Amorphous Ag cluster loaded defect-state TiO2 nano composite material and application thereof
The preparation of Ag nanoparticles load-defective TiO2 nanocomposites through high-temperature calcination method solves the problems of high cost and cumbersome preparation of precious metal catalysts, and achieves an efficient and economical catalytic reduction reaction.
Patent Information
- Application Number
- CN202411753976.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-02
- Publication Date
- 2025-05-27
AI Technical Summary
In the prior art, in the reaction of catalytic selective reduction of nitroaromatic hydrocarbons as aniline, the high cost and low selectivity of noble metal catalysts hinder their large-scale application, and the traditional two-step preparation method is cumbersome and inefficient.
Through high-temperature calcination method, the ligand-protected Ag33 nanocluster crystal-supported TiO2 sample was calcined under a nitrogen atmosphere, deligating and forming oxygen defects, thereby realizing the preparation of the Ag nanoparticle-loaded defective TiO2 nanocomposite.
The preparation process is simplified, yield and stability are improved, cost is reduced, and the reduction reaction of efficient catalytic nitroaromatics has great application potential.
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Figure CN120037903A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of nanomaterials, and particularly relates to an amorphous Ag cluster-loaded defective TiO 2 nanocomposite and its application. Background Art
[0002] The selective reduction of nitroarenes to anilines is an important reaction, and the resulting anilines are important raw materials for fine chemicals, pigments, dyes, biochemistry, agrochemicals, and pharmaceuticals. The commercial methods for realizing this reaction rely on non-catalytic reactions using stoichiometric reducing agents (such as sodium dithionite, tin, iron, or zinc). However, these methods not only have low conversion rates but also generate a large amount of solid waste that is difficult to handle. Metal nanoclusters with atomic-level precision have attracted increasing research interest in the catalytic field because they can reveal the precise correlation between structure and catalytic performance and have the potential as basic units for designing highly efficient catalysts. Noble metal catalysts such as Pb, Au, and Ru have been widely studied in the reaction of selectively reducing nitroarenes to anilines due to their excellent catalytic activity, but their high cost and low selectivity in dealing with reducible groups (such as C-Br, C=O, C=C, etc.) seriously hinder their large-scale application. Therefore, it is necessary to develop a catalyst based on low noble metals, high efficiency, and strong selectivity.
[0003] In current research, the use of nanoclusters as catalysts and sodium borohydride (NaBH 4 ) as a reducing agent for the reduction of nitroarenes has become a benchmark test for evaluating the catalytic activity of nanoclusters because the reaction conditions are mild and convenient for carrying out in a chemical laboratory. In this context, various ligand-protected nanoclusters (such as Au 11 , Au 19 / Au 20 / Ag 22 , Au 25 , Au 28 , Au 38 , Ag 25 Cu 4 C l6 , Ag 32 , Pd 6 , Pd 8 etc.) have been explored as efficient catalysts for this reaction. Among them, forming oxygen defects on TiO 2 and depositing noble metals is a method that can significantly enhance the catalytic activity. The more traditional method is to carry out in two steps: first, pyrolytic reduction to generate defects, and then load the noble metals. However, this method still requires step-by-step experiments when enhancing the catalytic activity, the steps are relatively cumbersome, and the efficiency is low. Therefore, an amorphous Ag cluster-loaded defective TiO 2 nanocomposite and its application are urgently needed to be proposed. Summary of the Invention
[0004] To solve the defects existing in the prior art, the present invention provides a non-crystalline Ag cluster-loaded defective TiO 2 nano-composite material and its application.
