CN1302226A - Zinc aluminate with high specific surface area, preparation method and use for treating motor vehicle exhaust gases - Google Patents

Zinc aluminate with high specific surface area, preparation method and use for treating motor vehicle exhaust gases Download PDF

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Publication number
CN1302226A
CN1302226A CN99806551A CN99806551A CN1302226A CN 1302226 A CN1302226 A CN 1302226A CN 99806551 A CN99806551 A CN 99806551A CN 99806551 A CN99806551 A CN 99806551A CN 1302226 A CN1302226 A CN 1302226A
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aluminate
zinc
hours
specific area
precursor composition
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CN1145524C (en
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C·海杜因
T·希古隆
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Rhodia Chimie SAS
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Rhone Poulenc Chimie SA
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
    • B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/06—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of zinc, cadmium or mercury
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2062—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/208—Hydrocarbons
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/202—Alkali metals
    • B01D2255/2025—Lithium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/206—Rare earth metals
    • B01D2255/2065—Cerium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
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    • B01D2255/20707—Titanium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20792—Zinc
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/209—Other metals
    • B01D2255/2092—Aluminium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/30—Silica
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/012—Diesel engines and lean burn gasoline engines
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • 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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Abstract

The invention concerns a zinc aluminate characterised in that it has, after calcination at 800 DEG C for 8 hours, a specific surface area of at least 85m<2>/g. The invention also concerns a precursor composition of said aluminate. The method for preparing the aluminate and the composition comprises the following steps: contacting in a solvent medium a salt, a zinc sol or alkoxide and an aluminium alkoxide; hydrolyzing the resulting mixture by adding an amount of water in excess relative to the aluminium alkoxide; recuperating the formed precipitate and optionally drying it, thereby obtaining the precursor composition; if required, calcining said precipitate, thereby obtaining the aluminate. Finally, the invention concerns the use of aluminate for treating motor vehicle exhaust gases.

Description

Zinc aluminate with high specific surface area, its preparation method and its purposes in vehicle exhaust is handled
The present invention relates to a kind ofly have the precursor composition of the zinc aluminate of high-specific surface area, described aluminate, described aluminate and described preparation of compositions method and described aluminate in the gas purposes in the processing method of vehicle exhaust particularly.
Known to reducing nitrogen oxide (NO in automobile engine or the factory's exhaust gas discharged x) the main environmental protection problem of discharge capacity formation.In automobile, special use " three-way catalyst ", this catalyst chemical metering ground uses the reducing gases that is present in the mixture.Yet any excessive oxygen all can cause the serious deterioration of catalyst performance.
Yet, though some engines but can give off and contain a large amount of for example tail gas of at least 5% excess of oxygen regularly for example with the diesel engine or the gasoline engine energy fuel saving of lean mixture mode operation.Thereby standard three-way catalyst is for give off NO from these engines xNot effect.And, because it is strict more to have expanded to the automobile after-burning standard of this class engine at present, make to be necessary to limit NO xDischarging.
With regard to these engines, the catalyst based on spinelle form aluminum and zinc had been proposed.Yet, because these catalyst do not have very high specific area when high temperature, therefore must be to they further modifications.At present, promptly can to keep the ability of high surface area when high temperature be might improve aspect of catalyst performance to surface stability.
The spinel-type catalyst that therefore need have high-specific surface area.
For this reason, zinc aluminate of the present invention is characterised in that after 8 hours, it has 85m at least 800 ℃ of quilt calcinings 2The specific area of/g.
The present invention also relates to the precursor composition of zinc aluminate, it is characterized in that comprising the compound of zinc and aluminium, and it can be in quilt calcining back formation zinc aluminate, this aluminate has 85m at least at 800 ℃ after calcining 8 hours 2The specific area of/g.
Another theme of the present invention is aluminate or the above-mentioned type preparation of compositions method, and described method is characterised in that and comprises following step:
-zinc salt is contacted in solvent medium with aluminum alkoxide;
-make the mixture hydrolysis that forms thus by adding the water excessive with respect to aluminum alkoxide;
-reclaim the sediment that forms also randomly to be dried, so obtain precursor composition;
-if desired, with described sediment calcining, so obtain aluminate.
By reading following description and being used to illustrate various concrete but non-limiting example of the present invention, further feature of the present invention, detailed content and advantage can obtain more fully representing.
