Titanium dioxide nanotube and preparation method and application thereof

Abstract

The application relates to the field of waste treatment, in particular to a titanium dioxide nanotube as well as a preparation method and application thereof. The nanotube is in an anatase crystal form, the tube diameter is 10 nm-10 mu m, the specific surface area is 39.81-151.77 cm 2 / g, the titanium dioxide nanotube has a mesoporous and microporous structure. The titanium dioxide nanotube can be used as a catalyst for the photothermal synergistic catalytic degradation of refrigerants, has high reaction activity in the photothermal synergistic catalytic degradation of refrigerants, and realizes effective degradation of low temperature, low energy consumption, large flow, high rate and high refrigerant component proportion.

Description

Technical Field

[0001] This invention relates to the field of waste treatment, and in particular to a titanium dioxide nanotube, its preparation method, and its application. Background Technology

[0002] The development of human civilization is inseparable from the widespread application of refrigeration and air conditioning technology. The core of refrigeration technology lies in the development of refrigerants. Existing technology discloses a method for treating CFC refrigerants, which involves high-temperature sintering of a CFC mixture with cement raw materials. The mass percentages of fluorine and chlorine in the system are less than 0.04% and 0.5% of the total weight of the CFC refrigerant and cement raw materials, respectively, and the sintering temperature is 1400-1600℃. However, this existing refrigerant treatment method is a high-temperature pyrolysis method, which is energy-intensive and costly. Therefore, there is an urgent need for efficient and environmentally friendly refrigerant degradation treatment methods.

[0003] Photothermal synergistic catalysis technology can achieve mild and efficient degradation of refrigerants. Existing technologies use anatase TiO2 nanosphere catalysts for refrigerant degradation, but a relatively long stationary reaction time is required to achieve more than 95% degradation. Therefore, there is an urgent need for a catalyst to achieve highly efficient photothermal synergistic catalytic degradation of refrigerants. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this invention provides a titanium dioxide nanotube, its preparation method, and its applications. This titanium dioxide nanotube possesses a larger specific surface area and a more abundant mesoporous and microporous structure, and can be used as a catalyst for the photothermal synergistic catalytic degradation of refrigerants, thereby significantly improving the degradation rate of the refrigerant.

[0005] Therefore, in a first aspect, the present invention provides a titanium dioxide nanotube, wherein the titanium dioxide nanotube is anatase in crystal form, has a diameter of 10 nm-10 μm, and a specific surface area of ​​39.81-151.77 cm². 2 / g, the titanium dioxide nanotubes have mesoporous and microporous structures.

[0006] To address the shortcomings of existing technologies, this invention provides titanium dioxide nanotubes with a larger specific surface area and a more abundant mesoporous and microporous structure, which can be used as a catalyst for the photothermal synergistic catalytic degradation of refrigerants. Specifically, due to the structural characteristics of titanium dioxide nanotubes, they exhibit high reactivity in the photothermal synergistic catalytic degradation of refrigerants, achieving efficient degradation at low temperatures, low energy consumption, high flow rates (up to 0.1 mol / L (at 2.5 standard atmospheres)), high rates, and high refrigerant component ratios.

[0007] According to an embodiment of the present invention, the titanium dioxide nanotubes have a diameter of 10-50 nm and a specific surface area of ​​99.66-151.77 cm². 2 / g.

[0008] According to an embodiment of the present invention, the volume percentage of the mesopores is 5%-15%, and the volume percentage of the micropores is 85%-95%.

[0009] A second aspect of this invention provides a method for preparing the titanium dioxide nanotubes described in the first aspect, comprising:

[0010] A titanium source and an alkaline reagent are mixed and subjected to a hydrothermal reaction to obtain a precipitate, which is then acid-washed.

[0011] The precipitate, after acid washing, is washed until the pH of the solution is neutral, mixed with a dispersant, and then separated to obtain the precursor.

[0012] The precursor was calcined to obtain the titanium dioxide nanotubes.

[0013] This yields the aforementioned titanium dioxide nanotubes with excellent properties.

[0014] According to an embodiment of the present invention, the titanium source includes at least one of titanium dioxide, titanium tetrachloride, and tetrabutyl titanate.

[0015] According to an embodiment of the present invention, the particle size of the titanium source is 25-500 nm.

