CN101541402A - Catalysts to reduce NOx in an exhaust gas stream and methods of preparation - Google Patents
Catalysts to reduce NOx in an exhaust gas stream and methods of preparation Download PDFInfo
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- CN101541402A CN101541402A CNA2007800430578A CN200780043057A CN101541402A CN 101541402 A CN101541402 A CN 101541402A CN A2007800430578 A CNA2007800430578 A CN A2007800430578A CN 200780043057 A CN200780043057 A CN 200780043057A CN 101541402 A CN101541402 A CN 101541402A
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- aluminium oxide
- pseudobochmite
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Abstract
Catalysts, systems and methods are described to reduce NOx emissions of an internal combustion engine. In one embodiment, an emissions treatment system for an exhaust stream is provided having a catalyst comprising silver on a particulate alumina support, the silver having a diameter of less than about 20 nm. Methods of manufacturing catalysts are described in which ionic silver is impregnated on particulate hydroxylated alumina particles.
Description
The government contract right
The paid in the present invention clear license fee of U.S. government, and the requirement title to patent that has the right under condition of limited permits other people to implement under the reasonable terms of the clause defined of the DE-FC26-02NT41218 that issues as USDOE.
Technical field
Generally, the present invention relates to be used for exhaust emissions treatment system, catalyst and the manufacture method thereof of internal combustion engine and in the poor burn engine purposes of (comprising diesel engine and poor combustion gasoline engine).
Background technology
The user that operates to of poor burn engine (for example diesel engine and poor combustion gasoline engine) provides excellent fuel economy, and owing to it has low-down gas phase hydrocarbon and carbon monoxide emission with high air/fuel than operation under poor fuel condition.Especially, diesel engine also produces in its durability and under low speed provides the significant advantage that is better than gasoline engine aspect the ability of high moment of torsion.But, be characterised in that from the waste gas of poor combustion gasoline engine and equaling or comparing near the conventional gasoline machine that moves under the stoichiometric air/fuel condition, it has higher NO
xDischarging.Be difficult to realize NO from poor burn engine
xEffective minimizing because high NO
xConversion ratio requires to be rich in the condition of reducing agent usually.For the operation under poor fuel condition, the NO of waste gas stream
xComponent needs special NO usually to the conversion of harmless components
xReduce strategy.
From diesel engine and poor combustion gasoline engine waste gas, effectively reduce nitrogen oxide (NO
x=NO+NO
2) be important for reaching discharge standard in the future and improving motor vehicle fuel economy.From the waste gas incoming flow that contains excess of oxygen, reduce NO
xDischarging is a challenge to the vehicular manufacturer to meet that various regulations require.For example, according to estimates, Bin 5 regulations that meet the U.S. may the needs after-treatment system, and this after-treatment system can be discharged NO at the engine based on present expection
xThe FTP of content (Federal TestProcedure) realizes 70 to 90%NO on the cycle
xTransformation efficiency.Reduce the NO in the exhaust gas from lean burn engines stream
xA kind of strategy use NO
xStorage reduces (NSR) catalyst, and it is known as " NO in the art again
xTrap ".The NSR catalyst contains and can adsorb under lean-burn condition or the NO of " capture " nitrogen oxide
xSorbent material and the platinum group metal component of oxidation and restoring function is provided for this catalyst.Be in operation, this NSR catalyst a series of basic steps of describing in the following formula 1 to 5.In oxidation environment, NO is oxidized to NO
2(formula 1), this is NO
xThe important step of storage.At low temperatures, this reaction is usually by platinum group metal component (for example platinum component) catalysis.Oxidizing process is not stopped at this point.NO
2To the further oxidation (wherein having incorporated elemental oxygen into) of nitrate also by the reaction of catalysis (formula 2).Under the situation that does not have platinum group metal component, even use NO
2As NO
xThe source also forms nitrate hardly.This platinum group metal component has the dual-use function of oxidation and reduction.With reducing agent, when for example CO (carbon monoxide) or HC (hydrocarbon) introduced waste gas, platinum group metal component was because the catalyzing N O of its reduction elder generation
xRelease (formula 3).This step can be recovered some NO
xThe storage site, but to NO
xThe minimizing of material is without any help.Then, the NO that discharges
xIn richness combustion environment, further be reduced into gaseous state N
2(formula 4 and 5).Even in clean oxidation environment, also can spray and cause NO by fuel
xDischarge.But, the NO that discharges
xRequired rich combustion condition by effective reduction of CO.Temperature fluctuation also can cause NO
xDischarge, because metal nitrate is unstable under higher temperature.NO
xTrap catalysis is cycling.Metallic compound is considered in poor combustion/richness combustion running carbonate/nitrate to take place and transforms as predominating path.
NO is oxidized to NO
2
NO+1/2O
2→NO
2 (1)
NO
xStore as nitrate
2NO
2+MCO
3+1/2O
2→M(NO
3)
2+CO
2 (2)
NO
xDischarge
M(NO
3)
2+2CO→MCO
3+NO
2+NO+CO
2 (3)
NO
xBe reduced into N
2
NO
2+CO→NO+CO
2 (4)
2NO+2CO→N
2+2CO
2 (5)
In formula 2 and 3, M represents divalent metal.M also can be monovalence or trivalent metal compound, and in this case, these formula need balance again.
