WO2014073068A1

WO2014073068A1 - Honeycomb structure and method for manufacturing same

Info

Publication number: WO2014073068A1
Application number: PCT/JP2012/078946
Authority: WO
Inventors: 雅文國枝; 吉村　健; 拓己堂前
Original assignee: イビデン株式会社
Priority date: 2012-11-08
Filing date: 2012-11-08
Publication date: 2014-05-15
Also published as: CN104797544A; JP5961699B2; JPWO2014073068A1

Abstract

Provided is a honeycomb structure which makes it possible to inhibit the metal corrosion of a molding machine or a mouthpiece in a case where a honeycomb body is molded using titanium oxide synthesized by the sulfate process. A honeycomb structure provided with a honeycomb unit which comprises titanium oxide and an inorganic binder as essential components and in which multiple cells extending lengthwise from one end face to the other end face are partitioned by cell walls, characterized by being produced by molding a composite material, which is obtained by mixing and kneading titanium oxide synthesized by the sulfate process, an inorganic binder and an alkaline material together and which has a pH of 5 or more, into a honeycomb body and firing the honeycomb body.

Description

Honeycomb structure and manufacturing method thereof

The present invention relates to a honeycomb structure for purifying NOx discharged from a diesel engine or the like using a SCR (Selective Catalytic Reduction) system and a method for manufacturing the same.

As one of systems for purifying automobile exhaust gas, an SCR system that decomposes nitrogen oxides into nitrogen and water using ammonia is known. As a catalyst in this SCR system, a material in which vanadium oxide or tungsten oxide is supported on titanium oxide is known. Moreover, in order to fully exhibit the performance of such a catalyst material, as a device for increasing the geometric surface area of the catalyst body, it is known to form into a honeycomb shape. Forming into a honeycomb shape is generally performed using a screw-type extruder and a die. Such a honeycomb type molding of a titanium oxide catalyst is disclosed in, for example, Patent Document 1 below.

JP 2001-239516 A

When the titanium oxide catalyst is formed into a honeycomb type, it has the following problems. That is, among titanium oxides, those used for automobile exhaust gas have a high specific surface area called anatase type. The sulfuric acid method is employed as an industrial method for obtaining this anatase type titanium oxide. However, the sulfuric acid method has a problem that sulfur oxide remains as an impurity in the titanium oxide. And when forming using such a titanium oxide in which sulfur oxide remains, the water in the forming clay reacts with sulfur oxide to produce sulfuric acid, and this sulfuric acid produces a screw or a die of a molding machine. The metal will corrode. For this reason, maintenance such as replacement is required, which causes problems in terms of manufacturing cost and manufacturing efficiency. In particular, in the production of titanium oxide, there is a trade-off relationship between the residual sulfur oxide and the specific surface area. If an attempt is made to obtain a material with a high specific surface area, the sulfur oxide remains without being sufficiently removed. Sometimes it is difficult to completely remove sulfur oxide. Therefore, in order to prevent corrosion of the metal of the molding machine, it is necessary to take measures other than removing sulfur oxide.
Further, the corrosion of the metal of the molding machine may have an adverse effect on the formed honeycomb structure, such as adhesion of the corroded metal.

The present invention has been made in view of the above-described conventional problems, and its purpose is to corrode metal of a molding machine or a die when forming into a honeycomb shape using titanium oxide synthesized by a sulfuric acid method. It is an object of the present invention to provide a honeycomb structure and a method for manufacturing the same.

The present invention for solving the above problems is as follows.
(1) A honeycomb structure including a honeycomb unit including at least a titanium oxide and an inorganic binder, and a plurality of cells extending from one end face to the other end face along a longitudinal direction are partitioned by cell walls Because
A composite material having a pH of 5 or more obtained by mixing and kneading at least a titanium oxide synthesized by a sulfuric acid method, an inorganic binder, and an alkaline material is formed into the shape and fired. A honeycomb structure.

(2) The honeycomb structure according to (1), wherein the alkaline material is a solution containing an alkaline substance having a boiling point of 500 ° C. or less.

(3) The alkaline material is a solution containing one or more selected from diethanolamine, monoethanolamine, dimethylaminoethanol, and aqueous ammonia, or one or more selected from diethanolamine, monoethanolamine, and dimethylaminoethanol. The honeycomb structure according to (1) or (2), wherein:

(4) The honeycomb structure according to (1) or (2), wherein the kneaded material further includes a vanadium raw material.

(5) The honeycomb structure according to any one of (1) to (4), wherein the vanadium raw material is ammonium metavanadate.

(6) The inorganic binder is a solid content contained in one or more selected from the group consisting of alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite, bentonite and boehmite. The honeycomb structure according to any one of (5).

