CN117000246A - Fe (Fe) 3 O 4 -TiO 2 Catalyst, preparation method and application thereof - Google Patents
Fe (Fe) 3 O 4 -TiO 2 Catalyst, preparation method and application thereof Download PDFInfo
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- CN117000246A CN117000246A CN202310976138.4A CN202310976138A CN117000246A CN 117000246 A CN117000246 A CN 117000246A CN 202310976138 A CN202310976138 A CN 202310976138A CN 117000246 A CN117000246 A CN 117000246A
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- 239000003054 catalyst Substances 0.000 title claims abstract description 189
- 229910010413 TiO 2 Inorganic materials 0.000 title claims abstract description 116
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 52
- 239000003546 flue gas Substances 0.000 claims abstract description 52
- 230000003197 catalytic effect Effects 0.000 claims abstract description 38
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 21
- 239000003513 alkali Substances 0.000 claims abstract description 20
- 230000003647 oxidation Effects 0.000 claims abstract description 19
- 239000000203 mixture Substances 0.000 claims abstract description 18
- 239000011261 inert gas Substances 0.000 claims abstract description 6
- 239000007788 liquid Substances 0.000 claims abstract description 6
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- 238000002347 injection Methods 0.000 claims description 26
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- 230000009467 reduction Effects 0.000 abstract description 18
- 238000001179 sorption measurement Methods 0.000 abstract description 17
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- 230000023556 desulfurization Effects 0.000 abstract description 10
- 230000009286 beneficial effect Effects 0.000 abstract description 8
- 230000002860 competitive effect Effects 0.000 abstract description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 171
- 229910052760 oxygen Inorganic materials 0.000 description 28
- NIPNSKYNPDTRPC-UHFFFAOYSA-N N-[2-oxo-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 NIPNSKYNPDTRPC-UHFFFAOYSA-N 0.000 description 27
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 26
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- 239000010936 titanium Substances 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 16
- 238000006722 reduction reaction Methods 0.000 description 16
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
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- 230000007246 mechanism Effects 0.000 description 5
- 239000007800 oxidant agent Substances 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 230000001737 promoting effect Effects 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- 239000004408 titanium dioxide Substances 0.000 description 5
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 238000003421 catalytic decomposition reaction Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
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- 239000010453 quartz Substances 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 238000007873 sieving Methods 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
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- 238000012360 testing method Methods 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
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- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
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- 229910001448 ferrous ion Inorganic materials 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- -1 hydroxyl radicals Chemical class 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
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Classifications
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- 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
-
- 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
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/74—Iron group metals
- B01J23/745—Iron
-
- 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
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/03—Precipitation; Co-precipitation
- B01J37/031—Precipitation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/02—Other waste gases
- B01D2258/0283—Flue gases
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Environmental & Geological Engineering (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Biomedical Technology (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- General Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Catalysts (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
The application provides Fe 3 O 4 ‑TiO 2 A catalyst, a preparation method and application thereof. The preparation method of the catalyst is characterized by comprising the following steps: nano TiO 2 Adding the mixture into first alkali liquor to obtain a mixture; adding Fe-containing material to the mixture 3+ 、Fe 2+ Under the protection of inert gas, reacting at 60-100 ℃, and separating solid from liquid to obtain Fe 3 O 4 ‑TiO 2 A catalyst. Fe prepared by the application 3 O 4 ‑TiO 2 Catalyst compared with Fe 3 O 4 The catalyst has larger specific surface area, smaller pore diameter and larger pore volume, and the reduction of the pore diameter and the increase of the specific surface area are beneficial to the reduction of SO 2 With NO and H 2 O 2 Competitive adsorption on active sites, fe 3 O 4 ‑TiO 2 Pore structure parameters of the catalyst compared to Fe 3 O 4 The catalyst is obviously improved; the catalyst of the application can be used for flue gas catalytic oxidation denitration and desulfurization.
Description
Technical Field
The application belongs to the technical field of desulfurization and denitrification, and particularly relates to Fe 3 O 4 -TiO 2 A catalyst, a preparation method and application thereof.
Background
The large amount of NOx emitted from coal-fired and waste-incineration plants has attracted considerable attention because its emissions can cause acid rain, photochemical smog and PM 2.5 pollution, severely jeopardizing the ecological environment and human health. At present, a plurality of different technologies are developed and applied to NOx removal, and the main stream desulfurization and denitrification method is (Selective Catalytic Reduction) SCR, but the SCR technology has the problems of complex system, equipment blockage caused by easy ammonia leakage, consumption of additional steam quantity, high investment and operation cost and the like. There is a need to develop a low cost and efficient NOx removal technology.
More than 95% of NOx in coal-fired flue gas exists in the form equation of NO. The oxidation absorption method is to oxidize NO into soluble NO by adding oxidant or UV equation 2 、HNO 2 And HNO 3 The suboxide is then absorbed by the alkaline solution. H 2 O 2 Low cost, can generate strong oxidative free radicals such as OH, OOH and the like, and the final decomposition product is clean and environment-friendly H 2 O and O 2 Therefore, it is widely used as an oxidizing agent in an oxidation absorption method. By using H alone 2 O 2 The oxidant has low catalytic efficiency and needsAnd adding auxiliary means such as a catalyst to perform catalytic decomposition. Fenton reactions generate highly oxidative hydroxyl radicals (. OH) by the Haber-Weiss mechanism, which are of increasing interest due to their high degradability to contaminants. Wherein Fe in the Fe-based catalyst 2+ Can effectively promote H 2 O 2 Generates OH free radical by decomposition and is oxidized to Fe by itself 3+ While Fe 3+ And can be excessively H 2 O 2 Reduction to Fe 2+ Thereby constituting a redox cycle. Heterogeneous Fenton method based on iron-based catalyst has excellent desulfurization and denitrification efficiency, proper reaction temperature interval and less H 2 O 2 Consumption and the like, and has potential for application in the industrial field. But iron-based catalyst catalyzes H 2 O 2 In the flue gas SO 2 And H 2 O will be H and H 2 O 2 Competitive adsorption at the active site, thereby affecting H 2 O 2 And further inhibit the catalytic oxidation of NO.
