyst had an extremely narrow particle size distribution, with an average particle size of about 2.4 nm and an aspect ratio of 0.78.

[0116] Example 5: Calcination of 2nm Pd / CeO2 at -600℃ and reduction at -200℃

[0117] The preparation process is basically the same as in Example 1, except that in step 3), the calcination temperature during calcination in an oxidizing atmosphere is increased from 500°C to 600°C.

[0118] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the CeO2-supported conformal nano-Pd metal catalyst prepared in this embodiment was 0.52%, which is basically consistent with the theoretical Pd loading mentioned above.

[0119] Transmission electron microscopy (TEM) results showed that the average particle size of the Pd nanoparticles in the prepared catalyst was approximately 1.6 nm, with an aspect ratio of 0.67. Compared to Example 1, the Pd nanoparticles exhibited a wider particle size distribution and less regular morphology.

[0120] Example 6: Calcination of 2nm Pd / CeO2 at -600℃ and reduction at -200℃

[0121] The preparation process is basically the same as in Example 1, except for step 3):

[0122] The calcination temperature during oxidizing atmosphere calcination was increased from 500℃ to 600℃, and the air atmosphere was replaced with a nitrogen atmosphere with an oxygen content of 15 vol%.

[0123] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the CeO2-supported conformal nano-Pd metal catalyst prepared in this embodiment was 0.52%, which is basically consistent with the theoretical Pd loading mentioned above.

[0124] Transmission electron microscopy results show that the Pd nanoparticles of the prepared catalyst have an extremely narrow particle size distribution, with an average particle size of about 1.8 nm and an aspect ratio of 0.72.

[0125] Example: 75nm Pd / CeO2 calcined at -500℃ and reduced at -200℃

[0126] The preparation process is basically the same as in Example 1, except that in step 1), the amount of polyvinylpyrrolidone (PVP, Mw = 58000) is replaced with 450 mg. Finally, a cerium dioxide-supported conformal Pd nano-metal catalyst is prepared.

[0127] Compared with Example 1, the amount of PVP used in the preparation of the cerium dioxide-supported conformal Pd nano-catalyst in this example was adjusted during the preparation process. Transmission electron microscopy characterization results showed that the Pd nanocrystals in the dispersion prepared in this example had a regular spherical polyhedral morphology with an aspect ratio of approximately 0.90; the size was uniform, with an average size of 5.1 nm.

[0128] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the cerium dioxide-supported conformal nano-Pd metal catalyst finally prepared in this embodiment was 0.52%, which is basically consistent with the theoretical Pd loading mentioned above.

[0129] X-ray diffraction results showed that characteristic diffraction peaks at 40.1° and 46.7° belonging to Pd metal could be observed in the catalyst, indicating that the average particle size of Pd nanoparticles is greater than 4 nm.

[0130] Transmission electron microscopy (TEM) results showed that the Pd nanoparticles in the prepared catalyst had an extremely narrow particle size distribution, with an average particle size of approximately 4.8 nm and an aspect ratio of 0.84. Comparison with Example 1 shows that the larger the particle size of the Pd nanocrystals in the dispersion, the smaller the variation in particle size and morphology of the Pd nanoparticles in the prepared catalyst.

[0131] Comparative Example 3: 8nm Pd / CeO2 calcined at -500℃ and reduced at -200℃

[0132] The preparation process is basically the same as in Example 1, except for step 1):

[0133] 100 mg of polyvinylpyrrolidone (PVP, Mw = 58000) and 60 mg of PdCl2 were dissolved in 30 mL of ethanol. The mixture was stirred at room temperature for 10 min, then heated to 165 °C and refluxed under argon for 60 min. A cerium dioxide-supported conformal Pd nano-catalyst was finally prepared.

[0134] Compared with Example 1, the amount of PVP used in the preparation of the cerium dioxide-supported conformal Pd nano-catalyst in this comparative example was adjusted during the preparation process. Transmission electron microscopy characterization results showed that the Pd nanocrystals in the dispersion prepared in this comparative example had a regular spherical polyhedral morphology with an aspect ratio of approximately 0.91; the size was uniform, with an average size of 8.1 nm.

[0135] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the cerium dioxide-supported conformal nano-Pd metal catalyst prepared in this embodiment was 0.51%, which is basically consistent with the theoretical Pd loading mentioned above.

[0136] X-ray diffraction results showed that characteristic diffraction peaks at 40.1° and 46.7° belonging to Pd metal could be observed in the catalyst, indicating that the average particle size of Pd nanoparticles is greater than 4 nm.

[0137] Transmission electron microscopy (TEM) results showed that Pd nanoparticles were uniformly dispersed on the surface of a commercial cerium dioxide support, with an extremely narrow particle size distribution, an average particle size of approximately 7.9 nm, and an aspect ratio of 0.88. Unlike the case in Example 1, the particle size and morphology of the Pd nanoparticles in this catalyst showed no significant change compared to the particle size and morphology of the Pd nanocrystals in the dispersion.

[0138] Example 8: Calcination of 2nm Pd / TiO2 at -500℃ and reduction at -200℃

[0139] The preparation process is basically the same as in Example 1, except that in step 2), commercial cerium dioxide is replaced with an equal mass of commercial nano-titanium dioxide. The final product is a conformal nano-Pd metal catalyst supported on nano-titanium dioxide.

[0140] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the conformal nano-Pd metal catalyst supported on nano-titanium dioxide prepared in this embodiment was 0.49%, which is basically consistent with the theoretical Pd loading mentioned above.

[0141] Transmission electron microscopy results showed that the Pd nanoparticles of the prepared catalyst had an extremely narrow particle size distribution, with an average particle size of about 2.5 nm and an aspect ratio of 0.82.

[0142] Example 9: 2nm Pd / CeO2 / Al2O3 composite support calcined at -500℃ and reduced at -200℃

[0143] Step 1) is exactly the same as in Example 1;

[0144] 2) Weigh 0.1g of cerium nitrate hexahydrate and dissolve it in 30mL of water. Add 1g of commercial γ-Al₂O₃, stir at room temperature for 1h, then heat to 80℃ and stir until dry. Then, calcine at 800℃ for 2h in a nitrogen atmosphere and cool naturally to room temperature at a heating rate of 5℃ / min. Grind and pulverize the calcined product to obtain the CeO₂ / Al₂O₃ composite material. Disperse the CeO₂ / Al₂O₃ composite material in 10mL of water and stir evenly. Adjust the pH of the mixture to 7, and add Pd nanocrystal dispersion dropwise until the theoretical loading mass fraction of Pd is 0.5%. Stir at room temperature for 4h, then filter and dry.

