JP3872354B2 - Filter type catalyst for diesel exhaust gas purification - Google Patents

Description

【０１２０】
パティキュレート堆積検知試験において、実施例１〜４のディーゼル排ガス浄化用フィルタ型触媒は、比較例１と比べて圧損が上昇するまでに要する時間が短い。パティキュレートはいずれのディーゼル排ガス浄化用フィルタ型触媒にも同じ割合で堆積しているので、この結果によって本発明のディーゼル排ガス浄化用フィルタ型触媒はパティキュレートの堆積を感度良く検知することが可能であることがわかる。
【０１２１】
パティキュレート燃焼試験において、実施例および比較例のディーゼル排ガス浄化用フィルタ型触媒の圧損が上昇するまでに要する時間には大きな違いがみられなかった。しかし、各ディーゼル排ガス浄化用フィルタ型触媒は圧損感度が異なるため、これらの結果を単純に比較することはできない。このため、これらの結果に圧損感度を加味して補正しＤＰＦ性能値を算出した。ＤＰＦ性能値を比較すると、実施例のＤＰＦ性能値は比較例のＤＰＦ性能値と比較して明らかに大きい値を示した。このことは、実施例のディーゼル排ガス浄化用フィルタ型触媒は比較例のディーゼル排ガス浄化用フィルタ型触媒と比較して、良好なパティキュレートＤＰＦ性能を持つことを示す。
【０１２２】
＜初期圧損試験＞
まず、実施例１〜４，比較例１および参考例のディーゼル排ガス浄化用フィルタ型触媒をエアー吸引装置に取付け、５ｍ³／ｍｉｎ，２０℃でエアー吸引を行った。
【０１２３】
上記エアー吸引を行った実施例１〜４，比較例１および参考例のディーゼル排ガス浄化用フィルタ型触媒の圧損を測定した。本試験はパティキュレート堆積前の各フィルタの圧損、つまり初期圧損を測定するものである。
【０１２４】
以上の実験によって求められた実施例１〜４，比較例１および参考例のディーゼル排ガス浄化用フィルタ型触媒の初期圧損値と、得られた圧損値を各ディーゼル排ガス浄化用フィルタ型触媒にコートしたＡｌ₂Ｏ₃のコート量を加味して補正した初期圧損値の補正値とを表２に示す。
【０１２５】
【表２】

【０１２６】
初期圧損試験において、実施例１〜４の各ディーゼル排ガス浄化用フィルタ型触媒の初期圧損値および補正値は、実施例１〜４と同量のＡｌ₂Ｏ₃をコートした参考例や、実施例１〜４の半量のＡｌ₂Ｏ₃をコートした比較例と比べて低い値を示した。このことは、本発明のディーゼル排ガス浄化用フィルタ型触媒は、通常のコートを行ったディーゼル排ガス浄化用フィルタ型触媒と比較して初期圧損が低いディーゼル排ガス浄化用フィルタ型触媒であることを示す。
【０１２７】
【発明の効果】
本発明のディーゼル排ガス浄化用フィルタ型触媒によれば、初期圧損の増大を抑制しつつ圧損感度を高めることができる。
【図面の簡単な説明】
【図１】平均粒径３μｍの触媒粉末がコートされたＤＰＦの電子顕微鏡写真である。
【図２】平均粒径０．６μｍの触媒粉末がコートされたＤＰＦの電子顕微鏡写真である。
【図３】平均粒径０．６μｍの触媒粉末をフィルタ本体の体積１リットルあたり１５０ｇコートしたＤＰＦの電子顕微鏡写真である。
【図４】平均粒径０．６μｍの触媒粉末をフィルタ本体の体積１リットルあたり１２０ｇコートし、その上層に平均粒径３μｍの触媒粉末を３０ｇコートしたＤＰＦの電子顕微鏡写真である。
【図５】本発明の実施例１のディーゼル排ガス浄化用フィルタ型触媒のガス流路に平行な断面図である。
【図６】本発明の実施例２のディーゼル排ガス浄化用フィルタ型触媒のガス流路に平行な断面図である。
【図７】本発明の実施例３のディーゼル排ガス浄化用フィルタ型触媒のガス流路に平行な断面図である。
【図８】本発明の実施例４のディーゼル排ガス浄化用フィルタ型触媒のガス流路に平行な断面図である。
【図９】本発明の比較例１のディーゼル排ガス浄化用フィルタ型触媒のガス流路に平行な断面図である。
【符号の説明】
１：フィルタ本体 ２：触媒層 ２ａ：多コート部 ３：フィルタ本体の径方向の外周部 ４：フィルタ隔壁 ５：ガス流入孔 ６：ガス流出孔 ７：フィルタ本体の径方向の内周部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diesel exhaust gas purification catalyst that collects particulates (particulate matter) contained in exhaust gas from a diesel engine and purifies harmful components in the exhaust gas.
[0002]
[Prior art]
As for gasoline engines, harmful components in exhaust gas have been steadily reduced due to strict regulations on exhaust gas and advances in technology that can cope with it. However, because diesel engines emit harmful components as particulates (particulate substances: carbon fine particles, sulfur fine particles such as sulfate, and high molecular weight hydrocarbon fine particles), regulations and technological progress are both gasoline. It is late compared to the engine.
[0003]
As exhaust gas purification devices for diesel engines that have been developed so far, a trap type exhaust gas purification device (wall flow) and an open type exhaust gas purification device (straight flow) are known. Among these, as a trap type exhaust gas purification device, a ceramic plug-type honeycomb body (diesel particulate filter (hereinafter referred to as DPF)) is known. This DPF includes a gas inflow side cell clogged with an opening at a cell downstream end of a ceramic honeycomb structure, a gas outflow side cell with a clogged opening at a cell upstream end, a gas inflow side cell, and a gas outflow side cell. And has a cell partition wall, that is, a filter partition wall that serves as a filter during gas flow. According to this DPF, the exhaust gas is filtered through the pores of the filter partition wall, and the particulates are collected by the filter partition wall, thereby suppressing the discharge.
[0004]
However, in the DPF, the pressure loss increases due to the accumulation of particulates. Therefore, it is necessary to periodically remove and regenerate the particulates deposited by some means.
[0005]
Conventionally, when pressure loss increases, DPF is regenerated by burning particulates accumulated by a burner or an electric heater. However, in this case, as the amount of accumulated particulates increases, the temperature at the time of combustion rises, and the DPF may be damaged by the thermal stress.
