Single-atom palladium catalyst and preparation method thereof

Abstract

The present invention relates to the field of catalyst technology, and specifically, to a single-atom palladium catalyst and a preparation method thereof. The atomic palladium catalyst comprises a carrier and an active component, palladium, wherein the carrier is a polymer metal complex, and the polymer ligand contained in the polymer metal complex is a nitrogen-containing polymer, and the metal ion contained is a platinum ion; wherein the active component palladium is distributed on the carrier in the form of a single atom. The single-atom palladium catalyst provided by the present invention uses a metal polymer complex that does not require modification as a carrier, realizes a single-atom dispersed loading of palladium metal, and can reduce the loading amount of palladium metal. At the same time, the method is simple, simplifies the process flow, and is convenient for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a single-atom palladium catalyst and a preparation method thereof. Background Art

[0002] Since the research group of Academician Zhang Tao proposed the concept of single-atom catalysts in 2011, polymer metal complexes have attracted extensive research in the preparation of single-atom dispersed catalysts.

[0003] CN111054424A discloses a palladium-containing single-atom monolithic catalyst, in which the palladium active ingredient is supported in the form of a single atom on the skeleton of a porous nitrogen-carbon sponge, which can maintain the overall properties of the nitrogen-carbon sponge. It is prepared by impregnating the nitrogen-carbon sponge with a solution of a palladium complex and then heat-treating it at 650-800°C. That is, the palladium metal is loaded on a nitrogen-containing carbon sponge (melamine-formaldehyde sponge). By virtue of the nitrogen atoms in the carrier, the palladium metal atoms are effectively fixed, achieving single-atom dispersion of the palladium metal. However, this method requires high-temperature treatment and is prone to producing nitrogen oxides, which does not meet the environmental protection requirements of green safety.

[0004] CN109420515A discloses a method for modifying a metal oxide support with a nitrogen-containing aminosilane organic compound, then loading the precious metal platinum or palladium onto the support through mechanical grinding. Due to the nitrogen atoms in the aminosilane, the aggregation of platinum or palladium atoms is successfully suppressed, resulting in a catalyst with a single metal atom dispersion. This method uses a metal oxide as a support and stabilizes the active component atoms through complexation with the modified aminosilane. However, subsequent metal recovery from the catalyst requires strong acid treatment, which does not meet the requirements of sustainable development.

[0005] CN111359629A discloses a method for preparing Fe, Pt, Cu, or Pd single-atom catalysts using microwave plasma chemical vapor deposition. Specifically, aluminum nitrate reacts with 2-methylimidazole to form a cage-encapsulated precursor that coats the metal-active precursor, acetylacetonate. Microwave plasma chemical vapor deposition is then used to dope the catalyst with S, P, and N elements to stabilize the loaded metal atoms. This method uses physical coating to secure the metal atoms, and ultimately requires complexation with heteroatoms such as S, P, and N for stabilization. The preparation process is complex and unsuitable for industrial application. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of the existing single-atom catalyst preparation method, such as complexity, high energy consumption, and large pollution, and to provide a single-atom palladium catalyst and a preparation method thereof. The catalyst preparation method is simple and convenient for industrial production.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a single-atom palladium catalyst, comprising a carrier and an active component palladium, wherein the carrier is a polymer metal complex, and the polymer ligand contained in the polymer metal complex is a nitrogen-containing polymer, and the metal ion contained is a platinum ion;

[0008] The active component palladium is distributed on the carrier in the form of single atoms.

[0009] A second aspect of the present invention provides a method for preparing a single-atom palladium catalyst, the method comprising the following steps:

[0010] (1) coordinating and copolymerizing an alcohol solution of a nitrogen-containing polymer with an alcohol solution containing a soluble palladium salt and peroxymolybdic acid, and filtering the obtained product to obtain a catalyst precursor;

[0011] (2) reducing the catalyst precursor with an alcohol solution of a reducing agent to obtain a single-atom palladium catalyst;

[0012] Wherein, the reducing agent is selected from sodium borohydride and / or potassium borohydride.

[0013] The third aspect of the present invention provides a single-atom palladium catalyst prepared by the method provided in the second aspect.

