Ni-doped / TiO2 coated synergistically modified manganese-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses a Ni-doped / TiO2-coated synergistically modified manganese-based catalyst as well as a preparation method and application thereof, and belongs to the technical field of volatile organic compound catalytic oxidation. According to the invention, based on a Ni-doped / TiO2 coating synergistic modification method, the Ni-doped / TiO2 coating synergistic modified manganese-based catalyst is obtained through a simple synthetic route. The catalyst has the advantages that materials are low in price and easy to obtain, the preparation method is simple, efficient, economical and feasible, requirements of used equipment and instruments are simple, and the yield is high. Compared with a traditional wet impregnation or single hydrothermal one-pot preparation method, the method has the advantages that accurate regulation, control and optimization of active sites of the catalyst are more effectively realized, and the surface acidity of the catalyst is optimized. Through TiO2 coating, the catalyst can effectively relieve carbon deposition and chlorine poisoning phenomena of active components.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalytic oxidation of volatile organic compounds, and particularly relates to a manganese-based catalyst with Ni doping and TiO2 coating and a preparation method and application thereof. BACKGROUND

[0002] With the acceleration of industrialization and urbanization, the emission of volatile organic compounds (VOCs) continues to increase, which has become one of the main atmospheric pollutants, causing serious threats to the ecological environment and human health. Therefore, strict control of VOCs emission is crucial for improving air quality. Among the existing end-of-pipe technologies for VOCs, catalytic oxidation technology is considered to be one of the most promising VOCs removal technologies because it can completely decompose VOCs into harmless CO2 and H2O at a relatively low temperature, with the advantages of low energy consumption, high efficiency, and no secondary pollution.

[0003] The core of catalytic oxidation technology lies in the design and performance of catalysts. Currently, although noble metal (such as Pt and Pd) catalysts have excellent low-temperature activity, their high price, easy poisoning and deactivation, and resource scarcity limit their large-scale industrial application. Transition metal oxide catalysts, especially manganese oxides, have attracted much attention due to their low cost, strong redox ability, and environmental friendliness. However, traditional single-component manganese oxide catalysts often have low low-temperature activity, low specific surface area, poor stability, and poor resistance to poisoning (such as resistance to sulfur, chlorine, and carbon deposition), which makes it difficult to meet the actual demand for catalytic performance and service life, especially when dealing with complex and variable industrial waste gas.

[0004] Therefore, it is of great theoretical research value and practical engineering significance to provide a simple and low-cost method to synthesize a new manganese-based catalyst with excellent low-temperature catalytic activity, high stability, and good resistance to poisoning. SUMMARY

[0005] To solve the above technical problems, the application provides a manganese-based catalyst with Ni doping and TiO2 coating and a preparation method and application thereof.

[0006] To achieve the above-mentioned purpose, the application provides the following technical solutions.

[0007] One of the technical solutions of the application is to provide a preparation method of a manganese-based catalyst with Ni doping and TiO2 coating, which comprises the following steps:

[0008] The urea, manganese source and nickel source are added into water, first stirred and reacted, then hydrothermally reacted, the obtained solid product is dried, ground, calcined once to obtain a Ni-doped manganese-based oxide; the Ni-doped manganese-based oxide is dispersed in an organic solvent, an organic solution containing n-butyl titanate is added, mixed and reacted, then hydrolyzed with water, the obtained solid product is dried, ground and calcined twice to obtain the Ni-doped / TiO2-coated synergistically modified manganese-based catalyst.

[0009] The dosage ratio of the Ni-doped manganese-based oxide to the n-butyl titanate is 0.6-0.8 g:0.1-0.5 mmol.

[0010] The present application is based on the synergistic effect of metal doping to regulate the bulk structure and acidic oxide coating to optimize the surface properties, which effectively improves the VOCs catalytic oxidation performance and chlorine poisoning resistance of the manganese-based catalyst. The reason is that the d-d orbital hybridization between Mn-Ni induced by nickel doping changes the d-electron cloud distribution and bonding characteristics of Mn, which not only effectively regulates the valence state of Mn and the bond length of Mn-O, but also stabilizes the defect structure, thereby promoting the generation of abundant oxygen vacancies; in addition, by coating with an appropriate amount of TiO2, the Lewis acid sites on the surface of the catalyst are optimized and more surface defects are generated. The synergistic effect of these abundant acid sites and defect sites not only significantly accelerates the adsorption and activation steps of VOCs, thereby improving the VOCs catalytic oxidation performance of the manganese-based catalyst, but also effectively alleviates the carbon deposition and chlorine poisoning of the active sites (an appropriate amount of TiO2 coating layer can act as a protective layer, partially inhibiting the direct contact between chlorine species and active sites, thereby alleviating the chlorine poisoning effect), thereby improving the stability of the manganese-based catalyst. The doping of Ni and the coating of TiO2 can also increase the specific surface area and pore volume of the manganese-based catalyst, which is beneficial to the diffusion of reactants and products, and provides more active sites. Through the dual optimization of the redox performance and surface acidity of the catalyst, the ability of the manganese-based catalyst to catalytically oxidize VOCs at low temperature is effectively improved.

