JP5010139B2 - Exhaust gas purification catalyst, method for producing the same, and exhaust gas purification apparatus - Google Patents

Description

  The present invention relates to an exhaust gas purification catalyst for removing nitrogen oxides, hydrocarbons, and carbon monoxide in exhaust gas discharged from a diesel engine or the like, a method for producing the same, and an exhaust gas purification device.

  As an exhaust gas purifying catalyst for removing nitrogen oxides in exhaust gas discharged from a diesel engine or the like, for example, a support on which a noble metal and an occlusion material for storing NOx are supported is applied to a honeycomb substrate. Things. Examples of the carrier include alumina, ceria, zirconia, and titania. Moreover, platinum and rhodium are mentioned as said noble metal. Examples of the occlusion material include alkali metals such as K and alkaline earth metals such as Ba.

  By installing such an exhaust gas purifying catalyst in an exhaust pipe of a diesel engine or the like, nitrogen oxides in the exhaust gas are removed. That is, when the exhaust gas is in a lean state (oxygen concentration is high (3% or more)), NO and oxygen react on the noble metal to generate NOx, and this NOx is occluded in the occlusion material.

  Further, NOx occluded in the occlusion material is sprayed with an organic compound or fuel as a reducing agent on the exhaust gas purification catalyst, or the amount of fuel injected by the engine is increased, so that the exhaust gas is in a rich state (oxygen concentration). NOx stored in the storage material moves onto the noble metal, and the NOx, hydrocarbons and CO react to produce water, nitrogen, and carbon dioxide. It is discharging. Therefore, in the exhaust gas purifying catalyst, occlusion of nitrogen oxides and discharge of the occluded nitrogen oxides as nitrogen are repeatedly performed (see Patent Document 1).

As a specific example of the exhaust gas purification catalyst as described above, there is a catalyst as shown in FIG. As shown in this figure, the exhaust gas-purifying catalyst 100 comprises a carrier 101 that is a complex oxide of ceria-zirconia, and the carrier 101 includes Pt 102, which is a noble metal, barium carbonate 103, which is a nitrogen oxide storage material, and WO ₃ / TiO ₂ —SiO ₂ 104 is supported.

  On the other hand, Patent Document 2 discloses an absorption reduction type NOx formed by mixing carrier particles carrying catalyst components and NOx absorbent particles as a catalyst having improved NOx purification performance at low temperature and SOx desorption properties. A purification catalyst is disclosed.

Japanese Patent No. 3311012 JP 2002-79096 A

However, in the exhaust gas purifying catalyst 100 described above, when it is kept at 700 ° C. for 200 hours and thermally deteriorated, the ceria-zirconia zirconium in the carrier 101 reacts with the barium carbonate 103 as shown in FIG. Barium such as BaZrO ₃ 105, a carrier component, and a composite oxide are formed. Therefore, barium carbonate 103, which is a storage material for nitrogen oxides, decreases, and the maximum denitration rate decreases from about 80% to about 40%, as shown in FIG. Further, due to the above-described thermal deterioration and the formation reaction of BaZrO ₃ , as shown in FIG. 17B, Pt 102 moves on the support 101 and sinters to become Pt 106. Therefore, as shown in FIG. 18, the temperature distribution of the denitration rate shifts to the high temperature side.

  Accordingly, the present invention has been proposed in view of the above-described problems, and provides an exhaust gas purification catalyst that improves heat resistance and suppresses a decrease in denitration performance due to thermal degradation, a method for manufacturing the same, and an exhaust gas purification device. Objective.

An exhaust gas purifying catalyst according to a first invention that solves the above-described problem includes a first support made of CeO ₂ , an oxide of Ti, Si, and W or a composite oxide thereof, and oxidation of Al, Zr, or La. A second carrier made of at least one kind of compound or a composite oxide thereof, and the first carrier carries a storage material and a noble metal that occlude nitrogen oxides, while the second carrier carries a noble metal. It is characterized by becoming.

The exhaust gas purifying catalyst according to the second invention for solving the above-mentioned problem is the exhaust gas purifying catalyst described in the first invention, wherein the storage material is an alkali metal or an alkaline earth metal. Features.
Examples of the alkali metal include K and Na. Examples of the alkaline earth metal include Ca and Ba.

An exhaust gas purifying catalyst according to a third invention for solving the above-mentioned problem is the exhaust gas purifying catalyst described in the first or second invention, wherein the first support is doped with a rare earth element. Features.
Examples of the rare earth element include La and the like.

  An exhaust gas purifying catalyst according to a fourth invention for solving the above-described problem is the exhaust gas purifying catalyst according to any one of the first to third inventions, wherein the noble metal is Pt, Rh, Pd, It is at least one selected from Ir, Ru, alloys thereof, or oxides thereof.

  An exhaust gas purifying catalyst according to a fifth invention for solving the above-mentioned problem is the exhaust gas purifying catalyst according to any one of the first to fourth inventions, wherein the noble metal is in contact with the first carrier. 0.1 to 10 wt%.

  An exhaust gas purifying catalyst according to a sixth invention that solves the above-described problem is the exhaust gas purifying catalyst according to any one of the first to fifth inventions, wherein the occlusion material is attached to the first carrier. On the other hand, it is 0.1 to 50 wt%.

  An exhaust gas purifying catalyst according to a seventh invention that solves the above-described problems is the exhaust gas purifying catalyst according to any one of the first to sixth inventions, wherein the first carrier, the second carrier, The component ratio is 0.05 to 20.

  An exhaust gas purifying catalyst according to an eighth invention for solving the above-described problem is the exhaust gas purifying catalyst according to any one of the first to seventh inventions, wherein the first carrier and the second carrier are The average particle size is 4 μm or more.

An exhaust gas purifying catalyst manufacturing method according to a ninth invention for solving the above-mentioned problem is an exhaust gas purifying catalyst manufacturing method for purifying exhaust gas containing nitrogen oxides, wherein the first support made of CeO ₂ is precious metal. And a step of impregnating and supporting an occlusion material that occludes nitrogen oxide, an oxide of Ti, Si, and W or a composite oxide thereof, and at least one of an oxide of Al, Zr, or La, or a composite oxide thereof A step of impregnating and supporting a noble metal on a second carrier comprising: a step of mixing the first carrier and the second carrier, adding a binder to form a slurry, and applying the slurry to a substrate. .