[0145] Step 3) is the same as in Example 1, and finally, a conformal nano-Pd metal catalyst supported on CeO2 / Al2O3 composite material is obtained.

[0146] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the conformal nano-Pd metal catalyst supported on the CeO2 / Al2O3 composite material prepared in this embodiment was 0.51%, which is basically consistent with the theoretical Pd loading mentioned above.

[0147] Compared with Example 1, the Pd nanoparticles of the CeO2 / Al2O3 composite supported conformal nano-Pd metal catalyst have smaller particle size, narrower distribution, and flatter shape, with an average particle size of 2.0 nm and an aspect ratio of 0.72.

[0148] Example 102nmRh / TiO2 calcined at -500℃ and reduced at -450℃

[0149] The preparation process is basically the same as in Example 8, except that:

[0150] In step 1), PdCl2 is replaced with an equimolar amount of RhCl3;

[0151] In step 3), the calcination temperature during the reducing atmosphere calcination is increased from 200℃ to 450℃.

[0152] This embodiment ultimately yields a conformal nano-Rh metal catalyst supported on nano-titanium dioxide.

[0153] Atomic emission spectroscopy analysis revealed that the actual Rh loading mass fraction in the conformal nano-Rh metal catalyst supported on nano-titanium dioxide prepared in this embodiment was 0.50%, which is basically consistent with the theoretical Rh loading.

[0154] Transmission electron microscopy results showed that the Rh nanoparticles of the prepared catalyst had an extremely narrow particle size distribution, with an average particle size of about 2.4 nm and an aspect ratio of 0.80. Furthermore, the surface of the Rh nanoparticles was partially coated with titanium oxide species.

[0155] Example 11: 2nm Pt / MoO3 / SiC calcination at -500℃ and reduction at -200℃

[0156] The preparation process is basically the same as in Example 9, except that:

[0157] In step 1), PdCl2 is replaced with an equimolar amount of [Pt(NH3)4](NO3)2;

[0158] 2) Weigh 0.1g of ammonium molybdate and dissolve it in 30mL of water. Add 1g of nano-SiC, stir at room temperature for 1h, then heat to 80℃ and stir until dry. Then, calcine at 600℃ for 2h in a nitrogen atmosphere and cool naturally to room temperature at a heating rate of 5℃ / min. Grind and pulverize the calcined product to obtain the MoO3 / SiC composite material. Disperse the MoO3 / SiC composite material in 10mL of water and stir evenly. Adjust the pH of the mixture to 2.5, and add Pt nanocrystal dispersion dropwise until the theoretical loading mass fraction of Pt is 0.5%. Stir at room temperature for 4h, then filter and dry.

[0159] The final product was a conformal nano-Pt metal catalyst supported on a MoO3 / SiC composite material.

[0160] Atomic emission spectroscopy analysis revealed that the actual mass fraction of Pt loaded in the conformal nano-Pt metal catalyst supported on the MoO3 / SiC composite material prepared in this embodiment was 0.49%, which is basically consistent with the theoretical Pt loading mentioned above.

[0161] Transmission electron microscopy results show that the Pt nanoparticles of the prepared catalyst have an extremely narrow particle size distribution, with an average particle size of about 1.9 nm and an aspect ratio of 0.77.

[0162] Example 12: 2nm Ru / Co3O4 / Al2O3 calcined at -500℃ and reduced at -200℃

[0163] The preparation process is basically the same as in Example 9, except that:

[0164] In step 1), PdCl2 is replaced with an equimolar amount of RuCl3;

[0165] 2) Weigh 0.15g of cobalt nitrate hexahydrate and dissolve it in 30mL of water. Add 1g of commercial γ-Al₂O₃, stir at room temperature for 1h, then heat to 80℃ and stir until dry. Then, calcine at 600℃ for 2h in a nitrogen atmosphere and cool naturally to room temperature at a heating rate of 5℃ / min. Grind and pulverize the calcined product to obtain the Co₃O₄ / Al₂O₃ composite material. Disperse the Co₃O₄ / Al₂O₃ composite material in 10mL of water and stir evenly. Adjust the pH of the mixture to 8, and add Ru nanocrystal dispersion dropwise until the theoretical loading mass fraction of Ru is 0.5%. Stir at room temperature for 4h, then filter and dry.

[0166] Atomic emission spectroscopy analysis revealed that the actual Ru loading mass fraction in the conformal nano-Ru metal catalyst supported on the Co3O4 / Al2O3 composite material prepared in this embodiment was 0.50%, which is basically consistent with the theoretical Ru loading mentioned above.

[0167] Transmission electron microscopy results showed that the Ru nanoparticles of the prepared catalyst had an extremely narrow particle size distribution, with an average particle size of about 1.6 nm and an aspect ratio of 0.69.

[0168] Example 13: 2nmRh / In2O3 / MgO calcined at 500℃ and reduced at 200℃

[0169] The preparation process is basically the same as in Example 9, except that:

[0170] In step 1), PdCl2 is replaced with an equimolar amount of RhCl3;

[0171] 2) Weigh 0.15g of indium nitrate and dissolve it in 30mL of water. Add 1g of commercial MgO, stir at room temperature for 1h, then heat to 80℃ and stir until dry. Then, calcine at 600℃ for 2h in a nitrogen atmosphere and cool naturally to room temperature at a heating rate of 5℃ / min. Grind and pulverize the calcined product to obtain the In2O3 / MgO composite material. Disperse the In2O3 / MgO composite material in 10mL of water and stir evenly. Adjust the pH of the mixture to 7, and add Rh nanocrystal dispersion dropwise until the theoretical loading mass fraction of Rh is 0.5%. Stir at room temperature for 4h, then filter and dry.

