Titanium dioxide nanotube as well as preparation method and application thereof

Abstract

The invention 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 to 10 [mu] m, the specific surface area is 39.81-151.77 cm < 2 > / g, and the titanium dioxide nanotube has a mesoporous and microporous structure. The catalyst can be used as a catalyst for photo-thermal synergistic catalytic degradation of a refrigerant, has high reaction activity in photo-thermal synergistic catalytic degradation of the refrigerant, and realizes effective degradation with low temperature, low energy consumption, large flow, high speed and high refrigerant component proportion.

Description

Technical Field

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

[0002] The construction of human production civilization is inseparable from the widespread application of refrigeration and air-conditioning technology. The core of refrigeration technology lies in the development of refrigerants. At present, refrigerants have undergone four generations of development, namely, chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs). At present, my country is the world's largest producer and consumer of HCFCs and HFCs refrigerants, and the annual production of the two types of refrigerants accounts for about 90% and 84% of the world. In order to avoid the destructive effect of refrigerants on the ozone layer and the impact on global warming, according to the Kigali Amendment to the Montreal Protocol (officially effective on January 1, 2019), the reduction and elimination of HCFCs and HFCs refrigerants in my country have been put on the agenda.

[0003] my country has a large demand for refrigerant destruction, but the existing refrigerant destruction technology is not yet mature. With the gradual elimination of HCFCs and HFCs refrigerants, my country will face tremendous pressure for refrigerant degradation treatment in the next few decades. The prior art discloses a method for treating CFCs refrigerants, which mixes CFCs substances with cement raw materials in a system for high-temperature sintering treatment. The mass proportion of fluorine and chlorine elements in the system is less than 0.04% and 0.5% of the total weight of CFCs refrigerants and cement raw materials, and the sintering temperature is 1400-1600°C. The existing refrigerant treatment method is a high-temperature pyrolysis method, which has high energy consumption and high cost, which is contrary to my country's original intention of energy conservation, emission reduction, low-carbon and environmental protection, and has low processing capacity. Therefore, there is an urgent need for efficient and environmentally friendly refrigerant degradation treatment methods.

[0004] Photothermal synergistic catalytic technology can achieve gentle and efficient degradation of refrigerants. The existing technology uses anatase TiO2 nanosphere catalyst to degrade refrigerants, but it takes a long time for steady-state reaction to achieve more than 95% degradation of refrigerants. Therefore, there is an urgent need for a catalyst to achieve photothermal synergistic and efficient catalytic degradation of refrigerants. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art to at least some extent. To this end, the present invention provides a titanium dioxide nanotube and a preparation method and application thereof. The titanium dioxide nanotube has a larger specific surface area and a richer mesoporous and microporous structure, and can be used as a catalyst for the photothermal synergistic catalytic degradation of refrigerants, thereby greatly improving the degradation rate of the refrigerants.

[0006] To this end, the first aspect of the present invention provides a titanium dioxide nanotube, wherein the titanium dioxide nanotube is anatase crystal, has a tube diameter of 10nm-10μm, and a specific surface area of ​​39.81-151.77cm 2 / g, the titanium dioxide nanotubes have mesoporous and microporous structures.

[0007] In order to solve the deficiencies in the prior art, the present invention provides a titanium dioxide nanotube having a larger specific surface area and a richer 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 have high reactivity in the photothermal synergistic catalytic degradation of refrigerants, achieving low temperature, low energy consumption, large flow (up to 0.1 mol / L (2.5 standard atmospheric pressure)), high rate, and high refrigerant component ratio. Effective degradation.

[0008] According to an embodiment of the present invention, the diameter of the titanium dioxide nanotubes is 10-50 nm, and the specific surface area is 99.66-151.77 cm 2 / g.

[0009] According to an embodiment of the present invention, the volume proportion of the mesopores is 5%-15%, and the volume proportion of the micropores is 85%-95%.

[0010] The second aspect of the present invention provides a method for preparing the titanium dioxide nanotubes according to the first aspect, comprising:

[0011] Mixing a titanium source and an alkaline reagent, performing a hydrothermal reaction to obtain a precipitate, and performing an acid washing treatment on the precipitate;

[0012] The acid-washed precipitate is washed until the pH value of the solution is neutral, mixed with a dispersant, and separated to obtain a precursor;

[0013] The precursor is calcined to obtain the titanium dioxide nanotubes.

