JP2009178625A - Exhaust gas purification device - Google Patents

Abstract

The present invention provides an exhaust gas purification apparatus capable of sufficiently reducing the amount of H ₂ S discharged while exhibiting sufficiently high catalytic activity as a three-way catalyst.
A first catalyst base, a first metal oxide support supported on the first catalyst base, and a first noble metal supported on the first metal oxide support. And satisfying the condition that the base point amount per 1 L of catalyst based on the CO ₂ desorption amount per 1 L of catalyst by CO ₂ temperature programmed desorption measurement is 3.0 to 20 mmol / L-cat, and gas A first catalyst disposed upstream of the flow path; and
A second catalyst base, a second metal oxide support supported on the second catalyst base, and a second noble metal supported on the second metal oxide support, and CO ₂ Satisfying the condition that the base point amount per 1 L of catalyst based on the desorption amount of CO ₂ per 1 L of catalyst by temperature-programmed desorption measurement is 2.0 mmol / L-cat or less, and downstream of the gas flow path A second catalyst arranged on the side,
An exhaust gas purification apparatus comprising:
[Selection figure] None

Description

  The present invention relates to an exhaust gas purification apparatus.

In order to remove harmful components such as hydrocarbon gas (HC), carbon monoxide (CO) and nitrogen oxides (NO _x ) in exhaust gas from automobile engines, various exhaust gas purification catalysts have been arranged in the past. Exhaust gas purification devices have been used. As such an exhaust gas purification catalyst, a three-way catalyst capable of simultaneously purifying HC, CO and NOx in exhaust gas burned at a stoichiometric air-fuel ratio is known. Such a three-way catalyst has the property of storing the sulfur (S) component contained in the exhaust gas as sulfate during use, and when used to purify the exhaust gas containing a high concentration of sulfur component, Sulfur components accumulate (sulfur poisoning). On the other hand, the sulfur component accumulated in the three-way catalyst is desorbed in a reducing atmosphere and reacts with hydrogen in the exhaust gas to become hydrogen sulfide (H ₂ S). Such hydrogen sulfide causes a strong odor (H ₂ S odor). Therefore, in such a three-way catalyst, research for reducing the generation of H ₂ S has been made, and various catalysts have been disclosed.

For example, Japanese Patent Laid-Open No. 2006-326495 (Patent Document 1) discloses an exhaust gas purifying catalyst containing a metal oxide carrier, a noble metal, and nickel oxide (NiO). In such an exhaust gas purifying catalyst, NiO forms a sulfide in a high-temperature reducing atmosphere to capture a sulfur component, thereby suppressing the generation of H ₂ S. However, the exhaust gas purifying catalyst described in Patent Document 1 has a problem that it is necessary to use NiO which is an environmentally hazardous substance. Further, in such an exhaust gas purifying catalyst, the amount of H ₂ S emission cannot be reduced sufficiently, and the operating state changes abruptly, particularly when climbing or traveling at high speed after traveling in a low-speed urban area. Under such high load conditions, the amount of H ₂ S discharged could not be reduced sufficiently.

In Non-Patent Document 1 (SAE Paper Number 900611), Mo is added to a catalyst in which platinum and rhodium (noble metal) are supported on ceria (metal oxide support) at 0.03 mol / L- A catalyst-supported exhaust gas purification catalyst is disclosed. However, there is a report that the exhaust gas purification catalyst described in Non-Patent Document 1 is used in the exhaust gas purification device, but the amount of H ₂ S emission has been reduced to ¼. The range of the amount of addition necessary for achieving compatibility was not specified.

In JP-A-2004-167354 (Patent Document 2), a composite oxide in which an acidic oxide composed of at least one of ZrO ₂ and TiO ₂ and Al ₂ O ₃ are mixed at the primary particle level, the composite oxide An exhaust gas purifying catalyst comprising a noble metal supported on an object and phosphorus added to the composite oxide is disclosed. However, even when such an exhaust gas purifying catalyst as described in Patent Document 2 is used in an exhaust gas purifying device, the amount of H ₂ S emitted cannot always be sufficiently reduced. Further, such an exhaust gas purifying catalyst does not function as a three-way catalyst, but contains an oxygen storage / release material (OSC material), a basic substance, or the like separately from the catalyst in order to function as a three-way catalyst. It was necessary to let them.
JP 2006-326495 A JP 2004-167354 A SAE Paper Number 900611 (Neechem Cat)

The present invention has been made in view of the above-described problems of the prior art, and an exhaust gas purifying apparatus capable of sufficiently reducing the amount of H ₂ S emitted while exhibiting sufficiently high catalytic activity as a three-way catalyst. The purpose is to provide.

As a result of intensive studies to achieve the above object, the present inventors have found that the first catalyst base, the first metal oxide support supported on the first catalyst base, and the first The first catalyst comprising the first noble metal supported on the metal oxide support of the first catalyst, the base point amount per 1L of the catalyst of the first catalyst is 3.0-20 mmol / L-cat, A second catalyst comprising: a catalyst base; a second metal oxide support supported on the second catalyst base; and a second noble metal supported on the second metal oxide support. And the amount of the base point per 1 L of the catalyst of the second catalyst is 2.0 mmol / L-cat or less, the first catalyst is arranged on the upstream side of the gas flow path, and the second catalyst is By arranging it downstream of the gas flow path, while exhibiting sufficiently high catalytic activity as a three-way catalyst, The inventors have found that an exhaust gas purifying catalyst capable of sufficiently reducing the amount of ₂ S emitted is obtained, and have completed the present invention.

That is, the exhaust gas purifying apparatus of the present invention includes a first catalyst base, a first metal oxide support supported on the first catalyst base, and a first metal oxide support. The amount of base points per liter of catalyst is 3.0 to 20 mmol / L-cat, based on the amount of CO ₂ desorbed per liter of catalyst measured by CO ₂ temperature programmed desorption measurement. A first catalyst that satisfies the conditions and is disposed upstream of the gas flow path; and
A second catalyst base, a second metal oxide support supported on the second catalyst base, and a second noble metal supported on the second metal oxide support, and CO ₂ Satisfying the condition that the base point amount per 1 L of catalyst based on the desorption amount of CO ₂ per 1 L of catalyst by temperature-programmed desorption measurement is 2.0 mmol / L-cat or less, and downstream of the gas flow path A second catalyst, arranged in
It is characterized by providing.

  In the exhaust gas purification apparatus of the present invention, the second catalyst has a condition that the amount of base points per liter of the catalyst is 1.5 mmol / L-cat or less (more preferably 1.0 mmol / L-cat or less). It is preferable to satisfy.

  In the exhaust gas purifying apparatus of the present invention, it is preferable that the first catalyst satisfies a condition that a base point amount per 1 L of the catalyst is 3.0 to 15 mmol / L-cat.

  Furthermore, in the exhaust gas purifying apparatus of the present invention, an element having an electronegativity greater than a cation of a metal element constituting the second metal oxide support (hereinafter referred to as a case) (Referred to as “acidic element”). The element having a greater electronegativity than the cation of the metal element constituting the second metal oxide support is selected from the group consisting of phosphorus, molybdenum, tungsten, titanium, niobium, iron and silicon. At least one element is preferred.

  In the exhaust gas purifying apparatus of the present invention, a capacity ratio ([first region]) between a first region where the first catalyst is disposed and a second region where the second catalyst is disposed. : [Second region]) is preferably in the range of 15:85 to 85:15, more preferably in the range of 25:75 to 75:25, and in the range of 35:65 to 65:35. More preferably it is.

  Furthermore, in the exhaust gas purification apparatus of the present invention, the average value of the amount of base points per liter of catalyst of the first catalyst and the amount of base points per liter of catalyst of the second catalyst is 1.2 to 11 mmol / L-cat (more preferably 2.0 to 9.0 mmol / L-cat), and the base point amount of the first catalyst is more than twice the base point amount of the second catalyst ( More preferably, it is 3 times or more.

The reason why the exhaust gas purification apparatus of the present invention can sufficiently reduce the amount of H ₂ S emission while exhibiting sufficiently high catalytic activity as a three-way catalyst is not necessarily clear, but the present inventors Guess as follows. First, a conventional exhaust gas purification device will be examined. In addition, in order to demonstrate the structure of the conventional exhaust gas purification apparatus, the schematic longitudinal cross-sectional view which shows one Embodiment of the conventional exhaust gas purification apparatus is shown in FIG. A conventional exhaust gas purification apparatus as shown in FIG. 1 includes an exhaust gas pipe 1 and an exhaust gas purification catalyst 2 disposed in the exhaust gas pipe 1. The exhaust gas-purifying catalyst 2 is a catalyst base and a catalyst component uniformly coated between the inlet 2a and the outlet 2b of the catalyst base. Here, a catalyst base having a distance of 105 mm between the inlet 2a and the outlet 2b is provided with a catalyst component (a carrier containing La-stabilized activated alumina and alumina ceria zirconia, and platinum and rhodium carried on the carrier. An example is a catalyst on which a component) is supported. As a result of examining the relationship between the temperature distribution during the use of such a catalyst and the sulfur poisoning amount and the generation rate of H ₂ S, sulfur in the downstream region that is easily maintained at a relatively high temperature even after the vehicle is stopped. By reducing the amount of poisoning, it is presumed that the generation of H ₂ S can be effectively prevented even under high load conditions where the operating state changes rapidly.