(7) The kneaded product further contains one or more selected from the group consisting of inorganic fibers, scale-like substances, tetrapot-like substances, and three-dimensional needle-like substances (1) to (6) The honeycomb structure according to any one of the above.

(8) The inorganic fiber is at least one selected from the group consisting of alumina, silica, silicon carbide, silica alumina, glass, wollastonite, potassium titanate and aluminum borate,
The scaly substance is at least one selected from the group consisting of glass, muscovite, alumina and silica,
The tetrapot-like substance is zinc oxide,
The three-dimensional acicular material is at least one selected from the group consisting of alumina, silica, silicon carbide, silica alumina, glass, wollastonite, potassium titanate, aluminum borate and boehmite. The honeycomb structure according to (7).

(9) A honeycomb structure including a honeycomb unit including at least a titanium oxide and an inorganic binder, and a plurality of cells extending from one end face to the other end face along the longitudinal direction are partitioned by cell walls A manufacturing method of
A step of mixing and kneading at least a titanium oxide synthesized by a sulfuric acid method, an inorganic binder, and an alkaline material to obtain a composite material having a pH of 5 or more;
Obtaining a molded body obtained by molding the composite material into the shape;
Firing the molded body;
A method for manufacturing a honeycomb structure, comprising:

(10) The method for manufacturing a honeycomb structured body according to (9), wherein the alkaline material is a solution containing an alkaline substance having a boiling point of 500 ° C. or less.

(11) The alkaline material is a solution containing one or more selected from diethanolamine, monoethanolamine, dimethylaminoethanol, and aqueous ammonia, or one or more selected from diethanolamine, monoethanolamine, and dimethylaminoethanol. The method for manufacturing a honeycomb structured body according to the above (9) or (10), wherein:

According to the present invention, there is provided a honeycomb structure that can prevent corrosion of a metal in a molding machine or a die when a titanium oxide synthesized by a sulfuric acid method is used to form a honeycomb shape, and a manufacturing method thereof. be able to. Accordingly, continuous formability can be maintained, and productivity can be dramatically improved.

FIG. 3 is a potential-pH diagram of an alloy of iron and chromium. (A) is a potential-pH diagram of SUS304, and (B) is a potential-pH diagram of DPS450R (alloy manufactured by Daido Steel Co., Ltd.). It is a perspective view which shows an example of the honeycomb structure of this invention. It is sectional drawing which shows an example of the exhaust gas purification apparatus which has a honeycomb structure of this invention. It is a perspective view which shows the other example of the honeycomb structure of this invention. FIG. 6 is a perspective view showing a honeycomb unit constituting the honeycomb structure of FIG. 5.

The honeycomb structure of the present invention includes a honeycomb unit having a shape in which a plurality of cells extending at least from one end face to the other end face along a longitudinal direction are divided by cell walls, including at least a titanium oxide and an inorganic binder. A honeycomb structure provided with at least a titanium oxide synthesized by a sulfuric acid method, an inorganic binder, and an alkaline material mixed and kneaded, and a composite material having a pH of 5 or more is formed into the shape. It is characterized by being fired.
Further, the method for manufacturing a honeycomb structure of the present invention includes at least a titanium oxide and an inorganic binder, and a plurality of cells extending from one end surface to the other end surface along the longitudinal direction are partitioned by cell walls. A method for manufacturing a honeycomb structure including a honeycomb unit having a shape, wherein at least a titanium oxide synthesized by a sulfuric acid method, an inorganic binder, and an alkaline material are mixed and kneaded to form a composite having a pH of 5 or more. The method includes a step of obtaining a material, a step of obtaining a molded body obtained by molding the composite material into the shape, and a step of firing the molded body.

In the present invention, a composite material containing titanium oxide synthesized by the sulfuric acid method, that is, titanium oxide in which sulfur oxide remains, is used in the step of obtaining a formed body having a honeycomb structure using a molding machine. Regardless, by adjusting the pH to be 5 or higher, corrosion of the metal in the molding machine and the die is prevented.
Thus, even in the case of a composite material using titanium oxide in which sulfur oxide remains, it is possible to prevent corrosion of the metal of the molding machine by adjusting the pH to 5 or more and introducing it into the molding machine. It is clear from the following discussion.
A potential-pH diagram (Pourbaix diagram) is known as a diagram showing a state of each metal depending on pH. The potential-pH diagram shows the existence region of chemical species in water, particularly metals, on two-dimensional coordinates of electrode potential and pH. Potential-pH diagrams have been calculated and created based on thermodynamic data, and currently there are potential-pH diagrams for most metals (eg, M. Pourbaix, Atlas of Electrochemical Equilibria in Aqueous Solutions, Pergamon Press, London). (1966)). The potential-pH diagram is also used as a corrosion area diagram, and is illustrated in three areas: the corrosion area of the metal species, the dead area, and the passive area that creates the passive state. In the case of an alloy, by overlaying the corrosion area diagrams of the contained metal species, if the corrosion area or dead area of one metal overlaps the passive area of the other metal, a passive film is formed and the passive area is formed. It is known that the progress of metal corrosion can be suppressed by becoming a zone.
From the above, even when a composite material using titanium oxide in which sulfur oxide remains is put into the molding machine, the composite material is classified as a passive region based on the potential-pH diagram of the metal (alloy) of the molding machine. If the pH is adjusted, corrosion of the metal of the molding machine can be prevented.

