α-MnO2 / TiO2 multi-defect ternary composite crystals and their preparation and application

Abstract

The present invention relates to the field of gas catalysis technology, and in particular to α-manganese dioxide / titanium dioxide multi-defect ternary composite crystals and their preparation and application. The present invention utilizes the surface of the catalytic material to contain different kinds of electron oxygen vacancy active sites (electron-holes). When the coverage of multi-electron highly active oxygen vacancies reaches a certain proportion, it is supplemented by voltage to increase the defect activity and thus increase the activity of the catalytic material; thus, low-temperature and high-efficiency catalytic oxidation of a series of concentrations of NO gas can be achieved. The catalytic oxidation device used in the α-MnO2 / TiO2 multi-defect ternary composite crystals of the present invention for the charge-enhanced catalytic oxidation of NO has a simple structure and is easy to operate, which can effectively shorten the catalytic process; and the device has low energy consumption, is simple and easy to understand, and reduces the operating cost of denitrification from the raw material and technical levels.

Description

Technical Field

[0001] The present invention relates to the field of gas catalysis technology, in particular to an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal and its preparation and application. Background Art

[0002] Flue gas denitrification has always been an important part of industrial production. Currently, the most widely used denitrification technology in the power and steel industries is selective catalytic reduction (SCR) technology. This technology converts NOx into N2 by consuming ammonia, ensuring that NOx emissions meet regulatory requirements. However, this technology results in a certain amount of ammonia waste and ammonia leakage. Furthermore, its final product is N2, which has low recycling value and does not utilize efficient resource recycling. In response to further demands from the environmental protection industry and new trends in resource utilization, oxidizing water-insoluble NO gas into more acidic NO2 gas with higher solubility, and then converting NOx into various usable nitrate compounds, biomass products, and other products with resource utilization value through methods such as acid, alkali, and biological absorption, is a more promising and economically beneficial technical route. For example, CN202110225741X discloses a technical means of introducing NOx flue gas into sludge and coordinating anaerobic digestion pretreatment. The article mentions that when the NOx ratio of flue gas is NO:NO2=1:1, the synergistic treatment effect is best, which also further illustrates the usefulness and importance of catalytic oxidation of NO.

[0003] In oxidation-based denitrification, the oxidation step primarily involves two methods: direct oxidation of NO using a gaseous or liquid oxidant and catalytic oxidation of NO using a catalyst. The former is a simple process, but oxidant consumption is positively correlated with NO emissions. The O3 generators and electron beam accelerators or high-voltage discharge equipment required for O3 oxidation, as well as plasma technology, are complex to operate, energy-intensive, and difficult to maintain, making large-scale applications difficult to ensure safety and economic efficiency. The latter utilizes residual oxygen in flue gas as an oxidant to oxidize NO, making it suitable for large-scale industrial production. In summary, developing catalysts with low raw material costs, simple preparation methods, and high activity for catalytic NO oxidation is a crucial step in this research. Summary of the Invention

[0004] To address the above-mentioned issues, the present invention provides a multi-defect ternary α-manganese dioxide / titanium dioxide composite crystal, and its preparation and application, namely, a multi-defect ternary α-MnO2 / TiO2 composite crystal. The present invention utilizes the presence of different electron-oxygen vacancy active sites on the surface of the catalytic material. When the coverage of the multi-electron, highly active oxygen vacancies reaches a certain ratio, voltage is applied to enhance the defect activity, thereby enhancing the activity of the catalytic material. This allows for the low-temperature, high-efficiency catalytic oxidation of NO gas over a range of concentrations.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The first object of the present invention is to provide an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal (α-position crystal form), wherein the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal includes a nanoscale P25 TiO2 carrier and MnO2 connected to TiO2 via chemical bonds and coordination bonds.

[0007] In one embodiment of the present invention, the specific surface area of ​​the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is 45-55 m 2 / g.

[0008] In one embodiment of the present invention, the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal contains MnO2 defect types of single electrons, double electron pairs and multi-electron oxygen vacancies, and the defect density is not less than 1 / 10 in normal oxygen units.

[0009] In one embodiment of the present invention, the Mn / O ratio in the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is 1 / 1.5 to 1 / 1.8.

[0010] In one embodiment of the present invention, the resistivity of the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is less than 50Ω / m.