An exhaust gas purification apparatus according to a tenth aspect of the present invention that solves the above-described problem is an exhaust gas purification apparatus that purifies exhaust gas containing nitrogen oxides, and is disposed in an exhaust pipe from which the exhaust gas is exhausted. An exhaust gas purifying catalyst according to any of the inventions, and a fuel injection means disposed on the upstream side of the exhaust gas purifying catalyst and injecting an organic reducing agent or fuel into the exhaust gas purifying catalyst. And
Examples of the organic reducing agent include hydrocarbons, alcohols, and ethers.

An exhaust gas purifying apparatus according to an eleventh invention for solving the above-mentioned problem is the exhaust gas purifying apparatus described in the tenth invention, wherein the first oxidation catalyst is arranged upstream of the exhaust gas purifying catalyst. It is characterized by.
By disposing the first oxidation catalyst on the upstream side of the exhaust gas purification catalyst, the temperature of the exhaust gas purification catalyst can be raised, and the nitrogen oxides stored in the exhaust gas purification catalyst can be removed as nitrogen. .

An exhaust gas purifying apparatus according to a twelfth invention for solving the above-described problem is the exhaust gas purifying apparatus described in the tenth or eleventh invention, wherein a second oxidation catalyst is disposed downstream of the exhaust gas purifying catalyst. It is characterized by arranging.
By disposing the second oxidation catalyst on the downstream side of the exhaust gas purification catalyst, nitrogen oxides, unburned hydrocarbons, and carbon monoxide in the exhaust gas can be removed.

An exhaust gas purifying apparatus according to a thirteenth invention for solving the above-described problem is the exhaust gas purifying apparatus according to any one of the tenth to twelfth inventions, wherein the exhaust gas purifying apparatus is located upstream or downstream of the exhaust gas purifying catalyst. A PM processing means for processing particulate matter in the exhaust gas is arranged.
Examples of the PM treatment means include a PM combustion catalyst, a PM collection filter, or a collection filter with a PM combustion catalyst.
By arranging the PM processing means on the upstream side or the downstream side of the exhaust gas purification catalyst, black smoke and nitrogen oxides in the exhaust gas can be removed.

  An exhaust gas purifying apparatus according to a fourteenth invention for solving the above-described problem is the exhaust gas purifying apparatus according to any of the tenth to thirteenth inventions, wherein the exhaust gas is exhaust gas discharged from a diesel engine. It is characterized by being.

  According to the exhaust gas purifying catalyst of the present invention, even if it is thermally deteriorated, the second component does not react with the occlusion material, and noble metals are not sintered. It is almost the same before and after. Further, the denitration rate of the exhaust gas purifying catalyst has substantially the same distribution before and after thermal degradation. That is, the heat resistance of the exhaust gas purifying catalyst is improved. By doping the rare earth element in the first support, it is possible to suppress a decrease in the specific surface area of the first support and suppress a decrease in the denitration rate after the heat deterioration in the exhaust gas purification catalyst.

  By setting the precious metal to a predetermined weight with respect to the first support, the precious metal is supported in a state of being appropriately dispersed in the first support and the second support, and the catalyst performance can be efficiently expressed. By setting the storage material to a predetermined weight ratio, the NOx removal rate is greater than or equal to a predetermined value at 200 to 550 ° C. By setting the first carrier and the second carrier to a predetermined weight ratio, the maximum denitration rate can be improved and the denitration rate on the high temperature side can be improved.

  By making the particle sizes of the first carrier and the second carrier equal to or larger than a predetermined size, the noble metal is appropriately dispersed in the first carrier and the second carrier, and the occlusion material is appropriately dispersed in the second carrier. Thus, sintering of the noble metal and the occlusion material is suppressed. When a binder is added to the exhaust gas purification catalyst to form a slurry, and when this slurry is applied to the base material, the first carrier and the second carrier are separated appropriately, thereby increasing the gas diffusion path and improving the denitration rate. . Furthermore, for example, when light oil is injected as fuel, diffusion of the light oil is facilitated, and the reactivity is improved. In addition, the contact area between the occlusion material and the second carrier is reduced, and the reaction between the occlusion material and the second carrier is suppressed. Therefore, the acid point in the exhaust gas purifying catalyst (active point that shows acidity, which is contained in a large amount of oxides of Ti, Si, and W) is increased, and the decomposition reaction of the acid gas SOx and the adsorption of S content to the occlusion material are suppressed. The performance deterioration of the catalytically active component is prevented.

  According to the method for producing an exhaust gas purifying catalyst according to the present invention, only one type of slurry containing the first carrier and the second carrier is applied to the base material, and the production process is simple. Can be suppressed.

  According to the exhaust gas purification apparatus of the present invention, the oxygen concentration in the exhaust gas is reduced by injecting an organic reducing agent or fuel onto the exhaust gas purification catalyst by the fuel injection means, and nitrogen stored in the exhaust gas purification catalyst. The oxide is reduced and discharged as nitrogen. Therefore, nitrogen oxides contained in the exhaust gas can be stored in the storage material of the exhaust gas purification catalyst, and the stored nitrogen oxides can be discharged as nitrogen, so that the nitrogen oxides in the exhaust gas can be purified.

In addition, by disposing the oxidation catalyst at a predetermined position, even if unburned hydrocarbons, oxides thereof, and carbon monoxide pass through the exhaust gas purification catalyst, they can be burned by the oxidation catalyst, or for exhaust gas purification. The processing temperature of the nitrogen oxide in the catalyst can be ensured.
And by arranging the PM treatment means at a predetermined position on the exhaust gas purification catalyst, in addition to removing nitrogen oxides in the exhaust gas, it is possible to collect particulate matter and remove the collected particulate matter. it can. The PM treatment means is regenerated at a high temperature, and the heat required at that time is obtained by oxidizing and burning the organic reducing agent injected onto the exhaust gas purification catalyst. Further, when the heat is insufficient, the temperature can be increased by adding the above-described oxidation catalyst. When the exhaust gas is exhaust gas from a diesel engine, emission of nitrogen oxides contained in the exhaust gas can be suppressed.

