Preparation method and application of composite photocatalyst

Abstract

The invention discloses a preparation method of a composite photocatalyst. Tetrabutyl titanate, titanium tetrachloride and the like are selected as a titanium source, melamine is selected as a carbon and nitrogen source, meanwhile, ammonium molybdate ((NH4) 6Mo7O24. 4H2O) and sodium vanadate (NaVO3) with specific contents are introduced as metal dopants, and the photoresponse performance can be obviously improved through the cooperation of molybdenum and vanadium, so that the composite photocatalyst disclosed by the invention has obviously better photocatalytic performance; the catalyst is suitable for nitro reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysis, and in particular to a preparation method and application of a composite photocatalyst. Background Art

[0002] High efficiency, green technology, and energy conservation have become the future trend of society. Therefore, semiconductor photocatalytic technology is particularly important in addressing environmental pollution. Currently, titanium dioxide (TiO2) is the most widely studied and applied photocatalyst due to its numerous advantages, including its non-toxicity, ease of preparation, and excellent stability.

[0003] Chinese patent CN107469833A discloses a method for preparing a titanium dioxide hollow core-shell structure composite photocatalyst coated with molybdenum disulfide, which mainly uses tetrabutyl titanate as a titanium source to react with titanium dioxide, urea as a carbon / nitrogen source, (NH4)6Mo7O 24 The introduction of Mo into 4H2O gives this composite photocatalyst excellent photocatalytic performance. However, this composite photocatalyst has the following drawbacks: 1. Due to the low melting point of urea (approximately 132.7°C), it may melt prematurely or even decompose during the reaction, making the reaction difficult to control and affecting the quality and performance of the photocatalyst; 2. The Mo element has limited effect on the photoresponsiveness. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above technical defects and provide a composite photocatalyst with better photocatalytic effect, and its preparation method and application.

[0005] The present invention is achieved through the following technical solutions: The preparation method of the composite photocatalyst of the present invention comprises the following steps: Step A: dissolving 1 part by weight of a titanium source in an organic solvent A to prepare a solution A, and dissolving 0.389-0.408 parts by weight of melamine, 0.036-0.182 parts by weight of ammonium molybdate, 0.0036-0.0287 parts by weight of sodium vanadate, and 0.10-0.15 parts by weight of an organic ligand in a solvent B to prepare a solution B; Step B: adding solution A to solution B, stirring at 50-70° C. for 1-8 hours to obtain a mixed solution; Step C: subjecting the mixed solution to a hot water reaction at 170-190° C. for 10-18 hours, and then centrifuging to separate the product. The product is washed 1-4 times, dried, and calcined at 450-550° C. for 2-6 hours in an atmosphere of nitrogen and hydrogen in a volume ratio of (1-8):1; Step D: dispersing the calcined product in a surfactant aqueous solution and subjecting it to ultrasonic treatment, followed by filtering, washing, and drying to obtain a composite photocatalyst.

[0006] The titanium source is selected from at least one of tetrabutyl titanate and titanium tetrachloride.

[0007] The organic solvent A is selected from at least one of anhydrous ethanol, methanol, n-propanol, ether, tetrahydrofuran, toluene and xylene, and the amount of the organic solvent A is in the range of 5-15 parts by weight.

[0008] The organic solvent B is selected from at least one of an ethylene glycol / water mixed solvent (volume ratio 1:0.5-2) and a glycerol / water mixed solvent (volume ratio 1:0.5-2). The amount of the organic solvent B is in the range of 3-7 parts by weight.

[0009] The organic ligand is selected from at least one of acetylacetone, citric acid, and ethylenediamine. The presence of the organic ligand can regulate the nanostructure and surface properties of the catalyst, thereby improving the photocatalytic performance.

[0010] In step D, the catalyst surface is modified with an aqueous surfactant solution. The surfactant is selected from at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol (PEG, molecular weight 500-20,000), and polyethersulfone (PES, molecular weight 3,000-10,000). The concentration of the aqueous surfactant solution ranges from 0.1% to 0.5%. The amount of the aqueous surfactant solution used, based on the weight of the calcined product, ranges from 0.5 to 10 times the weight of the product. The ultrasonic treatment time can be 0.5 to 24 hours.

[0011] The washing can be performed using deionized water and ethanol.

