Adsorbing catalyst for purifying exhaust gas

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to an exhaust gas purification adsorption catalyst, and more particularly to an exhaust gas purification adsorption catalyst capable of efficiently removing high-concentration hydrocarbons emitted when an engine is started.

【0002】

[Previous technology]

Conventionally, as a catalyst for purifying exhaust gas of an internal combustion engine of an automobile or the like, a catalyst that simultaneously oxidizes carbon monoxide (CO) and hydrocarbon (HC) and reduces nitrogen oxide (NOx) is widely used. Such catalysts include those in which a noble metal such as Pd, Pt, Rh is supported on an alumina-coated layer on a fire-resistant carrier, and if necessary, rare earth metals such as Ce and La, Ni and the like as co-catalyst components. It has been proposed that the base metal oxide of the above is added (Japanese Patent Publication No. 58-20307). The catalyst described in this patent gazette is strongly affected by the exhaust gas temperature and the set air-fuel ratio of the engine.

【0003】

On the other hand, the exhaust gas temperature at which the catalyst for automobiles exerts its purification function generally needs to be 300 ° C or higher, and the air-fuel ratio is a theoretical air-fuel ratio that balances the oxidation of hydrocarbons and carbon monoxide with the reduction of nitrogen oxides. The catalyst works most effectively near the fuel ratio (A / F = 14.6). Therefore, in an automobile equipped with an exhaust gas purification device that uses a conventional three-way catalyst, it is installed at a position where the three-way catalyst works effectively, and the oxygen concentration in the exhaust system is detected to make the air-fuel mixture theoretically empty. Feedback control is performed to keep the fuel ratio close to the fuel ratio.

【0004】

However, even when the conventional three-way catalyst is installed immediately after the exhaust manifold, the exhaust gas temperature is low (300 ° C or less), the catalyst activity is low immediately after the engine is started, and a large amount is generated immediately after the start (at the time of cold start). There is a drawback that the discharged hydrocarbon is discharged as it is without being purified. In order to solve this drawback, an exhaust gas purification device in which a hydrocarbon trapper filled with an adsorbent for adsorbing cold hydrocarbons is arranged on the upstream side of the exhaust gas of the catalytic converter has been proposed (Japanese Patent Laid-Open No. 2-135126). Japanese Patent Application Laid-Open No. 3-1411816).

【0005】

[Problems to be Solved by the Invention]

However, in the exhaust gas purification device according to Japanese Patent Application Laid-Open No. 2-135126, since the catalyst component is impregnated on the downstream side of the adsorbent, hydrocarbons are removed from the adsorbent on the upstream side before the catalyst reaches the active temperature. In addition to being separated, the zeolite is impregnated with the catalyst metal solution, so that there is a drawback that the durability of the catalyst component is poor.

【0006】

Further, in the exhaust gas purification device according to Japanese Patent Application Laid-Open No. 3-14816, the desorption control of the adsorbed hydrocarbon is performed by using a temperature sensor, a bypass pipe, a control device, etc., so that the system is complicated and unreliable. In addition, there was a drawback that it was not practical in terms of exhaust layout.

【0007】

Therefore, an object of the present invention is to provide an adsorption catalyst for exhaust gas purification capable of efficiently removing high-concentration hydrocarbons emitted when an engine is started.

【0008】

[Means and Actions for Solving Problems]

As a result of diligent studies to solve the above problems, the present inventors have selected from the group consisting of Pt, Pd and Rh as catalyst components in a powder containing active ceria and / or alumina as a main component on a zeolite layer. We have found that by using an adsorption catalyst for exhaust gas purification having a catalyst layer containing at least one type, it is possible to efficiently remove high-concentration hydrocarbons emitted when the engine is started, and arrived at the present invention.

