JP2018202403A - Reduction catalyst structure for automobile, exhaust gas treatment device for automobile, catalyst molded body and method for producing reduction catalyst structure for automobile - Google Patents

Abstract

To provide a highly active reduction catalyst structure for an automobile having excellent catalytic functions which suppresses the deterioration of catalytic function and to provide an exhaust gas treatment device for an automobile.SOLUTION: There is provided a reduction catalyst structure for an automobile which comprises a carrier with a porous structure composed of a zeolite-type compound and an NOreduction catalyst which is inherent in the carrier and composed of a solid acid, wherein the carrier has mutually communicating passages and the NOreduction catalyst is at least present in the passages of the carrier.SELECTED DRAWING: Figure 1

Description

The present invention is an automotive reduction catalyst structure comprising a porous structure carrier and _the NO _x reduction catalyst, automotive exhaust gas treatment apparatus, a method for producing a shaped catalyst bodies and automotive reduction catalyst structure.

With the recent increase in environmental awareness, automobile exhaust gas regulations have become stricter. The exhaust gas discharged from the automobile contains nitrogen oxides (NO _x ) and the like. Environmental standards require that the amount of NO _x contained in the exhaust gas be below a predetermined concentration. In particular, since the amount of NO _x contained in the exhaust gas discharged from an automobile equipped with a diesel engine is large, there is a strong demand for reducing the amount of NO _x in the exhaust gas.

Therefore, conventionally, an exhaust gas treatment device is built in an automobile, and the amount of NO _x contained in the exhaust gas is reduced so as to meet environmental standards. As a method for reducing the amount of NO _x , for example, a method of reducing NO _x by using ammonia generated by a hydrolysis reaction of urea is common. In order to efficiently perform the reduction of NO _x as described above, a selective catalytic reduction is usually performed, and a reduction catalyst is used for this treatment. This reduction catalyst generally has a form supported on a support having excellent heat resistance.

  As such a reduction catalyst, for example, Patent Document 1 discloses a urea SCR catalyst in which Cu ions are introduced into an Al isomorphous substituted iron silicate in which Al ions are introduced into an iron silicate skeleton.

JP2013-136034A

However, the urea SCR catalyst as disclosed in Patent Document 1 has low acid strength because iron is introduced into the silicate skeleton. The catalyst acid strength is controlled, the catalytic function is suppressed, in which is expected to reduce the amount of NO _x is required more strongly future is likely to not be in the future corresponding. In addition, it is possible to improve the life of the catalyst by controlling the acid strength. However, when metal ions such as Fe ions and Al ions are introduced into the silicate skeleton, the metal elements are desorbed at high temperatures. However, there is a problem that the catalyst function decreases with time.

  An object of the present invention is to provide a highly active automobile reduction catalyst structure, an automobile exhaust gas treatment device, a catalyst molded body, and a production method of an automobile reduction catalyst structure, in which a decrease in the catalyst function is suppressed and which has an excellent catalyst function Is to provide.

As a result of intensive studies to achieve the above object, the present inventors have obtained a porous structure carrier composed of a zeolite-type compound, a NO _x reduction catalyst comprising a solid acid, and present in the carrier, And the carrier has a passage communicating with each other, and the NO _x reduction catalyst is present in at least the passage of the carrier, thereby suppressing the deterioration of the function of the solid acid and realizing a long life. It was found that a catalyst structure capable of being obtained was obtained, and the present invention was completed based on such knowledge.

That is, the gist configuration of the present invention is as follows.
[1] A support having a porous structure composed of a zeolite-type compound and a NO _x reduction catalyst made of a solid acid, which is present in the support, the support having a passage communicating with each other, and the NO _x reduction catalyst, automotive reduction catalyst structure characterized by being retained in at least the passage of the carrier.
[2] The reduction catalyst for automobiles according to [1], wherein the passage has an enlarged diameter portion, and the NO _x reduction catalyst is at least enclosed by the enlarged diameter portion. Structure.
[3] The reduction in an automobile according to [2], wherein the enlarged diameter portion communicates a plurality of holes constituting any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. Catalyst structure.
[4] The solid acid is a fine particle, and the average particle diameter of the fine particle is larger than the average inner diameter of the passage and equal to or smaller than the inner diameter of the enlarged diameter portion. 3] The reduction catalyst structure for automobiles according to any one of 3).
[5] The reduction catalyst structure for automobiles according to [4], wherein the fine particles have an average particle diameter of 0.1 nmn to 50 nm.
[6] The reduction catalyst structure for automobiles according to [5], wherein the metal oxide fine particles have an average particle diameter of 0.45 nm to 18.5 nm.
[7] The reduction catalyst structure for automobiles according to [4] or [5], wherein the ratio of the average particle diameter of the fine particles to the average inner diameter of the passage is 0.06 to 500.
[8] The reduction catalyst structure for automobiles according to [7], wherein the ratio of the average particle diameter of the fine particles to the average inner diameter of the passage is 0.1 to 36.
[9] The reduction catalyst structure for automobiles according to [7] or [8], wherein the ratio of the average particle diameter of the fine particles to the average inner diameter of the passage is 1.7 to 4.5. .
[10] The metal element (M) of the metal oxide fine particles of the solid acid is contained in an amount of 0.5 to 2.5% by mass with respect to the catalyst structure, [1] to [9] The reduction catalyst structure for automobiles according to any one of [9].
[11] The passage includes any one of a one-dimensional hole, a two-dimensional hole, and a three-dimensional hole defined by a skeleton structure of the zeolite-type compound, and the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. Having an enlarged diameter part different from any of them,
Any one of [1] to [10], wherein an average inner diameter of the passage is 0.1 nm to 1.5 nm, and an inner diameter of the expanded portion is 0.5 nm to 50 nm. The reduction catalyst structure for automobiles according to 1.
[12] The reduction catalyst structure for automobiles according to any one of [1] to [11], further comprising at least one other NO _x reduction catalyst held on the outer surface of the carrier. body.
[13] The content of the NO _x reduction catalyst inherent in the carrier is greater than the content of the at least one other NO _x reduction catalyst held on the outer surface of the carrier, 12] The reduction catalyst structure for automobiles according to [12].
[14] The reduction catalyst structure for automobiles according to any one of [1] to [13], wherein the zeolite-type compound is a silicate compound.
[15] An automobile exhaust gas treatment device comprising the automobile reduction catalyst structure according to any one of [1] to [14].
[16] A catalyst molding comprising a honeycomb substrate and the oxidation catalyst structure for purifying exhaust gas according to any one of [1] to [15] provided on the surface of the honeycomb substrate. body.
[17] A firing step of firing a precursor material (B) obtained by impregnating a precursor material (A) with a metal-containing solution into a porous structure carrier composed of a zeolite-type compound, and the precursor material And a hydrothermal treatment step of hydrothermally treating the precursor material (C) obtained by firing (B). A method for producing a reduction catalyst structure for automobiles.
[18] The reduction for automobiles according to [17], wherein a nonionic surfactant is added in an amount of 50 to 500% by mass with respect to the precursor material (A) before the firing step. A method for producing a catalyst structure.
[19] Before the firing step, the precursor material (A) is impregnated with the metal-containing solution by adding the metal-containing solution to the precursor material (A) in a plurality of times. The method for producing a reduction catalyst structure for automobiles according to [17] or [18], which is characterized in that
[20] When the precursor material (A) is impregnated with the metal-containing solution before the firing step, the amount of the metal-containing solution added to the precursor material (A) is set to the precursor material. In terms of the ratio of silicon (Si) constituting the precursor material (A) to the metal element (M) contained in the metal-containing solution added to (A) (atomic ratio Si / M), It adjusts so that it may become 10-1000, The manufacturing method of the reduction catalyst structure for motor vehicles as described in any one of [17]-[19] characterized by the above-mentioned.
[21] The method for producing a reduction catalyst structure for an automobile according to [17], wherein the precursor material (C) and a structure directing agent are mixed in the hydrothermal treatment step.
[22] The method for producing a reduction catalyst structure for automobiles according to [17], wherein the hydrothermal treatment step is performed in a basic atmosphere.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of a catalyst function is suppressed and the highly active reduction catalyst structure for motor vehicles which has the outstanding catalyst function, and the exhaust gas processing apparatus for motor vehicles can be provided.