[0014] Thus, the titanium dioxide nanotubes with excellent properties mentioned above are obtained.

[0015] According to an embodiment of the present invention, the titanium source includes at least one of titanium dioxide, titanium tetrachloride, and tetrabutyl titanate.

[0016] According to an embodiment of the present invention, the particle size of the titanium source is 25-500 nm.

[0017] According to an embodiment of the present invention, the alkaline reagent includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water.

[0018] According to an embodiment of the present invention, the temperature of the hydrothermal treatment is 100-200°C.

[0019] According to an embodiment of the present invention, the hydrothermal treatment time is 24-72h.

[0020] According to an embodiment of the present invention, the preparation method further comprises: washing the precipitate until the pH value of the solution is neutral, and performing an acid washing treatment until the pH value of the solution is 0.5-2.

[0021] According to an embodiment of the present invention, the dispersant includes at least one of acetone and tert-butanol.

[0022] According to an embodiment of the present invention, the temperature of the calcination treatment is 400-600°C.

[0023] According to an embodiment of the present invention, the calcination treatment time is 2-6 hours.

[0024] The third aspect of the present invention provides a catalyst, which includes 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.

[0025] Therefore, the catalyst has high reactivity in the photothermal synergistic catalytic degradation of refrigerants, achieving effective degradation at low temperature, low energy consumption, large flow, high rate, and high refrigerant component ratio.

[0026] The fourth aspect of the present invention provides the use 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 catalytic degradation of refrigerants.

[0027] This can achieve effective degradation at low temperature, low energy consumption, large flow rate, high rate and high refrigerant component ratio.

[0028] The fifth aspect of the present invention provides a method for degrading a refrigerant, wherein the method uses 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 to perform photothermal synergistic catalytic degradation of the refrigerant.

[0029] This can achieve effective degradation at low temperature, low energy consumption, large flow rate, high rate and high refrigerant component ratio.

[0030] According to an embodiment of the present invention, the refrigerant includes at least one of 1,1,1,2-tetrafluoroethane, difluoromethane, difluorochloromethane, monochlorotrifluoromethane, 1,1,1,3,3-pentafluoropropane and hexafluoropropane.

[0031] According to an embodiment of the present invention, the photothermal synergistic catalytic degradation is carried out at 25-240°C, the degradation time is 0-1000min, and the light intensity is 0.5-3W / cm 2 .

[0032] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0034] Figure 1 The XRD pattern of TNT-120 prepared in Example 1 of the present invention is shown;

[0035] Figure 2 shows a high-magnification SEM image of TNT-120 prepared in Example 1 of the present invention;

[0036] Figure 3 The N2 adsorption-desorption curves of TNT-120 and anatase TiO2 nanospheres prepared in Example 1 of the present invention are shown;

[0037] 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;

[0038] Figure 5 The degradation curves of 1,1,1,2-tetrafluoroethane degradation by photothermal synergistic catalysis using anatase TiO2 nanospheres and TNT-120 prepared in Example 1 of the present invention are shown;

[0039] 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;

[0040] Figure 7 The degradation curve of 1,1,1,2-tetrafluoroethane by photothermal synergistic catalytic degradation of each catalyst in Comparative Example 1 of the present invention is shown;

[0041] Figure 8The reaction rates of various catalysts at different temperatures when the degradation rate of 1,1,1,2-tetrafluoroethane in Comparative Example 1 of the present invention is 50% are shown. Among them, from left to right, a-TiO2 catalyzes the degradation of 1,1,1,2-tetrafluoroethane at 120°C, a-TiO2 catalyzes the degradation of 1,1,1,2-tetrafluoroethane at 200°C, P25 catalyzes the degradation of 1,1,1,2-tetrafluoroethane at 120°C, P25 catalyzes the degradation of 1,1,1,2-tetrafluoroethane at 200°C, ZnO catalyzes the degradation of 1,1,1,2-tetrafluoroethane at 120°C, and ZnO catalyzes the degradation of 1,1,1,2-tetrafluoroethane at 200°C. Tetrafluoroethane, g-CN catalytic degradation of 1,1,1,2-tetrafluoroethane at 120°C, g-CN catalytic degradation of 1,1,1,2-tetrafluoroethane at 200°C, BP-1 catalytic degradation of 1,1,1,2-tetrafluoroethane at 120°C, BP-1 catalytic degradation of 1,1,1,2-tetrafluoroethane at 200°C, BP-2 catalytic degradation of 1,1,1,2-tetrafluoroethane at 120°C, BP-2 catalytic degradation of 1,1,1,2-tetrafluoroethane at 200°C. DETAILED DESCRIPTION

