CN114377670A - Composite metal oxide catalyst for low-temperature SCR denitration and preparation method thereof - Google Patents

Composite metal oxide catalyst for low-temperature SCR denitration and preparation method thereof Download PDF

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CN114377670A
CN114377670A CN202111514402.XA CN202111514402A CN114377670A CN 114377670 A CN114377670 A CN 114377670A CN 202111514402 A CN202111514402 A CN 202111514402A CN 114377670 A CN114377670 A CN 114377670A
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metal oxide
composite metal
vanadium
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CN114377670B (en
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高翔
刘少俊
宋浩
郑成航
张宇
吴卫红
张霄
林青阳
杨洋
徐甸
张涌新
翁卫国
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Zhejiang University ZJU
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • B01J23/28—Molybdenum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B01D53/8628—Processes characterised by a specific catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • B01J23/30—Tungsten
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/32—Manganese, technetium or rhenium
    • B01J23/34—Manganese
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
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    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

The invention relates to a composite metal oxide catalyst for low-temperature SCR denitration and a preparation method thereof, belonging to the technical field of catalysts. The catalyst is obtained by performing electrostatic spinning or centrifugal spinning on two catalyst precursor solutions to obtain nano composite fibers and performing dielectric barrier discharge calcination treatment, wherein one of the two catalysts is a vanadium-titanium SCR catalyst, and the main component is V2O5‑WO3/TiO2Or V2O5‑MoO3/TiO2Wherein the V content is 1-5 wt.%, and the W or Mo content is1-10 wt.%; the other is an oxidation type catalyst FMn with a mullite structurexOyWherein the molar ratio of F to Mn is 1: 1-2, and F is selected from Sm, La, Ce, Pr, Eu, Gd or Y; the mass ratio of the oxidation catalyst to the vanadium-titanium SCR catalyst is 1: 1-10.

Description

Composite metal oxide catalyst for low-temperature SCR denitration and preparation method thereof
Technical Field
The invention relates to a low-temperature catalyst, in particular to a composite metal oxide catalyst for low-temperature SCR denitration and a preparation method thereof, and belongs to the technical field of catalysts.
Background
Nitrogen oxides (NOx) are one of the main atmospheric pollutants, mainly including Nitric Oxide (NO) and nitrogen dioxide (NO)2). NOx, which can exist stably in the atmosphere, can cause environmental problems such as acid rain, photochemical smog, ozone layer destruction, and the like, and also can be harmful to human health. In recent years, as the total energy consumption of China is continuously improved, fossil energy such as coal is continuously consumed, NOx always keeps higher emission, and the serious environmental pollution problem is caused.
In order to meet regulated emission requirements, a range of nitrogen oxide control technologies have been developed for coal fired power plants and industrial boilers. The Selective Catalytic Reduction (SCR) has the advantages of high denitration efficiency (up to more than 90%), good product selectivity, simple system operation control, mature and reliable technology and the like, becomes a denitration technology widely applied to the current coal-fired power plant, and has good application prospect in denitration of non-electric industries such as industrial boilers and the like.
Although the vanadium-titanium based SCR catalyst V was developed2O5-WO3/TiO2Or V2O5-MoO3/TiO2The method has been successfully applied at present, but still has the defect of higher working temperature, and has outstanding denitration performance only at 300-400 ℃. Therefore, the development of SCR catalysts with high activity at low temperature of 150 ℃ and 300 ℃ has been the target of researchers in all countries around the world.
Disclosure of Invention
The invention aims to provide a preparation method of a composite metal oxide catalyst for low-temperature SCR denitration, which aims to solve the problems of narrow temperature range and poor low-temperature performance of the existing SCR catalyst.
The invention mainly adopts the technical scheme that the method comprises the following steps:
a composite metal oxide catalyst for low-temperature SCR denitration is prepared through preparing nano composite fiber by electrostatic spinning or centrifugal spinning of two catalyst precursor solutions, and calcining by dielectric barrier discharge
One is a vanadium-titanium SCR catalyst, the main component is V2O5-WO3/TiO2Or V2O5-MoO3/TiO2Wherein the V content is 1-5 wt.%, the W or Mo content is 1-10 wt.%;
the other is an oxidation type catalyst FMn with a mullite structurexOyWherein the molar ratio of F to Mn is 1: 1-2, and F is selected from Sm, La, Ce, Pr, Eu, Gd or Y;
the mass ratio of the oxidation catalyst to the vanadium-titanium SCR catalyst is 1: 1-10.