FIG. 1 schematically shows the internal structure of a reduction catalyst structure for an automobile according to an embodiment of the present invention. FIG. 1 (a) is a perspective view (a part is shown in cross section). FIG. 1B is a partially enlarged sectional view. 2 is a partially enlarged cross-sectional view for explaining an example of the function of the automobile reduction catalyst structure in FIG. 1, FIG. 2 (a) is a sieving function, and FIG. 2 (b) is a diagram for explaining the catalytic function. It is. FIG. 3 is a flowchart showing an example of a method for manufacturing the automobile reduction catalyst structure of FIG. FIG. 4 is a schematic view showing a modified example of the automobile reduction catalyst structure of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Composition of catalyst structure]
FIG. 1 is a view schematically showing a configuration of a reduction catalyst structure for automobiles (hereinafter simply referred to as “catalyst structure”) according to an embodiment of the present invention, and FIG. (B) is a partially enlarged sectional view. Note that the catalyst structure in FIG. 1 shows an example, and the shape, dimensions, etc. of each component according to the present invention are not limited to those in FIG.

As shown in FIG. 1 (a), the catalyst structure 1 includes a porous structure carrier 10 composed of a zeolite-type compound and a solid acid 20 contained in the carrier 10. The solid acid 20 functions as a NO _x reduction catalyst. In the catalyst structure 1, the plurality of solid acids 20, 20,... Are included in the porous structure of the support 10.

  The carrier 10 has a porous structure and, as shown in FIG. 1 (b), preferably has a plurality of holes 11a, 11a,. Here, the solid acid 20 is present in at least the passage 11 of the carrier 10, and is preferably held in at least the passage 11 of the skeleton 10.

  With such a configuration, the movement of the solid acid 20 in the carrier 10 is regulated, and aggregation of the solid acids 20 and 20 is effectively prevented. As a result, the reduction of the effective surface area as the solid acid 20 can be effectively suppressed, and the function of the solid acid 20 lasts for a long time. That is, according to the catalyst structure 1, it is possible to suppress a decrease in function due to the aggregation of the solid acid 20, and to extend the life of the catalyst structure 1. Further, by extending the life of the catalyst structure 1, the replacement frequency of the catalyst structure 1 can be reduced, the amount of used catalyst structure 1 discarded can be greatly reduced, and resource saving can be achieved. .

Usually, the catalyst structure, a fluid (e.g., heavy oil or reformed gas such as NO _x) when used in, may be subject to external force from the fluid. In this case, if the solid acid is only attached to the outer surface of the carrier 10, there is a problem that it is easily detached from the outer surface of the carrier 10 due to the influence of external force from the fluid. On the other hand, in the catalyst structure 1, since the solid acid 20 is held in at least the passage 11 of the carrier 10, the solid acid 20 is not easily detached from the carrier 10 even if an external force is received from the fluid. That is, when the catalyst structure 1 is in the fluid, the fluid flows into the passage 11 from the hole 11a of the carrier 10, so that the speed of the fluid flowing in the passage 11 depends on the flow path resistance (friction force). This is considered to be slower than the speed of the fluid flowing on the outer surface of the carrier 10. Due to the influence of the flow path resistance, the pressure that the solid acid 20 held in the passage 11 receives from the fluid is lower than the pressure that the solid acid receives from the fluid outside the carrier 10. Therefore, it is possible to effectively suppress the separation of the solid acid 20 existing in the carrier 11, and the function of the solid acid 20 can be stably maintained for a long period. The flow path resistance as described above is considered to increase as the passage 11 of the carrier 10 has a plurality of bends and branches and the inside of the carrier 10 has a more complicated and three-dimensional structure. .

