CN112295555B - Cerium-titanium composite nanorod catalyst for fixed source flue gas denitration reaction and preparation method thereof - Google Patents
Cerium-titanium composite nanorod catalyst for fixed source flue gas denitration reaction and preparation method thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 68
- 239000002131 composite material Substances 0.000 title claims abstract description 36
- 239000002073 nanorod Substances 0.000 title claims abstract description 36
- NEGBOTVLELAPNE-UHFFFAOYSA-N [Ti].[Ce] Chemical compound [Ti].[Ce] NEGBOTVLELAPNE-UHFFFAOYSA-N 0.000 title claims abstract description 34
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 15
- 239000003546 flue gas Substances 0.000 title claims abstract description 15
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 238000006243 chemical reaction Methods 0.000 title claims description 39
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims abstract description 33
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical group [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 claims abstract description 28
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 20
- 238000010531 catalytic reduction reaction Methods 0.000 claims abstract description 9
- 229910001954 samarium oxide Inorganic materials 0.000 claims abstract description 9
- 229940075630 samarium oxide Drugs 0.000 claims abstract description 9
- FKTOIHSPIPYAPE-UHFFFAOYSA-N samarium(iii) oxide Chemical group [O-2].[O-2].[O-2].[Sm+3].[Sm+3] FKTOIHSPIPYAPE-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910000314 transition metal oxide Inorganic materials 0.000 claims abstract description 9
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 8
- 229910001404 rare earth metal oxide Inorganic materials 0.000 claims abstract description 6
- 239000000243 solution Substances 0.000 claims description 42
- 238000003756 stirring Methods 0.000 claims description 21
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 15
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titanium dioxide Inorganic materials O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 13
- 238000000967 suction filtration Methods 0.000 claims description 11
- 238000005406 washing Methods 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 10
- 229910052751 metal Inorganic materials 0.000 claims description 9
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 8
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 8
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 8
- 239000011572 manganese Substances 0.000 claims description 8
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 claims description 8
- 239000002184 metal Substances 0.000 claims description 6
- 239000011259 mixed solution Substances 0.000 claims description 4
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims description 3
- YZDZYSPAJSPJQJ-UHFFFAOYSA-N samarium(3+);trinitrate Chemical compound [Sm+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O YZDZYSPAJSPJQJ-UHFFFAOYSA-N 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims description 2
- 238000011068 loading method Methods 0.000 claims description 2
- 230000008569 process Effects 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 9
- 230000003197 catalytic effect Effects 0.000 abstract description 4
- 239000006185 dispersion Substances 0.000 abstract description 2
- 239000012266 salt solution Substances 0.000 abstract description 2
- 230000000694 effects Effects 0.000 description 10
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 8
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 230000007613 environmental effect Effects 0.000 description 5
- 238000011160 research Methods 0.000 description 5
- 229910052717 sulfur Inorganic materials 0.000 description 5
- 239000011593 sulfur Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 238000006555 catalytic reaction Methods 0.000 description 4
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 4
- 231100000572 poisoning Toxicity 0.000 description 3
- 230000000607 poisoning effect Effects 0.000 description 3
- 229910052684 Cerium Inorganic materials 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- ZMIGMASIKSOYAM-UHFFFAOYSA-N cerium Chemical compound [Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce] ZMIGMASIKSOYAM-UHFFFAOYSA-N 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 231100000252 nontoxic Toxicity 0.000 description 2
- 230000003000 nontoxic effect Effects 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000003980 solgel method Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241001528553 Malus asiatica Species 0.000 description 1
- ODUCDPQEXGNKDN-UHFFFAOYSA-N Nitrogen oxide(NO) Natural products O=N ODUCDPQEXGNKDN-UHFFFAOYSA-N 0.000 description 1
- 229910052772 Samarium Inorganic materials 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000003916 acid precipitation Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 238000002159 adsorption--desorption isotherm Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 239000000383 hazardous chemical Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 231100000086 high toxicity Toxicity 0.000 description 1
- 229910003471 inorganic composite material Inorganic materials 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- -1 metal oxide modified cerium-titanium Chemical class 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Inorganic materials O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000011941 photocatalyst Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000002468 redox effect Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
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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
- 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
- B01J37/035—Precipitation on carriers
-
- 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
- B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
-
- 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
-
- B01J35/394—
-
- B01J35/50—
Abstract
The invention provides a catalyst for ammonia selective catalytic reduction of nitrogen oxides for fixed source flue gas denitration, and a preparation method and application thereof, wherein the catalyst comprises a carrier and active components; the carrier is a cerium-titanium composite nanorod; the active component is transition metal oxide or the combination of transition metal oxide and rare earth metal oxide, and the transition metal oxide is manganese oxide; the rare earth metal oxide is samarium oxide; the specific surface area of the cerium-titanium composite nanorod is more than or equal to 300 square meters per gram. According to the invention, the cerium-titanium composite oxide is prepared into the macroscopic morphology of the nanorod, so that the specific surface area of the material is improved, and the dispersion of active components is facilitated; when the active component is loaded, the precipitant is added firstly, and then the salt solution of the active component is added, so that the dispersity of the active component in the prepared catalyst is obviously improved, and the catalytic activity is provided.
