JP2000262897A - Exhaust gas purification catalyst and exhaust gas purification method - Google Patents

Abstract

(57) Abstract: indicate higher _the NO _x storage ability at a reaction temperature range of even 250 ° C. ~ 650 ° C. after the high temperature durability test, suppressing reduction of the NO _x purification performance even in exhaust gas containing SO _x . A first composite oxide represented by A MgO-Al ₂ O ₃
A carrier comprising the second composite oxide represented by TiO ₂ -ZrO ₂ , and a NO supported on the carrier and containing at least Na and Ba
It was configured to include an _x storage element and a noble metal supported on a carrier. MgO-Al ₂ O ₃ composite oxide compared to alumina, TiO ₂ -ZrO ₂ composite oxide has low reactivity with _the NO _x storage element as compared to TiO _2, Na is Mg released from the composite oxide and without causing the composite sulfate by reaction with SO _x, B
a is excellent in NO _x storage capacity in low temperature range, so high N after endurance
_Ox purification ability can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst and an exhaust gas purifying method for purifying exhaust gas discharged from an internal combustion engine of an automobile or the like, and more particularly, to an exhaust gas containing excess oxygen, that is, an exhaust gas contained in the exhaust gas. Carbon oxide (C
O), hydrogen (H ₂ ) and hydrocarbons (HC) efficiently remove nitrogen oxides (NO _x ) in exhaust gas containing oxygen in excess of the amount of oxygen necessary to completely oxidize reducing components. The present invention relates to an exhaust gas purifying catalyst capable of reduction purification and an exhaust gas purifying method.

[0002]

2. Description of the Related Art Conventionally, as a catalyst for purifying exhaust gas of automobiles, CO and CO in exhaust gas at a stoichiometric air-fuel ratio (stoichiometric) have been used.
A three-way catalyst that purifies by simultaneously oxidizing HC and reducing NO _x is used. As such a three-way catalyst, for example, a porous carrier layer made of γ-alumina is formed on a heat-resistant substrate made of cordierite or the like, and platinum (Pt), rhodium (Rh), or the like is formed on the porous carrier layer. What carried the catalyst noble metal is widely known. Further, a three-way catalyst using ceria (cerium oxide) having an oxygen storage ability and having enhanced low-temperature activity is also known.

On the other hand, in recent years, carbon dioxide (CO ₂ ) in exhaust gas discharged from internal combustion engines such as automobiles has become a problem from the viewpoint of protection of the global environment. As a solution, lean combustion in an oxygen-excess atmosphere has been proposed. Burn engines and direct injection gasoline engines have been commercialized. In these engines, the use of fuel is reduced to improve fuel efficiency, and the generation of CO ₂ , which is the combustion exhaust gas, can be suppressed.

On the other hand, in the conventional three-way catalyst, when the air-fuel ratio is at the stoichiometric air-fuel ratio (stoichiometric), CO, HC, NO
_It purifies by simultaneously oxidizing and reducing _x, and does not show sufficient purification performance for the reduction and removal of NO _x even when used for exhaust gas with excess oxygen discharged from lean burn engines and direct injection gasoline engines. . Therefore, development of a catalyst and purification system has been desired can purify NO _x even in an oxygen rich atmosphere.

For example, Japanese Patent Application Laid-Open No. 5-168860 discloses that
Barium (Ba) NO _x storage reduction catalyst for purifying an exhaust gas of an alkaline earth metal and Pt was supported on a porous support such as alumina, such as has been proposed. By using this exhaust gas purifying catalyst to control the air-fuel ratio from the lean side to the spike-like rich side (hereinafter referred to as transient combustion),
In the _lean-side NO _x is occluded in _the NO _x storage element such as an alkaline earth metal, because it is purified by reacting with reducing components such as HC and CO and H ₂ in the rich side, the oxygen excess in the exhaust gas it can efficiently purify NO _x contained in the.

