Patent Publication Number: US-2018030870-A1

Title: Method of manufacturing catalyzed particulate filter

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to and the benefit of Korean Patent Application No. 10-2016-0094741 filed on Jul. 26, 2016, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a method of manufacturing a catalyzed particulate filter. More particularly, the present invention relates to a method of manufacturing a catalyzed particulate filter including at least one porous wall defining a boundary between at least one inlet channel and at least one outlet channel and a support located within at least one among the at least one inlet channel and the at least one outlet channel, the method being related to effectively coating a catalyst on the at least one wall and the support. 
     Description of Related Art 
     An exhaust gas from internal combustion engines such as diesel engines or a variety of combustion equipment contains particulate matter (PM). Such PMs can cause environmental pollution when emitted into the atmosphere. For this reason, gas exhaust systems are equipped with a particulate filter for capturing PM. 
     The particulate filter may be categorized as a flow-through particulate filter or a wall-flow particulate filter depending on a flow of fluid. 
     In the flow-through particulate filter, a fluid flowing into a channel flows only within this channel without moving to another channel. This helps minimize an increase in back pressure, but necessitates a means for capturing particulate matter in the fluid and may result in low filter performance. 
     In the wall-flow particulate filter, a fluid flowing into a channel moves to an adjacent channel and is then discharged from the particulate filter through the adjacent channel. That is, a fluid flowing into an inlet channel moves to an outlet channel through a porous wall and is then discharged from the particulate filter through the outlet channel. When a fluid passes through the porous wall, particulate matter in the fluid is captured without passing through the porous wall. The wall-flow particulate filter is effective at removing particulate matter, although it may increase the back pressure to some extent. Hence, wall-flow particulate filters are primarily used. 
     A vehicle is equipped with at least one catalytic converter, along with a particulate filter. The catalytic converter is designed to remove carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx). 
     The catalytic converter may be physically separated from the particulate filter, or combined with the particulate filter by coating a catalyst in the particulate filter. The particulate filter coated with a catalyst may be called a catalyzed particulate filter (CPF). 
     In the CPF, the catalyst is coated on the porous wall that separates the inlet channel and the outlet channel from each other, and the fluid passes through the porous wall and contacts with the catalyst coating. There is a pressure difference between the inlet channel and outlet channel separated by the porous wall. This allows the fluid to pass fast through the porous wall. Accordingly, the contact time between the catalyst and the fluid is short, which makes it hard for a catalytic reaction to occur efficiently. 
     Also, a thick catalyst coating on the porous wall allows the catalyst to block the micropores on the wall, and this may disturb the flow of the fluid from the inlet channel to the outlet channel. Accordingly, the back pressure increases. To minimize the increase in back pressure, a catalyst is thinly coated on the walls in the CPF. Thus, an amount of catalyst coating in the CPF may be insufficient for the catalytic reaction to occur efficiently. 
     To overcome this problem, the surface area of walls to be coated with the catalyst may be increased by increasing the number (density) of inlet channels and outlet channels (hereinafter, collectively referred to as ‘cells’). However, the increase in cell density in the limited space reduces the wall thickness. The reduction in wall thickness may deteriorate the filter performance. Therefore, the cell density should not be increased to more than the density limit. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY 
     Various aspects of the present invention are directed to providing a method of manufacturing a catalyzed particulate filter having advantages of minimizing an increase in back pressure and increasing catalyst loading. 
     Another exemplary embodiment various aspects of the present invention are directed to providing a method of manufacturing a catalyzed particulate filter having advantages of increasing entire catalyst loading coated in the particulate filter but minimizing catalyst loading coated on a porous wall by disposing a support on which much catalyst is coated in inlet channels and outlet channels. 
