Gamma-MnO2 rich in oxygen vacancies as well as preparation method and application thereof
By irradiating γ-MnO2 with ultraviolet light, especially using mercury lamps, oxygen vacancy was successfully introduced into γ-MnO2, solving the problem of oxygen vacancy creating complex and polluting the environment, and achieving efficient and environmentally friendly γ-MnO2 preparation and improving its catalytic activity.
Patent Information
- Application Number
- CN202510451823.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-11
- Publication Date
- 2025-07-11
AI Technical Summary
In the prior art, the method of creating oxygen vacancy is complex and may cause pollution to the environment, making it difficult to effectively improve the catalytic activity of manganese dioxide.
By irradiating the dried γ-MnO2, especially using a mercury lamp, oxygen vacancies are introduced to prepare γ-MnO2 rich in oxygen vacancies.
A simple and low-cost large-scale preparation of γ-MnO2 rich in oxygen vacancy is achieved. This method is environmentally friendly and will not cause pollution to the environment, which improves the activity of γ-MnO2 in thermally catalytic CO oxidation.
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Figure CN120285973A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of γ-MnO2 materials, and in particular, to a γ-MnO2 rich in oxygen vacancies, a preparation method thereof, and an application thereof. Background Art
[0002] Carbon monoxide limits the use of high-efficiency internal combustion engines. Thermal catalytic CO oxidation is the best solution to achieve high efficiency and energy conservation, which can utilize the heat generated by the internal combustion engine itself.
[0003] Manganese, as a transition metal with multiple valence states, has significant potential in thermal catalytic CO oxidation. Manganese dioxide has more than 30 different phases. Based on the different connection modes of [MnO6] octahedrons, the phases of manganese dioxide can include tunnel ore (α) phase, quartz ore (β) phase, ramsdellite (R) phase, monoclinic ore (δ) phase, spinel (λ) phase, and nusseltite (γ) phase. Among them, α-MnO2, β-MnO2, and γ-MnO2 are all tunnel structures formed by the infinite extension of [MnO6] octahedrons along the c-axis. Among these phases, γ-MnO2 has two tunnels (1×1 tunnel and 1×2 tunnel), while others have only one tunnel. Therefore, γ-MnO2 can increase the activity compared with other forms of MnO2. In addition, creating oxygen vacancies is an effective method to improve catalytic activity by increasing the reducibility of materials, which has been widely used in material modification. The existing methods for creating oxygen vacancies include chelating agents and annealing, etc. However, these methods are not only complex in operation, but also the chemical substances used in the synthesis process may have an impact on the environment.
[0004] In view of this, the present invention is specifically proposed. Summary of the Invention
[0005] The purpose of the present invention is to provide a γ-MnO2 rich in oxygen vacancies, a preparation method thereof, and an application thereof to solve or improve the above technical problems.
[0006] The present invention can be implemented as follows:
[0007] In a first aspect, the present invention provides a preparation method of a γ-MnO2 rich in oxygen vacancies, including the following steps: subjecting the dried γ-MnO2 to ultraviolet light irradiation treatment.
[0008] In an optional embodiment, the ultraviolet light irradiation method includes: irradiating with a mercury lamp.
[0009] In an optional embodiment, irradiating with a mercury lamp of 950W - 1050W.
[0010] In an optional embodiment, the time of the ultraviolet light irradiation treatment is 0.25h - 2h.
[0011] In an alternative embodiment, the drying is carried out at a temperature of 55 °C to 65 °C for 6 h to 10 h.
[0012] In an alternative embodiment, γ-MnO2 is in a sea urchin-like shape.
[0013] In an alternative embodiment, the preparation of γ-MnO2 includes: mixing a divalent soluble manganese salt and a persulfate and then heating.
[0014] In an alternative embodiment, the divalent soluble manganese salt includes at least one of manganese sulfate, manganese chloride, and manganese acetate.
[0015] In an alternative embodiment, the persulfate includes at least one of ammonium persulfate and sodium persulfate.
[0016] In an alternative embodiment, the divalent soluble manganese salt is manganese sulfate monohydrate, the persulfate is ammonium persulfate, and the molar ratio of the divalent soluble manganese salt to the persulfate is 2:1 to 1:2.
[0017] In an alternative embodiment, the heating is carried out at a temperature of 88 °C to 92 °C for 20 h to 28 h.
