JP5756714B2 - Silicoaluminophosphate, honeycomb structure and exhaust gas purification device - Google Patents

Description

  The present invention relates to a silicoaluminophosphate, a honeycomb structure, and an exhaust gas purification device.

  2. Description of the Related Art Conventionally, an SCR (Selective Catalytic Reduction) system that uses ammonia to reduce NOx to nitrogen and water is known as one of systems for purifying automobile exhaust gas.

  In addition, zeolite is known as a material that adsorbs ammonia in the SCR system.

  Patent Document 1 discloses a honeycomb structure having a honeycomb unit including zeolite, inorganic fibers and / or whiskers, and an inorganic binder.

International Publication No. 06/137149

  However, higher NOx purification performance than such a honeycomb structure is required, and it is conceivable to use SAPO-34, which is superior in NOx purification performance, as zeolite.

  On the other hand, SAPO-34 contracts or expands by adsorbing or desorbing water to change the lattice constant. For this reason, the honeycomb structure having a honeycomb unit containing SAPO-34 has a problem that the honeycomb unit easily breaks when SAPO-34 adsorbs or desorbs water.

  In view of the problems of the above-described conventional technology, the present invention is a silicoaluminophosphate that is excellent in NOx purification performance and can suppress shrinkage due to water adsorption and expansion due to water desorption, It is an object of the present invention to provide a honeycomb structure having a honeycomb unit containing silicoaluminophosphate and an exhaust gas purification apparatus having the honeycomb structure.

In the silicoaluminophosphate of the present invention, the ratio of the amount of Si to the sum of the amounts of Al and P is 0.26 or more and 0.33 or less, and the acid point is 1.2 mmol / g or more.

  The silicoaluminophosphate of the present invention is preferably ion-exchanged with copper ions and / or iron ions.

  A honeycomb structure of the present invention includes a honeycomb unit including the silicoaluminophosphate of the present invention and an inorganic binder, and a plurality of through holes arranged in parallel in the longitudinal direction with a partition wall therebetween.

  In the honeycomb structure of the present invention, the silicoaluminophosphate desirably has an average primary particle diameter of 1 μm or more and 5 μm or less.

  The inorganic binder is preferably a solid content contained in one or more selected from the group consisting of alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite and boehmite.

  The honeycomb unit preferably 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 inorganic fiber is at least one selected from the group consisting of alumina fiber, silica fiber, silicon carbide fiber, silica alumina fiber, glass fiber, potassium titanate fiber, and aluminum borate fiber, and the scaly substance is a scale piece. It is at least one selected from the group consisting of glassy glass, scaly muscovite, scaly alumina and scaly silica, the tetrapot-like substance is tetrapot-like zinc oxide, and the three-dimensional acicular substance is 3D acicular alumina, 3D acicular silica, 3D acicular silicon carbide, 3D acicular silica alumina, 3D acicular glass, 3D acicular potassium titanate, 3D acicular aluminum borate and 3D It is desirable to be at least one selected from the group consisting of acicular boehmite.

  The honeycomb structure of the present invention preferably has a plurality of the honeycomb units.

  A honeycomb structure of the present invention includes a honeycomb unit including cordierite, in which a plurality of through holes are arranged in parallel in the longitudinal direction with a partition wall therebetween, and the silicoaluminophosphate of the present invention is supported on the partition wall. ing.

  An exhaust gas purification apparatus of the present invention includes a honeycomb structure of the present invention, a holding sealing material disposed on an outer peripheral portion of the honeycomb structure, and a metal tube in which the honeycomb structure and the holding sealing material are accommodated. Have.

  According to the present invention, silicoaluminophosphate having excellent NOx purification performance and capable of suppressing shrinkage due to water adsorption and expansion due to desorption of water, and a honeycomb including the silicoaluminophosphate A honeycomb structure having a unit and an exhaust gas purification apparatus having the honeycomb structure can be provided.

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 of this invention. It is a perspective view which shows the other example of the honeycomb structure of this invention. Fig. 4 is a perspective view showing a honeycomb unit constituting the honeycomb structure of Fig. 3.

  Next, the form for implementing this invention is demonstrated with drawing.

  FIG. 1 shows an example of the honeycomb structure of the present invention. The honeycomb structure 10 includes a silicoaluminophosphate and an inorganic binder, and an outer peripheral coating layer 12 is formed on the outer peripheral surface of a single honeycomb unit 11 in which a plurality of through holes 11a are arranged in parallel in the longitudinal direction with a partition wall 11b interposed therebetween. Is formed.

