BiOBr-TiO2-Bi2WO6 composite catalytic material as well as preparation method and application thereof

Abstract

The invention discloses a BiOBr-TiO2-Bi2WO6 composite catalytic material as well as a preparation method and application thereof, and belongs to the technical field of catalysts. The method comprises the following steps: taking acetic acid and ultrapure water as solvents, adding cetyl trimethyl ammonium bromide, TiO2, a sodium source and a bismuth source, preparing a TiO2-Bi2WO6 composite catalyst by a hydrothermal method, and then taking TiO2-Bi2WO6 as a substrate, taking ultrapure water as a solvent, taking the sodium source, the bismuth source and a bromine source as raw materials, and preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material by a hydrothermal method. When the catalyst is applied to preparation of benzaldehyde through photocatalytic selective oxidation of toluene, the recombination rate of photo-generated holes and electrons is effectively reduced, and the photocatalytic performance of a BiOBr-TiO2-Bi2WO6 composite material is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a BiOBr-TiO2-Bi2WO6 composite catalytic material. The invention also relates to a preparation method of the catalyst and application thereof. Background Art

[0002] Benzaldehyde is a most simple structure and the most important aromatic aldehyde in the chemical industry. It is widely used in synthetic materials and fine chemical industries, such as medicine, dyes, spices, cosmetic flavoring agents, plasticizers, etc. At present, the synthesis process of benzaldehyde mainly includes direct carbonylation of benzene, chlorination and hydrolysis of toluene, and gas phase oxidation of toluene. However, these methods have the disadvantages of high requirements for production equipment, unfriendly to the environment, easy deep oxidation and high energy loss. Therefore, it is of great significance to develop an economical and green method for preparing benzaldehyde.

[0003] The photocatalytic method has the advantages of achieving the conversion of toluene to benzaldehyde under mild conditions, and this method is atom-economical, selective and green. It has attracted the attention of many researchers and is a method with great potential for preparing benzaldehyde. The focus of this method is to study photocatalysts with excellent performance. Bismuth tungstate (Bi2WO6), a cheap and readily available photocatalyst, has the advantages of strong light absorption, suitable band gap structure and appropriate oxidation performance. Therefore, it is widely used in the field of photocatalysis, such as photocatalytic hydrogen production, photocatalytic water splitting, selective photoorganic synthesis and purification of organic pollutants in air or water. However, Bi2WO6 has the disadvantages of high recombination of photogenerated electron-hole pairs, lack of a sufficient number of surface active sites and poor recycling performance, which limits the application of this material. Summary of the invention

[0004] In view of the problems existing in the prior art, the first object of the present invention is to provide a BiOBr-TiO2-Bi2WO6 composite catalytic material. The material forms a ternary heterostructure by combining Bi2WO6 with TiO2 and BiOBr respectively, so that it has multi-channel charge transfer characteristics, can more effectively promote the transfer and separation of charges during photoreaction, and more efficiently reduce the recombination rate of photogenerated electrons and holes in Bi2WO6, thereby enhancing its photocatalytic performance.

[0005] The second object of the present invention is to provide a method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material.

[0006] The third object of the present invention is to provide an application of the BiOBr-TiO2-Bi2WO6 composite catalytic material in the preparation of benzaldehyde by photocatalytic selective oxidation of toluene.

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

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

[0009] Add TiO2, hexadecyltrimethylammonium bromide and bismuth source to acetic acid solution and stir continuously to form liquid a, add tungsten source to ultrapure water and stir continuously to form liquid b, after the tungsten source is fully dissolved, drip liquid b into liquid a drop by drop, adjust the pH of the solution, stir continuously for 1-3 hours, 100-180° C., perform hydrothermal reaction for 12-30 hours, and wash and dry the reaction product to obtain 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 is dissolved in ultrapure water, and then a bromine source and a bismuth source are added, mixed and dissolved, and then subjected to a hydrothermal reaction at 120-200°C for 12-24h. The reaction product is 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] Furthermore, in the above-mentioned method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, the tungsten source described in S1 is sodium tungstate dihydrate, and the bismuth source described in S1 and S2 is bismuth nitrate pentahydrate.

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

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

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

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

[0019] The second technical solution provided by the present invention is the above-mentioned BiOBr-TiO2-Bi2WO6 composite catalytic material, which is prepared by the method provided by the first technical solution.

[0020] Another technical solution of the present invention is to provide the above-mentioned BiOBr-TiO2-Bi2WO6 composite catalytic material for photocatalytic selective oxidation reaction of toluene.

