Exhaust gas purification catalyst filter for gasoline engines

Abstract

An object of the present invention is to provide an exhaust gas purification catalyst filter that improves soot capture performance without increasing the pressure loss associated with forming a catalyst layer within the partition walls of a wall-flow type substrate. The exhaust gas purification catalyst filter for gasoline engines purifies exhaust gas from gasoline engines and is formed of a wall-flow type substrate and a catalyst layer. The wall-flow type substrate is defined by porous partition walls to define an inlet-side cavity open at the exhaust gas inlet side and an outlet-side cavity adjacent to the inlet-side cavity and open at the exhaust gas outlet side. The catalyst layer is formed within the pores of the partition walls. The absolute value of the partiality of the catalyst layer formed within the pores of the partition walls is 4.50 or less. The amount of the washcoat layer, excluding the mass of the platinum group, formed within the pores of the partition walls is 40 g / L or more and 50 g / L or less. The catalyst layer formed within the pores of the partition walls is a single layer and does not contain Ba.

Description

Technical Field

[0001] The present invention relates to an exhaust gas purification catalyst filter for a gasoline engine. Background Art

[0002] Exhaust gas from internal combustion engines contains particulate matter (PM), primarily composed of carbon, and ash, composed of incombustible components, contributing to air pollution. Traditionally, diesel engines, which are more prone to PM emissions than gasoline engines, have been subject to strict PM emission limits. However, in recent years, PM emission limits for gasoline engines have also been tightened.

[0003] As a means of reducing particulate matter emissions, a known method involves installing a particulate filter in the exhaust passage of an internal combustion engine to accumulate and capture particulate matter. In recent years, research has focused on space savings and other considerations. To simultaneously suppress particulate matter emissions and remove harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx), a catalyst layer has been developed by applying a catalyst slurry to the particulate filter and then calcining the slurry to form a catalyst layer.

[0004] For a particulate filter having a wall-flow type substrate having an inlet side chamber whose end is open on the exhaust gas inlet side and which is adjacent to the inlet side chamber and has an end open on the exhaust gas discharge side and is defined by a porous partition wall, the following method is known as a method for forming such a catalyst layer: adjusting the viscosity, solid content and other properties of the slurry, pressurizing one of the inlet side chamber or the discharge side chamber to generate a pressure difference between the inlet side chamber and the discharge side chamber, thereby adjusting the penetration of the catalyst slurry into the partition wall (for example, see Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: WO2016 / 060048 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] From the perspective of removing particulate matter, the particulate filter described in Patent Document 1 has a wall-flow structure in which exhaust gas passes through pores in the partition walls. However, there is still room for improvement in soot capture performance.

[0010] The present invention has been completed in response to the above-mentioned challenges, and its object is to provide an exhaust gas purification catalyst filter that improves soot capture performance without increasing the pressure loss associated with forming a catalyst layer within the partition walls of a wall-flow type substrate. It should be noted that the present invention is not limited to the objectives described herein, and further objects of the present invention include achieving effects not achievable by conventional techniques and resulting from the various configurations described below as embodiments of the invention.

[0011] Means for solving problems

[0012] The inventors of this application have conducted extensive research to improve soot capture performance without increasing the pressure loss associated with forming a catalyst layer within the partition walls of a wall-flow substrate. They discovered that by adjusting the degree of localization of the catalyst layer formed within the partition walls of the wall-flow substrate and the amount of washcoat layer applied to the catalyst layer, increases in pressure loss can be suppressed while improving soot capture performance. This led to the completion of the present invention. Specifically, the present invention provides various specific embodiments as shown below.

[0013] [1]

[0014] Gasoline engine exhaust gas purification catalyst filter, which is an exhaust gas purification catalyst filter for purifying the exhaust gas of the gasoline engine.

[0015] The above-mentioned gasoline engine exhaust gas purification catalyst filter is formed by a wall flow type substrate and a catalyst layer.

[0016] The wall-flow type substrate is divided into an inlet-side chamber with an open end on the exhaust gas inlet side and an exhaust-side chamber adjacent to the inlet-side chamber and with an open end on the exhaust gas exhaust side by a porous partition wall.

[0017] The catalyst layer is formed in the pores of the partition wall.

[0018] The absolute value of the partiality of the catalyst layer formed in the pores of the partition wall is 4.50 or less,

[0019] The amount of the washcoat layer of the catalyst layer formed in the pores of the partition walls, excluding the mass of the platinum group, is 40 g / L or more and 50 g / L or less.

[0020] The catalyst layer formed in the pores of the partition wall is a single layer.

[0021] The catalyst layer does not contain Ba.

[0022] [2]

[0023] The exhaust gas purification catalyst filter for gasoline engines as described in [1], wherein the catalyst layer formed in the pores of the partition wall is composed of a catalyst metal and a support component, the catalyst metal is Pd and / or Rh, and the support component is an oxide of Al, Zr and / or Ce.

[0024] 〔3〕

[0025] A method for producing an exhaust gas purification catalyst filter for a gasoline engine, which is a method for producing an exhaust gas purification catalyst filter for purifying exhaust gas from a gasoline engine.