Aiming at the defects of the existing catalytic denitration technology, the inventor develops and researches a composite SCR catalyst based on a vanadium-titanium SCR catalyst on the basis of long-term research and development of a flue gas denitration catalyst, and the composite SCR catalyst is used for improving the low-temperature denitration efficiency of the vanadium-titanium SCR catalyst. The test result shows that the composite SCR catalyst successfully widens the high-efficiency reaction temperature window of the vanadium-titanium SCR catalyst, improves the denitration efficiency of the vanadium-titanium SCR catalyst below 300 ℃, is simple and easy to operate, and is a method for preparing the high-performance SCR catalyst with low cost and large quantity.
The inventor researches and discovers that NO can form intermediate species such as nitrite on the oxidation catalyst after the vanadium-titanium SCR catalyst and the oxidation catalyst are compounded, the intermediate species can migrate to the surface of the vanadium-titanium SCR catalyst to react with ammonia species adsorbed on the surface of the vanadium-titanium SCR catalyst to generate nitrogen and water, and the defect of poor low-temperature performance caused by weak catalytic oxidation of NO at low temperature of the vanadium-titanium SCR catalyst is overcome. The composite method of the two catalysts adopts electrostatic spinning combined with dielectric barrier discharge calcination, can avoid the mutual influence between atoms in the two catalyst components, and improves the low-temperature denitration efficiency of the SCR catalyst while keeping the good high-temperature activity of the SCR catalyst.
Preferably, the mass ratio of the oxidation catalyst to the vanadium-titanium SCR catalyst is 1: 1-2. The purpose of adding the oxidation catalyst is to improve the low-temperature activity of the medium-high temperature SCR catalyst, but too much amount of the oxidation catalyst easily causes the decrease of the high-temperature performance in the catalyst itself. The optimal mass ratio of the oxidation catalyst to the vanadium-titanium SCR catalyst is 1: 1.
Preferably, the diameter of the nano composite fiber obtained by spinning is 100-900 nm.
In the present invention, the oxidation catalyst is preferably SmMnxOy。
A preparation method of the composite metal oxide catalyst for low-temperature SCR denitration comprises the following steps:
s1, preparing precursor solutions of the vanadium-titanium SCR catalyst and the oxidation catalyst respectively as spinning solutions, preparing the composite metal oxide fiber through electrostatic spinning or centrifugal spinning,
and S2, calcining the composite metal oxide fiber through dielectric barrier discharge to obtain the composite metal oxide catalyst.
Preferably, the oxidation catalyst SmMnxOyThe preparation method of the precursor solution comprises the following steps:
1) mixing polyethylene glycol, Pluronic F127 and water, and heating to dissolve to obtain a solution A containing a surfactant; mixing and dissolving a manganese-containing precursor, a samarium-containing precursor and the solution A to obtain a solution B;
2) adding H to solution B2O2Solution of manganese element and H2O2The molar ratio is 1: 1.2-1.5;
3) stirring the mixed solution obtained in the previous step for more than 2 hours, adding polyvinylpyrrolidone (PVP) and continuously stirring for 10-24 hours to obtain an oxidation type catalyst SmMnxOyAnd (3) precursor solution. The manganese-containing precursor is generally manganese nitrate, and the samarium-containing precursor is generally samarium nitrate.
In the invention, polyethylene glycol is used as a surfactant, PEG-400-600 is generally adopted, and high molecular weight is easy to cause adhesion.
Preferably, the electrospinning method in S1 is: and (3) respectively extracting two precursor solutions by using a 5-20 mL needle cylinder, connecting a needle head with a 10-20 kV direct-current high-voltage negative power supply, performing electrostatic spinning to form composite fibers, and placing the composite fibers in a vacuum box at 20-50 ℃ for drying for 24 hours.
Preferably, the specific process of calcining the composite metal oxide fiber by dielectric barrier discharge described in S2 is: under the atmosphere of oxygen, nitrogen, argon or a mixture of more than two gases, the output voltage and the frequency are respectively 8-12 kV and 8-10 kHz, so that the gas inside the reactor is broken down to generate dielectric barrier discharge, and the dielectric barrier discharge is kept for 30-60 min to prepare the composite metal oxide catalyst.