On the other hand, in the exhaust gas purifying catalyst disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-168860, when exposed to a high temperature of 600 ° C. or more, particularly 700 ° C. or more, NO _x It became clear that there was a problem that the purification performance was reduced. This is because NO
_x Solid phase reaction occurs between the storage element and alumina, for example,
It is considered that the generation of BaAl ₂ O ₄ stabilizes the NO _x storage element as a composite oxide, resulting in a decrease in the NO _x storage capacity.

The applicant of the present application has proposed an exhaust gas purifying catalyst in which a composite oxide represented by MgO—Al ₂ O ₃ is used as a carrier and at least one of potassium (K) and Ba is supported as a NO _x storage element. (JP-A-10-249199). According to this catalyst, for reactivity with the composite oxide and _the NO _x storage element is lower than the reactivity of the alumina and _the NO _x storage element, occurs solid phase reaction between _the NO _x storage element in the high temperature range Nikuku, it is possible to suppress the reduction of the NO _x purifying performance even when exposed to high temperatures.

[0008]

When the NO _x storage-reduction type catalyst requires NO _x purification in a high temperature range of 500 ° C. or higher, Ba is not sufficient as a NO _x storage element, It is desirable to use K having high property. However, in the catalyst disclosed in JP-A-10-249199,
When K was used as the NO _x storage element, it was revealed that there was a problem that the NO _x purification performance was reduced (sulfur poisoning) when exposed to exhaust gas containing sulfur oxides (SO _x ). .

This is because K, MgO-Al_TwoO_ThreeComplex oxidation
Released from waste and SO in exhaust gas _xReaction between
For example, K_TwoMg_Two(SO_Four)_ThreeGenerates K
NO stabilized as a monosulfate_xBecause storage capacity decreases,
It is believed that. In addition, the formation of complex sulfates
MgO-Al partially released_TwoO_ThreeComplex oxide carrier
NO_xIt is thought that solid-state reactions with occluded elements are likely to occur.
Yes, this is also NO_xThe storage capacity is reduced.

Therefore, the applicant of the present application has proposed MgO-Al_TwoO_ThreeComplex acid
Containing at least sodium (Na) in the compound carrier_xOcclusion
A catalyst supporting an element has been proposed (Japanese Patent Application No. 11-010749).
issue). Na is slightly less basic than K, but more than 500 ℃
NO equivalent to K in the high temperature range_xShows occlusion ability. Only
Even Na, SO_xIn exhaust gas containing MgO-Al_TwoO_ThreeDuplicate
Mg and SO released from composite oxide_xWith complex sulfur
No stabilization due to the formation of acid salts. In addition, Na
Is less basic than SO_xReactivity with
And it is unlikely to be stabilized as sulfate.
No. Therefore NO _xUse at least Na as storage element
NO_xDeterioration of purification performance is suppressed and durability is improved
improves.

Further, the applicant of the present application_TwoO_ThreeRepresented by
Composite oxide carrier and TiO_TwoCombined with acidic carrier such as
(Japanese Patent Application No. 10-248459). TiO_Two
By using an acidic carrier such as_xNear
Since contact is suppressed, the production of complex sulfate is prevented. When
Roller MgO-Al_TwoO_ThreeFurther catalyst catalysis using composite oxide support
Research, NO _xWhen using Na as the storage element
In the low temperature range_xInsufficient purification performance
Became clear. Also TiO_TwoWhen a carrier is used, Ti
O_TwoThe carrier is MgO-Al_TwoO_ThreeMore heat-resistant than composite oxide carrier
Inferior, at 600 ° C or higher, especially 700 ° C or higher
NO after heat treatment_xPurification performance is not enough
It became clear.

The present invention has been made in view of such circumstances, and the reaction temperature has been reduced from a low temperature range of about 250 ° C. to 650 ° C.
Shows high NO _x storage and purification performance up to a high temperature range and SO _x
Suppressing deterioration of the NO _x purification performance even during the exhaust gas containing,
High NO even after exposure to high temperature exhaust gas of 700 ° C or more
_x It is intended to be able to maintain purification ability.

