Biobr-tio2-bi2wo6 composite catalytic material and preparation method and application thereof

Abstract

The application discloses a BiOBr-TiO2-Bi2WO6 composite catalytic material and a preparation method and application thereof, and belongs to the technical field of catalysts; the method is characterized by using acetic acid and ultrapure water as solvents, adding hexadecyl trimethyl ammonium bromide, TiO2, a sodium source and a bismuth source, preparing a TiO2-Bi2WO6 composite catalyst through a hydrothermal method, taking the TiO2-Bi2WO6 as a substrate, the ultrapure water as a solvent, the sodium source, the bismuth source and a bromine source as raw materials, and preparing the BiOBr-TiO2-Bi2WO6 composite catalytic material through a hydrothermal method; the catalyst is applied to the preparation of benzaldehyde from selective oxidation of toluene through photocatalysis, effectively reduces the recombination rate of photo-generated holes and electrons, and improves the photocatalytic performance of the BiOBr-TiO2-Bi2WO6 composite material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a BiOBr-TiO2-Bi2WO6 composite catalyst material, and the application also relates to a preparation method of the catalyst and application thereof. BACKGROUND

[0002] Benzaldehyde is a simple structure and the most important aromatic aldehyde in chemical industry, which is widely used in synthetic materials and fine chemical industry, such as medicine, dye, perfume, cosmetic flavoring agent, plasticizer and the like. At present, the synthesis processes of benzaldehyde mainly include benzene direct carbonylation method, toluene chlorination and hydrolysis method, toluene gas phase oxidation method and the like. However, these methods have the disadvantages of high requirement for production equipment, unfriendliness to environment, easy deep oxidation, high energy loss and the like. Therefore, it is of great significance to develop an economic and green method for preparing benzaldehyde.

[0003] The photocatalytic method has the advantages of realizing the conversion from toluene to benzaldehyde under mild conditions, and the method is atom-economical, selective, green and environment-friendly, and thus is extremely potential for preparing benzaldehyde. The research on the photocatalyst with excellent performance is the key to the method. Bismuth tungstate (Bi2WO6) is a cheap and easily available photocatalyst, which has the advantages of strong light absorption, suitable band gap structure and proper oxidation performance, and thus is widely used in the field of photocatalysis, such as photocatalytic hydrogen production, photocatalytic water splitting, selective photo-organic synthesis and purification of organic pollutants in air or water. SUMMARY

[0004] In view of the problems in the prior art, a first object of the application is to provide a BiOBr-TiO2-Bi2WO6 composite catalyst material, which is combined with TiO2 and BiOBr to form a ternary heterostructure, so that the material has a multi-channel charge transfer characteristic, can more effectively promote the transfer and separation of charges during photo-reaction, more efficiently reduces the recombination rate of photo-generated electrons and holes of Bi2WO6, and thus enhances the photocatalytic performance.

[0005] A second object of the application is to provide a preparation method of the BiOBr-TiO2-Bi2WO6 composite catalyst material.

[0006] A third object of the application is to provide application of the BiOBr-TiO2-Bi2WO6 composite catalyst material in the direction of photocatalytic selective oxidation of toluene to prepare benzaldehyde.

[0007] To this end, the first technical solution provided by the application is as follows:

[0008] S1. Preparation of TiO2-Bi2WO6 composite catalytic material:

[0009] TiO2, cetyltrimethylammonium bromide, bismuth source were added into acetic acid solution and stirred to form a liquid, and a tungsten source was added into ultrapure water and stirred to form b liquid. After the b liquid was fully dissolved, it was added dropwise into the a liquid, the pH of the solution was adjusted, and the stirring was continued for 1-3 h at 100-180°C for 12-30 h. The reaction product was washed and dried to obtain a TiO2-Bi2WO6 composite catalytic material;

[0010] The molar ratio of TiO2, tungsten source and bismuth source is (0.1-0.5):1:(1.6-2.4);

[0011] S2. Preparation of BiOBr-TiO2-Bi2WO6

[0012] The TiO2-Bi2WO6 prepared in S1 was dissolved in ultrapure water, then a bromine source and a bismuth source were added, mixed and dissolved, and then hydrothermal reaction was carried out at 120-200°C for 12-24 h. The reaction product was washed and dried to obtain BiOBr-TiO2-Bi2WO6;

[0013] The molar ratio of the bromine source, TiO2-Bi2WO6 and bismuth source is (0.15-0.35):(0.2:1):(0.15-0.35).

