CN110694671A - Molecular sieve type SCR denitration catalyst synthesized by using natural diatomite and preparation method thereof - Google Patents
Molecular sieve type SCR denitration catalyst synthesized by using natural diatomite and preparation method thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 80
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 73
- 239000002808 molecular sieve Substances 0.000 title claims abstract description 52
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 title claims abstract description 52
- 238000002360 preparation method Methods 0.000 title abstract description 11
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 31
- 239000003546 flue gas Substances 0.000 claims abstract description 31
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 30
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 30
- 239000010703 silicon Substances 0.000 claims abstract description 30
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229910052751 metal Inorganic materials 0.000 claims abstract description 12
- 229910052684 Cerium Inorganic materials 0.000 claims abstract description 9
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 9
- 239000011259 mixed solution Substances 0.000 claims description 22
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims description 20
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 18
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 16
- 238000000227 grinding Methods 0.000 claims description 16
- 238000006243 chemical reaction Methods 0.000 claims description 15
- 239000012298 atmosphere Substances 0.000 claims description 14
- 238000001354 calcination Methods 0.000 claims description 14
- 239000011572 manganese Substances 0.000 claims description 14
- 238000003756 stirring Methods 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- 238000005303 weighing Methods 0.000 claims description 13
- 239000000843 powder Substances 0.000 claims description 12
- 239000000243 solution Substances 0.000 claims description 12
- 239000006228 supernatant Substances 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 10
- 239000002994 raw material Substances 0.000 claims description 10
- 229940071125 manganese acetate Drugs 0.000 claims description 9
- UOGMEBQRZBEZQT-UHFFFAOYSA-L manganese(2+);diacetate Chemical compound [Mn+2].CC([O-])=O.CC([O-])=O UOGMEBQRZBEZQT-UHFFFAOYSA-L 0.000 claims description 9
- 238000001914 filtration Methods 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 6
- -1 polytetrafluoroethylene Polymers 0.000 claims description 6
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 6
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 6
- 239000012265 solid product Substances 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 5
- 238000002425 crystallisation Methods 0.000 claims description 4
- 230000008025 crystallization Effects 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 239000003795 chemical substances by application Substances 0.000 claims 1
- 238000005470 impregnation Methods 0.000 claims 1
- 239000002243 precursor Substances 0.000 claims 1
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 abstract 1
- 239000010936 titanium Substances 0.000 abstract 1
- 229910052719 titanium Inorganic materials 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 12
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 239000012530 fluid Substances 0.000 description 5
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 4
- 239000002156 adsorbate Substances 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 4
- 238000012512 characterization method Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 4
- 238000011056 performance test Methods 0.000 description 4
- 239000010453 quartz Substances 0.000 description 4
- 238000012216 screening Methods 0.000 description 4
- 230000003595 spectral effect Effects 0.000 description 4
- ZSDSQXJSNMTJDA-UHFFFAOYSA-N trifluralin Chemical compound CCCN(CCC)C1=C([N+]([O-])=O)C=C(C(F)(F)F)C=C1[N+]([O-])=O ZSDSQXJSNMTJDA-UHFFFAOYSA-N 0.000 description 4
- 230000003197 catalytic effect Effects 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titanium dioxide Inorganic materials O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000003916 acid precipitation Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 210000002345 respiratory system Anatomy 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/03—Catalysts comprising molecular sieves not having base-exchange properties
- B01J29/0308—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41
- B01J29/0341—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41 containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
-
- 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
- B01D53/46—Removing components of defined structure
- B01D53/54—Nitrogen compounds
- B01D53/56—Nitrogen oxides
-
- 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
-
- B01J35/61—
Abstract
A molecular sieve type SCR denitration catalyst synthesized by natural diatomite and a preparation method thereof, relating to low-temperature NH3The field of SCR flue gas denitration. The active components are metal elements Ce and Mn, the carrier is a pure silicon MCM-41 molecular sieve synthesized by natural diatomite, and the molar percentage is as follows: 20-30% of active component and 70-80% of carrier, wherein the molar ratio of Ce to Mn in the active component is (0.125-0.25): 1. The catalyst has higher specific surface area (850-2/g), high hydrothermal stability, low cost and the like, and the denitration efficiency can reach 93 percent when the flue gas temperature is less than 250 ℃, and N is2The selectivity can reach more than 90 percent. With traditional titanium-based SCR denitration catalysisCompared with the catalyst, the catalyst adopts cheap natural diatomite to prepare a pure silicon molecular sieve as a carrier, so that the specific surface area is greatly increased, the cost is reduced, and the emission reduction of nitrogen oxide flue gas is facilitated.