Although in richness combustion process in the presence of the NSR catalyst NO and NO
2Be reduced into N
2, but observe, also can form ammonia (NH as the accessory substance of the rich pulse regneration of NSR catalyst
3).For example, show that in following formula (6) NO is by CO and H
2The O reduction.
NO is reduced into NH
3
2NO+5CO+3H
2O→2NH
3+5CO
2 (6)
Must with itself the NH of harmful constituent also now before this character of NSR catalyst requires in discharging the exhaust to atmosphere
3Change into innocuous substance.
In the development of automobile purposes, be used to reduce NO
xAnother strategy (comprising the waste gas of processing) from poor burn engine use SCR (SCR) catalyst technology.The verified processing that is effective to stationary source (for example flue gas) of this strategy.In this strategy, the SCR catalyst through usually being made of base metal is with reducing agent (NH for example
3) with NO
xBe reduced into nitrogen (N
2).This technology can reduce the NO above 90%
x, so it has been represented and realizes heavy NO
xOne of best approach of restore target.
Ammonia is to use the SCR technology to be used for NO under lean-burn condition
xOne of the most effective reducing agent.Be studied the NO that is used for reducing diesel engine (mainly being heavy diesel vehicle)
xOne of method adopt urea to make reducing agent.Urea (it produces ammonia through hydrolysis) is being injected waste gas in 200 to 600 ℃ temperature range before the SCR catalyst.One of major defect of this technology is to need king-sized reservoir to hold urea on vehicle.The operating personnel that another important consideration item is these vehicles will replenish urea as required in reservoir, and need infrastructure to supply urea to operating personnel.Therefore, supply is used for the reducing agent NH of the SCR processing of waste gas
3With the lighter alternative source of burden be desirable.
Utilize NO in the waste gas
xCatalytic reduction to produce NH
3, replace NH with this
3Or NH
3The emission treatment systems of the outside reservoir of precursor is as known in the art.In other words, use a part of NO of waste gas
xComponent is as the NH in this type systematic
3Precursor.For example, United States Patent (USP) 6,176,079 discloses the method for handling the waste gas of the combustion system of alternate run under comfortable poor combustion and the rich combustion condition.In the method, intermediate storage nitrogen oxide in poor combustion running discharges it to form NH in richness combustion running
3And with NH
3Storage.The NH of storage
3Can be released, and nitrogen oxides reduction in follow-up poor combustion running thus.
Broad research use the NO of hydrocarbon
xSCR (HC-SCR) is as remove NO under excess oxygen
xPotential alternative approach.Ion-exchange base metal zeolite catalyst (for example Cu-ZSM5) is active not enough under typical vehicle operating condition usually, and degrades because of contact sulfur dioxide and water easily.Use platinum group metal (Pt/Al for example
2O
3) catalyst in the narrow temperature scope, effectively work, and to N
2The generation of O is a high selectivity.
Use the silver (Ag/Al of alumina load
2O
3) catalytic unit since its under poor exhaust gas conditions with multiple hydrocarbon selective reductive NO
xAbility and receive publicity.Through Ag/Al
2O
3Use hydrocarbon and alcohol, aldehyde and functionalized organic compound reductive NO at a lower temperature
xExcept that above-mentioned molecule, can also use diesel oil as reducing agent.For the vehicle of making the energy with diesel oil, diesel oil does not need extra storage tank.Can be by the change engine management or by provide extra diesel injection device that diesel oil is entered in the exhaust system for drain line.
Although these various alternatives are arranged, there is not commercially available actual hydrocarbon SCR catalyst.Therefore, need be used for vehicle and poor internal combustion engine other purposes, selective reduction waste gas stream NO
xEffective catalyst and make the method for the commericially feasible of this class catalyst.
Brief summary of the invention
According to one embodiment of the invention, provide the NO that is used to reduce from exhaust gas from lean burn engines stream
xThe catalyst of emission, it comprises the silver that loads on the aluminium oxide.
According to one or more embodiments, ionic silver is immersed on the hydroxylating alumina surface, and gained silver is well dispersed on the alumina surface." fully disperse " is meant that silver can not assemble in a large number, and is dispersed on the alumina surface with little entity form.According to one embodiment of the invention, the diameter of silver is less than or equal to about 20 nanometers.In certain embodiments, the diameter of silver is less than about 10 nanometers, and in other embodiments, the diameter of silver is less than about 5 nanometers, and in some embodiments again, the diameter of silver is less than about 2 nanometers.In a specific embodiments, the diameter of silver is less than about 1 nanometer.In one or more embodiments, this catalyst does not contain silver metal and/or aluminic acid silver substantially.
Another aspect of the present invention relates to the emission treatment systems that is used for waste gas stream, and it comprises the catalyst according to above-mentioned embodiment.According to an embodiment, this emission treatment systems can comprise controller, with the air/fuel ratio in the waste gas stream of regular reduction catalyst upstream.In other embodiments, this controller comprises injector, and at least a reductant metering that this injector regularly will be selected from hydrocarbon fuel, carbon monoxide and the hydrogen adds in the waste gas stream of catalyst upstream, to form rich fuel gas stream.