[0016] According to an embodiment of the present invention, the alkaline reagent includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water.

[0017] According to an embodiment of the present invention, the temperature of the hydrothermal treatment is 100-200 °C.

[0018] According to an embodiment of the present invention, the hydrothermal treatment time is 24-72 h.

[0019] According to an embodiment of the present invention, the preparation method further includes: washing the precipitate until the solution pH is neutral, and performing acid washing treatment until the solution pH is 0.5-2.

[0020] According to an embodiment of the present invention, the dispersant includes at least one of acetone and tert-butanol.

[0021] According to an embodiment of the present invention, the calcination temperature is 400-600 °C.

[0022] According to an embodiment of the present invention, the calcination treatment time is 2-6 h.

[0023] A third aspect of the present invention provides a catalyst comprising the titanium dioxide nanotubes described in the first aspect or titanium dioxide nanotubes obtained according to the preparation method described in the second aspect.

[0024] Therefore, this catalyst has high reactivity in the photothermal synergistic catalytic degradation of refrigerants, achieving effective degradation at low temperature, low energy consumption, high flow rate, high rate, and high refrigerant component ratio.

[0025] The fourth aspect of the present invention provides the application of the titanium dioxide nanotubes described in the first aspect, or the titanium dioxide nanotubes obtained according to the preparation method described in the second aspect, or the catalyst described in the third aspect, in the catalytic degradation of refrigerants.

[0026] This enables effective degradation at low temperatures, with low energy consumption, high flow rates, high speeds, and a high proportion of refrigerant components.

[0027] The fifth aspect of the present invention provides a method for degrading a refrigerant, wherein the method uses titanium dioxide nanotubes as described in the first aspect, or titanium dioxide nanotubes obtained according to the preparation method described in the second aspect, or the catalyst described in the third aspect to perform photothermal synergistic catalytic degradation of the refrigerant.

[0028] This enables effective degradation at low temperatures, with low energy consumption, high flow rates, high speeds, and a high proportion of refrigerant components.

[0029] According to embodiments of the present invention, the refrigerant includes at least one selected from 1,1,1,2-tetrafluoroethane, difluoromethane, difluorochloromethane, chloroform, 1,1,1,3,3-pentafluoropropane, and hexafluoropropane.

[0030] According to an embodiment of the present invention, the photothermal synergistic catalytic degradation is carried out at 25-240 °C, with a degradation time of 0-1000 min and a light intensity of 0.5-3 W / cm². 2 .

[0031] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0032] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0033] Figure 1 The XRD pattern of TNT-120 prepared in Example 1 of this invention is shown;

[0034] Figure 2 The image shown is a high-magnification SEM image of TNT-120 obtained in Embodiment 1 of the present invention;

[0035] Figure 3 The N2 adsorption-desorption curves of TNT-120 and anatase TiO2 nanospheres prepared in Example 1 of this invention are shown.

[0036] Figure 4 The BJH pore size distribution curves of TNT-120 and anatase TiO2 nanospheres prepared in Example 1 of the present invention are shown.

[0037] Figure 5 The degradation curves of 1,1,1,2-tetrafluoroethane by photothermal synergistic catalytic degradation using anatase TiO2 nanospheres and TNT-120 prepared in Example 1 of this invention are shown.

[0038] Figure 6 The degradation curve of 1,1,1,2-tetrafluoroethane by TNT-120 photothermal synergistic catalytic degradation in Example 2 of the present invention is shown.

[0039] Figure 7 The degradation curves of 1,1,1,2-tetrafluoroethane by photothermal synergistic catalytic degradation of each catalyst in Comparative Example 1 of the present invention are shown.