  In the silicoaluminophosphate, the ratio of the amount of Si (silicon) to the sum of the amounts of Al (aluminum) and P (phosphorus) is 0.22 to 0.33, and 0.26 to 0.33. The following is preferred. If the ratio of the amount of Si to the sum of the amounts of Al and P in the silicoaluminophosphate is less than 0.22, the shrinkage caused by the adsorption of water by the silicoaluminophosphate and the silicoaluminophosphate It becomes difficult to suppress expansion due to desorption of water. On the other hand, when the ratio of the amount of Si to the sum of the amounts of Al and P in the silicoaluminophosphate exceeds 0.33, the silicoaluminophosphate becomes amorphous and it is difficult to produce the honeycomb unit 11. become.

  In addition, the unit of the substance amount in the present invention is mol, and the ratio (molar ratio) of the substance amount [mol] of Si to the sum of the substance amounts [mol] of Al and P of the silicoaluminophosphate is an energy dispersion type. It can be measured using an X-ray analyzer (EDS).

The silicoaluminophosphate has an acid point of 1.2 mmol / g or more, preferably 1.5 mmol / g or more, and more preferably 2.2 mmol / g or more. When the acid point of the silicoaluminophosphate is less than 1.2 mmol / g, the ion exchange amount decreases when the silicoaluminophosphate is ion-exchanged, and the effect of improving the NOx purification performance becomes small. At this time, the upper limit of the acid point of silicoaluminophosphate is expressed by the formula (ratio of the amount of Si to the sum of the amounts of Al and P) × 12.9 [mmol / g].
It is a theoretical value calculated from

Note that the acid point of silicoaluminophosphate can be measured by an ammonia temperature programmed desorption (NH ₃ -TPD) method.

  Silicoaluminophosphate can be synthesized by adding phosphoric acid, aluminum hydroxide, silica and a structure directing agent (SDA) to water to prepare a precursor gel and then heating.

  The structure directing agent is a template used to form a regular pore structure when synthesizing silicoaluminophosphate.

  At this time, the ratio of the amount of Si to the sum of the amounts of Al and P of the silicoaluminophosphate is controlled by adjusting the ratio of the amount of silica to the sum of the amounts of phosphoric acid and aluminum hydroxide. can do. Moreover, the acid point of silicoaluminophosphate can be controlled by adjusting the addition amount of the structure directing agent.

  The structure directing agent is not particularly limited, and examples thereof include morpholine, diethylamine, tetraethylammonium hydroxide, triethylamine and the like, and two or more kinds may be used in combination.

  The silicoaluminophosphate is preferably ion-exchanged with copper ions and / or iron ions in consideration of NOx purification performance.

  The silicoaluminophosphate ion-exchanged with copper ions and / or iron ions preferably has an ion exchange amount of 1.0 to 5.0 mass%. When the ion exchange amount of the silicoaluminophosphate is less than 1.0% by mass, the effect of improving the NOx purification performance is reduced. On the other hand, when the ion exchange amount of the silicoaluminophosphate exceeds 5.0% by mass, the hydrothermal durability is lowered or, for example, the NOx purification performance at a high temperature of 500 ° C. or more is lowered.

  Silicoaluminophosphate may be ion-exchanged with metal ions other than those described above.

  The silicoaluminophosphate preferably has an average primary particle diameter of 1 to 5 μm. When the average particle size of the primary particles of the silicoaluminophosphate is less than 1 μm, the exhaust gas hardly penetrates into the partition walls 11b, and the silicoaluminophosphate is hardly used effectively for purification of NOx. On the other hand, when the average particle diameter of the primary particles of the silicoaluminophosphate exceeds 5 μm, the porosity of the honeycomb unit 11 increases and the strength of the honeycomb unit 11 decreases. Moreover, when the average particle diameter of the primary particles of the silicoaluminophosphate exceeds 5 μm, the specific surface area of the silicoaluminophosphate is reduced, and the NOx purification performance is lowered.

  The average particle diameter of the primary particles of the silicoaluminophosphate is usually 20 μm or less. However, when the silicoaluminophosphate is used as the material for the honeycomb unit 11, the silicoaluminophosphate is pulverized. To reduce the average particle size of the primary particles.

