CN104888845A - Platinum/cerium aluminum-molecular sieve catalyst for catalytic oxidation of ammonia gas and preparation method thereof - Google Patents
Platinum/cerium aluminum-molecular sieve catalyst for catalytic oxidation of ammonia gas and preparation method thereof Download PDFInfo
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- CN104888845A CN104888845A CN201510306885.2A CN201510306885A CN104888845A CN 104888845 A CN104888845 A CN 104888845A CN 201510306885 A CN201510306885 A CN 201510306885A CN 104888845 A CN104888845 A CN 104888845A
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- cerium
- platinum
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- molecular sieve
- aluminium
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 title claims abstract description 201
- 239000003054 catalyst Substances 0.000 title claims abstract description 184
- 229910052697 platinum Inorganic materials 0.000 title claims abstract description 98
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 84
- 239000002808 molecular sieve Substances 0.000 title claims abstract description 55
- 229910052684 Cerium Inorganic materials 0.000 title claims abstract description 45
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 title claims abstract description 44
- 238000002360 preparation method Methods 0.000 title claims abstract description 38
- 230000003197 catalytic effect Effects 0.000 title claims abstract description 33
- 230000003647 oxidation Effects 0.000 title claims abstract description 19
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 19
- 239000002131 composite material Substances 0.000 claims abstract description 64
- WLLURKMCNUGIRG-UHFFFAOYSA-N alumane;cerium Chemical compound [AlH3].[Ce] WLLURKMCNUGIRG-UHFFFAOYSA-N 0.000 claims abstract description 63
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 49
- 229910052878 cordierite Inorganic materials 0.000 claims abstract description 41
- 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 claims abstract description 41
- 239000000919 ceramic Substances 0.000 claims abstract description 40
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical class [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims abstract description 28
- PLDDOISOJJCEMH-UHFFFAOYSA-N neodymium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Nd+3].[Nd+3] PLDDOISOJJCEMH-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910000420 cerium oxide Inorganic materials 0.000 claims abstract description 6
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims abstract description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 81
- 229910052779 Neodymium Inorganic materials 0.000 claims description 49
- 229910021529 ammonia Inorganic materials 0.000 claims description 41
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims description 41
- 239000000843 powder Substances 0.000 claims description 38
- 239000002002 slurry Substances 0.000 claims description 25
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- 238000003756 stirring Methods 0.000 claims description 13
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 claims description 9
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- NWAHZABTSDUXMJ-UHFFFAOYSA-N platinum(2+);dinitrate Chemical compound [Pt+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O NWAHZABTSDUXMJ-UHFFFAOYSA-N 0.000 claims description 8
- 238000000227 grinding Methods 0.000 claims description 6
- 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 5
- 238000001704 evaporation Methods 0.000 claims description 5
- CFYGEIAZMVFFDE-UHFFFAOYSA-N neodymium(3+);trinitrate Chemical compound [Nd+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O CFYGEIAZMVFFDE-UHFFFAOYSA-N 0.000 claims description 5
- 239000002245 particle Substances 0.000 claims description 5
- 150000003057 platinum Chemical class 0.000 claims description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 2
- GBHHXUXUWINXQG-UHFFFAOYSA-H [Pt](F)(F)(F)(F)(F)F.[Xe] Chemical compound [Pt](F)(F)(F)(F)(F)F.[Xe] GBHHXUXUWINXQG-UHFFFAOYSA-H 0.000 claims description 2
- ZDYCQQFBTFDFOK-UHFFFAOYSA-N acetic acid;platinum Chemical compound [Pt].CC(O)=O ZDYCQQFBTFDFOK-UHFFFAOYSA-N 0.000 claims description 2
- 239000002253 acid Substances 0.000 claims description 2
- 238000001035 drying Methods 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 5
- 239000003344 environmental pollutant Substances 0.000 abstract description 4
- 231100000719 pollutant Toxicity 0.000 abstract description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 abstract 1
- 230000000452 restraining effect Effects 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 28
- 238000006243 chemical reaction Methods 0.000 description 22
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 13
- 229910052782 aluminium Inorganic materials 0.000 description 13
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 13
- 238000000034 method Methods 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 9
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 8
- 239000011159 matrix material Substances 0.000 description 8
- 229910052757 nitrogen Inorganic materials 0.000 description 7
- -1 cerium aluminium compound Chemical class 0.000 description 6
- 238000001914 filtration Methods 0.000 description 6
- 238000009616 inductively coupled plasma Methods 0.000 description 6
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 6
- 238000001556 precipitation Methods 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 description 5
- 238000000498 ball milling Methods 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000004202 carbamide Substances 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 229910052763 palladium Inorganic materials 0.000 description 4
- 150000001206 Neodymium Chemical class 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000003801 milling Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000010718 Oxidation Activity Effects 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000007717 exclusion Effects 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 229910010272 inorganic material Inorganic materials 0.000 description 2
- 239000011147 inorganic material Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 210000002345 respiratory system Anatomy 0.000 description 2
- 229910052703 rhodium Inorganic materials 0.000 description 2
- 239000010948 rhodium Substances 0.000 description 2
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 208000024891 symptom Diseases 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000001988 toxicity Effects 0.000 description 2
- 231100000419 toxicity Toxicity 0.000 description 2
- 206010013952 Dysphonia Diseases 0.000 description 1
- 206010014561 Emphysema Diseases 0.000 description 1
- 208000010473 Hoarseness Diseases 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 239000008346 aqueous phase Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000012876 carrier material Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 201000010099 disease Diseases 0.000 description 1
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 1
- 208000002173 dizziness Diseases 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- DNJIEGIFACGWOD-UHFFFAOYSA-N ethanethiol Chemical compound CCS DNJIEGIFACGWOD-UHFFFAOYSA-N 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000003205 fragrance Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 239000001272 nitrous oxide Substances 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- MUMZUERVLWJKNR-UHFFFAOYSA-N oxoplatinum Chemical compound [Pt]=O MUMZUERVLWJKNR-UHFFFAOYSA-N 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229910003446 platinum oxide Inorganic materials 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000000638 stimulation Effects 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)
Abstract
The invention provides a platinum/cerium aluminum-molecular sieve catalyst for catalytic oxidation of an ammonia gas. Cordierite ceramic is utilized as a carrier for the platinum/cerium aluminum-molecular sieve catalyst, the surface of the carrier is coated with a catalyst layer, and the catalytic active site of the catalyst layer consists of a noble metal platinum, a cerium-aluminum composite oxide and a neodymium-modified molecular sieve; the mass ratio of the cerium-aluminum composite oxide to the neodymium-modified molecular sieve to the noble metal platinum is (20-80):(20-80):(0.01-0.1), and the mass ratio of cerium oxide and aluminum oxide in the cerium-aluminum composite oxide is (1-3):(1-5); the mass ratio of neodymium oxide and a molecular sieve in the neodymium-modified molecular sieve is (1-10):(90-100). The platinum/cerium aluminum-molecular sieve catalyst is also capable of achieving wide low-temperature activity window, good catalytic activity and high selectivity even at a high space velocity (SV), and is capable of effectively restraining generation of secondary pollutants of N2O, NO and NO2. The invention further provides a preparation method of the platinum/cerium aluminum-molecular sieve catalyst.