Further, the passage 11 includes any one of a one-dimensional hole, a two-dimensional hole, and a three-dimensional hole defined by a skeleton structure of the zeolite type compound, and the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. It is preferable to have a diameter-expanded portion 12 that is different from each other. At this time, the solid acid 20 is preferably present at least in the diameter-expanded portion 12, and is included in at least the diameter-expanded portion 12. It is more preferable. As used herein, a one-dimensional hole means a tunnel-type or cage-type hole forming a one-dimensional channel, or a plurality of tunnel-type or cage-type holes forming a plurality of one-dimensional channels (a plurality of one-dimensional holes). Channel). A two-dimensional hole refers to a two-dimensional channel in which a plurality of one-dimensional channels are two-dimensionally connected. A three-dimensional hole refers to a three-dimensional channel in which a plurality of one-dimensional channels are three-dimensionally connected. Point to.
Thereby, the movement of the solid acid 20 in the carrier 10 is further restricted, and the separation of the solid acid 20 and the aggregation of the solid acids 20 and 20 can be more effectively prevented. Inclusion refers to a state in which the solid acid 20 is encapsulated in the carrier 10. At this time, the solid acid 20 and the carrier 10 do not necessarily need to be in direct contact with each other, and another substance (for example, a surfactant or the like) is interposed between the solid acid 20 and the carrier 10. Thus, the solid acid 20 may be indirectly held on the carrier 10.

Although FIG. 1B shows a case where the solid acid 20 is included in the enlarged diameter portion 12, the solid acid 20 is not limited to this configuration. You may hold | maintain at the channel | path 11 in the state which protruded outside. Further, the solid acid 20 may be partially embedded in a portion of the passage 11 other than the enlarged diameter portion 12 (for example, an inner wall portion of the passage 11), or may be held by fixing or the like.
Moreover, it is preferable that the enlarged diameter part 12 is connecting the some hole 11a and 11a which comprise either of the said one-dimensional hole, the said two-dimensional hole, and the said three-dimensional hole. Thereby, since the separate channel | path different from a one-dimensional hole, a two-dimensional hole, or a three-dimensional hole is provided in the inside of the support | carrier 10, the function of the solid acid 20 can be exhibited more.

  The passage 11 is three-dimensionally formed inside the carrier 10 including a branching portion or a merging portion, and the enlarged diameter portion 12 is preferably provided in the branching portion or the merging portion of the passage 11. .

The average inner diameter _DF of the passage 11 formed in the carrier 10 is calculated from the average value of the short diameter and the long diameter of the hole 11a constituting any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. The thickness is 0.1 nm to 1.5 nm, preferably 0.5 nm to 0.8 nm. Further, the inner diameter _DE of the enlarged diameter portion 12 is, for example, 0.5 nm to 50 nm, preferably 1.1 nm to 40 nm, and more preferably 1.1 nm to 3.3 nm. The inner diameter D _E of the enlarged diameter section 12 depends on for example the pore size of which will be described later precursor material (A), and the average particle diameter D _C of the solid acid 20 that is inclusion. The inner diameter _DE of the expanded diameter portion 12 is a size that can include the solid acid 20.

  The carrier 10 is composed of a zeolite type compound. Zeolite type compounds include, for example, zeolites (aluminosilicates), cation exchange zeolites, silicate compounds such as silicalite, zeolite related compounds such as aluminoborate, aluminoarsenate, germanate, molybdenum phosphate, etc. And phosphate-based zeolite-like substances. Among these, the zeolite type compound is preferably a silicate compound.

  The framework structure of the zeolite type compound is FAU type (Y type or X type), MTW type, MFI type (ZSM-5), FER type (ferrierite), LTA type (A type), MWW type (MCM-22). , MOR type (mordenite), LTL type (L type), BEA type (beta type), etc., preferably MFI type, more preferably ZSM-5. In the zeolite type compound, a plurality of pores having a pore size corresponding to each skeleton structure are formed. For example, the maximum pore size of the MFI type is 0.636 nm (6.36 mm), and the average pore size is 0.560 nm (5.60 mm). is there.

Hereinafter, the solid acid 20 will be described in detail.
When the solid acid 20 is a fine particle, the fine particle is held in the passage 11 in a state of primary particles, and the case where the fine particle is held in the passage 11 in a state of secondary particles formed by aggregation of the primary particles. There is. In any case, the average particle diameter D _C of the fine particles is preferably larger than the average inner diameter D _F of the passage 11 and not more than the inner diameter D _E of the enlarged diameter portion 12 (D _F <D _C ≦ D _E ). . Such a solid acid 20 is preferably enclosed by the enlarged diameter portion 12 in the passage 11, and movement of the solid acid 20 in the carrier 10 is restricted. Therefore, even when the solid acid 20 receives an external force from the fluid, the movement of the solid acid 20 in the carrier 10 is suppressed, and the enlarged diameter portions 12, 12,. It is possible to effectively prevent the solid acids 20, 20,.

Further, when the solid acid 20 is fine particles, the average particle diameter _{D C} of the fine particles, in any case of the primary particles and secondary particles, and preferably 0.1 nm to 50 nm, more preferably 0.1nm The thickness is less than 30 nm, more preferably 0.45 nm to 18.5 nm, and particularly preferably 1.0 nm to 3.3 nm. The ratio of the average particle diameter _{D C} of the solid acid 20 to the average inner diameter _{D F} of the passage 11 _(D C / D _F) is preferably from 0.06 to 500, more preferably at 0.1 to 36 More preferably, it is 1.1-36, Most preferably, it is 1.7-4.5.

