CN114887618A - MnO with magnesium-aluminum composite oxide as carrier x High-efficiency ultralow-temperature denitration catalyst - Google Patents
MnO with magnesium-aluminum composite oxide as carrier x High-efficiency ultralow-temperature denitration catalyst Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 56
- 239000002131 composite material Substances 0.000 title claims abstract description 32
- SNAAJJQQZSMGQD-UHFFFAOYSA-N aluminum magnesium Chemical compound [Mg].[Al] SNAAJJQQZSMGQD-UHFFFAOYSA-N 0.000 title claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 29
- 238000006243 chemical reaction Methods 0.000 claims abstract description 19
- 238000002360 preparation method Methods 0.000 claims abstract description 10
- 229940071125 manganese acetate Drugs 0.000 claims abstract description 9
- UOGMEBQRZBEZQT-UHFFFAOYSA-L manganese(2+);diacetate Chemical compound [Mn+2].CC([O-])=O.CC([O-])=O UOGMEBQRZBEZQT-UHFFFAOYSA-L 0.000 claims abstract description 9
- GDVKFRBCXAPAQJ-UHFFFAOYSA-A dialuminum;hexamagnesium;carbonate;hexadecahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Al+3].[Al+3].[O-]C([O-])=O GDVKFRBCXAPAQJ-UHFFFAOYSA-A 0.000 claims abstract description 7
- 229960001545 hydrotalcite Drugs 0.000 claims abstract description 7
- 229910001701 hydrotalcite Inorganic materials 0.000 claims abstract description 7
- 239000000243 solution Substances 0.000 claims description 24
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 18
- 239000008367 deionised water Substances 0.000 claims description 16
- 229910021641 deionized water Inorganic materials 0.000 claims description 16
- 239000011259 mixed solution Substances 0.000 claims description 14
- 239000003513 alkali Substances 0.000 claims description 10
- 239000012266 salt solution Substances 0.000 claims description 10
- 238000001354 calcination Methods 0.000 claims description 9
- 239000011777 magnesium Substances 0.000 claims description 8
- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 claims description 8
- 239000002243 precursor Substances 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 8
- 239000002585 base Substances 0.000 claims description 7
- 239000002244 precipitate Substances 0.000 claims description 6
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 4
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 claims description 4
- 238000001556 precipitation Methods 0.000 claims description 4
- 238000000967 suction filtration Methods 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- 238000005303 weighing Methods 0.000 claims description 4
- 238000001704 evaporation Methods 0.000 claims description 2
- 230000008020 evaporation Effects 0.000 claims description 2
- 229910021645 metal ion Inorganic materials 0.000 claims description 2
- 229910000861 Mg alloy Inorganic materials 0.000 claims 1
- 229910052782 aluminium Inorganic materials 0.000 claims 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims 1
- 238000000034 method Methods 0.000 abstract description 14
- 238000001179 sorption measurement Methods 0.000 abstract description 9
- 239000002994 raw material Substances 0.000 abstract description 4
- 239000000126 substance Substances 0.000 abstract description 4
- MFUVDXOKPBAHMC-UHFFFAOYSA-N magnesium;dinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MFUVDXOKPBAHMC-UHFFFAOYSA-N 0.000 abstract 2
- XNDZQQSKSQTQQD-UHFFFAOYSA-N 3-methylcyclohex-2-en-1-ol Chemical compound CC1=CC(O)CCC1 XNDZQQSKSQTQQD-UHFFFAOYSA-N 0.000 abstract 1
- RJZNFXWQRHAVBP-UHFFFAOYSA-I aluminum;magnesium;pentahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[Mg+2].[Al+3] RJZNFXWQRHAVBP-UHFFFAOYSA-I 0.000 abstract 1
- 238000000975 co-precipitation Methods 0.000 abstract 1
- 238000005470 impregnation Methods 0.000 abstract 1
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 49
- 239000011572 manganese Substances 0.000 description 15
- 230000000694 effects Effects 0.000 description 8
- 230000003197 catalytic effect Effects 0.000 description 5
- 239000006185 dispersion Substances 0.000 description 5
- 239000011148 porous material Substances 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 229910052748 manganese Inorganic materials 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- 229910010413 TiO 2 Inorganic materials 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 239000002041 carbon nanotube Substances 0.000 description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 description 2
- 238000010531 catalytic reduction reaction Methods 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000006477 desulfuration reaction Methods 0.000 description 2
- 230000023556 desulfurization Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 150000004679 hydroxides Chemical class 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 239000002086 nanomaterial Substances 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- 229910000314 transition metal oxide Inorganic materials 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- 241000282414 Homo sapiens Species 0.000 description 1
- 241001465754 Metazoa Species 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 238000003916 acid precipitation Methods 0.000 description 1
