Preparation method and application of oxygen-deficient rod-like core-shell structure catalyst

A core-shell structure and catalyst technology, which is applied in the field of new heterogeneous catalyst preparation, can solve the problems of differences in the number of oxygen vacancies and acid strength, the number of exposed active sites is reduced, and the size of metal nanoparticles is large. ability, improve catalytic activity, and the effect of simple preparation process

Pending Publication Date: 2022-07-29
JIANGSU UNIV +1
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AI-Extracted Technical Summary

Problems solved by technology

In addition, different crystal forms of ZrO 2 The number of oxygen vacancies and acidity strength are different
However, the commonly used co-precipitation method and hydrothermal method in the preparation of ZrO 2 It is not easy to control the crystal form in...
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Method used

Can observe that prepared rod-shaped core-shell structure catalyst 650 ℃-Au/2L-ZrO2@HNTs presents Bronsted acid (1542cm-1) and Lewis acid (1447cm-1) by Fig. 6 pyridine infrared spectrogram ) The characteristic band of the active site, the characteristic band at 1490cm-1 is assigned to the Bronsted and ...
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Abstract

The invention belongs to the field of preparation of novel heterogeneous catalysts, and discloses a preparation method of a catalyst with an oxygen-deficient rod-like core-shell structure and a method for preparing 2, 5-furandicarboxylic acid (FDCA) by applying the catalyst to efficient catalysis of selective oxidation of biomass platform molecule 5-hydroxymethylfurfural (HMF). The obtained Au/ZrO2-coated HNTs catalyst has both oxygen vacancies and Lewis acid sites, the chemical adsorption energy of an oxidizing agent O2 in the reaction process can be reduced due to the existence of the oxygen vacancies, O2 adsorbed on the surface of the catalyst can receive delocalized electrons from the oxygen vacancies to be converted into active oxygen, and therefore the catalytic reaction activity is improved. In addition, lone pair electrons of oxygen atoms of hydroxyl groups in an intermediate in the reaction process can be captured due to existence of Lewis acid sites, the adsorption capacity of the catalyst to the reaction intermediate is improved, and the catalytic reaction efficiency is improved.

Application Domain

Material nanotechnologyOrganic chemistry +2

Technology Topic

Oxygen vacancyActivated oxygen +13

Image

  • Preparation method and application of oxygen-deficient rod-like core-shell structure catalyst
  • Preparation method and application of oxygen-deficient rod-like core-shell structure catalyst
  • Preparation method and application of oxygen-deficient rod-like core-shell structure catalyst

Examples

  • Experimental program(4)

