A TiO2 catalyst containing heteroatoms and transition metals and its preparation method

Abstract

The present invention belongs to the field of titanium dioxide catalysts, and particularly relates to a TiO2 catalyst containing heteroatoms and transition metals and a preparation method thereof. The method comprises stirring a heteroatom source, a transition metal source, and a titanium source in a solvent to disperse them to form a gel; and drying, grinding, and calcining the gel to obtain the TiO2 catalyst containing heteroatoms and transition metals. The present invention significantly improves the photocatalytic degradation activity of TiO2 by adjusting the ratio of the heteroatom source and the composition of the transition metal source. Under the same heteroatom doping conditions, Fe and Mn doping exhibit better visible light absorption than Fe and Cu doping and Fe and Co doping, effectively reducing the band gap of TiO2. Adjusting the mass ratio of the transition metal source to the titanium source can regulate the particle size of the dopant and improve the visible light absorption performance of the TiO2 composite material.

Description

Technical Field

[0001] The present invention belongs to the field of titanium dioxide catalysts, and in particular relates to a TiO2 catalyst containing heteroatoms and transition metals and a preparation method thereof. Background Art

[0002] As a type of photocatalyst, TiO2 has been widely studied due to its low toxicity, long-term photosensitivity, high stability under ultraviolet light irradiation, and low cost. TiO2 mainly exists in two crystalline forms: anatase and rutile. Among them, anatase is more photosensitizing than rutile. TiO2 is widely used in photocatalytic processes such as photocatalytic water splitting, selective photoorganic synthesis, and the elimination of organic pollutants in air or water. However, the energy gap of pure phase TiO2 is about 3.2eV, and it can only utilize sunlight below 360nm. The product is a dense bulk particle with low specific surface area, weak photogenerated carrier separation ability, and poor photocatalytic activity, which limits the application range of the material.

[0003] Some studies have shown that doping TiO2 with heteroatoms or transition metals can enhance its photocatalytic ability. For example, CN110665529A discloses a method and evaluation method for the catalytic degradation of antibiotics using nitrogen-doped modified nano-titanium dioxide. The results demonstrate that nitrogen-doped modified nano-titanium dioxide has a significant degradation effect on ciprofloxacin, and the catalytic material is highly stable and recyclable. CN106955728A discloses a method for preparing and applying a highly efficient supported ozone oxidation catalyst. This method incorporates a Mn metal oxide catalyst into the internal pore structure of a titanium dioxide molecular sieve. The catalyst material exhibits an extremely high content of active components, a high pollutant removal rate, and high catalytic activity.

[0004] Currently, there are many reports on the improvement of catalytic performance of TiO2 by doping with heteroatoms or transition metals, but there are few methods for co-doping TiO2 with heteroatoms and transition metals. Therefore, it is necessary to invent a new method for preparing TiO2 catalysts. Summary of the Invention

[0005] In view of the above problems, the present invention provides a method for preparing a TiO2 catalyst containing heteroatoms and transition metals, comprising:

[0006] The heteroatom source, the transition metal source and the titanium source are stirred in a solvent to disperse them and form a gel;

[0007] The gel is dried, ground and calcined to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0008] A further preferred technical solution is that the heteroatom source is selected from one or a combination of urea, ammonium sulfate, ammonium chloride, thiourea, ammonium phosphate and amino acids.

[0009] A further preferred technical solution is that the heteroatom source is composed of urea and amino acid in a mass ratio of 5-10:0.5-2.

[0010] A further preferred technical solution is that the amino acid is one or a combination of alanine, glycine, serine, methionine or aspartic acid.

[0011] A further preferred technical solution is that the transition metal source is selected from one or a combination of soluble salts of Cu, Fe, Co and Mn.

[0012] A further preferred technical solution is that the mass ratio of the titanium source to the volume of the solvent is 5-10:20-100 g / mL.

[0013] A further preferred technical solution is: the solvent is selected from one or a combination of water, anhydrous ethanol, toluene, xylene or acetone, and the heteroatom is N or a combination of N and S.

[0014] A further preferred technical solution is as follows: drying is carried out by keeping the temperature at 80-120° C. for 8-15 hours; and calcining is carried out by keeping the temperature at 350-500° C. for 2-5 hours.