[0011] In the present application, an appropriate amount of TiO2 coating can effectively alleviate the carbon deposition and chlorine poisoning of the active sites, thereby improving the VOCs catalytic oxidation performance of the catalyst. However, if the amount of TiO2 coating is too high, it may change the optimal surface acidity or electronic structure of the catalyst, or even reduce the surface area due to the agglomeration of TiO2, thereby inhibiting the catalytic activity or even accelerating deactivation.

[0012] Preferably, the molar ratio of urea, manganese in manganese source and nickel in nickel source is 5:1:(0.05-0.5).

[0013] Most preferably, the molar ratio of urea, manganese in manganese source and nickel in nickel source is 5:1:0.05.

[0014] Preferably, the temperature of the stirring reaction is 40-50 DEG C, and the time is 40-60 min.

[0015] Preferably, the temperature of the hydrothermal reaction is 150-180 DEG C, and the time is 4-8 h.

[0016] Preferably, the temperature of the first calcination is 400-500 DEG C, the time is 4-8 h, and the temperature increasing rate is 5 DEG C / min.

[0017] Preferably, the ratio of the amount of the Ni-doped manganese-based oxide to the amount of the organic solvent is 0.6-0.8 g:40-50 mL.

[0018] Most preferably, the ratio of the amount of the Ni-doped manganese-based oxide to the amount of the organic solvent is 0.6 g:40 mL.

[0019] Optionally, the organic solvent is anhydrous ethanol.

[0020] Preferably, the temperature of the mixing reaction is 40-50 DEG C, and the time is 40-60 min.

[0021] Preferably, the temperature of the second calcination is 450-600 DEG C, the time is 3-5 h, and the temperature increasing rate is 10 DEG C / min.

[0022] The second technical scheme of the present application provides a Ni-doped / TiO2-coated manganese-based catalyst prepared by the preparation method of the Ni-doped / TiO2-coated manganese-based catalyst.

[0023] The third technical scheme of the present application provides an application of the Ni-doped / TiO2-coated manganese-based catalyst in catalytic oxidation of volatile organic compounds (VOCs).

[0024] The present application has the following beneficial technical effects:

[0025] In the present application, the metal nickel doping reduces the crystallinity of manganese oxide, increases the specific surface area of manganese oxide, regulates the valence state of Mn and the Mn-O bond length in manganese oxide, promotes the generation of oxygen vacancies, and can provide more active sites for the catalytic oxidation reaction of VOCs, which is conducive to improving the performance of catalytic oxidation of VOCs at low temperature. The coating of TiO2 optimizes the Lewis acid sites on the surface of the manganese-based catalyst, further reduces the crystallinity of Mn-Ni metal oxide, increases the specific surface area of Mn-Ni metal oxide, and generates more surface defects, which can provide more active sites for the catalytic oxidation reaction of VOCs, is conducive to improving the performance of catalytic oxidation of VOCs at low temperature, and improves the stability and chlorine poisoning resistance of the manganese-based catalyst.

[0026] This invention utilizes a Ni-doped / TiO2-coated synergistic modification method to synthesize a Ni-doped / TiO2-coated manganese-based catalyst via a simple synthetic route. This catalyst offers advantages such as inexpensive and readily available materials, a simple and efficient preparation method, cost-effectiveness, minimal equipment and instrument requirements, and high yield. Compared to traditional wet impregnation or single hydrothermal "one-pot" methods, this invention more effectively achieves precise control and optimization of catalyst active sites and surface acidity. Through TiO2 coating, the catalyst effectively alleviates carbon deposition and chlorine poisoning of the active components. In the preferred Mn... 0.95 On the TiO2-0.3 catalyst, for the typical pollutant toluene, T 90 Up to 212℃; for chlorobenzene, T 90 Reaching a temperature of 305℃, it exhibits superior catalytic performance. Compared with existing manganese-based catalysts, the manganese-based catalyst provided by this invention possesses higher low-temperature catalytic oxidation activity, better reaction stability, and resistance to carbon deposition and chlorine poisoning. It is suitable for the catalytic oxidation and removal of volatile organic compounds, especially for the low-temperature and efficient purification of pollutants such as toluene and chlorobenzene. This invention provides a theoretical basis and experimental support for the development of VOCs catalysts with good activity, high stability, and strong resistance to poisoning. Attached Figure Description

