A catalyst for the catalytic reduction of nox and a method for its production and use

Abstract

The application discloses a catalyst for catalytic reduction of NOx and a preparation method and application thereof. The catalyst comprises an active component, an auxiliary agent, a carrier and an amino group grafted and modified on the surface of the catalyst, wherein CeO2 is used as the main active component, Pr2O3 and WO3 are used as the auxiliary agent, SiO2 and TiO2 are used as the carrier, the catalyst is prepared by using a hydrothermal method, and the amino group is connected to the catalyst for surface modification. The catalyst has high NOx removal capacity. Meanwhile, the auxiliary agents Pr, W and Ce and the amino group and surface defects can have a good synergistic catalysis effect, the catalyst has high anti-poisoning performance, and the catalyst has a wide active catalysis temperature window.

Description

TECHNICAL FIELD

[0001] The present application relates to a catalyst for removing NOx, belonging to the field of atmospheric pollution control technology and environmental catalysis. BACKGROUND

[0002] Nitrogen oxides (NOx) is one of the main pollutants in the atmosphere, and is one of the main reasons for causing haze, photochemical smog, greenhouse effect and acid rain. It mainly includes NO, NO2 and N2O, among which NO accounts for more than 90%. In addition, NOx is also harmful to human health. Therefore, it is necessary to control the emission of NOx. The technology of efficiently removing NOx has very important value and has become a research hotspot. At present, the ammonia selective catalytic reduction method (NH3-SCR) is considered as the most universal, mature and efficient technology in the field of denitrification. This technology can effectively convert NOx into harmless N2 and H2O in a suitable temperature range of the catalyst, and can reduce the NOx emission by up to 90% or more.

[0003] The catalyst is the core of the selective catalytic reduction process, which can efficiently and selectively remove nitrogen oxides. The SCR catalyst can be roughly divided into noble metal catalyst, transition metal oxide catalyst, molecular sieve catalyst and activated carbon catalyst. Among them, the metal oxide catalyst is widely used in the NOx removal process due to its excellent catalytic activity, high material stability and controllability, and relatively low price. Transition metal oxides are a kind of catalyst with simple preparation, abundant resources and much lower price than noble metals. V2O5-WO3 / TiO2 catalyst has been widely used in commerce, but this catalyst still has some shortcomings in practical application, such as narrow catalytic temperature window, low N2 selectivity, poor water resistance and high temperature NH3 peroxidation. Therefore, a new catalyst for removing NOx is needed to remove NOx under different conditions.

[0004] Group modification grafting of the catalyst is an effective measure to improve the catalytic performance of the catalyst, and preparation of core-shell structure is a way to solve the poisoning problem of the catalyst. These modification methods can greatly improve the overall catalytic activity and poisoning resistance of the catalyst. Therefore, by further increasing the contact area between the NOx-containing exhaust gas and the surface of the catalyst, promoting the adsorption and mass transfer of the surface active substances, and strengthening the performance, the further improvement of the catalytic removal of NOx performance can be effectively realized.

[0005] At present, domestic non-vanadium titanium-based denitration catalysts have been studied more, such as a NOx removal catalyst disclosed in patent CN112452321A, which has good performance at a temperature window of 150-500 DEG C, but the catalytic effect is also obviously reduced at low temperature. Such as a molecular sieve catalyst disclosed in patent CN116510774A, which also has a significantly reduced catalytic effect at low temperature, and the preparation cost of the catalyst is relatively high, and the thermal stability of the catalyst is poor under high temperature and long time operation. Such as a molecular sieve catalyst disclosed in patent CN106111183A, which also has a significantly reduced catalytic effect at low temperature. The existing denitration catalysts have certain problems, including poor activity at low temperature, high cost, poor thermal stability and selectivity at high temperature, and easy generation of byproduct N2O. SUMMARY