[0172] Atomic emission spectroscopy analysis revealed that the actual Rh loading mass fraction in the conformal nano-Rh metal catalyst supported on the In2O3 / MgO composite material prepared in this embodiment was 0.50%, which is basically consistent with the theoretical Rh loading mentioned above.

[0173] Transmission electron microscopy results showed that the Rh nanoparticles of the prepared catalyst had an extremely narrow particle size distribution, with an average particle size of about 2.6 nm and an aspect ratio of 0.82. Furthermore, the surface of the Rh nanoparticles was partially coated with indium oxide species.

[0174] Example 14: 2nm Pd / CeO2 calcined at -500℃ and reduced at -200℃

[0175] The preparation process is basically the same as in Example 1, except that in step 3), the calcination time during calcination in an oxidizing atmosphere is reduced from 8 hours to 4 hours.

[0176] Atomic emission spectroscopy analysis revealed that the actual Pd loading mass fraction in the CeO2-supported conformal nano-Pd metal catalyst prepared in this embodiment was 0.51%, which is basically consistent with the theoretical Pd loading mentioned above.

[0177] Transmission electron microscopy results showed that the Pd nanoparticles of the prepared catalyst had an extremely narrow particle size distribution, with an average particle size of 2.4 nm and an aspect ratio of 0.79.

[0178] Comparative Example 4

[0179] Weigh 1g of commercial cerium dioxide and add it to 60mL of deionized water. Stir at room temperature, then add 0.85mL of a 10mg / mL PdCl2 aqueous solution. Continue stirring at room temperature for 1h, then heat to 50℃ and stir until dry. Place in an oven at 70℃ and continue drying for 12h. Calcinate the resulting solid in a tube furnace at 500℃ for 8h, then allow it to cool naturally to room temperature. The air flow rate is 5mL / min, and the heating rate is 5℃ / min. Switch to a hydrogen atmosphere and calcine at 200℃ for 2h, then allow it to cool naturally to room temperature. The air flow rate is 40mL / min, and the heating rate is 5℃ / min. Then passivate using the passivation conditions of Example 1 to obtain the cerium dioxide-supported nano-Pd catalyst, denoted as Pd / CeO2-h catalyst.

[0180] Compared to Example 1, the Pd / CeO2-h catalyst prepared in this comparative example uses PdCl2 solution as the metal source. Transmission electron microscopy results are as follows: Figure 4 As shown, the Pd nanoparticles on the prepared Pd / CeO2-h catalyst exhibit a normal distribution in particle size, with an average particle size of 1.5 nm and an aspect ratio of 0.64. The complete crystal morphology cannot be observed.

[0181] Comparative Example 5

[0182] Weigh 1g of commercial cerium dioxide and add it to 60mL of deionized water. Stir at room temperature, then add 0.85mL of a 10mg / mL PdCl2 aqueous solution. After stirring for half an hour, slowly add 100mg / mL NaOH aqueous solution dropwise to adjust the pH of the mixture to 10. Continue stirring at room temperature for 1 hour. Under stirring conditions, add 2mL of a 20mg / mL formic acid aqueous solution dropwise. Continue stirring at room temperature for 1 hour, then filter and wash until neutral to obtain the commercial cerium dioxide-supported Pd / CeO2-l catalyst.

[0183] In this comparative example, the catalyst was prepared using a conventional low-temperature liquid-phase reduction method, first by adding a Pd salt precursor and then adjusting the pH of the solution. Testing revealed that the Pd nanoparticles on the prepared Pd / CeO2-l catalyst exhibited a normal distribution, with an average particle size of approximately 5 nm. Pd nanoparticles with a diameter less than 4 nm accounted for approximately 40% of the total, and were spherical or ellipsoidal in shape.

[0184] Comparative Example 6

[0185] Weigh 1g of commercial cerium dioxide and add it to 60mL of deionized water. Stir at room temperature and slowly add 100mg / mL NaOH aqueous solution to adjust the pH of the mixture to 10. Add 0.85mL of 10mg / mL PdCl2 aqueous solution dropwise and continue stirring at room temperature for 1h. Under stirring conditions, add 2mL of 20mg / mL sodium borohydride aqueous solution dropwise and continue stirring at room temperature for 1h. Filter and wash until neutral to obtain the commercial cerium dioxide-supported Pd / CeO2-r catalyst.

[0186] In this comparative example, the order of adding the Pd salt precursor and the alkali solution was reversed; the pH of the solution was adjusted first, and then the Pd salt precursor was added. Testing revealed that the Pd nanoparticles on the prepared Pd / CeO2-r catalyst had a relatively uniform particle size, with an average particle size of approximately 8 nm. Furthermore, the content of Pd nanoparticles with a diameter less than 4 nm was extremely low, and they exhibited spherical or ellipsoidal polyhedral shapes.

[0187] Comparative Example 7

[0188] The preparation process is basically the same as in Example 1, except that in step 3), only one passivation process is used, that is, nitrogen with an oxygen content of 0.1% is used for passivation at room temperature for 2 hours, and the gas flow rate is 10 mL / min, so as to obtain a commercial cerium dioxide supported Pd / CeO2-o catalyst.

[0189] Tests showed that the particle size distribution and aspect ratio of Pd nanoparticles on the Pd / CeO2-o catalyst prepared by the one-step passivation method were basically the same as those of the catalyst in Example 1, but the content of high oxidation state Pd species was significantly increased.

[0190] Comparative Example 8

[0191] The preparation process is basically the same as that of Comparative Example 4, except that the PdCl2 solution is replaced with 1.01 mL of 10 mg / mL RhCl3 aqueous solution to obtain a commercial cerium dioxide supported Rh / CeO2-h catalyst.

[0192] The Rh nanoparticles on the prepared Rh / CeO2-h catalyst exhibit a normal distribution with a wide particle size distribution, an average particle size of 2.2 nm, an aspect ratio of 0.64, and an irregular morphology.

[0193] Comparative Example 9

[0194] The preparation process is basically the same as that of Comparative Example 5, except that the PdCl2 solution is replaced with 1.01 mL of 10 mg / mL RhCl3 aqueous solution to obtain a commercial cerium dioxide supported Rh / CeO2-l catalyst.