  The best mode for carrying out the exhaust gas purifying catalyst and the method for producing the same according to the present invention will be described below.

  FIG. 1 is a schematic diagram of an exhaust gas purifying catalyst according to the best mode of the present invention. FIG. 1 (a) shows a state before thermally degrading it, and FIG. 1 (b) shows a state after thermally degrading it. Indicates the state.

As shown in FIG. 1A, the exhaust gas purifying catalyst 7 according to the best mode of the present invention is an exhaust gas purifying catalyst that purifies nitrogen oxides contained in the exhaust gas, and is made of CeO ₂ (ceria). It has a first support 1, an oxide of Ti, Si and W or a composite oxide thereof, and a second support 2 made of at least one of an oxide of Al, Zr or La, or a composite oxide thereof. A noble metal 3 is supported on the first carrier 1 and the second carrier 2. The occlusion material 4 that occludes nitrogen oxides is supported only on the first carrier 1. However, in FIG. 1, the second support 2 is composed of at least one of oxides of Al, Zr, or La, or a first component 5 made of a composite oxide thereof, and an oxide of W, Ti, Si, or these And a second component 6 made of the complex oxide.

  In such an exhaust gas purifying catalyst 7, the second component 6 and the occlusion material 4 did not react even after aging (thermal deterioration) at 700 ° C. for 200 hours. Further, the noble metal 3 did not aggregate and sinter. As a result, the denitration rate of the exhaust gas purifying catalyst 7 was almost the same before and after thermal degradation. Further, the denitration rate of the exhaust gas purifying catalyst 7 had substantially the same temperature distribution before and after the thermal deterioration. That is, the heat resistance of the exhaust gas purifying catalyst 7 was improved.

  Examples of the occlusion material 4 include alkali metals such as K and Na, or alkaline earth metals such as Ca and Ba.

  The first support 1 may be doped with a rare earth element such as La. Thus, by doping the first support 1 with the rare earth element, it was possible to suppress a decrease in the specific surface area of the first support 1 due to thermal degradation. As a result, a decrease in the denitration rate after heat deterioration in the exhaust gas purification catalyst 7 was suppressed, and the heat resistance of the exhaust gas purification catalyst 7 was improved.

  Examples of the noble metal 3 include at least one selected from Pt, Rh, Pd, Ir, Ru, alloys thereof, and oxides thereof.

  The precious metal 3 is 0.1 to 10 wt% with respect to the first support 1. By setting such a weight ratio, the noble metal 3 was supported in a state of being appropriately dispersed in the first carrier 1 and the second carrier 2, and the catalyst performance could be efficiently expressed.

  The occlusion material 4 is 0.1 to 50 wt%, preferably 5 to 25 wt% with respect to the first carrier 1. By setting it as such a weight ratio, it had the denitration rate more than predetermined at 200-550 degreeC.

  The component ratio of the 1st support | carrier 1 and the 2nd support | carrier 2 shall be 0.05-20. By setting it as such a component ratio, in the exhaust gas purification catalyst before heat deterioration, the maximum denitration rate was improved and the denitration rate on the high temperature side was improved.

  The average particle size of the first carrier 1 and the second carrier 2 is 4 μm or more. By making the first carrier 1 and the second carrier 2 have such particle sizes, the noble metal 3 is appropriately dispersed in the first carrier 1 and the second carrier 2, and the occlusion material 4 is dispersed in the second carrier 2. Therefore, sintering of the noble metal 3 and the occlusion material 4 was suppressed. As a result, a decrease in the denitration rate after heat deterioration in the exhaust gas purification catalyst 7 was suppressed, and the heat resistance of the exhaust gas purification catalyst 7 was improved.

  In addition, when a binder is added to the exhaust gas purification catalyst 7 to form a slurry, and this slurry is applied to the base material, the gap between the first carrier 1 and the second carrier 2 is increased, and the gas diffusion path is increased. Denitration rate improved. Furthermore, for example, when light oil is injected as fuel, diffusion of the light oil is facilitated, and the reactivity is improved. Moreover, the contact area of the storage material 4 and the 2nd support | carrier 2 (1st component 5 and 2nd component 6) was reduced, and reaction with the storage material 4 and the 2nd support | carrier 2 was suppressed. Therefore, the acid point in the exhaust gas purification catalyst 7 can be maintained (it is an active point that shows acidity and is contained in a large amount of oxides of Ti, Si, and W), the decomposition reaction of the acid gas SOx is promoted, and the occlusion material 4 for S content is obtained. Adsorption was suppressed, and performance degradation of the catalytically active component was also prevented.

The exhaust gas purifying catalyst 7 described above is manufactured by the following procedure.
That is, a first support made of CeO ₂ is impregnated with a storage material that stores a noble metal and nitrogen oxide. Further, a noble metal is impregnated and supported on a second support made of at least one of an oxide of Ti, Si and W or a composite oxide thereof, and an oxide of Al, Zr or La, or a composite oxide thereof. Subsequently, the first carrier and the second carrier are mixed, a binder is added to form a slurry, and this slurry is applied to the substrate.

  According to the method for producing an exhaust gas purifying catalyst according to the above-described procedure, only one type of slurry containing the first carrier and the second carrier is applied to the base material, and the production process is simple. I was able to suppress it.

  An exhaust gas purification apparatus for purifying exhaust gas containing nitrogen oxides is disposed in an exhaust pipe from which the exhaust gas is exhausted, and is disposed upstream of the exhaust gas purification catalyst described above and the exhaust gas purification catalyst. It has an organic reducing agent (for example, hydrocarbons, alcohols, ethers, etc.) or fuel injection means for injecting fuel to the catalyst. By injecting an organic reducing agent or fuel onto the exhaust gas purification catalyst by the fuel injection means, the oxygen concentration in the exhaust gas is reduced, and nitrogen oxides stored in the exhaust gas purification catalyst are reduced and discharged as nitrogen. Is done. Therefore, nitrogen oxides contained in the exhaust gas can be stored in the storage material of the exhaust gas purification catalyst, and the stored nitrogen oxides can be discharged as nitrogen, so that the nitrogen oxides in the exhaust gas can be purified.