Therefore, in the exhaust gas purifying apparatus of the present invention, the basic point amount per 1 L of the catalyst of the first catalyst disposed on the upstream side of the gas flow path is 3.0 to 20 mmol / L-cat, and the downstream of the gas flow path. The amount of base points per liter of the second catalyst disposed on the side is set to 2.0 mmol / L-cat or less. Such a base point is a strong adhesion site of the sulfur component when the catalyst comes into contact with the exhaust gas containing the sulfur component in an oxidizing atmosphere. In the exhaust gas purifying apparatus of the present invention, since the amount of the base point per 1 L of the catalyst of the second catalyst is as small as 2.0 mmol / L-cat or less, in the reducing atmosphere (low temperature stoichiometric or rich condition), the downstream side Accumulation of sulfur components in the second catalyst is sufficiently prevented, and the amount of sulfur poisoning can be reduced on the downstream side. On the other hand, since the first catalyst is disposed on the upstream side of the gas flow path, the temperature of the catalyst is relatively easily lowered when the vehicle is stopped as described above. Here, a catalyst having a base point amount per catalyst of 5.1 mmol / L-cat based on the CO ₂ desorption amount per 1 L of catalyst measured by CO ₂ temperature programmed desorption measurement (lanthanum, alumina, platinum And a catalyst having a base point amount of 0.1 mmol / L-cat (a catalyst comprising ceria-zirconia composite oxide and platinum) per 1 L of catalyst, and sulfur of each catalyst. Graphs of the desorption temperatures of the components (H ₂ S and SO ₂ ) are shown in FIGS. FIG. 2 is a graph showing the relationship between the amount of sulfur component desorbed from the catalyst having a base point amount of 5.1 mmol / L-cat and the temperature, and FIG. It is a graph which shows the relationship between the desorption amount of the sulfur component of the catalyst of L-cat, and temperature. From the graph shown in FIG. 2, in the catalyst having a large amount of base points (base point amount is 5.1), H ₂ S is discharged even at a high temperature. It can be seen that it is retained. In addition, such a catalyst with a large amount of base sites generates a small amount of H ₂ S in a low temperature range. Therefore, in the present invention, the base point amount per 1 L of the catalyst of the second catalyst is controlled within the above range while sufficiently suppressing the amount of H ₂ S generated from the first catalyst. Sufficiently prevent the sulfur component from adhering to the second catalyst and effectively prevent the sulfur component from desorbing from the second catalyst, and the exhaust gas purification apparatus as a whole exhibits sufficiently high catalytic activity. However, it is possible to sufficiently reduce the discharge amount of H ₂ S. And according to such an exhaust gas purification apparatus of the present invention, even under high load conditions where the driving state changes suddenly, such as when climbing up or running at high speed after traveling at low speed urban areas, the H ₂ S The present inventors speculate that the occurrence can be sufficiently prevented. Furthermore, in the present invention, when an acidic element (for example, Ti) is further supported on the second metal oxide support, the base point amount of the second catalyst is reduced, and the sulfur poisoning amount is reduced. Therefore, the present inventors speculate that the generation of H ₂ S can be more sufficiently prevented.

According to the present invention, it is possible to provide an exhaust gas purifying apparatus capable of sufficiently reducing the emissions of H _{2 S} while exhibiting sufficiently high catalytic activity as a three-way catalyst.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

The exhaust gas purification apparatus of the present invention includes a first catalyst base, a first metal oxide support supported on the first catalyst base, and a first support supported on the first metal oxide support. The amount of base points per liter of catalyst is 3.0 to 20 mmol / L-cat based on the amount of CO ₂ desorbed per liter of catalyst measured by CO ₂ temperature-programmed desorption. A first catalyst that is filled and disposed upstream of the gas flow path; and
A second catalyst base, a second metal oxide support supported on the second catalyst base, and a second noble metal supported on the second metal oxide support, and CO ₂ Satisfying the condition that the base point amount per 1 L of catalyst based on the desorption amount of CO ₂ per 1 L of catalyst by temperature-programmed desorption measurement is 2.0 mmol / L-cat or less, and downstream of the gas flow path A second catalyst arranged on the side,
It is characterized by providing.

Here, the “base point amount” referred to in the present invention is a value based on the amount of CO ₂ desorbed per liter of the catalyst measured by CO ₂ temperature-programmed desorption as described above. Here, a method of calculating the “base point amount” in the present invention using CO ₂ temperature programmed desorption measurement will be described.

When calculating such “base point amount”, first, a sample having a diameter of 30 mm, a length of 50 mm, and a capacity of 35 cc is prepared. Such a sample is manufactured by coating a predetermined amount of a metal oxide carrier and a noble metal supported on the metal oxide carrier on a catalyst base having a diameter of 30 mm, a length of 50 mm, and a capacity of 35 cc. And such a sample is installed in the reaction apparatus as described in Unexamined-Japanese-Patent No. 2002-311013. Next, a gas composed of CO ₂ (5% by volume) and N ₂ (95% by volume) is brought into contact with the sample at a flow rate of 5 L / min for 2 minutes. At this time, the temperature of the gas is 90 ° C. Next, a rich gas composed of H ₂ (4% by volume) and N ₂ (96% by volume) and a lean gas composed of O ₂ (4% by volume) and N ₂ (96% by volume) are switched every 60 seconds. And contacting the sample. At this time, the temperature of the gas to be brought into contact with the sample (the rich gas and the lean gas) is increased to 810 ° C. with an initial temperature of 90 ° C. and a temperature increase rate of 40 ° C./min. Further, the flow rate of the gas brought into contact with the sample is 5 L / min with respect to the sample. After the gas temperature reaches 810 ° C., the gas temperature is maintained at 810 ° C., and the lean gas and the rich gas are switched every 10 seconds and 20 seconds, respectively, for 10 minutes and at 5 L / min. Contact the sample at a flow rate. Thereafter, N ₂ gas at 90 ° C. is brought into contact with the sample at a flow rate of 5 L / min for 20 minutes (pretreatment). Next, a gas composed of 90 ° C. CO ₂ (0.5% by volume) and N ₂ (99.5% by volume) is brought into contact with the exhaust gas purifier after pretreatment at a flow rate of 5 L / min for 10 minutes. Then, CO ₂ is adsorbed on the sample (CO ₂ adsorption treatment). Then, with respect to the sample from which CO ₂ has been adsorbed, contacting a 90 ° C. in _{N 2} gas for 5 minutes, after contacting at a flow rate of 10L / min, an additional 5 minutes, the _{N 2} gas at a flow rate of 5L / min Let Then, while raising the temperature to 810 ° C. The temperature of the gas at a heating rate of 40 ° C. / min, the _{N 2} gas is contacted at a flow rate of 5L / min, the CO ₂ desorbed (CO ₂ desorption process) . In such a CO ₂ desorption process, the amount of CO _{2 in} the output gas from the time when the temperature of the N ₂ gas begins to rise until the gas temperature reaches 810 ° C. is measured (CO ₂ temperature rise). Desorption measurement). For measurement of such a gas concentration, a trade name “MEXA-4300FT” manufactured by HORIBA, Ltd. is used as a measuring device. Then, the amount of CO ₂ desorbed from the sample is converted into the amount per 1 L of the catalyst, and the base point amount of the catalyst is calculated. In calculating the amount of such base points, it is predicted that a system error is included in the apparatus and measurement conditions used for the measurement because the background during the CO ₂ desorption treatment test is 20 to 30 ppm. Therefore, as a method for calculating the basic sites of the present invention, the background concentration of CO ₂ temperature increase start time and CO ₂ during desorption process completion of CO ₂ desorption treatment connected by straight lines, a concentration of more than background The base point amount of the sample can be calculated by integrating the peak area of the desorption peak observed in (1). The value of the base point amount of the sample calculated in this way is the catalyst of the component supported on the catalyst substrate (component consisting of the metal oxide support and the noble metal supported on the metal oxide support). It is proportional to the coating amount per liter (g / L-cat). For example, in the case where the base point amount of the sample (I) coated with the component (A) of a specific amount (g / L-cat) is 5.0 mmol / L-cat, the coating amount of the component (A) (g / The base point amount of sample (II) in which L-cat) is half of the specific amount is half the base point amount of sample (I) (2.5 mmol / L-cat), and the coating amount of the catalyst component The base point amount of the sample (III) in which (g / L-cat) is twice the specific amount is a value (10 mmol / L-cat) twice the base point amount of the sample (I). Therefore, if a sample is prepared by supporting a predetermined amount of the supported component on the catalyst base and the base point amount of the sample is calculated, the base point amount per 1 L of catalyst of the catalyst on which the same supported component is supported is calculated. It becomes possible to calculate based on the coating amount (g / L-cat). Therefore, if the amount of base points is measured using a sample coated with a predetermined amount of supported component, the amount of base points per liter of catalyst can be adjusted by adjusting the coat amount (g / L-cat) of the same supported component. It becomes possible to adjust appropriately. The “base point amount” mentioned here is exhaust gas in a new state (1000 km, more preferably less than 100 km travel may be included) that is most likely to generate H ₂ S under the use of high sulfur fuel. This is the base point amount of the catalyst in the purification apparatus.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description and drawings, the same or corresponding elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

  FIG. 4 is a schematic longitudinal sectional view of a preferred embodiment of the exhaust gas purifying apparatus of the present invention. The embodiment shown in FIG. 4 includes a catalyst case 10, a first catalyst 11 disposed on the upstream side of the gas flow path, and a second catalyst 12 disposed on the downstream side of the gas flow path. The catalyst case 10 is connected to the exhaust gas pipe 13. In this embodiment, one cordierite honeycomb substrate with a cell density of 400 cells / in is used, and a 50% by volume portion upstream of the gas flow path of the substrate is used as the first catalyst substrate. And the first catalyst 11 and the second catalyst 12 are placed in close contact with each other by using a 50% by volume portion downstream of the gas flow path of the substrate as the second catalyst substrate. Take the structure. In addition, the arrow A in FIG. 4 has shown notionally the direction through which gas flows.

  The first catalyst 11 includes a first catalyst base, a first metal oxide support supported on the first catalyst base, and a first metal support supported on the first metal oxide support. With precious metals.

  In the present embodiment, as described above, the 50% by volume portion upstream of the gas flow path of the cordierite honeycomb substrate is used as the first catalyst substrate. The form of the first catalyst base is not particularly limited, and is appropriately selected according to the use of the obtained catalyst. A DPF base, a monolith base, a pellet base, a plate base, etc. Can be suitably used. Moreover, the material of such a base material is not particularly limited, and ceramics such as cordierite, silicon carbide, mullite, and metals such as stainless steel including chromium and aluminum can be preferably used.