Description
Technical Field
The invention belongs to the technical field of nitrogen oxide control in environmental protection, and particularly relates to a cerium-titanium composite nanorod catalyst for fixed source flue gas denitration reaction, and preparation and performance research thereof.
Background
With the continuous increase of energy consumption, a fixed source mainly comprising a coal-fired boiler consumes a large amount of fossil fuel, and the pollution degree of acid substances is increased continuously due to tail gas discharged into the atmosphere. Wherein Nitrogen Oxide (NO)x) As an important atmospheric pollutant, the environment-friendly type inorganic composite material can cause direct harm to human health and can also cause serious environmental problems such as photochemical smog, acid rain and the like. Thus, NOxEmission control technology is a research hotspot in the field of environmental protection nowadays. NH (NH)3Selective Catalytic Reduction (SCR) NOx is considered a fixed-source emission of NOxOne of the most effective methods of pollution control, the technique utilizes a reductant NH3By reacting NO on a catalystxReduction to harmless N2And H2And O. The key of the SCR technology is to develop a high-efficiency and stable catalyst which is suitable for an application environment with high sulfur and high dust as main characteristics. At present, the SCR catalyst applied in industrialization is mostly TiO2Is a carrier, and is loaded with a certain amount of V2O5、WO3Or MoO3The catalyst has good catalytic performance in the range of 320-400 ℃. However, this catalyst has the following problems: active component V2O5The precursor has high toxicity and is easy to cause environmental pollution; and the catalyst has a narrow active temperature window, and when the flue gas temperature is lower than 300 ℃, the denitration performance of the catalyst is low.
A large amount of industrial combustion equipment exists in China, including industrial boilers, calcining kilns, cement rotary kilns and the like, and the temperature of flue gas between an air preheater and an economizer is usually between 250 and 350 ℃ and is lower than that of the flue gas of a coal-fired power station boiler (320 and 400 ℃). The flue gas emission temperature of the power plant boiler changes along with the load, the temperature before the air preheater can be reduced to below 250 ℃ even in the low-load operation, and the existing SCR catalyst at home and abroad can not be applied to the flue gas condition of the low-load operation of the power plant boiler. In order to meet the requirement of the exhaust gas temperature of most industrial boilers and power plants in China, the SCR catalyst with high activity at medium and low temperature (100-. TiO 22And CeO2Has received extensive attention and research as a cheap, non-toxic and highly efficient catalytic material. TiO 22Mainly used as various catalyst carriers and photocatalysts; CeO (CeO)2It is widely used in the field of environmental catalysis due to its strong ability to store-release free oxygen and excellent redox properties. Xu et al (W.Q.xu, Y.B.Yu, C.B.Zhang, H.He, Selective catalytic reduction of NO by NH3 over a Ce/TiO2catalysis Communications,9(2008)1453-2The catalyst can realize more than 95 percent of NO conversion rate (space velocity of 25000 h) within the range of 250-375 DEG C-1) (ii) a Gao et al (X.Gao, Y.Jiang, Z.Y.Luo, K.F.Cen, The activity and catalysis of CeO2-TiO2 catalysts prepared by the sol-gel method for selective catalytic reduction of NO with NH3Journal of Hazardous Materials, doi:10.1016/j.jhazmat.2009.09.112.) CeO prepared by the Sol-gel method2-TiO2The catalyst can realize 98.6 percent of NO conversion rate (space velocity of 50000 h) in the range of 300-400 DEG C-1). However, the above catalysts are less active in the region below 250 ℃. In 2001, Smironitis et al (P G, Smironitis, D A, Pena. B S Uphade, Low-temperature