Preferably, the preparation method of the vanadium-titanium SCR catalyst precursor solution comprises the following steps: dissolving a vanadium-containing precursor, a tungsten-containing precursor/molybdenum-containing precursor and a titanium-containing precursor in water, fully stirring, adding polyvinylpyrrolidone (PVP) and continuously stirring for 10-24 hours to obtain V2O5-WO3/TiO2Or V2O5-MoO3/TiO2The precursor solution of (1). The vanadium-containing precursor is generally ammonium metavanadate, and the tungsten-containing precursorThe body is generally ammonium metatungstate, the molybdenum-containing precursor is generally ammonium molybdate tetrahydrate, and the titanium-containing precursor is one of tetrabutyl titanate or titanium sulfate. The vanadium-titanium SCR catalyst can be prepared by adopting the technology known in the field.
The invention relates to an application of a composite metal oxide catalyst in low-temperature SCR denitration, wherein the lower limit of the low-temperature denitration is 150 ℃. The composite metal oxide catalyst for low-temperature SCR denitration can widen the lower temperature limit of a high-efficiency temperature window (more than 300 ℃) of a vanadium-titanium SCR catalyst to 150 ℃ and ensure that the denitration efficiency exceeds 90 percent.
Compared with the prior art, the invention has the advantages that:
1. compared with the vanadium-titanium SCR catalyst, the catalyst has the advantages that the composite oxidation type catalyst SmMn is adoptedxOyThe obtained composite metal oxide catalyst not only obviously improves the low-temperature denitration efficiency, but also has no obvious influence on the medium-high temperature denitration performance of the original vanadium-titanium series SCR catalyst, and widens the temperature window of high-efficiency denitration;
2. compared with the traditional impregnation method and coprecipitation method, the method adopts electrostatic spinning combined with dielectric barrier discharge calcination to oxidize the catalyst SmMnxOyThe preparation method can controllably reduce the distance between different active sites on the two catalysts to micron order, realize the close contact between the sites and obtain the wide-temperature composite metal oxide catalyst with good performance.
Drawings
FIG. 1 is a scanning electron microscope image of a composite metal oxide catalyst prepared in example 2 of the present invention.
Detailed Description
The technical solution of the present invention will be further specifically described below by way of specific examples. It is to be understood that the practice of the invention is not limited to the following examples, and that any variations and/or modifications may be made thereto without departing from the scope of the invention.
In the present invention, all parts and percentages are by weight, unless otherwise specified, and the equipment and materials used are commercially available or commonly used in the art. The methods in the following examples are conventional in the art unless otherwise specified. The reagents used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.
Pluronic F127 powder, purchased from Sigma-Aldrich.
Example 1
The core of the invention is a preparation method of a composite metal oxide catalyst for low-temperature SCR denitration, which comprises two main steps of electrostatic spinning and plasma calcination, and the method comprises the following steps:
s1 preparation of composite metal oxide catalyst by electrostatic spinning method
1) Preparing a spinning precursor solution:
two precursor solutions, wherein one precursor solution is used for preparing an oxidation type catalyst SmMnxOyThe preparation method of the precursor solution comprises the following steps:
preparing a solution containing a surfactant, dissolving PEG-600 and Pluronic F127 in deionized water, and heating in a water bath at 60 ℃ until the solution is completely dissolved to obtain a solution A;
dissolving precursors of manganese nitrate and samarium nitrate in the solution A completely to obtain a solution B;
then 30% of H is added2O21.3 molar parts of hydrogen peroxide if the molar part of manganese nitrate is 1;
and stirring the mixed solution at room temperature for at least 2 hours, adding polyvinylpyrrolidone (PVP) and continuously stirring for 10-24 hours for later use.
The preparation method of the precursor solution is as follows:
dissolving a precursor ammonium metavanadate, ammonium metatungstate, tetrabutyl titanate or titanium sulfate in deionized water, magnetically stirring the solution for 0.5-2 hours, adding polyvinylpyrrolidone (PVP), and continuously stirring for 10-24 hours for later use.
2) Electrostatic spinning: and (3) respectively extracting the two precursor solutions prepared in the step by using a 5-20 mL needle cylinder, installing a 21G needle, fixing the needle on an injection pump, connecting the needle to a direct-current high-voltage negative power supply, covering an aluminum foil on a receiving roller, grounding, and carrying out electrostatic spinning, wherein the voltage of the direct-current negative power supply is 10-20 kV. The two precursors form a Taylor cone on a needle head connected with a high-voltage power supply, the repulsive force of an electric field overcomes the surface tension of the precursors, so that the precursors are stretched and whiped in the electric field, partial solvent is volatilized, and finally composite fibers are formed on a receiving device;
3) and drying the obtained composite fiber in a vacuum box at the temperature of 20-50 ℃ for 24 hours.
