WO2013121636A1 - 卑金属を利用する排ガス浄化触媒システムとその制御方法 - Google Patents
卑金属を利用する排ガス浄化触媒システムとその制御方法 Download PDFInfo
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- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/54—Nitrogen compounds
- B01D53/56—Nitrogen oxides
- B01D53/565—Nitrogen oxides by treating the gases with solids
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- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
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- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
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- 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
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- 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
- B01D53/9431—Processes characterised by a specific device
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- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
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- B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
- B01J23/8933—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/894—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
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- B01D2251/2062—Ammonia
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- B01D2255/20746—Cobalt
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D2255/00—Catalysts
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- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/90—Physical characteristics of catalysts
- B01D2255/904—Multiple catalysts
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/40—Nitrogen compounds
- B01D2257/404—Nitrogen oxides other than dinitrogen oxide
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2510/00—Surface coverings
- F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
- F01N2510/068—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings
- F01N2510/0682—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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- F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
- F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
- F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
Definitions
- the present invention relates to an exhaust gas purification catalyst system using a base metal as a catalyst metal, and a control method thereof.
- an exhaust gas purifying catalyst is used in an internal combustion engine.
- this exhaust gas purification catalyst in order to efficiently remove hydrocarbons (hereinafter sometimes abbreviated as HC), CO and nitrogen oxides (hereinafter also abbreviated as NOx) in the exhaust gas.
- HC hydrocarbons
- CO carbon oxides
- NOx nitrogen oxides
- Various catalysts including platinum group elements such as Pt, Pd and Rh are used as catalyst components.
- Conventionally known noble metal catalysts are capable of decomposing HC, CO, and NOx in the vicinity of stoichiometry, but all have the problem of resource depletion, and other metals are used in the same manner as conventional noble metal catalysts. There is a need for a catalyst having a purification performance of a degree or more, or a purification catalyst capable of reducing the amount of noble metal used.
- Patent document 1 is a method for reducing nitrogen oxides in exhaust gas to nitrogen, comprising passing through a catalyst system including at least two catalyst beds in the presence of a reducing agent, wherein the first catalyst The above process is described wherein the bed is iron-beta-zeolite and the downstream second catalyst bed is silver supported on alumina.
- Reference 2 discloses an internal combustion engine that performs combustion at an air-fuel ratio smaller than the stoichiometric air-fuel ratio, a first catalyst provided in an exhaust path that discharges combustion gas from the internal combustion engine, and the first catalyst in the exhaust path.
- a secondary air introduction device that introduces secondary air into a portion between the first catalyst and the second catalyst in the exhaust path, with a second catalyst provided downstream of the first catalyst
- Each of the first catalyst and the second catalyst includes a noble metal component including at least one of Pt, Rh, Pd, and Au, and the first catalyst further includes a zeolite support,
- a saddle-ride type vehicle including Co or Fe supported on the zeolite carrier in a larger amount than that capable of ion exchange is described.
- the cited document 3 discloses a first catalyst device that is disposed in an exhaust passage of an internal combustion engine to purify harmful components in exhaust gas, and an exhaust gas that is disposed in the exhaust passage on the upstream side of the first catalyst device.
- a first exhaust concentration sensor having an output characteristic substantially proportional to the gas concentration, an operating state detecting means for detecting an operating state of the engine including at least an engine speed and an engine load state, and detection of the operating state detecting means
- the output signal is inverted in the vicinity of the first target air-fuel ratio calculating means for calculating the target air-fuel ratio based on the result and the target air-fuel ratio disposed in the exhaust passage on the downstream side of the first catalyst device.
- a second exhaust concentration sensor Detected by a second exhaust concentration sensor, enrichment means for setting the target air-fuel ratio to be slightly richer than the theoretical air-fuel ratio based on the output value of the second exhaust concentration sensor, and the first exhaust concentration sensor Mixed Control means for performing feedback control of the air / fuel ratio of the gas to the target air / fuel ratio set by the enrichment means, and a second catalyst device is disposed in the exhaust passage downstream of the second exhaust concentration sensor. And a secondary air supply means for supplying secondary air into the exhaust passage upstream of the second catalyst device and downstream of the second exhaust concentration sensor.
- a gold alloy catalyst characterized in that the solid solution amount of Au in the alloy is 20 to 80% by weight, M: Pt, Pd, Ag, Cu, Ni (Claim 4) 1) is described.
- base metal is used in the catalyst, base metal is more easily oxidized than noble metals such as Pt, Pd, Rh, etc., so that rich control is required to reduce the oxygen concentration in the exhaust gas, resulting in improved fuel efficiency. Often worsened.
- a system for adding a reducing agent such as NH 3 + H 2 is required. For example, a tank for the reducing agent is installed. There was a need to do.
- the inventors of the present invention dared to purify NOx by actively generating NH 3 in the exhaust gas, and thus a catalyst capable of actively generating NH 3 with the first stage catalyst.
- the present inventors have found that the above problem can be solved by using a control method that can effectively generate NH 3 while minimizing deterioration in fuel consumption.
- the present inventors have found that the first stage catalyst and actively catalyst that can generate NH 3, using a catalyst capable of adsorbing NH 3 in the second stage catalyst, momentarily to a rich state, the air It has been found that even if the catalyst is introduced, not only NH 3 but also HC and CO can be effectively purified by the second stage catalyst, and a catalyst having a high NOx purifying ability can be provided even when it is weakly rich, thereby solving the above problems. .
- An exhaust gas purification catalyst system comprising a first stage base metal catalyst located on the upstream side and a second stage base metal catalyst located on the downstream side,
- the first-stage base metal catalyst comprises Cu metal and / or Cu oxide supported on at least one oxide support selected from the group consisting of alumina, ceria, zirconia, yttria, titania,
- An exhaust gas purification catalyst system that switches the state of exhaust gas from weak rich to rich when the amount of NOx in the exhaust gas exceeds the NOx criteria.
- the exhaust gas purification catalyst system according to (2) wherein the oxide carrier of the first stage base metal catalyst is fine particles of a mixture of alumina, ceria, zirconia and yttria.
- the second stage base metal catalyst is selected from the group consisting of Cu, Fe, Co, and Ce on one or more oxide carriers selected from the group consisting of alumina, zirconia, titania, and zeolite.
