JP2010099633A - S storage catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an S storage catalyst exhibiting high S storage ability in the whole range of low temperature to intermediate/high temperature. <P>SOLUTION: The S storage catalyst includes: a catalytic carrier; a catalytic metal which is deposited on the catalytic carrier and used for oxidizing SO<SB>2</SB>in exhaust gas into SO<SB>3</SB>; and an S storage material which is deposited on the catalytic carrier and used for adsorbing a sulfur component in the exhaust gas. The S storage catalyst further includes a portion 2 containing Ba alone in which Ba is contained alone as the S storage material and a K-containing portion 1 in which K is contained at the least as the S storage material. The K-containing portion 1 is arranged on the upstream side of the exhaust gas and the portion 2 containing Ba alone is arranged on the downstream side of the exhaust gas. The portion 2 containing Ba alone exhibits extremely high S storage ability in an intermediate/high temperature range in which the temperature of the exhaust gas becomes about 400°C or higher and the K-containing portion exhibits comparatively high S storage ability even in a low temperature range of about 200°C or lower. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an S storage catalyst, and more particularly to an S storage catalyst that can be suitably used in an exhaust gas purification device that purifies exhaust gas discharged from a lean burn engine.

  2. Description of the Related Art Conventionally, as an exhaust gas purification catalyst for automobiles, oxidation of carbon monoxide (CO) and hydrocarbons (HC) and reduction of nitrogen oxides (NOx) in exhaust gas are performed simultaneously under a stoichiometric operating condition. A three-way catalyst that goes and purifies is used. As such a three-way catalyst, for example, a porous carrier layer made of γ-alumina or the like is formed on a heat resistant substrate made of cordierite or the like, and platinum (Pt) or rhodium (Rh) is formed on the porous carrier layer. A catalyst supporting a noble metal such as) is widely known.

On the other hand, in recent years, from the viewpoint of protecting the global environment, carbon dioxide (CO ₂ ) in exhaust gas discharged from internal combustion engines such as automobiles has become a problem, and so-called lean burn that causes lean combustion in an oxygen-excess atmosphere is promising as a solution. Is being viewed. In this lean burn, since the amount of fuel used can be reduced, the generation of CO _{2 as} the combustion exhaust gas can be suppressed.

  Incidentally, the performance of the exhaust gas purification catalyst greatly depends on the set air-fuel ratio (A / F) of the engine. That is, on the lean side where the air-fuel ratio is large, the amount of oxygen in the exhaust gas after combustion increases, so that the oxidation action becomes active and the reduction action becomes inactive. Therefore, the conventional three-way catalyst that can efficiently purify CO, HC, and NOx in the exhaust gas at the stoichiometric air-fuel ratio (stoichiometric) is sufficient for the reduction and removal of NOx in a lean atmosphere where oxygen is excessive. Does not show a good purification performance. Therefore, there has been a demand for an exhaust gas purification catalyst for a lean burn engine that can efficiently purify NOx even in an oxygen-excess atmosphere.

  As such an exhaust gas purification catalyst for a lean burn engine, a NOx occlusion reduction type catalyst in which a NOx occlusion material made of an alkaline earth metal such as barium (Ba) or the like and a catalyst noble metal such as Pt are supported on a porous carrier is used. It has been put into practical use. Unlike a three-way catalyst, this NOx occlusion reduction type catalyst for lean burn engines efficiently stores and reduces NOx even if it is an exhaust gas containing excess oxygen. That is, at all times when the fuel is burned under an oxygen-excess fuel lean condition, the NOx occlusion material occludes NOx in a lean atmosphere, while the exhaust gas becomes a reducing atmosphere by intermittently setting the fuel stoichiometric to rich condition, so that the NOx occlusion material NOx is released from the gas and purified by reacting with reducing components such as HC and CO. Note that HC and CO in the exhaust gas are oxidized by the noble metal catalyst and also consumed for the reduction of NOx, so that HC and CO are also efficiently purified.

