CN103495425B - NOx purification catalyst efficient and capable of being regenerated easily at low temperature - Google Patents

NOx purification catalyst efficient and capable of being regenerated easily at low temperature Download PDF

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CN103495425B
CN103495425B CN201310491628.1A CN201310491628A CN103495425B CN 103495425 B CN103495425 B CN 103495425B CN 201310491628 A CN201310491628 A CN 201310491628A CN 103495425 B CN103495425 B CN 103495425B
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catalyst
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bauxite
earth metal
metal
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CN103495425A (en
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王秀云
陈志林
王瑞虎
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Fujian Institute of Research on the Structure of Matter of CAS
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Fujian Institute of Research on the Structure of Matter of CAS
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Abstract

The invention provides automobile exhaust NOx purification catalyst which is high in activity and capable of being generated easily at low temperature. The catalyst is high in NOx purification activity in a wide air-fuel ratio range and is wide in operational window. The prepared catalyst comprises three layers. A first layer is a bauxite substrate going through acid and heat treatment. A second layer is a composite coating composed of rare earth metal, alkaline earth metal and transition metal. A third layer is reactive metal. The catalyst maintains high NOx purifying performance. Moreover, thermal inactivated catalyst can recover most lost activity after regenerating through reducing agents 5vol%H2/Ar and CO.

