A wheat ear-shaped Pd-Ag nanomaterial, a preparation method and application thereof
The wheat-ear-shaped Pd-Ag nanomaterials were prepared by an oil-water two-phase interface synthesis method, which solved the problems of poor selectivity and complex and energy-intensive preparation of Pd-based catalysts in the prior art. This method enables the efficient preparation of nanomaterials with high catalytic activity and selectivity under mild conditions for the selective hydrogenation reaction of p-nitrobenzaldehyde.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HENAN UNIV OF SCI & TECH
- Filing Date
- 2024-02-28
- Publication Date
- 2026-07-03
AI Technical Summary
Existing Pd-based catalysts exhibit poor catalytic selectivity in selective hydrogenation reactions, and their preparation methods are complex and energy-intensive, making it difficult to prepare bimetallic catalysts with high catalytic activity and selectivity under mild conditions.
A wheat-ear-shaped Pd-Ag nanomaterial was synthesized in one step under mild conditions using an oil-water two-phase interface synthesis method with DDTAB as an ionic surfactant. By forming an ordered arrangement at the oil-water interface, wheat-ear-shaped Pd-Ag nanomaterials with high catalytic activity and selectivity were prepared.
We have achieved low-energy preparation of wheat-ear-shaped Pd-Ag nanomaterials with high catalytic activity and selectivity under mild conditions. These nanomaterials are used for the selective hydrogenation of p-nitrobenzaldehyde and exhibit excellent catalytic activity and stability.
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Figure CN118080875B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of bimetallic nanomaterials technology, specifically relating to a wheat-ear-shaped Pd-Ag nanomaterial, its preparation method, and its application. Background Technology
[0002] Hydrogenation reactions are an important class of organic reactions that can convert compounds containing unsaturated functional groups into saturated compounds. Selective hydrogenation is achieved when a substance contains two or more unsaturated functional groups, allowing selective hydrogenation of one type of functional group while maintaining the other type. Such reactions have wide applications in pharmaceuticals, shampoos, pesticides, chemicals, and dyes. However, due to the generally poor selectivity of catalysts, hydrogenation reactions often result in completely hydrogenated products. Therefore, it is crucial that the prepared catalyst possesses not only high catalytic activity but also high catalytic selectivity.
[0003] Metallic phosphorus (Pd) possesses high hydrogen activation capacity and activity, making it widely used in heterogeneous hydrogenation reactions. However, Pd exhibits relatively low selectivity. An effective approach is to introduce a second metal to form alloys, intermetallic compounds, core-shell structures, or heterostructures with Pd. This allows for effective tuning of the electronic structure and geometric properties of Pd-based catalysts, thereby improving their catalytic selectivity.
[0004] In existing technologies, some PdCu bimetallic catalysts are obtained by introducing a second metal, Cu, onto Pd. These PdCu bimetallic catalysts exhibit high catalytic activity and selectivity for the selective hydrogenation of 2,3,6-trichloropyridine to 2,3-dichloropyridine. However, this method requires multiple steps to prepare the activated carbon-supported PdCu catalyst. Another method introduces an N-doped Pd-Co bimetallic magnetic catalyst, which exhibits high conversion and selectivity in the selective hydrogenation of furfural to furfuryl alcohol. The preparation of this catalyst requires first mixing Co salt, carbon source, Pd salt, and amine source into a gel, drying it at a certain temperature, and then calcining it at 200-900℃ under hydrogen for 1-5 h. This preparation method is complex, dangerous, and energy-intensive. Therefore, there is a need to develop a mild and simple one-step method to prepare Pd-based nanomaterials with high catalytic activity, selectivity, and stability. Summary of the Invention
[0005] To address the aforementioned issues, this invention proposes a wheat-ear-shaped Pd-Ag nanomaterial, its preparation method, and its applications. Using an oil-water two-phase reaction system, without the need for seeds, hard templates, high temperature, high pressure, or other stringent reaction conditions, a wheat-ear-shaped Pd-Ag alloy nanomaterial exhibiting excellent catalytic activity and selectivity in the hydrogenation reaction of p-nitrobenzaldehyde is synthesized in a one-step interface under mild conditions with low energy consumption.