Specific examples of the solid acid 20 include metal oxides and hydrates, sulfides, metal salts, composite oxides, and heteropoly acids. Examples of the metal oxide include iron oxide (FeOx), zinc oxide (ZnO), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), selenium trioxide (SeO ₃ ), dioxide dioxide Selenium (SeO ₂ ), tellurium trioxide (TeO ₃ ), tellurium dioxide (TeO ₂ ), tin dioxide (SnO ₂ ), manganese oxide (Mn ₂ O ₇ ), technetium oxide (Tc ₂ O ₇ ) and rhenium oxide (Re ₂ O ₇ ). Examples of the sulfide include cadmium sulfide (CdS) and zinc sulfide (ZnS). In addition, examples of the metal salt include magnesium sulfate (MgSO ₄ ), iron sulfate (FeSO ₄ ), and aluminum chloride (AlCl ₃ ). Examples of the composite oxide include SiO ₂ —TiO ₂ , SiO ₂ —MgO, and TiO ₂ —ZrO ₂ . Furthermore, examples of the heteropolyacid include phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, and silicomolybdic acid. These solid acids 20 may be used alone or in combination of a plurality of types. The solid acid 20 is distinguished from the zeolite type compound constituting the carrier 10. The solid acid 20 does not include, for example, zeolite.
Further, the metal element (M) of the solid acid 20 is preferably contained at 0.5 to 2.5% by mass with respect to the catalyst structure 1, and 0.5 to 1 with respect to the catalyst structure 1. More preferably, it is contained at 5% by mass. For example, when the metal element (M) is Zn, the content (mass%) of the Zn element is represented by (mass of Zn element) / (mass of all elements of the catalyst structure 1) × 100. When a plurality of metals are contained in the solid acid, the metal element (M) means the total mass of the plurality of metals.

  The ratio of the silicon (Si) constituting the support 10 to the metal element (M) constituting the solid acid 20 (atomic number ratio Si / M) is preferably 10 to 1000, and preferably 50 to 200. Is more preferable. If the ratio is greater than 1000, the activity is low, and the action as a solid acid may not be sufficiently obtained. On the other hand, when the ratio is smaller than 10, the ratio of the solid acid 20 becomes too large, and the strength of the carrier 10 tends to decrease. The solid acid 20 here refers to a solid acid held or supported inside the carrier 10 and does not include a solid acid attached to the outer surface of the carrier 10.

[Function of catalyst structure]
As described above, the catalyst structure 1 includes a porous support 10 and at least one solid acid 20 present in the support 10. The catalyst structure 1 exhibits a function corresponding to the function of the solid acid 20 when the solid acid 20 present in the carrier 10 comes into contact with the fluid. Specifically, the fluid that has contacted the outer surface 10a of the catalyst structure 1 flows into the carrier 10 through the holes 11a formed in the outer surface 10a, is guided into the passage 11, and moves through the passage 11. Then, it goes out of the catalyst structure 1 through another hole 11a. In the path in which the fluid moves through the passage 11, the reaction according to the function of the solid acid 20 (for example, catalytic reaction) occurs by contacting the solid acid 20 held in the passage 11. Moreover, the catalyst structure 1 has molecular sieving ability because the carrier has a porous structure.

First, the molecular sieving ability of the catalyst structure 1 will be described with reference to FIG. 2A as an example of an exhaust gas containing nitrogen oxides (NO _x ). As NO _x , specifically, nitric oxide (NO), nitrogen dioxide (NO ₂ ), nitrous oxide (N ₂ O), dinitrogen trioxide (N ₂ O ₃ ), dinitrogen tetroxide ( N ₂ O ₄ ), dinitrogen pentoxide (N ₂ O ₅ ), and the like. The exhaust gas of automobiles is mainly composed of nitric oxide.

As shown in FIG. 2A, NO _x composed of molecules having a size smaller than the diameter of the hole 11 a, in other words, smaller than the inner diameter of the passage 11 can flow into the carrier 10. On the other hand, the exhaust gas component 15 composed of molecules having a size exceeding the hole diameter of the hole 11 a cannot flow into the carrier 10. Thus, when the fluid contains a plurality of types of compounds, the reaction of the exhaust gas component 15 that cannot flow into the carrier 10 is restricted, and NO _x that can flow into the carrier 10 is reacted. be able to.

  Of the compounds produced in the carrier 10 by the reaction, only compounds composed of molecules having a size equal to or smaller than the pore diameter of the pores 11a can go out of the carrier 10 through the pores 11a and are obtained as reaction products. On the other hand, a compound that cannot go out of the carrier 10 through the holes 11a can be put out of the carrier 10 if converted into a compound composed of molecules of a size that can go out of the carrier 10. . Thus, a specific reaction product can be selectively obtained by using the catalyst structure 1.

In the catalyst structure 1, as shown in FIG. 2B, the solid acid 20 is preferably included in the enlarged diameter portion 12 of the passage 11. When the solid acid 20 is a fine particle, when the average particle diameter D _C of the solid acid 20 is larger than the average inner diameter D _F of the passage 11 and smaller than the inner diameter D _E of the enlarged diameter portion 12 (D _F <D _C <D _E ), a small passage 13 is formed between the solid acid 20 and the enlarged diameter portion 12. Therefore, as indicated by the arrow in FIG. 2B, the fluid that has flowed into the small passage 13 comes into contact with the solid acid 20. In the present embodiment, when NO _x flowing into the small passage 13 comes into contact with the solid acid 20, NO _x is reduced by a reduction reaction as shown in the following formula (1) or formula (2).
NO _x → 1 / 2N ₂ + x / 2O ₂ Formula (1)
NO _x + 2x / 3NH ₃ → (1/2 + x / 3) N ₂ + xH ₂ O Formula (2)

Since each solid acid 20 is included in the enlarged diameter portion 12, movement within the carrier 10 is restricted. Thereby, aggregation of the solid acids 20 in the carrier 10 is prevented. As a result, a large contact area between the solid acid 20 and NO _x can be stably maintained. Therefore, the solid acid 20 functions as a highly active NO _x reduction catalyst having an excellent catalytic function. Therefore, NO _x can be reduced with high efficiency even when the temperature of the exhaust gas of the automobile is low. In particular, NO _x can be efficiently removed by using the catalyst structure 1 for the reduction reaction of NO _x contained in the exhaust gas of an automobile.