Description
Technical Field
The invention relates to low temperature NH3An SCR flue gas denitration technology, in particular to a molecular sieve type SCR denitration catalyst synthesized by taking natural diatomite as a raw material and a preparation method thereof.
Background
Nitrogen Oxides (NO)x) As one of the main pollutants in the atmosphere, mainly NO is included2，N2O, and the like. The pollution of nitrogen oxides to the atmosphere mainly comprises the formation of acid rain, the generation of photochemical smog with hydrocarbons, the destruction of ozone layers and the like. In addition, nitrogen oxides have serious harm to the respiratory system and the nerve center of the human body. In recent years, the social economy of China is rapidly developed, the industrial scale is gradually enlarged, and the emission of nitrogen oxides becomes a problem to be solved urgently.
At present, with NH3Selective Catalytic Reduction (SCR) as a reductant is considered to remove the fixed source NOxThe most efficient method. SCR refers to the selective removal of NO using ammonia or other reducing agents under the action of a catalytic materialxReduction to N2While simultaneously producing water. The catalytic material acts to reduce NOxThe activation energy of the decomposition reaction enables the reaction to be carried out at a relatively low temperature. At present, with TiO2As a carrier, the catalyst prepared by taking oxides of Mn and Ce as active components is a relatively mature SCR denitration catalyst in commerce, and has the advantages of high denitration efficiency, low operation temperature and the like. But TiO 22The specific surface area is small and the price is expensive. Therefore, attempts have been made to utilize SiO which is inexpensive, has good thermal stability and a large specific surface area2Substituted TiO2As a catalyst carrier, preparation of an SCR denitration catalyst having a high specific surface area is a main research direction in the field of industrial denitration.
The MCM-41 molecular sieve is a mesoporous molecular sieve with a two-dimensional hexagonal structure, and was first synthesized and proposed in the nineties of the twentieth century by Beck et al, Mobil corporation. MCM-41 can be synthesized by using an organic surfactant as a template and an organic silicon source, and the molecular sieve has the advantages of large specific surface area, narrow pore size distribution, higher thermal stability, ordered pore channel arrangement and the like. Due to the structural characteristics of large specific surface area, large pore diameter and the like, the catalyst can be used as a catalyst carrier to load active components such as metal oxide and the like. The silicon sources used for synthesizing the MCM-41 molecular sieve at present are mostly organic silicon sources such as tetraethoxysilane and the like, the application cost is still high, if a method for extracting inorganic silicon sources by using natural minerals as raw materials can be found, and the inorganic silicon sources are used as carriers of SCR denitration catalysts and applied to the field of SCR denitration, the cost of the catalysts can be reduced, and the popularization of the SCR technology is facilitated.
Disclosure of Invention
In order to make up for the complement of the method, the invention provides a molecular sieve type SCR denitration catalyst synthesized by using natural diatomite and a preparation method thereof. The catalyst has a high specific surface area (850-2The catalyst has the characteristics of high hydrothermal stability, low cost and the like, and meets the requirements of SCR catalysts.
The purpose of the invention is realized by the following technical scheme:
a molecular sieve type SCR denitration catalyst synthesized by using natural diatomite comprises active components of metal elements Ce and Mn, a carrier is a pure silicon MCM-41 type molecular sieve prepared from the natural diatomite, and the molar percentages of the components are as follows:
20 to 30 percent of active component
70 to 80 percent of carrier
The molar ratio of the metal element Ce to the metal element Mn in the active component is (0.125-0.25): 1.
The preparation method of the SCR denitration catalyst is characterized by comprising the following steps:
(1) weighing natural diatomite as a raw material, heating the natural diatomite to 90 ℃ by using a sodium hydroxide solution for dissolving, filtering to obtain a supernatant, and extracting silicon elements in the diatomite. Cetyl Trimethyl Ammonium Bromide (CTAB) is weighed according to the molar ratio of the ingredients, and the mixture is added with the supernatant fluid and stirred uniformly. Adjusting the pH value of the mixed solution to 8-11, stirring the mixed solution, transferring the stirred mixed solution into a high-pressure reaction container with a polytetrafluoroethylene lining, and crystallizing for a certain time at a certain temperature.
