Preparation method of platinum-loaded phosphotungstic acid modified titanium dioxide material and application thereof

Abstract

The present application provides a preparation method of a platinum-loaded phosphotungstic acid-modified titanium dioxide material with high activity in efficient low-temperature photocatalytic degradation of toluene (C7H8). The inventors have found that when titanium dioxide (TiO2) is used as a base material, the material is modified by phosphotungstic acid (H3O 40 PW 12 xH2O), a trace amount of platinum is loaded thereon, and the oxidation state of platinum is changed by calcination, a higher toluene degradation activity can be achieved with an extremely low platinum (Pt) loading amount. The present application modifies titanium dioxide by phosphotungstic acid, and the interaction between platinum and phosphotungstic acid enables a higher toluene degradation activity at a low temperature with an extremely low platinum loading amount. Moreover, the catalyst has higher stability due to a higher carbon dioxide yield.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing a material in which platinum is supported on titanium dioxide modified by phosphotungstic acid and its application in degrading toluene, and belongs to the field of functional materials and the field of photocatalysis. BACKGROUND

[0002] With the development of science and technology, industrialization and urbanization are constantly advancing, which improves our daily life while causing serious environmental problems due to the emission of air pollutants. Volatile organic compounds (VOCs) such as toluene have become representative air pollutants, which can cause photochemical smog and lead to the formation of ozone. Therefore, it is urgent to study the degradation method of VOC gas to solve the increasingly serious environmental problems. People have studied from physical adsorption, high-temperature combustion, catalytic degradation, etc. Among them, the photocatalytic degradation is considered to be the most effective method, and the photo-thermal synergistic catalysis has received widespread attention due to its characteristics of utilizing solar energy to reduce the operating temperature and improve the catalytic performance. The photo-thermal synergistic catalytic degradation method has a strong dependence on the catalyst. TiO2 has been a hot spot in photocatalytic research as an n-type semiconductor. Its band gap is 3.2 eV. When it is irradiated by ultraviolet light, the electrons in the valence band will jump to the conduction band due to the energy of photons, thereby forming photo-generated electrons and holes in the conduction band and the valence band, and then redox reactions occur. Although the catalytic activity of non-noble metal catalysts for VOC gas treatment has been greatly improved, their activity is still lower than that of catalysts loaded with noble metals. Especially Pt, which is recognized as a highly active catalyst, but due to the economic consideration of high Pt loading, it has not been qualified for large-scale application in VOC gas treatment.

[0003] Based on the above research background, first, TiO2 is modified by using phosphotungstic acid, then Pt is loaded, and finally Pt supported on phosphotungstic acid modified TiO2 is prepared by high-temperature calcination. In this paper, the Pt loading is reduced by modification of phosphotungstic acid, and the prepared material can complete more than 90% toluene degradation under xenon lamp irradiation without using an external heat source. At the same time, the catalyst also effectively reduces the carbon deposition reaction during the reaction process, and has a long-term continuous reaction stability of more than 100 hours. SUMMARY

[0004] The present application first uses titanium dioxide nanoparticles and phosphotungstic acid as raw materials to prepare modified titanium dioxide with ethanol as a solution. Then, platinum is loaded by a wet impregnation method using chloroplatinic acid as a raw material. Finally, the preparation of the catalyst is completed by changing the valence state of platinum through high-temperature calcination.

[0005] The method for preparing the material in which platinum is supported on phosphotungstic acid modified titanium dioxide is as follows: TiO2 and H3PO3 are mixed to prepare modified TiO2, and then chloroplatinic acid is added to the modified TiO2 to complete the loading of platinum.40 PW 12 • xH2O is fully stirred in ethanol solution, and HPW can be obtained by rotary evaporation X TiO2. Then HPW X TiO2 is dissolved in water, and a precursor solution of platinum chloride hexahydrate is added. After stirring for four hours at room temperature, the water solution is evaporated to obtain the sample Pt / HPW X TiO2. Finally, Pt / HPW X TiO2 is calcined in an air atmosphere at a temperature range of 200-600°C to obtain platinum loaded phosphotungstic acid modified titanium dioxide.