[0014] Further, in the above method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, the tungsten source in S1 is sodium tungstate dihydrate, and the bismuth source in S1 and S2 is bismuth nitrate pentahydrate.

[0015] Further, in the above method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, the pH in S1 is 2-4.

[0016] Further, in the above method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, the bromine source in S2 is sodium bromide.

[0017] Further, in the above method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, the washing in step S1 is first water washing and then anhydrous ethanol washing.

[0018] Further, in the above method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, the washing in step S2 is anhydrous ethanol washing.

[0019] The second technical solution provided by the application is the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared by the method provided in the first technical solution.

[0020] The still another technical solution of the application is to provide the BiOBr-TiO2-Bi2WO6 composite catalytic material for the selective oxidation reaction of toluene.

[0021] The last technical solution of the application is to provide a method for preparing benzaldehyde by selective oxidation of toluene, which comprises the following steps in sequence:

[0022] 1) The BiOBr-TiO2-Bi2WO6 composite catalytic material is placed in a photoreactor;

[0023] 2) Acetonitrile and toluene are added to the reactor in step 1), the reactor is closed, and dry air is filled into the reactor at a pressure of 0.1-1 MPa;

[0024] 3) Stirring is carried out in the dark for 10-60 min;

[0025] 4) Circulating water is introduced into the reactor interlayer to control the reaction temperature at 15-25 DEG C;

[0026] 5) The reaction is carried out under xenon lamp irradiation for 1-4 h;

[0027] 6) After the reaction is completed, the reactor is cooled to room temperature, and detection is carried out.

[0028] Further, in the method for preparing benzaldehyde by selective oxidation of toluene, the ratio of the BiOBr-TiO2-Bi2WO6 composite catalytic material to toluene is 50 mg:1 ml.

[0029] Compared with the prior art, the technical solution provided by the application has the following technical advantages:

[0030] The BiOBr-TiO2-Bi2WO6 composite catalyst prepared by the application forms a heterostructure with multi-channel charge transfer characteristics by combining Bi2WO6 with TiO2 and BiOBr respectively, promotes charge separation, improves light absorption, effectively reduces the recombination rate of photo-generated holes and electrons, and improves the photocatalytic performance of the BiOBr-TiO2-Bi2WO6 composite material in selective oxidation of toluene. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The figure is a schematic diagram for preparing the BiOBr-TiO2-Bi2WO6 composite catalytic material of the application;

[0032] Figure 2The gas chromatogram of the Bi2WO6, TiO2-Bi2WO6 and BiOBr-TiO2-Bi2WO6 composite catalytic material photocatalytic toluene oxidation reaction performance diagram at 20℃;

[0033] Figure 3 The gas chromatogram of the Bi2WO6, TiO2-Bi2WO6 and BiOBr-TiO2-Bi2WO6 composite catalytic material photocatalytic toluene oxidation reaction performance diagram at 20℃;

[0034] Figure 4 The gas chromatogram of the Bi2WO6, TiO2-Bi2WO6 and BiOBr-TiO2-Bi2WO6 composite catalytic material photocatalytic toluene oxidation reaction performance diagram at 20℃;

[0035] Figure 5 The gas chromatogram of the Bi2WO6, TiO2-Bi2WO6 and BiOBr-TiO2-Bi2WO6 composite catalytic material photocatalytic toluene oxidation reaction performance diagram at 20℃;

[0036] Figure 6 The gas chromatogram of the Bi2WO6, TiO2-Bi2WO6 and BiOBr-TiO2-Bi2WO6 composite catalytic material photocatalytic toluene oxidation reaction performance diagram at 20℃;

[0037] Figure 7 The gas chromatogram of the Bi2WO6, TiO2-Bi2WO6 and BiOBr-TiO2-Bi2WO6 composite catalytic material photocatalytic toluene oxidation reaction performance diagram at 20℃;

[0038] Figure 8 The gas chromatogram of the Bi2WO6, TiO2-Bi2WO6 and BiOBr-TiO2-Bi2WO6 composite catalytic material photocatalytic toluene oxidation reaction performance diagram at 20℃;

[0039] Figure 9 The gas chromatogram of the Bi2WO6, TiO2-Bi2WO6 and BiOBr-TiO2-Bi2WO6 composite catalytic material photocatalytic toluene oxidation reaction performance diagram at 20℃; DETAILED DESCRIPTION

[0040] The claims of the present application are further described in detail below in conjunction with specific embodiments, but do not constitute any limitation on the present application, and any limited number of modifications made by anyone within the scope of the claims of the present application is still within the scope of the claims of the present application.