[0015] A further preferred technical solution is that the mass ratio of the heteroatom content in the atomic source, the metal element content in the transition metal source and the titanium content in the titanium source is 0.01-0.05:0.01-0.05:1.

[0016] A further preferred technical solution is: application of a TiO2 catalyst containing heteroatoms and transition metals for photocatalytic degradation of organic pollutants.

[0017] Beneficial effects of the present invention:

[0018] (1) The present invention significantly improves the photocatalytic degradation activity of TiO2 by adjusting the ratio of heteroatom sources and the composition of transition metal sources: under the same heteroatom doping conditions, the absorption performance of Fe and Mn doping to visible light is better than that of Fe and Cu doping and Fe and Co doping, which can effectively reduce the band gap width of TiO2; adjusting the mass ratio of transition metal source to titanium source can control the particle size of dopant and improve the absorption performance of TiO2 composite material to visible light.

[0019] (2) The combination of amino acids with smaller molecular weight and other heteroatom compounds can make transition metal doping more uniform and better form oxygen vacancies to reduce the band gap of TiO2.

[0020] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 The UV-visible diffuse reflectance spectra of the materials prepared in the comparative example, example 7, example 8 and example 11 of the present invention are shown;

[0023] Figure 2 shows a transmission electron microscope image of Example 3 of the present invention;

[0024] Figure 3 shows a transmission electron microscope image of Example 11 of the present invention;

[0025] Figure 4 shows a transmission electron microscope image of Example 14 of the present invention;

[0026] Figure 5 The graph shows the concentration ratio and time of the degradation of ciprofloxacin hydrochloride by the comparative example, example 9, example 10 and example 11 of the present invention. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0028] Example 1

[0029] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0030] Urea, FeCl3·6H2O, CuCl2·2H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0031] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0032] Among them, the mass ratio of N, Fe, Cu and Ti in the raw materials is 0.02:0.03:0.02:1.

[0033] Example 2

[0034] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0035] Urea, FeCl3·6H2O, (CH3COO)2Co·4H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% .wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0036] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0037] Among them, the mass ratio of N, Fe, Co and Ti in the raw materials is 0.02:0.03:0.02:1.

[0038] Example 3

[0039] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0040] Urea, FeCl3·6H2O, MnCl2·4H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% .wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0041] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0042] Among them, the mass ratio of N, Fe, Mn and Ti in the raw materials is 0.02:0.03:0.02:1.

[0043] Example 4

[0044] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0045] Thiourea, FeCl3·6H2O, CuCl2·2H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% .wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0046] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0047] Among them, the mass ratio of N+S, Fe, Cu and Ti in the raw materials is 0.02:0.03:0.02:1.

[0048] Example 5

[0049] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0050] Thiourea, FeCl3·6H2O, (CH3COO)2Co·4H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% .wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0051] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0052] Among them, the mass ratio of N+S, Fe, Co and Ti in the raw materials is 0.02:0.03:0.02:1.

[0053] Example 6

[0054] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0055] Thiourea, FeCl3·6H2O, MnCl2·4H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0056] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0057] Among them, the mass ratio of N+S, Fe, Mn and Ti in the raw materials is 0.02:0.03:0.02:1, and the mass ratio of urea and glycine is 5:1.

[0058] Example 7

[0059] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0060] Urea, glycine, FeCl3·6H2O, CuCl2·2H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% .wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0061] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0062] Among them, the mass ratio of N, Fe, Cu and Ti in the raw materials is 0.02:0.03:0.02:1, and the mass ratio of urea and glycine is 5:1.

[0063] Example 8

[0064] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0065] Urea, glycine, FeCl3·6H2O, (CH3COO)2Co·4H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% .wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0066] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0067] Among them, the mass ratio of N, Fe, Co and Ti in the raw materials is 0.02:0.03:0.02:1, and the mass ratio of urea and glycine is 5:1.

[0068] Example 9

[0069] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0070] Urea, glycine, FeCl3·6H2O, MnCl2·4H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% .wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0071] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0072] Among them, the mass ratio of N, Fe, Mn and Ti in the raw materials is 0.02:0.01:0.02:1, and the mass ratio of urea and glycine is 5:1.