Can make catalyst be positioned at pottery or honeycomb metal flows through in the type substrate.This emission treatment systems may further include and is positioned at two or more potteries or honeycomb metal flows through suprabasil two or more catalyst of type.In one or more embodiments, this emission treatment systems can further comprise smoke filter, smoke filter, the NO that is selected from diesel oxidation catalyst, catalysis
xTrap, part hydrocarbon oxidation catalyst, sulphur trap, be positioned at suprabasil noble metal catalyst, phosphorus trap and the assembly of one or more combination wherein.
According to one or more embodiments of described emission treatment systems, described catalyst is positioned on the smoke filter and serves as the hydrocarbon SCR catalyst.In one or more embodiments, this smoke filter is a wall-flow filter.According to an embodiment, this smoke filter is a wall-flow filter, comprise arrival end, the port of export and extend to the port of export and define the inwall that surpasses a path from arrival end, the described path that surpasses comprises admission passage side and passing away side, the passage that wherein replaces comprises the admission passage with open inlet and sealing outlet and has open outlet and the passing away of sealing inlet that wherein said catalyst is positioned on the passing away side.A variant as this embodiment, described system can further comprise NSR catalyst and SCR catalyst, described NSR catalyst extends from least a portion distance of the open sealing outlet that enters the mouth from arrival end, and described SCR catalyst extends at least a portion distance that exports to the sealing outlet from open from the port of export.According to an embodiment, existence is positioned at the inlet oxidation catalyst on a part of NSR catalyst with layer form and extends from least a portion distance of the open sealing outlet that enters the mouth from arrival end, and/or exists with layer form and be positioned at the outlet oxidation catalyst on a part of SCR catalyst and extend at least a portion distance that exports to the sealing outlet from open from the port of export.
Another aspect of the present invention relates to the method for preparing catalyst, comprising: the carrier that the aluminium oxide that comprises surface hydroxylation is provided; Flood this carrier with silver compound; With described carrier drying through dipping; With the described carrier of calcining through dipping.This method may further include the gained material is imposed hydrothermal treatment consists.
According to an embodiment, calcining is carried out at about 540 ℃.In another embodiment, carry out in aerial about at least 10% steam of hydrothermal treatment consists.Calcining can be carried out 1 to 48 hour.Hydrothermal treatment consists can be in about 400 ℃ to 700 ℃ temperature, preferably carried out about 1 to 48 hour at about 650 ℃.This processing was carried out about at least 1 hour in containing the air stream of about 10% steam usually, about 16 hours usually.According to one embodiment of the invention, in oxide, silver is with the amount dipping of about 2 weight % to 4 weight %.This dipping can be undertaken by just wet impregnation method.
Those skilled in the art read and understand the as detailed below of these embodiments after can clear find out of the present invention aspect these and other.
The accompanying drawing summary
The present invention can take entity form in some parts and arrangements of components, its embodiment is described in detail and is presented at and constitutes in its a part of accompanying drawing, and wherein:
Fig. 1 be show make according to an embodiment of the present invention, contain 2%, 3%, 4%, 5% and 6% silver (Ag on alumina support
2The figure of the properties of sample O form);
Fig. 2 is the transmission electron micrograph of the sample made according to an embodiment of the present invention; And
Fig. 3 is the transmission electron micrograph of the sample made according to an embodiment of the present invention; And
Embodiment of the present invention describe in detail
Before describing several exemplary embodiments of the present invention, it being understood that to the invention is not restricted to the structure of setting forth in the following description or the details of processing step.The present invention can have other embodiment and can implement in every way.
Exemplary silver-aluminium oxide catalyst comprise load on the aluminium oxide with Ag
2O counts the silver of about 3 to 4 weight %.In one embodiment, by being deposited on the highly hydroxylated aluminium oxide, ionic silver prepares this catalyst.The catalyst cupport of testing in the following example is on the cordierite monolith substrates of 400 hole/square inches.
Therefore, according to one or more embodiments, provide the NO that is used to reduce from exhaust gas from lean burn engines stream
xThe catalyst of emission, it comprises the silver that loads on the aluminium oxide, is to prepare by dipping ionic silver on the alumina support of surface hydroxylation.Term used herein " hydroxylating " is meant in the aluminium oxide that obtains, the surface of aluminium oxide has the surface hydroxyl of high concentration, for example boehmite, pseudobochmite or gel boehmite, diaspore, nordstrandite, bayerite and gibbsite, have the aluminium oxide that adds lip-deep hydroxyl to, and composition thereof.Pseudobochmite and gel boehmite are classified as amorphous or gel-like material usually, and diaspore, nordstrandite, bayerite, gibbsite and boehmite are classified as crystallization usually.According to one or more embodiments of the present invention, hydroxylating aluminium oxide formula Al (OH)
xO
yExpression, wherein x=3-2y and y=0 to 1 or its mark.In their preparation, this class aluminium oxide is removed high-temperature calcination many or the most surfaces hydroxyl without undergoing meeting.