Example Embodiment

[0037] Example 1:
[0038] 1. Oxygen-deficient rod-like core-shell structure 650℃-Au/2L-ZrO 2 Preparation of @HNTs catalysts.
[0039] (1) Weigh 40g of HNTs into a three-necked flask, measure 250mL of HNO with a graduated cylinder 3 The solution was placed in a three-necked flask. Then it was placed in an oil bath and a reflux condensing device was installed, and stirred at 75° C. for 12 h. After the reaction was completed, the obtained reaction mixture was washed with deionized water until neutral, and then collected by centrifugation. The obtained samples were dried in a vacuum drying oven at 60 °C for 12 h. The obtained solid was then ground into powder, placed in a tube furnace under an air atmosphere, and calcined at 200° C. for 2 h.
[0040] (2) Weigh 0.23 g of pretreated HNTs and 0.01 g of HPC, disperse them in 20 mL of ethanol, dropwise add 0.1 mL of deionized water, and disperse by ultrasonic to make the samples evenly mixed. The flask was then placed in a 25°C water bath and stirred for 30 min. Measure 0.6 mL of ZBOT solution into 4.5 mL of ethanol solution (5.1 mL of hydrolyzed zirconium salt solution), and after mixing evenly, slowly add it dropwise to the reaction solution for 20 h. After the reaction was completed, the obtained solution was washed with ethanol, the precipitate was collected by centrifugation, and dried in an oven at 60 °C for 12 h to obtain a sample loaded with amorphous zirconia 1L-ZrO 2 @HNTs.
[0041] (3) Weigh 0.23g of 1L-ZrO obtained in the previous step 2 @HNTs and 0.01 g HPC were redispersed into 20 mL of ethanol and stirred for 30 min. Then measure 0.6 mL of ZBOT, disperse it in 4.5 mL of ethanol (5.1 mL of hydrolyzed zirconium salt solution), and add it dropwise to the reaction system after mixing evenly. After the reaction system was reacted at 25 °C for 20 h, the obtained product was washed 3-4 times with ethanol, collected by centrifugation, and dried in an oven at 60 °C for 12 h. Then, the dried sample powder was placed in a tube furnace, calcined at 650 °C for 2 h in an air atmosphere, and the heating rate was 5 °C/min to obtain a mixed crystal (monoclinic phase ZrO) supported on the surface of HNTs. 2 and tetragonal ZrO 2 ) of the two-layer zirconia product 650℃-2L-ZrO 2 @HNTs.
[0042] (4) Measure 75ml of 1wt% PVA aqueous solution, add 0.8mL of 1wt% HAuCl 4 ·3H 2 O solution was added to it, stirred in a water bath at 25 °C for 5 min, and then 1 mL of 0.1 M NaBH was added dropwise 4 solution. After stirring uniformly, 0.4 mL of HCl was added to the reaction system to make the pH of the reaction system 7. Then weigh 0.2g of 650℃-2L-ZrO 2 @HNTs was added to the reaction system and stirred for 2h. After the reaction, the obtained product was washed 4-5 times with deionized water, collected by centrifugation, and vacuum-dried at 60 °C for 24 h to obtain a rod-shaped core-shell catalyst for catalyzing HMF oxidation to prepare FDCA. 650 °C-Au/2L- ZrO 2 @HNTs.
[0043] Depend on figure 1 The SEM images (a) and TEM images (d) show that the HNTs are hollow rod-like structures. According to the SEM images (b) and (c), it can be seen that 1L-ZrO 2 @HNTs and 2L-ZrO 2 The @HNTs still showed a rod-like structure. In addition, it can be observed from TEM images (e) and (f) that zirconia was successfully loaded onto the surface of HNTs. It is 93nm, and the transmission electron microscope image further proves that the prepared sample is a rod-like core-shell structure.
[0044] Depend on figure 2 TEM image (a) shows that Au nanoparticles were successfully loaded to 650℃-2L-ZrO 2 @HNTs surface, and it was observed after lattice measurement from the captured high-resolution images that ZrO calcined at 650 °C 2 It is a mixed crystal form (monoclinic m-ZrO 2 Phase and tetragonal t-ZrO 2 ). From the particle size distribution diagram (b), it can be observed that the particle size of the supported Au is small, and its average size is about 2.25 nm. The smaller the particle size of Au, the more active sites the catalyst provides for the reaction. The better the catalytic performance.
[0045] Depend on image 3 , the X-ray diffraction pattern shows that the prepared rod-like core-shell catalyst 650℃-Au/2L-ZrO 2 @HNTs show different crystal forms of ZrO 2 Characteristic peaks. The peaks at 28.2° and 31.5° correspond to the monoclinic phase ZrO, respectively 2 (m-ZrO 2 ) of the (-111) and (111) planes, while 30.2°, 35.3°, 50.4° and 59.7° correspond to the tetragonal phase ZrO, respectively 2 (t-ZrO 2) of the (111), (200), (220) and (311) crystal planes, which indicate that the zirconia obtained by calcination at 650 °C is a mixed crystal form (monoclinic and tetragonal). The characteristic peaks of Au should appear at 38.3°, 44.4° and 64.5°, but the characteristic peaks of Au are not observed in the spectrum. Combined with the results observed in the transmission electron microscope, it is speculated that this is because the Au nanoparticles are uniformly distributed On the support and small in size, below the limit of X-ray diffraction detection.
