Size-controllable palladium nanoparticles and preparation method and application thereof
By designing stable palladium nanoparticles and regulating their size using anionic ligands, the problem of complex preparation of p-nitrophenol hydrogenation catalysts in the prior art is solved, and the efficient catalysis of palladium nanoparticles is achieved. 4-nitrogen The effect of converting plasmophenol into 4-aminophenol is suitable for industrial production.
Patent Information
- Application Number
- CN202411382568.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2025-01-10
AI Technical Summary
In the prior art, the preparation method of the p-nitrophenol hydrogenation catalyst is complex, the catalytic effect is poor, and it is difficult to effectively catalyze the conversion of 4-nitrophenol to 4-aminophenol.
By designing and synthesizing palladium nanoparticles with multiple ligands (phosphine, thiol and anion), and regulating the size of palladium nanoparticles using different anionic ligands (such as SbF6- or BF4-) to prepare palladium nanoparticles of 0.4-3nm , and applied it to the reduction reaction of 4-nitrophenol to achieve efficient catalysis.
It has achieved high yield and good stability of palladium nanoparticles, and has excellent catalytic effect. The TOF can reach 1800h-1, which can efficiently catalyze the conversion of 4-nitrophenol to 4-aminophenol, which is suitable for industrial production.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of nanomaterials, and specifically relates to size-controllable palladium nanoparticles and a preparation method and application thereof. Background Art
[0002] Metallic nanoparticles (well-defined entities with a size in the range of 1-100 nm) have experienced tremendous development in the last four decades, as they possess unique physical and chemical properties compared to materials belonging to higher or lower scales. In fact, it is mainly thanks to the electronic and structural effects of nanomaterials that a large number of catalytic applications have been enabled. Nanocatalysis has emerged at the end of the 20th century, combining colloidal nanoparticles dispersed in solvents and the engineering of nanoentities, allowing control over the size, shape and surface state of the prepared objects. Advances in the characterization and tailoring of nanoobjects have allowed catalysts to be tuned and designed at the nanoscale.
[0003] The organic combination of metal and nanotechnology can prepare metal nanomaterials with excellent physical and chemical properties. Factors such as specific surface area, size, morphology, composition and structure have a great influence on the physical and chemical properties of metal nanomaterials. The smaller the size of the metal nanoparticles, the larger the specific surface area and the richer the active sites. It has higher catalytic activity and selectivity, and has become a very promising field in catalytic research. As an important catalyst, the preparation of metal palladium nanoparticles has important application prospects.
[0004] In catalytic research, common catalytic reactions of palladium nanoparticles include: coupling reaction, hydrogenation reaction and oxidation reaction. Coupling reactions mainly include Suzuki coupling reaction and Heck coupling reaction. Suzuki coupling reaction: Under the action of the catalyst, halogenated aromatics or olefins cross-couple with aromatic groups. Studies have shown that small-sized Pd nanocatalysts can catalyze Suzuki coupling reactions well. Heck coupling reaction: Under the action of the catalyst, halogenated hydrocarbons couple with activated unsaturated hydrocarbons to generate trans products. Hydrogenation reaction: Under the action of the catalyst, catalytic hydrogenation reactions of unsaturated hydrocarbons, aldehydes, ketones, alicyclics, aromatics and other compounds, such as benzene hydrogenation, cyclooctene hydrogenation, cinnamic acid hydrogenation, etc. p-Aminophenol is an important chemical and pharmaceutical intermediate. With the continuous development of the economy, the demand for p-aminophenol has increased rapidly, and the development of corresponding catalysts has also attracted much attention. The preparation of p-aminophenol by hydrogenation of p-nitrophenol is an effective method for synthesizing p-aminophenol, in which the selection of catalyst is one of the key technologies. At present, the p-nitrophenol hydrogenation catalyst generally has the problems of complex preparation method and poor catalytic effect. Therefore, it is of great significance to study a p-nitrophenol hydrogenation catalyst. Summary of the invention
[0005] In view of the shortcomings of the prior art, the present invention provides a size-controllable palladium nanoparticle and its preparation method and application. The present invention systematically designs and synthesizes palladium nanoparticles stabilized by multiple ligands (phosphine, thiol and anion). The preparation method is simple and the reaction conditions are easy to achieve. By changing the anion ligand SbF6 - or BF4 - , palladium nanoparticles of different sizes are obtained with good yield. The present invention applies palladium nanoparticles to catalyze the reduction reaction of 4-nitrophenol, showing excellent catalytic effect.