[0006] A method for preparing a platinum loaded phosphotungstic acid modified titanium dioxide material, wherein the loading amount of platinum is 0.1-0.5wt% relative to the platinum loaded phosphotungstic acid modified titanium dioxide material, and specifically comprising the following steps:

[0007] Step 1: titanium dioxide and phosphotungstic acid are dissolved in an ethanol solution, stirred and reacted, and the ethanol solution is evaporated to obtain a phosphotungstic acid modified titanium dioxide material, with a mass ratio of titanium dioxide to phosphotungstic acid of 1:0.1-0.4;

[0008] Step 2: after the phosphotungstic acid modified titanium dioxide is dissolved in water, a precursor solution of platinum is added dropwise, stirred and reacted, and the water solution is evaporated to obtain a precursor material;

[0009] Step 3: the precursor material is placed in a muffle furnace and calcined at a high temperature in an air atmosphere, with a temperature range of 200-600°C.

[0010] Further, in step 2, the precursor solution is a solution of platinum chloride hexahydrate.

[0011] Further, the loading amount of platinum is 0.3wt%.

[0012] Further, in step 3, the temperature range is 400°C.

[0013] Further, the mass ratio of titanium dioxide to phosphotungstic acid is 1:0.3.

[0014] Further, the platinum loaded phosphotungstic acid modified titanium dioxide material obtained according to the preparation method is applied in the process of low-temperature photocatalytic degradation of toluene.

[0015] Further, the temperature of photocatalytic degradation is 140-180°C, and the light power density of the light source is 500-1000Mw / cm 2 .

[0016] The advantages of the present application are embodied in

[0017] 1. The phosphotungstic acid supported on the titanium dioxide changes the valence state of platinum, making platinum more inclined to the metal state, and the modification of the titanium dioxide by the phosphotungstic acid reduces the loading amount of Pt, achieving the effect of improving the reaction activity while reducing the preparation cost.

[0018] 2. In the present application, the state of Pt can be controlled by simple calcination after the modification of the titanium dioxide by the phosphotungstic acid, so that the catalyst has higher activity and better stability.

[0019] 3. The catalyst can utilize light energy to achieve higher toluene degradation efficiency at a lower temperature. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 (a) is TiO2, Pt / TiO2, Pt / HPW 0.1 TiO2, Pt / HPW 0.2 TiO2, Pt / HPW 0.3 TiO2, Pt / HPW 0.4 TiO2, HPW 0.3 TiO2, Pt / HPW, X-ray diffraction pattern of the HPW sample, Figure 1 (b) is the Raman spectrum of the nine samples (the insert is an enlarged view of 900-1100 cm -1 ).

[0021] Figure 2 (a) is the SEM image of Comparative Example 1, Figure 2 (b) is the SEM image of Example 3, Figure 2 (C) is the transmission electron microscope (TEM) image of the sample in Example 3.

[0022] Figure 3 (a) is the photocatalytic toluene degradation activity test of the materials in Examples 3, 5, and 6 within 2 hours, Figure 3 (b) is the photocatalytic toluene degradation activity test of the materials in Examples 3, 7, and 8 within 2 hours.

[0023] Figure 4 (a) is the photocatalytic toluene degradation activity test of the materials in Examples 1-4 and Comparative Examples 1-4 within 2 hours, Figure 4 (b) is the stability test of the sample in Example 3. DETAILED DESCRIPTION

[0024] The present application will be described in more detail below through specific examples, but the scope of protection of the present application is not limited to these examples.

[0025] Example 1

[0026] Pt / HPW 0.1 Synthesis of TiO2

[0027] 1 g TiO2and 0.1 g H3PO4 40 PW 12 • xH2O was stirred in 60 ml CH3CH2OH at room temperature for 12 hours, then evaporated to dryness to obtain HPW 0.1 TiO2. 1 g HPW 0.1 TiO2was dissolved in 60 ml water and ultrasonically treated for 15 min. Then 5.67 ml of Pt precursor chloroplatinic acid hexahydrate solution was added dropwise into the above HPW 0.1 TiO2suspension. After the reaction was completed by continuously stirring the above solution for 4 h, the yellow product was obtained by evaporating to dryness. The final product Pt / HPW 0.1 TiO2, wherein the content of Pt was 0.3 wt%, and the mass ratio of titanium dioxide to phosphotungstic acid was 1:0.1.