Based on the defects existing in the current iron-based catalysts, improvements are needed.
Disclosure of Invention
In view of this, the present application proposes a Fe 3 O4-TiO 2 The catalyst and the preparation method and application thereof are used for solving the technical problems in the prior art.
In a first aspect, the present application provides Fe 3 O 4 -TiO 2 A method for preparing a catalyst comprising the steps of:
nano TiO 2 Adding the mixture into first alkali liquor to obtain a mixture;
adding Fe-containing material to the mixture 3+ 、Fe 2+ Under the protection of inert gas, reacting at 60-100 ℃, and separating solid from liquid to obtain Fe 3 O 4 -TiO 2 A catalyst.
Preferably, the Fe 3 O 4 -TiO 2 The first alkali liquor comprises NaOH solution and/or KOH solution.
PreferablyIs, fe as described 3 O 4 -TiO 2 Method for preparing a catalyst, said catalyst containing Fe 3+ 、Fe 2+ The preparation method of the metal ion solution comprises the following steps: feCl is added 3 、FeSO 4 Dissolving in HCl solution to obtain Fe-containing solution 3+ 、Fe 2+ Is a metal ion solution of (a).
Preferably, the Fe 3 O 4 -TiO 2 The concentration of the first alkali liquor is 0.1-0.3 mol/L;
fe in the metal ion solution 3+ 、Fe 2+ The concentration is 0.005-0.02 mol/L.
Preferably, the Fe 3 O 4 -TiO 2 The catalyst is prepared by the volume ratio of alkali liquor to metal ion solution being (1-3).
Preferably, the Fe 3 O 4 -TiO 2 Preparation method of catalyst, fe 3 O 4 -TiO 2 Fe in catalyst 3 O 4 And TiO 2 The molar ratio of (2) is 1 (1) to (3).
In a second aspect, the present application also provides Fe 3 O 4 -TiO 2 The catalyst is prepared by the preparation method.
In a third aspect, the application also provides Fe prepared by the preparation method 3 O 4 -TiO 2 Catalysts or said Fe 3 O 4 -TiO 2 The application of the catalyst in flue gas catalytic oxidation denitration.
Preferably, the application comprises the following steps:
providing a catalytic reactor for adding Fe 3 O 4 -TiO 2 The catalyst is placed in a catalytic reactor;
providing a mixing pipe, wherein the mixing pipe is communicated with the catalytic reactor, and a heating device is arranged on the mixing pipe;
utilize heating device to heat the compounding pipe, let in the flue gas and annotate in the compounding pipe with the syringe simultaneously to the compounding pipeIn H 2 O 2 Solution H 2 O 2 The solution is heated to form H 2 O 2 The steam and the flue gas are mixed to form mixed gas, the mixed gas enters a catalytic reactor for reaction, and the reacted mixed gas is introduced into the second alkali liquor.
Preferably, in the application, the flow rate of the flue gas is 0.25-2L/min, H 2 O 2 The concentration of the solution is 1-5 mol/L, the injection rate of the injector is 10-50 mu L/min, the temperature of the catalytic reactor is 100-240 ℃, and the second alkali solution comprises NaOH solution and/or KOH solution.
Fe of the present application 3 O 4 -TiO 2 Compared with the prior art, the catalyst and the preparation method and application thereof have the following beneficial effects:
1. fe prepared by the application 3 O 4 -TiO 2 Catalyst compared with Fe 3 O 4 The catalyst has larger specific surface area, smaller pore diameter and larger pore volume, and the reduction of the pore diameter and the increase of the specific surface area are beneficial to the reduction of SO 2 With NO and H 2 O 2 Competitive adsorption on active sites, fe 3 O 4 -TiO 2 Pore structure parameters of the catalyst compared to Fe 3 O 4 The catalyst is obviously improved; fe of the present application 3 O 4 -TiO 2 Catalyst, fe 3 O 4 With TiO 2 The interaction between the carriers results in Fe 3 O 4 The electron density around increases, promoting Fe 2+ Generating ions; tiO (titanium dioxide) 2 The loading of (2) can promote the increase of the concentration of oxygen vacancies, fe 2+ And Ti is 3+ The presence of (2) allows the catalyst surface to generate more oxygen vacancies through an oxygen vacancy compensation mechanism;
2. fe of the present application 3 O 4 -TiO 2 The catalyst can be used for flue gas catalytic oxidation denitration and desulfurization, and SOs are shown by desulfurization and denitration experiments 2 The removal of (2) is mainly dependent on the absorption of lye, while the oxidation of NO is mainly dependent on H 2 O 2 Catalytically formed OH; the optimal process for denitration and desulfurization of the catalyst comprises the following steps: the reaction temperature is 140 ℃; flow rate of flue gas0.5L/min；H 2 O 2 Concentration 2mol/L; h 2 O 2 The injection rate was 30. Mu.L/min.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are only some embodiments of the application, and that other drawings can be obtained according to these drawings without inventive effort to a person skilled in the art.
FIG. 1 is a schematic diagram of a flue gas catalytic oxidation denitration device;
FIG. 2 is Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 XRD pattern of the catalyst;
FIG. 3 is Fe 3 O 4 Catalyst, fe 3 O 4 -TiO 2 N of the catalyst 2 Adsorption and desorption curves;
FIG. 4 is Fe 3 O 4 Catalyst, fe 3 O 4 -TiO 2 Pore size distribution of the catalyst;
FIGS. 5 to 6 show Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 XPS spectrum of Fe 2p in the catalyst;
FIG. 7 is Fe in example 1 3 O 4 -TiO 2 Ti 2p map of the catalyst surface;
FIGS. 8 to 9 show Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 XPS spectrum of catalyst O1 s;
FIG. 10 is Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 VSM profile of catalyst;
FIG. 11 is Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 H of the catalyst 2 -a TPR profile;
FIG. 12 shows a different H 2 O 2 The concentration of the solution has an influence on the removal of NO;
FIG. 13 shows the reaction temperature versus NO and SO 2 Is influenced by the synergistic removal efficiency;
FIG. 14 shows a different H 2 O 2 Injection rate catalyst denitration performance impact;
FIG. 15 shows the NO removal effect of different flue gas flows;
FIG. 16 is a graph showing the effect of water vapor concentration in flue gas on denitration of a catalytic oxidation reaction system;
FIG. 17 is Fe 3 O 4 /TiO 2 Reaction stability of the catalyst.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions in the embodiments of the present application will be clearly and completely described in the following in conjunction with the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, are intended to fall within the scope of the present application.