[0006] This invention is achieved through the following technical solution:
[0007] A method for preparing wheat-ear-shaped Pd-Ag nanomaterials includes the following steps:
[0008] Step 1: Cut the glass slide into squares, soak them in a mixture of hydrogen peroxide and concentrated sulfuric acid to remove surface impurities, then clean them with anhydrous ethanol and set aside.
[0009] Step 2: Weigh 1-naphthol and add it to ethyl acetate to prepare a 1-naphthol mixed solution, which will be used as the oil phase in the reaction system for later use.
[0010] Step 3: Weigh out tetradecyl dimethyl ethylenediammonium dibromide and dissolve it in distilled water. Then add the Pd precursor and Ag precursor to the above solution and dissolve them to prepare a mixed aqueous solution, which will be used as the aqueous phase in the reaction system for later use.
[0011] Step 4: Place the glass slide from Step 1 into the cylindrical vial and set aside.
[0012] Step 5: Add the mixed aqueous solution from Step 3 to the vial from Step 4, then add the 1-naphthol mixed solution from Step 2 to form an oil-water two-phase reaction system, and let it stand to react.
[0013] Step 6: Slowly extract the aqueous phase, transfer the product to the glass slide from Step 4, then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, repeat several times, and set aside.
[0014] Step 7: Immerse the glass slide loaded with the product obtained in Step 6 in an ammonia solution, then remove the ammonia solution, immerse it in ethanol, remove it, repeat this process several times, and then air dry it naturally to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on the glass slide.
[0015] Furthermore, in step one, the block size is 1cm × 1cm, and the volume ratio of hydrogen peroxide to concentrated sulfuric acid is 1:1.
[0016] Furthermore, in step two, the concentration of 1-naphthol is 10-50 mM.
[0017] Furthermore, in step three, the concentration of tetradecyl dimethyl ethylenediammonium dibromide is 50 mM, the Pd precursor is Na2PdCl4, and its concentration in the aqueous phase is 1.2-3.8 mM; the Ag precursor is AgNO3, and its concentration in the aqueous phase is 1.2-3.8 mM.
[0018] Furthermore, the preparation method of tetramethylethylenediamine dibromide in step three is as follows: tetramethylethylenediamine and 1-tetradecane bromide are dissolved in anhydrous ethanol, heated under reflux for 20 h, and then the crude product is dissolved in ethyl acetate and recrystallized from ethyl acetate to obtain the product.
[0019] Furthermore, in step four, the diameter of the cylindrical vial is 2.1~2.3cm.
[0020] Furthermore, in step five, the reaction is allowed to stand for 72 hours, and the reaction temperature is 10-40℃.
[0021] The present invention also provides a wheat-ear-shaped Pd-Ag nanomaterial, which is prepared by the above preparation method. The Pd-Ag nanomaterial is formed by the orderly aggregation of particles into a wheat-ear-shaped structure.
[0022] This invention also provides an application of wheat-ear-shaped Pd-Ag nanomaterials as a catalyst in selective hydrogenation reactions. Specifically, it is applied to the selective hydrogenation of p-nitrobenzaldehyde to prepare p-aminobenzaldehyde. The method involves dispersing 1.5 mg of wheat-ear-shaped Pd-Ag alloy nanomaterials in 1 mL of anhydrous ethanol, adding it to 4 mL of anhydrous ethanol containing 0.25 mol of p-nitrobenzaldehyde, mixing the solution thoroughly, and reacting at 35°C under a normal pressure H2 atmosphere. Samples are taken at different time points and analyzed using gas chromatography-mass spectrometry (GC-MS).
[0023] The beneficial effects of this invention are as follows:
[0024] 1) The present invention uses an oil-water interface synthesis method that does not require strict reaction conditions such as seeds, hard templates, high temperature and high pressure, and is simple to operate and has low energy consumption;
[0025] 2) This invention uses a synthesized ionic surfactant DTDAB, which has two cations and a relatively long two alkyl chain (tetradecyl). This amphiphilic surfactant with a special structure will accumulate at the oil-water interface. The longer alkyl chain penetrates into the oil phase, while the two cations exist in the aqueous phase at the interface, forming an ordered arrangement at the interface. This guides the generation and orderly assembly of nanoparticles at the interface, forming wheat-ear-shaped Pd-Ag nanomaterials with a special structure.