Further, the first metal oxide support is not particularly limited, and can be used as a support for a three-way catalyst such as activated alumina, alumina-ceria-zirconia, ceria-zirconia, zirconia, lanthanum stabilized activated alumina, etc. A carrier made of a known metal oxide can be appropriately used. Examples of metal oxides used for such carriers include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium. (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), ruthenium (Lu), yttrium (Y), zirconium (Zr), aluminum At least one selected from the group consisting of oxides of (Al), magnesium (Mg) and vanadium (V), solid solutions thereof, and composite oxides thereof is preferable. Among such metal oxides, CeO ₂ , ZrO ₂ , Y ₂ O ₃ , TiO ₂ , Al ₂ O ₃ , solid solutions thereof, and these from the viewpoint that higher activity can be obtained as a three-way catalyst It is more preferable to contain at least one selected from the group consisting of the above complex oxides, and a complex oxide containing Al ₂ O ₃ and Ce is still more preferable.

As such a first metal oxide carrier, the amount of base points per liter of catalyst based on the amount of CO ₂ desorbed per liter of catalyst measured by CO ₂ temperature-programmed desorption of the first catalyst 11 is Ceria-zirconia composite support, θ-alumina, γ-alumina, BaSO from the viewpoint of more efficiently in the range of 2.0 to 20 mmol / L-cat and exhibiting a sufficient catalytic function when used in a three-way catalyst. ₄ is preferably used.

  Moreover, as the amount of base points of such a 1st metal oxide support | carrier, it is preferable that it is 3.0-15 mmol / L, and it is more preferable that it is 4.0-12 mmol / L. If the base point amount of the first metal oxide carrier exceeds the upper limit, the sulfur poisoning amount tends to be excessive when used. On the other hand, if the base point amount of the first metal oxide support is less than the lower limit, the base point amount per liter of the catalyst of the first catalyst is 3.0% while imparting sufficient catalytic activity to the first catalyst. It becomes difficult to set the range of ˜20 mmol / L-cat. The base point amount of the first metal oxide support is the same as the above-described method for calculating the base point amount except that a sample in which only the first metal oxide support is coated on the catalyst base is used. It can be calculated by adopting the method.

Moreover, such a specific surface area of the first metal oxide support is not particularly limited, is preferably from 5~150m ² / g, more preferably 10~120m ² / g. When the specific surface area exceeds the upper limit, the sulfur component adhesion sites tend to increase, and H ₂ S tends to be generated. On the other hand, when the specific surface area is less than the lower limit, the catalyst performance tends to decrease. Such a specific surface area can be calculated as a BET specific surface area from the adsorption isotherm using the BET isotherm adsorption equation. In addition, the manufacturing method in particular of such a 1st metal oxide support | carrier is not restrict | limited, A well-known method can be employ | adopted suitably. Moreover, as such a first metal oxide support, a commercially available product may be used.

  The amount of the first metal oxide carrier supported on the first catalyst substrate is preferably 50 to 400 g / L-cat per liter of catalyst, and 70 to 300 g / L-cat. More preferably. If the supported amount of the metal oxide carrier is less than the lower limit, it tends to be difficult to exhibit sufficient catalytic activity. On the other hand, if the upper limit is exceeded, the warm-up property is reduced or the pressure loss is reduced. Tend to be larger.

  Furthermore, the method for supporting the first metal oxide support on the first catalyst base is not particularly limited, and the catalyst base is coated with a slurry containing the first metal oxide support and fired. A publicly known method such as a method of supporting by the above can be appropriately employed. Moreover, when using a slurry, you may contain a binder component in a slurry.

  The first noble metal is preferably at least one selected from the group consisting of ruthenium, rhodium, palladium, silver, iridium, platinum and gold. By containing such a noble metal, it tends to be possible to exhibit higher catalytic activity. Of these first noble metals, platinum, rhodium, and palladium are preferably used from the viewpoint that higher catalytic activity can be exhibited. In addition, from the viewpoint of exhibiting sufficient catalytic activity by the upstream first catalyst and preventing sulfur poisoning, the coating of the first metal oxide support supported on the first catalyst base material It is particularly preferable that rhodium is supported on the outer surface side of the layer, and platinum or palladium is supported on the inner side of the coat layer (the surface side of the catalyst base). In addition, these 1st noble metals can be used individually by 1 type or in combination of 2 or more types. Further, the method for supporting the first noble metal on the first metal oxide support is not particularly limited, and a known method can be appropriately employed. For example, a salt of a noble metal (for example, a dinitrodiamine salt) A method in which an aqueous solution containing a complex (for example, a tetraammine complex) is impregnated in the metal oxide support, dried, and fired may be employed.

  The supported amount of the first noble metal is preferably 0.1 to 6.0 g / L-cat, more preferably 0.5 to 3.0 g / L-cat per liter of the catalyst. If the loading amount of the first noble metal is less than the lower limit, it tends to be difficult to exhibit sufficient catalytic activity. On the other hand, if the upper limit is exceeded, the activity is saturated, and the cost increases. There is a tendency. The first catalyst base material may contain a known additive (for example, alkali metal or alkaline earth metal) that can be used for the three-way catalyst.

  In the first catalyst 11, a known additive (for example, alkali metal or alkaline earth metal) that can be used as a three-way catalyst is appropriately supported on the first metal oxide support. Good.

The first catalyst 11 has a base point amount of 3.0 to 20 mmol / L-cat (based on CO ₂ desorption amount per 1 L of catalyst measured by CO ₂ temperature programmed desorption measurement). The condition of preferably 3.0 to 15 mmol / L-cat, more preferably 4.0 to 12 mmol / L-cat) is satisfied. When the amount of the base point per 1 L of the catalyst of the first catalyst 11 is less than the lower limit, there is a tendency that the OSC material used for sufficiently adjusting the atmosphere cannot be sufficiently added. If it exceeds, the warm-up property tends to decrease or the pressure loss tends to increase. In addition, the amount of base points per liter of the catalyst of the first catalyst 11 depends on the coating amount, etc., according to the type of the first metal oxide carrier to be supported on the catalyst substrate and the supported component consisting of the first noble metal. It is possible to adjust by adjusting appropriately.

Of further, as the first catalyst 11, it is preferable to satisfy the condition that the peak temperature of the desorption amount of CO ₂ during the CO ₂ temperature-programmed desorption measurement is 300 ° C. or less, 280 ° C. or less It is more preferable to satisfy the conditions. When the peak temperature of the CO ₂ desorption amount exceeds the upper limit, the base strength increases and the sulfur component is more easily accumulated, thereby sufficiently reducing the amount of H ₂ S discharged. Tend to be difficult. The temperature here is measured based on the temperature of the gas brought into contact with the catalyst in the CO ₂ temperature programmed desorption measurement.

  Further, the structure of the first catalyst 11 is not particularly limited, and is a structure in which one layer of the first metal oxide support on which the first noble metal is supported is coated on a first catalyst base. Alternatively, a multilayer structure in which two or more layers are coated may be used. Therefore, as the first catalyst 11, for example, the surface of the catalyst base is coated with the first metal oxide carrier supporting platinum in the lower layer and the first metal oxide carrier supporting rhodium in the upper layer. A two-layer structure coated with

  The second catalyst 12 includes a second catalyst base, a second metal oxide support supported on the second catalyst base, and a second metal oxide support supported on the second metal oxide support. With two precious metals.

  In the present embodiment, as described above, a 50% by volume portion on the downstream side of the gas flow path of the cordierite honeycomb substrate is used as the second catalyst substrate. As such a 2nd catalyst base material, the thing similar to what was demonstrated by the above-mentioned 1st catalyst base material can be used. In the present embodiment, one catalyst base is used, the upstream region of the catalyst base is used as the first catalyst base, and the downstream side is used as the second catalyst base. .

Such a second metal oxide support is not particularly limited, and can be used as a support for a three-way catalyst, such as activated alumina, alumina-ceria-zirconia, ceria-zirconia, zirconia, lanthanum stabilized activated alumina, etc. A carrier made of a known metal oxide can be appropriately used. The metal oxide constituting the second metal oxide support is not particularly limited, and a metal oxide similar to the metal oxide constituting the first metal oxide support can be appropriately used. In addition, as such a second metal oxide support, the amount of base points per liter of catalyst based on the amount of CO ₂ desorbed per liter of catalyst measured by CO ₂ temperature-programmed desorption of the second catalyst 12 is used. From the viewpoint of more efficiently having a range of 2.0 mmol / L-cat or less and exhibiting a sufficient catalytic function when utilized in a three-way catalyst, a support made of lanthanum-stabilized activated alumina, A carrier made of zirconia-ceria, a carrier made of high-purity alumina of 98% by mass or more, a carrier made of alumina carrying titanium which is an acidic element, and the like are preferable.

  Furthermore, the amount of base points per liter of the catalyst of the second metal oxide support is preferably 0.02 to 2.0 mmol / L, and preferably 0.03 to 1.5 mmol / L. Is more preferable. When the base point amount of the second metal oxide support exceeds the upper limit, it becomes difficult to set the base point amount of the exhaust gas purifying apparatus to 2.0 mmol / L-cat or less. The base point amount of the second metal oxide support is the same as the method for calculating the base point amount described above except that a sample in which only the second metal oxide support is coated on the catalyst base is used. It can be calculated by adopting the method.

It is preferable that the specific surface area of the second metal oxide support is 3~200m ² / g, and more preferably 10 to 150 m ² / g. When the specific surface area exceeds the upper limit, the sulfur component adhesion sites tend to increase, and H ₂ S tends to be generated. When the specific surface area is less than the lower limit, the catalyst performance tends to decrease. Such a specific surface area can be calculated as a BET specific surface area from the adsorption isotherm using the BET isotherm adsorption equation. In addition, the manufacturing method in particular of such a 2nd metal oxide support | carrier is not restrict | limited, A well-known method is employable suitably. Moreover, as such a second metal oxide support, a commercially available product may be used.