[0018] In a second aspect, the present invention provides a γ-MnO2 rich in oxygen vacancies, which is prepared by the preparation method of any one of the foregoing embodiments.
[0019] In a third aspect, the present invention provides an application of the γ-MnO2 rich in oxygen vacancies of the foregoing embodiment in thermal catalytic CO oxidation.
[0020] The beneficial effects of the present invention include:
[0021] The present invention creatively realizes the introduction of oxygen vacancies in γ-MnO2 by means of ultraviolet light irradiation. This method is simple to operate, has a short production cycle, low production cost, and can be used to prepare γ-MnO2 rich in oxygen vacancies on a large scale. In addition, this method does not require the addition of other substances and will not cause pollution to the environment.
[0022] The γ-MnO2 rich in oxygen vacancies prepared by this method can be applied to thermal catalytic CO oxidation and has high activity in thermal catalytic CO oxidation reaction. Description of the Drawings
[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.
[0024] Figure 1 It is the surface scanning electron microscope image of γ-MnO2 in Test Example 1;
[0025] Figure 2 It is the XRD diffraction pattern of γ-MnO2 in Test Example 1 and γ-MnO2 rich in oxygen vacancies obtained with different UV irradiation times;
[0026] Figure 3 It is the scanning electron microscope image of the γ-MnO2-0.5h sample in Test Example 1;
[0027] Figure 4 It is the transmission electron microscope image of the γ-MnO2-0.5h sample in Test Example 1;
[0028] Figure 5 It is the catalytic activity diagram of γ-MnO2 in Test Example 2 and γ-MnO2 rich in oxygen vacancies obtained with different UV irradiation times;
[0029] Figure 6 It is the Arrhenius diagram of γ-MnO2 in Test Example 2 and γ-MnO2 rich in oxygen vacancies obtained with different UV irradiation times. Detailed implementation manners
[0030] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.
[0031] The γ-MnO2 rich in oxygen vacancies provided by the present invention, its preparation method and application will be specifically described below.
[0032] The present invention provides a preparation method of γ-MnO2 rich in oxygen vacancies, including the following steps: performing ultraviolet light irradiation treatment on the dried γ-MnO2.
[0033] The present invention creatively realizes the introduction of oxygen vacancies in γ-MnO2 by means of ultraviolet light irradiation. This method has simple operation, short production cycle and low production cost, and can be used to prepare γ-MnO2 rich in oxygen vacancies on a large scale. In addition, this method does not require the addition of other substances and will not cause pollution to the environment.
[0034] The present invention does not limit the specific manner of the ultraviolet light irradiation treatment. In some optional embodiments, the ultraviolet light irradiation can be performed by means of mercury lamp irradiation. Exemplarily, a mercury lamp with a power of 950W to 1050W can be used for irradiation.
[0035] In some alternative embodiments, the time of ultraviolet light irradiation treatment can be 0.25 h to 2 h, such as 0.25 h, 0.5 h, 1 h, 1.5 h or 2 h, etc., or other values within the range of 0.25 h to 2 h.
[0036] In some relatively typical embodiments, the time of ultraviolet light irradiation treatment is 0.5 h.
[0037] In addition, in some other alternative embodiments, the time of ultraviolet light irradiation treatment can also be set to be less than 0.25 h or greater than 2 h according to the actual situation.
[0038] By different ultraviolet light irradiation times, oxygen vacancies with different concentrations can be obtained.
[0039] In some alternative embodiments, before the ultraviolet light irradiation treatment, γ-MnO2 is first dried to avoid the influence of moisture on the introduction of oxygen vacancies.
[0040] Exemplarily, the drying can be carried out for 6 h to 10 h (such as 6 h, 8 h or 10 h, etc.) under the condition of 55 °C to 65 °C (such as 55 °C, 60 °C or 65 °C, etc.).
[0041] In some relatively typical embodiments, the drying can be carried out for 8 h under the condition of 60 °C.
[0042] In the present invention, γ-MnO2 is in a sea urchin-like shape and is specifically composed of a plurality of nanorods.
[0043] In some alternative embodiments, the preparation of the above γ-MnO2 may include: mixing a divalent soluble manganese salt and a persulfate and then heating.
[0044] Among them, the divalent soluble manganese salt may include, by way of example but not limitation, at least one of manganese sulfate, manganese chloride and manganese acetate. The persulfate may include, by way of example but not limitation, at least one of ammonium persulfate and sodium persulfate.