The following description of the embodiments is not intended to limit the preferred embodiments. In addition, in the description of the present application, the term "comprising" means "including but not limited to". Various embodiments of the application may exist in a range of forms; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the application; it is therefore to be understood that the range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that a description of a range from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the ranges, such as 1, 2, 3, 4, 5, and 6, wherever applicable. In addition, whenever a numerical range is referred to herein, it is meant to include any reference number (fractional or integer) within the indicated range.
The application provides Fe 3 O 4 -TiO 2 A method for preparing a catalyst comprising the steps of:
s1, nanometer TiO 2 Adding the mixture into first alkali liquor to obtain a mixture;
s2, adding Fe to the mixture 3+ 、Fe 2+ Under the protection of inert gas, reacting at 60-100 ℃, and separating solid from liquid to obtain Fe 3 O 4 -TiO 2 A catalyst.
Fe prepared by the application 3 O 4 -TiO 2 Catalyst compared with Fe 3 O 4 The catalyst has larger specific surface area, smaller pore diameter and larger pore volume, and the reduction of the pore diameter and the increase of the specific surface area are beneficial to the reduction of SO 2 With NO and H 2 O 2 Competitive adsorption on active sites, fe 3 O 4 -TiO 2 Pore structure parameters of the catalyst compared to Fe 3 O 4 The catalyst is obviously improved; fe of the present application 3 O 4 -TiO 2 Catalyst, fe 3 O 4 With TiO 2 The interaction between the carriers results in Fe 3 O 4 The electron density around increases, promoting Fe 2+ Generating ions; tiO (titanium dioxide) 2 The loading of (2) can promote the increase of the concentration of oxygen vacancies, fe 2+ And Ti is 3+ The presence of (2) allows the catalyst surface to generate more oxygen vacancies through an oxygen vacancy compensation mechanism.
In some embodiments, the primary lye comprises NaOH solution and/or KOH solution.
In some embodiments, fe is contained 3+ 、Fe 2+ The preparation method of the metal ion solution comprises the following steps: feCl is added 3 、FeSO 4 Dissolving in HCl solution to obtain Fe-containing solution 3+ 、Fe 2+ Is a metal ion solution of (a).
In some embodiments, the concentration of the primary lye is 0.1 to 0.3mol/L;
fe in metal ion solution 3+ 、Fe 2+ The concentration is 0.005-0.02 mol/L.
In some embodiments, the volume ratio of lye to the metal ion solution is (1-3): 1-3.
In some embodiments, fe 3 O 4 -TiO 2 Fe in catalyst 3 O 4 And TiO 2 The molar ratio of (2) is 1 (1) to (3).
In some embodiments, a mixture containing Fe is added to the mixture 3+ 、Fe 2+ Under the protection of inert gas, reacting at 60-100 ℃, separating solid from liquid, washing with water, drying at 60-100 ℃, grinding and sieving to 120-180 meshes to obtain Fe 3 O 4 -TiO 2 A catalyst.
In some embodiments, inert gases include, but are not limited to, nitrogen, argon, helium, neon, and the like.
Based on the same inventive concept, the application also provides a Fe 3 O 4 -TiO 2 The catalyst is prepared by adopting the preparation method.
Based on the same inventive concept, the application also provides Fe prepared by the preparation method 3 O 4 -TiO 2 Catalysts or Fe as described above 3 O 4 -TiO 2 The application of the catalyst in flue gas catalytic oxidation denitration.
In some embodiments, the above-described application comprises the steps of:
s1, providing a catalytic reactor, and adding Fe 3 O 4 -TiO 2 The catalyst is placed in a catalytic reactor;
s2, providing a mixing pipe, wherein the mixing pipe is communicated with the catalytic reactor, and a heating device is arranged on the mixing pipe;
s3, heating the mixing pipe by using a heating device, simultaneously introducing smoke into the mixing pipe, and injecting H into the mixing pipe by using an injector 2 O 2 Solution H 2 O 2 The solution is heated to form H 2 O 2 The steam and the flue gas are mixed to form mixed gas, and the mixed gas enters a catalytic reactor to enterAnd (3) carrying out reaction, and introducing the reacted mixed gas into the second alkali liquor.
In some embodiments, the flow rate of the flue gas is 0.25-2L/min, H 2 O 2 The concentration of the solution is 1-5 mol/L, the injection rate of the injector is 10-50 mu L/min, the temperature of the catalytic reactor is 100-240 ℃, and the second alkali solution comprises NaOH solution and/or KOH solution.
Specifically, in the present application H 2 O 2 The solution is H with a certain concentration 2 O 2 An aqueous solution.
In the above examples, the mixed gas after the reaction oxidizes the product oxide (NO 2 、HNO 2 、HNO 3 And H 2 SO 4 ) And SO 2 Absorbed by the second alkaline solution.