[0013]

Means for Solving the Problems Claims for solving the above problems
The feature of the exhaust gas purifying catalyst according to item 1 is that MgO-Al_TwoO _Three
1st composite oxide and TiO_Two−ZrO_TwoThe number represented by
(2) a carrier comprising a composite oxide, an alkali metal, an alkali
At least sodium selected from lithium earth metals and rare earth elements
NO supported on a carrier containing chromium and barium_xOcclusion element
And a noble metal supported on a carrier.
You.

Further features of the exhaust gas purifying method according to claim 2, the first composite oxide represented by MgO-Al ₂ O ₃ and TiO ₂ -
A carrier composed of a second composite oxide represented by ZrO ₂ , a NO _x storage element selected from alkali metals, alkaline earth metals and rare earth elements and containing at least sodium and barium and carried on the carrier; An exhaust gas containing nitrogen oxides (NO _x ) is brought into contact with an exhaust gas purifying catalyst containing the obtained noble metal in an oxygen-excess atmosphere.

Further, the exhaust gas purification method according to the third aspect is characterized in that the first composite oxide represented by MgO—Al ₂ O ₃ and TiO ₂
A support comprising a _second composite oxide represented by -ZrO2,
An excess of oxygen is added to an exhaust gas purifying catalyst that is selected from alkali metals, alkaline earth metals, and rare earth elements and contains at least sodium and barium and contains a NO _x storage element supported on a carrier and a noble metal supported on the carrier. And contacting exhaust gas containing sulfur oxides (SO _x ) and nitrogen oxides (NO _x ) under an atmosphere of.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the exhaust gas purifying catalyst of the present invention,
 MgO-Al_TwoO_Three1st composite oxide and TiO_Two−ZrO_Twoso
Using a carrier comprising the second composite oxide represented
You. MgO-Al_TwoO _ThreeCrystal structure of the first composite oxide represented by
Is MgAl_TwoO_FourΓ-Al_TwoO_ThreeSpinel structure similar to
It has become.

MgO-Al_TwoO_ThreeThe first composite oxide represented by
Is NO compared to alumina_xLow reactivity with occlusion elements.
Therefore, the exhaust gas purifying catalyst of the present invention can be used in a high temperature range.
NO _xSince the reaction between the storage element and the carrier is suppressed, NO
_xDecrease in storage capacity is suppressed, and high NO even in transient combustion
_xHas purification ability. The composite oxide of Mg and Al is MgO-nAl_Two
O_ThreeAnd various values of n are known. Only
When n is less than 1, Mg Al_TwoO_ThreeBeyond the solid solution limit
Therefore, if it receives heat history, MgO and MgAl_TwoO_FourTo a two-phase system
In the presence of this free MgO, heat resistance decreases
Therefore, it is not preferable.

When n exceeds 1, MgO—xAl ₂ O ₃ and yA
It is a two-phase system of l ₂ O ₃ (1 <x, x + y = n). As n increases, the specific surface area tends to increase, but Al ₂ O ₃
As the proportion of the phase increases, the reaction with the NO _x storage element is more likely to occur. Therefore, in the present invention, n = 1. On the other hand, the second composite oxide represented by TiO ₂ -ZrO ₂
With ZrO ₂ forms a solid solution in the anatase phase of TiO _2, TiO ₂ is dissolved in the tetragonal phase of ZrO _2, these thermal stability is improved metastable phase by mutually dissolved with each other. Thereby, even when exposed to a high temperature, a decrease in the specific surface area is suppressed. Also, by forming a solid solution, NO
The solid-phase reaction with the _x- occluding element is suppressed, and the function of TiO ₂ for suppressing sulfur poisoning is promoted. Therefore, it is possible to achieve both heat resistance and sulfur poisoning resistance.