(2) And (2) washing, drying and grinding the solid product obtained in the step (1), and calcining in an air atmosphere to obtain the pure silicon MCM-41 molecular sieve as a carrier.
(3) Weighing cerium nitrate and manganese acetate according to a proportion, adding water to dissolve, adding the MCM-41 molecular sieve carrier obtained in the step (2) into the solution, continuously stirring for 10-12 hours, and then transferring into a drying oven to dry until water is evaporated.
(4) And (4) grinding the dried solid obtained in the step (3) into powder, and calcining the powder in an air atmosphere to finally obtain the molecular sieve type SCR denitration catalyst.
In the present invention, the molar ratio of silicon element to CTAB in the step (1) is 1: (0.1-0.4).
In the invention, the crystallization temperature in the step (1) is 80-100 ℃, and the crystallization time is 18-24 h.
In the invention, the calcination conditions in the step (2) and the step (4) are both 450-600 ℃ for 4-5 h.
In the invention, the molar ratio of the pure silicon MCM-41 molecular sieve carrier, the cerium nitrate and the manganese acetate in the step (3) is 1 (0.05-0.1) to 0.4.
The application of the molecular sieve type SCR denitration catalyst is characterized in that: the catalyst is used for carrying out denitration treatment on flue gas containing nitric oxide, and the denitration temperature range is 175-225 ℃.
The molecular sieve type SCR denitration catalyst has higher specific surface area (850-2The catalyst has uniform particle size (300-500nm), the MCM-41 molecular sieve used as the carrier has a hexagonal regular structure which provides more acid sites, the catalytic activity of SCR is ensured, and compared with the traditional SCR catalyst, the catalyst uses cheap diatomite as a raw material, and the cost is reduced. The denitration efficiency of the catalyst can reach 94 percent when the flue gas temperature is 175-225 ℃, and N is2The selectivity can reach more than 90 percent.
Detailed Description
The present invention will be further described with reference to specific examples.
Example 1
A molecular sieve type SCR denitration catalyst synthesized by using natural diatomite comprises active components of metal elements Ce and Mn, and a carrier is a pure silicon MCM-41 type molecular sieve prepared from the natural diatomite. The molar ratio of Ce element, Mn element and Si element in the catalyst is 0.1:0.4: 1. When the MCM-41 molecular sieve carrier is prepared, the molar ratio of CTAB to Si element is 0.1: 1.
The preparation method of the SCR denitration catalyst comprises the following steps:
(1) weighing natural diatomite as a raw material, heating the natural diatomite to 90 ℃ by using a sodium hydroxide solution for dissolving, filtering to obtain a supernatant, and extracting silicon elements in the diatomite. Cetyl Trimethyl Ammonium Bromide (CTAB) is weighed according to the proportion, and is added with the supernatant fluid and stirred evenly. Adjusting the pH value of the mixed solution to 10, stirring the mixed solution, transferring the mixed solution into a high-pressure reaction vessel with a polytetrafluoroethylene lining, and crystallizing the mixed solution at 100 ℃ for 20 hours.
(2) And (2) washing, drying and grinding the solid product obtained in the step (1), and calcining for 5 hours in an air atmosphere at 500 ℃ to obtain the pure silicon MCM-41 molecular sieve as a carrier.
(3) Weighing cerium nitrate and manganese acetate according to a proportion, adding water to dissolve, adding the MCM-41 molecular sieve carrier obtained in the step (2) into the solution, continuously stirring for 12 hours, transferring into a drying oven, and drying until water is evaporated.
(4) And (4) grinding the dried solid obtained in the step (3) into powder, and calcining for 4 hours at 500 ℃ in an air atmosphere to finally obtain the molecular sieve type SCR denitration catalyst.
BET characterization of the above catalysts
The BET test of the catalyst adopts a TriStar II 3020 full-automatic specific surface area and porosity analyzer manufactured by Micromeritics company, samples are pretreated for 1 hour at 90 ℃ and 3 hours at 350 ℃ under vacuum, and the adsorbate is nitrogen. The specific surface area of the powder was measured to be 876.4752m2/g。
Denitration performance test of the catalyst
Grinding, tabletting and screening the prepared catalyst, taking 2ml of sample particles of 40-60 meshes for denitration activity test, and simulating the concentration of NO in flue gas to be 1000ppm and ammoniaIn a molar ratio of 1:1 with nitric oxide, O2Content 5%, N2The total flow rate of the gas is 450ml/min for the balance gas. And (2) introducing each path of gas into a mixer after passing through a flowmeter, fully mixing and introducing into a reaction container, wherein the reactor is a quartz tube with the diameter of 30mm, a vertical tube type heating furnace with a temperature control system provides a reaction temperature environment, and introducing the flue gas at the outlet of the reactor into a TENSOR 27 type Fourier transform infrared spectrometer produced by Bruker spectral instruments to analyze the components of the outlet flue gas.