     A method of manufacturing a catalyzed particulate filter according to an exemplary embodiment of the present invention may include: preparing a bare particulate filter including at least one inlet channel which may have a first end being open and a second end being blocked, at least one outlet channel which may have a first end being blocked and a second end being open and which is positioned alternately with the at least one inlet channel, at least one porous wall which defines a boundary between adjacent inlet and outlet channels, and a support which is located within at least one among the at least one inlet channel and the at least one outlet channel; injecting a catalyst slurry into the at least one inlet channel and the at least one outlet channel; discharging a portion of the catalyst slurry by blowing gas into or drawing the gas from the at least one inlet channel or the at least one outlet channel; and drying/calcining the particulate filter from which the portion of the catalyst slurry is discharged. 
     The at least one inlet channel, the at least one outlet channel, the at least one porous wall, and the support may extend in a same direction. 
     An amount of the catalyst slurry removed from the at least one porous wall may be larger than that of the catalyst slurry removed from the support in the discharging a portion of the catalyst slurry. 
     An amount of a catalyst coated on the at least one porous wall may be controlled by adjusting a pressure of the gas which is blown or drawn. 
     In one aspect, the support and the at least one porous wall may include a same material. 
     In another aspect, the support and the at least one porous wall may include different materials from each other. 
     A viscosity of the catalyst slurry may be smaller than or equal to 200 cpsi. 
     The viscosity of the catalyst slurry may be controlled according to content of solid particle, pH of the catalyst slurry, and particle size of the solid particle. 
     A lean NOx trap (LNT) catalyst or a selective catalytic reduction (SCR) catalyst may be coated on the at least one porous wall and the support. 
     As described above, increase in back pressure may be minimized and entire catalyst loading may be increase by disposing a support within at least one among at least one inlet channel and at least one outlet channel and coating much catalyst on the support to reduce catalyst loading on a porous wall. 
     In addition, sufficient filter performance and catalyst performance can be achieved since larger catalyst loading and a larger contact area (time) between a fluid and the catalyst are provided while keeping the wall thickness. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a catalyzed particulate filter according to an exemplary embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the catalyzed particulate filter according to an exemplary embodiment of the present invention. 
         FIG. 3  is a front view illustrating some of inlet and outlet channels in the catalyzed particulate filter according to an exemplary embodiment of the present invention. 
         FIG. 4  is a graph illustrating the nitrogen oxide reduction vs. the amount of catalyst coating in a wall-flow particulate filter. 
         FIG. 5  is a graph illustrating the nitrogen oxide reduction vs. the amount of catalyst coating in a flow-through carrier. 
         FIG. 6  is a graph illustrating the back pressure vs. the amount of catalyst coating in the wall-flow particulate filter. 
         FIG. 7  is a graph illustrating the back pressure vs. the amount of catalyst coating in the flow-through media. 
         FIG. 8  is a graph illustrating the back pressure vs. the cell density in the flow-through media. 
         FIG. 9  is a graph illustrating the back pressure vs. the cell density in the wall-flow particulate filter. 
         FIG. 10  is a schematic diagram sequentially illustrating a method of manufacturing a catalyzed particulate filter according to an exemplary embodiment of the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
     A catalyzed particulate filter according to an exemplary embodiment of the present invention can be configured for use in variety of devices, as well as vehicles, that get energy by burning fossil fuels and emit gases produced in the burning process into the atmosphere. Although this specification illustrates an example of a catalyst particulate filter configured for use in a vehicle, the present invention should not be construed as limited to this example. 
     The vehicle is equipped with an engine for generating power. The engine converts chemical energy into mechanical energy by the combustion of a fuel-air mixture. The engine is connected to an intake manifold to draw air into a combustion chamber, and connected to an exhaust manifold where an exhaust gas produced during combustion is collected and emitted out. Injectors are mounted at the combustion chamber or intake manifold to spray fuel into the combustion chamber or intake manifold. 
     The exhaust gas produced from the engine is emitted out of the vehicle via an exhaust system. The exhaust system may include an exhaust pipe and exhaust gas recirculation (EGR) apparatus. 
     The exhaust pipe is connected to the exhaust manifold to emit the exhaust gas out of the vehicle. 