[0046] Depend on Figure 4 , 650℃-Au/2L-ZrO 2 The electron paramagnetic resonance spectrum of @HNTs can be observed to have a peak with g value of 2.003, which corresponds to the characteristic peak of oxygen deficiency, which indicates that the as-prepared catalyst 650℃-Au/2L-ZrO 2 @HNTs have oxygen vacancies.
[0047] Depend on Figure 5 , HNTs and 650℃-Au/2L-ZrO 2 NH of @HNTs 3 Temperature-programmed desorption diagrams show that there are hardly any acidic sites on the surface of HNTs, while the as-prepared catalyst 650℃-Au/2L-ZrO 2 There are strong acid sites on the surface of @HNTs, and the total amount of strong acid in the catalyst is 5.1057 mmol g after quantitative analysis of the curve integral. -1.
[0048] Depend on Image 6 The pyridine infrared spectrum shows that the prepared rod-like core-shell catalyst 650℃-Au/2L-ZrO 2 @HNTs also presented Bronsted acid (1542cm -1 ) and Lewis acid (1447cm -1 ) characteristic band of active site, 1490cm -1 The characteristic bands at are assigned to Bronsted and Lewis acid sites. Quantitative analysis of the curve integral shows that the Lewis acid sites on the surface of the prepared catalyst are 0.0556 mmol g -1. Among them, the Lewis acid site is conducive to the adsorption of the intermediate product by the catalyst, thereby improving the catalytic reaction activity.
[0049] Depend on Figure 7 Medium 650℃-2L-ZrO 2 @HNTs and the as-prepared rod-like core-shell catalyst 650℃-Au/2L-ZrO 2 The XPS full spectrum of @HNTs (a) shows the appearance of Zr 3d and Au 4f signal peaks, which proves that zirconia and Au nanoparticles have been successfully loaded onto HNTs. From Figure (b) Au/HNTs and 650℃-Au/2L-ZrO 2 The high-resolution spectra of the Au 4f region of @HNTs can be observed that compared with the binding energy of Au 4f of Au/HNTs, the catalyst 650°C-Au/2L-ZrO 2 The Au 4f binding energies of @HNTs are shifted towards lower. This shows that ZrO 2 The charge on the (mixed crystal form) carrier is transferred to the Au nanoparticles, so that the Au nanoparticles are in a negatively charged state, and there is charge transfer between the carrier and the metal. From Figure (c), it can be observed that 650℃-Au/2L-ZrO 2 The binding energies of Zr 3d in @HNTs shift towards an elevated direction, which indicates that the charge of Zr ions is transported to the Au nanoparticles. Figure (d) is the high-resolution spectrum of the O1s region, for the catalyst 650℃-Au/2L-ZrO 2 For @HNTs, the peak at 531.60 eV is attributed to the surface adsorbed oxygen (O ads ), and the surface adsorbed oxygen is closely related to oxygen vacancies, so this result indicates that the as-prepared ZrO has a mixed crystal form 2 The catalyst surface contains oxygen vacancies. In addition, it can be observed that the binding energy of O1s after the sample is loaded with Au moves to a lower direction, which further indicates that there is an interaction between the support and the metal.
[0050] 2. Catalytic activity test:
[0051] Weigh 0.05g HMF, 0.06g NaOH and 0.05g 650℃-Au/2L-ZrO 2 @HNTs, disperse it in 40mL deionized water, then fill the autoclave with O 2 , the pressure was 2MPa, the reaction system was reacted at 100°C for 3h, and the rotational speed was 600rpm. The liquid product obtained by the reaction was detected by a high performance liquid chromatograph (HPLC) equipped with an ultraviolet detector and a hydrogen column. The obtained liquid product was diluted 80 times with deionized water, and then the liquid was filtered with a 0.2 μm polytetrafluoroethylene filter membrane. The detection conditions are: the column temperature is 65°C; the mobile phase is 0.01M H 2 SO 4; The flow rate was 0.4 mL/min; the injection volume was 20 μL. The standard curve of FDCA sample is y=352.03x-81.042 (y represents the corresponding concentration of FDCA, the unit is mg/L, and x represents the peak area). According to the standard curve, the concentration of FDCA can be calculated and converted into molar concentration. Product yield is calculated as Y (molar yield)=n 1 /n 0 ×100, n 1 represents the molar amount of FDCA obtained, n 0 represents the molar amount of reaction substrate HMF. The calculation results show that the product FDCA can reach a higher yield, and the FDCA yield of the reaction for 3h is 99.36%.
[0052] 3. Regeneration performance test
[0053] In the present invention, the prepared rod-shaped core-shell structure catalyst 650°C-Au/2L-ZrO 2 @HNTs can be obtained by centrifugation, separation, and drying. The recovered catalyst was put back into the above-mentioned catalytic experiment to test its catalytic effect; four regeneration experiments were carried out in this way. The detection method and experimental conditions of the obtained liquid products are the same as the above-mentioned catalytic experiments. The results showed that the loss of catalyst activity during the regeneration process was relatively low, and the yields of FDCA were 95.04%, 89.02%, 88.40%, and 87.68% during the one to four regeneration experiments.