【0009】

The above object of the present invention is to select from the group consisting of Pt, Pd and Rh as catalyst components in a powder containing active ceria and / or alumina as a main component on the zeolite layer in an adsorption catalyst in which a catalyst carrier is coated with zeolite. It was achieved by an adsorption catalyst for exhaust gas purification, which is characterized by having a catalyst layer containing at least one of these. Hereinafter, the present invention will be described in more detail.

【0010】

In the present invention, as described above, a first layer made of zeolite effective for adsorbing hydrocarbons is provided on the catalyst carrier, and a powder containing active ceria and / or alumina as a main component is further formed on the first layer. A self-purifying adsorption catalyst A provided with a catalyst layer containing at least one selected from the group consisting of Pt, Pd and Rh as a catalyst component is placed on the exhaust inflow side to purify hydrocarbons, carbon monoxide and nitrogen oxides. It is an exhaust gas purification adsorption catalyst characterized in that catalyst B coated with a ternary catalyst is arranged on the exhaust outflow side, respectively.

【0011】

In the adsorption catalyst A on the inflow side, the catalyst layer supported on the zeolite layer is heated faster than the zeolite layer, so that the catalyst layer is activated at the stage where the hydrocarbon is desorbed from the zeolite layer, and the hydrocarbon is used. Purify well. Further, by arranging the catalyst B on the outflow side, it is possible to improve the purification of hydrocarbons, carbon monoxide and nitrogen oxides that could not be completely purified by the catalyst layer on the inflow side. As a result, hydrocarbons discharged from the exhaust gas, especially when the engine is started, can be efficiently removed.

【0012】

As the zeolite used in the present invention, it can be appropriately selected from known zeolites and used, but it has a sufficient ability to adsorb hydrocarbons even at a relatively high temperature from room temperature and in an atmosphere in which water is present. It is preferable to select a material having a high durability. As such a zeolite, it is preferable to use at least one selected from the group consisting of, for example, mordenite, USY, β-zeolite and ZSM-5. In particular, mordenite, β-zeolite and ZSM-5 are SiO₂/ Al₂O₃Molar ratio range 50-2000, USY is SiO₂/ Al₂O₃The molar ratio is preferably in the range of 50 to 300. Mordenite, β-zeolite, ZSM-5 and USY are SiO₂/ Al₂O₃When the molar ratio is less than 50, the adsorption of water molecules coexisting in the exhaust gas is greatly inhibited, and hydrocarbons cannot be effectively adsorbed. Conversely, when mordenite, β-zeolite and ZSM-5 exceed 2000 in molar ratio and USY exceeds 300 in molar ratio, the amount of hydrocarbon adsorbed decreases. By mixing two or more types of zeolite having different pore diameters and pore structures, it is possible to efficiently absorb many types of hydrocarbons in the exhaust gas.

【0013】

Hydrocarbons can be sufficiently adsorbed only with the adsorption catalyst thus obtained, but in order to be mounted on an exhaust system and put into practical use, an adsorption layer with an added ability to purify hydrocarbons desorbed as the temperature rises. It is preferable to use a self-purification type in which a three-way catalyst layer is coated on (zeolite). That is, in the present invention, at least one selected from the group consisting of active ceria and / or alumina as a main component is coated on the zeolite layer, and Pt, Pd and Rh are further applied as catalyst components on the powder. A catalyst layer containing the above can be provided.

【0014】

Various zeolites have sufficient adsorption capacity even in the H type, but by supporting Pd, Ag, Cu, Cr, Co, Nd, etc. using ordinary methods such as ion exchange method, impregnation method, immersion method, etc. The adsorption characteristics and the ability to suppress detachment can be further improved. The amount of each noble metal supported is not particularly limited, but is preferably in the range of 0.1 to 15% by weight. If the amount carried is less than 0.1% by weight, the adsorption characteristics and the ability to suppress detachment are lowered, and conversely, if it exceeds 15% by weight, no further effect can be obtained.