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

[0022] 1) placing the BiOBr-TiO2-Bi2WO6 composite catalytic material in a photoreactor;

[0023] 2) adding acetonitrile and toluene to the reactor in step 1), sealing the reactor, and filling it with dry air at 0.1-1 MPa;

[0024] 3) Stir for 10-60 min in dark conditions;

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

[0026] 5) reacting under xenon lamp irradiation for 1-4 hours;

[0027] 6) After the reaction is completed, wait for the reactor to cool to room temperature and then test.

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

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

[0030] The BiOBr-TiO2-Bi2WO6 composite catalyst prepared by the present invention combines Bi2WO6 with TiO2 and BiOBr in pairs to form a heterostructure with multi-channel charge transfer characteristics, thereby promoting charge separation, improving light absorption, effectively reducing the recombination rate of photogenerated holes and electrons, and improving the photocatalytic performance of the BiOBr-TiO2-Bi2WO6 composite material for selective oxidation of toluene. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the preparation of the BiOBr-TiO2-Bi2WO6 composite catalytic material of the present invention;

[0032] Figure 2The performance diagram of photocatalytic toluene oxidation reaction of Bi2WO6, TiO2-Bi2WO6 and BiOBr-TiO2-Bi2WO6 composite catalysts;

[0033] Figure 3 The gas chromatogram of the photocatalytic toluene oxidation reaction of the BiOBr-TiO2-Bi2WO6 composite catalyst with a molar ratio of 0.15:0.2:1 at 20°C for 3 hours;

[0034] Figure 4 The gas chromatogram of the photocatalytic toluene oxidation reaction of the BiOBr-TiO2-Bi2WO6 composite catalyst with a molar ratio of 0.20:0.2:1 at 20°C after 3 hours;

[0035] Figure 5 The gas chromatogram of the photocatalytic toluene oxidation reaction of the BiOBr-TiO2-Bi2WO6 composite catalyst with a molar ratio of 0.25:0.2:1 at 20°C for 3 hours;

[0036] Figure 6 The gas chromatogram of the photocatalytic toluene oxidation reaction of the BiOBr-TiO2-Bi2WO6 composite catalyst with a molar ratio of 0.30:0.2:1 at 20°C for 3 hours;

[0037] Figure 7 The gas chromatogram of the photocatalytic toluene oxidation reaction of the BiOBr-TiO2-Bi2WO6 composite catalyst with a molar ratio of 0.35:0.2:1 at 20°C for 3 hours;

[0038] Figure 8 This is the gas chromatogram of pure Bi2WO6 photocatalytic toluene oxidation reaction at 20°C after 3 hours;

[0039] Fig. 9 This is a gas chromatogram of the photocatalytic toluene oxidation reaction of the TiO2-Bi2WO6 composite catalyst with a molar ratio of 0.2:1 at 20°C after 3 hours; DETAILED DESCRIPTION

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

[0041] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the present technical field.

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

[0043] Example 1

[0044] This embodiment provides a method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, see Figure 1 , including the following steps:

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

[0046] 1mmol of bismuth nitrate pentahydrate, 16mg of TiO2 and 50mg of hexadecyl ammonium bromide were added to 40ml of glacial acetic acid, and stirred continuously to fully dissolve to form liquid a; 2mmol of sodium tungstate dihydrate was added to 30mL of ultrapure water, and stirred continuously to fully dissolve to form liquid b. Then, liquid b was dripped into liquid a drop by drop, and the pH of the solution was adjusted to 3, and stirred continuously at room temperature for 3h, and finally moved to a polytetrafluoroethylene reactor to react at 140℃ for 30h, cooled to room temperature, washed once with water, and then washed several times with anhydrous ethanol, and dried at 70℃ to obtain a TiO2-Bi2WO6 composite catalytic material, which was 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) and 0.15 mmol of sodium bromide were dissolved in 40 mL of ultrapure water, and then 0.15 mmol of bismuth nitrate pentahydrate was added to 30 ml of ultrapure water and stirred continuously to fully dissolve it, and then dripped into the above solution drop by drop, and stirred continuously at room temperature for 1 hour. Finally, the mixture was moved to a polytetrafluoroethylene reactor and reacted at 140° C. for 12 hours. After cooling to room temperature, the mixture was washed several times with anhydrous ethanol and dried at 70° C. to obtain a BiOBr-TiO2-Bi2WO6 composite catalytic material, which was marked as BTB-15.