[0041] Unless specifically stated, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field.

[0042] The preparation schematic diagram of the BiOBr-TiO2-Bi2WO6 composite catalytic material provided by the present application is shown in Figure 1 .

[0043] Example 1

[0044] The embodiment provides a preparation method of a BiOBr-TiO2-Bi2WO6 composite catalytic material. Figure 1 , and comprises the following steps.

[0045] 1) Synthesis of TiO2-Bi2WO6 composite catalytic material

[0046] 1 mmol of bismuth nitrate pentahydrate, 16 mg of TiO2 and 50 mg of cetyltrimethylammonium bromide are added into 40 ml of glacial acetic acid, and continuous stirring is conducted to fully dissolve to form a liquid a; 2 mmol of sodium tungstate dihydrate is added into 30 ml of ultrapure water, and continuous stirring is conducted to fully dissolve to form a liquid b. Then, the liquid b is added dropwise into the liquid a, the pH of the solution is adjusted to 3, and continuous stirring is conducted at room temperature for 3 h; finally, the solution is moved into a polytetrafluoroethylene reaction kettle to react at 140 DEG C for 30 h, and after being cooled to room temperature, the solution is washed once with water and then washed several times with anhydrous ethanol, and is dried at 70 DEG C to obtain the TiO2-Bi2WO6 composite catalytic material, which is marked as TB-20.

[0047] 2) Synthesis of BiOBr-TiO2-Bi2WO6

[0048] 0.55 g of the TiO2-Bi2WO6 composite catalytic material with a molar ratio of 0.2:1 prepared in step 1), 0.15 mmol of sodium bromide and 30 ml of ultrapure water are mixed, 0.15 mmol of bismuth nitrate pentahydrate is added into 30 ml of ultrapure water and continuous stirring is conducted to fully dissolve, and then the solution is added dropwise into the above solution, continuous stirring is conducted at room temperature for 1 h, finally, the solution is moved into a polytetrafluoroethylene reaction kettle to react at 140 DEG C for 12 h, and after being cooled to room temperature, the solution is washed several times with anhydrous ethanol, and is dried at 70 DEG C to obtain the BiOBr-TiO2-Bi2WO6 composite catalytic material, which is marked as BTB-15.

[0049] Example 2

[0050] The embodiment provides a preparation method of a BiOBr-TiO2-Bi2WO6 composite catalytic material.

[0051] 1) Synthesis of TiO2-Bi2WO6 composite catalytic material

[0052] 1 mmol of bismuth nitrate pentahydrate, 16 mg of TiO2 and 50 mg of cetyl ammonium bromide were added to 40 ml of glacial acetic acid, and continuously stirred until completely dissolved to form a liquid; 2 mmol of sodium tungstate dihydrate was added to 30 ml of ultrapure water, and continuously stirred until completely dissolved to form a liquid. Then, the liquid was added dropwise into the liquid, the pH of the solution was adjusted to 3, continuously stirred at room temperature for 3 h, and finally moved to a polytetrafluoroethylene reaction kettle for reaction at 140 °C for 30 h. After cooling to room temperature, it was washed once with water and then several times with anhydrous ethanol, and dried at 70 °C to obtain a TiO2-Bi2WO6 composite catalytic material.

[0053] 2) Synthesis of BiOBr-TiO2-Bi2WO6

[0054] 0.55 g of the TiO2-Bi2WO6 composite catalytic material prepared in step 1) with a molar ratio of 0.2:1, 0.20 mmol of sodium bromide was dissolved in 40 ml of ultrapure water, and 0.20 mmol of bismuth nitrate pentahydrate was added to 30 ml of ultrapure water and continuously stirred until completely dissolved. Then, it was added dropwise into the above solution, continuously stirred at room temperature for 1 h, and finally moved to a polytetrafluoroethylene reaction kettle for reaction at 140 °C for 12 h. After cooling to room temperature, it was washed several times with anhydrous ethanol, and dried at 70 °C to obtain a BiOBr-TiO2-Bi2WO6 composite catalytic material, marked as BTB-20.

