WO2006131995A1

WO2006131995A1 - Diesel particulate filter and purifier making use of the same

Info

Publication number: WO2006131995A1
Application number: PCT/JP2005/014739
Authority: WO
Inventors: Masahiko Matsumoto
Original assignee: Tosco Co., Ltd.
Priority date: 2005-06-06
Filing date: 2005-08-11
Publication date: 2006-12-14
Also published as: JP4918230B2; JP2008212759A

Abstract

A diesel particulate filter capable of eliminating particulate matter (PM) emitted from diesel engine exhaust gas and being a cause of air pollution and dust pollution, particularly together with particulate matter (PM) contained in diesel engine exhaust gas with NOx satisfactorily removed, more particularly capable of simultaneously eliminating suspended particulate matter (SPM) of small particle diameter and nitrogen oxides (NOx). There is provided a diesel particulate filter having a nonwoven fabric of thermostable fiber and, carried on the surface of the thermostable fiber, a perovskite composite oxide catalyst, characterized in that the composite oxide catalyst consists of particles of 0.1 to 100 nm average diameter.

Description

Specification

Diesel particulate filter and purification apparatus using the same

[0001] The present invention relates to a diesel particulate filter that enables simultaneous and complete removal of particulate matter (PM) and nitrogen oxides (NOx) contained in exhaust gas discharged from a diesel engine car. And a purification apparatus using the same.

Background art

[0002] Diesel engines are widely used mainly in trucks in Japan because of their excellent fuel economy and durability. Especially in Europe, excellent fuel economy and global warming gas CO emissions

2

Because it is scarce, it is also widely used in passenger cars.

On the other hand, diesel engines emit large amounts of harmful particulate matter (PM) and nitrogen oxides (NOx). PM is a solid massive substance mainly composed of carbon. PM is said to cause air pollution and dust pollution. Among PMs, those with a particle size of 10 / z m or less are called suspended particulate matter (SPM). SPM is said to float in the atmosphere for a long time, deposit in the lungs, trachea, etc., adversely affect the respiratory tract and possibly cause cancer. Nitrogen oxides (NOx) are said to cause acid rain and photochemical oxidants. Therefore, PM and NO emissions from diesel engine exhaust

X

Sufficient removal is required.

[0003] As a method for removing these particulate matter (PM) and nitrogen oxide (NOx), a method of providing a diesel particulate filter (DPF) on the exhaust gas side of a diesel engine is known. As a filter that has been used for a long time, a filter using a nonwoven fabric of silicon carbide-based inorganic fibers can be cited. This filter collects PM contained in exhaust gas with a non-woven fabric and heats it to a high temperature (approximately 600 ° C) to convert the components of PM, carbon (C) and hydrocarbons (HC), into CO.

Release in place of 2 or H 2 O. However, this filter has no effect on reducing NOx (patented)

2

Reference 1).

Also disclosed is a diesel particulate filter carrying a perovskite-type compound having a nitrogen oxide NOx reducing action on the surface of fibers contained in such a nonwoven fabric. (See Patent Document 2). However, even in Patent Document 2 where the powerful perovskite type compound lacks the ability to remove PM, PM is removed by heating and heat treatment in an oxidizing atmosphere, regardless of the catalyst. In addition, at the time of filing of Patent Document 2, as a method of obtaining a catalyst of a velovskite type compound having as small a particle size, high size and specific surface area as possible, a so-called ceramic method is used in which component oxides and carbonates are mixed and fired. There has been a method for producing particles of teplovskite type compounds. However, it usually has a specific surface area of about 1 to 5 m ² Zg, and the particle size stayed at about 1 to 3 μm. Therefore, particles of perovskite-type compounds of less than 1 μm were placed on the surface of the nonwoven fabric. There was no diesel particulate filter supported above.

[0004] Further, there is known a diesel particulate filter comprising a silicon carbide fiber having a perovskite type spinel type composite oxidation catalyst supported on the surface of a silicon carbide fiber by an alkoxide method or a simple nitrate dipping method. (See Patent Document 3).

However, the perovskite type spinel type composite oxidation catalyst manufactured by the alkoxide method or the simple nitrate dipping method has a small specific surface area (about 0.5m ² Zg), and the exhaust gas and the catalyst have sufficient contact. Not done. Further, this composite oxidation catalyst is supported so as to cover a support such as a non-woven fabric and does not have a particle structure. Therefore, in such a diesel particulate filter, PM (carbon) is converted to CO and NOx is completely converted to nitrogen.

2

It is difficult to reduce.

In light of the above, development of a high-performance diesel particulate filter that renders PM and NOx in exhaust gas discharged from a diesel engine harmless and a purifier using it is strongly desired.

Patent Document 1: Japanese Patent Laid-Open No. 7-11933

Patent Document 2: JP 2002-301320 A

Patent Document 3: Japanese Patent Laid-Open No. 2003-239722

Disclosure of the invention

Problems to be solved by the invention

[0006] The first object of the present invention is to sufficiently remove particulate matter (PM), especially NO, which causes air pollution and dust pollution that are emitted from diesel engine exhaust gas power. Providing diesel particulate filters with the ability to simultaneously remove particulate matter (PM), particularly small suspended particulate matter (SPM) and nitrogen oxides (NOx), contained in engine exhaust gas There is to do.