[0042] 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 understood as limiting the present invention.

[0043] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0044] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0045] In order to make the present invention more easily understood, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by those skilled in the art to which the present invention belongs.

[0046] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0047] As used herein, the terms "optionally", "optional" or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0048] According to an embodiment of the present invention, the first aspect of the present invention provides a titanium dioxide nanotube, wherein the titanium dioxide nanotube is anatase crystal, has a tube diameter of 10nm-10μm, and a specific surface area of ​​39.81-151.77cm 2 / g, the titanium dioxide nanotubes have mesoporous and microporous structures.

[0049] Compared with the catalyst types commonly used in the prior art (such as titanium dioxide nanospheres), the titanium dioxide nanotubes provided by the present invention have a larger specific surface area and a more abundant mesopore and micropore structure, so that the material has high adsorption, high catalytic activity and excellent mass transfer performance. Specifically, the titanium dioxide nanotubes have a larger specific surface area and can provide more adsorption sites, thereby improving the adsorption capacity for gas molecules. The larger specific surface area and more abundant mesopores and micropore structures of the titanium dioxide nanotubes can provide more contact opportunities and reaction paths for reactant molecules, thereby improving catalytic efficiency and selectivity. In addition, the mesopore and micropore structure of the material is also conducive to the transmission and diffusion of gas inside the material, reducing mass transfer resistance and improving the efficiency of the material in the mass transfer process.

[0050] In the present invention, the diameter of the titanium dioxide nanotubes can be obtained by scanning electron microscopy, and the specific surface area can refer to GB / T 19587-2004 gas adsorption BET method for determining the specific surface area of ​​solid substances.

[0051] 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 cm 2 / g

[0052] According to a specific embodiment of the present invention, the volume proportion of the mesopores is 5%-15%, and the volume proportion of the micropores is 85%-95%.

[0053] In the present invention, the volumes of mesopores and micropores can be measured by the BJH method.

[0054] According to an embodiment of the present invention, a second aspect of the present invention provides a method for preparing the titanium dioxide nanotubes according to the first aspect, comprising:

[0055] (1) A titanium source and an alkaline reagent are mixed and subjected to a hydrothermal reaction to obtain a precipitate, and the precipitate is subjected to an acid washing treatment.

[0056] In this step, the titanium source is contacted with an alkaline compound, so that the titanium element can exist in the form of titanate precipitation, and then the titanate is converted into titanic acid through acid washing.

[0057] According to a specific embodiment of the present invention, the type of titanium source is not particularly limited, and those skilled in the art may select it according to the circumstances, including but not limited to titanium dioxide, titanium tetrachloride, tetrabutyl titanate, etc.

[0058] According to a specific embodiment of the present invention, the particle size range of the titanium source is not particularly limited, and is preferably 25-500 nm, thereby achieving dispersed nucleation and accelerating the synthesis reaction rate.

[0059] According to a specific embodiment of the present invention, the type of the alkaline reagent is not particularly limited, and those skilled in the art may select it according to the circumstances, including but not limited to sodium hydroxide, potassium hydroxide, ammonia water, etc.

[0060] According to a specific embodiment of the present invention, the ratio of the titanium source to the alkaline reagent is not particularly limited, that is, titanate can be prepared.

[0061] 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 may select them according to the circumstances. The temperature of the hydrothermal treatment may be 100-200° C., and the time may be 24-72 hours.

[0062] According to a specific embodiment of the present invention, the type of acid used in the pickling treatment is not particularly limited, and those skilled in the art can select it according to the situation, such as hydrochloric acid. Specifically, the pH value of the solution can be adjusted to 0.5-2 by pickling treatment, thereby achieving a better pickling effect. The pickling time is also not particularly limited and can be adjusted according to the pickling situation.

