JP2010255615A - Exhaust gas purification fiber filter, diesel engine exhaust gas purification system and gasoline engine exhaust gas purification system - Google Patents

Abstract

An exhaust gas purification fiber filter capable of extending the regeneration interval of a diesel particulate filter, an exhaust gas purification system for a diesel engine using the same, and an exhaust gas purification fiber capable of improving the purification rate of PM in gasoline exhaust gas in a low temperature range Provided is an exhaust gas purification system for a gasoline engine using the filter.
An exhaust gas purifying fiber filter has a porosity of 70 to 90% and a thickness of 0.5 to 6 mm. The exhaust gas purifying fiber filter 4 is composed of fibers 4a.
The exhaust gas purification system 1 for a diesel engine includes a diesel particulate filter 2 disposed in an exhaust gas passage 8a of the diesel engine 8 and the exhaust gas purification disposed in an exhaust gas passage 8a upstream of the diesel particulate filter 2. Fiber filter 4.
[Selection] Figure 1

Description

The present invention relates to an exhaust gas purification fiber filter, an exhaust gas purification system for a diesel engine, and an exhaust gas purification system for a gasoline engine.
More specifically, the present invention relates to an exhaust gas purification fiber filter having a predetermined structure, an exhaust gas purification system for a diesel engine having an exhaust gas purification fiber filter having a predetermined structure disposed at a predetermined position, and an exhaust gas purification for a gasoline engine. About the system.

  Conventionally, in a diesel engine exhaust gas purification system, a diesel particulate filter is disposed in the exhaust gas flow path, and particulate matter (PM) in the exhaust gas is collected and burned to regenerate the diesel particulate filter. The particulate matter (PM) was purified (see Patent Document 1).

  Conventionally, in an exhaust gas purification system of a gasoline engine, a catalyst is disposed in an exhaust gas flow path, and hydrocarbons (HC), which are particulate matter (PM), in gasoline exhaust gas are burned and purified. .

JP 2006-125206 A

  However, in the exhaust gas purification system for a diesel engine described in Patent Document 1, when PM is collected in the diesel particulate filter, the exhaust pressure rises and the pressure loss increases. Therefore, the regeneration of the diesel particulate filter must be performed. There is a problem that it is necessary to carry out frequently and this leads to deterioration of fuel consumption.

  In addition, in the conventional exhaust gas purification system of a gasoline engine, the purification of PM in the gasoline exhaust gas was sufficient in the high temperature range, but the purification of the PM in the gasoline exhaust gas in the low temperature range was not sufficient. There was a problem.

  That is, both exhaust gas purification systems have a problem that the environmental load must be further reduced.

The present invention has been made in view of such problems of the prior art.
A first object is to provide an exhaust gas purification fiber filter capable of extending the regeneration interval of the diesel particulate filter, and an exhaust gas purification system for a diesel engine using the same.
A second object is to provide a fiber filter for exhaust gas purification that can improve the purification rate of PM in gasoline exhaust gas in a low temperature range, and an exhaust gas purification system for a gasoline engine using the same.

The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, the inventors have found that the above object can be achieved by adopting the configurations described in (1) to (3) below, and have completed the present invention.
(1): The exhaust gas-purifying fiber filter has a predetermined structure.
(2): It has a diesel particulate filter disposed in the exhaust gas passage of the diesel engine and an exhaust gas purification fiber filter having a predetermined structure disposed in the exhaust gas passage on the upstream side thereof.
(3): A catalyst disposed in the exhaust gas passage of the gasoline engine and an exhaust gas purification fiber filter having a predetermined structure disposed in the exhaust gas passage on the upstream side thereof.

  That is, the exhaust gas purifying fiber filter of the present invention is characterized in that the porosity is 70 to 90% and the thickness is 0.5 to 6 mm.

  The exhaust gas purification system for a diesel engine according to the present invention includes a diesel particulate filter disposed in the exhaust gas passage of the diesel engine, and the exhaust gas passage upstream of the diesel particulate filter, the void ratio 70 to 90% and a fiber filter for exhaust gas purification having a thickness of 0.5 to 6 mm.

  Furthermore, an exhaust gas purification system for a gasoline engine according to the present invention is provided with a catalyst disposed in an exhaust gas flow path of a gasoline engine, and the exhaust gas flow path upstream of the catalyst, with a porosity of 70 to 90%. And a fiber filter for exhaust gas purification having a thickness of 0.5 to 6 mm.

  According to the present invention, since it is configured as described in the above (1) to (3), the exhaust gas purification fiber filter capable of extending the regeneration interval of the diesel particulate filter, the exhaust gas purification system for diesel engines using the same, the low temperature An exhaust gas purification fiber filter that can improve the purification rate of PM in gasoline exhaust gas in the region, and an exhaust gas purification system for a gasoline engine using the same.

It is the perspective view (a) and enlarged view (b) which show the schematic structure of the fiber filter for exhaust gas purification of 1st Embodiment. It is the perspective view (a) and enlarged view (b) which show the schematic structure of the fiber filter for exhaust gas purification of 2nd Embodiment. It is explanatory drawing which shows the structure of the exhaust gas purification system for diesel engines of 1st Embodiment. It is explanatory drawing which shows the structure of the conventional exhaust gas purification system for diesel engines. It is explanatory drawing which shows the relationship between the diesel particulate filter regeneration interval and the amount of particulate matter deposition in the exhaust gas purification system for diesel engines of the conventional form and the exhaust gas purification system for diesel engines of the first embodiment. It is explanatory drawing which shows the structure of the exhaust gas purification system for diesel engines of 2nd Embodiment. It is explanatory drawing which shows the structure of the exhaust gas purification system for gasoline engines of 1st Embodiment. It is explanatory drawing which shows the structure which applied what is called a diesel particulate filter to the conventional exhaust gas purification system for gasoline engines. It is explanatory drawing which shows the structure of the exhaust gas purification system for gasoline engines of 2nd Embodiment. It is a graph which shows PM oxidation rate of the fiber filter of each example. It is a graph which shows the pressure loss of the fiber filter of each example. It is a graph which shows PM oxidation rate of the fiber filter of each example. It is a graph which shows PM oxidation rate of the fiber filter of each example. It is a graph which shows the pressure loss of the fiber filter of each example. It is a graph which shows PM oxidation rate of the fiber filter of each example.

  Hereinafter, an exhaust gas purification fiber filter, a diesel engine exhaust gas purification system, and a gasoline engine exhaust gas purification system according to embodiments of the present invention will be described in detail.

First, the fiber filter for exhaust gas purification which concerns on one Embodiment of this invention is demonstrated.
The fiber filter for exhaust gas purification of this embodiment has a porosity of 70 to 90% and a thickness in the exhaust gas flow direction of 0.5 to 6 mm.

When the porosity of the fiber filter for exhaust gas purification is less than 70%, the PM collection efficiency is improved, but the pressure loss is deteriorated. On the other hand, when the porosity of the fiber filter for exhaust gas purification exceeds 90%, the pressure loss is reduced. However, the PM collection efficiency deteriorates.
Moreover, when the thickness of the fiber filter for exhaust gas purification is less than 0.5 mm, the pressure loss decreases, but the PM collection efficiency deteriorates. On the other hand, when the thickness of the fiber filter for exhaust gas purification exceeds 6 mm, the PM collection efficiency Improves, but pressure loss worsens.

Moreover, the exhaust gas purifying fiber filter of the present embodiment is desirably an exhaust gas purifying fiber filter composed of fibers containing a catalyst component at least on the surface.
By using the fiber filter for exhaust gas purification comprising fibers containing a catalyst component on the surface, PM can be efficiently purified, and the PM purification performance of the fiber filter for exhaust gas purification can be further improved.