Description

Catalyst for purification of nitrogen oxides that is efficient under low temperature, that easily regenerate
Technical field
The invention belongs to Industrial Catalysis application, be specifically related to the NO of a kind of catalyst application in purifying automobile tail gas x.
Background technology
NO xbe one of major pollutants of atmospheric environment, one of its important sources is the tail gas of vehicular emission.NO in current vehicle exhaust xcleaning catalyst mainly comprises three part compositions, i.e. catalyst carrier, active coating and catalytic active component, in addition, in order to improve the performance of catalyst, a small amount of auxiliary agent is added, mainly rare earth oxide and alkaline earth oxide in active coating and catalyst component.Carrier has two kinds of geometric formats usually: spherical and honeycomb substrate, it is lower that spheroid carrier prepares simple cost, and there is higher specific area, but mechanical performance is undesirable, gas-flow resistance is large, the difficulty being much difficult to overcome is had during actual use, the domestic research to it is many, but external research and practical application little.In China, at present the research of purifying vehicle exhaust is reached to the three-way catalyst of Europe IV level, main ceramic honeycomb material or the metal of adopting, as matrix, is mainly high-ratio surface, cavernous A1 in coating 2o 3and CeO 2-ZrO 2component coating is on cordierite carrier, and active component is Pt-Pd-Rh [Hu Zhun, Sun Keqiang, the Xu Baiqing, " NO of Pt-BaO catalyst xstorage-reduction chemistry and structure-performance relation ", catalysis journal 2011,32,17-26], but the type catalyst under excess oxygen to NO xclean-up effect not good.The technology of denitration both at home and abroad mainly contains three kinds, NO at present xdirect Resolution, SCR (SCR) and NO xstore/reduction (NSR) technology.But be no matter current three-way catalyst or NSR or SCR catalyst, general what adopt is all noble metal type catalyst.What these 2 kinds of purification techniques adopted is all catalyst performance preferably precious metals pts, Pd or Rh, and its noble metal is expensive, and resource-constrained, the heat endurance of noble metal catalyst is low, anti-SO 2poisoning performance difference and the easy inactivation of catalyst, limit the NO in motor-vehicle tail-gas xthe further application of cleaning catalyst.
Current NO xthe forward position research of field of purification mainly concentrates on the heat endurance and anti-SO that improve catalyst 2poisoning capability, a lot of research is absorbed in constantly the new catalytic carrier of searching or is changed original carrier to improve the catalytic performance of catalyst, and the novel catalyst carrier tool therefore finding a kind of performance good is of great significance, NO xpurification common carrier has Al 2o 3, CeO 2-ZrO 2deng oxide or composite oxides.In recent years, correlative study both domestic and external mainly concentrates on the purification efficiency improving catalyst and the preparation cost reducing catalyst, research before our seminar combines, take bauxite as matrix, prepared three layers of vehicle exhaust NO by the composite coating of rare earth metal, alkaline-earth metal and transition metal and active metal composition xcleaning catalyst.And pass through the simulation of in esse various severe atmosphere in automobile, the NO of detecting catalyst xpurifying property.
Summary of the invention
The object of this invention is to provide the NO of a kind of low temperature, high activity, easily regeneration xsCR cleaning catalyst, this catalyst all shows high NO in wider air-fuel ratio range xpurification is active, and can action pane wider.
Cleaning catalyst for tail gases of automobiles provided by the invention comprises 3 layers, and ground floor adopts acid and heat treated bauxite matrix, and the second layer is the composite coating of rare earth metal, alkaline-earth metal and transition metal composition, and third layer is Ni, Ag, Mn, V 2o 5, a kind of or any two kinds of combinations in W and Mo etc.
Matrix in described catalyst is acid and heat treated bauxite, it is characterized in that: described acid and heat treatment bauxite adopt following way to prepare: through weak acid, hydro-thermal, reaming, roasting and hydrogen treat. specific as follows: the pretreatment of (1) bauxite matrix: a: weak acid pretreatment 2-10h, hydro-thermal 130-170 DEG C of process 48-96h, sintering temperature 400-550 DEG C, hydrogen reducing 4-8h.(2) second layer and third layer be coated on bauxite base by coating way, and dry under 60-80 DEG C and rapid stirring; (3) then 400-550 DEG C of roasting.Bauxite after process utilizes nitrogen adsorption/desorption test specific area to be 170-200m at liquid nitrogen temperature is for-196 DEG C 2/ g, preferred 190-200m 2/ g.
The described catalyst second layer is the composite coating of rare earth metal, alkaline-earth metal and transition metal composition, it is characterized in that: under agitation rare earth metal, alkaline-earth metal and transition metal are joined in the slurry of the matrix of bauxite, mixing time 1 ~ 6h.
Described catalyst third layer is by Ni, Ag, Mn, V 2o 5, a kind of or any two kinds of compositions in W and Mo etc., it is characterized in that: by close to real vehicle emission component simulation test, preferred Ag and Mn, then pass through the NO of Ag and Mn of different content xpurifying property is assessed, and the content optimizing Ag and Mn is about the 3-6% of carrier Theoretical Mass, continues to increase content and can cause NO xpurifying property reduces.
The renovation process of described decaying catalyst, is characterized in that: comprise and contacted by reducing gas by the catalyst of inactivation under the reducing conditions, catalyst is adopted reducing agent 5vol%H 2/ Ar and CO regeneration.Recovery time is 30min-12h, preferred 60-90min.
