Core-shell structure bifunctional catalyst for SCR (Selective Catalytic Reduction) reaction synergistic organic pollutant catalytic oxidation as well as preparation method and application of core-shell structure bifunctional catalyst

Abstract

The invention relates to a core-shell structure bifunctional catalyst for SCR reaction synergistic organic pollutant catalytic oxidation, the core of the core-shell structure bifunctional catalyst comprises a first composite active component for organic pollutant catalytic oxidation, and the first composite active component is wrapped with titanium dioxide; a second composite active component for catalyzing an SCR reaction is loaded outside the titanium dioxide. According to the invention, catalytic oxidation active sites of organic pollutants are limited in the catalyst, and NH3-SCR active sites are arranged outside the catalyst. The partition reaction of multiple pollutants is realized, and the synergistic removal efficiency of the catalyst on organic pollutants and nitrogen oxides is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-pollutant synergistic control in environmental catalysis, and particularly relates to a core-shell structured bifunctional catalyst for SCR reaction synergistic catalytic oxidation of organic pollutants, a preparation method thereof, and an application thereof. Background Art

[0002] Nitrogen oxides and volatile organic compounds (VOCs) are the main precursors of PM2.5 and O3 in the air. Industrial flue gas is one of the important sources of nitrogen oxides and volatile organic compounds, which cause serious harm to the ecological environment and human health. At present, the selective reduction technology of reducing nitrogen oxides with NH3 (NH3-SCR) is relatively mature and has been widely commercialized in fixed-source combustion devices. Most volatile organic compounds can cause tropospheric ozone decomposition, photochemical smog, and various diseases. For many years, catalytic oxidation has been considered one of the most effective VOCs emission reduction methods due to its low cost and less secondary pollution. The temperature window for VOCs decomposition is 50 - 260 °C. The existing SCR catalysts have poor performance in catalytic oxidation of VOCs and will generate a large amount of organic by-products. Therefore, preparing a catalyst that can effectively co-remove NO x and VOCs is an important task for flue gas treatment.

[0003] CN112774687A discloses an SCR catalyst for co-removing NO and VOCs and a preparation method thereof. The SCR catalyst is obtained by doping iron oxide into a VO5-WO3 / TiO2 catalyst. The preparation method of the SCR catalyst of the present invention includes the following steps: adding titanium dioxide, ammonium metavanadate, ammonium metatungstate, and soluble iron salt into water, adding oxalic acid, stirring, then evaporating to remove water, and then calcining the obtained solid product to obtain the SCR catalyst. The prepared SCR catalyst has strong catalytic oxidation and reduction ability and can co-remove NO and VOCs, but the selectivity of the catalyst of this invention still needs to be further improved.

[0004] CN110252332A discloses a method for preparing a honeycomb VOCs catalyst using waste SCR catalyst. After dusting, cleaning with clear liquid, and rinsing with alkali solution on the waste SCR catalyst module, it is pulverized to obtain SCR catalyst powder. Finally, the obtained SCR catalyst powder is mixed evenly with active substances, binders, and lubricants, and then through a series of steps of kneading, extrusion molding, drying, and calcining, a honeycomb catalyst for catalytic oxidation of VOCs is obtained. This catalyst can maximize the utilization of waste SCR catalyst resources and reduce production costs, but its VOCs removal efficiency still needs to be improved, and there is a problem of large floor area of the catalyst.

[0005] CN115445594B discloses a preparation method of an SCR catalyst for synergistic denitrification and toluene removal. Titanium source is synthesized into titanium nanotubes; metal manganese and metal cerium are made into a mixed solution, and the active metal components are deposited on the titanium nanotubes by aerosol-assisted chemical vapor deposition method. The mixed solution is heated and atomized into an aerosol mist, and then the aerosol mist is loaded on the titanium nanotubes by using an inert gas to obtain the SCR catalyst Mn x Ce (1-x) O2-TNTs. This invention has the disadvantage of complex catalyst preparation method, and the sulfur resistance of the catalyst under complex flue gas conditions still needs to be further improved.

[0006] In view of the deficiencies of the prior art, there is an urgent need to provide a catalyst that can efficiently synergistically remove organic pollutants and NO x and has excellent catalytic performance. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a core-shell structured bifunctional catalyst for SCR reaction synergistic catalytic oxidation of organic pollutants, its preparation method and application. The active components for catalytic oxidation of organic pollutants are restricted inside the catalyst and the NH3-SCR active components are loaded outside the catalyst by stepwise preparation to obtain the core-shell structured bifunctional catalyst, and the prepared catalyst is used for the synergistic removal of organic pollutants and NO x and has good catalytic performance.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a core-shell structured bifunctional catalyst for SCR reaction synergistic catalytic oxidation of organic pollutants. The inner core of the core-shell structured bifunctional catalyst includes a first composite active component for catalytic oxidation of organic pollutants, the first composite active component is wrapped with titanium dioxide, and the second composite active component for catalyzing SCR reaction is loaded outside the titanium dioxide.

[0010] For the core-shell structured catalyst provided by the present invention, the composite active components for catalytic oxidation of organic pollutants are restricted inside the catalyst by the titanium dioxide shell layer, and the active components for SCR reaction are loaded outside the titanium dioxide shell layer. Compared with traditional catalysts, the present invention separates the catalytic oxidation region of organic pollutants and the SCR reaction region of the catalyst, thereby effectively improving the removal efficiency of the catalyst for the two pollutants.

[0011] As a preferred technical solution of the present invention, the inner core of the core-shell structured bifunctional catalyst includes a composite active component of cerium dioxide and copper oxide, the composite active component of cerium dioxide and copper oxide is wrapped with titanium dioxide, and the composite active component of vanadium pentoxide and tungsten trioxide is loaded outside the titanium dioxide.

[0012] The core-shell structured catalyst provided by the present invention uses copper oxide and cerium dioxide as the main active components for the catalytic oxidation of organic pollutants, which are confined inside the catalyst by the titanium dioxide shell layer, and vanadium pentoxide and tungsten trioxide are loaded on the outside of the titanium dioxide shell layer as the main active components for SCR. The synergistic effect of several active components is utilized to jointly promote the removal of various pollutants.