A second object of the present invention is to provide a diesel particulate filter comprising a nonwoven fabric made of heat resistant fibers and a particulate composite oxide catalyst supported on the surface of the heat resistant fibers.

The third object of the present invention is to capture and remove particulate matter (PM), particularly suspended particulate matter (SPM) having a small particle diameter, on the surface of the nonwoven fabric, and to remove nitrogenous acid. The object is to provide a compact and high-performance diesel particulate filter and a purification device for diesel engine exhaust gas, which can reduce and remove substances (NOx) at the same time, detoxify diesel engine exhaust gas with high efficiency.

A fourth object of the present invention is to provide a method for producing a diesel particulate filter comprising a non-woven fabric made of heat-resistant fibers and a composite oxide catalyst supported on the surface of the heat-resistant fibers.

Means for solving the problem

As a result of diligent research to achieve the above object, the present inventors have supported the surface of a non-woven fabric made of a specific heat-resistant fiber with particles of a mouth-bushite complex oxide catalyst having a specific particle size. It was found that the diesel particulate filter showed good simultaneous removal performance of particulate matter (PM) and nitrogen oxides (NOx).

Specifically, the present invention

1. A diesel particulate filter comprising a nonwoven fabric composed of heat-resistant fibers and a perovskite-type composite oxide catalyst supported on the surface of the heat-resistant fibers, wherein the composite oxide catalyst is 0.1 to : It relates to a diesel particulate filter characterized by being particles having an average particle size of LOOnm.

2. The above-mentioned mouthbskite-type composite oxide catalyst has the formula (I):

A B C O (I)

P q r 3

(In the formula, A, B and C may be the same or different from each other. K, Ni, Sr, Co, La, Cu, V, Mn, Fe, Cs, Ba, Ce, Li, Pd force, etc. Group forces are selected; p and q are 0.5 <p <1, 0 <q <0.5, p + q = l, r is 0 or 1)

The diesel particulate filter according to 1 above, represented by:

[0008] 3. The perovskite-type composite oxide catalyst is La K CoO, La Sr CoO or La

0.9 0.1 3 0.8 02 3 0.75

2. The diesel particulate filter according to 1 above, which is K MnO.

0.25 3

4. The diesel particulate filter according to any one of the above 1 to 3, wherein the perovskite-type complex oxide catalyst has a specific surface area of 10 m ² / g or more measured by BET method.

5. The nonwoven fabric, thickness 0.1. 3 to: L0mm, and the force of density 0. 05～: having L OgZcm ^3, relates to a diesel particulate filter according to any force 1 above 1-4.

6. Diesel engine power using the diesel particulate filter described in any one of 1 to 5 above. The present invention relates to a purifier for exhaust gas discharged.

[0009] 7. A non-woven fabric comprising heat-resistant conductive fibers and particles of a perovskite-type composite oxide catalyst having an average particle diameter of 0.1 to 1 OOnm supported on the surface of the heat-resistant conductive fibers. A diesel particulate filter manufacturing method comprising:

(1) a step of immersing the nonwoven fabric in a suspension obtained by suspending particles of the perovskite-type composite oxide catalyst in an alcoholic aqueous solution;

(2) using the nonwoven fabric as a negative electrode, applying a potential difference between the positive electrode and the negative electrode in the suspension, and attaching the particles onto the heat-resistant conductive fiber surface of the nonwoven fabric; and

(3) removing the nonwoven fabric with the particles attached on the heat-resistant conductive fiber surface from the suspension, and sintering the nonwoven fabric;

Relates to a method comprising:

8. Non-woven fabric having heat-resistant conductive fiber strength obtained by the production method described in 7 above, and a pebskite type having an average particle diameter of 0.1 to: LOOnm supported on the surface of the heat-resistant conductive fiber BEST MODE FOR CARRYING OUT THE INVENTION Best Mode for Carrying Out the Invention A diesel particulate filter containing a composite oxide catalyst

[0010] (1) Diesel particulate filter

The diesel particulate filter of the present invention comprises a nonwoven fabric composed of heat-resistant fibers, And a mouth bumskite complex oxide catalyst supported on the surface of the heat resistant fiber. Hereinafter, the non-woven fabric and the mouthbushite complex oxide catalyst will be described.

[0011] (1-1) Nonwoven fabric

The nonwoven fabric of the present invention also has heat resistant fiber strength.

The heat-resistant fiber of the present invention is a fiber having a heat resistance of 800 ° C or higher, preferably 1000 ° C or higher.

The heat-resistant fiber of the present invention is preferably a heat-resistant conductive fiber in order to adhere the velovskite complex oxide catalyst particles by electrophoresis. Here, the heat-resistant conductive fiber of the present invention preferably has an electric resistance of, for example, 1.4 Ω′cm or less, preferably 0.1 Ω′cm or less.

Furthermore, it is appropriate that the heat resistant fiber of the present invention is alkali resistant in order to support an alkali metal oxide containing K or the like. Preferably, the degree of alkali resistance is appropriately determined by measuring the tensile strength of a fiber that has been immersed in a 2.0% NaCl aqueous solution and then heat-treated in air at 1000 ° C. for 2 hours to reduce the strength. .