Selective Catalytic Reduction (SCR) of NO with NH3 by using Mn,Cr,and Cu oxides supported on Hombikat TiO2Angewandte Chemie International Edition,40(2001)2479-3Mn/TiO Excellent in SCR Activity2The catalyst attracts the attention of relevant scholars to Mn-based oxide catalysts, and the related research reports are rapidly increased. The main application target of the Mn-based oxide catalyst is fixed source flue gas denitration after desulfurization and dust removal units. Although the catalyst has excellent low-temperature activity, the water resistance and the sulfur resistance are poor, the medium-high temperature activity is low, and a byproduct N is generated2More O, so that it cannot be practically used. Therefore, development of novel compounds having high NH content3SCR activity, wide operating temperature window, adaptation to high airspeed environment, high stability, non-toxic and harmless non-vanadium-based catalyst system for fixed source flue gas denitration, andthe research focus in the field of environmental catalysis is at present.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a cerium-titanium composite nanorod material for selective catalytic reduction of nitrogen oxides by ammonia and a preparation method thereof, and load Mn and Sm for modification, so that the composite nanorod material can be used as NH for fixed source flue gas denitration3-an SCR catalyst. The catalyst has high activity, better steam resistance and sulfur dioxide poisoning resistance, and overcomes the defects of the prior commonly used NH3Narrow operating temperature window and N at high temperature in the presence of SCR vanadium-based catalyst system2Low selectivity and biological toxicity.
In order to realize the purpose, the technical scheme of the invention is as follows:
in one aspect, the invention provides a catalyst for ammonia selective catalytic reduction of nitrogen oxides for fixed source flue gas denitration, which comprises a carrier and an active component; the carrier is a cerium-titanium composite nanorod; the active component is a transition metal oxide or a combination of a transition metal oxide and a rare earth metal oxide.
As a preferred technical solution, the transition metal oxide is manganese oxide; the rare earth metal oxide is samarium oxide; the specific surface area of the cerium-titanium composite nanorod is more than or equal to 300 square meters per gram.
According to the preferable technical scheme, when the active component is manganese oxide, the mass ratio of the manganese oxide to the cerium-titanium composite nanorod is 1 (5-20).
According to the preferable technical scheme, when the active components are manganese oxide and samarium oxide, the mass ratio of the manganese oxide, the samarium oxide and the cerium-titanium composite nanorod is 1 (0.03-0.3) to 5-20; wherein, manganese oxide is used as a main active component, and samarium oxide is used as a secondary active component.
In another aspect, the present invention provides a method for preparing the above catalyst, comprising the steps of:
step one, preparation of a carrier: CeO is weighed2And TiO2In terms of molar ratio of metal elements, the ratio of cerium to titanium is 0.1 to0.25; subjecting the CeO to2And TiO2Dispersing in a sodium hydroxide solution, stirring at room temperature, carrying out hydrothermal reaction at 130 ℃ for 12-48 hours, cooling to room temperature after the reaction is finished, carrying out suction filtration, washing and drying on the obtained reaction solution to obtain the cerium-titanium composite nanorod;
and step two, loading an active component on the cerium-titanium composite nanorod to obtain the catalyst.
As a preferred technical scheme, the hydrothermal reaction is carried out in a hydrothermal reaction kettle; the concentration of the sodium hydroxide solution is 8-12 mol/L; the stirring time is 10-40 minutes; the drying conditions are as follows: drying for 12-48 hours at 80 ℃.