Aluminate of the present invention is a zinc aluminate.It has the structure ZnAl of spinel-type 2O 4It can be with respect to ZnAl 2O 4Present one or more poor zinc or rich zinc phase form, these satisfy formula Zn mutually 1-xAl 2O 4-δAnd Zn 1+xAl 2O 4+ δ, 0＜x≤0.95 wherein.The relational expression of the numerical value of x below can more particularly satisfying: 0＜x≤0.85,0＜x≤0.8 and 0＜x≤0.5 more particularly.At last, x can satisfy relational expression 0.4≤x≤0.85.Described aluminate also can contain one or more additives.These additives can be selected from the element of periodic table of elements I A, II A, VII A～I B family and be selected from tin, gallium and rare earths.
The periodic table of elements that can reference is the periodic table of elements of publication in " association's communication supplementary issue Frenchifies " No. 1 (in January, 1966).In addition, term " rare earths " refers to yittrium group and the atomic number element between the periodic table of elements of 57～71 (comprising end value).
As VII A family element, more specifically mention manganese; As VIII family element, can mention iron especially; As I B family element, can mention copper and silver especially.
These additives can be present in the aluminate especially as the part substitute of zinc or aluminium.
A feature of aluminate of the present invention is its specific area.Term " specific area " refers to according to periodical " JACS " 60 at the remainder of this specification, 309 (1938) " the ASTM D3663-78 standard that the Brunauer-Emmett-Teller method described in is determined is by the BET specific area of nitrogen adsorption assay.
Even by after the calcining, aluminate of the present invention still has high surface area values under heating up.Therefore, after 8 hours, described specific area is 85m at least 800 ℃ of calcinings 2/ g.Be still after 800 ℃ of calcinings 8 hours, it can be 90m at least 2/ g, more especially 100m at least 2/ g.Can reach 120m at least 2The numerical value of/g.
Because after 2 hours, aluminate of the present invention can have 70m at least 900 ℃ of quilt calcinings 2/ g, 80m at least more especially 2Therefore the specific area of/g even also can keep high described surface area values under higher temperature.In addition, after 6 hours, can observe 50m at least 1000 ℃ of calcinings 2/ g, 70m at least more especially 2The specific area of/g.The surface area that this means this aluminate all is stable in very wide temperature range.The numerical value that has just provided above is applicable to the situation of calcining in air.In addition, notice that aluminate of the present invention has high ageing resistace.This means that under specific calcination condition its specific area changes less.Therefore, has 10vol%H at 1000 ℃ 2The H of O 2O/N 2Calcining is after 6 hours in the medium, and its surface area keeps identical basically with resulting surface area uniform temp is calcined the identical time in atmosphere after, i.e. 50m at least 2/ g.For having 10vol%H 2O and 10vol%O 2O 2/ H 2O/N 2Calcine in the medium, obtain identical result.
In addition, aluminate of the present invention can have the pore volume of 0.6ml/g at least, and this porosity is measured by mercury intrusion porosimetry.The powder that uses Micromeretics Auto Pore 9220 instruments that the degassing in 200 ℃ of heated oven is spent the night is tested.Operating parameter is as follows: the penetrometer constant: 21.63, and the capillary volume: 1.1, contact angle: 140 °.Porosity can be more especially 2ml/g at least, for example between 2.5～3.5ml/g.
The present invention also relates to the precursor composition of above-mentioned aluminate.
Said composition comprises zinc compound and aluminium compound and also comprises the compound of above-mentioned additive if desired.The principal character of described precursor composition is that it forms the ability of zinc aluminate after by calcining.The above-mentioned calcining heat that forms aluminate is about 500 ℃.In addition, thus obtained aluminate has the feature that provides above, that is to say, if calcined 8 hours 800 ℃ temperature, it keeps 85m at least 2/ g, 90m at least more especially 2/ g and 100m at least more specifically 2The high-specific surface area of/g.Certainly, with respect to the aluminate under 800 ℃ and 900 ℃ of temperature, all surface product value that provides above also all is fit to here.
The preparation method of described aluminate and its precursor composition is described below.