The ratio between TiO ₂ and ZrO ₂ constituting the second composite oxide is preferably in the range of TiO ₂ / ZrO ₂ = 95/5 to 5/95 by weight. If TiO ₂ is less than this range, the effect of suppressing sulfur poisoning is reduced, and if ZrO ₂ is less than this range, heat resistance is reduced. The method for producing the first composite oxide and the second composite oxide is not particularly limited, and examples thereof include a sol-gel method using an alkoxide or the like and a coprecipitation method using a mixed aqueous solution of an inorganic salt and aqueous ammonia. It is desirable to use a sol-gel method and a coprecipitation method, which are characterized in that a composite oxide having a high specific surface area is relatively easily obtained.

The mixing ratio of the first composite oxide and the second composite oxide is, as a weight ratio, the first composite oxide: the second composite oxide = 4:
It is desirable to set it in the range of 1-1: 4. If the amount of the first composite oxide is less than this range, the heat resistance and the activity at 450 ° C. or more will decrease, and if the amount of the second composite oxide is less than this range, the sulfur poisoning resistance will decrease. The first composite oxide and the second composite oxide may be used alone to constitute a carrier, or a carrier obtained by coating a surface of a mixed powder thereof with an alumina powder or the like may be used as the carrier. Further, the shape of the carrier can be the same as a conventional one such as a pellet or a honeycomb shape, and can be used by coating a cordierite carrier substrate or a metal carrier substrate.

In the exhaust gas purifying catalyst of the present invention, at least Na and Ba are used as NO _x storage elements. Na is slightly less basic than K, but exhibits the same NO _x storage ability as K in a high temperature range of 450 ° C. or higher. Moreover Na, in exhaust gas containing SO _x, it is not possible to stabilize generates a composite sulfate by reaction with liberated Mg and SO _x from MgO-Al ₂ O ₃ composite oxide. Further, since Na has a lower basicity than K, it has low reactivity with SO _{x in} the exhaust gas, and is unlikely to be stabilized as a sulfate.

On the other hand, by using Ba, the NO _x storage ability in a low temperature range of less than 450 ° C. is improved. Ba is K and
Because of the low basicity compared to Na, low reactivity with the SO _x in the exhaust gas, hardly occurs to be stabilized becomes sulfate. Therefore, by using at least Na and Ba as NO _x storage elements, high NO _x purification performance is exhibited from a low temperature range of 250 ° C. to a high temperature range of 650 ° C., and the durability of the NO _x purification performance is improved.

NO_xAs storage elements, at least Na and Ba
, It may consist of Na and Ba only, and K, L
Alkali metals such as i and Cs, alkaline earths such as Ca and Sr
Select from metals or rare earth elements such as La, Ce, Sc, Y
NO other than Na and Ba_xCan be used together with occlusion elements
You. Also NO_xThe amount of occluded elements supported per 100 g of carrier
It is desirable that the total amount be in the range of 0.02 to 1.0 mol. Responsible
NO if holding capacity is less than 0.02 mol_xNO storage capacity is small _xPurification
Performance decreases, and even if it exceeds 1.0 mol, NO_xSucking
Malfunctions such as saturating storage capacity and decreasing ternary activity
Confusion occurs. Note that sulfur poisoning resistance and N between 250 ° C and 650 ° C
O_xIn order to achieve both storage capacity, the supported amount of Na and Ba
Is at least 0.01 mol per 100 g of carrier
It is desirable to have.

As the noble metal, one or more of platinum (Pt), rhodium (Rh), palladium (Pd), iridium (Ir), osmium (Os) and the like can be used.
Pt is particularly desirable. Regardless of the noble metal, the supported amount is preferably 0.1 to 20 g, particularly preferably 0.5 to 10 g, per 100 g of the carrier. Even if the amount of the noble metal supported is further increased, the activity is not improved, and the effective use thereof cannot be achieved. On the other hand, if the amount of the noble metal supported is less than this, practically sufficient activity cannot be obtained.