- the embodiment according to the present invention can purify NOx with high efficiency while using base metals. Furthermore, the oxidation performance is dramatically improved, and the HC purification rate of the second stage catalyst can be dramatically improved.
- the catalyst for generating NH 3 according to the present invention and improving the control method so that the catalyst can generate NH 3 most efficiently, the rich operation time in the entire system can be reduced and used during control. The amount of fuel consumed can be reduced.
- the NH 3 produced in the first stage catalyst is retained in the second stage catalyst by the catalyst according to one embodiment of the present invention, so that N 2 O and NO x can be selectively prevented by the prior art. It can oxidize HC and CO while achieving reduction.
- FIG. 1 is a diagram specifically illustrating an exhaust gas purification catalyst system according to an aspect of the present invention.
- FIG. 2 is a diagram specifically illustrating the state of the exhaust gas after passing through the first stage catalyst and the second stage catalyst according to an aspect of the present invention.
- FIG. 3 is a diagram specifically illustrating a control flow of the exhaust gas purification catalyst system according to one aspect of the present invention.
- FIG. 4 is a diagram illustrating the relationship between the NOx, HC, and CO gas concentrations and the average A / F in the exhaust gas in the control flow of the exhaust gas purification catalyst system according to one aspect of the present invention.
- FIG. 1 is a diagram specifically illustrating an exhaust gas purification catalyst system according to an aspect of the present invention.
- FIG. 2 is a diagram specifically illustrating the state of the exhaust gas after passing through the first stage catalyst and the second stage catalyst according to an aspect of the present invention.
- FIG. 3 is a diagram specifically illustrating a control flow of the exhaust gas purification catalyst system according to one aspect of the present
- FIG. 5 is a schematic diagram illustrating a relationship between times t 1 and t 2 and an A / F value in the control flow of the exhaust gas purification catalyst system according to one aspect of the present invention.
- FIG. 6 is a schematic diagram of a mixture catalyst of Cu-supported alumina, ceria, zirconia, and yttria according to one embodiment of the present invention.
- FIG. 7 is a schematic diagram of a catalyst in which an alloy of Au and Cu is supported on particles of alumina, ceria, zirconia, and yttria according to one embodiment of the present invention.
- FIG. 8 is a diagram showing a schematic diagram of a Cu-supported zeolite catalyst according to one embodiment of the present invention.
- FIG. 9 is a graph showing the NOx purification rate (%) in Examples 1 to 5 and Comparative Examples 1 to 5.
- FIG. 10 is a graph showing the HC purification rate (%) in Examples 1 to 5 and Comparative Examples 1 to 5.
- FIG. 11 is a graph showing the NOx purification rate (%) in Examples 1, 6 to 11 and Comparative Examples 1, 6, and 7.
- FIG. 12 is a graph showing HC purification rates (%) in Examples 1 and 6 to 11 and Comparative Examples 1, 6, and 7.
- FIG. 13 is a graph plotting measurement results of NH 3 generation amount (ppm) against A / F value for the catalysts of Example 12 and Comparative Example 8.
- Example 14 shows that the N 2 O emission amount of Comparative Example 10 is 1, and (a) Example 12, (b) Example 13, (c) Example 14, (d) Example 15, (e) Example 16 and (f) the N 2 O emission amount of Comparative Example 10 and (g) Comparative Example 11 with respect to the A / F value (A / F 2 value for Examples 12 to 16 and Comparative Example 11). This is a plotted graph.
- impurities or the like may be generated even if they are generated so as to have these compositions by the name of the inorganic compound or the notation using the ratio of the contained metal (as exemplified below). Including a composition that is actually generated. Therefore, according to the notation using the name of the inorganic compound or the ratio of the contained metal, for example, in the structure of the inorganic compound, for example, elements such as oxygen, hydrogen, and nitrogen are excessive in the chemical formula within ⁇ 1 atom number or less.
- TiO to TiO 3 may be expressed as TiO x), and further includes those having hydrogen not represented in the compound as an impurity.
- NOx criteria refers to values of NOx concentration HC concentration and CO concentration determined from target regulation values when the vehicle is adapted to exhaust gas regulations, respectively. Unless otherwise specified, all parts, verses and ratios are by mass, except for the purification rate.
- the support may be abbreviated as “supported metal etc.” + “/” + “Oxide support”.
- the metals and metal oxides such as Cu and Fe according to the present invention can take any of a metal state, an ionic state, and an oxide state on the oxide carrier.
- particle size means a particle size calculated using a crystallite size calculation method by half-width measurement of powder X-ray diffraction unless otherwise specified.
- exhaust gas discharged from an internal combustion engine controlled by an engine control unit passes through an upstream first stage catalyst and then a downstream second stage catalyst.
- the catalyst system according to the present invention includes a temperature sensor and an air introduction valve between the first stage catalyst and the second stage catalyst, and further, NOx is disposed downstream of the second stage catalyst. It has a sensor.
- the exhaust gas purifying catalyst according to the present invention by NH 3 is a prone catalyst under rich conditions the first stage catalyst, utilizing NH 3 generated during the rich control effective purification of the exhaust gas purifying catalyst system The rate is improving.
- the exhaust gas is controlled to be leaner than the stoichiometric air-fuel ratio.
- the exhaust gas in the first stage catalyst By controlling the exhaust gas in the first stage catalyst richly, the production of NH 3 in the first stage catalyst is promoted, and not only the reduction of NOx by NH 3 in the second stage catalyst can be performed, but also the second By controlling the exhaust gas in the stage catalyst lean, the reduction of NOx in the second stage catalyst can be promoted. For example, as shown in FIG. 2, the amount of NOx at the outlet of the second stage catalyst can be greatly reduced.
- the second stage catalyst can be controlled lean by introducing air from between the first stage catalyst and the second stage catalyst.
- the lean state of the exhaust gas in the second stage catalyst may have an A / F of more than about 14.60, for example, about 15, about 20, or about 27.
- control method controls the exhaust gas from weakly rich to rich when the NOx amount exceeds a predetermined amount, and more efficiently controls the exhaust gas to deeper rich so as to generate NH 3 more efficiently.
- NOx concentration is detected and controlled at the outlet of the second stage catalyst, and the control center A / F is shifted closer to the stoichiometry even in the rich state to limit the rich frequency. It is.
- the control method according to the present invention will be described in more detail with reference to FIGS.