[0195] Tests showed that the particle size of Rh nanoparticles on the prepared Rh / CeO2-l catalyst conformed to a normal distribution, with an average particle size of about 5 nm. Among them, Rh nanoparticles with a particle size of less than 4 nm accounted for about 45%, and were spherical or ellipsoidal.

[0196] Comparative Example 10

[0197] The preparation process is basically the same as that of Comparative Example 8, except that commercial cerium dioxide is replaced with commercial nano titanium dioxide to obtain Rh / TiO2-h catalyst supported on commercial nano titanium dioxide.

[0198] The Rh nanoparticles on the prepared Rh / TiO2-h catalyst exhibit a normal distribution with a wide particle size distribution. The average particle size is 4.5 nm, the aspect ratio is 0.82, and the particles are irregularly ellipsoidal. Furthermore, the surface of the Rh nanoparticles is partially coated with titanium oxide species.

[0199] Application Example 1

[0200] The selective hydrogenation reaction of 2-methyl-3-butyn-2-ol (I) is catalyzed as follows:

[0201] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal nano-Pd metal catalyst prepared in Example 1 was added; 25 mmol of the substrate 2-methyl-3-butyn-2-ol (I) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0202]

[0203] The conversion rate of 2-methyl-3-butyn-2-ol (I) was 99.9%, and the selectivity of 2-methyl-3-buten-2-ol (II) was 97.5%.

[0204] Comparative Application Example 1

[0205] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with an equal mass of the material prepared in Comparative Example 1, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0206] The catalyst was tested and found to have a selectivity of 87.6% and a reaction time of 3 hours.

[0207] Therefore, it can be seen that in the selective hydrogenation reaction of alkynes, the high-temperature calcination conditions adopted in this invention are crucial to the catalytic performance of the conformal nano-Pd metal catalyst.

[0208] Comparative Application Example 2

[0209] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with an equal mass of the material prepared in Comparative Example 2, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0210] The catalyst was tested and found to have a selectivity of 91.4% and a reaction time of 3 hours.

[0211] Therefore, it can be seen that in the selective hydrogenation reaction of alkynes, the long-term high-temperature calcination conditions adopted in this invention are crucial to the catalytic performance of the conformal nano-Pd metal catalyst.

[0212] Compare and contrast examples 3-5

[0213] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with the Pd / CeO2-h, Pd / CeO2-l and Pd / CeO2-r catalysts prepared in Comparative Examples 4 to 6, respectively, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0214] The tests showed that the selectivity and reaction time of the Pd / CeO2-h catalyst were 94.3% and 1h40min, respectively; the selectivity and reaction time of the Pd / CeO2-l catalyst were 85.5% and 4h, respectively; and the selectivity and reaction time of the Pd / CeO2-r catalyst were 89.2% and 7h, respectively.

[0215] Therefore, it can be seen that the use of metal nanocrystals instead of corresponding salts as the noble metal source in this invention is crucial to the catalytic performance of conformal nano-Pd metal catalysts.

[0216] Application Example 2

[0217] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with an equal mass of the product prepared in Example 2, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0218] The catalyst was tested and found to have a selectivity of 93.3% and a reaction time of 2 hours and 40 minutes.

[0219] Therefore, it can be seen that in the selective hydrogenation reaction of alkynes, the oxygen content used in this invention under long-term high-temperature calcination conditions is crucial to the catalytic performance of the conformal nano-Pd metal catalyst.

[0220] Application Example 3

[0221] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with an equal mass of the material prepared in Example 3, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0222] The catalyst was tested and found to have a selectivity of 91.2% and a reaction time of 3 hours.

[0223] Application Example 4

[0224] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with an equal mass of the material prepared in Example 4, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0225] The catalyst was tested and found to have a selectivity of 96.8% and a reaction time of 2 h 30 min.

[0226] Application Example 5

[0227] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with an equal mass of the material prepared in Example 5, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0228] The catalyst was tested and found to have a selectivity of 95.4% and a reaction time of 1 hour and 40 minutes.

[0229] Application Example 6

[0230] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with an equal mass of the material prepared in Example 6, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0231] The catalyst was tested and found to have a selectivity of 97.2% and a reaction time of 1 hour and 50 minutes.

[0232] Application Example 7

[0233] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with an equal mass of the material prepared in Example 7, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0234] The catalyst was tested and found to have a selectivity of 96.2% and a reaction time of 5 hours.

[0235] Application Example 8

[0236] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with an equal mass of the material prepared in Example 8, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0237] The catalyst was tested and found to have a selectivity of 98.5% and a reaction time of 2 hours and 10 minutes.

[0238] Application Example 9

[0239] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with an equal mass of the material prepared in Example 9, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0240] The catalyst was tested and found to have a selectivity of 97.8% and a reaction time of 1 hour and 40 minutes.

[0241] Comparative Application Example 6

[0242] The process conditions were the same as in Application Example 1, except that the catalyst was replaced with the Pd / CeO2-o catalyst prepared by the one-step passivation method in Comparative Example 7, and the reaction time was appropriately extended to achieve a conversion rate of 99.9%.

[0243] The selectivity and reaction time of the Pd / CeO2-o catalyst were tested to be 92.2% and 10 h, respectively. This demonstrates that the two-step passivation method employed in this invention is crucial for the catalytic performance of the conformal nano-Pd metal catalyst in the selective hydrogenation of alkynes.

[0244] Therefore, it can be seen that the conformal nano-Pd metal catalysts prepared in Examples 1, 4 and 6-9 of the present invention maintain catalyst activity while greatly improving selectivity in the selective hydrogenation reaction of alkynes.

[0245] Application Example 10

[0246] The catalytic hydroformylation reaction of ethylene (XXXV) is as follows:

[0247] A 50 mL high-pressure reactor was used; 50 mg of the conformal nano-Rh metal catalyst supported on nano-titanium dioxide prepared in Example 10 was added; 100 mmol of ethylene (XXXV) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0248]

[0249] The test results showed that the ethylene (XXXV) conversion rate was 98.2%, the propionaldehyde (XXXVI) selectivity was 99.1%, and the Rh loss rate was 1.3%.