According to one embodiment of the invention, different with acicular particles, the hydroxylating aluminium oxide of the basic amorphous of plain film shape particulate forms can be used for preparing catalyst.The shape of used hydroxylating aluminium oxide is the plain film form in one or more embodiment of the present invention, and has the plain film surface slenderness ratio of 3 to 100 average diameter thickness rate and 0.3 to 1.0.Radius-thickness ratio is meant the ratio of particle " diameter " and " thickness ".Term used herein " diameter " is meant that area equals the diameter of a circle of particle projected area, and it gets by seeing through microscope or transmission electron microscope (TEM) observation hydrated alumina.The minimum diameter on plain film surface and the ratio of maximum gauge when slenderness ratio is meant and observes in the mode identical with radius-thickness ratio.
Can be used for making according to embodiments of the present invention, the hydroxylating plain film shape particulate oxide aluminium of catalyst is known and can buys.Its manufacture method also is known.For example at United States Patent (USP) 5,880,196 and PCT International Application No. WO 97/22476 in the illustrative methods of making pseudobochmite has been described.
Pseudobochmite has the structure of similar boehmite.But x-ray diffraction pattern is made of band of dispersing very much or halo.The spacing of wide reflection roughly is equivalent to the spacing of main line of the figure of crystalline boehmite, but especially, compares with the 0.611 nanometer reflection of 020 line of boehmite, and first reflection demonstrates the numerical value that obviously is displaced to big to 0.66 to 0.67 nanometer usually.Show that although the similar in some aspects boehmite of this structure, order has only very short scope.Those skilled in the art generally acknowledge that usually pseudobochmite is mutually visibly different with boehmite.Referring to Encyclopedia of ChemicalTechnology, the 5th edition, the 2nd volume, Wiley Inter science, 2004, the the 421st to 433 page, No. the 19th, " Oxides and Hydroxides of Aluminum, " Alcoa Technical Paper, Karl Wefers and Chanakya Misra revision, 1987, Copyright AluminumCompany of America.
Perhaps, can handle calcined alumina in the mode of adding surface hydroxyl for example by making aluminium oxide in steam, expose a period of time.In one or more embodiments, the aluminium oxide that is used for the silver dipping does not contain gamma-alumina substantially.Final catalyst after silver dipping, drying, calcining and/or hydrothermal treatment consists can comprise gamma-alumina or other high temperature alumina phase.
In one or more embodiments, the money base on the hydroxylating aluminium oxide does not originally contain silver metal and/or aluminic acid silver." not containing substantially " used herein is meant that silver metal or aluminic acid silver are less than 0.1 weight %." silver metal " used herein is the silver of nulling oxidation state, this means that silver atoms is neither positively charged not electronegative yet.Different with positively charged silver (it also is known as " ionization silver " or " ionic silver "), the oxidation state of the aggregation of zero normally uncharged silver atoms of oxidation state or silver metal.The ionic silver atom has positive charge (+1), and is called as and has+1 oxidation state.Because elemental silver has single electron in its outermost electronic shell, so Ag (I) or Ag
+ 1It is the modal so far oxidation state of ionic silver.If silver atoms is accepted electronics from more electropositive material, it can become electronegative, and is called as and has-1 oxidation state, or anion or anion.
According to one or more embodiments, the silver of this load has the particle mean size less than about 2 nanometers.In other embodiments, this silver-colored granularity is less than about 1 nanometer.
The preparation of carbon monoxide-olefin polymeric
One aspect of the present invention relates to the method for preparing catalyst and carbon monoxide-olefin polymeric.For example, as described belowly flood hydroxylated aluminium oxide with ionic silver.
As mentioned above, suitable aluminium oxide comprises that surface area is the boehmite or the pseudobochmite/gel aluminium oxide of about at least 20 meters squared per gram.According to one or more embodiments, hydroxylated aluminium oxide does not contain gamma-alumina substantially.Water soluble ion form (for example silver acetate, silver nitrate etc.) with silver is flooded hydroxylated aluminium oxide, then low under the temperature that is enough to fixing silver and reduces anions (if possible) with described aluminium oxide drying of being flooded by ionic silver with calcine.Usually, for nitrate, this can be about 450 to 550 ℃, does not contain the aluminium oxide of diameter greater than the silver ion of about 20 nanometers substantially to provide.In certain embodiments, the diameter of silver is less than 10 nanometers, and in other embodiments, the diameter of silver is less than about 2 nanometers.In one or more embodiments, process so that there is and does not exist substantially silver metal in silver with basic ionic species as the UV spectroscopic methodology records.In one or more embodiments, there is not aluminic acid silver substantially.Also confirm not exist silver metal and aluminic acid silver by the X-ray diffraction analytic approach.Behind calcining step, randomly, in aerial 10% steam this catalyst is imposed hydrothermal treatment consists.This hydrothermal treatment consists can be in about 400 ℃ to 700 ℃ temperature, preferably carried out 1 to 48 hour at about 650 ℃.