Catalyst of the present invention in wider air-fuel ratio (A/F) for all showing good NO in 0-16 xpurifying property, and can operating temperature window wider (100-500 DEG C).
Accompanying drawing explanation
Fig. 1 is the NO of different catalysts xcatalytic performance;
Fig. 2 is that different air-fuel ratio is to catalyst outlet NO ximpact.
Detailed description of the invention
The present invention is used for NO xthe catalyst of purifying and catalyzing, can use in granular form, also can make integral catalyzer as coating load on monolithic porous matrix.
NO of the present invention xcleaning catalyst can be carried on separately as catalyst on a matrix, also can mix composition multicomponent catalyst with current three-way catalyst component.
More specifically catalyst of the present invention is illustrated below in conjunction with embodiment, but these embodiments are without any restrictions to scope of the present invention.
Embodiment 1
(1) first step of the present invention is process bauxite matrix, the composite coating that the second layer of catalyst is made up of rare earth metal, alkaline-earth metal and transition metal, be specially: under agitation rare earth metal (La or Nd) alkaline-earth metal (K or Ba) alkaline-earth metal (Fe, Co) is joined in the slurry of the matrix of bauxite, stir 1 ~ 6h.Spend the night through 120 DEG C of oven dry, after oven dry, sample grind into powder is added a certain amount of water, by quick agitator, slurry agitation is even.Third layer is the coating of active metal, is specially: by the salting liquid of silver nitrate be furnished with containing 1-10wt%, be coated in the slurries prepared above.Spend the night through 120 DEG C of oven dry, 550 DEG C of roasting 4h, obtain cleaning catalyst for tail gases of automobiles.Be labeled as catalyst 1.
(2) sample Pt/Al is contrasted 2o 3and Ag/Al 2o 3preparation process: (i) Al 2o 3synthesis: Al (NO 3) 39H 2o is raw material, is dissolved in a certain amount of distilled water, with NH 3h 2o is precipitating reagent, centrifugal, dry, 400-550 DEG C roasting.(ii) H in coating 2ptCl 66H 2o and AgNO 3.Its mass fraction is all 1wt%, and it is for subsequent use that 20-30 order is got in oven dry.Be labeled as contrast sample.
Embodiment 2
The ground floor of catalyst and the second layer are with embodiment 1.Third layer is the coating of active metal is Ni, being specially: by being furnished with the nickel nitrate solution containing 1-10wt%, being coated in the slurries prepared above.Spend the night through 120 DEG C of oven dry, 550 DEG C of roasting 4h, obtain cleaning catalyst for tail gases of automobiles.Be labeled as catalyst 2
(2) sample Pt/Al is contrasted 2o 3and Ag/Al 2o 3preparation process: (i) Al 2o 3synthesis: Al (NO 3) 39H 2o is raw material, is dissolved in a certain amount of distilled water, with NH 3h 2o is precipitating reagent, centrifugal, dry, 400-550 DEG C roasting.(ii) H in coating 2ptCl 66H 2o and AgNO 3.Its mass fraction is all 1wt%, and it is for subsequent use that 20-30 order is got in oven dry.
Embodiment 3
(1) ground floor of catalyst and the second layer are with embodiment 1.Third layer is the coating of active metal is Mn, being specially: by being furnished with the manganese nitrate solution containing 1-10wt%, being coated in the slurries prepared above.Spend the night through 120 DEG C of oven dry, 550 DEG C of roasting 4h, obtain cleaning catalyst for tail gases of automobiles.Be labeled as catalyst 3.
(2) sample Pt/Al is contrasted 2o 3and Ag/Al 2o 3preparation process: (i) Al 2o 3synthesis: Al (NO 3) 39H 2o is raw material, is dissolved in a certain amount of distilled water, with NH 3h 2o is precipitating reagent, centrifugal, dry, 400-550 DEG C roasting.(ii) H in coating 2ptCl 66H 2o and AgNO 3.Its mass fraction is all 1wt%, and it is for subsequent use that 20-30 order is got in oven dry.
Below the performance of embodiment catalyst is evaluated
Under testing 1 different temperatures, catalyst is to NO xconversion ratio
Adopt embodiment 1-3 and contrast sample Pt/Al respectively 2o 3the each 0.5g of catalyst, gas flow rate 600mL/min, air speed 72,000h -1, the miniature fixed bed of continuous-flow carries out NO xpurifying property measures, NO in tail gas xchange in concentration is by chemiluminescence NO-NO 2-NO xanalyzer detects (Thermo, 42i-HL).Reacting gas consists of: 240ppm NO, 8vol%O 2, 8vol%CO 2, N 2for Balance Air.Respectively at 100 DEG C, 200 DEG C, 250 DEG C, 300 DEG C, 350 DEG C, measure catalyst at 400 DEG C to NO xchanging effect, test result is shown in Fig. 1.
As can be seen from Figure 1, described catalyst 1,2 and 3 is compared to contrast sample Pt/Al 2o 3there is good NO xconversion ratio, T=350 DEG C, the NO of catalyst 1,2 and 3 xbe converted into N 2conversion ratio be respectively 94.63%, 93.56% and 86.81%.Under equal conditions contrast sample Pt/Al 2o 3nO xconversion ratio is 60.81%.
Test the regeneration of 2 decaying catalysts
Catalyst, at inactivation after the test of 3 weeks 4%, adopts edetate solution washing, dry, roasting.Again catalyst is adopted reducing agent 5vol%H 2/ Ar and CO mist, at 550 DEG C of regeneration 30min, 60min, 90min, 12h not etc., research finds, catalyst is after the regeneration of 60-90min, and the catalyst activity of inactivation recovers about 3-3.5%, and continue to extend the recovery time, the activity of recovery remains unchanged.
Test the test of 3 different air-fuel ratios
That selects catalyst activity the best carries out different air-fuel ratio test (A/F), and probe temperature is 350 DEG C, and the gas component of test is 240ppm NO, 8vol%CO 2, N 2for Balance Air and a certain amount of O 2and H 2switch according to different air-fuel ratios.Air-fuel ratio excursion is 0-10.Experimental result is shown in Fig. 2.
The foregoing is only preferred embodiment of the present invention, every modification according to doing in the present patent application the scope of the claims with all become, all should belong to covering scope of the present invention.