[0045] In some relatively typical embodiments, the divalent soluble manganese salt used for preparing γ-MnO2 is manganese sulfate monohydrate, the persulfate is ammonium persulfate, and the molar ratio of the divalent soluble manganese salt to the persulfate is 2:1 to 1:2, such as 2:1, 1:1 or 1:2, etc.
[0046] In some alternative embodiments, the heating can be carried out for 20 h to 28 h (such as 20 h, 24 h or 28 h, etc.) under the condition of 88 °C to 92 °C (such as 88 °C, 90 °C or 92 °C, etc.).
[0047] In some relatively typical embodiments, the heating is carried out for 24 h under the condition of 90 °C.
[0048] The γ-MnO2 prepared by the above method is free of impurity phases and has stable performance. The γ-MnO2 prepared by this method has stable performance, and ultraviolet light irradiation does not cause phase transformation on its surface. Moreover, the crystal structure of this γ-MnO2 has many defects, which facilitates the introduction of oxygen vacancies.
[0049] Correspondingly, the present invention also provides a γ-MnO2 rich in oxygen vacancies, which is prepared by the above preparation method.
[0050] Furthermore, the present invention also provides an application of the above γ-MnO2 rich in oxygen vacancies in thermal catalytic CO oxidation. For example, the γ-MnO2 rich in oxygen vacancies is used as a catalyst material to improve the conversion rate of CO.
[0051] In some relatively typical embodiments, the γ-MnO2 rich in oxygen vacancies obtained after irradiating with a 1000W mercury lamp for 0.25 h to 2 h is used for thermal catalytic CO oxidation.
[0052] In some more typical embodiments, the γ-MnO2 rich in oxygen vacancies obtained after irradiating with a 1000W mercury lamp for 0.5 h is used for thermal catalytic CO oxidation. This γ-MnO2 rich in oxygen vacancies is more likely to convert reaction molecules into activated molecules, has a lower activation energy barrier, and exhibits high performance in CO oxidation.
[0053] The features and properties of the present invention are further described in detail below in conjunction with examples.
[0054] Example 1
[0055] This example provides a preparation method of γ-MnO2 rich in oxygen vacancies, and the preparation method includes the following steps:
[0056] S1: Manganese sulfate monohydrate and ammonium persulfate are dissolved in deionized water according to a molar ratio of 1:1, and stirred to obtain a homogeneous solution. The solution is poured into a stainless steel autoclave with a polytetrafluoroethylene lining, and heated at 90 °C for 24 h to obtain sea urchin-like γ-MnO2. The γ-MnO2 is washed with deionized water and absolute ethanol, and then dried at 60 °C for 8 h.
[0057] S2: The γ-MnO2 prepared in S1 is added to a glass test tube filled with deionized water, and ultraviolet light irradiation treatment is carried out with a 1000W mercury lamp for 0.25 h under stirring conditions to introduce oxygen vacancies, obtaining γ-MnO2 rich in oxygen vacancies, denoted as γ-MnO2-0.25h.
[0058] Example 2
[0059] The difference between this example and Example 1 is that in S2, the time of ultraviolet light irradiation treatment is 0.5 h.
[0060] The oxygen vacancy-rich γ-MnO2 prepared in this example is denoted as γ-MnO2-0.5h.
[0061] Example 3
[0062] The difference between this example and Example 1 is that in S2, the time of ultraviolet light irradiation treatment is 1 h.
[0063] The oxygen vacancy-rich γ-MnO2 prepared in this example is denoted as γ-MnO2-1h.
[0064] Example 4
[0065] The difference between this example and Example 1 is that in S2, the time of ultraviolet light irradiation treatment is 2 h.
[0066] The oxygen vacancy-rich γ-MnO2 prepared in this example is denoted as γ-MnO2-2h.
[0067] Example 5
[0068] This example provides a preparation method of oxygen vacancy-rich γ-MnO2, and the preparation method includes the following steps:
[0069] S1: Dissolve manganese chloride and sodium persulfate in deionized water according to a molar ratio of 2:1, and stir to obtain a homogeneous solution. Pour the solution into a stainless steel autoclave with a polytetrafluoroethylene lining, and heat it at 88 °C for 28 h to obtain sea urchin-like γ-MnO2. Wash γ-MnO2 with deionized water and absolute ethanol, and then dry it at 55 °C for 10 h.