- Step 1-1 The exhaust gas emitted from the engine is controlled to a weakly rich A / F 1 , for example, 14.55, in a preset state in the first stage catalyst.
- Step 1-2 The NOx concentration calculated from the output of the NOx sensor installed downstream of the second stage catalyst, the A / F value, and the intake gas amount and read from the MAP of the ECU is shown as NOx criteria in FIG.
- the predetermined value A (g / s) shown is higher than 0.5 (mg / s)
- the A / F value of the exhaust gas is richer than A / F 1 by adjusting the fuel injection amount.
- a / F 2 is controlled.
- the first stage catalyst that purifies NOx reduces and releases NOx to N 2 and NH 3 and the NOx gas concentration decreases (FIG. 4).
- Step 1-4 When the average A / F according to the formula (A)> 14.4, the NOx amount is measured by the NOx sensor. When the NOx amount ⁇ A (g / s), the A / F output from the engine Is controlled by A / F 1 and the process returns to step 1-1. Step 1-5: If average A / F> 14.4 according to formula (A) and NOx amount> A (g / s), repeat steps 1-3 and 1-4.
- the average A / F is determined from a predetermined value, for example, about 14.4, so as to increase the amount of NH 3 produced and not deteriorate HC and CO emissions by the above algorithm.
- a predetermined value for example, about 14.4
- the A / F 1 in the weakly rich state is about 14.41 or more, about 14.43 or more, about 14.45 or more, about 14.47 or more, about 14.50 or more, about 14.59 or less. About 14.57 or less, about 14.55 or less, or about 14.53 or less.
- the A / F 2 in the rich state is about 13.50 or more, about 13.55 or more, about 13.60 or more, about 13.65 or more, about 13.70 or more, about 13.75 or more, about 13.80. About 13.85 or more, about 13.90 or more, about 14.45 or less, about 14.40 or less, about 14.35 or less, about 14.30 or less, about 14.25 or less, about 14.20 or less Can be.
- a / F 1 is preferably about 14.4 to about 14.6, and about 14.45 to about 14.55. More preferably, the A / F 2 is preferably about 13.8 to about 14.4, more preferably about 13.9 to about 14.2.
- the first stage catalyst according to the present invention is a catalyst capable of generating NH 3 under rich conditions.
- any oxide carrier that can be generated is not particularly limited, and is a mixture of alumina, ceria, zirconia, and yttria (that is, alumina (Al 2 O 3 ), ceria (CeO 2 ), and zirconia (ZrO 2 ).
- yttria Y 2 O 3
- zirconia ZrO 2
- titania TiO 2
- alumina Al 2 O 3
- zirconia zirconia
- alumina Al 2 O 3
- Alumina such as a mixture of ceria (CeO 2 ), a mixture of alumina (Al 2 O 3 ), ceria (CeO 2 ) and zirconia (ZrO 2 ), a mixture of zirconia (ZrO 2 ) and titania (TiO 2 )
- An oxide carrier composed of one or more fine particles of ceria, zirconia, yttria, and titania can be used.
- the ratio of the respective oxides is not particularly limited as long as they are uniformly mixed, and can be arbitrarily selected depending on the characteristics to be obtained.
- the crystallite diameter of ceria zirconia (sometimes abbreviated as CZ diameter in the present specification) is a particle diameter measured by an X-ray diffraction method, and is about 3 nm or more, about 4 nm or more, about 5 nm or more, about 6 nm or more. , About 15 nm or less, about 14 nm or less, about 13 nm or less, about 12 nm or less, about 11 nm or less, about 10 nm or less. Since secondary particles in which the respective oxides are finely mixed are formed and the amount of NH 3 produced can be increased, the thickness is preferably 5 nm or more and 10 nm or less (FIG. 6).
- the 1st stage catalyst which concerns on 1 aspect of this invention uses Cu metal and / or Cu oxide as an active seed
- the NH 3 generation site is an interface where zirconia and / or ceria are in contact with Cu metal and / or Cu oxide.
- the first stage catalyst that is a base metal catalyst may support Cu metal and / or Au metal and / or an alloy of Cu and Au instead of Cu metal and / or Cu oxide. it can.
- the base metal of the first stage catalyst is preferably an alloy of Cu and Au because NH 3 is efficiently generated, and more preferably the oxide support is a mixture of alumina, ceria, zirconia and yttria. (FIG. 7).
- the supported amount of Cu metal and / or Cu oxide is about 0.5 wt or more, about 1 wt or more, about 1.5 wt or more, about 2 wt or more, about 10 wt or less, about 9 wt or less, about 8 wt or less with respect to the oxide support. , About 7 wt or less, about 6 wt or less, about 5 wt or less. Since a sufficient number of active points are generated and Cu can function effectively without agglomeration, Cu is preferably about 2 wt% or more and about 5 wt% or less.
- the particle size of the supported Cu metal and / or Cu oxide is not particularly limited, but can be about 2 nm or more, about 3 nm or more, about 4 nm or more, about 5 nm or more, about 70 nm or less, about 60 nm or less, It can be about 50 nm or less, about 40 nm or less, about 30 nm or less, about 20 nm or less, about 15 nm or less, about 10 nm or less.
- FIG. 6 shows an example of about 60 nm.
- the first stage catalyst which is a base metal catalyst, carries Cu metal and / or Au metal and / or an alloy of Cu and Au instead of Cu metal and / or Cu oxide
- the values described for the Cu metal and / or Cu oxide can be taken, a sufficient number of active points can be obtained, and the Au metal, Cu metal, and alloy particles of Au and Cu can function effectively without aggregation. From about 2 wt% to about 5 wt%, the particle size of the Au metal and Cu metal and the alloy of Au and Cu can take the values described for the Cu metal and / or Cu oxide. it can.
- the ratio of Cu / Au is the mass ratio. 75/25 or more, 90/10 or more, and 97/3 or less, preferably 90/10 or more and 97/3 or less.
- the crystallite size of the oxide support is not too small, the proportion of copper supported on alumina will decrease, the contact frequency with ceria and zirconia will increase, and the activity will increase, and if not too large, Cu and ceria This interaction suppresses the growth of Cu particles, increases the surface area of ceria and zirconia on which copper is supported, and enhances the activity. Therefore, it is preferably about 5 nm or more and about 10 nm or less.