Further, the device adopted in the flue gas catalytic oxidation denitration process is shown in fig. 1, and the flue gas mainly comprises NO and SO 2 、O 2 And N 2 (as a balance gas); in particular, the device comprises a NO gas cylinder 11, SO 2 Gas cylinder 12, O 2 Gas cylinder 13, N 2 Gas cylinder 14, NO gas cylinder 11, SO 2 Gas cylinder 12, O 2 Gas cylinder 13, N 2 The gas storage bottle 14 is communicated with the flue gas mixing pipe 16, and the NO gas storage bottle 11 and SO 2 Gas cylinder 12, O 2 Gas cylinder 13, N 2 The gas cylinders 14 are respectively used for storing NO and SO 2 、O 2 And N 2 NO gas cylinder 11, SO 2 Gas cylinder 12, O 2 Gas cylinder 13, N 2 A flowmeter 15 is arranged between the gas storage bottle 14 and the flue gas mixing pipe 16 and is used for controlling the flow of corresponding gas; NO, SO 2 、O 2 And N 2 Mixing the raw materials in a smoke mixing pipe 16 to obtain smoke, and controlling the composition of different gases to obtain smoke with different compositions; the flue gas mixing pipe 16 is communicated with the mixing pipe 18 through a three-way valve 17, H 2 O 2 The solution is injected into a mixing tube 18 through an injection pump 20, the mixing tube 18 is a quartz tube, the mixing tube 18 is wrapped with a heating belt 19, and the flue gas in the flue gas mixing tube 16 and H 2 O 2 The solution enters the mixing pipe 18 and simultaneously flows into the mixing pipe 18 heating (heating to 140-150 ℃) H 2 O 2 The solution is heated to become H 2 O 2 Steam, at this time, flue gas and H 2 O 2 Mixing the steam to form a mixed gas; the mixing pipe 18 is communicated with the catalytic reactor 21, and the flue gas and H 2 O 2 The vapor is mixed to form a mixed gas which enters the catalytic reactor 21 and is added with Fe 3 O 4 -TiO 2 The mixed gas after reaction enters a gas washing bottle 22 under the action of a catalyst, a second alkali liquor is arranged in the gas washing bottle 22, and an oxidation product generated by the mixed gas after reaction is absorbed by the second alkali liquor; the gas washing bottle 22 is also communicated with a dryer 23, and the gas absorbed by the gas washing bottle 22 enters the dryer 23 for drying and finally enters a smoke analyzer 24 for measuring the concentration of each component of the outlet smoke; the flue gas analyzer 24 is also communicated with the three-way valve 17 through the stop valve 25, and the gas passing through the flue gas analyzer 24 can also enter the mixing pipe 18 again through the stop valve 25 and the three-way valve 17 for reaction.
Specifically, NO and SO under different working conditions are tested after reaction 2 The removal efficiency of (2) is determined by the following formula:
wherein eta is the removal efficiency (%), C in And C out NO or SO respectively 2 Inlet and outlet concentrations of (a).
The Fe of the present application is described in more detail in the following examples 3 O 4 -TiO 2 A catalyst, a preparation method and application thereof. This section further illustrates the summary of the application in connection with specific embodiments, but should not be construed as limiting the application. The technical means employed in the examples are conventional means well known to those skilled in the art, unless specifically stated. Unless specifically stated otherwise, the reagents, methods and apparatus employed in the present application are those conventional in the art.
Example 1
The embodiment of the application provides Fe 3 O 4 -TiO 2 Preparation method of catalystA method comprising the steps of:
s1, adding a certain amount of TiO 2 Putting the powder into a three-neck flask, and then adding 100mL of 0.2mol/L NaOH solution to obtain a mixture;
s2, 2.7g FeCl 3 ·6H 2 O and 1.39g FeSO 4 ·7H 2 O is dissolved in 100mL of HCl solution (pH 0.5) with stirring to form a metal ion solution;
s3, adding a metal ion solution into the mixture, continuously stirring for 2 hours at the water bath of 80 ℃, introducing nitrogen, carrying out solid-liquid separation by using a magnet after the reaction is finished, washing a sample by using deionized water, drying for 24 hours at the temperature of 80 ℃, grinding and screening to 150 meshes to obtain Fe 3 O 4 -TiO 2 Catalyst, fe 3 O 4 -TiO 2 Fe in catalyst 3 O 4 And TiO 2 The molar ratio of (2) is 1:2.
Comparative example 1
This comparative example provides Fe 3 O 4 A method for preparing a catalyst comprising the steps of:
s1, 16.68g FeSO 4 ·7H 2 O is dissolved in 75mL of HCl solution (pH 0.5) with stirring to form a metal ion solution;
s2, 5g NaNO 3 And 10g of NaOH, stirring and dissolving in 75mL of ultrasonic deionized water to form alkali liquor;
s3, pouring alkali liquor into the three-neck flask, heating in a water bath at 90 ℃, slowly dripping a metal ion solution into the three-neck flask, continuously stirring for 2 hours, and introducing nitrogen to prevent ferrous ions from being oxidized by air; washing the precipitate with deionized water for three times, drying the obtained sample at 80deg.C for 24 hr, grinding and sieving to 150 mesh to obtain Fe 3 O 4 A catalyst.
1 characterization of the catalyst
1.1XRD analysis
FIG. 2 shows Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 XRD pattern of the catalyst.
As can be seen from fig. 2, 2θ=18.4 °, 30.2 °, 35.5 °, 43.2 °, 5%Characteristic diffraction peaks at 3.6 °, 57.1 °, 62.7 ° are respectively assigned to Fe 3 O 4 (111), (220), (311), (400), (422), (511) and (440) crystal planes. At Fe 3 O 4 -TiO 2 In the XRD pattern of the catalyst, characteristic diffraction peaks at 2θ=25.3°, 37.8 °, 48.0 °, 53.9 °, 55.1 °, 62.8 ° and 70.3 ° are characteristic diffraction peaks belonging to the anatase crystal phase (JCPDS 99-0008), corresponding to (101), (004), (200), (105), (211), (204) and (220) crystal planes, respectively. It can be seen that some Fe is also present in XRD diffraction peaks 3 O 4 Is shown to be supported on TiO 2 Fe on 3 O 4 Some of the aggregates occur.
1.2BET analysis
Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 The surface area and physical structure characteristics of the catalyst were tested on a 3H-2000PS1 analyzer manufactured by Bei Shide Instrument technology Co., ltd. N is carried out at-196 DEG C 2 Adsorption and desorption experiments. The specific surface area of the catalyst was calculated using the Brunauer-Emmett-Teller (BET) multi-layer adsorption theory equation, and the pore volume and pore size distribution of the catalyst were calculated using the Barrett-Joyner-Halenda (BJH) method.