[0026] 3) The wheat-ear-shaped Pd-Ag alloy nanomaterials of the present invention have the characteristics of high catalytic activity, high selectivity and high stability. Attached Figure Description
[0027] Figure 1 This is a 20,000x magnified SEM image of the Pd-Ag nanoalloy nano-wheat ears prepared in Example 1 of this invention.
[0028] Figure 2This is a 200,000x magnified SEM image of the wheat-ear-shaped Pd-Ag alloy nanomaterial prepared in Example 1 of this invention.
[0029] Figure 3 This is a TEM image of the wheat-ear-shaped Pd-Ag alloy nanomaterial prepared in Example 1 of the present invention;
[0030] Figure 4 The HAADF-STEM and elemental mapping diagrams of the wheat-ear-shaped Pd-Ag alloy nanomaterials prepared in Example 1 of this invention are shown.
[0031] Figure 5 The image shows the XRD pattern of the wheat-ear-shaped Pd-Ag alloy nanomaterial prepared in Example 1 of this invention.
[0032] Figure 6 The graph shows the changes in conversion rate and selectivity of the p-nitrobenzaldehyde hydrogenation catalyzed by the wheat-ear-shaped Pd-Ag alloy nanomaterials prepared in Example 1 of this invention over time.
[0033] Figure 7 The conversion rate and selectivity of the p-nitrobenzaldehyde hydrogenation cycle catalyzed by the wheat-ear-shaped Pd-Ag alloy nanomaterial prepared in Example 1 of this invention for 5 cycles are shown. Detailed Implementation
[0034] A method for preparing wheat-ear-shaped Pd-Ag nanomaterials includes the following steps:
[0035] Step 1: Cut the glass slide into 1cm×1cm squares, soak them in a mixture of hydrogen peroxide and concentrated sulfuric acid (volume ratio 1:1) to remove surface impurities, then clean them with anhydrous ethanol and set aside.
[0036] Step 2: Weigh 1-naphthol and add it to ethyl acetate to prepare a 1-naphthol mixed solution with a concentration of 10-50 mM. This solution will be used as the oil phase in the reaction system for later use.
[0037] Step 3: Weigh out tetradecyl dimethyl ethylenediamine dibromide (DTDAB) and dissolve it in distilled water. The concentration of tetradecyl dimethyl ethylenediamine dibromide is 50 mM. Then, add the Pd precursor and Ag precursor to the above solution and dissolve them to prepare a mixed aqueous solution, which will be used as the aqueous phase in the reaction system for later use. The Pd precursor is Na2PdCl4, and its concentration in the aqueous phase is 1.2-3.8 mM. The Ag precursor is AgNO3, and its concentration in the aqueous phase is 1.2-3.8 mM.
[0038] The preparation method of tetradecyl dimethyl ethylenediamine dibromide is as follows: 1 mol tetramethyl ethylenediamine and 2 mol 1-tetradecyl bromide are dissolved in 20 mL of anhydrous ethanol and heated under reflux for 20 h. The crude product is then dissolved in ethyl acetate and recrystallized from ethyl acetate to obtain the product.
[0039] Step 4: Place the glass slide from Step 1 into a cylindrical vial with a diameter of 2.1~2.3cm, and set aside.
[0040] Step 5: Add the mixed aqueous solution from Step 3 to the vial from Step 4, and then add the 1-naphthol mixed solution from Step 2. The mixed aqueous solution and the 1-naphthol mixed solution are taken in the same volume. The two form an oil-water two-phase reaction system. Let the reaction stand at a reaction temperature of 10-40℃ for 72 h.
[0041] Step 6: Slowly extract the aqueous phase with a syringe, transfer the product to the glass slide from Step 4, then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, repeat twice, and set aside.