  In addition, the amount of the second metal oxide carrier supported is preferably 10 to 200 g / L-cat, more preferably 30 to 150 g / L-cat per liter of the catalyst. If the amount of the second metal oxide carrier supported is less than the lower limit, it tends to be difficult to exhibit sufficient catalytic activity. On the other hand, if the upper limit is exceeded, the warm-up property may decrease. The pressure loss tends to increase.

  Furthermore, the method for supporting the second metal oxide support on the second catalyst base is not particularly limited, and the catalyst base is coated with a slurry containing the first metal oxide support and fired. A publicly known method such as a method of supporting by the above can be appropriately employed. Moreover, you may carry | support by including the component used as a binder.

  The second noble metal may be the same as the first noble metal described above. The second noble metal is preferably platinum, rhodium or palladium, more preferably platinum or rhodium, from the viewpoint that it can exhibit a higher level of catalytic activity with respect to particulate matter. It is more preferable to use rhodium from the viewpoints of exhibiting sufficient catalytic activity and preventing sulfur poisoning more sufficiently. In addition, these noble metals can be used individually by 1 type or in combination of 2 or more types. Further, the method for supporting the second noble metal on the second metal oxide support is not particularly limited, and a known method can be appropriately employed. For example, a salt of a noble metal (for example, a dinitrodiamine salt) Alternatively, a method may be employed in which the metal oxide support is impregnated with an aqueous solution containing a metal complex or a complex (for example, a tetraammine complex), dried, and fired.

  The amount of the second noble metal supported is preferably 0.01 to 2 g / L-cat, more preferably 0.05 to 1 g / L-cat per liter of catalyst. When the amount of the second noble metal supported is less than the lower limit, it tends to be difficult to exhibit sufficient catalytic activity. On the other hand, when the upper limit is exceeded, the activity is saturated and the cost increases. There is a tendency.

Further, in the second catalyst 12, the second metal oxide support is added to the second metal oxide support in order to make the amount of base points per liter of the catalyst 2.0 mmol / L-cat or less more efficiently. It is preferable that an element (acidic element) having a greater electronegativity than the cation of the metal element constituting the object carrier is supported. By supporting such an acidic element (for example, Ti or P) on the second metal oxide carrier, the amount of base sites per liter of the second catalyst 12 can be more efficiently reduced to 2.0 mmol / L−. It becomes possible to make it below cat. Furthermore, by supporting the acidic element, it is possible to efficiently reduce the amount of sulfur adhering sites, and in a reducing atmosphere, it becomes possible not to maintain the sulfur component up to a high temperature. Since the sulfur component is supplemented and the sulfur component supplemented in an oxidizing atmosphere can be desorbed as SO ₂ , the generation of H ₂ S tends to be further reduced.

In addition, such acidic element, intended varies depending on the kind of the metal element forming the second metal oxide support is, but from the viewpoint of reducing the more generation of efficient H _{2 S,} phosphorus, molybdenum, Tungsten, titanium, niobium, silicon or iron is more preferable, and phosphorus, molybdenum, tungsten or titanium is particularly preferable from the viewpoint of catalytic activity. In addition, such an acidic element can be used individually by 1 type or in mixture of 2 or more types.

The amount of the acidic element supported depends on the type of the second metal oxide support, the specific surface area of the second metal oxide support, the type of other additives, and the like in the second catalyst region of the catalyst. Since the amount of the acidic element required to make the point amount 2.0 mmol / L-cat or less is different, it cannot be generally stated, but while sufficiently reducing the discharge amount of H ₂ S, From the viewpoint of obtaining higher OSC ability, the supported amount of each of the acidic elements is 0.01 to 1.0 mol / L-cat (more preferably 0.03 to 0.3 mol / L per 1 L of catalyst). -Cat, more preferably 0.05 to 0.22 mol / L-cat). In addition, the amount of the acidic element supported is 0.03 to 0.3 mol / L-cat (more preferably 0.05 to 0.2 mol / L-cat) when the acidic element is phosphorus. In the case of molybdenum, it is particularly preferably 0.05 to 0.22 mol / L-cat (more preferably 0.08 to 0.2 mol / L-cat), tungsten or titanium. In this case, it is particularly preferably 0.01 to 0.2 mol / L-cat (more preferably 0.05 to 0.15 mol / L-cat). When the supported amount is less than the lower limit, it becomes difficult to efficiently make the amount of base points per 1 L of the catalyst of the second catalyst 12 2.0 mmol / L-cat or less, and the amount of H ₂ S discharged is sufficient. On the other hand, when the upper limit is exceeded, the OSC ability of the second catalyst 12 is lowered, and components such as HC, CO or NO _x tend not to be sufficiently purified. .

  Furthermore, the method for supporting the acidic element on the second metal oxide support is not particularly limited, and a known method capable of supporting the acidic element on the metal oxide is appropriately adopted. For example, a method in which the metal oxide carrier is impregnated with an acidic element salt (for example, an aqueous solution of chloride or nitrate) or an alcohol solution of an alkoxide, followed by drying and firing may be employed.

  Further, in the second catalyst 12, a known additive (for example, alkali metal or alkaline earth metal) that can be used for the three-way catalyst may be supported on the second metal oxide support. . When at least one additive element selected from alkali metals and alkaline earth metals is used as such an additive, the loading amount of the additive element is such that the second metal oxide support and the second metal oxide are supported. The amount is preferably 3% by mass or less, more preferably 2% by mass or less, based on the total amount of the noble metal and additive elements supported on the product carrier. When the loading amount of such an additional element exceeds the upper limit, it tends to be difficult to make the amount of base points per liter of the catalyst of the second catalyst 2.0 mmol / L-cat or less.

The second catalyst 12 is said to have a base point amount per 1 L of catalyst of 2.0 mmol / L-cat or less based on the CO ₂ desorption amount per 1 L of catalyst measured by CO ₂ temperature programmed desorption measurement. Meet the conditions. The base point amount per 1 L of the catalyst of the second catalyst 12 is preferably 1.5 mmol / L-cat or less, more preferably 1.0 mmol / L-cat or less, and More preferably, it is 8 mmol / L-cat or less, and particularly preferably 0.5 mmol / L-cat or less. When the amount of base points per liter of the catalyst of the second catalyst 12 exceeds the upper limit, the base point is an adhesion site with a strong sulfur component, so that the catalyst becomes an exhaust gas containing a sulfur component in an oxidizing atmosphere. upon contact, since the low-temperature stoichiometric or it can not be sufficiently prevented catalyst sulfur poisoning of rich conditions, the sulfur component resulting in H _{2 S} is generated by elimination in a high-temperature reducing atmosphere, H ₂ S emissions can not be sufficiently reduced further, as the second catalyst 12, to satisfy the condition that the CO ₂ peak temperature of desorption of CO ₂ during the temperature programmed desorption measurement is 250 ° C. or less Is preferable, and it is more preferable that the condition of 220 ° C. or lower is satisfied. When the peak temperature of the CO ₂ desorption amount exceeds the upper limit, the base strength increases and the sulfur component is more easily accumulated, thereby sufficiently reducing the amount of H ₂ S discharged. Tend to be difficult. In addition, it is surmised that the desorption temperature of H ₂ S is lowered in a catalyst having a lower peak temperature of the CO ₂ desorption amount. The temperature here is measured based on the temperature of the gas brought into contact with the catalyst in the CO ₂ temperature programmed desorption measurement.

  Further, the structure of the second catalyst 12 is not particularly limited, and is a catalyst having a structure in which the second metal oxide carrier and the second noble metal are coated on a second catalyst base. Alternatively, a catalyst having a multilayer structure in which two or more layers are coated may be used. In addition, as the second catalyst 12, from the viewpoint of more efficiently setting the amount of base points per liter of the catalyst of the second catalyst 12 to 2.0 mmol / L-cat or less, the second catalyst 12 on which the second noble metal is supported. It is preferable to use a catalyst having a structure in which the second metal oxide support is coated on one layer.

Moreover, as an average value of the amount of base points per liter of the catalyst of the first catalyst 11 and the amount of base points per liter of the catalyst of the second catalyst 12, 1.2 to 11 mmol / L-cat (more preferably 2 to 9 mmol) / L-cat). If the average value of the amount of base points (the amount of base points per liter of the catalyst in the entire catalyst) is less than the lower limit, sufficient OSC material cannot be supported, and the catalytic activity tends to decrease. Then, the sulfur poisoning amount increases and the generation of H ₂ S tends not to be sufficiently suppressed.

Further, as the first catalyst 11 and the second catalyst 12, the amount of base points of the first catalyst 11 is more than twice (more preferably more than 3 times) the amount of base points of the second catalyst 12. It is preferable to use those that satisfy the conditions. When the base point amount of the first catalyst 11 is less than twice the base point amount of the second catalyst 12, the effect of reducing the H ₂ S odor tends to be small.

In the present embodiment, the capacity ratio between the first region in which the first catalyst 11 is disposed and the second region in which the second catalyst 12 is disposed ([first region]: [first The second area]) is 50:50. The volume ratio between the first region in which the first catalyst 11 is disposed and the second region in which the second catalyst 12 is disposed is not particularly limited, but is 15:85 to 85:15. Is preferably in the range of 25:75 to 75:25, more preferably 35:65 to 65:35. If the ratio of the first region is less than the lower limit, the OSC material used to sufficiently adjust the atmosphere tends not to be sufficiently added. On the other hand, if the ratio exceeds the upper limit, the base point of the entire catalyst tends to be reduced. The amount increases and the catalyst poisoning amount tends to increase. Note that the preferred range of the volume ratio between the first region and the second region varies depending on the length of the catalyst base used. For example, when the length of the catalyst base used is short, it varies depending on the type of catalyst component used, but since the temperature distribution inside the catalyst is difficult to change, the amount of sulfur component attached to the entire catalyst can be further reduced. In order to more reliably prevent the generation of H ₂ S, it is preferable to reduce the ratio of the first catalyst 11, and from the viewpoint of catalytic activity, increase the ratio of the region occupied by the first catalyst 11. Is preferred. In addition, when the catalyst base is long, the difference in temperature distribution inside the catalyst becomes large, so that the amount of sulfur component attached to the entire catalyst is further reduced to more reliably generate H ₂ S. In order to prevent this, it is preferable to increase the ratio of the region 12 occupied by the second catalyst. Therefore, the design of the volume ratio between the first catalyst 11 and the second catalyst 12 can be appropriately changed within a suitable range according to the type of catalyst component used, the size of the catalyst base, and the like.