[0250] Application Example 11

[0251] The process conditions were the same as in Application Example 10, except that the catalyst was replaced with the material prepared in Example 13 and the reaction time was extended to 16 hours.

[0252] The test results showed that the ethylene (XXXV) conversion rate was 98.6%, the propionaldehyde (XXXVI) selectivity was 99.3%, and the Rh loss rate was 3.2%.

[0253] Compare and contrast examples 7-9

[0254] The process conditions were exactly the same as those in Application Example 10, except that the catalyst was replaced with Rh / CeO2-h, Rh / CeO2-l and Rh / TiO2-h catalysts prepared by conventional metal salts as noble metal sources in Comparative Examples 8 to 10, respectively.

[0255] The tests showed that the conversion rate and selectivity of the Rh / CeO2-h catalyst were 86.2% and 94.5%, respectively, with an Rh loss rate of 6.4%; the conversion rate and selectivity of the Rh / CeO2-l catalyst were 99.4% and 93.6%, respectively, with an Rh loss rate of 25.1%; and the conversion rate and selectivity of the Rh / TiO2-h catalyst were 67.8% and 96.2%, respectively, with an Rh loss rate of 1.9%.

[0256] Therefore, it can be seen that the supported conformal nano-Rh metal catalyst prepared in Examples 10 or 13 of the present invention greatly improves the reaction activity and aldehyde selectivity in the hydroformylation reaction of olefins while ensuring an extremely low noble metal loss rate.

[0257] Application Example 12

[0258] The selective hydrogenation reaction of 3,7-dimethyl-1-octyne-3-ol(III) was catalyzed as follows:

[0259] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of the substrate 3,7-dimethyl-1-octyne-3-ol(III) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0260]

[0261] The conversion of 3,7-dimethyl-1-octyne-3-ol (III) was 99.9%, and the selectivity of 3,7-dimethyl-1-octen-3-ol (IV) was 97.3%.

[0262] Application Example 13

[0263] The selective hydrogenation reaction of 3,7-dimethyl-6-octen-1-yn-3-ol (V) is catalyzed as follows:

[0264] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of the substrate 3,7-dimethyl-6-octen-1-yn-3-ol (V) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0265]

[0266] The conversion of 3,7-dimethyl-6-octen-1-yn-3-ol (V) was 99.9%, and the selectivity of 3,7-dimethyl-1,6-octen-3-ol (VI) was 97.6%.

[0267] Application Example 14

[0268] The selective hydrogenation reaction of 3,7,11-trimethyl-1-dodecyn-3-ol (VII) is catalyzed as follows:

[0269] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of the substrate 3,7,11-trimethyl-1-dodecyn-3-ol (VII) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0270]

[0271] The conversion rate of 3,7,11-trimethyl-1-dodecyn-3-ol (VII) was 99.9%, and the selectivity of 3,7,11-trimethyl-1-dodecyn-3-ol (VIII) was 97.5%.

[0272] Application Example 15

[0273] The selective hydrogenation reaction of 3,7,11-trimethyl-6-dodecen-1-yn-3-ol (IX) was catalyzed as follows:

[0274] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of the substrate 3,7,11-trimethyl-6-dodecen-1-yn-3-ol (IX) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0275]

[0276] The conversion rate of 3,7,11-trimethyl-6-dodecen-1-yn-3-ol (IX) was 99.9%, and the selectivity of 3,7,11-trimethyl-1,6-dodecadien-3-ol (X) was 97.4%.

[0277] Application Example 16

[0278] The selective hydrogenation reaction of 3,7,11-trimethyl-6,10-dodecadien-1-yn-3-ol (XI) was catalyzed as follows:

[0279] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-catalyst prepared in Example 1 was added; 25 mmol of the substrate 3,7,11-trimethyl-6,10-dodecadien-1-yn-3-ol (XI) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0280]

[0281] The conversion of 3,7,11-trimethyl-6,10-dodecanedien-1-yn-3-ol (XⅠ) was 99.9%, and the selectivity of 3,7,11-trimethyl-1,6,10-dodecanetrien-3-ol (XⅡ) was 97.2%.

[0282] Application Example 17

[0283] The selective hydrogenation reaction of 3,7,11,15-tetramethyl-1-hexadecyn-3-ol (XⅢ) was catalyzed as follows:

[0284] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal nano-Pd metal catalyst prepared in Example 1 was added; 25 mmol of the substrate 3,7,11,15-tetramethyl-1-hexadecyn-3-ol (XⅢ); 10 mL of ethanol; 0.2 MPa of hydrogen; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0285]

[0286] The conversion of 3,7,11,15-tetramethyl-1-hexadecyn-3-ol (XⅢ) was 99.9%, and the selectivity of 3,7,11,15-tetramethyl-1-hexadecyn-3-ol (XⅣ) was 97.5%.

[0287] Application Example 18

[0288] The selective hydrogenation reaction of 3-methyl-1-(2,6,6-trimethyl-1-cyclohexen-1-yl)-1-penten-4-yn-3-ol (XV) is described in detail below:

[0289] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of the substrate 3-methyl-1-(2,6,6-trimethyl-1-cyclohexen-1-yl)-1-penten-4-yn-3-ol (XV); 10 mL of ethanol; 0.2 MPa of hydrogen; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0290]

[0291] The tests showed that the conversion rate of 3-methyl-1-(2,6,6-trimethyl-1-cyclohexen-1-yl)-1-penten-4-yn-3-ol (XV) was 99.9%, and the selectivity of 3-methyl-1-(2,6,6-trimethyl-1-cyclohexen-1-yl)-1,4-pentadien-3-ol (XVI) was 97.3%.

[0292] Application Example 19

[0293] The selective hydrogenation reaction of norethindrone (XⅦ) is catalyzed as follows:

[0294] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of the substrate norethindrone (XⅦ) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0295]

[0296] The test results showed that the conversion rate of norethindrone (XⅦ) was 99.9%, and the selectivity of norethindrone (XⅦI) was 97.5%.

[0297] Application Example 20

[0298] The selective hydrogenation reaction of catalytic proton pump inhibitor (XIX) is as follows:

[0299] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-catalyst prepared in Example 1 was added; 25 mmol of the substrate Plutonium (XIX) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0300]

[0301] Tests showed that the conversion rate of Prbron (XIX) was 99.9%, and the selectivity of the Prbron hydrogenated olefin product (XX) was 97.5%.