[Automobile exhaust gas treatment equipment]
In the present embodiment, an automobile exhaust gas treatment device (not shown) having the catalyst structure 1 may be provided. The exhaust gas treatment apparatus for automobiles may have the catalyst structure 1 alone, or may be combined with other catalyst structures such as an oxidation catalyst structure for automobiles, a particulate matter collection filter, and the like. . By using the catalyst structure 1 in an apparatus having such a configuration, the same effects as described above can be obtained.

[Method for producing catalyst structure]
FIG. 3 is a flowchart showing a method for manufacturing the catalyst structure 1 of FIG. Hereinafter, an example of a method for producing a catalyst structure will be described, taking as an example the case where the solid acid present in the carrier is fine metal oxide particles.

(Step S1: Preparation process)
As shown in FIG. 3, first, a precursor material (A) for obtaining a porous support composed of a zeolite-type compound is prepared. The precursor material (A) is preferably a regular mesoporous material, and can be appropriately selected according to the type (composition) of the zeolite-type compound constituting the support of the catalyst structure.

  Here, when the zeolitic compound constituting the support of the catalyst structure is a silicate compound, the regular mesoporous material has 1-, 2- or 3-dimensional pores with a pore diameter of 1 to 50 nm. It is preferable that the compound is composed of a Si—O skeleton that has a uniform size and is regularly developed. Such regular mesoporous materials can be obtained as various composites depending on the synthesis conditions. Specific examples of the composites include, for example, SBA-1, SBA-15, SBA-16, KIT-6, FSM- 16, MCM-41, etc., among which MCM-41 is preferable. The pore diameter of SBA-1 is 10 nm to 30 nm, the pore diameter of SBA-15 is 6 nm to 10 nm, the pore diameter of SBA-16 is 6 nm, the pore diameter of KIT-6 is 9 nm, and the pore diameter of FSM-16 is 3 nm. The pore diameter of MCM-41 is 1 nm to 10 nm. Examples of such regular mesoporous materials include mesoporous silica, mesoporous aluminosilicate, and mesoporous metallosilicate.

  The precursor material (A) may be a commercially available product or a synthetic product. When synthesizing the precursor material (A), a known method for synthesizing regular mesoporous materials can be employed. For example, a mixed solution containing a raw material containing the constituent elements of the precursor material (A) and a templating agent for defining the structure of the precursor material (A) is prepared, and the pH is adjusted as necessary. Hydrothermal treatment (hydrothermal synthesis) is performed. Thereafter, the precipitate (product) obtained by hydrothermal treatment is recovered (for example, filtered), washed and dried as necessary, and further calcined to form a regular mesoporous material in powder form. A precursor material (A) is obtained. Here, as a solvent of the mixed solution, for example, an organic solvent such as water or alcohol, a mixed solvent thereof or the like can be used. Moreover, although a raw material is selected according to the kind of support | carrier, for example, silica agents, such as tetraethoxysilane (TEOS), fumed silica, quartz sand, etc. are mentioned. Further, as the templating agent, various surfactants, block copolymers and the like can be used, and it is preferable to select according to the type of the synthesized compound of regular mesoporous materials. For example, when preparing MCM-41 A surfactant such as hexadecyltrimethylammonium bromide is preferred. The hydrothermal treatment can be performed, for example, in a sealed container at 80 to 800 ° C., 5 hours to 240 hours, and treatment conditions of 0 to 2000 kPa. The baking treatment can be performed, for example, in air at 350 to 850 ° C. for 2 to 30 hours.

(Step S2: impregnation step)
Next, the prepared precursor material (A) is impregnated with the metal-containing solution to obtain the precursor material (B).

  The metal-containing solution may be a solution containing a metal component (for example, metal ion) corresponding to the metal element (M) constituting the metal oxide fine particles of the catalyst structure. For example, the metal element (M ) Can be prepared by dissolving the metal salt. Examples of such metal salts include chlorides, hydroxides, oxides, sulfates, nitrates, and the like, and nitrates are particularly preferable. As a solvent, organic solvents, such as water and alcohol, these mixed solvents, etc. can be used, for example.

  The method for impregnating the precursor material (A) with the metal-containing solution is not particularly limited. For example, a plurality of metal-containing solutions are mixed while stirring the powdery precursor material (A) before the firing step described later. It is preferable to add in small portions in portions. Further, from the viewpoint of facilitating the penetration of the metal-containing solution into the pores of the precursor material (A), a surfactant as an additive is added in advance to the precursor material (A) before adding the metal-containing solution. It is preferable to add it. Such an additive has a function of coating the outer surface of the precursor material (A), suppresses the metal-containing solution added thereafter from adhering to the outer surface of the precursor material (A), and the metal It is considered that the contained solution is more likely to enter the pores of the precursor material (A).

  Examples of such additives include nonionic surfactants such as polyoxyethylene oleyl ether, polyoxyethylene alkyl ether, and polyoxyethylene alkylphenyl ether. Since these surfactants have a large molecular size and cannot penetrate into the pores of the precursor material (A), they do not adhere to the inside of the pores, and the metal-containing solution penetrates into the pores. It is thought not to interfere. As a method for adding the nonionic surfactant, for example, it is preferable to add 50 to 500% by mass of the nonionic surfactant with respect to the precursor material (A) before the firing step described later. When the addition amount of the nonionic surfactant to the precursor material (A) is less than 50% by mass, the above-described inhibitory action is hardly exhibited, and the nonionic surfactant is added to the precursor material (A) at 500. Addition of more than% by mass is not preferable because the viscosity increases excessively. Therefore, the addition amount of the nonionic surfactant with respect to the precursor material (A) is set to a value within the above range.