FIGS. 3 to 4 show Fe respectively 3 O 4 Catalyst, fe 3 O 4 -TiO 2 N of the catalyst 2 Adsorption-desorption curve (a) and pore size distribution (b).
The adsorption and desorption isotherms of the catalyst are of typical IV type, and the hysteresis loop is of typical H3 type, which indicates that mesoporous exists on the surface of the catalyst. Fe (Fe) 3 O 4 -TiO 2 The pore size of the catalyst was concentrated at 7nm. Table 1 shows Fe 3 O 4 Catalyst, fe 3 O 4 -TiO 2 Specific surface area, average pore size and pore volume of the catalyst.
TABLE 1 specific surface area, average pore size and pore volume of catalysts
| Fe 3 O 4 | Fe 3 O 4 -TiO 2 | |
| Specific surface area (m) 2 /g) | 50.72 | 85.36 |
| Aperture (nm) | 11.39 | 7.37 |
| Pore volume (cm) 3 /g) | 0.124 | 0.150 |
As can be seen from Table 1, the larger the specific surface area of the sample, the more active sites exposed to the catalyst surface, kong Rongyue, which can be NO and H 2 O 2 Providing more channels into the core layer, the reduction of pore size and the increase of specific surface area facilitate the reduction of SO 2 With NO and H 2 O 2 Competitive adsorption on active sites, fe 3 O 4 -TiO 2 Pore structure parameters of the catalyst compared to Fe 3 O 4 The catalyst is improved obviously.
XPS analysis of Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 XPS patterns of Fe 2p in the catalyst are shown in figures 5-6. The XPS spectrum of Fe 2p mainly comprises four main peaks, wherein the vicinity of 724.8eV and 710.8eV are energy level peaks of Fe 2p 1/2 and Fe 2p3/2 respectively, while those at 733.3eV and 719.1eVThe peak is the corresponding satellite peak. The characteristic peak of Fe 2p3/2 can be further divided into two characteristic peaks, which respectively represent ferrous iron (Fe 2+ 709.8 eV) and ferric iron (Fe 3+ 710.9 eV). The binding energy of Fe 2p3/2 and the valence distribution of Fe element are shown in Table 2.
TABLE 2 binding energy and relative content of Fe element and O element on catalyst surface
As can be seen from Table 2, fe 3 O 4 Fe in catalyst 2+ /Fe 3+ Is 0.49, approaching 0.5 of the theoretical stoichiometric ratio; and Fe (Fe) 3 O 4 -TiO 2 Fe of catalyst 2+ /Fe 3+ A value of 0.602, indicating Fe 3 O 4 With TiO 2 There is also an interaction between the carriers, resulting in Fe 3 O 4 The electron density around increases, promoting Fe 2+ And (3) generating ions.
Fe 3 O 4 -TiO 2 The Ti 2p pattern of the catalyst surface is shown in fig. 7. The XPS profile of Ti 2p mainly contains two energy level peaks of Ti 2p 1/2 and Ti 2p3/2, which are located near 464.2eV and 458.6eV, respectively. Fe has electronegativity higher than Ti, has stronger electron attraction capability, and the electron density around Ti is reduced due to charge transfer between Ti and Fe, so that the shielding effect is reduced, and the electron binding energy is increased. Indicating that the synergistic effect between Ti and Fe is favorable for generating more Fe 2+ 。
Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 The XPS spectrum of the catalyst O1s is shown in FIGS. 8 to 9. The O1s spectrum can be mainly divided into lattice oxygen (O) lat 530.1 eV) and surface adsorption of oxygen (O) ads 531.7 eV) of the two characteristic peaks. Wherein O is lat Lattice oxygen as catalyst, and O ads The relative amounts of surface active oxygen produced for adsorbed molecules such as oxygen are shown in Table 2. The existence of oxygen vacancies can promote the generation of surface active oxygen, thereby improving the content of surface adsorbed oxygen,the latter has better reactivity due to its higher mobility. Thus, O ads /(O ads +O lat ) The value of (2) may indirectly reflect the relative content of oxygen vacancies at the catalyst surface. Oxygen vacancies can activate H as active sites 2 O 2 And generating OH, carrying out oxidation-reduction reaction, and regenerating oxygen vacancies on the surface of the catalyst after the reaction product is desorbed, so as to form a dynamic balance process of consumption-replenishment. The relative order of magnitude of the catalyst oxygen vacancy concentrations is: fe (Fe) 3 O 4 -TiO 2 >Fe 3 O 4 Catalysts, indicating TiO 2 The loading of (c) may promote an increase in the concentration of oxygen vacancies. Fe (Fe) 2+ And Ti is 3+ The presence of (2) allows the catalyst surface to generate more oxygen vacancies through an oxygen vacancy compensation mechanism.
1.3VSM analysis
The saturation magnetic strength, the remanence magnetic strength and the coercivity of the catalyst sample were measured using a ppmsdynaccol Vibrating Sample Magnetometer (VSM) manufactured by american quantum company. About 5mg of catalyst sample was used for each measurement, and the test was performed at room temperature with an applied magnetic field ranging from-20000 to 20000Oe.
Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 The VSM curve of the catalyst is shown in FIG. 10, fe 3 O 4 The saturation magnetization of the catalyst is 70.17emu/g and Fe 3 O 4 -TiO 2 The saturation magnetization of the catalyst is 22.54emu/g; visible Fe 3 O 4 -TiO 2 The saturation magnetization of the catalyst is still more than 20emu/g, can be regarded as a ferromagnetic material, and shows ferromagnetism with almost zero coercivity and remanence, which is beneficial to the recovery and reuse of the catalyst.
1.4H 2 TPR analysis
By temperature programmed reduction (H) 2 TPR) study of the redox properties of the catalyst. The test was performed on a full-automatic chemical adsorption instrument of the preceding claim TP-5080B. Weighing 50mg of sample, placing into a reaction tube, drying and pre-treating at a heating rate of 10 ℃/min from room temperature to 300 ℃ under Ar gas flow (30 mL/min) condition for 60min, and cooling to 30 DEG CTo remove impurities adsorbed on the surface of the catalyst. At 10% H 2 Heating to 800 ℃ at a heating rate of 10 ℃/min under Ar (30 mL/min) atmosphere, and using a Thermal Conductivity Detector (TCD) for H 2 The signal is detected.
