CN117504852A - Sulfur-tolerant ammonia selective catalytic oxidation catalyst suitable for control of escaped ammonia and its preparation and application - Google Patents
Sulfur-tolerant ammonia selective catalytic oxidation catalyst suitable for control of escaped ammonia and its preparation and application Download PDFInfo
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- CN117504852A CN117504852A CN202311455343.2A CN202311455343A CN117504852A CN 117504852 A CN117504852 A CN 117504852A CN 202311455343 A CN202311455343 A CN 202311455343A CN 117504852 A CN117504852 A CN 117504852A
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- ammonia
- cerium
- selective catalytic
- sulfur
- chromium
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 119
- 239000003054 catalyst Substances 0.000 title claims abstract description 91
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 59
- 230000003647 oxidation Effects 0.000 title claims abstract description 48
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 48
- 230000003197 catalytic effect Effects 0.000 title claims abstract description 40
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- 239000002131 composite material Substances 0.000 claims abstract description 32
- 239000011593 sulfur Substances 0.000 claims abstract description 29
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 29
- GACQBOJYMXJNSQ-UHFFFAOYSA-N [Ce].[Cr] Chemical compound [Ce].[Cr] GACQBOJYMXJNSQ-UHFFFAOYSA-N 0.000 claims abstract description 28
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 21
- 239000011258 core-shell material Substances 0.000 claims abstract description 10
- 239000013078 crystal Substances 0.000 claims abstract description 9
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 7
- TYAVIWGEVOBWDZ-UHFFFAOYSA-K cerium(3+);phosphate Chemical compound [Ce+3].[O-]P([O-])([O-])=O TYAVIWGEVOBWDZ-UHFFFAOYSA-K 0.000 claims abstract description 6
- 239000011651 chromium Substances 0.000 claims description 28
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims description 24
- 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 20
- 238000001354 calcination Methods 0.000 claims description 14
- 238000006243 chemical reaction Methods 0.000 claims description 14
- 239000011259 mixed solution Substances 0.000 claims description 12
- 229910052684 Cerium Inorganic materials 0.000 claims description 7
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 6
- 239000004202 carbamide Substances 0.000 claims description 6
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 6
- LPSKDVINWQNWFE-UHFFFAOYSA-M tetrapropylazanium;hydroxide Chemical compound [OH-].CCC[N+](CCC)(CCC)CCC LPSKDVINWQNWFE-UHFFFAOYSA-M 0.000 claims description 5
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- PHFQLYPOURZARY-UHFFFAOYSA-N chromium trinitrate Chemical compound [Cr+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O PHFQLYPOURZARY-UHFFFAOYSA-N 0.000 claims description 4
- 239000002244 precipitate Substances 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
- 238000010531 catalytic reduction reaction Methods 0.000 claims description 3
- XPPKVPWEQAFLFU-UHFFFAOYSA-N diphosphoric acid Chemical compound OP(O)(=O)OP(O)(O)=O XPPKVPWEQAFLFU-UHFFFAOYSA-N 0.000 claims description 3
- 229940005657 pyrophosphoric acid Drugs 0.000 claims description 3
- 239000002002 slurry Substances 0.000 claims description 3
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical group O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims description 2
- 229910000420 cerium oxide Inorganic materials 0.000 claims description 2
- 229910000423 chromium oxide Inorganic materials 0.000 claims description 2
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims description 2
- 239000007787 solid Substances 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 6
- 238000002156 mixing Methods 0.000 abstract description 3
- 238000000975 co-precipitation Methods 0.000 abstract description 2
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 22
- 230000000052 comparative effect Effects 0.000 description 17
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 12
- 239000003546 flue gas Substances 0.000 description 12
- 150000003839 salts Chemical class 0.000 description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 230000008569 process Effects 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 150000004706 metal oxides Chemical class 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 230000001276 controlling effect Effects 0.000 description 5
- 238000001035 drying Methods 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 239000002808 molecular sieve Substances 0.000 description 5
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 4
- 230000003993 interaction Effects 0.000 description 4
- 229910044991 metal oxide Inorganic materials 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 230000002829 reductive effect Effects 0.000 description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- 229910000510 noble metal Inorganic materials 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 241000894007 species Species 0.000 description 3
- 229910052723 transition metal Inorganic materials 0.000 description 3
- 150000003624 transition metals Chemical class 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000006356 dehydrogenation reaction Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000033116 oxidation-reduction process Effects 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000443 aerosol Substances 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 1
- 238000000231 atomic layer deposition 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
- 230000008901 benefit Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- RCFVMJKOEJFGTM-UHFFFAOYSA-N cerium zirconium Chemical compound [Zr].[Ce] RCFVMJKOEJFGTM-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000009993 protective function Effects 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000005067 remediation Methods 0.000 description 1
- 230000027756 respiratory electron transport chain Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 239000011973 solid acid Substances 0.000 description 1
- 238000013112 stability test Methods 0.000 description 1
- 230000003335 steric effect Effects 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000019635 sulfation Effects 0.000 description 1
- 238000005670 sulfation reaction Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
Classifications
-
- 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
-
- 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
- B01D53/8634—Ammonia
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/24—Chromium, molybdenum or tungsten
- B01J23/26—Chromium
-
- 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
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/14—Phosphorus; Compounds thereof
- B01J27/16—Phosphorus; Compounds thereof containing oxygen, i.e. acids, anhydrides and their derivates with N, S, B or halogens without carriers or on carriers based on C, Si, Al or Zr; also salts of Si, Al and Zr
- B01J27/18—Phosphorus; Compounds thereof containing oxygen, i.e. acids, anhydrides and their derivates with N, S, B or halogens without carriers or on carriers based on C, Si, Al or Zr; also salts of Si, Al and Zr with metals other than Al or Zr
- B01J27/1802—Salts or mixtures of anhydrides with compounds of other metals than V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, e.g. phosphates, thiophosphates
- B01J27/1804—Salts or mixtures of anhydrides with compounds of other metals than V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, e.g. phosphates, thiophosphates with rare earths or actinides
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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
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/14—Phosphorus; Compounds thereof
- B01J27/186—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J27/188—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with chromium, molybdenum, tungsten or polonium
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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
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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
- B01J37/08—Heat treatment
- B01J37/10—Heat treatment in the presence of water, e.g. steam
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
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Abstract
The invention discloses a sulfur-resistant ammonia selective catalytic oxidation catalyst suitable for escaped ammonia control, and a preparation method and application thereof. The catalyst of the invention takes chromium-cerium composite oxide as a core and cerium phosphate as a shellIs a core-shell structure. The preparation method of the invention comprises the steps of firstly preparing the chromium-cerium composite oxide core by a coprecipitation method, and then mixing the core with a small amount of CePO 4 Seed crystal is mixed and then CePO is grown by a hydrothermal method 4 A housing. The catalyst has the excellent characteristics of wide temperature window, high activity, high water sulfur stability and the like, can realize the removal of the escaped ammonia of the SCR section with low cost, and overcomes the existing NH (NH) 3 The SCO catalyst has the problems of poor temperature window matching performance, poor water-sulfur resistance stability and the like.
Description
Technical Field
The invention relates to the technical field of ammonia escape control in a denitration process, in particular to a sulfur-resistant ammonia selective catalytic oxidation catalyst suitable for escape ammonia control, and a preparation method and application thereof.
Background
As an index for controlling atmospheric pollutants, ammonia (NH 3 ) Is an important precursor for haze formation, and has serious influence on ecological environment and human health. In addition to industrial processes, animal husbandry and agricultural fertilisation, one of the main sources of ammonia emissions is in the industrial flue gas denitrification process (ammonia selective catalytic reduction, NH 3 -SCR) ammonia slip occurs when ammonia is used as a reducing agent. In order to overcome the complex working condition and changeable smoke Nitrogen Oxides (NO) x ) The influence of the content, poor ammonia nitrogen mixing effect and the like on the SCR denitration effect exceeds NH of stoichiometric ratio 3 Injected into SCR device, unreacted NH 3 Escape phenomena are formed, which can cause problems such as downstream air preheater blockage, secondary inorganic aerosol formation and the like.
Compared with the technologies such as absorption method, adsorption method, biological treatment method and the like which need additional structures, NH is arranged at the tail end of the SCR device 3 Selective oxidation of fugitive ammonia to nitrogen (N) by a SCO (ammonia selective catalytic oxidation) catalyst bed 2 ) Has significant advantages. Common NH 3 The SCO catalyst mainly comprises noble metal, transition metal and molecular sieve catalyst, and has obvious difference and different characteristics. Noble metal-based catalysts have narrow temperature windows, N 2 The problems of poor selectivity, high cost and the like limit the practical application of the catalyst in industrial flue gas treatment; the most widely studied transition metal based catalysts with Cu based catalysts, but the sulfur dioxide (SO) in flue gas has not been overcome yet 2 ) Is a stress problem; the supported molecular sieve based catalyst shows excellent activity by virtue of good structural characteristics, has good water and sulfur resistance stability, but has poor high-temperature stability and high catalyst cost, so that the industrial application of the supported molecular sieve based catalyst in the field of flue gas treatment is limited.
The Chinese patent publication No. CN114042452A discloses a preparation method of an ammonia oxidation catalyst for tail gas of diesel vehicles, which uses reductive P25 type titanium dioxide as a carrier, silver as an active component and adopts an atomic layer deposition methodCovering the nano oxide film. Although the catalyst has excellent catalytic activity at low temperature (T 100 As low as 200 deg.c), but the industrial application cost of the catalyst is increased due to the complicated preparation process and the high Ag content.
The chinese patent publication No. CN114904570a discloses a method for preparing a double-layer catalyst, which includes a uniformly distributed carrier composed of cordierite; a catalyst bottom layer composed of metal oxides such as alumina/cerium zirconium powder/molecular sieve added with Pt noble metal; cu-supported catalyst surface layer with SSZ-13 as molecular sieve. But it has the defect of N 2 Poor selectivity and no consideration of SO in flue gas 2 Influence of the composition.
Chinese patent publication No. CN114405541A discloses a selective oxidation of NH 3 The preparation method of the catalyst, which utilizes metal alkoxide to modify CuO/CeO 2 /ZrO 2 Composite metal catalyst with high catalytic activity and heat stability NH 3 SCO catalyst, but likewise does not relate to the H in the flue gas of the catalyst 2 O、SO 2 Influence of the composition.
Although the above-mentioned documents provide a certain help for the development of catalysts for treating ammonia slip, the disadvantages of mismatching temperature window, high preparation cost, poor water-resistant sulfur stability and the like still exist to prevent NH 3 Industrial application of SCO catalysts in the field of flue gas remediation.
Therefore, a new NH which can be used for controlling escaped ammonia in the flue gas SCR denitration process, has wide temperature window, high activity, high water-sulfur stability and relatively low preparation cost is developed 3 The SCO catalyst has wide application prospect and development significance.
Disclosure of Invention
Aiming at the technical problems and the defects existing in the field, the invention provides a sulfur-resistant ammonia selective catalytic oxidation catalyst suitable for controlling escaped ammonia, which has the excellent characteristics of wide temperature window, high activity, high water sulfur stability and the like, can realize the low-cost removal of escaped ammonia of an SCR section, and overcomes the defects of NH at present 3 The SCO catalyst has the problems of poor temperature window matching performance, poor water-sulfur resistance stability and the like.
A sulfur-resistant ammonia selective catalytic oxidation catalyst suitable for controlling escaped ammonia comprises a core composed of chromium-cerium composite oxide and cerium phosphate (CePO) 4 ) Is a core-shell structure of a shell;
the chromium-cerium composite oxide is a chromium oxide supported on a cerium oxide carrier, wherein the molar ratio of chromium element to cerium element is 1:3-10, for example, 1:5, 1:10 and the like.
The invention adopts a core-shell structure to solve the technical problems, and wraps the chromium-cerium composite oxide inner core with stronger oxidation-reduction performance in CePO 4 In the housing. Wherein the chromium-cerium composite oxide core is a good oxidation catalyst, and NH can be rapidly realized by the cooperation of the high oxygen carrying capacity of Ce oxide and the strong electron transfer capacity of Cr oxide 3 Is a dehydrogenation oxidation of (a). Under the combined actions of the anaerobic property of Cr element, the philic property of Ce element, the strong metal interaction and the like in the chromium-cerium composite oxide core, SO in the flue gas 2 Will be preferentially at CeO adjacent to Cr sites 2 The carrier interface is trapped to form special steric hindrance, which not only inhibits the further accumulation of the surface sulfate species, but also protects CeO 2 The surface is highly dispersed with Cr sites. The molar ratio of chromium to cerium of the chromium-cerium composite oxide can be regulated to adjust the strong interaction among metals, change the distribution uniformity of Cr elements on the surface, strengthen the steric effect and further influence the surface oxidation-reduction performance and sulfur resistance performance.
The catalyst of the invention is used for NH 3 In the process of SCO, the housing CePO 4 Not only can participate in the internal SCR process to promote NH 3 SCO performance, and can further strengthen SO resistance of the chromium-cerium composite oxide core 2 The performance is presented. CePO (CePO) 4 Surface-generated core oxidation product NO x And adsorbed state NH 3 Inhibit NH due to strong oxidizing property of the inner core, high temperature condition, etc 3 Excessive oxidation to give overall N 2 The selectivity is reduced, so that the reaction temperature window is widened, and the nitrogen selectivity is improved. Meanwhile, the shell layer CePO 4 Has stronger acidity and special electronic structure, can limit SO 2 The process of diffusing to the inner core delays the sulfation speed of the inner core catalyst, and further improves the sulfur resistance of the catalyst. Therefore, the catalyst can overcome SO in actual industrial flue gas 2 Is not influenced by the interference of (a).
The molar ratio of cerium element in the chromium-cerium composite oxide to the cerium phosphate may be 2:1-4, for example, 1:1, 1:2, 2:1, etc.
The invention also provides a preparation method of the sulfur-resistant ammonia selective catalytic oxidation catalyst, which comprises the following steps:
(1) Adjusting the pH of the mixed solution of chromium nitrate and cerium nitrate to 8-11 (for example, 8-10, 9-11, etc.), separating the obtained precipitate, washing, drying and calcining to obtain chromium-cerium composite oxide;
(2) Preparation of H in a molar ratio of 1:1 3 PO 4 And cerium nitrate, adjusting the pH to 9-11, and keeping the mixture sufficiently stirred during the preparation process to form uniform gel; then adding the chromium-cerium composite oxide obtained in the step (1), fully stirring, drying and calcining to obtain the CePO-loaded ceramic 4 Chromium-cerium composite oxide of seed crystal;
(3) Preparing a mixed solution of pyrophosphoric acid and cerium nitrate in a molar ratio of 1:1, and dropwise adding ammonia water until the mixed solution is clarified; then adding the CePO loaded material obtained in the step (2) 4 And adding urea and/or tetrapropylammonium hydroxide (TPAH) into the seed chromium-cerium composite oxide to form slurry, performing hydrothermal reaction, and washing, drying and calcining the obtained solid to obtain the sulfur-resistant ammonia selective catalytic oxidation catalyst.
In the preparation method of the invention, firstly, a chromium-cerium composite oxide inner core is prepared by a coprecipitation method, and then the inner core and a small amount of CePO are mixed 4 Seed crystal is mixed and then CePO is grown by a hydrothermal method 4 A housing. When NH 3 CePO on the shell during adsorption on the catalyst surface 4 Can absorb NH well as solid acid 3 Meanwhile, the chromium-cerium composite oxide inner core has higher catalytic oxidation performance and can convert NH 3 Oxidation to N 2 And NO x And excessively oxidize the generated NO x Migration to housing CePO 4 Back and surface adsorptionNH in state 3 Generating internal NH 3 SCR reaction to N 2 Complete the whole reaction process of the integral SCO, ensure high nitrogen selectivity and avoid NH 3 Is a secondary generation of nitrogen oxides. At the same time, the combination characteristic of the anaerobic sulfur-philic metal oxide in the core structure can resist SO 2 Is a toxic action of CePO 4 Has good SO as well 2 Resistance. The catalyst of this structure is therefore capable of achieving high NH 3 The conversion rate can effectively avoid NH at high temperature 3 The catalyst material has good sulfur resistance and is an excellent catalyst with wide temperature window, high activity and high water sulfur stability.
In step (1), ammonia may be used to adjust the pH.
In step (1), the calcination temperature may be 450-550 ℃ and the time may be 4-6 hours.
In step (2), ammonia may be used to adjust the pH.
In the step (2), the calcination temperature may be 350 to 450 ℃ and the time may be 3 to 5 hours.
In step (2), the support is CePO 4 The CePO is prepared from the chromium-cerium composite oxide of seed crystal 4 The mass percentage of the seed crystal can be 5-10%.
In step (3), the molar ratio of urea and/or tetrapropylammonium hydroxide to cerium nitrate may be 2-10:1.
In the step (3), the temperature of the hydrothermal reaction can be 150-200 ℃ and the time can be 8-24h.
In the step (3), the calcination temperature may be 450-550 ℃ and the time may be 4-6 hours.
The invention also provides application of the sulfur-resistant ammonia selective catalytic oxidation catalyst in ammonia selective catalytic oxidation.
The sulfur-resistant ammonia selective catalytic oxidation catalyst can be used for ammonia selective catalytic reduction denitration engineering back-end selective catalytic oxidation escaped ammonia.
As a general inventive concept, the invention also provides an ammonia selective catalytic oxidation method, which adopts the sulfur-tolerant ammonia selective catalytic oxidation catalyst to selectively catalyze and oxidize ammonia.
The temperature of the sulfur-tolerant ammonia selective catalytic oxidation catalyst for selectively catalyzing and oxidizing ammonia can be 200-450 ℃.
In the ammonia selective catalytic oxidation method, the reaction system can contain sulfur dioxide.
Compared with the prior art, the invention has the beneficial effects that:
1) The catalyst with the core-shell structure prepared by the invention can realize the escape of NH in a wide temperature window 3 Can effectively avoid NH 3 Is to raise N of reaction 2 Selectivity.
2) The catalyst prepared by the invention has certain sulfur resistance in both the inner core and the outer shell structure, improves the sulfur resistance stability of the catalyst, and can meet the complex working condition under the actual condition.
3) The invention adopts transition metal and rare earth metal as precursors to realize SO on the catalyst 2 NH under stress 3 The cost of removing pollutants is reduced.
Detailed Description
The invention will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention.
Example 1
And (3) preparing a catalyst:
(1) Preparing chromium-cerium composite metal oxide by a precipitation method, respectively weighing precursors of two metal elements of Cr and Ce with different masses, controlling the element molar ratio of Cr to Ce to be 1:10, mixing the two metal elements with 100mL of deionized water, stirring the mixture on a rotor stirrer until the mixture is uniformly dispersed, dropwise adding concentrated ammonia water to adjust the pH of the mixed solution to 10, and then washing, filtering and drying the precipitate, and calcining the precipitate at 500 ℃ for 5 hours to obtain the composite metal oxide catalyst core. The addition amounts of the components are as follows: cr salt Cr (NO) 3 ) 3 ·9H 2 O is added with 0.01mol of Ce salt Ce (NO) 3 ) 3 ·6H 2 O was added in an amount of 0.1mol.
(2) Respectively weighing different mass and equimolar ratiosH of (2) 3 PO 4 And Ce (NO) 3 ) 3 ·6H 2 O is prepared into a mixed solution, the pH of the mixed solution is regulated to 10 by dropwise adding concentrated ammonia water, and the mixed solution is kept fully stirred to form uniform gel in the preparation process. Then adding the chromium-cerium composite metal oxide core obtained in the step (1), fully stirring, drying, calcining at 400 ℃ to obtain the ceramic composite metal oxide core loaded with a small amount of CePO 4 A seed chromium cerium metal oxide core. Wherein, H in the mixed solution is controlled 3 PO 4 And Ce (NO) 3 ) 3 ·6H 2 The addition amount of O leads to a small amount of CePO on the obtained load 4 Seed (CePO) in the chromium cerium metal oxide core of the seed 4 Calculated) is 5% by mass.
(3) Cerium nitrate solution with the same concentration is dripped into the pyrophosphoric acid solution, so that the element molar ratio of Ce to P is ensured to be 1:1. Concentrated ammonia was added dropwise until the mixture was clear. Then adding the small amount of CePO loaded obtained in the step (2) 4 The seed chromium cerium metal oxide core and urea are added to form a slurry. Wherein 2mol of urea is added per mol of cerium nitrate. Then the mixture is fully stirred for 1h, the hydrothermal reaction is continued for 12h at 180 ℃, the obtained sample is washed, dried in vacuum and calcined for 5h at 500 ℃ to obtain Cr-CeO x @CePO 4 A catalyst. Wherein, the Ce element of the core and the CePO of the shell in the integral core-shell catalyst 4 The molar ratio of (2) is 1:2.
Example 2
The difference from example 1 is only the Ce element of the core and the CePO of the shell in the monolithic core-shell catalyst 4 The molar ratio of (2) was 1:1, the remainder being the same.
Example 3
The difference from example 1 is only the Ce element of the core and the CePO of the shell in the monolithic core-shell catalyst 4 The molar ratio of (2) to (1) is the same as the rest.
Example 4
The difference from example 1 is that the amount of Ce salt is not changed in the step (1), the amount of Cr salt is increased, the molar ratio of Cr to Ce is controlled to be 1:5, and the rest is the same.
Example 5
The difference from example 2 is that the amount of Ce salt is not changed in the step (1), the amount of Cr salt is increased, the molar ratio of Cr to Ce is controlled to be 1:5, and the rest is the same.
Example 6
The difference from example 3 is that the amount of Ce salt is not changed in the step (1), the amount of Cr salt is increased, the molar ratio of Cr to Ce is controlled to be 1:5, and the rest is the same.
Comparative example 1
Using the preparation method of example 1, only the catalyst core obtained in step (1) was obtained.
Comparative example 2
The preparation method of example 2 was used, wherein the metal Cr was not added in step (1), and the catalyst was obtained in the same manner as in the other steps. Wherein, ceO of the core in the integral core-shell catalyst 2 CePO with shell 4 The molar ratio of (2) is 1:1.
Comparative example 3
The preparation method of example 5 is adopted, wherein the calcining temperature in the step (1) and the step (3) is raised to 650 ℃, and the catalyst is obtained in the same steps.
Comparative example 4
The preparation method of the example 2 is adopted, wherein the dosage of Ce salt is not changed, the dosage of Cr salt is reduced, the element molar ratio of Cr to Ce is controlled to be 1:20, and the rest is the same.
Comparative example 5
The preparation method of example 2 is adopted, wherein the dosage of Ce salt is not changed, the dosage of Cr salt is increased, the molar ratio of elements of Cr to Ce is controlled to be 1:1, and the rest elements are the same.
Application example 1
NH-treatment of the catalysts prepared in examples 1 to 6 and comparative examples 1 to 2 3 To explore the optimum component proportions. The method comprises the following steps:
the activity experiment is carried out on a fixed bed reactor, the catalyst loading is 1.0mL, and the granularity is 40-60 meshes. The initial gas volume concentration is: [ NH ] 3 ]＝50ppm，[O 2 ]＝5vol％，[H 2 O]＝5vol％，N 2 GHSV (gas space velocity) =100000 mL.g as carrier gas -1 ·h -1 . The test reaction temperature is specifically 200 ℃ and 250 DEG CNH at 300 ℃, 350 ℃, 400 ℃, 450 ℃ for 1 hour 3 The conversion test data are detailed in table 1. In addition, NH 3 Should ideally be selectively oxidized to N 2 And H 2 O, thus N 2 Selectivity is also an important evaluation factor for catalyst performance. N in the activity experiment was further examined in this experiment 2 The selectivity and data are detailed in Table 2.