[0028] Example 2

[0029] Pt / HPW 0.2 Synthesis of TiO2

[0030] 1 g TiO2and 0.2 g H3PO4 40 PW 12 • xH2O was stirred in 60 ml CH3CH2OH at room temperature for 12 hours, then evaporated to dryness to obtain HPW 0.2 TiO2. 1 g HPW 0.2 TiO2was dissolved in 60 ml water and ultrasonically treated for 15 min. Then 5.67 ml of Pt precursor chloroplatinic acid hexahydrate solution was added dropwise into the above HPW 0.2 TiO2suspension. After the reaction was completed by continuously stirring the above solution for 4 h, the yellow product was obtained by evaporating to dryness. The final product Pt / HPW 0.2 TiO2, wherein the content of Pt was 0.3 wt%, and the mass ratio of titanium dioxide to phosphotungstic acid was 1:0.2.

[0031] Example 3

[0032] Pt / HPW 0.3 Synthesis of TiO2

[0033] 1 g TiO2and 0.3 g H3PO4 40 PW 12 • xH2O was stirred in 60 ml CH3CH2OH at room temperature for 12 hours, then evaporated to dryness to obtain HPW 0.3 TiO2. 1 g HPW 0.3TiO2was dissolved in 60 ml water and sonicated for 15 min. Then the above HPW 0.3 Pt precursor chloroplatinic acid hexahydrate solution 5.67 ml was added dropwise into the TiO2suspension. After the reaction was completed by continuously stirring the above solution for 4 h, the yellow product was obtained by rotary evaporation. The final product Pt / HPW 0.3 TiO2, wherein the content of Pt was 0.3 wt%, and the mass ratio of TiO2to HPW was 1:0.3.

[0034] Example 4

[0035] Pt / HPW 0.4 Synthesis of TiO2

[0036] 1 g TiO2and 0.4 g H3O 40 PW 12 HPW was obtained by stirring the mixture of 1 g TiO2and 0.4 g H3O 0.4 TiO2. 1 g HPW 0.4 TiO2was dissolved in 60 ml water and sonicated for 15 min. Then the above HPW 0.4 Pt precursor chloroplatinic acid hexahydrate solution 5.67 ml was added dropwise into the TiO2suspension. After the reaction was completed by continuously stirring the above solution for 4 h, the yellow product was obtained by rotary evaporation. The final product Pt / HPW 0.4 TiO2, wherein the content of Pt was 0.3 wt%, and the mass ratio of TiO2to HPW was 1:0.4.

[0037] Example 5

[0038] Pt 0.1 / HPW 0.3 Synthesis of TiO2

[0039] 1 g TiO2and 0.3 g H3O 40 PW 12 HPW was obtained by stirring the mixture of 1 g TiO2and 0.3 g H3O 0.3 TiO2. 1 g HPW 0.3 TiO2was dissolved in 60 ml water and sonicated for 15 min. Then the above HPW 0.3 Pt precursor chloroplatinic acid hexahydrate solution 1.89 ml was added dropwise into the TiO2suspension. After the reaction was completed by continuously stirring the above solution for 4 h, the yellow product was obtained by rotary evaporation. The final product Pt / HPW 0.3TiO2, wherein the content of Pt is 0.3wt%, the mass ratio of titanium dioxide to phosphotungstic acid is 1:0.3.

[0040] Example 6

[0041] Pt 0.5 / HPW 0.3 Synthesis of TiO2

[0042] 1 g TiO2and 0.3 g H3PO4 40 PW 12 HPW was obtained by stirring 1 g TiO2and 0.3 g H3PO4in 60 ml CH3CH2OH at room temperature for 12 hours, and then evaporating to dryness 0.3 TiO2. 1 g HPW 0.3 TiO2was dissolved in 60 ml water, and ultrasonic treated for 15 min. Then 9.45 ml of Pt precursor chloroplatinic acid hexahydrate solution was added dropwise into the above HPW 0.3 TiO2suspension. After the above solution was continuously stirred for 4 h, the reaction was completed, and then evaporated to dryness, a yellow product was obtained. The final product Pt / HPW 0.3 TiO2, wherein the content of Pt is 0.3wt%, the mass ratio of titanium dioxide to phosphotungstic acid is 1:0.3.