[0006] In view of the problems existing in the prior art, the present application provides a catalyst for catalytic reduction of NOx and a preparation method and use thereof. The catalyst of the present application is a PrW-Ce / SiO2-TiO2 composite oxide. The synergistic effect between W and Ce increases the acid sites on the surface of the catalyst, promotes the adsorption and activation of NH3 species in the gas, and at the same time improves the reaction activity of the adsorbed NH3 species. Adding a small amount of Pr can not only promote the high dispersion of the active component, but also strengthen the interaction between the additive, the active component and the carrier, thereby improving the low-temperature denitration activity of the catalyst. In addition, the synergistic effect between Pr and W not only widens the activity window of the catalyst, but also improves the anti-poisoning and deactivation performance of the catalyst in the presence of H2O. The core-shell structure improves the specific surface area of the catalyst, promotes the adsorption and mass transfer of the surface active substances. The surface defects of cerium oxide enable it to have abundant active oxygen and oxygen storage capacity, promote the conversion of NO to NO2, and make it proceed along the path of rapid SCR catalytic reaction. By grafting amino groups onto the surface of the catalyst and adding acid, the surface defects and oxygen free radicals of the catalyst are increased, more active sites are formed, and the adsorption and reaction rate of the catalyst for NOx are enhanced, thereby obtaining a catalyst with good NOx removal performance.

[0007] The preparation process is simple, the obtained catalyst has good stability and high selectivity, and has good catalytic activity and anti-poisoning properties in the entire catalytic activity range, which can solve the problems of narrow activity temperature window and poor water resistance of the denitration catalysts in the prior art. The catalyst can be used for the elimination of NOx emitted by stationary sources such as thermal power plants and industrial boilers, and mobile sources such as diesel vehicles.

[0008] To solve the above technical problems, the present application adopts the following technical scheme:

[0009] A catalyst for catalytic reduction of NOx, comprising the following components:

[0010] Support: core-shell structure SiO2-TiO2,

[0011] Active component: CeO2,

[0012] Auxiliary component: Pr2O3 and WO3,

[0013] Amino groups on the surface of the catalyst are modified;

[0014] The mass percentage of CeO2 is 4%-20%, the mass percentage of Pr2O3 is 1%-5%, and the mass percentage of WO3 is 1%-5%, based on the mass of the support; and the molar ratio of Ti to Si is 1-5.

[0015] The application provides a method for preparing the catalyst, comprising the following steps:

[0016] (1) uniformly mixing a dispersant, a solvent and a lye, adding a silicon source, performing suction filtration, washing, and drying to obtain a silicon nanometer core;

[0017] (2) grinding the silicon nanometer core into powder, adding the powder to a mixed solution of the solvent and the lye, then adding a titanium source, performing heat preservation, suction filtration, washing, drying, and calcination to obtain a core-shell structure support;

[0018] (3) grinding the core-shell structure support into powder, adding a precursor solution of an active component, and drying to obtain a core-shell catalyst loaded with the active component;

[0019] (4) grinding the core-shell catalyst loaded with the active component into powder, adding a precursor solution of an auxiliary component, and drying and calcination;

[0020] (5) grinding the product obtained in step (4) into powder, adding a mixed solution containing an amino-containing organic ligand, an organic solvent and an acid, performing suction filtration, washing, drying and calcination.

[0021] Further, the dispersant in step (1) comprises one or more of cetyltrimethylammonium bromide (CTAB), P123 and polyethylene glycol.

[0022] Further, the solvent in step (1) comprises ethanol and / or water.

[0023] Further, the lye in step (1) is selected from one or more of urea, ammonia, and tetramethylammonium hydroxide.

[0024] Further, the silicon source in step (1) is selected from one or more of tetraethyl orthosilicate, tetramethyl orthosilicate, silicon tetrachloride and silicic acid.

[0025] Further, the mass ratio of the dispersant to the silicon source in step (1) is 1:1-3.

[0026] Further, the stirring is used in step (1) to mix the materials uniformly, and the stirring time is 4-10 h.