[0063] According to a specific embodiment of the present invention, this step may further include: washing the precipitate until the pH value of the solution is neutral, and then performing an acid wash treatment, thereby better removing impurity ions in the precipitate.

[0064] (2) washing the acid-washed precipitate until the pH value of the solution is neutral, mixing it with a dispersant, and separating to obtain a precursor.

[0065] Since the acid washing treatment will generate some soluble impurities, these impurities can be removed by precipitation washing, so that the obtained precursor has higher purity. At the same time, mixing the washed precipitate with a dispersant can prevent the subsequent precursor from agglomerating.

[0066] According to a specific embodiment of the present invention, "neutral" is understood to mean a pH value of 6.5-8.

[0067] According to a specific embodiment of the present invention, the type of dispersant is not particularly limited, and those skilled in the art may select it according to the circumstances. Compounds with low surface tension are preferred, including but not limited to acetone, tert-butanol, and the like.

[0068] According to a specific embodiment of the present invention, the separation method is not particularly limited, and those skilled in the art may select it according to the circumstances, and may select centrifugation or the like.

[0069] According to a specific embodiment of the present invention, the obtained precursor can be dried and then calcined.

[0070] (3) calcining the precursor to obtain the titanium dioxide nanotubes.

[0071] According to a specific embodiment 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 according to the situation. The temperature of the calcination treatment can be 400-600°C, and the time can be 2-6 hours. The calcination atmosphere can be selected from air, argon, nitrogen, helium, etc.

[0072] According to an embodiment of the present invention, a third aspect of the present invention provides a catalyst, wherein the catalyst comprises 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.

[0073] The titanium dioxide nanotubes provided by the present invention can be used alone as a catalyst, or can be used together with other catalysts or additives.

[0074] According to an embodiment of the present invention, the fourth aspect of the present invention provides the use 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 catalytic degradation of refrigerants.

[0075] According to an embodiment of the present invention, the fifth aspect of the present invention provides a method for degrading refrigerant, which uses 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 to perform photothermal catalytic degradation of the refrigerant.

[0076] The titanium dioxide nanotubes provided by the present invention have a larger specific surface area and richer mesopore and micropore structures, and can be used as catalysts for the photothermal synergistic catalytic degradation of refrigerants, achieving effective degradation at low temperature, low energy consumption, large flow, high rate, and high refrigerant component ratio.

[0077] According to a specific embodiment of the present invention, the type of the refrigerant is not particularly limited, and those skilled in the art may select it according to the circumstances, such as 1,1,1,2-tetrafluoroethane, difluoromethane, difluorochloromethane, monochlorotrifluoromethane, 1,1,1,3,3-pentafluoropropane, hexafluoropropane, etc.

[0078] 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., and the degradation time is 0-1000 min.

[0079] According to a specific embodiment of the present invention, the light source for the photothermal synergistic catalytic degradation is not particularly limited, and can be a xenon lamp, etc., and the light intensity can be 0.5-3W / cm 2 .

[0080] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0081] The anatase TiO2 nanospheres used in the following examples are produced by MacLean Company, have a size of 5-10 nm, and are hydrophilic and lipophilic.

[0082] Example 1

[0083] This embodiment provides a method for preparing titanium dioxide nanotubes:

[0084] 2.5 g of P25-TiO2 powder (a titanium dioxide of mixed phase of anatase crystal and rutile crystal with an average particle size of 25 nm) was dissolved in 70 mL of 10 M NaOH solution and hydrothermaled at 120 ° C for 24 h. The obtained solid precipitate was washed with deionized water until neutral, and then 0.1 M HCl was added to adjust the solution pH to 2, and stirred for 24 h for acid washing;

[0085] The solid precipitate after acid washing was centrifuged and washed with deionized water until neutral, and then centrifuged and washed once with acetone. The powder after centrifugation was then slowly dried at 40°C to obtain a precursor (denoted as TNTP-120). 1 g of the obtained precursor powder was placed in a muffle furnace and heated at 5°C / min. -1 The temperature was raised to 500°C and calcined for 4 hours to obtain nanotubular TiO2 (denoted as TNT-120).