FIG. 1 shows a potential-pH diagram of an iron-chromium alloy generally used as a metal for a molding machine. In FIG. 1, the dotted line is the water existence region, but it is considered that sulfur oxide reacts and sulfuric acid is generated in the place where water is present, so the sulfuric acid existence region is a similar region. From the corrosion region diagram of this iron-chromium alloy (FIG. 1), it is considered that the iron-chromium alloy will be in a passive region, that is, in a state where corrosion does not occur if the pH is 5 or more even in the presence of sulfuric acid.
Two examples of potential-pH diagrams of alloys actually used in molding machines are shown. 2A is a potential-pH diagram of SUS304, and FIG. 2B is a potential-pH diagram of DPS450R (alloy manufactured by Daido Steel Co., Ltd.). Table 1 shows the composition of each alloy. FIG. 2 shows that in any case, the pH is 5 or more and it is a passive region.

Based on the above knowledge, it is considered that when the pH of the composite material is 5 or more, corrosion does not occur even when the composite material comes into contact with the metal of the molding machine. In addition, since corrosion of the metal of the molding machine does not occur, the corroded metal does not adhere to the honeycomb structure manufactured using the composite material.

FIG. 3 shows an example of the honeycomb structure of the present invention. The honeycomb structure 10 includes a single honeycomb unit 11 including at least a titanium oxide and an inorganic binder, and having a plurality of through holes 11a arranged in parallel in the longitudinal direction with a partition wall 11b interposed therebetween. Further, the outer peripheral coat layer 12 is formed on the outer peripheral surface excluding both end surfaces of the honeycomb unit 11.
The production method of the present invention capable of producing such a honeycomb structure will be described below.

In the honeycomb structure of the present invention, first, a titanium oxide synthesized by a sulfuric acid method, an inorganic binder, and an alkaline material are mixed and kneaded to obtain a composite material having a pH of 5 or more.

As the titanium oxide, anatase-type titanium dioxide synthesized by a sulfuric acid method and having a high specific surface area is used.
Moreover, you may contain a vanadium raw material and a tungsten raw material other than a titanium oxide as a catalyst source.
Examples of the vanadium raw material include ammonium metavanadate, sodium metavanadate, potassium metavanadate, vanadyl oxalate, vanadyl acetate, etc. Among them, ammonium metavanadate is preferable because it is easy to handle. V ₂ O ₅ is generated by a decomposition reaction such as ammonium metavanadate (NH ₄ VO ₃ ), NH ₄ VO ₃ → V ₂ O ₅ + 2NH ₃ + H ₂ O, and plays a role as a catalyst in the SCR system.

In the composite material, the content of titanium oxide is preferably 60 to 90% by mass, and more preferably 75 to 85% by mass.

The alkaline material is preferably a solution containing an alkaline substance having a boiling point of 500 ° C. or lower. Alkali metal and alkaline earth metal decrease NOx purification performance when added to titanium-vanadium, but if the solution contains an alkaline substance with a boiling point of 500 ° C. or less, it is removed by volatilization when the honeycomb unit is fired. Therefore, when the honeycomb structure is formed, the NOx purification performance is not deteriorated.

Specifically, the alkaline material includes one or more selected from diethanolamine, monoethanolamine, dimethylaminoethanol, and aqueous ammonia, or one or more selected from diethanolamine, monoethanolamine, and dimethylaminoethanol. A solution is preferred. This is because when the honeycomb unit is fired, it is removed by volatilization, so that when the honeycomb structure is formed, the NOx purification performance is not lowered.

The concentration and addition amount of the alkaline solution are not particularly limited, but the concentration and addition amount are set so that the pH of the composite material containing titanium oxide and inorganic binder is 5 or more.

The inorganic binder is not particularly limited, but from the viewpoint of maintaining the strength as a honeycomb structure, solid content contained in alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite, bentonite, boehmite and the like is preferable. 2 or more may be used in combination.

The content of the inorganic binder is preferably 5 to 30% by mass in the honeycomb unit 11 and more preferably 10 to 20% by mass. When the content of the inorganic binder in the honeycomb unit 11 is less than 5% by mass, the strength of the honeycomb structure is lowered. On the other hand, when the content of the inorganic binder in the honeycomb structure exceeds 30% by mass, it becomes difficult to extrude the honeycomb formed body.