[0027] Further, the washing in step (1) is carried out with ethanol and water respectively in sequence until the pH is 7.

[0028] Further, the drying temperature in step (1) is 80-120℃, and the drying time is 10-14 h.

[0029] Further, the solvent in step (2) is ethanol and / or water.

[0030] Further, the alkali solution in step (2) is selected from one or more of urea, ammonia, and tetramethylammonium hydroxide.

[0031] Further, the titanium source in step (2) is selected from tetrabutyl titanate and / or titanium tetrachloride.

[0032] Further, the mixing of materials in step (2) is carried out by stirring, and the stirring time is 4-10 h.

[0033] Further, the temperature of the heat preservation in step (2) is 100-200℃.

[0034] Further, the time of the heat preservation in step (2) is 10-24 h.

[0035] Further, the washing in step (2) is carried out with ethanol and water respectively in sequence until the pH is 7.

[0036] Further, the drying temperature in step (2) is 80-120℃, and the drying time is 10-14 h.

[0037] Further, the calcination temperature in step (2) is 200-600℃, and the calcination time is 2-6 h.

[0038] Further, the precursor solution of the active component in step (3) is a nitrate solution thereof.

[0039] Further, the mixing of materials in step (3) is carried out by stirring, and the stirring time is 4-10 h.

[0040] Further, the drying temperature in step (3) is 80-120℃, and the drying time is 10-14 h.

[0041] Further, the precursor solution of the auxiliary component in step (4) is a nitrate solution thereof.

[0042] Further, the mixing of materials in step (4) is carried out by stirring, and the stirring time is 4-10 h.

[0043] Further, the drying temperature in step (4) is 80-120 DEG C, and the drying time is 10-14 h.

[0044] Further, the calcination temperature in step (4) is 200-600 DEG C, and the calcination time is 2-6 h.

[0045] Further, in step (5), the amino-containing organic ligand is selected from one or more of 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 2-amino-4,4'-diphenyldicarboxylic acid, ethylenediamine, phenylenediamine.

[0046] Further, in step (5), the organic solvent is selected from one or more of DMF, ethanol, water.

[0047] Further, in step (5), the acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid.

[0048] Further, in step (5), the washing is ethanol and water respectively and sequentially to pH 7.

[0049] Further, the drying temperature in step (5) is 80-120 DEG C, and the drying time is 10-14 h.

[0050] Further, the calcination temperature in step (5) is 200-600 DEG C, and the calcination time is 2-6 h.

[0051] Further, in step (5), the mass-volume ratio of the product obtained in step (4) to the amino-containing organic ligand is 1 g:2-4 ml, the volume ratio of the amino-containing organic ligand to the organic solvent is 1:1-2, and the volume ratio of the amino-containing organic ligand to the acid is 1:1-3.

[0052] A method for removing NOx, comprising the following steps: 10-1000 ppm NO, 10-1000 ppm NH3, 10% H2O, the rest being air, the gas flow being 300 ml / min, the gas space velocity being 100000-180000 h-1, and the concentration ratio of NO to NH3 being 1:1. -1 The gas concentration is analyzed on-line by using a KM-9106 flue gas analyzer and a Fourier transform infrared spectrometer, and the reactor is a fixed bed reactor.

[0053] Compared with the prior art, the present application has the following beneficial effects:

[0054] (1) The synergistic effect between the carrier and the active component makes it have excellent redox performance and electron transfer ability and surface acid sites, the core-shell structure nanomaterial has a high specific surface area and a large pore volume, and can transiently and efficiently adsorb target gases NOx and NH3.

[0055] (2) The present application grafts amino groups on the surface of the catalyst and introduces acid to adjust the surface defects. Due to the introduction of the amino groups and the defects, more active sites and oxygen free radicals are formed, the adsorption and activation of NOx are stronger, and the adsorption and reaction activity of the catalyst for NOx are enhanced.