  The amount of the metal-containing solution added to the precursor material (A) is the amount of the metal element (M) contained in the metal-containing solution impregnated in the precursor material (A) (that is, the precursor material (B It is preferable to adjust appropriately in consideration of the amount of the metal element (M) contained in (). For example, before the firing step described later, the addition amount of the metal-containing solution added to the precursor material (A) is the metal element (M) contained in the metal-containing solution added to the precursor material (A), In terms of the ratio of silicon (Si) constituting the precursor material (A) (atomic number ratio Si / M), it is preferably adjusted to be 10 to 1000, and adjusted to be 50 to 200. It is more preferable. For example, when a surfactant is added as an additive to the precursor material (A) before the metal-containing solution is added to the precursor material (A), the addition of the metal-containing solution to be added to the precursor material (A) The metal element (M) of the metal oxide fine particles is contained in an amount of 0.5 to 2.5% by mass with respect to the catalyst structure by converting the amount to 50 to 200 in terms of the atomic ratio Si / M. Can be made. In the state of the precursor material (B), the amount of the metal element (M) present in the pores is the same as the metal concentration of the metal-containing solution, the presence or absence of the additive, and other conditions such as temperature and pressure. If so, it is roughly proportional to the amount of the metal-containing solution added to the precursor material (A). The amount of the metal element (M) inherent in the precursor material (B) is proportional to the amount of the metal element constituting the metal oxide fine particles inherent in the support of the catalyst structure. Therefore, by controlling the amount of the metal-containing solution added to the precursor material (A) within the above range, the metal-containing solution can be sufficiently impregnated inside the pores of the precursor material (A), and thus It is possible to adjust the amount of metal oxide fine particles incorporated in the support of the catalyst structure.

  After impregnating the precursor material (A) with the metal-containing solution, a cleaning treatment may be performed as necessary. As the washing solution, water, an organic solvent such as alcohol, a mixed solvent thereof or the like can be used. In addition, it is preferable to impregnate the precursor material (A) with a metal-containing solution and perform a cleaning treatment as necessary, followed by a drying treatment. Examples of the drying treatment include natural drying overnight or high temperature drying at 150 ° C. or lower. In addition, when the below-mentioned baking process is performed in the state in which the precursor material (A) contains a large amount of moisture contained in the metal-containing solution and the moisture of the cleaning solution, the regular mesoporous material of the precursor material (A) is obtained. Therefore, it is preferable to dry the skeleton structure sufficiently.

(Step S3: Firing step)
Next, the precursor material (B) obtained by impregnating the precursor material (A) for impregnating the porous material structure composed of the zeolite type compound with the metal-containing solution is calcined to obtain the precursor material (C). Get.

  The firing treatment is preferably performed, for example, in the air at 350 to 850 ° C. for 2 to 30 hours. By such a baking treatment, the metal component impregnated in the pores of the regular mesoporous material grows in crystal, and metal oxide fine particles are formed in the pores.

(Step S4: Hydrothermal treatment process)
Next, a mixed solution in which the precursor material (C) and the structure directing agent are mixed is prepared, and the precursor material (C) obtained by firing the precursor material (B) is hydrothermally treated to form a catalyst structure. Get the body.

  The structure directing agent is a templating agent for defining the skeletal structure of the support of the catalyst structure. For example, a surfactant can be used. The structure directing agent is preferably selected according to the skeleton structure of the support of the catalyst structure. For example, a surfactant such as tetramethylammonium bromide (TMABr), tetraethylammonium bromide (TEABr), tetrapropylammonium bromide (TPABr), etc. Is preferred.

  Mixing of the precursor material (C) and the structure directing agent may be performed during the main hydrothermal treatment step, or may be performed before the hydrothermal treatment step. Moreover, the preparation method of the said mixed solution is not specifically limited, A precursor material (C), a structure directing agent, and a solvent may be mixed simultaneously, or precursor material (C) and structure prescription | regulation are carried out to a solvent. After each agent is dispersed in each solution, each dispersion solution may be mixed. As a solvent, organic solvents, such as water and alcohol, these mixed solvents, etc. can be used, for example. Moreover, it is preferable to adjust pH of a mixed solution using an acid or a base before performing hydrothermal treatment.

Hydrothermal treatment can be performed by a well-known method, for example, it is preferable to perform in 80-800 degreeC, 5 hours-240 hours, and processing conditions of 0-2000 kPa in an airtight container. The hydrothermal treatment is preferably performed in a basic atmosphere.
Although the reaction mechanism here is not necessarily clear, by performing hydrothermal treatment using the precursor material (C) as a raw material, the skeleton structure of the precursor material (C) as a regular mesoporous material gradually collapses. While the position of the metal oxide fine particles inside the pores of the precursor material (C) is generally maintained, a new skeletal structure (porous structure) is formed as a support for the catalyst structure by the action of the structure directing agent. Is done. The catalyst structure thus obtained includes a porous structure carrier and metal oxide fine particles inherent in the carrier, and the carrier has a passage in which a plurality of pores communicate with each other due to the porous structure. At least a part of the metal oxide fine particles is held in the passage of the carrier.
In this embodiment, in the hydrothermal treatment step, a mixed solution in which the precursor material (C) and the structure directing agent are mixed is prepared, and the precursor material (C) is hydrothermally treated. Not limited to this, the precursor material (C) may be hydrothermally treated without mixing the precursor material (C) and the structure directing agent.

  The precipitate (catalyst structure) obtained after the hydrothermal treatment is preferably subjected to a washing treatment, a drying treatment and a calcination treatment as necessary after collection (for example, filtration). As the washing solution, water, an organic solvent such as alcohol, a mixed solvent thereof or the like can be used. Examples of the drying treatment include natural drying for about one night and high temperature drying at 150 ° C. or lower. In addition, if the calcination treatment is performed in a state where a large amount of moisture remains in the precipitate, the skeleton structure as a support of the catalyst structure may be broken. Moreover, a baking process can be performed on the process conditions of 350-850 degreeC and 2 to 30 hours, for example in the air. By such a calcination treatment, the structure directing agent attached to the catalyst structure is burned away. Further, the catalyst structure can be used as it is without subjecting the recovered precipitate to a calcination treatment depending on the purpose of use. For example, when the environment in which the catalyst structure is used is a high-temperature environment in an oxidizing atmosphere, the structure-directing agent is burned away by exposure to the environment in which it is used for a certain period of time. In this case, since the same catalyst structure as that obtained when the calcination treatment is performed is obtained, it is not necessary to perform the calcination treatment.