[0006] The technical solution of the present invention is as follows:
[0007] A size-controlled palladium nanoparticle having the following structure:
[0008]
[0009] Preferably according to the present invention, the particle size of the size-controlled palladium nanoparticles is 0.4-3 nm.
[0010] Preferably, the particle size of the size-controlled palladium nanoparticles is 2.0±0.3 nm or 1.2±0.4 nm.
[0011] The method for preparing the size-controllable palladium nanoparticles comprises the following steps:
[0012] Potassium tetrachloropalladate (K2PdCl4), tri(4-fluorophenyl)phosphine ((4-FC6H5)3P), 4,4-dichlorodiphenyl disulfide ((4-Cl-C6H4-S)2), sodium salt and a reducing agent are fully dispersed in a solvent, reacted, and then filtered, washed and dried to obtain size-controllable palladium nanoparticles; the sodium salt is sodium hexafluoroantimonate or sodium tetrafluoroborate.
[0013] According to the preferred embodiment of the present invention, the molar ratio of potassium chloropalladate (K2PdCl4), tri(4-fluorophenyl)phosphine ((4-FC6H5)3P), 4,4-dichlorodiphenyl disulfide ((4-Cl-C6H4-S)2), sodium salt and reducing agent is 1:1:0.5:0.33:2-4, preferably 1:1:0.5:0.33:3.
[0014] According to the preferred embodiment of the present invention, the reducing agent is 0.005-0.01mmolmL -1 The reducing agent is added dropwise into the reaction system.
[0015] According to the present invention, preferably, the solvent is N,N-dimethylformamide (DMF).
[0016] Preferably according to the present invention, the volume ratio of the molar amount of potassium chloropalladate (K2PdCl4) to the solvent is 0.5-2mmol / L.
[0017] According to the preferred embodiment of the present invention, the reaction temperature is room temperature, the reaction time is 0.5-5h, and the reaction is carried out under stirring conditions.
[0018] According to the present invention, a preferred implementation method, the preparation method of size-controlled palladium nanoparticles comprises the steps of: mixing potassium tetrachloropalladate, tri(4-fluorophenyl)phosphine, 4,4-dichlorodiphenyl disulfide, and NaSbF6 in DMF, and continuously stirring for 0.1-1 hour under air conditions; adding NaBH4 aqueous solution dropwise, stirring for 0.5-5 hours at room temperature, filtering, washing, and drying to obtain size-controlled palladium nanoparticles.
[0019] According to the present invention, when the sodium salt is sodium hexafluoroantimonate, the particle size of the palladium nanoparticles is 2.0±0.3 nm; when the sodium salt is sodium tetrafluoroborate, the particle size of the palladium nanoparticles is 1.2±0.4 nm.
[0020] The size-controllable palladium nanoparticles are used as catalysts to catalyze the reduction of 4-nitrophenol to prepare 4-aminophenol.
[0021] Preferably according to the present invention, the reducing agent used for reducing 4-nitrophenol to prepare 4-aminophenol is NaBH4.
[0022] The synthesis route of the size-controlled palladium nanoparticles of the present invention is as follows:
[0023]
[0024] The route for preparing 4-aminophenol by reduction of 4-nitrophenol is as follows:
[0025]
[0026] The technical features and beneficial effects of the present invention are as follows:
[0027] 1. The preparation method of the size-controllable palladium nanoparticles of the present invention is simple, the reaction conditions are easy to achieve, the yield of the target product is high, and it is suitable for industrial production.
[0028] 2. The present invention systematically designs and synthesizes palladium nanoparticles stabilized by multiple ligands (phosphine, thiol and anion). - or BF4 - The palladium nanoparticles of different sizes were obtained with good yield. The palladium nanoparticles (2.0±0.3 nm) obtained from sodium hexafluoroantimonate of the present invention have a larger particle size than the palladium nanoparticles (1.2±0.4 nm) obtained from sodium tetrafluoroborate.