The first step of described method comprises a kind of zinc salt, colloidal sol or alcoxylates is contacted in solvent medium with aluminum alkoxide, optional salt, colloidal sol or the alcoxylates that adds at least a above-mentioned additive.The salt of zinc salt or alcoxylates and additive or alcoxylates must dissolve in the solvent medium.The salt of zinc salt or additive for example is inorganic salts such as nitrate or chloride, or organic salt such as citrate, oxalates or acetate.Aluminum alkoxide can for example be ethoxylate, butoxy thing or isopropoxy thing.
It is soluble any medium that solvent medium is selected from wherein zinc salt or alcoxylates and aluminum alkoxide.Usually, use alcoholic solvent.As alcoholic solvent, can mention the saturated monohydroxy alcohol class, and more especially have short chain (C at the most for example 8) those, for example methyl alcohol, ethanol, propyl alcohol and butanols.Also may use undersaturated alcohols and polyalcohols, for example ethylene glycol, propane diols, hexylene glycol, propane diol and butanediol.Also can use for example acetylacetone,2,4-pentanedione of ketone.
Can by any way reactant be contacted with solvent medium.Yet, according to a particular of the present invention, by will be in solvent medium promptly in this medium in advance the zinc salt of dissolving join in the aluminum alkoxide as raw material, zinc salt is contacted with aluminum alkoxide.
Here notice, become example according to of the present invention another, might be with thus obtained mixture heating.This makes the easier dissolving of salt and make and to control follow-up hydrolysis and settling step better.
Second step of the inventive method is the mixture hydrolysis that will be obtained by preceding step.
Be hydrolyzed by in described mixture, adding entry.According to a feature of the inventive method, be hydrolyzed by using the water excessive with respect to aluminum alkoxide.The described excessive H that passes through 2The mole of O/ aluminum alkoxide is recently determined.Usually, this ratio can be at least 6, more especially at least 10 and even more especially at least 20.Yet under the preparation situation of poor zinc aluminate, this ratio can be lower.More specifically, Zn/Al than preparation situation less than 0.4 aluminate under, H 2The mol ratio of O/ aluminum alkoxide can be at least 3, more especially at least 4.
Can provide water with the form of water-alcohol mixture, alcohol might especially be selected from above with respect to solvent medium described those.Can mention ethanol more especially.
Hydrolysis causes the sediment of element to form.
By any known method centrifugal process particularly, the gained sediment is separated with reactant mixture.
If desired, can washing precipitate.
Be determined on a case-by-case basis, then can dry sediment.
At this moment, obtain precursor composition of the present invention.Prepare aluminate by temperature lower calcination sediment (precursor composition) at least 500 ℃.
If this aluminate or precursor comprise the above-mentioned type additive, then can mention another preparation method of aluminate of the present invention or precursor.This method is: be not in the aluminate building-up process, but by the sediment that for example dry sediment of dipping or precursor composition or aluminate itself are promptly calcined, add additive.Provide the salting liquid of the additive of type above for example using, flood.
More special use dry method dipping.Dry method dipping is to add the element aqueous solution of certain volume in the product that will flood, this volume equals the pore volume of the solid that will flood.
In addition, the present invention relates to a kind of processing method of vehicle exhaust, wherein use the catalyst system and catalyzing that comprises above-mentioned aluminate.
The present invention also relates to a kind of catalyst system and catalyzing that uses this aluminate that wherein comprises handles and may contain the gas of nitrogen oxide so that reduce the method for the discharging of these nitrogen oxide.
In this case, gas that can be processed for example is from those of the boiler of gas turbine, thermo-power station or internal combustion engine.Under the situation of back, these especially can be diesel engines or with the engine of lean mixture mode operation.
Therefore aluminate of the present invention is used to the processing of the gas that has elevated oxygen level and contain nitrogen oxide, so that reduce the discharging of these oxides.Term " gas with elevated oxygen level " refers to for the required amount of chemistry of fuel metering combustion, and the gas with excess of oxygen more properly is the gas that fixedly has excess of oxygen with respect to stoichiometric number λ=1.Numerical value λ with especially in field of internal combustion engine known mode itself and air/fuel than relevant.In other words, aluminate of the present invention is used for from aforementioned type and is making λ always strictly greater than the processing of the gas of the system of moving under 1 the condition always.Under the situation of gas with elevated oxygen level, aluminate of the present invention is used on the one hand from a kind of operation and have a processing of the gas of the engine of oxygen content (representing with volume) between 2.5～5% usually under the lean mixture pattern, on the other hand, be used to have in addition the gas of higher oxygen content for example from the gas of diesel version engine, promptly has oxygen content at least 5% or greater than 5%, more especially at least 10%, the processing of the gas that this content for example might be between 5～20%.
