Preparation method of PdAg nanosponge and application of the PdAg nanosponge

Abstract

The application relates to a preparation method of PdAg nanosponge and application of the PdAg nanosponge. A certain amount of ethylene glycol is configured into an ethylene glycol aqueous solution, a certain volume of the ethylene glycol aqueous solution is added into a reaction container, then a certain amount of a Pd precursor is quickly added into the ethylene glycol aqueous solution, a certain amount of an Ag precursor is further added, the reaction system is uniformly mixed through ultrasonic, and then the reaction system is statically reacted at 20-60 DEG C for 0.5-3.0 h. After the reaction is completed, the reaction product is centrifuged, the obtained precipitate after centrifugation is washed through ultrapure water, and the PdAg nanosponge is obtained after drying. The application does not need to use a surfactant and a template agent, does not need to additionally add a reducing agent, does not need high temperature, high pressure, stirring and other reaction conditions, and can be statically reacted at 20-60 DEG C, so that the reaction condition is mild and the reaction step is simple. The prepared PdAg nanosponge has a 3D sponge-like structure and is a self-supporting catalyst, the purity is high, and the PdAg nanosponge has excellent catalytic activity and selectivity for selective hydrogenation reaction of furfural.

Description

Technical Field

[0001] This invention relates to the field of bimetallic nanomaterial preparation technology, specifically to a method for preparing PdAg nanosponges in an alcohol solution under mild conditions without adding any surfactant, and the application of the PdAg nanosponges in the catalytic hydrogenation reaction of furfural. Background Technology

[0002] Furfural is a crucial biomass platform compound, and its efficient catalytic conversion into high-value chemicals, materials, and pharmaceuticals is significant for the high-value utilization of biomass. However, in the selective hydrogenation of furfural, its molecular structure contains multiple functional groups, such as C=O and C=C unsaturated functional groups, leading to complex products and low selectivity for single products. Currently, Pt and Rh are common high-performance catalytic materials for the selective hydrogenation of furfural to furfuryl alcohol, but their application in practical industry is limited by their demanding synthesis methods, easy deactivation of active components, and poor cycling performance. Therefore, developing a simple, mild, and low-cost method to prepare metal nanocatalysts with good catalytic performance for furfural hydrogenation remains a significant challenge.

[0003] In the selective hydrogenation of furfural, Pd-based nanomaterials have attracted considerable interest from researchers due to their high activity and excellent selectivity. To improve the catalytic performance of Pd nanomaterials, a support is typically used to enhance their stability, or a second metal is introduced to regulate the electronic and geometric structure of Pd, thereby modulating its catalytic selectivity. For example, the invention patent with application number CN202310148951.2 uses PdCl2 as a precursor, mixes it with hydrochloric acid aqueous solution, and then adds it dropwise to ethanol containing CeO2 and acidic SiO2. After stirring until the ethanol is completely evaporated, the mixture is calcined in air at 200°C and reduced in a hydrogen atmosphere for 3.0 h to obtain a Pd / CeO2 / SiO2 material. This material exhibits a 53% conversion rate in the hydrogenation of furfural under conditions of 150°C, 2.0 MPa, and H2, with a selectivity of 22% for the formation of furfuryl alcohol. However, this preparation method involves numerous steps and is time-consuming, requiring an acidic environment, high temperature conditions, and hydrogen reduction. The operation is hazardous, and the catalytic reaction needs to be carried out at a high temperature (160°C). The invention patent with application number CN202211503248.0 mixes Co(NO3)2, glucose, Pd(NO3)2, and melamine in a molar ratio of 30:30:1:30, and stirs at 100℃ for 8.0 h to form a uniform gel. The gel is then calcined at 900℃ for 5.0 h in a mixed stream of inert gas and hydrogen to obtain a solid powder. The solid powder is then acid-washed at 80℃ to obtain Pd-Co@N / C material. This Pd-Co@N / C material exhibits a 43% conversion rate of furfural and an 85% selectivity for converting it to furfuryl alcohol under conditions of 100℃ and 2.0 MPa H2. However, the preparation conditions for this catalyst are demanding, requiring high-temperature calcination and hydrogen reduction, as well as heated acid washing for purification. The conditions are cumbersome, and the catalysis of furfural also needs to be carried out at a relatively high temperature (100℃). The invention patent with application number CN202111383949.0 dissolves PdCl2 and CuCl2 in ammonia water, then adds a support MCM-41, filters under reduced pressure at room temperature, and calcines the resulting filter cake at 150℃ for 6.0 h. Then, it is heated to 400℃ and maintained for 2.0 h in a hydrogen atmosphere to obtain a PdCu / MCM-41 material. Using PdCu / MCM-41 material as a catalyst, at 160℃ and with isopropanol as the hydrogen source, the conversion rate of furfural hydrogenation is 95%, and the selectivity for furfuryl alcohol is 96%. However, the preparation of this catalyst requires ammonia water as a solvent, causing environmental pollution. It also requires MCM-41 as a support, high-temperature reaction conditions, and hydrogen reduction, making the process cumbersome and somewhat dangerous. Furthermore, the catalysis of furfural also needs to be carried out at a high temperature of 160℃.