Example Embodiment

[0054] Example 2:
[0055] 1. Oxygen-deficient rod-like core-shell structure 450℃-Au/2L-ZrO 2 Preparation of @HNTs catalysts.
[0056] (1) Weigh 10g of HNTs and place it in a three-necked flask, measure 63mL of HNTs with a graduated cylinder 2 SO 4 The solution was placed in a three-necked flask. Then it was placed in an oil bath and a reflux condensing device was installed, and the mixture was stirred at 75° C. for 8 h. After the reaction was completed, the obtained reaction mixture was washed with deionized water until neutral, and then collected by centrifugation. The obtained samples were dried in a vacuum drying oven at 60 °C for 24 h. The obtained solid was then ground into powder, placed in a tube furnace under air atmosphere, and calcined at 300° C. for 1 h.
[0057] (2) Weigh 0.92 g of pretreated HNTs and 0.04 g of HEC, disperse them in 80 mL of ethanol, dropwise add 0.4 mL of deionized water, and disperse by ultrasonic to make the samples evenly mixed. The flask was then placed in a 25°C water bath and stirred for 30 min. Measure 2.4 mL of ZBOT solution into 18 mL of ethanol solution (20.4 mL of hydrolyzed zirconium salt solution), and after mixing evenly, slowly add it dropwise to the flask to react for 24 h. After the reaction, the obtained solution was washed with ethanol, the precipitate was collected by centrifugation, and dried in an oven at 60 °C for 12 h to obtain a sample loaded with amorphous zirconia 1L-ZrO 2 @HNTs.
[0058] (3) Weigh 0.46g of 1L-ZrO 2 @HNTs, 0.02g HEC, was added to 40mL of ethanol and stirred for 30min to mix well. 10.2 mL of hydrolyzed zirconium salt solution (1.2 mL ZBOT, 9.0 mL ethanol) was prepared and slowly added dropwise to the reaction mixture. After the reaction system was reacted at 25° C. for 24 hours, the obtained product was washed with ethanol, collected by centrifugation, and dried in an oven at 60° C. for 12 hours. Then, the dried sample powder was placed in a tube furnace, calcined at 450 °C for 2 h in an air atmosphere, and the heating rate was 5 °C/min to obtain a tetragonal two-layer zirconia product supported on the outer surface of HNTs at 450 °C- 2L-ZrO 2 @HNTs.
[0059] (4) Measure 150ml of 1wt% PVP aqueous solution, add 1.6mL of 1wt% HAuCl 4 ·3H 2 O solution was added to it, stirred in a water bath at 25 °C for 5 min, and then 1 mL of 0.1 M KBH was added dropwise. 4 solution. After stirring evenly, add 0.4 mL of 1M HNO to the reaction system 3 The pH of the reaction system was made 7. Then weigh 0.4g of 450℃-2L-ZrO 2 @HNTs was added to the reaction system and stirred for 3 h. After the reaction, the obtained product was washed 4-5 times with deionized water, collected by centrifugation, and vacuum-dried at 70 °C for 12 h to obtain a rod-shaped core-shell catalyst for catalyzing HMF oxidation to prepare FDCA 450 °C-Au/2L- ZrO 2 @HNTs.
[0060] 2. Catalytic performance test:
[0061] Weigh 0.06g HMF, 0.16g NaHCO 3 and 0.06g 450℃-Au/2L-ZrO 2 @HNTs, disperse it in 50mL deionized water, then fill the reactor with O 2 , the pressure was 2MPa, the reaction system was reacted at 100°C for 8h, and the speed was 600rpm. The liquid product obtained by the reaction was detected by a high performance liquid chromatograph (HPLC) equipped with an ultraviolet detector and a hydrogen column, and the detection method was the same as that of step 2 in Example 1. The calculation results show that the product FDCA can reach a high yield, and the FDCA yield of the reaction for 8h is 97.07%.
[0062] 3. Regeneration performance test:
[0063] The test method of regeneration performance is the same as that of Example 1. The results showed that the activity of the catalyst did not lose too much during the regeneration reaction, and the yields of FDCA were 95.96%, 92.02%, 89.89%, and 88.98% during the one to four regeneration experiments.