[0049] Example 2

[0050] The present embodiment provides a method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, comprising the following steps:

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

[0052] Add 1mmol of bismuth nitrate pentahydrate, 16mg of TiO2 and 50mg of hexadecyl ammonium bromide to 40ml of glacial acetic acid, and stir continuously to fully dissolve it to form liquid a; add 2mmol of sodium tungstate dihydrate to 30mL of ultrapure water, and stir continuously to fully dissolve it to form liquid b. Then, drip liquid b into liquid a drop by drop, adjust the solution pH to 3, stir continuously at room temperature for 3h, and finally move to a polytetrafluoroethylene reactor to react at 140℃ for 30h. After cooling to room temperature, wash once with water, then wash several times with anhydrous ethanol, and dry at 70℃ to obtain TiO2-Bi2WO6 composite catalytic material.

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

[0054] 0.55 g of the TiO2-Bi2WO6 composite catalytic material with a molar ratio of 0.2:1 prepared in step 1) and 0.20 mmol of sodium bromide were dissolved in 40 mL of ultrapure water, and then 0.20 mmol of bismuth nitrate pentahydrate was added to 30 ml of ultrapure water and stirred continuously to fully dissolve it, and then dripped into the above solution drop by drop, and stirred continuously at room temperature for 1 hour. Finally, the mixture was moved to a polytetrafluoroethylene reactor and reacted at 140° C. for 12 hours. After cooling to room temperature, the mixture was washed several times with anhydrous ethanol and dried at 70° C. to obtain a BiOBr-TiO2-Bi2WO6 composite catalytic material, which was marked as BTB-20.

[0055] Example 3

[0056] The present embodiment provides a method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, comprising the following steps:

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

[0058] Add 1mmol of bismuth nitrate pentahydrate, 16mg of TiO2 and 50mg of hexadecyl ammonium bromide to 40ml of glacial acetic acid, and stir continuously to fully dissolve it to form liquid a; add 2mmol of sodium tungstate dihydrate to 30mL of ultrapure water, and stir continuously to fully dissolve it to form liquid b. Then, drop liquid b into liquid a drop by drop, adjust the solution pH to 3, stir continuously at room temperature for 3h, and finally move to a polytetrafluoroethylene reactor to react at 140℃ for 30h. After cooling to room temperature, wash once with water, then wash several times with anhydrous ethanol, and dry at 70℃ to obtain TiO2-Bi2WO6 composite catalytic material.

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

[0060] 0.55 g of the TiO2-Bi2WO6 composite catalytic material with a molar ratio of 0.2:1 prepared in step 1) and 0.25 mmol of sodium bromide were dissolved in 40 mL of ultrapure water, and then 0.25 mmol of bismuth nitrate pentahydrate was added to 30 ml of ultrapure water and stirred continuously to fully dissolve it, and then dripped into the above solution drop by drop, and stirred continuously at room temperature for 1 hour. Finally, the solution was moved to a polytetrafluoroethylene reactor and reacted at 140° C. for 12 hours. After cooling to room temperature, the solution was washed with anhydrous ethanol several times and dried at 70° C. to obtain a BiOBr-TiO2-Bi2WO6 composite catalytic material, which was marked as BTB-25.

[0061] Example 4

[0062] The present embodiment provides a method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, comprising the following steps:

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

[0064] Add 1mmol of bismuth nitrate pentahydrate, 16mg of TiO2 and 50mg of hexadecyl ammonium bromide to 40ml of glacial acetic acid, and stir continuously to fully dissolve it to form liquid a; add 2mmol of sodium tungstate dihydrate to 30mL of ultrapure water, and stir continuously to fully dissolve it to form liquid b. Then, drop liquid b into liquid a drop by drop, adjust the solution pH to 3, stir continuously at room temperature for 3h, and finally move to a polytetrafluoroethylene reactor to react at 140℃ for 30h. After cooling to room temperature, wash once with water, then wash several times with anhydrous ethanol, and dry at 70℃ to obtain TiO2-Bi2WO6 composite catalytic material.

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

[0066] 0.55 g of the TiO2-Bi2WO6 composite catalytic material with a molar ratio of 0.2:1 prepared in step 1) and 0.30 mmol of sodium bromide were dissolved in 40 mL of ultrapure water, and then 0.30 mmol of bismuth nitrate pentahydrate was added to 30 ml of ultrapure water and stirred continuously to fully dissolve it, and then dripped into the above solution drop by drop, and stirred continuously at room temperature for 1 hour. Finally, it was moved to a polytetrafluoroethylene reactor and reacted at 140° C. for 12 hours. After cooling to room temperature, it was washed with anhydrous ethanol several times and dried at 70° C. to obtain a BiOBr-TiO2-Bi2WO6 composite catalytic material, which was marked as BTB-30.