[0014] Through the above technical solution, the present invention provides a single-atom palladium catalyst that uses a metal polymer complex that does not require modification as a carrier, achieving single-atom dispersed loading of palladium metal, thereby reducing the amount of palladium metal loaded. Furthermore, the method is simple, with a simplified process flow, facilitating industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a TEM image of the single-atom palladium catalyst S1 prepared in Example 1;

[0016] Figure 2 is a TEM image of the single-atom palladium catalyst S2 prepared in Example 2;

[0017] Figure 3 is a TEM image of the single-atom palladium catalyst S3 prepared in Example 3;

[0018] Figure 4 is a TEM image of the single-atom palladium catalyst S4 prepared in Example 4;

[0019] Figure 5 is a TEM image of the single-atom palladium catalyst S5 prepared in Example 5;

[0020] Figure 6 This is a TEM image of the palladium / polymer composite catalyst D1 prepared in Comparative Example 1. DETAILED DESCRIPTION

[0021] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0022] The first aspect of the present invention provides a single-atom palladium catalyst, comprising a carrier and an active component palladium, wherein the carrier is a polymer metal complex, and the polymer ligand contained in the polymer metal complex is a nitrogen-containing polymer, and the metal ion contained is a platinum ion;

[0023] The active component palladium is evenly distributed on the carrier in the form of single atoms.

[0024] The inventors of the present invention have discovered that using a polymer metal complex as a carrier, and further limiting the polymer metal complex to be obtained by coordination crosslinking of a nitrogen-containing polymer and peroxymolybdic acid, the active component palladium can be stably loaded on the carrier in the form of a single atom. Due to the presence of O atoms containing lone pairs of electrons in peroxymolybdic acid, palladium can be dispersed in the solution through coordination, while its strong acidity inhibits the hydrolysis and agglomeration of palladium in the solution; the nitrogen-containing polymer (polyvinyl imidazole) contains N atoms with lone pairs of electrons, which has a strong coordination effect with peroxymolybdic acid and palladium. Polyvinyl imidazole fixes peroxymolybdic acid and palladium in the solution through quaternization (with peroxymolybdic acid) and coordination (with peroxymolybdic acid or palladium). The presence of coordinated N atoms and O atoms around palladium suppresses its tendency to agglomerate. The preparation method of the single-atom palladium catalyst provided by the present invention is simple and convenient for industrial production; and the subsequent recovery operation can remove the nitrogen-containing polymer in the single-atom palladium catalyst and recover the metal component by combustion.

[0025] In some embodiments of the present invention, preferably, based on the total weight of the carrier, the loading amount of the active component palladium is 0.01-0.5wt%, for example, 0.01wt%, 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.5wt%, and any value in the range consisting of any two values, preferably 0.01-0.3wt%.

[0026] In the present invention, the source of the polymer metal complex has a wide range of options, and can be obtained by purchase or preparation. The present invention will not be described in detail here, as long as the polymer and metal in the polymer metal complex meet the above definitions.

[0027] In some embodiments of the present invention, preferably, in the polymer metal complex, the molar ratio of the nitrogen-containing polymer to the metal ion is 4-20:1, for example, 4:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, and any value in the range consisting of any two values, preferably 6-10:1.

[0028] In the present invention, there is a wide range of selection for the type of the nitrogen-containing polymer. Preferably, the nitrogen-containing polymer is a polymer containing imidazole side chains, preferably polyvinylimidazole.

[0029] In some embodiments of the present invention, preferably, the weight average molecular weight of the nitrogen-containing polymer is 1×10 4 -2×10 6 g / mol, preferably 1×10 5 -1×10 6 g / mol.

[0030] According to a particularly preferred embodiment of the present invention, the single-atom palladium catalyst comprises a carrier and an active component palladium, wherein the carrier is a polymer metal complex, and the polymer ligand contained in the polymer metal complex is a nitrogen-containing polymer, and the metal ion contained is a platinum ion;

[0031] wherein the active component palladium is uniformly distributed on the carrier in the form of single atoms;

[0032] Wherein, in the polymer metal complex, the molar ratio of the nitrogen-containing polymer to the metal ion is 6-10:1;

[0033] Wherein, the nitrogen-containing polymer is polyvinyl imidazole, and the weight average molecular weight of the nitrogen-containing polymer is 1×10 5 -1×10 6 g / mol.