- the crystallite diameter of alumina can take the value described in the crystallite diameter of the ceria zirconia, and the activity can be enhanced, so that it is 5 nm or more and 10 nm or less. And preferred (FIG. 7).
- the second-stage base metal catalyst according to the present invention is a catalyst that can adsorb NH 3 produced in the first-stage catalyst and can react with NOx.
- a large amount of NH 3 produced by the first-stage base metal catalyst during rich control can be retained by having an active site excellent in NH 3 adsorption.
- any one or more of alumina, zirconia, titania, and zeolite can be used as the oxide carrier.
- the ratio of the respective oxides is not particularly limited as long as they are uniformly mixed, and can be arbitrarily selected depending on the characteristics to be obtained.
- the second-stage base metal catalyst according to the present invention is one in which at least one of Cu, Fe, Co, Ce metal and / or oxide is supported on an oxide support. Since a sufficient number of active points can be generated, the supported metal and / or metal oxide and oxide support have a nano-level particle size of about 1 nm or more and about 50 nm or less, preferably about 2 nm or more and about 10 nm or less. It is preferable to be in a mixed state (FIG. 7).
- the amount of Cu, Fe, Co, Ce supported on the oxide support is not particularly limited, but is about 0.1 wt% or more, about 0.2 wt% or more, about 0.3 wt% or more in terms of metal amount, About 0.4 wt% or more, about 0.5 wt% or more, about 0.6 wt% or more, about 10 wt% or less, about 9 wt% or less, about 8 wt% or less, about 7 wt% or less, about 6 wt% or less , About 5 wt% or less, about 4 wt% or less.
- a sufficient number of active sites is generated, and the metal and / or oxide can function effectively without agglomeration, so that the amount is preferably about 0.5 wt% or more and about 5 wt% or less.
- the particle size of the supported metal or oxide of Cu, Fe, Co, Ce is not particularly limited, but can be about 2 nm or more, about 3 nm or more, about 4 nm or more, about 5 nm or more, about 70 nm or less, about It can be 60 nm or less, about 50 nm or less, about 40 nm or less, about 30 nm or less, about 20 nm or less, about 15 nm or less, about 10 nm or less.
- an oxide carrier such as a mixture of alumina, ceria, zirconia and yttria, alumina, zeolite, etc. used for the first stage catalyst and the second stage catalyst
- known methods such as coprecipitation method and citric acid method are known.
- This method can be adopted.
- an Al-containing compound, a Ce-containing compound, a Zr-containing compound and a Y-containing compound having a desired molar ratio are dissolved in ammonia water.
- any solvent that can dissolve these compounds for example, an aqueous solvent such as water, An organic solvent or the like can be used.
- a slurry obtained by dissolving a fired oxide on a commercially available ceramic substrate may be used as an oxide carrier.
- the shape of the substrate is not particularly limited, and can be used according to applications such as a metal honeycomb shape and a cell shape.
- the first stage catalyst according to the present invention comprises a mixture of alumina, ceria, zirconia and yttria, a calcined oxide carrier such as alumina and zirconia, Cu metal and / or Cu oxide, or Cu metal and Au metal, / Or can be produced by supporting an alloy of Cu and Au, and the second stage catalyst is selected from Cu, Fe, Co, and Ce in addition to the calcined oxide carrier such as alumina, zirconia, titania, and zeolite. It can be produced by supporting at least one supported metal and / or metal oxide.
- the form of loading is not particularly limited, and it is sufficient that the metal and / or metal oxide is supported substantially uniformly on the fired body.
- a calcined oxide carrier such as a mixture of alumina, ceria, zirconia and yttria, alumina, zeolite, etc., a mixture of alumina, ceria, zirconia and yttria
- general methods such as an ion exchange method, an impregnation support method, and a chemical vapor deposition method can be used without particular limitation.
- the oxide carrier already supporting the metal and / or metal oxide may be used as it is or by slurrying to coat the substrate and baking.
- BEA or MFI type manufactured by Tosoh
- SAPO-34 is preferred because of its excellent heat resistance
- CHA type can also be used preferably.
- Cu, Fe, etc. are held in an ionic state in the second stage catalyst, and it is considered that Cu, etc. in the ionic state acts on oxygen, etc. (FIG. 8 (1) ), (2)). Therefore, it is considered that the ion exchange amount with respect to the acid point of the zeolite needs to leave the acid point in order to adsorb ammonia, and therefore, it is preferably 80 wt% or less.
- This raw material solution was sprayed onto the stirring aqueous ammonia at a rate of 60 (g / min) to form a precipitate.
- synthesis was performed while appropriately adding NH 3 water so that the pH did not become 9.0 or less.
- the synthesized slurry was centrifuged, washed with ion-exchanged water, dried at 120 ° C., and calcined at 500 ° C. for 2 hours to obtain a powder of a mixture of alumina, ceria, zirconia and yttria.
- a predetermined amount of a chloroauric acid solution was taken in a 100 ml beaker, and a solution obtained by dissolving 45 ml of tetraethylene glycol was added to the solution containing anhydrous copper acetate. While this was cooled in an ice-water bath, 8 ml of 1N aqueous sodium hydroxide solution was added to adjust the pH to 9-10, and this was transferred to a separable flask. After stirring at room temperature for 10 minutes with nitrogen, a solution of 1 g of sodium borohydride dissolved in 45 ml of tetraethylene glycol was gradually added.
- Step 2-1 137 parts by mass of powder of the mixture of alumina, ceria, zirconia and yttria, and 13 parts by mass (solid content conversion) of binder (manufacturer name: Nissan Chemical Industries, Ltd., product number: AS200) Was slurried in water to 150 g / liter.
- Step 2-2 The slurry obtained in Step 2-1 was coated on a ceramic substrate (manufacturer name: manufactured by NGK, cell shape: square / 4 mil / 400 cell).
- Step 2-3 The water absorption amount of the coated catalyst obtained in Step 2-2 is measured, and the water absorption amount is adjusted so that Cu becomes 0.118 mol / liter (corresponding to 5.0 wt% support in terms of Cu metal). Copper (II) nitrate trihydrate was dissolved in water and supported by water absorption.
- Step 2-4 The substrate was dried for 20 minutes in a microwave drier at 120 ° C.
- Step 2-5 A mixture catalyst of Cu-supported alumina, ceria, zirconia and yttria obtained by calcining in an electric furnace at 250 ° C. for 2 hours to decompose nitrate is used as the first stage catalyst of (Example 1). used.