  As mentioned above, although preferred embodiment of the exhaust gas purification apparatus of this invention was described, the exhaust gas purification apparatus of this invention is not limited to the said embodiment. For example, in the above embodiment, a single catalyst base is used, the upstream portion of the catalyst base is used as the first catalyst base, and the downstream portion is used as the second catalyst base. However, in the present invention, the first catalyst base and the second catalyst base may each be composed of separate bases. As described above, when the first catalyst base and the second catalyst base are used as separate bases, the types of the catalyst base may be the same or different. In addition, in the case of using separate catalyst bases for the first catalyst base and the second catalyst base, respectively, the first catalyst and the second catalyst may be arranged adjacent to each other, They may be spaced apart. In the above embodiment, a single catalyst base is used, a 50% by volume site upstream of the catalyst base is used as the first catalyst base, and a 50% by volume downstream site is used as the first catalyst base. Although it is used as the second catalyst base, the arrangement relationship between the first catalyst and the second catalyst is not particularly limited in the present invention, for example, nothing is supported on the central region of the catalyst base, Using the upstream site as the first catalyst and the downstream site as the second catalyst, the first catalyst and the second catalyst may be arranged apart from each other, The first catalyst and the second catalyst may be partially overlapped, and the volume ratio between the region where the first catalyst is disposed and the region where the second catalyst is disposed is appropriately changed. You may arrange | position a 1st catalyst and a 2nd catalyst. Further, the first catalyst and the second catalyst are, for example, a ceria zirconia composite in which an Rh-supported alumina catalyst layer or a Rh-supported zirconia-ceria composite oxide catalyst layer is disposed in the upper layer, and Pt and Pd are separately supported in the lower layer. It may be a multi-layer coated catalyst in which an oxide catalyst layer, an alumina powder catalyst layer on which Pt and Pd are separated and supported, and the like are arranged.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Synthesis Example 1)
First, a slurry containing θ-alumina powder (specific surface area of about 100 m ² / g) and alumina hydrate (trade name “Alumina Sol 200” manufactured by Nissan Chemical Industries, Ltd.) as a binder is 30 mm in diameter and long. After wash-coating a honeycomb substrate made of cordierite having a thickness of 50 mm, a volume of 35 cc, 400 cells / in ² , and 4 mil so that the supported amount of θ-alumina per liter of catalyst is 100 g / L-cat, Firing was performed for 1 hour at a temperature of 500 ° C., and θ-alumina (metal oxide support) was supported on the honeycomb substrate to obtain a catalyst support.

  Next, using a nitric acid aqueous solution of dinitrodiamine platinum, the catalyst precursor was impregnated and supported with Pt so that the supported amount of platinum (Pt) per liter of the catalyst was 1 g / L-cat, and 1 at 500 ° C. By firing for a time, a noble metal was supported on θ-alumina (metal oxide support) to obtain a Pt / activated alumina supporting substrate.

(Synthesis Example 2)
Amount of molybdenum (Mo) supported per liter of catalyst using ammonium molybdate ((NH ₄ ) Mo ₇ O ₂₄ · 4H ₂ O) on the Pt / activated alumina-supported substrate obtained in Synthesis Example 1 The catalyst sample 1 ((Pt / activated alumina) + 0.1Mo) was produced by impregnating and supporting Mo on the Pt / activated alumina supporting substrate so that the amount of the catalyst was 0.1 mol / L-cat.

(Synthesis Example 3)
A catalyst sample 2 ((Pt / activated alumina) +0.1 P) was produced in the same manner as in Synthesis Example 2 except that phosphoric acid was used instead of ammonium molybdate and phosphorus was supported at 0.1 mol / L-cat. .

(Synthesis Example 4)
A catalyst sample 3 ((Pt / activated alumina) was prepared in the same manner as in Synthesis Example 2 except that titanium was supported by 0.1 mol / L-cat using an ethyl alcohol solution of titanium (IV) tetrabutoxide monomer instead of ammonium molybdate. ) +0.1 Ti).

(Synthesis Example 5)
Catalyst sample 4 ((Pt / activated alumina) + 0.1Si) was produced in the same manner as in Synthesis Example 2, except that tetraethyl orthosilicate was used in place of ammonium molybdate and silicon was supported at 0.1 mol / L-cat. .

(Synthesis Example 6)
Catalyst sample 5 ((Pt / activated alumina) was prepared in the same manner as in Synthesis Example 2, except that iron (III) nitrate nonahydrate was used instead of ammonium molybdate and iron was supported at 0.1 mol / L-cat. ) + 0.1Fe).

(Synthesis Example 7)
Catalyst sample 6 ((Pt / activated alumina) +0. 0) was prepared in the same manner as in Synthesis example 2 except that magnesium was supported by 0.1 mol / L-cat using an aqueous solution of magnesium acetate tetrahydrate instead of ammonium molybdate. 1 Mg) was produced.

(Synthesis Example 8)
Catalyst sample 7 ((Pt / activated alumina) + 0.1Ba) was produced in the same manner as in Synthesis Example 2, except that barium was supported at 0.1 mol / L-cat using an aqueous solution of barium nitrate instead of ammonium molybdate. did.

(Synthesis Example 9)
Catalyst sample 8 (supported after 0.1 P (Pt / active alumina)) in the same manner as in Synthesis Example 2 except that an aqueous solution of ammonium phosphate was used instead of ammonium molybdate to support 0.1 mol / L-cat phosphorus. Manufactured.

(Synthesis Example 10)
Catalyst sample 9 (similar to Synthesis Example 1) except that phosphorus-supported activated alumina was used instead of the θ-alumina powder, and the phosphor-supported activated alumina was supported on the honeycomb substrate and then washed and dried. Pt / 0.1P-supported activated alumina) was obtained. The phosphorus-supported alumina was produced as follows. That is, after the aqueous solution of ammonium phosphate was supported on the θ-alumina powder (specific surface area of about 100 m ² / g), the amount of phosphorus supported on 100 g of the θ-alumina powder was 0.1 mol, and the feed water was supported. And firing to obtain phosphorus-supported activated alumina.

(Synthesis Example 11)
A catalyst sample 10 (Pt / 0.1P-added activated alumina) was obtained in the same manner as in Synthesis Example 1 except that phosphorus-added activated alumina was used instead of the θ-alumina powder. The phosphorus-added activated alumina was produced as follows. That is, first, aluminum nitrate having a solid content of 100 g was precipitated with ammonia water, and then washed with water and stretched. Thereafter, the obtained precipitate is dispersed in water, ammonium phosphate is added so that the amount of phosphorus added to 100 g of aluminum is 0.1 mol, and the mixture is stirred well to form a precipitate, which is dried and calcined. As a result, phosphorus-added activated alumina was obtained.

(Synthesis Example 12)
A catalyst sample 11 (Rh / 0.1P-supported activated alumina) was obtained in the same manner as in Synthesis Example 10 except that the type of noble metal was changed from platinum to rhodium and the supported amount of rhodium was changed to 0.2 g / L-cat. It was.

(Synthesis Example 13)
A catalyst sample 12 (Rh / 0.1P-added activated alumina) was obtained in the same manner as in Synthesis Example 11 except that the kind of noble metal was changed from platinum to rhodium and the supported amount of rhodium was changed to 0.2 g / L-cat. It was.

(Synthesis Example 14)
In the same manner as in Synthesis Example 1 except that ceria zirconia powder (specific surface area of about 30 m ² / g, molar ratio of each component (ceria: zirconia) is 9:11) was used instead of θ-alumina powder. A Pt / ceria zirconia-supporting substrate was obtained.

(Synthesis Examples 15 to 21)
A catalyst sample 13 ((Pt / ceria zirconia)) was prepared in the same manner as in Synthesis Examples 2 to 8 except that the Pt / ceria zirconia support substrate obtained in Synthesis Example 14 was used instead of the Pt / activated alumina support substrate. +0.1 Mo), catalyst sample 14 ((Pt / ceria zirconia) +0.1 P), catalyst sample 15 ((Pt / ceria zirconia) +0.1 Ti), catalyst sample 16 ((Pt / ceria zirconia) +0.1 Si), Catalyst sample 17 ((Pt / ceria zirconia) + 0.1Fe), catalyst sample 18 ((Pt / ceria zirconia) +0.1 Mg), and catalyst sample 19 ((Pt / ceria zirconia) + 0.1Ba) were obtained.

(Synthesis Example 22)
A cordierite-made honeycomb substrate having a diameter of 30 mm, a length of 50 mm, a volume of 35 cc, 400 cells / in ² , and 4 mil of a slurry containing a catalyst supporting platinum and rhodium and alumina hydrate as a binder The platinum and rhodium supported catalyst per liter of the catalyst was wash coated so that the supported amount of the catalyst was 200 g / L-cat, and then calcined at 500 ° C. for 1 hour to obtain Pt and Rh. Was supported on a honeycomb substrate to obtain a Pt-Rh catalyst-supported catalyst substrate. The support in such a catalyst includes La-stabilized activated alumina (specific surface area of about 180 m ² / g, La content: 3% by mass (4% by mass as La ₂ O ₃ )) and alumina ceria zirconia (OSC). Material: a specific surface area of about 85 m ² / g, a mixed powder of each component molar ratio (alumina: ceria: zirconia) is 20: 9: 11), and the mixing ratio of La stabilized activated alumina and alumina ceria zirconia Is 1: 1 by mass ratio (La stabilized activated alumina: alumina ceria zirconia). The supported amount of platinum was 1 g / L-cat per liter of catalyst, and the supported amount of rhodium was 0.2 g per liter of catalyst.