[0027] Figure 1 The images show the XRD patterns of the manganese-based catalysts prepared in Comparative Example 1, Example 1(a), and Example 2(b) of this invention.

[0028] Figure 2 The manganese-based catalyst (a) prepared in Comparative Example 1 of this invention, and the Mn in Example 1 0.95 Ni 0.05 O x (b) and Mn in Example 2 0.95 SEM image of @TiO2-0.3(c).

[0029] Figure 3 The figures show the VOCs catalytic oxidation performance of the manganese-based catalysts obtained in Examples 1-2 and Comparative Example 1 of this invention; wherein, (a) is a graph showing the relationship between toluene conversion rate and temperature when each catalyst in Comparative Examples 1-2 and Example 1 catalytically oxidizes toluene, and (b) is a graph showing the relationship between Mn in Example 1. 0.95 Ni 0.05 O x The graph shows the relationship between toluene conversion and temperature during the catalytic oxidation of toluene using various catalysts in Example 2. (c) shows the relationship between Mn in Comparative Examples 1-2 and Example 1. 0.95 Ni 0.05 O x In Example 2, Mn 0.95Figure 2 shows the relationship between the conversion of chlorobenzene and the temperature when TiO2-0.3 catalyzes the oxidation of chlorobenzene.

[0030] Figure 4 Mn 0.95 Ni 0.05 O x Mn 0.95 @The results of the 24 h stability test of TiO2-0.3 catalyzing the oxidation of toluene (a) and chlorobenzene (b). DETAILED DESCRIPTION

[0031] The following detailed description is presented to enable any person skilled in the art to make and use the present application. It is not intended to limit the present application as it is to be applied to the embodiments set forth in the description and claims.

[0032] It should be noted that the present application is not limited in scope by the foregoing detailed description, which is intended as an aid in enabling others skilled in the art to practice the application. Examples of the application are provided for purposes of clarity and enhance understanding. It is intended that all such variations that come within the scope of the present application are to be considered as included in the present application.

[0033] Further, for numerical ranges expressed in the disclosure, it is intended that every numerical value within the range, including the upper and lower limits, is specifically recited. Any smaller ranges that fall within the broader ranges are also specifically recited. The upper and lower limits of these smaller ranges are also independently combinable with one another to embrace ranges not otherwise mentioned.

[0034] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application.

[0035] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended terms that are intended to mean "including but not limited to".

[0036] Unless otherwise specified, the room temperature or normal temperature in the examples and comparative examples of the present application refers to 25±3°C.

[0037] Unless otherwise specified, the raw materials in the examples and comparative examples of the present application are purchased through the market.

[0038] Example 1

[0039] Preparation method of Ni-doped manganese-based catalyst:

[0040] (1) Urea, manganese nitrate tetrahydrate and nickel acetate tetrahydrate with molar ratio of 5:1:0.05, 5:1:0.1, 5:1:0.5 respectively were dissolved in 50 mL deionized water at 40°C (urea concentration was 0.2 mol / L) to obtain a uniform solution;

[0041] (2) The uniform solution was placed in a high-pressure reaction kettle with a polytetrafluoroethylene lining and was sealed, and was reacted at 180°C for 6 h, and was naturally cooled to room temperature to obtain a suspension 1;

[0042] (3) The obtained suspension 1 was washed with deionized water and ethanol by centrifugation for 3 times, and was placed in a 60°C oven for drying for 10 h to obtain a solid powder 1;

[0043] (4) The solid powder 1 was ground with a mortar and was placed in a crucible for calcination, the calcination temperature was 400°C (the temperature rising rate was 10°C / min), and the calcination time was 6 h to obtain a Ni-doped manganese-based catalyst (denoted as Mn 0.95 Ni 0.05 O x , Mn 0.9 Ni 0.1 O x and Mn 0.67 Ni 0.33 O x ) respectively.