- 239000000443 aerosol Substances 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 239000000809 air pollutant Substances 0.000 description 1
- 231100001243 air pollutant Toxicity 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
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- 238000010438 heat treatment Methods 0.000 description 1
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- 230000000607 poisoning effect Effects 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
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- 238000012216 screening Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
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- 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
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- 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
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
- B01J35/61—Surface area
- B01J35/613—10-100 m2/g
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- B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
- B01J35/63—Pore volume
- B01J35/633—Pore volume less than 0.5 ml/g
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Abstract
The invention relates to a method for deriving MgAlO from hydrotalcite x The composite oxide is used as a carrier and supports MnO x The high-efficiency ultralow-temperature denitration catalyst has a chemical structural formula of MnA/MgAlO x . The catalyst is prepared by taking magnesium nitrate hexahydrate and aluminum nitrate nonahydrate as raw materials through a coprecipitation method and high-temperature roasting to obtain MgAl-LDH (magnesium aluminum hydroxide) -derived MgAlO x The composite oxide carrier is loaded with active component manganese acetate by impregnation method. The raw materials used in the invention are cheap and easily available, the conditions are mild, the preparation process is simple, and the method has important scientific significance and good application prospect. The prepared MnA/MgAlO x The catalyst makes full use of hydrotalciteDerivatized MgAlO x The composite oxide has high specific surface area and adsorption performance, so that the active components are highly dispersed and the composite oxide is applied to NH 3 Shows excellent ultra-low temperature denitration performance and high N in SCR reaction 2 Selectivity and water resistance.
Description
Technical Field
The invention relates to MnO taking magnesium-aluminum composite oxide as a carrier x Preparation of base efficient ultralow temperature denitration catalyst and catalytic reduction (NH) of base efficient ultralow temperature denitration catalyst by taking ammonia as reducing agent 3 -SCR) in the reaction of removing nitrogen oxides, belonging to the field of nano material preparation and catalytic application.
Background
Nitrogen Oxides (NO) x Mainly comprising NO and NO 2 ) Is one of the major air pollutants. At present, NO x Including stationary sources (industrial activities such as power plants) and mobile sources (diesel vehicles, gasoline vehicles, etc.) combustion of fossil fuels. NO x The emission of (A) not only causes acid rain, photochemical smog, ozone depletion and greenhouse effect, but also accelerates secondary pollutants such as aerosol and PM 2.5 And the formation of fine particles. The environmental problems caused by the corrosion can corrode buildings, and great threats can be caused to the health of human beings, animals and plants. Thus how to remove NO efficiently x Is a hot issue of current concern.
Selective catalytic reduction (NH) with ammonia as a reducing agent, in contrast to numerous denitration techniques 3 SCR) is one of the most efficient and promising technologies, and has been widely used for effective denitration reactions of fixed sources and mobile sources. The catalyst being NH 3 Core and critical in the SCR reaction. Many transition metal oxide catalysts are used at NH 3 Excellent activity in SCR reactions, where V 2 O 5 -WO 3 (MoO 3 )/TiO 2 As a typical and efficient catalyst, NH has been commercialized for medium temperature processes (300- 3 -SCR technology. For optimum effect, NH 3- The SCR reaction device needs to be installed before the dust removing device and the desulfurization device. Although V-based catalyst to SO 2 The poisoning sensitivity is low, but after long-term operation, the catalyst still can be subjected to high-concentration SO in flue gas 2 And ash, leading to deactivation of the active sites on the catalyst surface by plugging or capping. If the influence of toxic smoke on the catalyst is reduced, the effect is prolongedService life of the catalyst, NH 3 The SCR reactor is generally installed downstream of the dust removal device and the desulfurization device. The temperature of the gas reaching the position is lower than about 200 ℃, and in order to ensure that the gas temperature is in an active temperature window of the V-based catalyst, a heating device needs to be additionally arranged, so that the operation cost of the reaction is increased. And the V-based catalyst has the defects of biotoxicity, low selectivity at high temperature and the like, so that the development of the low-cost, low-temperature and high-activity catalyst to replace the V-based catalyst has important significance.