[Modification of Catalyst Structure 1]
FIG. 4 is a schematic view showing a modification of the catalyst structure 1 of FIG.
The catalyst structure 1 in FIG. 1 includes a support 10 and a solid acid 20 inherent in the support 10, but is not limited to this configuration. For example, as shown in FIG. It may further include at least one other NO _x reduction catalyst 30 held on the outer surface 10a.

The NO _x reduction catalyst 30 is a substance that exhibits one or more catalytic capabilities. The catalytic ability of the NO _x reduction catalyst 30 may be the same as or different from the catalytic ability of the solid acid 20. Further, the NO _x reduction catalyst 30 may be a solid acid or a substance other than the solid acid. When the NO _x reduction catalyst 30 is a solid acid, the NO _x reduction catalyst 30 may be the same material as the solid acid 20 or a different material. In particular, when the NO _x reduction catalyst 30 is a solid acid, the content of the solid acid held in the catalyst structure 2 can be increased, and the catalytic activity of the solid acid can be further promoted.

In this case, the content of the solid acid 20 inherent in the carrier 10 is preferably larger than the content of the NO _x reduction catalyst 30 held on the outer surface 10 a of the carrier 10. As a result, the catalytic ability of the solid acid 20 held inside the carrier 10 becomes dominant, and the catalytic ability of the solid acid is stably exhibited.

[Catalyst compact]
In one embodiment, a molded catalyst body having a reduced catalyst structure for automobiles may be provided. The catalyst molded body may have a reduction catalyst structure for automobiles alone or may have another catalyst structure. By using the reduction catalyst structure for automobiles in the catalyst molded body having such a configuration, the same effects as described above can be obtained.

  The catalyst molded body preferably has a base material and a reduction catalyst structure for automobiles provided on the surface of the base material. The base material is a member having a tubular passage through which exhaust gas passes in the axial direction. That is, by providing a structure having a tubular passage through which the exhaust gas passes, the contact area of the automobile reduction catalyst structure with the exhaust gas is increased. Thus, by increasing the contact area of the reduction catalyst structure for automobiles with the exhaust gas, the purification ability of the exhaust gas can be improved. As such a base material, Preferably, a honeycomb-shaped base material can be mentioned. The shape of the honeycomb substrate is not particularly limited, and can be selected from known honeycomb substrates (integrated structure type carriers). Examples of the material for the honeycomb substrate include metals such as stainless steel and heat-resistant ceramics such as cordierite.

[Method for producing catalyst molded body]
In the manufacturing method of the catalyst molded body of one embodiment, the reduction catalyst structure for automobiles is pulverized and the like to obtain a particulate automobile reduction catalyst structure. Next, the particulate reduction catalyst structure for automobiles is mixed with a medium such as water to obtain a slurry. Thereafter, the slurry is applied to the honeycomb-shaped substrate and dried to produce a catalyst molded body having the honeycomb-shaped substrate and the reduction catalyst structure for automobiles on the surface of the honeycomb-shaped substrate. . A method for applying the slurry to the honeycomb-shaped substrate is not particularly limited, but a wash coat method is preferable. 100-300 degreeC is preferable and the temperature at the time of the said drying has more preferable 100-200 degreeC. About a heating means, well-known heating means, such as an electric furnace and a gas furnace, can be used.

  As mentioned above, although the catalyst structure which concerns on embodiment of this invention was described, this invention is not limited to the said embodiment, A various deformation | transformation and change are possible based on the technical idea of this invention.

(Examples 1-288)
[Synthesis of Precursor Material (A)]
A mixed aqueous solution in which a silica agent (tetraethoxysilane (TEOS), manufactured by Wako Pure Chemical Industries, Ltd.) and a surfactant as a templating agent was mixed was prepared, pH was adjusted as appropriate, and 80 to 80 in a sealed container. Hydrothermal treatment was performed at 350 ° C. for 100 hours. Thereafter, the produced precipitate is filtered off, washed with water and ethanol, and further fired in air at 600 ° C. for 24 hours to obtain a precursor material (A) having the types and pore sizes shown in Tables 1 to 6. It was. The following surfactants were used according to the type of the precursor material (A) (“type of precursor material (A): surfactant”).
MCM-41: hexadecyltrimethylammonium bromide (CTAB) (manufactured by Wako Pure Chemical Industries, Ltd.)
・ SBA-1: Pluronic P123 (manufactured by BASF)

[Preparation of Precursor Materials (B) and (C)]
Next, in accordance with the metal element (M) constituting the solid acid fine particles of the types shown in Tables 1 to 6, a metal salt containing the metal element (M) is dissolved in water to prepare a metal-containing aqueous solution. did. The following metal salts were used according to the type of solid acid fine particles (“solid acid fine particles: metal salt”).
ZnO _X : zinc nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.)
・ AlO _X : Aluminum nitrate nonahydrate (manufactured by Wako Pure Chemical Industries, Ltd.)
・ ZrO _X : Zirconyl nitrate dihydrate (manufactured by Wako Pure Chemical Industries, Ltd.)

  Next, the metal-containing aqueous solution is added to the powdery precursor material (A) in small portions in small portions, and dried at room temperature (20 ° C. ± 10 ° C.) for 12 hours or more to obtain the precursor material (B). Got.