(Synthesis Example 23)
With respect to the Pt—Rh catalyst-supported catalyst base material obtained in Synthesis Example 22, tetraethyl orthosilicate is used so that the supported amount of silicon (Si) per liter of the catalyst is 0.11 mol / L-cat. A catalyst sample 20 (Pt—Rh catalyst + 0.11 Si) was produced by impregnating and supporting Si on the Pt—Rh catalyst supporting catalyst base.

(Synthesis Example 24)
Using the ethyl alcohol solution of titanium (IV) tetrabutoxide monomer to the Pt—Rh catalyst-supported catalyst base obtained in Synthesis Example 22, the supported amount of titanium (Ti) per 1 L of catalyst was 0.16 mol / A catalyst sample 21 (Pt-Rh catalyst + 0.16Ti) was produced by impregnating and supporting Ti on the Pt-Rh catalyst-supported catalyst base material so as to be L-cat.

(Synthesis Example 25)
With respect to the Pt—Rh catalyst-carrying catalyst base material obtained in Synthesis Example 22, an ammonium paratungstate aqueous solution is used so that the supported amount of tungsten (W) per liter of the catalyst becomes 0.02 mol / L-cat. Thus, the catalyst sample 22 (Pt-Rh catalyst + 0.02 W) was manufactured by impregnating and supporting W on the Pt-Rh catalyst-supported catalyst base material.

(Synthesis Example 26)
A catalyst sample 23 (Pt—Rh catalyst + 0.01 W) was produced in the same manner as in Synthesis Example 25 except that the supported amount of tungsten (W) was 0.01 mol / L-cat.

(Synthesis Example 27)
With respect to the Pt—Rh catalyst-supported catalyst base material obtained in Synthesis Example 22, a phosphoric acid aqueous solution is used so that the supported amount of phosphorus (P) per 1 L of catalyst is 0.02 mol / L-cat. Catalyst sample 24 (Pt-Rh catalyst + 0.02P) was produced by impregnating and supporting P on the Pt-Rh catalyst-supported catalyst base material.

(Synthesis Example 28)
The Pt / activated alumina supporting substrate obtained in Synthesis Example 1 was used as the catalyst sample 25 (Pt / activated alumina) as it was.

(Synthesis Example 29)
The Pt / ceria zirconia-supporting substrate obtained in Synthesis Example 14 was directly used as a catalyst sample 26 (Pt / ceria zirconia).

(Synthesis Example 30)
A cordierite-made honeycomb substrate having a diameter of 30 mm, a length of 50 mm, a volume of 35 cc, 400 cells / in ² , and 4 mil of a slurry containing a catalyst supporting platinum and rhodium and alumina hydrate as a binder The platinum and rhodium supported catalyst per liter of the catalyst was wash coated so that the supported amount of the catalyst was 200 g / L-cat, and then calcined at 500 ° C. for 1 hour to obtain Pt and Rh. A catalyst sample 27 (Pt—Rh catalyst) was obtained. The supported amount of platinum was 1 g / L-cat per liter of catalyst, and the supported amount of rhodium was 0.2 g per liter of catalyst. Further, the carrier in such a catalyst is the same as the carrier used in Synthesis Example 22.

(Synthesis Example 31)
Instead of θ-alumina powder, alumina ceria zirconia powder [specific surface area of about 85 m ² / g, molar ratio of each component (alumina (Al ₂ O ₃ ): ceria (CeO ₂ ): zirconia (ZrO ₂ )) is 1: In the same manner as in Example 1 except that 0.9: 1.1 powder] was used, alumina ceria zirconia carrying Pt was carried on a honeycomb substrate, and catalyst sample 28 (Pt / alumina ceria zirconia) was used. Got.

(Synthesis Example 32)
Except that zirconia powder (specific surface area of about 100 m ² / g) was used instead of the θ-alumina powder, zirconia carrying Pt was carried on the honeycomb substrate in the same manner as in Example 1, and catalyst sample 29 (Pt / zirconia) was obtained.

(Synthesis Example 33)
Catalyst sample 30 was prepared by supporting ceria supporting Pt on a honeycomb substrate in the same manner as in Example 1 except that ceria powder (specific surface area of about 30 m ² / g) was used instead of θ-alumina powder. (Pt / ceria) was obtained.

(Synthesis Example 34)
In the same manner as in Example 1 except that La stabilized alumina powder (specific surface area of about 180 m ² / g) was used instead of θ-alumina powder, La stabilized activated alumina carrying Pt was used as the honeycomb substrate. The catalyst sample 31 (Pt / La stabilized activated alumina) was obtained by loading.

(Synthesis Example 35)
A slurry containing a catalyst in which platinum and rhodium are supported and NiO powder is added and alumina hydrate as a binder is 30 mm in diameter, 50 mm in length, 35 cc in volume, 400 cells / in ² , 4 mil. A cordierite honeycomb substrate was wash coated so that the amount of the catalyst supported per liter of the catalyst was 100 g / L-cat, then fired at 500 ° C. for 1 hour, and Pt and Rh A catalyst sample 32 (Pt—Rh / NiO powder-added catalyst) was obtained by supporting the NiO powder-added catalyst supporting No. on a honeycomb substrate. The supported amount of platinum was 1 g / L-cat per liter of catalyst, and the supported amount of rhodium was 0.2 g per liter of catalyst. The amount of NiO supported was 0.05 mol / L-cat per liter of catalyst. The support of the NiO powder-added catalyst was La stabilized activated alumina (specific surface area of about 180 m ² / g, La content: 3 mass%) and alumina ceria zirconia (specific surface area of about 85 m ² / g, moles of each component). NiO is supported on a mixed powder with a ratio (alumina: ceria: zirconia) of 20: 9: 11). The mixing ratio of La stabilized activated alumina and alumina ceria zirconia is 1: 1 by mass ratio (La stabilized activated alumina: alumina ceria zirconia).

  Table 1 summarizes the supported amount of the metal oxide carrier of catalyst samples 1 to 32 obtained in Synthesis Examples 2 to 13, 15 to 21, and 23 to 35, types of additive elements, and the like.

[Evaluation of characteristics of catalyst samples 1 to 32 (Synthesis Examples 2 to 13, 15 to 21, and 23 to 35)]
<Measurement of base point amount>
The amount of base points per liter of catalyst of catalyst samples 1 to 32 was determined by employing the above-described method for calculating the amount of base points. The measurement values of the basic site amount, the apparatus and measurement conditions used in the measurement, CO ₂ background during desorption treatment test is because of 20 to 30 ppm, is expected to contain systematic errors. Therefore, as described above, when calculating the basic site amount, the background of the CO ₂ concentration of temperature increase start time and CO ₂ during desorption process completion of CO ₂ desorption treatment connected by straight lines, a concentration of more than background The method of calculating the base point amount by integrating the peak area of the desorption peak observed in FIG. Further, Table 2 shows the base point amounts of the respective catalysts thus measured. For reference, a graph of the relationship between the CO ₂ desorption amount of the catalyst sample 25 and the temperature is shown in FIG.

<Measurement of H ₂ S emission (generated amount)>
After performing sulfur poisoning treatment on the catalyst samples 1 to 32 after the measurement of the amount of base points, as shown below, a temperature-programmed desorption test of sulfur components was performed in a reducing atmosphere, The H ₂ S emission when each catalyst was used was measured.

In measuring the amount of H ₂ S discharged, first, the catalyst samples 1 to 32 were respectively installed in the reaction apparatus exemplified in JP-A-2002-311013. Next, a gas composed of H ₂ (2% by volume), CO ₂ (10% by volume), H ₂ O (9.9% by volume), and N ₂ (78.1% by volume) is added to each catalyst. Contact was made at a flow rate of 25 L / min. In this case, the initial gas temperature is 90 ° C., the temperature is raised to 780 ° C. at a rate of temperature increase of 40 ° C./min, and after reaching 780 ° C., the temperature is maintained at 780 ° C. for 20 minutes. Thereafter, the temperature was lowered to 480 ° C. and held at 480 ° C. for 5 minutes (pretreatment). _Next, H 2 _(0.3% by _volume), O 2 (0.1 _{volume%), SO 2 (20ppm)} , CO 2 (10 _volume%), H 2 O (9.9 volume%) and the remaining N ₂ rich gas, H ₂ (0.2 vol%), O ₂ (0.15 vol%), SO ₂ (20 ppm), CO ₂ (10 vol%), H ₂ O (9.9 vol%) Further, while switching the remaining lean gas composed of N ₂ every 30 seconds, each catalyst sample was allowed to flow for 15 minutes, and SO ₂ was brought into contact with each catalyst sample. At this time, the temperatures of the rich gas and the lean gas were maintained at 480 ° C. (sulfur poisoning treatment). Thereafter, a rich gas composed of CO (3% by volume), H ₂ (2% by volume), CO ₂ (10% by volume), H ₂ O (9.9% by volume) and N _{2 is} supplied to each catalyst for 5 minutes. Made contact. The gas temperature at this time was 300 ° C.

Next, hydrogen sulfide desorption treatment comprising CO (0.9 vol%), H ₂ (0.3 vol%), CO ₂ (10 vol%), H ₂ O (9.9 vol%) and the remaining N ₂ H ₂ S was removed by bringing the reducing gas for use into contact with the catalyst at a flow rate of 25 L / min while raising the temperature of the gas from 300 ° C. to 780 ° C. at a rate of 30 ° C./min. (H ₂ S desorption treatment). Then, to measure the emissions of such _{H 2} S _{H 2} S in exit gas during desorption process _{(H 2} S concentration (ppm)). For measurement of such gas concentration, “Hydrogen sulfide analysis system MODL43C” manufactured by Nippon Thermo Electron was used as a measuring machine. Furthermore, Table 2 shows the generation amount and generation rate of H ₂ S per 1 L of each catalyst sample measured in this way. The generation rate of H ₂ S was determined by calculating the ratio of the amount of sulfur in the outgas to the amount of sulfur circulated through the catalyst during the test. For reference, a graph showing the relationship between the amount of H ₂ S generated in the catalyst sample 25 and the temperature is shown in FIG.