Ionic silver is well dispersed on the alumina surface.The transmission electron microscope of the sample of making according to an embodiment of the present invention (TEM) the analysis showed that ionic silver has the size less than 2 nanometers, so ionic silver is well dispersed on the aluminium oxide particles surface.
With before the silver dipping with described hydroxylated alumina modified may also be desirable.This can adopt various chemical reagent and/or processing to handle (for example heat or steam treatment method) and realize, to change alumina surface character and/or physical property.This change of aluminium oxide character can improve the performance of catalyst, for example active, stable, silver-colored dispersiveness, anti-agglutinatting property, anti-sulphur and other poisoning property etc.But this processing should proceed to and make the chemical modification of alumina surface can influence silver-aluminium oxide interaction substantially sharply.
Can be by various infusion processes, comprise just wet impregnation method and wet infusion process, with deposition of silver to alumina surface.In wet infusion process, excess solution is mixed with carrier, evaporate excess liq then.Also can pass through other coating technique, for example chemical vapour deposition (CVD) realizes silver-colored deposition.
Emission treatment systems
Emission treatment systems according to one or more embodiments of the present invention can comprise above-mentioned silver-colored NO on aluminium oxide
xReducing catalyst and various other component.For example, the silver catalyst on the aluminium oxide can be comprised in a plurality of materials all in one piece or the substrate, wherein one or more base part or contain silver catalyst on aluminium oxide fully.Should the silver catalyst on aluminium oxide can be the part of following hydrocarbon SCR (HCSCR) system: wherein by engine control system or engine management device provisioning hydrocarbon.Perhaps, silver catalyst that should be on aluminium oxide can be the part of following HC SCR system: wherein by injection apparatus supply hydrocarbon independently.In another embodiment, HC SCR system can have and for example uses PO
xReactor, on-board hydrogen supply or use the compound that when decomposing, discharges hydrogen or complex compound and add hydrogen in the waste gas system to.HC SCR can be provided system, wherein 1% or more reducing agent contain oxygen containing carbon-containing molecules, for example aldehyde, alcohol or carbon monoxide.Above-mentioned NO
xCatalyst can be the part of system that comprises one or more add-on assembles of waste gas system, and described add-on assemble includes but not limited to smoke filter, smoke filter, the NO of diesel oxidation catalyst, catalysis
xTrap, NSR catalyst, part hydrocarbon oxidation catalyst, air pump, external heat device, noble metal catalyst, sulphur trap, phosphorus trap etc.
Emission treatment systems can comprise that above-mentioned silver catalyst on aluminium oxide is to handle NO
xDescribed silver catalyst on aluminium oxide can be positioned at NSR catalyst downstream.Described silver catalyst on aluminium oxide can be the catalyst particle form from supporting, or the honeycomb monolith form that is formed by the SCR carbon monoxide-olefin polymeric.In one or more embodiments, described silver-catalyst composition on aluminium oxide is positioned at pottery or metallic substrates, preferred cellular flowing through in the type substrate as the combination of washcoated layer or washcoated layer.
According to one or more embodiments, in the time of on being deposited on the honeycomb monolith substrate, the silver-catalyst composition of this class on aluminium oxide is with the concentration deposition of at least 1 gram/cubic inch, to guarantee to realize desirable NO
xReduction is also guaranteed the sufficient durability of this catalyst in long-time the use.In one embodiment, have at least 1.6 gram/cubic inch SCR compositions on material all in one piece, particularly at least 1.6 to about 4.0 gram/cubic inch SCR compositions.
Substrate
In one or more embodiments, one or more carbon monoxide-olefin polymerics are positioned in the substrate.This substrate can be any material that is usually used in preparing catalyst, and preferably comprises pottery or metal honeycomb structure.Can use any suitable substrate, the monolith substrates type that for example has thin parallel airflow path, described current path runs through substrate from the inlet or the exit face of substrate, so that path is open (being known as the cellular type substrate of flowing through) for the fluid stream that flows through wherein.These paths (they are the straight substantially paths from its fluid intake to its fluid issuing) are defined by wall, scribble catalysis material on the wall as washcoated layer, contact with catalysis material so that flow through the gas of path.The flow passage of this monolith substrates is a thin-walled channels, and they can have any suitable cross-sectional shape and size, for example trapezoidal, rectangle, square, sinusoidal, hexagon, ellipse, circle etc.This class formation can contain per square inch cross section about 60 to about 600 or more gas access (being hole).
This substrate also can be the wall-flow filter substrate, wherein alternately sealing of passage, so that cross conduit wall from the air flow stream of a direction (Way in) admission passage, and leave this passage from other direction (Way out).NSR and/or SCR carbon monoxide-olefin polymeric can be coated on the wall-flow filter.If adopt this class substrate, particulate matter and gaseous contaminant can be removed by the gained system so.The wall-flow filter substrate can be made by material well known in the art, for example cordierite or carborundum.
Ceramic bases can be made by any suitable refractory material, for example cordierite, cordierite-aluminium oxide, silicon nitride, zirconium mullite, spodumene, alumina silica magnesia, zirconium silicate, sillimanite, magnesium silicate, zircon, petalite, aluminium oxide and alumino-silicate, or the like.