[0011] A second object of the present invention is to provide a method for preparing an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal, comprising the following steps:

[0012] (1) Add 3.68 g of manganese acetate to 200 ml of deionized water and stir magnetically for 30 minutes to form a homogeneous manganese acetate solution;

[0013] 6.58 g of P25 TiO2 powder was placed in the above manganese acetate solution and stirred continuously to obtain a mixed solution;

[0014] 0.5 g of hexadecyltrimethylammonium bromide was added to the mixed solution to increase its particle dispersion, and NaOH was added to adjust its pH to 8-9 to increase the loading capacity and dispersion, thereby obtaining a uniform colloidal phase A.

[0015] (2) Dissolve 1.58 g of potassium permanganate in 50 ml of water and stir with a magnetic stirrer for 30 minutes to obtain a homogeneous phase B;

[0016] (3) The oxidant solution is dropped into the colloidal phase A, and then the homogeneous phase B is added and stirred to form a brown MnO2 precipitate;

[0017] (4) the mixture obtained in step (3) was placed in a polytetrafluoroethylene-lined reactor and heated at 140-180° C. for 2-4 hours;

[0018] (5) After step (4), the obtained liquid was cooled to room temperature, placed in a centrifuge tube, and centrifuged at 3500 r / min for 10 min. The centrifuge tube was removed, the supernatant was discarded, and the precipitate was washed with deionized water. This operation was repeated 3 times. After that, the bottom material was removed and placed in a heating kiln, sealed with a perforated protective film, and placed in a vacuum drying oven for vacuum drying at 80°C for 12 hours.

[0019] (6) The dried material is taken out, crushed, ground, and sieved to obtain an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal.

[0020] The dosage ratio of P25 TiO2, manganese acetate, sodium hydroxide, and cetyltrimethylammonium bromide can be adjusted according to the following chemical formula:

[0021] 2KMnO4(158)+3(CH3COO)2Mn·4H2O(245)+2H2O=5MnO2↓(87)+

[0022] 2CH3COOK+4CH3COOH

[0023] The added P25 TiO2 needs to be in a ratio of Mn / Ti = 0.3 compared to the final generated MnO, a suitable amount of surfactant can be added, and sodium hydroxide can be added until the alkalinity of the solution is 8-9.

[0024] In one embodiment of the present invention, in step (1), the TiO2 material is nano-sized TiO2 with a particle size of 25-50 nm.

[0025] In one embodiment of the present invention, in step (3), the oxidant is selected from potassium permanganate or ammonium persulfate.

[0026] In one embodiment of the present invention, in step (6), the particle size of the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is 200 mesh.

[0027] A third object of the present invention is to provide a device for charge-enhanced catalytic oxidation of NO. During use, an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is placed in the device for reaction (α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal charge-enhanced catalytic oxidation of NO). The device comprises an organic glass reactor, a power supply, and an electrical transmission device.

[0028] The screw caps at both ends of the organic glass reactor are connected by insulating polyester plastic, with a middle metal inside. The middle metal in the organic glass tube reactor is connected to the power supply using an electric transmission device;

[0029] The electrical transmission device is an organic metal wire, a conductor and aluminum foil, and the resistivity of the organic metal wire is less than 10 -3 Ω / cm;

[0030] The power supply is a 32V AC power supply voltage, and the AC frequency conversion frequency is above 60hz.

[0031] The application steps of the device for charge-enhanced catalytic oxidation of NO are as follows:

[0032] (A1) placing an α-MnO2 / TiO2 multi-defect ternary composite crystal in an organic glass tube reactor, and connecting the middle metal of the organic glass tube reactor to an AC power supply using an electrical transmission device;

[0033] (A2) connecting a nitric oxide gas source and an oxygen gas source to a plexiglass tube reactor using conduits, respectively, and then connecting the plexiglass tube reactor to an alkali solution absorption tank using a conduit glass tube, wherein a composite gas detector is also provided on the conduit glass tube;

[0034] (A3) Start the reaction. When the catalytic efficiency of the reaction is lower than 50% of the initial oxidation efficiency, turn off the nitric oxide gas source and the composite gas detector; turn off the oxygen gas source after the nitric oxide gas is completely expelled.

[0035] In one embodiment of the present invention, during the reaction, the voltage is 0.5 V, the NO concentration is 500 ppm to 2500 ppm, and the oxygen content in the air is 21%.