[0043] Example 7

[0044] 200-Pt / HPW 0.3 Synthesis of TiO2

[0045] 1 g TiO2and 0.3 g H3PO4 40 PW 12 HPW was obtained by stirring 1 g TiO2and 0.3 g H3PO4in 60 ml CH3CH2OH at room temperature for 12 hours, and then evaporating to dryness 0.3 TiO2. 1 g HPW 0.3 TiO2was dissolved in 60 ml water, and ultrasonic treated for 15 min. Then 5.67 ml of Pt precursor chloroplatinic acid hexahydrate solution was added dropwise into the above HPW 0.3 TiO2suspension. After the above solution was continuously stirred for 4 h, the reaction was completed, and then evaporated to dryness, a yellow product was obtained. The final product Pt / HPW 0.3 TiO2, wherein the content of Pt is 0.3wt%, the mass ratio of titanium dioxide to phosphotungstic acid is 1:0.3.

[0046] Example 8

[0047] 600-Pt / HPW 0.3 Synthesis of TiO2

[0048] 1 g TiO2and 0.3 g H3PO4 40 PW 12 • xH2O was stirred in 60 ml CH3CH2OH at room temperature for 12 hours, and then HPW was obtained by rotary evaporation 0.3 TiO2. 1 g HPW 0.3 TiO2was dissolved in 60 ml water and ultrasonic treated for 15 min. Then 5.67 ml of Pt precursor chloroplatinic acid hexahydrate solution was added dropwise into the above TiO2suspension. After the reaction was completed by continuously stirring the above solution for 4 h, the yellow product was obtained by rotary evaporation. The final product Pt / HPW was obtained by calcination at 600 °C for 4 h in a muffle furnace. 0.3 TiO2. 1 g HPW 0.3 TiO2, wherein the content of Pt was 0.3 wt%, and the mass ratio of titanium dioxide to phosphotungstic acid was 1:0.3.

[0049] Comparative Example 1

[0050] Synthesis of Pt / TiO2

[0051] 1 g TiO2was dissolved in 60 ml water and ultrasonic treated for 15 min. Then 5.67 ml of Pt precursor chloroplatinic acid hexahydrate solution was added dropwise into the above TiO2suspension. After the reaction was completed by continuously stirring the above solution for 4 h, the yellow product was obtained by rotary evaporation. The final product Pt / TiO2, wherein the content of Pt was 0.3 wt%, was obtained by calcination at 400 °C for 4 h in a muffle furnace.

[0052] Comparative Example 2

[0053] Synthesis of HPW 0.3 TiO2

[0054] 1 g TiO2and 0.3 g H3PO4 40 PW 12 • xH2O was stirred in 60 ml CH3CH2OH at room temperature for 12 hours, and then HPW was obtained by rotary evaporation 0.3 TiO2. 1 g HPW 0.3 TiO2, wherein the mass ratio of titanium dioxide to phosphotungstic acid was 1:0.3.

[0055] Comparative Example 3

[0056] Synthesis of Pt / HPW

[0057] 1 g H3PO4 40 PW 12 • xH2O was dissolved in 60 ml water and ultrasonic treated for 15 min. Then 5.67 ml of Pt precursor chloroplatinic acid hexahydrate solution was added dropwise into the above H3PO4 40 PW 125.67 ml of a Pt precursor chloroplatinic acid hexahydrate solution was added dropwise to an xH₂O solution. After stirring the solution continuously for 4 h and the reaction was complete, the product was dried by rotary evaporation to obtain a yellow product. Calcination at 400 °C for 4 h in a muffle furnace yielded the final product Pt / HPW, with a Pt content of 0.3 wt%.