In recent years, much of the research on V-free catalysts has focused on transition metal oxides and rare earth metal oxides, including Ce, Fe, Cu and Mn-based catalysts. Wherein Mn with strong oxidation-reduction capability and rich variable valence state is in NH 3 Excellent low temperature performance in SCR reactions. The manganese supported catalyst can further solve single MnO x The catalyst has the defects of narrow operation temperature window, poor thermal stability and the like. Suitable supports not only promote dispersion of the active metal components, but also provide ample space for the catalytic reaction. Hitherto, Al 2 O 3 、TiO 2 、SiO 2 Activated Carbon Fibers (ACF) and Carbon Nanotubes (CNT) have all been investigated as support materials for manganese-based catalysts. However, in previous studies, MnO x The aggregation on the surface of the support limits the activity of the catalyst to a large extent, so that the search for a suitable support to achieve a high dispersion of the active components is critical to the breakthrough of the barrier to the use of manganese-based catalysts.
Layered double hydroxides (also called hydrotalcite, LDHs) are two-dimensional nano materials with great application potential, and the chemical composition of the layered double hydroxides is expressed as [ M 1-x 2+ M x 3+ (OH) 2 ][A n− ] x/n •mH 2 O, wherein M 2+ And M 3+ Respectively represent the divalent metal cation and the trivalent metal cation occupying the center of an octahedron in the main body laminate and are distributed orderly in atomic level; a. the n− Being interlayer anions, e.g. NO 3 - And CO 3 2- . After high-temperature roasting, the layered structure of LDHs collapses and is converted into composite metal oxideAn object (LDO). LDO has a large specific surface area and a strong adsorption capacity, not only allows high dispersion of active components, but also provides abundant adsorption sites for adsorption of gaseous reactants. In addition, the adjustment of the physical and chemical properties of the LDO can be realized by changing the roasting conditions and the synthesis method. While MgAl-LDH-derived MgAlO x Composite oxide in NO only x Storage Reduction (NSR) reactions, which are considered as NH, are well studied 3 SCR catalyst supports have been studied only rarely.
For the reasons, the invention aims to research and develop MnO taking magnesium-aluminum composite oxide as a carrier x A high-efficiency ultralow-temperature denitration catalyst is disclosed.
Disclosure of Invention
The invention aims to provide MnO taking magnesium-aluminum composite oxide as a carrier x A high-efficiency ultralow-temperature denitration catalyst is disclosed.
The invention relates to MnO taking magnesium-aluminum composite oxide as a carrier x The high-efficiency ultralow-temperature denitration catalyst comprises the following preparation steps:
(1) weighing proper amount of magnesium nitrate (Mg (NO) in proportion 3 ) 2 ·6H 2 O), aluminum nitrate (Al (NO) 3 ) 2 ·9H 2 O) is dissolved in deionized water to obtain a mixed salt solution with the configured concentration of 2 mol.L -1 NaOH and 1 mol. L -1 Na of (2) 2 CO 3 Water solution to form mixed alkali solution;
(2) dropwise adding the mixed salt solution and the mixed alkali solution obtained in the step (1) into deionized water under the condition of continuous stirring, controlling the pH value of the solution to be 10 +/-0.5 by adjusting the dropping speed, and continuously stirring the obtained mixed solution for 1-24 hours after the precipitation is finished;
(3) after cooling to room temperature, carrying out suction filtration and washing on the mixed solution obtained in the step (2) to neutrality, and drying the obtained precipitate at the temperature of 100 ℃ and 150 ℃ overnight to obtain an MgAl-LDH precursor;
(4) calcining the MgAl-LDH precursor obtained in the step (3) for 4-10 h at different calcining temperatures (600-900 ℃), and preparing MgAlO x A composite oxide support;
(5) MgAlO obtained in the step (4) x Dissolving the composite oxide carrier in deionized water, adding a certain amount of manganese acetate (MnC) 4 H 6 O 6 ·4H 2 O), after the hydrotalcite is fully dissolved, putting the obtained solution into a water bath kettle for evaporation to dryness, transferring the solution to a muffle furnace for calcination at 500 ℃ for 4-10 h, and finally obtaining the hydrotalcite-derived MgAlO x Composite oxide as carrier and loaded with high-dispersion MnO x The high-efficiency denitration catalyst.