[0004] Given the shortcomings of the existing technologies, it is necessary to develop mild and simple preparation techniques to prepare Pd-based nanomaterials with 3D self-supporting structures and high selectivity in the selective hydrogenation reaction of furfural. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing PdAg nanosponges and their applications. The preparation method of this invention is carried out in an alcohol solution, without the use of surfactants and template agents, nor the addition of additional reducing agents. It does not require high temperature, high pressure, stirring, or other reaction conditions; the reaction can be carried out by static reaction at 20-60℃. The reaction conditions are mild and the reaction steps are simple. The prepared PdAg nanosponges have a 3D sponge-like structure and are a self-supporting catalyst. They have high purity, abundant pore structure, and excellent catalytic activity and selectivity for the selective hydrogenation of furfural to furfuryl alcohol.

[0006] This invention is specifically achieved through the following technical solution: a method for preparing PdAg nanosponges according to this invention includes the following steps:

[0007] (1) Prepare an ethylene glycol aqueous solution by mixing a certain amount of ethylene glycol with water for later use;

[0008] (2) Take a certain volume of the ethylene glycol aqueous solution from step (1) and add it to the reaction vessel. Quickly add a certain amount of Pd precursor to it, and then add a certain amount of Ag precursor. After ultrasonically mixing the reaction system, let it stand at 20-60℃ for 0.5-3.0h.

[0009] (3) Centrifuge the reaction product obtained in step (2), discard the supernatant to obtain the lower precipitate, wash the precipitate with ultrapure water by centrifugation 3-5 times, and then dry it at 40-60℃ for 8-12h to obtain PdAg nano sponge.

[0010] Preferably, the volume ratio of ethylene glycol to water in step (1) is 5:5-10:0.

[0011] Preferably, the concentration of Pd precursor in the reaction system of step (2) is 1.0-9.0 mmol / L and the concentration of Ag precursor is 1.0-9.0 mmol / L.

[0012] Preferably, the molar concentration ratio of the Pd precursor to the Ag precursor is 1:3 to 3:1.

[0013] Preferably, the Pd precursor is selected as Pd(OAc)2, and the Ag precursor is selected as AgNO3.

[0014] The aforementioned method for preparing PdAg nanosponges produces PdAg nanosponges with a 3D sponge-like structure. The PdAg nanosponges are composed of smaller nanoparticles with a diameter of 26 nm, and the PdAg nanosponges have a face-centered cubic structure.

[0015] Furthermore, the reaction vessel in the aforementioned preparation method can be a round-bottom flask, an Erlenmeyer flask, or a beaker, etc.