Description
Technical field
The invention belongs to catalyst technical field, relate to a kind of Catalysts and its preparation method for catalytic oxidation ammonia, particularly a kind of platinum for catalytic oxidation ammonia/cerium aluminium-molecular sieve catalyst and preparation method thereof.
Background technology
Diesel engine obtains applying more and more widely with its low oil consumption, high-power feature, but the HTHP in cylinder of diesel engine can produce a large amount of nitrogen oxide, brings serious environmental problem.At present, China is the nitrogen oxide adopting SCR (SCR) to process diesel engine generation substantially, and wherein applying maximum reducing agents is aqueous solution of urea, and hydrolysis of urea generates ammonia.In order to reach stricter NOx emission standard, the following two kinds of methods of main employing in the world: (1) sprays more urea liquid, and the shortcoming of this method is to cause unnecessary ammonia leakage; (2) use the catalyst of absorbing ammonia, the shortcoming of this method be when diesel vehicle carry out urgency accelerate time, the exhaust temperature of discharge can be made sharply to raise, and the ammonia of desorption exacerbates the leakage of ammonia, causes new secondary environmental pollution.
Ammonia is a kind of colourless and have the gas of intense stimulus stench, and can dissolve each other with any ratio and aqueous phase and separate and highly volatile.It has stimulation and corrosiveness to human respiratory tract, reduces human body to the resistance of disease.People sucks a large amount of ammonias in a short time, may occur shedding tears, pharyngalgia, hoarseness, dizziness, the symptom such as nauseating, uncomfortable in chest, weak, severe patient there will be pulmonary emphysema, also respiratory tract symptom can occur simultaneously.Ammonia is listed in odorant pollutant discharge by China, becomes field of Environment Protection item controlled, must the strict discharge controlling ammonia.
At present, the method removing ammonia mainly contains chemical absorption method, physisorphtion, catalystic pyrolysis, biofiltration process and catalytic oxidation.Although chemical absorption method and physisorphtion simple to operate, need regularly replace adsorbent, easily produce secondary pollution.Catalystic pyrolysis needs could decompose at relatively high temperatures, and permanent plant investment is larger.Biofiltration process, though do not produce secondary pollution, is difficult to realize industrialization because ammonia removal efficiency is low.
Catalytic oxidation is a kind of ideal Treatment process, is under the atmosphere of catalyst and oxygen, ammonia Catalytic Oxygen is changed into free of contamination nitrogen and water.In practical application, need catalyst cryogenic property good, ammonia just can be made farthest to be converted into nitrogen and water, reduce the generation of nitrogen oxide accessory substance.Conventional catalyst system mainly contains following a few class: metal-oxide catalyst, Ion exchange-Size exclusion type catalyst and noble metal type catalyst.Get well and low price although metal-oxide catalyst is selective, its low temperature active is lower, and the conversion ratio 250 DEG C time is only 60%.Although Ion exchange-Size exclusion type catalyst low temperature window is wide, easily produces nitrous oxide at 250 ~ 300 DEG C, cause secondary pollution.
Noble metal type catalyst is that have higher catalytic oxidation activity at 250 ~ 450 DEG C, good low temperature active window, is oxidized the ammonia of leakage by platinum, palladium even load in the inorganic material such as aluminium oxide, and its reaction equation is as shown in the formula shown in (1).
4NH
3+3O
2→2N
2+6H
2O (1)
But current existing noble metal type catalyst is take aluminium oxide as carrier material mostly, noble metal distribution on alumina, causes noble metal catalyst while carrying out ammonia oxidation, easily causes N
2o, NO, NO
2pollutant produces, and therefore seriously limits the application in practice of noble metal type catalyst, specifically reacts as shown in the formula shown in (2) ~ (3).
4NH
3+5O
2→4NO+6H
2O (2)
4NH
3+7O
2→4NO
2+6H
2O (3)
2NH
3+2O
2→N
2O+3H
2O (4)
CN 103476495A discloses a kind of ammoxidation catalyst and employs its waste gas purification apparatus and using method, adopts double-deck coating, and the inorganic material of lower floor's noble metal that has been load, upper strata is molecular sieve catalyst, although at 250 ~ 400 DEG C to NH
3there is higher catalytic oxidation activity, but also create higher concentration N simultaneously
2o and NO
x.
Therefore, at use aqueous solution of urea as in SCR (SCR) system of diesel engine reducing agent, develop low-temperature catalytic oxidation ammonia performance good, and effectively can suppress N
2o, NO, NO
2the noble metal type catalyst produced Deng pollutant is very urgent and necessary.