[0040] Figure 8 The reaction rates of each catalyst at different temperatures are shown when the degradation rate of 1,1,1,2-tetrafluoroethane in Comparative Example 1 of the present invention is 50%. The data, from left to right, represent the catalytic degradation of 1,1,1,2-tetrafluoroethane by a-TiO2 at 120 °C, the catalytic degradation of 1,1,1,2-tetrafluoroethane by a-TiO2 at 200 °C, the catalytic degradation of 1,1,1,2-tetrafluoroethane by P25 at 120 °C, the catalytic degradation of 1,1,1,2-tetrafluoroethane by P25 at 200 °C, the catalytic degradation of 1,1,1,2-tetrafluoroethane by ZnO at 120 °C, the catalytic degradation of 1,1,1,2-tetrafluoroethane by ZnO at 200 °C, the catalytic degradation of 1,1,1,2-tetrafluoroethane by g-CN at 120 °C, the catalytic degradation of 1,1,1,2-tetrafluoroethane by g-CN at 200 °C, the catalytic degradation of 1,1,1,2-tetrafluoroethane by BP-1 at 120 °C, and the catalytic degradation of 1,1,1,2-tetrafluoroethane by BP-1 at 200 °C. Catalytic degradation of 1,1,1,2-tetrafluoroethane at ℃, BP-2 catalytic degradation of 1,1,1,2-tetrafluoroethane at 120 ℃, and BP-2 catalytic degradation of 1,1,1,2-tetrafluoroethane at 200 ℃. Detailed Implementation

[0041] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0042] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0043] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0044] To facilitate understanding of the invention, certain technical and scientific terms are specifically defined below. Unless otherwise expressly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains.

[0045] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this invention, but do not exclude other aspects.

[0046] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0047] According to embodiments of the present invention, a first aspect provides titanium dioxide nanotubes, wherein the titanium dioxide nanotubes are anatase crystals with a diameter of 10 nm-10 μm and a specific surface area of ​​39.81-151.77 cm². 2 / g, the titanium dioxide nanotubes have mesoporous and microporous structures.

[0048] Compared to commonly used catalyst types in existing technologies (such as titanium dioxide nanospheres), the titanium dioxide nanotubes provided by this invention have a larger specific surface area and a more abundant mesoporous and microporous structure, resulting in high adsorption capacity, high catalytic activity, and excellent mass transfer performance. Specifically, the larger specific surface area of ​​these titanium dioxide nanotubes provides more adsorption sites, thereby enhancing their adsorption capacity for gas molecules. The larger specific surface area and more abundant mesoporous and microporous structure of these titanium dioxide nanotubes provide reactant molecules with more contact opportunities and reaction pathways, thus improving catalytic efficiency and selectivity. Furthermore, the mesoporous and microporous structure of the material also facilitates gas transport and diffusion within the material, reducing mass transfer resistance and improving the efficiency of the material in the mass transfer process.

[0049] In this invention, the diameter of the titanium dioxide nanotubes can be obtained by scanning electron microscopy, and the specific surface area can be determined by gas adsorption BET method according to GB / T 19587-2004.

[0050] According to a specific embodiment of the present invention, the diameter of the titanium dioxide nanotubes is preferably 10-50 nm, and the specific surface area is preferably 99.66-151.77 cm². 2 / g

[0051] According to a specific embodiment of the present invention, the volume percentage of the mesopores is 5%-15%, and the volume percentage of the micropores is 85%-95%.

[0052] In this invention, the volumes of mesopores and micropores can be obtained by testing using the BJH method.

[0053] According to embodiments of the present invention, a second aspect provides a method for preparing the titanium dioxide nanotubes described in the first aspect, comprising:

[0054] (1) Mix the titanium source and alkaline reagent and carry out a hydrothermal reaction to obtain a precipitate, and then perform acid washing on the precipitate.

[0055] In this step, the titanium source is brought into contact with an alkaline compound, which allows the titanium element to exist in the form of titanate precipitate. The titanate is then converted into titanic acid by acid washing.

[0056] According to specific embodiments of the present invention, the type of titanium source is not particularly limited, and those skilled in the art can select it as appropriate, including but not limited to titanium dioxide, titanium tetrachloride, tetrabutyl titanate, etc.

[0057] According to a specific embodiment of the present invention, the particle size range of the titanium source is not particularly limited, but is preferably 25-500 nm, thereby enabling dispersed nucleation and accelerating the synthesis reaction rate.

[0058] According to specific embodiments of the present invention, the type of alkaline reagent is not particularly limited, and those skilled in the art can select it as appropriate, including but not limited to sodium hydroxide, potassium hydroxide, ammonia, etc.

[0059] According to specific embodiments of the present invention, the ratio of titanium source to alkaline reagent is not particularly limited, that is, titanate can be prepared.