[0034] A second aspect of the present invention provides a method for preparing a single-atom palladium catalyst, the method comprising the following steps:

[0035] (1) performing a coordination crosslinking reaction on an alcohol solution of a nitrogen-containing polymer and an alcohol solution containing a soluble palladium salt and peroxymolybdic acid, and filtering and drying the obtained product to obtain a catalyst precursor;

[0036] (2) reducing the catalyst precursor with an alcohol solution of a reducing agent to obtain a single-atom palladium catalyst;

[0037] Wherein, the reducing agent is selected from sodium borohydride and / or potassium borohydride.

[0038] In the present invention, the coordination cross-linking reaction is intended to load a soluble palladium salt on a polymer metal complex carrier, and the polymer metal complex is obtained by coordination cross-linking of a nitrogen-containing polymer polymer and molybdic acid. Preferably, in step (1), the conditions of the coordination cross-linking reaction include: a temperature of 0-40°C, preferably 5-25°C; a time of 1-20h, preferably 5-15h; a rotation speed ≥100rpm, preferably 100-300rpm. In the present invention, the temperature limit in the coordination cross-linking reaction can avoid the agglomeration of the metal palladium in the single-atom palladium catalyst; the time limit in the coordination cross-linking reaction allows the coordination complex of the metal palladium and the nitrogen-containing polymer to reach a stable state; the rotation speed limit in the coordination cross-linking reaction can make the dropwise addition more uniform.

[0039] In some embodiments of the present invention, preferably, the molar ratio of the nitrogen-containing polymer in the alcoholic solution of the nitrogen-containing polymer to the peroxymolybdic acid in the alcoholic solution containing the soluble palladium salt and peroxymolybdic acid is 4-20:1, preferably 6-10:1.

[0040] In some embodiments of the present invention, preferably, in the alcoholic solution of the nitrogen-containing polymer, the concentration of the nitrogen-containing polymer is 0.1-1 mmol / mL, for example, 0.1 mmol / mL, 0.2 mmol / mL, 0.3 mmol / mL, 0.4 mmol / mL, 0.5 mmol / mL, 0.8 mmol / mL, 1 mmol / mL, and any value in the range consisting of any two values, preferably 0.1-0.5 mmol / mL.

[0041] In the present invention, there is a wide range of choices for the source of the alcohol solution of the nitrogen-containing polymer, which can be obtained by preparation or purchase.

[0042] In some embodiments of the present invention, preferably, the alcohol solution of the nitrogen-containing polymer is prepared by the following method: dissolving the nitrogen-containing polymer in alcohol to obtain an alcohol solution of the nitrogen-containing polymer with a concentration of 0.1-1 mmol / mL, preferably 0.1-0.5 mmol / mL.

[0043] In the present invention, there is a wide range of selection for the type of the nitrogen-containing polymer. Preferably, the nitrogen-containing polymer is a polymer containing imidazole side chains, preferably polyvinylimidazole.

[0044] In some embodiments of the present invention, preferably, the weight average molecular weight of the nitrogen-containing polymer is 1×10 4 -2×10 6 g / mol, preferably 1×10 5 -1×10 6 g / mol.

[0045] In some embodiments of the present invention, preferably, in the alcohol solution containing a soluble palladium salt and peroxymolybdic acid, the concentration of peroxymolybdic acid is 0.01-0.1 mmol / mL, for example, 0.01 mmol / mL, 0.02 mmol / mL, 0.03 mmol / mL, 0.04 mmol / mL, 0.05 mmol / mL, 0.08 mmol / mL, 0.1 mmol / mL, and any value in the range of any two values, preferably 0.01-0.05 mmol / mL; the concentration of the soluble palladium salt is 1×10 -6 -1×10 -4 mmol / mL, for example, 1×10 -6 mmol / mL, 1×10 5 mmol / mL, 5×10 -5 mmol / mL, 1×10 -4 mmol / mL, and any value in the range of any two values, preferably 1×10 -5 -1×10 -4 mmol / mL.

[0046] In the present invention, the soluble palladium salt is purchased; peroxymolybdic acid is prepared in the laboratory, specifically, molybdenum powder (purchased from Aladdin, brand M141395) is dissolved in 30% hydrogen peroxide to obtain peroxymolybdic acid; for specific reference, "Preparation of MoO3 Nanobelts from Peroxymolybdic Acid Sol and Study on Their Electrochemical Properties" (Qi Yanyuan, Chen Wen, Mai Liqiang, Hu Bin, Jin Wei, Rare Metals [J]., 2007(01):67-71).