[0056] (3) The catalyst is not affected by H2O during low-temperature catalysis, can maintain high catalytic efficiency for a long time, does not affect the service life of the catalyst, has good catalytic activity in the range of 100℃-600℃, exhibits excellent low-temperature and high-temperature denitration performance, and solves the problems of narrow temperature window, poor water resistance and easy poisoning of existing commercial catalysts. DETAILED DESCRIPTION

[0057] Example 1 (1% Pr2O3 3% WO3-10% CeO2 / SiO2-TiO2)

[0058] (1) 20ml water, 100ml ethanol, 30ml of a 28%wt ammonia solution were mixed, 2g of a dispersant hexadecyltrimethylammonium bromide (CTAB) was added, and stirring was performed at room temperature for 2h. 4.7g of tetraethyl orthosilicate was added to the above mixed solution, and stirring was performed at room temperature for 4h. Then, suction filtration was performed, and washing was performed with ethanol and water respectively 3 times until the pH was 7, and then the filter cake was dried in an oven at 110℃ for 12h, to obtain a silicon nanocore.

[0059] (2) The silicon nanocore was ground into powder and added to a mixed solution of 20ml water, 100ml ethanol and 30ml of a 28%wt ammonia solution, and stirring was performed at room temperature for 2h. 7.68g of tetrabutyl titanate was added to the above mixed solution, and stirring was performed at room temperature for 4h. The reaction liquid was moved to a polytetrafluoroethylene-lined stainless steel reaction kettle, and incubation was performed at 160℃ for 24h. After the incubation was completed and the temperature was lowered to room temperature, suction filtration was performed, and washing was performed with ethanol and water respectively 3 times until the pH was 7, the filter cake was dried in an oven at 110℃ for 12h, and then calcination was performed in a muffle furnace at 500℃ for 4h (the temperature rising rate was 2℃ / min), to obtain a core-shell structure carrier, and the mol ratio of SiO2 to TiO2 was 1:2.

[0060] (3) 2g of the above carrier was ground into powder and added to a 7.26ml 0.16mol / l cerium nitrate solution, stirring was performed at room temperature for 4h, and then drying was performed in an oven at 110℃ for 12h, to obtain a catalyst loaded with an active component.

[0061] (4) 2 g of the above support was ground to powder and added to 2.16 ml of 0.01 mol / l ammonium metatungstate solution and 3.03 ml of 0.04 mol / l praseodymium nitrate solution, stirred at room temperature for 4 h, dried in an oven at 110°C for 12 h, and then calcined in a muffle furnace at 200°C for 2 h and at 500°C for 4 h (temperature increase rate 2°C / min) to obtain the supported catalyst.

[0062] (5) 2 g of the above support was ground to powder and added to 5 ml of 3- aminopropyltrimethoxysilane, 6 ml of DMF, and 8 ml of nitric acid mixed solution, stirred at room temperature for 4 h, suction filtered, washed with ethanol and water respectively for 3 times until the pH was 7, the filter cake was dried in an oven at 110°C for 12 h, and then calcined in a muffle furnace at 200°C for 2 h and at 400°C for 2 h (temperature increase rate 2°C / min) to obtain the final amino-modified core-shell catalyst.

[0063] The test conditions were: 500 ppm NO, 500 ppm NH3, H2O 10%, the rest being air, gas flow 300 ml / min, gas space velocity 150000 h-1, and the concentration ratio of NO to NH3 being 1:1. -1

[0064] Example 2 (3% Pr2O3 1% WO3-10% CeO2 / SiO2-TiO2)

[0065] (1) 20 ml of water, 100 ml of ethanol, and 30 ml of 28% wt ammonia water solution were mixed, 5 g of dispersant cetyltrimethylammonium bromide (CTAB) was added, and stirred at room temperature for 2 h. 9.2 ml of methyl orthosilicate was added to the above mixed solution, stirred at room temperature for 4 h. Then suction filtered, washed with ethanol and water respectively for 3 times until the pH was 7, and then the filter cake was dried in an oven at 110°C for 12 h to obtain the silica nanocore.

