CN1762585A - Preparation process of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide - Google Patents
Preparation process of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide Download PDFInfo
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- CN1762585A CN1762585A CNA2005100865500A CN200510086550A CN1762585A CN 1762585 A CN1762585 A CN 1762585A CN A2005100865500 A CNA2005100865500 A CN A2005100865500A CN 200510086550 A CN200510086550 A CN 200510086550A CN 1762585 A CN1762585 A CN 1762585A
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- 239000003054 catalyst Substances 0.000 title claims abstract description 67
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 title claims abstract description 36
- 238000002360 preparation method Methods 0.000 title claims abstract description 33
- 239000007789 gas Substances 0.000 title claims abstract description 30
- 230000009467 reduction Effects 0.000 title claims description 18
- 239000000919 ceramic Substances 0.000 claims abstract description 18
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052878 cordierite Inorganic materials 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims abstract description 7
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000004202 carbamide Substances 0.000 claims abstract description 5
- 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 5
- 239000000843 powder Substances 0.000 claims abstract description 5
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000002270 dispersing agent Substances 0.000 claims abstract description 4
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 19
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 19
- 239000011247 coating layer Substances 0.000 claims description 17
- 239000011248 coating agent Substances 0.000 claims description 16
- 238000000576 coating method Methods 0.000 claims description 16
- 230000008569 process Effects 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 13
- 239000004411 aluminium Substances 0.000 claims description 7
- 238000001802 infusion Methods 0.000 claims description 6
- 238000000643 oven drying Methods 0.000 claims description 6
- 229910052709 silver Inorganic materials 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 230000000274 adsorptive effect Effects 0.000 claims description 4
- 229910001593 boehmite Inorganic materials 0.000 claims description 4
- 238000001354 calcination Methods 0.000 claims description 4
- 239000003292 glue Substances 0.000 claims description 4
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims description 4
- XRRQZKOZJFDXON-UHFFFAOYSA-N nitric acid;silver Chemical compound [Ag].O[N+]([O-])=O XRRQZKOZJFDXON-UHFFFAOYSA-N 0.000 claims description 4
- 229920006395 saturated elastomer Polymers 0.000 claims description 4
- 239000004332 silver Substances 0.000 claims description 4
- 238000000498 ball milling Methods 0.000 claims description 3
- 239000003795 chemical substances by application Substances 0.000 claims description 3
- 239000002994 raw material Substances 0.000 claims description 3
- 230000015572 biosynthetic process Effects 0.000 claims 2
- 239000002002 slurry Substances 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 30
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 abstract description 8
- 229910052760 oxygen Inorganic materials 0.000 abstract description 7
- 238000007598 dipping method Methods 0.000 abstract description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 5
- 239000001301 oxygen Substances 0.000 abstract description 5
- 230000003197 catalytic effect Effects 0.000 abstract description 4
- 229910001961 silver nitrate Inorganic materials 0.000 abstract description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 abstract description 3
- 230000008901 benefit Effects 0.000 abstract description 3
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 229910052593 corundum Inorganic materials 0.000 abstract 1
- 229910001648 diaspore Inorganic materials 0.000 abstract 1
- 239000011148 porous material Substances 0.000 abstract 1
- 229910001845 yogo sapphire Inorganic materials 0.000 abstract 1
- 238000006722 reduction reaction Methods 0.000 description 16
- 239000000446 fuel Substances 0.000 description 10
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 6
- 230000008859 change Effects 0.000 description 5
- 239000003638 chemical reducing agent Substances 0.000 description 5
- 238000007599 discharging Methods 0.000 description 5
- 229930195733 hydrocarbon Natural products 0.000 description 4
- 150000002430 hydrocarbons Chemical class 0.000 description 4
- 238000005470 impregnation Methods 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 3
- 238000010531 catalytic reduction reaction Methods 0.000 description 3