[0047] In some embodiments of the present invention, preferably, the alcohol solution containing the soluble palladium salt and peroxymolybdic acid is prepared by the following method: first dissolving the peroxymolybdic acid in alcohol, and then adding the soluble palladium salt.

[0048] In some embodiments of the present invention, preferably, the soluble palladium salt is selected from at least one of palladium nitrate, palladium chloride, palladium acetate, and palladium acetylacetonate. In the present invention, unless otherwise specified, soluble means readily soluble in water, or soluble in water with the aid of an additive.

[0049] In the present invention, the filtering method has a wide range of options. Preferably, the filtration is vacuum filtration, and the obtained solid is washed with alcohol (eg, methanol, ethanol, etc.) for 1-5 times and then dried to obtain a catalyst precursor.

[0050] In some embodiments of the present invention, preferably, the drying temperature is room temperature under vacuum conditions; and the drying time is 1-48 h, preferably 4-24 h.

[0051] In some embodiments of the present invention, preferably, in step (2), the ratio of the amount of the catalyst precursor measured in g to the alcohol solution of the reducing agent measured in mL is 1:5-100, for example, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, and any value in the range consisting of any two values, preferably 1:10-50.

[0052] In some embodiments of the present invention, preferably, in the alcohol solution of the reducing agent, the reducing agent concentration is 0.01-1 mmol / mL, for example, 0.01 mmol / mL, 0.02 mmol / mL, 0.05 mmol / mL, 0.1 mmol / mL, 0.15 mmol / mL, 0.2 mmol / mL, 0.5 mmol / mL, 1 mmol / mL, and any value in the range consisting of any two values, preferably 0.02-0.2 mmol / mL.

[0053] In a specific embodiment of the present invention, the reducing agent is dissolved in alcohol to obtain an alcohol solution of the reducing agent with a concentration of 0.01-1 mmol / mL, preferably 0.02-0.2 mmol / mL.

[0054] In the present invention, the reduction is to reduce the soluble palladium salt in the catalyst precursor to metallic palladium. Preferably, the reduction conditions include: a temperature of -10 to 50°C, preferably -5 to 5°C, and a time of 1 to 10 hours, preferably 4 to 6 hours.

[0055] In some embodiments of the present invention, preferably, the alcohol in the alcohol solution of the nitrogen-containing polymer, the alcohol solution containing the soluble palladium salt and peroxymolybdic acid, and the alcohol solution of the reducing agent is independently selected from at least one of methanol, ethanol, propanol and isopropanol.

[0056] In a preferred embodiment of the present invention, the alcohol in the alcoholic solution of the nitrogen-containing polymer is selected from methanol and / or ethanol, preferably methanol; the alcohol in the alcoholic solution containing the soluble palladium salt and peroxymolybdic acid is selected from methanol and / or ethanol, preferably methanol; and the alcohol in the alcoholic solution of the reducing agent is isopropanol.

[0057] The preparation method of the single-atom palladium catalyst provided by the present invention is simple. Specifically, the active component palladium in the single-atom palladium catalyst is inhibited from agglomerating due to the presence of lone-pair oxygen atoms in peroxymolybdic acid and lone-pair nitrogen atoms in the nitrogen-containing polymer, allowing the palladium to be stably loaded on the carrier in the form of single atoms. Furthermore, the single-atom palladium catalyst can be easily recovered by removing the metal component from the polymer through combustion.

[0058] The third aspect of the present invention provides a single-atom palladium catalyst prepared by the method provided in the second aspect.

[0059] The present invention will be described in detail below through examples.

[0060] Polyvinyl imidazole (PVIM) was purchased from Bailingwei Technology Co., Ltd. and is a commercial product with the brand name P3904. The weight average molecular weight of polyvinyl imidazole is 1×10 6 g / mol.

[0061] Peroxymolybdic acid was prepared in the laboratory by dissolving molybdenum powder (purchased from Aladdin, brand M141395) in 30% hydrogen peroxide to obtain peroxymolybdic acid; for specific reference, "Preparation of MoO3 Nanobelts from Peroxymolybdic Acid Sol and Study on Their Electrochemical Properties" (Qi Yanyuan, Chen Wen, Mai Liqiang, Hu Bin, Jin Wei, Rare Metals [J]., 2007(01):67-71).