<Measurement of CO ₂ desorption peak temperature>
Desorption amount of CO ₂ obtained in the measurement of the aforementioned basic sites of the graph of the relationship between the temperature were measured desorption peak temperature of CO _2. The results thus measured are shown in Table 3.

As is clear from the results shown in Tables 2 and 3, it was found that the catalyst sample having a base point amount of 2.0 mmol / L-cat or less has a low H ₂ S generation rate. Further, it is considered that the lower the CO ₂ desorption peak temperature, the lower the H ₂ S generation rate.

(Examples 1-12 and Comparative Examples 1-7)
First, a 50% by volume upstream portion of a honeycomb substrate made of cordierite having a diameter of 105 mm, a length of 105 mm, a volume of 900 cc, 400 cells / in ² , and 4 mil (when the gas channel is disposed in the gas channel) The part arranged on the upstream side) was used as the first catalyst substrate, and the remaining 50% by volume of the downstream part was used as the second catalyst substrate (note that only Comparative Example 2 was 300 cells / in ^2. The honeycomb substrate was used.) Next, after supporting the first metal oxide supports described in Tables 4 to 5 on the first catalyst base, the first noble metals described in Tables 4 to 5 are supported on the supports, respectively. Further, in some cases, an additional element was supported to produce a first catalyst. In addition, after supporting the second metal oxide supports described in Tables 6 to 7 on the second catalyst base, the second noble metals described in Tables 6 to 7 are supported on the supports, respectively. Furthermore, a second catalyst was produced by optionally supporting additional elements. Thus, each exhaust gas purification apparatus was manufactured. Tables 4 and 5 show the components and loadings of the first catalyst in the exhaust gas purification apparatuses obtained in the examples and comparative examples. Tables 6 to 7 show the components and loadings of the second catalyst. Shown in

In addition, the OSC materials described in Tables 4 to 7 indicate powders of alumina ceria zirconia (specific surface area of about 85 m ² / g, molar ratio of each component (alumina: ceria: zirconia) is 20: 9: 11). Moreover, in each Example and each comparative example, the 1st and 2nd metal oxide support | carriers described in Tables 4-7 are each support | carrier and an alumina hydrate (product name made by Nissan Chemical Industries Ltd. " The catalyst base was supported in the same manner as in Synthesis Example 1 except that each of the slurry containing alumina sol 200 ": binder) was used. Moreover, the load of the 1st and 2nd metal oxide support | carrier was adjusted so that it might become the quantity described in Tables 4-7. The first and second noble metals listed in Tables 4 to 7 are each fired at 500 ° C. for 1 hour after each of the aqueous solutions is supported on a carrier using a nitric acid aqueous solution of dinitrodiamine platinum and an aqueous rhodium nitrate solution, respectively. This was supported on each carrier. Furthermore, the loading amount of the first noble metal in the first catalyst was such that the loading amount of Pt was 2 g / L-cat per liter of catalyst and the loading amount of Rh was 0.2 g per liter of catalyst. The amount of the second noble metal supported on the second catalyst (the amount of Rh supported) was 0.2 g / L-cat per liter of the catalyst. Further, in Examples 4 to 8, Example 10 and Comparative Examples 5 to 6, the additive elements Mo, P, Ti and W described in Tables 5 to 7 are the carriers used in Tables 5 to 7, respectively. A method similar to that employed in Synthesis Example 2, Synthesis Example 3, Synthesis Example 4, and Synthesis Example 25 was adopted except that the carrier was used and the loading was changed to the loadings shown in Tables 4 to 7, respectively. Supported on each carrier. In the second catalyst of Example 9, the same method as in Synthesis Example 2 was adopted except that the carrier used was the carrier shown in Table 6 and an ethanol solution of niobium chloride was used instead of ammonium molybdate. Nb was supported on the carrier. In addition, Table 10 shows the base point amounts of the first catalyst and the second catalyst.

(Example 13)
Site of 50% by volume upstream of honeycomb substrate made of cordierite having a diameter of 105 mm, a length of 105 mm, a volume of 900 cc, 400 cells / in ² , and 4 mil (on the upstream side of the gas channel when placed in the gas channel) 1) was used as the first catalyst base, and the remaining 50% by volume of the downstream side was used as the second catalyst base to produce an exhaust gas purification apparatus. In addition, the 1st catalyst and the 2nd catalyst were manufactured as follows.

First, Pr-La-added ceria zirconia to which praseodymium (Pr) and La are added, θ-alumina powder (specific surface area of about 100 m ² / g), and alumina hydrate (manufactured by Nissan Chemical Industries, Ltd.) as a binder Was washed on the first catalyst substrate and calcined at 500 ° C. for 1 hour, and then a nitric acid aqueous solution of dinitrodiamine platinum and an aqueous rhodium nitrate solution. Was used to carry Pt and Rh to produce a first catalyst. In the first catalyst, the total supported amount of Pr-La-added ceria zirconia and θ-alumina was set to 148 g / L-cat per liter of the catalyst. Moreover, the content ratio of Pr-La addition ceria zirconia and (theta) -alumina in the said slurry was 52:32 by mass ratio (Pr-La addition ceria zirconia: (theta) -alumina). Furthermore, the supported amount of Pt in the first catalyst was 1.2 g / L-cat per liter of catalyst, and the supported amount of Rh in the first catalyst was 0.03 g / L-cat per liter of catalyst.

Next, Ti-added θ-alumina (specific surface area of about 100 m ² / g, Ti content: 20% by mass) and alumina hydrate as a binder (Nissan Chemical Industrial Co. The slurry containing the trade name “Alumina sol 200”) manufactured by the company was wash coated and calcined for 1 hour at a temperature of 500 ° C., and then the supported amount per liter of the catalyst was 0.00 using an aqueous rhodium nitrate solution. Rh was supported so as to be 21 g / L-cat to produce a second catalyst. The constituent components and supported amounts of the first catalyst are shown in Table 8, the constituent components and supported amounts of the second catalyst are shown in Table 9, and the base point amounts of the first catalyst and the second catalyst are shown in Table 10. Shown in

(Example 14)
Using a honeycomb substrate made of cordierite having a diameter of 105 mm, a length of 105 mm, a volume of 900 cc, 400 cells / in ² , and 4 mil, a first catalyst having a two-layer structure is formed on the upstream side of the gas flow path. A second catalyst having a single-layer structure was formed on the downstream side of the passage to produce an exhaust gas purification device. The first catalyst and the second catalyst were produced as follows. Moreover, the layer structure of a 1st catalyst and a 2nd catalyst is typically shown in FIG.

  First, a slurry similar to the slurry used when the first catalyst was manufactured in Example 13 in a region from the upstream inlet of the gas flow channel to 35 mm when being arranged in the gas flow channel of the honeycomb substrate. Was coated with Pr-La added ceria zirconia and θ-alumina so that the total supported amount was 150 g / L-cat per liter of catalyst, calcined at 500 ° C. for 1 hour, and Pr- La-added ceria zirconia and θ-alumina were supported. Next, Pt was supported on the Pr—La-added ceria zirconia and θ-alumina using a nitric acid aqueous solution of dinitrodiamine platinum, and the first layer 21 was formed. The amount of Pt supported on the first layer 21 was 1.2 g / L-cat per liter of catalyst.

  Next, the amount of Rh supported was 0.12 g / L-cat per liter of catalyst, and the amount of θ-alumina supported was 100 g / L-cat. By adopting the same method as the method for producing the second catalyst, the second catalyst 12 was produced in an area (downstream area) from the outlet of the honeycomb substrate to 70 mm.

Next, Nd—Y in which neodymium (Nd) and yttrium (Y) are added to a region from the upstream inlet of the gas flow path of the honeycomb substrate on which the first layer and the second catalyst are formed to 70 mm. Additive zirconia ceria composite oxide, Ti-added θ-alumina (specific surface area of about 100 m ² / g, Ti content: 20% by mass), and alumina hydrate as a binder (trade name, manufactured by Nissan Chemical Industries, Ltd.) The slurry containing “alumina sol 200”) was wash-coated and fired at 500 ° C. for 1 hour to form a coating layer. Then, the supported amount per liter of catalyst was 0 using an aqueous rhodium nitrate solution. The first catalyst 12 comprising the first layer 21 and the second layer 22 on the upstream side of the gas flow path is formed by supporting Rh on the coating layer so as to be 12 g / L-cat. The Formed. The content ratio of the Nd—Y-added zirconia ceria composite oxide and the Ti-added θ-alumina in the slurry is 26.5 in terms of mass ratio (Nd—Y-added zirconia ceria composite oxide: Ti-added θ-alumina). : 16, and the total supported amount of the Nd—Y-added zirconia ceria composite oxide and Ti-added θ-alumina in the second layer was 150 g / L-cat per liter of the catalyst. Further, the constituent components and supported amounts of the first catalyst are shown in Table 8, the constituent components and supported amounts of the second catalyst are shown in Table 9, and the base point amounts of the first catalyst and the second catalyst are shown in Table 10. Shown in

(Example 15)
Site of 50% by volume upstream of honeycomb substrate made of cordierite having a diameter of 105 mm, a length of 105 mm, a volume of 900 cc, 400 cells / in ² , and 4 mil (on the upstream side of the gas channel when placed in the gas channel) The first catalyst having a two-layer structure and the one-layer structure using the remaining 50% by volume downstream as the second catalyst substrate. An exhaust gas purification apparatus comprising the second catalyst was manufactured. The layer structure of the first catalyst and the second catalyst is schematically shown in FIG. In the first catalyst 11, both the first layer 21 and the second layer 22 are formed in a 50% by volume portion on the upstream side, and when forming the second layer, instead of Ti-added θ-alumina, θ- The same production method as that of the first catalyst employed in Example 14 was used except that alumina was used. Further, the second catalyst 12 was produced by adopting the same method as the production method of the second catalyst adopted in Example 14, except that it was formed at a site of 50% by volume on the downstream side. Further, the constituent components and supported amounts of the first catalyst are shown in Table 8, the constituent components and supported amounts of the second catalyst are shown in Table 9, and the base point amounts of the first catalyst and the second catalyst are shown in Table 10. Shown in