It can be the reducing agent of one or more hydro carbons that described gas contains, and one of reaction that needs catalysis in this case is HC (hydro carbons)+NO xReaction.
Can be used as reducing agent and be used to eliminate NO xHydro carbons especially from following gas or liquid: saturated hydrocarbons, olefin(e), alkyne series, aromatic hydrocarbon and petroleum distillate hydro carbons be methane, ethane, propane, butane, pentane, hexane, ethene, propylene, acetylene, butadiene, benzene,toluene,xylene, kerosene and gas-oil for example.
Described gas also can contain the oxygen-containing organic compound as reducing agent.These compounds especially can be alcohols, for example saturated alcohols such as methyl alcohol, ethanol or propyl alcohol; Ethers is methyl ether or ether for example; The ester class is methyl acetate and ketone for example.
Described gas also can contain ammonia as reducing agent.
In the application of gas treatment, aluminate can be used to take various forms as in various sizes particle, bead, column or the cellular carbon monoxide-olefin polymeric, these compositions might comprise aluminate of the present invention on any carrier of using always in catalytic field, and described carrier for example is ZrO 2, Al 2O 3, TiO 2, CeO 2, SiO 2Or its mixture.
The present invention also relates more specifically to be used for the catalyst system and catalyzing of above-mentioned gas processing method.Described system is characterised in that and comprises the aluminate that is on the matrix.This system generally comprises the wash coat of having introduced aluminate and the carrier of the above-mentioned type, and wash coat is deposited on the matrix, for example metal or ceramic integral type matrix.
In vent gas treatment is used, in a known way described system is installed in the automobile exhaust pipe.
At last, the present invention also relates to for example above-mentioned aluminate or the precursor composition purposes in the preparation catalyst system and catalyzing.Provide embodiment below.
Embodiment 1
This embodiment relates to ZnAl 2O 4Preparation.
Raw material below using:
99% purity Zn (NO of-crystallization 3) 26H 2O, molecular weight: 297.47
Tri sec-butoxy aluminum (the C of-97% purity 2H 5CH 2CH 2O) 3Al
The hexylene glycol of-99% purity (2-methyl-2,4-pentanediol)
-absolute ethyl alcohol, molecular weight: 46.07; D:0.79g/cm 3
The 1.25mol zinc salt is dissolved in 1 liter of hexylene glycol.Once and under brute force stirs (500rpm) joins in the 2.5mol tri sec-butoxy aluminum that is incorporated in advance in the reactor with this solution.Mixture is heated to 70 ℃ and kept 2 hours under this temperature.Then the speed of dividing with 5ml/ adds entry/ethanol (volume ratio is 50/50) mixture.The ratio of water/tri sec-butoxy aluminum is 28.With mixture cool overnight under agitation.By the separating obtained sediment of centrifugal process.Sediment was become skim in 48 hours at 70 ℃ of oven dryings.At last, calcined product.Temperature rise is 5 ℃/minute.The then numerical value that in the following time, temperature constant is provided below.
After 6 hours, the specific area of product is 136m 600 ℃ of calcinings 2/ g.
After 6 hours, the specific area of product is 125m 700 ℃ of calcinings 2/ g.
After 8 hours, the specific area of product is 115m 800 ℃ of calcinings 2/ g.
After 2 hours, the specific area of product is 101m 900 ℃ of calcinings 2/ g.
After 2 hours, the specific area of product is 76m 1000 ℃ of calcinings 2/ g was 53m after under the same temperature 6 hours 2/ g.
At 1000 ℃ at H with 10vol% water 2O/N 2Calcining is after 6 hours in the mixture, and surface area is 53m 2/ g.Have 10vol% water and 10vol%O at 1000 ℃ 2O 2/ H 2O/N 2Calcining obtained identical result after 6 hours in the medium.