[0086] Structural characterization:

[0087] (1) The prepared TNT-120 was subjected to an X-ray diffraction (XRD) test to obtain Figure 1 The results showed that the prepared TNT-120 was anatase crystal;

[0088] (2) The prepared TNT-120 was subjected to a scanning electron microscope (SEM) test. Figure 2 This is a 100,000x scanning electron microscope photo, which shows that a clear nanotube structure has been formed, with a tube diameter of about 20nm;

[0089] (3) The prepared TNT-120 was subjected to gas adsorption and desorption test, and its N2 adsorption and desorption curve is shown in Figure 3 It can be seen that compared with anatase TiO2 nanospheres, TNT-120 has a larger specific surface area, about 150 cm 2 / g (the specific surface area of ​​anatase TiO2 nanospheres is about 60 cm 2 / g);

[0090] (4) The prepared TNT-120 was subjected to BJH pore size distribution analysis. The results are shown in Figure 4 Compared with anatase TiO2 nanospheres, TNT-120 has more mesopores and micropores. At the same time, the mesopore volume of TNT-120 is calculated to be 0.8021 cm according to the BJH pore size distribution curve. 3 / g, micropore volume is 0.08998cm 3 / g, the corresponding mesopore volume accounts for 89.9% and the micropore volume accounts for 10.1%.

[0091] Performance Test:

[0092] Anatase TiO2 nanospheres and TNT-120 were used for photothermal catalytic degradation of 1,1,1,2-tetrafluoroethane (R134a). The initial concentration of 1,1,1,2-tetrafluoroethane was 3.5 mmol·L -1 , the temperature is 120℃, the light source is a full-spectrum xenon lamp, and the light intensity is 0.87W / cm 2 . Before the reaction, 100 mg of the catalyst was ultrasonically dispersed in 1 mL of ethanol, and then the obtained suspension was evenly dripped on the catalyst carrier (a Ti metal sheet with a diameter of 4 cm) and dried. The Ti sheet loaded with the catalyst was then placed in a photothermal catalytic reactor, the reactor was evacuated, and the reaction gas of the corresponding concentration was injected. After the temperature was raised to a stable level, the xenon lamp was turned on and the detection was started. The concentration of R134a was detected using an Agilent 7890B gas chromatograph. The results are shown in Figure 5,It can be seen that under the same conditions, anatase TiO2 nanospheres need more than 100 min to achieve more than 95% degradation, while TNT-120 can achieve more than 95% degradation in less than 20 min, and the degradation rate is greatly improved.

[0093] Example 2

[0094] The TNT-120 prepared in Example 1 was used to perform photothermal catalytic degradation of R134a:

[0095] The specific method is similar to the performance test part 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°C, and a Perfek monochromatic light 365nm-100W LED lamp is used as the light source. The degradation data results are shown in Figure 6 , which is consistent with the model prediction.

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 1 is that a different catalyst type is used. For specific information, see Table 1.

[0098] Table 1

[0099] Catalyst type source Structural features Code of this article <![CDATA[TiO2]]> Maclean <![CDATA[Anatase TiO2]]> <![CDATA[a-TiO2]]> <![CDATA[TiO2]]> Maclean Anatase + rutile mixed phase P25 ZnO Maclean Wurtzite ZnO ZnO <![CDATA[C3N4]]> Prepared according to the literature <![CDATA[Graphitic carbon nitride]]> g-CN <![CDATA[BiPO4]]> Prepared according to the literature <![CDATA[Monoclinic monazite-structured BiPO4]]> BP-1 <![CDATA[BiPO4]]> Sigma-Aldrich <![CDATA[Monoclinic BiPO4]]> BP-2

[0100] Wherein a-TiO2 is the anatase TiO2 nanospheres mentioned above, and P25 is the P25-TiO2 mentioned above. The preparation method of g-CN is: weigh 20g of urea and calcine it in a muffle furnace at 520℃ for 4h; the preparation method of BP-1 is: stir and mix 9mmol of Bi(NO3)3·5H2O and 54mmol of NaH2PO4 in 65mL of aqueous solution, hydrothermally heat at 160℃ for 24h, and then use water and ethanol to wash by centrifugation for 4 rounds alternately and then dry.