[0026] The aforementioned manufacturing method has the following features:

[0027] a step of preparing a wall-flow type substrate, wherein the wall-flow type substrate is defined by porous partition walls to define an inlet-side chamber having an open end on an exhaust gas inlet side and an exhaust-side chamber adjacent to the inlet-side chamber and having an open end on an exhaust gas exhaust side;

[0028] an impregnation step of impregnating the end portion of the wall-flow type substrate on the exhaust gas inlet side or the exhaust gas outlet side with a catalyst slurry containing ammonium carbonate;

[0029] a coating step of introducing gas into the wall-flow type substrate from the end portion impregnated with the catalyst slurry, thereby coating the catalyst slurry impregnated in the wall-flow type substrate on the pore surfaces of the partition walls; and

[0030] The calcining step is to calcine the applied catalyst slurry to obtain an exhaust gas purification catalyst filter having an absolute value of the partiality of the catalyst layer formed in the pores of the partition wall of 4.50 or less, and a washcoat amount of the catalyst layer excluding the mass of the platinum group per 1L of the wall-flow type substrate of 40 g / L or more and 50 g / L or less.

[0031] The catalyst layer formed in the pores of the partition wall is a single layer.

[0032] The catalyst layer does not contain Ba.

[0033] [4]

[0034] The method for manufacturing a gasoline engine exhaust gas purification catalyst filter as described in [3] comprises the following steps:

[0035] After the calcination step to obtain the exhaust gas purifying catalyst filter, the catalyst layer in the pores of the partition walls of the exhaust gas purifying catalyst filter was measured using an electron probe microanalyzer to examine the absolute value of the eccentricity of the catalyst layer.

[0036] Effects of the Invention

[0037] According to the present invention, a gasoline engine exhaust gas purification catalyst filter can be provided that improves soot capture performance without increasing pressure loss. By installing such a catalyst filter, further performance of the exhaust gas treatment system can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] [ Figure 1 ] is a cross-sectional view schematically showing one form of the exhaust gas purification catalyst of the present embodiment.

[0039] [ Figure 2 ] is a graph showing the partial distribution of the catalyst layers of Examples 1 to 3 and Comparative Examples 1 to 3.

[0040] [ Figure 3 ] is a graph showing the correlation between the soot capture rate and the pressure loss in Examples 1 to 3 and Comparative Examples 1 to 3. DETAILED DESCRIPTION

[0041] Hereinafter, embodiments of the present invention will be described in detail. The following embodiments are examples (representative examples) of embodiments of the present invention, and the present invention is not limited thereto. In addition, the present invention can be implemented by any changes without departing from the scope of its purpose. It should be noted that, in this specification, unless otherwise specified, positional relationships such as up and down, left and right are based on the positional relationships shown in the drawings. In addition, the dimensional ratios in the drawings are not limited to the ratios shown in the drawings.

[0042] In this specification, when "to" is used to indicate a numerical value or property value before or after it, it is used to include the values ​​before and after it. For example, the expression "1 to 100" includes both the lower limit "1" and the upper limit "100". The same applies to the expression of other numerical ranges.

[0043] [Exhaust gas purification catalyst]

[0044] The exhaust gas purification catalyst filter of the present embodiment is an exhaust gas purification catalyst filter 100 for purifying exhaust gas discharged from a gasoline engine, and is characterized by comprising: a wall-flow type substrate 10, which utilizes a porous partition wall 13 to demarcate an inlet side chamber 11 with an opening at an end 11a on the exhaust gas inlet side, and a discharge side chamber 12 adjacent to the inlet side chamber 11 and with an opening at an end 12a on the exhaust gas discharge side; and a catalyst layer 21 formed in the pores of the partition wall 13, wherein the skewness of the catalyst layer when forming the catalyst layer 21 is 4.50 or less, the carrier coating amount of the catalyst layer 21 excluding the platinum group mass (hereinafter also referred to as "WC amount") is 40 g / L or more and 50 g / L or less, the catalyst layer 21 formed in the pores of the partition wall 13 is a single layer, and the catalyst layer 21 does not contain Ba.

[0045] For each component, see Figure 1 The exhaust gas purification catalyst filter of this embodiment is described below with reference to a cross-sectional view schematically showing the exhaust gas purification catalyst filter. The exhaust gas purification catalyst filter of this embodiment has a wall-flow structure. In the exhaust gas purification catalyst filter 100 having such a structure, exhaust gas discharged from a gasoline engine flows into the inlet-side chamber 11 from the end 11a (opening) on ​​the exhaust gas inlet side, passes through the pores of the partition wall 13, flows into the adjacent discharge-side chamber 12, and flows out from the end 12a (opening) on ​​the exhaust gas discharge side. During this process, particulate matter (PM) that is difficult to pass through the pores of the partition wall 13 generally accumulates on the partition wall 13 and / or in the pores of the partition wall 13 within the inlet-side chamber 11. The accumulated particulate matter is then removed by the catalytic function of the catalyst layer 21 or by combustion at a predetermined temperature (e.g., approximately 500 to 700°C). Furthermore, the exhaust gas contacts the catalyst layer 21 formed within the pores of the partition walls 13. As a result, carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust gas are oxidized into water (H2O), carbon dioxide (CO2), and the like, while nitrogen oxides (NOx) are reduced to nitrogen (N2), thereby purifying (detoxifying) harmful components. It should be noted that in this specification, the removal of particulate matter and the purification of harmful components such as carbon monoxide (CO) are collectively referred to as "exhaust gas purification performance." Each component is described in more detail below.