[0036] In one embodiment of the present invention, the flow volume space velocity of nitric oxide is 500~5000h -1 ; The oxygen flow volume space velocity is 500~5000h -1 .

[0037] The α-MnO2 / TiO2 multi-defect ternary composite crystal of the present invention serves as an adsorbent for gas-phase adsorption and a catalyst for gas-catalyzed oxidation reactions. For polar or dipole gas molecules, their corresponding surface electrical properties are induced by the electrostatic attraction of the active sites on the catalytic material, which are enhanced by the charge. The charged catalytic material exhibits varying adsorption and catalytic abilities for gas molecules of different polarities. When surface oxygen vacancies reach a certain concentration and electricity is applied, the material's gas adsorption and catalytic abilities also change accordingly, allowing it to respond to flue gases of varying composition based on varying voltages and the material's activity. During the adsorption process, the surface oxygen vacancies form a stronger redox trend after being charged, and become easy to adsorb gas molecules with lone electrons, electron pairs or unstable delocalized electrons. The greater the degree of polarization of the gas molecules, the easier it is for their corresponding points to be adsorbed by the charged materials and coordinate to form shared electrons. During the catalytic process, due to the influence of oxygen vacancies on the adsorbed gas, the chemical bonds of the adsorbed gas itself are affected, the electron cloud is shifted, and bond breaking is more likely to occur, which provides conditions for the subsequent reactions, reduces some reaction energy barriers, and makes the reaction easier to proceed, thereby achieving the ultimate goal of improving catalytic efficiency and reducing reaction conditions.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The catalytic oxidation device used in the charge-enhanced catalytic oxidation of NO by the α-MnO2 / TiO2 multi-defect ternary composite crystal of the present invention has a simple structure and is easy to operate, which can effectively shorten the catalytic process; it also has low energy consumption, is simple and easy to understand, and reduces the operating cost of denitrification from the raw material and technical levels.

[0040] (2) The α-MnO2 / TiO2 multi-defect ternary composite crystal of the present invention does not involve any toxic or hazardous substances and does not cause secondary risks due to leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of the connection of a device for charge-enhanced catalytic oxidation of NO using an α-MnO2 / TiO2 multi-defect ternary composite crystal;

[0042] Numbers in the figure: 101, nitric oxide gas source; 102, oxygen gas source; 201, nitric oxide flow conduit; 202, oxygen flow conduit; 301, first electromagnetic flowmeter; 302, second electromagnetic flowmeter; 401, first one-way vent valve; 402, second one-way vent valve; 501, first three-way valve air inlet; 502, second three-way valve air inlet; 503, three-way valve air outlet; 6, organic glass tube reactor; 7, catalyst; 8, AC power supply; 9, electrical transmission device; 10, gas-conducting glass tube; 11, composite gas detector; 12, alkali solution absorption tank. DETAILED DESCRIPTION

[0043] The present invention provides an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal (α-position crystal form), which includes a nano-scale P25 TiO2 carrier and MnO2 connected to TiO2 via chemical bonds and coordination bonds.

[0044] In one embodiment of the present invention, the specific surface area of ​​the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is 45-55 m 2 / g.

[0045] In one embodiment of the present invention, the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal contains MnO2 defect types of single electrons, double electron pairs and multi-electron oxygen vacancies, and the defect density is not less than 1 / 10 in normal oxygen units.

[0046] In one embodiment of the present invention, the Mn / O ratio in the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is 1 / 1.5 to 1 / 1.8.

[0047] In one embodiment of the present invention, the resistivity of the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is less than 50Ω / m.

[0048] The present invention provides a method for preparing an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal, comprising the following steps:

[0049] (1) Add 3.68 g of manganese acetate to 200 ml of deionized water and stir magnetically for 30 minutes to form a homogeneous manganese acetate solution;

[0050] 6.58 g of P25 TiO2 powder was placed in the above manganese acetate solution and stirred continuously to obtain a mixed solution;

[0051] 0.5 g of hexadecyltrimethylammonium bromide was added to the mixed solution to increase its particle dispersion, and NaOH was added to adjust its pH to 8-9 to increase the loading capacity and dispersion, thereby obtaining a uniform colloidal phase A.