Furthermore, in this embodiment, it is desirable that the fibers are either one or both of metal fibers and inorganic fibers.
As the metal fiber and the inorganic fiber, those having heat resistance that is stable at 1000 ° C. or less are desirable. For example, the metal fiber can include a ferritic stainless steel fiber, and the inorganic fiber can be an alumina fiber or silica. Mention may be made of fibers.

In this embodiment, the catalyst component is platinum (Pt), palladium (Pd), rhodium (Rh), cerium (Ce), praseodymium (Pr), gallium (Ga), manganese (Mn), or yttrium (Y Or a catalyst component contained in any combination thereof. Among these, cerium praseodymium oxide, cerium oxide, and platinum can be cited as preferred examples.
Such a catalyst component has PM purification performance, and can further improve the PM purification performance of the exhaust gas purification fiber filter described above.

  Furthermore, it is desirable that the fiber has irregularities on the surface, the fiber diameter is desirably 5 to 50 μm, and more desirably 10 to 35 μm. When the surface has irregularities, for example, when a catalyst layer is formed on the surface, the adhesion with the catalyst layer forming slurry is improved, and a desired catalyst layer can be formed. Moreover, it is also possible to improve the PM trapping property by forming irregularities on the surface of the fiber. Furthermore, when the fiber diameter is 5 to 50 μm, preferably 10 to 35 μm, it is possible to improve the PM trapping property.

  Hereinafter, the fiber filter for exhaust gas purification of this embodiment is demonstrated in detail, referring drawings.

FIG. 1 is a perspective view (a) and an enlarged view (b) showing a schematic configuration of an exhaust gas purifying fiber filter of the first embodiment.
As shown in the figure, the circular exhaust gas purifying fiber filter 4 is composed of fibers 4a.
Needless to say, this exhaust gas purifying fiber filter has a porosity of 70 to 90% and a thickness of 0.5 to 6 mm.

FIG. 2 is a perspective view (a) and an enlarged view (b) illustrating a schematic configuration of the exhaust gas purifying fiber filter of the second embodiment.
As shown in the figure, the circular exhaust gas purifying fiber filter 4 is composed of fibers 4a containing a catalyst component 4b at least on the surface.
Needless to say, this exhaust gas-purifying fiber filter also has a porosity of 70 to 90% and a thickness of 0.5 to 6 mm.

The manufacturing method of the said exhaust gas purification fiber filter will be described in detail.
An example of a method for producing an exhaust gas purifying fiber filter when the exhaust gas purifying fiber filter is made of metal fibers will be described.
It is possible to form irregularities on the surface of the metal fiber by performing ultrasonic treatment or microwave treatment while immersing metal fiber (metal fiber before treatment) containing at least aluminum in an alcohol solvent or hydrocarbon solvent. it can.
Here, the pre-treatment metal fiber needs to contain aluminum, but the other components are not particularly limited, and for example, ferritic stainless steel can be used.

By forming irregularities on the surface of the metal fiber in this manner, for example, when a catalyst layer is formed on the surface, adhesion with the slurry for forming the catalyst layer is improved, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.
At the present time, when an oxidation / reduction reaction takes place between the alcohol solvent and the metal fiber, and aluminum is deposited on the surface portion, bubbles existing on the surface of the metal fiber can be removed. It is presumed that alcoholic solvents and the like can be distributed throughout, and a high-temperature field can be created as when heat treatment is performed by cavitation such as ultrasonic treatment.

Moreover, as an alcohol solvent to be used, it is desirable that it is a hydrophilic alcohol or contains it. Such hydrophilic alcohol acts on the pre-treatment metal fiber to deposit aluminum over the entire surface of the metal fiber, and uniformly forms a plurality of recesses and protrusions on the entire surface of the metal fiber. The adhesion with the slurry for forming the catalyst layer is improved, and a desired catalyst layer can be formed. Further, when a hydrophilic alcohol is used, a catalyst layer can be more uniformly formed on the surface of the metal fiber due to the reduction effect. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.
Here, “hydrophilic alcohol” refers to a substance that is uniformly mixed as a whole when mixed with water.

Further, the alcohol solvent preferably contains 70 to 99% by mass of a hydrophilic alcohol, more preferably 90 to 99% by mass.
When the content of the hydrophilic alcohol is in the range of 70 to 99% by mass, a plurality of concave portions and convex portions can be particularly uniformly formed on the entire surface of the metal fiber, and adhesion with the slurry for forming the catalyst layer is improved. The desired catalyst layer can be formed uniformly. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber. In addition, when content of hydrophilic alcohol is less than 70 mass%, it may become impossible to form a catalyst layer on the surface of a metal fiber uniformly.
In addition, as other containing components, although water can be mentioned typically, it is not limited to this, For example, ethylene, hexane, isopropyl alcohol, etc. may be contained.

  Examples of such hydrophilic alcohols include, but are not limited to, methanol, ethanol, 1-propanol or 2-propanol, and mixtures of any combination thereof. That is, hydrocarbon solvents such as ethylene, hexane, ethylene glycol, and glycerin can be used.

In addition, although not particularly limited, in performing ultrasonic treatment or microwave treatment, it is preferable that the treatment time is a time in which the precipitation amount of iron or chromium is smaller than the precipitation amount of aluminum.
By setting it as such processing time, adhesiveness with the slurry for catalyst layer formation improves, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.

Furthermore, it is desirable to perform further baking after ultrasonic treatment or microwave treatment.
If it does in this way, adhesiveness with the slurry for catalyst layer formation improves, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.
The firing conditions can be set as appropriate, and may be in an inert atmosphere such as argon or nitrogen or in an oxidizing atmosphere such as air. The firing temperature may be about 300 to 500 ° C., for example. For example, the time may be about 0.5 to 1.0 hour.
It is also preferable to set the firing temperature to a melting point temperature of not less than 800 ° C. and a metal fiber containing at least aluminum (transition metal before treatment) × 0.9 ° C. or less. Even if it does in this way, adhesiveness with the slurry for catalyst layer formation improves, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.

Next, an exhaust gas purification system for a diesel engine according to an embodiment of the present invention will be described.
The exhaust gas purification system for a diesel engine according to this embodiment includes a diesel particulate filter disposed in an exhaust gas passage of the diesel engine, and an exhaust gas purification fiber filter disposed in an exhaust gas passage upstream of the diesel particulate filter. It has.
The fiber filter for purifying exhaust gas has a porosity of 70 to 90% and a thickness in the exhaust gas flow direction of 0.5 to 6 mm.
Here, the diesel particulate filter has a plurality of cells that are closed at one end, and has end faces in which the closed ends and open ends of these cells are alternately arranged. It is called a monolith.

When the porosity of the fiber filter for exhaust gas purification is less than 70%, the PM collection efficiency is improved, but the pressure loss is deteriorated. On the other hand, when the porosity of the fiber filter for exhaust gas purification exceeds 90%, the pressure loss is reduced. However, the PM collection efficiency deteriorates.
Moreover, when the thickness of the fiber filter for exhaust gas purification is less than 0.5 mm, the pressure loss decreases, but the PM collection efficiency deteriorates. On the other hand, when the thickness of the fiber filter for exhaust gas purification exceeds 6 mm, the PM collection efficiency Improves, but pressure loss worsens.