[0067] Example 5

[0068] The present embodiment provides a method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, comprising the following steps:

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

[0070] Add 1mmol of bismuth nitrate pentahydrate, 16mg of TiO2 and 50mg of hexadecyl ammonium bromide to 40ml of glacial acetic acid, and stir continuously to fully dissolve it to form liquid a; add 2mmol of sodium tungstate dihydrate to 30mL of ultrapure water, and stir continuously to fully dissolve it to form liquid b. Then, drop liquid b into liquid a drop by drop, adjust the solution pH to 3, stir continuously at room temperature for 3h, and finally move to a polytetrafluoroethylene reactor to react at 140℃ for 30h. After cooling to room temperature, wash once with water, then wash several times with anhydrous ethanol, and dry at 70℃ to obtain TiO2-Bi2WO6 composite catalytic material.

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

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

[0073] Application Example 1

[0074] This application example uses the BiOBr-TiO2-Bi2WO6 composite catalyst material provided in Example 1 to catalyze the photocatalytic reaction of toluene, and the reaction process specifically includes the following steps:

[0075] 1) Weigh 50 mg of the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared in Example 1 and place it in a photoreactor;

[0076] 2) Add 2 ml of acetonitrile solvent and 1 ml of toluene reactant into the reactor of step 1), seal the reactor, and fill it with dry air at 0.2 MPa;

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

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

[0079] 5) React under xenon lamp irradiation for 3 hours;

[0080] 6) After the reaction was completed, the reactor was cooled to room temperature, and the solution after the reaction was taken out and subjected to gas chromatography to obtain a conversion rate of 4.85%, a selectivity of 87.42%, and a benzaldehyde generation rate of 1843.07 umol·g -1 ·h -1 , gas chromatography see Figure 3 .

[0081] Application Example 2

[0082] This application example uses the BiOBr-TiO2-Bi2WO6 composite catalyst material provided in Example 2 to catalyze the photocatalytic reaction of toluene, and the reaction process specifically includes the following steps:

[0083] 1) Weigh 50 mg of the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared in Example 2 and place it in a photoreactor;

[0084] 2) Add 2 ml of acetonitrile solvent and 1 ml of toluene reactant into the reactor of step 1), seal the reactor, and fill it with dry air at 0.2 MPa;

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

[0086] 4) circulating water was introduced into the reactor interlayer to control the reaction temperature at 20°C;

[0087] 5) React under xenon lamp irradiation for 3 hours;

[0088] 6) After the reaction was completed, the reactor was cooled to room temperature, and the solution after the reaction was taken out and subjected to gas chromatography to obtain a conversion rate of 5.02%, a selectivity of 88.31%, and a benzaldehyde generation rate of 2270.23 umol·g -1 ·h -1 , gas chromatography see Figure 4 .

[0089] Application Example 3

[0090] This application example uses the BiOBr-TiO2-Bi2WO6 composite catalyst material provided in Example 3 to catalyze the photocatalytic reaction of toluene, and the reaction process specifically includes the following steps:

[0091] 1) Weigh 50 mg of the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared in Example 3 and place it in a photoreactor;

[0092] 2) Add 2 ml of acetonitrile solvent and 1 ml of toluene reactant into the reactor of step 1), seal the reactor, and fill it with dry air at 0.2 MPa;

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

[0094] 4) circulating water was introduced into the reactor interlayer to control the reaction temperature at 20°C;

[0095] 5) React under xenon lamp irradiation for 3 hours;

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

[0097] Application Example 4

[0098] This application example uses the BiOBr-TiO2-Bi2WO6 composite catalyst material provided in Example 4 to catalyze the photocatalytic reaction of toluene, and the reaction process specifically includes the following steps:

[0099] 1) Weigh 50 mg of the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared in Example 4 and place it in a photoreactor;

[0100] 2) Add 2 ml of acetonitrile solvent and 1 ml of toluene reactant into the reactor of step 1), seal the reactor, and fill it with dry air at 0.2 MPa;

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

[0102] 4) circulating water was introduced into the reactor interlayer to control the reaction temperature at 20°C;

[0103] 5) React under xenon lamp irradiation for 3 hours;

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

[0105] Application Example 5

[0106] This application example uses the BiOBr-TiO2-Bi2WO6 composite catalyst material provided in Example 5 to catalyze the photocatalytic reaction of toluene, and the reaction process specifically includes the following steps:

[0107] 1) Weigh 50 mg of the BiOBr-TiO2-Bi2WO6 composite catalytic material prepared in Example 5 and place it in a photoreactor;