[0060] According to a specific embodiment of the present invention, the temperature and time of the hydrothermal treatment are not particularly limited, and those skilled in the art can select them according to the circumstances. The temperature of the hydrothermal treatment can be 100-200 °C, and the time can be 24-72 h.

[0061] According to specific embodiments of the present invention, the type of acid used in the pickling process is not particularly limited, and those skilled in the art can select it as appropriate, such as hydrochloric acid. Specifically, the pH value of the solution can be adjusted to 0.5-2 through pickling, thereby achieving a better pickling effect. The pickling time is also not particularly limited and can be adjusted according to the pickling situation.

[0062] According to a specific embodiment of the present invention, this step may further include: washing the precipitate until the solution pH is neutral, followed by acid washing. This can better remove impurity ions from the precipitate.

[0063] (2) The precipitate after acid washing is washed until the pH value of the solution is neutral, mixed with the dispersant, and separated to obtain the precursor.

[0064] Acid washing generates some soluble impurities, which can be removed by precipitation washing, resulting in a higher purity precursor. Furthermore, mixing the washed precipitate with a dispersant prevents subsequent precursor aggregation.

[0065] According to a specific embodiment of the present invention, "neutral" should be understood as a pH value of 6.5-8.

[0066] According to specific embodiments of the present invention, the type of dispersant is not particularly limited, and those skilled in the art can select it as appropriate. Preferably, it is a compound with low surface tension, including but not limited to acetone, tert-butanol, etc.

[0067] According to specific embodiments of the present invention, the separation method is not particularly limited, and those skilled in the art can choose according to the circumstances, such as centrifugation.

[0068] According to a specific embodiment of the present invention, the obtained precursor can be dried and then calcined.

[0069] (3) The precursor is calcined to obtain the titanium dioxide nanotubes.

[0070] According to specific embodiments of the present invention, the temperature and time of the calcination treatment are not particularly limited, and those skilled in the art can select them as appropriate. The calcination temperature can be 400-600℃, and the time can be 2-6 hours. The calcination atmosphere can be air, argon, nitrogen, helium, etc.

[0071] According to embodiments of the present invention, a third aspect of the present invention provides a catalyst comprising the titanium dioxide nanotubes described in the first aspect or titanium dioxide nanotubes obtained according to the preparation method described in the second aspect.

[0072] The titanium dioxide nanotubes provided by this invention can be used alone as a catalyst, or in combination with other catalysts or additives.

[0073] According to embodiments of the present invention, a fourth aspect of the present invention provides the application of the titanium dioxide nanotubes described in the first aspect, or the titanium dioxide nanotubes obtained according to the preparation method described in the second aspect, or the catalyst described in the third aspect, in the catalytic degradation of refrigerants.

[0074] According to an embodiment of the present invention, a fifth aspect of the present invention provides a method for degrading a refrigerant, the method employing titanium dioxide nanotubes as described in the first aspect, or titanium dioxide nanotubes obtained according to the preparation method described in the second aspect, or a catalyst as described in the third aspect to perform photothermal synergistic catalytic degradation of the refrigerant.

[0075] The titanium dioxide nanotubes provided by this invention have a larger specific surface area and a richer mesoporous and microporous structure, and can be used as catalysts for the photothermal synergistic catalytic degradation of refrigerants, achieving effective degradation at low temperature, low energy consumption, high flow rate, high rate, and high refrigerant component ratio.

[0076] According to specific embodiments of the present invention, the type of refrigerant is not particularly limited, and those skilled in the art can select it as appropriate, such as 1,1,1,2-tetrafluoroethane, difluoromethane, difluorochloromethane, chloroform, 1,1,1,3,3-pentafluoropropane, hexafluoropropane, etc.

[0077] According to a specific embodiment of the present invention, the temperature of the photothermal synergistic catalytic degradation is not particularly limited and can be carried out at 25-240 °C, with a degradation time of 0-1000 min.

[0078] According to a specific embodiment of the present invention, the light source for the photothermal synergistic catalytic degradation is not particularly limited and may be a xenon lamp, etc., with a light intensity of 0.5-3 W / cm². 2 .

[0079] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0080] The anatase TiO2 nanospheres used in the following examples were manufactured by McLean Corporation, with a size of 5-10 nm, and are hydrophilic and oleophilic.