The denitration efficiency of the catalyst is 71.102% when the flue gas temperature is 175 ℃, and the denitration efficiency of the catalyst is 84.998% when the flue gas temperature is 200 ℃. The denitration efficiency of the catalyst is 89.625% when the flue gas temperature is 225 ℃.
Example 2
A molecular sieve type SCR denitration catalyst synthesized by using natural diatomite comprises active components of metal elements Ce and Mn, and a carrier is a pure silicon MCM-41 type molecular sieve prepared from the natural diatomite. The molar ratio of Ce element, Mn element and Si element in the catalyst is 0.1:0.4: 1. When the MCM-41 molecular sieve carrier is prepared, the molar ratio of CTAB to Si element is 0.2: 1.
The preparation method of the SCR denitration catalyst comprises the following steps:
(1) weighing natural diatomite as a raw material, heating the natural diatomite to 90 ℃ by using a sodium hydroxide solution for dissolving, filtering to obtain a supernatant, and extracting silicon elements in the diatomite. Cetyl Trimethyl Ammonium Bromide (CTAB) is weighed according to the proportion, and is added with the supernatant fluid and stirred evenly. Adjusting the pH value of the mixed solution to 10, stirring the mixed solution, transferring the mixed solution into a high-pressure reaction vessel with a polytetrafluoroethylene lining, and crystallizing the mixed solution at 100 ℃ for 20 hours.
(2) And (2) washing, drying and grinding the solid product obtained in the step (1), and calcining for 5 hours in an air atmosphere at 500 ℃ to obtain the pure silicon MCM-41 molecular sieve as a carrier.
(3) Weighing cerium nitrate and manganese acetate according to a proportion, adding water to dissolve, adding the MCM-41 molecular sieve carrier obtained in the step (2) into the solution, continuously stirring for 12 hours, transferring into a drying oven, and drying until water is evaporated.
(4) And (4) grinding the dried solid obtained in the step (3) into powder, and calcining for 4 hours at 500 ℃ in an air atmosphere to finally obtain the molecular sieve type SCR denitration catalyst.
BET characterization of the above catalysts
The BET test of the catalyst adopts a TriStar II 3020 full-automatic specific surface area and porosity analyzer manufactured by Micromeritics company, samples are pretreated for 1 hour at 90 ℃ and 3 hours at 350 ℃ under vacuum, and the adsorbate is nitrogen. The specific surface area of the powder was measured to be 941.7961m2/g。
Denitration performance test of the catalyst
Grinding, tabletting and screening the prepared catalyst, taking 2ml of sample particles of 40-60 meshes for denitration activity test, simulating that the concentration of NO in flue gas is 1000ppm, the ratio of ammonia to nitric oxide is 1:1, and O is2Content 5%, N2The total flow rate of the gas is 450ml/min for the balance gas. And (2) introducing each path of gas into a mixer after passing through a flowmeter, fully mixing and introducing into a reaction container, wherein the reactor is a quartz tube with the diameter of 30mm, a vertical tube type heating furnace with a temperature control system provides a reaction temperature environment, and introducing the flue gas at the outlet of the reactor into a TENSOR 27 type Fourier transform infrared spectrometer produced by Bruker spectral instruments to analyze the components of the outlet flue gas.
The denitration efficiency of the catalyst is 76.203% when the flue gas temperature is 175 ℃, and the denitration efficiency of the catalyst is 89.343% when the flue gas temperature is 200 ℃. The denitration efficiency of the catalyst is 94.617% when the flue gas temperature is 225 ℃.
Example 3
A molecular sieve type SCR denitration catalyst synthesized by using natural diatomite comprises active components of metal elements Ce and Mn, and a carrier is a pure silicon MCM-41 type molecular sieve prepared from the natural diatomite. The molar ratio of Ce element, Mn element and Si element in the catalyst is 0.07:0.4: 1. When the MCM-41 molecular sieve carrier is prepared, the molar ratio of CTAB to Si element is 0.3: 1.