[0016] This invention also provides an application of the PdAg nanosponges prepared according to the aforementioned method in the selective hydrogenation of furfural to furfuryl alcohol. The specific method includes: dispersing the prepared PdAg nanosponges in a certain volume of ultrapure water, gently shaking to ensure uniform dispersion, and then adding them to a certain volume of anhydrous ethanol containing furfural. After mixing, the concentrations of PdAg nanosponges and furfural in the mixed system are 0.2-0.6 g / L and 0.05-0.30 mol / L, respectively. The mixed system is subjected to a catalytic hydrogenation reaction at 60℃ and a 1.5 MPa hydrogen atmosphere, and the reaction process is monitored using gas chromatography-mass spectrometry. After 15 h of reaction, the conversion rate of furfural was ≥82%, and the selectivity for furfuryl alcohol was ≥97%; after 21 h of reaction, the conversion rate of furfural was ≥94%, and the selectivity for furfuryl alcohol was ≥97%; after 27 h of reaction, the conversion rate of furfural was ≥98%, and the selectivity for furfuryl alcohol was ≥98%; after 30 h of reaction, the conversion rate of furfural was 100%, and the selectivity for furfuryl alcohol was ≥97%. This indicates that the prepared PdAg nanosponges possess good catalytic activity and selectivity in the catalytic hydrogenation of furfural.

[0017] Compared with existing technologies, this invention has significant advantages and beneficial effects. Through the above technical solution, this invention achieves considerable technological advancement and practicality, and has broad application value, possessing at least the following advantages:

[0018] (1) The preparation method of this invention is carried out in an alcohol solution. No surfactants or template agents are required during the reaction, thus producing a "clean" sample with high catalytic activity. The method also does not require additional reducing agents; simply add the Pd and Ag precursors to the solution and allow the reaction to proceed statically. High temperature, high pressure, and stirring are not required, resulting in mild reaction conditions, simple steps, easy separation, and low energy consumption. The ethylene glycol used has a dual function: it acts not only as a solvent but also as a reducing agent due to its weak reducing properties, reducing the Pd and Ag precursors to catalytically active metallic Pd and Ag, respectively.

[0019] (2) The PdAg nanosponges prepared by the method of this invention have a 3D sponge-like structure and are a 3D self-supporting catalyst that does not require a template agent or support. The 3D sponge-like structure is composed of smaller nanoparticles with a diameter of approximately 26 nm. The PdAg nanosponges have a face-centered cubic structure, with Pd and Ag elements uniformly distributed throughout the 3D nanosponge region. The diffraction peaks of the PdAg nanosponges are located between the characteristic peaks of Pd and Ag, indicating an alloy structure. Furthermore, the purified sample has high purity.

[0020] (3) The selective hydrogenation reaction of furfural by the PdAg nanosponges prepared in this invention does not require high temperature conditions or acid washing and purification steps. The catalytic reaction conditions are mild, safe and energy-efficient. After 27 hours of reaction, the conversion rate of furfural is ≥98% and the selectivity of furfuryl alcohol is ≥98%, indicating that the PdAg nanosponges prepared in this invention have high catalytic activity and conversion rate for the selective hydrogenation reaction of furfural. Attached Figure Description

[0021] Figure 1 This is a 20,000x magnified SEM image of the PdAg nanosponges prepared in Example 1;

[0022] Figure 2 This is a SEM image of the PdAg nanosponges prepared in Example 1, magnified 50,000 times.

[0023] Figure 3 This is a TEM image of the PdAg nanosponges prepared in Example 1;

[0024] Figure 4 The XRD patterns of PdAg nanosponges prepared with different proportions are shown.