[0081] Example 1

[0082] This embodiment provides a method for preparing titanium dioxide nanotubes:

[0083] 2.5 g of P25-TiO2 powder (titanium dioxide of anatase and rutile mixed phase with an average particle size of 25 nm) was dissolved in 70 mL of 10 M NaOH solution and hydrothermally heated at 120 °C for 24 h. The resulting solid precipitate was washed with deionized water until neutral, and then 0.1 M HCl was added to adjust the pH of the solution to 2. The solution was stirred for 24 h for acid washing.

[0084] The acid-washed solid precipitate was centrifuged with deionized water until neutral, and then washed once more with acetone. The centrifuged powder was then slowly dried at 40°C to obtain the precursor (denoted as TNTP-120). One g of the obtained precursor powder was placed in a muffle furnace and dried at 5°C / min. -1 The temperature was increased to 500℃ and calcined for 4 h to obtain nanotube-shaped TiO2 (denoted as TNT-120).

[0085] Structural characterization:

[0086] (1) The prepared TNT-120 was subjected to X-ray diffraction (XRD) test to obtain... Figure 1 The results showed that the prepared TNT-120 was in the anatase crystal form;

[0087] (2) The prepared TNT-120 was tested by scanning electron microscopy (SEM). Figure 2 The 100,000x scanning electron microscope image shows a distinct nanotube structure with a diameter of about 20 nm.

[0088] (3) The prepared TNT-120 was subjected to gas adsorption-desorption tests, and its N2 adsorption-desorption curve is shown in the figure. Figure 3 It can be seen that TNT-120 has a larger specific surface area, approximately 150 cm², compared to anatase TiO₂ nanospheres. 2 / g (the specific surface area of ​​anatase TiO2 nanospheres is approximately 60 cm²) 2 / g);

[0089] (4) The prepared TNT-120 was subjected to BJH pore size distribution analysis, and the results are shown in the figure. Figure 4 Compared to anatase TiO2 nanospheres, TNT-120 exhibits a greater number of mesoporous and microporous structures. Furthermore, the mesopore volume of TNT-120 was calculated to be 0.8021 cm³ based on the BJH pore size distribution curve. 3 / g, micropore volume is 0.08998 cm³ 3 / g, corresponding to a mesoporous volume ratio of 89.9% and a microporous volume ratio of 10.1%.

[0090] Performance testing:

[0091] Anatase TiO2 nanospheres and TNT-120 were used for photothermal synergistic catalytic degradation of 1,1,1,2-tetrafluoroethane (R134a). The initial concentration of 1,1,1,2-tetrafluoroethane was 3.5 mmol·L⁻¹. -1 The temperature was 120℃, the light source was a full-spectrum xenon lamp, and the light intensity was 0.87 W / cm². 2 Before the reaction, 100 mg of catalyst was ultrasonically dispersed in 1 mL of ethanol. The resulting suspension was then uniformly drop-coated onto a catalyst support (a 4 cm diameter Ti metal sheet) and dried. The catalyst-loaded Ti sheet was then placed in a photothermal catalytic reactor, which was evacuated and injected with the corresponding concentration of reaction gas. After the temperature stabilized, the xenon lamp was turned on, and detection began. The concentration of R134a was detected using an Agilent 7890B gas chromatograph. Results are shown below. Figure 5 It can be seen that under the same conditions, anatase TiO2 nanospheres require more than 100 minutes to achieve more than 95% degradation, while TNT-120 can achieve more than 95% degradation in less than 20 minutes, with a significant improvement in degradation rate.

[0092] Example 2

[0093] The photothermal synergistic catalytic degradation of R134a was performed using TNT-120 prepared in Example 1.

[0094] The specific method is similar to the performance test section in Example 1, except that: a mixed gas with an initial R134a concentration of 0.1 mol / L and an O2 concentration of 0.2 mol / L is introduced into the reactor; the reactor temperature is set to 180 ℃; and a Pofil monochromatic 365 nm-100 W LED lamp is used as the light source. The degradation data is shown in […]. Figure 6 The result is consistent with the model's prediction.

[0095] Comparative Example 1

[0096] The only difference between this comparative example and Example 1 is the use of a different type of catalyst, as detailed in Table 1.