  The honeycomb unit 11 preferably has a silicoaluminophosphate content of 230 to 360 g / L per apparent volume. If the silicoaluminophosphate content per apparent volume of the honeycomb unit 11 is less than 230 g / L, the apparent volume of the honeycomb unit 11 must be increased in order to improve the NOx purification performance. On the other hand, when the content of silicoaluminophosphate per apparent volume of the honeycomb unit 11 exceeds 360 g / L, the strength of the honeycomb unit 11 becomes insufficient and the aperture ratio of the honeycomb unit 11 becomes small.

  The inorganic binder contained in the honeycomb unit 11 is not particularly limited, and examples thereof include solids contained in alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite, boehmite and the like, and two or more kinds may be used in combination.

  The content of the inorganic binder in the honeycomb unit 11 is preferably 5 to 30% by mass, 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 unit 11 is lowered. On the other hand, when the content of the inorganic binder in the honeycomb unit 11 exceeds 30% by mass, it becomes difficult to extrude the honeycomb unit 11.

  In order to improve the strength, the honeycomb unit 11 preferably 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 inorganic fiber contained in the honeycomb unit 11 is not particularly limited, and examples thereof include alumina fiber, silica fiber, silicon carbide fiber, silica alumina fiber, glass fiber, potassium titanate fiber, and aluminum borate fiber. You may use together.

  The aspect ratio of the inorganic fiber is preferably 2 to 1000, more preferably 5 to 800, and particularly preferably 10 to 500. When the aspect ratio of the inorganic fibers 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 fiber exceeds 1000, the mold is clogged when the honeycomb unit 11 is extruded, or the inorganic fiber breaks and the effect of improving the strength of the honeycomb unit 11 is small. It becomes.

  The scaly substance means a flat substance, preferably having a thickness of 0.2 to 5 μm, preferably having a maximum length of 10 to 160 μm, and a ratio of the maximum length to the thickness of 3 to 250. It is preferable that

  The scale-like substance contained in the honeycomb unit 11 is not particularly limited, and examples thereof include scale-like glass, scale-like muscovite, scale-like alumina, and scale-like silica, and two or more kinds may be used in combination.

  The tetrapot-like substance means a substance in which the needle-like portion extends three-dimensionally. The average needle-like length of the needle-like portion is preferably 5 to 30 μm, and the average diameter of the needle-like portion is 0.5. It is preferably ~ 5 μm.

  Examples of the tetrapot-like substance include single crystals and whiskers.

  The tetrapot-like substance contained in the honeycomb unit 11 is not particularly limited, and examples thereof include tetrapot-like zinc oxide, and two or more kinds may be used in combination.

  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. It is preferable that the average diameter of the acicular portion is 0.5 to 5 μm.

  The three-dimensional needle-like substance may have a plurality of needle-like portions that are three-dimensionally connected. The needle-like portion preferably has a diameter of 0.1 to 5 μm and a length of 0.3 to 30 μm. It is preferable that the ratio of length to diameter is 1.4 to 50.

  Although it does not specifically limit as a three-dimensional acicular material contained in the honeycomb unit 11, Three-dimensional acicular alumina, three-dimensional acicular silica, three-dimensional acicular silicon carbide, three-dimensional acicular silica alumina, three-dimensional acicular glass , Three-dimensional needle-like potassium titanate, three-dimensional needle-like aluminum borate, three-dimensional needle-like boehmite, and the like may be used in combination.

  The content of one or more selected from the group consisting of inorganic fibers, scale-like substances, tetrapot-like substances and three-dimensional needle-like substances in the honeycomb unit 11 is preferably 3 to 50% by mass, and 3 to 30 % By mass is more preferable, and 5% by mass to 20% by mass is particularly preferable. When the content of one or more selected from the group consisting of inorganic fibers, scale-like substances, tetrapot-like substances and three-dimensional needle-like substances in the honeycomb unit 11 is less than 3% by mass, the strength of the honeycomb unit 11 is improved. The effect to make becomes small. On the other hand, when the content of one or more selected from the group consisting of inorganic fibers, scale-like substances, tetrapot-like substances and three-dimensional needle-like substances in the honeycomb unit 11 exceeds 50% by mass, The content of aluminophosphate is lowered, and the NOx purification performance is lowered.

  The honeycomb unit 11 preferably has a porosity of 25 to 40%. When the porosity of the honeycomb unit 11 is less than 25%, the exhaust gas hardly penetrates into the partition walls 11b, and the silicoaluminophosphate is not effectively used for NOx purification. On the other hand, when the porosity of the honeycomb unit 11 exceeds 40%, the strength of the honeycomb unit 11 becomes insufficient.