However, the exhaust gas contains SO ₂ produced by burning sulfur (S) contained in the fuel. This SO ₂ is oxidized by catalytic noble metal in high-temperature exhaust gas to become SO ₃ . And this SO ₃ becomes sulfuric acid by the water vapor contained in the exhaust gas. When SO ₃ or sulfuric acid is generated in the exhaust gas in this way, sulfite or sulfate is generated by the reaction of the SO ₃ or sulfuric acid and the NOx storage material, and the NOx storage material is poisoned and deteriorated. When the NOx occlusion material deteriorates due to sulfur poisoning (S poisoning) in this manner, NOx can no longer be occluded, and the NOx purification performance after durability is lowered.

  Therefore, an exhaust gas purifying device is known in which an S storage catalyst that stores S component from exhaust gas is disposed in front of the NOx storage reduction catalyst (see, for example, Patent Documents 1 and 2).

  The S storage catalyst in this exhaust gas purifying apparatus comprises a carrier made of alumina, an S storage material made of an alkali metal such as potassium or sodium, or an alkaline earth metal such as calcium or barium, and a catalyst noble metal such as platinum or palladium. It is supported. According to such an S storage catalyst, the S component in the exhaust gas can be stored. Therefore, by disposing the S storage catalyst in the preceding stage of the NOx storage reduction catalyst, the S coverage of the NOx storage reduction catalyst is increased. Can suppress poison.

The NOx occlusion reduction type catalyst is composed of a first catalyst located on the exhaust gas upstream side and a second catalyst located on the exhaust gas downstream side, and the first catalyst contains Ba as the first NOx occlusion material, and the second catalyst Is known to contain K as the second NOx storage material (see, for example, Patent Document 3).
JP 2006-329018 A JP 2006-116431 A JP 2001-86345 A

  However, in the S storage catalyst, depending on the type and combination of the S storage material used, the S storage capacity is extremely lowered in a low temperature range where the exhaust gas temperature is about 200 ° C. or lower, or the exhaust gas temperature is about 400 ° C. or higher. It became clear that S occlusion ability fell in the middle and high temperature range. For this reason, with the conventional S storage catalyst, it was difficult to exhibit a high S storage capacity in all regions from low temperature to medium high temperature.

  This invention is made | formed in view of the said situation, and it aims at providing the S occlusion catalyst which can exhibit high S occlusion ability in all the area | regions of low temperature-medium high temperature.

The S storage catalyst of the present invention that solves the above problems comprises a catalyst carrier, a catalyst metal that is supported on the catalyst carrier and oxidizes SO ₂ in the exhaust gas to SO ₃ , and a sulfur component in the exhaust gas that is supported on the catalyst carrier. An S storage catalyst comprising an S storage material for storage, wherein the S storage material includes at least Ba and K, the Ba storage portion including Ba alone as the S storage material, and at least the S storage material. A K-containing portion containing K, wherein the K-containing portion is disposed on the exhaust gas upstream side, and the Ba single-containing portion is disposed on the exhaust gas downstream side.

  Ba as an S-occlusion material has an extremely low S occlusion ability in a low temperature range where the exhaust gas temperature is about 200 ° C. or lower, while the exhaust gas temperature is about 400 ° C. or higher, as shown in Examples described later. It has S occlusion characteristics that S occlusion ability is greatly improved at high temperatures.