[0042] Step 7: Immerse the glass slide loaded with the product obtained in Step 6 in an ammonia solution, then remove the ammonia solution, immerse and remove it in ethanol, repeat this process 3 times, and then air dry it naturally to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on the glass slide.
[0043] The present invention also provides a wheat-ear-shaped Pd-Ag nanomaterial, which is prepared by the above preparation method. The diameter of the material is 44~46 nm and the length is 339~341 nm. The Pd-Ag nanomaterial is formed by the orderly aggregation of particles into a wheat-ear-shaped structure, which helps to have more active sites.
[0044] This invention also provides an application of wheat-ear-shaped Pd-Ag nanomaterials as a catalyst in selective hydrogenation reactions. When applied to the selective hydrogenation of p-nitrobenzaldehyde to p-aminobenzaldehyde, it exhibits excellent p-nitrobenzaldehyde conversion rate and selectivity, along with good stability. Specifically, 1.5 mg of wheat-ear-shaped Pd-Ag alloy nanomaterials were dispersed in 1 mL of anhydrous ethanol, which was then added to 4 mL of anhydrous ethanol containing 0.25 mol of p-nitrobenzaldehyde. The solution was mixed thoroughly, and the reaction was carried out at 35°C under a normal pressure H2 atmosphere. Samples were taken at different time points and analyzed using gas chromatography-mass spectrometry (GC-MS).
[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.
[0046] Example 1:
[0047] 1) Cut the glass slide into 1cm×1cm squares, soak them in a mixture of hydrogen peroxide and concentrated sulfuric acid in a 1:1 volume ratio to remove surface impurities, then clean them with anhydrous ethanol and set aside.
[0048] 2) Weigh a certain amount of 1-naphthol and add it to ethyl acetate to prepare a 40 mM 1-naphthol mixed solution, which will be used as the oil phase in the reaction system;
[0049] 3) Weigh a certain amount of DTDAB and dissolve it in distilled water to a concentration of 50 mM. Then, add a certain amount of Na₂PdCl₄ and AgNO₃ to the above solution as the aqueous phase in the reaction system. The molar concentrations of Na₂PdCl₄ and AgNO₃ in the aqueous phase solution are 3.8 mM and 1.2 mM, respectively.
[0050] 4) Place the glass slide from step one into a cylindrical vial with a diameter of approximately 2.2 cm;
[0051] 5) Take 4 mL of the mixed aqueous solution from step 3) and add it to the vial from step 4), then add 4 mL of the 1-naphthol mixed solution from step 2) to form an oil-water two-phase reaction system. Let it stand at 40°C for 72 h to react.
[0052] 6) Slowly extract the aqueous phase with a syringe, transfer the product to the glass slide from step 4), then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, and repeat twice.
[0053] 7) Soak the product obtained in step 6) in an ammonia solution for 20 min, then remove the ammonia. Soak and remove the product in ethanol, repeating this process three times, and then air dry to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on a glass slide.
[0054] Figure 1 The images show SEM images of the prepared Pd-Ag alloy nanomaterials. It can be seen that the synthesized Pd-Ag products have uniform size and a wheat-ear-like morphology. From the magnified SEM images (…),… Figure 2 The diameter of these nano-wheat ears was measured to be approximately 45 nm, and the length was approximately 340 nm. The Pd-Ag product prepared in this invention consists of particles orderly aggregated into a wheat ear-like structure. Figure 3 This helps nano-wheat ears form multiple active sites. From the elemental mapping diagram ( Figure 4 It can be observed that Pd and Ag elements are uniformly distributed throughout the nano-wheat ear region, indicating that it is an alloy structure. From its X-ray diffraction (XRD) pattern... Figure 5 It can be seen that the Pd-Ag nano-wheat ears have a face-centered cubic structure, and the peak position is between Pd and Ag, which proves its alloy structure.
[0055] Example 2:
[0056] 1) Cut the glass slide into 1cm×1cm squares, soak them in a mixture of hydrogen peroxide and concentrated sulfuric acid in a 1:1 volume ratio to remove surface impurities, then clean them with anhydrous ethanol and set aside.