In the present embodiment, it is desirable that the exhaust gas purifying fiber filter is disposed at a position where the temperature is highest in the exhaust gas flow path.
Since the exhaust gas purification fiber filter has a function of assisting the purification of PM in the diesel particulate filter disposed on the downstream side thereof, the exhaust gas purification fiber filter is disposed at the highest temperature position. Thus, the assist performance can be exhibited more effectively.
As such a position, a position where the exhaust gas flowing out from the diesel engine directly flows in can be mentioned, and a specific example can include an upstream side of a catalyst arranged at a so-called exhaust manifold outlet. The exhaust gas temperature here is 200 to 500 ° C. (however, it varies depending on the engine and displacement / running conditions) and is usually the highest temperature. Moreover, the position into which the exhaust gas which flowed out from the catalyst arrange | positioned upstream from a diesel particulate filter flows in directly can also be mentioned. This is because the temperature of the exhaust gas heated in such a catalyst may be higher than the temperature of the exhaust gas flowing out from the diesel engine. The exhaust gas temperature here may be 150 to 400 ° C. (however, it varies depending on the engine, displacement and running conditions).

Furthermore, in the present embodiment, it is desirable that the exhaust gas purifying fiber filter is an exhaust gas purifying fiber filter made of fibers containing a catalyst component at least on the surface.
By using the fiber filter for exhaust gas purification comprising fibers containing a catalyst component on the surface, PM can be efficiently purified, and the assist performance described above of the fiber filter for exhaust gas purification can be further improved.

In the present embodiment, it is desirable that the fiber is one or both of a metal fiber and an inorganic fiber.
As the metal fiber and the inorganic fiber, those having heat resistance that is stable at 1000 ° C. or less are desirable. For example, the metal fiber can include a ferritic stainless steel fiber, and the inorganic fiber can be an alumina fiber or silica. Mention may be made of fibers.

Furthermore, in this embodiment, the catalyst component is platinum (Pt), palladium (Pd), rhodium (Rh), cerium (Ce), praseodymium (Pr), gallium (Ga), manganese (Mn), or yttrium (Y Or a catalyst component contained in any combination thereof.
Such a catalyst component has PM purification performance, and can further improve the above-described assist performance of the exhaust gas purification fiber filter.

  Furthermore, it is desirable that the fiber has irregularities on the surface, the fiber diameter is desirably 5 to 50 μm, and more desirably 10 to 35 μm. When the surface has irregularities, for example, when a catalyst layer is formed on the surface, the adhesion with the catalyst layer forming slurry is improved, and a desired catalyst layer can be formed. Moreover, it is also possible to improve the PM trapping property by forming irregularities on the surface of the fiber. Furthermore, when the fiber diameter is 5 to 50 μm, preferably 10 to 35 μm, it is possible to improve the PM trapping property.

The manufacturing method of the fiber filter for exhaust gas purification applied to the said embodiment is demonstrated in detail.
An example of a method for producing an exhaust gas purifying fiber filter when the exhaust gas purifying fiber filter is made of metal fibers will be described.
It is possible to form irregularities on the surface of the metal fiber by performing ultrasonic treatment or microwave treatment while immersing metal fiber (metal fiber before treatment) containing at least aluminum in an alcohol solvent or hydrocarbon solvent. it can.
Here, the pre-treatment metal fiber needs to contain aluminum, but the other components are not particularly limited, and for example, ferritic stainless steel can be used.

By forming irregularities on the surface of the metal fiber in this manner, for example, when a catalyst layer is formed on the surface, adhesion with the slurry for forming the catalyst layer is improved, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.
At the present time, when an oxidation / reduction reaction takes place between the alcohol solvent and the metal fiber, and aluminum is deposited on the surface portion, bubbles existing on the surface of the metal fiber can be removed. It is presumed that alcoholic solvents and the like can be distributed throughout, and a high-temperature field can be created as when heat treatment is performed by cavitation such as ultrasonic treatment.

Moreover, as an alcohol solvent to be used, it is desirable that it is a hydrophilic alcohol or contains it. Such hydrophilic alcohol acts on the pre-treatment metal fiber to deposit aluminum over the entire surface of the metal fiber, and uniformly forms a plurality of recesses and protrusions on the entire surface of the metal fiber. The adhesion with the slurry for forming the catalyst layer is improved, and a desired catalyst layer can be formed. Further, when a hydrophilic alcohol is used, a catalyst layer can be more uniformly formed on the surface of the metal fiber due to the reduction effect. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.
Here, “hydrophilic alcohol” refers to a substance that is uniformly mixed as a whole when mixed with water.

Further, the alcohol solvent preferably contains 70 to 99% by mass of a hydrophilic alcohol, more preferably 90 to 99% by mass.
When the content of the hydrophilic alcohol is in the range of 70 to 99% by mass, a plurality of concave portions and convex portions can be particularly uniformly formed on the entire surface of the metal fiber, and adhesion with the slurry for forming the catalyst layer is improved. The desired catalyst layer can be formed uniformly. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber. In addition, when content of hydrophilic alcohol is less than 70 mass%, it may become impossible to form a catalyst layer on the surface of a metal fiber uniformly.
In addition, as other containing components, although water can be mentioned typically, it is not limited to this, For example, ethylene, hexane, isopropyl alcohol, etc. may be contained.

  Examples of such hydrophilic alcohols include, but are not limited to, methanol, ethanol, 1-propanol or 2-propanol, and mixtures of any combination thereof. That is, hydrocarbon solvents such as ethylene, hexane, ethylene glycol, and glycerin can be used.

In addition, although not particularly limited, in performing ultrasonic treatment or microwave treatment, it is preferable that the treatment time is a time in which the precipitation amount of iron or chromium is smaller than the precipitation amount of aluminum.
By setting it as such processing time, adhesiveness with the slurry for catalyst layer formation improves, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.

Furthermore, it is desirable to perform further baking after ultrasonic treatment or microwave treatment.
If it does in this way, adhesiveness with the slurry for catalyst layer formation improves, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.
The firing conditions can be set as appropriate, and may be in an inert atmosphere such as argon or nitrogen or in an oxidizing atmosphere such as air. The firing temperature may be about 300 to 500 ° C., for example. For example, the time may be about 0.5 to 1.0 hour.
It is also preferable to set the firing temperature to a melting point temperature of not less than 800 ° C. and a metal fiber containing at least aluminum (transition metal before treatment) × 0.9 ° C. or less. Even if it does in this way, adhesiveness with the slurry for catalyst layer formation improves, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.

Furthermore, the exhaust gas purification system for a diesel engine of the present embodiment includes an exhaust gas flow path upstream of the fiber filter for exhaust gas purification, and an exhaust gas flow downstream of the fiber filter for exhaust gas purification and upstream of the diesel particulate filter. It may have a catalyst disposed in one or both of the paths.
As such a catalyst, for example, a catalyst in which a catalyst layer containing an oxidation catalyst or a three-way catalyst is formed on the inner wall of a cell of an integral structure type carrier can be used.
Here, as the monolithic structure type carrier, for example, a monolith carrier or a honeycomb carrier made of a heat-resistant material such as ceramics such as cordierite or metals such as ferrite-based stainless steel is used.

  Hereinafter, the exhaust gas purification system for a diesel engine of the present embodiment will be described in detail with reference to the drawings.

FIG. 3 is an explanatory diagram illustrating a configuration of the exhaust gas purification system for a diesel engine according to the first embodiment.
As shown in the figure, an exhaust gas purification system 1 for a diesel engine according to the present embodiment includes a diesel particulate filter 2 disposed in an exhaust gas passage 8a of a diesel engine 8 and an exhaust gas upstream of the diesel particulate filter 2. An exhaust gas purification fiber filter 4 disposed in the flow path 8a, and an integral structure type three disposed in the exhaust gas flow path 8a downstream of the exhaust gas purification fiber filter 4 and upstream of the diesel particulate filter 2. The original catalyst 6 is included.
The exhaust gas-purifying fiber filter 4 has a porosity of 70 to 90% and a thickness in the exhaust gas flow direction of 0.5 to 6 mm. Further, the PM collection rate of the exhaust gas-purifying fiber filter is 40%.
Here, the collection rate of the exhaust gas purifying fiber filter can be calculated, for example, by measuring the PM distribution at the entrance and exit of the exhaust gas purifying fiber filter using, for example, a particle counter device (SMPS model 3936 manufactured by Tokyo Direc Co., Ltd.). it can.
The exhaust gas-purifying fiber filter 4 and the monolithic three-way catalyst 6 are disposed in the case 8b, and the diesel particulate filter 2 is also disposed in the case 8b.