  The S storage catalyst of the present invention has a Ba single-containing portion containing Ba having such S storage characteristics alone. Here, if an S occlusion material made of an alkali metal such as K is included as an S occlusion material other than Ba in the Ba-only containing part, it becomes made of a strongly basic alkali metal as SOx in the exhaust gas is adsorbed. The S occlusion material moves to and adheres to the surface of the coat layer. As a result, gas diffusion to the inside of the coat layer is hindered, and utilization efficiency of Ba existing inside the coat layer is lowered. In that respect, in the S storage catalyst of the present invention, the Ba-only containing part contains Ba alone, and does not contain the S storage material made of an alkali metal such as K. For this reason, the utilization efficiency of Ba in the coating layer is not lowered, and the S occlusion characteristic of Ba is ensured that the S occlusion ability is greatly improved in the middle and high temperature range where the exhaust gas temperature is about 400 ° C. or higher. To be demonstrated.

  Moreover, the S storage catalyst of this invention has a K containing part containing at least K as S storage material other than Ba single containing part. K as the S occlusion material exhibits a relatively high S occlusion ability from a low temperature range to a medium to high temperature range (a range of about 20 to 300 ° C.), as shown in Examples described later. That is, K does not extremely reduce the S storage capacity in a low temperature range of about 200 ° C. or lower. For this reason, the S occlusion material of the present invention exhibits a relatively high S occlusion ability even in a low temperature range of about 200 ° C. or less.

  Therefore, the S storage catalyst of the present invention can exhibit a high S storage capacity in all regions from low temperature to medium high temperature.

  In the S storage catalyst of the present invention, the K-containing portion is disposed on the exhaust gas upstream side, and the Ba single-containing portion is disposed on the exhaust gas downstream side. When the K-containing portion is arranged on the exhaust gas upstream side in this way, it is advantageous in that SOx is occluded on the exhaust gas upstream side with a low temperature.

  Here, in the S storage catalyst of the present invention, the K-containing part is preferably formed in a length range of 2/15 to 2/3 with respect to the total length of the S storage catalyst in the exhaust gas flow direction. When the K-containing part is formed in this length range, as shown in the examples described later, a high S occlusion ability is exhibited from a low temperature range to a middle to high temperature range (a range of about 20 to 600 ° C.).

  Therefore, according to the S storage catalyst of the present invention, it is possible to exhibit a high S storage capacity in all regions from low temperature to medium high temperature.

  Further, in an exhaust gas purification apparatus comprising the S storage catalyst of the present invention disposed on the exhaust gas upstream side and the NOx storage reduction catalyst disposed on the exhaust gas downstream side, the NOx storage reduction catalyst of the NOx storage reduction catalyst can be used even when the exhaust gas temperature is low. S poisoning can be satisfactorily suppressed. Therefore, by approaching such an exhaust gas purification device, it is possible to efficiently store and reduce NOx in the exhaust gas discharged from the lean burn engine for a long period of time and purify it.

  Hereinafter, embodiments of the S storage catalyst of the present invention will be described in detail. The embodiment to be described is merely an example of the embodiment, and the S storage catalyst of the present invention is not limited to the following embodiment. The S occlusion catalyst of the present invention can be implemented in various forms with modifications, improvements, etc. that can be made by those skilled in the art without departing from the gist of the present invention.

The S storage catalyst 10 of the present embodiment is an application of the SOx storage catalyst of the present invention to a so-called monolithic catalyst. The S storage catalyst 10 is a catalyst carrier composed of a base material, a coating layer formed on the surface of the base material, and a catalyst support. A catalyst metal that is supported and oxidizes SO ₂ in the exhaust gas to SO ₃ and an S occlusion material that is supported on the catalyst carrier and occludes the sulfur (S) component in the exhaust gas are provided.

  As the substrate, a honeycomb body made of ceramics such as cordierite or a heat-resistant alloy can be used. In addition, the shape of the substrate may be any of a straight flow type, a filter type, and other types.

  The catalyst carrier is formed into a layer on the surface of the substrate by wash-coating a slurry containing porous oxide powder on the surface of the substrate. This catalyst carrier is formed with a uniform or substantially uniform composition from the exhaust gas upstream end of the substrate to the exhaust gas downstream end.