[0012] The heat-resistant fiber of the present invention is suitably an inorganic or organic fiber. Here, examples of the inorganic fibers include silicon fibers mainly composed of silicon, silicon carbide fibers, and alumina fibers. More preferably, the silicon carbide fiber may contain components such as Ti, Zr and / or A1 in order to improve alkali resistance. These components are suitably contained in an amount of 0.1 to 2% by mass based on the entire fiber.

Examples of such fibers include silicon carbide fibers, two-calon fibers (Si—O—C composition ratio 57.2: 32.7: 10, manufactured by Nippon Carbon Co., Ltd.), Tyranno Fiber (registered trademark) heat-resistant Darade ZM ( Si—C—O—Zr composition ratio 56: 34: 9: 1), Tyranno Fiber (registered trademark) heat-resistant grade S (Si-OC-Ti composition ratio 50: 30: 18: 2) Tyranno fiber (registered trademark) heat resistant Grade SA (Si-OC-Al composition ratio 67: 31: 1: 2) (Tyranno fiber (registered trademark) is all manufactured by Ube Industries, Ltd.) is preferable.

Moreover, as an organic fiber, carbon fiber is mentioned, for example.

The heat-resistant fiber of the present invention may be a combination of two or more of these fibers. [0013] The average diameter of the heat-resistant fiber of the present invention is, for example, 3 to 20 μm, preferably 9 to 14 μm. If the diameter is 3 μm or more, it is preferable because the fibers themselves scatter and do not release gas-generating substances into the atmosphere.

The fiber length of the heat-resistant fiber of the present invention is, for example, 10 to: LOOmm, preferably 3

It is appropriate to be 0 to 60 mm.

The tensile strength of the heat resistant fiber of the present invention is, for example, 1 to 5 GPa, preferably 2 to 4 GPa as measured by JIS K-7023.

[0014] The nonwoven fabric of the present invention is obtained by converting the above heat-resistant fiber into a nonwoven fabric by a known method, for example, a spunbond method, or JP-A 2000-199160 "Method and apparatus for producing inorganic short fiber felt". It can be.

The thickness of the nonwoven fabric of the present invention is, for example, 0.3 to LOmm, preferably 0.5 to 5 mm, more preferably 1 to 3 mm.

The basis weight of the nonwoven fabric of the present invention is, for example, 50 to: LOOOgZm ² , preferably 100 to 500 g, more preferably 150 to 400 gZm ² .

The strength density of the nonwoven fabric of the present invention is, for example, 0.05-: L Og / cm ³ , preferably 0.1-0.8 gZcm ³ , more preferably 0.2-0.6 gZcm ³ . Is appropriate. If the force density is 0.2 gZcm ³ or more, the PM collection performance can be sufficiently maintained, and if it is 1. OgZcm ³ or less, the exhaust gas using the diesel particulate filter of the present invention is used. This is preferable because the exhaust gas pressure of the water purification apparatus can be kept low.

[0015] (1-2) Velobskite complex oxide catalyst

On the surface of the heat-resistant fiber of the non-woven fabric, a velovskite complex oxide catalyst is supported. Here, the perovskite complex oxide is represented by a basic composition ABO,

It has a structure in which 3 6 bodies occupy each corner of the cubic unit cell. Oxygen 12-coordinate void enters A ion and 6-coordinate void enters B ion to stabilize the structure. In general, A contains a metal ion having a large ion radius, such as a rare earth metal or an alkaline earth metal, and B contains a transition metal ion.

The perovskite complex oxide catalyst of the present invention contains at least two elements selected from K, Ni, Sr, Co, La, Cu, V, Mn, Fe, Cs, Ba, Ce, Li and Pd. Perovsky A complex oxide catalyst having a structure.

[0016] More specifically, the velovskite complex oxide catalyst of the present invention has the following formula (I):

A B C O (I)

P q r 3

(In the formula, A, B and C may be the same or different from each other. K, Ni, Sr, Co, La, Cu, V, Mn, Fe, Cs, Ba, Ce, Li, Pd force, etc. P and q are 0.5 <p <1.0, preferably ί, 0.575≤ρ≤0.95, 0 <q <0.5, preferably ί, 0. 05≤q≤0. 2 5, p + q = l, r is 0 or 1)

It may be represented by

A preferred perovskite type complex oxide catalyst of the present invention contains at least two elements selected from La, K, Co, Sr and Mn. In particular, in formula (I), A is La, B is selected from K, Sr, Li or Cs, C is selected from Co or Mn, and p and q are p = 0.7 to 0.9 , Q = 0. 1 to 0.3, p + q = 1, and r is 1. More preferred perovskite complex oxide catalysts of the present invention are La K CoO, La Sr

0.9 0.1 3 0.8 0.2

CoO or La K MnO.