[0006]
Therefore, in recent years, a continuous regeneration type DPF has been developed in which a coating layer is formed of alumina or the like on the cell partition of the DPF, and an oxidation catalyst made of a noble metal such as Pt is supported on the coating layer. According to this continuous regeneration type DPF, the collected particulates are oxidized and burned at a relatively low temperature by the oxidation catalyst, so that the DPF is burned simultaneously with the collection or continuously with the collection. Can be played. This continuous regeneration type DPF has a catalytic reaction that occurs at a relatively low temperature and can burn while the amount of particulates collected is relatively small. Therefore, the thermal stress acting on the DPF is small, and damage due to heat is prevented. There are advantages.
[0007]
However, even in such a continuous regeneration type DPF, the temperature of the outer peripheral portion in the radial direction of the filter main body tends to decrease because the exhaust gas is less circulated and the heat radiation to the outside air is large. For this reason, in this part, particulates are not easily oxidized and burned, and the particulates remain unburned even after the DPF is regenerated, which may cause clogging of the filter partition walls.
[0008]
Furthermore, the downstream part of the exhaust gas flow of the filter body is the part where the temperature becomes highest when the particulates burn. For this reason, if the particulate deposition progresses in the downstream portion of the exhaust gas flow of the filter body, this portion becomes higher temperature during particulate combustion, which may be a starting point of DPF melting damage.
[0009]
DPFs that have been clogged or melted due to the accumulation of particulates in the DPF in this way need to be replaced because the purification ability of exhaust gas decreases, but the DPF must be replaced frequently. Is not preferable in terms of cost.
[0010]
On the other hand, in order not to cause melting damage, it is necessary to regenerate the DPF before the amount of accumulated particulate reaches the amount at which melting damage occurs. As a method for this, a method is used in which the pressure loss is detected from the exhaust gas pressure before and after the DPF to determine the timing of the regeneration process of the DPF.
[0011]
However, if the particulates are deposited unevenly in the DPF, even if the pressure loss of the DPF as a whole does not increase so much, the partial particulate accumulation amount may reach the amount that causes melting, so that It was difficult to detect with high sensitivity the amount of accumulated particulates.
[0012]
Further, if the pressure loss sensitivity, which is a sensitivity for detecting particulate deposition due to an increase in pressure loss, is simply increased by increasing the coating amount of the catalyst layer coated on the DPF, there arises a problem that the initial pressure loss of the DPF increases.
[0013]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a filter catalyst for purifying diesel exhaust gas that has improved pressure loss sensitivity while suppressing an increase in initial pressure loss.
[0014]
[Means for Solving the Problems]
  The filter catalyst for diesel exhaust gas purification of the present invention that solves the above problems is a ceramic honeycomb structure, in which a gas inflow hole clogging an opening at a cell downstream end and an opening at a cell upstream end are clogged. Diesel exhaust gas having a gas outflow hole, a filter body having the gas inflow hole and a filter partition wall that partitions the gas outflow hole and serves as a filter for gas flow, and a catalyst layer containing a porous oxide and a noble metal A filter type catalyst for purification, and the catalyst layer has a coating portion mainly composed of the porous oxide having a particle size of 1 μm or less on the filter partition wall at a specific portion of the filter body.The specific portion is a radially outer peripheral portion of the filter body.It is characterized by that.
  Further, the filter catalyst for diesel exhaust gas purification of the present invention that solves the above problems is a ceramic honeycomb structure, and has a gas inflow hole clogged with an opening at the cell downstream end and an opening at the cell upstream end. A filter main body having a packed gas outflow hole, a filter partition wall that partitions the gas outflow hole and the gas outflow hole and serves as a filter for gas flow, and a catalyst layer including a porous oxide and a noble metal A filter-type catalyst for purifying diesel exhaust gas, wherein the catalyst layer has a coating portion mainly composed of the porous oxide having a particle size of 1 μm or less on the filter partition wall at a specific portion of the filter body. The part is a downstream part of the exhaust gas flow of the filter body.
[0015]
At least a catalyst layer having a coating portion mainly composed of the porous oxide having a particle size of 1 μm or less on the filter partition wall at a specific part of the filter body is preferentially provided for pores having a pore diameter of 10 μm or less of the filter partition wall. Filled. Therefore, in the filter catalyst for diesel exhaust gas purification of the present invention, the pores having a pore diameter of 10 μm or less are filled with the porous oxide, or the pore diameter is still smaller. For this reason, when the particulates are deposited on the filter partition wall, the pressure loss is likely to increase. From this, the particulate deposition can be detected at the initial stage of the deposition due to the increased pressure loss, and the pressure loss sensitivity is improved.
[0016]
  The coating amount of the catalyst layer on the filter partition wall in the specific part isIt can be made larger than the coating amount on the filter partition wall in the part excluding the specific part.
[0017]
The catalyst layer on the filter partition partitioning the gas outflow holes of the specific portion is formed on the surface of the first coat portion and the first coat portion made of a porous oxide having an average particle size of 1 μm or less, and an average particle size of 1 to It can comprise from the 2nd coat part which consists of 5 micrometers porous oxide.
[0018]
The catalyst layer further includes NO._XAn occlusion material is preferably included.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The filter type catalyst for purifying diesel exhaust gas of the present invention has a filter body and a catalyst layer.
[0020]
The filter main body is a porous ceramic honeycomb structure, and has a gas inflow hole, a gas outflow hole, and a filter partition wall that divides these and serves as a filter for gas flow. Here, the porous ceramic honeycomb structure is composed of a honeycomb-shaped cell composite having a cell diameter of about 1 to 1.5 mm, and each cell of the cell composite is surrounded by filter partition walls. It is formed. The filter partition has a wall thickness of about 0.2 to 0.4 mm.
[0021]
The gas inflow hole is a cell hole that serves as an inlet when the exhaust gas enters the filter body. The cell upstream end located on the exhaust gas upstream side is opened, and the cell downstream end located on the exhaust gas downstream side is clogged. This is a closed cell hole. Further, the gas outflow hole is a cell hole that becomes an outlet of the exhaust gas when the exhaust gas flows through the filter main body, and is a cell hole in which the cell upstream end is clogged and closed, and the cell downstream end is opened. The exhaust gas that has entered the filter main body from the gas inflow hole passes through the filter partition, is purified, and is discharged from the gas outflow hole. Here, the filter partition has pores serving as a gas flow path in the flow of gas inside and / or on the surface thereof. The ratio of the pores in the filter partition wall, that is, the porosity, is preferably in the range of 50 to 80%, and the pores are preferably in the range of the average pore diameter of 10 μm to 40 μm.
[0022]
The filter body is formed of heat-resistant ceramics, and a filter body made by a conventional method such as extrusion molding can be used. Specifically, a commercially available porous honeycomb ceramic DPF can also be used, and a commonly used heat-resistant ceramic raw material can be used. In order to purify the exhaust gas satisfactorily, the cell density consisting of the gas outflow holes and the gas inflow holes is 45 cells / cm.²The above is preferable.
[0023]
The catalyst layer includes a porous oxide and a noble metal.