No particular limitation is imposed on the kind of the catalyst _{support, Al 2 O 3, CeO 2,} ZrO 2, zeolite, at least one selected from TiO ₂ and SiO _2, and / or _{Al 2 O 3, CeO 2,} ZrO 2, zeolite , TiO ₂ and SiO ₂ can be used as at least one kind of composite oxide composed of two kinds. As the composite oxide, especially composite oxide containing CeO _2, such as _CeO 2 -ZrO ₂ is preferred.

  For example, in the case of a monolith type catalyst, the coating amount of the catalyst carrier is preferably 30 g or more, more preferably 50 g or more, and particularly preferably 100 g or more per liter of monolith (honeycomb body) volume. . If the coating amount of the catalyst carrier is too small, the acidity of the SOx occlusion material becomes worse and the occlusion amount decreases. On the other hand, when the coating amount of the catalyst carrier is too large, the pressure loss becomes high. Therefore, the coating amount of the catalyst carrier is preferably 350 g or less, and more preferably 300 g or less.

The type of catalytic metal is not particularly limited as long as SO ₂ in exhaust gas can be oxidized to SO _3, and can be at least one selected from, for example, Pt, Pd, Rh, Fe, and Ag. Among these, it is preferable to use Pt having a particularly high oxidation activity as a catalyst metal.

  For example, in the case of a monolith type catalyst, the amount of catalyst metal supported can be about 0.5 to 10 g per liter of monolith (honeycomb body) volume.

  Here, the S storage catalyst 10 of the present embodiment includes at least Ba and K as the S storage material. Then, as schematically shown in FIG. 1, the S storage catalyst 10 of the present embodiment includes a K-containing portion 1 disposed on the exhaust gas upstream side and a Ba single-containing portion 2 disposed on the exhaust gas downstream side. Become.

  The K-containing part 1 contains at least K as the S storage material. The K-containing portion 1 may contain only K as the S occlusion material, or may contain K and an S occlusion material other than K. The S storage material other than K that can be included in the K-containing portion 1 can be at least one selected from alkali metals other than K and alkaline earth metals. Specific examples of S occlusion materials other than K that can be included in the K-containing portion 1 include alkali metals such as Li, Na, Rb, and Cs, and alkaline earth metals such as Mg, Ca, Sr, and Ba. be able to. Among these, Ba is particularly preferable, and when the K-containing portion 1 contains K and Ba, it is advantageous in terms of improving the S storage performance.

  Ba single containing part 2 contains Ba independently as S occlusion material. That is, Ba single containing part 2 contains only Ba as S occlusion material, and does not contain S occlusion materials other than Ba.

  For example, in the case of a monolith type catalyst, the supported amount of the S storage material in the S storage catalyst 10 of the present embodiment is preferably 0.05 mol or more per liter of monolith (honeycomb body) volume, and 0.3 mol or more. More preferably.

  For example, in the case of a monolith type catalyst, the loading amount of the S storage material in the K-containing portion 1 is preferably 0.1 mol or more, more preferably 0.3 mol or more per liter of monolith (honeycomb body) volume. preferable. In addition, in the case of a monolithic catalyst, for example, in the case of a monolithic catalyst, the amount of K supported in the K-containing portion 1 is preferably 0.1 mol or more, more preferably 0.3 mol or more per liter of monolith (honeycomb body) volume. preferable. If the amount of K supported in the K-containing portion 1 is too small, the SOx occlusion performance in the low temperature range is lowered. On the other hand, if the amount of K supported in the K-containing portion 1 is too large, the substrate is damaged. For this reason, for example, in the case of a monolith type catalyst, the amount of K supported in the K-containing portion 1 is preferably 1.0 mol or less, and preferably 0.6 mol or less per liter of monolith (honeycomb body) volume. More preferred.