3 0.75 0.25 3

[0017] The perovskite complex oxide catalyst of the present invention is a particle having an average particle diameter of 0.1 to: L00 nm, preferably 0.5 to 50 nm, more preferably 1 to 20 nm. By using a catalyst having such a particle size, a catalyst having a large specific surface area can be carried on the fiber surface of the nonwoven fabric, and the catalyst performance can be improved. In addition, when the catalyst adhering to the fiber surface of the nonwoven fabric is supported by sintering, the sintering temperature can be lowered appropriately. For example, usually: When using catalyst particles of about m, it is necessary to sinter at 1000 ° C for 2 hours, but when using a catalyst with a small particle size as in the present invention, 400-800 If it is sintered at about ° C for 2 hours, it can be supported with sufficient strength.

Furthermore, by using the catalyst having the above particle diameter, the heat-resistant fiber surface can be completely and uniformly coated with a small amount of support. In addition, the contact between the catalyst and the heat-resistant fiber surface can be kept stronger.

[0018] The specific surface area of the perovskite-type composite oxide catalyst of the present invention measured by the BET method is 10 m ² m ² / g or more, more preferably 30 m ² / g or more, and still more preferably 50 m ² / g. As described above, for example, 50-: L00m ² / g is appropriate. Here, the perovskite type composite of the present invention The specific surface area of the acid oxide catalyst is measured by the BET method according to JIS R1626.

[0019] (1-3) Diesel particulate filter

The diesel particulate filter of the present invention comprises a nonwoven fabric composed of the above-mentioned heat-resistant fiber, preferably a heat-resistant conductive fiber, and particles of the above-mentioned belobskite complex oxide catalyst supported on the fiber surface of this nonwoven fabric. .

It is appropriate that the particles of the velovskite type complex oxide catalyst are contained in an amount of, for example, 0.120% by mass, preferably 0.55% by mass, with respect to the mass of the nonwoven fabric made of heat-resistant fibers.

The particles of the perovskite complex oxide catalyst are uniformly supported on the surface of the heat-resistant fiber of the nonwoven fabric without gaps. It is preferable that the surface of the non-woven heat-resistant fiber is substantially coated with particles of the perovskite complex oxide catalyst.

[0020] The layer of the particles of the open-bumskite complex oxide catalyst supported on the heat-resistant fiber surface is at least one layer, more preferably two or more layers.

The particle size of the particles of the velovskite complex oxide catalyst of the present invention supported on the heat-resistant fiber surface is the same as that before the support, for example, 0.1 to: LOOnm, preferably 0.5 50 nm More preferably, l is 20 nm.

The layer thickness of the particles of the perovskite complex oxide catalyst of the present invention is, for example, 0.1 1 00, preferably 50 nm, more preferably 20 50 nm.

[0021] (2) Diesel particulate filter manufacturing method

The diesel particulate filter of the present invention is produced by preparing a perovskite-type composite oxide catalyst having a specific particle size, and supporting this bottom-bskite-type composite oxide catalyst on the surface of a heat resistant fiber of a nonwoven fabric. Is done.

[0022] (2-1) Method for producing a velovskite complex oxide catalyst

The velovskite type complex oxide catalyst of the present invention may be produced by any known method, but is suitably produced by the ethylene glycol method shown below. Specifically, first, K ゝNi ゝ Sr ゝ Co, La ゝ Cu ゝ V, Mn, Fe ゝ Cs ゝ Ba ゝ Ce ゝ Li ゝ Pd and other formulas (I): Salts of elements constituting A, B and C of ABCO, preferably Nitrates,

P qr 3 Prepare sulfate or hydrochloride. The salt is weighed and dissolved in a solvent such as alkylene glycol, such as ethylene glycol, propylene glycol, or preferably ethylene glycol, at room temperature so that the salt concentration is 1M. Stir at normal pressure for 1 to 10 hours, preferably about 6 hours.

[0023] Next, the obtained solution is transferred to a baking container, and it is 0.1 to 10 per minute from normal temperature under normal pressure. C, preferably at a rate of 0.5 to 5 ° C per minute and heated to 100 to 200 ° C, preferably 200 ° C, to completely remove the solvent. Thereafter, the temperature is further increased to 400 ° C to 800 ° C, preferably 600 ° C at a rate of 5 to 30 ° C per minute, preferably 10 to 20 ° C per minute. While maintaining, for example, the residue is calcined for 1 to 10 hours, preferably about 5 hours, to fix the perovskite structure of the catalyst. Here, in order to obtain a perovskite structure in the above temperature rising and firing step, oxygen or air is introduced into the firing container at a flow rate of 0.5 liter Z minutes or more, preferably 1 liter Z minutes or more. Do it while sending.

[0024] The obtained fired product is cooled to room temperature and then pulverized to obtain particles of a perovskite complex oxide catalyst having a target particle size. Here, it is appropriate that the pulverization is performed using a mortar, for example, if it is 50 g of catalyst particles, 20 minutes, and crushing for a total of 1 to 6 hours, preferably about 4 hours.

[0025] (2-2) Method for supporting perovskite complex oxide catalyst on the surface of heat-resistant fiber of nonwoven fabric

The diesel particulate filter of the present invention can be manufactured, for example, according to the following steps.

(1) a step of immersing the nonwoven fabric of the present invention in a suspension in which the particles of the perovskite type composite oxide catalyst of the present invention are suspended in an alcoholic aqueous solution;

(2) using a nonwoven fabric as a negative electrode, applying a potential difference between the positive electrode and the negative electrode in the suspension, and attaching the catalyst particles onto the heat-resistant conductive fiber surface of the nonwoven fabric of the present invention; and

(3) A step of removing the nonwoven fabric of the present invention in which the catalyst particles are adhered on the surface of the heat-resistant conductive fiber from the suspension and sintering the nonwoven fabric.