  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 silicoaluminophosphate is not effectively used for the purification of NOx. 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 11 a 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 exhaust gas and the silicoaluminophosphate are difficult to contact with each other, and the NOx purification performance is lowered. 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 0.10 to 0.50 mm, and more preferably 0.15 to 0.35 mm. When the thickness of the partition wall 11b is less than 0.10 mm, the strength of the honeycomb unit 11 is lowered. On the other hand, if the thickness of the partition wall 11b exceeds 0.50 mm, the exhaust gas hardly penetrates into the partition wall 11b, and the silicoaluminophosphate is not effectively used for the purification of NOx.

  The outer peripheral coat layer 12 preferably has a thickness of 0.1 to 2 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 mm, the content of silicoaluminophosphate per unit volume of the honeycomb structure 10 is lowered, and the NOx purification performance is lowered.

  The honeycomb structure 10 has a columnar shape, but is not particularly limited, and may have a prismatic shape, an elliptical column shape, or the like. Moreover, although the shape of the through-hole 11a is a quadrangular prism shape, it is not specifically limited, A triangular prism shape, a hexagonal column shape, etc. may be sufficient.

  Next, an example of a method for manufacturing the honeycomb structure 10 will be described. First, a raw material paste containing silicoaluminophosphate and an inorganic binder, and further containing at least one selected from the group consisting of inorganic fibers, scaly substances, tetrapot-like substances, and three-dimensional acicular substances, if necessary. A cylindrical raw honeycomb formed body in which a plurality of through holes are arranged in parallel in the longitudinal direction with a partition wall therebetween is produced. Thereby, even if the firing temperature is lowered, the cylindrical honeycomb unit 11 having sufficient strength can be obtained.

  The inorganic binder contained in the raw material paste is not particularly limited, but is added as alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite, boehmite, etc., and two or more kinds may be used in combination.

  Moreover, you may add an organic binder, a dispersion medium, a shaping | molding adjuvant, etc. to a raw material paste suitably as needed.

  Although it does not specifically limit as an organic binder, Methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, polyethyleneglycol, a phenol resin, an epoxy resin etc. are mentioned, You may use 2 or more types together. In addition, the addition amount of the organic binder is based on one or more total mass selected from the group consisting of silicoaluminophosphate, inorganic binder, inorganic fiber, scaly substance, tetrapot-like substance, and three-dimensional acicular substance. It is preferable that it is 1 to 10%.

  Although it does not specifically limit as a dispersion medium, Alcohol, such as water, organic solvents, such as benzene, methanol, etc. are mentioned, You may use 2 or more types together.

  Although it does not specifically limit as a shaping | molding adjuvant, Ethylene glycol, dextrin, a fatty acid, fatty acid soap, a polyalcohol etc. are mentioned, You may use together 2 or more types.

  When preparing the raw material paste, 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 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.

  Further, the dried honeycomb formed body is degreased. The degreasing conditions can be appropriately selected depending on the type and amount of the organic substance contained in the molded body, but it is preferably 2 hours at 400 ° C.

  Next, by firing the degreased honeycomb formed body, the cylindrical honeycomb unit 11 is obtained. The firing temperature is preferably 600 to 1200 ° C, more preferably 600 to 1000 ° C. When the firing temperature is less than 600 ° C., the sintering does not proceed and the strength of the honeycomb unit 11 is lowered. On the other hand, when the firing temperature exceeds 1200 ° C., the sintering proceeds too much and the reaction sites of silicoaluminophosphate decrease.

  Next, the outer periphery coating layer paste is applied to the outer peripheral surface 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.

  Moreover, the outer periphery coating layer paste may further contain an organic binder.

  Although it does not specifically limit as an organic binder, Polyvinyl alcohol, methylcellulose, ethylcellulose, carboxymethylcellulose, etc. are mentioned, You may use 2 or more types together.

  Next, by drying and solidifying the honeycomb unit 11 to which the outer periphery coating layer paste has been applied, a cylindrical honeycomb structure 10 is obtained. 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 kind and amount of the organic matter, but it is preferably 20 minutes at 700 ° C.

  The silicoaluminophosphate can be ion-exchanged by immersing the honeycomb unit 11 in an aqueous solution containing copper ions and / or iron ions. Moreover, you may use the raw material paste containing the silicoaluminophosphate ion-exchanged with a copper ion and / or an iron ion.