FIG. 4 is an explanatory diagram showing a configuration of a conventional exhaust gas purification system for a diesel engine.
As shown in the figure, a conventional diesel engine exhaust gas purification system 10 includes a diesel particulate filter 2 disposed in an exhaust gas passage 8 a of a diesel engine 8, and an exhaust gas upstream of the diesel particulate filter 2. And a monolithic three-way catalyst 6 disposed in the flow path 8a.
The monolithic three-way catalyst 6 and the diesel particulate filter 2 are disposed in the case 8b.

FIG. 5 is an explanatory diagram showing the relationship between the diesel particulate filter regeneration interval and the particulate matter deposition amount in the exhaust gas purification system for diesel engines of the conventional form and the exhaust gas purification system for diesel engines of the first embodiment.
As shown in the figure, when the PM collection rate in the exhaust gas purification fiber filter is 40%, the diesel filter according to the first embodiment with respect to the particulate filter regeneration interval in the conventional exhaust gas purification system for diesel engines. The regeneration interval of the diesel particulate filter in the engine exhaust gas purification system can be increased by 40%.
Thus, the diesel engine exhaust gas purification system which is an example of this embodiment can improve fuel efficiency. In other words, the diesel particulate filter can be reduced in size and the cost can be reduced. Thereby, the freedom degree of the layout of an exhaust system improves. Furthermore, since PM can be reduced, an operation for further reducing NOx can be performed, and the exhaust gas purification rate can be improved.

FIG. 6 is an explanatory diagram showing a configuration of an exhaust gas purification system for a diesel engine according to the second embodiment.
As shown in the drawing, an exhaust gas purification system 1 ′ for a diesel engine according to the present embodiment includes a diesel particulate filter 2 disposed in an exhaust gas passage 8 a of the diesel engine 8, and an upstream side of the diesel particulate filter 2. An exhaust gas purification fiber filter 4 disposed in the exhaust gas flow path 8a and an integral structure type three-way catalyst 6 disposed in the exhaust gas flow path 8a upstream of the exhaust gas purification fiber filter 4 are provided.
The exhaust gas-purifying fiber filter 4 has a porosity of 70 to 90% and a thickness in the exhaust gas flow direction of 0.5 to 6 mm.

Even with such an exhaust gas purification system for a diesel engine, the same effects as those of the first embodiment can be obtained.
Such a configuration is particularly effective when the temperature of the exhaust gas flowing out from the monolithic three-way catalyst is higher than the temperature of the exhaust gas flowing out from the diesel engine.

Next, an exhaust gas purification system for a gasoline engine according to an embodiment of the present invention will be described.
The exhaust gas purification system for a gasoline engine according to the present embodiment includes a catalyst disposed in an exhaust gas passage of the gasoline engine and an exhaust gas purification fiber filter disposed in an exhaust gas passage upstream of the catalyst. .
The fiber filter for purifying exhaust gas has a porosity of 70 to 90% and a thickness in the exhaust gas flow direction of 0.5 to 6 mm.
Here, examples of the catalyst include those in which a catalyst layer containing an oxidation catalyst or a three-way catalyst is formed on the inner wall of a cell of a monolithic structure type carrier.
Further, as the monolithic structure type carrier, for example, a monolith carrier or a honeycomb carrier made of a heat resistant material such as ceramics such as cordierite or metals such as ferritic stainless steel is used.

When the porosity of the fiber filter for exhaust gas purification is less than 70%, the PM collection efficiency is improved, but the pressure loss is deteriorated. On the other hand, when the porosity of the fiber filter for exhaust gas purification exceeds 90%, the pressure loss is reduced. However, the PM collection efficiency deteriorates.
Moreover, when the thickness of the fiber filter for exhaust gas purification is less than 0.5 mm, the pressure loss decreases, but the PM collection efficiency deteriorates. On the other hand, when the thickness of the fiber filter for exhaust gas purification exceeds 6 mm, the PM collection efficiency Improves, but pressure loss worsens.
In addition, PM in gasoline exhaust gas is easily oxidized such as paraffin, olefin, naphthene, etc., but the purification of PM in gasoline exhaust gas in a low temperature region by arranging such a predetermined exhaust gas purification fiber filter. The improvement effect is remarkable.
Moreover, such an exhaust gas purification system for a gasoline engine is remarkably excellent in terms of cost and layout. In other words, when a so-called diesel particulate filter called a checkered honeycomb or a wall flow monolith is disposed in the exhaust gas flow path of a gasoline engine, there is a risk that the pressure loss will be extremely high, and the collected PM is burned. There is a need to increase the cost to control them. Moreover, it is necessary to consider heat resistance, and the freedom degree of a layout will fall.

In the present embodiment, it is desirable that the exhaust gas purifying fiber filter is disposed at a position where the temperature is highest in the exhaust gas flow path.
An exhaust gas purification fiber filter improves the purification rate of PM in gasoline exhaust gas in a low temperature range. By arranging the exhaust gas purification fiber filter at the highest temperature position, the PM purification performance is further improved. It can be exhibited effectively, and so-called continuous reproduction can also be performed.
Examples of such a position include a position where exhaust gas flowing out from a gasoline engine directly flows (exhaust uppermost stream), and specific examples include an upstream side of a catalyst disposed at a so-called exhaust manifold outlet. it can. The exhaust gas temperature here is 200 to 500 ° C. (however, it varies depending on the engine and displacement / running conditions) and is usually the highest temperature.

Furthermore, in the present embodiment, it is desirable that the exhaust gas purifying fiber filter is an exhaust gas purifying fiber filter made of fibers containing a catalyst component at least on the surface.
By using the fiber filter for exhaust gas purification comprising fibers containing a catalyst component on the surface, PM can be efficiently purified, and the PM purification performance of the fiber filter for exhaust gas purification can be further improved.

In the present embodiment, it is desirable that the fiber is one or both of a metal fiber and an inorganic fiber.
As the metal fiber and the inorganic fiber, those having heat resistance that is stable at 1000 ° C. or less are desirable. For example, the metal fiber can include a ferritic stainless steel fiber, and the inorganic fiber can be an alumina fiber or silica. Mention may be made of fibers.

Furthermore, in this embodiment, the catalyst component is platinum (Pt), palladium (Pd), rhodium (Rh), cerium (Ce), praseodymium (Pr), gallium (Ga), manganese (Mn), or yttrium (Y Or a catalyst component contained in any combination thereof. Among these, cerium praseodymium oxide, cerium oxide, and platinum can be cited as preferred examples.
Such a catalyst component has PM purification performance, and can further improve the PM purification performance of the exhaust gas purification fiber filter described above.

  Furthermore, it is desirable that the fiber has irregularities on the surface, the fiber diameter is desirably 5 to 50 μm, and more desirably 10 to 35 μm. When the surface has irregularities, for example, when a catalyst layer is formed on the surface, the adhesion with the catalyst layer forming slurry is improved, and a desired catalyst layer can be formed. Moreover, it is also possible to improve the PM trapping property by forming irregularities on the surface of the fiber. Furthermore, when the fiber diameter is 5 to 50 μm, preferably 10 to 35 μm, it is possible to improve the PM trapping property.