[0044] Example 2

[0045] Preparation method of Ni-doped / TiO2-coated synergistically modified manganese-based catalyst:

[0046] (1) 0.6 g of Mn 0.95 Ni 0.05 O x prepared in Example 1 was uniformly dispersed in 40 mL of anhydrous ethanol, and was uniformly dispersed using an ultrasonic cleaner, and the ultrasonic time was 40 min to obtain a suspension 2;

[0047] (2) Ethanol solutions containing 0.1 mmol, 0.3 mmol and 0.5 mmol of n-butyl titanate were added dropwise to the suspension 2 in sequence, and after 3 min of reaction, 1 mL of deionized water was continuously added dropwise to initiate the hydrolysis reaction to obtain a suspension 3;

[0048] (3) The suspension 3 was stirred at 90°C for 1.5 h to obtain a suspension 4;

[0049] (4) After the suspension 4 was placed to room temperature, it was washed with deionized water and ethanol by centrifugation for 3 times respectively, and was placed in a 60°C oven for drying for 10 h to obtain a solid powder 2;

[0050] (5) After grinding solid powder 2 in a mortar, it was placed in a crucible for calcination at a temperature of 450℃ (heating rate of 5℃ / min) for 3 hours to obtain Ni-doped / TiO2-coated synergistic modified manganese-based catalyst (hereinafter referred to as Mn). 0.95 @TiO2-0.1、Mn 0.95 @TiO2-0.3 and Mn 0.95 @TiO2-0.5).

[0051] Comparative Example 1

[0052] Preparation of manganese-based catalysts:

[0053] Compared with Example 1, the only difference is that the raw materials in step (1) are replaced with urea and manganese nitrate tetrahydrate in a molar ratio of 5:1. The other steps are the same as in Example 1, and the resulting manganese-based catalyst is denoted as MnO. x .

[0054] Comparative Example 2

[0055] Preparation of nickel-based catalysts:

[0056] Compared with Example 1, the only difference is that the raw materials in step (1) are replaced with urea and nickel acetate tetrahydrate in a molar ratio of 5:1. The other steps are the same as in Example 1, and the resulting nickel-based catalyst is denoted as NiO.

[0057] Performance testing:

[0058] 1. The manganese-based catalysts prepared in Examples 1-2 and Comparative Example 1 were characterized by XRD. The characterization results are shown in the figure. Figure 1 In this paper, (a) shows the XRD patterns of the manganese-based catalysts prepared in Comparative Example 1 and Example 1, and (b) shows the XRD patterns of the manganese-based catalysts prepared in Example 2.

[0059] Figure 1 The results show that the synergistic modification of Ni doping and TiO2 coating is beneficial to reducing the crystallinity of Mn3O4 in manganese-based oxide catalysts, weakening the bond energy of Mn-O bonds, and inhibiting the aggregation of Mn3O4 crystals.

[0060] 2. The manganese-based catalyst prepared in Comparative Example 1 and the Mn in Example 1 were examined using a scanning electron microscope. 0.95 Ni 0.05 O x and Mn in Example 2 0.95 Characterization was performed using @TiO2-0.3, and the characterization results are shown below. Figure 2 In this image, (a) is a SEM image of the manganese-based catalyst prepared in Comparative Example 1, and (b) is a SEM image of the Mn catalyst prepared in Example 1. 0.95 Ni 0.05 O xSEM images of (a) MnNiO2-0.3, (b) MnTiO2-0.3, and (c) MnO2-0.3 in Example 2. 0.95 SEM images of (a) MnNiO2-0.3, (b) MnTiO2-0.3, and (c) MnO2-0.3 in Example 2.

[0061] By comparing Figure 2 the micro-morphology of the manganese oxide catalysts. By comparing the SEM images of Example 1 and Comparative Example 1, it can be found that the introduction of an appropriate amount of nickel element reduces the particle size of the manganese oxide catalyst. By comparing the SEM images of Example 1 and Example 2, it can be found that TiO2coating does not significantly change the micro-morphology of the catalyst.

[0062] 3, Nitrogen adsorption-desorption experiments were performed on each manganese-based catalyst prepared in Example 1, 2 and Comparative Example 1 to determine the specific surface area, pore volume and pore size of each manganese-based catalyst. The test results are shown in Table 1.