     The exhaust gas recirculation apparatus is mounted on the exhaust pipe, and the exhaust gas emitted from the engine pass through the exhaust gas recirculation apparatus. Also, the exhaust gas recirculation apparatus is connected to the intake manifold and mixes some of the exhaust gas with air to control the combustion temperature. The combustion temperature may be regulated by controlling ON/OFF of an exhaust gas recirculation (EGR) valve in the exhaust gas recirculation apparatus. That is, the amount of exhaust gases supplied to the intake manifold is adjusted by controlling the ON/OFF of the EGR valve. 
     The exhaust system may further include a particulate filter that is mounted on the exhaust pipe and captures particulate matter in the exhaust gas. The particulate filter may be a catalyzed particulate filter according to an exemplary embodiment of the present invention that removes harmful substances as well as particulate matter in exhaust gases. 
     Hereinafter, a catalyzed particulate filter according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a perspective view of a catalyzed particulate filter according to an exemplary embodiment of the present invention;  FIG. 2  is a cross-sectional view of the catalyzed particulate filter according to an exemplary embodiment of the present invention;  FIG. 3  is a front view illustrating some of inlet and outlet channels in the catalyzed particulate filter according to an exemplary embodiment of the present invention. 
     As illustrated in  FIG. 1 , a catalyzed particulate filter according to an exemplary embodiment of the present invention includes at least one inlet channel  10  and at least one outlet channel  20  within a housing. The at least one inlet channel  10  and the at least one outlet channel  20  are separated from each other by walls  30 . A support  40  may be located within at least one among the at least one inlet channel  10  and the at least one outlet channel  20 . 
     In this specification, the inlet channel  10  and the outlet channel  20  may be collectively referred to as ‘cells’. Although, in this specification, the housing has a cylindrical shape and the cells have a rectangular shape, the housing and the cells are not limited to such shapes. 
     Referring to  FIG. 2  and  FIG. 3 , the inlet channel  10  extends along the flow of the exhaust gas. The front end of the inlet channel  10  is open so that the exhaust gas is introduced into the particulate filter  1  through the inlet channel  10 . The rear end of the inlet channel  10  is blocked by a first plug  12 . Thus, the exhaust gas in the particulate filter  1  does not flow out of the particulate filter  1  through the inlet channel  10 . 
     The outlet channel  20  extends along the flow of the exhaust gas, and may be placed parallel to the inlet channel  10 . At least one inlet channel  10  is located around the outlet channel  20 . 
     For example, when the cells have a rectangular shape, each outlet channel  20  is surrounded by walls  30  on four sides. At least one of the four sides is located between each outlet channel  20  and an adjacent inlet channel  10 . When the cells have a rectangular shape, each outlet channel  20  may be surrounded by four adjacent inlet channels  10  and each inlet channel  10  may be surrounded by four adjacent outlet channels  20 , but the present invention is not limited thereto. 
     Since the front end of the outlet channel  20  is blocked by a second plug  22 , the exhaust gas does not flow into the particulate filter  1  through the outlet channel  20 . The rear end of the outlet channel  20  is open so that the exhaust gas in the particulate filter  1  flows out of the particulate filter  1  through the outlet channel  20 . 
     A wall  30  is placed between adjacent inlet and outlet channels  10  and  20  to define the boundary between them. The wall  30  may be a porous wall  30  with at least one micropore therein. The porous wall  30  allows the adjacent inlet and outlet channels  10  and  20  to fluidly communicate with each other. Thus, the exhaust gas introduced into the inlet channel  10  may move to the outlet channel  20  through the porous wall  30 . Moreover, the porous wall  30  does not cause particulate matter in the exhaust gas to pass therethrough. When the exhaust gas moves from the inlet channel  10  to the outlet channel  20  through the porous wall  30 , the particulate matter in the exhaust gases is filtered by the porous wall  30 . The porous wall  30  may be made from aluminum titanate, codierite, silicon carbide, etc. 