[0005] To solve the above technical problems, the present invention provides the following technical solutions:
[0006] The first object of the present invention is to provide a non-crystalline Ag cluster-loaded defective TiO 2 nano-composite material, and its preparation method includes the following steps:
[0007] S1. Under stirring conditions, add AgNO 3 , Pd(PPh 3 ) 4 and PPh 3 to a mixed solution of methanol and dichloromethane. After the solution becomes clear, add 4-chlorobenzyl mercaptan; continue to stir the solution, and then add an aqueous solution of NaBH 4 to obtain a purple-red reaction solution;
[0008] S2. Purify the obtained reaction solution by rotary evaporation and centrifugation. Finally, add n-hexane in layers to the saturated CHCl 3 solution of the purified product, and perform liquid-phase diffusion crystallization at 4 °C to obtain Ag 33 nano-cluster crystals;
[0009] S3. Dissolve the Ag 33 nano-cluster crystals in dichloromethane to form a clear solution; then add TiO 2 powder, seal the solution in a rotary evaporator, and evaporate dichloromethane in a water bath at 30 °C; collect the obtained solid and grind it to obtain the Ag 33 -loaded TiO 2 sample, abbreviated as Ag 33 / TiO 2 ;
[0010] S4. Place the Ag 33 / TiO 2 powder in a tube furnace for calcination; after calcination, cool the sample to room temperature, and the obtained product is the non-crystalline Ag cluster-loaded defective TiO 2 nano-composite material.
[0011] Preferably, in step S1, the volume ratio of methanol to dichloromethane is 1:4 to 6, and the AgNO 3 , Pd(PPh 3 ) 4 and PPh 3The molar ratio is 1:0.03:(0.30 - 0.50).
[0012] Preferably, in step S1, 4-chlorobenzyl mercaptan is added and after reacting for 1 hour, an aqueous solution of NaBH 4 is added in 4 portions and the reaction is carried out at 10 °C for 24 - 28 h.
[0013] Preferably, in step S2, the molecular formula of the Ag 33 nanocluster crystal is: Ag 33 (SCH 2 PhCl) 24 (PPh 3 ) 4 .
[0014] Preferably, in step S3, the mass ratio of the Ag 33 nanocluster crystal, dichloromethane, and TiO 2 powder is (1 - 3):(300 - 1000):10.
[0015] Preferably, in step S4, the diameter of the tubular furnace is 50 mm, and the calcination conditions of the tubular furnace are: heating to 350 - 500 °C at a heating rate of 5 °C / min under a nitrogen flow rate of 100 mL / min and calcining for 1.5 - 2.5 h.
[0016] The second object of the present invention provides an application of an amorphous Ag cluster-loaded defective TiO 2 nanocomposite material in the preparation of a reducing agent, characterized in that the reducing agent is used for the catalytic reduction of nitroaromatics.
[0017] Compared with the prior art, the present invention has the following beneficial effects:
[0018] By means of a high-temperature calcination method, the present invention loads a ligand-protected Ag 33 nanocluster crystal on TiO 2 samples are calcined in a nitrogen atmosphere. Through the ligand de-ligating during the calcination process and obtaining oxygen from the TiO 2 lattice to generate carbon dioxide and H 2 O, a novel Ag nanoparticle-loaded defective TiO 2 nanocomposite material with abundant oxygen vacancies is successfully obtained. It breaks through the traditional two-step preparation method and successfully realizes the effect of simultaneously constructing oxygen defects and Ag loading through a surface calcination method. This method has a simple preparation process, high yield, low cost, a green and environmentally friendly production process, high stability, meets the actual production needs, and has great application potential. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1a-1b is the Ag nanoparticle-loaded defective TiO obtained from Example 1 of the present invention 2 Transmission electron microscope images of the Ag nanoparticle-loaded defective TiO nanocomposite obtained from Example 1 of the present invention before and after calcination at 50 nm;