【0015】

The distance between the adsorption catalyst A on the inflow side and the catalyst B on the outflow side is not particularly limited, but if it is too close, it may cause a decrease in engine performance due to an increase in back pressure. The purification rate of desorbed hydrocarbons, carbon monoxide and nitrogen oxides may decrease without increasing the temperature. Therefore, the distance between the catalyst A and the adsorption catalyst B is preferably in the range of 10 to 50 mm.

【0016】

In the present invention, the catalyst carrier can be appropriately selected from known catalyst carriers and used, and examples thereof include a monolith carrier and a metal carrier. The shape of the catalyst carrier is not particularly limited, but it is usually preferably used in the shape of a honeycomb, and the catalyst powder is applied to various honeycomb-shaped substrates. As the honeycomb material, a material of cozierite quality is generally often used, but a honeycomb made of a metal material can also be used, and further, the catalyst powder itself may be molded into a honeycomb shape. By making the shape of the catalyst honeycomb, the contact area between the catalyst and the exhaust gas becomes large, and the pressure loss can be suppressed, which is extremely advantageous when used for automobiles.

【0017】

[Example]

Hereinafter, the present invention will be described in more detail by way of examples. Unless otherwise specified in the examples, parts indicate parts by weight.

【0018】

Example 1 Active ceria powder carrying Pt (hereinafter, Pt / CeO)₂100 parts, 50 parts of alumina and 150 parts of 2% nitric acid were put into a magnetic pot and mixed and pulverized with a vibration mill for 40 minutes or a universal ball mill for 6.5 hours to produce a wash coat slurry. After the monolith carrier made by Cordierite was subjected to water absorption treatment by the suction coating method, the produced slurry was added so as to be uniform over the entire cross section of the carrier, and the excess slurry was removed by the suction coating method. Then, after drying, it was calcined at 400 ° C. for 1 hour. This will result in Pt / CeO₂The layer was coated on the carrier with a coating amount of 100 g / L. The above wash coat, drying and firing are repeated to obtain a total of 200 g / L of Pt / CeO.₂The layer was coated. Next, the alumina powder carrying Rh (hereinafter, Rh / Al)₂0₃100 parts, 50 parts of alumina and 150 parts of 2% nitric acid are put into a magnetic pot to produce a wash coat slurry in the same manner as above, and Pt / CeO is produced in the same manner.₂50g / L Rh / Al on the layer₂O₃After coating the catalyst layer and drying, it was calcined at 650 ° C for 3 hours in an air atmosphere to obtain catalyst 1 on the exhaust outflow side. In addition, H type ZSN-5 (SiO)₂/ Al₂O₃= 700) 100 parts, silica sol (solid content 20%) 215 parts, 10% nitric acid 100 parts and water 15 parts were put into a magnetic pot to produce a ZSM-5 slurry in the same manner as above, and monolith was supported by the same method. After coating 150 g / L on top and drying, it was calcined at 400 ° C. for 1 hour. 100 g / L Pt / CeO on ZSM-5 layer in the same way as above₂The catalyst layer was coated, dried, and then calcined at 400 ° C. for 1 hour. In addition, Pt / CeO₂Rh / Al on the layer₂O₃The catalyst layer was coated with 50 g / L, dried, and then calcined at 650 ° C for 3 hours in an air atmosphere to obtain an adsorption catalyst 1 on the exhaust inflow side. A tandem type adsorption catalyst 1 was obtained by combining the adsorption catalyst 1 on the exhaust inflow side and the catalyst 1 on the exhaust outflow side.

【0019】

Example 2 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃The adsorption catalyst 2 was obtained in exactly the same manner as in Example 1, and the adsorption catalyst 2 was combined on the exhaust inflow side and the catalyst 1 obtained in Example 1 was combined on the exhaust outflow side in a tandem type. Adsorption catalyst 2 was obtained.

【0020】

Example 3 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 50 copies and H-type USY (SiO)₂/ Al₂O₃= 50) The adsorption catalyst 3 was obtained in exactly the same manner as in Example 1 except that 50 parts were used, and the adsorption catalyst 3 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. The tandem type adsorption catalyst 3 was obtained by combining them.