[0055] Example 3

[0056] The preparation method of the BiOBr-TiO2-Bi2WO6 composite catalytic material provided in this embodiment comprises the following steps:

[0057] 1) Synthesis of TiO2-Bi2WO6 composite catalytic material

[0058] 1 mmol of bismuth nitrate pentahydrate, 16 mg of TiO2 and 50 mg of cetyl ammonium bromide were added to 40 ml of glacial acetic acid, and continuously stirred until completely dissolved to form a liquid; 2 mmol of sodium tungstate dihydrate was added to 30 ml of ultrapure water, and continuously stirred until completely dissolved to form a liquid. Then, the liquid was added dropwise into the liquid, the pH of the solution was adjusted to 3, continuously stirred at room temperature for 3 h, and finally moved to a polytetrafluoroethylene reaction kettle for reaction at 140 °C for 30 h. After cooling to room temperature, it was washed once with water and then several times with anhydrous ethanol, and dried at 70 °C to obtain a TiO2-Bi2WO6 composite catalytic material.

[0059] 2) Synthesis of BiOBr-TiO2-Bi2WO6

[0060] The 0.55 g of TiO2-Bi2WO6 composite catalytic material prepared in step 1) with a molar ratio of 0.2:1, 0.30 mmol of sodium bromide is dissolved in 40 mL of ultrapure water, and then 0.30 mmol of bismuth nitrate pentahydrate is added to 30 mL of ultrapure water and continuously stirred to fully dissolve, and then added dropwise into the above solution, continuously stirred at room temperature for 1 h, and finally moved to a polytetrafluoroethylene reaction kettle at 140°C for 12 h, cooled to room temperature, washed with anhydrous ethanol several times, and dried at 70°C to obtain a BiOBr-TiO2-Bi2WO6 composite catalytic material, marked as BTB-30.

[0061] Example 4

[0062] The BiOBr-TiO2-Bi2WO6 composite catalytic material provided in this embodiment is prepared by the following steps:

[0063] 1) Synthesis of TiO2-Bi2WO6 composite catalytic material

[0064] 1 mmol of bismuth nitrate pentahydrate, 16 mg of TiO2, and 50 mg of cetyltrimethylammonium bromide are added to 40 mL of glacial acetic acid, continuously stirred to fully dissolve to form a liquid a; 2 mmol of sodium tungstate dihydrate is added to 30 mL of ultrapure water, continuously stirred to fully dissolve to form a liquid b. Then, the liquid b is added dropwise into the liquid a, the pH of the solution is adjusted to 3, continuously stirred at room temperature for 3 h, and finally moved to a polytetrafluoroethylene reaction kettle at 140°C for 30 h. After cooling to room temperature, it is first washed with water once, then washed with anhydrous ethanol several times, and dried at 70°C to obtain a TiO2-Bi2WO6 composite catalytic material.

[0065] 2) Synthesis of BiOBr-TiO2-Bi2WO6

[0066] The 0.55 g of TiO2-Bi2WO6 composite catalytic material prepared in step 1) with a molar ratio of 0.2:1, 0.30 mmol of sodium bromide is dissolved in 40 mL of ultrapure water, and then 0.30 mmol of bismuth nitrate pentahydrate is added to 30 mL of ultrapure water and continuously stirred to fully dissolve, and then added dropwise into the above solution, continuously stirred at room temperature for 1 h, and finally moved to a polytetrafluoroethylene reaction kettle at 140°C for 12 h, cooled to room temperature, washed with anhydrous ethanol several times, and dried at 70°C to obtain a BiOBr-TiO2-Bi2WO6 composite catalytic material, marked as BTB-30.