[0108] 2) Add 2 ml of acetonitrile solvent and 1 ml of toluene reactant into the reactor of step 1), seal the reactor, and fill it with dry air at 0.2 MPa;

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

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

[0111] 5) React under xenon lamp irradiation for 3 hours;

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

[0113] Comparative application example 1

[0114] In this comparative application example, Bi2WO6 catalyzes the photocatalytic reaction of toluene, and the reaction process specifically includes the following steps:

[0115] 1) Weigh 50 mg of Bi2WO6 photocatalytic material into a photoreactor;

[0116] 2) Add 2 ml of acetonitrile solvent and 1 ml of toluene reactant into the reactor of step 1), seal the reactor, and fill it with dry air at 0.2 MPa;

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

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

[0119] 5) React under xenon lamp irradiation for 3 hours;

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

[0121] Comparative Application Example 2

[0122] In this comparative application example, TiO2-Bi2WO6 catalyzes the photocatalytic reaction of toluene, and the reaction process specifically includes the following steps:

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

[0124] 2) Add 2 ml of acetonitrile solvent and 1 ml of toluene reactant into the reactor of step 1), seal the reactor, and fill it with dry air at 0.2 MPa;

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

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

[0127] 5) React under xenon lamp irradiation for 3 hours;

[0128] 6) After the reaction was completed, the reactor was cooled to room temperature, and the solution after the reaction was taken out and subjected to gas chromatography 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 , gas chromatography see Fig. 9 .

[0129] It can be seen from the above application examples and comparative application examples that the BiOBr-TiO2-Bi2WO6 composite catalytic materials prepared in all examples have more excellent photocatalytic performance. Figure 2 Compared with Bi2WO6 and TiO2-Bi2WO6, the conversion rate and benzaldehyde generation rate of the BiOBr-TiO2-Bi2WO6 composite catalytic material in the photocatalytic selective oxidation of toluene to prepare benzaldehyde are 2.55 times and 2.70 times of pure Bi2WO6, and 1.60 times and 1.50 times of TiO2-Bi2WO6, respectively. This shows that the photocatalytic performance of the BiOBr-TiO2-Bi2WO6 composite material in the photocatalytic selective oxidation of toluene is stronger than that of pure Bi2WO6 and TiO2-Bi2WO6, and its heterojunction does inhibit the recombination of photogenerated holes and electrons, thereby improving the photocatalytic performance of the material.

Claims

1. A method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material, characterized in that: The following steps are included in sequence: S1. Preparation of TiO2-Bi2WO6 composite catalytic material: Add TiO2, hexadecyltrimethylammonium bromide and bismuth source to acetic acid solution and stir continuously to form liquid a, add tungsten source to ultrapure water and stir continuously to form liquid b, after the tungsten source is fully dissolved, drip liquid b into liquid a drop by drop, adjust the pH of the solution, stir continuously for 1-3 hours, 100-180° C., perform hydrothermal reaction for 12-30 hours, and wash and dry the reaction product to obtain TiO2-Bi2WO6 composite catalytic 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 The TiO2-Bi2WO6 prepared in S1 is dissolved in ultrapure water, and then a bromine source and a bismuth source are added, mixed and dissolved, and then subjected to a hydrothermal reaction at 120-200°C for 12-24h. The reaction product is 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 method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 1, characterized in that: The tungsten source described in S1 is sodium tungstate dihydrate, and the bismuth source described in S1 and S2 is bismuth nitrate pentahydrate.

3. The method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 1, characterized in that: The pH of S1 is 2-4.

4. The method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 1, characterized in that: The bromine source described in S2 is sodium bromide.

5. The method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 1, characterized in that: The washing in step S1 is first performed with water and then with anhydrous ethanol.

6. The method for preparing a BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 1, characterized in that: The washing in step S2 is performed by washing with anhydrous ethanol.

7. A BiOBr-TiO2-Bi2WO6 composite catalytic material, characterized in that: The method is prepared by the method described in claims 1 to 6.

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

9. A method for preparing benzaldehyde by selective oxidation of toluene, characterized in that: The steps are as follows: 1) placing the BiOBr-TiO2-Bi2WO6 composite catalytic material according to claim 7 in a photoreactor; 2) adding acetonitrile and toluene to the reactor in step 1), sealing the reactor, and filling it with dry air at 0.1-1 MPa; 3) Stir for 10-60 min in dark conditions; 4) circulating water is introduced into the reactor interlayer to control the reaction temperature at 15-25°C; 5) reacting under xenon lamp irradiation for 1-4 hours; 6) After the reaction is completed, wait for the reactor to cool to room temperature and then test.

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

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