[0302] Application Example 21

[0303] The selective hydrogenation reaction of catalytic diphenylacetylene (XXI) is as follows:

[0304] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of diphenylacetylene (XXI) substrate was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0305]

[0306] Tests showed that the conversion rate of diphenylacetylene (XXI) was 99.9%, and the selectivity of stilbene (XXII) was 99.7%.

[0307] Application Example 22

[0308] The selective hydrogenation reaction of 4-heptyne(XXIII) was carried out as follows:

[0309] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of 4-heptyne(XXIII) substrate was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0310]

[0311] The test results showed that the conversion rate of 4-heptyne (XXIII) was 99.9%, and the selectivity of 4-hepten (XXIV) was 99.7%.

[0312] Application Example 23

[0313] The selective hydrogenation reaction of 1,4-butynediol (XXV) is catalyzed as follows:

[0314] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of 1,4-butynediol (XXV) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0315]

[0316] The test results showed that the conversion rate of 1,4-butynediol (XXV) was 99.9%, and the selectivity of 1,4-butenediol (XXVI) was 99.5%.

[0317] Application Example 24

[0318] The selective hydrogenation reaction of catalytically catalyzed 3-hexyne-1-ol (XXVII) is as follows:

[0319] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of the substrate 3-hexyn-1-ol (XXVII) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0320]

[0321] The tests showed that the conversion rate of 3-hexyn-1-ol (XXVII) was 99.9%, and the selectivity of 3-hexen-1-ol (XXVIII) was 99.5%.

[0322] Application Example 25

[0323] The selective hydrogenation reaction of 6-hydroxy-3-(3-hydroxy-3-methylpent-4-en-1-yn-1-yl)-2,4,4-trimethylcyclohex-2-en-1-one (XXIX) is described in detail below:

[0324] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of the substrate 6-hydroxy-3-(3-hydroxy-3-methylpent-4-en-1-yn-1-yl)-2,4,4-trimethylcyclohexyl-2-en-1-one (XXIX) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0325]

[0326] The conversion rate of 6-hydroxy-3-(3-hydroxy-3-methylpent-4-en-1-yn-1-yl)-2,4,4-trimethylcyclohex-2-en-1-one (XXIX) was 99.9%, and the selectivity of 6-hydroxy-3-(3-hydroxy-3-methylpent-1,4-dien-1-yl)-2,4,4-trimethylcyclohex-2-enone (XXX) was 99.4%.

[0327] Application Example 26

[0328] The selective hydrogenation reaction of 3,6-dimethyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,7-octadien-4-yn-1,6-diol (XXXI) was carried out as follows:

[0329] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of the substrate 3,6-dimethyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,7-octadien-4-yn-1,6-diol (XXXI) was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0330]

[0331] The conversion of 3,6-dimethyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,7-octadien-4-yn-1,6-diol (XXXI) was 99.9%, and the selectivity of 3,6-dimethyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,7-octtrien-1,6-diol (XXXII) was 99.2%.

[0332] Application Example 27

[0333] The selective hydrogenation reaction of mifepristone (XXXIII) was catalyzed as follows:

[0334] A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal Pd nano-metal catalyst prepared in Example 1 was added; 25 mmol of mifepristone (XXXIII) substrate was added; 10 mL of ethanol was added; hydrogen gas was added at 0.2 MPa; the reaction temperature was 35 °C; and the reaction time was 2 h. The reaction structure is as follows:

[0335]

[0336] Tests showed that the conversion rate of mifepristone (XXXIII) was 99.9%, and the selectivity of the mifepristone hydrogenated olefin product (XXXIV) was 99.4%.

[0337] Application Example 28

[0338] The catalytic hydroformylation reaction of ethylene (XXXV) is as follows:

[0339] A 50 mL high-pressure reactor was used; 50 mg of a conformal nano-Rh metal catalyst supported on commercial nano-titanium dioxide prepared in Example 10 was added; 100 mmol of ethylene (XXXV) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0340]

[0341] The test results showed that the ethylene (XXXV) conversion rate was 98.4%, the propionaldehyde (XXXVI) selectivity was 99.6%, and the Rh loss rate was 1.3%.

[0342] Application Example 29

[0343] The catalytic hydroformylation reaction of acrylamide (XXXVII) is as follows:

[0344] A 50 mL high-pressure reactor was used; 50 mg of a conformal nano-Rh metal catalyst supported on commercial nano-titanium dioxide prepared in Example 10 was added; 100 mmol of acrylamide (XXXVII) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0345]

[0346] The tests showed that the conversion rate of acrylamide (XXXVII) was 99.4%, the selectivity of 3-oxopropionamide (XXXVIII) was 98.1%, and the Rh loss rate was 1.3%.

[0347] Application Example 30

[0348] The catalytic hydroformylation reaction of isobutylene (XXXIX) is as follows:

[0349] A 50 mL high-pressure reactor was used; 50 mg of the commercially available nano-titanium dioxide-supported conformal Rh metal catalyst prepared in Example 10 was added; 100 mmol of isobutylene (XXXIX) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0350]

[0351] The test results showed that the conversion rate of isobutylene (XXXIX) was 98.4%, the selectivity of isovaleraldehyde (XXXX) was 99.6%, and the Rh loss rate was 1.3%.

[0352] Application Example 31

[0353] The catalytic hydroformylation reaction of 1,1-stilbene (XXXXI) is as follows:

[0354] A 50 mL high-pressure reactor was used; 50 mg of conformal nano-Rh metal catalyst supported on commercial nano-titanium dioxide prepared in Example 10 was added; 100 mmol of 1,1-stilbene (XXXXI) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0355]

[0356] The test results showed that the conversion rate of 1,1-stilbene (XXXXI) was 98.2%, the selectivity of 3,3-diphenylpropanal (XXXXII) was 96.1%, and the Rh loss rate was 1.3%.