[0057] 2) Weigh a certain amount of 1-naphthol and add it to ethyl acetate to prepare a 40 mM 1-naphthol solution, which will be used as the oil phase in the reaction system;
[0058] 3) Weigh a certain amount of DTDAB and dissolve it in distilled water to a concentration of 50 mM. Then, add a certain amount of Na₂PdCl₄ and AgNO₃ to the above solution as the aqueous phase in the reaction system. The molar concentrations of Na₂PdCl₄ and AgNO₃ in the aqueous phase solution are 2.5 mM and 2.5 mM, respectively.
[0059] 4) Place the glass slide from step one into a cylindrical vial with a diameter of approximately 2.2 cm;
[0060] 5) Take 4 mL of the precursor aqueous solution from step 3) and add it to the vial from step 4), then add 4 mL of the 1-naphthol solution from step 2) to form an oil-water two-phase reaction system. Let it stand at 40°C for 72 h to react.
[0061] 6) Slowly extract the aqueous phase with a syringe, transfer the product to the glass slide from step 4), then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, and repeat twice.
[0062] 7) Soak the product obtained in step 6) in an ammonia solution for 20 min, then remove the ammonia. Soak and remove the product in ethanol, repeating this process three times, and then air dry to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on a glass slide.
[0063] Example 3:
[0064] 1) Cut the glass slide into 1cm×1cm squares, soak them in a mixed solution of hydrogen peroxide and concentrated sulfuric acid in a volume ratio of 1:1 to remove surface impurities, and then clean them with anhydrous ethanol for later use.
[0065] 2) Weigh a certain amount of 1-naphthol and add it to ethyl acetate to prepare a 40 mM 1-naphthol solution, which will be used as the oil phase in the reaction system;
[0066] 3) Weigh a certain amount of DTDAB and dissolve it in distilled water to a concentration of 50 mM. Then, add a certain amount of Na₂PdCl₄ and AgNO₃ to the above solution as the aqueous phase in the reaction system. The molar concentrations of Na₂PdCl₄ and AgNO₃ in the aqueous phase solution are 1.2 mM and 3.8 mM, respectively.
[0067] 4) Place the glass slide from step one into a cylindrical vial with a diameter of approximately 2.2 cm;
[0068] 5) Take 4 mL of the precursor aqueous solution from step 3) and add it to the vial from step 4), then add 4 mL of the 1-naphthol solution from step 2) to form an oil-water two-phase reaction system. Let it stand at 40°C for 72 h to react.
[0069] 6) Slowly extract the aqueous phase with a syringe, transfer the product to the glass slide from step 4), then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, and repeat twice.
[0070] 7) Soak the product obtained in step 6) in an ammonia solution for 20 min, then remove the ammonia. Soak and remove the product in ethanol, repeating this process three times, and then air dry to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on a glass slide.
[0071] Example 4:
[0072] 1) Cut the glass slide into 1cm×1cm squares, soak them in a mixed solution of hydrogen peroxide and concentrated sulfuric acid in a volume ratio of 1:1 to remove surface impurities, and then clean them with anhydrous ethanol for later use.
[0073] 2) Weigh a certain amount of 1-naphthol and add it to ethyl acetate to prepare a 30 mM 1-naphthol solution, which will be used as the oil phase in the reaction system;
[0074] 3) Weigh a certain amount of DTDAB and dissolve it in distilled water to a concentration of 50 mM. Then, add a certain amount of Na₂PdCl₄ and AgNO₃ to the above solution as the aqueous phase in the reaction system. The molar concentrations of Na₂PdCl₄ and AgNO₃ in the aqueous phase solution are 3.8 mM and 1.2 mM, respectively.
[0075] 4) Place the glass slide from step one into a cylindrical vial with a diameter of approximately 2.2 cm;
[0076] 5) Take 4 mL of the precursor aqueous solution from step 3) and add it to the vial from step 4), then add 4 mL of the 1-naphthol solution from step 2) to form an oil-water two-phase reaction system. Let it stand at 40°C for 72 h to react.
[0077] 6) Slowly extract the aqueous phase with a syringe, transfer the product to the glass slide from step 4), then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, and repeat twice.