[0029] 3. The ligands (4-F-C6H5)3P, (4-ClC6H5S)2 and anionic ligands of the present invention form coordination bonds with palladium, which helps to maintain the stability and dispersibility of the nanoparticles, control the size of the nanoparticles, and prevent the aggregation of nanoparticles. The anionic ligand sodium salt of sodium hexafluoroantimonate or sodium tetrafluoroborate of the present invention plays an important role in the size, stability and catalytic activity of the nanoparticles; by changing the anionic ligands, the size of palladium nanoparticles can be successfully regulated, thereby affecting the catalytic activity; different anionic ligands will affect the growth rate of nanoparticles during the reduction process, thereby affecting the size of the final particles. If the concentration of the anionic ligands of the present invention is not appropriate, it may lead to inaccurate control of the size of PdNPs, affecting its performance in the catalytic reaction. The present invention achieves the regulation of the size of PdNPs by controlling the reaction conditions and the type of ligands; if the raw material ratio, reaction temperature, etc. are not appropriate, the size of PdNPs may be uneven, affecting its catalytic activity and selectivity. The DMF solvent selected in the present invention not only provides a good dissolving environment, but also contributes to the formation and long-term stability of PdNPs due to its thermal stability and antioxidant properties; if an inappropriate solvent is used, the stability of PdNPs may be reduced, affecting its catalytic performance. The nanoparticles prepared by the present invention show good stability in the air, and can catalyze and stably exist in the air for more than one month.
[0030] 4. The size-controlled palladium nanoparticles of the present invention are applied to catalyze the preparation of 4-aminophenol from 4-nitrophenol and show excellent catalytic effect. The TOF of the palladium nanoparticles obtained by using sodium hexafluoroantimonate as the sodium salt can reach 1800h -1 The TOF of palladium nanoparticles obtained by using sodium tetrafluoroborate as sodium salt can reach 1500h -1 The palladium nanoparticles obtained from the sodium salt sodium hexafluoroantimonate of the present invention have a better catalytic effect than the palladium nanoparticles obtained from the sodium salt sodium tetrafluoroborate. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 TEM image (a), HRTEM image (b), size distribution graph (c) and SAED graph (d) of the palladium nanoparticles 6a prepared in Example 1, and TEM image (e), HRTEM image (f), size distribution graph (g) and SAED graph (h) of the palladium nanoparticles 6b prepared in Example 2.
[0032] Figure 2 The ultraviolet absorption spectra of the palladium nanoparticles 6a prepared in Example 1 and the palladium nanoparticles 6b prepared in Example 2;
[0033] Figure 3 X-ray photoelectron spectra of palladium nanoparticles 6a(ag) prepared in Example 1 and palladium nanoparticles 6b(hn) prepared in Example 2;
[0034] Figure 4 The present invention is a graph showing the ultraviolet spectra of 4-nitrophenol catalyzed by palladium nanoparticles prepared in Example 1(a), Example 2(b), Comparative Example 1(c) and Comparative Example 2(d); a graph showing the relationship between time and ln(C / C0) of 4-nitrophenol catalyzed by palladium nanoparticles prepared in Example 1-2 and Comparative Example 1-2; and a graph showing the relationship between C / C0 and reaction time of 4-nitrophenol catalyzed by palladium nanoparticles prepared in Example 1 at different sodium borohydride dosages. DETAILED DESCRIPTION
[0035] The technical solution of the present invention is described clearly and completely below.
[0036] The experimental methods used in the examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the examples are all commercially available unless otherwise specified.
[0037] Example 1 (Pd Nanoparticles 6a)
[0038] A method for preparing size-controllable palladium nanoparticles comprises the following steps:
[0039] As in Synthesis Route 1, potassium tetrachloropalladate (0.05mmol, 16.3mg), tri(4-fluorophenyl)phosphine (0.05mmol, 15.8mg), 4,4-dichlorodiphenyl disulfide (4-ClC6H5S)2 (0.025mmol, 7.2mg), and NaSbF6 (0.0167mmol, 4.3mg) were mixed in 60mL DMF and stirred continuously for 0.5h under air. NaBH4 aqueous solution (20mL, 0.0075mmolmL) was added dropwise. -1 ), the resulting mixture turned gray and was stirred at room temperature for 1 hour to obtain a dispersion of palladium nanoparticles 6a. The dispersion was then filtered, washed and dried to obtain palladium nanoparticles 6a. The yield of the product was 100%.