  Further, an oxidation catalyst may be arranged on the upstream side, the downstream side, or the upstream side and the downstream side of the exhaust gas purification catalyst. By disposing the oxidation catalyst on the upstream side of the exhaust gas purification catalyst, the temperature of the exhaust gas purification catalyst was raised, and nitrogen oxides occluded in the exhaust gas purification catalyst could be removed as nitrogen. Moreover, the processing temperature of the nitrogen oxide in the exhaust gas purification catalyst could be secured. By disposing the oxidation catalyst on the downstream side of the exhaust gas purification catalyst, it was possible to remove nitrogen oxides, unburned hydrocarbons, and carbon monoxide in the exhaust gas.

  Furthermore, the PM combustion catalyst, the PM collection filter, or the trap with the PM combustion catalyst, which is a PM processor (PM processing means) for processing particulate matter in the exhaust gas, upstream or downstream of the exhaust gas purification catalyst. A collection filter is placed. By arranging the PM processor at such a position, the particulate matter in the exhaust gas is collected, and the heat necessary for high-temperature regeneration treatment that burns and removes the collected particulate matter is removed by exhaust gas purification. It was obtained by oxidative combustion of the fuel injected into the catalyst. As a result, black smoke and nitrogen oxides in the exhaust gas could be removed. By disposing the PM treatment means upstream of the exhaust gas purification catalyst, poisoning substances are removed by the PM treatment means, so that the life of the exhaust gas purification catalyst can be extended. By disposing the PM treatment means downstream of the exhaust gas purification catalyst, the exhaust gas temperature rises due to waste heat during the function of the exhaust gas purification catalyst. Improved.

  Examples of the exhaust gas include exhaust gas discharged from an internal combustion engine, boiler exhaust gas from a factory, heating furnace exhaust gas, and the like. In particular, when the exhaust gas is exhaust gas from a lean combustion internal combustion engine or a diesel engine, it was possible to suppress emission of nitrogen oxides contained in the exhaust gas.

  In order to confirm the effects of the exhaust gas purifying catalyst, the manufacturing method thereof, and the exhaust gas purifying apparatus according to the present invention, the following experiment was conducted.

[Evaluation of catalyst performance with a mixture of two supports]
FIG. 2 is a schematic diagram before and after thermal degradation of the first specimen, FIG. 2 (a) shows the state before thermal degradation of the first specimen, and FIG. 2 (b) shows after thermal degradation of the first specimen. Indicates the state. FIG. 3 is a graph showing the relationship between the denitration rate and temperature before and after thermal degradation of the first specimen. The white squares in FIG. 3 indicate the denitration rate before thermal degradation, and the white circles in FIG. 3 indicate the denitration rate after thermal degradation.

<First specimen>
As shown in FIG. 2A, the first test body 10 is a mixture of a first carrier 11 made of powdered ceria (CeO ₂ ) and a second carrier 12 made of powdered zirconia (ZrO ₂ ). Being done. The first carrier 11 and the second carrier 12 carry a noble metal Pt13. The first carrier 11 carries barium carbonate 14 as a storage material and WO ₃ / TiO ₂ —SiO ₂ 15.

[Exhaust gas treatment test]
The first test specimen 10 was subjected to an exhaust gas treatment test with the denitration activity evaluation conditions shown in Table 1 below.

表１において、ＳＶは空間速度（流体の流量／試験体の体積）を示し、Lean/Richは、リーン／リッチの処理時間の比を示す。
また、第１試験体１０を熱劣化する際の条件は、以下の通りである。
熱劣化温度：７００℃、熱劣化時間：２００時間、熱劣化雰囲気：大気中

In Table 1, SV indicates space velocity (fluid flow rate / test body volume), and Lean / Rich indicates the ratio of lean / rich processing time.
Moreover, the conditions at the time of carrying out the thermal deterioration of the 1st test body 10 are as follows.
Thermal degradation temperature: 700 ° C, thermal degradation time: 200 hours, thermal degradation atmosphere: in the air

As shown in FIG. 2 (b), in the first test body 10 after heat deterioration, the first carrier 11 carrying Pt13 and WO ₃ / TiO ₂ —SiO ₂ 15 and the second carrier carrying Pt13. Twelve. However, the titanium of WO ₃ / TiO ₂ —SiO ₂ 15 reacts with the barium of barium carbonate 14 to produce WO ₃ / SiO ₂ 16 and BaTiO ₃ 17. Thus, although BaTiO ₃ 17 was produced, it was found that BaZrO ₃ formed by the reaction of BaCO ₃ and ZrO ₂ was not produced.

Here, the first test body 10 was measured for the relationship between the denitration rate and the temperature before and after thermal degradation. The denitration rate was calculated by the following formula.
Denitrification rate (%) = (1 - outlet NO _X concentration / inlet NO _X concentration) × 100

  As shown in FIG. 3, in the first test body 10 before heat deterioration, it was found that the maximum denitration rate was about 80% at 350 ° C., and the denitration rate was 10% or more at 200-550 ° C. Moreover, in the 1st test body 10 after heat deterioration, it turned out that a maximum NOx removal rate will be about 60% at about 350 degreeC, and a NOx removal rate will be 10% or more in the temperature range of 200-550 degreeC. Therefore, it was found that the first test body 10 had the same maximum denitration temperature. Moreover, in the conventional exhaust gas purification catalyst described above, the denitration rate was reduced by 40% before and after thermal degradation, and thus it was found that the decrease in the denitration rate was suppressed as compared with the conventional exhaust gas purification catalyst.

  Therefore, according to the 1st test body 10, when it was set as the mixed powder of the 1st support | carrier 11 and the 2nd support | carrier 12, it turned out that the fall of a denitration rate is suppressed and heat resistance improves.

[Evaluation of catalyst performance by a carrier on which a composite oxide of W, Ti and Si is supported]
4A and 4B are schematic diagrams of the first test body and the second test body. FIG. 4A shows a state before and after thermal degradation of the first test body, and FIG. 4B shows before and after thermal degradation of the second test body. Shows the state. However, the first specimen is the same as described above, and the same reference numerals are added and the description thereof is omitted. FIG. 5 is a graph showing the relationship between the denitration rate and the temperature in the first test body and the second test body. The white squares in FIG. 5 indicate the denitration rate after thermal degradation in the first specimen, and the white circles in FIG. 5 indicate the denitration rate after thermal degradation in the second specimen. FIG. 6 is a graph showing the relationship between the CO concentration and the temperature in the first test body and the second test body. FIG. 6 (a) shows the CO concentration in the first test body, and FIG. The CO concentration in the test body is shown.