  In the case of a monolith type catalyst, for example, in the case of a monolith type catalyst, the supported amount of Ba in the Ba-only containing part 2 is preferably 0.1 mol or more, more preferably 0.3 mol or more, per liter of monolith (honeycomb body). . If the amount of Ba supported in the Ba-only containing part 2 is too small, it becomes difficult to maintain a high S occlusion ability in the middle and high temperature range of about 400 ° C. or higher. On the other hand, if the amount of Ba supported in the Ba-only containing part 2 is too large, the base material is damaged. For this reason, for example, in the case of a monolith type catalyst, the supported amount of Ba in the Ba-only containing part 2 is preferably 1.0 mol or less, and 0.6 mol or less per liter of monolith (honeycomb body) volume. Is more preferable.

  The K-containing portion 1 is preferably formed in a length range of 2/15 to 2/3 with respect to the entire length of the S storage catalyst 10 in the exhaust gas flow direction P. That is, when the total length of the S storage catalyst 10 in the exhaust gas flow direction P is L and the length of the K-containing portion 1 in the exhaust gas flow direction is L1, it is preferable that 2/15 ≦ L1 / L ≦ 2/3. . If the length L1 of the K-containing part 1 is too short, the capacity of the K-containing part 1 becomes small, so that the S occlusion ability decreases in a low temperature range of about 200 ° C. or lower. On the other hand, if the length L1 of the K-containing part 1 is too long, the capacity of the Ba-only containing part 2 becomes small, so that the S occlusion ability decreases in the middle and high temperature range of about 400 ° C. or higher.

  In addition, you may mix | blend another component with the S storage catalyst 10 of this embodiment as needed.

  In the S storage catalyst 10 of the present embodiment having the above-described configuration, the K-containing portion 1 disposed on the exhaust gas upstream side has a relatively high S from the low temperature range to the mid-high temperature range where the exhaust gas temperature is about 20 to 300 ° C. Demonstrate occlusion ability. Moreover, Ba single containing part 2 arrange | positioned in exhaust gas downstream shows the extremely high S occlusion ability in the middle-high temperature range from which exhaust gas temperature becomes about 400 degreeC or more.

  Further, in the S storage catalyst 10 of the present embodiment, the Ba single containing portion 2 does not include an S storage material made of an alkali metal such as K as the S storage material. For this reason, there is no inhibition of gas diffusion due to adhesion of alkali metal such as K on the surface of the coat layer, and utilization efficiency of Ba existing inside the coat layer is not lowered.

  Therefore, in the S storage catalyst 10 of the present embodiment, a high S storage capacity can be exhibited in all regions from low temperature to medium high temperature.

  Further, in the S storage catalyst 10 of the present embodiment, since the K-containing portion 1 is arranged on the exhaust gas upstream side, it is advantageous in that SOx is stored on the exhaust gas upstream side with a low temperature.

  Then, as shown in FIG. 2, the S storage catalyst 10 of the present embodiment is disposed on the downstream side of the exhaust gas from the S storage catalyst 10 in the catalytic converter 20 and the S storage catalyst 10 disposed in the catalytic converter 20. The NOx occlusion reduction catalyst 30 thus made can be suitably used for the exhaust gas purification device 50 disposed in the exhaust gas flow path 40 from the lean burn engine in the exhaust gas purification system.

  According to such an exhaust gas purifying device 50, the S poisoning of the NOx occlusion reduction type catalyst 30 can be satisfactorily suppressed over the entire range from low temperature to medium high temperature, and the exhaust gas discharged from the lean burn engine over a long period of time. It is possible to efficiently store and reduce NOx contained therein and purify it.

(Other embodiments)
In the above-described embodiment, an example in which one monolith type catalyst is used and the exhaust gas upstream side is the K-containing portion 1 and the exhaust gas downstream side is the Ba-only containing portion 2 has been described. As a tandem type arranged in series in the exhaust gas flow path, the monolith catalyst on the exhaust gas upstream side has the configuration of the K-containing portion 1, and the monolith catalyst on the exhaust gas downstream side has the configuration of the Ba-only containing portion 2 Also good.