[0052] (2) Dissolve 1.58 g of potassium permanganate in 50 ml of water and stir with a magnetic stirrer for 30 minutes to obtain a homogeneous phase B;

[0053] (3) The oxidant solution is dropped into the colloidal phase A, and then the homogeneous phase B is added and stirred to form a brown MnO2 precipitate;

[0054] (4) the mixture obtained in step (3) was placed in a polytetrafluoroethylene-lined reactor and heated at 140-180° C. for 2-4 hours;

[0055] (5) After step (4), the obtained liquid was cooled to room temperature, placed in a centrifuge tube, and centrifuged at 3500 r / min for 10 min. The centrifuge tube was removed, the supernatant was discarded, and the precipitate was washed with deionized water. This operation was repeated 3 times. After that, the bottom material was removed and placed in a heating kiln, sealed with a perforated protective film, and placed in a vacuum drying oven for vacuum drying at 80°C for 12 hours.

[0056] (6) The dried material is taken out, crushed, ground, and sieved to obtain an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal.

[0057] The dosage ratio of P25 TiO2, manganese acetate, sodium hydroxide, and cetyltrimethylammonium bromide can be adjusted according to the following chemical formula:

[0058] 2KMnO4(158)+3(CH3COO)2Mn·4H2O(245)+2H2O=5MnO2↓(87)+

[0059] 2CH3COOK+4CH3COOH

[0060] The added P25 TiO2 needs to be in a ratio of Mn / Ti = 0.3 compared to the final generated MnO, a suitable amount of surfactant can be added, and sodium hydroxide can be added until the alkalinity of the solution is 8-9.

[0061] In one embodiment of the present invention, in step (1), the TiO2 material is nano-sized TiO2 with a particle size of 25-50 nm.

[0062] In one embodiment of the present invention, in step (3), the oxidant is selected from potassium permanganate or ammonium persulfate.

[0063] In one embodiment of the present invention, in step (6), the particle size of the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is 200 mesh.

[0064] The present invention provides a device for charge-enhanced catalytic oxidation of NO. When in use, an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is placed in the device for reaction (α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal charge-enhanced catalytic oxidation of NO). The device includes an organic glass reactor, a power supply, and an electrical transmission device.

[0065] The screw caps at both ends of the organic glass reactor are connected by insulating polyester plastic, with a middle metal inside. The middle metal in the organic glass tube reactor is connected to the power supply using an electric transmission device;

[0066] The electrical transmission device is an organic metal wire, a conductor and aluminum foil, and the resistivity of the organic metal wire is less than 10-3 Ω / cm;

[0067] The power supply is a 32V AC power supply voltage, and the AC frequency conversion frequency is above 60hz.

[0068] The application steps of the device for charge-enhanced catalytic oxidation of NO are as follows:

[0069] (A1) placing an α-MnO2 / TiO2 multi-defect ternary composite crystal in an organic glass tube reactor, and connecting the middle metal of the organic glass tube reactor to an AC power supply using an electrical transmission device;

[0070] (A2) connecting a nitric oxide gas source and an oxygen gas source to a plexiglass tube reactor using conduits, respectively, and then connecting the plexiglass tube reactor to an alkali solution absorption tank using a conduit glass tube, wherein a composite gas detector is also provided on the conduit glass tube;

[0071] (A3) Start the reaction. When the catalytic efficiency of the reaction is lower than 50% of the initial oxidation efficiency, turn off the nitric oxide gas source and the composite gas detector; turn off the oxygen gas source after the nitric oxide gas is completely expelled.

[0072] In one embodiment of the present invention, during the reaction, the voltage is 0.5 V, the NO concentration is 500 ppm to 2500 ppm, and the oxygen content in the air is 21%.

[0073] In one embodiment of the present invention, the flow volume space velocity of nitric oxide is 500~5000h -1 ; The oxygen flow volume space velocity is 500~5000h -1 .

[0074] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0075] The following materials were used in the examples:

[0076] Potassium permanganate: granular, purchased from the exploration platform, brand Greagent.

[0077] P25 TiO2: Powdered, purchased from the exploration platform, brand Acros.

[0078] Manganese sulfate: powdered, purchased from the exploration platform, brand Adamas.

[0079] Manganese acetate tetrahydrate: granular, purchased from the exploration platform, brand Adamas.

[0080] Ammonium persulfate: granular, purchased from the exploration platform, brand Adamas.

[0081] Unless otherwise specified, all reagents used are commercially available reagents; and all detection means and methods used are conventional detection means and methods in the field unless otherwise specified.