[0020] Figure 1 c-1d is the Ag nanoparticle-loaded defective TiO obtained from Example 1 of the present invention 2 Transmission electron microscope images of the Ag nanoparticle-loaded defective TiO nanocomposite obtained from Example 1 of the present invention before and after calcination at 20 nm;
[0021] Figure 1 e-1f is the Ag nanoparticle-loaded defective TiO obtained from Example 1 of the present invention 2 Transmission electron microscope images of the Ag nanoparticle-loaded defective TiO nanocomposite obtained from Example 1 of the present invention after calcination at 5 nm and 2 nm;
[0022] Figure 2 is the Ag nanoparticle-loaded defective TiO obtained from Example 1 of the present invention 2 nanocomposite and pure TiO 2 TG diagram;
[0023] Figure 3 is the Ag nanoparticle-loaded defective TiO obtained from Example 1 of the present invention 2 PXRD pattern of the nanocomposite;
[0024] Figure 4 is the Ag nanoparticle-loaded defective TiO obtained from Example 1 of the present invention 2 EPR pattern of the nanocomposite;
[0025] Figure 5 is the Ag nanoparticle-loaded defective TiO obtained from Example 1 of the present invention 2 XPS pattern of the nanocomposite;
[0026] Figure 6 is the Ag nanoparticle-loaded defective TiO obtained from Example 1 of the present invention 2 Catalytic activity diagram of the nanocomposite as a function of time;
[0027] Figure 7 a-7f is the Ag nanoparticle-loaded defective TiO obtained from Example 1 of the present invention 2 Time-dependent UV-visible spectra of the Ag nanoparticle-loaded defective TiO nanocomposite obtained from Example 1 of the present invention for the catalytic reduction of 4-nitrophenol at 0 °C, 200 °C, 300 °C, 400 °C, 500 °C, and 600 °C;
[0028] Figure 8 is the Ag nanoparticle-loaded defective TiO obtained from Example 1 of the present invention 2Cyclic experiment diagram for the activity evaluation of the nanocomposite. Detailed implementation manners
[0029] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.
[0030] Unless otherwise specified in the following examples, the reagents used are commercially available chemical reagents or industrial products.
[0031] Example 1
[0032] This example provides an Ag nanoparticle-loaded defective TiO 2 nanocomposite, and its preparation method includes the following steps:
[0033] 1) Add 1 mmol AgNO 3 , 0.03 mmol Pd(PPh 3 ) 4 and 0.3 mmol PPh 3 to a mixed solution of 100 mL of methanol and 400 mL of dichloromethane. After stirring, when the solution becomes clear, add 1.5 mL of 4-chlorobenzyl mercaptan. After the solution continues to stir and react for 1 hour, add the aqueous solution of NaBH 4 to the solution in 4 portions, each portion being 2.5 mL. React at 10 °C for 24 h to obtain a purple-red reaction solution.
[0034] 2) Purify the obtained reaction solution by rotary evaporation and centrifugation. Finally, add n-hexane in layers to the saturated CHCl 3 solution of the purified product, and carry out liquid-phase diffusion crystallization at 4 °C for one week to obtain Ag 33 nanocluster crystals.
[0035] 3) Dissolve 10 mg of Ag 33 nanocluster crystals in 10 mL of dichloromethane to make a clear solution. Subsequently, add 100 mg of TiO 2 powder, seal the solution in a rotary evaporator, and evaporate dichloromethane in a water bath at 30 °C. The obtained solid is collected and ground to obtain the Ag 33 -loaded TiO 2 sample (abbreviated as Ag 33 / TiO 2 ).
[0036] 4) Take 100 mg of Ag 33 / TiO 2The powder was placed in a tubular furnace with a diameter of 50 mm and heated to 400 °C at a heating rate of 5 °C / min under a nitrogen flow (100 mL / min) for calcination for 2 h. After calcination, the sample was cooled to room temperature, and the obtained product was the sintered Ag-loaded TiO 2 nanocomposite.