[0013] As a preferred technical solution of the present invention, the core-shell structured bifunctional catalyst comprises, by weight percentage: 0.1-1 part of copper oxide, for example, it can be 0.1 part, 0.2 part, 0.5 part, 0.8 part or 1 part, etc.; 70-80 parts of cerium dioxide, for example, it can be 70 parts, 72 parts, 75 parts, 78 parts or 80 parts, etc.; 10-16 parts of titanium dioxide, for example, it can be 10 parts, 11 parts, 12 parts, 14 parts or 16 parts, etc.; 1-5 parts of vanadium pentoxide, for example, it can be 1 part, 2 part, 3 parts, 4 parts or 5 parts, etc.; and 5-10 parts of tungsten trioxide, for example, it can be 5 parts, 6 parts, 7 parts, 8 parts or 10 parts, etc.

[0014] Preferably, the titanium dioxide is anatase titanium dioxide.

[0015] In a second aspect, the present invention provides a preparation method of the core-shell structured bifunctional catalyst as described in the first aspect, and the preparation method comprises the following steps:

[0016] (1) Mix the first precursor solution, the second precursor solution and the first solvent and carry out the first hydrothermal treatment;

[0017] (2) Add the titanium precursor to the first hydrothermal mixture obtained in step (1) and then carry out the second hydrothermal treatment. After the obtained second hydrothermal mixture is post-treated, it is subjected to the first calcination to obtain an intermediate powder;

[0018] (3) Disperse the intermediate powder in the second solvent, inject the third precursor solution and the fourth precursor solution and heat them for reaction. After the obtained mixture is post-treated, it is subjected to the second calcination to obtain the core-shell structured bifunctional catalyst.

[0019] The present invention prepares the composite active components for the catalytic oxidation of organic pollutants by the hydrothermal method; wraps the titanium precursor on the surface of the composite active components by the hydrothermal method; forms the core and shell layer structures of the core-shell catalyst; and loads the SCR composite active components on the outside of the shell layer to obtain the core-shell structured bifunctional catalyst.

[0020] As a preferred technical solution of the present invention, the first solvent in step (1) comprises ethylene glycol.

[0021] Preferably, the first precursor in step (1) comprises copper nitrate trihydrate.

[0022] Preferably, the second precursor in step (1) includes cerium nitrate hexahydrate.

[0023] Preferably, the mass-to-volume ratio of the first precursor to the solvent in the first precursor solution in step (1) is (0.05 - 0.1) g:50 mL, for example, it can be 0.05 g:50 mL, 0.06 g:50 mL, 0.07 g:50 mL, 0.08 g:50 mL, 0.09 g:50 mL, or 0.1 g:50 mL, etc.

[0024] Preferably, the mass-to-volume ratio of the second precursor to the solvent in the second precursor solution in step (1) is (18 - 28) g:50 mL, for example, it can be 18 g:50 mL, 20 g:50 mL, 22 g:50 mL, 24 g:50 mL, 26 g:50 mL, or 28 g:50 mL, etc.

[0025] Preferably, the solvent includes deionized water.

[0026] Preferably, the volume ratio of the first precursor solution to the first solvent in step (1) is 50:(200 - 400), for example, it can be 50:200, 50:250, 50:300, 50:350, 50:370, 50:380, or 50:400, etc.

[0027] Preferably, the volume ratio of the second precursor solution to the first solvent in step (1) is 50:(200 - 400), for example, it can be 50:200, 50:250, 50:300, 50:350, 50:370, 50:380, or 50:400, etc.

[0028] Preferably, the temperature of the first hydrothermal treatment in step (1) is 150 - 200 °C, for example, it can be 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, or 200 °C, etc.

[0029] Preferably, the time of the first hydrothermal treatment in step (1) is 6 - 10 h, for example, it can be 6 h, 7 h, 8 h, 9 h, or 10 h, etc.

[0030] By controlling the first hydrothermal treatment, temperature, and time within the above ranges and using deionized water and ethylene glycol as solvents, the present invention can form spherical cerium dioxide and copper oxide composite active components, avoiding incomplete conversion of the copper solution and cerium solution into composite active components caused by too low a temperature of the first hydrothermal treatment and destruction of the active components caused by too high a temperature of the first hydrothermal treatment.

[0031] As a preferred technical solution of the present invention, the titanium precursor in step (2) includes tetrabutyl titanate and / or titanium isopropoxide.

[0032] Preferably, the volume ratio of the titanium precursor to the first solvent in step (2) is (12 - 18):300, for example, it can be 12:300, 13:300, 14:300, 15:300, 16:300, 17:300 or 18:300, etc.

[0033] Preferably, the temperature of the second hydrothermal treatment in step (2) is 150 - 200 °C, for example, it can be 150 °C, 160 °C, 170 °C, 180 °C, 190 °C or 200 °C, etc.

[0034] Preferably, the time of the second hydrothermal treatment in step (2) is 1 - 5 h, for example, it can be 1 h, 2 h, 3 h, 4 h or 5 h, etc.

[0035] In the present invention, the shaping of the titanium precursor and its coating on the surfaces of spherical cerium dioxide and copper oxide active components are simultaneously achieved through the second hydrothermal treatment. By controlling the hydrothermal temperature and time within the above ranges, the titanium precursor can be uniformly coated on the surfaces of spherical cerium dioxide and copper oxide active components, avoiding the formation of amorphous titanium dioxide and incomplete coating of spherical cerium dioxide and copper oxide active components.

[0036] Preferably, the post-treatment includes solid-liquid separation, washing and drying carried out in sequence.

[0037] Preferably, the washing is carried out at least twice successively with deionized water and ethanol.

[0038] The present invention places no limitation on the solid-liquid separation, and any method well-known to those skilled in the art for solid-liquid separation can be used, for example, it can be filtration, sedimentation or centrifugation, etc.

[0039] The present invention places no limitation on the drying, and any method well-known to those skilled in the art for drying can be used, for example, it can be rotary evaporation, vacuum drying, etc. There is no special requirement for the drying time, as long as the solvent in the mixed liquid can be evaporated to dryness.