[0078] 7) Soak the product obtained in step 6) in an ammonia solution for 20 min, then remove the ammonia. Soak and remove the product in ethanol, repeating this process three times, and then air dry to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on a glass slide.
[0079] Example 5:
[0080] 1) Cut the glass slide into 1cm×1cm squares, soak them in a mixed solution of hydrogen peroxide and concentrated sulfuric acid in a volume ratio of 1:1 to remove surface impurities, and then clean them with anhydrous ethanol for later use.
[0081] 2) Weigh a certain amount of 1-naphthol and add it to ethyl acetate to prepare a 20 mM 1-naphthol solution, which will be used as the oil phase in the reaction system;
[0082] 3) Weigh a certain amount of DTDAB and dissolve it in distilled water to a concentration of 50 mM. Then, add a certain amount of Na₂PdCl₄ and AgNO₃ to the above solution as the aqueous phase in the reaction system. The molar concentrations of Na₂PdCl₄ and AgNO₃ in the aqueous phase solution are 3.8 mM and 1.2 mM, respectively.
[0083] 4) Place the glass slide from step one into a cylindrical vial with a diameter of approximately 2.2 cm;
[0084] 5) Take 4 mL of the precursor aqueous solution from step 3) and add it to the vial from step 4), then add 4 mL of the 1-naphthol solution from step 2) to form an oil-water two-phase reaction system. Let it stand at 40°C for 72 h to react.
[0085] 6) Slowly extract the aqueous phase with a syringe, transfer the product to the glass slide from step 4), then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, and repeat twice.
[0086] 7) Soak the product obtained in step 6) in an ammonia solution for 20 min, then remove the ammonia. Soak and remove the product in ethanol, repeating this process three times, and then air dry to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on a glass slide.
[0087] Example 6:
[0088] 1) Cut the glass slide into 1cm×1cm squares, soak them in a mixed solution of hydrogen peroxide and concentrated sulfuric acid in a volume ratio of 1:1 to remove surface impurities, and then clean them with anhydrous ethanol for later use.
[0089] 2) Weigh a certain amount of 1-naphthol and add it to ethyl acetate to prepare a 10 mM 1-naphthol solution, which will be used as the oil phase in the reaction system;
[0090] 3) Weigh a certain amount of DTDAB and dissolve it in distilled water to a concentration of 50 mM. Then, add a certain amount of Na₂PdCl₄ and AgNO₃ to the above solution as the aqueous phase in the reaction system. The molar concentrations of Na₂PdCl₄ and AgNO₃ in the aqueous phase solution are 3.8 mM and 1.2 mM, respectively.
[0091] 4) Place the glass slide from step one into a cylindrical vial with a diameter of approximately 2.2 cm;
[0092] 5) Take 4 mL of the precursor aqueous solution from step 3) and add it to the vial from step 4), then add 4 mL of the 1-naphthol solution from step 2) to form an oil-water two-phase reaction system. Let it stand at 40°C for 72 h to react.
[0093] 6) Slowly extract the aqueous phase with a syringe, transfer the product to the glass slide from step 4), then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, and repeat twice.
[0094] 7) Soak the product obtained in step 6) in an ammonia solution for 20 min, then remove the ammonia. Soak and remove the product in ethanol, repeating this process three times, and then air dry to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on a glass slide.
[0095] Example 7:
[0096] 1) Cut the glass slide into 1cm×1cm squares, soak them in a mixed solution of hydrogen peroxide and concentrated sulfuric acid in a volume ratio of 1:1 to remove surface impurities, and then clean them with anhydrous ethanol for later use.
[0097] 2) Weigh a certain amount of 1-naphthol and add it to ethyl acetate to prepare a 40 mM 1-naphthol solution, which will be used as the oil phase in the reaction system;
[0098] 3) Weigh a certain amount of DTDAB and dissolve it in distilled water to a concentration of 50 mM. Then, add a certain amount of Na₂PdCl₄ and AgNO₃ to the above solution as the aqueous phase in the reaction system. The molar concentrations of Na₂PdCl₄ and AgNO₃ in the aqueous phase solution are 3.8 mM and 1.2 mM, respectively.