In the method, in the step (1), the Mg/Al molar ratio of the mixed salt solution is 1-4, and the total metal ion concentration is 1.5 mol.L -1 。
In the method, in the step (5), the mass fraction of the manganese oxide is 30-50%.
Compared with the prior art, the invention has the following obvious substantive characteristics.
The catalyst synthesized by the invention is MnO taking magnesium-aluminum composite oxide as a carrier x A high-efficiency ultralow-temperature denitration catalyst is disclosed.
The invention fully utilizes the physical and chemical properties of larger specific surface area, strong adsorption capacity and the like of the hydrotalcite derived magnesium-aluminum composite oxide carrier, and realizes MnO x High dispersion on the surface of the support.
The catalyst synthesized by the invention is applied to low-temperature NH 3 Excellent catalytic performance in SCR reaction (NO in the range of 100 ℃ and 300℃) x Conversion rate up to more than 80%), high N 2 Selectivity and excellent water resistance.
The method is simple and easy to implement, mild in preparation conditions, cheap and easily available in raw materials, and free of toxic reaction raw materials, so that the catalyst is an environment-friendly green synthetic catalyst.
Drawings
FIG. 1 shows Mn/MgAlO prepared by the present invention x NO of catalyst x And (4) conversion rate.
FIG. 2 shows Mn/MgAlO prepared by the present invention x Water resistance performance curve diagram of catalyst.
FIG. 3 shows MgAl-LDH and MgAlO prepared by the present invention x Carrier and Mn/MgAlO x XRD pattern of catalyst.
FIG. 4 shows Mn/MgAlO prepared by the present invention x Pore size distribution curve pattern of the catalyst.
Detailed Description
The present invention is further illustrated by the following specific examples, which include, but are not limited to, the following examples.
Example one:
(1) 14.4g of magnesium nitrate (Mg (NO) was weighed 3 ) 2 ·6H 2 O), 7.0g of aluminum nitrate (Al (NO) 3 ) 2 ·9H 2 O) is dissolved in 50mL deionized water to obtain a mixed salt solution, 8.0g of sodium hydroxide and 10.6g of sodium carbonate are weighed and dissolved in a small amount of deionized water, the dissolved alkali solution is transferred to a 100mL volumetric flask, and the prepared concentration is 2 mol.L -1 NaOH and 1 mol. L -1 Na of (2) 2 CO 3 Water solution to form mixed alkali solution;
(2) dropwise adding the mixed salt solution and the mixed alkali solution obtained in the step (1) into deionized water under the condition of continuous stirring, controlling the pH value of the solution to be 10 +/-0.5, and continuously stirring the obtained mixed solution for 24 hours after precipitation is finished;
(3) after cooling to room temperature, carrying out suction filtration on the mixed solution obtained in the step (2), repeatedly washing with deionized water until the mixed solution is neutral, and drying the obtained precipitate at 100 ℃ overnight to obtain a MgAl-LDH precursor;
(4) calcining the MgAl-LDH precursor obtained in the step (3) at the calcining temperature of 800 ℃ for 4 h to prepare MgAlO x A composite oxide support;
(5) weighing 0.5g of MgAlO obtained in the step (4) x The composite oxide support was dissolved in 50mL of deionized water, and 2.6g of manganese acetate (MnC) was weighed 4 H 6 O 6 ·4H 2 O) is added into the mixed solution, after the mixed solution is fully dissolved, the obtained solution is evaporated to dryness and dried overnight, the obtained precipitate is placed into a muffle furnace to be calcined for 4 hours at the temperature of 500 ℃, and MnO taking magnesium-aluminum composite oxide as a carrier is finally obtained x High-efficiency ultralow-temperature denitration catalystAbbreviated as MnA/Mg 3 Al 1 O x -800。