In order to improve the strength, it is preferable to add one or more selected from the group consisting of inorganic fibers, scale-like substances, tetrapot-like substances and three-dimensional needle-like substances into the composite material.

The inorganic fiber is at least one selected from the group consisting of alumina, silica, silicon carbide, silica alumina, glass, wollastonite, potassium titanate and aluminum borate, and the scaly substance is glass, muscovite. One or more selected from the group consisting of alumina and silica, the tetrapot-like substance is zinc oxide, and the three-dimensional needle-like substance is alumina, silica, silicon carbide, silica alumina, glass, wallast It is preferably at least one selected from the group consisting of knight, potassium titanate, aluminum borate and boehmite.
This is because all of them have high heat resistance, and even when used as a catalyst carrier in an SCR system, there is no melting damage and the effect as a reinforcing material can be maintained.

The aspect ratio of the inorganic fiber is preferably 2 to 1000, more preferably 5 to 800, and still more preferably 10 to 500. When the aspect ratio of the inorganic fibers contained in the honeycomb unit 11 is less than 2, the effect of improving the strength of the honeycomb unit 11 is reduced. On the other hand, when the aspect ratio of the inorganic fibers contained in the honeycomb unit 11 exceeds 1000, the mold is clogged when the honeycomb unit 11 is extruded, or the inorganic fibers break and the strength of the honeycomb unit 11 is increased. The effect of improving the quality is reduced.

The scaly substance means a flat substance, preferably having a thickness of 0.2 to 5.0 μm, preferably having a maximum length of 10 to 160 μm, and having a ratio of the maximum length to the thickness. It is preferably 3 to 250.

The tetrapot-like substance means a substance in which the needle-like portion extends three-dimensionally, the needle-like portion preferably has an average needle-like length of 5 to 30 μm, and the needle-like portion has an average diameter of 0.00. It is preferably 5 to 5.0 μm.

The three-dimensional acicular substance means a substance in which the acicular parts are bonded by an inorganic compound such as glass near the center of each acicular part, and the average acicular length of the acicular parts is 5 to 30 μm. The average diameter of the needle-like part is preferably 0.5 to 5.0 μm.

The three-dimensional acicular substance may have a plurality of acicular portions that are three-dimensionally connected, and preferably has a needle-like diameter of 0.1 to 5.0 μm and a length of 0.3 to It is preferably 30.0 μm, and the ratio of length to diameter is preferably 1.4 to 50.0.

The content of the inorganic fiber, scale-like substance, tetrapot-like substance and three-dimensional needle-like substance is preferably 3 to 50% by mass in the honeycomb unit 11, more preferably 3 to 30% by mass. More preferred is mass%. When the content of the inorganic fiber, the scale-like substance, the tetrapot-like substance, and the three-dimensional needle-like substance in the honeycomb structure is less than 3% by mass, the effect of improving the strength of the honeycomb structure becomes small. On the other hand, when the content of inorganic fibers, scale-like substances, tetrapot-like substances and three-dimensional needle-like substances in the honeycomb structure exceeds 50% by mass, TiO ₂ / V ₂ O ₅ / WO _{3 in the} honeycomb structure is obtained. The catalyst content decreases, and the NOx purification performance decreases.

In addition, an organic binder, a dispersion medium, a molding aid and the like may be appropriately added to the composite material as necessary.

The organic binder is not particularly limited, and examples thereof include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyethylene glycol, phenol resin, and epoxy resin, and two or more kinds may be used in combination. Note that the amount of the organic binder added is from 1 to the total mass of titanium oxide, vanadium oxide, tungsten oxide, inorganic binder, inorganic fiber, scaly substance, tetrapot-like substance, and three-dimensional acicular substance. 10% is preferable.

The dispersion medium is not particularly limited, and examples thereof include water, organic solvents such as benzene, alcohols such as methanol, and the like.

The molding aid is not particularly limited, and examples thereof include ethylene glycol, dextrin, fatty acid, fatty acid soap, polyalcohol and the like, and two or more kinds may be used in combination.

When preparing the composite material, it is preferable to mix and knead, and it may be mixed using a mixer, an attritor or the like, or may be kneaded using a kneader or the like.

Next, the composite material obtained as described above is extruded to obtain a honeycomb formed body in which a plurality of through holes are arranged in parallel in the longitudinal direction with a partition wall therebetween. The extrusion molding is not particularly limited and can be performed according to a conventional method.

Next, the honeycomb formed body is dried using a dryer such as a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, or a freeze dryer.

Next, the honeycomb formed body obtained as described above is fired. The firing temperature is preferably 450 to 750 ° C., more preferably 550 to 650 ° C.
The firing time may be set as appropriate until the firing is completed, and may be, for example, 1 to 4 hours.