Embodiment 2
With the sediment that obtains among the embodiment 1 70 ℃ of dryings 48 hours.Then, it is used the SnCl that is dissolved in the ethanol 22H 2The O solution impregnation.Used technology is the dry method dipping.The Sn deposition is 1.6wt% with respect to the zinc aluminate oxide.The product of gained is in 110 ℃ of baking ovens dry 2 hours and 8 hours (temperature rise rate is 5 ℃/minute) of 800 ℃ of calcinings thus.
The specific area of the product of gained is 115m thus 2/ g.
Embodiment 3
This embodiment relates to ZnAl 1.8Ga 0.2O 4Preparation.
Use with embodiment 1 in identical raw material, 1.807mol/l Ga (NO in addition in addition 3) 3Solution, d=1.365g/cm 3
The 1.25mol zinc salt is dissolved in 1 liter of hexylene glycol, adds the 0.25mol gallium nitrate then.
(500rpm) joins this solution in the 2.25mol tri sec-butoxy aluminum that is incorporated in advance in the reactor under brute force stirs.Mixture is heated to 70 ℃ and kept 2 hours under this temperature.Then the speed of dividing with 5ml/ adds entry/ethanol (volume ratio is 50/50) mixture.The ratio of water/tri sec-butoxy aluminum is 25.With mixture cool overnight under agitation.By the separating obtained sediment of centrifugal process.The sediment that obtains was become skim in 48 hours 70 ℃ of dryings, then 8 hours (temperature rise speed is 5 ℃/minute) of 800 ℃ of calcinings.
The specific area of products therefrom is 113m thus 2/ g.
Embodiment 4
This embodiment relates to Zn 0.95Ca 0.05Al 2O 4Preparation.
Use with embodiment 1 in identical raw material, the Ca (NO of 98% purity in addition in addition 3) 24H 2The solution of O.
The 1.19mol zinc salt is dissolved in 1 liter of hexylene glycol, adds 0.06mol calcium nitrate then.
(500rpm) joins this solution in the 2.5mol tri sec-butoxy aluminum that is incorporated in advance in the reactor under brute force stirs.Mixture is heated to 70 ℃ and kept 2 hours under this temperature.Then the speed of dividing with 5ml/ adds entry/ethanol (volume ratio is 50/50) mixture.The ratio of water/tri sec-butoxy aluminum is 28.With mixture cool overnight under agitation.By the separating obtained sediment of centrifugal process.The sediment that obtains was become skim in 48 hours 70 ℃ of dryings, then 8 hours (temperature rise speed is 5 ℃/minute) of 800 ℃ of calcinings.
The specific area of products therefrom is 119m thus 2/ g.
Embodiment 5
This embodiment relates to Zn 0.95Li 0.05Al 2O 4Preparation.
Use with embodiment 1 in identical raw material, the Li (NO of 99% purity in addition in addition 3) solution.
The 1.19mol zinc salt is dissolved in 1 liter of hexylene glycol, adds the 0.06mol lithium nitrate then.
(500rpm) joins this solution in the 2.5mol tri sec-butoxy aluminum that is incorporated in advance in the reactor under brute force stirs.Mixture is heated to 70 ℃ and kept 2 hours under this temperature.Then the speed of dividing with 5ml/ adds entry/ethanol (volume ratio is 50/50) mixture.The ratio of water/tri sec-butoxy aluminum is 28.With mixture cool overnight under agitation.By the separating obtained sediment of centrifugal process.The sediment that obtains was become skim in 48 hours 70 ℃ of dryings, then 8 hours (temperature rise speed is 5 ℃/minute) of 800 ℃ of calcinings.
The specific area of products therefrom is 108m thus 2/ g.
Embodiment 6
This embodiment relates to and comprises the formula ZnAl of silver as additive 2O 4Shown in aluminate.
With the sediment of gained among the embodiment 1 70 ℃ of dryings 48 hours.Then, it is used AgNO 3(99.8%) solution impregnation.Used technology is the dry method dipping.The deposition of silver is 1.6wt% with respect to the zinc aluminate oxide.Products therefrom is 110 ℃ of oven dryings 2 hours, then 8 hours (temperature rise rate is 5 ℃/minute) of 800 ℃ of calcinings thus.
The specific area of products therefrom is 90m thus 2/ g.
Embodiment 7
According to the method operation of embodiment 1, so that preparation has the zinc aluminate of different Zn/Al ratios.Use identical raw material according to required ratio.For product 7-1～7-3, H 2The mol ratio of O/ aluminum alkoxide is 28.For product 7-4～7-6, this ratio is 4.The feature of the product of preparation is as follows.