As a preferred technical solution, the step two includes the following steps:
(1) preparing 0.005-0.02 mol/L manganese nitrate solution;
(2) dispersing the cerium-titanium composite nano-rods in ammonia water;
(3) dropwise adding the solution obtained in the step (1) into the solution obtained in the step (2) under the stirring condition, stirring at room temperature for 3-24 hours, carrying out suction filtration on the obtained reaction solution, washing, drying at 80 ℃ for 12-48 hours, and roasting at 400 ℃ in a muffle furnace for 4-8 hours to obtain the catalyst.
As a preferred technical solution, the step two includes the following steps:
(1) preparing a mixed solution of manganese nitrate and samarium nitrate with the total concentration of 0.005-0.02 mol/L, wherein the mass ratio of metal Mn to metal Sm is 1 (0.03-0.3);
(2) dispersing the cerium-titanium composite nano-rods in ammonia water;
(3) dropwise adding the solution obtained in the step (1) into the solution obtained in the step (2) under the stirring condition, stirring at room temperature for 3-24 hours, carrying out suction filtration on the obtained reaction solution, washing, drying at 80 ℃ for 12-48 hours, and roasting at 400 ℃ in a muffle furnace for 4-8 hours to obtain the catalyst.
As a preferred technical scheme, the temperature rise rate in the roasting process is 2-5 ℃/min.
On the other handThe catalyst is used for the reaction of selectively catalyzing and reducing the nitrogen oxide by the low-temperature ammonia, the catalyst is placed in a fixed bed reactor, the reaction temperature is 100-400 ℃, the concentration of the nitrogen oxide at a reaction inlet is 100-2000ppm, and the volume ratio of the ammonia to the nitrogen oxide is 1-1.1; the volume space velocity of the reaction is 50000-100000h-1。
Advantageous effects
1. The catalyst of the invention makes the cerium-titanium composite oxide into the macroscopic morphology of the nano-rod, which is beneficial to the dispersion of active components while improving the specific surface area of the material.
2. When the active component is loaded, the precipitant is added firstly, and then the salt solution of the active component is added, so that the dispersity of the active component in the catalyst is obviously improved, and the catalytic activity is improved.
3. The manganese oxide with variable valence state is dispersed on the cerium-titanium composite nanorod, so that the low-temperature NH is obviously improved3-SCR denitration performance; manganese oxide and samarium oxide are simultaneously dispersed on the cerium-titanium composite nanorod to improve low-temperature NH3And the reaction temperature window is widened while the SCR denitration performance is improved.
4. The catalyst has wide active temperature window, has better activity at 100-400 ℃, can reach more than 90% of conversion rate at 150-350 ℃, and is expected to be used as a low-temperature SCR catalyst for fixed source flue gas denitration.
5. The catalyst provided by the invention has better water resistance and sulfur poisoning resistance, and has stronger adaptability to harsh working conditions in the presence of sulfur dioxide, water and the like.
6. The catalyst provided by the invention has excellent N2The selectivity of the product can reach more than 80% in the range of the whole temperature window.
Drawings
FIG. 1 is an adsorption-desorption isotherm of a cerium-titanium composite nanorod material.
Fig. 2 TEM image of cerium titanium composite nanorod material.
FIG. 3 NH of cerium-titanium composite nanorod material modified by metal oxides with different contents3SCR reaction Performance comparison results.
Figure 4 differs from the previous oneNH containing metal oxide modified cerium-titanium composite nanorod material3N in SCR reaction2And (6) selectively comparing the results.
FIG. 5 shows the results of water and sulfur resistance of catalyst H at 300 ℃.
NH of catalyst E provided in the example of FIG. 6 with catalyst I of comparative example 13SCR reaction Performance comparison results.
NH of catalyst E provided in the example of FIG. 7 and catalyst J of comparative example 23SCR reaction Performance comparison results.
Detailed Description
The following non-limiting examples, in which CeO is used, will allow one of ordinary skill in the art to more fully understand the present invention without limiting it in any way2TiO available from Tianjin Huahong New Material Co., Ltd2Model P25, available from degussa chemical ltd, Qingdao.