[0099] 4) Place the glass slide from step one into a cylindrical vial with a diameter of approximately 2.2 cm;
[0100] 5) Take 4 mL of the precursor aqueous solution from step 3) and add it to the vial from step 4), then add 4 mL of the 1-naphthol solution from step 2) to form an oil-water two-phase reaction system. Let it stand at 25°C for 72 h to react.
[0101] 6) Slowly extract the aqueous phase with a syringe, transfer the product to the glass slide from step 4), then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, and repeat twice.
[0102] 7) Soak the product obtained in step 6) in an ammonia solution for 20 min, then remove the ammonia. Soak and remove the product in ethanol, repeating this process three times, and then air dry to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on a glass slide.
[0103] Example 8:
[0104] 1) Cut the glass slide into 1cm×1cm squares, soak them in a mixed solution of hydrogen peroxide and concentrated sulfuric acid in a volume ratio of 1:1 to remove surface impurities, and then clean them with anhydrous ethanol for later use.
[0105] 2) Weigh a certain amount of 1-naphthol and add it to ethyl acetate to prepare a 40 mM 1-naphthol solution, which will be used as the oil phase in the reaction system;
[0106] 3) Weigh a certain amount of DTDAB and dissolve it in distilled water to a concentration of 50 mM. Then, add a certain amount of Na₂PdCl₄ and AgNO₃ to the above solution as the aqueous phase in the reaction system. The molar concentrations of Na₂PdCl₄ and AgNO₃ in the aqueous phase solution are 3.8 mM and 1.2 mM, respectively.
[0107] 4) Place the glass slide from step one into a cylindrical vial with a diameter of approximately 2.2 cm;
[0108] 5) Take 4 mL of the precursor aqueous solution from step 3) and add it to the vial from step 4), then add 4 mL of the 1-naphthol solution from step 2) to form an oil-water two-phase reaction system. Let it stand at 5°C for 72 h.
[0109] 6) Slowly extract the aqueous phase with a syringe, transfer the product to the glass slide from step 4), then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, and repeat twice.
[0110] 7) Soak the product obtained in step 6) in an ammonia solution for 20 min, then remove the ammonia. Soak and remove the product in ethanol, repeating this process three times, and then air dry to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on a glass slide.
[0111] This invention also provides an application of wheat-ear-shaped Pd-Ag nanomaterials as a catalyst in selective hydrogenation reactions. Specifically, it is applied to the selective hydrogenation of p-nitrobenzaldehyde to prepare p-aminobenzaldehyde. The method involves dispersing 1.5 mg of wheat-ear-shaped Pd-Ag alloy nanomaterials in 1 mL of anhydrous ethanol, adding it to 4 mL of anhydrous ethanol containing 0.25 mol of p-nitrobenzaldehyde, mixing the solution thoroughly, and reacting at 35°C under a normal pressure H2 atmosphere. Samples are taken at different time points and analyzed using gas chromatography-mass spectrometry (GC-MS).
[0112] In the selective hydrogenation of p-nitrobenzaldehyde to p-aminobenzaldehyde, the Pd-Ag nanoparticles prepared in this invention exhibit excellent catalytic activity and stability. The reaction was carried out in anhydrous ethanol at 35°C and atmospheric pressure, under mild conditions and with a small amount of catalyst. After 60 min of reaction, the conversion rate of p-nitrobenzaldehyde reached as high as 99.78%, and the selectivity of p-aminobenzaldehyde reached as high as 99.40%. Figure 6 After 5 cycles, the conversion rate was 99.41%, and the selectivity was 97.98%. Figure 7 This indicates that the catalyst possesses excellent catalytic activity and stability.
[0113] It should be noted that although the present invention has been described through the above embodiments, the present invention may have many other embodiments. Without departing from the spirit and scope of the present invention, those skilled in the art can obviously make various corresponding changes and modifications to the present invention, but all such changes and modifications should fall within the scope of protection of the appended claims and their equivalents.