Example Embodiment

[0064] Example 3:
[0065] 1. Oxygen-deficient rod-like core-shell structure 350℃-Au/2L-ZrO 2 Preparation of @HNTs catalysts.
[0066] (1) Weigh 20g of HNTs into a three-necked flask, measure 126mL of HNO with a graduated cylinder 3 The solution was placed in a three-necked flask. Then it was placed in an oil bath and a reflux condensing device was installed, and stirred at 80° C. for 8 h. After the reaction was completed, the obtained reaction mixture was washed with deionized water until neutral, and then collected by centrifugation. The obtained samples were dried in a vacuum drying oven at 50 °C for 24 h. The obtained solid was then ground into powder, placed in a tube furnace under air atmosphere, and calcined at 200° C. for 2 h.
[0067](2) Weigh 0.69 g of pretreated HNTs and 0.03 g of HPC, disperse them in 60 mL of ethanol, add 0.3 mL of deionized water dropwise, and disperse by ultrasonic to make the samples evenly mixed. The flask was then placed in a 25°C water bath and stirred for 30 min. Measure 1.8 mL of ZBOT solution into 13.5 mL of ethanol solution (15.3 mL of hydrolyzed zirconium salt solution), and after mixing evenly, slowly add it dropwise to the flask to react for 20 h. After the reaction, the obtained solution was washed with ethanol, the precipitate was collected by centrifugation, and dried in an oven at 70 °C for 12 h to obtain a sample loaded with amorphous zirconia 1L-ZrO 2 @HNTs.
[0068] (3) Add 0.92g of 1L-ZrO to 80mL of ethanol 2 @HNTs and 0.04 g HPC, followed by ultrasonic dispersion and stirring in a 25°C water bath for 30 min. Then, 2.4 mL of ZBOT (20.4 mL of hydrolyzed zirconium salt solution) was added to 18 mL of ethanol, and it was slowly added dropwise to the reaction solution after mixing uniformly. After 20 h of reaction, the obtained reaction solution was washed with ethanol, and then the precipitate was collected by centrifugation, and then the obtained sample was dried in an oven at 70° C. for 12 h. Then, under the air atmosphere, the dried sample powder was placed in a tube furnace and calcined at 350 °C for 2 h, and the heating rate was 5 °C/min to obtain a monoclinic phase two-layer zirconia product supported on the outer surface of HNTs at 350 °C- 2L-ZrO 2 @HNTs.
[0069] (4) 4.0 mL of 1 wt% HAuCl 4 ·3H 2 Aqueous O solution was added to 375 ml of 1 wt% PVP solution. After stirring for 5 min in a water bath at 25 °C, 5 mL of 0.1 M NaBH was added dropwise to the reaction solution. 4 solution. After stirring evenly, 2 mL of HCl was added dropwise to adjust the pH of the solution to 7. Then weigh 1.0g of 350℃-2L-ZrO 2 @HNTs was added to the reaction system and stirred for 4 h. After the reaction, the reaction solution was washed with deionized water, and the precipitate was collected by centrifugation and dried in vacuum at 60 °C for 12 h to prepare a catalyst 350 °C-Au/2L-ZrO 2 @HNTs.
[0070] 2. Catalytic performance test:
[0071] Weigh 0.08g HMF, 0.26g Na 2 CO 3 and 0.08g 350℃-Au/2L-ZrO 2 @HNTs, disperse it in 60mL deionized water, then fill the autoclave with O 2 , the pressure was 2MPa, the reaction system was reacted at 110°C for 12h, and the rotational speed was 600rpm. The detection method of the liquid product obtained by the reaction is the same as that of Step 2 in Example 1. The calculation results show that the product FDCA can achieve a high yield, and the FDCA yield of the reaction for 8h is 93.20%.
[0072] 3. Regeneration performance test:
[0073] The test method of regeneration performance is the same as that of Example 1. The results showed that the activity of the catalyst did not lose too much during the regeneration reaction, and the yields of FDCA were 92.02%, 90.92%, 89.48%, and 88.86% during the one to four regeneration experiments. Example 4:

PUM

PropertyMeasurementUnit
Diameter88.0nm
Diameter93.0nm

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