The manufacturing method of the fiber filter for exhaust gas purification applied to the said embodiment is demonstrated in detail.
An example of a method for producing an exhaust gas purifying fiber filter when the exhaust gas purifying fiber filter is made of metal fibers will be described.
It is possible to form irregularities on the surface of the metal fiber by performing ultrasonic treatment or microwave treatment while immersing metal fiber (metal fiber before treatment) containing at least aluminum in an alcohol solvent or hydrocarbon solvent. it can.
Here, the pre-treatment metal fiber needs to contain aluminum, but the other components are not particularly limited, and for example, ferritic stainless steel can be used.

By forming irregularities on the surface of the metal fiber in this manner, for example, when a catalyst layer is formed on the surface, adhesion with the slurry for forming the catalyst layer is improved, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.
At the present time, when an oxidation / reduction reaction takes place between the alcohol solvent and the metal fiber, and aluminum is deposited on the surface portion, bubbles existing on the surface of the metal fiber can be removed. It is presumed that alcoholic solvents and the like can be distributed throughout, and a high-temperature field can be created as when heat treatment is performed by cavitation such as ultrasonic treatment.

Moreover, as an alcohol solvent to be used, it is desirable that it is a hydrophilic alcohol or contains it. Such hydrophilic alcohol acts on the pre-treatment metal fiber to deposit aluminum over the entire surface of the metal fiber, and uniformly forms a plurality of recesses and protrusions on the entire surface of the metal fiber. The adhesion with the slurry for forming the catalyst layer is improved, and a desired catalyst layer can be formed. Further, when a hydrophilic alcohol is used, a catalyst layer can be more uniformly formed on the surface of the metal fiber due to the reduction effect. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.
Here, “hydrophilic alcohol” refers to a substance that is uniformly mixed as a whole when mixed with water.

Further, the alcohol solvent preferably contains 70 to 99% by mass of a hydrophilic alcohol, more preferably 90 to 99% by mass.
When the content of the hydrophilic alcohol is in the range of 70 to 99% by mass, a plurality of concave portions and convex portions can be particularly uniformly formed on the entire surface of the metal fiber, and adhesion with the slurry for forming the catalyst layer is improved. The desired catalyst layer can be formed uniformly. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber. In addition, when content of hydrophilic alcohol is less than 70 mass%, it may become impossible to form a catalyst layer on the surface of a metal fiber uniformly.
In addition, as other containing components, although water can be mentioned typically, it is not limited to this, For example, ethylene, hexane, isopropyl alcohol, etc. may be contained.

  Examples of such hydrophilic alcohols include, but are not limited to, methanol, ethanol, 1-propanol or 2-propanol, and mixtures of any combination thereof. That is, hydrocarbon solvents such as ethylene, hexane, ethylene glycol, and glycerin can be used.

In addition, although not particularly limited, in performing ultrasonic treatment or microwave treatment, it is preferable that the treatment time is a time in which the precipitation amount of iron or chromium is smaller than the precipitation amount of aluminum.
By setting it as such processing time, adhesiveness with the slurry for catalyst layer formation improves, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.

Furthermore, it is desirable to perform further baking after ultrasonic treatment or microwave treatment.
If it does in this way, adhesiveness with the slurry for catalyst layer formation improves, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.
The firing conditions can be set as appropriate, and may be in an inert atmosphere such as argon or nitrogen or in an oxidizing atmosphere such as air. The firing temperature may be about 300 to 500 ° C., for example. For example, the time may be about 0.5 to 1.0 hour.
It is also preferable to set the firing temperature to a melting point temperature of not less than 800 ° C. and a metal fiber containing at least aluminum (transition metal before treatment) × 0.9 ° C. or less. Even if it does in this way, adhesiveness with the slurry for catalyst layer formation improves, and a desired catalyst layer can be formed. Moreover, it is also possible to improve PM trapping properties by forming irregularities on the surface of the metal fiber.

  Hereinafter, the exhaust gas purification system for a gasoline engine of this embodiment will be described in detail with reference to the drawings.

FIG. 7 is an explanatory diagram showing the configuration of the exhaust gas purification system for a gasoline engine according to the first embodiment.
As shown in the figure, an exhaust gas purification system 1 '' for a gasoline engine according to this embodiment includes an integral structure type three-way catalyst 6 disposed at an exhaust manifold hole outlet of an exhaust gas passage 8a of a gasoline engine 8 '; And an exhaust gas purification fiber filter 4 disposed in the exhaust gas flow path 8a upstream of the monolithic three-way catalyst 6.
The exhaust gas-purifying fiber filter 4 has a porosity of 70 to 90% and a thickness in the exhaust gas flow direction of 0.5 to 6 mm. Further, the PM collection rate of the exhaust gas-purifying fiber filter is 40%.
Here, the collection rate of the exhaust gas purifying fiber filter can be calculated, for example, by measuring the PM distribution at the entrance and exit of the exhaust gas purifying fiber filter using, for example, a particle counter device (SMPS model 3936 manufactured by Tokyo Direc Co., Ltd.). it can.
The monolithic three-way catalyst 6 and the exhaust gas purification fiber filter 4 are disposed in the case 8b.

FIG. 8 is an explanatory diagram showing a configuration in which a so-called diesel particulate filter is applied to a conventional exhaust gas purification system for a gasoline engine.
As shown in the figure, an exhaust gas purification system 10 ′ for a gasoline engine includes a so-called diesel particulate filter 2 disposed in an exhaust gas flow path 8 a of the gasoline engine 8 ′, and an exhaust gas flow upstream of the diesel particulate filter 2. And a monolithic three-way catalyst 6 disposed at the outlet of the exhaust manifold in the path 8a.
The diesel particulate filter 2 and the integral structure type three-way catalyst 6 are respectively disposed in the case 8b.
Further, the PM collection rate of this diesel particulate filter is almost 100%.

FIG. 9 is an explanatory diagram showing a configuration of an exhaust gas purification system for a gasoline engine according to the second embodiment.
As shown in the figure, an exhaust gas purification system 1 ′ ″ for a gasoline engine according to this embodiment includes two integrated three-way catalysts 6, 6 ′ disposed in an exhaust gas flow path 8a of a gasoline engine 8 ′. The exhaust gas purification fiber filter 4 is disposed in the exhaust gas flow path 8a upstream of the monolithic three-way catalyst 6. The monolithic three-way catalyst 6 disposed together with the exhaust gas purification fiber filter 4 is located at the exhaust manifold outlet of the exhaust gas passage 8a.
The exhaust gas-purifying fiber filter 4 has a porosity of 70 to 90% and a thickness in the exhaust gas flow direction of 0.5 to 6 mm. Further, the PM collection rate of the exhaust gas-purifying fiber filter is 40%.
The integral structure type three-way catalyst 6 and the exhaust gas purifying fiber filter 4 and the integral structure type three-way catalyst 6 'are respectively disposed in the case 8b.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

(Example 1-1-1)
<Fabrication of exhaust gas purification fiber filter>
A nonwoven fabric was produced by paper making using metal fibers (material: ferritic stainless steel).
The obtained non-woven fabric is subjected to ultrasonic treatment for 15 minutes while being immersed in ethanol (concentration: 99% by mass), which is an example of an alcohol solvent, and is naturally dried all day and night, and further dried at 130 ° C. for 1 hour. Then, it was fired in the atmosphere at 400 ° C. for 30 minutes to produce a fiber filter for exhaust gas purification.
A catalyst layer forming slurry containing cerium (Ce) was applied to the obtained exhaust gas purifying fiber filter, excess slurry was removed, dried and fired to obtain an exhaust gas purifying fiber filter of this example.
The obtained fiber filter for exhaust gas purification had a porosity of 70% and a thickness of 3 mm. Further, the fiber constituting the exhaust gas purifying fiber filter had a fiber diameter of 35 μm.