[0058] Comparative Example 4

[0059] Synthesis of TiO2

[0060] Weigh 1g of TiO2 and dissolve it in 60ml of water, then sonicate for 15min. After stirring the solution continuously for 4h and the reaction is complete, dry it by rotary evaporation to obtain a white product. Calcine the product in a muffle furnace at 400℃ for 4h to obtain the final product TiO2.

[0061] Comparative Example 5

[0062] HPW Synthesis

[0063] Weigh 1g H3O 40 PW 12 • xH₂O was dissolved in 60 ml of water and sonicated for 15 min. After the reaction was completed by stirring the solution continuously for 4 h, the product was dried by rotary evaporation to obtain a white product. Calcination at 400 °C for 4 h in a muffle furnace yielded the final product HPW.

[0064] Experiments and Data

[0065] The method for evaluating the photocatalytic toluene degradation activity provided by this invention is as follows:

[0066] First, 100 mg of catalyst was placed in a quartz reactor, and the toluene concentration of the introduced gas was 500 ppm. The total flow rate of the gas (air + toluene) was 40 mL / min. -1 Under laboratory lighting (using a 300W xenon lamp), without external power supply and utilizing only the heat generated by the light, the photocatalytic degradation temperature was 165℃, and the light power density of the light source was 700 Mw / cm². 2 The gaseous products were analyzed using a gas chromatograph (GC, Fuli, China, GC-9790Ⅱ). Carbon-containing gases such as toluene and carbon dioxide were analyzed using a flame ionization detector (FID). The total reaction time was 2 hours, and the long-term stability reaction was 30 hours.

[0067] Figure 1 (a) The peak of titanium dioxide can be seen, but due to the relatively uniform dispersion of phosphotungstic acid and platinum, the peaks of both cannot be observed. Figure 1 (b) The peaks of titanium dioxide and phosphotungstic acid can be seen, which proves the successful synthesis of our target product.

[0068] Figure 2(a) SEM image of Comparative Example 1, Figure 2 (b) SEM images of Example 3, from which Pt / HPW can be seen. 0.3 Compared to Pt / TiO2, TiO2 does indeed encapsulate titanium dioxide particles due to the modification with phosphotungstic acid. Figure 2 (C) is a transmission electron microscope (TEM) image of the sample in Example 3. The image shows that Pt / HPW 0.3 TiO2 consists of phosphotungstic acid coated on the surface of titanium dioxide nanoparticles, with platinum particles loaded on the surface of the nanoparticles.

[0069] Figure 3 (a) The photocatalytic degradation activity of the materials in Examples 3, 5, and 6 on toluene was tested within 2 hours. Figure 3 (b) The photocatalytic activity of the materials in Examples 3, 7, and 8 on toluene degradation within 2 hours was tested. The test conditions for both were: 100 mg of 40-60 mesh catalyst particles at a gas flow rate of 40 ml / min, a toluene concentration of 500 ppm, and a xenon lamp light power density of 1000 mW / cm². 2 The reaction takes place under certain conditions. For example... Figure 3 As shown in a, Pt 0.5 / HPW 0.3 TiO2 catalyst, compared to Pt 0.1 / HPW 0.3 TiO2, Pt 0.3 / HPW 0.3 TiO2 showed the best activity, but considering the cost-effectiveness, a platinum loading of 0.3 wt% was chosen for in-depth research. Figure 3 (b) studied the effect of different calcination temperatures on the catalyst activity. The results in the figure show that 400℃ is the optimal temperature for this catalyst.

[0070] Figure 4 (a) The photocatalytic degradation activity of the materials in Examples 1-4 and Comparative Examples 1-4 on toluene was tested within 2 hours. Figure 4 (b) Stability testing of the samples in Example 3. Both tests were conducted under the following conditions: 100 mg of 40-60 mesh catalyst particles in an airflow of 40 ml / min, toluene concentration of 500 ppm, and xenon lamp light power density of 1000 mW / cm². 2 The reaction takes place under certain conditions. For example... Figure 4 As shown in a, Pt / HPW X Compared to the individual activities of titanium dioxide, platinum, and phosphotungstic acid, or the activity of any two of these phases combined, TiO2 catalyst showed a significant improvement in activity. Furthermore, by adjusting the ratio of phosphotungstic acid, the highest activity was found when the mass ratio of titanium dioxide to phosphotungstic acid was 1:0.3. Figure 4(b) is to prove that the catalyst has good stability and can maintain more than 90% of the toluene degradation rate for up to 30 hours.