[0067] Example 5

[0068] The BiOBr-TiO2-Bi2WO6 composite catalytic material provided in this embodiment is prepared by the following steps:

[0069] 1) Synthesis of TiO2-Bi2WO6 composite catalytic material

[0070] 1 mmol of bismuth nitrate pentahydrate, 16 mg of TiO2 and 50 mg of cetyl ammonium bromide were added to 40 ml of glacial acetic acid, and continuously stirred to fully dissolve to form a liquid; 2 mmol of sodium tungstate dihydrate was added to 30 ml of ultrapure water, and continuously stirred to fully dissolve to form a liquid. Then, the liquid was added dropwise into the liquid, the pH of the solution was adjusted to 3, and continuously stirred at room temperature for 3 h. Finally, it was moved to a polytetrafluoroethylene reaction kettle and reacted at 140 °C for 30 h. After cooling to room temperature, it was washed once with water and then several times with anhydrous ethanol, and dried at 70 °C to obtain the TiO2-Bi2WO6 composite catalytic material.

[0071] 2) Synthesis of BiOBr-TiO2-Bi2WO6

[0072] 0.55 g of the TiO2-Bi2WO6 composite catalytic material prepared in step 1) with a molar ratio of 0.2:1, 0.35 mmol of sodium bromide were dissolved in 40 ml of ultrapure water, and 0.35 mmol of bismuth nitrate pentahydrate was added to 30 ml of ultrapure water and continuously stirred to fully dissolve. Then, it was added dropwise into the above solution, continuously stirred at room temperature for 1 h, and finally moved to a polytetrafluoroethylene reaction kettle and reacted at 140 °C for 12 h. After cooling to room temperature, it was washed several times with anhydrous ethanol, and dried at 70 °C to obtain the BiOBr-TiO2-Bi2WO6 composite catalytic material, marked as BTB-35.

[0073] Application Example 1

[0074] In this application example, the BiOBr-TiO2-Bi2WO6 composite catalytic material provided in Example 1 was used to catalyze the photocatalytic reaction of toluene, and the reaction process specifically included the following steps:

[0075] 1) 50 mg of the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared in Example 1 was weighed into a photoreactor;

[0076] 2) 2 ml of acetonitrile solvent and 1 ml of toluene reactant were added to the reactor of step 1), and the reactor was sealed and filled with 0.2 MPa of dry air;

[0077] 3) Stirring in the dark for 30 min to reach adsorption equilibrium;

[0078] 4) Circulating water was introduced into the reactor interlayer to control the reaction temperature at 20 °C;

[0079] 5) Reaction under xenon lamp irradiation for 3 h;

[0080] 6) After the reaction, the reactor is cooled to room temperature, and the reacted solution is taken out. The conversion rate is 4.85%, the selectivity is 87.42%, and the generation rate of benzaldehyde is 1843.07 umol·g -1 ·h -1 , see Figure 3 .

[0081] Application Example 2

[0082] In this application example, the BiOBr-TiO2-Bi2WO6 composite catalytic material provided in Example 2 is used to catalyze the photocatalytic reaction of toluene. The reaction process specifically includes the following steps:

[0083] 1) 50 mg of the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared in Example 2 is weighed into a photo-reactor;

[0084] 2) 2 ml of acetonitrile solvent and 1 ml of toluene reactant are added to the reactor of step 1), the reactor is sealed, and 0.2 MPa of dry air is filled;

[0085] 3) Stirring in the dark for 30 min to reach adsorption equilibrium;

[0086] 4) Circulating water is introduced into the reactor interlayer to control the reaction temperature at 20℃;

[0087] 5) Reaction under xenon lamp irradiation for 3 h;

[0088] 6) After the reaction, the reactor is cooled to room temperature, and the reacted solution is taken out. The conversion rate is 5.02%, the selectivity is 88.31%, and the generation rate of benzaldehyde is 2270.23 umol·g -1 ·h -1 , see Figure 4 .

[0089] Application Example 3

[0090] In this application example, the BiOBr-TiO2-Bi2WO6 composite catalytic material provided in Example 3 is used to catalyze the photocatalytic reaction of toluene. The reaction process specifically includes the following steps:

[0091] 1) 50 mg of the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared in Example 3 is weighed into a photo-reactor;

[0092] 2) 2 ml of acetonitrile solvent and 1 ml of toluene reactant are added to the reactor of step 1), the reactor is sealed, and 0.2 MPa of dry air is filled;

[0093] 3) Stirring in the dark for 30 min to reach adsorption equilibrium;

[0094] 4) Circulating water is introduced into the reactor interlayer to control the reaction temperature at 20℃;

[0095] 5) Reaction for 3h under xenon lamp irradiation;

[0096] 6) After the reaction is completed, the reactor is cooled to room temperature, and the reacted solution is taken out to obtain a conversion rate of 5.63%, a selectivity of 88.09%, and a benzaldehyde generation rate of 2527.29umol·g -1 ·h -1 by gas chromatography. See Figure 5 .