[0037] The product obtained in Example 1 was characterized by transmission electron microscopy (TEM), and the results are shown in Figure 1 , Ag 33 -loaded TiO 2 The TEM image of the sample showed a particle morphology with a particle size range of 30 - 60 nm. In addition, many nanodots with a diameter of less than 5 nm were evenly distributed on the surface of these TiO 2 particles ( Figure 1 a), corresponding to Ag 33 nanocluster crystals. These nanodots became invisible after calcination ( Figure 1 b and 1c), indicating that the structure of Ag 33 was destroyed. The HAADF images corresponding to the sample ( Figure 1 d-1f) showed that calcination led to the decomposition of Ag 33 nanocluster crystals into polydisperse Ag species, including nanoparticles, cluster crystals, and even single Ag atoms anchored on the surface of TiO 2 This indicates that calcination induces the structural evolution of nanocluster crystals by removing organic ligands and reconstructing the metal core, resulting in the sintering of polydisperse Ag species on the surface of TiO 2 as the active species for catalyzing the reduction of nitroarenes.
[0038] Figure 2 The TG diagram of the product obtained in Example 1 and pure TiO 2 is shown. It can be seen from the figure that the weight loss of Ag 33 -loaded TiO 2 occurs in two distinct stages, indicating that the removal of ligands by Ag 2 nanocluster crystals on the surface of TiO 33 is not a simple step but proceeds in two steps.
[0039] Figure 3 The PXRD diagram of the product obtained in Example 1 is shown. It can be seen from the figure that all samples are composed of anatase and rutile, and no impurity peaks are observed, proving that the Ag species are amorphous on the TiO 2 sample.
[0040] Figure 4 The EPR diagram of the product obtained in Example 1 is shown. It can be seen from the figure that after calcination, an obvious unpaired electron signal was observed at g = 2.003, indicating that in Ag 33Calcination in the presence of nanocluster crystals results in the removal of oxygen in the TiO 2 lattice.
[0041] Figure 5 It is the XPS spectrum of Product 1 obtained in Example 1. As can be seen from the figure, both samples are mainly composed of Ti, O, C, and Ag elements, while S and P elements are hardly visible due to their low concentration on the TiO 2 surface.
[0042] Application Example 1
[0043] In this example, the application of Ag nanoparticles loaded on defective TiO 2 nanocomposites in the catalytic reduction of 4-nitrophenol is described.
[0044] Weigh 1 mg of the product obtained in Example 1 and disperse it in 5 mL of a 500 mg / L aqueous solution of 4-nitrophenol under ultrasonic action. Subsequently, add 15 mL of an aqueous solution containing 75 mg of NaBH 4 to the mixture and continue ultrasonic treatment. At each specified time interval, take out 0.5 mL of the suspension from the mixture and filter it using a 0.45 μm MCE filter membrane. Monitor the characteristic absorption peak of 4-nitrophenol in the solution at 400 nm during the reaction process by a UV-vis spectrophotometer.
[0045] Figure 6 It is the catalytic activity diagram of the Ag nanoparticles loaded on defective TiO 2 nanocomposites obtained in Example 1 as a function of time. As can be seen from the figure, the catalytic activity increases with the increase in temperature.
[0046] Figure 7 It is the time-dependent UV-visible spectrum of the catalytic reduction of 4-nitrophenol by the Ag nanoparticles loaded on defective TiO 2 nanocomposites obtained in Example 1. As can be seen from the figure, it reaches the maximum value at 400 °C, and the complete conversion of 4-NP only takes 30 seconds. Further increasing the temperature to 600 °C leads to a decrease in catalytic activity, indicating that too high a calcination temperature is not conducive to catalysis.
[0047] The above results show that the optimal calcination temperature for the catalytic reduction of 4-nitrophenol by the Ag nanoparticles loaded on defective TiO 2 nanocomposites prepared in this invention is 400 °C.
[0048] Figure 8 It is the Ag nanoparticles loaded on defective TiO 2Cyclic experiment diagram for the activity evaluation of the nanocomposite, which shows that the obtained sample still maintains its catalytic efficiency even after being used 9 times, demonstrating excellent reusability.