[0024]
Here, the porous oxide is an oxide having a large specific surface area. As the porous oxide, a commonly used one can be used.₂O_Three, ZrO₂, CeO₂TiO₂, SiO₂It is preferable to use oxides such as these or complex oxides composed of a plurality of these.
[0025]
As the noble metal, any noble metal that can be an oxidation catalyst that promotes oxidation of particulates by catalytic reaction can be used, but one kind selected from platinum group noble metals such as Pt, Rh, Pd, Ir, and Ru, or It is preferable to use multiple types.
[0026]
In the filter catalyst for purifying diesel exhaust gas according to the present invention, the catalyst layer has a coat portion mainly composed of the porous oxide having a particle size of 1 μm or less on the filter partition wall at a specific portion of the filter body.
[0027]
Here, the catalyst layer can be formed by a usual method. That is, the filter partition may be coated with a porous oxide to form a coating layer, and the coating layer may be loaded with a noble metal, or the filter partition may be coated with a catalyst powder having a porous oxide loaded with a noble metal. May be.
[0028]
When the filter partition is coated with a porous oxide having an average particle diameter of 1 μm or less, the porous oxide is preferentially filled into pores having a pore diameter of 10 μm or less in the filter partition, and pores having a pore diameter of 40 to 100 μm are The remaining ratio is high.
[0029]
Therefore, the catalyst layer has a coating portion mainly composed of a porous oxide having a particle diameter of 1 μm or less, so that most of the pores having a pore diameter of 10 μm or less of the filter partition wall are filled with the catalyst layer, or the catalyst layer As a result, the pore diameter is further reduced. The filter partition wall on which such a catalyst layer is formed has a porosity of 45 to 60% and an average pore diameter of 15 to 20 μm.
[0030]
An electron micrograph of DPF coated with 75 g of catalyst powder with an average particle size of 3 μm per liter of filter body is shown in FIG. 1, and DPF coated with 75 g of catalyst powder with an average particle size of 0.6 μm per liter of filter body. The electron micrograph of is shown in FIG. In the figure, the white portion is the catalyst layer. Compared with the DPF coated with a catalyst powder having an average particle diameter of 3 μm in FIG. 1, the DPF coated with the catalyst powder having an average particle diameter of 0.6 μm in FIG. You can see that
[0031]
In a general diesel exhaust gas purifying filter type catalyst, pores having a pore diameter of 10 μm or less remain. In such a filter catalyst for purifying diesel exhaust gas, pores having a pore diameter of 10 μm or less do not contribute much to the collection of particulates but can serve as gas flow paths. For this reason, even when other pores having a large pore diameter collect clogged particulates, the pressure loss does not increase so much because gas flows through the pores having a pore diameter of 10 μm or less. Therefore, the pressure loss sensitivity is not so high.
[0032]
On the other hand, in the filter catalyst for purification of diesel exhaust gas according to the present invention, the catalyst powder is filled in the pores having a pore diameter of 10 μm or less that are not so much involved in the collection of the particulates, so that it does not become a gas flow path. The relationship between the collection of particulates by the pores and the increase in the pressure loss of the filter body becomes more direct, and the pressure loss sensitivity is improved.
[0033]
In the filter catalyst for purifying diesel exhaust gas of the present invention, the catalyst powder is filled in the pores having a pore diameter of 10 μm or less, but the pores having an average pore diameter of 10 to 100 μm remain. In the non-deposited state, gas is circulated through the pores having a pore diameter of 10 to 100 μm, and the initial pressure loss does not increase so much.
[0034]
Therefore, the filter catalyst for purification of diesel exhaust gas of the present invention can detect particulate deposition with good sensitivity at the initial stage of deposition while maintaining the ability to collect particulates and preventing an increase in initial pressure loss. As a result, it is possible to regenerate the DPF before the amount of particulate deposition reaches the amount at which melting occurs, so that it is possible to prevent the deterioration of the DPF due to the progress of particulate deposition.
[0035]
In the filter catalyst for purifying diesel exhaust gas of the present invention, the amount of the porous oxide having an average particle diameter of 1 μm or less coated on the filter partition wall is preferably 50 g to 200 g per liter volume of the filter body. The amount is preferably 1 to 5 g per liter volume of the filter body. When the amount is larger than this, the pressure loss of the filter body increases, and when the amount is less than this, the oxidation and combustion of the particulates are not performed well. In this specification, the volume of the filter body represents the volume of the filter body.
[0036]
In the diesel exhaust gas purifying filter catalyst of the present invention, the catalyst layer has at least a coat portion mainly composed of a porous oxide having a particle size of 1 μm or less on a filter partition wall at a specific portion of the filter body.
[0037]
As described above, the catalyst layer has a coating portion mainly composed of a porous oxide having a particle diameter of 1 μm or less, so that the diesel exhaust gas purification filter-type catalyst maintains the ability to collect particulates and reduces the initial pressure loss. It is possible to detect particulate deposition with high sensitivity at the initial stage of deposition while preventing increase. Here, the portion where the coat portion mainly composed of a porous oxide having a particle size of 1 μm or less is provided at least on the filter partition wall of a specific portion of the filter body. That is, it can be provided on the partition wall of the entire filter body, or can be provided only on the filter partition wall of a specific part of the filter body.
[0038]
  In the filter catalyst for purifying diesel exhaust gas according to the present invention, the specific portion is the outer peripheral portion of the filter body in the radial directionOrDownstream part of the filter body in the exhaust gas flow directionIs.
[0039]
And it is desirable for the catalyst layer on the filter partition of a specific part to have a coat amount larger than the coat amount on the filter partition of a part except a specific part.
[0040]
Here, the range of the outer peripheral portion in the radial direction of the filter main body is a range in which the ratio of the volume of the inner peripheral portion in the radial direction of the filter main body to the outer peripheral portion in the radial direction of the filter main body is 1: 2 to 4: 1. It is.
[0041]
The range of the downstream part of the exhaust gas flow of the filter body is such that the ratio of the volume of the upstream part of the exhaust gas flow of the filter body and the downstream part of the exhaust gas flow of the filter body is 1: 2 to 2: 1. .
[0042]
In general, in the DPF, the outer peripheral portion of the filter body in the radial direction (hereinafter referred to as the outer peripheral portion) has a small amount of exhaust gas flow and a large amount of heat released to the outside air. For this reason, the temperature of the outer peripheral portion is likely to decrease, and the particulates are not easily oxidized and burned. As a result, the outer peripheral portion tends to deposit particulates.
[0043]
In the diesel exhaust gas purifying filter catalyst of the present invention, it is preferable that the catalyst layer formed on the filter partition located on the outer peripheral portion has a coat portion mainly composed of a porous oxide having a particle size of 1 μm or less.