[0025] Figure 5 These are HAADF-STEM and elemental surface scan images of the PdAg nanosponges prepared in Example 1;

[0026] Figure 6 This is a bar graph showing the changes of each component over time in the PdAg nanosponges prepared in Example 1 catalyzing the hydrogenation reaction of furfural. Detailed Implementation

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

[0028] Example 1:

[0029] 1) Prepare an ethylene glycol aqueous solution by mixing a certain amount of ethylene glycol and water, with a volume ratio of ethylene glycol to water of 10:0;

[0030] 2) Take 10 mL of the ethylene glycol aqueous solution from step 1) into a round-bottom flask, and quickly add 0.03 mmol of Pd(OAc)2 to make the molar concentration of Pd(OAc)2 in the ethylene glycol aqueous solution 3.0 mmol / L; gently shake the round-bottom flask to mix the reaction solution evenly; then add 0.03 mmol of AgNO3 to the round-bottom flask to make the molar concentration ratio of AgNO3 to Pd(OAc)2 1:1; after ultrasonically mixing the reaction system, let it stand at 40℃ for 1 h.

[0031] 3) The reaction product obtained in step 2) is centrifuged and the supernatant is discarded to obtain the lower precipitate. The lower precipitate is washed three times by centrifugation with ultrapure water and then dried under vacuum at 60°C for 12 hours to obtain PdAg nano sponge.

[0032] Figure 1 and Figure 2 The images shown are scanning electron microscope (SEM) images of the PdAg nanosponges prepared in Example 1 at magnifications of 20,000 and 50,000 times, respectively. It can be seen from the SEM images at different magnifications that the prepared PdAg nanosponges have a 3D sponge-like structure, and the 3D sponge-like structure is composed of even smaller nanoparticles.

[0033] Figure 3 This is a TEM image of the PdAg nanosponges prepared in Example 1. Its sponge-like structure can be clearly seen, and the diameter of the nanoparticles that make up the PdAg nanosponges is about 26 nm.

[0034] Figure 4 These are the XRD patterns of PdAg nanosponges prepared with different proportions; where Pd2Ag1 indicates a molar ratio of Pd to Ag of 2:1, Pd1Ag2 indicates a molar ratio of Pd to Ag of 1:2, and Pd1Ag1 indicates a molar ratio of Pd to Ag of 1:1. Figure 4 It can be seen that the PdAg nanosponges have a face-centered cubic structure, and the diffraction peaks are located between the characteristic peaks of Pd and Ag, proving that they are an alloy structure. The absence of other impurity peaks indicates that the purified sample has high purity.

[0035] Figure 5 The images show HAADF-STEM and elemental surface scans of the PdAg nanosponges prepared in Example 1. It can be seen that Pd and Ag elements are uniformly distributed throughout the 3D nanosponge region, proving that PdAg has an alloy structure.

[0036] The prepared PdAg nanosponges were used for the selective hydrogenation of furfural. The specific method included: dispersing the prepared PdAg nanosponges in 4 mL of ultrapure water, gently shaking to ensure uniform dispersion, and then adding them to 1 mL of anhydrous ethanol containing furfural. After mixing, the concentrations of PdAg nanosponges and furfural in the mixture were 0.4 g / L and 0.10 mol / L, respectively. The mixture was subjected to catalytic hydrogenation at 60 °C under a 1.5 MPa hydrogen atmosphere, and the reaction process was monitored using gas chromatography-mass spectrometry (GC-MS). Figure 6 This is a bar graph showing the changes in various components over time in the catalytic hydrogenation reaction of furfural catalyzed by the PdAg nanosponges prepared in Example 1. It can be seen that after 15 h of reaction, the conversion rate of furfural is ≥82%, and the selectivity for furfuryl alcohol is ≥97%; after 21 h of reaction, the conversion rate of furfural is ≥94%, and the selectivity for furfuryl alcohol is ≥97%; after 27 h of reaction, the conversion rate of furfural is ≥98%, and the selectivity for furfuryl alcohol is ≥98%; after 30 h of reaction, the conversion rate of furfural is 100%, and the selectivity for furfuryl alcohol is ≥97%. This indicates that the prepared PdAg nanosponges have good catalytic activity and selectivity in the catalytic hydrogenation reaction of furfural.