[0070] S2: Add the γ-MnO2 prepared in S1 into a glass test tube filled with deionized water, and perform ultraviolet light irradiation treatment with a 950 W mercury lamp for 0.25 h under stirring conditions to introduce oxygen vacancies, so as to obtain oxygen vacancy-rich γ-MnO2.
[0071] Example 6
[0072] This example provides a preparation method of oxygen vacancy-rich γ-MnO2, and the preparation method includes the following steps:
[0073] S1: Dissolve manganese acetate and ammonium persulfate in deionized water in a molar ratio of 1:2, and stir to obtain a homogeneous solution. Pour the solution into a stainless-steel autoclave with a polytetrafluoroethylene liner, and heat it at 92 °C for 20 h to obtain sea urchin-like γ-MnO₂. Wash the γ-MnO₂ with deionized water and absolute ethanol, and then dry it at 65 °C for 6 h.
[0074] S2: Add the γ-MnO₂ prepared in S1 into a glass test tube filled with deionized water, and perform ultraviolet light irradiation treatment with a 1050 W mercury lamp for 0.25 h under stirring conditions to introduce oxygen vacancies, obtaining oxygen vacancy-rich γ-MnO₂.
[0075] Test Example 1
[0076] Taking the oxygen vacancy-rich γ-MnO₂ prepared in Example 2 as an example, perform a structure test.
[0077] In this example, the surface scanning electron microscope image of the sea urchin-like γ-MnO₂ prepared in S1 is as Figure 1 shown. It can be seen from the figure that the synthesized γ-MnO₂ is formed by self-assembly of many nanorods, and its shape is sea urchin-like. The diameter of this γ-MnO₂ is 5 μm - 6 μm.
[0078] In this example, the XRD diffraction patterns of the sea urchin-like γ-MnO₂ prepared in S1 and the oxygen vacancy-rich γ-MnO₂ prepared in S2 are as Figure 2 shown. In addition, the oxygen vacancy-rich γ-MnO₂ prepared in Example 1 and Examples 3 - 4 was also observed for its structure, and the corresponding XRD diffraction patterns are also as Figure 2 shown. It can be seen from the figure that the synthesized γ-MnO₂ has no impurity phase, and its structure is not damaged under the irradiation of a high-energy mercury lamp.
[0079] In this example, the surface scanning electron microscope image of the oxygen vacancy-rich γ-MnO₂ prepared in S2 is as Figure 3 shown. It can be seen from the figure that the morphology of the product after mercury lamp irradiation has no obvious change compared with that before irradiation, and the oxygen vacancy-rich γ-MnO₂ is still composed of many nanorods.
[0080] In this example, the transmission electron microscope image of the oxygen vacancy-rich γ-MnO₂ after mercury lamp irradiation is as Figure 4 shown, Figure 4 where (b) in the figure is an enlarged view of the boxed area in (a). It can be seen from the figure that there are many defects in the crystal structure of the oxygen vacancy-rich γ-MnO₂, and the crystal plane spacing of 0.242 nm corresponds well to the (131) crystal plane of γ-MnO₂.
[0081] Test Example 2
[0082] The γ-MnO2 rich in oxygen vacancies prepared in Examples 1 to 4 was used as a catalyst material for the CO conversion experiment, and the γ-MnO2 prepared by S1 in Example 1 was used as a control.
[0083] The XRD diffraction patterns of γ-MnO2 and the oxygen vacancy-rich γ-MnO2 prepared by S2 in each of the above examples are also as Figure 2 shown.
[0084] The experimental method is as follows: 100 mg of the sample was mixed with 1000 mg of quartz sand and loaded into a quartz reaction tube equipped with a silicon wool block. Then, the tube was placed in a reactor, and the inlet gas (1% CO + 20% O2 + 79% N2) was introduced at a rate of 30 mL / min, and the gas hourly space velocity (GHSV) was 18000 ml·gcat -1 ·h -1 . The gas concentration during the CO catalytic oxidation reaction was detected by gas chromatography. The catalytic activity of the catalyst was measured by the CO conversion rate, as follows:
[0085]
[0086] In the formula:
[0087] [CO] in refers to the CO concentration at the reactor inlet;
[0088] [CO] out refers to the CO concentration at the reactor outlet.
