KR101344890B1 - Diesel Particulate Filter using metal structure having unevenness on the surface - Google Patents

Abstract

The present invention relates to a soot filtration device comprising a metal support and a porous carrier layer of a ceramic material formed on the surface of the metal support, and has excellent characteristics of interface stability in a thermal, chemical and vibration environment. The particulate filter of the present invention uses a metal foam or metal plate having a concave-convex structure on its surface as a metal support, and comprises a porous carrier layer of ceramic material coated by a washcoat method.

Description

Diesel Particulate Filter using metal structure having unevenness on the surface}

The present invention relates to a soot filtration device comprising a porous carrier layer of a ceramic material formed on a metal support having a concave-convex structure on its surface, and a technique of a soot filtration device having a high specific surface area and excellent thermal shock, vibration and chemical durability. to be.

Diesel Particulate Filter (DPF) is a device that reduces Particulate Matter (PM) contained in exhaust gas of diesel engine which is regarded as an important cause of air pollution. It is considered a strong solution. DPF is a technology that can reduce more than 80% of particulate matter emitted from diesel engine. It is divided into PM trapping technology and regeneration technology. The system is composed of filter, catalyst, canning, and regeneration control system. do. Filter requirements for DPF include high filtering efficiency, large filtration surface per unit volume, large filtration capacity, low back pressure to prevent engine power degradation, easy regeneration after PM collection, Thermal and mechanical stability, chemical durability and low cost.

In particular, the environment where the filter is exposed is 250 ° C in the case of natural regeneration according to the regeneration method, and 450 ~ 500 ° C in the case of forced regeneration using a fuel additive. Is about 600 ° C., so thermal stability is required. In addition, chemicals such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO _x ), which are the main exhaust gases, are exposed to vibrations from the engine at all times, so stability in chemical and vibration environments is required.

Most of the soot filters used in the prior art are ceramic materials, which are brittle and easily damaged by a weak impact, requiring special care in the production process design and mass production design. In addition, since ceramics have very poor thermal conductivity, they cannot rapidly release heat generated during PM regeneration to the outside, which causes a sharp increase in local temperature. As a result, the ceramic filter melts itself or concentrates heat. It may be broken.

On the other hand, metal filters, which have been recently developed in response, have less damage due to impact due to superior ductility characteristics than ceramics, have high assembly properties and high productivity, and have superior thermal conductivity than ceramics. Locally generated heat is quickly transferred to the outside, so there is little damage due to local heat concentration phenomenon or difference in thermal expansion coefficient.

Currently developed metal filters include metal fiber filters from Fluid Dynamic Inc. of Belgium and Bekaert of Belgium, metal powder filters from Korea Institute of Machinery and Materials, and HJS of Germany. Partial filter from Emitec of Germany.

In the case of the metal fiber filter, the applied material is limited to stainless steel. In the case of the metal powder filter, the number of welding processes is high and the price problem has not been overcome. Partial filter has low PM reduction rate when it keeps operating under low temperature, and there is a problem that soot collected in the filter is blow-off during rapid acceleration operation.

Recently, an exhaust gas filtration device (Korean Patent Application KR 2010-0047597) using a metal foam having a higher porosity than a metal fiber or a metal powder filter has been developed. This reduces the soot by using the volume filtering principle (volume filtering) can be effectively used in applications that require a low filtering efficiency, particularly mechanical properties such as impact resistance has a strong advantage. In addition, since the specific surface area of the metal foam itself is wider than other metal filters, a relatively small amount of catalyst can be used. In addition, when laminating metal foam in radial type and using it as a soot filtration device, the average pore size (400 ~ 1200㎛) is large, so it maintains a lower back pressure than the wall flow type ceramic monolith filter, and the average pore is 450 The micron metal foam can reduce soot by about 50% at all speeds and can be used as a substitute for ceramic filters when laminated. (Lee Sang-soo and 8 others, "Study on the Performance of Semi-Current Metal Foam DFP", 2006 Korea Society of Automotive Engineers Spring Papers pp. 414 ~ 419)