[0040] The HRTEM image, size distribution diagram and SAED diagram of the obtained product are shown in Figure 1 As shown in (a)-(d), it can be seen that palladium nanoparticles with a size of 2.0±0.3nm were successfully prepared.
[0041] UV absorption spectrum Figure 2 As shown, there is no obvious absorption peak in the UV absorption diagram.
[0042] X-ray photoelectron spectroscopy Figure 3As shown in (a)-(g), XPS measurements show two different binding energies, 342.0 and 336.8 eV, corresponding to Pd(0)3d3 / 2 and Pd 3d5 / 2, respectively. These values are consistent with the binding energy of Pd(0) and are completely different from those of the Pd(II) complex, indicating that potassium tetrachloropalladate has been successfully reduced.
[0043] Example 2 (Pd Nanoparticles 6b)
[0044] A method for preparing size-controllable palladium nanoparticles comprises the following steps:
[0045] As in Synthesis Route 1, potassium tetrachloropalladate (0.05 mmol, 16.3 mg), tri(4-fluorophenyl)phosphine (0.05 mmol, 15.8 mg), 4,4-dichlorodiphenyl disulfide (4-ClC6H5S)2 (0.025 mmol, 7.2 mg), and NaBF4 (0.0167 mmol, 1.8 mg) were mixed in 60 mL DMF and stirred continuously for 0.5 h under air. NaBH4 aqueous solution (20 mL, 0.0075 mmol mL -1 ), the resulting mixture turned gray and was stirred at room temperature for 1 hour to obtain a dispersion of palladium nanoparticles 6b. The dispersion was then filtered, washed and dried to obtain palladium nanoparticles 6b. The yield of the product was 100%.
[0046] The HRTEM image, size distribution diagram and SAED diagram of the obtained product are shown in Figure 1 As shown in (e)-(h), it can be seen that palladium nanoparticles with a size of 1.2±0.4nm were successfully prepared.
[0047] UV absorption spectrum Figure 2 As shown, there is no obvious absorption peak in the UV absorption diagram.
[0048] X-ray photoelectron spectroscopy Figure 3 As shown in (h)-(n), XPS measurements show two different binding energies, 342.0 and 336.8 eV, corresponding to Pd(0)3d3 / 2 and Pd 3d5 / 2, respectively. These values are consistent with the binding energy of Pd(0) and are completely different from those of the Pd(II) complex, indicating that potassium tetrachloropalladate has been successfully reduced.
[0049] Comparative Example 1
[0050] Tripalladium cluster ([Pd3] + -1) Synthesis
[0051] Pd(dba)2 (bis(dibenzylideneacetonepalladium, 0.2mmol), triphenylphosphine (0.2mmol) and 4,4-dichlorodiphenyl disulfide (4-ClC6H5S)2 (0.1mmol) were added to a 50mL Schlenk tube. The vessel was subjected to at least three vacuum / N2 cycles. Then, 20mL of freshly degassed CHCl3 was added by syringe under N2. The resulting solution was kept stirring at room temperature for 2 hours. Then, silver hexafluoroantimonate (0.067mmol) was added under N2 and the solution was kept stirring at room temperature in the dark for 1 hour. Then, the mixture was filtered through a short pad of celite under N2. The solvent was removed in vacuo to obtain a dark red solid, which was further purified by precipitation with CHCl3 / hexane 3 times (each time, 1 / 30 v / v, 3×30mL) and dried to obtain a tripalladium cluster [Pd3] + -1.
[0052] Comparative Example 2
[0053] Tripalladium cluster ([Pd3] + -2) Synthesis
[0054] Pd(dba)2 (bis(dibenzylideneacetonepalladium, 0.2mmol), triphenylphosphine (0.2mmol) and 4,4-dichlorodiphenyl disulfide (4-ClC6H5S)2 (0.1mmol) were added to a 50mL Schlenk tube. The vessel was subjected to at least three vacuum / N2 cycles. Then, 20mL of freshly degassed CHCl3 was added by syringe under N2. The resulting solution was kept stirring at room temperature for 2 hours. Then, silver tetrafluoroborate (0.067mmol) was added under N2 and the solution was kept stirring at room temperature in the dark for 1 hour. Then, the mixture was filtered through a short pad of celite under N2. The solvent was removed in vacuo to obtain a dark red solid, which was further purified by precipitation with CHCl3 / hexane 3 times (each time, 1 / 30 v / v, 3×30mL) and dried to obtain a tripalladium cluster [Pd3] + -2.