[0046] (Partiality of the catalyst layer)

[0047] In this embodiment, the catalyst layer localization is an index indicating the dispersion of the catalyst layer within the partition walls 13. The localization in this embodiment can be calculated using the following formula based on the catalyst layer within each wall measured using an electron probe microanalyzer (hereinafter also referred to as "EPMA").

[0048] Degree of unevenness=|(degree of unevenness D1 of the catalyst layer in the exhaust gas inlet side portion 13a of the partition wall 13)-(degree of unevenness D2 of the catalyst layer in the exhaust gas outlet side portion 13b of the partition wall 13)|

[0049] Degree of partial distribution D1 within the wall = (Degree of partial distribution D11 of the catalyst in the region 13at on the inlet chamber 11 side of the portion 13a) - (Degree of partial distribution D12 of the catalyst in the region 13ab on the outlet chamber 12 side of the portion 13a)

[0050] Partial partiality D11 = the sum of the local partiality of the catalyst in regions 1 to 5, among the local partialities of the catalyst in regions 1 to 10 derived by dividing the portion 13a into 10 equal parts

[0051] Partial partiality D12 = the sum of the partial partialities of the catalysts in regions 6 to 10, among the partial partialities of the catalysts in regions 1 to 10 derived by dividing the portion 13a into 10 equal parts.

[0052] Degree of partial distribution D2 on the wall = (Degree of partial distribution D21 of the catalyst in the region 13bt on the inlet chamber 11 side of the portion 13b) - (Degree of partial distribution D22 of the catalyst in the region 13bb on the outlet chamber 12 side of the portion 13b)

[0053] Partial partiality D21 = the sum of the partial partiality of the catalyst in regions 1 to 5, among the partial partialities of the catalyst in regions 1 to 10 derived by dividing the portion 13b into 10 equal parts.

[0054] Partial partiality D22 = the sum of the partial partiality of the catalyst in regions 6 to 10, among the partial partialities of the catalyst in regions 1 to 10 derived by dividing the portion 13b into 10 equal parts.

[0055] As described above, with regard to the bias in this embodiment, the bias in the amount of catalyst in the thickness direction of the partition wall 13 (intra-wall bias D1 and D2) can be calculated in the exhaust gas inlet side portion 13a and the exhaust gas discharge side portion 13b respectively, and expressed as the difference between them.

[0056] Here, the exhaust gas inlet side portion 13a can be defined as the portion extending 0.15T inward of the exhaust gas purifying catalytic filter 100 from the exhaust gas inlet side end 11a (opening), and the exhaust gas discharge side portion 13b can be defined as the portion extending 0.15T inward of the exhaust gas purifying catalytic filter 100 from the exhaust gas discharge side end 12a (opening). Note that, here, T represents the total length of the exhaust gas purifying catalytic filter 100 in the extension direction. The width W of the portions 13a and 13b is not particularly limited as long as it is a sample width that can be measured using EPMA, and can be, for example, 200 to 1000 μm.

[0057] Regions 13at and 13ab of portion 13a, and regions 13bt and 13bb of portion 13b, respectively, divide portion 13a and portion 13b into two halves in the thickness direction. Within portion 13a, region 13at is located on the inlet chamber 11 side, and region 13ab is located on the outlet chamber 12 side. Similarly, within portion 13b, region 13bt is located on the inlet chamber 11 side, and region 13bb is located on the outlet chamber 12 side. From the perspective of the exhaust gas flow, the exhaust gas passes through region 13at or region 13bt before passing through region 13ab or region 13bb.

[0058] The intra-wall distribution D1, represented by the difference in the catalyst abundance between regions 13at and 13ab obtained in the above manner, indicates the distribution of the catalyst abundance in the thickness direction of portion 13a. In-wall distribution D1 will be described in detail. Portion 13a is divided into 10 equal parts in the thickness direction to obtain the catalyst abundance in regions 1 to 10. From this, the average value Ave of the catalyst abundance in regions 1 to 10 is calculated, and the local distribution of the catalyst in each region 1 to 10 is calculated.

[0059] (Example) Local bias in region 1 = ((Amount of catalyst in region 1) - (Average value Ave)) / (Average value Ave)

[0060] The partial distribution D11 of the catalyst in region 13at (regions 1-5) is calculated from the local distribution in regions 1-5, as shown below. Similarly, the partial distribution D12 of the catalyst in region 13ab (regions 6-10) is calculated from the local distribution in regions 6-10, as shown below. It should be noted that, except for the case where the partial distribution D11 and D12 are the same value, one of the partial distribution D11 and D12 is positive and the other is negative.

[0061] Partial partiality D11 = Σ(local partiality of catalyst in regions 1 to 5)

[0062] Partial partiality D12 = Σ(local partiality of catalyst in regions 6 to 10)

[0063] Here, the difference between the partial deviation D11 and the partial deviation D12 corresponds to the in-wall deviation D1. Therefore, the in-wall deviation D1 can be expressed by the following formula. Therefore, the in-wall deviation D1 expressed by the above formula represents the deviation in the amount of catalyst present in the thickness direction of portion 13a. This also applies to the in-wall deviation D2.