Product Chemical formula Specific area (following 8 hours) at 800 ℃, m 2/g
??7-1 ??Zn 1.05Al 2O 4 ????88
??7-2 ??Zn 0.95Al 2O 4 ????92
??7-3 ??Zn 0.8Al 2O 4 ????140
??7-4 ??Zn 0.6Al 2O 4 ????102
??7-5 ??Zn 0.4Al 2O 4 ????139
??7-6 ??Zn 0.3Al 2O 4 ????110
Embodiment 8
In this embodiment, the product that obtains among the test front embodiment is so that estimate their catalytic performance.
The 0.2g catalyst fines of in quartz reactor, packing into.Used powder is pre-compacted, and grinds then and sieves, so that isolate the particle of particle size range between 0.125～0.250mm.
The reactant mixture that enters into reactor has following composition (volume):
-NO=300ppmv
-C 3H 6=150ppmv or 450ppmv
-C 3H 8=150ppmv or 450ppmv
-CO=350ppmv
-O 2=10％
-CO 2=10％
-H 2O=10％
-N 2=in right amount to 100%
Overall flow rate is 30Nl/h.
HSV is about 200,000h -1
Recording occurring continuously HC (C 3H 6+ C 3H 8), NO and NO x(NO x=NO+NO 2) temperature of signal and reactor.
Utilize spark ionization to detect principle, provide the HC signal by total HC Beckman detector.
By Ecophysics NO based on chemiluminescence principle xAnalyzer provides NO and NO xSignal: provide NO, NO xAnd NO 2Numerical value, the latter is by NO xCalculate with the difference of NO signal.
In the process with 150～700 ℃ of 15 ℃/minute speed temperature programmings, catalytic activity is by HC, NO and NO as the function of temperature xSignal and following equation are measured:
The conversion degree (%) of-NO (TNO) is provided by following:
T(NO)=100(NO 0-NO)/NO 0
NO wherein 0Be the NO signal when time t=0, it is equivalent to the NO signal that obtained by the reactant mixture through the catalytic reactor bypass, and NO is the NO signal when time t.
The conversion degree (%) of-HC (THC) is provided by following:
T(HC)=100(HC 0-HC)/HC 0
HC wherein 0Be the HC signal when time t=0, it is equivalent to the HC signal that obtained by the reactant mixture through the catalytic reactor bypass, and HC is the HC signal when time t.
-NO x(TNO x) conversion degree (%) provide by following:
T(NO x)=100(NO x 0-NO x)/NO x 0
NO wherein x 0Be the NO when time t=0 xSignal, it is equivalent to the NO that obtained by the reactant mixture through the catalytic reactor bypass xSignal, NO xBe the NO when time t xSignal.
Below table 1 provided the result who obtains by at 8 hours the product of embodiment 1 of 800 ℃ of calcinings, and be used for reactant mixture, NO=300ppmv wherein, C 3H 6=C 3H 8=150ppmv, i.e. HC 1/ NO ratio is 3 (HC 1Representing with carbon number, promptly is 6 * 150/300 here).
Table 1
Temperature (℃) ????THC ????(％) ????TNO ????(％) ????TNO x????(％)
????350 ????0.6 ????1.1 ????1.3
????400 ????1 ????2.1 ????2
????450 ????6 ????8.8 ????7.9
????500 ????24.8 ????23.3 ????23.7
????550 ????46.4 ????44.5 ????44.3
????600 ????75.6 ????59.5 ????59.4
????650 ????99 ????28 ????25.8
Following table 2 has provided the result who is obtained by the product at 8 hours embodiment 1 of 800 ℃ of calcinings, NO=300ppmv in the reactant mixture, C 3H 6=C 3H 8=450ppmv, i.e. HC 1/ NO ratio is 9.
Table 2
Temperature (℃) ????THC ????(％) ????TNO ????(％) ????TNO x????(％)
????350 ????0.8 ????0.2 ????1.4
????400 ????1.8 ????0 ????1.4
????450 ????7.5 ????4.8 ????6.2
????500 ????29 ????32.1 ????32.8
????550 ????50.9 ????71.5 ????70.9
????600 ????71.9 ????87.9 ????86.4
????650 ????95 ????69 ????63.9
Below table 3 provided the result who obtains by at 2 hours the product of embodiment 1 of 900 ℃ of calcinings, in the reactant mixture identical with embodiment 1, HC 1/ NO ratio is 3.