[0089] Compared with γ-MnO2, the samples treated with ultraviolet light showed higher catalytic activity. The experimental results are as Figure 5 shown. It can be seen from this figure that the complete conversion temperatures (T100) of γ-MnO2, γ-MnO2-0.25h, γ-MnO2-0.5h, γ-MnO2-1h, and γ-MnO2-2h are 214 °C, 174 °C, 156 °C, 160 °C, and 165 °C, respectively.
[0090] The evaluation of the activation energy (Ea) is as follows:
[0091]
[0092] In the formula:
[0093] The unit of r is mol·g -1 s -1 ;
[0094] F refers to the total flow rate of the reaction gas;
[0095] U CORefers to the percentage of CO in the test gas;
[0096] X CO Refers to the CO conversion rate during the carbon dioxide generation process;
[0097] W cat Refers to the weight of the catalyst in the quartz reaction tube, g.
[0098] The activation energy (Ea) is calculated as follows:
[0099]
[0100] Where:
[0101] A is the pre-exponential factor in the formula;
[0102] T is the reaction temperature;
[0103] R is the ideal gas constant;
[0104] Is the partial pressure of O2;
[0105] P CO Is the partial pressure of CO;
[0106] C is a constant,
[0107] r is calculated when the CO conversion rate is less than 15%, so the effects of the generated H2O and CO2 can be ignored. xlnP CO 、ylnP O2 And lnA are considered to be approximately constant.
[0108] Therefore, Ea can be obtained from the slope of the Arrhenius plot (as Figure 6 Shown): The activation energy (Ea) values of γ-MnO2, γ-MnO2-0.25h, γ-MnO2-0.5h, γ-MnO2-1h, and γ-MnO2-2h are 62.6, 54.5, 45.2, 57.6, and 59.9 kJ / mol, respectively. The low Ea value of the γ-MnO2-0.5h sample is generally 45.2 kJ / mol, indicating that γ-MnO2-0.5h is more likely to convert reaction molecules into activated molecules, has a lower activation energy barrier, and thus exhibits high performance in CO oxidation.
[0109] In summary, the preparation method of oxygen vacancy-rich γ-MnO2 provided by the present invention is simple to operate, has a short production cycle, low production cost, and can be prepared on a large scale. The oxygen vacancy-rich γ-MnO2 prepared by this method has stable performance, and ultraviolet light irradiation does not cause phase transformation on the material surface. The oxygen vacancy-rich γ-MnO2 can be applied to thermal catalytic CO oxidation. In particular, the oxygen vacancy-rich γ-MnO2 obtained after 0.5 h of ultraviolet light irradiation has high thermal catalytic CO oxidation reaction activity and can achieve complete conversion of CO at 156 °C.
[0110] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A preparation method of oxygen vacancy-rich γ-MnO2, characterized in that, It includes the following steps: Perform ultraviolet light irradiation treatment on the dried γ-MnO2.
2. The preparation method according to claim 1, characterized in that, The way of ultraviolet light irradiation includes: using a mercury lamp for irradiation; Preferably, use a mercury lamp with a power of 950W - 1050W for irradiation.
3. The preparation method according to claim 2, wherein The time of ultraviolet light irradiation treatment is 0.25h - 2h.
4. The preparation method according to any one of claims 1 to 3, characterized in that Drying is carried out at 55°C - 65°C for 6h - 10h.
5. The preparation method according to any one of claims 1 to 3, characterized in that, The γ-MnO2 is in a sea urchin-like shape.
6. The preparation method according to claim 5, characterized in that, The preparation of the γ-MnO2 includes: mixing divalent soluble manganese salt and persulfate and then heating; Preferably, the divalent soluble manganese salt includes at least one of manganese sulfate, manganese chloride and manganese acetate; Preferably, the persulfate includes at least one of ammonium persulfate and sodium persulfate.
7. The preparation method according to claim 6, characterized in that, The divalent soluble manganese salt is manganese sulfate monohydrate, the persulfate is ammonium persulfate, and the molar ratio of the divalent soluble manganese salt to the persulfate is 2:1 to 1:
2.
8. The preparation method according to claim 6, characterized in that, Heating is carried out at 88°C - 92°C for 20h - 28h.
9. A γ-MnO₂ rich in oxygen vacancies, characterized in that, Prepared by the preparation method according to any one of claims 1 - 8.
10. Use of the oxygen vacancy-rich γ-MnO2 as described in claim 9 in thermal catalytic CO oxidation.