[0040] Preferably, the drying temperature is 80 - 120 °C, for example, it can be 80 °C, 90 °C, 100 °C, 110 °C or 120 °C, etc.

[0041] Preferably, the temperature of the first calcination in step (2) is 400 - 900 °C, for example, it can be 400 °C, 500 °C, 600 °C, 700 °C, 800 °C or 900 °C, etc.

[0042] Preferably, the time of the first calcination in step (2) is 3 - 6 h, for example, it can be 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h, etc.

[0043] In the preparation method provided by the present invention, the titanium precursor described in step (2) is further subjected to hydrothermal treatment and calcination to form titanium dioxide coated on the spherical cerium dioxide and copper oxide composite component, obtaining a core-shell structured copper-cerium-titanium catalyst powder. Preferably, the hydrothermal temperature and calcination temperature are within the above ranges, so that the precursor is fully converted into anatase-type titanium dioxide, and at the same time, it is uniformly coated on the cerium dioxide and copper oxide composite component to form a stable core-shell structure.

[0044] As a preferred technical solution of the present invention, the mass-volume ratio of the intermediate powder described in step (3) to the second solvent is (4-6) g: 60 mL, for example, it can be 4 g: 60 mL, 4.5 g: 60 mL, 4.8 g: 60 mL, 5 g: 60 mL, 5.2 g: 60 mL, 5.5 g: 60 mL, 5.8 g: 60 mL or 6 g: 60 mL, etc.

[0045] Preferably, heating and stirring are carried out during the dispersion process in step (3).

[0046] Preferably, the heating temperature in step (3) is 30-60 °C, for example, it can be 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C or 60 °C, etc.

[0047] Preferably, the stirring time in step (3) is 10-20 min, for example, it can be 10 min, 12 min, 14 min, 15 min, 16 min, 17 min, 18 min or 20 min, etc.

[0048] Preferably, the stirring speed in step (3) is 50-80 r / min, for example, it can be 50 r / min, 55 r / min, 60 r / min, 65 r / min, 70 r / min, 75 r / min or 80 r / min, etc.

[0049] Preferably, the second solvent described in step (3) includes deionized water.

[0050] As a preferred technical solution of the present invention, the third precursor described in step (3) includes ammonium metavanadate.

[0051] Preferably, the third precursor solution in step (3) further includes a cosolvent;

[0052] Preferably, the cosolvent includes oxalic acid dihydrate.

[0053] Preferably, the fourth precursor described in step (3) includes ammonium metatungstate.

[0054] Preferably, the molar ratio of the cosolvent to ammonium metavanadate is (0.5 - 2):1, for example, it can be 0.5:1, 0.8:1, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, or 2:1, etc.

[0055] Preferably, in the third precursor solution in step (3), the mass-to-volume ratio of the third precursor to the solvent is (0.1 - 0.6) g:100 mL, for example, it can be 0.1 g:100 mL, 0.2 g:100 mL, 0.3 g:100 mL, 0.4 g:100 mL, 0.5 g:100 mL, or 0.6 g:100 mL, etc.

[0056] Preferably, in step (3), the mass ratio of the third precursor to the intermediate powder is (4 - 20):100, for example, it can be 4:100, 8:100, 10:100, 15:100, or 20:100, etc.

[0057] Preferably, in the fourth precursor solution in step (3), the mass-to-volume ratio of the fourth precursor to the solvent is (0.5 - 1) g:100 mL, for example, it can be 0.5 g:100 mL, 054 g:100 mL, 0.58 g:100 mL, 0.62 g:100 mL, 0.66 g:100 mL, 0.70 g:100 mL, 0.74 g:100 mL, 0.78 g:100 mL, 0.82 g:100 mL, 0.86 g:100 mL, 0.90 g:100 mL, or 1 g:100 mL, etc.

[0058] Preferably, in step (3), the mass ratio of the fourth precursor to the intermediate powder is (10 - 20):100, for example, it can be 20:100, 20:100, 20:100, 20:100, 20:100, 20:100, 20:100, etc.

[0059] Preferably, the solvent includes deionized water.

[0060] Preferably, in step (3), the heating temperature is 60 - 80 °C, for example, it can be 60 °C, 64 °C, 68 °C, 72 °C, 76 °C, or 80 °C, etc.

[0061] Preferably, in step (3), the heating time is 0.5 - 2 h, for example, it can be 0.5 h, 0.75 h, 1 h, 1.25 h, 1.5 h, 1.75 h, or 2 h, etc.

[0062] Preferably, the heating reaction in step (3) is a reflux reaction.

[0063] Preferably, stirring is carried out during the heating reaction in step (3).

[0064] Preferably, the rotation speed of the stirring is 50-80 r / min, for example, it can be 80 r / min, 80 r / min, 80 r / min, 80 r / min, 80 r / min, 80 r / min, 80 r / min, etc.

[0065] The present invention has no limitation on the heating, and any heating method well-known to those skilled in the art can be adopted, for example, it can be a water bath or an oil bath, etc.

[0066] In the present invention, the temperature and time of the heating reaction are controlled within the above ranges, so that the third precursor and the fourth precursor can be uniformly and sufficiently dispersed on the surface of the intermediate powder.

[0067] Preferably, the temperature of the second calcination in step (3) is 400-900 °C, for example, it can be 400 °C, 500 °C, 600 °C, 700 °C, 800 °C or 900 °C, etc.

[0068] Preferably, the time of the second calcination in step (3) is 3-6 h, for example, it can be 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h.

[0069] The second calcination in the present invention converts the metal salt into its oxide, improving the activity and stability of the catalyst. At the same time, it can improve the pore structure of the material, contributing to improving its adsorption capacity and catalytic performance. Preferably, calcining within the above temperature range can distribute the active components more uniformly on the surface of the catalyst. Too low a calcination temperature will cause some metal salts not to be converted into oxides, and too high a calcination temperature will cause the core-shell structure of the catalyst to collapse.