<Second specimen>
As shown in FIG. 4B, the second test body 20 is formed by mixing a first carrier 21 made of ceria (CeO ₂ ) and a second carrier 22 made of zirconia (ZrO ₂ ). The first carrier 21 and the second carrier 22 carry a noble metal Pt23. The first carrier 21 carries a barium carbonate 24 which is a nitrogen oxide storage material. The second carrier 22 carries WO ₃ / TiO ₂ —SiO ₂ 25. That is, the first test body 10 and the second test body 20 are different from each other on which WO ₃ / TiO ₂ —SiO ₂ is supported.

[Exhaust gas treatment test]
The first test body 10 and the second test body 20 were subjected to an exhaust gas treatment test with the evaluation conditions for the denitration activity as shown in Table 1 above.
Moreover, the conditions at the time of carrying out the thermal deterioration of the 1st test body 10 and the 2nd test body 20 are as follows.
Thermal degradation temperature: 800 ° C, thermal degradation time: 10 hours, thermal degradation atmosphere: in the air

As shown in FIG. 4A, in the first test body 10 after the thermal deterioration, WO ₃ / TiO ₂ —SiO ₂ 15 reacts with barium carbonate 14, and WO ₃ / SiO ₂ 16 and BaTiO ₃ 17 become Generated. Pt13 was sintered after thermal deterioration to become Pt18. Moreover, in the 2nd test body 20, it turned out that Pt23 does not sinter even if thermally deteriorated.

As shown in FIG. 4B, the second test specimen 20 after the thermal degradation is similar to the first specimen 21 on which Pt23 and barium carbonate 24 are supported, Pt23 and WO ₃ / TiO ₂ as before the thermal degradation. The second carrier 22 on which —SiO ₂ 25 is supported is mixed. Therefore, in the 2nd test body 20, it turned out that the chemical composition does not change before and after thermal deterioration.

  Here, the first test body 10 and the second test body 20 were measured for the relationship between the denitration rate and the temperature after thermal degradation.

  As shown in FIG. 5, it was found that the first test body 10 and the second test body 20 had a denitration rate of about 10% or higher at 250-550 ° C. In the first specimen 10, the maximum denitration rate was found to be about 40% at about 500 ° C. In the second specimen 20, it was found that the maximum denitration rate was about 60% at about 500 ° C. Therefore, it was found that the maximum denitration rate was higher in the second test body 20 than in the first test body 10. Further, the denitration rate at 550 ° C. is about 40% in the first test body 10, but is about 50% in the second test body 20, and the second test body 20 is more in the first test body 10. It was found that the heat resistance was higher than that.

  Here, the relationship between the temperature and the CO concentration on the exhaust side was measured for the first test body 10 and the second test body 20. Thus, the CO concentration was measured, and the oxidation performance of the catalyst was observed. That is, when the concentration of CO is greatly reduced to the low temperature side, it indicates that the activity of the noble metal is high, which corresponds to the fact that the noble metal does not sinter.

  In the first test body 10, as shown in FIG. 6 (a), it was found that the CO concentration gradually decreased from 400 ° C. to 550 ° C. and became 500 ppm or less at about 530 ° C. In the 2nd test body 20, as shown in FIG.6 (b), it turned out that CO concentration reduces gradually from 400 degreeC toward 550 degreeC, and becomes 500 ppm or less at about 470 degreeC. Therefore, it was found that the second test body 20 was more suppressed in sintering the noble metal than the first test body 10.

Therefore, it was found that by supporting WO ₃ / TiO ₂ —SiO ₂ on zirconia, the maximum denitration rate can be improved, and further, the denitration rate in a high temperature range can be improved.

[Evaluation of catalyst performance by adding second support]
FIG. 7 is a schematic diagram of the second test body and the third test body. FIG. 7A shows the third test body, and FIG. 7B shows the second test body. However, the second specimen is the same as described above, and the same reference numerals are added and description thereof is omitted. FIG. 8 is a graph showing the relationship between the denitration rate and the temperature in the second specimen and the third specimen. The white circle in FIG. 8 indicates the initial denitration rate in the second test body, and the white square in FIG. 8 indicates the initial denitration rate in the third test body.

<Third specimen>
As shown in FIG. 7A, the third test body 30 is formed by mixing a first carrier 31 and a second carrier 32 made of ceria (CeO ₂ ). The first carrier 31 and the second carrier 32 carry a noble metal Pt33. The first carrier 31 carries a barium carbonate 34 as an occlusion material. The second carrier 32 carries WO ₃ / TiO ₂ —SiO ₂ 35.

  With respect to the second test body 20 and the third test body 30, the relationship between the denitration rate and the temperature was measured.

  As shown in FIG. 8, in the third specimen 30, the denitration rate is about 10% at about 230 ° C. and gradually increases as the temperature rises to about 70% which is the maximum denitration rate at about 340 ° C. Further, it was found that the temperature gradually decreased as the temperature increased to 20% at 550 ° C. In the second test body 20, the denitration rate is 10% at 200 ° C. and gradually increases as the temperature rises, reaches a maximum denitration rate of 75% at about 350 ° C., and gradually decreases as the temperature rises to 550. It was found to be 25% at ° C.

  Therefore, by adding zirconia, which is a carrier having a composition different from that of ceria, which is the first carrier 31, as the second carrier 32, the maximum denitration rate can be improved, and further, the denitration rate in a high temperature region can be improved. I understood that I could do it.

[Evaluation of catalyst performance by La dope]
FIG. 9 is a graph showing the denitration rate after thermal degradation in the second test body described above and the fourth test body in which La is doped in the first carrier of the second test body.

<4th specimen>
The fourth specimen is obtained by doping La on the first carrier of the second specimen.