Claims
1. A method for preparing wheat-ear-shaped Pd-Ag nanomaterials, characterized in that: Includes the following steps: Step 1: Cut the glass slide into squares, soak them in a mixture of hydrogen peroxide and concentrated sulfuric acid to remove surface impurities, then clean them with anhydrous ethanol and set aside. Step 2: Weigh 1-naphthol and add it to ethyl acetate to prepare a 1-naphthol mixed solution, which will be used as the oil phase in the reaction system for later use. Step 3: Weigh out tetradecyl dimethyl ethylenediammonium dibromide and dissolve it in distilled water. Then add Pd precursor and Ag precursor and dissolve to prepare a mixed aqueous solution, which will be used as the aqueous phase in the reaction system for later use. Step 4: Place the glass slide from Step 1 into the cylindrical vial and set aside. Step 5: Add the mixed aqueous solution from Step 3 to the vial from Step 4, then add the 1-naphthol mixed solution from Step 2 to form an oil-water two-phase reaction system, and let it stand to react. Step 6: Slowly extract the aqueous phase, transfer the product to the glass slide from Step 4, then extract the organic solution, load the obtained product onto the glass slide, soak in ethanol, extract, repeat several times, and set aside. Step 7: Immerse the glass slide loaded with the product obtained in Step 6 in an ammonia solution, then remove the ammonia solution, immerse it in ethanol, remove it, repeat this process several times, and then air dry it naturally to prepare wheat-ear-shaped Pd-Ag alloy nanomaterials loaded on the glass slide.
2. The method for preparing wheat-ear-shaped Pd-Ag nanomaterials according to claim 1, characterized in that: In step one, the block size is 1cm × 1cm, and the volume ratio of hydrogen peroxide to concentrated sulfuric acid is 1:
1.
3. The method for preparing wheat-ear-shaped Pd-Ag nanomaterials according to claim 1, characterized in that: In step two, the concentration of 1-naphthol is 10-50 mM.
4. The method for preparing wheat-ear-shaped Pd-Ag nanomaterials according to claim 1, characterized in that: In step three, the concentration of tetradecyl dimethyl ethylenediammonium dibromide is 50 mM, the Pd precursor is Na2PdCl4 with a concentration of 1.2-3.8 mM in the aqueous phase, and the Ag precursor is AgNO3 with a concentration of 1.2-3.8 mM in the aqueous phase.
5. A method for preparing wheat-ear-shaped Pd-Ag nanomaterials according to claim 1 or 4, characterized in that: The preparation method of tetramethylethylenediamine dibromide in step three is as follows: dissolve tetramethylethylenediamine and 1-tetradecane bromide in anhydrous ethanol, heat under reflux for 20 h, then dissolve the crude product in ethyl acetate, and recrystallize with ethyl acetate to obtain the product.
6. The method for preparing wheat-ear-shaped Pd-Ag nanomaterials according to claim 1, characterized in that: In step four, the diameter of the cylindrical vial is 2.1~2.3cm.
7. The method for preparing wheat-ear-shaped Pd-Ag nanomaterials according to claim 1, characterized in that: In step five, the reaction is allowed to stand for 72 hours, and the reaction temperature is 10-40℃.
8. A wheat-ear-shaped Pd-Ag nanomaterial, characterized in that: The Pd-Ag nanomaterial is prepared by the preparation method according to any one of claims 1 to 7, wherein the nanomaterial is formed by the orderly aggregation of particles into a wheat ear-like structure.
9. The application of the wheat-ear-shaped Pd-Ag nanomaterial of claim 8 as a catalyst in selective hydrogenation reactions, characterized in that: It was applied to the selective hydrogenation of p-nitrobenzaldehyde to prepare p-aminobenzaldehyde. Specifically, 1.5 mg of wheat-ear-shaped Pd-Ag alloy nanomaterial was dispersed in 1 mL of anhydrous ethanol and added to 4 mL of anhydrous ethanol containing 0.25 mol of p-nitrobenzaldehyde. The solution was mixed evenly and the reaction was carried out at 35 °C under normal pressure and H2 atmosphere. Samples were taken out at different time periods and analyzed by gas chromatography-mass spectrometry.