[0044]
As described above, the catalyst layer formed on the filter partition located at the outer peripheral portion is a coating portion mainly composed of a porous oxide having a particle size of 1 μm or less, and the particulates are easily deposited as described above. The amount of curate deposited can be detected with high sensitivity, and even when particulate is deposited, the DPF can be regenerated before melting damage occurs.
[0045]
In addition, by setting the outer peripheral portion as a specific portion and increasing the coating amount of the catalyst layer on the filter partition located in the outer peripheral portion more than the coating amount of the portion excluding the specific portion, the heat capacity of this portion increases, The temperature is prevented from lowering and the particulates are oxidized and burned well.
[0046]
Hereinafter, the specific part with a large amount of coating is referred to as a multi-coated part.
[0047]
The amount of the porous oxide having an average particle diameter of 1 μm or less coated on the inner peripheral part in the radial direction of the filter main body is preferably 50 g to 200 g per liter of the volume of the filter main body, and the average particle coated on the outer peripheral part The amount of the porous oxide having a diameter of 1 μm or less is preferably 150 to 300 g per liter of the filter body.
[0048]
Further, the amount of the porous oxide having an average particle size of 1 μm or less coated on the upstream portion of the gas flow of the filter body is preferably 50 g to 200 g per liter of the filter body, and the average particle size of 1 μm coated on the downstream portion. The amount of the following porous oxide is preferably 150 to 300 g per liter volume of the filter body.
[0049]
In the filter catalyst for purifying diesel exhaust gas of the present invention, a porous oxide coating layer is first formed on the DPF, and then noble metal or NO_XWhen the occlusion material is supported, noble metals and NO in the multi-coat part_XThe loading density of the occlusion material decreases. For this reason, precious metals and NO_XIt can suppress the grain growth and sulfur poisoning of the occlusion material._XImproves purification durability.
[0050]
In the filter catalyst for purifying diesel exhaust gas according to the present invention, the catalyst layer on the filter partition wall defining the gas outflow hole at the specific portion includes a first coat portion made of a porous oxide having an average particle size of 1 μm or less, and a first coat portion. It consists of a second coat part formed of a porous oxide having an average particle diameter of 1 to 5 μm formed on the surface.
[0051]
Here, the catalyst powder having an average particle diameter of 1 to 5 μm is a catalyst powder composed of a noble metal and a porous oxide having an average particle diameter of 1 to 5 μm.
[0052]
An electron micrograph of DPF coated with 150 g of catalyst powder with an average particle size of 0.6 μm per liter of filter body is shown in FIG. FIG. 4 shows an electron micrograph of a DPF whose upper layer is coated with 30 g of catalyst powder having an average particle size of 3 μm. In the figure, the white portion is the catalyst layer. Compared with the DPF in FIG. 3 in which the catalyst layer is dispersed on the entire surface, the DPF in FIG. It turns out that many catalyst layers are formed in the filter partition.
[0053]
The catalyst powder having an average particle diameter of 1 to 5 μm is preferentially coated on pores having a pore diameter of 10 μm or less near the surface of the filter partition wall defining the gas outflow holes. For this reason, the catalyst powder filled in the pores having a pore diameter of 10 μm or less of the filter partition walls defining the gas outflow holes is increased. As a result, the pressure loss when the particulates are accumulated further increases, so that the particulate accumulation can be detected earlier.
[0054]
In general, in the DPF, the particulates are collected by a filter partition that partitions the gas inflow hole, and the filter partition that partitions the gas outflow hole does not participate in the collection of the particulates. In the diesel exhaust gas purifying filter type catalyst of the present invention, by increasing the coating amount of the filter partition wall that partitions the gas outflow hole that does not participate in the particulate collection, the particulates in the filter partition wall that partitions the gas inflow hole The pressure loss sensitivity can be further improved while maintaining the collection ability.
[0055]
Here, the coating amount of the specific portion where the first coating portion and the second coating portion are formed can be larger than the coating amount of the portion excluding the specific portion, or can be the same amount. it can. In other words, the coating amount of the first part in the specific part is less than the coating amount of the part excluding the specific part, and the second coat part is further coated on the upper layer, so that the part other than the coating amount of the specific part and the specific part The coating amount can be equal to the coating amount. In addition, the first coat portion is formed with the same coating amount on the entire filter partition wall, and then the second coat portion is coated only on the specific portion, so that the coating amount on the specific portion is larger than the coating amount on the portion other than the specific portion. You can also In this case, since both the effect by the multicoat part mentioned above and the effect by a 2nd coat part are acquired, it is more preferable.
[0056]
The amount of the porous oxide having an average particle size of 1 μm or less coated on the filter partition wall is preferably 50 to 200 g per liter of the volume of the filter body, and the amount of the porous oxide having an average particle size of 1 to 5 μm is The volume of the filter body is preferably 20 to 100 g per liter. When the amount is larger than this, the pressure loss of the filter body increases, and when the amount is less than this, the oxidation and combustion of the particulates are not performed well.
[0057]
Furthermore, since a large amount of catalyst powder is coated on the filter partition walls that define the gas outflow holes, noble metals and NO are coated after the porous oxide coating._XSupports precious metals and NO if it supports the storage material_XThe carrying amount with the occlusion material can be lowered to increase the carrying amount. For this reason, precious metals and NO_XThe durability of the occlusion material is improved and the activity is improved.
[0058]
In the filter type catalyst for purifying diesel exhaust gas according to the present invention, the multi-coat portion having a catalyst powder having an average particle diameter of 1 to 5 μm in the upper layer is a radially outer portion of the filter body and / or a downstream portion of the filter body in the exhaust gas flow direction. It is preferable to form in the filter partition which divides the gas outflow hole located in this.
[0059]
In this configuration, a large amount of porous oxide having an average particle diameter of 1 to 5 μm is coated on the filter partition walls that define gas outflow holes located on the outer peripheral portion. By forming a large number of catalyst layers on the outer peripheral portion, the heat capacity of this portion is increased, and a decrease in temperature is prevented. For this reason, particulates are favorably oxidized and burned at the outer peripheral portion where the particulates are likely to be deposited, and the particulates are prevented from being deposited. Further, according to this configuration, it is possible to detect the accumulation of particulates at an early stage, and it is possible to more reliably prevent the amount of particulate deposition from reaching the amount at which melting occurs.
[0060]
In addition, the multi-coat part having the catalyst powder with an average particle diameter of 1 to 5 μm in the upper layer is formed in the filter partition wall that partitions the gas outflow holes located in the downstream part, so that the accumulation of particulates can be detected with high sensitivity. It is possible to more reliably prevent the amount of particulates from reaching the amount that causes melting.