[0073] Example 10

[0074] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0075] Urea, glycine, FeCl3·6H2O, MnCl2·4H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% .wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0076] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0077] Among them, the mass ratio of N, Fe, Mn and Ti in the raw materials is 0.02:0.05:0.02:1, and the mass ratio of urea and glycine is 5:1.

[0078] Example 11

[0079] A method for preparing a TiO2 catalyst containing heteroatoms and transition metals comprises the following steps:

[0080] Urea, glycine, FeCl3·6H2O, MnCl2·4H2O and 6 g of n-butyl titanate were dissolved in 30 mL of a 75% .wt ethanol aqueous solution and stirred at a stirring rate of 300 r / min until sol-gel transition occurred to obtain a gel;

[0081] The gel was transferred to a constant temperature oven and kept at 100°C for 10 hours for drying. The dried gel was ground through a 300-mesh sieve to obtain a powder. The powder was placed in a muffle furnace with a nitrogen atmosphere at 400°C for 3 hours and then naturally cooled to room temperature to obtain a TiO2 catalyst containing heteroatoms and transition metals.

[0082] Among them, the mass ratio of N, Fe, Mn and Ti in the raw materials is 0.02:0.03:0.02:1, and the mass ratio of urea and glycine is 5:1.

[0083] Examples 12-17

[0084] It is basically the same as Example 11, and the only difference is shown in Table 1.

[0085] Table 1 Composition of heteroatom sources in Examples 12-17

[0086]

[0087]

[0088] Comparative Example 1

[0089] A preparation method of a TiO2 catalyst is basically the same as that of Example 1, except that it does not contain urea, FeCl3·6H2O and CuCl2·2H2O.

[0090] Comparative Example 2

[0091] A preparation method of a heteroatom-doped TiO2 catalyst is basically the same as that of Example 1, except that FeCl3·6H2O and CuCl2·2H2O are not contained.

[0092] Test Case

[0093] XPS characterization of the materials prepared in Examples 1-17 and the comparative example revealed the successful preparation of the corresponding TiO2 and TiO2 catalysts containing heteroatoms and transition metals. Dopant ions can replace some Ti ions in the Ti-O matrix, creating lattice and oxygen vacancies, which can reduce the band gap of TiO2.

[0094] The materials prepared in the comparative example, example 7, example 8 and example 11 were characterized by UV-visible diffuse reflectance spectroscopy. Figure 1 As shown, the comparative example, embodiment 7, embodiment 8 and embodiment 11 correspond to curves a, b, c and d, respectively. It can be seen that, relative to TiO2, the absorption peak of the TiO2 catalyst containing heteroatoms and transition metals is red-shifted, and the red-shift of embodiment 7, embodiment 8 and embodiment 11 is more obvious. The calculated band gap energy results of the comparative example, embodiment 7, embodiment 8 and embodiment 11 are 3.16eV, 3.03eV, 3.01eV, and 2.93eV, respectively. This shows that heteroatom and transition metal doping can improve the absorption performance of TiO2 to visible light; under the same heteroatom doping conditions, the absorption performance of Fe and Mn doping to visible light is better than that of Fe and Cu doping and Fe and Co doping.

[0095] The morphology of the materials prepared in Examples 1-17 and the comparative example was observed by scanning electron microscopy. The results showed that the TiO2 or TiO2 matrix were all spherical or elliptical particles of nanometer size. Further, the structural characteristics of Example 3, Example 11 and Example 14 were characterized by transmission electron microscopy. The results were as follows: Figure 2 、 Figure 3 and Figure 4 shown.

[0096] contrast Figure 2 and Figure 3 It can be seen that adding a certain amount of glycine to replace urea is beneficial to the dispersion of transition metal dopants in the TiO2 matrix; Figure 3 and Figure 4 It can be seen that a larger proportion of glycine in the heteroatom source will cause the aggregation of transition metal dopants in the TiO2 matrix.