[Evaluation of characteristics of exhaust gas purification apparatuses obtained in Examples 1 to 15 and Comparative Examples 1 to 7]
<Measurement of H ₂ S generation amount>
The exhaust gas purification devices obtained in Examples 1 to 15 and Comparative Examples 1 to 7 instead of the catalyst sample 1 were attached to the underfloor position of a 2.4 L gasoline engine automobile, respectively, and conditions of 60 km / h or less simulating urban driving After running for 20 minutes and fully accelerating from idling conditions to 90 km / h, the vehicle is stopped to enter an idling state, and the amount of H ₂ S (H ₂ S) in the gas discharged in one minute immediately after the stop. Amount generated) was measured. In this measurement, the first catalyst was arranged on the upstream side of the gas flow path, and the second catalyst was arranged on the downstream side of the gas flow path. Then, the ratio of H _{2 S} generation of the exhaust gas purifying apparatus of the case of the 1 H _{2 S} generation amount of the obtained exhaust gas purifying device in Comparative Example 1 (Examples 1 to 15 and Comparative Examples 1 to 7) Asked. Table 10 shows the obtained results. Further, the ratio of H _{2 S} generation of the exhaust gas purifying apparatus of the case of the 1 H _{2 S} generation amount of the obtained exhaust gas purifying device in Comparative Example 1, the second catalyst in each exhaust gas purifying apparatus base A graph showing the relationship with the point amount is shown in FIG.

<Measurement of NOx emissions>
First, in the exhaust gas purification apparatuses obtained in Examples 1 to 15 and Comparative Examples 1 to 7, the first catalyst is arranged on the upstream side of the gas flow path in the exhaust pipe of a commercially available 4.3L gasoline engine automobile. And it attached so that the 2nd catalyst might be arrange | positioned in the downstream of the said gas flow path. Next, using the automobile, a model running imitating market running (running such that the temperature of the gas entering the exhaust gas purification device was 950 ° C. for 50 hours) was performed. Thereafter, each exhaust gas purifying device is taken out from the automobile, and each obtained exhaust gas purifying apparatus is placed in the exhaust pipe of an automobile having a 4-cylinder 2.4L gasoline engine on the upstream side of the gas flow path. And the second catalyst was mounted so as to be arranged downstream of the gas flow path. Then, using an automobile having a 4-cylinder 2.4L gasoline engine, the vehicle was run about 20 minutes twice under American mode test conditions (LA # 4), and after contacting the exhaust gas purifiers during the second run. The amount of NOx in the exhaust gas was measured, and the total amount of NOx contained in the exhaust gas discharged by the second run (NOx emission amount) was determined. And the ratio of the NOx emission amount of each exhaust gas purification device (Examples 1-15 and Comparative Examples 1-7) when the NOx emission amount of the exhaust gas purification device obtained in Comparative Example 1 was set to 1 was obtained. Table 10 shows the obtained results. Further, the ratio of the NOx emission amount of each exhaust gas purification device when the NOx emission amount of the exhaust gas purification device obtained in Comparative Example 1 is 1, and the base point amount of the first catalyst in each exhaust gas purification device A graph showing the relationship is shown in FIG.

From the results shown in FIG. 9, it can be seen that in the exhaust gas purifying apparatus in which the base point amount of the second catalyst is 2.0 mmol / L-cat or less, the generation of H ₂ S tends to be sufficiently prevented. Further, from the results shown in FIG. 10, in the exhaust gas purifying apparatus including the first catalyst having a base point amount of 3.0 mmol / L-cat or more, the NOx emission amount is sufficiently small, and a high degree of catalytic activity is obtained. I understand that Further, from the results shown in FIGS. 9, 10 and Table 10, the first catalyst satisfying the condition that the base point amount is 3.0 to 20 mmol / L-cat, and the base point amount is 2.0 mmol / L- It was found that the catalyst activity and the function of preventing the generation of H ₂ S can be exhibited at a high level and in a well-balanced manner by combining with the second catalyst that satisfies the condition of cat or less. Then, in the exhaust gas purifying apparatus of the present invention (Examples 1 to 15), compared to the exhaust gas purifying device for comparison (Comparative Examples 1 to 7), to prevent the occurrence of catalyst activity performance and H _{2 S} function However, it was confirmed that it was demonstrated in a well-balanced manner at a high level. In the exhaust gas purifying apparatuses obtained in Comparative Examples 1 and 2 and Comparative Example 7, the pressure loss was increased as compared with the exhaust gas purifying apparatuses (Examples 1 to 15) of the present invention. However, in Table 10 and FIG. 10, the NOx emission amount of Example 13 is higher than that of Comparative Example 1. This is because Examples 13 to 15 have 40% less noble metal loading than Comparative Example 1. When Example 13 and Comparative Example 1 were compared with the same noble metal loading as Example 13, Example 13 It has been confirmed that the NOx emission amount is smaller than the NOx emission amount of Comparative Example 1.

As described above, according to the present invention, it is possible to provide an exhaust gas purification device capable of sufficiently reducing the amount of H ₂ S emitted while exhibiting sufficiently high catalytic activity as a three-way catalyst. Become. Therefore, the exhaust gas purifying apparatus of the present invention can be used, for example, for an exhaust gas apparatus for purifying NOx in exhaust gas discharged from an automobile engine.

It is a schematic longitudinal cross-sectional view which shows one Embodiment of the conventional exhaust gas purification apparatus. Basic sites of the catalyst per 1L relative to the desorption amount of CO ₂ is a graph showing the relationship between the desorption quantity and temperature of the catalyst of the sulfur component of 5.1 (H 2 _S and SO _2). Basic sites of the catalyst per 1L relative to the desorption amount of CO ₂ is a graph showing the relationship between the desorption quantity and temperature of the sulfur component of 0.1 of the catalyst (H 2 _S and SO _2). It is a schematic longitudinal cross-sectional view which shows suitable one Embodiment of the exhaust gas purification apparatus of this invention. 4 is a graph showing the relationship between the amount of CO ₂ desorbed from a catalyst sample 25 and temperature. 3 is a graph showing the relationship between the amount of H ₂ S generated in a catalyst sample 25 and the temperature. It is a schematic diagram which shows the layer structure of the 1st catalyst in the exhaust gas purification apparatus obtained in Example 14, and the 2nd catalyst. 16 is a schematic diagram showing a layer configuration of a first catalyst and a second catalyst in the exhaust gas purifying apparatus obtained in Example 15. FIG. Basic sites of the second catalyst of H _{2 S} and generation amount of the specific, in each exhaust gas purifying apparatus of the exhaust gas purifying apparatus in the case where the H _{2 S} generation amount of the exhaust gas purification device obtained in Comparative Example 1 and 1 It is a graph which shows the relationship. The relationship between the ratio of the NOx emission amount of each exhaust gas purification device when the NOx emission amount of the exhaust gas purification device obtained in Comparative Example 1 is 1, and the base point amount of the first catalyst in each exhaust gas purification device It is a graph to show.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Exhaust gas pipe, 2 ... Exhaust gas purification catalyst, 2a ... Catalyst substrate inlet, 2b ... Catalyst substrate outlet, 10 ... Catalyst case, 11 ... First catalyst, 12 ... Second catalyst, 13 ... Exhaust gas Pipe, A ... direction of gas flow, 21 ... first layer, 22 ... second layer.

Claims (8)

Comprises a first catalyst substrate, a first metal oxide support supported on said first catalyst substrate, and a first noble metal supported on the first metal oxide support, CO ₂ Satisfying the condition that the amount of base points per liter of catalyst is 3.0 to 20 mmol / L-cat based on the desorption amount of CO ₂ per liter of catalyst measured by temperature programmed desorption, and upstream of the gas flow path A first catalyst arranged on the side, and
A second catalyst base, a second metal oxide support supported on the second catalyst base, and a second noble metal supported on the second metal oxide support, and CO ₂ Satisfying the condition that the base point amount per 1 L of catalyst based on the desorption amount of CO ₂ per 1 L of catalyst by temperature-programmed desorption measurement is 2.0 mmol / L-cat or less, and downstream of the gas flow path A second catalyst arranged on the side,
An exhaust gas purification apparatus comprising:   2. The exhaust gas purifying apparatus according to claim 1, wherein the second catalyst satisfies a condition that a base point amount per 1 L of the catalyst is 1.5 mmol / L-cat or less.   The exhaust gas purifying apparatus according to claim 1 or 2, wherein the first catalyst satisfies a condition that a base point amount per 1 L of the catalyst is 3.0 to 15 mmol / L-cat.   The element according to claim 1, wherein an element having a greater electronegativity than a cation of a metal element constituting the second metal oxide support is supported on the second metal oxide support. The exhaust gas purification apparatus as described in any one of them.   The element having an electronegativity greater than the cation of the metal element constituting the second metal oxide support is at least one selected from the group consisting of phosphorus, molybdenum, tungsten, titanium, niobium, iron and silicon. The exhaust gas purifying apparatus according to claim 4, wherein the exhaust gas purifying apparatus is an element.   The volume ratio ([first region]: [second region]) between the first region in which the first catalyst is disposed and the second region in which the second catalyst is disposed is 15:85. It exists in the range of -85: 15, The exhaust gas purification apparatus as described in any one of Claims 1-5 characterized by the above-mentioned.   The average value of the amount of base points per liter of catalyst of the first catalyst and the amount of base points per liter of catalyst of the second catalyst is in the range of 1.2 to 11 mmol / L-cat, and The exhaust gas purifying apparatus according to any one of claims 1 to 6, wherein the base point amount of one catalyst is twice or more the base point amount of the second catalyst.   The exhaust gas purifying apparatus according to claim 7, wherein the basic point amount of the first catalyst is three times or more the basic point amount of the second catalyst.