[0082] Example 1

[0083] This embodiment provides an α-MnO2 / TiO2 multi-defect ternary composite crystal and a preparation method thereof, which specifically includes the following steps:

[0084] (S1) 3.68 g of manganese acetate was added to 200 ml of deionized water and magnetically stirred for 30 minutes to fully dissolve it, forming a homogeneous phase A. 6.58 g of P25 TiO2 powder was slowly poured into the homogeneous phase A with continuous stirring. 0.5 g of hexadecyltrimethylammonium bromide was then added to the solution to increase the dispersion of the particles. NaOH was then added to adjust the pH to 8-9 to increase the loading capacity and dispersion, thereby forming a uniform colloidal phase A.

[0085] (S2) Dissolve 1.58 g of potassium permanganate in 50 ml of water and stir with a magnetic stirrer for 30 min to obtain a homogeneous phase B.

[0086] (S3) adding the homogeneous phase B prepared in step (S2) dropwise to the colloidal phase A prepared in step (S1) while stirring continuously to produce a brown MnO2 precipitate; then charging the obtained mixture liquid into a polytetrafluoroethylene reactor and heating at 140°C for 2 hours.

[0087] (S4) After the reaction is completed, the obtained liquid is cooled to room temperature, placed in a centrifuge tube, and centrifuged at 3500 r / min for 10 minutes. The centrifuge tube is removed, the supernatant is skimmed off, and the mixture is washed with deionized water. This operation is repeated three times. After that, the bottom material is removed and placed in a heating kiln, sealed with a perforated protective film, placed in a vacuum drying oven, and vacuum dried at 80° C. for 12 hours to obtain a dry material.

[0088] (S5) taking out the dried material obtained in step (S4), crushing and grinding it, and then passing it through a 200-mesh sieve to finally obtain a finished catalyst product with a particle size of 200 mesh: α-MnO2 / TiO2 multi-defect ternary composite crystal.

[0089] The further application of α-MnO2 / TiO2 multi-defect ternary composite crystal in charge-enhanced catalytic oxidation of NO is as follows:

[0090] This embodiment uses Figure 1The device shown in the figure is connected as shown: the nitric oxide source 101 and the oxygen source 102 are connected to the three-way valve through the nitric oxide flow conduit 201 and the oxygen flow conduit 202 respectively, and the three-way valve is connected to one end of the organic glass tube reactor 6. The organic glass tube reactor 6 is used to accommodate the catalyst 7: α-MnO2 / TiO2 multi-defect ternary composite crystal. The other end of the organic glass tube reactor 6 is connected to the alkali solution absorption tank 12 through the gas-conducting glass tube 10. The middle metal of the organic glass tube reactor 6 is connected to the AC power supply 8 through the electric transmission device 9, and the electrode at the other end of the AC power supply 8 is grounded;

[0091] Furthermore, the nitric oxide flow conduit 201 is provided with a first electromagnetic flowmeter 301 and a first one-way vent valve 401, and is connected to the first three-way valve air inlet 501 of the three-way valve; the oxygen flow conduit 202 is provided with a second electromagnetic flowmeter 302 and a second one-way vent valve 402, and is connected to the second three-way valve air inlet 502 of the three-way valve; the first three-way valve air outlet 503 of the three-way valve is connected to the organic glass tube reactor 6; the two ends of the organic glass tube reactor 6 are sealed with glass fiber wool; a composite gas detector 11 is provided on the gas-conducting glass tube 10, and the end of the gas-conducting glass tube 10 away from the organic glass tube reactor 6 is inserted into the inside of the alkali solution absorption tank 12, and the alkali solution absorption tank 12 contains 2wt% NaOH solution; the electrical transmission device 9 is an organic metal wire, and its resistivity is less than 10 -3 Ω / cm; the AC power supply 8 is 32V AC power supply 8, and the AC frequency conversion frequency is above 60hz.

[0092] The catalyst 7 prepared in this example: α-MnO2 / TiO2 multi-defect ternary composite crystal is further applied to charge-enhanced catalytic oxidation of NO:

[0093] The specific operation includes the following steps:

[0094] (D1) Insert glass fiber wool into one end of the organic glass tube reactor 6, then pour the catalyst 7 into the organic glass tube reactor 6 to form a 4-5 cm cylinder, and then insert glass fiber wool into the other end as well. Screw on the plastic cap and seal it tightly to ensure airtightness.