     The porous wall  30  may be coated with a catalyst  50 . The catalyst  50  coated on the porous wall  30  is not limited to particular ones. In other words, the wall  30  may be coated with a variety of catalysts  50  including a lean NOx trap (LNT) catalyst, a three-way catalyst, an oxidation catalyst, a hydrocarbon trap catalyst, a selective catalytic reduction (SCR) catalyst, etc., depending on the design intent. Moreover, at least two types of catalyst  50  may be coated on the wall  30 . For example, the LNT catalyst may be coated on an inside surface of the inlet channel  10  and the SCR catalyst may be coated on an inside surface of the outlet channel  20 , but the present invention is not limited thereto. 
     The support  40  may be located within at least one among the at least one inlet channel  10  and the at least one outlet channel  20 . The support  40  may be located within the at least one inlet channel  10  or within the at least one outlet channel  20 . Although  FIGS. 1 through 3  illustrate that the support  40  extends parallel to the direction in which the inlet channel  10  and/or the outlet channel  20  extend, the present invention is not limited thereto. That is, the support  40  may extend perpendicular or obliquely to the direction in which the inlet channel  10  and/or the outlet channel  20  extend. In the case that the support  40  extends perpendicular or obliquely to the direction in which the inlet channel  10  and/or the outlet channel  20  extend, at least one of the two ends of the support  40  may not contact with the porous wall  30  that separates the cells from one another. In the case that the support  40  extends parallel to the direction in which the inlet channel  10  and/or the outlet channel  20  extend, the support  40  may extend over an entire length of the channel  10  or  20  or extend over part of the length of the channel  10  or  20 . 
     The support  40  is coated with a catalyst  50 . The catalyst  50  coated on the support  40  is not limited to particular ones. In other words, the support  40  may be coated with a variety of catalysts  40  including a lean NOx trap (LNT) catalyst, a three-way catalyst, an oxidation catalyst, a hydrocarbon trap catalyst, a selective catalytic reduction (SCR) catalyst, etc. depending on the design intention. Moreover, at least two types of catalyst  50  may be coated on the support  40 . For example, the LNT catalyst and the SCR catalyst may be sequentially coated on the support  40 , but the present invention is not limited thereto. Furthermore, different types of catalyst  50  may be coated on a first side and a second side of the support  40 . Also, the catalyst  50  coated on the support  40  may be a same type as or a different type from the catalyst  50  coated on the wall  30 . 
     Meanwhile, the support  40  is provided to hold the catalyst  50  in place, rather than serving as a filter. Thus, the support  40  is not necessarily made from a porous material. That is, the support  40  may be made from a same material as the porous wall  30  or a different material. Even in the case that the support  40  is made from a porous material, the exhaust gas mostly moves along the support  40  and wall  30  without passing through the support  40 , because there is little difference in pressure between the two parts of the channel  10  or  20  separated by the support  40 . Also, the support  40  does not need to be thick since it is not required to serve as a filter. That is, the support  40  may be thinner than the wall  30 , which minimizes an increase in back pressure. When the support  40  is made from a porous material, the catalyst  50  is coated on a surface of the support  40  and on the micropores in the support  40 . On the contrary, when the support  40  is made from a non-porous material, the catalyst  50  is coated on the surface of the support  40 . 
     As mentioned previously, the catalyst  50  may be coated on both the support  40  and the porous wall  30 . In the instant case, an amount of catalyst  50  coated on the support  40  may be greater than that coated on the porous wall  30 . The catalyst  50  may be thinly coated on the porous wall  30  since the porous wall  40  serves as a filter. On the contrary, the catalyst  50  may be thickly coated on the support  40  since the support  40  is not required to serve as a filter. Accordingly, the amount of catalyst coating in the particulate filter  1  may be increased. Here, the amount of catalyst  50  refers to the amount of catalyst coating per unit length or unit area. 
     Operation of the catalyzed particulate filter according to the exemplary embodiment of the present invention will be described below. 
       FIG. 4  is a graph illustrating the nitrogen oxide reduction vs. the amount of catalyst coating in a wall-flow particulate filter; and  FIG. 5  is a graph illustrating the nitrogen oxide reduction vs. the amount of catalyst coating in a flow-through carrier. 