[0063] Table 1

[0064]

[0065] As can be seen from Table 1, after nickel element doping, the specific surface area of the catalyst increases to a certain extent, Mn 0.95 Ni 0.05 O x The specific surface area of the catalyst is 51.75 m 2 / g. After TiO2coating, the specific surface area of the catalyst increases significantly, Mn 0.95 @TiO2-0.3 is 75.48 m 2 / g. It shows that nickel modification and appropriate TiO2coating are beneficial to increase the specific surface area of the catalyst, promote the effective transmission and transfer of substances in the reaction process, and improve the VOCs low-temperature catalytic oxidation performance.

[0066] 4, The VOCs catalytic oxidation performance of each catalyst prepared in Example 1, 2 and Comparative Example 1, 2 was tested, and the test results are shown in Figure 3 (a) is a graph showing the relationship between the conversion rate of toluene and the temperature when toluene is catalytically oxidized by each catalyst in Comparative Example 1-2 and Example 1, (b) is a graph showing the relationship between the conversion rate of toluene and the temperature when toluene is catalytically oxidized by each catalyst in Example 1 and Example 2, and (c) is a graph showing the relationship between the conversion rate of chlorobenzene and the temperature when chlorobenzene is catalytically oxidized by Mn 0.95 Ni 0.05 O x and Example 2, (c) is a graph showing the relationship between the conversion rate of toluene and the temperature when toluene is catalytically oxidized by each catalyst in Example 1 and Example 2, and (c) is a graph showing the relationship between the conversion rate of chlorobenzene and the temperature when chlorobenzene is catalytically oxidized by Mn 0.95 Ni 0.05 O x TiO2-0.3 in Example 2. 0.95 @TiO2-0.3.

[0067] Specifically, the reaction conditions during the test were: toluene / chlorobenzene concentration of 1000 ppm, O2 volume concentration of 20 vol.%, N2 as the equilibrium gas, total flow rate of the mixed gas of 1000 mL / min, and gas hourly space velocity of 60000 h⁻¹. -1 The catalyst loading was 0.2 g. During the experiment, a programmed temperature-controlled reactor was used to control the catalyst bed temperature, and the inlet and outlet concentrations of VOCs were detected by gas chromatography. The toluene / chlorobenzene conversion rate was calculated using the following formula:

[0068]

[0069] In equation (1), X toluene Indicates the conversion rate of toluene. in The concentration of toluene in the inlet gas (ppm) indicates the concentration of toluene in the air. out This indicates the concentration of toluene in the gas (ppm).

[0070] In equation (2), X chlorobenzene Indicates the conversion rate of chlorobenzene. [Chlorobenzene] in The concentration of chlorobenzene in the inlet gas (ppm) is [Chlorobenzene]. out This indicates the concentration of chlorobenzene in the gas (ppm).

[0071] from Figure 3 As can be seen from the catalyst in Example 1, Mn 0.95 Ni 0.05 O x The catalyst exhibits the best catalytic oxidation performance for toluene and chlorobenzene under low-temperature conditions, with the To value for the catalytic oxidation of toluene being the highest. 90 The temperature is 222℃; the T-phase of chlorobenzene catalytic oxidation. 90 The temperature was 328℃. In the catalyst of Example 2, Mn... 0.95 The TiO2-0.3 catalyst exhibits optimal catalytic oxidation performance for toluene and chlorobenzene, with a To value for the catalytic oxidation of toluene. 90 The temperature is 212℃; the T-phase of chlorobenzene catalytic oxidation. 90was 305℃. The performance of the catalysts prepared in the comparative examples and the reference example in catalyzing the oxidation of VOCs showed that the metal nickel and the appropriate amount of TiO2coating effectively improved the performance of the manganese-based catalyst in catalyzing the oxidation of VOCs at low temperature. The reason could be that the d-d orbital hybridization between Mn-Ni induced by nickel doping changed the d-electron cloud distribution and bonding characteristics of Mn, which not only effectively regulated the valence state of Mn and the Mn-O bond length, but also stabilized the defect structure, thereby generating abundant oxygen vacancies; in addition, through the appropriate amount of TiO2coating, the Lewis acid sites on the surface of the catalyst were optimized and more surface defects were generated. The rich acid sites and defect sites acted together, not only significantly accelerating the adsorption and activation steps of toluene and chlorobenzene, but also improving the stability of the catalyst, effectively alleviating the carbon deposition and chlorine poisoning of the active sites, further improving the performance of the catalyst in catalyzing the oxidation of VOCs. In addition, nickel modification and appropriate TiO2coating were beneficial to increasing the specific surface area of the catalyst, promoting the effective transmission and transfer of substances in the reaction process, and thereby improving the performance of the catalyst in catalyzing the oxidation of VOCs at low temperature.