In order to support the NO _x storage element and the noble metal on the carrier, it is necessary to use an acetate, a nitrate or the like to carry the NO _x storage element and the noble metal in the same manner as in the prior art using an impregnation method, a spray method, a slurry mixing method or the like. Can be. The exhaust gas purifying catalyst of the present invention may also contain cerium oxide or cerium oxide stabilized with zirconia. This makes it possible to further improve the NO _x purification performance in transient combustion by the oxygen storage / release action of the cerium oxide.

By contacting the exhaust gas purifying catalyst of the present invention with exhaust gas in an oxygen-excess atmosphere, NO _x is stored in the NO _x storage element containing at least Na and Ba. Then, when the exhaust gas in the stoichiometric or rich atmosphere is temporarily supplied by the transient combustion, the NO _{x in} the exhaust gas and the stored NO _x are converted into HC and CO in the exhaust gas by the catalytic action of the noble metal.
It reacts with reducing components such as to reduce and purify.

[0027] The first composite oxide and the second composite oxide are both because of very low reactivity with _the NO _x storage element, hardly occurs reaction between _the NO _x storage element even in a high temperature range. Further, Na and Ba as NO _x storage elements do not produce complex sulfate together with free Mg even in an exhaust gas containing SO _x, and it is difficult to produce sulfate due to SO _x . In addition, Ba improves the NO _x storage ability in a low temperature range of 250 ° C. to 450 ° C. In the exhaust gas purifying catalyst of the present invention, therefore, without the original NO _x storage capacity _the NO _x storage element is impaired, NO _x purifying performance is maintained even higher at a wide temperature range of 250 ° C. ~ 650 ° C. in a transient combustion .

[0028]

The present invention will be described in detail with reference to examples and comparative examples, but the claims of the present invention are not limited by the examples. Table 1 shows the compositions of the catalysts of Examples and Comparative Examples. (Example) M having a specific surface area of 100 m ² / g synthesized by the coprecipitation method
and gO-Al ₂ O ₃ composite oxide powder, and a TiO ₂ -ZrO ₂ composite oxide powder of ZrO ₂ was synthesized in 10% by weight comprises coprecipitation, mixed 1: 1 by weight, a ball mill And mixed for 1 hour.

A predetermined amount of the mixed carrier powder is immersed in a predetermined amount of a mixed solution of a dinitrodiammineplatinum nitric acid solution and a rhodium nitrate aqueous solution having a predetermined concentration, stirred for 5 hours, evaporated to dryness, and then dried in air. Firing at 300 ℃ for 3 hours
Rh was loaded. The supported amount of Pt is 2 g per 100 g of the mixed carrier, and the supported amount of Rh is 0.
1 g.

Next, the carrier powder carrying Pt and Rh is immersed in a predetermined amount of a mixed aqueous solution of barium acetate and sodium acetate at a predetermined concentration, stirred for 5 hours, and evaporated to dryness.
It was calcined at 300 ° C. for 3 hours in the air to support Ba and Na as NO _x storage elements. Ba is for 100g of mixed carrier
0.1 mol is supported, and Na is 0.2 mol per 100 g of the mixed carrier.

Finally, the mixed carrier powder supporting Pt, Rh, Ba and Na was treated in a hydrogen stream at 500 ° C. for 3 hours to prepare a catalyst powder of an example. (Comparative Example 1) The amount of Ba supported on the mixed carrier was 100
A catalyst powder of Comparative Example 1 was prepared in the same manner as in Example 1 except that the amount was 0.3 mol per g.

Comparative Example 2 A catalyst powder of Comparative Example 2 was prepared in the same manner as in Example 1 except that Ba was not supported and the amount of Na supported was 0.3 mol per 100 g of the mixed carrier. (Comparative Example 3) in place of the MgO-Al ₂ O ₃ composite oxide gamma-Al ₂ O ₃
A catalyst powder of Comparative Example 3 was prepared in the same manner as in Example 1 except for using.