【0021】

Example 4 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃The adsorption catalyst 4 was obtained in exactly the same manner as in Example 3, the adsorption catalyst 4 was obtained on the exhaust inflow side, and the catalyst 1 obtained in Example 1 was combined on the exhaust outflow side in a tandem type. Adsorption catalyst 4 was obtained.

【0022】

Example 5 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 67 parts and H-type USY (SiO)₂/ Al₂O₃= 50) The adsorption catalyst 5 was obtained in exactly the same manner as in Example 1 except that 33 parts were used, and the adsorption catalyst 5 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. The tandem type adsorption catalyst 5 was obtained by combining them.

【0023】

Example 6 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃A tandem type is obtained by combining the adsorption catalyst 6 on the exhaust inflow side and the catalyst 1 obtained in Example 1 on the exhaust outflow side in exactly the same manner as in Example 5. An adsorption catalyst 6 was obtained.

【0024】

Example 7 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 50 parts and H-type mordenite (SiO)₂/ Al₂O₃= 200) The adsorption catalyst 7 was obtained in exactly the same manner as in Example 1 except that 50 parts were used, and the adsorption catalyst 7 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. The tandem type adsorption catalyst 7 was obtained by combining them.

【0025】

Example 8 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃A tandem type is obtained by combining the adsorption catalyst 8 obtained in the same manner as in Example 7, the adsorption catalyst 8 on the exhaust inflow side, and the catalyst 1 obtained in Example 1 on the exhaust outflow side. An adsorption catalyst 8 was obtained.

【0026】

Example 9 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 50 parts and H-type β-zeolite (SiO)₂/ Al₂O₃= 100) The adsorption catalyst 9 was obtained in exactly the same manner as in Example 1 except that 50 parts were used, and the adsorption catalyst 9 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. A tandem type adsorption catalyst 9 was obtained by combining each of them.

【0027】

Example 10 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃A tandem type is obtained by combining the adsorption catalyst 10 on the exhaust inflow side and the catalyst 1 obtained in Example 1 on the exhaust outflow side in exactly the same manner as in Example 9. An adsorption catalyst 10 was obtained.

【0028】

Example 11 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 67 parts and H-type β-zeolite (SiO)₂/ Al₂O₃= 100) The adsorption catalyst 11 was obtained in exactly the same manner as in Example 1 except that 33 parts were used, and the adsorption catalyst 11 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. The tandem type adsorption catalyst 11 was obtained by combining them.

【0029】

Example 12 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃The adsorption catalyst 12 was obtained in exactly the same manner as in Example 12, and the adsorption catalyst 12 was combined on the exhaust inflow side and the catalyst 1 obtained in Example 1 was combined on the exhaust outflow side in a tandem type. An adsorption catalyst 12 was obtained.

【0030】

Example 13 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type USY (SiO) instead of 100 copies₂/ Al₂O₃= 50) The adsorption catalyst 13 was obtained in exactly the same manner as in Example 1 except that 100 parts were used, and the adsorption catalyst 13 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. A tandem type adsorption catalyst 13 was obtained by combining each of them.

【0031】

Example 14 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃A tandem type is obtained by combining the adsorption catalyst 14 on the exhaust inflow side and the catalyst 1 obtained in Example 1 on the exhaust outflow side in exactly the same manner as in Example 13. An adsorption catalyst 14 was obtained.

【0032】

Example 15 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type β-zeolite (SiO) instead of 100 parts₂/ Al₂O₃= 100) The adsorption catalyst 15 was obtained in exactly the same manner as in Example 1 except that 100 parts were used, and the adsorption catalyst 15 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. A tandem type adsorption catalyst 15 was obtained by combining each of them.