       FIG. 4  and  FIG. 5  illustrate measurement data obtained by running the same engine in the same mode. The particulate filter used in the test has the same cross-sectional area, volume, and catalyst coating amount as the carrier used in the test, and the number of cells in the particular filter is different from the number of cells in the carrier. The walls in the particulate filter cannot be made thin since they are required to function as filters, which results in a small number of cells. On the contrary, the walls in the carrier can be made thin since they are not required to function as filters, which results in a larger number of cells. A cell density of the particulate filter used in the test is 300 cpsi (cells per square inch) and a wall thickness is 12 mil (1/1,000 inch), and the cell density of the carrier is 400 cpsi and the wall thickness is 3 mil. 
     Referring to  FIG. 4  and  FIG. 5 , the nitrogen oxide reduction with the particulate filter is 5 to 15% lower than the nitrogen oxide reduction with the carrier, under the condition that the same amount of catalyst coating is used. Moreover, the greater the amount of catalyst coating on the particulate filter or carrier is, the larger the difference in nitrogen oxide reduction is. As the number of cells provided for the same volume increases, the contact area (contact time) between the walls and the exhaust gas increases. Accordingly, even with the same amount of catalyst coating, the flow-through carrier allows for a larger contact area (longer contact time) between the catalyst and the exhaust gas, compared to the wall-flow particulate filter, thereby improving the nitrogen oxide reduction. As mentioned previously, the support  40  in the present exemplary embodiment plays the same role as the flow-through carrier. Accordingly, the nitrogen oxide reduction can be improved by coating the catalyst  50  on the support  40  rather than on the wall  30 . 
       FIG. 6  is a graph illustrating the back pressure vs. the amount of catalyst coating in the wall-flow particulate filter; and  FIG. 7  is a graph illustrating the back pressure vs. the amount of catalyst coating in the flow-through carrier. 
       FIG. 6  and  FIG. 7  illustrate measurement data obtained by running the same engine in the same mode. The particulate filter used in the test has the same cross-sectional area, volume, and catalyst coating amount as the carrier used in the test. The cell density in the particulate filter used in the test is 300 cpsi (cells per square inch) and the wall thickness is 12 mil (1/1,000 inch), and the cell density in the carrier is 400 cpsi and the wall thickness is 3 mil. 
     Referring to  FIG. 6  and  FIG. 7 , it can be seen that the back pressure applied to the particulate filter is five times higher than the back pressure applied to the carrier, under the condition that the same amount of catalyst coating is used. Also, it can be seen that the back pressure applied to the particulate filter increases greatly as the amount of catalyst coating on the particulate filter increases, whereas the back pressure applied to the carrier increases only slightly even if the amount of catalyst coating on the media increases. Accordingly, it is concluded that, in terms of back pressure, the flow-through carrier has more advantages over the wall-flow particulate filter as the amount of catalyst coating becomes increase. As mentioned previously, in this exemplary embodiment, the support  40  plays the same role as the flow-through carrier. Therefore, coating the catalyst  50  on the support  40  rather than on the wall  40  minimizes the increase in back pressure. 
       FIG. 8  is a graph illustrating the back pressure vs. the cell density in the flow-through carrier; and  FIG. 9  is a graph illustrating the back pressure vs. the cell density in the wall-flow particulate filter. 
     The X-axis in  FIG. 8  describes both the cell density and the wall thickness. For example, 300 cpsi/4 mil means a cell density is 300 cpsi and a wall thickness is 4 mil.  FIG. 8  shows measurement data obtained only by varying the number of cells in flow-through carriers having the same cross-sectional area. Referring to  FIG. 8 , it can be seen that there is only a slight increase in back pressure even if the number of cells in the flow-through carrier increases. As mentioned previously, the support  40  in the present exemplary embodiment plays the same role as the flow-through carrier. Accordingly, it is expected that even an increase in the number of supports  40  will result in a slight increase in back pressure. 