[0066] (2) The silica nanocore was ground to powder and added to 20 ml of water, 100 ml of ethanol, and 30 ml of 28% wt ammonia water solution, stirred at room temperature for 2 h. 4.66 g of titanium tetrachloride was added to the above mixed solution, stirred at room temperature for 4 h. The reaction solution was moved to a stainless steel reaction kettle with a polytetrafluoroethylene liner, and kept at 180°C for 24 h. After the incubation was completed and the temperature was lowered to room temperature, it was suction filtered, washed with ethanol and water respectively for 3 times until the pH was 7, the filter cake was dried in an oven at 110°C for 12 h, and then calcined in a muffle furnace at 500°C for 4 h (temperature increase rate 2°C / min) to obtain the core-shell structured support, the mol ratio of SiO2 to TiO2 being 2:1.

[0067] ​(3) Take 2 g of the above support and grind to powder, add to 7.2 ml of a 0.16 mol / l cerium nitrate solution, stir at room temperature for 4 h, then dry in an oven at 110°C for 12 h to obtain the catalyst loaded with active components.

[0068] (4) Take 2 g of the above support and grind to powder, add to 0.72 ml of a 0.01 mol / l ammonium metatungstate solution and 9.1 ml of a 0.04 mol / l praseodymium nitrate solution, stir at room temperature for 4 h, dry in an oven at 110°C for 12 h, then calcine in a muffle furnace at 200°C for 2 h and at 400°C for 2 h (heating rate 2°C / min) to obtain the loaded catalyst.

[0069] (5) Take 2 g of the above support and grind to powder, add to a mixture of 7 ml of 2-amino-4,4'-biphenyldicarboxylic acid, 7.2 ml of DMF and 8.7 ml of hydrochloric acid, stir at room temperature for 4 h, then perform suction filtration, wash with ethanol and water three times each until the pH is 7, dry the filter cake in an oven at 110°C for 12 h, then calcine in a muffle furnace at 200°C for 2 h and at 400°C for 2 h (heating rate 2°C / min) to obtain the final amino-modified core-shell catalyst.

[0070] The test conditions are: 500 ppm NO, 500 ppm NH3, 10% H2O, the remainder being air, gas flow 300 ml / min, gas space velocity 150 000 h-1, NO to NH3 concentration ratio 1 : 1. -1

[0071] Example 3 (3% Pr2033% WO3-12% CeO2 / SiO2-TiO2)

[0072] (1) Mix 20 ml of water, 100 ml of ethanol and 30 ml of a 28% wt ammonia solution, add 3.85 g of the dispersant polyP123, stir at room temperature for 2 h. Add 9.4 g of tetraethyl orthosilicate to the above mixture, stir at room temperature for 4 h. Then perform suction filtration, wash with ethanol and water three times each until the pH is 7, then dry the filter cake in an oven at 110°C for 12 h to obtain the silica nanocore.

[0073] ​(2) The silicon nanocore was ground into powder and added to a solution of 20 ml of water, 100 ml of ethanol, and 30 ml of 28% wt ammonia water, and stirred at room temperature for 2 h. 5.12 g of tetrabutyl titanate was added to the above solution, and stirred at room temperature for 4 h. The reaction solution was transferred to a polytetrafluoroethylene-lined stainless steel reactor, and incubated at 200°C for 24 h. After incubation, the solution was cooled to room temperature, and filtered, and washed with ethanol and water three times until the pH was 7. The filter cake was dried in an oven at 110°C for 12 h, and then calcined in a muffle furnace at 500°C for 4 h (heating rate 2°C / min), to obtain a core-shell structured carrier, with a SiO2:TiO2 molar ratio of 3:1.