Summary of the invention
The object of the invention is to overcome above-mentioned deficiency existing in prior art, a kind of platinum for catalytic oxidation ammonia/cerium aluminium-molecular sieve catalyst and preparation method thereof is provided.This platinum/cerium aluminium-molecular sieve catalyst take cordierite ceramic as carrier, with noble metal platinum, cerium-aluminium composite oxide (Ce-Al composite oxides) and neodymium modified molecular screen (Nd/ZSM-5) for catalytic active center, noble metal platinum is distributed on cerium-aluminium composite oxide and neodymium modified molecular screen, and regulate its weight, even if it is wide to make described platinum/cerium aluminium-molecular sieve catalyst also can realize low temperature active window under high air speed (SV), catalytic activity is good, selective height, effectively can suppress N
2o, NO, NO
2the generation of secondary pollution.
In order to realize foregoing invention object, the invention provides following technical scheme:
Platinum for catalytic oxidation ammonia of the present invention/cerium aluminium-molecular sieve catalyst, take cordierite ceramic as carrier, carrier surface is coated with catalyst layer, it is characterized in that: the catalytic active center of described catalyst layer is made up of noble metal platinum, cerium-aluminium composite oxide and neodymium modified molecular screen; The weight ratio of described cerium-aluminium composite oxide, neodymium modified molecular screen and noble metal platinum (in Pt) is 20 ~ 80:20 ~ 80:0.01 ~ 0.1; In described cerium-aluminium composite oxide, the weight ratio of cerium oxide and aluminium oxide is 1 ~ 3:1 ~ 5; In described neodymium modified molecular screen, the weight ratio of neodymia and molecular sieve is 1 ~ 10:90 ~ 100.
Platinum/cerium aluminium-the molecular sieve catalyst of catalytic oxidation ammonia of the present invention, noble metal platinum exists with the form of simple substance platinum and platinum oxide.In prior art, usually using precious metal palladium, rhodium or gold as catalytic active center.Wherein, precious metal palladium is not strong to the oxidation susceptibility of ammonia, can not be nitrogen by ammonia complete oxidation, causes generating a large amount of oxynitrides, causes secondary pollution; And the sulfur resistance of palladium is very poor, easily causes sulfur poisoning.Noble Metal Rhodium does not have oxidation susceptibility substantially to ammonia, and its price comparison is expensive.Although gold has good oxidation susceptibility and selective at low temperatures, ageing resistace is poor.Applicant finds through test of many times, is distributed in by noble metal platinum on cerium-aluminium composite oxide and neodymium modified molecular screen, not only can significantly improve the low-temperature catalytic activity of platinum/cerium aluminium-molecular sieve catalyst, and selective height, and ammonia is being oxidized to N
2while effectively inhibit N
2o, NO, NO
2the generation of secondary pollution.Its main mechanism provides active sites for noble metal platinum, ammonia is oxidized to oxynitrides or nitrogen, and oxynitrides is adsorbed on above molecular sieve, provides secondary response, is converted into nitrogen, inhibits N
2o, NO, NO
2the generation of secondary pollution.
In catalyst layer, cerium-aluminium composite oxide, as the carrier of noble metal platinum, makes ammonia react rapidly; The effect of neodymium modified molecular screen, simultaneously can the oxynitrides of adsorption reaction not only as the carrier of noble metal, makes oxynitrides react generation nitrogen further, suppresses N
2o, NO, NO
2the generation of secondary pollution.In the prior art, usually noble metal is directly distributed on the molecular sieve of non-modified, can N be caused
2o, NO, NO
2the generation of secondary pollution; The present invention adopts neodymium to carry out modification to molecular sieve, efficiently avoid this defect.
Preferably, described catalyst carrier surface coated weight according to the dry weight of catalyst layer be 120 ~ 180g/L calculate.Namely catalyst pulp is after carrier surface drying, roasting, and the coated weight on its surface should reach often liter of carrier cordierite ceramic surface coated catalysts 120 ~ 180g.When the dry weight of catalyst layer is less than 120g/L, ammonia oxidation not exclusively, does not reach high conversion ratio; When the dry weight of catalyst layer is greater than 180g/L, the back pressure of diesel engine can be increased, bad impact is caused on the fuel economy of diesel engine.Further preferably, the dry weight of described catalyst layer is 150 ~ 170g/L.Preferably, the dry weight of described catalyst layer is 155 ~ 165g/L to the best.
Preferably, described molecular sieve is ZSM-5 molecular sieve.ZSM-5 molecular sieve basic structural unit is made up of eight five-membered rings, and its crystal structure belongs to orthorhombic system, is beneficial to the absorption of oxynitrides.
Applicant finds through many experiments, and in catalyst layer, the weight ratio of cerium-aluminium composite oxide, neodymium modified molecular screen and noble metal platinum affects platinum/cerium aluminium-molecular sieve catalyst catalytic activity and optionally one of key factor.When the weight ratio of cerium-aluminium composite oxide, neodymium modified molecular screen and noble metal platinum is in the scope of 20 ~ 80:20 ~ 80:0.01 ~ 0.1, platinum/cerium aluminium-molecular sieve catalyst is to ammonia catalytic activity and selective all better.Further preferably, the weight ratio of described cerium-aluminium composite oxide, neodymium modified molecular screen and noble metal platinum is 40 ~ 70:30 ~ 60:0.04 ~ 0.06.Preferably, the weight ratio of described cerium-aluminium composite oxide, neodymium modified molecular screen and noble metal platinum is 50:50:0.0441 to the best.By above preferably, the catalytic activity of platinum/cerium aluminium-molecular sieve catalyst can be made and selectively reach best, while raising catalytic activity, farthest suppressing N
2o, NO, NO
2the generation of secondary pollution.