Fe in comparative example 1 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 H of the catalyst 2 The TPR profile is shown in FIG. 11.
The redox performance of the catalyst plays an important role in the catalytic reaction by using H 2 TPR to investigate the performance of the catalyst. TiO (titanium dioxide) 2 Chemically inert and no corresponding reduction peak can be observed. Fe (Fe) 3 O 4 The main reduction peak of (C) is in the range of 400-700 ℃, and the temperature range corresponds to Fe 3 O 4 →FeO→Fe 0 Is a reduction process of (a). Fe (Fe) 3 O 4 -TiO 2 The low-temperature reduction peak temperature of the catalyst is lower, which shows that the catalyst has excellent oxidation-reduction performance. Fe (Fe) 3 O 4 The reduction peak intensity of the FeO is higher than other catalysts, which shows that more Fe is present 3+ Needs to be reduced to Fe 2+ Consistent with the XPS analysis results. At H 2 In TPR, the reduction temperature depends on the dispersibility of the active substances and on their interactions with the carrier.
2 analysis of denitration and desulfurization performances of catalyst
Providing a flue gas catalytic oxidation denitration device shown in figure 1, adding 0.1g of the catalyst prepared in comparative example 1 or example 1 into a catalytic reactor, mixing in a flue gas mixing tube to obtain O in flue gas 2 NO and SO 2 The concentrations were set to 6vol%, 500ppm and 1000ppm, respectively, with the remainder being N 2 The method comprises the steps of carrying out a first treatment on the surface of the 500mL of 0.1mol/L NaOH solution is arranged in the gas washing bottle 22; in the reaction, the heating belt 19 heats the mixing tube 18 to 140 ℃; the reaction control process conditions are that the temperature of the catalytic reactor is 100-240 ℃, the flow rate of the flue gas entering the mixing pipe is 0.25-2L/min, and H 2 O 2 The concentration of the solution is 1-5 mol/L, and the injection rate of the injection pump is 10-50 mu L/min.
2.1 catalyst species and H 2 O 2 Influence of concentration
According to the above method, fe in comparative example 1 was studied 3 O 4 Catalyst and Fe in example 1 3 O 4 -TiO 2 Catalyst and TiO 2 At different H 2 O 2 Under the concentration of the solution (under the change of H 2 O 2 At the concentration of the solution, the temperature of the catalytic reactor was 140 ℃, the flow rate of the flue gas into the mixing pipe was 0.5L/min, and the injection rate of the injection pump was 30. Mu.L/min), and the result was shown in FIG. 12.
Experimental results show that SO 2 The removal efficiency of (a) is always 100%, SO 2 Is not subjected to H 2 O 2 The effect of concentration and catalyst species, indicating that NaOH solution is absorbed as SO 2 Is a main removal process.
In the reaction system, only H 2 O 2 In the case of (2), the highest removal efficiency of NO was only 30.6%, indicating H 2 O 2 Relatively poor oxidation properties. After the catalyst is added, the NO removal efficiency is rapidly improved. TiO (titanium dioxide) 2 /H 2 O 2 The denitration efficiency of the system is lower, probably because of amorphous TiO 2 Does not have higher catalytic activity. According to the Haber-Weiss reaction, an iron-based catalyst is reacted with H 2 O 2 The reaction generates a large amount of OH, thereby promoting the oxidation removal of NO; h 2 O 2 The increase in concentration is beneficial to the improvement of H 2 O 2 The OH content of the decomposition product. When H is 2 O 2 At a concentration of 2mol/L, fe 3 O 4 -TiO 2 The removal efficiency of the catalyst is 82.4 percent, which is higher than that of Fe 3 O 4 A catalyst. This is because of the comparison with Fe 3 O 4 Catalyst, fe 3 O 4 -TiO 2 The catalyst has higher Fe 2+ Content and a higher number of oxygen vacancies. In addition, the transition metal redox couple can directly catalyze H 2 O 2 To decompose to generate reactive radicals. When H is 2 O 2 The further improvement of the removal efficiency is inhibited by a series of self-consuming reactions initiated by excessive OH in the system when the concentration is increased from 2mol/L to 5mol/L, and the chemical reactions involved in the specific reactions are as follows:
Fe 2+ +H 2 O 2 →Fe 3+ +·OH+OH-(k 1 ＝70M/s)
Fe 3+ +H 2 O 2 →Fe 2+ +·OOH+H + (k 2 ＝0.001～0.1M/s)
Ti 3+ +H 2 O 2 →Ti 4+ +·OH
Ti 4+ +H 2 O 2 →Ti 3+ +·OOH
H 2 O 2 +·OH→·OOH+H 2 O
·OOH→H 2 O 2 +O 2
·OH+·OH→H 2 O 2
·OH+·OOH→H 2 O+O 2
comprehensively consider H 2 O 2 The concentration of the solution was 2mol/L.
2.2 influence of the reaction temperature
At different reaction temperatures (the flow rate of the flue gas entering the mixing pipe is 0.5L/min when the reaction temperature is changed, H) 2 O 2 The concentration of the solution is 2mol/L, the injection rate of a syringe pump is 30 mu L/min) to NO and SO 2 The co-removal efficiency of (2) is shown in figure 13.
The law of influence of the reaction temperature on the catalyst is similar: with the rise of the temperature, the NO removal efficiency is gradually increased, then kept relatively stable in the range of 140-200 ℃ and finally gradually decreased. As known from Arrhenius equation, H as the reaction temperature increases 2 O 2 The reaction rate of catalytic decomposition and NO oxidation can be accelerated, which is beneficial to generating more active free radicals and the oxidation removal of NO. However, an increase in the reaction temperature also leads to reactive radicals and H 2 O 2 The self-consuming reaction rate therebetween increases, reducing the concentration of free radicals in the reaction, thereby reducing the rate of the catalytic reaction, accompanied by decomposition of a portion of the oxidation product (as shown in the following reaction). When the reaction temperature is in the range of 140 ℃ to 200 ℃, the interaction between the influencing factors is in an equilibrium state,the highest NO removal efficiency at this time means that the catalyst may be placed after the electric dust collector in practical applications.