[0074] (3) 2 g of the above carrier was ground into powder and added to 8.72 ml of a 0.16 mol / l cerium nitrate solution, and stirred at room temperature for 4 h, and then dried in an oven at 110°C for 12 h, to obtain a catalyst loaded with active components.

[0075] (4) 2 g of the above carrier was ground into powder and added to 2.16 ml of a 0.01 mol / l ammonium metatungstate solution and 9.1 ml of a 0.04 mol / l praseodymium nitrate solution, and stirred at room temperature for 4 h, and then dried in an oven at 110°C for 12 h, and then calcined in a muffle furnace at 200°C for 2 h and at 400°C for 2 h (heating rate 2°C / min), to obtain a loaded catalyst.

[0076] (5) 2 g of the above carrier was ground into powder and added to a mixed solution of 6 ml of ethylenediamine, 9 ml of DMF, and 12 ml of nitric acid, and stirred at room temperature for 4 h, and then filtered, and washed with ethanol and water three times until the pH was 7. The filter cake was dried in an oven at 110°C for 12 h, and then calcined in a muffle furnace at 200°C for 2 h and at 400°C for 2 h (heating rate 2°C / min), to obtain a final amino-modified core-shell catalyst.

[0077] The test conditions were: 500 ppm NO, 500 ppm NH3, 10% H2O, the remainder being air, gas flow rate was 300 ml / min, gas space velocity was 150000 h-1, and the concentration ratio of NO to NH3 was 1:1. -1

[0078] Example 4 (1% Pr2O3 1% WO3-4% CeO2 / SiO2-TiO2)

[0079] ​(1) Mix 20 ml of water, 100 ml of ethanol, 30 ml of 28% wt ammonia solution, and add 1.71 g of dispersant P123, stir at room temperature for 2 h. Add 5.12 g of methyl orthosilicate to the above mixed solution, stir at room temperature for 4 h. Then perform suction filtration, wash with ethanol and water 3 times respectively until the pH is 7, and then dry the filter cake in an oven at 110°C for 12 h to obtain the silicon nanocore.

[0080] (2) Grind the silicon nanocore into powder and add it to 20 ml of water, 100 ml of ethanol, 30 ml of 28% wt ammonia solution, and stir at room temperature for 2 h. Add 8.36 g of tetrabutyl titanate to the above mixed solution, stir at room temperature for 4 h. Move the reaction solution to a polytetrafluoroethylene-lined stainless steel reaction kettle, and heat at 160°C for 18 h. After the heat preservation is completed and the temperature is reduced to room temperature, perform suction filtration, wash with ethanol and water 3 times respectively until the pH is 7, dry the filter cake in an oven at 110°C for 12 h, and then calcine in a muffle furnace at 500°C for 4 h (heating rate 2°C / min) to obtain the core-shell structured carrier, with a SiO2 to TiO2 molar ratio of 1:1.

[0081] (3) Take 2 g of the above carrier and grind it into powder, add it to 2.91 ml of 0.16 mol / l cerium nitrate solution, stir at room temperature for 4 h, and then dry in an oven at 110°C for 12 h to obtain the catalyst loaded with active components.

[0082] (4) Take 2 g of the above carrier and grind it into powder, add it to 0.72 ml of 0.01 mol / l ammonium metatungstate solution and 3.03 ml of 0.04 mol / l praseodymium nitrate solution, stir at room temperature for 4 h, dry in an oven at 110°C for 12 h, and then calcine in a muffle furnace at 200°C for 2 h and at 400°C for 2 h (heating rate 2°C / min) to obtain the loaded catalyst.

[0083] (5) Take 2 g of the above carrier and grind it into powder, add it to 4 ml of 3- aminopropyltrimethoxysilane, 4 ml of ethanol, and 4 ml of hydrochloric acid mixed solution, stir at room temperature for 4 h, perform suction filtration, wash with ethanol and water 3 times respectively until the pH is 7, dry the filter cake in an oven at 110°C for 12 h, and then calcine in a muffle furnace at 200°C for 2 h and at 400°C for 2 h (heating rate 2°C / min) to obtain the final amino-modified core-shell catalyst.