The substrate that can be used for catalyst of the present invention also can be a metalline, and is made of one or more metal or metal alloy.Metallic substrates can be used with different shape, for example corrugated plating or material all in one piece form.Preferred metallic carrier comprises heating resisting metal and metal alloy, for example titanium and stainless steel and be substantially or other alloy of key component with iron.This class alloy can contain one or more in nickel, chromium and/or the aluminium, and the total amount of these metals can advantageously account at least 15 weight % of this alloy, for example aluminium of the chromium of 10 to 25 weight %, 3 to 8 weight % and the most nearly nickel of 20 weight %.This alloy also can contain one or more other metals of a small amount of or trace, for example manganese, copper, vanadium, titanium etc.The surface of metallic substrates can be in oxidation under for example 1000 ℃ and the higher high temperature, with by form the corrosion resistance that oxide layer is improved alloy on substrate surface.The oxidation of this high-temperature induction can strengthen the bonding of refractory metal oxide carriers and catalytic metal component and substrate.
In other embodiments, one or more carbon monoxide-olefin polymerics can be deposited in the open celled foam substrate.This class substrate is as known in the art, and is formed by refractory or metal material usually.
The preparation of washcoated layer
Carbon monoxide-olefin polymeric of the present invention can be easily by method preparation commonly known in the art.Set forth the exemplary process that is used to prepare double-deck washcoated layer below.It being understood that and different embodiments according to the present invention to change following method, prepare the washcoated layer of individual layer, or on the washcoated layer of following bilayer, increase one or more extra plays with the step that applies the second layer by omission.
Can easily catalyst composite be formed on the material all in one piece honeycomb substrates one or more layers.For the washcoated layer of bilayer, with bottom, the slurrying in appropriate excipients (for example water) of the finely-divided particle of high surface refractory metal oxides (for example gamma-alumina).Substrate can be flooded one or many in this class slurry then, maybe this slurry can be coated in the substrate (for example cellular flow through type substrate), so as in this substrate the required carrying capacity of depositing metal oxide.Can in this slurry, mix for example silver metal, noble metal or platinum group metal, transition metal oxide, stabilizing agent, co-catalyst and NO with the form of mixtures of water-soluble or water dispersible compound or complex compound
xThe component of absorbent component and so on.After this, usually by for example heating 1 to 3 hour with applied substrate calcining at 400 to 600 ℃.
In one or more embodiments, this slurry is pulverized, so that basic all solids has average diameter less than 20 microns, 1 to 15 micron granularity for example.Pulverizing can be carried out in ball mill or other similar devices, and this solid content of slurry can be for example 20 to 60 weight %, preferred 35 to 45 weight %.
The further illustration the present invention of the following example, but should not be regarded as limiting by any way its scope certainly.
Embodiment
Preparation of Catalyst
Prepare catalyst by the just wet impregnation technology of the standard of using follow procedure.Use deionized water to prepare the 1M solution of silver nitrate.Gained solution is stored in the dark-colored bottle to avoid light source.Mix simultaneously until realizing initial humidity by the naked carrier of water titration, measure the available pores volume of various carriers.This has obtained the liquid volume of every gram carrier.Use final goal Ag
2O content and every gram carrier available volume are calculated required 1M AgNO
3The amount of solution.If desired, in this silver solution, add deionized water, so that total liquid volume equals support samples is flooded to the required amount of initial humidity.If required AgNO
3The pore volume that the amount of solution surpasses carrier then repeatedly floods.
With suitable AgNO
3Solution slowly adds in the carrier and mixes.After reaching initial humidity, with the gained solid about 90 ℃ of dryings 16 hours, then 540 ℃ of calcinings 2 hours.In each of the embodiments described below, randomly, also make this catalyst 650 ℃ stand aerial about 10% steam mobile flow to less about, about 16 hours usually.
The catalyst evaluation and test
Evaluate and test catalyst performance in two ways.First kind comprises that use contains the microchannel catalytic reactor of about 12.6 cubic millimeters of catalyst beds.Make flow velocity (standard temperature and pressure (STP)) pass through this bed down in different temperatures (150,175,200,225,250,300,350,400,500 ℃), to measure the reactivity of catalyst for the reactant of 15sccm (under the concentration shown in the following table 1)+0.75sccm steam.Use mass spectrometer by the 100 * (NO that sends into
xThe NO of-output
xThe NO that)/(sent into
x) mensuration NO
xConversion ratio.
Table 1
| Material | Concentration |
| NO x | 400ppm |
| O 2 | 10 |
| CO | |
| 2 | 5％ |
| HC(C1) | 4000ppm |
| C1/ |
10 |
| CO | 745ppm |
| H 2 | 245ppm |
| He | Surplus |
| H
2O is expressed as the % of flow of dried |
5％ |
Also 400 holes/cubic inch small cylindrical cordierite material all in one piece (3/4 " diameter * 1.0 " length) dip-coating is coated onto catalyst fines on this material all in one piece in the catalyst water slurry, evaluates and tests catalyst thus by standard technique.Final catalyst loading is generally 2.5 to 3.0 gram/cubic inches.In the following example, under similar carrying capacity and equal air speed, compare catalyst.