The preparation method of platinum of the present invention/cerium aluminium-molecular sieve catalyst, is characterized in that, comprise the following steps:
(1) preparation of cerium-aluminium composite oxide
Get the aluminum nitrate solution of 0.1 ~ 0.4g/ml and the cerous nitrate solution of 0.1 ~ 0.4g/ml, mix, join in the citric acid solution of 0.1 ~ 0.3g/ml, stir 1 ~ 2h, evaporating water, dry 20 ~ 24h at 100 ~ 120 DEG C, then roasting, obtains cerium-aluminium composite oxide;
(2) preparation of neodymium modified molecular screen
The neodymium nitrate solution of 0.1 ~ 0.4g/ml is joined in molecular sieve powder, dry 8 ~ 10h at 100 ~ 120 DEG C; Then roasting, obtains neodymium modified molecular screen powder;
(3) preparation of slurry
Cerium-aluminium composite oxide, neodymium modified molecular screen powder, citric acid and platinum salt are joined in deionized water, fully stirs, obtain catalyst pulp;
(4) ground slurry: grind catalyst pulp, until catalyst pulp particle is 2 ~ 5 μm;
(5) slurry is applied: take cordierite ceramic as carrier, be immersed into by cordierite ceramic in the catalyst pulp after grinding, submergence 3 ~ 5min; Then cordierite ceramic is taken out from catalyst pulp, blow remainder catalyst slurry in duct off, obtain the cordierite ceramic that surface is coated with catalyst pulp;
(6) dry and roasting: the cordierite ceramic dry 4 ~ 6h, the then roasting at 100 ~ 120 DEG C that surface are coated with catalyst pulp, be finally cooled to room temperature, obtain platinum/cerium aluminium-molecular sieve catalyst; Wherein the coated weight of catalyst pulp after roasting is 120 ~ 180g/L.
Preparation method's cost of the present invention is low, and toxicity is little, simple to operate, easily controls, and obtained platinum/cerium aluminium-molecular sieve catalyst low-temperature catalytic activity is good, ammonia can be transformed completely at 225 DEG C, and selective height, effectively can suppress N simultaneously
2o, NO, NO
2the generation of secondary pollution.
Preferably, in described step (1), the volume ratio of aluminum nitrate solution and citric acid solution is 1:1 ~ 4.In the preparation process of cerium aluminium compound, the effect of citric acid enters in the duct of cerium-aluminium composite oxide crystal, increases its specific area.When the volume ratio of aluminum nitrate solution and citric acid solution is less than 1:1, the cerium-aluminium composite oxide of preparation has less specific area, is unfavorable for the reaction of ammonia.When the volume ratio of aluminum nitrate solution and citric acid solution is greater than 1:4, excessive citric acid can enter in cerium-aluminium composite oxide crystal, because heat release is large during roasting, can cause the tunnel collapse of a part, cause specific area to reduce equally, be unfavorable for the reaction of ammonia.
Preferably, the roasting in described step (1) is roasting 3 ~ 4h at 550 ~ 650 DEG C.Be less than 3h upon firing, citric acid incomplete combustion can be caused, simultaneously cerium-aluminium composite oxide poor stability.Be greater than 4h upon firing, under causing cerium-aluminium composite oxide to be in the condition of high temperature for a long time, cause cerium-aluminium composite oxide to sinter, reduce its specific area.Preferably, the roasting time in described step (1) is 3h to the best.
Preferably, the roasting in described step (2) is roasting 3 ~ 4h at 550 ~ 650 DEG C.Preferably, the roasting time in described step (2) is 3.5h to the best.
Preferably, the platinum salt in described step (3) is one or more in platinum nitrate, chloroplatinic acid, acetic acid platinum, cyaniding platinum, platinic hydroxide, xenon platinum hexafluoride and ammonium chloroplatinate.
Preferably, in described step (3), the weight ratio of citric acid and cerium-aluminium composite oxide is 1:3 ~ 9.In the preparation process of catalyst pulp, the effect of citric acid is the pH value regulating slurry, changes slurry fluidity.When the weight ratio of citric acid and cerium-aluminium composite oxide is 1:3 ~ 9, can be made by the mode of dipping that slurry is better must be coated in cordierite ceramic surface.Citric acid, in roasting process, can generate carbon dioxide and water with oxygen reaction, can not remain in catalyst coat.Preferably, in described step (3), the weight ratio of citric acid and cerium-aluminium composite oxide is 1:5 ~ 9.Preferably, in described step (3), the weight ratio of citric acid and cerium-aluminium composite oxide is 1:5 to the best.
Preferably, the roasting time in described step (6) is 2 ~ 3h.The platinum obtained/cerium aluminium-molecular sieve catalyst catalytic activity is good, selective height.Preferably, described roasting time is 2.5h to the best.
Beneficial effect of the present invention is:
(1) platinum of the present invention/cerium aluminium-molecular sieve catalyst take cordierite ceramic as carrier, with noble metal platinum, cerium-aluminium composite oxide and neodymium modified molecular screen are catalytic active center, noble metal platinum is distributed on cerium-aluminium composite oxide and neodymium modified molecular screen, and by regulating catalyst layer at the coated weight of carrier surface, and noble metal platinum in catalyst layer, the weight of cerium-aluminium composite oxide and neodymium modified molecular screen, even if it is wide to make described platinum/cerium aluminium-molecular sieve catalyst also can realize low temperature active window under high air speed (SV), catalytic activity is good, ammonia can be transformed completely at 225 DEG C, selective height simultaneously, effectively can suppress N
2o, NO, NO
2the generation of secondary pollution.
(2) preparation method's cost of platinum of the present invention/cerium aluminium-molecular sieve catalyst is low, and toxicity is little, simple to operate, easily controls.
Accompanying drawing explanation
Fig. 1 is the NH of various ammonia VPO catalysts
3conversion ratio chart.
The N of the various ammonia VPO catalysts of Fig. 2
2o discharges concentration chart.
Fig. 3 is the NO of various ammonia VPO catalysts
xdischarge concentration chart.
Detailed description of the invention
Below in conjunction with test example and detailed description of the invention, the present invention is described in further detail.But this should be interpreted as that the scope of the above-mentioned theme of the present invention is only limitted to following embodiment, all technology realized based on content of the present invention all belong to scope of the present invention.
In embodiment of the present invention and comparative example, the cordierite ceramic adopted is diameter 25.4mm, the cylindrical cordierite pottery of high 25.4mm.