- Step 3-1 167 parts by mass of Cu-supported zeolite powder (manufacturer name: manufactured by Mitsubishi Plastics), 20 parts by mass of alumina powder (manufacturer name: Sasol), and 13 parts by mass (solid content conversion) binder (Manufacturer name: Nissan Chemical Industries, Ltd., product name: AS200) was slurried in water to a concentration of 200 g / liter.
- Step 3-2 The slurry obtained in Step 3-1 was coated on a ceramic substrate (manufacturer name: NGK, cell shape: square / 4 mil / 400 cell).
- Step 3-3 The ceramic substrate obtained in Step 3-2 was calcined in an electric furnace at 500 ° C. for 2 hours, and the obtained catalyst was used as the second stage catalyst of (Example 1).
- first stage catalysts of Examples 2 to 5 and Comparative Examples 1 to 5 were prepared by the same process as Example 1.
- the second stage catalyst the Cu-supported zeolite of Example 1 was used.
- Example 2 The heat treatment temperature of the powder of the mixture of alumina, ceria, zirconia and yttria was set to 800 ° C.
- Example 3 The heat treatment temperature of the powder of the mixture of alumina, ceria, zirconia and yttria was 950 ° C.
- Examples 4 and 5 The composition of the powder of the mixture of alumina, ceria, zirconia and yttria was changed.
- Comparative Example 1 Alumina powder (manufacturer name: Sasol) was used in place of the powder of the mixture of alumina, ceria, zirconia, and yttria.
- Comparative Example 4 In the above ⁇ Production of powder of a mixture of alumina, ceria, zirconia and yttria>, 0.5 g of a dispersant polyethyleneimine (manufacturer name) per 1 g of a mixture of alumina, ceria, zirconia and yttria : Wako Pure Chemical Industries, Ltd.). Comparative Example 5: In the above ⁇ Production of powder of mixture of alumina, ceria, zirconia and yttria>, the spraying rate of the spray was increased 5 times, and the heat treatment temperature of the powder of the mixture of alumina, ceria, zirconia and yttria was 950 C.
- Example 6 Fe-supported zeolite powder was used instead of Cu-supported zeolite powder.
- Example 7 40 parts by mass of Cu-supported zeolite powder was changed to Fe-supported titania powder.
- Example 8 40 parts by mass of the Cu-supported zeolite powder was changed to Fe-supported TiOx powder prepared by coprecipitation using Fe and Ti.
- the coprecipitation method using Fe and Ti involves dissolving 49.5 g of Ti (SO 4 ) 2 ⁇ 5H 2 O and 60.6 g of Fe (NO 3 ) 3 ⁇ 9H 2 O in water. The solution was made up to 1 L, sprayed with 0.5 M NH 3 water while adjusting the pH so that it was not lower than 10 to synthesize oxide, filtered, washed and calcined at 600 ° C.
- Example 9 Fe-supported zeolite was used instead of Cu-supported zeolite powder, and 40 parts by mass of Fe-supported zeolite was changed to Cu-supported zirconia powder.
- Example 10 Fe-supported zeolite was used instead of Cu-supported zeolite powder, and 40 parts by mass of the Fe-supported zeolite was changed to Co-supported zirconia powder.
- Example 11 Fe-supported zeolite was used instead of Cu-supported zeolite powder, and 40 parts by mass of Fe-supported zeolite was changed to Cu-supported alumina powder.
- Comparative Example 6 The same catalyst system as in Example 8 was used. Comparative Example 7: 40 parts by mass of Cu zeolite powder was replaced with Ag-supported alumina powder.
- first stage catalysts of Examples 12 to 17 and Comparative Examples 8 to 11 were prepared by the same process as Example 1.
- the Cu-supported zeolite of Example 1 was used as the second stage catalyst except that the second stage catalyst of Example 8 was used in Example 17.
- Comparative Example 9 For the first stage catalyst of Example 12, alumina powder (manufacturer name: Sasol) was used instead of the powder of the mixture of alumina, ceria, zirconia and yttria. Comparative Examples 10 and 11: Same as Example 12.
- the first stage catalyst and the second stage catalyst are arranged downstream of the exhaust manifold of the engine with engine displacement of 2400cc.
- FT-IR NH 3 meter other component analyzer (manufacturer name: HORIBA, model number: 9500D) , Engine speed: 2000 rpm, torque: 58 Nm, intake gas amount: 16 (g / s), first stage catalyst temperature: 580 ° C., second stage catalyst temperature: 400 ° C.
- the NOx purification rate is given by the formula: (Engine NOx Amount-Second Stage Catalyst Out NOx Amount) / (Engine Out NOx Amount) --- Calculated by Formula (B).
- Fuel cut is performed for 5 seconds, air is introduced, initialization is performed, and control is started.
- the purification rate for 10 minutes was determined by the above formula (B).
- Control 1 A / F 1 is set to 14.55, and the above steps 1-1 to 1-5 are used.
- Control 2 In step 1-3, the comparison between the average A / F of formula (A) and 14.4 is not performed, and it is always assumed that the average A / F of (A)> 14.4. ⁇ Same as Control 1 except using Step 1-5. However, in this usage, the rich frequency increases, causing deterioration in fuel consumption and increase in HC emissions. Rich control 1: A / F in the first stage catalyst is controlled to be 14.40 without using the control method according to the present invention.
- the A / F value of the second stage catalyst of exhaust gas was set to a lean condition of 20 to 27 by taking in air upstream of the second stage catalyst.
- Table 1 below shows the type of the first stage catalyst, the composition of the powder, the CZ diameter in the powder of the mixture of alumina, ceria, zirconia and yttria, the control method of the first stage catalyst, the type of the second stage catalyst, The composition is shown.
- FIG. 9 shows the NOx purification rates of the catalysts of Examples 1 to 5 and Comparative Examples 1 to 5, and FIG. 10 shows the HC purification rates.
- NOx can be effectively purified, and the HC purification rate is improved.
- FIG. 11 shows the NOx purification rates of the catalysts of Examples 6 to 11 and Comparative Examples 1 and 6 to 7, and FIG. 12 shows the HC purification rates.
- Example 6 to 11 both the NOx purification rate and the HC purification rate were significantly improved.