Other steps such as a step of forming an outer peripheral coat layer can be provided after the above baking step.
In the step of forming the outer peripheral coat layer, the outer peripheral coat layer paste is applied to the outer peripheral surface excluding both end surfaces of the columnar honeycomb unit 11.

Although it does not specifically limit as a paste for outer periphery coating layers, The mixture of an inorganic binder and an inorganic particle, the mixture of an inorganic binder and an inorganic fiber, the mixture of an inorganic binder, an inorganic particle, and an inorganic fiber etc. are mentioned.

The inorganic binder contained in the outer periphery coating layer paste is not particularly limited, but is added as silica sol, alumina sol or the like, and two or more kinds may be used in combination. Among these, it is preferable to add as silica sol.

The inorganic particles contained in the outer periphery coating layer paste are not particularly limited, but may include carbide particles such as silicon carbide particles, nitride particles such as silicon nitride particles and boron nitride particles, and the like. Good. Of these, silicon carbide particles are preferred because of their excellent thermal conductivity.

The inorganic fiber contained in the outer periphery coat layer paste is not particularly limited, and examples thereof include silica alumina fiber, mullite fiber, alumina fiber, silica fiber and the like, and two or more kinds may be used in combination. Among these, alumina fibers are preferable.

The outer periphery coating layer paste may further contain an organic binder.

Although it does not specifically limit as an organic binder contained in the paste for outer periphery coating layers, Polyvinyl alcohol, methylcellulose, ethylcellulose, carboxymethylcellulose, etc. are mentioned, You may use 2 or more types together.

The outer peripheral coat layer paste may further contain balloons, pore formers, and the like, which are fine hollow spheres of oxide ceramics.

The balloon contained in the outer periphery coating layer paste is not particularly limited, and examples thereof include alumina balloons, glass micro balloons, shirasu balloons, fly ash balloons, mullite balloons, and the like, and two or more kinds may be used in combination. Among these, an alumina balloon is preferable.

Although it does not specifically limit as a pore making material contained in the paste for outer periphery coating layers, A spherical acrylic particle, a graphite, etc. are mentioned, You may use 2 or more types together.

Next, the honeycomb unit 11 to which the outer peripheral coat layer paste has been applied is dried and solidified to produce a columnar honeycomb structure 10. At this time, when the outer peripheral coat layer paste contains an organic binder, it is preferably degreased. The degreasing conditions can be appropriately selected depending on the type and amount of the organic substance, but it is preferably 20 minutes at 700 ° C.

The honeycomb unit 11 manufactured as described above preferably has a porosity of 30 to 60%. If the porosity of the honeycomb unit 11 is less than 30%, the exhaust gas hardly enters the partition walls 11b of the honeycomb unit 11, and the TiO ₂ / V ₂ O ₅ / WO ₃ catalyst is effectively used for NOx purification. It will not be done. On the other hand, when the porosity of the honeycomb unit 11 exceeds 60%, the strength of the honeycomb unit 11 becomes insufficient.

Note that the porosity of the honeycomb unit 11 can be measured using a mercury intrusion method.

The honeycomb unit 11 preferably has an opening ratio of a cross section perpendicular to the longitudinal direction of 50 to 75%. When the opening ratio of the cross section perpendicular to the longitudinal direction of the honeycomb unit 11 is less than 50%, the TiO ₂ / V ₂ O ₅ / WO ₃ catalyst is not effectively used for NOx purification. On the other hand, if the opening ratio of the cross section perpendicular to the longitudinal direction of the honeycomb unit 11 exceeds 75%, the strength of the honeycomb unit 11 becomes insufficient.

In the honeycomb unit 11, the density of the through holes 11a having a cross section perpendicular to the longitudinal direction is preferably 31 to 155 / cm ² . When the density of the through-holes 11a having a cross section perpendicular to the longitudinal direction of the honeycomb unit 11 is less than 31 / cm ² , the TiO ₂ / V ₂ O ₅ / WO ₃ catalyst and the exhaust gas are less likely to come into contact with each other, thereby purifying NOx. Performance decreases. On the other hand, when the density of the through holes 11a having a cross section perpendicular to the longitudinal direction of the honeycomb unit 11 exceeds 155 / cm ² , the pressure loss of the honeycomb structure 10 increases.

The thickness of the partition wall 11b of the honeycomb unit 11 is preferably 0.1 to 0.4 mm, and more preferably 0.1 to 0.3 mm. When the thickness of the partition wall 11b of the honeycomb unit 11 is less than 0.1 mm, the strength of the honeycomb unit 11 decreases. On the other hand, when the thickness of the partition wall 11b of the honeycomb unit 11 exceeds 0.4 mm, the exhaust gas hardly enters the partition wall 11b of the honeycomb unit 11, and the TiO ₂ / V ₂ O ₅ / WO ₃ catalyst is NOx. It will not be used effectively for purification.

The outer peripheral coat layer 12 preferably has a thickness of 0.1 to 2.0 mm. When the thickness of the outer peripheral coat layer 12 is less than 0.1 mm, the effect of improving the strength of the honeycomb structure 10 becomes insufficient. On the other hand, when the thickness of the outer peripheral coat layer 12 exceeds 2.0 mm, the content of the TiO ₂ / V ₂ O ₅ / WO ₃ catalyst per unit volume of the honeycomb structure 10 is reduced, and the NOx purification performance is improved. descend.

The shape of the honeycomb structure 10 is not limited to a cylindrical shape, and examples thereof include a prismatic shape, an elliptical cylindrical shape, a long cylindrical shape, and a rounded chamfered prismatic shape (for example, a rounded chamfered triangular prism shape).

The shape of the through hole 11a is not limited to a quadrangular prism shape, but may be a triangular prism shape, a hexagonal prism shape, or the like.

FIG. 4 shows an example of an exhaust gas purifying apparatus having the honeycomb structure of the present invention. The exhaust gas purification apparatus 100 can be manufactured by canning the metal container (shell) 30 in a state where the holding sealing material 20 is disposed on the outer peripheral portion of the honeycomb structure 10. Further, the exhaust gas purification apparatus 100 includes an injection nozzle that injects ammonia or a compound that decomposes to generate ammonia into a pipe (not shown) on the upstream side of the honeycomb structure 10 with respect to the direction in which the exhaust gas flows. Injecting means (not shown) is provided. As a result, ammonia is added to the exhaust gas flowing through the pipe, so that the NOx contained in the exhaust gas is reduced by the TiO ₂ / V ₂ O ₅ / WO ₃ catalyst contained in the honeycomb unit 11.

The compound that decomposes to generate ammonia is not particularly limited as long as it can be heated by exhaust gas in the pipe and generate ammonia, but urea water is preferable because of excellent storage stability.

The urea water is heated by the exhaust gas in the pipe and hydrolyzes to generate ammonia.

FIG. 5 shows another example of the honeycomb structure of the present invention. In the honeycomb structure 10 ′, a plurality of honeycomb units 11 ′ (see FIG. 6) in which a plurality of through holes 11 a are arranged in parallel in the longitudinal direction with a partition wall 11 b therebetween are bonded via an adhesive layer 13. Other than this, the configuration is the same as that of the honeycomb structure 10.

The honeycomb unit 11 ′ preferably has a cross-sectional area of 10 to 200 cm ² in a cross section perpendicular to the longitudinal direction. When the cross-sectional area of the cross section perpendicular to the longitudinal direction of the honeycomb unit 11 ′ is less than 10 cm ² , the pressure loss of the honeycomb structure 10 ′ increases. On the other hand, when the cross-sectional area of the cross section perpendicular to the longitudinal direction of the honeycomb unit 11 ′ exceeds 200 cm ² , the strength against the thermal stress generated in the honeycomb unit 11 ′ becomes insufficient.

Note that the honeycomb unit 11 ′ has the same configuration as the honeycomb unit 11 except for the cross-sectional area of the cross section perpendicular to the longitudinal direction.

The adhesive layer 13 preferably has a thickness of 0.5 to 2.0 mm. When the thickness of the adhesive layer 13 is less than 0.5 mm, the adhesive strength of the honeycomb unit 11 ′ becomes insufficient. On the other hand, when the thickness of the adhesive layer 13 exceeds 2.0 mm, the pressure loss of the honeycomb structure 10 ′ increases.

Next, an example of a method for manufacturing the honeycomb structure 10 ′ will be described. First, in the same manner as the honeycomb structure 10, a quadrangular columnar honeycomb unit 11 ′ is manufactured. Next, an adhesive layer paste is applied to the outer peripheral surface excluding both end faces of the honeycomb unit 11 ′, the honeycomb units 11 ′ are sequentially bonded, and dried and solidified to produce an aggregate of the honeycomb units 11 ′.

The adhesive layer paste is not particularly limited, and examples thereof include a mixture of inorganic binder and inorganic particles, a mixture of inorganic binder and inorganic fibers, a mixture of inorganic binder, inorganic particles, and inorganic fibers.

The inorganic binder contained in the adhesive layer paste is not particularly limited, but is added as silica sol, alumina sol or the like, and two or more kinds may be used in combination. Among these, it is preferable to add as silica sol.

The inorganic particles contained in the adhesive layer paste are not particularly limited, and examples thereof include carbide particles such as silicon carbide particles, nitride particles such as silicon nitride particles and boron nitride particles, and the like. . Of these, silicon carbide particles are preferred because of their excellent thermal conductivity.