[0064] Inner wall deviation D1 = local deviation D11 - local deviation D12

[0065] =Σ(local distribution of catalyst in regions 1 to 5)-Σ(amount of catalyst in regions 6 to 10)

[0066] =Σ((the amount of catalyst present in regions 1 to 5)-(the average value Ave) / (the average value Ave))-Σ((the amount of catalyst present in regions 6 to 10)-(the average value Ave) / (the average value Ave))

[0067] =(Σ(the amount of catalyst present in regions 1 to 5)-Σ(the amount of catalyst present in regions 6 to 10)) / average value Ave

[0068] Regarding the amount of catalyst present in regions 13at and 13ab, the corresponding regions of portion 13a can be measured using EPMA, and the EPMA measurement data obtained by two-dimensionally mapping the catalyst's presence position can be binarized. Based on the area ratio of the binarized measurement data, the amount of catalyst present in each region can be calculated as a cumulative value of the catalyst amount in each region. Similarly, the amount of catalyst present in regions 13bt and 13bb can also be calculated using EPMA measurement of the corresponding regions of portion 13b as a cumulative value of the catalyst amount in each region. The two-dimensionally mapped EPMA measurement data includes information on the amount of catalyst present in the depth direction. Therefore, it is preferable to perform binarization as described above and calculate the amount of catalyst present in each region based on the area ratio of the binarized measurement data to appropriately evaluate the amount of catalyst present in the measured two-dimensional cross-section.

[0069] In this embodiment, the catalyst layer localization degree formed within each wall is set to 4.50 or less. The catalyst layer localization degree formed within each wall is set to 4.50 or less, preferably 3.50 or less, more preferably 2.50 or less, even more preferably 1.50 or less, and even more preferably 1.00 or less. Setting the catalyst layer localization degree to 4.50 or less tends to suppress increases in pressure loss of the gasoline engine exhaust gas purification catalyst filter and further improve soot capture.

[0070] Furthermore, the WC content of the catalyst layer within each wall is preferably 40 g / L to 50 g / L, more preferably 40 g / L to 49 g / L, and even more preferably 42 g / L to 46 g / L. By adjusting the WC content of the catalyst layer within this range, the balance between the pressure loss and soot capture performance of the gasoline engine exhaust gas purification catalyst filter tends to be further improved.

[0071] (Base material)

[0072] The wall-flow type substrate 10 has a wall-flow type structure in which a porous partition wall 13 is used to separate an inlet-side chamber 11 with an open end 11a on the exhaust gas inlet side and an exhaust-side chamber 12 adjacent to the inlet-side chamber 11 and open end 12a on the exhaust gas exhaust side.

[0073] As the substrate 10, substrates of various materials and shapes that have been used in the past for such applications can be used. For example, as for the material of the substrate, in order to be able to cope with the situation of being exposed to high-temperature (for example, above 400°C) exhaust gas generated when a gasoline engine is running under high-load conditions, and the situation of removing particulate matter by high-temperature combustion, a substrate formed of a heat-resistant material is preferably used. Examples of heat-resistant materials include ceramics such as cordierite, mullite, aluminum titanate, and silicon carbide (SiC), and alloys such as stainless steel. In addition, the shape of the substrate can be appropriately adjusted from the perspectives of exhaust gas purification performance and suppressing the increase in pressure loss. For example, the outer shape of the substrate can be cylindrical, elliptical, or polygonal. In addition, although it also varies depending on the space of the assembly location, the capacity of the substrate (the total volume of the chamber) is preferably 0.1 to 5 L, and more preferably 0.5 to 3 L. In addition, the total length of the substrate in the extension direction (the total length of the partition wall 13 in the extension direction) is preferably 10 to 500 mm, and more preferably 50 to 300 mm.

[0074] The inlet chamber 11 and the outlet chamber 12 are regularly arranged along the axial direction of the cylindrical shape, and the openings of adjacent chambers are alternately sealed at one end and the other end in the extension direction. The inlet chamber 11 and the outlet chamber 12 can be set to an appropriate shape and size, taking into account the flow rate and composition of the exhaust gas supplied. For example, the opening shape of the inlet chamber 11 and the outlet chamber 12 can be set to a triangle; a rectangle such as a square, parallelogram, rectangle, or trapezoid; another polygon such as a hexagon or octagon; or a circle. Alternatively, a shape having a High Ash Capacity (HAC) structure in which the cross-sectional area of ​​the inlet chamber 11 is different from that of the outlet chamber 12 can be used.

[0075] It should be noted that the number of inlet-side chambers 11 and outlet-side chambers 12 can be appropriately set to promote turbulent flow of the exhaust gas and suppress clogging caused by particulates contained in the exhaust gas. There is no particular limitation, but the pressure is preferably 200 to 400 cpsi. Furthermore, the thickness of the partition walls 13 (the length in the thickness direction perpendicular to the extension direction) is preferably 6 to 12 mils, more preferably 6 to 10 mils.