Embodiment 1
(1) cerium-aluminium composite oxide preparation
Get the aluminum nitrate solution 261.0ml of 0.4g/ml, the cerous nitrate solution 236.7ml of 0.2g/ml, and the citric acid solution 758.7ml of 0.2g/ml mixes; Stir 2h, re-use Rotary Evaporators evaporating water, dry 20h at 120 DEG C, finally put into Muffle furnace, from room temperature to 650 DEG C, and at 650 DEG C roasting 3h, obtain cerium-aluminium composite oxide, in this cerium-aluminium composite oxide, the mass ratio of aluminium oxide and cerium oxide is 1:1.
(2) neodymium modified molecular screen preparation
The neodymium nitrate solution 29.5ml getting 0.2g/ml joins in 47g ZSM-5 molecular sieve powder, then puts into baking oven, dry 10h at 100 DEG C; Then put into Muffle furnace, at 600 DEG C of roasting 3.5h, obtain neodymium modified molecular screen; In this neodymium modified molecular screen, neodymium element exists with the form of neodymia, and the mass ratio of neodymia and ZSM-5 molecular sieve is 6:94.
(3) preparation of catalyst pulp
Get 50g cerium-aluminium composite oxide, 50g neodymium modified molecular screen powder, 10g citric acid, 1.588g platinum nitrate solution (metal platinum 2.78wt%) join in 112.3ml deionized water, stir, obtain catalyst pulp.
(4) ball milling catalyst pulp: ground through planetary ball mill by catalyst pulp, makes pulp particle be 2 ~ 5 μm, obtains catalyst pulp; Wherein the rotating speed of planetary ball mill is 380 ~ 400 revs/min, and milling time is 1 ~ 1.5h.
(5) slurry is applied: be immersed into by cordierite ceramic matrix in the catalyst pulp after grinding, submergence 3 ~ 5min; Taken out from slurry by cordierite ceramic matrix, blow leftover slurry in duct off, obtain the cordierite ceramic being coated with catalyst pulp, wherein the weightening finish of cordierite ceramic surface is 4.42g, and in final catalyst unit volume, Pt content is 2g/ft
3.
(6) dry and roasting: cordierite ceramic surface being coated with catalyst pulp, at 100 DEG C of dry 6h, then puts into Muffle furnace, roasting 2.5h at 600 DEG C, obtains platinum/cerium aluminum molecular screen catalyst, the Pt-1/CA-ZSM namely in accompanying drawing; Wherein the coated weight of catalyst pulp after roasting reaches 155 ~ 165g/L.
Get catalyst pulp 20g prepared by above-mentioned steps (4) and put into Muffle furnace, at 550 ~ 650 DEG C, roasting 1 ~ 2h, is finally cooled to room temperature, weighs, and it is 9.348g that result obtains powder quality, and namely the solid content of catalyst pulp is 46.74%.Take powder 10g more subsequently, after the steps such as dissolving, precipitation, filtration, dissolving, adopt inductively coupled plasma to carry out the mensuration of noble metal platinum content, it is 0.0441 (platinum that result obtains the content of noble metal platinum in powder, g)/100 (powder, g).
From the above, in platinum of the present invention/cerium aluminum molecular screen catalyst, the weight ratio of cerium-aluminium composite oxide, neodymium modified molecular sieve catalyst and noble metal platinum is 50:50:0.0441.
Embodiment 2
(1) cerium-aluminium composite oxide preparation
Get the aluminum nitrate solution 835.3ml of 0.2g/ml, the cerous nitrate solution 252.2ml of 0.3g/ml, and the citric acid solution 1213.6ml of 0.2g/ml mixes; Stir 2h, re-use Rotary Evaporators evaporating water, dry 20h at 120 DEG C, finally put into Muffle furnace, from room temperature to 650 DEG C, and at 650 DEG C roasting 3h, obtain cerium-aluminium composite oxide, in this cerium-aluminium composite oxide, the mass ratio of aluminium oxide and cerium oxide is 4:3.
(2) neodymium modified molecular screen preparation
Get the neodymium nitrate solution 23.6ml of 0.1g/ml, join in 28.8g ZSM-5 molecular sieve powder, then put into baking oven, dry 8h at 120 DEG C; Then put into Muffle furnace, at 650 DEG C of roasting 3h, obtain neodymium modified molecular screen; In this neodymium modified molecular screen, neodymium element exists with the form of neodymia, and the mass ratio of neodymia and ZSM-5 molecular sieve is 4:96.
(3) preparation of catalyst pulp
Get 70g cerium-aluminium composite oxide, 30g neodymium modified molecular screen powder, 10.0g citric acid, 2.054g platinum nitrate solution (metal platinum 2.78wt%) join in 110.8ml deionized water, stir, obtain catalyst pulp.
(4) ball milling catalyst pulp: ground through planetary ball mill by catalyst pulp, makes pulp particle be 2 ~ 5 μm, obtains catalyst pulp; Wherein the rotating speed of planetary ball mill is 380 ~ 400 revs/min, and milling time is 1 ~ 1.5h.
(5) slurry is applied: be immersed into by cordierite ceramic matrix in the catalyst pulp after grinding, submergence 3 ~ 5min; Taken out from slurry by cordierite ceramic matrix, blow leftover slurry in duct off, obtain the cordierite ceramic being coated with catalyst pulp, wherein the weightening finish of cordierite ceramic surface is 3.39g, and in final catalyst unit volume, Pt content is 2g/ft
3.
(6) dry and roasting: cordierite ceramic surface being coated with catalyst pulp, at 120 DEG C of dry 4h, then puts into Muffle furnace, roasting 2h at 650 DEG C, obtains platinum/cerium aluminum molecular screen catalyst, the Pt-2/CA-ZSM namely in accompanying drawing; Wherein the coated weight of catalyst pulp after roasting reaches 120 ~ 130g/L.
Get catalyst pulp 20g prepared by above-mentioned steps (4) and put into Muffle furnace, at 550 ~ 650 DEG C, roasting 1 ~ 2h, is finally cooled to room temperature, weighs, and it is 9.506g that result obtains powder quality, and namely the solid content of catalyst pulp is 47.03%.Take powder 10g more subsequently, after the steps such as dissolving, precipitation, filtration, dissolving, adopt inductively coupled plasma to carry out the mensuration of noble metal platinum content, it is 0.0571 (platinum that result obtains the content of noble metal platinum in powder, g)/100 (powder, g).