On the other hand, the current soot filtration device is used to add a catalyst in order to increase the PM collection efficiency and to facilitate regeneration after collection, mainly to increase the surface area of the catalyst particles, such as aluminum oxide (Al ₂ O ₃ ) Catalyst particles were coated on the porous material layer, and the porous material layer was coated on the surface of the support with a washcoat. However, when the support is a metal, the washcoat has been mainly tried on the plate-shaped surface, and there is a problem in that the bonding strength at the interface is very weak due to the physical properties between the support and the material to be coated. Exhaust gas filtration device using the metal foam (Korean Patent Application KR 2010-0047597), which was introduced earlier, also shows whether desorption of catalyst particles from the metal foam occurs after long exposure to impact environment such as automobile engine. Durability performance is unknown.

In order to solve the above problems, the present invention is to provide a soot filtration device using a metal support having a porous carrier layer of a ceramic material on which a catalyst particle is supported and having thermal and chemical and mechanical stability.

The present invention provides a soot filtration device comprising a metal support having a concave-convex structure on the surface and a porous carrier layer formed on the metal support.

Preferably, the porous carrier layer is gamma alumina (γ-Al ₂ O ₃ ), silica (SiO ₂ ), titania (TiO ₂ ), zeolite, ceria (Ce ₂ O ₃ ), magnesia, vanadate (V ₂ O ₅ ), cobalt oxide (CoOx), iron oxide (FeOx), tungsten oxide (WO ₃ ), molybdenum oxide (MoO ₃ ), antimony oxide (SbO ₂ ) and rare earth oxides (Sc, Y, La-based element oxides) At least one ceramic material selected from the group consisting of:

Preferably, it comprises a catalytically active component supported on the porous carrier layer.

Preferably, the catalytically active component is at least one member selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, tungsten, chromium, manganese, iron, cobalt, copper, zinc.

Preferably, the porous carrier layer is formed by coating the ceramic material by wash coating method.

Preferably, the metal support is coated with metal particles having a particle size in the range of 1 to 100 μm and a thickness of 5 to 300 μm on the surface of the metal foam, the metal plate, the metal rod, the metal pipe, the metal rod, or the metal structure of the metal cylinder.

According to the present invention, the adhesion between the ceramic material and the metal support used as the porous carrier layer is improved, so that the catalyst can be removed from the interface or the surface from the surface even under severe vibration, high temperature, and easy chemical damage of the exhaust gas, which are used in the automotive engine. There can be provided a soot filtration device which does not occur desorption of the active ingredient and can be used very stably for a long time.

In addition, the soot filtration device provided by the present invention has an advantage of having a fast temperature response characteristic and a high specific surface area characteristic by using a metal support.

1 is a SEM photograph of the surface of the metal foam on which the carrier layer of aluminum oxide (Al ₂ O ₃ ) prepared in the embodiment of the present invention is formed.
Figure 2 is a measurement of the change in mass and specific surface area after the evaluation of thermal fatigue 1000 times in a section of the room temperature-700 ℃ the metal foam formed with a carrier layer of aluminum oxide (Al ₂ O ₃ ) prepared in the embodiment of the present invention.
Figure 3 is a measurement of the mass reduction rate with time by applying ultrasonic vibration in a petroleum ether solution of a metal foam formed with a carrier layer of aluminum oxide (Al ₂ O ₃ ) prepared in the embodiment of the present invention.

The present invention relates to a soot filtration device which uses a metal as a support of a ceramic material carrying a catalyst component in a soot filtration device. The present invention relates to a metal support surface and a surface formed thereon by forming an uneven structure on the support surface of the metal. Increased stability at the interface between the coated ceramic materials, which can be used stably over long periods of time under physical vibration or impact, as well as thermal and chemical harsh environments encountered during use of the soot filter. to provide.

The metal used as the support of the metal in the particulate filter of the present invention is Al alloy, Cu alloy, Mg alloy, Ni alloy, Ti alloy, Zr alloy, carbon steel / low alloy steel / high alloy steel (ferritic), austenitic high alloy steel or their Combinations may be used, and forms thereof may be used without limitation, such as foams, plates, rods, pipes, rods, and cylinders. In addition, the various types of metal support may include a pore structure.