Example two:
(1) 12.8g of magnesium nitrate (Mg (NO) was weighed 3 ) 2 ·6H 2 O), 9.375g of aluminum nitrate (Al (NO) 3 ) 2 ·9H 2 O) is dissolved in 50mL deionized water to obtain a mixed salt solution, 8.0g of sodium hydroxide and 10.6g of sodium carbonate are weighed and dissolved in a small amount of deionized water, the dissolved alkali solution is transferred to a 100mL volumetric flask, and the prepared concentration is 2 mol.L -1 NaOH and 1 mol. L -1 Na (b) of 2 CO 3 Water solution to form mixed alkali solution;
(2) dropwise adding the mixed salt solution and the mixed alkali solution obtained in the step (1) into deionized water under the condition of continuous stirring, controlling the pH value of the solution to be 10 +/-0.5, and continuously stirring the obtained mixed solution for 24 hours after precipitation is finished;
(3) after cooling to room temperature, carrying out suction filtration on the mixed solution obtained in the step (2), repeatedly washing with deionized water until the mixed solution is neutral, and drying the obtained precipitate at 100 ℃ overnight to obtain a MgAl-LDH precursor;
(4) calcining the MgAl-LDH precursor obtained in the step (3) at the calcining temperature of 800 ℃ for 4 h to prepare MgAlO x A composite oxide support;
(5) weighing 0.5g of MgAlO obtained in the step (4) x The composite oxide support was dissolved in 30mL of deionized water, and 2.6g of manganese acetate (MnC) was weighed 4 H 6 O 6 ·4H 2 O) is added into the mixed solution, after the mixed solution is fully dissolved, the obtained solution is evaporated to dryness and dried overnight, the obtained precipitate is placed into a muffle furnace to be calcined for 4 hours under the condition of 500 ℃, and finally MnO taking magnesium-aluminum composite oxide as a carrier is obtained x Base high-efficiency ultralow-temperature denitration catalyst abbreviated as MnA/Mg 2 Al 1 O x -800。
Example three:
the prepared Mn/MgAlO x The catalyst is used in the denitration process, is pressed into 40-60 mesh particles through tabletting and screening, is filled into a quartz tube with the inner diameter of 5mm, and is tested in a fixed bed reactor. The simulation denitration process is 500 ppm NO、500 ppm NH 3 、5%O 2 、5%H 2 O (when used), N 2 In a reaction atmosphere as an equilibrium gas, with a total gas flow rate of 200ml min −1 . The reaction temperature range is 100-300 ℃, one test point is taken at every 50 ℃, and the reaction is stabilized for 20min at each test point. Nitrogen oxide analyzer with chemiluminescence method is adopted to monitor NO at outlet in experiment process x The concentration of (2). Mn/MgAlO prepared by the invention x NO of catalyst x The conversion is shown in FIG. 1, which shows excellent catalytic activity over a wide temperature range (100 ℃ C. and 300 ℃ C.). Mn/MgAlO x Water resistance of the catalyst is shown in FIG. 2, NO at 200 ℃ for fresh catalyst x The conversion is almost 100%, when 5% by volume of H is fed 2 After O, NO thereof x The conversion rate only dropped from 99% to 91.7% within 8 h. After the water supply was stopped, the catalytic activity of the catalyst was almost restored to the initial state. The catalyst prepared by the invention has good catalytic activity, high selectivity and good water resistance, which is mainly attributed to MgAlO x The carrier has larger specific surface area and adsorption performance, and promotes MnO on one hand x On the other hand, provides rich adsorption sites for the adsorption of the reaction gas.