Example 1
Weighing a certain amount of CeO2And TiO2The ratio of cerium to titanium is 0.1:1 in terms of molar ratio of metal elements; dispersing the two solids in 10mol/L sodium hydroxide solution, wherein the molar ratio of sodium hydroxide to metal elements is 190:1, stirring for 30 minutes at room temperature, transferring the mixed solution into a hydrothermal reaction kettle, carrying out hydrothermal reaction for 48 hours at 130 ℃, and then cooling to room temperature. And (3) carrying out suction filtration and washing on the obtained reaction solution, and drying for 12-48 hours at the temperature of 80 ℃ to obtain the cerium-titanium composite nanorod, which is marked as a catalyst A.
Example 2
(1) Respectively preparing 50mL of manganese nitrate solution with the concentration of 0.005, 0.01, 0.015 and 0.02 mol/L;
(2) 0.35g of the cerium-titanium composite nanorod of the embodiment 1 is weighed and dispersed in ammonia water;
(3) and (3) dropwise adding the solution obtained in the step (1) into the solution obtained in the step (2) under continuous stirring, stirring at room temperature for 24 hours, carrying out suction filtration on the obtained reaction solution, washing, drying at 80 ℃ for 20 hours, and roasting at 400 ℃ in a muffle furnace for 5 hours to respectively obtain the catalyst B, C, D, E.
Example 3
(1) Preparing 50mL of mixed solution of manganese nitrate and samarium nitrate with the total concentration of 0.02mol/L, wherein the mass ratio of metal Mn to metal Sm is 1:0.03, 1:0.15 and 1:0.3 respectively;
(2) 0.35g of the cerium-titanium composite nanorod prepared in the example 1 is weighed and dispersed in ammonia water;
(3) and (3) dropwise adding the solution obtained in the step (1) into the solution obtained in the step (2) under the condition of continuous stirring, stirring at room temperature for 24 hours, carrying out suction filtration on the obtained reaction solution, washing, drying at 80 ℃ for 20 hours, and roasting at 400 ℃ in a muffle furnace for 5 hours to respectively obtain the catalyst F, G, H.
Comparative example 1
(1) Preparing 0.2mol/L ammonia water solution;
(2) preparing 50mL of 0.02mol/L manganese nitrate solution, weighing 0.35g of the cerium-titanium composite nanorod of the embodiment 1, and dispersing the cerium-titanium composite nanorod in the solution;
(3) and (3) dropwise adding the solution obtained in the step (1) into the solution obtained in the step (2) under continuous stirring, stirring at room temperature for 24 hours, carrying out suction filtration on the obtained reaction solution, washing, drying at 80 ℃ for 20 hours, and roasting at 400 ℃ in a muffle furnace for 5 hours to obtain a catalyst I.
Comparative example 2
(1) Preparing 50mL of 0.02mol/L manganese nitrate solution;
(2) 0.35g of CeO was weighed2And TiO2Dispersing the carrier obtained after mechanical mixing in ammonia water;
(3) and (3) dropwise adding the solution obtained in the step (1) into the solution obtained in the step (2) under continuous stirring, stirring at room temperature for 24 hours, carrying out suction filtration on the obtained reaction solution, washing, drying at 80 ℃ for 20 hours, and roasting at 400 ℃ in a muffle furnace for 5 hours to respectively obtain a catalyst J.
Application example 1
80mg of catalysts A-I are respectively placed in a tubular fixed bed reactor for reaction, and the experimental conditions are as follows: NO 500ppm, NH3:500ppm,O2:10％，N2For balancing gas, the total flow of the gas is 200mL/min, and the reaction space velocity is 95000h-1The reaction temperature range is from 100 DEG CThe results are shown in FIG. 2 and Table 1, when the temperature reached 400 ℃. NO, NO2Determination of NH by chemiluminescence3And N2NH for O3/N2The O analyzer is used for measurement, and the test result shows that when the catalyst A, B, G, H is used, the product N is obtained2The selectivity is more than 90 percent within the temperature range of 100 ℃ and 300 ℃.
Application example 2
80mg of catalyst H was placed in a tubular fixed bed reactor for reaction under the following experimental conditions: NO 500ppm, NH3:500ppm,O2:10％，H2O:5％,SO2:50ppm,N2For balancing gas, the total flow of the gas is 200mL/min, and the reaction space velocity is 95000h-1The reaction temperature was 300 ℃ and the results are shown in FIG. 3. NO, NO2Measured by chemiluminescence. The results of activity evaluation gave: the catalyst has good water resistance and sulfur poisoning resistance, and the activity is kept above 95% within 10 hours of investigation.