S2 composite fiber calcined by dielectric barrier discharge
The sample is placed between a rod-shaped electrode and the inner wall of a quartz tube in a discharge reactor, and the introduced gas can be oxygen, nitrogen, argon or a mixture of more than two gases. One end of a high-voltage high-frequency alternating current power supply is connected with a rod-shaped electrode of the low-temperature plasma reactor, the other end of the high-voltage high-frequency alternating current power supply is connected with an aluminum foil wrapped on the outer wall of the quartz tube, and the aluminum foil is grounded, and the output voltage and the frequency are respectively adjusted to be 8-12 kV and 8-10 kHz, so that gas inside the reactor can be broken down to generate dielectric barrier discharge, the dielectric barrier discharge is kept for 30-60 min, and the composite metal oxide catalyst is prepared.
Example 2
This example further defines that the oxidation catalyst is determined to have a mullite structure SmMn that is superior in NO oxidation performance based on example 12O5Wherein the molar ratio of Sm to Mn is 1: 2; SCR catalyst determined as V2O5-WO3/TiO2In which V is2O5The content is 1%: WO35% of carrier TiO294% (the precursor is selected to be tetrabutyl titanate); the mass ratio of the two catalysts is 1: 1.
The preparation method of the composite metal oxide catalyst for low-temperature SCR denitration comprises the following specific steps:
s1 preparation of composite metal oxide catalyst by electrostatic spinning method
S1.1 Oxidation catalyst SmMn2O5Preparing a precursor:
preparation of surfactant-containing solutions: dissolving PEG-600 and Pluronic F127 in deionized water, and heating in water bath at 60 ℃ until the solution is completely dissolved to obtain a solution A;
dissolving manganese nitrate and samarium nitrate in a molar ratio of 2: 1 in the solution A, and completely dissolving to obtain a solution B;
then 30% of H is added2O2Solution of manganese nitrate and H2O2The molar ratio of the solution is 1: 1.3;
the mixture was stirred at room temperature for 2 hours, and polyvinylpyrrolidone (PVP) was added and stirring was continued for 10 hours to obtain solution C for use.
S1.2, preparing a vanadium-titanium SCR catalyst precursor: dissolving precursors of ammonium metavanadate, ammonium metatungstate and tetrabutyl titanate in deionized water, magnetically stirring the solution for 2 hours, adding polyvinylpyrrolidone (PVP) and continuously stirring for 10 hours to obtain a solution D for later use.
S1.3 preparing the composite metal oxide fiber by an electrostatic spinning method:
respectively extracting the precursor solutions C and D prepared in the steps by using a 10mL needle cylinder, installing a 21G needle, connecting with a 15kV direct-current negative power supply voltage for electrostatic spinning, and obtaining composite fibers on a receiving roller device;
and (3) drying the composite fiber obtained in the step in a vacuum box at the temperature of 20 ℃ for 24 hours to obtain the uncalcined composite fiber.
S2 composite fiber calcined by dielectric barrier discharge
And (2) placing the composite fiber obtained in the step into a plasma reactor, exposing the composite fiber to a mixed atmosphere of 5% of oxygen and 95% of nitrogen, keeping the mixed atmosphere for 30min, adjusting the output voltage and the frequency to 10kV and 8kHz respectively, treating the composite fiber in a dielectric barrier discharge mode for 30min, and finally obtaining the composite metal oxide catalyst for low-temperature SCR denitration.
FIG. 1 is a scanning electron micrograph of a composite metal oxide catalyst prepared in example 2 of the present invention, in which the left and right two graphs show the change in the average diameter of composite fibers between 600nm and 500 m.
Application example catalyst Activity test
0.1g of the composite metal oxide catalyst prepared in the experimental example 2 and a common vanadium-titanium SCR catalyst are taken to carry out catalyst activity test, and the catalyst activity evaluation is carried out in a fixed bed reactor with the inner diameter of 5 mm.