[0037] Example 2:

[0038] 1) Prepare an ethylene glycol aqueous solution by mixing a certain amount of ethylene glycol and water, with a volume ratio of ethylene glycol to water of 10:0;

[0039] 2) Take 10 mL of the ethylene glycol aqueous solution from step 1) into a round-bottom flask, and quickly add 0.04 mmol of Pd(OAc)2 to make the molar concentration of Pd(OAc)2 in the ethylene glycol aqueous solution 4.0 mmol / L; gently shake the round-bottom flask to mix the reaction solution evenly; then add 0.02 mmol of AgNO3 to the round-bottom flask to make the molar concentration ratio of AgNO3 to Pd(OAc)2 1:2; after ultrasonically mixing the reaction system, let it stand at 50°C for 0.5 h.

[0040] 3) The reaction product obtained in step 2) is centrifuged and the supernatant is discarded to obtain the lower precipitate. The lower precipitate is washed three times by centrifugation with ultrapure water and then dried under vacuum at 60°C for 12 hours to obtain PdAg nano sponge.

[0041] Example 3:

[0042] 1) Prepare an ethylene glycol aqueous solution by mixing a certain amount of ethylene glycol and water, with a volume ratio of ethylene glycol to water of 8:2;

[0043] 2) Take 10 mL of the ethylene glycol aqueous solution from step 1) into a round-bottom flask, and quickly add 0.09 mmol of Pd(OAc)2 to make the molar concentration of Pd(OAc)2 in the ethylene glycol aqueous solution 9.0 mmol / L; gently shake the round-bottom flask to mix the reaction solution evenly; then add 0.03 mmol of AgNO3 to the round-bottom flask to make the molar concentration ratio of AgNO3 to Pd(OAc)2 1:3; after ultrasonically mixing the reaction system, let it stand at 60℃ for 3 h.

[0044] 3) The reaction product obtained in step 2) is centrifuged and the supernatant is discarded to obtain the lower precipitate. The lower precipitate is washed three times by centrifugation with ultrapure water and then dried under vacuum at 40°C for 10 hours to obtain PdAg nano sponge.

[0045] Example 4:

[0046] 1) Prepare an ethylene glycol aqueous solution by mixing a certain amount of ethylene glycol and water, with a volume ratio of ethylene glycol to water of 5:5;

[0047] 2) Take 10 mL of the ethylene glycol aqueous solution from step 1) into a round-bottom flask, and quickly add 0.01 mmol of Pd(OAc)2 to make the molar concentration of Pd(OAc)2 in the ethylene glycol aqueous solution 1.0 mmol / L; gently shake the round-bottom flask to mix the reaction solution evenly; then add 0.03 mmol of AgNO3 to the round-bottom flask to make the molar concentration ratio of AgNO3 to Pd(OAc)2 3:1; after ultrasonically mixing the reaction system, let it stand at 20℃ for 2 h.

[0048] 3) The reaction product obtained in step 2) is centrifuged and the supernatant is discarded to obtain the lower precipitate. The lower precipitate is washed with ultrapure water by centrifugation 4 times and then dried under vacuum at 40°C for 8 hours to obtain PdAg nano sponge.

[0049] Example 5:

[0050] 1) Prepare an ethylene glycol aqueous solution by mixing a certain amount of ethylene glycol and water, with a volume ratio of ethylene glycol to water of 6:4;

[0051] 2) Take 10 mL of the ethylene glycol aqueous solution from step 1) into a round-bottom flask, and quickly add 0.05 mmol of Pd(OAc)2 to make the molar concentration of Pd(OAc)2 in the ethylene glycol aqueous solution 5.0 mmol / L; gently shake the round-bottom flask to mix the reaction solution evenly; then add 0.05 mmol of AgNO3 to the round-bottom flask to make the molar concentration ratio of AgNO3 to Pd(OAc)2 1:1; after ultrasonically mixing the reaction system, let it stand at 30℃ for 1.5 h.