[0012] The composite photocatalyst prepared by the composite photocatalyst preparation method of the present invention mainly includes titanium dioxide, graphite carbon nitride, molybdenum oxide, and vanadium oxide. Graphite carbon nitride (g-C3N4) is converted into melamine. Molybdenum oxide is converted into ammonium molybdate ((NH4)6Mo7O 24 4H2O); wherein the molybdenum oxide is a mixture of MoO3 and MoO2, and the weight ratio of MoO3 to MoO2 ranges from (1.8-6.6):1. Vanadium oxide is converted into sodium vanadate (NaVO3); wherein the vanadium oxide is a mixture of V2O5 and VO2, and the weight ratio of V2O5 to VO2 ranges from (2-8.1):1.

[0013] The composite photocatalyst of the present invention is used for photocatalytically reducing nitro groups in organic matter to amino groups.

[0014] The composite photocatalyst of the present invention is used to reduce 4,4-dinitrodiphenyl ether (or other nitro-containing organic substances, such as nitro-containing aromatic compounds) to 4,4-diaminodiphenyl ether.

[0015] Specifically, the reduction method of 4,4-dinitrodiphenyl ether can be as follows: The photocatalyst, 4,4-dinitrodiphenyl ether and solvent were added to the reactor, nitrogen was introduced to replace the air, and the photocatalyst was irradiated with light (wavelength 400-760nm, light intensity 70-100mW / cm 2 ), react at 40-60°C for 6-10 hours to obtain 4,4-diaminodiphenyl ether. During the photoreaction, the light intensity and wavelength can be adjusted to control the reaction rate. The solvent can be: N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylhexamide, acetonitrile, etc.

[0016] The present invention has the following beneficial effects: The present invention uses tetrabutyl titanate, titanium tetrachloride, etc. as titanium sources, melamine with good stability and high C / N content as carbon and nitrogen sources, and introduces a specific content of ammonium molybdate (NH4)6Mo7O 24 ·4H2O) and sodium vanadate (NaVO3) are used as metal dopants, wherein the synergy of molybdenum / vanadium can significantly improve the light response performance, so that the composite photocatalyst of the present invention has significantly better photocatalytic performance and is suitable for reducing nitro groups. DETAILED DESCRIPTION

[0017] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0018] The raw materials used in the present invention are from the following sources: Tetrabutyl titanate: purity 99%.

[0019] Titanium tetrachloride: purity 99.5%.

[0020] Melamine: purity 99.8%.

[0021] Urea: Total nitrogen content 99%.

[0022] Ammonium molybdate: purity 99%.

[0023] Sodium vanadate: purity 99%.

[0024] Anhydrous ethanol: purity 99.9%.

[0025] Ethylene glycol: purity 99.8%.

[0026] Acetylacetone: purity 99.5%.

[0027] Citric acid: purity 99.5%.

[0028] Sodium dodecylbenzenesulfonate: purity 98%.

[0029] Polyethylene glycol: molecular weight is 500-20000.

[0030] Preparation method of composite photocatalyst of embodiment and comparative example: step A: dissolving titanium source (tetrabutyl titanate or titanium tetrachloride) in organic solvent A (anhydrous ethanol) to prepare solution A, dissolving melamine (or urea), ammonium molybdate, sodium vanadate and organic ligand (acetylacetone or citric acid) in solvent B (ethylene glycol / water mixed solvent, volume ratio 1:1) to prepare solution B (the amount of each component is shown in the table); step B: adding solution A to solution B, stirring at 60°C for 4 hours to obtain a mixed solution; step C: mixing the mixture The combined solution was subjected to hot water reaction at 180°C for 13 hours, and the product was then centrifuged and separated. The product was washed three times with deionized water, dried, and calcined at 500°C for 4 hours in an atmosphere of nitrogen and hydrogen with a volume ratio of 4:1. Step D: The calcined product was dispersed in 3 parts of surfactant aqueous solutions (A: sodium dodecylbenzenesulfonate / water solution, mass concentration is 0.2%; B: polyethylene glycol / water solution, mass concentration is 0.5%) and ultrasonically treated for 2 hours, and then filtered and dried to obtain a composite photocatalyst.