3HNO 2 →HNO 3 +H 2 O+2NO
4HNO 3 →4NO 2 +2H 2 O+O 2
Comprehensively, the reaction temperature of the catalytic reactor was 140 ℃.
2.3H 2 O 2 Influence of injection Rate
H 2 O 2 Injection rate (in varying H 2 O 2 At the injection rate, the temperature of the catalytic reactor is 140 ℃, the flow rate of the flue gas entering the mixing pipe is 0.5L/min, and H 2 O 2 Solution concentration of 2 mol/L) for Fe 3 O 4 /TiO 2 Catalyst (i.e. Fe prepared in example 1 3 O 4 -TiO 2 Catalyst), fe in comparative example 1 3 O 4 The effect of catalyst denitration performance is shown in fig. 14.
With H 2 O 2 The injection rate is increased from 10 mu L/min to 30 mu L/min, fe 3 O 4 /TiO 2 The NO removal efficiency of the catalyst increased from 42.8% to 82% because of H 2 O 2 Mole ratio of NO with H 2 O 2 The injection amount increases rapidly, the content of the oxidant participating in vaporization and catalytic reaction increases, and more OH is promoted. However, when H 2 O 2 As the injection rate of (c) continues to increase, the NO removal efficiency does not change much, since the oxidant is excessive at this time, and self-consuming reactions occur. H 2 O 2 An increase in the injection rate also results in H in the flue gas 2 The increase in O concentration also has a negative effect. In addition, the higher injection rate may be higher than H in the reaction tube 2 O 2 Is a part of H 2 O 2 The solution was deposited in the quartz tube instead of participating in the reaction. H after comprehensive consideration 2 O 2 The optimal injection rate of the solution was 30. Mu.L/min.
2.4 influence of flue gas flow
Flue gas flow (when changing flue gas flow, the temperature of the catalytic reactor is 140 ℃, H 2 O 2 The concentration of the solution is 2mol/L, and the injection rate of the injection pump is 30 mu L/min. ) For Fe 3 O 4 /TiO 2 Catalyst (i.e. Fe prepared in example 1 3 O 4 -TiO 2 Catalyst) the effect of catalytic efficiency is shown in fig. 15.
Fe when the gas flow rate is increased from 0.25L/min to 0.5L/min 3 O 4 /TiO 2 The NO removal efficiency of the catalyst was slightly reduced, indicating H at this time 2 O 2 Compared with the NO excess, the flue gas stays on the catalyst for a long time, which is sufficient for oxidizing most NO, so that the stability and high efficiency of the denitration efficiency can be ensured. However, when the gas flow rate is more than 0.5L/min, the NO removal efficiency starts to decrease until it is drastically decreased to 70.8% at 2L/min, at which time Fe 3 O 4 /TiO 2 The NO removal efficiency of the catalyst is 75.8%. The increase of the flue gas flow rate leads to H 2 O 2 The amount of NO is insufficient, and the OH generated during the reaction cannot completely oxidize NO. At the same time, the increase in the flue gas flow rate brings the catalyst surface to the reaction mass of reactant molecules (H 2 O 2 And NO), resulting in a substantial reduction of the contact time between H and NO) 2 O 2 No decomposition occurs during the passage through the catalyst, reducing the yield of active radicals. It can be seen that when the Gas Hourly Space Velocity (GHSV) is out of a certain range, the increase in GHSV is accompanied by the increase in comparison with Fe 3 O 4 /TiO 2 The NO removal efficiency of the catalyst, which is a core-shell catalyst, is greatly reduced due to the adsorption characteristic of the core-shell catalyst. The presence of a smaller pore shell layer increases the resistance of the reactants to the catalyst core layer, thereby increasing their adsorption time on the shell structure. During the reaction, part of SO 2 Is coated with TiO 2 The shell layer blocks or adsorbs most NO and a small amount of SO 2 Penetrating the shell layer to reach the surface of the core and being adsorbed, weakening SO on the core layer 2 Inhibition of NO adsorption, SO 2 And layered adsorption of NO on a core-shell structured catalyst. Longer residence time of the flue gas at low airspeed allows more NO and H 2 O 2 Enters the nuclear layer reaction, so that the NO removal efficiency is higher. And the NO removal efficiency of the core-shell catalyst is reduced more than that of the supported catalyst at a high space velocity.
2.5H 2 O 2 Influence of concentration
H 2 O 2 The volume of the solution expands by more than 1100 times when heated and evaporated, and H in the flue gas 2 The O content is not negligible. By controlling H 2 O 2 Concentration and H 2 O 2 Injection rate to ensure H 2 O 2 The ratio of the/NO is unchanged, and H in the flue gas is indirectly controlled 2 O content. H 2 O 2 When the concentration is more than 2mol/L, the denitration efficiency of the catalyst is along with H 2 O 2 The increase in concentration did not change much. So H is 2 O content (volume content) of 2% and 6% despite the corresponding H 2 O 2 The concentration is different, but the influence on the NO removal efficiency is small, and the main factors influencing the NO removal performance are only H 2 O content. When the flow rate of the flue gas is 0.5L/min, H 2 O 2 The concentration is 2mol/L, H 2 O 2 At an injection rate of 30. Mu.L/min, H in the flue gas 2 The O content was about 6%. Fig. 16 shows the effect law of water vapor concentration in flue gas on denitration of catalytic oxidation reaction system. When H in flue gas 2 When the O content is changed from 2% to 6%, fe 3 O 4 /TiO 2 The catalyst removal efficiency was reduced by about 4%. H 2 O will be H and H 2 O 2 Competitive adsorption is formed on the active sites and oxygen vacancies of the catalyst surface, thereby affecting the generation of active radicals. Amorphous TiO 2 The material is easy to adsorb H 2 O molecule, so the core-shell catalyst has stronger water resistance and can be used in H 2 The denitration efficiency of more than 86% can still be maintained under the condition that the O concentration is 6%, and the denitration device can adapt to the working condition of an actual power plant. At the same time, H is changed again 2 When the O concentration is 2%, both catalysts can restore to the original denitration efficiency, which shows that the catalysts have better reversibility.