Use tubular type to flow through the analysis that the type reactor carries out these properties of sample.Use simulation diesel oil, make the simulated exhaust incoming flow by the Ag-Al catalyst sample on 400 holes/square inch cordierite monolith substrates.This reactor assembly is equipped with suitable sensor, comprises FTIS, enters/leave the NO of SCR catalyst with mensuration
xConcentration level (with other material), and be furnished with flowmeter to measure the waste gas flow velocity that can change into catalyst air speed (SV).Air speed is represented the gas feed speed by volume of per unit volume catalyst, and with hour inverse be the (h of unit
-1).The baseline laboratory condition is included in the following calibrating gas in the simulated exhaust incoming flow: 10%O
2, 5%CO
2, 5%H
2O, 750/1000000ths parts of (hereinafter being called " ppm ") CO and 250ppm H
2For all laboratory reaction device operations, use the simulation diesel fuel mixtures as NO
xReducing agent, described simulation diesel fuel mixtures is made of the volume mixture thing of n-dodecane (67 volume % long-chain alkane) and meta-xylene (33 volume % aromatic compounds).
In all the following example, after calcining, in 10% steam, handled this catalyst 16 hours at 650 ℃.
Embodiment 1
The comparison of pseudobochmite and boehmite
Use commercially available pseudobochmite (
C1,270 meters squared per gram, 0.41cc/g pore volume, 6.1 nanometer average pore sizes, Sasol, North America makes) and boehmite (P200 is from Sasol, 100 meters squared per gram, 0.47cc/g pore volume, 17.9 nanometer average pore sizes) alumina support prepares catalyst.The silver content of final catalyst is with Ag
2O counts 1%.At 400 ℃, NO
xRelative conversion ratio be 1.0 and 0.69.Thus, this pseudobochmite is than active high about 30% of boehmite.
Embodiment 2
Use commercially available boehmite and commercially available pseudobochmite (HiPal 10, can be available from EngelhardCorporation, Iselin, NJ) preparation catalyst.The silver content of final catalyst is with Ag
2O counts 2%.Relative activity at 400 ℃ is presented in the table 2.
Table 2
| Carrier | Relative conversion ratio |
| Pseudobochmite | 1.0 |
| δ/θ aluminium oxide | 0.74 |
| HiPal-10 | 0.81 |
The influence of Ag concentration
By the pseudobochmite carrier with 2,3,4,5 and 6% Ag
2O content prepares silver catalyst.Then that these materials are washcoated to the cordierite material all in one piece, and use simulation diesel oil, 106ppm NO, 8%O
2And C1: N ratio=8 are tested in the laboratory reaction device.Conversion ratio shown in Fig. 1 shows that with respect to the gained figure of temperature 2% catalyst behaves oneself best.
The transmission electron microscope of sample (TEM) is analyzed
Silver with pseudobochmite carrier and 2% and 6% silver oxide form is raw material, by the slice acquisition TEM image of silver catalyst.These two kinds of catalyst are all carried out hydrothermal treatment consists.Sample is to disperse (solvent-free) dry powder form preparation on the Cu carrier grid of lace carbon (lacy carbon) coating.Collect data with the JEOL that under 200Kv, moves 2011 transmission electron microscopes that have the LaB6 filament.Use Gatan 2K CCD camera to collect digital picture.Fig. 2 has shown 2% sample, and Fig. 3 has shown 6% sample.In both cases, silver all so fully disperses consequently not observe silver micro-crystallite.There is not the silver particles of diameter greater than 1 to 2 nanometer.
Specifically the present invention is described with reference to above-mentioned embodiment and variant thereof.Other people can expect other modifications and change in reading with after understanding this specification.The invention is intended to comprise all these classes modification and changes of dropping in the protection domain of the present invention.
Claims (25)
1. be used to reduce NO from exhaust gas from lean burn engines stream
xThe catalyst of emission, it comprises the silver that is dispersed on the aluminium oxide particles, and this silver-colored diameter is less than about 20 nanometers.
2. the catalyst of claim 1, wherein Yin diameter is less than about 10 nanometers.
3. the catalyst of claim 1, wherein this catalyst does not contain silver metal substantially.
4. the catalyst of claim 3, wherein this catalyst does not contain aluminic acid silver substantially.
5. the catalyst of claim 1, wherein said aluminium oxide particles is a sheet, and the diameter of silver is less than about 2 nanometers.
6. the catalyst of claim 1, wherein this catalyst prepares by dipping ionic silver on hydroxylated aluminium oxide particles surface.
The 7. catalyst of claim 6, the aluminium oxide of wherein said surface hydroxylation be selected from boehmite, pseudobochmite or gel boehmite, diaspore, nordstrandite, bayerite, gibbsite, have the aluminium oxide that adds lip-deep hydroxyl to, and composition thereof.
8. the catalyst of claim 6, wherein said hydroxylated aluminium oxide comprises pseudobochmite.
9. the catalyst of claim 8, wherein said pseudobochmite is the platy particle form.
10. the catalyst of claim 1, wherein silver is well dispersed on the aluminium oxide particles.