Comparative Example 4 A catalyst powder of Comparative Example 4 was prepared in the same manner as in Example 1 except that rutile type TiO ₂ was used instead of the TiO ₂ -ZrO ₂ composite oxide. (Comparative Example 5) instead of the MgO-Al ₂ O ₃ composite oxide γ-Al ₂ O ₃
The catalyst powder of Comparative Example 5 was prepared in the same manner as in Example 1 except that rutile-type TiO ₂ was used instead of the TiO ₂ -ZrO ₂ composite oxide, and the same amount of K was supported instead of Na. Prepared.

[0034]

[Table 1]

[0035] <Test> in the above-mentioned respective catalyst powders were respectively pelletized by filling the durability test apparatus, was carried out respectively two kinds of durability test of high-temperature durability test and SO _x poisoning durability test. In the high-temperature endurance test, a model exhaust gas in a lean atmosphere and a model exhaust gas in a rich atmosphere shown in Table 2 were flowed for 5 hours at an inlet gas temperature of 800 ° C. while alternately switching between lean and rich at 4 minutes / 4 minutes.

In the SO _x poisoning durability test, a model exhaust gas in a lean atmosphere shown in Table 3 was flowed at an inlet gas temperature of 600 ° C. for 5 hours, and then a model exhaust gas in a rich atmosphere shown in Table 3 was injected at an inlet gas temperature of 700 ° C. for 10 minutes. Shed.

[0037]

[Table 2]

[0038]

[Table 3]

The catalyst after the high-temperature endurance test and the catalyst after the SO _x poisoning endurance test were respectively mounted on a normal-pressure fixed-bed flow reactor,
Using the lean and rich model exhaust gases shown in Table 4,
The mixture was circulated in the order of the rich pretreatment shown in FIG. 1 → lean → rich spike → lean, and the catalyst output gas during that time was analyzed.

[0040]

[Table 4]

FIG. 1 shows a bold line in the gas containing a catalyst.
NO is _x amount, a NO _x amount in the gas leaving the catalyst is lower curve, for NO _x storage amount with the passage of time is saturated, NO _x amount leaving the catalyst in the gas is NO in the catalyst filled in the gas _x asymptotically. Therefore, a rich spike was introduced when the NO _x occlusion amount was saturated, the atmosphere was made rich for 3 seconds, and then the atmosphere was made lean again.

Then, the NO _x occlusion amount after the rich spike was calculated from the area of the solid portion shown in FIG. Table 5 The results after high-temperature durability test, indicates the results of post-SO _x poisoning durability test are shown in Table 6.

[0043]

[Table 5]

[0044]

[Table 6]

<Evaluation> As shown in Table 5, the catalyst of the example after the high-temperature durability test was inferior in activity at 350 ° C. or lower as compared with Comparative Example 1, but was excellent in activity at 450 ° C. or higher. In comparison with Comparative Example 2, the activity was inferior at 550 ° C. or higher, but excellent at 450 ° C. or lower. Further Comparative Example 3,
Compared with Comparative Example 4, the activity was excellent in all temperature ranges.
Is almost equivalent to

[0046] Also from Table 6, the catalyst of Example after SO _x poisoning durability test, although inferior in Comparative Example 1 as compared the 350 ° C. or less of the active, are excellent at 450 ° C. or more active. In comparison with Comparative Example 2, the activity was inferior at 550 ° C. or higher, but excellent at 450 ° C. or lower. Further Comparative Example 3,
Compared with Comparative Example 4, the activity was excellent in all temperature ranges.
550 ° C or more, but less active than 550 ° C
The following activities are excellent.