[0070] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0071] (1) Mix a copper nitrate trihydrate solution, a cerium nitrate hexahydrate solution and ethylene glycol, and carry out the first hydrothermal treatment at 150-200 °C for 6-10 h;

[0072] (2) Add tetrabutyl titanate and / or titanium isopropoxide to the first hydrothermal mixture obtained in step (1), carry out the second hydrothermal treatment at 150-200 °C for 1-5 h, and the obtained second hydrothermal mixture is post-treated and calcined at 400-900 °C for 3-6 h to obtain an intermediate powder;

[0073] (3) Disperse the intermediate powder in deionized water, inject an ammonium metavanadate solution and an ammonium metatungstate solution to carry out a heating reaction, and the obtained mixture is post-treated and calcined at 400-900 °C for 3-6 h to obtain the core-shell structured bifunctional catalyst.

[0074] In a third aspect, the present invention provides an application of the core-shell structured bifunctional catalyst as described in the first aspect, and the core-shell structured bifunctional catalyst is used for the catalytic oxidation of organic pollutants in cooperation with the SCR reaction.

[0075] Preferably, the organic pollutants include toluene.

[0076] Preferably, the reaction temperature for the catalytic oxidation of organic pollutants in cooperation with the SCR reaction is 100-400 °C, and for example, it can be 100 °C, 150 °C, 200 °C, 300 °C or 400 °C, etc.

[0077] Compared with the prior art, the present invention has at least the following beneficial effects:

[0078] (1) For the core-shell bifunctional catalyst provided by the present invention, the internal part of the core-shell structure is a copper-cerium composite active component, with titanium dioxide as the shell carrier, and the vanadium pentoxide active component and the trioxide promoter are loaded on the outside of the titanium dioxide shell carrier. Aiming at the different reaction characteristics of the catalytic oxidation of organic pollutants and NH3-SCR, different active components are selected for catalysis respectively. Copper oxide and cerium dioxide are the active components for the catalytic oxidation of organic pollutants, vanadium pentoxide is the active component for NH3-SCR, and tungsten trioxide is the reaction promoter for NH3-SCR.

[0079] (2) Compared with the traditional bifunctional catalyst, the core-shell structured bifunctional catalyst realizes the separation of active sites, and the NH3-SCR reaction area and the toluene oxidation area are effectively separated, avoiding the competitive adsorption between different atmospheres on the catalyst, and effectively improving the removal efficiency of the catalyst for toluene and NO x .

[0080] (3) The present invention synthesizes a bifunctional catalyst with a core-shell structure through a simple hydrothermal method. The maximum conversion rates of NO and toluene can both reach 100%. Among them, the reaction temperature for NO to reach the maximum conversion rate is 225 °C, and the reaction temperature for toluene to reach the maximum conversion rate is 250 °C. The obtained core-shell structured bifunctional catalyst has excellent synergy performance and selectivity at medium and low temperatures. Description of the Drawings

[0081] Figure 1 is the TEM image of the core-shell structured bifunctional catalyst provided in Example 1 of the present invention;

[0082] Figure 2 is the partially enlarged TEM image of the core-shell structured bifunctional catalyst provided in Example 1 of the present invention;

[0083] Figure 3 is the elemental mapping image of the core-shell structured bifunctional catalyst provided in Example 1 of the present invention;

[0084] Figure 4 XRD patterns of the catalysts provided in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 of the present invention;

[0085] Figure 5 NH3-TPD and Toluene-TPD patterns of the catalysts provided in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 of the present invention. Detailed implementation manners

[0086] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation manners. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0087] Example 1

[0088] This example provides a core-shell structured bifunctional catalyst. The core of the core-shell structured bifunctional catalyst includes a composite active component of mesoporous cerium dioxide nanospheres and copper oxide. The composite active component of cerium dioxide and copper oxide is wrapped with titanium dioxide, and vanadium pentoxide and tungsten trioxide are loaded on the titanium dioxide.

[0089] The core-shell structured bifunctional catalyst includes, by weight percentage: 0.5 part of copper oxide, 77.5 parts of cerium dioxide, 13.5 parts of titanium dioxide, 3 parts of vanadium pentoxide, and 5 parts of tungsten trioxide.

[0090] The preparation method of the core-shell structured bifunctional catalyst includes the following steps:

[0091] (1) Copper nitrate trihydrate is dissolved in deionized water at a mass-to-volume ratio of 0.09 g:50 mL to obtain a copper solution. Cerium nitrate hexahydrate is dissolved in deionized water at a mass-to-volume ratio of 25 g:50 mL to obtain a cerium solution. The copper solution, the cerium solution, and ethylene glycol are mixed and then kept at 180 °C for 8 h for the first hydrothermal treatment. The volume ratio of the copper solution to ethylene glycol is 50:300, and the volume ratio of the cerium solution to ethylene glycol is 50:300;

[0092] (2) Tetrabutyl titanate is added to the first hydrothermal mixture obtained in step (1) and then kept at 180 °C for 3 h for the second hydrothermal treatment. The volume ratio of the titanium precursor to ethylene glycol is 15:300. After centrifugation, washing, and drying, it is calcined at 600 °C for 4 h to obtain copper-cerium-titanium powder;

[0093] (3) Disperse the copper-cerium-titanium powder obtained in step (2) in deionized water at a mass-volume ratio of 5 g: 60 mL to obtain a dispersed turbid liquid, heat it to 50 °C, and stir it at a rotation speed of 60 r / min for 20 min; dissolve ammonium metavanadate and oxalic acid dihydrate in deionized water at a molar ratio of 1:1. The mass ratio of ammonium metavanadate to the copper-cerium-titanium powder is 7.6:100, and the mass-volume ratio of ammonium metavanadate to deionized water is 0.38 g:100 mL; dissolve ammonium metatungstate in deionized water at a mass-volume ratio of 0.54 g:100 mL. The mass ratio of the tungsten precursor to the copper-cerium-titanium powder is 10.8:100; inject the ammonium metavanadate solution and the ammonium metatungstate solution into the obtained dispersed turbid liquid, carry out centrifugation, washing and drying in a water bath under reflux at 60 °C for 1 h, and perform a second calcination at 600 °C for 4 h to obtain the core-shell structured bifunctional catalyst.