[Exhaust gas treatment test]
With respect to these second test body and fourth test body, the evaluation conditions of the denitration activity were as shown in Table 1 above, and an exhaust gas treatment test was conducted.
Moreover, the conditions at the time of carrying out thermal deterioration of the 2nd test body and the 4th test body are as follows.
Thermal degradation temperature: 700 ° C, thermal degradation time: 200 hours, thermal degradation atmosphere: in the air

  As shown in FIG. 9, the denitration rate at 400 ° C. was about 45% in the second test body and about 55% in the fourth test body. Therefore, by doping La to the first carrier, the heat resistance is improved, that is, the decrease in specific surface area due to thermal degradation is suppressed, the reactivity with Ba is suppressed, and the catalyst performance is decreased due to thermal degradation. It turned out to be suppressed.

[Evaluation of catalyst performance by production method]
FIG. 10 is a schematic diagram of the fifth test body and the sixth test body. FIG. 10 (a) shows the fifth test body and FIG. 10 (b) shows the sixth test body. FIG. 11 is a graph showing the relationship between the denitration rate and the temperature after thermal degradation in the fifth test body and the sixth test body. The white circles in FIG. 11 indicate the denitration rate after thermal degradation in the fifth specimen, and the square white lines in FIG. 8 indicate the denitration rate after thermal degradation in the sixth specimen.

<5th specimen>
As shown in FIG. 10A, the fifth test body 50 is coated with PtRh / (ZrO ₂ + WO ₃ / TiO ₂ —SiO ₂ ) as the first layer 52 on the surface of the honeycomb-shaped substrate 51. PtRhBa / CeO ₂ is applied as a second layer 53 on the surface of the first layer 52.

<Sixth specimen>
As shown in FIG. 10 (b), the sixth specimen 60 has (PtRhBa / CeO ₂ ) + [PtRh / (ZrO ₂ + WO ₃ / TiO ₂ ) as the first layer 62 on the surface of the honeycomb-shaped substrate 61. -SiO _2)] it is formed by coating.

[Exhaust gas treatment test]
With respect to the fifth test body 50 and the sixth test body 60, the evaluation conditions of the denitration activity were set to Table 2 below, and an exhaust gas treatment test was performed.

表２において、ＳＶは空間速度（流体の流量／試験体の体積）を示し、Lean/Richは、リーン／リッチの処理時間の比を示す。
また、第５試験体５０および第６試験体６０を熱劣化する際の条件は、以下の通りである。
熱劣化温度：７００℃、熱劣化時間：２００時間、熱劣化雰囲気：大気中

In Table 2, SV indicates space velocity (fluid flow rate / test body volume), and Lean / Rich indicates the ratio of lean / rich processing time.
Moreover, the conditions at the time of carrying out the thermal deterioration of the 5th test body 50 and the 6th test body 60 are as follows.
Thermal degradation temperature: 700 ° C, thermal degradation time: 200 hours, thermal degradation atmosphere: in the air

  As shown in FIG. 11, in the fifth specimen 50, the denitration rate is 10% at about 280 ° C. and gradually increases as the temperature rises to about 35%, which is the maximum denitration rate at about 400 ° C. It was found that the temperature gradually decreased as the temperature increased to 10% at 550 ° C. In the sixth specimen 60, the NOx removal rate gradually increased as the temperature increased to 15% at 200 ° C., reached about 75%, which was the maximum NOx removal rate at about 400 ° C., and further decreased gradually as the temperature increased. It was found to be 50% at 550 ° C.

  Therefore, it was found that the denitration rate was higher for the sixth test body 60 than for the fifth test body 50. It was also found that sufficient denitration performance was obtained by applying only one type of slurry containing the first carrier and the second carrier to the substrate. Moreover, since a manufacturing process was simple, it turned out that the increase in manufacturing cost can be suppressed.

[Evaluation of catalyst performance by carrier particle size]
FIG. 12 is a graph showing the relationship between the denitration rate after thermal degradation and the temperature in the seventh test body, the eighth test body, and the ninth test body. A white square in FIG. 12 indicates the denitration rate of the seventh test body, a white circle in FIG. 12 indicates the denitration rate of the eighth test body, and a white triangle in FIG. 12 indicates the 9th test. Indicates the denitration rate of the body. FIG. 13 is a graph showing the relationship between the CO concentration and the temperature in the seventh test body, the eighth test body, and the ninth test body. FIG. 13 (a) shows the CO concentration in the seventh test body, and FIG. ) Shows the CO concentration of the eighth specimen, and FIG. 13C shows the CO concentration of the ninth specimen.

<Seventh specimen>
The seventh test specimen was prepared by adjusting the average particle diameters of the first carrier and the second carrier in the above-mentioned second specimen to 1 μm each using a ball mill, and adding a binder or the like to form a slurry. It is applied to the surface of a honeycomb substrate.

<Eighth specimen, ninth specimen>
The eighth specimen is prepared in the same manner as the seventh specimen except that the average particle diameters of the first carrier and the second carrier are each adjusted to 2 μm. The ninth specimen is prepared in the same manner as the seventh specimen except that the average particle diameters of the first carrier and the second carrier are adjusted to 4 μm.

[Exhaust gas treatment test]
An exhaust gas treatment test was performed on the seventh test body, the eighth test body, and the ninth test body with the evaluation conditions for the denitration activity as shown in Table 2 above.
Moreover, the conditions at the time of carrying out thermal degradation of the 7th test body, the 8th test body, and the 9th test body are as follows.
Thermal degradation temperature: 800 ° C, thermal degradation time: 10 hours, thermal degradation atmosphere: in the air

  As shown in FIG. 12, in the seventh test body, it was found that the denitration rate was 10% at 270 ° C., and gradually increased as the temperature increased to 28%, which is the maximum denitration rate at 500 ° C. . In the eighth specimen, it was found that the denitration rate became 10% at 250 ° C., gradually increased as the temperature increased, and reached a maximum denitration rate of 52% at 500 ° C. In the ninth test body, the denitration rate becomes 10% at 290 ° C., and gradually increases as the temperature rises, reaches a maximum denitration rate of 52% at 400 ° C., and gradually decreases as the temperature rises at 500 ° C. It was found to be 40%.