TABLE 1 NH of catalysts prepared in examples 1-2 and comparative examples 1-23Results of the SCR reaction
Claims (9)
1. A preparation method of a catalyst for ammonia selective catalytic reduction of nitrogen oxides for fixed source flue gas denitration is characterized in that the catalyst comprises a carrier and active components; the carrier is a cerium-titanium composite nanorod; the active component is transition metal oxide or the combination of transition metal oxide and rare earth metal oxide; the transition metal oxide is manganese oxide; the rare earth metal oxide is samarium oxide;
the preparation method of the catalyst comprises the following steps:
step one, preparation of a carrier: CeO is weighed2And TiO2Adding the CeO2And TiO2Dispersing in sodium hydroxide solution, stirring at room temperature, performing hydrothermal reaction at 120-140 ℃ for 12-48 hours, and reactingCooling to room temperature, carrying out suction filtration, washing and drying on the obtained reaction solution to obtain the cerium-titanium composite nanorod;
loading an active component on the cerium-titanium composite nanorod to obtain the catalyst;
wherein, in the first step, the hydrothermal reaction is carried out in a hydrothermal reaction kettle; the concentration of the sodium hydroxide solution is 8-12 mol/L; the stirring time is 10-40 minutes;
the specific surface area of the cerium-titanium composite nanorod is more than or equal to 300 square meters per gram.
2. The preparation method of the catalyst according to claim 1, wherein when the active component is manganese oxide, the mass ratio of the manganese oxide to the cerium-titanium composite nanorod is 1 (5-20); when the active components are manganese oxide and samarium oxide, the mass ratio of the manganese oxide, the samarium oxide and the cerium-titanium composite nanorod is 1 (0.03-0.3) to 5-20.
3. The method for preparing a catalyst according to claim 1, wherein, in the step one, CeO is used2And TiO2The molar ratio of (A) to (B) is 0.1 to 0.25.
4. The method for preparing a catalyst according to claim 1, wherein the drying conditions are: drying for 12-48 hours at 80 ℃.
5. The method for preparing a catalyst according to claim 1,
the second step comprises the following steps:
(1) preparing 0.005-0.02 mol/L manganese nitrate solution;
(2) dispersing the cerium-titanium composite nano-rods in ammonia water;
(3) dropwise adding the solution obtained in the step (1) into the solution obtained in the step (2) while stirring, stirring at room temperature for 3-24 hours, carrying out suction filtration on the obtained reaction solution, washing, drying at 80 ℃ for 12-48 hours, and roasting at 400 ℃ in a muffle furnace for 4-8 hours to obtain the catalyst.
6. The method for preparing according to claim 1, wherein the second step comprises the steps of:
(1) preparing a mixed solution of manganese nitrate and samarium nitrate with the total concentration of 0.005-0.02 mol/L, wherein the mass ratio of metal Mn to metal Sm is 1 (0.03-0.3);
(2) dispersing the cerium-titanium composite nano-rods in ammonia water;
(3) dropwise adding the solution obtained in the step (1) into the solution obtained in the step (2) under the stirring condition, stirring at room temperature for 3-24 hours, carrying out suction filtration on the obtained reaction solution, washing, drying at 80 ℃ for 12-48 hours, and roasting at 400 ℃ in a muffle furnace for 4-8 hours to obtain the catalyst.
7. The method for preparing the catalyst according to claim 5 or 6, wherein the temperature rise rate in the calcination process is 2 to 5 ℃/min.
8. The catalyst prepared by the preparation method of any one of claims 1 to 6 is applied to the reaction of selective catalytic reduction of nitrogen oxides by ammonia at low temperature.
9. The use as claimed in claim 8, wherein the reaction is carried out in a fixed bed reactor, the reaction temperature is 100-400 ℃, the concentration of nitrogen oxide at the reaction inlet is 100-2000ppm, and the volume ratio of ammonia/nitrogen oxide is 1-1.1; the volume space velocity of the reaction is 50000-100000h-1。
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