Claims (7)

1. the cleaning catalyst for purifying nitrogen oxide, it is characterized in that, this catalyst comprises three layers, ground floor adopts the bauxite after acid and heat treatment to be matrix, the second layer is composite coating, third layer is active metal, it is characterized in that: described composite coating is made up of rare earth metal, alkaline-earth metal and transition metal, and described active metal adopts Ni, Ag, Mn, V 2o 5, one in W and Mo or any two kinds of combinations, described rare earth metal is selected from La or Nd, and described alkaline-earth metal is selected from K or Ba, and described transition metal is selected from Fe or Co.
2. catalyst according to claim 1, is characterized in that: described acid and heat treatment bauxite are adopted and prepared with the following method: through weak acid, hydro-thermal, reaming, roasting and hydrogen treat.
3. catalyst according to claim 2, is characterized in that: the method for described acid and heat treatment bauxite is as follows: weak acid pretreatment 2-10h, hydro-thermal 130-170 DEG C of process 48-96h, sintering temperature 400-550 DEG C, hydrogen reducing 4-8h.
4., according to the arbitrary described catalyst of claims 1 to 3, it is characterized in that: described active metal accounts for the 3-10% of catalyst gross mass mark.
5. prepare a method for the arbitrary described catalyst of Claims 1-4, comprise the steps:
(1) pretreatment of bauxite matrix: (a) weak acid pretreatment 2-10h, hydro-thermal 130-170 DEG C, process 48-96h, sintering temperature 400-550 DEG C, hydrogen reducing 4-8h;
(2) second layer and third layer are coated in bauxite matrix by coating way under 60-80 DEG C and rapid mixing conditions, and dry;
(3) then 400-550 DEG C of roasting.
6. the application of catalyst described in any one of Claims 1-4, is characterized in that, the nitrogen oxide of described catalyst application in purification moving source.
7. the renovation process of catalyst described in any one of Claims 1-4: comprise the steps:
(1) temperature programmed desorption;
(2) desorption gas is 5Vol%H 2/ Ar and CO, the recovery time is 30min-12h.
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CN104437512A (en) * 2014-11-02 2015-03-25 中国科学院福建物质结构研究所 Transition-metal-modified Cu/CeO2 ordered mesopore material for NOx purification of stationary source
CN105251543B (en) * 2015-10-20 2018-08-28 清华大学 A kind of hydrogen reducing regeneration method of the out of stock catalyst of arsenic poisoning
CN105879924A (en) * 2016-04-27 2016-08-24 北京石油化工学院 Method for reduction pretreatment of supported noble metal catalyst
WO2019021244A1 (en) * 2017-07-27 2019-01-31 Basf Corporation N 2o removal from automotive exhaust for lean/rich systems
CN107930637A (en) * 2017-12-05 2018-04-20 内蒙古科技大学 A kind of high entropy solid solution catalyst of rare-earth-based iron content and preparation method thereof
CN116688987B (en) * 2023-07-28 2023-10-10 四川大学 Biological catalyst for producing ROS, preparation method and application thereof

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CN102580764A (en) * 2012-02-06 2012-07-18 中国科学院福建物质结构研究所 Catalyst for purifying nitric oxide, and preparation method thereof
CN102580730A (en) * 2011-01-12 2012-07-18 北京化工大学 Catalyst for purifying automobile tail gas and preparation method thereof

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