[0076] The partition wall 13 that separates adjacent chambers from each other is not particularly limited as long as it has a porous structure through which exhaust gas can pass. Its composition can be appropriately adjusted from the perspectives of exhaust gas purification performance, suppressing the increase in pressure loss, and improving the mechanical strength of the substrate. For example, when the catalyst slurry described later is used to form the catalyst layer 21 on the surface of the pores in the partition wall 13, when the pore diameter (for example, the mode diameter (the pore diameter with the largest ratio in the frequency distribution of the pore diameter (the maximum value of the distribution))) and the pore volume are large, there is a tendency that pore clogging caused by the catalyst layer 21 is less likely to occur, and the pressure loss of the resulting exhaust gas purification catalyst filter is less likely to increase, but there is also a tendency that the particulate matter capture capacity is reduced and the mechanical strength of the substrate is also reduced. On the other hand, when the pore diameter and the pore volume are small, the pressure loss is likely to increase, but there is a tendency that the particulate matter capture capacity is improved and the mechanical strength of the substrate is also improved.

[0077] (Catalyst layer)

[0078] Next, the catalyst layer 21 formed in the pores of the partition wall 13 will be described. The catalyst layer 21 in this embodiment is a single layer formed of a catalyst metal and a support component and does not contain Ba. In the catalyst layer 21, the catalyst metal is preferably Pd and / or Rh, and the support component is preferably an oxide of Al, Zr, and / or Ce.

[0079] Examples of such a catalyst layer 21 include a catalyst layer formed by firing a catalyst slurry containing predetermined catalyst metal particles and predetermined support particles. The catalyst layer 21 formed by firing a catalyst slurry containing various particles in this manner has a microporous structure in which the particles are bonded to each other by firing.

[0080] The catalyst metal contained in the catalyst layer 21 is preferably palladium (Pd) and / or rhodium (Rh). Among them, palladium (Pd) is preferred from the perspective of oxidation activity, and rhodium (Rh) is preferred from the perspective of reduction activity. In addition, by using these two catalyst metals together, a synergistic effect due to different catalytic activities can be expected.

[0081] It should be noted that the presence of a catalytic metal in the catalyst layer 21 can be confirmed using a scanning electron microscope, for example, to examine a cross section of the partition wall 13 of the exhaust gas purification catalyst filter 100. Specifically, this can be confirmed by performing energy-dispersive X-ray analysis within the field of view of the scanning electron microscope. Furthermore, the support component is preferably an oxide of Al, Zr, and / or Ce, and the catalyst layer does not contain Ba.

[0082] The catalyst metal-supporting carrier particles contained in catalyst layer 21 are oxides of Al, Zr, and / or Ce. These oxides are not particularly limited, and examples include oxygen storage materials (OSC materials) such as ceria (ceria: CeO2) and ceria-zirconia composite oxides (CZ composite oxides), oxides such as alumina (Al2O3) and zirconium oxide (ZrO2), and composite oxides primarily composed of these oxides. These may also be composite oxides or solid solutions containing rare earth elements such as lanthanum and yttrium, or transition metal elements. It should be noted that these carrier particles may be used singly or in combination of two or more. Here, the oxygen storage material (OSC material) stores oxygen in the exhaust gas when the air-fuel ratio is lean (i.e., in an oxygen-rich atmosphere) and releases the stored oxygen when the air-fuel ratio is rich (i.e., in a fuel-rich atmosphere).

[0083] [Method for manufacturing exhaust gas purification catalyst filter]

[0084] The manufacturing method of the present embodiment is a manufacturing method for an exhaust gas purification catalyst filter 100 for purifying exhaust gas discharged from a gasoline engine, and is characterized by comprising: a step S0 of preparing a wall-flow type substrate 10, wherein the wall-flow type substrate 10 is defined by a porous partition wall 13 to define an inlet side chamber 11 with an opening at an end 11a on the exhaust gas inlet side, and a discharge side chamber 12 adjacent to the inlet side chamber 11 and with an opening at an end 12a on the exhaust gas discharge side; and a catalyst layer forming step S1, wherein a catalyst slurry is applied to at least a portion of the pore surface in the partition wall 13 of the wall-flow type substrate 10 to form a catalyst layer 21, An exhaust gas purification catalyst filter 100 is manufactured in the catalyst layer forming step S1. In the exhaust gas purification catalyst filter 100, the absolute value of the bias of the catalyst layer formed in the pores of the partition wall of the wall-flow type substrate is less than 4.50, the carrier coating amount of the catalyst layer excluding the mass of the platinum group per 1L of the wall-flow type substrate is more than 40g / L and less than 50g / L, the catalyst layer 21 formed in the pores of the partition wall 13 is a single layer and is formed of a catalyst metal and a carrier component, the catalyst metal is Pd and / or Rh, the carrier component is an oxide of Al, Zr and / or Ce, and the catalyst layer 21 does not contain Ba.

[0085] In the following, each step is described. Note that, in this specification, the wall-flow type substrate before the catalyst layer 21 is formed is referred to as "substrate 10," and the wall-flow type substrate after the catalyst layer 21 is formed is referred to as "exhaust gas purification catalyst filter 100."

[0086] <Preparation process>

[0087] In the preparation step S0 , the wall-flow type substrate 10 described above in connection with the exhaust gas purifying catalyst filter 100 is prepared as a substrate.