- the NH 3 produced when rich in the first stage catalyst is retained in the second stage catalyst and used for the oxidation of N 2 O and NO x , thereby enabling not only selective oxidation. Improvement of the purification efficiency per fuel and further NH 3 oxidation treatment became unnecessary. Further, by the selective oxidation, even if the second stage catalyst is in a lean state, NOx and the like can be purified, so that it is not necessary to finely control the amount of air introduced, thereby simplifying the system.
- the base metal oxidation catalyst and the control method thereof according to the present invention can provide an exhaust gas purification catalyst system that can purify NOx with high efficiency and good fuel efficiency, as described above.
- the use of the oxidation catalyst according to the present invention is not limited to the exhaust gas purification catalyst, and can be used for various applications in a wide field.
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Abstract
Description
また、NH3、尿素等の還元剤を用いて排ガス中の窒素酸化物を還元する場合、NH3+H2等の還元剤を添加するシステムが必要であり、例えば、還元剤用のタンクを搭載する必要があった。
(1)上流側に位置する第1段卑金属触媒と、下流側に位置する第2段卑金属触媒とからなる排ガス浄化触媒システムであって、
該第1段卑金属触媒が、アルミナ、セリア、ジルコニア、イットリア、チタニアから成る群から選択された少なくとも1種以上の酸化物担体上に、Cu金属および/またはCu酸化物を担持してなり、
排ガス中のNOxの量がNOxクライテリア以上になった場合に、排気ガスの状態を弱リッチからリッチに切り替える、排ガス浄化触媒システム。
(2)第1段卑金属触媒と、第2段卑金属触媒との間において空気が導入されて、第2段卑金属触媒において、排ガスがリーンに制御されている、(1)に記載の排ガス浄化触媒システム。
(3)該第1段卑金属触媒の該酸化物担体がアルミナとセリアとジルコニアとイットリアとの混合物の微粒子である、(2)に記載の排ガス浄化触媒システム。
(4)該第1段卑金属触媒が、Cu金属および/またはCu酸化物の代わりに、AuとCuとの合金を担持してなる、(3)に記載の排ガス浄化触媒システム。
(5)該第2段卑金属触媒が、アルミナ、ジルコニア、チタニア、ゼオライトからなる群から選択される1種以上の酸化物担体上に、Cu、Fe、Co、Ceからなる群から選択される1種以上の金属および/または金属酸化物を担持してなる、(1)~(4)のいずれか一項に記載の排ガス浄化触媒システム。
(6)該第2段卑金属触媒が、ゼオライトを含む酸化物担体上に、Cuおよび/またはFeの金属および/または金属酸化物を担持してなる、(5)に記載の排ガス浄化触媒システム。
「NOxクライテリア」、「HCクライテリア」、「COクライテリア」とは、それぞれ、車両を排ガス規制に適合させる場合に、目的とする規制値から決定されるNOx濃度HC濃度、CO濃度の値をいう。
特に記載のない場合、浄化率を除き、部、バーセント、割合は、すべて質量による。
担持を、「担持される金属等」+「/」+「酸化物担体」と略記する場合がある。
なお、本発明に係るCu、Fe等の金属、金属酸化物は、酸化物担体上で、金属状態、イオン状態、酸化物状態のいずれをも取り得るものである。
さらに、本明細書中において、「粒径」とは、特に断りのない限り、粉末X線回折の半価幅測定による結晶子径算出法を用いて算出した粒径のことをいう。
本発明に係る制御方法を、図3~5を用いてさらに詳しく説明する。
式:平均A/F値=(A/F1×t1+A/F2×t2)/(t1+t2)---式(A)
により平均A/F値を計算し、式(A)による平均A/Fと、一定数値14.4とを比較し、式(A)による平均A/F≦14.4の場合、エンジンから出力されるA/FをA/F1に制御し、工程1-1に戻る。
工程1-5:式(A)による平均A/F>14.4、かつNOx量>A(g/s)の場合、工程1-3、工程1-4を繰り返す。
具体的には、生成できる酸化物担体であれば、特に制限なく、アルミナとセリアとジルコニアとイットリアとの混合物(すなわち、アルミナ(Al2O3)とセリア(CeO2)とジルコニア(ZrO2)とイットリア(Y2O3)との混合物)、ジルコニア(ZrO2)、チタニア(TiO2)、アルミナ(Al2O3)とジルコニア(ZrO2)との混合物、アルミナ(Al2O3)とセリア(CeO2)との混合物、アルミナ(Al2O3)とセリア(CeO2)とジルコニア(ZrO2)との混合物、ジルコニア(ZrO2)とチタニア(TiO2)との混合物などの、アルミナ、セリア、ジルコニア、イットリア、チタニアの1種以上の微粒子からなる酸化物担体を用いることができる。混合物である場合、それぞれの酸化物の比は、一様に混合されていれば特に制限されず、得られる特性などにより任意に選択できる。
何らかの理論に拘束されることを望まないが、NH3生成サイトは、ジルコニアおよび/またはセリアと、Cu金属および/またはCu酸化物とが接触した界面と考えられる。
充分な活性点数を生じ、かつCu同士が凝集しないで有効に機能できるため、約2wt%以上、約5wt%以下であると好ましい。
何らかの理論に拘束されることを望まないが、NH3吸着に優れた活性点を有することで、リッチ制御時に第1段卑金属触媒で生成したNH3を多く保持できるものと考えることができる。
充分な活性点数を生じることができるので、被担持金属および/または金属酸化物と酸化物担体が、約1nm以上、約50nm以下、好ましくは、約2nm以上、約10nm以下の粒径のナノレベルで混合した状態であることが好ましい(図7)。