  In the above-described embodiment, an example in which the present invention is applied to a monolith type catalyst has been described. However, the present invention may be applied to a pellet type catalyst and incorporated in a catalytic converter.

  In accordance with the above embodiment, the S storage catalyst 10 of this example was prepared.

  First, the alumina powder was immersed in an aqueous dinitrodiamine platinum solution, dried and fired to obtain a Pt-supported alumina powder in which Pt was supported on the alumina powder. A predetermined slurry was prepared using this Pt-supported alumina powder and ceria powder.

  Then, the slurry was washcoated on the surface of a base material (diameter: φ30 mm, length: L50 mm) made of a cordierite honeycomb body, dried and fired to form a catalyst coat layer on the surface of the base material.

  Next, half of the one end side corresponding to the exhaust gas upstream side of the base material on which the catalyst coat layer is formed is immersed in a mixed solution of barium acetate and potassium acetate, and the excess solution is blown off. After baking for 2 hours, Ba and K were supported on one half of the catalyst coat layer of the substrate corresponding to the upstream side of the exhaust gas.

  Thereafter, the other half of the base material corresponding to the downstream side of the exhaust gas is immersed in a barium acetate solution, and the excess solution is blown off, followed by calcination at 500 ° C. for 2 hours. Ba was supported on the other half of the layer corresponding to the exhaust gas downstream side.

  Thus, the S storage catalyst 10 of this example was obtained. In the S storage catalyst 10, K and Ba as S storage materials are supported on the K-containing portion 1 on the exhaust gas upstream side. Further, only Ba as an S occlusion material is carried in the Ba-only containing portion 2 on the exhaust gas downstream side.

  The supported amount of each component in the S storage catalyst 10 of this example is Pt: 2 g, alumina: 100 g, ceria: 100 g, K: 0.3 mol, Ba: 0.3 mol per liter of the honeycomb body volume. is there. In addition, the Ba carrying amount in the K-containing portion 1 and the Ba carrying amount in the Ba single containing portion 2 are equal, and both are 0.3 mol / L.

  Further, the K-containing portion 1 is formed in a length range of ½ with respect to the total length L in the exhaust gas flow direction P of the S storage catalyst 10. That is, L1 / L = 1/2, where L is the total length of the S storage catalyst 10 in the exhaust gas flow direction P and L is the length of the K-containing portion 1 in the exhaust gas flow direction.

(Comparative Example 1)
In the S storage catalyst of Comparative Example 1, only Ba as the S storage material is uniformly supported on the entire catalyst. The supported amount of Ba is 0.3 mol / L, as in the above example.

  Since other configurations are the same as those in the embodiment, the description thereof is omitted.

(Comparative Example 2)
In the S storage catalyst of Comparative Example 2, only K as the S storage material is uniformly supported on the entire catalyst. The amount of K supported is 0.3 mol / L, as in the above example.

  The other configuration is the same as that of the above embodiment, and the description thereof is omitted.

(Comparative Example 3)
In the S storage catalyst of Comparative Example 3, K and Ba are uniformly supported on the entire catalyst as the S storage material. As in the previous examples, the loading amount of K is 0.3 mol / L, and the loading amount of Ba is 0.3 mol / L.

  The other configuration is the same as that of the above embodiment, and the description thereof is omitted.

(Performance evaluation of Examples and Comparative Examples 1-3)
The SOx occlusion amounts of the S occlusion catalysts of Examples and Comparative Examples 1 to 3 were examined by the evaluation test shown below.