【0033】

Example 16 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃The adsorption catalyst 16 was obtained in exactly the same manner as in Example 15, except that the adsorption catalyst 16 was obtained on the exhaust inflow side and the catalyst 1 obtained in Example 1 was combined on the exhaust outflow side in a tandem type. An adsorption catalyst 16 was obtained.

【0034】

Example 17 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type mordenite (SiO) instead of 100 parts₂/ Al₂O₃= 200) The adsorption catalyst 17 was obtained in exactly the same manner as in Example 1 except that 100 parts were used, and the adsorption catalyst 17 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. A tandem type adsorption catalyst 17 was obtained by combining each of them.

【0035】

Example 18 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃The adsorption catalyst 18 was obtained in exactly the same manner as in Example 17, and the adsorption catalyst 18 was combined on the exhaust inflow side and the catalyst 1 obtained in Example 1 was combined on the exhaust outflow side in a tandem type. An adsorption catalyst 18 was obtained.

【0036】

Example 19 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 34 parts, H type USY (SiO)₂/ Al₂O₃= 50) 33 parts and H-type mordenite (SiO)₂/ Al₂O₃= 200) The adsorption catalyst 19 was obtained in exactly the same manner as in Example 1 except that 33 parts were used, and the adsorption catalyst 19 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. A tandem type adsorption catalyst 19 was obtained by combining each of them.

【0037】

Example 20 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃The adsorption catalyst 20 was obtained in exactly the same manner as in Example 19 except that the adsorption catalyst 20 was obtained on the exhaust inflow side, and the catalyst 1 obtained in Example 1 was combined on the exhaust outflow side in a tandem type. An adsorption catalyst 20 was obtained.

【0038】

Example 21 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 34 parts, H type USY (SiO)₂/ Al₂O₃= 50) Obtain the adsorption catalyst 21 in exactly the same way as in Example 1 except that 33 parts and H-type β zeolite were used, and obtain this adsorption catalyst 21 on the exhaust inflow side and in Example 1 on the exhaust outflow side. The catalysts 1 were combined to obtain a tandem type adsorption catalyst 21.

【0039】

Example 22 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃A tandem type is obtained by combining the adsorption catalyst 22 obtained in the same manner as in Example 21 with the adsorption catalyst 22 on the exhaust inflow side and the catalyst 1 obtained in Example 1 on the exhaust outflow side. An adsorption catalyst 22 was obtained.

【0040】

Example 23 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 34 parts, Ag ion-exchanged ZSM-5 (hereinafter referred to as Ag-supported ZSM-5. Ag-supported amount 5% by weight, SiO₂/ Al₂O₃= 30) 33 parts and H type USY (SiO)₂/ Al₂O₃= 50) The adsorption catalyst 23 was obtained in exactly the same manner as in Example 1 except that 33 parts were used, and the adsorption catalyst 23 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. A tandem type adsorption catalyst 23 was obtained by combining them.

【0041】

Example 24 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃A tandem type is obtained by combining the adsorption catalyst 24 on the exhaust inflow side and the catalyst 1 obtained in Example 1 on the exhaust outflow side in exactly the same manner as in Example 23. An adsorption catalyst 24 was obtained.

【0042】

Example 25 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 34 parts, Pd ion-exchanged ZSM-5 (hereinafter referred to as Pd-supported ZSM-5. Pd-supported amount 2% by weight, SiO₂/ Al₂O₃= 30) 33 parts and H type USY (SiO)₂/ Al₂O₃= 50) The adsorption catalyst 23 was obtained in exactly the same manner as in Example 1 except that 33 parts were used, and the adsorption catalyst 23 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. A tandem type adsorption catalyst 23 was obtained by combining them.

【0043】

Example 26 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃The adsorption catalyst 26 was obtained in exactly the same manner as in Example 25 except that the adsorption catalyst 26 was obtained on the exhaust inflow side, and the catalyst 1 obtained in Example 1 was combined on the exhaust outflow side in a tandem type. An adsorption catalyst 26 was obtained.