[0095] (D2) Connect the metal wire at the middle end of the organic glass tube reactor 6 to the electric transmission device 9, which is then connected to the AC power supply 8. Adjust the voltage to approximately 0.5V. The other end of the AC power supply 8 is grounded to complete the charging of the catalytic material. Connect the gas pipes sequentially according to the diagram, and insert the final gas pipe 10 into the alkali solution absorption tank 12.

[0096] (D3) Turn on the composite gas detector 11 and adjust the parameters to "Custom - Flue Gas Test Item". Control the NO concentration to 500ppm-2500ppm and the oxygen concentration to about 21% (normal oxygen units) in the air. Adjust the oxygen and nitric oxide flow rates to 500-5000h / s via the first electromagnetic flowmeter 301, the first one-way vent valve 401, the first three-way valve inlet 501, the second electromagnetic flowmeter 302, the second one-way vent valve 402, and the second three-way valve inlet 502. -1 . When the mixed gas (nitric oxide and oxygen) flows into the organic glass tube reactor 6 containing the catalyst 7, observe the changes in the composite gas detector 11. After the reading is stable, the catalytic reaction results can be recorded. After 10 hours, when the catalytic efficiency of the reaction is less than or equal to 50% of the initial oxidation efficiency, turn off the power supply of the nitrogen monoxide gas source 101 and the composite gas detector 11. After the oxygen gas source 102 pushes out the remaining nitrogen monoxide, turn off all gas sources and open the organic glass tube reactor 6. Take out the catalyst 7, replace it or calcine it at high temperature for a long time and vacuum deoxidize it to regenerate the catalyst 7.

[0097] In this embodiment, the average NO oxidation rate is over 50%, and the highest oxidation rate can reach 60%.

[0098] Comparative Example 1

[0099] This comparative example provides a β-MnO2 / TiO2 multi-defect ternary composite crystal and a preparation method thereof, which specifically includes the following steps:

[0100] (S1) 3.78 g of manganese acetate was added to 200 ml of deionized water and magnetically stirred for 30 minutes to fully dissolve it, forming a homogeneous phase A. 6.58 g of P25 TiO2 powder was slowly poured into the homogeneous phase A with continuous stirring. 0.5 g of hexadecyltrimethylammonium bromide was then added to the solution to increase the dispersion of the particles. NaOH was then added to adjust the pH to 8-9 to increase the loading capacity and dispersion, thereby forming a uniform colloidal phase A.

[0101] (S2) 5.71 g of ammonium persulfate was dissolved in 100 ml of water and stirred with a magnetic stirrer for 30 min to obtain a homogeneous phase b.

[0102] (S3) adding the homogeneous phase B prepared in step (S2) dropwise to the colloidal phase A prepared in step (S1) while stirring continuously to produce a brown MnO2 precipitate; then, the resulting mixture liquid is placed in a polytetrafluoroethylene reactor and heated at 180°C for 18 hours.

[0103] (S4) After the reaction is completed, the obtained liquid is cooled to room temperature, placed in a centrifuge tube, and centrifuged at 3500 r / min for 10 minutes. The centrifuge tube is removed, the supernatant is skimmed off, and the mixture is washed with deionized water. This operation is repeated three times. After that, the bottom material is removed and placed in a heating kiln, sealed with a perforated protective film, placed in a vacuum drying oven, and vacuum dried at 80° C. for 12 hours to obtain a dry material.

[0104] (S5) taking out the dried material obtained in step (S4), crushing and grinding it, and then passing it through a 200-mesh sieve to finally obtain a finished catalyst product with a particle size of 200 mesh: β-MnO2 / TiO2 multi-defect ternary composite crystal.

[0105] The further application of β-MnO2 / TiO2 multi-defect ternary composite crystal in charge-enhanced catalytic oxidation of NO is as follows:

[0106] Compared with Example 1, this comparative example is the same as Example 1 except that the catalyst is the β-MnO2 / TiO2 multi-defect ternary composite crystal prepared as described above in this comparative example.

[0107] In this comparative example, after the composite gas detector has been running for a period of time and stabilized, the NO catalytic oxidation efficiency is generally lower than 50%, which does not meet the requirements of daily flue gas treatment and preliminary pretreatment, and the catalytic effect is worse than that of Example 1.