[0084] The test conditions are: 500 ppm NO, 500 ppm NH3, 10% H2O, the rest being air, gas flow is 300 ml / min, gas space velocity is 150000 h-1, and the concentration ratio of NO to NH3 is 1:1. -1 ​

[0085] Example 5 (5% Pr2O3 5% WO3-20% CeO2 / SiO2-TiO2)

[0086] (1) 20 ml of water, 100 ml of ethanol, 30 ml of 28% wt ammonia solution were mixed, 9.4 g of dispersant polyethylene glycol was added, and stirred at room temperature for 2 h. 9.4 g of tetraethyl orthosilicate was added to the above mixed solution, and stirred at room temperature for 4 h. Then, suction filtration was performed, and washed with ethanol and water three times each until the pH was 7, and then the filter cake was dried in an oven at 110°C for 12 h to obtain a silicon nanocore.

[0087] (2) The silicon nanocore was ground into powder and added to 20 ml of water, 100 ml of ethanol, and 30 ml of 28% wt ammonia solution, and stirred at room temperature for 2 h. 3.07 g of tetrabutyl titanate was added to the above mixed solution, and stirred at room temperature for 4 h. The reaction solution was moved to a stainless steel reaction kettle with a polytetrafluoroethylene liner, and incubated at 180°C for 16 h. After the incubation was completed and the temperature was reduced to room temperature, suction filtration was performed, and washed with ethanol and water three times each until the pH was 7, and then the filter cake was dried in an oven at 110°C for 12 h, and then calcined in a muffle furnace at 500°C for 4 h (temperature increase rate 2°C / min) to obtain a core-shell structured carrier, and the mol ratio of SiO2 to TiO2 was 5:1.

[0088] (3) 2 g of the above carrier was ground into powder and added to 14.53 ml of 0.16 mol / l cerium nitrate solution, and stirred at room temperature for 4 h, and then dried in an oven at 110°C for 12 h to obtain a catalyst loaded with an active component.

[0089] (4) 2 g of the above carrier was ground into powder and added to 3.59 ml of 0.01 mol / l ammonium metatungstate solution and 15.16 ml of 0.04 mol / l praseodymium nitrate solution, and stirred at room temperature for 4 h, and then dried in an oven at 110°C for 12 h, and then calcined in a muffle furnace at 200°C for 2 h and at 400°C for 2 h (temperature increase rate 2°C / min) to obtain a loaded catalyst.

[0090] (5) 2 g of the above carrier was ground into powder and added to a mixed solution of 8 ml of 2-amino-4,4'-biphenyldicarboxylic acid, 16 ml of DMF, and 24 ml of hydrochloric acid, and stirred at room temperature for 4 h, and then suction filtration was performed, and washed with ethanol and water three times each until the pH was 7, and then the filter cake was dried in an oven at 110°C for 12 h, and then calcined in a muffle furnace at 200°C for 2 h and at 400°C for 2 h (temperature increase rate 2°C / min) to obtain a final amino-modified core-shell catalyst.

[0091] Test conditions: 500 ppm NO, 500 ppm NH3, H2O 10%, the rest is air, gas flow is 300 ml / min, gas space velocity is 150000 h -1 , the concentration ratio of NO and NH3 is 1:1.

[0092] Comparative Example 1

[0093] Compared with Example 1, the difference between the preparation method of the catalyst and Example 1 is that the amino modification is not performed in the present comparative example, and the rest of the preparation method and test conditions are the same as those of Example 1.

[0094] Comparative Example 2

[0095] Compared with Example 1, the difference between the preparation method of the catalyst and Example 1 is that the present comparative example only does not add a dispersant, and the rest of the preparation method and test conditions are the same as those of Example 1.