Preparation of a common vanadium-titanium SCR catalyst (an equivalent volume impregnation method):
1) weighing appropriate amount of ammonium metavanadate powder, dissolving in deionized water, adding oxalic acid (H)2C2O4·2H2O) is used for assisting in dissolving, and the molar weight is twice of that of ammonium metavanadate. The mixed solution was continuously stirred at 60 ℃ until the solution turned dark blue (VO)2 +)；
2) Weighing a proper amount of ammonium metatungstate powder, and dissolving the ammonium metatungstate powder in deionized water. Adding oxalic acid (H)2C2O4·2H2O) is used for assisting in dissolving, and the molar weight is twice of that of the ammonium metatungstate. Continuously stirring the mixed solution at 60 ℃ until the ammonium metatungstate is completely dissolved;
3) weighing appropriate amount of TiO2Powder, measuring appropriate ammonium metavanadate solution and ammonium metatungstate solution (the volume of the solution is the same as that of the carrier), and tiO2Pouring the powder into a mixed solution of ammonium metavanadate solution and ammonium metatungstate, fully stirring, and standing overnight;
4) the catalyst which had been left standing overnight was dried at a constant temperature of 110 ℃ for a period of 300 min. Calcining at 500 deg.C for 300min in a muffle furnace under air environment, and heating at 10 deg.C/min to obtain impregnation V2O5-WO3/TiO2A catalyst.
O2、NO/N2、NH3/N2Mixing with N2 controlled by mass flow meter to obtain simulated flue gas with composition of 5% O2、350ppmNO、350ppmNH3N2 is balance gas, and the space velocity is 73000h-1. The reaction temperature is 150-300 ℃, NH3The NO is 1. Gas components are detected by an infrared flue gas analyzer to compare the denitration efficiency of the composite metal oxide catalyst and the conventional vanadium-titanium SCR catalyst at different temperaturesThe results are shown in Table 1.
TABLE 1 denitration efficiency comparison results (%)
Temperature (. degree.C.) 150 175 200 225 250 300
Vanadium-titanium SCR catalyst 9.99 14.19 20.57 29.03 42.78 95.83
The invention relates to a composite catalyst 91.41 100 100 100 100 100
The key point of the invention is the synergistic enhancement effect of the two catalysts on the low-temperature denitration performance after the two catalysts are compounded. The test proves that the oxidation type catalyst SmMn2O5After the catalyst is compounded with the existing vanadium-titanium SCR catalyst, the catalytic performance of the vanadium-titanium SCR catalyst is enhanced. The composite metal oxide catalyst is applied to the catalysis of flue gas denitration, wherein the low temperature is 150-300 ℃, and the denitration efficiency can reach more than 90% at 150 ℃.
In addition, the inventors compared the oxidation catalyst SmMn2O5The catalyst activity (measured under the same experimental conditions) when the catalyst is mixed with the vanadium-titanium SCR catalyst at a mass ratio of 1: 1 to 1: 2, respectively. SmMn as oxidation catalyst2O5When the mass ratio of the catalyst to the vanadium-titanium SCR catalyst is 1: 2, the denitration efficiency of the obtained composite metal oxide catalyst at the temperature of 150 ℃ is 50.79%, and the denitration efficiency at the temperature of 175 ℃ is 88.01%; SmMn as oxidation catalyst2O5When the mass ratio of the catalyst to the vanadium-titanium SCR catalyst is 1: 1, the denitration efficiency of the obtained composite metal oxide catalyst at the temperature of 150 ℃ is 91.41%, and the denitration efficiency of the obtained composite metal oxide catalyst at the temperature of 175 ℃ is 100%, so that the amount of the oxidation catalyst in the composite catalyst determines the low-temperature denitration performance of the composite catalyst, namely the higher the content of the oxidation catalyst is, the better the low-temperature denitration performance of the composite catalyst is.
In conclusion, the composite metal oxide catalyst for low-temperature SCR denitration provided by the invention improves the denitration efficiency of the vanadium-titanium SCR catalyst at low temperature (150-300 ℃) by 4.17-85.81% under the same condition, and obviously improves the low-temperature performance.
Example 3
Based on the preparation method of the composite metal oxide catalyst for low-temperature SCR denitration, the formula of the oxidation catalyst is changed, and the performance of the composite catalyst in a low-temperature range is observed under the same reaction conditions. The test method refers to the catalyst activity test, and the comparison result of the activity of the composite metal oxide catalyst of different oxidation catalysts and the activity of the common vanadium-titanium SCR catalyst is shown in the table 2.