- 239000000356 contaminant Substances 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 230000018109 developmental process Effects 0.000 description 3
- 235000019441 ethanol Nutrition 0.000 description 3
- 229910044991 metal oxide Inorganic materials 0.000 description 3
- 229910000510 noble metal Inorganic materials 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- 206010013786 Dry skin Diseases 0.000 description 2
- 229910021536 Zeolite Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 230000007812 deficiency Effects 0.000 description 2
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000005431 greenhouse gas Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000001939 inductive effect Effects 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002808 molecular sieve Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 2
- 239000010457 zeolite Substances 0.000 description 2
- 101100203596 Caenorhabditis elegans sol-1 gene Proteins 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000001994 activation Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 150000001335 aliphatic alkanes Chemical class 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000295 fuel oil Substances 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- NJPPVKZQTLUDBO-UHFFFAOYSA-N novaluron Chemical compound C1=C(Cl)C(OC(F)(F)C(OC(F)(F)F)F)=CC=C1NC(=O)NC(=O)C1=C(F)C=CC=C1F NJPPVKZQTLUDBO-UHFFFAOYSA-N 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
Images
Classifications
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
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- Catalysts (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
The preparation method for catalyst to selective reduce nitrogen oxide in tail gas from gasoline vehicle comprises: with quasi-thin diaspore dry powder as material, nitric acid as peptizer and urea as dispersant, grinding to obtain aluminum solution; dipping the 200-800 pores/inch2 cordierite honeycomb ceramic carrier into said solution, taking out to dry and form Al2O3 coat; excessive immersing into silver nitrate solution, taking out to calcine and obtain the product. This catalyst has high catalytic conversion rate to NOx special at low temperature, solves the difficulty that it is hard to remove NOx on oxygen-enriched condition, and has well environmental benefit.
Description
Technical field
The present invention relates to a kind of preparation method of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide, belong to catalyst for reduction of oxides of nitrogen preparing technical field in the environmental protection.
Background technology
Along with increasingly sharpening of global energy crisis situation and greenhouse gases effect, feasible economy and the reduction CO that how to improve fuel
2The isothermal chamber gas emissions has become the energy and environment problem of countries in the world common concern.The gasoline engine that generally uses is to work near theoretical air-fuel ratio at present, and purpose is to make the three-way catalyst that is installed in the tail-gas from gasoline automobiles after-treatment system CO in the engine discharging tail gas, HC and NOx efficiently can be changed into harmless CO
2, H
2O and N
2, but the above-mentioned this several contaminants efficient simultaneously mechanism that transforms is to be based upon the fuel oil imperfect combustion with on the basis that produces reducing agents such as a large amount of CO, HC, therefore becomes the less economical basic reason of gasoline engine fuel.
The gasoline engine that lean-burn gasoline motor car is installed is a kind of engine of working under greater than the chemically correct fuel operating condition in air-fuel ratio.Owing in engine, add excessive air, make fuel can obtain burning more completely, therefore determined this engine to have the fuel economy more superior, lower CO, HC, NOx pollutant and greenhouse gases CO than chemically correct fuel gasoline engine
2Generation.Because gasoline engine discharging tail gas is in the poor gas atmosphere, that is to say at engine discharging tail gas and have excessive oxygen, and be widely used at present contain noble metal such as Pt, Pd, the three-way catalyst of Rh only can be in theoretical air-fuel ratio environs work, could be with CO, three kinds of contaminant gases of HC and NOx effectively transform simultaneously, it is under the exhaust emissions situation of excessive oxygen, can only better conversion CO and HC, but be difficult to effectively carry out the catalytic reduction conversion of NOx, therefore use three-way catalyst to be used for the gasoline engine vent gas treatment, can cause the NOx conversion ratio of being on duty mutually.