In the present invention, it characterized in that to form an uneven structure on the surface of the metal support. The uneven structure on the surface of the metal support may be formed by physical or chemical treatment, for example etching, or may be preferably formed by coating metal particles on the surface of the metal support.

The metal particles coated to form the uneven structure on the surface of the metal support are preferably those having a particle size of 0.5 μm to 100 μm. When the size of the metal particles is smaller than the above range, a dense coating film made of the metal particles is more likely to be formed than the uneven structure when the coating is applied, whereas the metal particles having a size larger than the above range have poor adhesion to the surface of the support. , The effect of improving the specific surface area of the support by the uneven structure does not appear.

In addition, the metal particles are coated on the surface of the metal support by sprinkling the metal particles on the surface of the metal support and sintering in an inert gas or reducing atmosphere, or by coating a slurry of the metal particles on the surface of the metal support and then sintering them to join the metal support. Metal particles may be spun on the surface of the support at high or normal temperature, or sputtered and rolled onto the surface of the metal support, followed by sintering and bonding.

Sintering in the coating process of the metal particles is to allow the metal particles to be bonded onto the metal support by diffusion between the metal support and the coated metal particles. At this time, the sintering temperature and time is adjusted differently according to the type of metal used as the metal support. For example, in the case of using ferritic high-alloy steel, one or more metal particle layers are formed by sintering at 1000 ° C. for about 3 hours. In addition, when Al alloy or Mg alloy with low melting point is used as metal structure, the heat treatment temperature after coating the metal particles is controlled in the range of 200 ~ 600 ℃, and in the alloy with melting point around 1,000 ℃ like Cu alloy, the heat treatment temperature is 300 It is preferable to set it as the range of -800 degreeC, and to set it to 600-1200 degreeC with Ni alloy and Fe alloy. In addition, when the heat treatment temperature is increased, the heat treatment time is decreased, and when the temperature is decreased, the time is increased, but it is preferable that the temperature is usually 0.5 hours or more and not exceeding 24 hours. If the heat treatment time is too short, sufficient bonding does not occur, which causes the metal particles to easily peel off from the metal structure. If the heat treatment is too long, the bonding is perfect, but coalescing between the metal particles occurs to reduce the sharpness of irregularities. There is a risk of deformation. In addition, as time increases, unnecessary energy is used, which is a factor that deteriorates the economy.

The thickness of the metal particle layer is about several to several hundred micrometers normally. Preferably, you may be 1-300 micrometers. If the thickness is thicker than 300 μm, the amount of metal particles required to form the metal particle layer is increased, and the coating amount of the porous carrier layer formed thereafter is unnecessarily increased. The holding force is reduced to decrease the bonding strength between the coating layer and the metal structure.

Next, a porous carrier layer of a ceramic material is coated on the metal support including the uneven structure. For this purpose, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), titania (TiO ₂ ), zeolite, ceria (Ce ₂ O ₃ ), magnesia, vanadate (V ₂ O ₅ ), cobalt oxide (CoO _x ) , Iron oxide (FeO _x ), tungsten oxide (WO ₃ ), molybdenum oxide (MoO ₃ ), antimony oxide (SbO ₂ ) and rare earth oxides (Sc, Y, La-based element oxides) Wash-coating with a slurry containing the above ceramic material.

After coating the ceramic material on the metal support, a process of heat treatment at 150 ° C. to 900 ° C. may be performed to increase adhesion at the interface between the surface of the metal support and the porous carrier layer. In this process, components such as moisture contained in the porous carrier layer are removed, and the porous carrier layer is partially sintered and adhered to the metal support surface.

After the porous carrier layer is formed on the surface of the metal support, a process of supporting the catalytically active component is performed. For this purpose, a metal comprising a porous carrier layer in a solution in which at least one catalytically active component selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, tungsten, chromium, manganese, iron, cobalt, copper and zinc is dissolved. The support may be immersed in such a way that the solution penetrates into the porous structure, or the catalyst particles may be introduced into the porous structure by dipping the porous carrier on a slurry in which the catalytically active component is dispersed.