Hereinafter, each step will be described in detail.

(2-2-1) Particles of the perovskite complex oxide catalyst of the present invention in an alcoholic aqueous solution Step of immersing the nonwoven fabric of the present invention in the suspension suspended in

First, the particles of the perovskite complex oxide catalyst of the present invention are suspended in an alcoholic aqueous solution. Here, the alcoholic aqueous solution contains alcohol and water which are liquid at room temperature (25 ° C). Examples of the alcohol include alcohols having 1 to 3 carbon atoms such as methanol, ethanol, n-propanol, and isopropanol. Ethanol is preferable. Alcohol is contained, for example, 85 to 99%, preferably 92 to 97%, based on the total volume of the alcoholic aqueous solution.

For example, ion-exchanged water can be used as the water. Further, water is contained, for example, in an amount of 1 to 15%, preferably 3 to 8%, based on the total volume of the alcoholic aqueous solution.

Furthermore, the alcoholic aqueous solution may contain a ionic surfactant that dissolves in alcohol as a dispersant. The dispersant may be contained in an amount of 0.2 to 0.6% by mass, preferably 0.4 to 0.5% by mass, based on the mass of the velovskite complex oxide catalyst of the present invention.

The suspension suitably contains, for example, 5 to 50 g, preferably 10 to 30 g of the perovskite complex oxide catalyst particles of the present invention in 1 liter of an alcoholic aqueous solution. (2-2-2) A step in which the nonwoven fabric is used as a negative electrode, a potential difference is applied between the positive electrode and the negative electrode in the suspension, and the catalyst particles are adhered on the heat-resistant conductive fiber surface of the nonwoven fabric of the present invention.

Next, a potential difference is applied to the suspension, and the catalyst particles of the present invention are adhered to the surface of the heat-resistant conductive fibers of the nonwoven fabric of the present invention using so-called electrophoresis. In the suspension, particles of the perovskite complex oxide catalyst of the present invention are dispersed. Around these particles, hydrogen ions separated by hydraulic force are attached and are positively charged in the suspension. Therefore, by applying a potential difference between the positive electrode and the negative electrode in the suspension using the nonwoven fabric as the negative electrode, the positively charged catalyst particles gather on the surface of the heat-resistant fiber of the nonwoven fabric, which is the negative electrode, and adhere by electrostatic energy.

Here, as the positive electrode, for example, a carbon electrode or CZC (carbon composite) can be used. As the negative electrode, a non-woven fabric of the present invention, preferably a metal mesh sandwiching the non-woven fabric of the present invention, for example, a stainless steel mesh (pore diameter 0.5 to 5 mm, preferably 1 to 3 mm, opening 5 to 50 mm, preferably 10 ~ 30mm). A potential difference is applied between the positive electrode and the negative electrode. The potential difference is, for example, voltage: 50 to 200V, preferably <100 to 150V, current: 100 to 2000 mA, preferably 200 to 1000 mA, more preferably 200 to 800 mA, 5 to 30 minutes, preferably 5 Give ~ 20 minutes.

(2-2-3) A step of taking out the nonwoven fabric of the present invention in which the catalyst particles are adhered on the surface of the heat-resistant conductive fiber from the suspension and sintering the nonwoven fabric.

The nonwoven fabric of the present invention in which the catalyst particles adhere to the surface of the heat-resistant conductive fiber is taken out of the suspension after the electrophoresis. Thereafter, the aqueous alcoholic solution is naturally dried at room temperature, for example, for 1 to 10 hours, preferably for about 5 hours, and the suspension is also removed. Further, the nonwoven fabric is sintered to carry the catalyst particles on the surface of the heat-resistant conductive fiber. Sintering uses, for example, an electric furnace or the like, for example, 400 to 1000 ° C, preferably 600 to 900 ° C, more preferably 800 ° C for 1 to 5 hours, preferably 1.5 to 3 For 2 hours, more preferably 2 hours. The catalyst particles supported on the heat-resistant conductive fiber surface in this way have no change in the size or structure of the particles before and after the support.

[0028] (3) Diesel engine exhaust gas purification device

The diesel particulate filter of the present invention is used in a purification apparatus for diesel engine exhaust gas. Specifically, a diesel engine exhaust gas purifier is attached to the rear of the diesel engine combustion chamber and in front of the exhaust port for releasing the exhaust gas into the atmosphere. A diesel engine exhaust gas purification apparatus includes the diesel particulate filter of the present invention. The exhaust gas is introduced into the purification device, passes through a diesel particulate filter in the purification device, and then released to the outside of the purification device. When passing through the diesel particulate filter, particulate matter (PM) and nitrogen oxides (NOx) contained in the exhaust gas are trapped and put into the gaps (holes) of the heat-resistant fibers contained in the diesel particulate filter. accumulate. The deposited particulate matter (PM) and nitrogen oxides (NOx) react on the bottom bskite-type complex oxide catalyst supported on the surface of the heat-resistant fiber and react with carbon C, which is the main component of PM. NOx O undergoes oxidation reaction to become CO, and at the same time NO

2

X is reduced to N, detoxified, exits the purifier, and is released into the atmosphere through the above outlet

2

Is done.

c + o → co NO → N +0

x 2 2

(However, coefficient is omitted)

When the ignition temperature of diesel combustion reaction is low (250 ° C),

2NO + C → 2NO + CO

twenty two

Such a reaction also occurs. Also, the reaction of NOx and hydrocarbon power N, CO and water

twenty two

NOx may be decomposed due to the fact that the reaction formula of the actual reaction is more complicated.