The inorganic fiber contained in the adhesive layer paste is not particularly limited, and examples thereof include silica alumina fiber, mullite fiber, alumina fiber, silica fiber and the like, and two or more kinds may be used in combination. Among these, alumina fibers are preferable.

Further, the adhesive layer paste may contain an organic binder.

The organic binder contained in the adhesive layer paste is not particularly limited, and examples thereof include polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose and the like, and two or more kinds may be used in combination.

The adhesive layer paste may further contain balloons that are fine hollow spheres of oxide ceramics, a pore-forming agent, and the like.

The balloon contained in the adhesive layer paste is not particularly limited, and examples thereof include an alumina balloon, a glass microballoon, a shirasu balloon, a fly ash balloon, and a mullite balloon, and two or more kinds may be used in combination. Among these, an alumina balloon is preferable.

The pore former contained in the adhesive layer paste is not particularly limited, and examples thereof include spherical acrylic particles and graphite, and two or more kinds may be used in combination.

Next, after the aggregate of the honeycomb units 11 ′ is cut into a cylindrical shape, the aggregate of the cylindrical honeycomb units 11 ′ is manufactured by polishing as necessary.

Instead of cutting the aggregate of the honeycomb units 11 ′ into a columnar shape, the honeycomb unit 11 ′ whose cross section perpendicular to the longitudinal direction is formed into a predetermined shape is bonded to the columnar honeycomb unit 11 ′. You may produce the aggregate | assembly of. At this time, the shape of the cross section perpendicular to the longitudinal direction of the honeycomb unit 11 ′ is preferably a sector shape with a central angle of 90 °.

Next, the outer peripheral coat layer paste is applied to the outer peripheral surface excluding both end surfaces of the aggregate of the cylindrical honeycomb unit 11 ′.

The outer periphery coat layer paste may be the same as or different from the adhesive layer paste.

Next, a columnar honeycomb structure 10 ′ is manufactured by drying and solidifying the aggregate of columnar honeycomb units 11 ′ coated with the outer periphery coating layer paste. At this time, when an organic binder is contained in the adhesive layer paste and / or the outer peripheral coat layer paste, it is preferable to degrease. The degreasing conditions can be appropriately selected depending on the type and amount of the organic substance, but it is preferably 20 minutes at 700 ° C.

Note that the outer peripheral coat layer 12 may not be formed in the

honeycomb structures

10 and 10 ′.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[Example 1]
59% by mass of titanium / vanadium powder mainly composed of titanium oxide, 2% by mass of ammonium metavanadate as a vanadium oxide source, 4% by mass of methylcellulose as an organic thickener, 3% by mass of alumina fiber as an inorganic fiber, and as a binder The composite material obtained by mixing and kneading 4% by mass of an alumina binder, 1% by mass of sorbitan trioleate as a molding aid, 25% by mass of ion-exchanged water, and 2% by mass of diethanolamine as an alkaline material has a pH of 5.5. When molding was performed using a screw-type extrusion molding machine and a die, the molded body was not discolored and the molding machine metal was not corroded. The metal of the molding machine was DPS450R.

[Example 2]
59% by mass of titanium / vanadium powder mainly composed of titanium oxide, 2% by mass of ammonium metavanadate as a vanadium oxide source, 4% by mass of methylcellulose as an organic thickener, 3% by mass of alumina fiber as an inorganic fiber, and as a binder The composite material obtained by mixing and kneading 4% by mass of an alumina binder, 1% by mass of sorbitan trioleate as a molding aid, 26% by mass of ion-exchanged water, and 1% by mass of monoethanolamine as an alkaline material has a pH of 6.0. As a result, when molding was performed using a screw-type extrusion molding machine and a die, there was no discoloration of the molded body, and no corrosion of the molding machine metal occurred. The metal of the molding machine was DPS450R.

[Example 3]
59% by mass of titanium / vanadium powder mainly composed of titanium oxide, 2% by mass of ammonium metavanadate as a vanadium oxide source, 4% by mass of methylcellulose as an organic thickener, 3% by mass of alumina fiber as an inorganic fiber, and as a binder The composite material obtained by mixing and kneading 4% by mass of an alumina binder, 1% by mass of sorbitan trioleate as a molding aid, 25% by mass of ion-exchanged water, and 2% by mass of dimethylaminoethanol as an alkaline material has a pH of 5.3. As a result, when molding was performed using a screw-type extrusion molding machine and a die, there was no discoloration of the molded body, and no corrosion of the molding machine metal occurred. The metal of the molding machine was DPS450R.