Table 3
Temperature (℃) ????THC ????(％) ????TNO ????(％) ????TNO x????(％)
????350 ????0.3 ????0 ????0
????400 ????0.7 ????0 ????0
????450 ????2.1 ????1.2 ????2
????500 ????10.5 ????11 ????11.3
????550 ????3.1 ????28.2 ????28.5
????600 ????68.6 ????52.6 ????52.9
????650 ????97.9 ????28.7 ????27.5
Below table 4 provided the result who obtains by at 2 hours the product of embodiment 1 of 1000 ℃ of calcinings, in the reactant mixture identical with embodiment 1, HC 1/ NO ratio is 3.
Table 4
Temperature (℃) ????THC ????(％) ????TNO ????(％) ????TNO x????(％)
????350 ????0 ????0 ????0
????400 ????0 ????0 ????0
????450 ????1.3 ????1.5 ????1.2
????500 ????9.4 ????12.5 ????12.2
????550 ????34.1 ????37.6 ????37.5
????600 ????80.9 ????51.7 ????51.2
????650 ????100 ????21.5 ????18.3
Below table 5 provided the result who obtains by at 2 hours the product of embodiment 2 of 800 ℃ of calcinings, in the reactant mixture identical with first kind of situation of the product of embodiment 1, i.e. HC 1/ NO ratio is 3.
Table 5
Temperature (℃) ????THC ????(％) ????TNO ????(％) ????TNO x????(％)
????350 ????0 ????2.2 ????2.6
????400 ????0.9 ????3.3 ????3.7
????450 ????5.6 ????10.9 ????11.2
????500 ????25 ????32 ????32.2
????550 ????49 ????38.4 ????38.1
????600 ????63.3 ????31.1 ????28.6
????650 ????87.4 ????26.8 ????21.2
Following table 6 has provided the result who is obtained by the product at 2 hours embodiment 2 of 800 ℃ of calcinings, in the reactant mixture, and NO=300ppmv, C 3H 6=C 3H 8=450ppmv, i.e. HC 1/ NO ratio is 9.
Table 6
Temperature (℃) ????THC ????(％) ????TNO ????(％) ????TNO x????(％)
????350 ????2.6 ????1.3 ????1.3
????400 ????6.1 ????3.8 ????3.2
????450 ????13.9 ????12.5 ????12.4
????500 ????35.1 ????47.3 ????47.3
????550 ????55.4 ????54.4 ????54.1
????600 ????71.8 ????42 ????41.7
????650 ????96.7 ????31.9 ????29.8
Following table 7 has provided the result who is obtained by the product at 2 hours embodiment 7 of 800 ℃ of calcinings, and is used for HC 1The ratio of/NO is in 3 the reactant mixture.In addition, in 100mgSiC, the consumption of product is the 100mg powder.
Table 7
Temperature (℃) ????THC ????(％) ????TNO ????(％) ????TNO x????(％)
????350 ????2.6 ????2.1 ????2.6
????400 ????2.9 ????1.4 ????2.1
????450 ????4.8 ????4.2 ????4.2
????500 ????21.1 ????26.6 ????26.2
????550 ????63 ????46.4 ????45
????600 ????90 ????34.5 ????30.1
????650 ????98.9 ????24.5 ????7
Below table 8 provided by the maximum %NO of product gained at 2 hours embodiment 8 of 800 ℃ of calcinings xValue and corresponding temperature, and be used for HC 1The ratio of/NO is in 3 the reactant mixture.In addition, in 100mg SiC, the consumption of product is the 100mg powder.
Table 8
Product ????％NO xAnd temperature
????7-3 ????35％????620?℃
????7-4 ????38％????625?℃
????7-5 ????42％????600℃
????7-6 ????46％????600?℃

Claims (20)

1, zinc aluminate is characterized in that 800 ℃ of quilt calcinings it has 85m at least after 8 hours 2The specific area of/g.
2, the zinc aluminate of claim 1 is characterized in that 800 ℃ of quilt calcinings it has 100m at least after 8 hours 2The specific area of/g.