[0029] Furthermore, due to the characteristics of the diesel engine, if the combustion temperature in the combustion chamber of a diesel engine with a high engine speed is high, such as when the car is running! /, The NOx is contained in the exhaust gas. If the combustion temperature in the combustion chamber of a diesel engine with a low engine speed is low, such as when the car is stopped, the PM, that is, C will be excessive. Even in such a case, the velovskite complex oxide catalyst of the present invention works well. In other words, under excessive NOx, ionic conductivity is improved at high temperatures, the catalytic reduction action is activated, and nitrogen oxides NOx are decomposed well. On the other hand, even under excessive C, the perovskite-type composite oxide catalyst of the present invention can efficiently oxidize C due to the activity of the catalytic reaction between NOx and C, which has high low-temperature activity. Can do.

[0030] The diesel particulate filter in the purification apparatus for diesel engine exhaust gas of the present invention has one layer or two layers of a non-woven fabric of heat-resistant fiber carrying the velovskite type composite oxide catalyst of the present invention. It may be a laminate of more than one layer. In particular, by using a plurality of nonwoven fabric layers having different basis weights, it becomes possible to supplement particulate matter (PM) having different particle sizes well. For example, it is preferable to have a three-layer structure in which the upstream portion force of the exhaust gas flow is provided with the following nonwoven fabric layers in order in the purification apparatus.

[0031] Table 1

[0032] More preferably, a three-layer structure provided with the following nonwoven fabric layer is appropriate.

Table 2 Fiber diameter (n Nonwoven fabric thickness ( _mm ) Nonwoven fabric weight (g Upstream non-woven fabric layer 10 ~ 20 1 ~ 3 200 ~ 500

Middle stream nonwoven fabric layer 3 ~ 10 1 ~ 3 200-500

Downstream nonwoven fabric layer 3 to 10 to 3 200-500 In this case, the thickness of the nonwoven fabric laminate is, for example, 5 to 50 mm, and preferably 10 to 30 mm. is there.

Moreover, you may provide the space layer of 1-20 mm between these nonwoven fabric layers, for example, Preferably, 3-: LOmm.

[0033] Further, the diesel particulate filter in the diesel engine exhaust gas purification apparatus of the present invention comprises a non-woven fabric made of a heat-resistant fiber carrying the bevelskite-type composite oxide catalyst of the present invention. The laminate may be sandwiched between a sheet of heat-resistant metal plates and the resulting laminate may be bent into a bellows shape. By making the bellows shape, the contact area of the exhaust gas can be increased, pressure loss when particulate matter (PM) remains on the nonwoven fabric can be prevented, and the purification equipment can be made compact. it can.

Here, examples of the heat-resistant metal plate include stainless steel (such as SUS301 and SUS304). The thickness of the heat-resistant metal plate is, for example, 1 to 8 mm, preferably 2 to 5 mm.

Furthermore, the diesel engine exhaust gas purification device of the present invention is a diesel particulate filter heating device for preventing clogging of the diesel particulate filter due to particulate matter (PM) remaining on the nonwoven fabric. May be included. Heating temperature is below the heat resistant temperature of the heat resistant fiber or catalyst used, for example, when using silicon carbide fiber or when using a perovskite complex oxide catalyst containing Mn as the catalyst, 800 ° C or less, More preferably, the temperature is set to 600 ° C or lower. As the heating device, a microwave irradiation device is preferable. The microwave irradiation device can raise the temperature of the nonwoven fabric in a short time and is easy to control the temperature. When using the microwave irradiation apparatus, it is necessary to use silicon carbide fiber or silicon fiber, which is a microwave absorber, as the heat-resistant fiber of the present invention.

Example

Hereinafter, examples of the present invention will be described. [Example 1]

90 g of lanthanum nitrate hexahydrate, 10 g of strontium nitrate, and 80 g of cobalt nitrate were weighed and added to 500 ml of ethylene glycol and dissolved. The resulting solution was stirred for 6 hours and then transferred to a baking container. The temperature was raised from room temperature to 200 ° C at a rate of 1 ° C per minute under normal pressure to vaporize and remove ethylene glycol, and remove the residue. Obtained. Thereafter, the 200 ° C. force was also raised to 600 ° C. at a rate of 10 ° C. per minute, and the residue was fired by maintaining at 600 ° C. for 5 hours. During the above temperature rise and firing, air was fed into the firing container at a flow rate of 1 liter Z. Thereafter, the mixture was cooled to room temperature and pulverized in a mortar to obtain 50 g of catalyst particles. The obtained catalyst particles are used for X-ray analysis and confirmed to have a perovskite structure with a composition ratio of La Sr CoO.