(Examples 1-1-2 to 1-1-16)
Except having replaced the catalyst component as shown in Table 1, the same operation as Example 1-1-1 was repeated, and the exhaust gas purification fiber filter of each example was obtained.

[PM oxidation performance]
The PM oxidation rate of the exhaust gas purifying fiber filter of each example was calculated as follows. The obtained results are also shown in Table 1.
First, the fiber filter for exhaust gas purification obtained in Example 1-1-1 was arranged so that the fiber filter inlet temperature was 350 ° C. in the exhaust gas passage of a diesel engine (displacement: 2500 cc, manufactured by Nissan Motor Co., Ltd.). And particulate matter was deposited. The amount of particulate matter deposition (B _PM ) was measured from the mass difference before and after deposition.
Next, a diesel particulate filter for collecting particulate matter is disposed in the exhaust gas flow channel upstream of the fiber filter for exhaust gas purification on which particulate matter has been deposited so that the inlet temperature of the exhaust gas purification fiber filter becomes 480 ° C. Then, the deposited particulate matter was oxidized, and the remaining particulate matter deposition amount (A _PM ) was measured.
The PM oxidation rate was calculated from the following formula (1).

PM oxidation rate (%) = (B _PM −A _PM ) / B _PM (1)

  For Examples 1-1-2 to 1-1-16, the PM oxidation rate was calculated in the same manner.

(Examples 1-2-1 to 1-2-8, Comparative Examples 1-2-1 to 1-2-3)
The porosity of the exhaust gas purifying fiber filter and the thickness of the exhaust gas purifying fiber filter were respectively set (Example 1-2-1: 70%, 1.5 mm, Example 1-2-2: 70%, 0.5 mm Example 1-2-3: 85%, 3 mm, Example 1-2-4: 85%, 1.5 mm, Example 1-2-5: 85%, 0.5 mm, Example 1-2-6 90%, 6 mm, Example 1-2-7: 90%, 3 mm, Example 1-2-8: 90%, 1.5 mm, Comparative Example 1-2-1: 50%, 3 mm, Comparative Example 1 2-2: 50%, 1.5 mm, Comparative Example 1-2-3: 50%, 0.5 mm) An exhaust gas purification fiber filter was obtained.
The PM oxidation rate of the exhaust gas purification fiber filter in each example was calculated in the same manner as in Example 1-1-1. The obtained results (including Example 1-1-3) are shown in FIG.

[Pressure loss]
The pressure loss of the exhaust gas purification fiber filter in each example was calculated as follows. The obtained results (including Example 1-1-3) are shown in FIG.
First, the exhaust gas purification fiber filter obtained in Example 1-2-1 was disposed in the exhaust gas passage of a diesel engine (displacement: 2500 cc, manufactured by Nissan Motor Co., Ltd.). The pressure was measured to determine the pressure loss value. In addition, the value of the pressure loss was assumed to be when 120 minutes had elapsed.
For Examples 1-2-2 to 1-2-8, Comparative Examples 1-2-1 to 1-2-3 and Example 1-1-3, the pressure loss was calculated by the same operation.

(Examples 1-3-1 to 1-3-6, Comparative Examples 1-3-1 to 1-3-3)
The fiber diameter of the fiber constituting the exhaust gas purifying fiber filter, the porosity of the exhaust gas purifying fiber filter, and the thickness of the exhaust gas purifying fiber filter (Example 1-3-1: 50 μm, 70%, 3 mm, Example 1), respectively. 3-3-2: 50 μm, 70%, 1.5 mm, Example 1-3-3: 50 μm, 70%, 0.5 mm, Example 1-3-4: 50 μm, 90%, 6 mm, Example 1 3-5: 50 μm, 90%, 3 mm, Example 1-3-6: 50 μm, 90%, 1.5 mm, Comparative Example 1-3-1: 50 μm, 50%, 3 mm, Comparative Example 1-3-2 : 50 μm, 50%, 1.5 mm, Comparative Example 1-3-3: 50 μm, 50%, 0.5 mm) An example exhaust gas purifying fiber filter was obtained.
The PM oxidation rate of the exhaust gas purification fiber filter in each example was calculated in the same manner as in Example 1-1-1. The obtained result is shown in FIG.

  10 and 11, it can be seen that the exhaust gas purifying fiber filter belonging to the scope of the present invention can have a longer regeneration interval than the exhaust gas purifying fiber filter outside the present invention.

(Example 2-1-1)
<Fabrication of exhaust gas purification fiber filter>
A nonwoven fabric was produced by paper making using metal fibers (material: ferritic stainless steel).
The obtained non-woven fabric is subjected to ultrasonic treatment for 15 minutes while being immersed in ethanol (concentration: 99% by mass), which is an example of an alcohol solvent, and is naturally dried all day and night, and further dried at 130 ° C. for 1 hour. Then, it was fired in the atmosphere at 400 ° C. for 30 minutes to produce a fiber filter for exhaust gas purification.
A catalyst layer forming slurry containing cerium (Ce) was applied to the obtained exhaust gas purifying fiber filter, excess slurry was removed, dried and fired to obtain the exhaust gas purifying fiber filter used in this example.
The obtained fiber filter for exhaust gas purification had a porosity of 70% and a thickness of 3 mm. Further, the fiber constituting the exhaust gas purifying fiber filter had a fiber diameter of 35 μm.

<Production of three-way catalyst>
The three-way catalyst used in this example is a Pd and Rh supported catalyst, the catalyst honeycomb capacity is 0.94 L, the supported amount of Pt and Rh is 3.5 g, and the supported weight ratio of Pt and Rh is Pt: Rh = 11: 1.

<Production of diesel particulate filter>
The particulate filter used in this example supported Pt, the catalyst honeycomb capacity was 2.5 L, and the supported amount of Pt was 2.5 g.

<Construction of exhaust gas purification system>
As shown in FIG. 3, the produced exhaust gas purification fiber filter, three-way catalyst, and diesel particulate filter were disposed in the exhaust gas flow path of the diesel engine to construct an exhaust gas purification system for a diesel engine of this example.

(Examples 2-1 to 2-1-16)
In the production of the exhaust gas purification fiber filter, the same operation as in Example 2-1-1 was repeated except that the catalyst component was changed as shown in Table 1, and the exhaust gas purification system for a diesel engine of each example was constructed. did.

(Examples 2-2-1 to 2-2-8, Comparative Examples 2-2-1 to 2-2-3)
In the production of the exhaust gas purifying fiber filter, the porosity of the exhaust gas purifying fiber filter and the thickness of the exhaust gas purifying fiber filter were respectively set to (Example 2-2-1: 70%, 1.5 mm, Example 2-2-2). : 70%, 0.5 mm, Example 2-2-3: 85%, 3 mm, Example 2-2-4: 85%, 1.5 mm, Example 2-2-5: 85%, 0.5 mm Example 2-2-6: 90%, 6 mm, Example 2-2-7: 90%, 3 mm, Example 2-2-8: 90%, 1.5 mm, Comparative Example 2-2-1: 50%, 3 mm, Comparative Example 2-2-2: 50%, 1.5 mm, Comparative Example 2-2-3: 50%, 0.5 mm) The same operation was repeated, and the exhaust gas purification system for diesel engines of each example was constructed.

(Examples 2-3-1 to 2-3-6, Comparative Examples 2-3-1 to 2-3-3)
In the production of the exhaust gas purifying fiber filter, the fiber diameter of the fiber constituting the exhaust gas purifying fiber filter, the porosity of the exhaust gas purifying fiber filter, and the thickness of the exhaust gas purifying fiber filter were respectively set (Example 2-3-1: 50 μm). 70%, 3 mm, Example 2-3-2: 50 μm, 70%, 1.5 mm, Example 2-3-3: 50 μm, 70%, 0.5 mm, Example 2-3-4: 50 μm, 90%, 6 mm, Example 2-3-5: 50 μm, 90%, 3 mm, Example 2-3-6: 50 μm, 90%, 1.5 mm, Comparative Example 2-3-1: 50 μm, 50%, 3 mm, Comparative Example 2-3-2: 50 μm, 50%, 1.5 mm, Comparative Example 2-3-3: 50 μm, 50%, 0.5 mm) Repeat the same operation as in step 1 to To construct a scan purification system.