Table 2 catalyst activity comparison (%)
Figure BDA0003403580840000081
As can be seen from table 2, when the oxidation catalyst in the composite metal oxide catalyst is replaced with other formula having oxidation ability, the improvement of the denitration efficiency still exists at low temperature, and the improvement effect changes with the change of the oxidation ability, the stronger the oxidation ability is, the better the improvement effect is. Therefore, the preparation method of the composite metal oxide catalyst for low-temperature SCR denitration provided by the invention has certain universality aiming at different composite metal oxides.
The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
The composite metal oxide catalyst for low-temperature SCR denitration and the preparation method thereof provided by the present invention are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims (9)

1. A composite metal oxide catalyst for low-temperature SCR denitration is characterized in that: the catalyst is obtained by electrostatic spinning or centrifugal spinning of two catalyst precursor solutions to obtain nano composite fibers and then dielectric barrier discharge calcination treatment, wherein the two catalysts are
One is a vanadium-titanium SCR catalyst, the main component is V2O5-WO3/TiO2Or V2O5-MoO3/TiO2Wherein the V content is 1-5 wt.%, the W or Mo content is 1-10 wt.%;
the other is an oxidation type catalyst FMn with a mullite structurexOyWherein the molar ratio of F to Mn is 1: 1-2, and F is selected from Sm, La, Ce, Pr, Eu, Gd or Y;
the mass ratio of the oxidation catalyst to the vanadium-titanium SCR catalyst is 1: 1-10.
2. The composite metal oxide catalyst according to claim 1, characterized in that: the mass ratio of the oxidation catalyst to the vanadium-titanium SCR catalyst is 1: 1-2.
3. The composite metal oxide catalyst according to claim 1, characterized in that: the diameter of the nano composite fiber obtained by spinning is 100-900 nm.
4. A method for preparing the composite metal oxide catalyst for low-temperature SCR denitration according to claim 1, characterized by comprising the steps of:
s1, preparing precursor solutions of the vanadium-titanium SCR catalyst and the oxidation catalyst respectively as spinning solutions, preparing the composite metal oxide fiber through electrostatic spinning or centrifugal spinning,
and S2, calcining the composite metal oxide fiber through dielectric barrier discharge to obtain the composite metal oxide catalyst.
5. The method of claim 4, wherein: the oxidation catalyst SmMnxOyThe preparation method of the precursor solution comprises the following steps:
1) mixing polyethylene glycol, Pluronic F127 and water, and heating to dissolve to obtain a solution A containing a surfactant; mixing and dissolving a manganese-containing precursor, a samarium-containing precursor and the solution A to obtain a solution B;
2) adding H to solution B2O2Solution of manganese element and H2O2The molar ratio is 1: 1.2-1.5;
3) stirring the mixed solution obtained in the previous step for more than 2 hours, adding polyvinylpyrrolidone (PVP) and continuously stirring for 10-24 hours to obtain an oxidation type catalyst SmMnxOyAnd (3) precursor solution.
6. The method of claim 4, wherein: the electrostatic spinning method in S1 comprises the following steps: and (3) respectively extracting two precursor solutions by using a 5-20 mL needle cylinder, connecting a needle head with a 10-20 kV direct-current high-voltage negative power supply, performing electrostatic spinning to form composite fibers, and placing the composite fibers in a vacuum box at 20-50 ℃ for drying for 24 hours.
7. The method of claim 4, wherein: s2 the specific process of calcining the composite metal oxide fiber by dielectric barrier discharge is as follows: under the atmosphere of oxygen, nitrogen, argon or a mixture of more than two gases, the output voltage and the frequency are respectively 8-12 kV and 8-10 kHz, so that the gas inside the reactor is broken down to generate dielectric barrier discharge, and the dielectric barrier discharge is kept for 30-60 min to prepare the composite metal oxide catalyst.
8. The method of claim 4, wherein: the preparation method of the vanadium-titanium SCR catalyst precursor solution comprises the following steps:
dissolving a vanadium-containing precursor, a tungsten-containing precursor/molybdenum-containing precursor and a titanium-containing precursor in water, fully stirring, adding polyvinylpyrrolidone (PVP) and continuously stirring for 10-24 hours to obtain V2O5-WO3/TiO2Or V2O5-MoO3/TiO2The precursor solution of (1).
9. The application of the composite metal oxide catalyst in low-temperature SCR denitration according to claim 1, wherein the low-temperature denitration lower limit is 150 ℃.
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