11. the catalyst of claim 1, wherein the silver-colored carrying capacity on this catalyst is about 2 weight % to 4 weight %.
12. be used for the emission treatment systems of waste gas stream, it comprises the catalyst according to claim 1.
13. be used for the emission treatment systems of waste gas stream, it comprises the catalyst according to claim 11.
14. the emission treatment systems of claim 13, wherein said catalyst are positioned at pottery or honeycomb metal flows through in the type substrate.
15. the emission treatment systems of claim 14, this system comprises and is positioned at second pottery or honeycomb metal flows through suprabasil second catalyst of type.
16. the emission treatment systems of claim 15 further comprises the smoke filter, smoke filter, the NO that are selected from diesel oxidation catalyst, catalysis
xTrap, part hydrocarbon oxidation catalyst, sulphur trap, be positioned at suprabasil noble metal catalyst, phosphorus trap and the assembly of one or more combination wherein.
17. prepare the method for catalyst, comprising:
The carrier of the alumina wafer shape particle that comprises surface hydroxylation is provided;
Flood this carrier with silver compound;
With described carrier drying through dipping; With
Calcine described carrier through dipping.
18. the method for claim 17 further comprises described carrier hydrothermal treatment consists.
19. the method for claim 17 is wherein calcined at about 540 ℃ and is carried out.
20. the method for claim 18 is carried out in aerial about 10% steam of wherein said hydrothermal treatment consists.
21. the method for claim 20, wherein said hydrothermal treatment consists were carried out about at least 1 hour.
22. the method for claim 17, wherein in oxide, silver is with the amount dipping of about 2 weight % to 4 weight %.
23. the method for claim 17, the aluminium oxide of wherein said surface hydroxylation be selected from boehmite, pseudobochmite or gel boehmite, diaspore, nordstrandite, bayerite, gibbsite, have the aluminium oxide that adds lip-deep hydroxyl to, and composition thereof.
24. the method for claim 23, the aluminium oxide of wherein said surface hydroxylation comprises pseudobochmite.
25. the method for claim 17, wherein said catalyst do not contain silver metal and aluminic acid silver substantially, and the diameter of silver is less than about 20 nanometers.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US82626706P | 2006-09-20 | 2006-09-20 | |
| US60/826,267 | 2006-09-20 | ||
| US11/857,896 | 2007-09-19 |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201510018635.9A Division CN104667915A (en) | 2006-09-20 | 2007-09-20 | Catalysts to Reduce NOx in an Exhaust Gas Stream and Methods of Preparation |
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| Publication Number | Publication Date |
|---|---|
| CN101541402A true CN101541402A (en) | 2009-09-23 |
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| ZA (1) | ZA200902623B (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102580728A (en) * | 2011-01-07 | 2012-07-18 | 通用电气公司 | Catalyst and preparation method |
| CN102686841A (en) * | 2009-12-28 | 2012-09-19 | 丰田自动车株式会社 | Exhaust gas purification device for internal combustion engine |
| CN103159242A (en) * | 2011-12-16 | 2013-06-19 | 中国科学院生态环境研究中心 | Preparation method of nordstrandite and purpose thereof |
| CN103952719A (en) * | 2014-03-28 | 2014-07-30 | 中国科学院物理研究所 | Catalyst used for preparation of hydrogen through water electrolysis, and preparation method thereof |
| CN102580728B (en) * | 2011-01-07 | 2016-12-14 | 通用电气公司 | catalyst and preparation method |
| US9687819B2 (en) | 2009-11-24 | 2017-06-27 | General Electric Company | Catalyst and method of manufacture |
-
2007
- 2007-09-20 CN CNA2007800430578A patent/CN101541402A/en active Pending
-
2009
- 2009-04-16 ZA ZA200902623A patent/ZA200902623B/en unknown
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9687819B2 (en) | 2009-11-24 | 2017-06-27 | General Electric Company | Catalyst and method of manufacture |
| CN102686841A (en) * | 2009-12-28 | 2012-09-19 | 丰田自动车株式会社 | Exhaust gas purification device for internal combustion engine |
| US8677735B2 (en) | 2009-12-28 | 2014-03-25 | Toyota Jidosha Kabushiki Kaisha | Exhaust purification system of internal combustion engine |
| CN102580728A (en) * | 2011-01-07 | 2012-07-18 | 通用电气公司 | Catalyst and preparation method |
| CN102580728B (en) * | 2011-01-07 | 2016-12-14 | 通用电气公司 | catalyst and preparation method |
| CN103159242A (en) * | 2011-12-16 | 2013-06-19 | 中国科学院生态环境研究中心 | Preparation method of nordstrandite and purpose thereof |
| CN103952719A (en) * | 2014-03-28 | 2014-07-30 | 中国科学院物理研究所 | Catalyst used for preparation of hydrogen through water electrolysis, and preparation method thereof |
| CN103952719B (en) * | 2014-03-28 | 2017-05-03 | 中国科学院物理研究所 | Catalyst used for preparation of hydrogen through water electrolysis, and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| ZA200902623B (en) | 2010-06-30 |
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Application publication date: 20090923 |