[0062] Molybdenum powder was purchased from Aladdin Company and is a commercial product with the brand name M141395.

[0063] In the present invention, unless otherwise specified, the room temperature is 25°C.

[0064] Example 1

[0065] (1) Take 10 mL of methanol solution with a concentration of 0.1 mmol / mL of polyvinyl imidazole, add 0.01 mmol / mL of peroxymolybdic acid and 1×10 -5 10 mL of a mmol / mL methanol solution was prepared, and the two solutions were added dropwise to 10 mL of methanol at room temperature and a rotation speed of 200 rpm. The coordination cross-linking reaction was carried out for 10 h. The obtained product was filtered, and the obtained solid was washed with methanol three times and then dried in a vacuum drying oven at 25°C for 12 h to obtain a catalyst precursor.

[0066] (2) The catalyst precursor and a sodium borohydride solution with a concentration of 0.02 mmol / mL were reduced in an isopropanol solution under the following conditions: temperature of 0°C and time of 6 h to obtain a single-atom palladium catalyst S1.

[0067] Among them, the TEM image of the single-atom palladium catalyst S1 is as follows Figure 1 As shown by Figure 1 It can be seen that the metallic palladium is dispersed on the support in a monatomic state.

[0068] Among them, in the single-atom palladium catalyst S1, the loading amount of metal palladium was 0.023wt% according to X-ray fluorescence spectroscopy analysis; in the polymer metal complex, the molar ratio of polyvinyl imidazole to molybdenum was 10:1.

[0069] Example 2

[0070] (1) Take 10 mL of methanol solution with a concentration of 0.1 mmol / mL of polyvinyl imidazole, a concentration of 0.01 mmol / mL of peroxymolybdic acid, and a concentration of 1×10 -4 10 mL of a mmol / mL methanol solution was prepared, and the two solutions were added dropwise to 10 mL of methanol at room temperature and a rotation speed of 200 rpm. The coordination cross-linking reaction was carried out for 10 h. The obtained product was filtered, and the obtained solid was washed with methanol three times and then dried in a vacuum drying oven at 25°C for 12 h to obtain a catalyst precursor.

[0071] (2) The catalyst precursor and sodium borohydride were reduced in an isopropanol solution with a concentration of 0.2 mmol / mL. The reduction conditions included: temperature of -5°C and time of 4 h to obtain a single-atom palladium catalyst S2.

[0072] Among them, the TEM image of the single-atom palladium catalyst S2 is as follows Figure 2 As shown by Figure 2 It can be seen that the metallic palladium is dispersed on the support in a monatomic state.

[0073] Among them, in the single-atom palladium catalyst S2, the loading amount of metal palladium was 0.292wt% according to X-ray fluorescence spectroscopy analysis; in the polymer metal complex, the molar ratio of polyvinyl imidazole to molybdenum was 10:1.

[0074] Example 3

[0075] (1) Take 10 mL of methanol solution with a concentration of 0.5 mmol / mL of polyvinyl imidazole, a concentration of 0.05 mmol / mL of peroxymolybdic acid, and a concentration of 1×10 -5 10 mL of a mmol / mL methanol solution was added dropwise to 10 mL of methanol at room temperature and a rotation speed of 200 rpm. The coordination cross-linking reaction was carried out for 10 h. The obtained product was filtered, and the obtained solid was washed with methanol three times and then dried in a vacuum drying oven at 25°C for 24 h to obtain a catalyst precursor.

[0076] (2) The catalyst precursor and sodium borohydride were reduced in an isopropanol solution with a concentration of 0.02 mmol / mL. The reduction conditions included: temperature of 5° C. and time of 6 h to obtain a single-atom palladium catalyst S3.

[0077] Among them, the TEM image of the single-atom palladium catalyst S3 is as follows Figure 3 As shown by Figure 3 It can be seen that the metallic palladium is dispersed on the support in a monatomic state.

[0078] Among them, in the single-atom palladium catalyst S3, the loading amount of metal palladium was 0.011wt% according to X-ray fluorescence spectroscopy analysis; in the polymer metal complex, the molar ratio of polyvinyl imidazole to molybdenum was 10:1.