[0094] The TEM image of the core-shell structured bifunctional catalyst is as Figure 1 shown, Figure 1 The partial enlarged view of the scribed area in Figure 2 shown, Figure 3 is the elemental mapping spectrum of the core-shell structured bifunctional catalyst. The active components are successfully loaded on the catalyst and are evenly distributed; the XRD pattern of the core-shell structured bifunctional catalyst is as Figure 4 shown. It can be seen from the figure that the crystal phase of the cerium dioxide active component is the fluorite phase, and the crystallinity of the (1 1 1) crystal plane is relatively high; the crystal phase of the titanium dioxide support is the anatase phase, and the crystallinity of the (1 0 1) crystal plane is relatively high; the NH3-TPD and Toluene-TPD patterns are as Figure 5 shown. It can be seen from the figure that the core-shell structured bifunctional catalyst provided in this example has relatively strong NH3 and toluene desorption peaks, which indicates that it has more sites for NH3 and toluene adsorption.

[0095] Example 2

[0096] This example provides a core-shell structured bifunctional catalyst. The inner core of the core-shell structured bifunctional catalyst includes a mesoporous cerium dioxide nano-microsphere and a copper oxide composite active component. The cerium dioxide and copper oxide composite active component is wrapped with titanium dioxide, and vanadium pentoxide and tungsten trioxide are loaded on the outside of the titanium dioxide.

[0097] The core-shell structured bifunctional catalyst includes, by weight percentage: 1 part of copper oxide, 70 parts of cerium dioxide, 10 parts of titanium dioxide, 5 parts of vanadium pentoxide, and 10 parts of tungsten trioxide.

[0098] The preparation method of the core-shell structured bifunctional catalyst includes the following steps:

[0099] (1) Dissolve copper nitrate trihydrate in deionized water at a mass - volume ratio of 0.18 g:50 mL to obtain a copper solution, dissolve cerium nitrate hexahydrate in deionized water at a mass - volume ratio of 18 g:50 mL to obtain a cerium solution. Mix the copper solution, cerium solution and ethylene glycol, and then keep them at 180 °C for 6 h for the first hydrothermal treatment; the volume ratio of the copper solution to ethylene glycol is 50:400, and the volume ratio of the cerium solution to ethylene glycol is 50:400;

[0100] (2) Add tetrabutyl titanate to the first hydrothermal mixture obtained in step (1), and then keep it at 180 °C for 1 h for the second hydrothermal treatment. The volume ratio of the titanium precursor to ethylene glycol is 12:300. After centrifugation, washing and drying, perform the first calcination at 600 °C for 3 h to obtain copper - cerium - titanium powder;

[0101] (3) Disperse the copper - cerium - titanium powder obtained in step (2) in deionized water at a mass - volume ratio of 4 g:60 mL to obtain a dispersed turbid liquid, heat it to 30 °C and stir it at a rotation speed of 60 r / min for 10 min; dissolve ammonium metavanadate and oxalic acid dihydrate in deionized water at a molar ratio of 2:1. The mass ratio of ammonium metavanadate to the copper - cerium - titanium powder is 20:100, and the mass - volume ratio of ammonium metavanadate to deionized water is 0.6 g:100 mL; dissolve ammonium metatungstate in deionized water at a mass - volume ratio of 1 g:100 mL. The mass ratio of the tungsten precursor to the copper - cerium - titanium powder is 20:100; inject the ammonium metavanadate solution and ammonium metatungstate solution into the obtained dispersed turbid liquid, perform water - bath reflux at 80 °C for 0.5 h, then perform centrifugation, washing and drying in sequence, and perform the second calcination at 600 °C for 3 h to obtain the core - shell structured bifunctional catalyst.

[0102] Example 3

[0103] This example provides a core - shell structured bifunctional catalyst. The inner core of the core - shell structured bifunctional catalyst includes a composite active component of mesoporous cerium dioxide nanospheres and copper oxide. The composite active component of cerium dioxide and copper oxide is wrapped with titanium dioxide, and vanadium pentoxide and tungsten trioxide are loaded on the titanium dioxide.

[0104] The core - shell structured bifunctional catalyst includes, by weight percentage: 0.1 part of copper oxide, 80 parts of cerium dioxide, 15 parts of titanium dioxide, 1 part of vanadium pentoxide and 8 parts of tungsten trioxide.

[0105] The preparation method of the core - shell structured bifunctional catalyst includes the following steps:

[0106] (1) Dissolve copper nitrate trihydrate in deionized water at a mass-to-volume ratio of 0.05 g:50 mL to obtain a copper solution, dissolve cerium nitrate hexahydrate in deionized water at a mass-to-volume ratio of 28 g:50 mL to obtain a cerium solution, mix the copper solution, cerium solution and ethylene glycol, and keep them at 180 °C for 10 h for the first hydrothermal treatment; the volume ratio of the copper solution to ethylene glycol is 50:200, and the volume ratio of the cerium solution to ethylene glycol is 50:200;

[0107] (2) Add tetrabutyl titanate to the first hydrothermal mixture obtained in step (1), and keep it at 180 °C for 1 h for the second hydrothermal treatment. The volume ratio of the titanium precursor to ethylene glycol is 12:300. After centrifugation, washing and drying, perform the first calcination at 600 °C for 6 h to obtain copper-cerium-titanium powder;

[0108] (3) Disperse the copper-cerium-titanium powder obtained in step (2) in deionized water at a mass-to-volume ratio of 6 g:60 mL to obtain a dispersion turbid liquid, heat it to 60 °C and stir it at a rotation speed of 60 r / min for 15 min; dissolve ammonium metavanadate and oxalic acid dihydrate in deionized water at a molar ratio of 0.5:1. The mass ratio of ammonium metavanadate to copper-cerium-titanium powder is 4:100, and the mass-to-volume ratio of ammonium metavanadate to deionized water is 0.1 g:100 mL; dissolve ammonium metatungstate in deionized water at a mass-to-volume ratio of 0.5 g:100 mL. The mass ratio of the tungsten precursor to copper-cerium-titanium powder is 10:100; inject the ammonium metavanadate solution and ammonium metatungstate solution into the obtained dispersion turbid liquid, perform water bath reflux at 70 °C for 2 h, then perform centrifugation, washing and drying in sequence, and perform the second calcination at 600 °C for 6 h to obtain the core-shell structured bifunctional catalyst.