[0097] Table 1

[0098]

[0099] a-TiO2 refers to the anatase TiO2 nanospheres mentioned earlier, and P25 refers to the P25-TiO2 mentioned earlier. The preparation method of g-CN is as follows: weigh 20 g of urea and calcine it in a muffle furnace at 520 ℃ for 4 h. The preparation method of BP-1 is as follows: mix 9 mmol of Bi(NO3)3·5H2O and 54 mmol of NaH2PO4 in 65 mL of aqueous solution, hydrothermally heat at 160 ℃ for 24 h, and then wash with water and ethanol alternately for 4 rounds each, and then dry.

[0100] The results of photothermal synergistic catalytic degradation of R134a using the catalysts in Table 1 (specific method as in Example 1) are shown below. Figure 7 ,and Figure 5 The comparison shows that the TNT-120 provided by this invention has higher catalytic activity and can significantly improve the degradation rate of the refrigerant. Furthermore, the catalysts in Table 1 were further analyzed, and the reaction rates of each catalyst were tested at different degradation temperatures (120 °C and 200 °C) when the R134a degradation rate reached 50%. The results are shown in [Table 1]. Figure 8 Using TNT-120 as a catalyst, the reaction rate was 28.7 μmol·min⁻¹ when the R134a degradation rate reached 50% at 120 °C. -1 At 200 °C, the reaction rate was 40.3 μmol·min when the degradation rate of R134a reached 50%. -1 ,and Figure 8 The results show that the catalyst provided by this invention has a higher reaction rate and higher catalytic efficiency.

[0101] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0102] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing titanium dioxide nanotubes, characterized in that, The titanium dioxide nanotubes are in the anatase crystal form, with a diameter of 10 nm-50 nm and a specific surface area of ​​151.77 m². 2 / g, the titanium dioxide nanotubes have mesoporous and microporous structures, and the mesoporous volume is 0.8021 cm³. 3 / g, the micropore volume is 0.08998 cm³. 3 / g, corresponding to a mesoporous volume ratio of 89.9% and a microporous volume ratio of 10.1%. The method includes: Titanium dioxide and sodium hydroxide are mixed and subjected to a hydrothermal reaction to obtain a precipitate. The precipitate is washed until the pH value is neutral, and then subjected to acid washing. The particle size of the titanium dioxide is 25-500 nm. The hydrothermal treatment temperature is 100-200 °C, and the hydrothermal treatment time is 24-72 h. The precipitate, after acid washing, is washed until the pH of the solution is neutral, and then mixed with at least one of acetone and tert-butanol to obtain the precursor. The precursor is calcined to obtain the titanium dioxide nanotubes. The calcination temperature is 400-600 °C, and the calcination time is 2-6 h. The calcination is carried out in at least one of air, argon, nitrogen, and helium.

2. A titanium dioxide nanotube prepared by the preparation method of claim 1, characterized in that, The titanium dioxide nanotubes are in the anatase crystal form, with a diameter of 10 nm-50 nm and a specific surface area of ​​151.77 m². 2 / g, the titanium dioxide nanotubes have mesoporous and microporous structures, and the mesoporous volume is 0.8021 cm³. 3 / g, the micropore volume is 0.08998cm³. 3 / g, corresponding to a mesoporous volume ratio of 89.9% and a microporous volume ratio of 10.1%.

3. A catalyst, characterized in that, The catalyst includes the titanium dioxide nanotubes of claim 2 or the titanium dioxide nanotubes obtained by the preparation method of claim 1.

4. The application of the titanium dioxide nanotubes of claim 2, or the titanium dioxide nanotubes obtained by the preparation method of claim 1, or the catalyst of claim 3 in the catalytic degradation of refrigerants.

5. A method for degrading a refrigerant, characterized in that, The method uses the titanium dioxide nanotubes described in claim 2, or the titanium dioxide nanotubes obtained by the preparation method described in claim 1, or the catalyst described in claim 3 to perform photothermal synergistic catalytic degradation of the refrigerant.

6. The method according to claim 5, characterized in that, The refrigerant includes at least one of 1,1,1,2-tetrafluoroethane, difluoromethane, difluorochloromethane, chloroform, 1,1,1,3,3-pentafluoropropane, and hexafluoropropane. The photothermal synergistic catalytic degradation was carried out at 25-240 °C, with a degradation time of 0-1000 min and a light intensity of 0.5-3 W / cm². 2 .

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