[0061]
The amount of the porous oxide having an average particle diameter of 1 to 5 μm coated on the multi-coat part of the filter partition wall defining the gas outflow holes located on the outer peripheral part is preferably 20 to 100 g per liter of the volume of the filter body. Further, the amount of the catalyst powder having an average particle diameter of 1 to 5 μm coated on the multi-coat part of the filter partition wall defining the gas outflow hole located in the downstream part is preferably 20 to 100 g per liter volume of the filter body. . When the amount is larger than this, the pressure loss of the filter body increases, and when the amount is less than this, the oxidation and combustion of the particulates are not performed well.
[0062]
The multi-coat part of the present invention is NO._XOcclusion material can be included. NO_XThe catalyst layer containing the occlusion material is used for NO in exhaust gas._XNO to purify_XPurifying ability is improved.
[0063]
NO_XAs the occlusion material, at least one selected from alkali metals such as K, Na, Li and Cs, alkaline earths such as Ba and Ca, and rare earths such as La and Y can be used.
[0064]
NO contained in the catalyst layer_XThe amount of the occlusion material is preferably 0.2 to 0.5 ml per liter of the filter body. If it exceeds this, precious metals will be NO_XSince it is covered with a storage agent, its activity is reduced._XPurification is not good.
[0065]
【Example】
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0066]
Example 1
FIG. 5 shows a cross-sectional view parallel to the gas flow path of the diesel exhaust gas purifying filter catalyst of Example 1 of the present invention.
[0067]
The filter catalyst for diesel exhaust gas purification of the first embodiment has a filter body 1 and a catalyst layer 2, and the catalyst layer 2 is formed in a large amount on the filter partition 4 located on the outer peripheral portion 3 in the radial direction of the filter body 1. The multi-coating part 2a is provided.
[0068]
The material of the filter body 1 is an end face area of 130 cm.²A cordierite porous honeycomb structure having a length of 150 mm was used. This porous honeycomb structure has a volume of 2 liters, a porosity of 60%, and a cell density of 46.5 cells / cm.²A plug 7 made of cordierite of the same material as the main body has a wall thickness of 0.3 mm, and the cell downstream end of the cell hole serving as the gas inflow hole 5 and the cell upstream end of the cell hole serving as the gas outflow hole 6. The filter body 1 is clogged with.
[0069]
The catalyst layer 2 is made of Al having an average particle diameter of 0.5 to 1 μm as a porous oxide.₂O_ThreePt as a noble metal and NO_XA large number of filter partitions 4 including Ba, K, and Li as occlusion materials and located on the outer peripheral portion 3 in the radial direction of the filter body 1 were formed. The range of the outer peripheral portion 3 in the radial direction of the filter main body 1 is a range in which the volume ratio of the inner peripheral portion 8 in the radial direction of the filter main body 1 to the outer peripheral portion 3 in the radial direction of the filter main body 1 is 1: 1.
[0070]
In Example 1, Al having an average particle size of 1 μm or less₂O_ThreeThe filter partition 4 located in the radially inner periphery 7 of the filter body 1 is coated with 150 g per liter of the filter body volume, and the filter partition 4 located in the outer periphery 3 has a filter body volume of 1 liter. 180 g per coat.
[0071]
Pt was uniformly coated on the entire surface of the filter partition 4, and 3 g was coated per liter of the volume of the filter body 1. Similarly, Ba, K, and Li were also uniformly coated on the entire surface of the filter partition, and 0.3 mol per liter of the volume of the filter body 1 was coated.
[0072]
A method for producing a filter catalyst for purifying diesel exhaust gas according to the first embodiment will be described below.
[0073]
Al with an average particle size of 0.5-1 μm₂O_ThreeA slurry containing 95% by weight of powder and 5% by weight of alumina binder was prepared, and the filter body was immersed in this slurry. After the immersion, excess slurry was removed and baked at 500 ° C. for 30 minutes. By this process, Al₂O_ThreeWas uniformly coated on the entire filter partition wall of the filter body.
[0074]
Next, Al having an average particle size of 0.5 to 1 μm₂O_ThreeThe filter body coated with is masked with a resin plate on the inner periphery in the radial direction. The masked filter body is made of Al having an average particle size of 0.5 to 1 μm.₂O_ThreeIt was dipped again in a slurry containing 95% by weight of powder and 5% by weight of alumina binder, and then the excess slurry was removed and baked at 500 ° C. for 30 minutes.
[0075]
The filter partition located on the outer periphery in the radial direction of the filter body is made of Al by the above process.₂O_ThreeA multi-coat part 2a coated with a large amount of was formed.
[0076]
On the other hand, a 5% by weight dinitrodiamine platinum aqueous solution was prepared. This dinitrodiamine platinum aqueous solution was mixed with Al.₂O_ThreeIs injected into the gas inflow hole side cell of the filter body coated with Pt, and sucked from the gas outflow hole side cell, Pt is divided into the Al gas in the filter partition wall.₂O_ThreeTo be adsorbed and supported. Similarly, an aqueous solution of dinitrodiamine platinum is injected into the gas outflow hole, and Pt is Al in the filter partition wall defining the gas outflow hole.₂O_ThreeTo be adsorbed and supported. Then baked at 500 ° C for 30 minutes and Al₂O_ThreeAnd a catalyst layer containing Pt.
[0077]
Further, the amount of water that can be absorbed by the filter body is measured in advance, an aqueous solution in which nitrates of K, Ba, and Li are each adjusted to 0.4 mol / L is prepared in the amount of water, and the filter body is immersed in this aqueous solution. Water absorption was carried. After that, it is dried at 250 ° C. and baked at 500 ° C. for 30 minutes.₂O_ThreeAnd Pt, and a catalyst layer containing K, B, and Li was formed. As a result, a diesel exhaust gas purifying filter catalyst of Example 1 of the present invention was obtained.
[0078]
(Example 2)
FIG. 6 shows a sectional view parallel to the gas flow path of the filter catalyst for purifying diesel exhaust gas according to the second embodiment of the present invention.
[0079]
The filter catalyst for diesel exhaust gas purification of the second embodiment has a filter body 9 and a catalyst layer 10, and the catalyst layer 10 is formed in a large amount on the filter partition wall 12 located in the downstream portion 11 of the exhaust gas flow of the filter body. And a multi-coat portion 10a. In addition, the filter catalyst for diesel exhaust gas purification of Example 2 was manufactured in the same manner as Example 1 except for the part where the multi-coat part was formed and the coating method.