[0031] Table 1: Addition amount of each component of composite photocatalyst in Examples and Comparative Examples (parts by weight) Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tetrabutyl titanate 1 1 1 1 1 Titanium tetrachloride 1 Solvent A 5 15 10 5 5 5 Melamine 0.389 0.408 0.397 0.389 0.389 urea 0.389 Ammonium molybdate 0.073 0.036 0.182 0.073 0 0.073 Sodium vanadate 0.0036 0.0120 0.0287 0.036 0.036 0 Acetylacetone 0.12 0.15 0.12 0.12 0.12 Citric acid 0.1 Solvent B 5 4 6 5 5 5 Selection of surfactant aqueous solution A A B A A A The composite photocatalyst prepared in the above examples and comparative examples was used to catalyze the reduction of 4,4-dinitrodiphenyl ether: 0.2 g of photocatalyst, 0.05 mol of 4,4-dinitrodiphenyl ether, 0.1 mol of sodium formate, and 100 mL of solvent were added to a reactor, nitrogen was introduced to replace the air, and the reaction mixture was heated under light irradiation (wavelength 400-760 nm, light intensity 80 mW / cm 2 ), react at 40-60°C for 7 hours to obtain 4,4-diaminodiphenyl ether. After the reaction is completed, the mixture is cooled to room temperature and the photocatalyst is recovered by centrifugation. The filtrate is then distilled under reduced pressure to remove NMP, and deionized water is added to separate the product and the ionic liquid. After the product layers are separated, they are purified using silica gel column chromatography (eluent: petroleum ether: ethyl acetate = 2-7:1) to obtain the 4,4-diaminodiphenyl ether product as a white solid. The yield and purity are shown in the following table: Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Yield, % 97.1 93.7 96.2 90.4 87.2 89.2 purity,% 99.6 99 99.3 98.7 95.3 96.8 As can be seen from Comparative Example 1, when urea is selected as the nitrogen source, due to its insufficient stability, it will decompose prematurely in the high-temperature process of the catalyst, resulting in insufficient catalyst performance.

[0032] It can be seen from Comparative Examples 2 / 3 that the catalytic performance of the catalyst is poor when ammonium molybdate or sodium vanadate is not added, which shows that ammonium molybdate and sodium vanadate play a synergistic role, and the effect is poor when one is missing.

Claims

1. A method for preparing a composite photocatalyst, characterized in that: The following steps are involved: Step A: dissolving 1 part by weight of a titanium source in an organic solvent A to prepare a solution A, and dissolving 0.389-0.408 parts by weight of melamine, 0.036-0.182 parts by weight of ammonium molybdate, 0.0036-0.0287 parts by weight of sodium vanadate, and 0.10-0.15 parts by weight of an organic ligand in a solvent B to prepare a solution B; Step B: adding solution A to solution B, stirring at 50-70° C. for 1-8 hours to obtain a mixed solution; Step C: subjecting the mixed solution to a hot water reaction at 170-190° C. for 10-18 hours, and then centrifuging to separate the product. The product is washed 1-4 times, dried, and calcined at 450-550° C. for 2-6 hours in an atmosphere of nitrogen and hydrogen in a volume ratio of (1-8):1; Step D: dispersing the calcined product in a surfactant aqueous solution and subjecting it to ultrasonic treatment, followed by filtering, washing, and drying to obtain a composite photocatalyst.

2. The method for preparing the composite photocatalyst according to claim 1, wherein: The organic solvent A is selected from at least one of anhydrous ethanol, methanol, n-propanol, ether, tetrahydrofuran, toluene and xylene, and the amount of the organic solvent A is in the range of 5-15 parts by weight.

3. The method for preparing the composite photocatalyst according to claim 1, wherein: The organic ligand is selected from at least one of acetylacetone, citric acid and ethylenediamine.

4. The method for preparing a composite photocatalyst according to claim 1, wherein: The titanium source is selected from at least one of tetrabutyl titanate and titanium tetrachloride.

5. The method for preparing the composite photocatalyst according to claim 1, wherein: The organic solvent B is selected from at least one of a mixed solvent of ethylene glycol / water, glycerol / water, ethanol / water, and DMF / water. The amount of the organic solvent B is in the range of 3-7 parts by weight.

6. The method for preparing the composite photocatalyst according to claim 1, wherein: The washing is performed with deionized water and ethanol.

7. The method for preparing the composite photocatalyst according to claim 1, wherein: The surfactant is selected from at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol with a molecular weight of 500-20,000, and polyethersulfone with a molecular weight of 3,000-10,000; the mass concentration range of the surfactant aqueous solution is 0.1-0.5%.

8. The composite photocatalyst obtained by the composite photocatalyst preparation method according to any one of claims 1 to 7.

9. Use of the composite photocatalyst prepared by the composite photocatalyst preparation method according to any one of claims 1 to 7, characterized in that: Used to reduce 4,4-dinitrodiphenyl ether to 4,4-diaminodiphenyl ether.