[0049] Example 2
[0050] 1) Add 1 mmol AgNO 3 , 0.03 mmol Pd(PPh 3 ) 4 and 0.40 mmol PPh 3 to a mixed solution of 100 mL of methanol and 400 mL of dichloromethane. After stirring, when the solution becomes clear, add 1.5 mL of 4-chlorobenzyl mercaptan. After the solution continues to stir and react for 1 hour, add an aqueous solution of NaBH 4 to the solution in 4 portions, 2.5 mL each. React at 10 °C for 24 h to obtain a purple-red reaction solution.
[0051] 2) Purify the obtained reaction solution by rotary evaporation and centrifugation. Finally, add n-hexane in layers to the saturated CHCl 3 solution of the purified product, and carry out liquid-phase diffusion crystallization at 4 °C for one week to obtain Ag 33 nanocluster crystals.
[0052] 3) Dissolve 10 mg of Ag 33 nanocluster crystals in 10 mL of dichloromethane to make a clear solution. Subsequently, add 100 mg of TiO 2 powder, seal the solution in a rotary evaporator, and evaporate dichloromethane in a water bath at 30 °C. The obtained solid is collected and ground to obtain the Ag 33 -loaded TiO 2 sample (abbreviated as Ag 33 / TiO 2 ).
[0053] 4) Place 100 mg of Ag 33 / TiO 2 powder in a tubular furnace with a diameter of 50 mm, and heat it to 350 °C at a heating rate of 5 °C / min under a nitrogen flow (100 mL / min) for calcination for 2.5 h. After calcination, the sample is cooled to room temperature, and the obtained product is the sintered Ag-loaded TiO 2 nanocomposite.
[0054] Example 3
[0055] 1) Add 1 mmol AgNO 3 , 0.03 mmol Pd(PPh 3 ) 4and 0.45 mmol PPh 3 , under stirring conditions, add When the solution becomes clear, add 1.5 mL of 4-chlorobenzyl mercaptan. After the solution continues to stir and react for 1 hour, add NaBH 4 aqueous solution to the solution in 4 portions, 2.5 mL each. React at 10 °C for 24 h to obtain a purplish-red reaction solution.
[0056] 2) Purify the obtained reaction solution by rotary evaporation and centrifugation. Finally, add n-hexane in layers to the saturated CHCl 3 solution of the purified product, and carry out liquid-phase diffusion crystallization at 4 °C for one week to obtain Ag 33 nanocluster crystals.
[0057] 3) Dissolve 10 mg of Ag 33 nanocluster crystals in 10 mL of dichloromethane to make a clear solution. Subsequently, add 100 mg of TiO 2 powder, seal the solution in a rotary evaporator, and evaporate dichloromethane in a water bath at 30 °C. The obtained solid is collected and ground to obtain the TiO 33 supported with Ag 2 sample (abbreviated as Ag 33 / TiO 2 ).
[0058] 4) Place 100 mg of Ag 33 / TiO 2 powder in a tube furnace, heat it to 450 °C at a heating rate of 5 °C / min under a nitrogen flow (100 mL / min) and calcine for 1.5 h. After calcination, cool the sample to room temperature, and the obtained product is the sintered Ag-supported TiO 2 nanocomposite
[0059] Example 4
[0060] 1) Add 1 mmol of AgNO 3 , 0.03 mmol of Pd(PPh 3 ) 4 and 0.50 mmol of PPh 3 to a mixed solution of 100 mL of methanol and 400 mL of dichloromethane. Under stirring conditions, add When the solution becomes clear, add 1.5 mg of 4-chlorobenzyl mercaptan. After the solution continues to stir and react for 1 hour, add NaBH 4 aqueous solution to the solution in 4 portions, 2.5 mL each. React at 10 °C for 24 h to obtain a purplish-red reaction solution.
[0061] 2) Purify the obtained reaction solution by rotary evaporation and centrifugation. Finally, add n-hexane in layers to the saturated CHCl 3In the solution, Ag nanocluster crystals were obtained by liquid-phase diffusion crystallization at 4 °C for one week. 33 The nanocluster crystals.