  An exhaust gas purification apparatus of the present invention includes a honeycomb structure of the present invention, a holding sealing material disposed on an outer peripheral portion excluding the end of the honeycomb structure, and a metal tube in which the honeycomb structure and the holding sealing material are accommodated. Have.

  FIG. 2 shows an example of the exhaust gas purifying apparatus of the present invention. The exhaust gas purification apparatus 100 is obtained by canning the metal tube 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 purifying apparatus 100 has an injection means (not shown) such as an injection nozzle for injecting ammonia or a compound that generates ammonia by decomposition on the upstream side of the honeycomb structure 10 with respect to the flow direction of the exhaust gas. Is provided. Thereby, since ammonia is added to the exhaust gas, NOx contained in the exhaust gas is reduced by the silicoaluminophosphate contained in the honeycomb unit 11.

  The compound that decomposes to generate ammonia is not particularly limited as long as ammonia can be generated in the exhaust gas, but urea water is preferable in consideration of storage stability.

  The urea water is heated by the exhaust gas and hydrolyzed to generate ammonia.

  FIG. 3 shows another example of the honeycomb structure of the present invention. In the honeycomb structure 10 ′, a plurality of honeycomb units 11 ′ (see FIG. 4) in which a plurality of through holes 11 a are arranged in parallel in the longitudinal direction with the partition walls 11 b interposed 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 5 to 50 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 5 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 50 cm ² , the strength against the thermal stress generated in the honeycomb unit 11 ′ becomes insufficient.

  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 mm. When the thickness of the adhesive layer 13 is less than 0.5 mm, the adhesive strength between the honeycomb units 11 ′ becomes insufficient. On the other hand, when the thickness of the adhesive layer 13 exceeds 2 mm, the pressure loss of the honeycomb structure 10 ′ increases.

  Further, the shape of the honeycomb unit 11 ′ excluding the honeycomb unit 11 ′ located on the outer peripheral portion of the honeycomb structure 10 ′ is a quadrangular prism shape, but is not particularly limited, and may be, for example, a hexagonal column shape.

  Next, an example of a manufacturing method of 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 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 ′. Further, the aggregate of the honeycomb units 11 ′ may be cut into a cylindrical shape and polished as necessary.

  Note that an aggregate of the cylindrical honeycomb units 11 ′ may be manufactured by bonding the honeycomb units 11 ′ whose cross sections perpendicular to the longitudinal direction are formed in a fan shape, a square shape, or the like. This eliminates the need to cut the aggregate of the honeycomb units 11 ′ into a cylindrical shape.

  Although it does not specifically limit as a paste for contact bonding 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 adhesive layer paste may contain an organic binder.

  Although it does not specifically limit as an organic binder, Polyvinyl alcohol, methylcellulose, ethylcellulose, carboxymethylcellulose, etc. are mentioned, You may use 2 or more types together.

  Next, the outer peripheral coat layer paste is applied to the outer peripheral surface of the aggregate of columnar honeycomb units 11 ′.

  The outer peripheral coat layer paste may contain the same material as the adhesive layer paste, or may contain a different material. Further, the outer peripheral coat layer paste may have the same composition as the adhesive layer paste.

  Next, by drying and solidifying the aggregate of the honeycomb units 11 ′ to which the outer peripheral coat layer paste has been applied, a cylindrical honeycomb structure 10 ′ is obtained. 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 kind and amount of the organic matter, but it is preferably 20 minutes at 700 ° C.

  Note that the outer peripheral coat layer 12 may not be formed on the honeycomb structures 10 and 10 ′.

  As described above, the honeycomb structure including the honeycomb unit including the silicoaluminophosphate and the inorganic binder and having the plurality of through holes arranged in parallel in the longitudinal direction with the partition walls therebetween is described. It may have a honeycomb unit including cordierite, in which a plurality of through-holes are juxtaposed in the longitudinal direction across the partition walls, and the silicoaluminophosphate may be supported on the partition walls. Thereby, NOx contained in the exhaust gas can be purified. In addition, generation of cracks in the silicoaluminophosphate and desorption of the silicoaluminophosphate due to shrinkage or expansion due to adsorption or desorption of water can be suppressed.

  In addition, when using silicoaluminophosphate as a material for such a honeycomb structure, the average particle diameter of primary particles is reduced by grinding the silicoaluminophosphate.