From the above, in platinum of the present invention/cerium aluminum molecular screen catalyst, the weight ratio of cerium-aluminium composite oxide, neodymium modified molecular sieve catalyst and noble metal platinum is 70:30:0.0571.
Embodiment 3
(1) cerium-aluminium composite oxide preparation
Get the aluminum nitrate solution 348.0ml of 0.3g/ml, the cerous nitrate solution 71.1ml of 0.4g/ml, and the citric acid solution 664.2ml of 0.2g/ml mixes; Stir 1.5h, re-use Rotary Evaporators evaporating water, dry 24h at 100 DEG C, finally put into Muffle furnace, from room temperature to 550 DEG C, and at 550 DEG C roasting 4h, obtain cerium-aluminium composite oxide, in this cerium-aluminium composite oxide, the mass ratio of aluminium oxide and cerium oxide is 5:3.
(2) neodymium modified molecular screen preparation
Get the neodymium nitrate solution 11.8ml of 0.2g/ml, join in 58.8g ZSM-5 molecular sieve powder, then put into baking oven, dry 8h at 120 DEG C; Then put into Muffle furnace, at 550 DEG C of roasting 4h, obtain neodymium modified molecular screen; In this neodymium modified molecular screen, neodymium element exists with the form of neodymia, and the mass ratio of neodymia and ZSM-5 molecular sieve is 2:98.
(3) preparation of catalyst pulp
Get 40g cerium-aluminium composite oxide, 60g neodymium modified molecular screen powder, 10g citric acid, 1.469g platinum nitrate solution (metal platinum 2.78wt%) join in 115.2ml deionized water, stir, obtain catalyst pulp.
(4) ball milling catalyst pulp: ground through planetary ball mill by catalyst pulp, makes pulp particle be 2 ~ 5 μm, obtains catalyst pulp; Wherein the rotating speed of planetary ball mill is 380 ~ 400 revs/min, and milling time is 1 ~ 1.5h.
(5) slurry is applied: be immersed into by cordierite ceramic matrix in the catalyst pulp after grinding, submergence 3 ~ 5min; Taken out from slurry by cordierite ceramic matrix, blow leftover slurry in duct off, obtain the cordierite ceramic being coated with catalyst pulp, wherein the weightening finish of cordierite ceramic surface is 4.82g, and in final catalyst unit volume, Pt content is 2g/ft
3.
(6) dry and roasting: cordierite ceramic surface being coated with catalyst pulp, at 120 DEG C of dry 4h, then puts into Muffle furnace, roasting 3h at 550 DEG C, obtains platinum/cerium aluminum molecular screen catalyst, the Pt-3/CA-ZSM namely in accompanying drawing; Wherein the coated weight of catalyst pulp after roasting reaches 170 ~ 180g/L.
Get catalyst pulp 20g prepared by above-mentioned steps (4) and put into Muffle furnace, at 550 ~ 650 DEG C, roasting 1 ~ 2h, is finally cooled to room temperature, weighs, and it is 9.23g that result obtains powder quality, and namely the solid content of catalyst pulp is 46.15%.Take powder 10g more subsequently, after the steps such as dissolving, precipitation, filtration, dissolving, adopt inductively coupled plasma to carry out the mensuration of noble metal platinum content, it is 0.0408 (platinum that result obtains the content of noble metal platinum in powder, g)/100 (powder, g).
From the above, in platinum of the present invention/cerium aluminum molecular screen catalyst, the weight ratio of cerium-aluminium composite oxide, neodymium modified molecular sieve catalyst and noble metal platinum is 40:60:0.0408.
Comparative example 1
Step (1) is with embodiment 1.
(2) preparation of catalyst pulp
Get 100g cerium-aluminium composite oxide, 10g citric acid, 1.588g platinum nitrate solution (metal platinum 2.78wt%) join in 107.5ml deionized water, stir, obtain catalyst pulp.
(3) with the step (4) in embodiment 1.
(4) apply slurry: with the step (5) in embodiment 1, the weightening finish of cordierite ceramic surface is 4.31g, and in final catalyst unit volume, Pt content is 2g/ft
3.
(5) dry and roasting: with the step (6) in embodiment 1, obtain ammonia VPO catalysts, the Pt-1/CA-1 namely in accompanying drawing.
Get catalyst pulp 20g prepared by step (4) and put into Muffle furnace, at 550 ~ 650 DEG C, roasting 1 ~ 2h, is finally cooled to room temperature, weighs, and it is 9.569g that result obtains powder quality, and namely the solid content of catalyst pulp is 47.85%.Take powder 10g more subsequently, after the steps such as dissolving, precipitation, filtration, dissolving, adopt ICP to carry out the mensuration of noble metal platinum content, it is 0.0441 platinum that result obtains the content of noble metal platinum in powder, g)/100 (powder, g).
From the above, in platinum of the present invention/cerium aluminum molecular screen catalyst, the weight ratio of cerium-aluminium composite oxide, neodymium modified molecular sieve catalyst and noble metal platinum is 100:0:0.0441.
Comparative example 2
(1) cerium-aluminium composite oxide preparation
With the step (1) in embodiment 1.
(2) preparation of catalyst pulp
Get 100g cerium-aluminium composite oxide, 10g citric acid, 3.113g platinum nitrate solution (metal platinum 2.78wt%) join in 104.6ml deionized water, stir, obtain catalyst pulp.
(3) ball milling catalyst pulp: with the step (4) in embodiment 1.
(4) slurry is applied: be immersed into by cordierite ceramic matrix in the catalyst pulp after grinding, submergence 3 ~ 5min; Taken out from slurry by cordierite ceramic matrix, blow leftover slurry in duct off, obtain the cordierite ceramic being coated with catalyst pulp, wherein the weightening finish of cordierite ceramic surface is 2.18g, and in final catalyst unit volume, Pt content is 2g/ft
3.