[0357] Application Example 32

[0358] The catalytic hydroformylation reaction of vinyl acetate (XXXXIII) is as follows:

[0359] A 50 mL high-pressure reactor was used; 50 mg of a conformal nano-Rh metal catalyst supported on commercial nano-titanium dioxide prepared in Example 10 was added; 100 mmol of vinyl acetate (XXXXIII) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0360]

[0361] The tests showed that the conversion rate of vinyl acetate (XXXXIII) was 98.8%, the selectivity of 2-acetoxypropionaldehyde (XXXXIV) was 94.2%, and the Rh loss rate was 1.3%.

[0362] Application Example 33

[0363] The catalytic hydroformylation reaction of 3,4-butenediol diacetate (XXXXV) is as follows:

[0364] A 50 mL high-pressure reactor was used; 50 mg of the commercially available nano-titanium dioxide-supported conformal Rh metal catalyst prepared in Example 10 was added; 20 mmol of the substrate 3,4-butenediol diacetate (XXXXV) was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 30 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0365]

[0366] The tests showed that the conversion rate of 3,4-butenediol diacetate (XXXXV) was 99.4%, the selectivity of 2-formylbutane-3,4-diacetyldiacetate (XXXXVI) was 98.6%, and the Rh loss rate was 0.4%.

[0367] Application Example 34

[0368] The catalytic hydroformylation reaction of 1,4-butenediol diacetate (XXXXVII) is as follows:

[0369] A 50 mL high-pressure reactor was used; 50 mg of the commercially available nano-titanium dioxide-supported conformal Rh metal catalyst prepared in Example 10 was added; 100 mmol of the substrate 1,4-butenediol diacetate (XXXXVII) was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0370]

[0371] The tests showed that the conversion rate of 1,4-butenediol diacetate (XXXXVII) was 99.5%, the selectivity of 2-formylbutane-1,4-diacetyldiacetate (XXXXVIII) was 99.1%, and the Rh loss rate was 1.3%.

[0372] Application Example 35

[0373] The catalytic hydroformylation reaction of cyclopentene (XXXXIX) is as follows:

[0374] A 50 mL high-pressure reactor was used; 50 mg of a conformal nano-Rh metal catalyst supported on commercial nano-titanium dioxide prepared in Example 10 was added; 100 mmol of cyclopentene (XXXXIX) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0375]

[0376] The test results showed that the conversion rate of cyclopentene (XXXXIX) was 99.3%, the selectivity of cyclopentylformaldehyde (XXXXX) was 96.1%, and the Rh loss rate was 1.3%.

[0377] Application Example 36

[0378] The catalytic hydroformylation reaction of cyclohexene (XXXXXI) is as follows:

[0379] A 50 mL high-pressure reactor was used; 50 mg of conformal nano-Rh metal catalyst supported on commercial nano-titanium dioxide prepared in Example 10 was added; 100 mmol of cyclohexene (XXXXXI) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0380]

[0381] The test results showed that the conversion rate of cyclohexene (XXXXXII) was 98.4%, the selectivity of cyclohexylformaldehyde (XXXXXII) was 96.1%, and the Rh loss rate was 1.3%.

[0382] Application Example 37

[0383] The catalytic hydroformylation reaction of cyclooctene (XXXXXIII) is as follows:

[0384] A 50 mL high-pressure reactor was used; 50 mg of a conformal nano-Rh metal catalyst supported on commercial nano-titanium dioxide prepared in Example 10 was added; 100 mmol of cyclooctene (XXXXXIII) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0385]

[0386] The test results showed that the conversion rate of cyclooctene (XXXXXIII) was 97.4%, the selectivity of cyclooctylformaldehyde (XXXXXIV) was 94.1%, and the Rh loss rate was 1.3%.

[0387] Application Example 38

[0388] The catalytic hydroformylation reaction of dicyclopentadiene (XXXXXV) is as follows:

[0389] A 50 mL high-pressure reactor was used; 50 mg of the commercially available nano-titanium dioxide-supported conformal Rh metal catalyst prepared in Example 10 was added; 100 mmol of dicyclopentadiene (XXXXXV) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 12 h. The reaction structure is as follows:

[0390]

[0391] The test results showed that the conversion rate of dicyclopentadiene (XXXXXV) was 96.4%, the selectivity of tricyclodecane unsaturated monoaldehyde (XXXXXVI) was 95.1%, and the Rh loss rate was 1.3%.

[0392] Application Example 39

[0393] The performance comparison of the catalysts for the selective hydrogenation of 2-methyl-3-butyn-2-ol (I) is as follows:

[0394] The catalyst reuse was conducted in a parallel dual-reactor experiment. A 50 mL high-pressure reactor was used; 50 mg of the cerium dioxide-supported conformal nano-Pd metal catalyst from Example 1, 25 mmol of 2-methyl-3-butyn-2-ol (I), 10 mL of ethanol, and 0.2 MPa of hydrogen were added to each reactor; the reaction temperature was 35 °C, and the reaction time was 1 h 50 min. After the reaction, the catalysts from both reactors were removed by centrifugation, washed three times with ethanol, and dried under vacuum at 40 °C. The catalyst from one reactor was then replenished with catalyst from the parallel reactor and used for the selective hydrogenation reaction of 2-methyl-3-butyn-2-ol (I).

[0395] The results of the application are shown in Table 1. It can be found that the cerium dioxide-supported conformal nano-Pd metal catalyst of Example 1 has stable performance. After 60 applications, the selectivity can still be maintained and the activity only decreases slightly.

[0396] Table 1

[0397]

[0398] Application Example 40

[0399] The following is a comparison of the catalytic performance of the hydroformylation reaction of 1,4-butenediol diacetate (XXXXVII):

[0400] The catalyst was used in a parallel dual-reactor experiment. A 50 mL high-pressure reactor was used; 50 mg of the commercial nano-titanium dioxide-supported conformal nano-Rh metal catalyst prepared in Example 10 was added to each reactor; 100 mmol of 1,4-butenediol diacetate (XXXXVII) substrate was added; 10 mL of toluene was added; syngas was added at 5 MPa; the reaction temperature was 85 °C; and the reaction time was 11 h 50 min. After the reaction, the catalysts from both reactors were removed by centrifugation, washed three times with ethanol, and dried under vacuum at 40 °C. The catalyst from one reactor was then used for the hydroformylation reaction of 1,4-butenediol diacetate (XXXXVII) after replenishing the catalyst from the parallel reactor.