【0044】

Example 27 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 34 parts, Ag-supported ZSM-5 (Ag-supported amount 5% by weight, SiO₂/ Al₂O₃= 30) 33 parts, H-type β-zeolite (SiO)₂/ Al₂O₃= 100) The adsorption catalyst 27 was obtained in exactly the same manner as in Example 1 except that 33 parts were used, and this adsorption catalyst 27 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. The tandem type adsorption catalyst 27 was obtained by combining them.

【0045】

Example 28 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃The adsorption catalyst 28 was obtained in exactly the same manner as in Example 27 except that the adsorption catalyst 28 was obtained on the exhaust inflow side and the catalyst 1 obtained in Example 1 was combined on the exhaust outflow side in a tandem type. An adsorption catalyst 28 was obtained.

【0046】

Example 29 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) 34 parts, Pd-supported ZSM-5 (Pd-supported amount 2% by weight, SiO₂/ Al₂O₃= 30) 33 parts, H-type β-zeolite (SiO)₂/ Al₂O₃= 100) The adsorption catalyst 29 was obtained in exactly the same manner as in Example 1 except that 33 parts were used, and this adsorption catalyst 29 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. A tandem type adsorption catalyst 29 was obtained by combining each of them.

【0047】

Example 30 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃A tandem type is obtained by combining the adsorption catalyst 30 on the exhaust inflow side and the catalyst 1 obtained in Example 1 on the exhaust outflow side in exactly the same manner as in Example 29. An adsorption catalyst 30 was obtained.

【0048】

Example 31 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) H-type ZSM-5 (SiO) instead of 100 copies₂/ Al₂O₃= 700) USY in which 50 parts and Ag are ion-exchanged (hereinafter referred to as Ag-supported USY. Ag-supported amount 5% by weight, SiO₂/ Al₂O₃= 12) The adsorption catalyst 31 was obtained in exactly the same manner as in Example 1 except that 50 parts were used, and this adsorption catalyst 31 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. The tandem type adsorption catalyst 31 was obtained by combining them.

【0049】

Example 32 Pt / CeO as a catalyst component₂Pd / Al instead of₂O₃The adsorption catalyst 32 was obtained in exactly the same manner as in Example 31, except that the adsorption catalyst 32 was obtained on the exhaust inflow side and the catalyst 1 obtained in Example 1 was combined on the exhaust outflow side in a tandem type. An adsorption catalyst 32 was obtained.

【0050】

Example 33 Pd / CeO in the same way as in Example 1₂The layer was coated with 200 g / L, dried, and then calcined. In addition, Pd / CeO in a similar way₂Rh / Al on the layer₂O₃The layer was coated with 50 g / L, dried, and then calcined at 650 ° C for 3 hours in an air atmosphere to obtain catalyst 2. A tandem type adsorption catalyst 33 was obtained by combining the adsorption catalyst 5 on the exhaust inflow side and the catalyst 2 on the exhaust outflow side.

【0051】

Example 34 A tandem type adsorption catalyst 34 was obtained by combining the adsorption catalyst 9 on the exhaust inflow side and the catalyst 2 on the exhaust outflow side.

【0052】

Example 35 Pt / CeO as a catalyst component₂Instead of Pt / CeO₂And Pd / Al₂O₃The adsorption catalyst 35 was obtained in exactly the same manner as in Example 3, and the adsorption catalyst 35 was combined on the exhaust inflow side and the catalyst 1 obtained in Example 1 was combined on the exhaust outflow side in a tandem type. An adsorption catalyst 35 was obtained.

【0053】

Example 36 H-type ZSM-5 (SiO) as zeolite₂/ Al₂O₃= 700) 50 copies and H-type USY (SiO)₂/ Al₂O₃= 50) H-type ZSM-5 (SiO) instead of 50 parts₂/ Al₂O₃= 700) 67 parts and H-type USY (SiO)₂/ Al₂O₃= 50) The adsorption catalyst 36 was obtained in exactly the same manner as in Example 35 except that 37 parts were used, and the adsorption catalyst 36 was placed on the exhaust inflow side and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. The tandem type adsorption catalyst 36 was obtained by combining them.