[0079] Example 4

[0080] (1) Take 10 mL of methanol solution with a concentration of 0.5 mmol / mL of polyvinyl imidazole, 0.05 mmol / mL of peroxymolybdic acid, and 1×10 -4 10 mL of a mmol / mL methanol solution was added dropwise to 10 mL of methanol at room temperature and a rotation speed of 200 rpm. The coordination cross-linking reaction was carried out for 10 h. The obtained product was filtered, and the obtained solid was washed with methanol three times and then dried in a vacuum drying oven at 25°C for 12 h to obtain a catalyst precursor.

[0081] (2) The catalyst precursor and sodium borohydride were reduced in an isopropanol solution with a concentration of 0.02 mmol / mL. The reduction conditions included: temperature of 0° C. and time of 5 h to obtain a single-atom palladium catalyst S4.

[0082] Among them, the TEM image of the single-atom palladium catalyst S4 is as follows Figure 4 As shown by Figure 4 It can be seen that the metallic palladium is dispersed on the support in a monatomic state.

[0083] Among them, in the single-atom palladium catalyst S4, the loading amount of metal palladium was 0.13wt% according to X-ray fluorescence spectroscopy analysis; in the polymer metal complex, the molar ratio of polyvinyl imidazole to molybdenum was 10:1.

[0084] Example 5

[0085] The method of Example 1 was followed, except that in step (1), 0.1 mmol of peroxymolybdic acid was replaced by 0.17 mmol of peroxymolybdic acid, resulting in a peroxymolybdic acid concentration of 0.017 mmol / mL and a palladium nitrate concentration of 1×10 -5 mmol / mL methanol solution, and the other conditions were the same to obtain single-atom palladium catalyst S5.

[0086] Among them, the TEM image of the single-atom palladium catalyst S5 is as follows Figure 5 As shown by Figure 5 It can be seen that the metal palladium is dispersed on the support in a monatomic state.

[0087] Among them, in the single-atom palladium catalyst S5, the loading amount of metal palladium was 0.016wt% according to X-ray fluorescence spectroscopy analysis; in the polymer metal complex, the molar ratio of polyvinyl imidazole to platinum ion was 6:1.

[0088] Comparative Example 1

[0089] The method of Example 4 is followed, except that in step (1), a peroxymolybdic acid solution is first added dropwise to obtain a polymer metal complex carrier; and then a Pd / polymer composite catalyst with a loading of 0.1 wt% is prepared by a conventional equal amount impregnation method.

[0090] Catalyst D1, after X-ray fluorescence spectroscopy analysis, the metal palladium loading is 0.093wt%; the TEM image of D1 is as follows Figure 6 As shown, the palladium metal appears in agglomerated form.

[0091] Compared with Comparative Example 1, the active component palladium in the single-atom palladium catalyst prepared by the method provided by the present invention is distributed on the carrier in the form of single atoms; specifically, the single-atom palladium catalyst provided by the present invention uses a metal polymer complex that does not require modification as a carrier, realizes single-atom dispersed loading of palladium metal, and can reduce the loading amount of palladium metal.

[0092] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A single-atom palladium catalyst comprising a carrier and an active component palladium, characterized in that: The carrier is a polymer metal complex, and the polymer ligand contained in the polymer metal complex is a nitrogen-containing polymer, and the metal ion contained is a molybdenum ion; The active component palladium is distributed on the carrier in the form of single atoms; the loading amount of the active component palladium is 0.01-0.15wt%; The preparation method of the single-atom palladium catalyst comprises the following steps: (1) performing a coordination crosslinking reaction on an alcohol solution of a nitrogen-containing polymer and an alcohol solution containing a soluble palladium salt and peroxymolybdic acid, and filtering and drying the obtained product to obtain a catalyst precursor; (2) reducing the catalyst precursor with an alcohol solution of a reducing agent to obtain a single-atom palladium catalyst; Wherein, the reducing agent is selected from sodium borohydride and / or potassium borohydride.

2. The single-atom palladium catalyst according to claim 1, wherein In the polymer metal complex, the molar ratio of the nitrogen-containing polymer to the metal ion is 4-20:

1.

3. The single-atom palladium catalyst according to claim 2, wherein In the polymer metal complex, the molar ratio of the nitrogen-containing polymer to the metal ion is 6-10:

1.

