JPWO2014014059A1 - Honeycomb filter - Google Patents

Abstract

An object of the present invention is to provide a honeycomb filter that can suppress thermal decomposition of ceramics constituting a barrier and has both an SCR function and a diesel particulate filter function. And this invention is a honey-comb filter which is provided with the partition which forms a some flow path, and has a 1st end surface and a 2nd end surface, Comprising: The edge part by the side of a 2nd end surface is a plurality of flow paths. A plurality of first flow paths and a plurality of second flow paths whose ends on the first end face side are sealed, and the honeycomb filter has a partition wall surface in the first flow path, a second flow path A type selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rh, Pd, Ag, and Pt formed in one or more locations in the partition wall surface and in the partition pores. A catalyst layer containing the above metal element and zeolite is provided, and the partition includes an aluminum titanate ceramic containing one or more elements selected from Mg, Ca, Sr, Y, Ba, lanthanoid, and Bi.

Description

  The present invention relates to a honeycomb filter.

  The honeycomb filter is used to remove the collected matter from the fluid containing the collected matter. For example, the honeycomb filter collects fine particles such as carbon particles contained in exhaust gas discharged from an internal combustion engine such as a diesel engine. Is used as a ceramic filter (diesel particulate filter). The honeycomb filter has a plurality of parallel flow paths partitioned by partition walls, and one end of a part of the plurality of flow paths and the other end of the remaining part of the plurality of flow paths are sealed. . As a honeycomb structure constituting such a honeycomb filter, for example, structures described in Patent Documents 1 and 2 below are known.

Further, as a method of decomposing the NO _X contained in the exhaust gas, the method of decomposing the NO _X by reaction such as the following formulas (2) to (4) are known from the ammonia. This method is called SCR (Selective Catalytic Reduction) because NO _x is selectively reduced by ammonia. As shown in the following formula (1), ammonia can be generated by hydrolyzing urea water at a high temperature. A method of decomposing NO _X in exhaust gas using ammonia generated from urea is called urea SCR.
CO (NH ₂ ) ₂ + H ₂ O → 2NH ₃ + CO ₂ (1)
4NH ₃ + 4NO + O ₂ → 4N ₂ + 6H ₂ O (2)
2NH ₃ + NO + NO ₂ → 2N ₂ + 3H ₂ O (3)
8NH ₃ + 6NO ₂ → 7N ₂ + 12H ₂ O (4)

In diesel vehicles, in order to perform the reduction of the NO _X by the SCR efficiently, for example, a honeycomb structure was supported adsorbed easily zeolite ammonia is used. Further, as the zeolite, a metal ion exchanged zeolite ion-exchanged with a metal ion such as a copper ion is used in order to improve NO _X reduction. The honeycomb structure for SCR and the diesel particulate filter are arranged in series to construct an exhaust gas purification system. On the other hand, from the viewpoint of space saving and cost reduction, a honeycomb filter having both a SCR function and a diesel particulate filter function by supporting a metal ion exchange zeolite on the partition wall surface of the diesel particulate filter has also been proposed. (For example, refer to Patent Document 3).

JP 2006-239603 A Japanese Patent Laid-Open No. 2001-46886 JP 2010-227767 A

  However, the honeycomb filter having both the SCR function and the diesel particulate filter function has a problem that, when exposed to a high temperature, the metal ion exchange zeolite thermally decomposes the ceramics constituting the partition walls of the honeycomb filter. is there.

  An object of the present invention is to provide a honeycomb filter having both an SCR function and a diesel particulate filter function that can suppress thermal decomposition of ceramics constituting the partition wall.

  In order to achieve the above object, the present invention provides a honeycomb filter including partition walls that form a plurality of flow paths parallel to each other, wherein the honeycomb filter includes a first end surface and a side opposite to the first end surface. A plurality of first flow paths whose end portions on the second end face side are sealed, and ends on the first end face side. A plurality of second flow paths whose parts are sealed, wherein the honeycomb filter has a partition wall surface in the first flow path, a partition wall surface in the second flow path, and partition pores A catalyst layer formed in at least one of the layers, wherein the catalyst layer is selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, rhodium, palladium, silver, and platinum. Including at least one metal element and zeolite. Partition walls, magnesium, calcium, strontium, yttrium, barium, aluminum titanate-based ceramics containing at least one element selected from the group consisting of lanthanoid, and bismuth, provides a honeycomb filter.

  In the honeycomb filter, the partition wall is made of an aluminum titanate-based ceramic containing at least one element selected from the group consisting of magnesium, calcium, strontium, yttrium, barium, lanthanoid and bismuth. Thermal decomposition of the aluminum-based ceramics can be suppressed.

  The honeycomb filter includes first and second flow paths whose opposite end faces are sealed, and a partition wall surface in the first flow path, a partition wall surface in the second flow path, and Since the catalyst layer (SCR catalyst layer) is formed in at least one of the pores in the partition wall, both the diesel particulate filter function and the SCR function are provided.

  In the honeycomb filter, the partition wall preferably further contains silicon dioxide. For example, by containing silicon dioxide in the partition wall material, the partition walls of the honeycomb filter can contain silicon dioxide. At this time, since the partition wall material contains silicon dioxide, the silicon dioxide acts as a sintering aid when the honeycomb filter is fired, and is present at the interface between the aluminum titanate-based crystals. The mechanical strength of the glass can be increased, and a glass phase is formed in the partition walls. This glass phase not only increases the strength of the partition walls by bonding the crystals, but also the metal element in the catalyst layer that comes into contact with the partition walls and the metal element contained in the ash remaining after the soot combustion is aluminum titanate. It has the effect of suppressing movement into the system crystal.

  ADVANTAGE OF THE INVENTION According to this invention, the honeycomb filter provided with both the function of SCR and the function of a diesel particulate filter which can suppress the thermal decomposition of the ceramics which comprise a partition can be provided.

It is a figure showing typically a honeycomb filter concerning a 1st embodiment of the present invention. Fig. 2 (a) is an enlarged view of the end face on the opposite side of Fig. 1 (b) in the honeycomb filter shown in Fig. 1, and Fig. 2 (b) is an enlarged view of a partition wall cross section. It is the III-III arrow line view of Fig.1 (a). It is a figure which shows typically the honey-comb filter which concerns on 2nd Embodiment of this invention. Fig.5 (a) is an enlarged view of the end surface on the opposite side to FIG.4 (b) in the honey-comb filter shown in FIG. 4, FIG.5 (b) is an enlarged view of a partition cross section. It is VI-VI arrow line view of Fig.4 (a). It is the schematic of the exhaust gas purification system provided with the honey-comb filter of this invention. FIG. 8A is a scanning electron microscope (SEM) photograph of the partition wall cross section after the heat treatment of the honeycomb fired body obtained in Experimental Example 1, and FIG. 8B is a region R3 in FIG. 8A. FIG. 8C is an enlarged photograph, and FIG. 8C is an enlarged photograph of the region R4 in FIG. 8B. FIG. 9A is an EDX element mapping image of Al in the region R4, and FIG. 9B is an EDX element mapping image of Ti in the region R4. FIG. 10 (a) is a scanning electron microscope (SEM) photograph of the cross section of the partition wall after the heat treatment of the honeycomb fired body obtained in Experimental Example 2, and FIG. 10 (b) is a region R5 in FIG. 10 (a). It is an enlarged photo. FIG. 11A is an EDX element mapping image of Al in the region R5, and FIG. 11B is an EDX element mapping image of Ti in the region R5. FIG. 12A is a scanning electron microscope (SEM) photograph of a cross section of the partition wall of the catalyst layer-supporting honeycomb filter A obtained in Example 1, and FIG. 12B is an enlarged view of a region R6 in FIG. It is a photograph. 2 is a scanning electron microscope (SEM) photograph of a partition wall cross section of a catalyst layer-supporting honeycomb filter B obtained in Example 1. FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as the case may be. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

<Honeycomb filter>
Fig. 1 is a diagram schematically showing a honeycomb filter according to the first embodiment. Fig. 1 (a) is a perspective view and an enlarged view of an end face of the honeycomb filter, and Fig. 1 (b) is a diagram of Fig. 1 (b). It is an enlarged view of area | region R1 in a). Fig. 2 (a) is an enlarged view of the end face on the opposite side of Fig. 1 (b) in the honeycomb filter shown in Fig. 1, and Fig. 2 (b) is an enlarged view of a partition wall cross section. FIG. 3 is a view taken along arrow III-III in FIG. The honeycomb filter 100 has one end face (first end face) 100a and the other end face (second end face) 100b located on the opposite side of the end face 100a.

  The honeycomb filter 100 is a cylindrical body having a plurality of flow paths 110 extending in parallel to each other. The plurality of flow paths 110 are partitioned by partition walls 120 extending in parallel to the central axis of the honeycomb filter 100. The plurality of channels 110 have a plurality of channels (first channels) 110a and a plurality of channels (second channels) 110b adjacent to the channels 110a. The flow path 110a and the flow path 110b extend from the end face 100a to the end face 100b perpendicular to the end faces 100a and 100b.

  One end of the flow path 110a constituting a part of the flow path 110 is open at the end face 100a, and the other end of the flow path 110a is sealed by the sealing portion 130 at the end face 100b. One end of the flow path 110b constituting the remaining part of the plurality of flow paths 110 is sealed by the sealing portion 130 at the end face 100a, and the other end of the flow path 110b is opened at the end face 100b. In the honeycomb filter 100, for example, an end portion on the end surface 100a side of the flow path 110a is opened as a gas inlet, and an end portion on the end face 100b side of the flow path 110b is opened as a gas outlet.

  Cross sections perpendicular to the axial direction of the flow paths 110a and 110b are hexagonal. The cross section of the flow path 110b is, for example, a regular hexagonal shape in which the lengths of the sides 140 forming the cross section are substantially equal to each other, but may be a flat hexagonal shape. The cross section of the flow path 110a has, for example, a flat hexagonal shape, but may have a regular hexagonal shape. The lengths of the sides facing each other in the cross section of the channel 110a are substantially equal to each other. The cross section of the flow path 110a includes two long sides 150a having substantially the same length as the sides 150 forming the cross section, and four (two pairs) short sides 150b having substantially the same length. ,have. The short side 150b is disposed on each side of the long side 150a. The long sides 150a face each other in parallel, and the short sides 150b face each other in parallel.

  The partition 120 has the partition 120a as a part which partitions off the flow path 110a and the flow path 110b. That is, the channel 110a and the channel 110b are adjacent to each other through the partition wall 120a. By arranging one channel 110a between adjacent channels 110b, the channels 110b are alternately arranged with the channels 110a in the arrangement direction of the channels 110b (a direction substantially orthogonal to the side 140). ing.

  Each of the sides 140 of the channel 110b is opposed to the long side 150a of any one of the plurality of channels 110a in parallel. That is, each of the wall surfaces forming the flow channel 110b faces the one wall surface forming the flow channel 110a in parallel in the partition wall 120a located between the flow channel 110a and the flow channel 110b. Further, the flow path 110 has a structural unit including one flow path 110b and six flow paths 110a surrounding the flow path 110b. In the structural unit, all the sides 140 of the flow path 110b are included. Opposite the long side 150a of the channel 110a. In the honeycomb filter 100, at least one length of the side 140 of the flow path 110b may be substantially equal to the length of the opposed long side 150a, and each length of the side 140 is equal to the length of the opposed long side 150a. It may be substantially equal.

  The partition 120 has the partition 120b as a part which partitions the mutually adjacent flow paths 110a. That is, the flow paths 110a surrounding the flow path 110b are adjacent to each other via the partition wall 120b.

  Each of the short sides 150b of the channel 110a is opposed to the short side 150b of the adjacent channel 110a in parallel. That is, the wall surfaces forming the flow paths 110a face each other in parallel in the partition wall 120b located between the adjacent flow paths 110a. In the honeycomb filter 100, at least one length of the short side 150b of the flow path 110a between the adjacent flow paths 110a may be substantially equal to the length of the opposing short side 150b. The length may be substantially equal to the length of the opposing short side 150b.

  A catalyst layer 160 is formed on the surfaces of the partition walls 120a and 120b in the channel 110a, the surfaces of the partition walls 120a and 120b in the channel 110b, and the pores (inside the communication holes) of the partition walls 120a and 120b. The catalyst layer 160 is formed on at least one of the surfaces of the partition walls 120a and 120b in the channel 110a, the surfaces of the partition walls 120a and 120b in the channel 110b, and the pores of the partition walls 120a and 120b. However, from the viewpoint of obtaining an excellent SCR function, as shown in FIGS.

  Fig. 4 is a diagram schematically showing the honeycomb filter according to the second embodiment. Fig. 4 (a) is a perspective view and an enlarged view of the end face of the honeycomb filter, and Fig. 4 (b) is a diagram of Fig. 4 (b). It is an enlarged view of area | region R2 in a). Fig.5 (a) is an enlarged view of the end surface on the opposite side to FIG.4 (b) in the honey-comb filter shown in FIG. 4, FIG.5 (b) is an enlarged view of a partition cross section. FIG. 6 is a view taken along arrow VI-VI in FIG. The honeycomb filter 200 has one end face (first end face) 200a and the other end face (second end face) 200b located on the opposite side of the end face 200a.

  The honeycomb filter 200 is a cylindrical body having a plurality of flow paths 210 extending in parallel to each other. The plurality of flow paths 210 are partitioned by partition walls 220 extending in parallel with the central axis of the honeycomb filter 200. The plurality of flow paths 210 include a plurality of flow paths (first flow paths) 210a and a plurality of flow paths (second flow paths) 210b adjacent to the flow paths 210a. The channel 210a and the channel 210b extend from the end surface 200a to the end surface 200b perpendicular to the end surfaces 200a and 200b.

  One end of the flow path 210a forming a part of the flow path 210 is open at the end face 200a, and the other end of the flow path 210a is sealed by the sealing portion 230 at the end face 200b. One end of the flow path 210b forming the remaining part of the plurality of flow paths 210 is sealed by the sealing portion 230 at the end face 200a, and the other end of the flow path 210b is opened at the end face 200b. In the honeycomb filter 200, for example, an end portion on the end surface 200a side of the flow path 210a is opened as a gas inlet, and an end portion of the flow path 210b on the end surface 200b side is opened as a gas outlet.

  Cross sections perpendicular to the axial direction of the flow paths 210a and 210b are hexagonal. The cross section of the flow path 210b is, for example, a regular hexagonal shape in which the lengths of the sides 240 forming the cross section are substantially equal to each other, but may be a flat hexagonal shape. The cross section of the flow path 210a is, for example, a flat hexagonal shape, but may be a regular hexagonal shape. The lengths of the sides facing each other in the cross section of the flow path 210a are different from each other. The cross section of the channel 210a has three long sides 250a having substantially the same length and three short sides 250b having substantially the same length as the sides 250 forming the cross section. The long side 250a and the short side 250b face each other in parallel, and the short side 250b is disposed on each side of the long side 250a.

  The partition 220 has the partition 220a as a part which partitions off the flow path 210a and the flow path 210b. That is, the flow path 210a and the flow path 210b are adjacent to each other through the partition wall 220a. Between the adjacent flow paths 210b, two flow paths 210a adjacent to each other in a direction substantially orthogonal to the arrangement direction of the flow paths 210b are arranged, and the two adjacent flow paths 210a are adjacent to each other. They are arranged symmetrically across a line connecting the centers of the cross sections of the paths 210b.

  Each of the sides 240 of the flow path 210b faces the long side 250a of any one of the plurality of flow paths 210a in parallel. That is, each of the wall surfaces forming the flow path 210b faces the one wall surface forming the flow path 210a in parallel in the partition wall 220a positioned between the flow path 210a and the flow path 210b. The flow path 210 includes a structural unit including one flow path 210b and six flow paths 210a surrounding the flow path 210b. In the structural unit, all the sides 240 of the flow path 210b are included. It faces the long side 250a of the flow path 210a. Each vertex of the cross section of the flow path 210b is opposed to the apex of the adjacent flow path 210b in the arrangement direction of the flow paths 210b. In the honeycomb filter 200, at least one length of the side 240 of the flow path 210b may be substantially equal to the length of the opposed long side 250a, and each length of the side 240 is equal to the length of the opposed long side 250a. It may be substantially equal.

  The partition 220 has the partition 220b as a part which partitions off the mutually adjacent flow paths 210a. That is, the flow paths 210a surrounding the flow path 210b are adjacent to each other through the partition 220b.

  Each of the short sides 250b of the flow path 210a faces the short side 250b of the adjacent flow path 210a in parallel. In other words, the wall surfaces forming the flow path 210a face each other in parallel in the partition 220b located between the adjacent flow paths 210a. One flow path 210a is surrounded by three flow paths 210b. In the honeycomb filter 200, between adjacent flow paths 210a, at least one length of the short side 250b of the flow path 210a may be substantially equal to the length of the opposing short side 250b. The length may be substantially equal to the length of the opposing short side 250b.

  A catalyst layer 260 is formed on the surfaces of the partition walls 220a and 220b in the flow path 210a, the surfaces of the partition walls 220a and 220b in the flow path 210b, and inside the pores (inside the communication holes) of the partition walls 220a and 220b. The catalyst layer 260 is formed on at least one of the surfaces of the partition walls 220a and 220b in the channel 210a, the surfaces of the partition walls 220a and 220b in the channel 210b, and the pores of the partition walls 220a and 220b. However, from the viewpoint of obtaining an excellent SCR function, as shown in FIGS.

  The lengths of the honeycomb filters 100 and 200 in the axial direction of the flow path are, for example, 50 to 300 mm. The outer diameter of the honeycomb filters 100 and 200 is, for example, 50 to 250 mm. In the honeycomb filter 100, the length of the side 140 is, for example, 0.4 to 2.0 mm. The length of the long side 150a is, for example, 0.4 to 2.0 mm, and the length of the short side 150b is, for example, 0.3 to 2.0 mm. In the honeycomb filter 200, the length of the side 240 is, for example, 0.4 to 2.0 mm. The length of the long side 250a is, for example, 0.4 to 2.0 mm, and the length of the short side 250b is, for example, 0.3 to 2.0 mm. The thickness (cell wall thickness) of the partition walls 120 and 220 is, for example, 0.1 to 0.8 mm. The cell density in the honeycomb filters 100 and 200 (for example, in the honeycomb filter 100, the sum of the densities of the flow paths 110a and 110b in the end face 100a) is preferably 50 to 600 cpsi (cells per square inch), and more preferably 100 to 500 cpsi. preferable.

The supported amount of the catalyst layers 160 and 260 per unit volume of the honeycomb filters 100 and 200 is 20 to 300 mg / cm ³ from the viewpoint of obtaining sufficient NO _X resolution without impairing the function as a diesel particulate filter. Is preferable, and it is more preferable that it is 50-200 mg / cm < ³ >.

  In the honey-comb filter 100, it is preferable that the sum total of the opening area of the some flow path 110a in the end surface 100a is larger than the sum of the opening area of the flow path 110b in the end surface 100b. In the honeycomb filter 200, the total opening area of the plurality of flow paths 210a on the end face 200a is preferably larger than the total opening area of the flow paths 210b on the end face 200b.

  The hydraulic diameter of the flow paths 110a and 210a on the end faces 100a and 200a is preferably 1.4 mm or less from the viewpoint of maintaining the mechanical strength of the honeycomb filter. The hydraulic diameters of the flow paths 110a and 210a are preferably 0.5 mm or more, and more preferably 0.7 mm or more, from the viewpoint of further suppressing accumulation of collected substances in the region on the end face side in the flow path.

  The hydraulic diameter of the flow paths 110b and 210b at the end faces 100b and 200b is preferably larger than the hydraulic diameter of the flow paths 110a and 210a at the end faces 100a and 200a. From the viewpoint of maintaining the mechanical strength of the honeycomb filter, the hydraulic diameter of the flow paths 110b and 210b at the end faces 100b and 200b is preferably 1.7 mm or less, and more preferably 1.6 mm or less. The hydraulic diameter of the channels 110b and 210b is preferably 0.5 mm or more, and more preferably 0.7 mm or more, from the viewpoint of reducing the pressure loss of exhaust gas ventilation.

  The shape of the honeycomb filter is such that the cross section of the first channel perpendicular to the axial direction of the first channel (channels 110a and 210a) is the first side as in the honeycomb filters 100 and 200 described above. (Long sides 150a, 250a) and second sides (short sides 150b, 250b) respectively disposed on both sides of the first side, and a second channel (channels 110b, 210b). ) Each of the sides (sides 140 and 240) forming a cross section of the second flow path perpendicular to the axial direction of the first flow path are opposed to the first side of the first flow path. Each of the second sides may be in a form facing the second side of the adjacent first flow path, but is not necessarily limited to the shape described above.

  Further, the cross section of the channel perpendicular to the axial direction of the channel in the honeycomb filter is not limited to the hexagonal shape, and may be a triangular shape, a rectangular shape, an octagonal shape, a circular shape, an elliptical shape, or the like. . Moreover, in the flow path, those having different diameters may be mixed, or those having different cross-sectional shapes may be mixed. In addition, the arrangement of the flow paths is not particularly limited, and the arrangement of the central axes of the flow paths may be an equilateral triangle arrangement, a staggered arrangement, or the like arranged at the apex of the equilateral triangle. Furthermore, the honeycomb filter is not limited to a cylindrical body, and may be an elliptical column, a triangular column, a quadrangular column, a hexagonal column, an octagonal column, or the like.

  In the honeycomb filters 100 and 200, the partition walls are porous, and include, for example, a porous ceramic sintered body. The partition has a structure that allows fluid to pass therethrough. Specifically, a large number of communication holes (flow channels) through which fluid can pass are formed in the partition wall.

  The porosity of the partition walls is preferably 20% by volume or more and more preferably 30% by volume or more from the viewpoint of improving the collection efficiency of the honeycomb filter and realizing lower pressure loss. The porosity of the partition walls is preferably 70% by volume or less, and more preferably 60% by volume or less. The average pore diameter of the partition walls is preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of improving the collection efficiency of the honeycomb filter and realizing a lower pressure loss. The average pore diameter of the partition walls is preferably 35 μm or less, and more preferably 30 μm or less. The porosity and average pore diameter of the partition walls can be adjusted by the particle diameter of the raw material, the amount of pore former added, the kind of pore former, and the firing conditions, and can be measured by mercury porosimetry.

  The partition includes aluminum titanate-based ceramics containing at least one element selected from the group consisting of magnesium, calcium, strontium, yttrium, barium, lanthanoid, and bismuth. The aluminum titanate-based ceramics preferably contains at least one element selected from the group consisting of magnesium, calcium, strontium, barium and lanthanum from the viewpoint of sufficiently suppressing thermal decomposition by metal ion exchange zeolite. It is particularly preferable to contain magnesium. When the partition wall supporting the metal ion exchanged zeolite is exposed to high temperature, the metal in the zeolite promotes the movement of aluminum atoms and titanium atoms in the aluminum titanate ceramics and causes thermal decomposition. For example, magnesium magnesium titanate Then, since magnesia exists in the lattice position of the crystal structure, the movement of aluminum atoms and titanium atoms can be inhibited, and thermal decomposition can be suppressed. Similarly, when the specific element other than magnesium is included, the movement of aluminum atoms and titanium atoms can be similarly inhibited to suppress thermal decomposition.

The oxide content of at least one element selected from the group consisting of magnesium, calcium, strontium, yttrium, barium, lanthanoid and bismuth in the partition wall is Al ₂ O ₃ in which aluminum and titanium are converted into oxides. and the total amount 100 parts by weight of TiO _2, preferably 0.1 to 20 mass parts, more preferably from 1.0 to 15 parts by weight, it is 4.0 to 10 parts by weight Particularly preferred. When the content of the specific element is equal to or higher than the lower limit, the thermal decomposition of the aluminum titanate-based ceramics tends to be more sufficiently suppressed, and when the content is lower than the upper limit, the mechanical strength is sufficiently increased. There is a tendency to be able to keep.

In the aluminum titanate-based ceramics, the molar ratio (aluminum: titanium) of aluminum converted to Al ₂ O ₃ and titanium converted to TiO ₂ is preferably 35:65 to 45:55, and 40:60 to 45: 55 is more preferred. When the partition contains aluminum magnesium titanate, the composition formula of aluminum magnesium titanate is, for example, Al _{2 (1-x)} Mg _x Ti _{(1 + x)} O ₅ , and the value of x is preferably 0.03 or more. 0.03-0.20 is more preferable, and 0.03-0.18 is still more preferable.

  The partition containing the aluminum titanate-based ceramics is formed of, for example, porous ceramics mainly made of aluminum titanate-based crystals. “Mainly composed of an aluminum titanate crystal” means that the main crystal phase constituting the ceramic fired body is an aluminum titanate crystal phase. The aluminum titanate-based crystal phase contains at least one element selected from the group consisting of magnesium, calcium, strontium, yttrium, barium, lanthanoid and bismuth.

The partition containing the aluminum titanate ceramic may contain a glass phase derived from silicon source powder. The glass phase refers to an amorphous phase in which SiO ₂ (silicon dioxide) is a main component. Moreover, the partition containing an aluminum titanate ceramic may contain crystal phases other than an aluminum titanate crystal phase and a glass phase. Examples of such a crystal phase include a phase derived from a raw material used for producing a ceramic fired body. The phase derived from the raw material is, for example, a phase derived from an aluminum source powder, a titanium source powder, a magnesium source powder, or the like remaining without forming an aluminum titanate-based crystal phase during the manufacture of the honeycomb filter, such as alumina, titania, magnesia. And the like. The crystal phase forming the partition can be confirmed by an X-ray diffraction spectrum.

If the partition wall contains SiO _2, the content thereof is preferably from 0.5 to 30 wt% of the partition wall based on the total, more preferably from 1.0 to 25 wt%, 2.0 It is especially preferable that it is 20 mass%. The content of SiO ₂ by the above-described lower limit, compared to the case is less than the above lower limit, the mechanical strength after sintering can be increased, there is a tendency for sintering the honeycomb hardly broken When the upper limit value is not exceeded, the thermal expansion coefficient of the sintered honeycomb tends to be smaller than when the upper limit value is exceeded.

The catalyst layer is a layer mainly composed of porous zeolite, and is further selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, rhodium, palladium, silver and platinum. It is a layer containing a kind of metal element. Since the zeolite is a metal ion-exchanged zeolite ion-exchanged with the ions of the above metal elements, the NO _X reducing property is improved. In the metal ion exchanged zeolite, cations such as sodium ions contained in the zeolite are replaced with other metal ions. Since the effect of improving NO _X reduction is great, the metal element is preferably at least one selected from the group consisting of copper, iron, vanadium, cobalt, nickel and silver, and particularly preferably copper. . Examples of the zeolite include ZSM-5, β zeolite, mordenite, ferrierite, chabazite, A-type zeolite, X-type zeolite, Y-type zeolite, and MCM-22. Among these, zeolite is preferably one containing a ZSM-5 or chabazite since it is excellent in the NO _X reducing.

  The catalyst layer has a structure that allows fluid to permeate. Specifically, a large number of communication holes (flow paths) through which fluid can pass are formed in the catalyst layer. The catalyst layer is provided so as not to block the communication hole (flow path) of the partition wall so that the fluid can pass through both the catalyst layer and the partition wall.

From the viewpoint of not impairing the function of the honeycomb filter as a diesel particulate filter, the porosity of the catalyst layer is preferably 20% by volume or more, and more preferably 30% by volume or more. The porosity of the catalyst layer is preferably 70% by volume or less, and more preferably 60% by volume or less, from the viewpoint of obtaining an excellent ammonia adsorption amount and NO _X reduction ability. The average pore diameter of the catalyst layer is preferably 5 μm or more, and more preferably 8 μm or more from the viewpoint of not impairing the function of the honeycomb filter as a diesel particulate filter. The average pore diameter of the catalyst layer is preferably 30 μm or less, and more preferably 25 μm or less, from the viewpoint of obtaining excellent NO _X reducing ability. The porosity and average pore diameter of the catalyst layer can be adjusted by the type of zeolite used and the granulation of the zeolite powder, and can be measured by mercury porosimetry.

The content of at least one metal element selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, rhodium, palladium, silver, and platinum in the catalyst layer is the aluminum titanate ceramics. while suppressing the thermal decomposition, from the viewpoint of obtaining excellent NO _X reducing ability is preferably 0.01 to 1.0 wt% of the catalyst layer based on the total from 0.05 to 0.5 wt% It is more preferable.

The molar ratio of silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) of zeolite in the catalyst layer (silica / alumina) has excellent NO _X reduction ability while suppressing thermal decomposition of the aluminum titanate ceramics. From the viewpoint of obtaining, it is preferably 10 to 10000, more preferably 20 to 5000.

The honeycomb filter 100, 200, for example, a diesel engine, as well as collecting the trapped material such as soot contained in exhaust gas from an internal combustion engine such as a gasoline engine, for purifying NO _X in the exhaust gas, the exhaust gas purification filter Suitable as For example, in the honeycomb filter 100, as shown in FIG. 3, the gas G supplied from the end face 100a to the flow path 110a passes through the communication holes in the catalyst layer 160 and the partition wall 120 and reaches the adjacent flow path 110b. And is discharged from the end face 100b. At this time, NO _X in the gas G is reduced by the catalyst layer 160 and decomposed into N ₂ and H ₂ O, and the trapped material is collected on the surface of the partition wall 120 and / or in the communication hole. By being removed from G, the honeycomb filter 100 functions as an exhaust gas purification filter. Similarly, the honeycomb filter 200 functions as an exhaust gas purification filter.

  FIG. 7 is a schematic view showing an embodiment of the exhaust gas purification system. The exhaust gas purification system of the present embodiment includes the honeycomb filter 100 described above. The exhaust gas purification system may include a honeycomb filter 200 instead of the honeycomb filter 100.

In the exhaust gas purification system shown in FIG. 7, the gas G discharged from the internal combustion engine 500 such as a diesel engine or a gasoline engine is first supplied to an oxidation catalyst (DOC: Diesel Oxidation Catalyst) 510. For the oxidation catalyst 510, for example, a noble metal catalyst such as platinum or palladium is used. These noble metal catalysts are used, for example, supported on a honeycomb structure. The oxidation catalyst 510 removes hydrocarbons, carbon monoxide and the like contained in the gas G. Further, the oxidation catalyst 510, also occurs conversion to NO ₂ in the NO. Since NO ₂ functions as a strong oxidant, soot can be oxidized (combusted) efficiently due to the presence of NO ₂ when soot accumulated in the subsequent honeycomb filter 100 is combusted.

Next, the gas G is supplied to the honeycomb filter 100, and removal of trapped substances such as soot and NO _X purification are performed. Ammonia as a reducing agent for purifying NO _X is produced by ejecting from the urea water supply device 520 urea water U in the gas G. Thereby, as shown in the above formulas (1) to (4), NO _X in the gas G is decomposed into N ₂ and H ₂ O.

  The exhaust gas purification system may further include an oxidation catalyst (DOC) at the subsequent stage of the honeycomb filter 100. The oxidation catalyst provided in the subsequent stage of the honeycomb filter 100 is effective for removing the remaining ammonia.

<Honeycomb filter manufacturing method>
Next, a method for manufacturing a honeycomb filter will be described. A method for manufacturing a honeycomb filter includes, for example, a raw material preparation step for preparing a raw material mixture containing an inorganic compound powder and an additive, a forming step for forming a raw material mixture to obtain a formed body having a flow path, and firing the formed body. A firing step, and a sealing step of sealing one end of each flow path between the molding step and the firing step, or after the firing step, and a step of forming a catalyst layer after the firing step and the sealing step, Is further provided. Hereinafter, each step will be described.

[Raw material preparation process]
In the raw material preparation step, the inorganic compound powder and the additive are mixed and then kneaded to prepare a raw material mixture. Examples of the inorganic compound powder include aluminum source powder such as α-alumina powder, titanium source powder such as anatase type or rutile type titania powder (titanium source powder), and magnesium, calcium, strontium, yttrium, barium, lanthanoid and A raw material powder of at least one element selected from the group consisting of bismuth is included, and a silicon source powder such as silicon oxide powder and glass frit can be further included as necessary. Examples of the magnesium source powder include magnesia powder and magnesia spinel powder. Examples of the calcium source powder include calcia powder, calcium carbonate powder, anorthite, and the like. Examples of the strontium source powder include strontium oxide powder and strontium carbonate powder. Examples of the yttrium source powder include yttrium oxide powder. Examples of the barium source powder include barium oxide powder, barium carbonate powder, and feldspar. Examples of the bismuth source powder include bismuth oxide powder. Each raw material powder may be one type or two or more types. Each raw material powder may contain a trace component derived from the raw material or inevitably contained in the production process.

  For each raw material powder, the volume-based cumulative particle size equivalent to 50% (center particle size, D50) measured by a laser diffraction method is preferably in the following range. D50 of the aluminum source powder is, for example, 20 to 60 μm. D50 of the titanium source powder is, for example, 0.1 to 25 μm. D50 of the magnesium source powder is, for example, 0.5 to 30 μm. D50 of the silicon source powder is, for example, 0.5 to 30 μm.

  The raw material mixture may contain aluminum titanate and / or aluminum magnesium titanate. For example, when aluminum magnesium titanate is used as a constituent of the raw material mixture, the aluminum magnesium titanate corresponds to a raw material mixture having an aluminum source, a titanium source, and a magnesium source.

  Examples of the additive include a pore-forming agent (pore-forming agent), a binder, a plasticizer, a dispersant, and a solvent.

  As the pore-forming agent, one formed by a material that disappears at a temperature lower than the temperature at which the molded body is degreased or fired in the firing step can be used. In degreasing or firing, when a molded body containing a pore forming agent is heated, the pore forming agent disappears due to combustion or the like. As a result, a space is created at the location where the pore-forming agent was present, and the communication hole through which the fluid can flow is formed in the partition wall by shrinking the inorganic compound powder located between the spaces during firing. Can be formed.

  Examples of the pore-forming agent include corn starch, barley starch, wheat starch, tapioca starch, bean starch, rice starch, pea starch, coral starch, canna starch, and potato starch (potato starch). In the pore-forming agent, the volume-based cumulative particle size (D50) corresponding to a volume-based cumulative percentage measured by a laser diffraction method (D50) is, for example, 5 to 50 μm. When the raw material mixture contains a pore-forming agent, the content of the pore-forming agent is, for example, 1 to 25 parts by mass with respect to 100 parts by mass of the inorganic compound powder.

  The binder is, for example, celluloses such as methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose; alcohols such as polyvinyl alcohol; salts such as lignin sulfonate; waxes such as paraffin wax and microcrystalline wax. Content of the binder in a raw material mixture is 20 mass parts or less with respect to 100 mass parts of inorganic compound powder, for example.

  Examples of the plasticizer include alcohols such as glycerin; higher fatty acids such as caprylic acid, lauric acid, palmitic acid, alginic acid, oleic acid and stearic acid; stearic acid metal salts such as Al stearate, polyoxyalkylene alkyl ether ( For example, polyoxyethylene polyoxypropylene butyl ether). Content of the plasticizer in a raw material mixture is 10 mass parts or less with respect to 100 mass parts of inorganic compound powder, for example.

  Examples of the dispersant include inorganic acids such as nitric acid, hydrochloric acid, and sulfuric acid; organic acids such as oxalic acid, citric acid, acetic acid, malic acid, and lactic acid; alcohols such as methanol, ethanol, and propanol; and ammonium polycarboxylate. Content of the dispersing agent in a raw material mixture is 20 mass parts or less with respect to 100 mass parts of inorganic compound powder, for example.

  The solvent is, for example, water, and ion-exchanged water is preferable in terms of few impurities. When a raw material mixture contains a solvent, content of a solvent is 10-100 mass parts with respect to 100 mass parts of inorganic compound powder, for example.

[Molding process]
In the forming step, a green honeycomb formed body having a honeycomb structure is obtained. In the molding step, for example, a so-called extrusion molding method in which the raw material mixture is extruded from a die while being kneaded by a single screw extruder can be employed.

[Baking process]
In the firing step, the honeycomb structured green honeycomb formed body obtained in the forming step is fired to obtain a honeycomb fired body. In the firing step, calcination (degreasing) for removing a binder or the like contained in the molded body (in the raw material mixture) may be performed before the molded body is fired. In the firing of the molded body, the firing temperature is usually 1300 ° C. or higher, preferably 1400 ° C. or higher. Moreover, a calcination temperature is 1650 degrees C or less normally, Preferably it is 1550 degrees C or less. The temperature raising rate is not particularly limited, but is usually 1 to 500 ° C./hour. The firing time may be a time sufficient for the inorganic compound powder to transition to the aluminum titanate-based crystal, and varies depending on the amount of raw material, type of firing furnace, firing temperature, firing atmosphere, etc., but usually 10 minutes to 24 hours.

[Sealing process]
The sealing step is performed between the molding step and the firing step or after the firing step. When a sealing step is performed between the forming step and the firing step, one end of each flow path of the green honeycomb molded body obtained in the forming step is sealed with a sealing material, and then green honeycomb forming is performed in the firing step. By firing the sealing material together with the body, a honeycomb structure including a sealing portion that seals one end of the flow path is obtained. When performing the sealing step after the firing step, after sealing one end of each flow path of the honeycomb fired body obtained in the firing step with the sealing material, the flow path is obtained by firing the sealing material together with the honeycomb fired body. A honeycomb structure provided with a sealing portion that seals one end of the above is obtained. As the sealing material, a mixture similar to the raw material mixture for obtaining the green honeycomb molded body can be used.

[Catalyst layer forming step]
The catalyst layer forming step is performed after the firing step and the sealing step. First, zeolite is wet-mixed with at least one metal element selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, rhodium, palladium, silver and platinum, and dried and crushed. Then, if necessary, this is mixed with silica sol and / or alumina sol and water to prepare a slurry. For example, among the above metal elements, copper can be exchanged into the pores of the zeolite by using copper acetate and iron as an ammine complex. Next, the produced slurry is subjected to the inside of the channel (first channel) in which the gas inlet side of the honeycomb structure is open and the channel (second channel) in which the gas outlet side is open. ) And apply to the partition wall surface. After application, the film is dried at 500 to 700 ° C. for about 1 hour to remove moisture. In this way, a catalyst layer containing zeolite and the specific metal element is produced. The catalyst layer also enters inside the pores of the partition walls (inside the communication holes), and is formed not only on the surface of the partition walls in the flow path but also on the surfaces inside the pores of the partition walls. As described above, a honeycomb filter provided with a catalyst layer in the partition wall surfaces and partition pores in the first and second flow paths can be obtained.

  EXAMPLES Hereinafter, although an experiment example and an Example demonstrate this invention further in detail, this invention is not limited to these experiment examples and Examples.

(Experimental example 1)
The following aluminum source powder, titanium source powder, magnesium source powder, silicon source powder, aluminum magnesium titanate powder and pore former were mixed to obtain a mixed powder. The volume-based cumulative particle size equivalent to 50% (D50) was measured using a laser diffraction particle size distribution measuring device (“Microtrac HRA (X-100)” manufactured by Nikkiso Co., Ltd.).
[Components of mixed powder]
(1) Aluminum source powder: 37.5 parts by mass Aluminum oxide powder (α-alumina powder) having a center particle size (D50) of 29 μm
(2) Titanium source powder: 36.8 parts by mass Titanium oxide powder having a D50 of 0.6 μm (rutile crystal)
(3) Magnesium source powder: 1.96 mass parts Magnesium oxide powder with D50 of 3.4 μm (4) Silicon source powder: 3.18 mass parts Glass frit with D50 of 8.5 μm (deflection point: 642 ° C.)
(5) Pore forming agent: 11.7 parts by weight Potato starch powder having a D50 of 31 μm (6) Aluminum magnesium titanate powder: 8.83 parts by weight As the aluminum magnesium titanate powder, a sintered body of aluminum magnesium titanate is pulverized. The powder obtained was used.

The charged composition of each component in the mixed powder was [Al ₂ O ₃ ] / [TiO _{2 in} a molar ratio in terms of alumina [Al ₂ O ₃ ], titania [TiO ₂ ], magnesia [MgO] and silica [SiO ₂ ]. ] / [MgO] / [SiO ₂ ] = 35.1% / 51.3% / 9.6% / 4.0%. Moreover, content of the silicon source powder with respect to the total amount of aluminum source powder, titanium source powder, magnesium source powder, silicon source powder, and aluminum magnesium titanate powder was 3.6 mass%.

  5.49 parts by mass of methylcellulose, 2.35 parts by mass of hydroxypropylmethylcellulose, 0.40 parts by mass of glycerin and 4.64 parts by mass of polyoxyethylene polyoxypropylene butyl ether were added to 100 parts by mass of the mixed powder. Furthermore, after adding 28.44 parts by mass of water, the mixture was extruded using a kneading extruder and dried by microwave drying to obtain a dried honeycomb structure having a number of through holes in the longitudinal direction. The dried honeycomb structure was fired in an air atmosphere including a calcination (degreasing) step of removing the organic binder. The maximum temperature during firing was 1500 ° C., and the holding time at the maximum temperature was 5 hours. Thereby, a honeycomb fired body having the honeycomb structure shown in FIGS. 4 to 6 (however, the catalyst layer and the sealing portion are not formed) (the shape of the fired body: a columnar shape, the cross-sectional shape of the through hole: a regular hexagonal shape and a flat hexagonal shape) Shape, diameter of fired body: 25 mm, height of fired body: 50 mm, cell density: 300 cpsi, cell wall thickness: 0.3 mm).

(Experimental example 2)
As a ceramic powder, a powder obtained by pulverizing an aluminum titanate-based ceramic containing strontium as a constituent element with a mortar was prepared. When the chemical composition of this ceramic powder was analyzed by XRF (fluorescence X-ray analysis), the ceramic powder was found to be 38.4% by mass of Al in terms of Al ₂ O ₃ , 35.4% by mass of Ti in terms of TiO ₂ , SiO 2 It was confirmed that 16.3% by mass of Si in terms of ₂ and 8.29% by mass of Sr in terms of SrO were confirmed.

  88.3 parts by mass of the above ceramic powder and 11.7 parts by mass of a pore former (potato starch powder having a D50 of 31 μm) were mixed to obtain a mixed powder. 5.49 parts by mass of methylcellulose, 2.35 parts by mass of hydroxypropylmethylcellulose, 0.40 parts by mass of glycerin and 4.64 parts by mass of polyoxyethylene polyoxypropylene butyl ether were added to 100 parts by mass of the mixed powder. Furthermore, after adding 28.44 parts by mass of water, the mixture was extruded using a kneading extruder and dried by microwave drying to obtain a dried honeycomb structure having a number of through holes in the longitudinal direction. The dried honeycomb structure was fired in an air atmosphere including a calcination (degreasing) step of removing the organic binder. The maximum temperature during firing was 1500 ° C., and the holding time at the maximum temperature was 5 hours. Thereby, a honeycomb fired body having the honeycomb structure shown in FIGS. 4 to 6 (however, the catalyst layer and the sealing portion are not formed) (the shape of the fired body: a columnar shape, the cross-sectional shape of the through hole: a regular hexagonal shape and a flat hexagonal shape) Shape, diameter of fired body: 25 mm, height of fired body: 50 mm, cell density: 300 cpsi, cell wall thickness: 0.3 mm).

(Comparative Experimental Example 1)
The following aluminum source powder, titanium source powder, silicon source powder and pore former were mixed to obtain a mixed powder. The volume-based cumulative particle size equivalent to 50% (D50) was measured using a laser diffraction particle size distribution measuring device (“Microtrac HRA (X-100)” manufactured by Nikkiso Co., Ltd.).
[Components of mixed powder]
(1) Aluminum source powder: 46.9 parts by mass Aluminum oxide powder (α-alumina powder) having a center particle size (D50) of 29 μm
(2) Titanium source powder: 37.6 parts by mass Titanium oxide powder having a D50 of 0.6 μm (rutile crystal)
(3) Silicon source powder: 3.5 parts by weight Light anhydrous silicic acid having a D50 of 3.5 μm (bending point: 642 ° C.)
(4) Pore forming agent: 12 parts by mass Potato starch powder having a D50 of 31 μm

The charged composition of each component in the mixed powder is [Al ₂ O ₃ ] / [TiO ₂ ] / [SiO _{2 in} terms of a molar ratio in terms of alumina [Al ₂ O ₃ ], titania [TiO ₂ ] and silica [SiO ₂ ]. ] = 47.0% / 47.0% / 6.0%. Moreover, content of the silicon source powder with respect to the total amount of aluminum source powder, titanium source powder, and silicon source powder was 4.0 mass%.

  Hydroxypropyl methylcellulose 6.82 parts by mass, glycerin 0.45 parts by mass and polyoxyethylene polyoxypropylene butyl ether 5.11 parts by mass were added to 100 parts by mass of the mixed powder. Furthermore, after adding 27.84 parts by mass of water, the mixture was extruded using a kneading extruder and dried by microwave drying to obtain a dried honeycomb structure having a number of through holes in the longitudinal direction. The dried honeycomb structure was fired in an air atmosphere including a calcination (degreasing) step of removing the organic binder. The maximum temperature during firing was 1500 ° C., and the holding time at the maximum temperature was 5 hours. Thereby, a honeycomb fired body having the honeycomb structure shown in FIGS. 4 to 6 (however, the catalyst layer and the sealing portion are not formed) (the shape of the fired body: a columnar shape, the cross-sectional shape of the through hole: a regular hexagonal shape and a flat hexagonal shape) Shape, diameter of fired body: 25 mm, height of fired body: 50 mm, cell density: 300 cpsi, cell wall thickness: 0.3 mm).

<Evaluation of heat-resistant decomposition 1>
The honeycomb fired bodies obtained in Experimental Examples 1 and 2 and Comparative Experimental Example 1 were immersed in a Cu (NO ₃ ) ₂ aqueous solution having a predetermined concentration for 1 minute at room temperature, and then dried at room temperature for 1 hour to remove moisture. A copper-supported honeycomb fired body was obtained. The obtained copper-supported honeycomb fired body was heat-treated at a predetermined temperature and time, and the thermal decomposition resistance was evaluated by evaluating the state of the partition walls after the heat treatment. Here, Cu _{(NO 3) 2} aqueous solution concentration, 0 ppm (control experiment), 6000 ppm, or was set to 30000 ppm. The heating conditions were 850 ° C. for 5 hours, 900 ° C. for 5 hours, 950 ° C. for 5 hours, 1000 ° C. for 5 hours, 1000 ° C. for 1 hour, or 1100 ° C. for 0.5 hour. For evaluation of the partition walls of the honeycomb fired body after the heat treatment, partition X-ray diffraction (XRD) measurement of the partition walls, scanning electron microscope (SEM) observation of the partition wall sections, and partition wall cross sections by energy dispersive X-ray analysis (EDX) Elemental mapping was performed.

  Using a powder X-ray diffractometer (trade name “RINT-2200HL”, manufactured by Rigaku), powder X-ray diffraction measurement of the partition walls was performed. Peaks attributed to aluminum titanate, titania and alumina are detected by powder X-ray diffraction measurement, and the ratio of the peak area of aluminum titanate to the total peak area of aluminum titanate, titania and alumina from those peak areas (%) Was calculated. The measurement results of Experimental Example 1 are shown in Table 1, the measurement results of Experimental Example 2 are shown in Table 2, and the measurement results of Comparative Experimental Example 1 are shown in Table 3, respectively. In this measurement result, the smaller the decrease from the control experiment result, the more the thermal decomposition is suppressed. From the following results, it can be seen that when copper is not present (control experiment), thermal decomposition of aluminum titanate does not occur, and thermal decomposition occurs as the concentration of copper increases. Moreover, it turns out that thermal decomposition arises, so that heating conditions are made high temperature and a long time. However, in the honeycomb fired body of Experimental Example 1, it was confirmed that there was almost no decrease in the proportion of aluminum titanate under any condition, and the thermal decomposition resistance was extremely high.

Scanning analytical electron microscope (SEM-EDX, SEM: manufactured by Hitachi High-Technologies Corporation, trade name “S-4800”, EDX: manufactured by HORIBA, Ltd., trade name “ENERGY EX-350”) was used to observe the section of the partition wall and EDX Elemental mapping was performed. 8A to 8C are SEM photographs of the cross section of the partition walls of the honeycomb fired body when the concentration of the aqueous Cu (NO ₃ ) ₂ solution in Experimental Example 1 is 30000 ppm and the heating condition is 1000 ° C. for 5 hours. Element mapping images are shown in FIGS. FIG. 8B is an enlarged photograph of the region R3 in FIG. 8A, and FIG. 8C is an enlarged photograph of the region R4 in FIG. 8B. FIG. 9A is an element mapping image of Al in the region R4, and FIG. 9B is an element mapping image of Ti in the region R4. Further, SEM photographs of the cross section of the partition wall of the honeycomb fired body when the concentration of the Cu (NO ₃ ) ₂ aqueous solution in Experimental Example 2 is 30000 ppm and the heating condition is 900 ° C. for 5 hours are shown in FIGS. , EDX element mapping images are shown in FIGS. FIG. 10B is an enlarged photograph of the region R5 in FIG. 11A is an element mapping image of Al in the region R5, and FIG. 11B is an element mapping image of Ti in the region R5. In the element mapping images shown in FIGS. 9 and 11, the whiter (brighter) portion means that the concentration of the element to be measured is higher.

From the analysis results of Al and Ti shown in FIGS. 9 and 11, the degree of thermal decomposition of aluminum titanate can be grasped. That is, the portion (AT in the figure) that can be confirmed by both the Al element mapping image and the Ti element mapping image is a portion where the aluminum titanate is maintained without being thermally decomposed. The part that can be confirmed only (Al in the figure) is Al ₂ O ₃ , and the part that can be confirmed only by the element mapping image of Ti (Ti in the figure) is TiO ₂ . It can be said that the thermal decomposition of aluminum titanate is suppressed as there are more AT parts and fewer Al and Ti parts. In addition, the part (Si in the figure) that cannot be confirmed in the element mapping image while the image is shown in the SEM photograph is the glass phase part.

In the result of Experimental Example 1 shown in FIG. 9, most of them are AT parts, and even when immersed in a high concentration Cu (NO ₃ ) ₂ aqueous solution and subjected to heat treatment at a high temperature for a long time, It was confirmed that the aluminum titanate was maintained without being thermally decomposed. Even in the result of Experimental Example 2 shown in FIG. 11, the AT portion can be confirmed, and even when immersed in a high concentration Cu (NO ₃ ) ₂ aqueous solution and subjected to heat treatment at a high temperature for a long time, titanic acid is used. It was confirmed that there was a portion where aluminum was maintained without being thermally decomposed.

Example 1
In the same manner as in Experimental Example 1, a dried honeycomb structure in which the catalyst layer and the sealing portion were not formed was produced. The dry honeycomb structure was sealed in the following procedure. As the sealing material, a mixture of aluminum titanate powder (powder obtained by pulverizing the honeycomb fired body obtained in Experimental Example 1), an organic binder (hydroxypropylmethylcellulose), a lubricant (glycerin), and water (solvent) was used. . The mass ratio thereof was aluminum titanate powder / organic binder / lubricant / water = 66 mass% / 1 mass% / 4 mass% / 29 mass%. A film is previously applied to both end faces of the gas outlet of the dried honeycomb structure, and a sealing material is introduced into one end of each flow path through an opening in which the film is melted and perforated with a soldering iron. Dried. The dried honeycomb structure into which the sealing material was introduced was fired in an air atmosphere including a calcination (degreasing) step of removing the organic binder. The maximum temperature during firing was 1500 ° C., and the holding time at the maximum temperature was 5 hours. Thereby, a honeycomb fired body having a first flow path and a second flow path (the shape of the fired body: a columnar shape, a cross-sectional shape of a through hole: a regular hexagonal shape and a flat hexagonal shape, a diameter of the fired body: 25 mm, The height of the fired body: 50 mm, cell density: 300 cpsi, cell wall thickness: 0.3 mm) was obtained. Two honeycomb fired bodies were produced.

Copper (II) chloride dihydrate 68.21 parts by mass was dissolved in 8000 parts by mass of pure water, and this solution was dissolved in zeolite (SiO ₂ / Al ₂ O ₃ ratio = 18 ammonium-type ZSM-5) 31.28 parts by mass. The mixture was stirred at room temperature for 6 hours. The dispersion was filtered, the wet cake on the filter cloth was diffused in 2000 parts by mass of pure water, and after 10 minutes of stirring, filtered again. Thereafter, the wet cake obtained by filtration was dried at 80 ° C. for 12 hours. These operations were repeated a total of 3 times, and the obtained dried product was air calcined at 500 ° C. for 6 hours to obtain a zeolite catalyst supporting copper ions.

  Formation of the catalyst layer was performed for each of the honeycomb fired bodies by the following two methods.

  The first method is as follows. To a 100 mL poly beaker, 70 parts by mass of pure water and 30 parts by mass of the zeolite catalyst supporting the copper ions were added and stirred for 30 minutes. Furthermore, 6 parts by mass of a dispersant (made by NOF Corporation, trade name “Marialim”) was added and stirred for 1 hour. The honeycomb fired body was immediately dipped in this suspension solution until the gas inlet side of the honeycomb fired body was on the bottom, and the end surface on the gas outlet side was not soaked. Air was blown from the gas inlet side, and the excess suspension solution that blocked the first channel and the second channel was discharged to the outside of the honeycomb fired body. This honeycomb fired body was dried at 500 ° C. for about 1 hour to obtain a catalyst layer-supporting honeycomb filter A. As an evaluation of the catalyst layer, a scanning electron microscope (SEM) observation of the partition wall cross section was performed. FIG. 12A is a scanning electron microscope (SEM) photograph of the partition wall cross section of the catalyst layer-supporting honeycomb filter A, and FIG. 12B is an enlarged photograph of the region R6 in FIG. As shown in FIGS. 12A and 12B, it was confirmed that the catalyst layer was filled in the pores of the porous structure of the partition walls. In the figure, AT is aluminum titanate constituting the partition, and CL is a catalyst layer.

  The second method is as follows. To a 100 mL poly beaker, 70 parts by mass of pure water and 30 parts by mass of the zeolite catalyst supporting the copper ions were added and stirred for 30 minutes. Furthermore, 2.85 parts by mass of a viscosity modifier (manufactured by Ashland, ethyl cellulose) was added and stirred for 1 hour. A negative pressure was applied to the gas outlet side of the honeycomb fired body, and 8 parts by mass of this suspension solution was sucked from the gas inlet side. It dried at 500 degreeC for about 1 hour, and the catalyst layer carrying honeycomb filter B was obtained. As an evaluation of the catalyst layer, a scanning electron microscope (SEM) observation of the partition wall cross section was performed. FIG. 13 is a scanning electron microscope (SEM) photograph of the partition wall cross section of the catalyst layer-supporting honeycomb filter B. As shown in FIG. 13, it was confirmed that the catalyst layer was filled in the surfaces of the partition walls and the pores of the porous structure.

(Example 2)
In the same manner as in Experimental Example 2, a dried honeycomb structure in which the catalyst layer and the sealing portion were not formed was produced. The dry honeycomb structure was sealed in the following procedure. As the sealing material, a mixture of aluminum titanate powder (ceramic powder used in Experimental Example 2), organic binder (hydroxypropylmethylcellulose), lubricant (glycerin), and water (solvent) was used. The mass ratio thereof was aluminum titanate powder / organic binder / lubricant / water = 66 mass% / 1 mass% / 4 mass% / 29 mass%. A film is previously applied to both end faces of the gas outlet of the dried honeycomb structure, and a sealing material is introduced into one end of each flow path through an opening in which the film is melted and perforated with a soldering iron. Dried. The dried honeycomb structure into which the sealing material was introduced was fired in an air atmosphere including a calcination (degreasing) step of removing the organic binder. The maximum temperature during firing was 1500 ° C., and the holding time at the maximum temperature was 5 hours. Thereby, a honeycomb fired body having a first flow path and a second flow path (the shape of the fired body: a columnar shape, a cross-sectional shape of a through hole: a regular hexagonal shape and a flat hexagonal shape, a diameter of the fired body: 25 mm, The height of the fired body: 50 mm, cell density: 300 cpsi, cell wall thickness: 0.3 mm) was obtained.

  To a 100 mL poly beaker, 70 parts by mass of pure water and 30 parts by mass of the zeolite catalyst supporting the copper ion prepared in Example 1 were added and stirred for 30 minutes. Furthermore, 2.85 parts by mass of a viscosity modifier (manufactured by Ashland, ethyl cellulose) was added and stirred for 1 hour. A negative pressure was applied to the gas outlet side of the honeycomb fired body, and 8 parts by mass of this suspension solution was sucked from the gas inlet side. It dried at 500 degreeC for about 1 hour, and the catalyst layer carrying honeycomb filter C was obtained. As an evaluation of the catalyst layer, a scanning electron microscope (SEM) observation of the partition wall cross section was performed. It was confirmed that the catalyst layer was filled in the surfaces of the partition walls and the pores of the porous structure.

(Comparative Example 1)
In the same manner as in Comparative Experimental Example 1, a dried honeycomb structure in which the catalyst layer and the sealing portion were not formed was produced. The dry honeycomb structure was sealed in the following procedure. As the sealing material, a mixture of aluminum titanate powder (powder obtained by pulverizing the honeycomb fired body obtained in Comparative Experimental Example 1), organic binder (hydroxypropylmethylcellulose), lubricant (glycerin) and water (solvent) is used. It was. The mass ratio thereof was aluminum titanate powder / organic binder / lubricant / water = 66 mass% / 1 mass% / 4 mass% / 29 mass%. A film is previously applied to both end faces of the gas outlet of the dried honeycomb structure, and a sealing material is introduced into one end of each flow path through an opening in which the film is melted and perforated with a soldering iron. Dried. The dried honeycomb structure into which the sealing material was introduced was fired in an air atmosphere including a calcination (degreasing) step of removing the organic binder. The maximum temperature during firing was 1500 ° C., and the holding time at the maximum temperature was 5 hours. Thereby, a honeycomb fired body having a first flow path and a second flow path (the shape of the fired body: a columnar shape, a cross-sectional shape of a through hole: a regular hexagonal shape and a flat hexagonal shape, a diameter of the fired body: 25 mm, The height of the fired body: 50 mm, cell density: 300 cpsi, cell wall thickness: 0.3 mm) was obtained.

  To a 100 mL poly beaker, 70 parts by mass of pure water and 30 parts by mass of the zeolite catalyst supporting the copper ion prepared in Example 1 were added and stirred for 30 minutes. Furthermore, 2.85 parts by mass of a viscosity modifier (manufactured by Ashland, ethyl cellulose) was added and stirred for 1 hour. A negative pressure was applied to the gas outlet side of the honeycomb fired body, and 8 parts by mass of this suspension solution was sucked from the gas inlet side. It dried at 500 degreeC in about 1 hour, and the catalyst layer carrying honeycomb filter D was obtained. As an evaluation of the catalyst layer, a scanning electron microscope (SEM) observation of the partition wall cross section was performed. It was confirmed that the catalyst layer was filled in the surfaces of the partition walls and the pores of the porous structure.

<Evaluation 2 of thermal decomposition resistance>
The catalyst layer-supporting honeycomb filters B to D obtained in Examples 1 and 2 and Comparative Example 1 are heat-treated at a predetermined temperature and time, and the thermal decomposition resistance is evaluated by evaluating the state of the partition walls after the heat treatment. did. The heating conditions were 850 ° C. for 5 hours, 900 ° C. for 5 hours, 950 ° C. for 5 hours, 1000 ° C. for 5 hours, 1000 ° C. for 1 hour, or 1100 ° C. for 0.5 hour. As evaluation of the partition walls of the honeycomb filters B to D after the heat treatment, powder X-ray diffraction measurement of the partition walls was performed using a powder X-ray diffractometer (trade name “RINT-2200HL” manufactured by Rigaku). Peaks attributed to aluminum titanate, titania and alumina are detected by powder X-ray diffraction measurement, and the ratio of the peak area of aluminum titanate to the total peak area of aluminum titanate, titania and alumina from those peak areas (%) Was calculated. The results are shown in Table 4. In the catalyst layer-carrying honeycomb filter B of Example 1, it was confirmed that there was almost no decrease in the proportion of aluminum titanate under any condition, and the thermal decomposition resistance was extremely high.

  As described above, according to the present invention, it is possible to provide a honeycomb filter having both an SCR function and a diesel particulate filter function that can suppress thermal decomposition of ceramics constituting the partition wall.

  DESCRIPTION OF SYMBOLS 100,200 ... Honeycomb filter, 100a, 200a ... One end surface (1st end surface), 100b, 200b ... The other end surface (2nd end surface), 110, 210 ... Channel, 110a, 210a ... Channel (first) 1 channel), 110b, 210b ... channel (second channel), 120, 220 ... partition wall, 160, 260 ... catalyst layer.

Claims (2)

A honeycomb filter including partition walls that form a plurality of parallel flow paths,
The honeycomb filter has a first end face and a second end face located on the opposite side of the first end face;
The plurality of flow paths include a plurality of first flow paths whose end portions on the second end face side are sealed, and a plurality of second flow paths whose end portions on the first end face side are sealed. Have
The honeycomb filter includes a catalyst layer formed in at least one of the partition wall surface in the first channel, the partition wall surface in the second channel, and the partition pores,
The catalyst layer comprises at least one metal element selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, rhodium, palladium, silver and platinum, and zeolite;
A honeycomb filter, wherein the partition wall includes an aluminum titanate ceramic containing at least one element selected from the group consisting of magnesium, calcium, strontium, yttrium, barium, lanthanoid and bismuth.   The honeycomb filter according to claim 1, wherein the partition wall further contains silicon dioxide.