     In  FIG. 9 , the dotted line represents a wall thickness of 8 mil, the one-dot chain line represents a wall thickness of 12 mil, and the solid line represents a wall thickness of 13 mil.  FIG. 9  shows a ratio of the back pressure relative to a reference back pressure vs. cell density because the back pressure varies greatly with cell density.  FIG. 9  shows measurement data obtained only by varying the number of cells in wall-flow particulate filters having the same cross-sectional area. Referring to  FIG. 9 , in the wall-flow particulate filter, the back pressure increases as the number of cells increases. It can be seen that the increase in back pressure is large especially if the wall thickness is large. Since the particulate filter functions as a filter, the larger the wall thickness is, the better the filter performance is. However, if the wall thickness is large, this limits the number of cells and causes a large increase in back pressure. 
     Referring overall to  FIG. 4  through  FIG. 9 , the nitrogen oxide reduction rises as the amount of catalyst coating on the particulate filter  1  increases. However, the increase in the amount of catalyst coating on the particulate filter  1  causes a rise in back pressure. Moreover, the number of cells in the wall-flow particulate filter  1  is limited because of the back pressure and a thickness of the wall  30  (required to achieve sufficient filter performance). 
     On the other hand, in the case of the flow-through carrier, the increase in back pressure is small even with an increase in the amount of catalyst coating, and there is no need to achieve sufficient filter performance. Thus, the number of cells can be increased a lot by making the walls sufficiently thin. As mentioned previously, the support  40  according to the present exemplary embodiment is not required to function as a filter but only serves as a carrier for holding the catalyst  50 . Accordingly, the support  40  according to the present exemplary embodiment performs the same function as the flow-through carrier. Consequently, the increase in back pressure is minimized even with an increase in the number of supports  40 . Moreover, a sufficient number of supports  40  can be mounted in the particulate filter  1  since the supports  40  can be made thin. In addition, the support  40  allows for an increase in the amount of catalyst  50  supported on it and a longer contact time (larger contact area) between the catalyst  50  and the exhaust gas, thereby improving the nitrogen oxide reduction. 
       FIG. 10  is a schematic diagram sequentially illustrating a method of manufacturing a catalyzed particulate filter according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 10 , the catalyzed particulate filter  1  is started to be manufactured by preparing a bare particulate filter at step  5100 . As described above, the bare particulate filter includes the at least one inlet channel  10 , the at least one outlet channel  20 , the at least one porous wall  30  defining the boundary between the adjacent inlet and outlet channels  10  and  20 , and the support  40  located within the at least one among the at least one inlet channel and the at least one outlet channel. After the bare particulate filter is manufactured through extrusion and so on, the both ends of the bare particulate filter are covered by the first and second plugs  12  and  22 . 
     If the bare particulate filter is manufactured at the step S 100 , a catalyst slurry  52  is injected into the at least one inlet channel  10  and the at least one outlet channel  20  at step S 110 . In the instant case, the at least one inlet channel  10  and the at least one outlet channel  20  are filled with the catalyst slurry  52 . 
     Herein, making the catalyst slurry will be briefly described. 
     Firstly, a catalyst solid particle having a same ingredients as a target catalyst is prepared. For example, when the target catalyst is an LNT catalyst, the catalyst solid particle including Al 2 O 3 , CeO 2 , Ba, Pt, Pd, Rh, etc. is prepared. In addition, when the target catalyst is an SCR catalyst, the catalyst solid particle including zeolite, Cu, etc. is prepared. 
     After that, the catalyst solid particle is mixed with water to wet-grind the catalyst solid particle. At this time, content of the catalyst solid particle is approximately 20 wt %-40 wt %. Herein, the catalyst solid particle wet-grinded and mixed with the water is called the catalyst slurry. 
     In addition, pH of the catalyst slurry can be adjusted by adding acid component such as acetic acid into the catalyst slurry, and a viscosity of the catalyst slurry can be changed by the pH of the catalyst slurry. That is, the viscosity of the catalyst slurry is controlled according to content of the solid particle, the pH of the catalyst slurry, and particle size of the solid particle. According to the present exemplary embodiment, the viscosity of the catalyst slurry  52  is controlled to be smaller than or equal to 200 cpsi to prevent the catalyst slurry from blocking the micropores on the porous wall. 