[0080]
The filter type catalyst for purifying diesel exhaust gas according to the second embodiment has a filter main body 9, a catalyst layer 10, a gas inflow hole 13, a gas outflow hole 14, a gas inflow hole 13 and a gas outflow hole 14 which are partitioned. 9, a filter partition wall 12 positioned in the downstream portion 11 in the exhaust gas flow direction, a gas inlet hole 13 and a gas outlet hole 14, and a filter partition wall 12 positioned in the upstream portion 15 of the filter body 9 in the exhaust gas flow direction, And a plug 16. Here, the range of the downstream portion 11 of the exhaust gas flow of the filter body 9 is such that the ratio of the volume of the upstream portion 15 of the exhaust gas flow of the filter body 9 and the downstream portion 11 of the exhaust gas flow of the filter body 9 is 2: 1. It is a range.
[0081]
In Example 2, Al having an average particle diameter of 0.5 to 1 μm₂O_ThreeThe filter partition 12 located in the upstream portion 15 of the exhaust gas flow of the filter body 9 is coated with 150 g per liter of the filter body, and the filter partition 12 located in the downstream portion 11 is coated per liter of the filter body. 180 g was coated.
Pt and K were coated in the same manner as in Example 1.
[0082]
A method for manufacturing a filter catalyst for purifying diesel exhaust gas according to the second embodiment will be described below.
[0083]
Al with an average particle size of 0.5-1 μm₂O_ThreeA slurry containing 95% by weight of powder and 5% by weight of alumina binder was prepared, and the filter body was immersed in this slurry. After the immersion, excess slurry was removed and baked at 500 ° C. for 30 minutes. By this process, Al₂O_ThreeWas uniformly coated on the entire filter partition wall of the filter body.
[0084]
Next, Al having an average particle size of 0.5 to 1 μm₂O_ThreeOnly the downstream part of the filter main body coated with NOx in the exhaust gas flow direction is made of Al having an average particle diameter of 0.5 to 1 μm.₂O_ThreeIt was dipped again in a slurry containing 95% by weight of powder and 5% by weight of alumina binder, and then the excess slurry was removed and baked at 500 ° C. for 30 minutes.
[0085]
The filter partition located in the downstream part of the filter body in the exhaust gas flow direction is₂O_ThreeI coated a lot.
[0086]
Further, in the same manner as in Example 1, Pt, K, B, and Li are used as the filter partition walls.₂O_ThreeSupported on Al₂O_ThreeThen, a catalyst layer containing Pt, K, B, and Li was formed. As a result, a diesel exhaust gas purifying filter catalyst of Example 2 of the present invention was obtained.
[0087]
(Example 3)
FIG. 7 shows a cross-sectional view parallel to the gas flow path of the diesel exhaust gas purifying filter type catalyst of Example 3 of the present invention.
[0088]
The filter catalyst for diesel exhaust gas purification of the third embodiment has a filter main body 17 and a catalyst layer 18, and the catalyst layer 18 defines a gas outflow hole 20 located in the outer peripheral portion 19 in the radial direction of the filter main body. The filter partition wall 21 has a multi-coat portion 18a formed in large numbers. Further, the filter catalyst for diesel exhaust gas purification of Example 3 was manufactured in the same manner as Example 1 except for the configuration of the multi-coat part and the coating method.
[0089]
The diesel exhaust gas purifying filter type catalyst according to the third embodiment includes a filter main body 17, a catalyst layer 18, a filter partition wall 21 that defines a gas outflow hole 20 located in a radially outer peripheral portion 19 of the filter main body 17, and a filter main body. 17 includes a filter partition wall 21 that partitions the gas outflow hole 20 located in the radially inner peripheral portion 22, a gas inflow hole 23, and a capping plug 24. Here, the range of the outer peripheral portion 19 in the radial direction of the filter main body 17 was the same as that of the outer peripheral portion 3 in the radial direction of the filter main body 1 of Example 1.
[0090]
In Example 3, Al having an average particle diameter of 0.5 to 1 μm₂O_ThreeThe filter partition wall 21 is uniformly coated with 150 g / L to form a first coating portion, and then the filter partition wall 21 defining the gas outflow holes 20 located on the outer peripheral portion 19 is only coated with Al having an average particle diameter of 3 μm.₂O_ThreeWas coated at 30 g / L to form a second coat portion, thereby forming a multi-coat portion 18a. Pt and K, Ba, Li were coated in the same manner as in Example 1.
[0091]
A method for manufacturing a filter catalyst for purifying diesel exhaust gas according to the third embodiment will be described below.
[0092]
Al with an average particle size of 0.5-1 μm₂O_ThreeA slurry containing 95% by weight of powder and 5% by weight of alumina binder was prepared, and the filter body was immersed in this slurry. After the immersion, excess slurry was removed and baked at 500 ° C. for 30 minutes. By this process, Al₂O_ThreeWas uniformly coated on the entire filter partition wall of the filter body to form a first coating portion.
[0093]
Next, Al having an average particle size of 0.5 to 1 μm₂O_ThreeIn the gas outflow hole located in the radial outer periphery of the filter main body coated with Al, Al having an average particle diameter of 3 μm₂O_ThreeA slurry containing 95% by weight of powder and 5% by weight of alumina binder was injected, and then the slurry was sucked from a gas outflow hole located in the outer peripheral portion of the filter body in the radial direction. Thereafter, the filter main body was baked at 500 ° C. for 30 minutes to form a second coat portion on the first coat portion on the outer peripheral portion.
[0094]
The multi-coat part 18a which consists of a 1st coat part and a 2nd coat part was formed in the outer peripheral part of the radial direction of a filter main body by the above process.
[0095]
Further, in the same manner as in Example 1, Pt and K were used as filter partition walls.₂O_ThreeSupported on Al₂O_ThreeAnd a catalyst layer containing Pt and K was formed. Thus, a filter catalyst for purifying diesel exhaust gas according to Example 3 of the present invention was obtained.
[0096]
(Example 4)
FIG. 8 shows a sectional view parallel to the gas flow path of the diesel exhaust gas purifying filter type catalyst of Example 4 of the present invention.
[0097]
The diesel exhaust gas purifying filter type catalyst of the fourth embodiment has a filter body 25 and a catalyst layer 26, and the catalyst layer 26 defines a gas outflow hole 28 located in the downstream portion 27 of the exhaust gas flow of the filter body 25. The filter partition wall 29 to be formed has a multi-coat portion 26a formed in a large amount. Further, the filter catalyst for diesel exhaust gas purification of Example 4 was manufactured in the same manner as Example 2 except for the configuration of the multi-coat part and the coating method.
[0098]
The filter catalyst for diesel exhaust gas purification of the fourth embodiment includes a filter main body 25, a catalyst layer 26, a filter partition wall 29 that defines a gas outflow hole 28 located in the downstream portion 27 of the exhaust gas flow of the filter main body 25, and a filter main body. 25, a filter partition wall 29 that divides the gas outflow hole 28 located in the upstream portion 30 of the exhaust gas flow 25, a gas inflow hole 31, and a plug plug 32. Here, the range of the downstream portion 27 of the exhaust gas flow of the filter body 25 is the same as that of the downstream portion 12 of the exhaust gas flow of the filter body 8 of the second embodiment.