[0109] Example 4

[0110] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the first hydrothermal treatment is 150 °C.

[0111] Example 5

[0112] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the first hydrothermal treatment is 200 °C.

[0113] Example 6

[0114] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the first hydrothermal treatment is 100 °C.

[0115] Example 7

[0116] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the first hydrothermal treatment is 250 °C.

[0117] Example 8

[0118] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the second hydrothermal treatment is 150°C.

[0119] Example 9

[0120] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the second hydrothermal treatment is 200°C.

[0121] Example 10

[0122] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the second hydrothermal treatment is 100°C.

[0123] Example 11

[0124] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the second hydrothermal treatment is 250°C.

[0125] Example 12

[0126] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the first calcination is 400°C.

[0127] Example 13

[0128] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the first calcination is 900°C.

[0129] Example 14

[0130] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the first calcination is 350°C.

[0131] Example 15

[0132] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the first calcination is 950°C.

[0133] Example 16

[0134] A core-shell structured bifunctional catalyst provided in this example is the same as that in Example 1 except that the temperature of the second calcination is 400°C.

[0135] Example 17

[0136] A core-shell structured bifunctional catalyst provided in this embodiment is the same as that in Embodiment 1 except that the temperature of the second calcination is 900 °C.

[0137] Embodiment 18

[0138] A core-shell structured bifunctional catalyst provided in this embodiment is the same as that in Embodiment 1 except that the temperature of the second calcination is 350 °C.

[0139] Embodiment 19

[0140] A core-shell structured bifunctional catalyst provided in this embodiment is the same as that in Embodiment 1 except that the temperature of the second calcination is 950 °C.

[0141] Comparative Example 1

[0142] This comparative example provides a catalyst. The difference from Embodiment 1 is that vanadium pentoxide and tungsten trioxide are not loaded on the outside of the titanium dioxide shell layer, and ammonium metatungstate and ammonium metavanadate are not added in step (3) of the preparation method. The rest are the same as those in Embodiment 1.

[0143] The XRD pattern of the catalyst is as Figure 4 shown. It can be seen from the figure that the core-shell structured bifunctional catalyst provided in this comparative example shows the spectral peaks of fluorite phase cerium dioxide and anatase titanium dioxide; as Figure 5 shown in NH3-TPD and Toluene-TPD, it can be seen from the figure that the amount of NH3 desorption in the low-temperature section of the core-shell structured bifunctional catalyst provided in this comparative example is significantly reduced, and the NH3 adsorption sites are greatly reduced. The toluene desorption amount and toluene adsorption sites are not significantly reduced.

[0144] Comparative Example 2

[0145] This comparative example provides a catalyst. The difference from Embodiment 1 is that the internal active component only contains cerium dioxide and is not doped with copper oxide. In step (1) of the preparation method of the core-shell structured bifunctional catalyst, copper solution is not added in the first hydrothermal treatment. The rest are the same as those in Embodiment 1.

[0146] The XRD pattern of the catalyst is as Figure 4 shown. It can be seen from the figure that the core-shell structured bifunctional catalyst provided in this comparative example shows the spectral peaks of fluorite phase cerium dioxide and anatase titanium dioxide; as Figure 5 shown in NH3-TPD and Toluene-TPD, it can be seen from the figure that the amount of NH3 desorption in the low-temperature section and the NH3 adsorption sites of the core-shell structured bifunctional catalyst provided in this comparative example are not significantly reduced, the toluene desorption amount in the medium-low temperature section is significantly reduced, and the toluene adsorption sites are significantly reduced.

[0147] Comparative Example 3

[0148] This comparative example provides a catalyst, which is different from that of Example 1 in that only cerium dioxide is contained in the internal active component and copper oxide is not doped; vanadium pentoxide and tungsten trioxide are not loaded outside the anatase titanium dioxide. In step (1) of the preparation method of the core-shell structured bifunctional catalyst, no copper solution is added; in step (3) of the preparation method of the core-shell structured bifunctional catalyst, ammonium metavanadate and ammonium metatungstate are not added, and the rest are the same as those in Example 1.

[0149] The XRD pattern of the catalyst is as Figure 4 shown. It can be seen from the figure that the core-shell structured bifunctional catalyst provided by this comparative example shows the spectral peaks of fluorite-phase cerium dioxide and anatase titanium dioxide; as Figure 5 shown by NH3-TPD and Toluene-TPD, it can be seen from the figure that the amounts of NH3 desorbed and toluene desorbed in the low-temperature section of the core-shell structured bifunctional catalyst provided by this comparative example are both significantly reduced, and the NH3 adsorption sites and toluene adsorption sites are also significantly reduced.

[0150] Comparative Example 4

[0151] This comparative example provides a catalyst, which is different from that of Example 1 in that the catalyst does not have a titanium dioxide shell layer wrapped; vanadium pentoxide and tungsten trioxide are not loaded. In step (2) of the preparation method of the catalyst, tetrabutyl titanate is not added in the second hydrothermal treatment; in step (3), ammonium metavanadate and ammonium metatungstate are not added, and the rest are the same as those in Example 1.

[0152] The XRD pattern of the catalyst is as Figure 4 shown. It can be seen from the figure that the core-shell structured bifunctional catalyst provided by this comparative example shows the spectral peak of fluorite-phase cerium dioxide; as Figure 5 shown by NH3-TPD and Toluene-TPD, it can be seen from the figure that the amount of NH3 desorbed in the low-temperature section of the core-shell structured bifunctional catalyst provided by this comparative example is significantly reduced, and the NH3 adsorption sites are also significantly reduced.

[0153] Comparative Example 5

[0154] This comparative example provides a catalyst, which is different from that of Example 1 in that the catalyst does not have a titanium dioxide shell layer wrapped; in step (2) of the preparation method of the catalyst, tetrabutyl titanate is not added in the second hydrothermal treatment.