The preparation method of the SCR denitration catalyst comprises the following steps:
(1) weighing natural diatomite as a raw material, heating the natural diatomite to 90 ℃ by using a sodium hydroxide solution for dissolving, filtering to obtain a supernatant, and extracting silicon elements in the diatomite. Cetyl Trimethyl Ammonium Bromide (CTAB) is weighed according to the proportion, and is added with the supernatant fluid and stirred evenly. Adjusting the pH value of the mixed solution to 10, stirring the mixed solution, transferring the mixed solution into a high-pressure reaction vessel with a polytetrafluoroethylene lining, and crystallizing the mixed solution at 100 ℃ for 20 hours.
(2) And (2) washing, drying and grinding the solid product obtained in the step (1), and calcining for 5 hours in an air atmosphere at 500 ℃ to obtain the pure silicon MCM-41 molecular sieve as a carrier.
(3) Weighing cerium nitrate and manganese acetate according to a proportion, adding water to dissolve, adding the MCM-41 molecular sieve carrier obtained in the step (2) into the solution, continuously stirring for 12 hours, transferring into a drying oven, and drying until water is evaporated.
(4) And (4) grinding the dried solid obtained in the step (3) into powder, and calcining for 4 hours at 500 ℃ in an air atmosphere to finally obtain the molecular sieve type SCR denitration catalyst.
BET characterization of the above catalysts
The BET test of the catalyst adopts a TriStar II 3020 full-automatic specific surface area and porosity analyzer manufactured by Micromeritics company, samples are pretreated for 1 hour at 90 ℃ and 3 hours at 350 ℃ under vacuum, and the adsorbate is nitrogen. The specific surface area of the powder was measured to be 1008.7873m2/g。
Denitration performance test of the catalyst
Grinding, tabletting and screening the prepared catalyst, taking 2ml of sample particles of 40-60 meshes for denitration activity test, simulating that the concentration of NO in flue gas is 1000ppm, the ratio of ammonia to nitric oxide is 1:1, and O is2Content 5%, N2The total flow rate of the gas is 450ml/min for the balance gas. And (2) introducing each path of gas into a mixer after passing through a flowmeter, fully mixing and introducing into a reaction container, wherein the reactor is a quartz tube with the diameter of 30mm, a vertical tube type heating furnace with a temperature control system provides a reaction temperature environment, and introducing the flue gas at the outlet of the reactor into a TENSOR 27 type Fourier transform infrared spectrometer produced by Bruker spectral instruments to analyze the components of the outlet flue gas.
The denitration efficiency of the catalyst is 72.189% when the flue gas temperature is 175 ℃, and the denitration efficiency of the catalyst is 92.890% when the flue gas temperature is 200 ℃. The denitration efficiency of the catalyst is 93.588% when the flue gas temperature is 225 ℃.
Example 4
A molecular sieve type SCR denitration catalyst synthesized by using natural diatomite comprises active components of metal elements Ce and Mn, and a carrier is a pure silicon MCM-41 type molecular sieve prepared from the natural diatomite. The molar ratio of Ce element, Mn element and Si element in the catalyst is 0.05:0.4: 1. When the MCM-41 molecular sieve carrier is prepared, the molar ratio of CTAB to Si element is 0.2: 1.
The preparation method of the SCR denitration catalyst comprises the following steps:
(1) weighing natural diatomite as a raw material, heating the natural diatomite to 90 ℃ by using a sodium hydroxide solution for dissolving, filtering to obtain a supernatant, and extracting silicon elements in the diatomite. Cetyl Trimethyl Ammonium Bromide (CTAB) is weighed according to the proportion, and is added with the supernatant fluid and stirred evenly. Adjusting the pH value of the mixed solution to 10, stirring the mixed solution, transferring the mixed solution into a high-pressure reaction vessel with a polytetrafluoroethylene lining, and crystallizing the mixed solution at 100 ℃ for 20 hours.
(2) And (2) washing, drying and grinding the solid product obtained in the step (1), and calcining for 5 hours in an air atmosphere at 500 ℃ to obtain the pure silicon MCM-41 molecular sieve as a carrier.
(3) Weighing cerium nitrate and manganese acetate according to a proportion, adding water to dissolve, adding the MCM-41 molecular sieve carrier obtained in the step (2) into the solution, continuously stirring for 12 hours, transferring into a drying oven, and drying until water is evaporated.
(4) And (4) grinding the dried solid obtained in the step (3) into powder, and calcining for 4 hours at 500 ℃ in an air atmosphere to finally obtain the molecular sieve type SCR denitration catalyst.