Alternatively, the catalyst active ingredient may be uniformly distributed in the ceramic material constituting the porous carrier layer to include the catalytically active ingredient in advance, and then coated on the surface of the metal support including the uneven structure.

In any case, the porous carrier layer and the catalytically active component formed on the metal support including the uneven structure on the surface have excellent interfacial adhesion when exposed to various environments in which soot filtration devices such as heat, chemical fatigue and vibration are used. The resulting ceramic material or catalytically active component can be detached from the surface of the metal support to reduce filtration performance.

The invention will be described in more detail with reference to the following examples. However, this is only for the understanding of the present invention and the present invention should not be regarded as being limited thereto.

Example

In order to form a porous carrier layer of ceramic material on a metal foam (Alantum FeCrAl alloy foam), a high-surface area aluminum oxide (Al ₂ O ₃ ) powder (AEROXIDE® AluC) was washed with distilled water to form a porous carrier layer of ceramic material. Attrition mill) was ground and mixed. The mixed concentration of distilled water and aluminum oxide powder was 40 weight%. The pH was adjusted to 4 with nitric acid (HNO ₃ ) for uniform dispersion and ground and mixed for 90 minutes. The metal foam having irregularities on the surface was dipped for several seconds in the alumina slurry formed above, and then taken out. Blowed with air to remove residual alumina washcoat. The metal foam formed on the surface of aluminum oxide was dried at 120 ° C. for 1 hour and then calcined at 750 ° C. for 2 hours. 1 shows a SEM photograph of the alumina powder prepared as described above and the wash-coated metal foam.

The prepared metal foam had a high specific surface area of about 87 m ² / g by aluminum oxide on the surface.

Thermal fatigue evaluation

The thermal fatigue evaluation was performed 1000 times at room temperature to 700 ° C. for the metal foam prepared in Example. The results are shown in FIG. The specific surface area and mass were measured every 200 times, and the specific surface area decreased by about 17% to about 71 m ² / g after 1000 times, but the change in mass was not measured. In other words, the aluminum oxide / metal foam interface showed excellent bonding to thermal fatigue.

Chemical and Vibration Fatigue Assessment

In order to evaluate the interfacial bonding characteristics of the metal foam prepared in Example under chemical and vibration environments, the mass loss was measured for about 80 minutes in an ultrasonic vibration environment of 40 KHz after immersion in petroleum ether solution at room temperature. . The change in mass was measured for 20 minutes, but no decrease occurred. That is, the aluminum oxide / metal foam showed excellent bonding characteristics chemically and mechanically at the interface.

Claims (6)

Metal support;
A porous metal particle layer in which metal particles are coated and sintered and bonded to the metal support surface; And
On the porous metal particle layer, comprising a ceramic ceramic carrier layer formed by penetrating the pores of the porous metal particle layer,
The average particle diameter of the metal particles is 0.5㎛ to 100㎛,
The porous metal particle layer is a soot filtration device, characterized in that the adjacent metal particles have a network structure bonded by partial sintering.
In claim 1,
The ceramic carrier layer may be alumina (Al ₂ O ₃ ), silica (SiO ₂ ), titania (TiO ₂ ), zeolite, ceria (Ce ₂ O ₃ ), magnesia, vanadate (V ₂ O ₅ ), cobalt oxide ( 1 selected from the group consisting of CoOx, iron oxide (FeOx), tungsten oxide (WO ₃ ), molybdenum oxide (MoO ₃ ), antimony oxide (SbO ₂ ), and rare earth oxides (Sc, Y, La-based element oxides) A soot filtration device comprising at least one ceramic material.
In claim 1,
A soot filtration device comprising a catalytically active component supported on the ceramic carrier layer.
4. The method of claim 3,
Wherein said catalytically active component is at least one selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, tungsten, chromium, manganese, iron, cobalt, copper and zinc.
3. The method of claim 2,
The ceramic carrier layer is a soot filtration device, characterized in that formed by coating the ceramic material by wash coating method.
In claim 1,
The metal support is a soot filtration device, characterized in that at least one selected from a metal foam, a metal plate, a metal rod, a metal pipe, a metal rod and a metal cylinder.

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