[0088] <Catalyst layer formation step>

[0089] In the catalyst layer forming step S1, the catalyst layer 21 is formed by applying a catalyst slurry to the pore surface of the partition wall 13, drying it, and firing it. The method of applying the catalyst slurry is not particularly limited. For example, a method of impregnating a portion of the substrate 10 with the catalyst slurry and spreading it to the entire partition wall 13 of the substrate 10 can be cited. More specifically, a method having the following steps can be cited: an impregnation step S1a, in which the end portion 11a on the exhaust gas inlet side or the end portion 12a on the exhaust gas discharge side is impregnated with a catalyst slurry containing ammonium carbonate; a coating step S1b, in which a gas is introduced into the substrate 10 from the end portion impregnated with the catalyst slurry, thereby coating the catalyst slurry impregnated in the substrate 10 on the partition wall 13; a drying step S1c, in which the applied catalyst slurry is dried; and a firing step S1d, in which the applied catalyst slurry is fired.

[0090] The method for impregnating the substrate 10 with the catalyst slurry in the impregnation step S1a is not particularly limited. For example, one method includes immersing the end of the substrate 10 in the catalyst slurry. In this method, the catalyst slurry can be raised by exhausting (suctioning) gas from the opposite end as needed. The end impregnated with the catalyst slurry can be either the end 11a on the exhaust gas inlet side or the end 12a on the exhaust gas outlet side.

[0091] Furthermore, in the coating step S1b, the catalyst slurry moves from the inlet side of the substrate 10 toward the depth along the flow of the gas F, reaching the end portion on the outlet side of the gas F. During this process, the catalyst slurry passes through the inside of the pores of the partition wall 13, thereby coating the inside of the pores with the catalyst slurry, thereby coating the entire partition wall with the catalyst slurry.

[0092] In the drying step S1c, the applied catalyst slurry is dried. The drying conditions in the drying step S1c are not particularly limited as long as the solvent evaporates from the catalyst slurry. For example, the drying temperature is preferably 100 to 225°C, more preferably 100 to 200°C, and even more preferably 125 to 175°C. The drying time is preferably 0.5 to 2 hours, more preferably 0.5 to 1.5 hours.

[0093] In the calcining step S1d, the catalyst slurry is calcined to form the catalyst layer 21. The calcining conditions in the calcining step S1d are not particularly limited as long as the catalyst layer 21 can be formed from the catalyst slurry. For example, the calcining temperature is not particularly limited, but is preferably 400 to 650°C, more preferably 450 to 600°C, and even more preferably 500 to 600°C. The calcining time is preferably 0.5 to 2 hours, more preferably 0.5 to 1.5 hours.

[0094] (Catalyst slurry)

[0095] The catalyst slurry used to form the catalyst layer 21 is described. The catalyst slurry contains ammonium carbonate, catalyst powder, and a solvent such as water. The catalyst powder is a group of catalyst particles containing a plurality of catalyst metal particles and carrier particles that support the catalyst metal particles, and forms the catalyst layer 21 through a calcination process described later. The catalyst particles are not particularly limited and can be appropriately selected from known catalyst particles for use. It should be noted that, from the perspective of coating properties in the pores of the partition wall 13, the solid content of the catalyst slurry is preferably 1 to 50% by mass, more preferably 15 to 40% by mass, and further preferably 20 to 35% by mass. By setting it to such a solid content, there is a tendency to easily apply the catalyst slurry to the inlet side chamber 11 side in the partition wall 13.

[0096] The D90 particle size of the catalyst powder contained in the catalyst slurry is preferably 1 to 8 μm, more preferably 1 to 6 μm, and further preferably 1 to 4 μm. By making the D90 particle size 1 μm or more, there is a tendency to shorten the crushing time when crushing the catalyst powder with a grinding device and further improve the operating efficiency. In addition, by making the D90 particle size 8 μm or less, there is a tendency to suppress the clogging of the pores in the partition wall 13 by coarse particles and suppress the increase of the pressure loss. It should be noted that, in this specification, the D90 particle size can be measured using a laser diffraction particle size distribution measuring device (for example, a laser diffraction particle size distribution measuring device SALD-3100 manufactured by Shimadzu Corporation).

[0097] The catalyst metal contained in the catalyst slurry is not particularly limited, and various metal species that can function as oxidation catalysts and reduction catalysts can be used. For example, palladium (Pd) and rhodium (Rh) can be mentioned. Among them, palladium (Pd) is preferred from the perspective of oxidation activity, and rhodium (Rh) is preferred from the perspective of reduction activity.

[0098] As carrier particles supporting the catalytic metal particles, inorganic compounds conventionally used in this type of exhaust gas purification catalyst filter can be considered. Examples include oxygen storage materials (OSC materials) such as ceria (ceria: CeO2) and ceria-zirconia composite oxides (CZ composite oxides), oxides such as alumina (alumina: Al2O3) and zirconium oxide (zirconium dioxide: ZrO2), and composite oxides containing these oxides as main components. These can also be composite oxides or solid solutions to which rare earth elements such as lanthanum and yttrium or transition metal elements are added. It should be noted that these carrier particles can be used alone or in combination of two or more. Here, the oxygen storage material (OSC material) refers to a material that stores oxygen in the exhaust gas when the air-fuel ratio of the exhaust gas is lean (i.e., in an oxygen-rich atmosphere) and releases the stored oxygen when the air-fuel ratio of the exhaust gas is rich (i.e., in a fuel-rich atmosphere). It should be noted that from the perspective of exhaust gas purification performance, the specific surface area of ​​the carrier particles contained in the catalyst slurry is preferably 10 to 500 m2. 2 / g, more preferably 30 to 200 m 2 / g.