BET characterization of the above catalysts
The BET test of the catalyst adopts a TriStar II 3020 full-automatic specific surface area and porosity analyzer manufactured by Micromeritics company, samples are pretreated for 1 hour at 90 ℃ and 3 hours at 350 ℃ under vacuum, and the adsorbate is nitrogen. The specific surface area of the powder was measured to be 924.1182m2/g。
Denitration performance test of the catalyst
Grinding, tabletting and screening the prepared catalyst, taking 2ml of sample particles of 40-60 meshes for denitration activity test, simulating that the concentration of NO in flue gas is 1000ppm, the ratio of ammonia to nitric oxide is 1:1, and O is2Content 5%, N2The total flow rate of the gas is 450ml/min for the balance gas. And (2) introducing each path of gas into a mixer after passing through a flowmeter, fully mixing and introducing into a reaction container, wherein the reactor is a quartz tube with the diameter of 30mm, a vertical tube type heating furnace with a temperature control system provides a reaction temperature environment, and introducing the flue gas at the outlet of the reactor into a TENSOR 27 type Fourier transform infrared spectrometer produced by Bruker spectral instruments to analyze the components of the outlet flue gas.
The denitration efficiency of the catalyst is 74.125% when the flue gas temperature is 175 ℃, and the denitration efficiency of the catalyst is 90.310% when the flue gas temperature is 200 ℃. The denitration efficiency of the catalyst is 92.380% when the flue gas temperature is 225 ℃.
Claims (5)
1. A molecular sieve type SCR denitration catalyst synthesized by using natural diatomite comprises active components and a carrier, and is characterized in that: the active components are metal elements Ce and Mn, the carrier is a pure silicon MCM-41 type molecular sieve prepared from natural diatomite, wherein the molar percentage is as follows:
20 to 30 percent of active component
70 to 80 percent of carrier
The molar ratio of the metal element Ce to the metal element Mn in the active component is (0.125-0.25): 1.
2. The molecular sieve-type SCR denitration catalyst according to claim 1, characterized in that: the carrier is a pure silicon MCM-41 molecular sieve prepared by taking natural diatomite as a raw material and Cetyl Trimethyl Ammonium Bromide (CTAB) as a template agent, and the specific surface area of the carrier is 850-2(ii)/g, particle size 300-500 nm.
3. The molecular sieve-type SCR denitration catalyst according to claim 1, characterized in that: precursors of the active component metal elements Ce and Mn are cerium nitrate and manganese acetate, and are loaded on the carrier by an impregnation method.
4. A method for preparing the molecular sieve-type SCR denitration catalyst according to any one of claims 1 to 3, which is sequentially performed according to the following steps:
(1) weighing natural diatomite as a raw material, heating the natural diatomite to 90 ℃ by using a sodium hydroxide solution for dissolving, filtering to obtain a supernatant, and extracting silicon elements in the diatomite; according to the molar ratio of silicon element to CTAB of 1: (0.1-0.4) weighing Cetyl Trimethyl Ammonium Bromide (CTAB), adding the supernatant, and stirring uniformly; adjusting the pH value of the mixed solution to 8-11, vigorously stirring the mixed solution, and transferring the mixed solution into a high-pressure reaction vessel with a polytetrafluoroethylene lining for crystallization at the crystallization temperature of 80-100 ℃ for 18-24 h;
(2) washing, drying and grinding the solid product obtained in the step (1), and calcining in an air atmosphere to obtain a pure silicon MCM-41 molecular sieve as a carrier;
(3) weighing cerium nitrate and manganese acetate, adding water to dissolve, adding the MCM-41 molecular sieve carrier obtained in the step (2) into the solution, continuously stirring for 10-12 hours, and then transferring into a drying oven to dry until water is evaporated; the molar ratio of the pure silicon MCM-41 molecular sieve carrier to the cerium nitrate and the manganese acetate is 1 (0.05-0.1) to 0.4;
(4) grinding the dried solid obtained in the step (3) into powder, and calcining the powder in an air atmosphere to finally obtain the molecular sieve type SCR denitration catalyst;
the calcination conditions in the step (2) and the step (4) are both 450-600 ℃ for 4-5 h.
5. Use of the molecular sieve type SCR denitration catalyst according to claim 1, characterized in that: the catalyst is used for carrying out denitration treatment on flue gas containing nitric oxide, and the denitration temperature range is 175-225 ℃.
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