0.8 0.2 3

It was. The average particle size of the obtained catalyst particles was about 10 nm as measured with a scanning electron microscope. The specific surface area was measured by the BET method according to JIS R1626 and found to be 50 m ² / g.

In a glass container, 2 liters of ethanol and 100 ml of ion-exchanged water were added, and 30 g of the perovskite type complex oxide catalyst obtained above was suspended to obtain a suspension. The suspension was dispersed and crushed with ultrasonic waves in advance using a homogenizer (ultrasonic cleaner) (manufactured by Branson, 15 10 J-MT) in order to crush the aggregated particles. One flat plate negative electrode and two flat plate positive electrodes placed horizontally and parallel to the upper and lower portions of the flat plate negative electrode were immersed in this suspension. Here, as the negative electrode, a non-woven fabric made of silicon carbide fiber (Tyranno Fiber (registered trademark) heat-resistant grade ZM (Si-CO-Zr composition ratio 56: 34: 9: 1))) (Tosco Ceramic manufactured by Tosco Corporation) Fiber felt) (length x width x thickness: 290 x 210 x I. 57 mm) sandwiched between stainless steel wire meshes with a hole diameter of 2 mm and openings of 20 mm was used. The silicon carbide fiber used has a fiber diameter of 10 / ζ πι, a fiber length of 40 mm, a tensile strength of 3.4 GPa (measured in accordance with JIS K-7023), and the nonwoven fabric has a basis weight of 380 g / m ² and a strength. It has a density of 0.24 g / cm ³ . In addition, two carbon plates (length X width X thickness: 300 X 240 X 5 mm) were used as the positive electrode. These positive electrodes were placed above and below the negative electrode so as to be parallel to the negative electrode with an interval of 15 mm. A DC voltage of 100 V and 800 mA was applied to the positive electrode and the negative electrode for 15 minutes, and particles of the velovskite complex oxide catalyst were supported on the silicon carbide fiber. Thereafter, the nonwoven fabric was taken out of the suspension, naturally dried at room temperature for 5 hours, and then sintered at 800 ° C. for 2 hours. Gain On the resulting non-woven silicon carbide fiber, 1.0% by mass of catalyst particles was supported with respect to the total mass of the non-woven fabric and the catalyst particles. In addition, the supported catalyst particles are perovskite type complex oxides having a composition of La Sr CoO by X-ray analysis.

08 0.2 3

confirmed.

Further, when the surface of the silicon carbide fiber was observed with a scanning electron microscope, as shown in FIG. 1, it was confirmed that catalyst particles having an average particle diameter of 10 nm were uniformly supported without gaps.

The particles of the velovskite complex oxide catalyst of the present invention have a multilayer structure, and the thickness of the layer was about 50 nm as measured by a scanning electron microscope.

[0037] [Comparative Example 1]

Test as in Example 1 except that acetone was used instead of ethanol as a suspension component! On the other hand, particles of a velovskite complex oxide catalyst were supported on silicon carbide fibers. On the obtained silicon carbide fibers of the nonwoven fabric, 7.0% by mass of catalyst particles was supported with respect to the mass of the nonwoven fabric and the entire catalyst particles.

Composition of La Sr CoO by X-ray analysis of catalyst layer formed on the surface of silicon carbide fiber

It was confirmed to be a complex acid oxide having a velovskite structure having 08 0.2 3.

Further, when the surface of the silicon carbide fiber was observed with a scanning electron microscope, as shown in FIG. 2, two catalyst particles having a particle diameter of 10 to 50 nm and an average particle diameter of 30 nm were found on the silicon carbide fiber. It then agglomerated and existed as larger 50-300 nm agglomerates. The catalyst particles were heterogeneously supported on the silicon carbide fibers. Further, the catalyst particles, or the catalyst particles having weak adhesion between the catalyst particles and the silicon carbide fiber, can be easily removed.

[0038] [Evaluation]

The diesel particulate filters obtained in Example 1 and Comparative Example 1 were evaluated for their ability to decompose particulate matter (PM) and nitrogen oxides (NOx). The evaluation was conducted by preparing a test gas simulating the exhaust gas emitted from the diesel engine and passing this test gas to the purification equipment filled with the diesel particulate filter obtained in Example 1 and Comparative Example 1. The gas components that passed through the filter were analyzed by gas chromatography. As a test gas, a gas having a composition of 5% 0 -0.5% NO-He was used. In addition, purification

2

The equipment used was a stainless steel SUS304 cylindrical reaction tube with an inner diameter of 15 mm and a height of 300 mm, with an exhaust gas inlet and outlet on the upper and lower surfaces. In this reaction tube, three diesel particulate filters having a diameter of 15 mm and a thickness of 1.57 mm were stacked and filled, and the exhaust gas was set to pass through the three diesel particulate filters. The diesel particulate filter used was carbon black (Tokai Black # 8500 grade 14nm (particle size 14nm) manufactured by Tokai Carbon Co., Ltd.) in order to reproduce the state where particulate matter (PM) was collected by the filter. , 6% by mass was used with respect to the mass of the diesel particulate filter used.