4. The single-atom palladium catalyst according to claim 1, wherein The nitrogen-containing polymer is a polymer containing imidazole side chains; And / or, the weight average molecular weight of the nitrogen-containing polymer is 1×10 4 -2×10 6 g / mol.

5. The single-atom palladium catalyst according to claim 4, wherein The nitrogen-containing polymer is polyvinyl imidazole; And / or, the weight average molecular weight of the nitrogen-containing polymer is 1×10 5 -1×10 6 g / mol.

6. A method for preparing a single-atom palladium catalyst, characterized in that: The method comprises the following steps: (1) performing a coordination crosslinking reaction on an alcohol solution of a nitrogen-containing polymer and an alcohol solution containing a soluble palladium salt and peroxymolybdic acid, and filtering and drying the obtained product to obtain a catalyst precursor; (2) reducing the catalyst precursor with an alcohol solution of a reducing agent to obtain a single-atom palladium catalyst; Wherein, the reducing agent is selected from sodium borohydride and / or potassium borohydride.

7. The preparation method according to claim 6, wherein In step (1), the conditions of the coordination cross-linking reaction include: temperature of 0-40°C; time of 1-20h; rotation speed ≥100 rpm; and / or, in the alcohol solution of the nitrogen-containing polymer, the concentration of the nitrogen-containing polymer is 0.1-1 mmol / mL; and / or, the nitrogen-containing polymer is a polymer containing imidazole side chains; And / or, the weight average molecular weight of the nitrogen-containing polymer is 1×10 4 -2×10 6 g / mol; And / or, the alcohol solution containing soluble palladium salt and peroxymolybdic acid, the concentration of peroxymolybdic acid is 0.01-0.1 mmol / mL; the concentration of soluble palladium salt is 1×10 -6 -1×10 -4 mmol / mL.

8. The preparation method according to claim 7, wherein The conditions of the coordination crosslinking reaction include: temperature of 5-25°C; time of 5-15h; rotation speed of 100-300 rpm; and / or, in the alcohol solution of the nitrogen-containing polymer, the concentration of the nitrogen-containing polymer is 0.1-0.5 mmol / mL; and / or, the nitrogen-containing polymer is polyvinyl imidazole; And / or, the weight average molecular weight of the polyvinyl imidazole is 1×10 5 -1×10 6 g / mol; And / or, the alcohol solution containing soluble palladium salt and peroxymolybdic acid has a peroxymolybdic acid concentration of 0.01-0.05 mmol / mL; the soluble palladium salt concentration is 1×10 -5 -1×10 -4 mmol / mL.

9. The preparation method according to claim 6, wherein The alcohol solution containing the soluble palladium salt and peroxymolybdic acid is prepared by the following method: first dissolving the peroxymolybdic acid in alcohol, and then adding the soluble palladium salt; And / or, the soluble palladium salt is selected from at least one of palladium nitrate, palladium chloride, palladium acetate and palladium acetylacetonate.

10. The preparation method according to claim 6, wherein In step (2), the ratio of the catalyst precursor in g to the alcohol solution of the reducing agent in mL is 1:5-100; and / or, the reducing agent concentration in the alcohol solution of the reducing agent is 0.01-1 mmol / mL; And / or, the reduction conditions include: temperature of -10 to 50° C., and time of 1 to 10 h.

11. The preparation method according to claim 10, wherein In step (2), the ratio of the catalyst precursor in g to the alcohol solution of the reducing agent in mL is 1:10-50; and / or, in the alcohol solution of the reducing agent, the reducing agent concentration is 0.02-0.2 mmol / mL; And / or, the reduction conditions include: temperature of -5 to 5°C and time of 4-6 hours.

12. The preparation method according to claim 6, wherein The alcohol in the alcohol solution of the nitrogen-containing polymer, the alcohol solution containing the soluble palladium salt and peroxymolybdic acid, and the alcohol solution of the reducing agent is independently selected from at least one of methanol, ethanol, propanol, and isopropanol; and / or, the alcohol in the alcoholic solution of the nitrogen-containing polymer is selected from methanol and / or ethanol; And / or, the alcohol in the alcohol solution containing the soluble palladium salt and peroxymolybdic acid is selected from methanol and / or ethanol; And / or, the alcohol in the alcohol solution of the reducing agent is isopropyl alcohol.

Images