The NOx selective reduction catalyst uses hydro carbons as reducing agent, can effectively transform the NOx in the discharging tail gas under the vehicle exhaust excess oxygen.The NOx selective reduction catalyst is applied to the lean-burn gasoline motor car vent gas treatment, is expected to satisfy the strict more automobile exhaust emission standard of issuing and implementation from now on.The discharging exhaust temperature of gasoline engine generally hangs down 200-600 ℃ than the gasoline car of chemically correct fuel, so compare with three-way catalyst, the NOx selective reduction catalyst must have the catalytic reduction reaction activity under lower exhaust temperature condition, can make just that NOx obtains more conversions in the tail gas.
At present the NOx selective reduction catalyst can roughly be divided into three types of noble metal, zeolite and metal oxides.For noble metal type catalyst, its low temperature active is better, still has the active temperature narrow range, produces a large amount of N
2The deficiency of O; And there is the problem of hydrothermal stability difference in the zeolite type catalyst; In the metallic oxide type catalyst, some metal oxide oxidation catalyst active components such as Ag, Cu, In etc. show good selectivity and high reaction activity and high to the NOx reduction reaction, therefore have potential application prospect.
For Ag/Al
2O
3Catalyst, with hydro carbons such as the alkane of alkene, high carbon number and alcohols is reducing agent, between middle high-temperature region, show good NOx reduction reaction activity, especially with ethanol as reducing agent, its active temperature scope can drop within the exhaust emissions temperature range of lean-burn automotive engine especially, therefore has the possibility of Application and Development largely.Countries in the world are to Ag/Al at present
2O
3Catalyst has carried out more deep basic theoretical research, but for how optimizing integral catalyzer preparation technology so that the NOx reduction reaction performance of this catalyst improves, the research of this respect report is not a lot.
With microwave technology be applied to the inducing catalysis reaction, Preparation of Catalyst is the latest developments that obtained in catalytic field in the last few years, as in oxidation of the decomposition that aspect the inducing catalysis reaction microwave technology is applied to the halogenated organic hydrocarbon, methane conversion, hydrocarbon etc.; Aspect Preparation of Catalyst, utilize microwave that the dielectric heat effect of water is carried out the synthetic of A type, X type, Y type, ZSM-5 type equimolecular sieve, compare with traditional hydrothermal synthesis method, microwave process for synthesizing can simultaneously a large amount of nucleation and can be shortened crystallization time significantly, obtain evenly tiny crystal grain, specific area increases; Also there are some scholars to utilize microwave technology some inorganic salts to be loaded on the dust carrier such as molecular sieve recently,, thereby catalyst shown than better activity of conventional load mode and selectivity because microwave has improved the active component dispersiveness.Compare with traditional mode of loading, on carriers such as molecular sieve, have the following advantages: the decentralization height with the microwave method load active component; Processing time is short, the efficient height; The processing sample is simple, has avoided mixing, oven dry and the roasting of solution.
In the Preparation of catalysts process, our beyond thought discovery is compared in conjunction with the preparation technology that conventional heat drying combines with incipient impregnation, the Ag/Al for preparing with excessive infusion process and microwave drying or conventional drying process combined
2O
3Integral catalyzer shows the low-temperature reactivity of excellent more NOx conversion performance, especially catalyst.When transforming the simulation lean-burn gasoline tail gas of same composition, the catalyst that the highest transformation efficiency of NOx of the catalyst of invention is prepared in conjunction with the oven drying method than traditional incipient impregnation will exceed more than 30%, and temperature window has also taken place obviously to move to low-temperature space.Therefore, the catalyst of present invention has overcome the Ag/Al of preparation in the past
2O
3The deficiency of integral catalyzer can better be used for the lean-burn vehicle exhaust and handle.
Summary of the invention
The present invention on cordierite honeycomb ceramic carrier coated with the high-specific surface area activated alumina (Al of Prepared by Sol Gel Method
2O
3) coating material, and with excessive infusion process with the Ag spread loads at active A l
2O
3On the coating material,, promptly obtain required catalyst then by step of preparation process such as microwave drying, calcination activations.The constituent content of this catalyst is: Ag, 0.5-4wt% (accounting for the mass percent of coating amount); Al
2O
3Coating material content, 2-50wt% (accounting for the mass percent of ceramic monolith weight).