【0054】

Comparative example 1 H type USY (SiO)₂/ Al₂O₃= 50) 100 parts, silica sol (solid content 20%) 215 parts, 10% nitric acid 100 parts and water 15 parts were put into a magnetic pot, and a wash coat slurry was produced by the same method as in Example 1 to produce the same coat. The monolith carrier was coated with 150 g / L, dried and calcined by the method to obtain an adsorption catalyst 37. A tandem type adsorption catalyst 37 was obtained by combining the adsorption catalyst 37 on the exhaust inflow side and the catalyst 1 on the exhaust outflow side.

【0055】

Comparative example 2 H type USY (SiO)₂/ Al₂O₃H-type USY (SiO) instead of = 50)₂/ Al₂O₃The adsorption catalyst 38 was obtained by the same method as in Comparative Example 1 except that = 7) was used, the adsorption catalyst 38 was placed on the exhaust inflow side, and the catalyst 1 obtained in Example 1 was placed on the exhaust outflow side. In combination, a tandem type adsorption catalyst 38 was obtained.

【0056】

Test example Using the tandem type adsorption catalysts obtained in Examples 1 to 34 and Comparative Examples 1 and 2, the HC adsorption / cleaning characteristics were evaluated under the following evaluation conditions. The results are shown in Tables 1, 2 and 3.

【0057】

[table 1]

<img file="JPH07213910A_D0001.tif" />【0058】

[Table 2]

<img file="JPH07213910A_D0002.tif" />【0059】

[Table 3]

<img file="JPH07213910A_D0003.tif" />【0060】

In the evaluation, as shown in Fig. 1, a Pt-Ph catalyst was placed in the exhaust manifold 2 of the engine 1 as a pre-three-way catalyst 3 (0.5 L), and a Pt-Rh catalyst of the underfloor catalyst 5 (1.3 L). An exhaust gas purification device equipped with an adsorption catalyst 4 (1.3 L) was used in front of the above, and the performance was compared with the case where the adsorption catalyst was not installed. In the evaluation, (1) The emission reduction rate for Abag 0 to 125 seconds was measured to evaluate the adsorption capacity of hydrocarbons discharged when the engine was started. (2) Temporarily adsorbed hydrocarbons are also desorbed before the three-way catalyst downstream of the adsorption catalyst is activated, and there is no emission reduction effect. Therefore, in order to evaluate the desorption suppression ability and self-purification ability of the adsorption catalyst, the emission reduction rate for Abag 0 to 505 seconds was measured.

【0061】

Evaluation conditions Catalyst capacity 1.3L Evaluation vehicle Nissan Motor Co., Ltd., V-type 6-cylinder 300cc engine Evaluation mode LA4-CH (Abag) Hydrocarbons (in the gas at the catalyst inlet) emitted when the engine is started Carbon number C₂~ C₃ 21.2% (C₁Excluding ingredients) C₄~ C₆ 33.0% C₇~ C₉ 45.8% 【0062】

[Effect of the invention]

In the exhaust gas purification adsorption catalyst of the present invention, an adsorption catalyst in which a catalyst layer is coated on an adsorption layer effective for adsorbing hydrocarbons is arranged on the exhaust inflow side, and an inorganic substance containing a catalytically active component on the catalyst carrier. By arranging the catalyst coated with the above on the exhaust outflow side, it is possible to efficiently remove the high-concentration hydrocarbon discharged when the engine is started.

[Simple explanation of drawings]

[Figure 1]

It is a system diagram of the exhaust gas purification device used in the test example.

[Explanation of symbols]

1 engine 2 Exhaust manifold 3 Pre-three-way catalyst 4 Adsorption catalyst 5 Underfloor three-way catalyst