Example four:
FIG. 2 shows MgAl-LDH and MgAlO prepared by the present invention x Carrier and Mn/MgAlO x XRD pattern of catalyst. The XRD pattern shows that the MgAl-LDH is successfully prepared by the method, and the MgAl-LDH is converted into MgAlO after high-temperature calcination x A composite metal oxide. After loading Mn, MgAlO x The diffraction peak of MgO in the composite metal oxide disappears, the crystallinity of the carrier is reduced, and the SCR activity is facilitated.
Example five:
the specific surface area, pore size distribution and pore volume of the catalyst were measured on a fully automated specific surface area and porosity analyzer, model ASAP 2460, manufactured by Micromeritics, usa. Mn/MgAlO x N of catalyst 2 The adsorption and desorption curve conforms to the IV-type isotherm in IUPAC, and is accompanied by H3-type hysteresis loop in a relatively high pressure interval, which indicates the generation of the mesoporous structure in the sampleAnd (4) generating. Specific surface area (S) of sample BET ) Pore volume (V) p ) And average pore diameter (D) p ) Are respectively 56.4 m 2 /g、0.29 cm 3 G and 17.2 nm.
Claims (4)
1. MnO with magnesium-aluminum composite oxide as carrier x The preparation method of the base efficient ultralow temperature denitration catalyst is characterized by comprising the following steps:
(1) weighing a certain amount of magnesium nitrate (Mg (NO) according to the proportion 3 ) 2 ·6H 2 O), aluminum nitrate (Al (NO) 3 ) 2 ·9H 2 O) is dissolved in deionized water to obtain a mixed salt solution with the preparation concentration of 2 mol.L -1 NaOH and 1 mol. L -1 Na of (2) 2 CO 3 Water solution to form mixed alkali solution;
(2) dropwise adding the mixed salt solution and the mixed alkali solution obtained in the step (1) into deionized water under the condition of continuous stirring, controlling the pH value of the solution to be 10 +/-0.5, and continuously stirring the obtained mixed solution for 1-24 hours after precipitation is finished;
(3) after cooling to room temperature, carrying out suction filtration and washing on the mixed solution obtained in the step (2) to neutrality, and drying the obtained precipitate at the temperature of 100 ℃ and 150 ℃ overnight to obtain an MgAl-LDH precursor;
(4) calcining the MgAl-LDH precursor obtained in the step (3) at different temperatures (600 ℃ and 900 ℃) for 4 to 10 hours to prepare MgAlO x A composite oxide support;
(5) MgAlO obtained in the step (4) x Dissolving the composite oxide carrier in deionized water, adding a certain amount of manganese acetate (MnC) 4 H 6 O 6 ·4H 2 O), after the hydrotalcite is fully dissolved, putting the obtained solution into a water bath kettle for evaporation to dryness, transferring the solution to a muffle furnace for calcination at 500 ℃ for 4-10 h, and obtaining MgAlO derived from hydrotalcite x The composite oxide is used as a carrier and supports MnO x The high-efficiency denitration catalyst.
2. The magnesium alloy of claim 1MnO with aluminum composite oxide as carrier x The preparation method of the base efficient ultralow temperature denitration catalyst is characterized by comprising the following steps of: in the step (1), the Mg/Al molar ratio of the mixed salt solution is 1 to 4, and the total metal ion concentration is 1.5 mol.L -1 。
3. The MnO containing magnesium aluminum composite oxide as carrier according to claim 1 x The preparation method of the base efficient ultralow temperature denitration catalyst is characterized by comprising the following steps of: in the step (5), the mass fraction of the manganese oxide is 30-50%.
4. The MnO containing magnesium aluminum composite oxide as carrier according to claim 1 x The preparation method of the base efficient ultralow temperature denitration catalyst is characterized by comprising the following steps of: application of the obtained catalyst to NH 3 Excellent ultra-low temperature denitration performance in SCR reaction, N 2 Selectivity and water resistance.
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| CN117504579A (en) * | 2023-11-13 | 2024-02-06 | 中国科学院过程工程研究所 | SCR denitration system taking CO as reducing agent, application of SCR denitration system and SCR denitration method |
| CN117563586A (en) * | 2023-11-24 | 2024-02-20 | 山东长泽新材料科技有限公司 | Solid catalyst and method for efficiently synthesizing methacrolein |
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