[0039] In the test, the test gas was passed through a purification apparatus at a flow rate of 40 mlZ, and then generated CO, CO, and N N O were analyzed at 15 minute intervals with a gas chromatograph (manufactured by Shimadzu Corporation). Examination

2 2, 2

The test gas temperature (temperature outside the reaction tube) was increased from 200 ° C to 700 ° C at 1 ° C / min.

The decomposition of particulate matter (PM) is based on the following formula:

c + o 2 → co,

2

C + 1/20 → CO or

2

2NO + C → 2NO + CO

twenty two

As the concentration of CO and CO in the test gas increases, particulate matter

2

It was judged that the removal of quality (PM) proceeded well.

In addition, decomposition of nitrogen oxides (NO), NO is the following formula,

2NO → N +0, and

twenty two

4NO → 2N O + O,

twenty two

In addition, it is decomposed by the reaction of NOx and hydrocarbon power N, CO and water.

twenty two

If the concentration of N and N 2 O in the test gas is high, decomposition of nitrogen oxides (NO) is good

twenty two

Judged to have progressed.

The test result of Example 1 is shown in Graph 1, and the test result of Comparative Example 1 is shown in Graph 2.

[0040] Graph 1

Sample gas temperature c

[0041] Graph 2

¾g + o¾oo + / fsooooi- "

Sample gas temperature / ¾

[0042] As shown in graphs 1 and 2, the concentration of CO and CO in the test gas was determined in Example 1. Indicates a higher concentration than Comparative Example 1. Further, although not shown in the graph, in Example 1, CO is not generated (Oppm) —in the comparative example, CO is generated in each temperature region (for example, 485. 290 ppm at C, 500. 375ppm for C, 515. 298ppm for C). Therefore, it can be seen that the diesel particulate filter of Example 1 has a high particulate matter (PM) decomposition capacity, and that the treated carbon C becomes completely CO and can be released into the atmosphere.

2

The

In addition, regarding the concentration of N and N 2 O in the test gas, Example 1 has a higher concentration than that of Comparative Example 1.

twenty two

Shows the degree. The temperature at which N and N O start to be generated is 365 ° C in Example 1.

twenty two

In contrast, Comparative Example 1 is around 410 ° C. Therefore, the diesel particulate filter of Example 1 has a high ability to decompose nitrogen oxides (NOx) and can effectively remove nitrogen oxides (NOx) even when the sample gas is at a relatively low temperature. It can be seen that it can be decomposed. Brief Description of Drawings

FIG. 1 is a scanning electron micrograph on the surface of silicon carbide fiber of the diesel particulate filter obtained in Example 1.

FIG. 2 is a scanning electron micrograph on the surface of silicon carbide fiber of the diesel particulate filter obtained in Comparative Example 1.

Claims

The scope of the claims

[1] A diesel particulate filter comprising a nonwoven fabric composed of heat-resistant fibers and a perovskite-type composite oxide catalyst supported on the surface of the heat-resistant fibers, wherein the composite oxide catalyst is 0.1. ~: A diesel particulate filter characterized by being particles having an average particle size of LOOnm.

[2] The above-mentioned mouthbskite-type complex oxide catalyst has the formula (I):

A B C O (I)

P q r 3

(In the formula, A, B and C may be the same or different from each other. K, Ni, Sr, Co, La, Cu, V, Mn, Fe, Cs, Ba, Ce, Li, Pd force, etc. And p and q satisfy 0.5 <p <1, 0 <q <0.5, p + q = l, and r is 0 or 1)

The diesel particulate filter according to claim 1, represented by:

[3] The perovskite complex oxide catalyst is La K CoO, La Sr CoO, or La K

0.9 0.1 3 0.8 0.2 3 0.75 0

The diesel particulate filter according to claim 1, wherein the diesel particulate filter is MnO.

.25 3

[4] The diesel particulate filter according to any one of claims 1 to 3, wherein a specific surface area of the perovskite-type composite acid catalyst is measured by BET method is 10 m ² Zg or more.

[5] The nonwoven fabric, thickness 0.1. 3 to: L0mm, and the force of density 0. 05～: having L OgZcm ^3, diesel particulate filter according to any force one of claims 1 to 4.

[6] Diesel engine power using the diesel particulate filter according to any one of claims 1 to 5. A purifier for exhaust gas discharged.

[7] Non-woven fabric made of heat-resistant conductive fiber and supported on the surface of the heat-resistant conductive fiber

1 to: a method for producing a diesel particulate filter comprising particles of a perovskite complex oxide catalyst having an average particle size of LOOnm,

(2) using the nonwoven fabric as a negative electrode, applying a potential difference between the positive electrode and the negative electrode in the suspension, and attaching the particles on the heat-resistant conductive fiber surface of the nonwoven fabric;

(3) The non-woven fabric with the particles attached on the surface of the heat-resistant conductive fiber is the suspension. Removing the nonwoven fabric and sintering the nonwoven fabric,

Including methods.

A non-woven fabric having a heat-resistant conductive fiber strength obtained by the production method according to claim 7, and a paper bskite-type composite having an average particle diameter of 0.1 to 1 OOnm supported on the surface of the heat-resistant conductive fiber A diesel particulate filter comprising an acid catalyst.