[0052] 3) The reaction product obtained in step 2) is centrifuged and the supernatant is discarded to obtain the lower precipitate. The lower precipitate is washed three times by centrifugation with ultrapure water and then dried under vacuum at 60°C for 8 hours to obtain PdAg nano sponge.

[0053] Example 6:

[0054] 1) Prepare an ethylene glycol aqueous solution by mixing a certain amount of ethylene glycol and water, with a volume ratio of ethylene glycol to water of 9:1;

[0055] 2) Take 10 mL of the ethylene glycol aqueous solution from step 1) into a round-bottom flask, and quickly add 0.02 mmol of Pd(OAc)2 to make the molar concentration of Pd(OAc)2 in the ethylene glycol aqueous solution 2.0 mmol / L; gently shake the round-bottom flask to mix the reaction solution evenly; then add 0.04 mmol of AgNO3 to the round-bottom flask to make the molar concentration ratio of AgNO3 to Pd(OAc)2 2:1; after ultrasonically mixing the reaction system, let it stand at 50℃ for 3 h.

[0056] 3) The reaction product obtained in step 2) is centrifuged and the supernatant is discarded to obtain the lower precipitate. The lower precipitate is washed five times by centrifugation with ultrapure water and then dried under vacuum at 50°C for 10 hours to obtain PdAg nano sponge.

[0057] It should be noted that the preparation method of the present invention is not limited to using a round-bottom flask as a reaction vessel. In other embodiments, transparent glass reaction vessels such as conical flasks or beakers may also be used. The description of the specific embodiments is not to be regarded as any form of limitation on the present invention.

[0058] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing PdAg nanosponges, characterized in that... Includes the following steps: (1) Take a certain amount of ethylene glycol and water to prepare an ethylene glycol aqueous solution for later use. The volume ratio of ethylene glycol to water is 5:5-10:

0. (2) Take a certain volume of the ethylene glycol aqueous solution from step (1) and add it to the reaction vessel. Quickly add a certain amount of Pd precursor and then add a certain amount of Ag precursor. After ultrasonically mixing the reaction system, let it stand at 20-60°C for 0.5-3.0 h. The Pd precursor is Pd(OAc)2, and the molar ratio of Pd precursor to Ag precursor in the reaction system is 1:3-3:

1. (3) Centrifuge the reaction product obtained in step (2), discard the supernatant to obtain the lower precipitate, wash the precipitate with ultrapure water by centrifugation 3-5 times, and then dry it at 40-60°C for 8-12 h to obtain PdAg nano sponge, which has a 3D sponge-like structure. The PdAg nano sponge is composed of smaller nanoparticles with a diameter of 26 nm.

2. The method for preparing PdAg nanosponges as described in claim 1, characterized in that... In step (2), the concentration of Pd precursor in the reaction system is 1.0-9.0 mmol / L and the concentration of Ag precursor is 1.0-9.0 mmol / L.

3. The method for preparing PdAg nanosponges as described in claim 1 or 2, characterized in that... The Ag precursor is AgNO3.

4. The PdAg nanosponges obtained by the preparation method described in claim 1 or 2.

5. The application of the PdAg nanosponges obtained by the preparation method according to claim 1 or 2 in the selective hydrogenation of furfural to furfuryl alcohol, characterized in that... Specifically, the process involves dispersing PdAg nanosponges in water, gently shaking to ensure uniform dispersion, and then adding them to anhydrous ethanol containing furfural. After mixing, the concentrations of PdAg nanosponges and furfural in the mixture are 0.2-0.6 g / L and 0.05-0.30 mol / L, respectively, with a volume ratio of anhydrous ethanol to water of 1:

4. The mixture is then subjected to catalytic hydrogenation at 60℃ and a 1.5 MPa hydrogen atmosphere.

6. The application as described in claim 5, characterized in that... The conversion rate of PdAg nanosponges for selective hydrogenation of furfural is ≥98%, and its selectivity for furfuryl alcohol is ≥98%.

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