[0062] 3) Dissolve 10 mg of Ag nanocluster crystals in 10 mL of dichloromethane to make a clear solution. Then add 100 mg of TiO powder, seal the solution in a rotary evaporator, and evaporate dichloromethane in a water bath at 30 °C. The obtained solid was collected and ground to obtain the Ag-loaded TiO sample (abbreviated as Ag / TiO). 33 2 33 -loaded TiO 2 33 / TiO 2 )
[0063] 4) Place 100 mg of Ag / TiO powder in a tubular furnace and heat it to 500 °C at a heating rate of 5 °C / min under a nitrogen flow (100 mL / min) for 2 h. After calcination, the sample was cooled to room temperature, and the obtained product was the sintered Ag-loaded TiO nanocomposite. 33 / TiO 2 2 The nanocomposite.
[0064] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. An amorphous Ag cluster-loaded defective TiO2 nanocomposite material, characterized in that: The preparation method thereof comprises the following steps: S1. Add AgNO3, Pd(PPh3)4 and PPh3 to a mixed solution of methanol and dichloromethane under stirring. When the solution becomes clear, add 4-chlorobenzyl mercaptan; The solution was stirred continuously, and then an aqueous NaBH4 solution was added to react to obtain a purple-red reaction solution; S2. The obtained reaction solution was purified by rotary evaporation and centrifugation. Finally, n-hexane was added to the saturated CHCl3 solution of the purified product in layers, and Ag was obtained by liquid phase diffusion crystallization at 4°C. 33 Nanocluster crystals; S3, Ag 33 The nanocluster crystals were dissolved in dichloromethane to form a clear solution. TiO2 powder was then added, the solution was sealed in a rotary evaporator, and dichloromethane was evaporated in a water bath at 30°C. The resulting solid was collected and ground to obtain Ag. 33 Loaded TiO2 sample, referred to as Ag 33 / TiO2; S4, Ag 33 / TiO2 powder is placed in a tube furnace and calcined; after calcination, the sample is cooled to room temperature, and the obtained product is a non-crystalline Ag cluster-loaded defective TiO2 nanocomposite material.
2. The amorphous Ag cluster-loaded defective TiO2 nanocomposite material according to claim 1, characterized in that: In the step S1, the volume ratio of methanol to dichloromethane is 1:4-6, and the molar ratio of AgNO3, Pd(PPh3)4 and PPh3 is 1:0.03:(0.30-0.50).
3. The amorphous Ag cluster-loaded defective TiO2 nanocomposite material according to claim 1, characterized in that: In the step S1, 4-chlorobenzyl mercaptan is added and reacted for 1 hour, and then NaBH4 aqueous solution is added in 4 portions and reacted at 10° C. for 24 to 28 hours.
4. The amorphous Ag cluster-loaded defective TiO2 nanocomposite material according to claim 1, characterized in that: In step S2, Ag 33 The molecular formula of the nanocluster crystal is: Ag 33 (SCH2PhCl) 24 (PPh3)4.
5. The amorphous Ag cluster-loaded defective TiO2 nanocomposite material according to claim 1, characterized in that: In step S3, Ag 33 The mass ratio of nanocluster crystals, dichloromethane and TiO2 powder is (1-3):(300-1000):
10.
6. The amorphous Ag cluster-loaded defective TiO2 nanocomposite material according to claim 1, characterized in that: The diameter of the tubular furnace in step S4 is 50 mm, and the calcination conditions in the tubular furnace are: heating to 350-500° C. at a heating rate of 5° C. / min under a nitrogen flow of 100 mL / min, and calcining for 1.5-2.5 h.
7. Use of the amorphous Ag cluster-loaded defective TiO2 nanocomposite material as claimed in any one of claims 1 to 6 in the preparation of a reducing agent, characterized in that: The reducing agent is used for the catalytic reduction of nitroaromatic hydrocarbons.