[0055] Application Examples
[0056] The catalytic steps for the reduction of 4-nitrophenol are as follows:
[0057] 4-nitrophenol (4-NP) aqueous solution (2.5mL, 0.12mM) and newly prepared NaBH aqueous solution (0.5mL, 0.5M) were mixed in a cuvette. Subsequently, the palladium nanoparticle dispersion liquid (16 μL) prepared by the embodiment or the dispersion liquid of the three palladium clusters prepared by the comparative example (the solvent is DMF / H2O, and the volume ratio is 3 / 1, and the concentration of the palladium nanoparticle dispersion liquid prepared by the embodiment is the same, and the consumption is 16 μL). Use a UV-visible spectrophotometer to rapidly measure the absorbance of the reaction solution at different time intervals in the wavelength range of 250nm to 500nm.
[0058] Depend on Figure 4 (a)-(e) show that the palladium nanoparticles prepared in the present invention have a better catalytic effect than the comparative example, and the palladium nanoparticles prepared in Example 1 (PdNPs-1) have a better catalytic effect than Example 2 (PdNPs-2).
[0059] On the basis of the above, the palladium nanoparticles prepared in Example 1 were used as catalysts, and the concentration of the NaBH4 aqueous solution was changed, such as Figure 4 As shown in (f), the reaction rate increases with the increase of the concentration of NaBH4 aqueous solution.
[0060] The palladium nanoparticles 6a prepared in Example 1 were used to catalyze the above reaction, and the TOF (switching frequency or turnover frequency) was 1800h -1 The conversion rate of 4-nitrophenol was 100%. The TOF of palladium nanoparticles 6b prepared in Example 2 was 1500 h -1 , the conversion rate of 4-nitrophenol was 100%.
Claims
1. A size-controllable palladium nanoparticle, characterized in that: Has the following structure:
2. The size-controlled palladium nanoparticles according to claim 1, characterized in that: The particle size of the size-controlled palladium nanoparticles is 0.4-3 nm; preferably, the particle size of the size-controlled palladium nanoparticles is 2.0±0.3 nm or 1.2±0.4 nm.
3. The method for preparing size-controlled palladium nanoparticles according to claim 1 or 2, comprising the steps of: Potassium tetrachloropalladate (K2PdCl4), tri(4-fluorophenyl)phosphine ((4-FC6H5)3P), 4,4-dichlorodiphenyl disulfide ((4-Cl-C6H4-S)2), sodium salt and a reducing agent are fully dispersed in a solvent, reacted, and then filtered, washed and dried to obtain size-controllable palladium nanoparticles; the sodium salt is sodium hexafluoroantimonate or sodium tetrafluoroborate.
4. The method for preparing size-controlled palladium nanoparticles according to claim 3, characterized in that: The molar ratio of potassium chloropalladate (K2PdCl4), tri(4-fluorophenyl)phosphine ((4-FC6H5)3P), 4,4-dichlorodiphenyl disulfide ((4-Cl-C6H4-S)2), sodium salt and reducing agent is 1:1:0.5:0.33:2-4, preferably 1:1:0.5:0.33:
3.
5. The method for preparing size-controlled palladium nanoparticles according to claim 3, characterized in that: The reducing agent is 0.005-0.01mmolmL -1 The reducing agent is added dropwise into the reaction system.
6. The method for preparing size-controlled palladium nanoparticles according to claim 3, characterized in that: The solvent was N,N-dimethylformamide (DMF).
7. The method for preparing size-controlled palladium nanoparticles according to claim 3, characterized in that: The molar amount of potassium chloropalladate (K2PdCl4) and the volume ratio of the solvent are 0.5-2mmol / L.
8. The method for preparing size-controlled palladium nanoparticles according to claim 3, characterized in that: The reaction temperature is room temperature, the reaction time is 0.5-5h, and the reaction is carried out under stirring conditions.
9. The use of size-controlled palladium nanoparticles according to claim 1 or 2, characterized in that: As a catalyst, it can catalyze the reduction of 4-nitrophenol to prepare 4-aminophenol.
10. The use of size-controlled palladium nanoparticles according to claim 9, characterized in that: The reducing agent used in the reduction of 4-nitrophenol to prepare 4-aminophenol is NaBH4.