[0099]
In Example 4, Al having an average particle diameter of 0.5 to 1 μm₂O_ThreeThe filter partition wall 29 is uniformly coated with 150 g / L to form a first coating portion, and then only the filter partition wall 29 partitioning the gas outflow holes 28 located in the downstream portion 27 is Al having an average particle diameter of 3 μm.₂O_ThreeWas coated at 30 g / L to form a second coat portion, thereby forming a multi-coat portion 26a. Pt and K, Ba, Li were coated in the same manner as in Example 1.
[0100]
A method for producing a filter catalyst for purifying diesel exhaust gas according to the fourth embodiment will be described below.
[0101]
Al with an average particle size of 0.5-1 μm₂O_ThreeA slurry containing 95% by weight of powder and 5% by weight of alumina binder was prepared, and the filter body was immersed in this slurry. After the immersion, excess slurry was removed and baked at 500 ° C. for 30 minutes. By this process, Al₂O_ThreeWas uniformly coated on the entire filter partition wall of the filter body to form a first coating portion.
[0102]
Next, Al having an average particle size of 0.5 to 1 μm₂O_ThreeThe downstream part of the exhaust gas flow of the filter body coated with is coated with Al with an average particle diameter of 3 μm.₂O_ThreeThe slurry was immersed in a slurry containing 95% by weight of powder and 5% by weight of an alumina binder, and then the slurry was sucked from the gas inlet hole of the filter body. Thereafter, the filter main body was baked at 500 ° C. for 30 minutes to form a second coat portion.
[0103]
The multi-coat part was formed in the downstream part of the exhaust gas flow of a filter main body by the above process. Further, in the same manner as in Example 1, Pt, K, Ba, and Li are used as the filter partition walls.₂O_ThreeSupported on Al₂O_ThreeAnd a catalyst layer containing Pt and K, Ba, Li were formed. As a result, a diesel exhaust gas purifying filter catalyst of Example 4 of the present invention was obtained.
[0104]
In contrast to Examples 1 and 2, in Examples 3 and 4, the gas flow resistance at the gas inflow hole did not increase even when the coating amount of the outer peripheral part or the downstream part was increased.
[0105]
(Comparative Example 1)
FIG. 9 shows a sectional view parallel to the gas flow path of the filter catalyst for purifying diesel exhaust gas of Comparative Example 1 of the present invention.
[0106]
The diesel exhaust gas purifying filter catalyst of Comparative Example 1 has a filter main body 33 and a catalyst layer 34, and the catalyst layer 34 was uniformly formed on the entire filter partition wall 37 of the filter main body 33. Moreover, the filter type catalyst for diesel exhaust gas purification of this comparative example 1 is Al.₂O_ThreeThis was produced in the same manner as in Example 1 except that the average particle size of the polymer and no multi-coat part were formed.
[0107]
The diesel exhaust gas purifying filter catalyst of the first comparative example includes a filter body 33, a catalyst layer 34, a filter partition wall 37 that partitions the gas inflow hole 35 and the gas outflow hole 36, and a plug 38.
[0108]
In this comparative example 1, Al₂O_ThreeUsed were those having an average particle diameter of 3 μm. Al with an average particle size of 3 μm₂O_ThreeWas uniformly coated on the entire filter partition wall 37 of the filter body 33, and 75 g was coated per liter of the volume of the filter body 33. Pt and K, Ba, Li were coated in the same manner as in Example 1.
[0109]
Hereinafter, a method for producing a filter catalyst for purifying diesel exhaust gas according to Comparative Example 1 will be described.
[0110]
Al with an average particle size of 3 μm₂O_ThreeA slurry containing 95% by weight of powder and 5% by weight of alumina binder was prepared, and the filter body was immersed in this slurry. After the immersion, excess slurry was removed and baked at 500 ° C. for 30 minutes. By this process, Al₂O_ThreeWas uniformly coated on the entire filter partition wall of the filter body.
[0111]
Further, in the same manner as in Example 1, Pt, K, Ba, and Li are used as the filter partition walls.₂O_ThreeSupported on Al₂O_ThreeAnd a catalyst layer containing Pt and K, Ba, Li were formed. As a result, a diesel exhaust gas purifying filter catalyst of Example 4 of the present invention was obtained.
[0112]
(Reference example)
The filter type catalyst for purifying diesel exhaust gas of the present reference example had a filter body and a catalyst layer, and the catalyst layer was uniformly formed on the entire filter partition wall of the filter body. Further, the filter type catalyst for purifying diesel exhaust gas of this reference example is Al having the same particle size as that of Comparative Example 1.₂O_ThreeUsing this Al₂O_ThreeWas manufactured in the same manner as Comparative Example 1 except that 150 g was coated per liter of the filter body.
[0113]
(Examination / Evaluation)
About the filter type | mold catalyst for diesel exhaust gas purification of Examples 1-4 and the comparative example 1, the evaluation test about the following items was done.
[0114]
<Particulate deposition detection test>
First, the diesel exhaust gas purifying filter catalysts of Examples 1 to 4 and Comparative Example 1 were attached to a particulate generator, and the particulates were 20 mg / m.^ThreeThe contained gas was circulated at 150 ° C. through each diesel exhaust gas purifying filter catalyst. At this time, the temperature of the gas is less than the temperature at which the soot in the particulates is combusted. Therefore, when a gas containing particulates is circulated, the soot in the particulates accumulates on the filter partition walls of the diesel exhaust gas purifying filter catalyst. To do.
[0115]
The pressure loss of the diesel exhaust gas purifying filter catalyst of Examples 1 to 4 and Comparative Example 1 in which the gas was circulated was measured, and the time required for the pressure loss to rise to 5 KPa was measured.
[0116]
<Particulate combustion test>
First, the diesel exhaust gas purifying filter catalysts of Examples 1 to 4 and Comparative Example 1 were attached to a particulate generator, and the particulates were 20 mg / m.^ThreeThe contained gas was circulated at 350 ° C. to each diesel exhaust gas filter type catalyst. At this time, since the gas temperature is the exhaust gas temperature of the actual diesel vehicle, when the gas containing particulates is circulated, the particulates collected in the filter partition walls of the diesel exhaust gas purification filter catalyst burn and burn. The remaining particulates accumulate.
[0117]
The pressure loss of the diesel exhaust gas purifying filter catalyst of Examples 1 to 4 and Comparative Example 1 in which the gas was circulated was measured, and the time required for the pressure loss to rise to 5 KPa was measured.
[0118]
Table 1 shows the time required for increasing the pressure loss of the diesel exhaust gas purifying filter catalysts of Examples 1 to 4 and Comparative Example 1 obtained by the above experiment. Table 1 shows the DPF performance values obtained by correcting the results of the particulate combustion test in consideration of the difference in pressure loss sensitivity between the example and the comparative example.