10 and 11, it can be seen that the exhaust gas purification system for diesel engines belonging to the scope of the present invention can have a longer regeneration interval than the exhaust gas purification system for diesel engines outside the present invention.
In addition, as shown in FIG. 3, it can be seen that more excellent PM purification performance can be exhibited by disposing an exhaust gas purification fiber filter at a position where the exhaust gas flowing out of the diesel engine directly flows.
Furthermore, it can be seen that more excellent PM purification performance can be exhibited by applying an exhaust gas purification fiber filter made of fibers containing a predetermined catalyst component at least on the surface.
Furthermore, it can be seen that metal fibers and inorganic fibers can be suitably applied with excellent heat resistance as the fibers constituting the exhaust gas purifying fiber filter.

(Example 3-1-1)
<Fabrication of exhaust gas purification fiber filter>
A nonwoven fabric was produced by paper making using metal fibers (material: ferritic stainless steel).
The obtained non-woven fabric is subjected to ultrasonic treatment for 15 minutes while being immersed in ethanol (concentration: 99% by mass), which is an example of an alcohol solvent, and is naturally dried all day and night, and further dried at 130 ° C. for 1 hour. Then, it was fired in the atmosphere at 400 ° C. for 30 minutes to produce a fiber filter for exhaust gas purification.
A catalyst layer forming slurry containing cerium (Ce) was applied to the obtained exhaust gas purifying fiber filter, excess slurry was removed, dried and fired to obtain an exhaust gas purifying fiber filter of this example.
The obtained fiber filter for exhaust gas purification had a porosity of 70% and a thickness of 3 mm. Further, the fiber constituting the exhaust gas purifying fiber filter had a fiber diameter of 35 μm.

(Examples 3-1-2 to 3-1-16)
Except that the catalyst component was changed as shown in Table 2, the same operation as in Example 3-1-1 was repeated to obtain an exhaust gas purification fiber filter of each example.

[PM oxidation performance]
The PM oxidation rate of the exhaust gas purifying fiber filter of each example was calculated as follows. The obtained results are also shown in Table 2.
First, the exhaust gas purification fiber filter obtained in Example 3-1-1 has an exhaust gas purification fiber filter inlet temperature of 350 ° C. in the exhaust gas passage of a gasoline engine (displacement: 2500 cc, manufactured by Nissan Motor Co., Ltd.). The particulate matter was deposited. The amount of particulate matter deposition (B _PM ) was measured from the mass difference before and after deposition.
Next, a diesel particulate filter for collecting particulate matter is disposed in the exhaust gas flow channel upstream of the fiber filter for exhaust gas purification on which particulate matter has been deposited so that the fiber filter inlet temperature is 480 ° C. The deposited particulate matter was oxidized, and the remaining particulate matter deposition amount (A _PM ) was measured.
The PM oxidation rate was calculated from the following formula (2).

PM oxidation rate (%) = (B _PM −A _PM ) / B _PM (2)

  For Examples 3-1-2 to 3-1-16, the PM oxidation rate was calculated in the same manner.

(Examples 3-2-1 to 2-3-2-8, Comparative Examples 3-2-1 to 2-3-2-3)
The porosity of the exhaust gas purifying fiber filter and the thickness of the exhaust gas purifying fiber filter were respectively set (Example 3-2-1: 70%, 1.5 mm, Example 3-2-2: 70%, 0.5 mm. Example 3-2-3: 85%, 3 mm, Example 3-2-4: 85%, 1.5 mm, Example 3-2-5: 85%, 0.5 mm, Example 3-2-6: 90%, 6 mm, Example 3-2-7: 90%, 3 mm, Example 3-2-8: 90%, 1.5 mm, Comparative Example 3-2-1: 50%, 3 mm, Comparative Example 3- 2-2: 50%, 1.5 mm, Comparative Example 3-2-3: 50%, 0.5 mm) An exhaust gas purification fiber filter was obtained.
The PM oxidation rate of the exhaust gas purifying fiber filter in each example was calculated in the same manner as in Example 3-1-1. The obtained results (including Example 3-1-3) are shown in FIG.

[Pressure loss]
The pressure loss of the exhaust gas purification fiber filter in each example was calculated as follows. The obtained results (including Example 3-1-3) are shown in FIG.
First, the exhaust gas purification fiber filter obtained in Example 3-2-1 was disposed in the exhaust gas passage of a gasoline engine (displacement: 2500 cc, manufactured by Nissan Motor Co., Ltd.) The pressure was measured to determine the pressure loss value. In addition, the value of the pressure loss was assumed to be when 120 minutes had elapsed.
For Examples 3-2-2 to 3-2-8, Comparative Examples 3-2-1 to 2-3-2-3 and Example 3-1-3, the pressure loss was calculated in the same manner.

(Examples 3-3-1 to 3-3-6, Comparative examples 3-3-1 to 3-3-3)
The fiber diameter of the fiber constituting the exhaust gas purifying fiber filter, the porosity of the exhaust gas purifying fiber filter, and the thickness of the exhaust gas purifying fiber filter (Example 3-3-1: 50 μm, 70%, 3 mm, Example 3), respectively. 3-3-2: 50 μm, 70%, 1.5 mm, Example 3-3-3: 50 μm, 70%, 0.5 mm, Example 3-3-4: 50 μm, 90%, 6 mm, Example 3- 3-5: 50 μm, 90%, 3 mm, Example 3-3-6: 50 μm, 90%, 1.5 mm, Comparative Example 3-3-1: 50 μm, 50%, 3 mm, Comparative Example 3-3-2 : 50 μm, 50%, 1.5 mm, Comparative Example 3-3-3: 50 μm, 50%, 0.5 mm) An example exhaust gas purifying fiber filter was obtained.
The PM oxidation rate of the exhaust gas purifying fiber filter in each example was calculated in the same manner as in Example 3-1-1. The obtained result is shown in FIG.

  From FIG. 13 and FIG. 14, it can be seen that the exhaust gas purification fiber filter belonging to the scope of the present invention can improve the cold PM purification performance.

(Example 4-1-1)
<Fabrication of exhaust gas purification fiber filter>
A nonwoven fabric was produced by paper making using metal fibers (material: ferritic stainless steel).
The obtained non-woven fabric is subjected to ultrasonic treatment for 15 minutes while being immersed in ethanol (concentration: 99% by mass), which is an example of an alcohol solvent, and is naturally dried all day and night, and further dried at 130 ° C. for 1 hour. Then, it was fired in the atmosphere at 400 ° C. for 30 minutes to produce a fiber filter for exhaust gas purification.
A catalyst layer forming slurry containing cerium (Ce) was applied to the obtained exhaust gas purifying fiber filter, excess slurry was removed, dried and fired to obtain the exhaust gas purifying fiber filter used in this example.
The obtained fiber filter for exhaust gas purification had a porosity of 70% and a thickness of 3 mm. Further, the fiber constituting the exhaust gas purifying fiber filter had a fiber diameter of 35 μm.

<Production of three-way catalyst>
The three-way catalyst used in this example is a Pd and Rh supported catalyst, the catalyst honeycomb capacity is 0.94 L, the supported amount of Pt and Rh is 3.5 g, and the supported weight ratio of Pt and Rh is Pt: Rh = 11: 1.