[0071] By the attached Figure 4 It can be seen that compared with TiO2 as a catalyst, the catalytic performance can only be partially improved after Pt is loaded, because when Pt is loaded on TiO2, the active site of Pt / TiO2 is mainly Pt, so the catalytic performance is partially improved.

[0072] By the attached Figure 4 It can be seen that the catalytic performance of TiO2 modified by phosphotungstic acid is greatly reduced, and the catalytic performance of Pt / HPW is greatly reduced. The catalytic activity of TiO2 modified by phosphotungstic acid is lower than that of Pt / HPW, and the catalytic activity of TiO2 without modification is much lower. However, when platinum is loaded on TiO2 modified by phosphotungstic acid, its catalytic activity is unexpectedly greatly improved, and even compared with the sample of Pt loaded on TiO2, its catalytic activity is increased by more than 2 times, and the improvement is unpredictable. This is because phosphotungstic acid itself has no activity, and the modification of TiO2 by phosphotungstic acid will cover the active sites of TiO2 itself, thereby causing a large decrease in catalytic activity. The reason why the performance of Pt loaded on TiO2 modified by phosphotungstic acid can be greatly improved is that phosphotungstic acid and TiO2 work together to change the valence state of platinum during sintering, so that platinum is more biased towards the metal state. Pt / TiO2 presents yellow, while Pt / HPW X TiO2 presents gray, that is, when phosphotungstic acid and platinum are simultaneously loaded on the surface of TiO2, a synergistic effect occurs among the three, which makes platinum more biased towards the metal state, thereby increasing the active sites of the catalyst. The above experimental results prove that the Pt loaded on the TiO2 modified by phosphotungstic acid synthesized by us has excellent activity and stability in photocatalytic degradation of toluene.

[0073] Although the content of the present application has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present application.

Claims

1. A method for preparing a platinum-supported phosphotungstic acid-modified titanium dioxide material, characterized in that, Based on platinum-supported phosphotungstic acid modified titanium dioxide material, the platinum loading is 0.1-0.5 wt%, specifically including the following steps: Step 1: Dissolve titanium dioxide and phosphotungstic acid in an ethanol solution, stir to react, evaporate the ethanol solution to remove it, and then obtain phosphotungstic acid modified titanium dioxide material. The mass ratio of titanium dioxide to phosphotungstic acid is 1:0.1-0.

4. Step 2: After dissolving phosphotungstic acid-modified titanium dioxide in water, a platinum precursor solution is added dropwise, the reaction is stirred, and the aqueous solution is evaporated to obtain the precursor material; Step 3: Place the precursor material into a muffle furnace and calcine it at high temperature in an air atmosphere, with a temperature range of 200-600℃. Phosphotungstic acid and TiO2 work together to change the valence state of platinum during sintering, making platinum more metallic. When phosphotungstic acid and platinum are simultaneously loaded on the TiO2 surface, the three have a synergistic effect, making platinum more metallic, thereby increasing the active sites of the catalyst, and obtaining the platinum-supported phosphotungstic acid modified titanium dioxide material.

2. The preparation method according to claim 1, characterized in that: In step 2, the precursor solution is a chloroplatinic acid hexahydrate solution.

3. The preparation method according to claim 1, characterized in that: The platinum loading is 0.3 wt%.

4. The preparation method according to claim 1, characterized in that: In step 3, the temperature range is 400℃.

5. The preparation method according to claim 1, characterized in that: The mass ratio of titanium dioxide to phosphotungstic acid is 1:0.

3.

6. The application of the platinum-supported phosphotungstic acid modified titanium dioxide material obtained by the preparation method according to any one of claims 1-5 in the low-temperature photocatalytic degradation of toluene.

7. The application according to claim 6, wherein the photocatalytic degradation temperature is 140-180℃ and the optical power density of the light source is 500-1000 mW / cm². 2 .

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