[0401] The results of the application are shown in Table 2. It can be found that the conformal nano-Rh metal catalyst supported on commercial nano-titanium dioxide prepared in Example 10 has stable performance. After 20 applications, the selectivity can still be maintained and the activity only decreases slightly.

[0402] Table 2

[0403]

[0404]

[0405] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A method for preparing a supported conformal nano-metal catalyst, characterized in that, include: 1) Preparation of metal nanocrystal dispersion; 2) After mixing the carrier with the solvent, it is then mixed with the metal nanocrystal dispersion prepared in step 1). After filtration, washing and drying, an intermediate product is obtained. The carrier is selected from reducible metal oxides, or a mixture of reducible metal oxides and inert supports; The inert support is selected from non-reducing oxides and / or carbides; When the carrier is selected from a mixture of reducible metal oxide and inert support, after mixing the carrier with the solvent, the pH value of the mixture needs to be adjusted first so that only the isoelectric point of the surface of the reducible oxide component in the carrier is opposite to the isoelectric point of the surface of the metal nanocrystal in the metal nanocrystal dispersion, and then it is mixed with the metal nanocrystal dispersion. 3) The intermediate product is subjected to calcination in an oxidizing atmosphere, calcination in a reducing atmosphere, and passivation treatment in sequence.

2. The method for preparing the supported conformal nano-metal catalyst according to claim 1, characterized in that, In step 1): The metal nanocrystal dispersion contains one or more of the following metal elements: Ru, Rh, Pd, Os, Ir, and Pt. The metal nanocrystals are regular polyhedral in shape, with an average size of 2–7 nm and a height-to-width ratio of 0.9–1.

0. The solvent in the metal nanocrystal dispersion is selected from one or more of methanol, ethanol, isopropanol, acetone, butanone, acetonitrile, formamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and dioxane. The concentration of the metal nanocrystal dispersion is 1–50 mg / mL.

3. The method for preparing the supported conformal nano-metal catalyst according to claim 1, characterized in that, In step 2): The reducible metal oxide is selected from one or more of cerium oxide, titanium oxide, zirconium oxide, indium oxide, tungsten oxide, molybdenum oxide, manganese oxide, cobalt oxide, iron oxide, nickel oxide, and vanadium oxide. The non-reducing oxide is selected from one or more of silicon oxide, aluminum oxide, and magnesium oxide; The carbide is selected from silicon carbide; When the carrier is selected from a mixture of reducible metal oxide and inert support, the mass ratio of reducible metal oxide to inert support is 1:(2-20).

4. The method for preparing the supported conformal nano-metal catalyst according to claim 1, characterized in that, In step 2): The solvent is selected from water or an aqueous solution of polar organic molecules, wherein the mass ratio of water to polar organic molecules in the aqueous solution of polar organic molecules is 1:(0.01~1). The polar organic molecule is selected from one or more of methanol, ethanol, isopropanol, acetone, butanone, acetonitrile, dimethyl carbonate, formamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and dioxane. The mass-to-volume ratio of the carrier to the solvent is 1:(5-600)g / mL; The mass ratio of the reducible metal oxide in the carrier to the metal nanocrystals in the metal nanocrystal dispersion is (5-1000):

1.

5. The method for preparing the supported conformal nano-metal catalyst according to claim 1, characterized in that, In step 3): The calcination is carried out in an oxidizing atmosphere with an oxygen content of 10-100 vol%, a calcination temperature of 350-700℃, a calcination time of 4-48 h, and a gas flow rate of 1-200 mL / min. The calcination is carried out in a reducing atmosphere, wherein the content of reducing gas in the reducing atmosphere is 1-100%, the calcination temperature is 25-500℃, the calcination time is 0.1-3.0h, and the gas flow rate is 5-200mL / min. The passivation treatment is carried out under an oxidizing atmosphere and consists of two steps: The first step, passivation, uses an oxidizing atmosphere with an oxygen content of (0.1–2.0)%, a gas flow rate of (1–20) mL / min, a passivation temperature of -20–50℃, and a time of 1–6 h. The second step is passivation, which uses an oxidizing atmosphere with an oxygen content of (2-10)%, a gas flow rate of (1-5) mL / min, a passivation temperature of -20-35℃, and a time of 4-12 h.

6. The method for preparing the supported conformal nano-metal catalyst according to claim 5, characterized in that, Calcination in the oxidizing atmosphere: When the calcination temperature is 350–450℃, the oxygen content in the oxidizing atmosphere is 30–70 vol%. When the calcination temperature is 450–600℃, the oxygen content in the oxidizing atmosphere is 20–50 vol%. When the calcination temperature is 600–700℃, the oxygen content in the oxidizing atmosphere is 10–20 vol%.

7. The method for preparing the supported conformal nano-metal catalyst according to any one of claims 1 to 6, characterized in that: In step 1), the average size of the metal nanocrystals is 2–5 nm; In step 2), the carrier is selected from a mixture of reducible metal oxide and inert support.

8. A supported conformal nano-metal catalyst prepared according to any one of claims 1 to 7, comprising a support and nano-metal uniformly supported on the support, characterized in that: When the carrier is selected from reducible metal oxides, the nano-metals are uniformly distributed on the surface of the carrier; at an appropriate reduction temperature, some types of reducible metal oxides can selectively cover the edges and corners of the nano-metals. When the carrier is selected from a mixture of reducible metal oxide and inert support, the reducible metal oxide is uniformly distributed on the surface of the inert support.

9. The supported conformal nano-metal catalyst according to claim 8, characterized in that: In the supported conformal nano-metal catalyst, the nano-metal particles have a particle size of 1-7 nm, are regular flat polyhedral in shape, and have an aspect ratio of no more than 0.

85. The mass fraction of the nano-metal particles is 0.1% to 10% based on the total mass of the catalyst.

10. The application of a supported conformal nanometal catalyst according to claim 8 or 9 in catalytic hydrogenation reaction.

11. The application of a supported conformal nanometal catalyst according to claim 8 or 9 in the catalytic hydroformylation reaction.

Images