SO ₂ is constantly flowed into a model gas in a lean atmosphere simulating lean exhaust gas, and the test materials related to the S storage catalyst of Example 1 and Comparative Example 1 are placed therein, and the input gas temperature is 100 ° C., 200 ° C. The SOx occlusion amount was examined under the steady temperature conditions of 300 ° C, 400 ° C, and 500 ° C. The gas composition of the test atmosphere is SO ₂ : 100 ppm, NO: 200 ppm, C ₃ H ₆ : 200 ppm, O ₂ : 10%, CO ₂ : 10%, H ₂ O: 5%, N ₂ : the balance. . The gas flow rate was 30 liters / min.

  As shown in FIG. 3, in the S storage catalyst of Comparative Example 1 in which only Ba is supported as the S storage material on the entire catalyst, the S storage capacity is extremely reduced in a low temperature range of about 200 ° C. or less. The S occlusion capacity was extremely high in the middle and high temperature range of about 400 ° C or higher.

  In the S storage catalyst of Comparative Example 2 in which only K as the S storage material is supported on the entire catalyst, the S storage capacity in the low temperature range of about 200 ° C. or less is higher than that of the S storage catalyst of Comparative Example 1, The S occlusion ability in the middle and high temperature range of about 400 ° C. or higher was low.

  In the S storage catalyst of Comparative Example 3 in which K and Ba are supported on the entire catalyst as the S storage material, as compared with the S storage catalyst of Comparative Example 1, the S storage catalyst of Comparative Example 2 has a temperature of about 200 ° C. or less. Although the S occlusion ability in the low temperature range was high, the S occlusion ability in the middle and high temperature range of about 400 ° C. or higher was low.

  On the other hand, all the S storage catalysts 10 of the Example showed a high S storage capacity over a temperature range of 100 to 500 ° C.

(Evaluation of the relationship between the length of the K-containing part and the S occlusion amount)
In Example 1, the length L1 of the K-containing portion 1, that is, the value of L1 / L is set to 0, 1/15, 2/15, 1/5, 1/3, 1/2, 2/3, 4/5. 1 and variously changed, and the relationship with the S occlusion amount was examined. The supported amount of K and the supported amount of Ba were both constant at 0.3 mol / L.

  As shown in FIG. 4, when the value of L1 / L is smaller than 2/15, the proportion of Ba-containing part 2 is increased, and the S occlusion ability at 400 ° C. is high. The S occlusion ability at ℃ was low. On the other hand, when the value of L1 / L is larger than 2/3, the proportion of the K-containing portion 1 is increased, so that the S storage capacity at 200 ° C. is high, but the S storage capacity at 400 ° C. is low.

  From these results, if the relationship of 2/15 ≦ L1 / L ≦ 2/3 is satisfied, it can be confirmed that a high S occlusion ability is exhibited from a low temperature range of about 200 ° C. or lower to a medium high temperature range of about 400 ° C. or higher. It was.

It is explanatory drawing which illustrates typically the structure of the S storage catalyst of embodiment. It is explanatory drawing which illustrates typically the example of application of the S storage catalyst of embodiment. It is a graph which shows the result of having investigated the relationship between entrance gas temperature and SOx occlusion amount about S occlusion catalyst of an Example and Comparative Examples 1-3. It is a graph which shows the result of having investigated the relationship between the length of a K containing part, and S occlusion amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... K containing part 2 ... Ba single containing part 10 ... S occlusion catalyst

Claims (2)

An S storage catalyst comprising a catalyst support, a catalyst metal supported on the catalyst support for oxidizing SO ₂ in exhaust gas to SO ₃ , and an S storage material supported on the catalyst support and storing sulfur components in the exhaust gas. There,
Including at least Ba and K as the S storage material,
Ba containing part containing Ba alone as the S storage material, and K containing part containing at least K as the S storage material,
The S storage catalyst, wherein the K-containing portion is disposed on the exhaust gas upstream side, and the Ba single-containing portion is disposed on the exhaust gas downstream side.   2. The S storage catalyst according to claim 1, wherein the K-containing portion is formed in a length range of 2/15 to 2/3 with respect to a total length of the S storage catalyst in the exhaust gas flow direction.

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