(6) dry and roasting: cordierite ceramic surface being coated with catalyst pulp, at 100 DEG C of dry 6h, is then put into Muffle furnace, roasting 2.5h at 600 DEG C, obtained ammonia VPO catalysts, the Pt-1/CA-2 namely in accompanying drawing; Wherein the coated weight of catalyst pulp after roasting reaches 78 ~ 83g/L.
Get catalyst pulp 20g prepared by above-mentioned steps (4) and put into Muffle furnace, at 550 ~ 650 DEG C, roasting 1 ~ 2h, is finally cooled to room temperature, weighs, and it is 9.632g that result obtains powder quality, and namely the solid content of catalyst pulp is 48.16%.Take powder 10g more subsequently, after the steps such as dissolving, precipitation, filtration, dissolving, adopt inductively coupled plasma to carry out the mensuration of noble metal platinum content, it is 0.0865 (platinum that result obtains the content of noble metal platinum in powder, g)/100 (powder, g).
From the above, in platinum of the present invention/cerium aluminum molecular screen catalyst, the weight ratio of cerium-aluminium composite oxide, neodymium modified molecular sieve catalyst and noble metal platinum is 100:0:0.0865.
Comparative example 3
(1) cerium-aluminium composite oxide preparation
With embodiment 1.
(2) preparation of catalyst pulp
Get 50g cerium-aluminium composite oxide, 50g ZSM-5 molecular sieve powder, 10g citric acid, 1.588g platinum nitrate solution join in 113.1ml deionized water, stir, obtain catalyst pulp.
(3) ball milling catalyst pulp: with the step (4) in embodiment 1.
(4) apply slurry: with the step (5) in embodiment 1, wherein the weightening finish of cordierite ceramic surface is 4.35g, and in final catalyst unit volume, Pt content is 2g/ft
3.
(5) dry and roasting: with the step (6) in embodiment 1, obtain ammonia VPO catalysts.Namely the Pt-1/CA-3 in accompanying drawing.
Get catalyst pulp 20g prepared by above-mentioned steps (3) and put into Muffle furnace, at 550 ~ 650 DEG C, roasting 1 ~ 2h, is finally cooled to room temperature, weighs, and it is 9.324g that result obtains powder quality, and namely the solid content of catalyst pulp is 46.62%.Take powder 10g more subsequently, after the steps such as dissolving, precipitation, filtration, dissolving, adopt inductively coupled plasma to carry out the mensuration of noble metal platinum content, it is 0.0441 (platinum that result obtains the content of noble metal platinum in powder, g)/100 (powder, g).
From the above, in platinum of the present invention/cerium aluminum molecular screen catalyst, the weight ratio of cerium-aluminium composite oxide, molecular sieve catalyst and noble metal platinum is 50:50:0.0441.
Experimental example 1
Catalytic performance test is carried out to catalyst prepared by above-described embodiment 1 ~ 3 and comparative example 1 ~ 3.
By the ammonia (NH of 200ppm
3), 10% oxygen (O
2), 7% carbon dioxide (CO
2), 8% steam (H
2o), all the other are nitrogen (N
2) mist pass into model gas experimental rig, reaction velocity is 150000 ~ 160000h
-1under 200 DEG C, 225 DEG C, 250 DEG C, 300 DEG C, 350 DEG C, 400 DEG C, 450 DEG C and 500 DEG C of eight temperature conditions, reach set point of temperature and concentration gases circulation start after have passed through 30 minutes after, measure under the concentration of various gas componant is stable state.Metered catalyst entrance and exit place NH respectively
3, NO
2, NO, N
2the gas concentration of O, utilizes NH
3conversion ratio, NOx discharge concentration, N
2o discharges these 3 indexs of concentration and evaluates catalyst (ASC) performance.
Wherein: NH
3conversion ratio %=(entrance NH
3concentration-outlet NH
3concentration)/(entrance NH
3concentration) × 100
(NOx discharges concentration ppm)=(outlet NO concentration ppm)+(outlet NO
2concentration ppm)
Result is as shown in table 1 ~ 3.
Fig. 1 is that each catalyst is to NH
3conversion ratio chart.Known as shown in Figure 1, the catalyst prepared due to the embodiment of the present invention 1 ~ 3 comprises specific cerium-aluminium composite oxide and neodymium modified molecular screen (Nd/ZSM-5) powder as catalyst carrier, namely noble metal platinum is distributed on cerium-aluminium composite oxide and neodymium modified molecular screen, in 225 ~ 500 DEG C of intervals to NH
3conversion ratio all reach more than 90%, NH
3substantially be converted completely.
And catalyst prepared by comparative example 1,2 is not owing to adopting the molecular sieve of neodymium modification, cause NH
3conversion ratio comparatively embodiment 1 ~ 3 have obvious decline, especially 225 DEG C time, to NH
3conversion ratio be only about 70%, when catalyst-coated quantity not sufficient, catalytic performance obviously reduces.
Catalyst prepared by comparative example 3 carries out modification owing to not adopting neodymium to molecular sieve, causes NH
3conversion ratio comparatively embodiment 1 ~ 3 has decline, especially 225 DEG C time, to NH
3low conversion rate in 90%.
Fig. 2 is the N of each catalyst
2o discharges concentration chart.As shown in Figure 2, catalyst prepared by the embodiment of the present invention 1 ~ 3, its exit N
2the discharge concentration of O is very low, within the scope of 200 ~ 500 DEG C, is all less than 30ppm, especially within the scope of 200 ~ 250 DEG C and 400 ~ 500 DEG C, is all less than 15ppm.Show, platinum of the present invention/cerium aluminum molecular screen catalyst is to NH
3while there is the conversion ratio of more than 90%, can also significantly suppress harmful side product N
2the generation of O.
By the N of comparative example 1 ~ 3
2o discharges concentration compared with embodiment 1 ~ 3, within the scope of 200 ~ 500 DEG C, and its N
2the eliminating concentration of O has raising in various degree, especially within the scope of 300 ~ 400 DEG C, improves about 5 ~ 15ppm respectively.