  Therefore, by adjusting the average particle size of the carrier to 4 μm, the noble metal is appropriately dispersed in the first carrier and the second carrier, and the occlusion material is appropriately dispersed in the first carrier. Sintering of precious metals and storage materials was suppressed. As a result, it was found that the reduction of the denitration rate after heat deterioration in the exhaust gas purification catalyst was suppressed, and the heat resistance of the exhaust gas purification catalyst was improved. Furthermore, for example, when light oil is injected as a fuel, it has been found that the diffusion of the light oil is facilitated and the reactivity is improved. Further, the contact area between the occlusion material and the second carrier was reduced, and the reaction between the occlusion material and the second carrier was suppressed. In addition, it can maintain acid sites (active sites that show acidity and are contained in many oxides of Ti, Si, and W) in the specimen, promote the decomposition reaction of the acid gas SOx, and suppress the adsorption of S to the storage material It was also found that the performance deterioration of the catalytically active component was prevented.

  As shown in FIG. 13, in the seventh test body, CO is 1800 ppm even at 500 ° C., in the eighth test body, it is 500 ppm or less at 430 ° C., and in the ninth test body, it is 500 ppm or less at 380 ° C. I understood. Therefore, it was found that the eighth test body suppressed sintering of the noble metal compared to the seventh test body, and the ninth test body suppressed sintering of the noble metal compared to the eighth test body. .

[First exhaust gas purification device]
Hereinafter, an exhaust gas purification apparatus using the above-described exhaust gas purification catalyst will be described.
FIG. 14 is a schematic view of a first exhaust gas purification apparatus according to the present invention. FIG. 15 is a graph showing the relationship between the denitration rate and the temperature in the first exhaust gas purifying catalyst according to the present invention. The white circles in FIG. 15 are exhaust gas purification catalysts composed of the above-mentioned third test body, and the white triangles are exhaust gas purification catalysts composed of the above-mentioned second test body.

  As shown in FIG. 14, the first exhaust gas purification device 70 has an exhaust gas purification catalyst 73 disposed in an exhaust pipe 72 through which the exhaust gas 71 flows. The exhaust gas purifying catalyst 73 is a slurry obtained by adding a binder to the above-described second test body and applying this slurry to the surface of a honeycomb-shaped substrate. A fuel injection nozzle (fuel injection means) 74 is disposed upstream of the exhaust gas purification catalyst 73. By injecting light oil 75 as fuel as a reducing agent from the fuel injection nozzle 74 only for 3 seconds in 1 minute and supplying it to the exhaust gas purification catalyst 73, the oxygen concentration in the exhaust gas 71 is lowered, and the exhaust gas purification catalyst 73 is supplied to the exhaust gas purification catalyst 73. The stored nitrogen oxides are reduced and discharged as nitrogen.

  Here, in the first exhaust gas purification device 70, as the exhaust gas purification catalyst 73, a binder is added to the above-mentioned second test body to form a slurry, and this slurry is applied to the surface of a honeycomb-shaped substrate. (Refer to the white circles in FIG. 15), and when the above-mentioned third test body is added with a binder to form a slurry, and this slurry is applied to the surface of a honeycomb substrate (in FIG. 15) The denitration rate was measured.

  As shown in FIG. 15, in the exhaust gas purification catalyst comprising the third test body, that is, the exhaust gas purification catalyst having no zirconia, the denitration rate is 25% at 300 ° C. and gradually increases, and the maximum denitration rate at 400 ° C. It was found to be 45% and gradually decreased to 40% at 450 ° C. It was found that the exhaust gas purifying catalyst comprising the second test body, that is, the catalyst for exhaust gas purification having zirconia, showed a denitration rate of 25% at 300 ° C. and gradually increased to a maximum denitration rate of 60% at 450 ° C. Therefore, it was found that the NOx removal rate at 450 ° C. was higher in the exhaust gas purifying catalyst having zirconia.

[Second exhaust gas purification device]
FIG. 16 is a schematic view of a second exhaust gas purifying apparatus according to the present invention. FIG. 16 (a) shows an outline of a state in which a PM processor is disposed on the downstream side of the exhaust gas purifying catalyst, FIG. 16 (b). ) Shows an outline of a state in which the PM processor is arranged on the upstream side of the exhaust gas purifying catalyst it has. However, the second exhaust gas purification device is a device in which a PM processor and an oxidation catalyst are added to the first exhaust gas purification device. Other than that, the second exhaust gas purification device has the same configuration as the first exhaust gas purification device, and the same reference numerals denote the same components. Additional description is omitted.

  The second exhaust gas purification devices 80a and 80b are PM processing devices (for example, PM combustion catalyst, PM collection filter, PM collecting means for collecting and processing particulate matter in the first exhaust gas purification device 70). Alternatively, a collection filter with a PM combustion catalyst or the like) 81 and an oxidation catalyst 82 are added. Specifically, in the second exhaust gas purification device 80a, as shown in FIG. 16A, a PM processor 81 is disposed downstream of the exhaust gas purification catalyst 73. By arranging in this way, it was possible to remove nitrogen oxides and black smoke. Further, exhaust gas temperature rises due to waste heat when the exhaust gas purifying catalyst 73 functions, so that the reaction speed of the PM processor 81 is increased and its performance is improved, and regeneration processing of the PM processor 81 is possible. Met. In the second exhaust gas purification device 80b, as shown in FIG. 16B, a PM processor 81 is disposed on the upstream side of the exhaust gas purification catalyst 73. By arranging in this way, it was possible to remove nitrogen oxides and black smoke. Further, since poisonous substances are removed by the PM processor 81, the life of the exhaust gas purifying catalyst 73 can be extended.

On the other hand, in the second exhaust gas purification apparatuses 80a and 80b, the first and second exhaust gas purification devices 80a and 80b are located upstream of the combination of the exhaust gas purification catalyst 73 and the PM processor 81, between the combustion injection nozzle 74 and the combination, and downstream of the combination. Second oxidation catalysts 82 are respectively disposed.
By arranging the PM processor 81 between the combustion injection nozzle 74 and the combination, the temperature of the exhaust gas purification catalyst 73 is raised, and nitrogen oxides stored in the exhaust gas purification catalyst 73 are removed as nitrogen. I was able to. By disposing the oxidation catalyst 82 on the downstream side of the combination, nitrogen oxides, unburned hydrocarbons, and carbon monoxide in the exhaust gas could be removed.