As a result, NH was used 3 Conversion, N 2 Expressed selectively, the calculation method is as follows:
the test data are detailed in tables 1 and 2.
TABLE 1 catalyst vs NH 3 Catalytic oxidation efficiency/%
TABLE 2 catalyst catalyzed NH 3 Oxidized N 2 Selectivity/%
As is clear from the results of tables 1 and 2, the core-shell catalyst core according to the present invention was NH-verified 3 Has strong dehydrogenation and oxidation capability, and the shell CePO 4 Strengthening NH 3 Adsorption, participation in internal SCR process, regulation of excessive oxidation, promotion of NH 3 N of SCO procedure 2 Selectivity.
The preferred catalyst in the present invention is example 5, having a broad temperature window, high activity, N 2 Good selectivity and the like.
According to comparative examples1, the strong oxidizing nature of the catalyst core results in NH 3 Non-selective catalytic oxidation of N 2 The selectivity is very poor. Comparison of example 3 with comparative example 1 shows that the coating of cerium phosphate has little effect on the ammoxidation activity of the catalyst at low temperature (250 ℃), but can significantly improve nitrogen selectivity. Comparison of example 5 with comparative example 3 shows that too high a calcination temperature severely damages the catalyst structure affecting catalytic performance. The catalytic performance of comparative example 2, comparative example 4 and comparative example 5 demonstrates that the Cr species participates in NH as the predominant active site 3 SCO oxidation process, but Cr/Ce ratio affects catalytic performance. Greatly reducing the Cr/Ce ratio of the chromium-cerium composite oxide can lead to the reduction of the oxidation performance of the catalyst, thereby leading to the NH of the catalyst 3 -the SCO activity temperature window is substantially retarded; while when the Cr content in the chromium-cerium composite oxide is too high, although NH 3 Conversion is relatively higher, but N 2 Too low a selectivity affects its practical application.
Application example 2
Catalytic oxidation of NH by a catalyst 3 Stability test of (c) in the test equipment.
The following experiments were carried out on a fixed bed reactor with a catalyst loading of 1.0mL and a particle size of 40-60 mesh. The initial gas volume concentration is: [ NH ] 3 ]＝50ppm，[O 2 ]＝5vol％，[H 2 O]＝5vol％，[SO 2 ]＝300ppm，N 2 GHSV (gas space velocity) =100000 mL.g as carrier gas -1 ·h -1 . The test reaction temperature was specifically 350 ℃, and the test data are shown in Table 3.
TABLE 3 NH under catalyst sulfur conditions 3 Is tested at 350 ℃ C.)
As can be seen from Table 3, the catalysts of the examples of the present invention SO in the flue gas 2 Stable realization of NH under the influence of components 3 Oxidation, NH 3 The conversion rate is hardly affected, and the catalyst provided by the invention has good sulfur resistance and can stably operate for a long time.
A preferred catalyst in the present invention is example 5, at 300ppm SO 2 Can maintain more than 95 percent of NH under the flue gas atmosphere 3 The conversion rate has a certain potential for industrial application.
According to comparative example 1, the catalyst core itself has a strong oxidizing ability but is resistant to SO 2 Poor stability, comparison with example 3 further illustrates CePO 4 Is a protective function of the above. Comparison of example 5 with comparative example 3 shows that too high a calcination temperature affects Cr, ce interactions and CePO in the core by destroying the core, shell structure 4 Thereby resulting in SO resistance 2 Stability decreases. Comparison of the catalytic performances of comparative example 2, comparative example 4 and comparative example 5 reveals that both the Cr species content versus NH 3 The influence of SCO activity further proves the influence of the molar ratio of Cr/Ce in the inner core on the interface effect, steric hindrance effect, dispersity of active species, strong intermetallic interaction and the like of the catalyst, so that the overall ammoxidation activity, nitrogen selectivity and sulfur resistance of the catalyst are influenced.
Further, it will be understood that various changes and modifications may be made by those skilled in the art after reading the foregoing description of the invention, and such equivalents are intended to fall within the scope of the claims appended hereto.
Claims (10)
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