[0047]

According to the exhaust gas purifying catalyst and exhaust gas purifying method of the present invention, high temperature durability is excellent and
SO _x poisoning can be suppressed. Therefore it is possible after use in a high temperature range, or that _the NO _x purification performance can be impaired even after use in exhaust gas containing SO _x without a long time maintain high _the NO _x purification performance in a wide temperature range in the transient combustion .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a method of evaluating the NO _x storage amount after a rich spike.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/28 301 B01D 53/36 D 102H (72) Inventor Toshiyuki Tanaka Okuchochu character, Nagakute-cho, Aichi-gun, Aichi prefecture 41, Yokomichi, Toyota Central Research Institute, Inc. (72) Inventor Kiyoshi Yamazaki Ochi, Nagakute-cho, Aichi, Aichi, Japan 41-Yokomichi, Toyota Central Research Institute, Inc. (72) Inventor Akihiko Suda Aichi, Aichi (71) Inventor: Shinichi Matsunaga, 41, Nagachite-cho, Aichi-gun, Aichi-gun, Aichi-gun, Japan 41 Toyota Chuo Research Institute, Inc. (72) Invention Person: Toshio Yamamoto 41, Chukku Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture 1 Toyota Central R & D Laboratories Co., Ltd. 41 Toyota Chuo R & D Co., Ltd., No. 41, Nagachute-cho, Nagakute-cho, Aichi-gun, Japan. (72) Inventor Masataka Sugiura. 41 Toyota-Chuo Research Laboratory, Co., Ltd. F-term (reference) 3G091 AA02 AB06 BA07 BA11 BA14 BA39 CB02 FA04 FA11 FA16 FB02 FB03 FB10 FB12 FC07 FC08 GA01 GA06 GB01X GB02W GB03W GB04W GB05W GB06W GB10X GB17X 4D048 AA06 AA13 AA18 AB01 BA03 BA01 BA01 BA03 BAX BA42X BB01 BB02 BC05 4G069 AA03 BA01A BA01B BA04A BA04B BA05A BA05B BA06A BA06B BA17 BA20A BA20B BB02A BB02B BB04A BB04B BB06A BB06B BC01A BC02A BC02B BC03A BC04A BC08A BC09A BC10A BC10B BC12A BC13A BC13B BC16A BC16B BC38A BC40A BC42A BC43A BC50A BC50B BC51A BC51B BC69A BC71A BC71B BC72A BC73A BC74A BC75A BC75B CA02 CA03 CA09 DA05 DA06 EA02Y EA19 EC02Y EC22Y ED07

Claims (3)

[Claims] 1. A carrier comprising a first composite oxide represented by MgO—Al ₂ O ₃ and a second composite oxide represented by TiO ₂ —ZrO ₂ , an alkali metal, an alkaline earth metal and a rare earth element and _the NO _x storage element supported on the carrier contains at least sodium and barium is selected from, the exhaust gas purifying catalyst of a noble metal supported on the carrier, characterized in that it comprises a. 2. A carrier comprising a first composite oxide represented by MgO—Al ₂ O ₃ and a second composite oxide represented by TiO ₂ —ZrO ₂ , an alkali metal, an alkaline earth metal and a rare earth element at least sodium and barium is selected from the _the NO _x storage element supported on the carrier, the exhaust gas purifying catalyst comprising a noble metal supported on the carrier, nitrogen oxides in an oxygen excess atmosphere ( exhaust gas purification method, characterized in contacting the exhaust gas containing NO _x). 3. A carrier comprising a first composite oxide represented by MgO—Al ₂ O ₃ and a second composite oxide represented by TiO ₂ —ZrO ₂ , an alkali metal, an alkaline earth metal and a rare earth element at least sodium and barium is selected from the _the NO _x storage element supported on the carrier, the exhaust gas purifying catalyst comprising a noble metal supported on the carrier, the sulfur oxides in an oxygen excess atmosphere ( SO _x ) and nitrogen oxides (NO _x )
An exhaust gas purification method comprising contacting an exhaust gas containing: