Method for producing exhaust gas purification catalyst

Abstract

To provide a method for manufacturing an exhaust gas purification catalyst which shortens stand-by time of a shower nozzle.SOLUTION: A method for manufacturing an exhaust gas purification catalyst includes: a slurry supply step S10 of supplying a catalyst metal-containing slurry to one end of one honeycomb substrate from a shower nozzle; a first suction step S21 of pressurizing or decompressing the one honeycomb substrate to which the slurry is supplied in the other end direction of the honeycomb substrate using a first suction device, and sucking the supplied slurry to the inside of the honeycomb substrate; and a second suction step S22 of pressurizing or decompressing the one honeycomb substrate after the first suction step S21 in the other end direction of the honeycomb substrate using a second suction device, and sucking the supplied slurry to the inside of the honeycomb substrate. The slurry supply step S10 and the plurality of suction steps S21 and S22 are performed in the same production line in parallel.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for producing an exhaust gas purifying catalyst provided in an exhaust system of an internal combustion engine of a vehicle. [Background technology]

[0002] Hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NO x A so-called three-way catalyst (TWC) is used as an exhaust gas purification catalyst for removing exhaust gas components such as benzene, benzene, and benzene through oxidation or reduction reactions. Generally, a three-way catalyst has a honeycomb substrate made of cordierite or the like on which a porous carrier made of an inorganic oxide such as alumina (Al2O3) or zirconia (ZrO2) is formed, and a catalyst coating layer containing a metal such as palladium (Pd) or rhodium (Rh) (hereinafter also referred to as "catalytic metal") that functions as an oxidation catalyst and / or reduction catalyst supported on the carrier.

[0003] As an example of a method for manufacturing an exhaust gas purification catalyst, a technique is known in which a catalyst coating layer forming slurry is supplied to an end face of a honeycomb substrate and the slurry is drawn into the honeycomb substrate by suction. For example, Patent Document 1 discloses a manufacturing technique including supplying a catalyst metal-containing solution to the upper part of a honeycomb substrate by a shower nozzle. Patent Document 2 discloses a technique in which a coating suspension is coated on a substrate by suction, and then the coating amount is adjusted by suctioning again. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-99837 A [Patent Document 2] JP 2012-148280 A Summary of the Invention [Problem to be solved by the invention]

[0005] In one example of a production line for exhaust gas purification catalysts, a slurry supplying process in which a catalyst coating layer forming slurry is supplied to a honeycomb substrate by a shower nozzle, and a suction process in which the honeycomb substrate to which the slurry has been supplied is sucked to draw the slurry into the honeycomb substrate are carried out successively. In general, the time required for the suction process is longer than the time required for the slurry supplying process, so there is a time (standby time) during which the supply of the slurry from the shower nozzle is stopped until the suction process is completed. If such a waiting time is long, the slurry near the outlet of the shower nozzle may dry out, causing clogging of the outlet. If the outlet of the shower nozzle is clogged, the slurry will be supplied to the substrate non-uniformly, and the catalyst coating layer will be easily formed non-uniformly.

[0006] The present invention has been made in view of the above circumstances, and its main object is to provide a method for producing an exhaust gas purification catalyst which shortens the standby time of the shower nozzle. [Means for solving the problem]

[0007] The present disclosure provides a method for manufacturing a plurality of exhaust gas purification catalysts using a production line. The method for manufacturing an exhaust gas purification catalyst disclosed herein includes a slurry supplying step of supplying catalytic metal-containing slurry to one end of one honeycomb substrate from a shower nozzle, a first suction step of pressurizing or depressurizing the one honeycomb substrate to which the slurry has been supplied in the direction of the other end of the honeycomb substrate using a first suction device, and drawing the supplied slurry into the honeycomb substrate, and a second suction step of pressurizing or depressurizing the one honeycomb substrate after the first suction step in the direction of the other end of the honeycomb substrate using a second suction device, and drawing the supplied slurry into the honeycomb substrate. The slurry supplying step and the plurality of suction steps are performed in parallel on the same production line.

[0008] With this configuration, by using multiple suction devices, the suction process can be divided into at least two separate steps, shortening the time it takes for one suction device to suction, thereby shortening the standby time of the shower nozzle and preventing clogging of the shower nozzle outlet.

[0009] In a preferred embodiment of the manufacturing method of the exhaust gas purification catalyst disclosed herein, after the second suction step, one or more suction steps may be added in which another suction device applies pressure or pressure to the one honeycomb base material in the direction of the other end of the honeycomb base material to draw the supplied slurry into the honeycomb base material. This further shortens the suction time per suction device, thereby further shortening the standby time of the shower nozzle.

[0010] In one aspect of the method for producing an exhaust gas purifying catalyst disclosed herein, after the plurality of suction steps, a drying step of drying the one honeycomb substrate may be included.

[0011] In a preferred embodiment of the method for producing an exhaust gas purification catalyst disclosed herein, the time required for the shower nozzle to supply the catalytic metal-containing slurry to each honeycomb substrate is longer than the standby time from when the shower nozzle supplies the catalytic metal-containing slurry to one honeycomb substrate until when the shower nozzle starts supplying the catalytic metal-containing slurry to another honeycomb substrate, thereby shortening the standby time of the shower nozzle and effectively preventing clogging of the shower nozzle outlet.

[0012] In a preferred embodiment of the method for producing an exhaust gas purification catalyst disclosed herein, the waiting time is 4 seconds or less, which more effectively prevents clogging of the outlet of the shower nozzle.

[0013] In a preferred embodiment of the method for producing an exhaust gas purification catalyst disclosed herein, the suction times in the above-mentioned multiple suction steps are all the same. If the suction times in the multiple suction steps are different, the suction with the longest suction time becomes the rate-limiting step, so by using the above-mentioned configuration, the standby time of the shower nozzle can be further shortened.

[0014] In one embodiment of the manufacturing method of the exhaust gas purification catalyst disclosed herein, the honeycomb substrate may be a wall-flow type honeycomb substrate. Since the wall-flow type honeycomb substrate requires a longer suction time than the straight-flow type honeycomb substrate, the standby time of the shower nozzle tends to be longer. However, the present technology shortens the standby time of the shower nozzle, so that the productivity can be increased even for the wall-flow type exhaust gas purification catalyst.

[0015] In one embodiment of the method for producing an exhaust gas purification catalyst disclosed herein, the catalytic metal-containing slurry may contain a catalytic metal that functions as a catalyst capable of oxidizing or reducing at least one type of exhaust gas component, thereby making it possible to produce an exhaust gas purification catalyst having high exhaust gas purification performance. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of an exhaust gas purification catalyst. [Diagram 2] 1 is a diagram showing an example of a cross-sectional configuration of an exhaust gas purification catalyst taken along a cylinder axis direction; [Diagram 3] 1 is a flowchart showing general steps of a method for producing an exhaust gas purification catalyst according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, some preferred embodiments of the technology disclosed herein will be described with reference to the drawings as appropriate. Matters other than those specifically mentioned in this specification and necessary for implementing this technology can be understood as design matters for a person skilled in the art based on the prior art in the field. This technology can be implemented based on the contents disclosed in this specification and technical knowledge in the field. In this specification, when a numerical range is described as "A to B (where A and B are arbitrary numerical values)", it means "A or more and B or less", and also includes the meanings of "more than A and less than B", "more than A and B or less", and "more than A and less than B".

[0018] First, an example of the configuration of an exhaust gas purification catalyst 1 provided by the present technology will be described. Fig. 1 is a perspective view that shows a schematic example of the configuration of the exhaust gas purification catalyst. Fig. 2 is a diagram that shows a schematic example of the configuration of a cross section of the exhaust gas purification catalyst 1 along the cylinder axis direction X. In Figs. 1 and 2, the symbol A indicates the flow direction of the exhaust gas. Also, the symbol X indicates the cylinder axis direction of the substrate.

[0019] As shown in FIGS. 1 and 2, the exhaust gas purifying catalyst 1 includes a substrate 10 and a catalyst coating layer 20. The substrate 10 ... As shown in FIG.

[0020] <Base material> The substrate 10 is a member that constitutes the framework of the exhaust gas purification catalyst 1. As the substrate 10, various materials and shapes that have been conventionally used as substrates that constitute exhaust gas purification catalysts can be adopted. For example, ceramic substrates such as cordierite, aluminum titanate, and silicon carbide (SiC) that have high heat resistance, or metal substrates such as stainless steel can be used.

[0021] The shape of the substrate may be the same as that of a conventional exhaust gas purification catalyst. The substrate is preferably of a honeycomb structure. In this specification, the honeycomb structure refers to a structure in which a plurality of cells serving as a flow path for a fluid (e.g., exhaust gas) are assembled. As an example, the substrate 10 of the exhaust gas purification catalyst 1 shown in FIG. 1 has a honeycomb structure made of, for example, cordierite, and has a cylindrical outer shape. The outer shape of the substrate 10 may be, for example, an elliptical cylindrical shape or a polygonal cylindrical shape other than a cylindrical shape. The overall length and capacity of the substrate 10 are not particularly limited, and may be appropriately changed depending on the dimensions of the exhaust pipe in which the exhaust gas purification catalyst 1 is installed, the performance of the internal combustion engine that emits the exhaust gas, and the like. The capacity (volume) of the substrate 10 may be, for example, 0.5 L to 10 L, and may be 0.9 L to 2.0 L.

[0022] The exhaust gas purification catalyst 1 shown in FIG. 1 and FIG. 2 includes a so-called wall-flow type substrate 10. The substrate 10 includes inlet cells 12 that are open only at the end on the exhaust gas inlet side, outlet cells 14 that are open only at the end on the exhaust gas outlet side, and a porous partition wall 16 that separates the inlet cells 12 and the outlet cells 14. Specifically, the inlet cells 12 are gas flow paths that are open at the end on the exhaust gas inlet side and blocked at the end on the exhaust gas outlet side with a plug 12a. On the other hand, the outlet cells 14 are gas flow paths that are blocked at the end on the exhaust gas inlet side with a plug 14a and open at the end on the exhaust gas outlet side. The partition wall 16 is a partition material that has a plurality of pores formed therein through which exhaust gas can pass. The partition wall 16 has a plurality of pores that communicate between the inlet cells 12 and the outlet cells 14. In the exhaust gas purification catalyst 1 shown in FIG. 2, the shape of the inlet cell 12 (outlet cell 14) in a cross section perpendicular to the cylinder axis direction X is a square. However, the shape of the inlet cell (outlet cell) in such a cross section is not limited to a square, and various shapes can be adopted. For example, it may be various geometric shapes such as a parallelogram, a rectangle, a trapezoid, or other rectangular shape, a triangle, other polygonal shapes (for example, a hexagon, an octagon), a circle, etc. In addition, the thickness of the partition wall 16 is not particularly limited, but is, for example, 0.05 mm to 2 mm, and preferably 0.1 mm to 1 mm. The substrate 10 is not limited to a wall-flow type, and may be, for example, a so-called straight-flow type substrate having a plurality of through-holes as exhaust gas passages in the cylindrical axis direction X of the substrate 10.

[0023] <Catalyst coating layer> The catalyst coating layer 20 typically comprises a catalyst metal that functions as a catalyst capable of oxidizing or reducing at least one exhaust gas component, and an inorganic carrier that supports the catalyst metal. Examples of the catalyst metal include metals belonging to the platinum group elements such as palladium (Pd), rhodium (Rh), and platinum (Pt), as well as other metals that function as oxidation or reduction catalysts. Pd and Pt have excellent purification performance (oxidation purification ability) for carbon monoxide and hydrocarbons, and Rh has excellent purification performance (oxidation purification ability) for NO x These are particularly preferred catalytic metals for use as three-way catalysts because they have excellent purification performance (reduction purification ability). In addition to these, metals such as barium (Ba), strontium (Sr), and other alkaline earth metals, alkali metals, and transition metals may be used in combination as promoter components. The average particle size of the catalytic metal is not particularly limited, but may be, for example, 0.5 nm to 50 nm, and preferably 1 nm to 20 nm.

[0024] In this specification, the term "average particle size" refers to the cumulative 50% particle size (D 50 Specifically, first, an electron microscope image of the catalyst coating layer is subjected to image analysis, and the circular equivalent diameters of 100 observed particles of interest are measured to create a particle size distribution based on the number of particles. Then, in the particle size distribution, the particle diameter corresponding to the cumulative 50% from the smallest particle diameter is defined as the "average particle diameter D 50 ". In this specification, the average particle size is calculated by including the particle size of secondary particles formed by aggregation, sintering, etc. That is, when calculating the average particle size, the circle-equivalent diameters of particles confirmed by observation under an electron microscope are measured without distinguishing between primary particles and secondary particles, and the average particle size is measured based on the circle-equivalent diameters of the particles thus measured.

[0025] The inorganic carrier for supporting the catalytic metal is not particularly limited as long as it can support the catalytic metal, and a carrier made of inorganic compound particles known in the art can be used. For example, inorganic compound particles having oxygen storage capacity (OSC) such as ceria (CeO2) and composite oxides containing the ceria (for example, ceria-zirconia composite oxide (CZ or ZC composite oxide)) (so-called OSC materials); oxide particles such as alumina (Al2O3), titania (TiO2), zirconia (ZrO2), and silica (SiO2); and the like can be mentioned. These can be used alone or in combination of two or more. Since the OSC material can function as a promoter for purifying exhaust gas, a carrier containing an OSC material is more preferable. For example, OSC materials such as ceria and ceria-zirconia composite oxides to which a small amount of oxides containing yttrium (Y), lanthanum (La), niobium (Nb), praseodymium (Pr), and other rare earth elements are added are preferable because they have improved heat resistance.

[0026] The catalyst coating layer 20 may further contain components other than the catalytic metal component and the inorganic carrier, such as a binder, a promoter component, and other additives. As the binder, alumina sol, silica sol, and the like can be used, as in the conventional catalyst coating layer of this type. As the promoter component, the above-mentioned metals such as Ba and Sr can be mentioned. The content of the catalytic metal in the catalyst coating layer 20 is not particularly limited. For example, the content of the catalytic metal may be 0.01% by mass to 10% by mass, and is preferably 0.1% by mass to 5% by mass, based on the total mass of the inorganic carrier contained in the catalyst coating layer 20.

[0027] In the exhaust gas purification catalyst 1 shown in FIG. 2, the catalyst coating layer 20 is formed inside the partition wall 16 (so-called in-wall). Specifically, the catalyst coating layer 20 is formed on the wall surface of the pores of the partition wall 16 in a predetermined range (thickness) from the surface of the partition wall 16 on the inlet cell 12 side toward the outlet cell 14 side. The thickness of the catalyst coating layer 20 is not particularly limited, and may be formed, for example, over the entire thickness direction of the partition wall 16, or may be formed to be 80% or less, 60% or less, or 40% or less of the thickness of the partition wall 16. In addition, the catalyst coating layer 20 may be formed over the entire length of the partition wall 16 in the cylindrical axis direction, or may be formed at a predetermined ratio from the end of the substrate 10. For example, the catalyst coating layer 20 may be formed to be 100% of the entire length of the partition wall 16 in the cylindrical axis direction, or may be formed to be 80% or less, 60% or less, or 40% or less of the length of the partition wall 16. The thickness and length of the catalyst coating layer 20 may be appropriately determined depending on the size of the inlet cells 12 and outlet cells 14 of the substrate 10, the flow rate of the exhaust gas introduced into the exhaust gas passage, and the like.

[0028] The amount of the catalyst coating layer 20 coated per 1 L of the volume of the substrate 10 is not particularly limited, but may be, for example, 20 g / L or more, 30 g / L or more, or 50 g / L or more from the viewpoint of improving the exhaust gas purification performance. On the other hand, the upper limit of the amount of the catalyst coating layer 20 formed is preferably 200 g / L or less, more preferably 150 g / L or less, and even more preferably 120 g / L or less from the viewpoint of reducing the pressure loss. In this specification, the volume of the substrate 10 refers to a bulk volume including the net volume of the substrate 10 as well as the volume of voids such as the inlet cells 12, the outlet cells 14, and the pores of the partition walls 16.

[0029] The catalyst coating layer 20 is not limited to being formed inside the partition wall 16, and may be formed on the surface of the partition wall 16. The catalyst coating layer 20 may be formed inside and / or on the surface of the partition wall 16 on the outlet cell 14 side, not on the inlet cell 12 side. The catalyst coating layer 20 may be formed on both the inlet cell 12 side and the outlet cell 14 side of the partition wall 16.

[0030] The exhaust gas purification catalyst 1 can be used as a purification catalyst for exhaust gas emitted from various internal combustion engines. For example, it can be suitably used as an exhaust gas purification catalyst for gasoline engines or diesel engines.

[0031] <Method of manufacturing exhaust gas purification catalyst> Hereinafter, the method for producing the exhaust gas purification catalyst disclosed herein will be described with reference to a preferred example. FIG. 3 is a flow chart showing the general steps of the method for producing the exhaust gas purification catalyst according to one embodiment. The method for producing the exhaust gas purification catalyst disclosed herein includes a slurry supplying step S10 in which a catalyst coat layer forming slurry (catalyst metal-containing slurry) is supplied to a substrate using a shower nozzle, and a suctioning step S20 in which the substrate to which the slurry has been supplied is subjected to suction multiple times (at least two times). The method for producing the exhaust gas purification catalyst disclosed herein may also include a drying step S30. The method for producing the exhaust gas purification catalyst disclosed herein may also include a calcining step S40. The method for producing the exhaust gas purification catalyst disclosed herein may further include other steps at any stage.

[0032] In order to industrially produce a plurality of exhaust gas purification catalysts, for example, a production line is used in which a slurry supplying step using a shower nozzle and a suctioning step of suctioning the substrate to which the slurry has been supplied are performed in sequence. Generally, one suction device used in the suctioning step is installed per production line. In such a production line, after the slurry is supplied to one substrate using a shower nozzle, suctioning is performed using the one suction device. Then, in parallel with the suctioning of the one substrate, the slurry is supplied to another substrate using a shower nozzle. However, particularly when the substrate has a relatively large capacity (e.g., 0.9 L or more) or when a catalyst coating layer is formed inside the partition of a wall-flow type substrate, the time required for suction is significantly longer than the time for supplying the slurry using the shower nozzle. Therefore, in the production line, the time for the suctioning step to end becomes the rate limiting factor, and the time for stopping the supply of the slurry using the shower nozzle (standby time) becomes longer. As a result, the slurry near the outlet of the shower nozzle is easily dried, which may cause clogging of the outlet of the shower nozzle. If the outlet of the shower nozzle becomes clogged, the slurry will be supplied to the substrate non-uniformly, which will lead to an uneven formation of the catalyst coating layer, and this may reduce the quality reliability of the exhaust gas purification catalyst.

[0033] Therefore, the manufacturing method of the exhaust gas purification catalyst disclosed herein is characterized in that a plurality of suction devices are prepared, and the suction that has been conventionally performed by one suction device is divided and performed. Through the study by the present inventors, it has been found that when a process that requires X seconds to complete suction with one suction device is performed sequentially using N suction devices (N is a natural number of 2 or more), if the total suction time is X seconds, a catalyst coat layer equivalent to that of suction with one suction device can be formed. As a result, while the stop time of the shower nozzle was conventionally controlled to coincide with the end of suction for X seconds by one suction device, according to the present technology, for example, when three suction devices are prepared and the suction time of each of the three suction devices is set to the same, the time required for suction by each device can be X / 3 seconds, and the standby time of the shower nozzle can be shortened. As a result, clogging of the discharge port of the shower nozzle is prevented, and the catalyst coat layer is easily formed uniformly, so that the quality reliability and productivity of the exhaust gas purification catalyst can be improved. In addition, wall-flow type honeycomb substrates require longer suction times than straight-flow type honeycomb substrates, which means that the shower nozzle tends to have a longer standby time. However, this technology shortens the standby time of the shower nozzle, making it possible to increase productivity even with wall-flow type exhaust gas purification catalysts.

[0034] <Slurry supplying process S10> In the slurry supply step S10, the catalyst metal-containing slurry is supplied to one end (end face) of the substrate using a shower nozzle. Here, the end (end face) of the substrate refers to the end (end face) in the cylindrical axis direction. As the substrate, the same as the substrate 10 exemplified for use in the exhaust gas purification catalyst 1 described above can be used, and a substrate having a honeycomb structure (honeycomb substrate) is preferably used. As for the shower nozzle, a conventionally known shower nozzle used in this type of technology can be used without any particular restrictions. Typically, the shower nozzle has a plurality of outlets for discharging the slurry. The average hole diameter of the outlets of the shower nozzle may be, for example, 0.3 mm or more and 3 mm or less, or 0.5 mm or more and 1.5 mm or less.

[0035] The time for supplying the catalytic metal-containing slurry from the shower nozzle is not particularly limited and may be appropriately changed depending on the amount of the catalyst coating layer to be formed, the size of the substrate, etc. The supply time may be, for example, 2 to 10 seconds.

[0036] The catalytic metal-containing slurry contains, for example, a catalytic metal, an inorganic carrier for supporting the catalytic metal, and a dispersion medium for dispersing them. The catalytic metal and the inorganic carrier may be the same as those exemplified as those that may be contained in the catalyst coating layer 20 of the exhaust gas purification catalyst 1 described above. As the dispersion medium, any dispersion medium that has been used in this type of slurry in the past may be used without particular limitation, and for example, an aqueous dispersion medium such as water is preferably used.

[0037] The catalytic metal-containing slurry may further contain a binder, a promoter component, a thickener, a dispersant, an additive therefor, etc. The binder and the promoter component may be the same as those exemplified as those that may be contained in the catalyst coating layer 20 of the above-mentioned exhaust gas purification catalyst 1. The thickener may be a water-soluble organic polymer.

[0038] The viscosity of the catalyst metal-containing slurry is not particularly limited, but may be, for example, 1 mPa·s or more and 10,000 mPa·s or less, 5 mPa·s or more and 1,000 mPa·s or less, or 10 mPa·s or more and 300 mPa·s or less. The viscosity may be measured using an E-type viscometer (TVE-35H, manufactured by Toki Sangyo Co., Ltd.) with a rotor type of 1°34'×R24 at a measurement temperature of 25° C. In addition, in this specification, the viscosity is defined as the viscosity at a shear rate of 0.4 s -1 This refers to the viscosity measured at

[0039] <Suction process S20> The suction step S20 includes at least a first suction step S21 and a second suction step S22. Furthermore, the suction step S20 may further include one or more additional suction steps after the second suction step. In other words, the suction step S20 may include a plurality of suction steps, from a first suction step to an N-th suction step (N is a natural number of 2 or more). In the present embodiment shown in FIG. 3, the suction step S20 is configured to include a first suction step S21, a second suction step S22, and a third suction step S23.

[0040] In the plurality of suction steps (first suction step to Nth suction step) included in the suction step S20, a suction device is used to apply pressure or pressure to the base material to which the catalyst metal-containing slurry has been supplied in the direction opposite to the end (end face) to which the slurry has been supplied, thereby performing suction to draw the slurry into the base material. One suction device is prepared for each of the plurality of suction steps (i.e., N devices are prepared). The type of suction device may be the same for the plurality of suction steps, or different types of suction devices may be prepared for each step. Note that, as the suction device, any device that has been conventionally used in this type of technology may be used without any particular limitation.

[0041] The total suction time required for the multiple suction steps (the first suction step to the Nth suction step) including the suction step S20 is not particularly limited, but may be the same as the suction time required for one conventional suction device, for example. If the suction time required for one conventional suction device is X seconds, the suction time required for each of the multiple suction steps may be, for example, X / N seconds, or different suction times may be set so that the total suction time for the multiple suction steps is X seconds. From the viewpoint of reducing the rate limit in the production line and shortening the standby time of the shower nozzle, it is preferable that the suction times for the multiple suction steps are the same (i.e., X / N seconds). The suction time for each of the multiple suction steps may be, for example, 1 to 15 seconds, or 5 to 7 seconds.

[0042] The conditions for sucking the substrate may be appropriately changed according to the type and size of the substrate, the shape and location of the catalyst coating layer to be formed, and may be the same as the conditions conventionally performed with one suction device. For example, when suction is conventionally performed with one suction device at a wind speed of Ym / sec, the wind speed of suction in each of the multiple suction processes may be Ym / sec. In addition, the wind speeds of suction in the multiple suction processes may be set to be different from each other as long as the required suction can be achieved. Although not particularly limited, the wind speed Ym / sec can be set to, for example, 20 m / sec to 80 m / sec, or 30 m / sec to 50 m / sec.

[0043] The number of suction steps included in the suction step S20 (i.e., the value of N in the Nth suction step) may be 2 or more, and the upper limit is not particularly limited, but from the viewpoint of reducing costs, it may be, for example, 10 or less, and preferably 5 or less, 4 or less, or 3 or less.

[0044] In addition, it is preferable to set the number of suction steps so that the time required for the shower nozzle to supply the catalytic metal-containing slurry to each substrate is longer than the waiting time from when the shower nozzle supplies the catalytic metal-containing slurry to one substrate until the shower nozzle starts supplying the catalytic metal-containing slurry to another substrate. For example, the waiting time may be 4 seconds or less, preferably 3 seconds or less, and more preferably 2 seconds or less. Furthermore, the number of suction steps may be set so that the rate-determining step of the production line is the slurry supplying step S10, not the suction step S20 (i.e., the longest suction time among the multiple suction steps is shorter than the waiting time). The shorter the waiting time of the shower nozzle, the less likely the clogging of the outlet of the shower nozzle occurs, which is preferable.

[0045] The slurry supplying step S10 and the suctioning step S20 are carried out on the same production line, and the respective steps are carried out in parallel. For example, when the slurry supplying step is carried out on the substrate A, the first suctioning step S21 may be carried out on the substrate B, and the Nth suctioning step may be carried out on the substrate C. In this way, the manufacturing method of the exhaust gas purification catalyst disclosed herein can carry out the manufacture of a plurality of exhaust gas purification catalysts in parallel. Note that the notations of substrates A, B, and C indicate that they are different substrates.

[0046] <Drying process S30> The drying step S30 can be performed under the same conditions as those used in conventional drying techniques of this type, and is not particularly limited. For example, drying can be performed at a temperature of 50° C. to 200° C. for about 1 minute to 30 minutes.

[0047] <Firing process S40> The firing step S40 can be performed under the same conditions as those used in conventional firing methods of this type, and is not particularly limited. For example, firing can be performed at a temperature of 400° C. to 1000° C. for about 30 seconds to 5 hours.

[0048] In the embodiment shown in Fig. 3, the firing step S40 is performed after the drying step S30, but for example, the slurry supplying step S10 may be performed again after the drying step S30. This allows multiple catalyst coating layers to be formed. For example, a catalyst coating layer can be formed on each of the inlet cell side and the outlet cell side of the wall-flow type substrate.

[0049] Hereinafter, examples of the present technology will be described, but it is not intended that the present technology be limited to the specific examples shown.

[0050] <Production Example> As the substrate, a wall-flow type cylindrical honeycomb substrate (made of cordierite, cell number 300 cpsi, partition wall thickness 8 mil (1 mil is 1 / 1000 inch), average pore diameter 15 μm) with a substrate volume of 1.314 L and a cylindrical axial length of 122 mm was prepared. In addition, alumina powder and ceria-zirconia powder were added to an aqueous solution containing palladium nitrate, and a catalytic metal-containing slurry was prepared by suspending the powder. Next, the catalytic metal-containing slurry was filled in a solution continuous discharge device equipped with a shower nozzle at the discharge port, and the slurry was set to be automatically discharged in the cycle shown in each example described later. Then, 10 hours after the start of automatic discharge of the slurry, the slurry was supplied to the substrate. Using the substrate, an exhaust gas purification catalyst was manufactured, and the catalyst coat layer state and the shower nozzle clogging state were evaluated. The catalyst metal slurry discharge cycle and substrate suction conditions for each example will be described below.

[0051] <Comparative Example 1> In Comparative Example 1, the discharge cycle of the continuous solution discharge device was set assuming a production line using one suction device. Specifically, the slurry supply time from the shower nozzle was set to 4 seconds (similar to the following examples), the suction time by the suction device was set to 6 seconds, and the slurry discharge for 4 seconds and the waiting time for 2 seconds (time when the slurry is not discharged) were set to be repeated. After the continuous solution discharge device was operated for 10 hours in such a cycle, the catalyst metal-containing slurry discharged from the shower nozzle was supplied to one end face in the cylindrical axis direction of the substrate. Next, suction was performed for 6 seconds at a wind speed of 50 m / sec. using a commercially available suction device from the other end face in the cylindrical axis direction of the substrate to which the catalyst metal-containing slurry was not supplied. Thereafter, the substrate after suction was dried and then fired to obtain the exhaust gas purification catalyst in Comparative Example 1.

[0052] <Comparative Example 2> In Comparative Example 1, the suction time was changed to 18 seconds. That is, the production line was set so that after the shower nozzle supplied the catalyst metal-containing slurry to one substrate, there was a waiting time of 14 seconds before the slurry was supplied to the next substrate. Therefore, the discharge cycle of the continuous solution discharge device was set so that a slurry discharge of 4 seconds and a waiting time of 14 seconds were repeated. Except for this, the exhaust gas purification catalyst in Comparative Example 2 was obtained in the same manner as in Comparative Example 1.

[0053] <Example 1> In Example 1, three commercially available suction devices were used, and the discharge cycle of the continuous solution discharge apparatus was set on the assumption of a production line in which suction of one substrate was performed in sequence by the three suction devices. The suction by the three suction devices was referred to as "first suction", "second suction", and "third suction", respectively. The suction conditions for each of the three suction devices were all set to a wind speed of 50 m / sec. and 6 seconds. That is, the production line was set such that after the shower nozzle supplied the catalytic metal-containing slurry to one substrate, there was a waiting time of 2 seconds before the slurry was supplied to the next substrate. Therefore, the discharge cycle of the continuous solution discharge apparatus was set so that 4 seconds of slurry discharge and 2 seconds of waiting time were repeated. After the continuous solution discharge apparatus was operated for 10 hours in such a cycle, the catalytic metal-containing slurry discharged from the shower nozzle was supplied to one end face in the cylindrical axis direction of the substrate, and suction was performed from the other end face in the cylindrical axis direction of the substrate to which the catalytic metal-containing slurry was not supplied in any of the first suction, second suction, and third suction. Except for this, the exhaust gas purifying catalyst in Example 1 was obtained in the same manner as in Comparative Example 1.

[0054] <Example 2> In Example 1, the suction conditions in the first suction were changed to a wind speed of 40 m / sec. for 6 seconds, the suction conditions in the second suction were changed to a wind speed of 50 m / sec. for 6 seconds, and the suction conditions in the third suction were changed to a wind speed of 60 m / sec. for 6 seconds. In addition, the discharge cycle of the continuous solution discharge device was set to be the same as in Example 1. Except for this, the exhaust gas purification catalyst in Example 2 was obtained in the same manner.

[0055] <Example 3> In Example 1, the suction conditions in the first suction were a wind speed of 60 m / sec. for 6 seconds, the suction conditions in the second suction were a wind speed of 50 m / sec. for 6 seconds, and the suction conditions in the third suction were a wind speed of 40 m / sec. for 6 seconds. The discharge cycle of the continuous solution discharge device was set to be the same as in Example 1. Except for this, the exhaust gas purification catalyst in Example 3 was obtained in the same manner.

[0056] <Example 4> In Example 1, the suction conditions in the first suction were changed to a wind speed of 50 m / sec. for 7 seconds, the suction conditions in the second suction were changed to a wind speed of 50 m / sec. for 5 seconds, and the suction conditions in the third suction were changed to a wind speed of 50 m / sec. for 6 seconds. Accordingly, the discharge cycle of the continuous solution discharge device was set so that a slurry discharge for 4 seconds and a waiting time for 3 seconds were repeated. The exhaust gas purification catalyst in Example 4 was obtained in the same manner except for this.

[0057] <Example 5> In Example 1, another commercially available suction device was prepared, and a fourth suction was added. In Example 5, the suction conditions were a wind speed of 50 m / sec. and 5 seconds in all of the first suction to fourth suction. Accordingly, the discharge cycle of the continuous solution discharge device was set so that a slurry discharge for 4 seconds and a waiting time of 1 second were repeated. After the continuous solution discharge device was operated for 10 hours in such a cycle, the catalyst metal-containing slurry discharged from the shower nozzle was supplied to one end face in the cylindrical axis direction of the substrate, and suction was performed from the other end face in the cylindrical axis direction of the substrate to which the catalyst metal-containing slurry was not supplied in all of the first suction, second suction, third suction, and fourth suction. The exhaust gas purification catalyst in Example 5 was obtained in the same manner as in Example 1 except for this.

[0058] <Evaluation of clogging of shower nozzles> In each example, the continuous solution discharge device was operated for 10 hours, and the catalyst metal-containing slurry was supplied to the substrate, after which the clogging rate of the shower nozzle outlet was confirmed. Specifically, the clogging rate [%] was calculated as (number of clogged outlets) / (total number of outlets) x 100. If the clogging rate was less than 1%, it was marked as "Good", and if it was 1% or more, it was marked as "Bad". The results are shown in Table 1.

[0059] <Evaluation of catalyst coating layer> In the exhaust gas purification catalysts manufactured in each example, it was confirmed whether the catalyst coating layer was formed over the entire partition wall of the substrate. Specifically, a sample for scanning electron microscope (SEM) measurement of the partition wall of the exhaust gas purification catalyst was prepared, and the sample was embedded in resin, and then the partition cross section was observed with a scanning electron microscope (Hitachi High-Tech Fielding Corporation, TM4000Plus). The results are shown in Table 1, with "◯" indicating that the catalyst coating layer was formed over the entire partition cross section, and "×" indicating that it was not formed.

[0060] [Table 1]

[0061] As is clear from Table 1, clogging of the shower nozzle was suppressed in Examples 1 to 5, which imitated a production line in which the catalyst metal-containing slurry was sucked in several times. This is believed to be because the standby time of the shower nozzle was kept to a short time of 3 seconds or less, and the catalyst metal-containing slurry near the outlet of the shower nozzle could be supplied to the next substrate before the slurry dried. In addition, as for the catalyst coat layer, it was confirmed that the catalyst coat layer was formed on the entire partition cross section in Examples 1 to 5, similar to that in Comparative Example 2, which was sucked in by one suction device as conventionally carried out. In addition, it was confirmed that the catalyst coat layer was formed uniformly in Examples 1 to 5. This is believed to be because the shower nozzle was prevented from clogging, and the catalyst metal-containing slurry was uniformly supplied by the shower nozzle. It was also confirmed that the catalyst metal-containing slurry could be sufficiently sucked in even when the suction process was divided into several times.

[0062] On the other hand, in Comparative Example 1, although clogging of the shower nozzle was suppressed, the catalyst coating layer was not formed over the entire length of the substrate. This is believed to be due to the short suction time. Also, in Comparative Example 2, the clogging rate of the shower nozzle was high. This is believed to be due to the relatively long standby time of the shower nozzle, 14 seconds, causing the catalyst metal-containing slurry near the shower nozzle outlet to dry out.

[0063] Although specific examples of the technology disclosed herein have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Explanation of symbols]

[0064] 1. Exhaust gas purification catalyst 10 Base material 12 Ingress Cell 12a Sealing part 14 Outgoing Cell 14a Sealing part 16 Bulkhead 20 Catalyst coating layer

Claims

1. A method for producing a plurality of exhaust gas purification catalysts, comprising the steps of: a slurry supplying step of supplying a catalytic metal-containing slurry from a shower nozzle to one end of one honeycomb substrate; a first suction step of applying pressure or pressure to the one honeycomb base material to which the slurry has been supplied in a direction toward the other end of the honeycomb base material using a first suction device, thereby drawing the supplied slurry into the honeycomb base material; a second suction step of further pressurizing or depressurizing the one honeycomb substrate after the first suction step in the direction of the other end of the honeycomb substrate by using a second suction device, thereby drawing the supplied slurry into the inside of the honeycomb substrate; After the second suction step, one or more suction steps are further performed in which the one honeycomb base material is pressurized or depressurized in the direction of the other end of the honeycomb base material by another suction device, and the supplied slurry is drawn into the inside of the honeycomb base material. Inclusive of wherein the slurry supplying step and the plurality of suction steps are carried out in parallel on the same production line, a time required for the shower nozzle to supply the catalytic metal-containing slurry to each honeycomb substrate is longer than a waiting time from when the shower nozzle has supplied the catalytic metal-containing slurry to one honeycomb substrate until when the shower nozzle starts supplying the catalytic metal-containing slurry to another honeycomb substrate; The waiting time is 4 seconds or less. A method for producing an exhaust gas purification catalyst.

2. The manufacturing method according to claim 1 , further comprising a drying step of drying the one honeycomb substrate after the plurality of suction steps.

3. The method according to claim 1 or 2, wherein the suction times in the plurality of suction steps are all the same.

4. The manufacturing method according to any one of claims 1 to 3, wherein the honeycomb substrate is a wall-flow type honeycomb substrate.

5. The method according to any one of claims 1 to 4, wherein the catalytic metal-containing slurry contains a catalytic metal that functions as a catalyst capable of oxidizing or reducing at least one exhaust gas component.

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