A kind of preparation process of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide, this preparation method may further comprise the steps:
(1) be that raw material, nitric acid are that peptizing agent, urea are dispersant with the boehmite dry glue powder, by the aluminium colloidal sol that ball milling obtains having the narrow particle diameter distribution and the viscosity that suits, its solid content is 5-50wt%;
(2) with 200-800 hole/inch
2Cordierite honeycomb ceramic carrier immerses the time of second of 20-180 in the aluminium sol solutions of above-mentioned preparation, takes out the back and blows out colloidal sol unnecessary in the carrier duct gently with compressed air, and at 80-200 ℃ of dry 2-10 hour, 400-800 ℃ formed Al in roasting 2-6 hour
2O
3Coating; The Al that forms
2O
3Coating material is high surface active A l
2O
3, the load capacity of coating is the 2-50wt% of honeycomb ceramic carrier weight;
(3) measure Al on the described honeycomb ceramic carrier
2O
3The saturated water adsorptive value of coating also calculates Al
2O
3The load capacity of silver on the coating, the liquor argenti nitratis ophthalmicus of preparation respective concentration;
(4) will apply Al
2O
3The carrier of coating is excessive to be immersed in the liquor argenti nitratis ophthalmicus of described preparation and to take out after 30-120 minute, redundant nitric acid silver solution residual in the catalyst carrier duct is blown out with compressed air, obtain the catalyst of loaded Ag, its Ag load capacity is the 0.5-4wt% of aluminum oxide coating layer amount;
(5) will carry out drying with microwave drying 5-20 minute or conventional Electric heat oven drying mode in the mode of 60-200 ℃, 2-12 hour with the catalyst of above-mentioned excessive infusion process loaded Ag, in the 300-700 ℃ of air atmosphere calcination process 2-6 hour, promptly prepare Ag/Al
2O
3Catalyst.
Heating using microwave is body phase Fast Heating mode, and the gradient that can reduce integral catalyzer temperature inside and humidity to a considerable extent distributes, and reduces migration and the gathering of Ag active component in dry run, makes the Ag active component at active A l
2O
3The coating material surface evenly distributes, and has improved the decentralization of Ag, thereby the NOx reduction reaction performance of catalyst is improved.
The preparation method of a kind of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide provided by the invention, the NOx selection type catalytic reduction catalysts for preparing by this kind preparation method, in the scope of lean-burn motor vehicle exhaust emission temperature, especially low temperature range, can obtain the catalytic conversion efficiency very high to gaseous contaminant NOx, catalyst also has very high reduction selectivity simultaneously, both can revert to N fully to NO
2, solved the problem that NOx is difficult to remove under excess oxygen, reach the purpose of control lean-burn motor vehicle exhaust emission, can obtain good benefits in environment.
Description of drawings
Fig. 1 is Ag/Al
2O
3The NOx conversion ratio of catalyst is with the change curve of reaction temperature, and wherein abscissa is a reaction temperature, unit ℃, and ordinate is the NOx conversion ratio, the % of unit.
The specific embodiment
Fig. 1 is Ag/Al
2O
3The NOx conversion ratio of catalyst is with the change curve of reaction temperature, and wherein abscissa is a reaction temperature, unit ℃, and ordinate is the NOx conversion ratio, the % of unit.Three curves in the accompanying drawing 1: the square line is represented the Ag/Al for preparing in conjunction with conventional Electric heat oven drying with incipient impregnation
2O
3The NOx conversion ratio of catalyst is with the change curve of reaction temperature; Round wire is represented the Ag/Al for preparing in conjunction with conventional Electric heat oven drying with excessive dipping
2O
3The NOx conversion ratio of catalyst is with the change curve of reaction temperature; The triangle line is represented the Ag/Al for preparing in conjunction with microwave drying with excessive dipping
2O
3The NOx conversion ratio of catalyst is with the change curve of reaction temperature.
Specify the present invention below in conjunction with embodiment.
Embodiment 1
In the boehmite dry glue powder, add rare HNO
3And urea, promptly obtain the alumina sol that solid content is 21wt% behind the high-speed stirred 5h.The whole samples of 400 hole cordierite honeycomb ceramics are immersed in the above-mentioned colloidal sol 1 minute, take out the back and blow unnecessary colloidal sol in the carrier duct off with compressed air, subsequently the carrier sample is placed at room temperature dry in the shade (32 ℃) 6 hours, 110 ℃ of dryings are 6 hours in the baking oven, 600 ℃ of roastings 2 hours in muffle furnace at last promptly prepare the ceramic monolith of active oxidation aluminized coating.
Certain density silver nitrate aqueous solution is flooded above-mentioned ceramic monolith with aluminum oxide coating layer in isopyknic mode, 110 ℃ of oven dryings then, 600 ℃ of roasting 3h in muffle furnace promptly get Ag/Al at last
2O
3Integral catalyzer, wherein the Ag load capacity is 2wt%.
Embodiment 2
Certain density silver nitrate aqueous solution is flooded the ceramic monolith with aluminum oxide coating layer for preparing in the example 1 in the mode of following excessive dipping: according to the load capacity of silver on the saturated water adsorptive value of aluminum oxide coating layer on the honeycomb ceramic carrier and the aluminum oxide coating layer, calculate the concentration of liquor argenti nitratis ophthalmicus, prepare corresponding liquor argenti nitratis ophthalmicus, will apply Al
2O
3The carrier of coating is immersed in the liquor argenti nitratis ophthalmicus of above-mentioned preparation and after 30-120 minute carrier is taken out, and redundant nitric acid silver solution residual in the catalyst carrier duct is blown out with compressed air.Then with catalyst at 110 ℃ of baking oven heat dryings, 600 ℃ of roasting 3h in muffle furnace promptly get Ag/Al at last
2O
3Integral catalyzer, wherein the Ag load capacity is 2wt%.
Embodiment 3
With the ceramic monolith with aluminum oxide coating layer of certain density silver nitrate aqueous solution to prepare in the excessive impregnation method dipping example 1 described in the example 2, microwave drying is 10 minutes then, and 600 ℃ of roasting 3h in muffle furnace promptly get Ag/Al at last
2O
3Integral catalyzer, wherein the Ag load capacity is 2wt%.
Embodiment 4
With the above-mentioned catalyst sample chamber lean-burn simulative automobile tail gas performance evaluation that experimentizes.The catalyst carrier sample is put into quartz tube reactor, distribution simulation lean-burn motor vehicle exhaust emission composition, with the reducing agent of ethanol as NOx, the reacting gas that uses is 1.01%NO/He (99.995%), O
2(99.995%), N
2(99.995%), absolute ethyl alcohol (analyzing pure), the reaction air inlet consist of 0.07%NOx, 0.19%C
2H
5OH, 8.0%O
2, N
2Be balance gas.Charge flow rate is 564ml/min, and air speed is 21500h
-1In evaluation procedure, keep each gas flow constant, and programme-control catalytic bed temperature, the while is by NO, the NO of process catalyst under the chemiluminescence formula NOx gas analyzer surveying record differential responses temperature
2With the NOx gas component concentrations, the NOx conversion ratio when calculating the differential responses temperature.
The experimental result of above-mentioned example as shown in Figure 1, the catalyst for preparing in the example 3 has 81.5% NOx maximum conversion rate at 375 ℃, the temperature operation window that NOx transforms has taken place obviously to move to low-temperature space, shows that the NOx SCR integral catalyzer that adopts excessive dipping to prepare in conjunction with microwave drying process has the wide and higher NOx conversion ratio of NOx conversion temperature window of very low NOx reduction reaction temperature, broad.In addition, the Preparation of catalysts good process repeatability, technological process is simple, energy consumption is relatively low.The monoblock type Ag/Al that also shows invention by the engine pedestal experiment
2O
3Catalyst can reach the purpose of effective control lean-burn automobile NOx discharge capacity, has the good application development prospect.