Fig. 3 is the NO of each catalyst
xget rid of concentration chart.As shown in Figure 3, catalyst prepared by the embodiment of the present invention 1 ~ 3, its exit NO
xdischarge concentration very low, within the scope of 200 ~ 500 DEG C, be all less than 110ppm, especially at 200 ~ 300 DEG C, be all less than 20ppm.Show, platinum of the present invention/cerium aluminum molecular screen catalyst is to NH
3while there is the conversion ratio of more than 90%, can also significantly suppress harmful side product NO
xgeneration.This is due to NH
3with NO or NO
2reaction, generates nontoxic N
2and H
2o discharges.
By the NO of comparative example 1 ~ 3
xdischarge concentration compared with embodiment 1 ~ 3, within the scope of 200 ~ 500 DEG C, its NO
xeliminating concentration have raising in various degree, and obvious with the eliminating concentration difference of embodiment 1 ~ 3.
From Fig. 1 ~ 3, platinum of the present invention/cerium aluminium-molecular sieve catalyst can obtain the NH higher than prior art
3transformation efficiency, and significantly can suppress N
2o accessory substance and adjoint NH
3the NO that incomplete oxidation causes
xthe generation of accessory substance.Therefore, platinum of the present invention/cerium aluminum molecular screen catalyst can be widely used in Diesel engine and leak NH
3purification.
The NH of the platinum again prepared by embodiment 1/cerium aluminium-molecular sieve catalyst
3conversion ratio, N
2o discharges concentration and NO
xplatinum/cerium aluminum molecular screen catalyst that discharge concentration is prepared with embodiment 2 and 3 is compared: at 200 ~ 500 DEG C, the NH of embodiment 1
3conversion ratio higher than embodiment 2, only a little less than embodiment 3.But the N of embodiment 1
2o, NO
xdischarge concentration compared with embodiment 3, all have and reduce in various degree; And the coated weight of embodiment 3 is larger, cost increases, and affects Fuel Economy.To sum up, embodiment 1 is in preferably effect with less advantage, is optimum implementation of the present invention.
Claims (10)
1. the platinum for catalytic oxidation ammonia/cerium aluminium-molecular sieve catalyst, take cordierite ceramic as carrier, carrier surface is coated with catalyst layer, it is characterized in that: the catalytic active center of described catalyst layer is made up of noble metal platinum, cerium-aluminium composite oxide and neodymium modified molecular screen; The weight ratio of described cerium-aluminium composite oxide, neodymium modified molecular screen and noble metal platinum is 20 ~ 80:20 ~ 80:0.01 ~ 0.1; In described cerium-aluminium composite oxide, the weight ratio of cerium oxide and aluminium oxide is 1 ~ 3:1 ~ 5; In described neodymium modified molecular screen, the weight ratio of neodymia and molecular sieve is 1 ~ 10:90 ~ 100.
2. platinum according to claim 1/cerium aluminium-molecular sieve catalyst, is characterized in that: described catalyst carrier surface coated weight according to the dry weight of catalyst layer be 120 ~ 180g/L calculate.
3. platinum according to claim 1/cerium aluminium-molecular sieve catalyst, is characterized in that: described molecular sieve is ZSM-5 molecular sieve.
4. platinum according to claim 1/cerium aluminium-molecular sieve catalyst, is characterized in that: the weight ratio of described cerium-aluminium composite oxide, neodymium modified molecular screen and noble metal platinum is 40 ~ 70:30 ~ 60:0.04 ~ 0.06.
5. the preparation method of platinum/cerium aluminium-molecular sieve catalyst as described in any one of Claims 1 to 4, is characterized in that, comprise the following steps:
(1) preparation of cerium-aluminium composite oxide
Get the aluminum nitrate solution of 0.1 ~ 0.4g/ml and the cerous nitrate solution of 0.1 ~ 0.4g/ml, mix, join in the citric acid solution of 0.1 ~ 0.3g/ml, stir 1 ~ 2h, evaporating water, then dry, roasting, obtains cerium-aluminium composite oxide;
(2) preparation of neodymium modified molecular screen
Join in molecular sieve powder by the neodymium nitrate solution of 0.1 ~ 0.4g/ml, dry, then roasting, obtains neodymium modified molecular screen powder;
(3) preparation of slurry
Cerium-aluminium composite oxide, neodymium modified molecular screen powder, citric acid and platinum salt are joined in deionized water, fully stirs, obtain catalyst pulp;
(4) ground slurry: grind catalyst pulp, until catalyst pulp particle is 2 ~ 5 μm;
(5) slurry is applied: take cordierite ceramic as carrier, be immersed into by cordierite ceramic in the catalyst pulp after grinding; Then cordierite ceramic is taken out from catalyst pulp, blow remainder catalyst slurry in duct off, obtain the cordierite ceramic that surface is coated with catalyst pulp;
(6) dry and roasting: cordierite ceramic surface being coated with catalyst pulp carries out drying, and then roasting, is finally cooled to room temperature, obtains platinum/cerium aluminium-molecular sieve catalyst; Wherein the coated weight of catalyst pulp after roasting is 120 ~ 180g/L.
6. preparation method according to claim 5, is characterized in that: in described step (1), the volume ratio of aluminum nitrate solution and citric acid solution is 1:1 ~ 4.
7. preparation method according to claim 5, is characterized in that: the roasting in described step (1) is roasting 3 ~ 4h at 550 ~ 650 DEG C.
8. preparation method according to claim 5, is characterized in that: the platinum salt in described step (3) is one or more in platinum nitrate, chloroplatinic acid, acetic acid platinum, cyaniding platinum, platinic hydroxide, xenon platinum hexafluoride and ammonium chloroplatinate.
9. the preparation method according to claim 5 or 8, is characterized in that: in described step (3), the weight ratio of citric acid and cerium-aluminium composite oxide is 1:3 ~ 9.
10. preparation method according to claim 5, is characterized in that: the roasting in described step (6) is roasting 2 ~ 3h at 550 ~ 650 DEG C.
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| CN116139923A (en) * | 2022-12-28 | 2023-05-23 | 济南大学 | Method for preparing Cu-based small-pore molecular sieve catalyst by gradient loading method, obtained product and application |
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