3, each zinc aluminate in the top claim is characterized in that 900 ℃ of quilt calcinings it has 70m at least after 2 hours 2/ g, 80m at least more especially 2The specific area of/g.
4, each zinc aluminate in the top claim is characterized in that 1000 ℃ of quilt calcinings it has 50m at least after 6 hours 2/ g, 70m at least more especially 2The specific area of/g.
5, each zinc aluminate in the top claim is characterized in that having 10vol%H 2The H of O 2O/N 2In the medium, after 6 hours, it has 50m at least 1000 ℃ of quilt calcinings 2The specific area of/g.
6, each zinc aluminate in the top claim is characterized in that comprising at least a additive that is selected from the element of periodic table of elements I A, II A, VII A～I B family and is selected from tin, gallium and rare earths.
7, the precursor composition of zinc aluminate is characterized in that comprising zinc compound and aluminium compound, and it is characterized in that and can formed zinc aluminate by the calcining back, and this aluminate is had at least 85m by calcining after 8 hours at 800 ℃ 2The specific area of/g.
8, the composition of claim 7 is characterized in that and can formation have 90m at least after 800 ℃ of quilts are calcined 8 hours 2/ g, 100m at least more especially 2The aluminate of/g specific area.
9, claim 7 or 8 composition is characterized in that also comprising at least a compound that is selected from periodic table of elements I A, II A, VII A～I B family and is selected from the element of tin, gallium and rare earths.
10, the preparation method of each precursor composition in each aluminate or the claim 7～9 in the claim 1～6 is characterized in that comprising following step:
-with zinc salt, colloidal sol or alcoxylates, aluminum alkoxide with randomly salt, colloidal sol or the alcoxylates of at least a above-mentioned additive add in the solvent medium;
-make the mixture hydrolysis that forms thus by adding the water excessive with respect to aluminum alkoxide;
-reclaim the sediment that forms also randomly to be dried, so obtain precursor composition;
-if desired, with described sediment calcining, so obtain aluminate.
11, comprise claim 6 additive aluminate or comprise the preparation method of precursor composition of compound of the element of claim 9, it is characterized in that comprising following step:
-zinc salt, colloidal sol or alcoxylates are contacted in solvent medium with aluminum alkoxide;
-make the mixture hydrolysis that forms thus by adding the water excessive with respect to aluminum alkoxide;
-reclaim the sediment that forms also randomly to be dried, so obtain precursor composition;
-if desired, with described sediment calcining, so obtain aluminate;
-with precursor composition or aluminate salt solution impregnation with additive or above-mentioned element.
12, claim 10 or 11 method is characterized in that alcoholic solvent is used as solvent medium.
13, claim 10,11 or 12 method is characterized in that adding the water of water-alcohol mixture form.
14, each method in the claim 10～13 is characterized in that by add the zinc salt that is in the solvent medium in aluminum alkoxide zinc salt being contacted with aluminum alkoxide.
15, each method in the claim 10～14 is characterized in that sediment is at least 500 ℃ temperature lower calcination.
16, be used to reduce the gas processing method of discharged nitrous oxides, it is characterized in that using the catalyst system and catalyzing that comprises each aluminate in the claim 1～6.
17, the processing method of vehicle exhaust is characterized in that using the catalyst system and catalyzing that comprises each aluminate in the claim 1～6.
18, from the processing method of the gas of automobile, it is characterized in that using the catalyst system and catalyzing that comprises each aluminate in the claim 1～6, described gas has high oxygen content.
19, be used to implement the catalyst system and catalyzing of claim 16,17 or 18 method, it is characterized in that comprising in the claim 1～6 that is on a kind of matrix each aluminate.
20, in the claim 1～6 in each aluminate or the claim 7～9 each precursor composition the preparation claim 19 catalyst system and catalyzing aspect purposes.
CNB99806551XA 1998-05-26 1999-05-21 Zinc aluminate with high specific surface area, preparation method and use for treating motor vehicle exhaust gases Expired - Fee Related CN1145524C (en)

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FR9806610A FR2779071B1 (en) 1998-05-26 1998-05-26 ZINC ALUMINATE WITH HIGH SPECIFIC SURFACE, PREPARATION METHOD THEREOF AND USE THEREOF IN THE TREATMENT OF AUTOMOTIVE EXHAUST GASES
FR98/06610 1998-05-26

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