[0099] [use]

[0100] A mixture of oxygen and fuel gas is supplied to a gasoline engine (engine), where it combusts, converting the combustion energy into mechanical energy. The combusted mixture then becomes exhaust gas and is discharged into the exhaust system. The exhaust system is equipped with an exhaust gas purification device equipped with an exhaust gas purification catalyst filter. The exhaust gas purification catalyst filter purifies harmful components (e.g., carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx)) contained in the exhaust gas, while simultaneously capturing and removing particulate matter (PM) contained in the exhaust gas. In particular, the exhaust gas purification catalyst filter 100 of this embodiment is preferably used in a gasoline particulate filter (GPF) capable of capturing and removing particulate matter contained in the exhaust gas of a gasoline engine.

[0101] Example

[0102] Hereinafter, test example, embodiment and comparative example are given to further specifically illustrate the feature of the present invention, but the present invention is not subject to any limitation thereof. That is, as long as it does not depart from the gist of the present invention, the material, usage, ratio, processing content, processing step etc. shown in the following examples can be appropriately changed. In addition, the values ​​of the various manufacturing conditions and evaluation results in the following examples have the meaning of the preferred upper limit or preferred lower limit in the embodiment of the present invention, and the preferred range can be the scope specified by the combination of the value of the aforementioned upper limit or lower limit and the value of the following examples or the values ​​of the embodiments each other.

[0103] (Example 1)

[0104] Alumina powder was impregnated with a palladium nitrate aqueous solution and then calcined at 500°C for 1 hour to obtain a Pd-loaded powder. Alumina-zirconium dioxide composite oxide powder was impregnated with a rhodium nitrate aqueous solution and then calcined at 500°C for 1 hour to obtain a Rh-loaded powder.

[0105] Mix 1.0 kg of the obtained Pd-loaded powder and 1.0 kg of Rh-loaded powder, 1.0 kg of ceria-zirconium dioxide composite oxide powder, 190 g of 23% lanthanum nitrate aqueous solution, 60% nitric acid, and ion-exchanged water, and put the resulting mixture into a ball mill. After the catalyst powder becomes a specified particle size distribution (D90 particle size is 3.0 μm), 44 g of ammonium carbonate is added to obtain a catalyst slurry.

[0106] Next, a cordierite wall-flow honeycomb substrate (number of chambers / mil thickness: 300 cpsi / 8.5 mil, diameter: 118.4 mm, total length: 127 mm, pore size (median particle size): 20 μm, porosity: 63%) is prepared. The end of the exhaust gas inlet side of the substrate is immersed in the catalyst slurry, and the catalyst slurry is impregnated and retained in the end of the substrate by vacuum suction from the opposite end side. The gas is allowed to flow into the substrate from the end of the exhaust gas inlet side, and the catalyst slurry is applied to the pore surface in the partition wall, and at the same time, the excess catalyst slurry is blown off from the end of the exhaust gas discharge side of the substrate to stop the flow of gas. Then, the substrate coated with the catalyst slurry is dried at 150°C and sintered at 550°C in an atmospheric atmosphere to produce an exhaust gas purification catalyst filter. It should be noted that the WC amount of the catalyst layer after sintering is 44 g per 1L of substrate (excluding the mass of platinum group metals).

[0107] (Example 2)

[0108] An exhaust gas purifying catalyst filter was prepared in the same manner as in Example 1 except that the WC content of the catalyst layer on the partition walls of the wall-flow honeycomb substrate was changed. The WC content of the catalyst layer after firing was 49 g per 1 L of the substrate (excluding the mass of platinum group metals).

[0109] (Example 3)

[0110] An exhaust gas purifying catalyst filter was produced in the same manner as in Example 1 except that the WC content of the catalyst layer on the partition walls of the wall-flow honeycomb substrate was changed. The WC content of the catalyst layer after firing was 40 g per 1 L of the substrate (excluding the mass of platinum group metals).

[0111] (Comparative Example 1)

[0112] Except that ammonium carbonate was not added in the catalyst slurry production process, an exhaust gas purification catalyst filter was produced in the same manner as in Example 1. The WC amount of the catalyst layer after firing was 44 g per 1 L of the substrate (excluding the mass of the platinum group metal).

[0113] (Comparative Example 2)

[0114] An exhaust gas purifying catalyst filter was prepared in the same manner as in Comparative Example 1 except that the WC content of the catalyst layer on the partition walls of the wall-flow honeycomb substrate was changed. The WC content of the catalyst layer after firing was 61 g per 1 L of the substrate (excluding the mass of platinum group metals).

[0115] (Comparative Example 3)

[0116] An exhaust gas purifying catalyst filter was prepared in the same manner as in Example 1 except that the WC content of the catalyst layer on the partition walls of the wall-flow honeycomb substrate was changed. The WC content of the catalyst layer after firing was 61 g per 1 L of the substrate (excluding the mass of platinum group metals).

[0117] [Measurement of particle size distribution]

[0118] The D90 particle size of the catalyst slurry was measured by a laser scattering method using a laser diffraction particle size distribution measuring apparatus SALD-3100 manufactured by Shimadzu Corporation.