[0097] also, Figure 2 、 Figure 3 and Figure 4It shows that the size of the transition metal dopants is concentrated in the range of 20-80 nm, with an average size of 48.8 nm for Example 3, 45.3 nm for Example 11, and 58.7 nm for Example 14. Small size and narrow size distribution are beneficial to improving photocatalysis. The test results of the UV-visible diffuse reflectance spectrum for Example 3, Comparative Example 11, and Comparative Example 14 also show that the band gap energies of Example 3, Comparative Example 11, and Comparative Example 14 are 3.02 eV, 2.93 eV, and 3.05 eV, respectively. These results indicate that controlling the type of heteroatom source and adjusting its ratio can facilitate the dispersion of transition metal dopants in the TiO2 matrix, regulate the size of transition metal dopants, and improve its absorption performance for visible light.

[0098] Example 18

[0099] The materials prepared in Comparative Example, Example 9, Example 10 and Example 11 were used to degrade ciprofloxacin hydrochloride.

[0100] A 500 mg / L ciprofloxacin hydrochloride solution was prepared as a mother liquor and diluted to 1 L of a 5 mg / L ciprofloxacin hydrochloride test solution. The catalyst (materials prepared in the comparative example, example 9, example 10, and example 11) was added to the ciprofloxacin hydrochloride test solution in an amount of 0.2 g. The catalyst was catalyzed and degraded under ultraviolet light at 200 rpm. The results were as follows: Figure 5 The degradation rate of ciprofloxacin hydrochloride is shown in Table 2.

[0101] Table 2 Degradation rate of ciprofloxacin hydrochloride

[0102] Degradation rate (%) Comparative Example 91.7 Example 9 95.2 Example 10 94.3 Example 11 97.4

[0103] The results in Table 2 indicate that the TiO2 catalyst containing heteroatoms and transition metals, prepared in accordance with the present invention, exhibits superior photocatalytic degradation of ciprofloxacin hydrochloride compared to pure TiO2. This is likely due to the increased number of reactive sites on the material surface after heteroatom doping, and the combined effects of Fe and Mn doping and N on the transition metals to reduce the band gap energy.

[0104] In addition, the material prepared in Example 11 of the present invention was used to degrade 10 mg / L tetracycline antibiotics, such as tetracycline, oxytetracycline and chlortetracycline, and the degradation rate exceeded 65% after 300 minutes of reaction under ultraviolet light; the material prepared in Example 11 of the present invention was used to degrade phenol and halogenated hydrocarbons (such as 1,2,3-trichloropropane, 1,3-dibromopropane, 1,4-dibromobutane), and the degradation rate exceeded 50%.

[0105] In summary, the present invention significantly improves the photocatalytic degradation activity of TiO2 by adjusting the ratio of heteroatom sources and the composition of transition metal sources. The prepared TiO2 catalyst containing heteroatoms and transition metals has good prospects for photocatalytic degradation of organic pollutants.

[0106] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a TiO2 catalyst containing heteroatoms and transition metals, characterized in that: include: The heteroatom source, the transition metal source and the titanium source are stirred in a solvent to disperse them and form a gel; The gel is dried, ground and calcined to obtain a TiO2 catalyst containing heteroatoms and transition metals; The heteroatom source is composed of urea and amino acid in a mass ratio of 5-10:0.5-2; The amino acid is one or a combination of alanine, glycine, serine, methionine or aspartic acid; The transition metal sources are soluble salts of Fe and Mn.

2. The method for preparing a TiO2 catalyst containing heteroatoms and transition metals according to claim 1, wherein: The mass ratio of the titanium source to the volume ratio of the solvent is 5-10:20-100 g / mL.

3. The method for preparing a TiO2 catalyst containing heteroatoms and transition metals according to claim 1, wherein: The solvent is selected from one or a combination of water, anhydrous ethanol, toluene, xylene or acetone, and the heteroatom is N or a combination of N and S.

4. The method for preparing a TiO2 catalyst containing heteroatoms and transition metals according to claim 1, wherein: The drying step is to keep the temperature at 80-120° C. for 8-15 hours, and the calcining step is to keep the temperature at 350-500° C. for 2-5 hours.

5. A TiO2 catalyst containing heteroatoms and transition metals prepared by the method according to any one of claims 1 to 4, characterized in that: The mass ratio of the heteroatom content in the heteroatom source, the metal element content in the transition metal source and the titanium content in the titanium source is 0.01-0.05:0.01-0.05:

1.

6. The use of a TiO2 catalyst containing heteroatoms and transition metals according to claim 5, characterized in that: Used for photocatalytic degradation of organic pollutants.

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