Claims (8)
1, a kind of preparation method of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide is characterized in that, this preparation method may further comprise the steps:
(1) be that raw material, nitric acid are that peptizing agent, urea are dispersant with the boehmite dry glue powder, ball milling obtains aluminium colloidal sol, and its solid content is 5-50wt%;
(2) with 200-800 hole/inch
2Cordierite honeycomb ceramic carrier immerses 20-180 second in the aluminium sol solutions of above-mentioned preparation, takes out, and blows out colloidal sol unnecessary in the carrier duct gently with compressed air, and at 80-200 ℃ of dry 2-10 hour, 400-800 ℃ formed aluminum oxide coating layer in roasting 2-6 hour;
(3) measure the saturated water adsorptive value of aluminum oxide coating layer on the described cordierite honeycomb ceramic carrier and calculate the load capacity of silver on the aluminum oxide coating layer, the liquor argenti nitratis ophthalmicus of preparation respective concentration;
(4) will be take out after 30-120 minute in the excessive liquor argenti nitratis ophthalmicus that is immersed in step (3) preparation of the cordierite honeycomb ceramic carrier of covering aluminum oxide coating, redundant nitric acid silver solution residual in the catalyst carrier duct is blown out with compressed air, obtain the catalyst of loaded Ag active component;
(5) will be with the catalyst of above-mentioned excessive infusion process loaded Ag active component with microwave drying 5-20 minute, in the 300-700 ℃ of air atmosphere calcination process 2-6 hour, promptly prepare Ag/Al
2O
3Catalyst.
2, the preparation method of a kind of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide according to claim 1 is characterized in that, the aluminum oxide coating layer load capacity of formation is the 2-50wt% of honeycomb ceramic carrier weight.
3, the preparation method of a kind of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide according to claim 1 is characterized in that, the catalyst A g load capacity of described loaded Ag active component is the 0.5-4wt% of aluminum oxide coating layer amount.
4, the preparation method of a kind of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide according to claim 1, it is characterized in that, step (5) is carried out the dry conventional Electric heat oven drying that adopts to catalyst, 60-200 ℃ temperature range inner drying 2-12 hour, under 300-700 ℃ of air atmosphere condition calcination process 2-6 hour at last, promptly prepare Ag/Al
2O
3Catalyst.
5, the preparation method of a kind of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide according to claim 1 is characterized in that, the loaded Ag active component is used excessive infusion process on aluminum oxide coating layer.
6, the preparation method of a kind of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide according to claim 5, it is characterized in that, with excessive infusion process be: the load capacity of at first measuring silver on the saturated water adsorptive value of aluminum oxide coating layer on the honeycomb ceramic carrier and the aluminum oxide coating layer in the step that loaded Ag active component on the aluminum oxide coating layer is used, calculate the concentration of liquor argenti nitratis ophthalmicus, prepare corresponding liquor argenti nitratis ophthalmicus, then will be the carrier of covering aluminum oxide coating be immersed in the liquor argenti nitratis ophthalmicus of above-mentioned preparation and after 30-120 minute carrier taken out, blow out redundant nitric acid silver solution residual in the catalyst carrier duct with compressed air at last.
7, a kind of preparation method of aluminium colloidal sol is characterized in that, uses the boehmite dry glue powder to be dispersant as raw material, nitric acid as peptizing agent, urea, and ball milling obtains aluminium colloidal sol, and its solid content is 5-50wt%.
8, a kind of preparation method of aluminum oxide coating layer is characterized in that, with 200-400 hole/inch
2Honeycomb ceramic carrier immerse 20-180 in the coating material aluminium sol solution that solid content is 4-50wt% and take out after the time of second, after with compressed air slurries unnecessary in the duct being blown out gently, at 80-200 ℃ of dry 2-10 hour, 400-800 ℃ of roasting 2-6 hour formation aluminum oxide coating layer.
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