<Construction of exhaust gas purification system>
As shown in FIG. 7, the produced exhaust gas purification fiber filter and the three-way catalyst were arranged in the exhaust gas passage of the gasoline engine to construct an exhaust gas purification system for the gasoline engine of this example.

(Examples 4-1-2 to 4-1-16)
In the production of the exhaust gas purification fiber filter, the same operation as in Example 4-1-1 was repeated except that the catalyst component was changed as shown in Table 1, and the exhaust gas purification system for a gasoline engine of each example was constructed. did.

(Comparative Example 4-1-1)
<Preparation of particulate filter>
The particulate filter used in this example supported Pt, the catalyst honeycomb capacity was 2.5 L, and the supported amount of Pt was 2.5 g.

<Construction of exhaust gas purification system>
As shown in FIG. 8, the produced particulate filter and the three-way catalyst were arranged in the exhaust gas flow path of the gasoline engine to construct the exhaust gas purification system for gasoline engine of this example.

(Examples 4-2-1 to 4-2-8, comparative examples 4-2-1 to 4-2-3)
In the production of the exhaust gas purifying fiber filter, the porosity of the exhaust gas purifying fiber filter and the thickness of the exhaust gas purifying fiber filter were respectively set to (Example 4-2-1: 70%, 1.5 mm, Example 4-2-2). : 70%, 0.5 mm, Example 4-2-3: 85%, 3 mm, Example 4-2-4: 85%, 1.5 mm, Example 4-2-5: 85%, 0.5 mm Example 4-2-6: 90%, 6 mm, Example 4-2-7: 90%, 3 mm, Example 4-2-8: 90%, 1.5 mm, Comparative Example 4-2-1 50%, 3 mm, Comparative Example 4-2-2: 50%, 1.5 mm, Comparative Example 4-2-3: 50%, 0.5 mm) The same operation was repeated to construct an exhaust gas purification system for a gasoline engine of each example.

(Examples 4-3-1 to 4-3-6, Comparative examples 4-3-1 to 4-3-3)
In the production of the exhaust gas purifying fiber filter, the fiber diameter of the fiber constituting the exhaust gas purifying fiber filter, the porosity of the exhaust gas purifying fiber filter, and the thickness of the exhaust gas purifying fiber filter were respectively set (Example 4-3-1: 50 μm). 70%, 3 mm, Example 4-3-2: 50 μm, 70%, 1.5 mm, Example 4-3-3: 50 μm, 70%, 0.5 mm, Example 4-3-4: 50 μm, 90%, 6 mm, Example 4-3-5: 50 μm, 90%, 3 mm, Example 4-3-6: 50 μm, 90%, 1.5 mm, Comparative Example 4-3-1: 50 μm, 50%, 3 mm, Comparative Example 4-3-2: 50 μm, 50%, 1.5 mm, Comparative Example 4-3-3: 50 μm, 50%, 0.5 mm) Repeat the same operation to remove the gasoline engine exhaust gas for each example. To construct a purification system.

[PM purification performance in low temperature range]
In the exhaust gas purification system for a gasoline engine in each example, PM purification performance in a low temperature region was measured by the following measurement method. The obtained results are shown in Table 3. Table 3 also shows a part of the specifications of each system and the pressure loss value of the used exhaust gas purification fiber filter. In addition, the value of the pressure loss was assumed to be when 120 minutes had elapsed.

(Measuring method)
The PM purification rate from 0 to 300 seconds in LA4 evaluation was determined and evaluated as the PM purification performance in a low temperature range. The catalyst inlet temperature was 300 ° C. on average.

From Table 3, it can be seen that each Example belonging to the scope of the present invention has better cold PM purification performance than each Comparative Example outside the present invention. In addition, the pressure loss of Comparative Example 4-2-1 was significantly higher than that of Example 4-2-1.
Further, as shown in FIG. 7, it can be seen that more excellent PM purification performance can be exhibited by disposing an exhaust gas purification fiber filter at a position where the exhaust gas flowing out from the gasoline engine directly flows.
Furthermore, it can be seen that more excellent PM purification performance can be exhibited by applying an exhaust gas purification fiber filter made of fibers containing a predetermined catalyst component at least on the surface.
Furthermore, it can be seen that metal fibers and inorganic fibers can be suitably applied with excellent heat resistance as the fibers constituting the exhaust gas purifying fiber filter.

  As mentioned above, although this invention was demonstrated with some embodiment and an Example, this invention is not limited to these, A various deformation | transformation is possible within the range of the summary of this invention.

  For example, in the above-described embodiment of the exhaust gas purification system for a gasoline engine, as an example of the case where two catalysts are provided, the case where two integral structure type three-way catalysts are provided has been described, but the present invention is not limited thereto. Absent. For example, various catalysts such as an oxidation catalyst, a three-way catalyst, and a NOx purification catalyst can be appropriately combined. Further, three or more catalysts may be provided.

1, 1 ', 10 Exhaust gas purification system for diesel engine 1 ", 1'", 10 'Exhaust gas purification system for gasoline engine 2 Diesel particulate filter 4 Exhaust gas purification fiber filter 4a Fiber 4b Catalyst component 6, 6' Integrated Structural type three way catalyst 8 Diesel engine 8 'Gasoline engine 8a Exhaust gas flow path 8b Case

Claims (12)

  A fiber filter for exhaust gas purification having a porosity of 70 to 90% and a thickness of 0.5 to 6 mm. A diesel particulate filter disposed in the exhaust gas flow path of the diesel engine;
An exhaust gas purification fiber filter disposed in the exhaust gas flow channel upstream of the diesel particulate filter, having a porosity of 70 to 90% and a thickness of 0.5 to 6 mm. A featured exhaust gas purification system for diesel engines.   The exhaust gas purification system for a diesel engine according to claim 2, wherein the exhaust gas purification fiber filter is disposed at a position where the temperature is highest in the exhaust gas flow path.   4. The exhaust gas purification system for diesel engines according to claim 2, wherein the exhaust gas purification fiber filter is an exhaust gas purification fiber filter comprising at least a surface-containing fiber containing a catalyst component. 5.   The exhaust gas purification system for diesel engines according to claim 4, wherein the fibers are metal fibers and / or inorganic fibers.   6. The catalyst component according to claim 4, wherein the catalyst component is a catalyst component containing at least one selected from the group consisting of platinum, palladium, rhodium, cerium, praseodymium, gallium, manganese, and yttrium. Exhaust gas purification system for diesel engines.   The exhaust gas flow path upstream of the exhaust gas purification fiber filter and the catalyst disposed in at least one of the exhaust gas flow path downstream of the exhaust gas purification fiber filter and upstream of the diesel particulate filter The exhaust gas purification system for diesel engines according to any one of claims 2 to 6, further comprising: A catalyst disposed in an exhaust gas passage of a gasoline engine;
And an exhaust gas purification fiber filter having a porosity of 70 to 90% and a thickness of 0.5 to 6 mm, which is disposed in the exhaust gas flow channel upstream of the catalyst. Exhaust gas purification system for gasoline engines.   9. The exhaust gas purification system for a gasoline engine according to claim 8, wherein the exhaust gas purification fiber filter is disposed at a position where the temperature is highest in the exhaust gas flow path.   The exhaust gas purification system for a gasoline engine according to claim 8 or 9, wherein the exhaust gas purification fiber filter is a fiber filter made of a fiber containing a catalyst component on at least a surface thereof.   The exhaust gas purification system for gasoline engines according to claim 10, wherein the fibers are metal fibers and / or inorganic fibers.   12. The catalyst component according to claim 10 or 11, wherein the catalyst component is a catalyst component containing at least one selected from the group consisting of platinum, palladium, rhodium, cerium, praseodymium, gallium, manganese, and yttrium. Exhaust gas purification system for gasoline engines.

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