[0097] Application Example 4

[0098] In this application example, the BiOBr-TiO2-Bi2WO6 composite catalytic material provided in Example 4 is used to catalyze the photocatalytic reaction of toluene, and the reaction process specifically includes the following steps:

[0099] 1) 50mg of the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared in Example 4 is weighed into a photo-reactor;

[0100] 2) 2ml of acetonitrile solvent and 1ml of toluene reactant are added to the reactor of step 1), the reactor is sealed, and 0.2MPa of dry air is filled;

[0101] 3) Stirring for 30min in the dark to reach adsorption equilibrium;

[0102] 4) Circulating water is introduced into the reactor interlayer to control the reaction temperature at 20℃;

[0103] 5) Reaction for 3h under xenon lamp irradiation;

[0104] 6) After the reaction is completed, the reactor is cooled to room temperature, and the reacted solution is taken out to obtain a conversion rate of 5.87%, a selectivity of 88.46%, and a benzaldehyde generation rate of 2594.15umol·g -1 ·h -1 by gas chromatography. See Figure 6 .

[0105] Application Example 5

[0106] In this application example, the BiOBr-TiO2-Bi2WO6 composite catalytic material provided in Example 5 is used to catalyze the photocatalytic reaction of toluene, and the reaction process specifically includes the following steps:

[0107] 1) 50mg of the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared in Example 5 is weighed into a photo-reactor;

[0108] 2) 2 ml of acetonitrile solvent and 1 ml of toluene reactant were added to the reactor of step 1), the reactor was closed, and dry air was filled at 0.2 MPa;

[0109] 3) stirring for 30 min in dark conditions to reach adsorption equilibrium;

[0110] 4) circulating water was introduced into the reactor interlayer to control the reaction temperature at 20°C;

[0111] 5) reaction for 3 h under xenon lamp irradiation;

[0112] 6) after the reaction was completed, the reactor was cooled to room temperature, and the reacted solution was taken out to measure the conversion rate of 5.02% and the selectivity of 86.71% by gas chromatography, and the generation rate of benzaldehyde was 1848.59 umol·g -1 ·h -1 , see Figure 7 .

[0113] Comparative Application Example 1

[0114] In this comparative application example, Bi2WO6 was used to catalyze the photocatalytic reaction of toluene, and the reaction process specifically included the following steps:

[0115] 1) 50 mg of Bi2WO6 photocatalytic material was weighed into a photo reactor;

[0116] 2) 2 ml of acetonitrile solvent and 1 ml of toluene reactant were added to the reactor of step 1), the reactor was closed, and dry air was filled at 0.2 MPa;

[0117] 3) stirring for 30 min in dark conditions to reach adsorption equilibrium;

[0118] 4) circulating water was introduced into the reactor interlayer to control the reaction temperature at 20°C;

[0119] 5) reaction for 3 h under xenon lamp irradiation;

[0120] 6) after the reaction was completed, the reactor was cooled to room temperature, and the reacted solution was taken out to measure the conversion rate of 2.30% and the selectivity of 87.11% by gas chromatography, and the generation rate of benzaldehyde was 959.49 umol·g -1 ·h -1 , see Figure 8 .

[0121] Comparative Application Example 2

[0122] In this comparative application example, TiO2-Bi2WO6 was used to catalyze the photocatalytic reaction of toluene, and the reaction process specifically included the following steps:

[0123] 1) 50 mg of TiO2-Bi2WO6 composite catalytic material with a molar ratio of 0.2:1 was weighed in a photoreactor;

[0124] 2) 2 ml of acetonitrile solvent and 1 ml of toluene reactant were added to the reactor of step 1), the reactor was closed, and 0.2 MPa of dry air was filled;

[0125] 3) Stirring for 30 min in the dark to reach adsorption equilibrium;

[0126] 4) Circulating water was introduced into the reactor interlayer to control the reaction temperature at 20°C;

[0127] 5) Reaction for 3 h under xenon lamp irradiation;

[0128] 6) After the reaction was completed, the reactor was cooled to room temperature, and the reacted solution was taken out to obtain a conversion rate of 3.67%, a selectivity of 85.81%, and a benzaldehyde generation rate of 1725.41 umol·g -1 ·h -1 by gas chromatography. See Figure 9 .