[Comparative Example 1]
59% by mass of titanium / vanadium powder mainly composed of titanium oxide, 2% by mass of ammonium metavanadate as a vanadium oxide source, 4% by mass of methylcellulose as an organic thickener, 3% by mass of alumina fiber as an inorganic fiber, and as a binder A composite material obtained by mixing and kneading 4% by mass of an alumina binder, 1% by mass of sorbitan trioleate as a molding aid and 27% by mass of ion-exchanged water has a pH of 3.0, and a screw-type extruder and a die are used. As a result, the molded body was discolored and corrosion occurred in the molding machine metal. The metal of the molding machine was DPS450R.

[Comparative Example 2]
59% by mass of titanium / vanadium powder mainly composed of titanium oxide, 2% by mass of ammonium metavanadate as a vanadium oxide source, 4% by mass of methylcellulose as an organic thickener, 3% by mass of alumina fiber as an inorganic fiber, and as a binder The pH of the composite material obtained by mixing and kneading 4% by mass of an alumina binder, 1% by mass of sorbitan trioleate as a molding aid, 26.5% by mass of ion-exchanged water, and 0.5% by mass of monoethanolamine as an alkaline material is It became 4.5, and when it shape | molded using a screw type extrusion molding machine and a nozzle | cap | die, a molded object discolored and corrosion generate | occur | produced in the metal of a molding machine. The metal of the molding machine was DPS450R.

In any of the above Examples 1 to 3, the pH of the composite material was 5 or more, the obtained molded product was not discolored, and the molding machine metal did not corrode. On the other hand, in Comparative Example 1 in which the pH of the composite material was 3 and Comparative Example 2 in which the pH was 4.5, the molded body was discolored and corrosion of the molding machine metal was observed. Therefore, it turns out that corrosion of the metal of a molding machine or a nozzle | cap | die can be prevented by making pH of a composite material 5 or more.

DESCRIPTION OF SYMBOLS 10, 10 'Honeycomb structure 11, 11' Honeycomb unit 11a Through- hole 11b Partition 12 Outer periphery coating layer 13 Adhesive layer 20 Holding sealing material 30 Metal container 100 Exhaust gas purification apparatus

Claims

A honeycomb structure including a honeycomb unit including at least a titanium oxide and an inorganic binder, wherein a plurality of cells extending from one end face to the other end face along a longitudinal direction are partitioned by cell walls. ,
A composite material having a pH of 5 or more obtained by mixing and kneading at least a titanium oxide synthesized by a sulfuric acid method, an inorganic binder, and an alkaline material is formed into the shape and fired. A honeycomb structure.
The honeycomb structure according to claim 1, wherein the alkaline material is a solution containing an alkaline substance having a boiling point of 500 ° C or lower.
The alkaline material is a solution containing one or more selected from diethanolamine, monoethanolamine, dimethylaminoethanol, and aqueous ammonia, or one or more selected from diethanolamine, monoethanolamine, and dimethylaminoethanol. The honeycomb structure according to claim 1 or 2.
The honeycomb structure according to claim 1 or 2, wherein the kneaded material further contains a vanadium raw material.
The honeycomb structure according to any one of claims 1 to 4, wherein the vanadium raw material is ammonium metavanadate.
The inorganic binder is any one of solids contained in one or more selected from the group consisting of alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite bentonite and boehmite. The honeycomb structure according to item.
7. The method according to claim 1, wherein the kneaded product further includes one or more selected from the group consisting of inorganic fibers, scale-like substances, tetrapot-like substances, and three-dimensional needle-like substances. The honeycomb structure described.
The inorganic fiber is at least one selected from the group consisting of alumina, silica, silicon carbide, silica alumina, glass, wollastonite, potassium titanate and aluminum borate,
The scaly substance is at least one selected from the group consisting of glass, muscovite, alumina and silica,
The tetrapot-like substance is zinc oxide,
The three-dimensional acicular material is at least one selected from the group consisting of alumina, silica, silicon carbide, silica alumina, glass, wollastonite, potassium titanate, aluminum borate and boehmite. Item 8. The honeycomb structure according to Item 7.
A manufacturing method of a honeycomb structure including a honeycomb unit having a shape in which a plurality of cells extending at least from one end face to the other end face along a longitudinal direction are partitioned by cell walls, including at least a titanium oxide and an inorganic binder Because
A step of mixing and kneading at least a titanium oxide synthesized by a sulfuric acid method, an inorganic binder, and an alkaline material to obtain a composite material having a pH of 5 or more;
Obtaining a molded body obtained by molding the composite material into the shape;
Firing the molded body;
A method for manufacturing a honeycomb structure, comprising:
The method for manufacturing a honeycomb structured body according to claim 9, wherein the alkaline material is a solution containing an alkaline substance having a boiling point of 500 ° C or lower.
The alkaline material is a solution containing one or more selected from diethanolamine, monoethanolamine, dimethylaminoethanol, and aqueous ammonia, or one or more selected from diethanolamine, monoethanolamine, and dimethylaminoethanol. A method for manufacturing a honeycomb structure according to claim 9 or 10.