[0072] 5. Mn 0.95 Ni 0.05 O x and Mn 0.95 @TiO2-0.3 in Example 2 in catalyzing the oxidation of toluene and chlorobenzene, the test conditions being as above, the test temperature being toluene: Mn 0.95 Ni 0.05 O x : 225℃, Mn 0.95 @TiO2-0.3: 215℃; chlorobenzene: Mn 0.95 Ni 0.05 O x : 354℃, Mn 0.95 @TiO2-0.3: 310℃, the 24h stability test results of the catalysts being shown in Figure 4 , wherein (a) is the 24h stability test results of Mn 0.95 Ni 0.05 O x and Mn 0.95 @TiO2-0.3 in Example 2 in catalyzing the oxidation of toluene, (b) is the 24h stability test results of Mn 0.95 Ni 0.05 O x and Mn 0.95 @TiO2-0.3 in Example 2 in catalyzing the oxidation of chlorobenzene.

[0073] Figure 4 , which shows that Mn 0.95After a 24-hour stability test, the toluene conversion rate of the TiO2-0.3 catalyst decreased from 100% to approximately 80%, and the chlorobenzene conversion rate decreased from 100% to approximately 85%. Meanwhile, the Mn catalyst in Example 1... 0.95 Ni 0.05 O x Catalyst in T 100 The catalyst exhibits poor stability under certain temperature conditions. After a 24-hour stability test under the same conditions, the toluene conversion rate decreased from 100% to approximately 70%, and the chlorobenzene conversion rate decreased from 100% to approximately 45%. During the catalytic oxidation of chlorobenzene, if the Cl species generated from the breaking of the C-Cl bond in the chlorobenzene molecule cannot be removed, they will adsorb onto the catalyst surface, covering the active sites and thus reducing the catalyst activity. Figure 4 As can be seen from this, Mn in Example 2 0.95 The thermal stability of the TiO2-0.3 catalyst is significantly improved, and it has strong application prospects in the low-temperature catalytic oxidation of VOCs.

[0074] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a Ni-doped / TiO2-coated manganese-based catalyst with synergistic modification, characterized in that, Includes the following steps: Urea, manganese source, and nickel source are added to water, stirred and reacted, and then subjected to a hydrothermal reaction. The resulting solid product is dried, ground, and calcined once to obtain Ni-doped manganese-based oxide. The Ni-doped manganese-based oxide is dispersed in an organic solvent, and an organic solution containing n-butyl titanate is added. The mixture is reacted, and then hydrolyzed with water. The resulting solid product is dried, ground, and calcined a second time to obtain the Ni-doped / TiO2-coated synergistically modified manganese-based catalyst. The ratio of the Ni-doped manganese-based oxide to the tetrabutyl titanate is 0.6–0.8 g: 0.1–0.5 mmol.

2. The preparation method according to claim 1, characterized in that, The molar ratio of manganese in the urea source and nickel in the nickel source is 5:1:(0.05~0.5).

3. The preparation method according to claim 1, characterized in that, The stirring reaction is carried out at a temperature of 40–50°C for 40–60 minutes.

4. The preparation method according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 150–180°C for 4–8 hours.

5. The preparation method according to claim 1, characterized in that, The calcination temperature is 400–500℃, the time is 4–8 hours, and the heating rate is 5℃ / min.

6. The preparation method according to claim 1, characterized in that, The ratio of the Ni-doped manganese-based oxide to the organic solvent is 0.6–0.8 g: 40–50 mL.

7. The preparation method according to claim 1, characterized in that, The mixing reaction is carried out at a temperature of 40–50°C for 40–60 minutes.

8. The preparation method according to claim 1, characterized in that, The secondary calcination temperature is 450–600℃, the time is 3–5 hours, and the heating rate is 10℃ / min.

9. A Ni-doped / TiO2-coated synergistically modified manganese-based catalyst prepared by the method of preparing the Ni-doped / TiO2-coated synergistically modified manganese-based catalyst according to any one of claims 1 to 8.

10. The application of the Ni-doped / TiO2-coated synergistically modified manganese-based catalyst of claim 9 in the catalytic oxidation of volatile organic compounds.

Images