[0129] As can be seen from the above application examples and comparative application examples, the BiOBr-TiO2-Bi2WO6 composite catalytic materials prepared in all examples have more excellent photocatalytic performance. See Figure 2 , compared with Bi2WO6 and TiO2-Bi2WO6, the conversion rate and benzaldehyde generation rate of the BiOBr-TiO2-Bi2WO6 composite catalytic material in application example 4 in the selective oxidation of toluene to prepare benzaldehyde are 2.55 times and 2.70 times that of pure Bi2WO6, and 1.60 times and 1.50 times that of TiO2-Bi2WO6. It shows that the photocatalytic performance of BiOBr-TiO2-Bi2WO6 composite material in the selective oxidation of toluene is stronger than that of pure Bi2WO6 and TiO2-Bi2WO6, and the heterojunction indeed inhibits the recombination of photo-generated holes and electrons, and improves the photocatalytic performance of the material.

Claims

1. A method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, characterized in that, The steps are as follows: S1. Preparation of TiO2-Bi2WO6 composite catalytic material: TiO2, hexadecyltrimethylammonium bromide, and bismuth source were added to acetic acid solution and stirred continuously to form solution a. Tungsten source was added to ultrapure water and stirred continuously to form solution b. After the solution was fully dissolved, solution b was added dropwise to solution a. The pH of the solution was adjusted and stirred continuously for 1-3 hours. The hydrothermal reaction was carried out at 100-180℃ for 12-30 hours. The reaction product was washed and dried to obtain TiO2-Bi2WO6 composite catalyst material. The molar ratio of TiO2, tungsten source, and bismuth source is (0.1-0.5):1:(1.6-2.4). S2. Preparation of BiOBr-TiO2-Bi2WO6 TiO2-Bi2WO6 prepared by S1 was dissolved in ultrapure water, and then bromine source and bismuth source were added. After mixing and dissolving, the mixture was hydrothermally reacted at 120-200℃ for 12-24h. The reaction product was washed and dried to obtain BiOBr-TiO2-Bi2WO6. The molar ratio of the bromine source, TiO2-Bi2WO6, and bismuth source is (0.15-0.35):(0.2:1):(0.15-0.35).

2. The preparation method of the BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 1, characterized in that, The tungsten source mentioned in S1 is sodium tungstate dihydrate, and the bismuth source mentioned in S1 and S2 is bismuth nitrate pentahydrate.

3. The preparation method of the BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 1, characterized in that, The pH value described in S1 is 2-4.

4. The preparation method of the BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 1, characterized in that, The bromine source mentioned in S2 is sodium bromide.

5. The preparation method of the BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 1, characterized in that, The washing process described in step S1 involves first washing with water, followed by washing with anhydrous ethanol.

6. The preparation method of a BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 1, characterized in that, The washing process described in step S2 uses anhydrous ethanol.

7. A BiOBr-TiO2-Bi2WO6 composite catalytic material, characterized in that, It is prepared by the method according to any one of claims 1-6.

8. The BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 7 is used for the photocatalytic selective oxidation of toluene to prepare benzaldehyde.

9. A method for the selective oxidation of toluene to prepare benzaldehyde, characterized in that, The steps are as follows: 1) The BiOBr-TiO2-Bi2WO6 composite catalytic material as described in claim 7 is placed in a photoreactor; 2) Add acetonitrile and toluene to the reactor in step 1), seal the reactor, and purge with dry air at 0.1-1 MPa; 3) Stir for 10-60 minutes in the dark; 4) Introduce circulating water into the reactor jacket to control the reaction temperature at 15-25℃; 5) React under xenon lamp irradiation for 1-4 hours; 6) After the reaction is complete, wait for the reactor to cool to room temperature before testing.

10. The method for selective oxidation of toluene to prepare benzaldehyde according to claim 9, characterized in that, The ratio of BiOBr-TiO2-Bi2WO6 composite catalyst to toluene is 50mg:1ml.

Images