なお、何らかの理論に拘束されることを望まないが、第2段触媒においてCu、Feなどはイオン状態で保持されており、イオン状態のCuなどが酸素などに作用すると考えられる(図8(1)、(2))。そうしたことから、ゼオライトの酸点に対するイオン交換量は、アンモニアを吸着させるために酸点を残す必要があると考えられるため、80wt%以下であることが望ましい。
ここでは逆共沈法にて合成した。0.5Mのアンモニア水を調製し、ビーカーに1L分取した。次に121.9gの硝酸アルミニウム(III)9水和物、35.64gの硝酸アンモニウムセリウム(IV)、26.73gのオキシ硝酸ジルコニウム(IV)2水和物、3.83gの硝酸イットリウム6水和物を秤量し、イオン交換水に溶解させた後、1Lにメスアップした。
この原料溶液を、撹拌中のアンモニア水に60(g/分)の速度でスプレー噴霧し、沈殿物を生成させた。
このとき、pHが9.0以下にならないよう、適宜NH3水を追加しながら合成した。
合成したスラリーを遠心分離し、イオン交換水で洗浄したのち、120℃で乾燥させ、500℃で2時間焼成して、アルミナとセリアとジルコニアとイットリアとの混合物の粉末を得た。
得られたアルミナとセリアとジルコニアとイットリアとの混合物の粉末の組成は、Al2O3:CeO2:ZrO2:Y2O3(ただし、明細書中において、A:C:Z:Yと省略することがある。)=65:13:20:2wt%(酸化物換算、以下、酸化物担体の組成は、酸化物換算である。)であり、CZの粒径は、X線回折装置(メーカー名:(株)リガク、型番:RINT-TTR)を用いてX線回折法により測定して5nmであった。
300mlビーカーにテトラエチレングリコール135mlを入れ、約80℃に加熱してポリビニルピロリドン(k-25、和光純薬工業(株)製)7.5gを加えて完全に溶解させた。続いて無水酢酸銅1.22gを加えて攪拌し、完全に溶解させ、その後氷水浴で溶液を10℃以下まで冷却した。
100mlビーカーに塩化金酸溶液を所定量取り、テトラエチレングリコール45mlを加えて溶解させた溶液を、上記無水酢酸銅を含む溶液に加えた。
これを氷水浴で冷却しながら、1Nの水酸化ナトリウム水溶液8mlを加えてpHを9~10にし、これをセパラブルフラスコに移した。
室温で攪拌しながら、窒素で10分間バブリングした後に、テトラエチレングリコール45ml中に1gの水素化ホウ素ナトリウムを溶解させた溶液を徐々に加え、30分間室温で攪拌後、オイルバス中で、オイルバスの温度を150℃まで加熱して1時間攪拌し他後、室温まで冷却した。
この溶液を5Lのビーカーに移してアセトンで10倍に希釈して、3000回転/分、10分間の遠心分離の後に、得られた沈殿を約80mlのエタノール中に再分散させた。
これに金属成分の質量が5wt%となるように、アルミナとセリアとジルコニアとイットリアとの混合物の粉末を10.45gを加えて蒸発乾固させ、さらに120℃で乾燥後、300℃で30時間焼成した。
上記<AuとCuとの合金粒子の合成>で合成した合金粒子と、上記<アルミナとセリアとジルコニアとイットリアとの混合物の粉末の製造>で合成した酸化物粉末を用いて、含浸担持法により調製した。AuとCuとの合金粒子の担持量が5wt%となるようにし、担持後に粉末を120℃で一晩乾燥後、脱脂炉中300℃で30時間焼成後、500で2時間焼成した。
工程2-1:137質量部の上記アルミナとセリアとジルコニアとイットリアとの混合物の粉末と、13質量部(固形分換算)のバインダー(メーカー名:日産化学工業(株)、品番:AS200)とを、150g/リットルとなるように、水中でスラリー化した。
工程2-2:セラミック基材(メーカー名:日本ガイシ製、セル形状:四角/4ミル/400セル)に工程2-1で得たスラリーをコートした。
工程2-3:工程2-2で得たコート触媒の吸水量を計測し、Cuが0.118モル/リットル(Cu金属換算で5.0wt%担持に相当)となるように吸水量分の水に硝酸銅(II)3水和物を溶解させ、吸水担持させた。
工程2-4:マイクロ波乾燥器にて、120℃通風中で、20分間乾燥させた。
工程2-5:電気炉で250℃で、2時間焼成し、硝酸塩を分解させ得られたCu担持アルミナとセリアとジルコニアとイットリアとの混合物触媒を、(実施例1)の第1段触媒として使用した。
工程3-1:167質量部のCuを担持したゼオライト粉末(メーカー名:三菱樹脂製)と、20部質量のアルミナ粉末(メーカー名:サソール社)と、13質量部(固形分換算)のバインダー(メーカー名:日産化学工業(株)、品名:AS200)を、200g/リットルの濃度になるように、水中でスラリー化した。
工程3-2:セラミック基材(メーカー名:日本ガイシ、セル形状:四角/4ミル/400セル)に、工程3-1で得たスラリーをコートした。
工程3-3:工程3-2で得たセラミック基材を電気炉内で500℃で、2時間焼成し、得られた触媒を(実施例1)の第2段触媒として使用した。
実施例2:アルミナとセリアとジルコニアとイットリアとの混合物の粉末の熱処理温度を800℃にした。
実施例3:アルミナとセリアとジルコニアとイットリアとの混合物の粉末の熱処理温度を950℃にした。
実施例4,5:アルミナとセリアとジルコニアとイットリアとの混合物の粉末の組成を変更した。
比較例2:アルミナとセリアとジルコニアとイットリアとの混合物の粉末の代わりに、アルミナ粉末(メーカー名:サソール社)を使用し、セリアジルコニア粉末(Ce:Zr=50wt%:50wt%)を2:1の質量割合で混合させた。
比較例4:上記<アルミナとセリアとジルコニアとイットリアとの混合物の粉末の製造>において、1gのアルミナとセリアとジルコニアとイットリアとの混合物の粉末当り、0.5gの分散剤ポリエチレンイミン(メーカー名:和光純薬工業(株))を用いた。
比較例5:上記<アルミナとセリアとジルコニアとイットリアとの混合物の粉末の製造>において、スプレーの噴霧速度を5倍にし、アルミナとセリアとジルコニアとイットリアとの混合物の粉末の熱処理温度を、950℃にした。
実施例6:Cu担持ゼオライト粉末の代わりに、Fe担持ゼオライト粉末を用いた。
実施例7:Cu担持ゼオライト粉末のうち40質量部を、Fe担持チタニア粉末に変更した。
実施例8:Cu担持ゼオライト粉末のうち40質量部を、FeとTiとを用いて共沈法により作製したFe担持TiOx粉末に変更した。
実施例10:Cu担持ゼオライト粉末の代わりにFe担持ゼオライトを用い、かつ、Fe担持ゼオライトのうち40質量部を、Co担持ジルコニア粉末に変更した。
実施例11:Cu担持ゼオライト粉末の代わりにFe担持ゼオライトを用い、かつ、Fe担持ゼオライトのうち40質量部を、Cu担持アルミナ粉末に変更した。
比較例6:実施例8の触媒システムと同じものを用いた。
比較例7:Cuゼオライト粉末40質量部をAg担持アルミナ粉末に置き換えた。