[0155] Comparative Example 6

[0156] This comparative example provides a catalyst, which is different from that of Example 1 in that copper oxide, cerium dioxide, titanium dioxide, vanadium pentoxide and tungsten trioxide in the catalyst are separately prepared and then physically mixed, and there is no core-shell structure.

[0157] The preparation method of the catalyst includes the following steps:

[0158] (1) Dissolve copper nitrate trihydrate in deionized water at a mass - to - volume ratio of 0.09 g:50 mL to obtain a copper solution, dissolve cerium nitrate hexahydrate in deionized water at a mass - to - volume ratio of 25 g:50 mL to obtain a cerium solution. Mix the copper solution, cerium solution and ethylene glycol, and then keep it at 180 °C for 8 h for the first hydrothermal treatment; the volume ratio of the copper solution to ethylene glycol is 50:300, and the volume ratio of the cerium solution to ethylene glycol is 50:300, to obtain copper oxide and cerium dioxide composite powder;

[0159] (2) Add tetrabutyl titanate to ethylene glycol and keep it at 180 °C for 3 h for the second hydrothermal treatment. The volume ratio of tetrabutyl titanate to ethylene glycol is 15:300. After centrifugation, washing and drying, perform the first calcination at 600 °C for 4 h to obtain titanium dioxide powder;

[0160] (3) Dissolve ammonium metavanadate and oxalic acid dihydrate in deionized water at a molar ratio of 1:1. The mass ratio of ammonium metavanadate to the copper - cerium - titanium powder is 7.6:100, and the mass - to - volume ratio of ammonium metavanadate to deionized water is 0.38 g:100 mL; dissolve ammonium metatungstate in deionized water at a mass - to - volume ratio of 0.54 g:100 mL. The mass ratio of the tungsten precursor to the copper - cerium - titanium powder is 10.8:100; after mixing, perform water - bath reflux at 60 °C for 1 h, then perform centrifugation, washing and drying in sequence, and perform the second calcination at 600 °C for 4 h to obtain vanadium pentoxide and tungsten trioxide composite powder.

[0161] Grind and mix the copper oxide and cerium dioxide composite powder, titanium dioxide powder, vanadium pentoxide and tungsten trioxide composite powder obtained in steps (1), (2) and (3) to obtain the catalyst.

[0162] Testing method:

[0163] Perform catalytic performance tests on the catalysts provided in Examples 1 - 19 and Comparative Examples 1 - 6. The test conditions include: flue gas composition: [NO]=500 ppm, [NH3]=500 ppm, [C7H8]=100 ppm, [O2]=16 vol%, with N2 as the carrier gas, and the catalyst dosage is 100 mg; the reaction furnace temperature is 100 - 400 °C, the flue gas flow rate is 200 mL / min. The maximum conversion rate of NO in the catalytic SCR reaction and the reaction temperature at which the maximum conversion rate is reached are shown in Table 1, and the maximum conversion rate of toluene in the catalytic toluene oxidation and the reaction temperature at which the maximum conversion rate is reached are shown in Table 2.

[0164] Table 1

[0165]

[0166]

[0167] Table 2

[0168]

[0169]

[0170] It can be seen from the test results that:

[0171] (1) It can be seen from Examples 1 to 3 that by preparing a core-shell structure catalyst, the toluene oxidation active sites of the present invention are restricted inside the catalyst, and the NH3-SCR active sites are placed outside the catalyst, achieving excellent NH3-SCR synergistic toluene oxidation performance. The NO removal efficiency reaches 100% within 300 °C, and the toluene removal efficiency reaches 100% within 325 °C. Among them, in the best example, the NO removal efficiency reaches 100% at 225 °C, and the toluene removal efficiency reaches 100% at 250 °C.

[0172] (2) It can be seen from Examples 1 and 4-11 that by further optimizing the temperatures of the first hydrothermal treatment and the second hydrothermal treatment, better synergistic catalytic effects can be achieved. When the temperature of the first hydrothermal treatment in Example 6 is too low, the metal precursor cannot be completely converted into the active components inside the catalyst, and the maximum toluene conversion rate drops suddenly from 100% in Example 1 to 41%, and at the same time, the maximum conversion temperature rises from 250 °C to 400 °C. When the temperature of the first hydrothermal treatment in Example 7 is too high, the copper-cerium active components are damaged, reducing the catalyst activity. The maximum toluene conversion rate drops from 100% in Example 1 to 80%, and at the same time, the maximum conversion temperature rises from 250 °C to 400 °C. Improper second hydrothermal treatment temperature will result in amorphous titanium dioxide and incomplete coating of spherical cerium dioxide and copper oxide active components. When the second hydrothermal treatment temperature in Example 10 is too low, the maximum toluene conversion rate drops suddenly from 100% in Example 1 to 50%, and at the same time, the maximum conversion temperature rises from 250 °C to 400 °C. When the second hydrothermal treatment temperature in Example 11 is too high, the maximum toluene conversion rate drops suddenly from 100% in Example 1 to 40%, and at the same time, the maximum conversion temperature rises from 250 °C to 400 °C.

[0173] (3) It can be seen from Examples 1 and 12-19 that by further optimizing the temperatures of the first calcination and the second calcination, the catalyst activity and stability are improved. At the same time, the pore structure of the material is improved, and its adsorption capacity and catalytic performance are enhanced. When the temperatures of the first calcination and the second calcination in Examples 14 and 18 are too low, part of the metal salt precursor cannot be converted into the corresponding oxide, resulting in a decrease in catalytic activity. When the temperature of the first calcination in Example 15 is too high, titanium dioxide is transformed from anatase phase to rutile phase, reducing the catalytic activity; in Example 19, the too high temperature of the second calcination causes the core-shell structure of the catalyst to collapse, unable to realize the advantages of site separation, and the catalytic effect is reduced.