2.6 catalyst stability Studies
To evaluate Fe 3 O 4 Catalyst Fe 3 O 4 /TiO 2 The reaction stability of the catalyst was tested under the same experimental conditions for 6 hours (reaction temperature 140 ℃ C.; flue gas flow 0.5L/min; H) 2 O 2 Concentration 2mol/L; h 2 O 2 Injection rate 60. Mu.L/min), and the experimental results are shown in FIG. 17. As can be seen from the figure, fe within 3h 3 O 4 /TiO 2 Stability of the catalyst is higher than that of Fe 3 O 4 The catalyst is better. The reason why the denitration efficiency of the catalyst is reduced during the long-time operation is H which is continuously added during the reaction 2 O 2 Will lead to Fe in the catalyst 2+ Conversion to Fe with lower catalytic activity 3+ Thereby reducing H 2 O 2 Leading to a decrease in the denitration efficiency.
In summary, the present application can draw the following conclusions:
(1) Fe prepared by the application 3 O 4 -TiO 2 Catalyst compared with Fe 3 O 4 The catalyst has larger specific surface area, smaller pore diameter and larger pore volume, and the reduction of the pore diameter and the increase of the specific surface area are beneficial to the reduction of SO 2 With NO and H 2 O 2 Competitive adsorption on active sites, fe 3 O 4 -TiO 2 Pore structure parameters of the catalyst compared to Fe 3 O 4 The catalyst is obviously improved; fe of the present application 3 O 4 -TiO 2 Catalyst, fe 3 O 4 With TiO 2 The interaction between the carriers results in Fe 3 O 4 The electron density around increases, promoting Fe 2+ Generating ions; tiO (titanium dioxide) 2 The loading of (2) can promote the increase of the concentration of oxygen vacancies, fe 2+ And Ti is 3+ The presence of (2) allows the catalyst surface to generate more oxygen vacancies through an oxygen vacancy compensation mechanism;
(2) The desulfurization and denitrification experiment shows that SO 2 The removal of (2) is mainly dependent on the absorption of lye, while the oxidation of NO is mainly dependent on H 2 O 2 Catalytically formed OH; the optimal process for denitration and desulfurization of the catalyst comprises the following steps: the reaction temperature is 140 ℃; the flow rate of the flue gas is 0.5L/min; h 2 O 2 Concentration 2mol/L; h 2 O 2 The injection rate was 30. Mu.L/min.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the application.
Claims (10)
1. Fe (Fe) 3 O 4 -TiO 2 The preparation method of the catalyst is characterized by comprising the following steps:
nano TiO 2 Adding the mixture into first alkali liquor to obtain a mixture;
adding Fe-containing material to the mixture 3+ 、Fe 2+ Under the protection of inert gas, reacting at 60-100 ℃, and separating solid from liquid to obtain Fe 3 O 4 -TiO 2 A catalyst.
2. Fe as claimed in claim 1 3 O 4 -TiO 2 The preparation method of the catalyst is characterized in that the first alkali liquor comprises NaOH solution and/or KOH solution.
3. Fe as claimed in claim 1 3 O 4 -TiO 2 A process for producing a catalyst, characterized in that the catalyst contains Fe 3+ 、Fe 2+ The preparation method of the metal ion solution comprises the following steps: feCl is added 3 、FeSO 4 Dissolving in HCl solution to obtain Fe-containing solution 3+ 、Fe 2+ Is a metal ion solution of (a).
4. Fe as claimed in claim 1 3 O 4 -TiO 2 The preparation method of the catalyst is characterized in that the concentration of the first alkali liquor is 0.1-0.3 mol/L;
fe in the metal ion solution 3+ 、Fe 2+ The concentration is 0.005-0.02 mol/L.
5. Fe as claimed in claim 1 3 O 4 -TiO 2 The preparation method of the catalyst is characterized in that the volume ratio of the alkali liquor to the metal ion solution is (1-3), namely (1-3).
6. A Fe as defined in any one of claims 1 to 5 3 O 4 -TiO 2 A process for producing a catalyst, characterized in that the Fe 3 O 4 -TiO 2 Fe in catalyst 3 O 4 And TiO 2 The molar ratio of (2) is 1 (1) to (3).
7. Fe (Fe) 3 O 4 -TiO 2 The catalyst is characterized by being prepared by the preparation method according to any one of claims 1 to 6.
8. A Fe prepared by the method according to any one of claims 1 to 6 3 O 4 -TiO 2 Catalyst or Fe according to claim 7 3 O 4 -TiO 2 The application of the catalyst in flue gas catalytic oxidation denitration.
9. The use of claim 8, comprising the steps of:
providing a catalytic reactor for adding Fe 3 O 4 -TiO 2 The catalyst is placed in a catalytic reactor;
providing a mixing pipe, wherein the mixing pipe is communicated with the catalytic reactor, and a heating device is arranged on the mixing pipe;
utilize heating device to heat the compounding pipe, let in the flue gas and utilize the syringe to pour into H into in the compounding pipe into to the compounding pipe in the mixing pipe simultaneously 2 O 2 Solution H 2 O 2 The solution is heated to form H 2 O 2 The steam and the flue gas are mixed to form mixed gas, the mixed gas enters a catalytic reactor for reaction, and the reacted mixed gas is introduced into the second alkali liquor.
10. The use according to claim 8, wherein the flow rate of the flue gas is 0.25-2L/min,H 2 O 2 the concentration of the solution is 1-5 mol/L, the injection rate of the injector is 10-50 mu L/min, the temperature of the catalytic reactor is 100-240 ℃, and the second alkali solution comprises NaOH solution and/or KOH solution.
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