  Further, the oxidation catalyst 82 may be disposed only in the final stage. By arranging at such a position, even if uncombusted hydrocarbons, oxides thereof, and carbon monoxide pass through the combination, the combination could be burned by the oxidation catalyst 82.

  INDUSTRIAL APPLICABILITY The present invention can be used for an exhaust gas purification catalyst that removes nitrogen oxides, hydrocarbons, and carbon monoxide in exhaust gas discharged from a diesel engine or the like, a manufacturing method thereof, and an exhaust gas purification device.

1 is a schematic view of an exhaust gas purifying catalyst according to the best mode of the present invention. It is a schematic diagram before and after thermal degradation of the first specimen. It is a graph which shows the relationship between the NOx removal rate before and behind thermal degradation of a 1st test body, and temperature. It is a schematic diagram of a 1st test body and a 2nd test body. It is a graph which shows the relationship between the denitration rate and temperature in a 1st test body and a 2nd test body. It is a graph which shows the relationship between CO concentration and temperature in a 1st test body and a 2nd test body. It is a schematic diagram of a 2nd test body and a 3rd test body. It is a graph which shows the relationship between the NOx removal rate and temperature in a 2nd test body and a 3rd test body. It is a graph which shows the denitration rate after thermal degradation in the 4th test body which doped La to the 2nd test body and the 1st support | carrier of the 2nd test body. It is a schematic diagram of a 5th test body and a 6th test body. It is a graph which shows the relationship between the denitration rate after thermal degradation, and temperature in a 5th test body and a 6th test body. It is a graph which shows the relationship between the denitration rate before and behind thermal degradation in 7th test body, 8th test body, and 9th test body, and temperature. It is a graph which shows the relationship between CO density | concentration and temperature in a 7th test body, an 8th test body, and a 9th test body. It is the schematic of the 1st exhaust gas purification apparatus which concerns on this invention. It is a graph which shows the relationship between the denitration rate and temperature in the 1st exhaust gas purification catalyst which concerns on this invention. It is the schematic of the 2nd exhaust gas purification apparatus which concerns on this invention. It is a schematic diagram before and after thermal degradation of a conventional exhaust gas purifying catalyst. It is a graph which shows the relationship between the denitration rate before and behind thermal degradation of the catalyst for exhaust gas purification, and temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st support | carrier 2 2nd support | carrier 3 Noble metal 4 Occlusion material 5 1st component 6 2nd component 7 Exhaust gas purification catalyst 70 Exhaust gas purification apparatus 71 Exhaust gas 72 Exhaust pipe 73 Exhaust gas purification catalyst 74 Fuel injection nozzle 75 Fuel

Claims (14)

A first support comprising CeO ₂ ;
An oxide of Ti, Si and W or a composite oxide thereof, and a second support made of at least one of an oxide of Al, Zr or La or a composite oxide thereof,
A catalyst for purifying exhaust gas, wherein the first carrier supports a storage material and a noble metal that store nitrogen oxides, and the second carrier supports a noble metal. An exhaust gas purifying catalyst according to claim 1,
The exhaust gas purifying catalyst, wherein the occlusion material is an alkali metal or an alkaline earth metal. The exhaust gas-purifying catalyst according to claim 1 or 2,
An exhaust gas purifying catalyst, wherein the first support is doped with a rare earth element. An exhaust gas purifying catalyst according to any one of claims 1 to 3,
The exhaust gas purifying catalyst, wherein the noble metal is at least one selected from Pt, Rh, Pd, Ir, Ru, alloys thereof, or oxides thereof. An exhaust gas purifying catalyst according to any one of claims 1 to 4,
The exhaust gas purifying catalyst, wherein the precious metal is 0.1 to 10 wt% with respect to the first carrier. An exhaust gas purifying catalyst according to any one of claims 1 to 5,
The exhaust gas purifying catalyst, wherein the occlusion material is 0.1 to 50 wt% with respect to the first carrier. An exhaust gas purifying catalyst according to any one of claims 1 to 6,
The exhaust gas purifying catalyst, wherein a component ratio of the first carrier to the second carrier is 0.05-20. An exhaust gas purifying catalyst according to any one of claims 1 to 7,
An exhaust gas purifying catalyst, wherein the first carrier and the second carrier have an average particle size of 4 μm or more. A method for producing an exhaust gas purifying catalyst for purifying exhaust gas containing nitrogen oxides,
Impregnating and supporting a precious metal and a storage material that stores nitrogen oxides on a first support made of CeO ₂ ;
A step of impregnating and supporting a noble metal on a second support comprising at least one of an oxide of Ti, Si and W or a composite oxide thereof, and an oxide of Al, Zr or La, or a composite oxide thereof;
A method for producing an exhaust gas purifying catalyst, comprising: mixing the first carrier and the second carrier, adding a binder to form a slurry, and applying the slurry to a substrate. An exhaust gas purification device for purifying exhaust gas containing nitrogen oxides,
The exhaust gas purifying catalyst according to any one of claims 1 to 8, wherein the exhaust gas purifying catalyst is disposed in an exhaust pipe from which the exhaust gas is exhausted.
An exhaust gas purification apparatus, comprising: a fuel injection unit that is disposed upstream of the exhaust gas purification catalyst and injects an organic reducing agent or fuel into the exhaust gas purification catalyst. An exhaust gas purifying device according to claim 10,
An exhaust gas purifying apparatus, wherein a first oxidation catalyst is disposed upstream of the exhaust gas purifying catalyst. An exhaust gas purifying apparatus according to claim 10 or claim 11, wherein
An exhaust gas purification apparatus, wherein a second oxidation catalyst is disposed downstream of the exhaust gas purification catalyst. An exhaust gas purification device according to any one of claims 10 to 12,
An exhaust gas purification apparatus, wherein PM treatment means for treating particulate matter in the exhaust gas is disposed upstream or downstream of the exhaust gas purification catalyst. An exhaust gas purification device according to any one of claims 10 to 13,
An exhaust gas purification apparatus, wherein the exhaust gas is exhaust gas discharged from a diesel engine.

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