[0096] Comparative Example 3

[0097] Compared with Example 1, the difference between the preparation method of the catalyst and Example 1 is that the present comparative example only does not contain the auxiliary Pr2O3, and the rest of the preparation method and test conditions are the same as those of Example 1.

[0098] Comparative Example 4

[0099] Compared with Example 1, the difference between the preparation method of the catalyst and Example 1 is that the present comparative example only does not contain the auxiliary WO3, and the rest of the preparation method and test conditions are the same as those of Example 1.

[0100] Comparative Example 5

[0101] Compared with Example 1, the difference between the preparation method of the catalyst and Example 1 is that the present comparative example only does not contain the active component CeO2, and the rest of the preparation method and test conditions are the same as those of Example 1.

[0102] Performance detection:

[0103] The catalysts provided by the above examples and comparative examples are subjected to catalytic performance test, and the conversion rate of catalytic removal of NOx is shown in Table 1 as follows:

[0104] Table 1

[0105]

[0106] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1.A catalyst for catalytic reduction of NOx, comprising the following components: a carrier: a core-shell structure SiO2-TiO2, an active component: CeO2, an auxiliary component: Pr2O3 and WO3, and amino groups on the surface of the catalyst; wherein the mass percentage of CeO2 is 4%-20%, the mass percentage of Pr2O3 is 1%-5%, the mass percentage of WO3 is 1%-5%, and the molar ratio of Ti to Si is 1-5, based on the mass of the carrier. 2.A method for preparing the catalyst of claim 1, comprising the following steps: (1) mixing a dispersant, a solvent and a lye uniformly, adding a silicon source, and then performing suction filtration, washing, drying, to obtain a silicon nano core; (2) grinding the silicon nano core into powder, adding it to a mixed solution of the solvent and the lye, and then adding a titanium source, and then performing heat preservation, suction filtration, washing, drying, and calcination, to obtain a core-shell structure carrier; (3) grinding the core-shell structure carrier into powder, adding a precursor solution of an active component, and then performing drying, to obtain a core-shell catalyst loaded with the active component; (4) grinding the core-shell catalyst loaded with the active component into powder, adding a precursor solution of an auxiliary component, and then performing drying and calcination; and (5) grinding the product obtained in step (4) into powder, adding a mixed solution containing an amino-containing organic ligand, an organic solvent and an acid, and then performing suction filtration, washing, drying and calcination. The dispersant in step (1) comprises one or more of cetyltrimethylammonium bromide (CTAB), P123 and polyethylene glycol; and the silicon source is selected from one or more of tetraethyl orthosilicate, tetramethyl orthosilicate, silicon tetrachloride and silicic acid. The titanium source in step (2) is selected from tetrabutyl titanate and / or titanium tetrachloride. The calcination temperature in step (2) is 200-600℃, and the calcination time is 2-6h. The calcination temperature in step (4) is 200-600℃, and the calcination time is 2-6h. In step (5), the amino-containing organic ligand is selected from one or more of 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 2-amino-4,4'-diphenyldicarboxylic acid, ethylenediamine and phenylenediamine. In step (5), the acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, acetic acid and formic acid. In step (5), the mass-volume ratio of the product obtained in step (4) to the amino-containing organic ligand is 1g:2-4ml, the volume ratio of the amino-containing organic ligand to the organic solvent is 1:1-2, and the volume ratio of the amino-containing organic ligand to the acid is 1:1-3. The catalyst is used for catalyzing the SCR reaction of NOx; and the temperature of the SCR reaction is 100℃-600℃. ​ ​ 3. The method of claim 2, wherein, ​ 4. The method of claim 2, wherein, ​ 5. The method of claim 2, wherein, ​ 6. The method of claim 2, wherein, ​ 7. The method of claim 2, wherein, ​ 8. The method of claim 2, wherein, ​ 9. The method of claim 2, wherein, ​ 10. Use of a catalyst as claimed in claim 1 or a catalyst prepared by the process as claimed in any one of claims 2 to 9, characterized in that, ​

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