[0119] [Measurement of the Localization Degree of the Catalyst Layer in the Partition Walls]

[0120] The presence of the catalyst layer in the partition walls of the gasoline engine exhaust gas purification catalyst filters produced in Examples and Comparative Examples was measured using an Electron Probe MicroAnalyzer (EPMA) JXA-8100 manufactured by JEOL, and the degree of eccentricity was calculated from the obtained two-dimensional data.

[0121] [Measurement of pressure loss]

[0122] The exhaust gas purification catalyst filters prepared in the examples and comparative examples, and the substrates before being coated with the catalyst slurry, were placed in a pressure loss measuring device (manufactured by Tsukuba Rika Seiki Co., Ltd.), and room temperature air was introduced into the installed exhaust gas purification catalyst filters. The air discharge rate from the exhaust gas purification catalyst filters was set to 4m 3 The value obtained by measuring the pressure difference between the air inlet side and the air outlet side at 100 rpm was defined as the pressure loss of the exhaust gas purification catalyst filter.

[0123] [Determination of soot capture performance]

[0124] The exhaust gas purification catalysts prepared in the examples and comparative examples were installed in a 1.5L direct injection turbo engine equipped vehicle, and the soot emission amount (PN) during WLTC mode driving was measured using a solid particle number counting device (manufactured by Horiba, Ltd., trade name: MEXA-2100SPCS). test It should be noted that the soot collection rate is the soot amount (PN blank ) compared to the reduction rate, calculated using the following formula.

[0125] Soot capture rate (%) = (PN blank -PN test ) / PN blank ×100(%)

[0126] The results are shown below.

[0127] [Table 1]

[0128]

[0129] From the above, it can be seen that in the embodiment, by making the eccentricity of the catalyst layer below the specified value, the WC content of the catalyst layer is within the specified value, thereby suppressing the increase in pressure loss and achieving an improvement in the capture rate of soot. In the comparative example, the pressure loss increases or the capture rate of soot decreases.

[0130] Industrial applicability

[0131] The exhaust gas purification catalyst filter of the present invention can be widely and effectively utilized as an exhaust gas purification catalyst filter for removing particulate matter contained in exhaust gas of a gasoline engine.

[0132] Description of Reference Numerals

[0133] 10…Wall flow substrate

[0134] 11…Introduction side chamber

[0135] 11a…End of the exhaust gas inlet side

[0136] 12…Discharge side chamber

[0137] 12a…End of the exhaust gas discharge side

[0138] 13…Next door

[0139] 21…Catalyst layer

[0140] 100…Exhaust gas purification catalyst filter.

Claims

1. Exhaust gas purification catalyst filter for gasoline engines, which is an exhaust gas purification catalyst filter for purifying the exhaust gas of gasoline engines, The exhaust gas purification catalyst filter for gasoline engines is formed by a wall flow type substrate and a catalyst layer. The wall-flow type substrate is divided into an inlet-side chamber with an open end on the exhaust gas inlet side and an exhaust-side chamber adjacent to the inlet-side chamber and with an open end on the exhaust gas exhaust side by porous partition walls. The catalyst layer is formed in the pores of the partition wall. The absolute value of the partiality of the catalyst layer formed in the pores of the partition wall is 0.10 to 0.95, The amount of the washcoat layer of the catalyst layer formed in the pores of the partition wall, excluding the mass of the platinum group, is 40 g / L or more and 50 g / L or less. The catalyst layer formed in the pores of the partition wall is a single layer, The catalyst layer does not contain Ba.

2. The exhaust gas purification catalyst filter for a gasoline engine according to claim 1, wherein: The catalyst layer formed in the pores of the partition walls is composed of a catalyst metal and a support component. The catalyst metal is Pd and / or Rh, and the support component is an oxide of Al, Zr, and / or Ce.

3. A method for producing a catalyst filter for purifying exhaust gas from a gasoline engine, the method being a method for producing a catalyst filter for purifying exhaust gas from a gasoline engine. The manufacturing method has the following features: a step of preparing a wall-flow type substrate having a porous partition wall defining an inlet-side chamber open at an end on an exhaust gas inlet side and an exhaust-side chamber adjacent to the inlet-side chamber and open at an end on an exhaust gas exhaust side; an impregnation step of impregnating the end portion of the wall-flow type substrate on the exhaust gas inlet side or the exhaust gas outlet side with a catalyst slurry containing ammonium carbonate; a coating step of introducing gas into the wall-flow type substrate from the end portion impregnated with the catalyst slurry, thereby coating the catalyst slurry impregnated in the wall-flow type substrate on the pore surfaces of the partition walls; and The calcining step is to calcine the applied catalyst slurry to obtain an exhaust gas purification catalyst filter having an absolute value of the partiality of the catalyst layer formed in the pores of the partition wall of 0.10 to 0.95, and a carrier coating amount of the catalyst layer excluding the mass of the platinum group per 1L of the wall-flow type substrate of 40 g / L or more and 50 g / L or less. The catalyst layer formed in the pores of the partition wall is a single layer, The catalyst layer does not contain Ba.

4. The method for producing a gasoline engine exhaust gas purification catalyst filter according to claim 3, comprising the following steps: After the calcination step to obtain the exhaust gas purifying catalyst filter, the catalyst layer in the pores of the partition walls of the exhaust gas purifying catalyst filter is measured using an electron probe microanalyzer to examine the absolute value of the eccentricity of the catalyst layer.

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