  The silicoaluminophosphate preferably has an average primary particle diameter of 1 to 5 μm. When the average particle size of the primary particles of the silicoaluminophosphate is less than 1 μm, it is difficult to support the silicoaluminophosphate on the partition walls. On the other hand, when the average particle diameter of the primary particles of the silicoaluminophosphate exceeds 5 μm, the specific surface area of the silicoaluminophosphate becomes small, and the NOx purification performance decreases.

  Such a honeycomb structure preferably has a single honeycomb unit similarly to the honeycomb structure 10 (see FIG. 1).

  In addition, such a honeycomb structure may have an outer peripheral coat layer formed thereon or may not have an outer peripheral coat layer formed thereon.

  Further, like the honeycomb structure 10, such a honeycomb structure can be applied to an exhaust gas purification apparatus as shown in FIG.

  In this embodiment, the part means part by mass.

[Example 1]
In water, 9.83 parts of 85% by weight phosphoric acid aqueous solution, 7 parts of 95% by weight aqueous aluminum hydroxide, 11.1 parts of silica sol having a solid content of 30% by weight and 15 parts of morpholine as a structure directing agent are sequentially added. Then, the mixture was stirred to obtain a precursor gel. Next, after encapsulating the precursor gel in an autoclave (200 ml), while rotating at a rotation speed of 10 rpm, the temperature was increased to 200 ° C. at a temperature increase rate of 5 ° C./min and held for 24 hours. Was synthesized. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.32, and the acid point was 3.0 mmol / g.

[Example 2]
Silicoaluminophosphate was synthesized in the same manner as in Example 1 except that the amount of morpholine added was changed to 13.1 parts. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.32, and the acid point was 2.2 mmol / g.

[Example 3]
Silicoaluminophosphate was synthesized in the same manner as in Example 1 except that the addition amounts of silica sol having a solid content of 30% by mass and morpholine were changed to 9.4 parts and 11.25 parts, respectively. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.26, and the acid point was 2.2 mmol / g.

[Example 4]
Silicoaluminophosphate was synthesized in the same manner as in Example 3 except that the amount of morpholine added was changed to 7.5 parts. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.26, and the acid point was 1.5 mmol / g.

[Example 5]
Silicoaluminophosphate was synthesized in the same manner as in Example 4 except that 6.3 parts of diethylamine was added instead of 7.5 parts of morpholine. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.26, and the acid point was 1.5 mmol / g.

[Example 6]
Silicoaluminophosphate was synthesized in the same manner as in Example 4 except that the addition amount of silica sol having a solid content of 30% by mass was changed to 7.7 parts. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.22, and the acid point was 1.9 mmol / g.

[Example 7]
Silicoaluminophosphate was synthesized in the same manner as in Example 5 except that the amount of silica sol having a solid content of 30% by mass was changed to 7.7 parts. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.22, and the acid point was 1.5 mmol / g.

[Comparative Example 1]
Silicoaluminophosphate was synthesized in the same manner as in Example 3 except that the amount of silica sol having a solid content of 30% by mass was changed to 4.3 parts. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.11, and the acid point was 1.6 mmol / g.

[Comparative Example 2]
Silicoaluminophosphate was synthesized in the same manner as in Example 3 except that the amount of silica sol having a solid content of 30% by mass was changed to 7.3 parts. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.20, and the acid point was 1.6 mmol / g.

[Comparative Example 3]
Silicoaluminophosphate was synthesized in the same manner as in Example 5 except that the amount of silica sol having a solid content of 30% by mass was changed to 9.0 parts. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.25, and the acid point was 0.7 mmol / g.

[Comparative Example 4]
Silicoaluminophosphate was synthesized in the same manner as in Example 5 except that the addition amount of silica sol having a solid content of 30% by mass was changed to 10.7 parts. In the silicoaluminophosphate, the ratio of the amount of Si to the sum of the amounts of Al and P was 0.30, and the acid point was 0.7 mmol / g.

[Ratio of the amount of Si to the sum of the amounts of Al and P]
Using a silicon drift energy dispersive X-ray analyzer XFlash5030 (manufactured by Bruker), the ratio of the amount of Si to the sum of the amounts of Al and P in silicoaluminophosphate was measured.

[Acid point]
The acid point of silicoaluminophosphate was measured using a fully automatic temperature-programmed desorption spectrometer TPD-1-ATw (manufactured by Bell Japan). Specifically, first, 0.05 g of silicoaluminophosphate was heated to 500 ° C. at a heating rate of 10 ° C./min, held for 60 minutes, cooled to 300 ° C., and then in a steady state (room temperature 25 ° C.). It was. In this state, ammonia was introduced for 30 minutes to adsorb the ammonia to the silicoaluminophosphate, and then the ammonia was exhausted and held for 30 minutes. Next, while introducing helium at 50 ml / min, the temperature was raised to 600 ° C. at a temperature rising rate of 10 ° C./min. The ammonia desorbed during this period was quantified by detecting the peak of NH ₂ ⁺ (m / z = 16) using a quadrupole mass spectrometer, and the acid point was calculated.

[Expansion rate]
Using an X-ray diffractometer Rint-Ultina IV (manufactured by Rigaku Corporation), 2θ is 9 to 9 using silicoaluminophosphate adsorbing 20% by mass of water and silicoaluminophosphate desorbed at 200 ° C. Measured in the range of 21 °, Bragg's equation 2 d sin θ = nλ
(In the formula, d is an interval between lattice planes, θ is an oblique angle (a complementary angle of an incident angle), λ is an X-ray wavelength, and n is a positive integer.)
From the above, the distance d between the lattice planes of the (101) plane, the (110) plane, the (021) plane, the (003) plane, and the (211) plane was calculated. Next, the lattice constant a of the (hkl) plane of the cubic lattice is expressed by the formula a = d / (h ² + k ² + l ² ) ^1/2
Therefore, the average value A of the lattice constant a of the (101) plane, the (110) plane, the (021) plane, the (003) plane, and the (211) plane was calculated. Furthermore, when the average value of the lattice constant of silicoaluminophosphate adsorbed with 20% by mass of water is A _x and the average value of the lattice constant of silicoaluminophosphate desorbed at 200 ° C. is A _y , (A _x −A _y ) / A _x
From this, the expansion coefficient was calculated.

[Preparation of honeycomb structure]
First, the silicoaluminophosphates of Examples 1 to 7 and Comparative Examples 1 to 4 were pulverized so that the average particle diameter of primary particles was 3 μm. Next, the silicoaluminophosphate was ion-exchanged with copper ions by immersing it in an aqueous copper nitrate solution. Using ICPS-8100 (manufactured by Shimadzu Corporation), the amount of exchange of the silicoaluminophosphate by copper ions was measured by ICP emission analysis.

  3100 g of silicoaluminophosphate ion-exchanged with copper ions, 895 g of boehmite, 485 g of alumina fibers having an average fiber diameter of 6 μm and an average fiber length of 100 μm, 380 g of methylcellulose, 280 g of oleic acid and 2425 g of ion-exchanged water are mixed and kneaded. A raw material paste was prepared.

  Next, the raw material paste was extrusion-molded using an extruder to produce a cylindrical honeycomb formed body. Then, using a microwave dryer and a hot air dryer, the honeycomb formed body was dried at 110 ° C. for 10 minutes to dry the honeycomb formed body. Further, the dried honeycomb formed body was degreased at 400 ° C. for 5 hours. Next, the degreased honeycomb formed body was fired at 700 ° C. for 2 hours to produce a cylindrical honeycomb unit.

  On the other hand, 767 g of alumina fibers having an average fiber diameter of 0.5 μm and an average fiber length of 15 μm, 2500 g of silica glass, 17 g of carboxymethylcellulose, 600 g of silica sol having a solid content of 30% by mass, 167 g of polyvinyl alcohol and 17 g of alumina balloon were mixed and kneaded. A paste for the outer periphery coating layer was prepared.

The outer peripheral coat layer paste was applied to the outer peripheral surface excluding the end face of the honeycomb unit, and then dried and solidified at 120 ° C. to prepare a honeycomb structure. The honeycomb structure had a cylindrical shape with a diameter of 225.4 mm and a length of 76.2 mm, a partition wall thickness of 0.28 mm, and a density of through holes of 62 / cm ² .

[NOx purification rate]
While the simulated gas at 200 ° C. was flowed at a space velocity (SV) of 70000 / h to each honeycomb structure manufactured using the silicoaluminophosphates of Examples 1 to 7 and Comparative Examples 1 to 4, the catalyst evaluation apparatus SIGU (Horiba Mfg. Co., Ltd.) was used to measure the amount of NOx flowing out from the honeycomb structure, and the formula (NOx inflow−NOx outflow) / (NOx inflow) × 100
The NOx purification rate [%] expressed by The constituent components of the simulated gas are NOx 350 ppm with a nitrogen dioxide content of 25%, ammonia 350 ppm, oxygen 14%, water 10%, and nitrogen (balance).

  In Table 1, Si / (Al + P), acidity, and expansion rate of the silicoaluminophosphates of Examples 1 to 7 and Comparative Examples 1 to 4, and silicoaluminophosphates of Examples 1 to 7 and Comparative Examples 1 to 4 The measurement result of the NOx purification rate of each honeycomb structure manufactured using salt is shown.

なお、Ｓｉ／（Ａｌ＋Ｐ）は、Ａｌ及びＰの物質量の和に対するＳｉの物質量の比を意味する。

In addition, Si / (Al + P) means the ratio of the substance amount of Si to the sum of the substance quantities of Al and P.

  From Table 1, it can be seen that the silicoaluminophosphates of Examples 1 to 7 have an expansion rate of 1% or less. For this reason, it is thought that generation | occurrence | production of the crack of the honeycomb unit resulting from the shrinkage | contraction or expansion | swelling by silicoaluminophosphate adsorb | sucking or desorbing water can be suppressed. Moreover, it turns out that the honeycomb structure produced using the silicoaluminophosphate of Examples 1-7 has a NOx purification rate of 80% or more, and is excellent in NOx purification performance.

  On the other hand, in the silicoaluminophosphates of Comparative Examples 1 and 2, the ratio of the amount of Si to the sum of the amounts of Al and P is 0.11 and 0.20, so the expansion coefficient exceeds 1%. I understand. For this reason, it is considered that it is difficult to suppress the occurrence of cracks in the honeycomb unit due to contraction or expansion due to the silicoaluminophosphate adsorbing or desorbing water.

  Further, since the silicoaluminophosphate of Comparative Examples 3 and 4 has an acid point of 0.7 mmol / g, the honeycomb structure produced using the silicoaluminophosphate of Comparative Examples 3 and 4 is NOx. It can be seen that the purification rate is 60% or less, and the NOx purification performance decreases.

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

Claims (10)

The ratio of the amount of Si to the sum of the amounts of Al and P is 0.26 or more and 0.33 or less,
A silicoaluminophosphate having an acid point of 1.2 mmol / g or more.   2. The silicoaluminophosphate according to claim 1, which is ion-exchanged with copper ions and / or iron ions.   A honeycomb structure comprising a honeycomb unit comprising the silicoaluminophosphate according to claim 1 or 2 and an inorganic binder, wherein a plurality of through holes are arranged in parallel in a longitudinal direction with a partition wall therebetween.   The honeycomb structure according to claim 3, wherein the silicoaluminophosphate has an average primary particle diameter of 1 µm or more and 5 µm or less.   The honeycomb structure according to claim 3 or 4, wherein the inorganic binder is a solid content contained in at least one selected from the group consisting of alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite, and boehmite. body.   The honeycomb unit according to any one of claims 3 to 5, further comprising at least one 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 fiber, silica fiber, silicon carbide fiber, silica alumina fiber, glass fiber, potassium titanate fiber and aluminum borate fiber,
The scaly substance is at least one selected from the group consisting of scaly glass, scaly muscovite, scaly alumina, and scaly silica,
The tetrapot-like substance is tetrapot-like zinc oxide,
The three-dimensional acicular material is three-dimensional acicular alumina, three-dimensional acicular silica, three-dimensional acicular silicon carbide, three-dimensional acicular silica alumina, three-dimensional acicular glass, three-dimensional acicular potassium titanate, three-dimensional The honeycomb structure according to claim 6, wherein the honeycomb structure is at least one selected from the group consisting of acicular aluminum borate and three-dimensional acicular boehmite.   The honeycomb structure according to any one of claims 3 to 7, comprising a plurality of the honeycomb units. Including a cordierite, and having a honeycomb unit in which a plurality of through holes are arranged in parallel in a longitudinal direction with a partition wall therebetween,
A honeycomb structure, wherein the silicoaluminophosphate according to claim 1 or 2 is supported on the partition walls. A honeycomb structure according to any one of claims 3 to 9,
A holding sealing material disposed on the outer periphery of the honeycomb structure;
An exhaust gas purifier having a metal tube in which the honeycomb structure and the holding sealing material are accommodated.

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