[0174] (4) It can be seen from Example 1 and Comparative Examples 1-6 that by preparing a core-shell structured catalyst with multiple active sites, the present invention can achieve good catalytic effects. However, when one or more of the active components are lacking, the technical effect of synergistic catalysis cannot be achieved. In Comparative Example 5, when the titania shell layer is not coated, the reaction temperatures for the maximum conversions of NO and toluene both increase. This is because the anatase titania shell layer of the catalyst can effectively separate the NH3-SCR reaction region and the toluene oxidation reaction region of the catalyst, preventing competitive adsorption between different gas components and thus enhancing the performance of the catalyst. At the same time, when in Example 6 the same active components as in Example 1 are used, but the catalyst does not have a core-shell structure and instead is prepared by physical mixing through grinding, the separation of different adsorption sites cannot be achieved, competitive adsorption is enhanced, resulting in a decrease in the catalytic activity of the catalyst. The reaction temperature for the maximum conversion of NO increases from 225 °C to 300 °C, and the reaction temperature for the maximum conversion of toluene increases from 250 °C to 275 °C.

[0175] In summary, the present invention restricts the active components for catalytic oxidation of VOCs inside the catalyst and loads the NH3-SCR active components on the outside of the catalyst through stepwise preparation, obtaining a core-shell structured bifunctional catalyst with copper oxide and cerium dioxide inside and titania, vanadium pentoxide, and tungsten trioxide outside. Aiming at the different reaction characteristics of toluene catalytic oxidation and NH3-SCR, different active components are respectively selected for catalysis. Compared with traditional bifunctional catalysts, the core-shell structured bifunctional catalyst realizes the separation of active sites, effectively separates the NH3-SCR reaction region and the toluene oxidation region, avoids competitive adsorption between different atmospheres on the catalyst, and effectively improves the removal efficiency of the catalyst for organic pollutants and NO x and reduces the reaction temperature.

[0176] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A core-shell structured bifunctional catalyst for the catalytic oxidation of SCR reaction synergistic organic pollutants, characterized in that, The core of the core-shell structured bifunctional catalyst includes a first composite active component for the catalytic oxidation of organic pollutants. The first composite active component is wrapped with titanium dioxide, and the second composite active component for the catalytic SCR reaction is loaded on the titanium dioxide.

2. The core-shell structured bifunctional catalyst according to claim 1, wherein, The core of the core-shell structured bifunctional catalyst includes a composite active component of cerium dioxide and copper oxide. The composite active component of cerium dioxide and copper oxide is wrapped with titanium dioxide, and the composite active component of vanadium pentoxide and tungsten trioxide is loaded on the titanium dioxide.

3. The core-shell structured bifunctional catalyst according to claim 1 or 2, characterized in that, The core-shell structured bifunctional catalyst includes, by weight: 0.1 - 1 part of copper oxide, 70 - 80 parts of cerium dioxide, 10 - 16 parts of titanium dioxide, 1 - 5 parts of vanadium pentoxide, and 5 - 10 parts of tungsten trioxide; Preferably, the titanium dioxide is anatase titanium dioxide.

4. A method for preparing a core-shell structured bifunctional catalyst according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) Mix a first precursor solution, a second precursor solution, and a first solvent, and then perform a first hydrothermal treatment; (2) Add a titanium precursor to the first hydrothermal mixture obtained in step (1), and then perform a second hydrothermal treatment. After the obtained second hydrothermal mixture is post-treated, it is subjected to a first calcination to obtain an intermediate powder; (3) Disperse the intermediate powder in a second solvent, inject a third precursor solution and a fourth precursor solution, heat and react. After the obtained mixture is post-treated, it is subjected to a second calcination to obtain the core-shell structured bifunctional catalyst.

5. The preparation method according to claim 4, characterized in that, The first solvent in step (1) includes ethylene glycol; Preferably, the first precursor in step (1) includes copper nitrate trihydrate; Preferably, the second precursor in step (1) includes cerium nitrate hexahydrate; Preferably, the temperature of the first hydrothermal treatment in step (1) is 150 - 200 °C; Preferably, the time of the first hydrothermal treatment in step (1) is 6 - 10 h.

6. The preparation method according to claim 4 or 5, characterized in that, The titanium precursor in step (2) includes tetrabutyl titanate and / or titanium isopropoxide; Preferably, the temperature of the second hydrothermal treatment in step (2) is 150 - 200 °C; Preferably, the time of the second hydrothermal treatment in step (2) is 1 - 5 h; Preferably, the temperature of the first calcination in step (2) is 400 - 900 °C; Preferably, the time of the first calcination in step (2) is 3 - 6 h.

7. The preparation method according to any one of claims 4 to 6, characterized in that, The second solvent in step (3) includes deionized water; Preferably, the third precursor in step (3) includes ammonium metavanadate; Preferably, the fourth precursor in step (3) includes ammonium metatungstate.

8. The preparation method according to any one of claims 4-7, characterized in that, The heating temperature in step (3) is 60 - 80 °C; Preferably, the heating time in step (3) is 0.5 - 2 h; Preferably, the temperature of the second calcination in step (3) is 400 - 900 °C; Preferably, the time of the second calcination in step (3) is 3 - 6 h.

9. The preparation method according to any one of claims 4-8, characterized in that, The preparation method includes the following steps: (1) Mix a copper nitrate trihydrate solution, a cerium nitrate hexahydrate solution, and ethylene glycol, and perform a first hydrothermal treatment at 150 - 200 °C for 6 - 10 h; (2) Add tetrabutyl titanate and / or titanium isopropoxide to the first hydrothermal mixture obtained in step (1), conduct the second hydrothermal treatment at 150 - 200 °C for 1 - 5 h, and subject the obtained second hydrothermal mixture to post-treatment and then conduct the first calcination at 400 - 900 °C for 3 - 6 h to obtain intermediate powder; (3) Disperse the intermediate powder in deionized water, inject ammonium metavanadate solution and ammonium metatungstate solution and heat for reaction, subject the obtained mixture to post-treatment and then conduct the second calcination at 400 - 900 °C for 3 - 6 h to obtain the core-shell structured bifunctional catalyst.

10. Use of a core-shell structured bifunctional catalyst as described in any one of claims 1-3, characterized in that, The core-shell structured bifunctional catalyst is used for the catalytic oxidation of organic pollutants in cooperation with the SCR reaction; Preferably, the organic pollutants include toluene; Preferably, the reaction temperature for the catalytic oxidation of organic pollutants in cooperation with the SCR reaction is 100 - 400 °C.

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