[0119]
[Table 1]

[0120]
In the particulate accumulation detection test, the filter type catalyst for purifying diesel exhaust gas of Examples 1 to 4 has a shorter time required for the pressure loss to increase than that of Comparative Example 1. Since particulates are deposited in the same proportion in any diesel exhaust filter-type catalyst, this result allows the diesel exhaust filter-type catalyst of the present invention to detect particulate deposition with high sensitivity. I know that there is.
[0121]
In the particulate combustion test, there was no significant difference in the time required for the pressure loss of the diesel exhaust gas purifying filter catalyst of the example and the comparative example to increase. However, each diesel exhaust gas purifying filter type catalyst has a different pressure drop sensitivity, so these results cannot be simply compared. Therefore, the DPF performance value was calculated by correcting the pressure loss sensitivity in consideration of these results. Comparing the DPF performance values, the DPF performance values of the examples were clearly larger than the DPF performance values of the comparative examples. This indicates that the diesel exhaust gas purifying filter type catalyst of the example has better particulate DPF performance as compared with the diesel exhaust gas purifying filter type catalyst of the comparative example.
[0122]
<Initial pressure loss test>
First, the filter catalysts for purifying diesel exhaust gas of Examples 1 to 4, Comparative Example 1 and Reference Example are attached to an air suction device, and 5 m^Three/ Min, air suction was performed at 20 ° C.
[0123]
The pressure loss of the filter catalyst for purifying diesel exhaust gas of Examples 1 to 4, Comparative Example 1 and Reference Example in which the air was sucked was measured. This test measures the pressure loss of each filter before particulate deposition, that is, the initial pressure loss.
[0124]
Each diesel exhaust gas purification filter type catalyst was coated with the initial pressure loss value of the diesel exhaust gas purification filter type catalyst of Examples 1 to 4, Comparative Example 1 and Reference Example obtained by the above experiment, and the obtained pressure loss value. Al₂O_ThreeTable 2 shows the correction values of the initial pressure loss values corrected in consideration of the coating amount.
[0125]
[Table 2]

[0126]
In the initial pressure loss test, the initial pressure loss value and the correction value of each diesel exhaust gas purifying filter catalyst of Examples 1 to 4 are the same amount of Al as in Examples 1 to 4.₂O_ThreeExample of coating with a half amount of Al in Examples 1-4₂O_ThreeThe value was lower than that of the comparative example coated with No .. This indicates that the filter catalyst for purifying diesel exhaust gas according to the present invention is a filter catalyst for purifying diesel exhaust gas having a low initial pressure loss as compared with the filter catalyst for purifying diesel exhaust gas subjected to normal coating.
[0127]
【The invention's effect】
According to the diesel exhaust gas purifying filter catalyst of the present invention, it is possible to increase the pressure loss sensitivity while suppressing an increase in the initial pressure loss.
[Brief description of the drawings]
FIG. 1 is an electron micrograph of DPF coated with catalyst powder having an average particle size of 3 μm.
FIG. 2 is an electron micrograph of DPF coated with catalyst powder having an average particle size of 0.6 μm.
FIG. 3 is an electron micrograph of a DPF coated with 150 g of catalyst powder having an average particle size of 0.6 μm per liter volume of a filter body.
FIG. 4 is an electron micrograph of a DPF in which 120 g of a catalyst powder having an average particle diameter of 0.6 μm is coated per 120 liter of filter body volume and 30 g of a catalyst powder having an average particle diameter of 3 μm is coated on the upper layer.
FIG. 5 is a sectional view parallel to the gas flow path of the filter catalyst for purifying diesel exhaust gas according to the first embodiment of the present invention.
FIG. 6 is a cross-sectional view parallel to a gas flow path of a diesel exhaust gas purifying filter catalyst according to a second embodiment of the present invention.
FIG. 7 is a cross-sectional view parallel to a gas flow path of a filter catalyst for purifying diesel exhaust gas according to a third embodiment of the present invention.
FIG. 8 is a cross-sectional view parallel to the gas flow path of a filter catalyst for purifying diesel exhaust gas according to a fourth embodiment of the present invention.
FIG. 9 is a cross-sectional view parallel to the gas flow path of the diesel exhaust gas purifying filter catalyst of Comparative Example 1 of the present invention.
[Explanation of symbols]
1: Filter body 2: Catalyst layer 2a: Multi-coated part 3: Filter body outer peripheral part 4: Filter partition wall 5: Gas inflow hole 6: Gas outflow hole 7: Inner part of filter main body in the radial direction

Claims (5)

A ceramic honeycomb structure, wherein a gas inflow hole clogging an opening at a cell downstream end, a gas outflow hole clogging an opening at a cell upstream end, and the gas inflow hole and the gas outflow hole are partitioned. A filter type catalyst for purifying diesel exhaust gas, having a filter body having a filter partition wall that serves as a filter during gas flow, and a catalyst layer containing a porous oxide and a noble metal,
The catalyst layer has at least a coat portion mainly composed of the porous oxide having a particle size of 1 μm or less on the filter partition wall at a specific portion of the filter body ,
The filter-type catalyst for purifying diesel exhaust gas, wherein the specific portion is an outer peripheral portion in a radial direction of the filter body . A ceramic honeycomb structure, wherein a gas inflow hole clogging an opening at a cell downstream end, a gas outflow hole clogging an opening at a cell upstream end, and the gas inflow hole and the gas outflow hole are partitioned. A filter type catalyst for purifying diesel exhaust gas, having a filter body having a filter partition wall that serves as a filter during gas flow, and a catalyst layer containing a porous oxide and a noble metal,
The catalyst layer has at least a coat portion mainly composed of the porous oxide having a particle size of 1 μm or less on the filter partition wall at a specific portion of the filter body ,
The filter part catalyst for purifying diesel exhaust gas, wherein the specific part is a downstream part of the exhaust gas flow of the filter body . Wherein the catalyst layer on the filter septum of a particular site, for diesel exhaust gas purification according to claim 1 or claim 2, wherein the coating amount is larger than the coated amount on the filter septum of the portion except for the specific portion Filter type catalyst. The catalyst layer on the filter partition partitioning the gas outflow holes of the specific part is formed on the surface of the first coat part made of a porous oxide having an average particle diameter of 1 μm or less and an average particle diameter of 1 to The filter type catalyst for diesel exhaust gas purification according to any one of claims 1 to 3 , wherein the filter type catalyst comprises a second coat portion made of a porous oxide of 5 µm. Wherein the catalyst layer further claims 1 to diesel exhaust gas purifying filter catalyst according to claim 4, characterized in that includes _the NO _X storage material.

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