[0101] The results of photothermal catalytic degradation of R134a using the catalyst in Table 1 (the specific method is the same as in Example 1) are shown in Figure 7 ,and Figure 5 By comparison, it can be seen that the TNT-120 provided by the present invention has higher catalytic activity and can significantly increase the degradation rate of the refrigerant. At the same time, the catalysts in Table 1 were further analyzed to test the reaction rates of each catalyst when the degradation rate of R134a reached 50% at different degradation temperatures (120°C and 200°C). The results are shown in Table 1. Figure 8 TNT-120 was used as the catalyst, and the reaction rate was 28.7 μmol·min at 120°C when the degradation rate of R134a reached 50%. -1At 200℃, the reaction rate was 40.3μmol·min when the degradation rate of R134a reached 50%. -1 ,and Figure 8 From the comparison of the results, it can be seen that the catalyst provided by the present invention has a higher reaction rate and a higher catalytic efficiency.

[0102] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0103] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A titanium dioxide nanotube, characterized in that: The titanium dioxide nanotubes are anatase crystals with a tube diameter of 10 nm-10 μm and a specific surface area of ​​39.81-151.77 cm 2 / g, the titanium dioxide nanotubes have mesoporous and microporous structures.

2. The titanium dioxide nanotube according to claim 1, characterized in that: The diameter of the titanium dioxide nanotubes is 10-50 nm, and the specific surface area is 99.66-151.77 cm 2 / g; Optionally, the volume proportion of the mesopores is 5%-15%, and the volume proportion of the micropores is 85%-95%.

3. A method for preparing titanium dioxide nanotubes according to claim 1 or 2, characterized in that: include: Mixing a titanium source and an alkaline reagent, performing a hydrothermal reaction to obtain a precipitate, and performing an acid washing treatment on the precipitate; The acid-washed precipitate is washed until the pH value of the solution is neutral, mixed with a dispersant, and separated to obtain a precursor; The precursor is calcined to obtain the titanium dioxide nanotubes.

4. The preparation method according to claim 3, characterized in that: The titanium source includes at least one of titanium dioxide, titanium tetrachloride, and tetrabutyl titanate; Optionally, the particle size of the titanium source is 25-500 nm; Optionally, the alkaline agent includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water.

5. The preparation method according to claim 3, characterized in that: The temperature of the hydrothermal treatment is 100-200°C; Optionally, the hydrothermal treatment time is 24-72 hours.

6. The preparation method according to claim 3, characterized in that: The preparation method further comprises: washing the precipitate until the pH value of the solution is neutral, and performing acid washing until the pH value of the solution is 0.5-2.

7. The preparation method according to claim 3, characterized in that: The dispersant includes at least one of acetone and tert-butyl alcohol; Optionally, the calcination temperature is 400-600°C; Optionally, the calcination treatment time is 2-6h; Optionally, the calcination treatment is performed in at least one of air, argon, nitrogen and helium.

8. A catalyst, characterized in that The catalyst comprises the titanium dioxide nanotube according to claim 1 or 2 or the titanium dioxide nanotube obtained by the preparation method according to any one of claims 3-7.

9. Use of the titanium dioxide nanotube according to claim 1 or 2, or the titanium dioxide nanotube obtained by the preparation method according to any one of claims 3 to 7, or the catalyst according to claim 8 in catalytic degradation of refrigerants.

10. A method for degrading a refrigerant, characterized in that: The method uses the titanium dioxide nanotubes described in claim 1 or 2, or the titanium dioxide nanotubes obtained by the preparation method according to any one of claims 3 to 7, or the catalyst described in claim 8 to perform photothermal synergistic catalytic degradation of the refrigerant.

11. The method according to claim 10, characterized in that The refrigerant includes at least one of 1,1,1,2-tetrafluoroethane, difluoromethane, difluorochloromethane, monochlorotrifluoromethane, 1,1,1,3,3-pentafluoropropane and hexafluoropropane; Optionally, the photothermal synergistic catalytic degradation is carried out at 25-240°C, the degradation time is 0-1000 min, and the light intensity is 0.5-3 W / cm 2 .

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