[0108] Comparative Example 2

[0109] This comparative example provides the use of a commercially available catalyst: P25 TiO2-based material in charge-enhanced catalytic oxidation of NO.

[0110] Compared with Example 1, this comparative example is the same as Example 1 except that the catalyst is a commercially available catalyst: P25 TiO2 base material.

[0111] In this comparative example, after the composite gas detector has been running for a period of time and stabilized, the NO catalytic oxidation efficiency is generally lower than 30%, which does not meet the requirements of daily flue gas treatment and preliminary pretreatment, and the catalytic effect is worse than that of Example 1.

[0112] Comparative Example 3

[0113] Compared with Example 1, this comparative example is the same as Example 1 except that the organic glass tube reactor is not connected to the AC power supply.

[0114] In this comparative example, after the composite gas detector has been running for a period of time and stabilized, the NO catalytic oxidation efficiency is generally lower than 45%, which does not meet the requirements of daily flue gas treatment and preliminary pretreatment, and the catalytic effect is worse than that of Example 1.

[0115] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. An α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal, characterized in that: The α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal includes a nano-scale P25 TiO2 carrier and MnO2 connected to TiO2 via chemical bonds and coordination bonds; The α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal contains MnO2 defect types such as single electrons, double electron pairs and multi-electron oxygen vacancies, and has a resistivity of less than 50Ω / m.

2. The α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal according to claim 1, characterized in that: The specific surface area of ​​the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is 45-55m 2 / g.

3. The α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal according to claim 1, characterized in that: The defect density of the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is not less than 1 / 10 in a normal oxygen unit.

4. The α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal according to claim 3, characterized in that: The Mn / O ratio in the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is 1 / 1.5 to 1 / 1.

8.

5. A method for preparing the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Add 3.68 g of manganese acetate to 200 ml of deionized water and stir magnetically for 30 minutes to form a homogeneous manganese acetate solution; 6.58 g of TiO2 powder was placed in the above manganese acetate solution and stirred continuously to obtain a mixed solution; 0.5 g of hexadecyltrimethylammonium bromide was added to the mixed solution to increase its particle dispersion, and NaOH was added to adjust its pH to 8-9 to increase the loading capacity and dispersion, thereby obtaining a uniform colloidal phase A. (2) Dissolve 1.58 g of potassium permanganate in 50 ml of water and stir with a magnetic stirrer for 30 minutes to obtain a homogeneous phase B; (3) Drop the homogeneous phase B into the colloidal phase A and stir to generate a brown MnO2 precipitate; (4) The mixture obtained in step (3) was placed in a polytetrafluoroethylene-lined reactor and heated at 140-180°C for 2-4 hours; (5) After step (4), the obtained liquid was cooled to room temperature, placed in a centrifuge tube, and centrifuged at 3500 r / min for 10 min. The centrifuge tube was removed, the supernatant was discarded, and the precipitate was washed with deionized water. This operation was repeated 3 times. After that, the bottom material was removed and placed in a heating kiln, sealed with a perforated protective film, and placed in a vacuum drying oven for vacuum drying at 80°C for 12 hours. (6) The dried material is taken out, crushed, ground, and sieved to obtain α-manganese dioxide / titanium dioxide multi-defect ternary composite crystals.

6. The method for preparing an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal according to claim 5, characterized in that: In step (1), the TiO2 material is nano-sized TiO2 with a particle size of 25-50 nm.

7. The method for preparing an α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal according to claim 5, characterized in that: In step (6), the particle size of the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is 200 mesh.

8. A method for using the α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal according to any one of claims 1 to 4, characterized in that: The α-manganese dioxide / titanium dioxide multi-defect ternary composite crystal is placed in a device for charge-enhanced catalytic oxidation of NO. The device includes an organic glass reactor, a power supply and an electric transmission device; The screw caps at both ends of the organic glass reactor are connected by insulating polyester plastic, and a middle metal connecting the inside and outside is provided inside. The middle metal in the organic glass tube reactor is connected to the power supply using an electric transmission device; The electrical transmission device is an organic metal wire, a conductor and aluminum foil, and the resistivity of the organic metal wire is less than 10 -3 Ω / cm; The power supply is a 32V AC power supply voltage, and the AC frequency conversion frequency is above 60hz.

Images