実施例12~17:<第1段触媒の製造>の工程2-1において、137質量部のアルミナとセリアとジルコニアとイットリアとの混合物の粉末の代わりに、<AuとCuとの合金粒子を担持したアルミナとセリアとジルコニアとイットリアとの混合物の粉末の調製>で得たAuとCuとの合金粒子を担持したアルミナとセリアとジルコニアとイットリアとの混合物の粉末を145質量部用いて158g/リットルとなるように水中でスラリー化した。さらに工程2-3を行わなかった。
比較例8:<第1段触媒の製造>の工程2-1において、アルミナとセリアとジルコニアとイットリアとの混合物の粉末の代わりに、アルミナ粉末(メーカー名:サソール社)を用いた。
比較例9:実施例12の第1段触媒に、アルミナとセリアとジルコニアとイットリアとの混合物の粉末の代わりにアルミナ粉末(メーカー名:サソール社)を用いた。
比較例10、11:実施例12と同じである。
エンジン排気量2400ccのエンジンのエキゾーストマニホールドの下流側に第1段触媒と第2段触媒を配置し、FT-IR式NH3計、他成分分析計(メーカー名:堀場製作所、型番:9500D)により,エンジン回転数:2000rpm、トルク:58Nm、吸入ガス量:16(g/s)、第1段触媒温度:580℃、第2段触媒温度:400℃の条件で、評価した。
(エンジン出NOx量-第2段触媒出NOx量)/(エンジン出NOx量)---式(B)により算出した。
触媒温度が安定した後、前処理として、フュエルカットを5秒実施して空気を入れて初期化後、制御を開始して。10分間の浄化率を上式(B)により求めた。
制御1:A/F1を14.55に設定し、上記工程1-1~工程1-5を用いたもの。
制御2:工程1-3において、式(A)の平均A/Fと14.4との比較を行わず、常に(A)による平均A/F>14.4であるとして上記工程1-1~工程1-5を用いた以外は、制御1と同じもの。
ただし、この使い方では、リッチ頻度が大きくなり、燃費悪化およびHC排出増加を引き起こす。
リッチ制御1:本発明に係る制御方法を使用せず、第1段触媒におけるA/Fを14.40になるように制御したもの。
何らかの理論に拘束されることを望まないが、第2段触媒へ添加する触媒として、NH3のNOxへの酸化を抑制することも必要な要件と考えられる。
実施例12~17および比較例8~11において、上記(触媒の評価)に記載した条件下で、実施例12~17、比較例11については、制御1でA/F2をそれぞれ、14.4、14.3、14.2、14.0、13,8、14.4、14.5とし、比較例8~10についてはリッチ制御1でA/F値をそれぞれ、14.4、14.6、14.55として、NOx浄化率、HC浄化率、CO浄化率、N2O生成量(相対比)を測定した。
実施例12と比較例8の第1段触媒を用いて、リッチ制御1の条件下で、実施例12の触媒については、A/Fを14.4,14.5、14.55とし、比較例8の触媒については、A/Fを14.4、14.5として、NH3の生成濃度を測定した。
その結果、いずれのA/F値においても、比較例8の触媒より、実施例12の触媒が高いNH3の生成能力を示した(図13)。
そして、上記選択的酸化により、第2段触媒がリーン状態であっても、NOx等を浄化できることで、空気導入量の細かい制御が不要になるため、システムの簡素化が可能となった。
Claims (6)
- 上流側に位置する第1段卑金属触媒と、下流側に位置する第2段卑金属触媒とからなる排ガス浄化触媒システムであって、
該第1段卑金属触媒が、アルミナ、セリア、ジルコニア、イットリア、チタニアから成る群から選択された少なくとも1種以上の酸化物担体上に、Cu金属および/またはCu酸化物を担持してなり、
排ガス中のNOxの量がNOxクライテリア以上になった場合に、排気ガスの状態を弱リッチからリッチに切り替える、排ガス浄化触媒システム。 - 第1段卑金属触媒と、第2段卑金属触媒との間において空気が導入されて、第2段卑金属触媒において、排ガスがリーンに制御されている、請求項1に記載の排ガス浄化触媒システム。
- 該第1段卑金属触媒の該酸化物担体がアルミナとセリアとジルコニアとイットリアとの混合物の微粒子である、請求項2に記載の排ガス浄化触媒システム。
- 該第1段卑金属触媒が、Cu金属および/またはCu酸化物の代わりに、AuとCuとの合金を担持してなる、請求項3に記載の排ガス浄化触媒システム。
- 該第2段卑金属触媒が、アルミナ、ジルコニア、チタニア、ゼオライトからなる群から選択される1種以上の酸化物担体上に、Cu、Fe、Co、Ceからなる群から選択される1種以上の金属および/または金属酸化物を担持してなる、請求項1~4のいずれか一項に記載の排ガス浄化触媒システム。
- 該第2段卑金属触媒が、ゼオライトを含む酸化物担体上に、Cuおよび/またはFeの金属および/または金属酸化物を担持してなる、請求項5に記載の排ガス浄化触媒システム。
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EP12868908.0A EP2815812B1 (en) | 2012-02-15 | 2012-11-09 | A system for exhaust gas purification utilizing base metals |
CN201280069920.8A CN104114276B (zh) | 2012-02-15 | 2012-11-09 | 利用贱金属的排气净化催化剂系统及其控制方法 |
JP2014500041A JP5880682B2 (ja) | 2012-02-15 | 2012-11-09 | 卑金属を利用する排ガス浄化触媒システムとその制御方法 |
US14/378,753 US9517434B2 (en) | 2012-02-15 | 2012-11-09 | Catalyst system for exhaust gas purification utilizing base metals, and controlling method therefor |
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US9561469B2 (en) * | 2014-03-24 | 2017-02-07 | Johnson Matthey Public Limited Company | Catalyst for treating exhaust gas |
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EP3696394B1 (en) * | 2019-02-13 | 2023-08-16 | FCA Italy S.p.A. | System and method for controlling the emissions of a spark-ignition internal combustion engine of a motor-vehicle |
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