     After the step S 110  is performed, gas is blown into or is drawn from the at least one inlet channel  10  or the at least one outlet channel  20  so that a portion of the catalyst slurry  52  is discharged from the channels  10  and  20  at step S 120 . For example, a blower is connected to any one channel  10  (inlet channel  10  in  FIG. 10 ) of the channels  10  and  20  and blows the gas into a first channel  10 . On the contrary, a vacuum pump is connected to a second channel  20  (outlet channel  20  in  FIG. 10 ) of the channels  10  and  20  and draws the gas from the second channel  20 . In addition, blowing gas into the first channel  10  and drawing the gas from the second channel  20  may be simultaneously gas performed. 
     When the gas is blown into or drawn from the channel  10  or  20  at the step S 120 , a pressure difference between the inlet channel  10  and the outlet channel  20  is generated. The gas passes through the inlet channel  10  and is then discharged from the outlet channel  20  or passes through the outlet channel  20  and is then discharged from the inlet channel  10  by the pressure difference. At this time, the portion of the catalyst slurry  52  filling the inlet channel  10  or the outlet channel  20  is discharged from the outlet channel  20  or the inlet channel  10  with the gas. 
     Since the pressure difference between the inlet channel  10  and the outlet channel  20  across the porous wall  30  is greatly generated, the gas passes through the porous wall  30  relatively quickly at the step S 120 . Therefore, a substantial amount of the catalyst slurry  52  on the porous wall  30  is removed from the porous wall  30  and is discharged from the outlet channel  20  or the inlet channel  10 . 
     As described above, since any one support  40  is located within any one channel  10  or  20 , a pressure difference between two parts of the channel  10  or  20  divided by the support  40  is hardly generated. Therefore, the gas hardly passes through the support  40  and moves along the support  40  and the wall  30 . Therefore, a little amount of the catalyst slurry  52  on the support  40  is removed from the support  40  and is discharged from the outlet channel  20  or the inlet channel  10 . 
     When the gas is blown into or drawn from the inlet channel  10  or the outlet channel  20  filled with the catalyst slurry  52 , an amount of the catalyst slurry  52  removed from the porous wall  30  is larger than that of the catalyst slurry  52  removed from the surface of the support  40 . Resultantly, the catalyst loading coated on the porous wall  30  is small and the catalyst loading coated on the support  40  is large. The increase in the back pressure when using the CPF may be suppressed by reducing the catalyst loading coated on the porous wall  30 , but the entire catalyst loading in the CPF may be increased by increasing the catalyst loading coated on the support  40 . In addition, the catalyst loading coated on the porous wall  30  can be controlled by adjusting a pressure of the gas which is blown into or drawn from the channel  10  or  20 . When the pressure of the gas is high, the catalyst loading coated on the porous wall  30  decreases. When the pressure of the gas is low, on the contrary, the catalyst loading coated on the porous wall  30  increases. At this time, the catalyst loading coated on the support  40  is hardly dependent upon the pressure of the gas which is blown into or drawn from the channel  10  or  20 . 
     After that, the particulate filter from which the portion of the catalyst slurry  52  is discharged is dried/calcined at step S 130  so that the catalyzed particulate filter  1  is manufactured. 
     When the CPF is manufactured through the manufacturing method according to the exemplary embodiment of the present invention, the same type of the catalyst is coated on the porous wall  30  and the support  40 . In addition, the catalyst loading on the porous wall  30  serving as a filter is small so that the increase in the back pressure may be suppressed. Further, much of the catalyst can be coated on the support  40  which does not serve as a filter and only supports the catalyst. Therefore, performance of the catalyst may be improved. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner”, “outer”, “up”, “down”, “upper”, “lower”, “upwards”, “downwards”, “front”, “rear”, “back”, “inside”, “outside”, “inwardly”, “outwardly”, “interior”, “exterior”, “inner”, “outer”, “forwards”, and “backwards” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.