  In addition, when the conditions of the presence or absence of the additive shown in Tables 1 to 6 are “Yes”, polyoxyethylene (15) as an additive with respect to the precursor material (A) before adding the metal-containing aqueous solution A pretreatment of adding an aqueous solution of oleyl ether (NIKKOL BO-15V, manufactured by Nikko Chemicals Co., Ltd.) was performed, and then the metal-containing aqueous solution was added as described above. In the case where the condition for the presence or absence of the additive is “none”, the pretreatment with the additive as described above is not performed.

  Moreover, the addition amount of the metal-containing aqueous solution added to the precursor material (A) is the ratio of silicon (Si) constituting the precursor material (A) to the metal element (M) contained in the metal-containing aqueous solution ( The numerical values when converted to atomic ratio (Si / M) were adjusted to the values shown in Tables 1-6.

  Next, the precursor material (B) impregnated with the metal-containing aqueous solution obtained as described above was baked in air at 600 ° C. for 24 hours to obtain a precursor material (C).

[Synthesis of catalyst structure]
The precursor material (C) obtained as described above and the structure directing agent shown in Tables 1 to 6 are mixed to prepare a mixed aqueous solution, and 80 to 350 ° C. and Tables 1 to 6 in a sealed container. Hydrothermal treatment was performed under the conditions of pH and time shown in FIG. Thereafter, the produced precipitate is filtered off, washed with water, dried at 100 ° C. for 12 hours or more, and further calcined in air at 600 ° C. for 24 hours to obtain the carriers and solid acid fine particles shown in Tables 1 to 6. The catalyst structure which has was obtained (Examples 1-288).

(Comparative Example 1)
In Comparative Example 1, cobalt oxide powder (II, III) (manufactured by Sigma Aldrich Japan LLC) having an average particle size of 50 nm or less was mixed with MFI type silicalite, and a functional substance was formed on the outer surface of silicalite as a skeleton. As a result, a functional structure having cobalt oxide fine particles adhered thereto was obtained. MFI type silicalite was synthesized in the same manner as in Examples 52 to 57 except for the step of adding metal.

(Comparative Example 2)
In Comparative Example 2, MFI type silicalite was synthesized by the same method as Comparative Example 1 except that the step of attaching the cobalt oxide fine particles was omitted.

[Evaluation]
With respect to the catalyst structures of Examples 1 to 288 and the silicalites of Comparative Examples 1 and 2, various characteristics were evaluated under the following conditions.

[A] Cross-sectional observation About the catalyst structure of Examples 1-288 and the silicalite of Comparative Examples 1-2, an observation sample was prepared by a pulverization method, and a transmission electron microscope (TEM) (TITAN G2, manufactured by FEI) was used. Using this, cross-sectional observation was performed.

As a result, in the catalyst structures of the above examples, it was confirmed that the solid acid fine particles were contained and held inside the support made of silicalite. On the other hand, in the catalyst structure of the comparative example, the solid acid fine particles were only attached to the outer surface of the carrier, and were not present inside the carrier.
Moreover, about the catalyst structure whose metal oxide is a zirconium oxide oxide (ZrOx) microparticles | fine-particles in the said Example, a cross section is cut out by FIB (focused ion beam) processing, SEM (SU8020, Hitachi High-Technologies Corporation make), Cross-sectional elemental analysis was performed using EDX (X-Max, manufactured by Horiba, Ltd.). As a result, Zr element was detected from the inside of the skeleton.
From the results of cross-sectional observation using the TEM and SEM / EDX, it was confirmed that ZrOx fine particles were present inside the carrier.

[B] Average inner diameter of carrier passage and average particle diameter of solid acid fine particles In the TEM image taken by the cross-sectional observation performed in the above evaluation [A], arbitrarily select 500 passages of the carrier, and each major diameter is selected. Then, the inner diameter was calculated from the average value (N = 500), and the average inner diameter was obtained as the average inner diameter _DF of the carrier passage. Similarly, for solid acid fine particles, arbitrarily select 500 solid acid fine particles from the above TEM image, measure the particle diameter of each (N = 500), determine the average value, and calculate the solid acid fine particles. It was defined as the average particle diameter D _C of the fine particles. The results are shown in Tables 1-6.
Moreover, in order to confirm the average particle diameter and dispersion state of a solid acid, it analyzed using SAXS (small angle X-ray scattering). The SAXS measurement was performed using Spring-8 beam line BL19B2. The obtained SAXS data was fitted with a spherical model by the Guinier approximation method, and the particle size was calculated. The particle size was measured for a catalyst structure in which the metal oxide was iron oxide fine particles. Further, as a comparison object, commercially available iron oxide fine particles (manufactured by Wako) were observed and measured with an SEM.
As a result, in the commercial product, iron oxide fine particles of various sizes are randomly present in the particle size range of about 50 nm to 400 nm, whereas the average particle size obtained from the TEM image is 1.2 nm to 2.0 nm. In the catalyst structure of each Example, a scattering peak having a particle size of 10 nm or less was detected in the SAXS measurement results. From the SAXS measurement result and the cross-sectional measurement result by SEM / EDX, it was found that a solid acid having a particle size of 10 nm or less was present in the support in a very dispersed state with a uniform particle size.

[C] Relationship between the addition amount of the metal-containing solution and the amount of metal included in the skeleton body The atomic ratio Si / M = 50, 100, 200, 1000 (M = Al, Zr, Zn) Then, a catalyst structure in which metal oxide fine particles were included in the inside of the support was prepared, and then the amount of metal (mass%) included in the support of the catalyst structure prepared in the above addition amount was measured. In this measurement, the functional structure having an atomic ratio of Si / M = 100, 200, 1000 is the same as the catalyst structure having an atomic ratio of Si / M = 100, 200, 1000 in Examples 1 to 288, respectively. A catalyst structure having an atomic ratio Si / M = 50 was prepared by adjusting the addition amount of the metal-containing solution in the same manner, except that the addition amount of the metal-containing solution was changed. It was produced by the same method as the catalyst structure of M = 100, 200, 1000.
The amount of metal was determined by using ICP (high frequency inductively coupled plasma) alone or a combination of ICP and XRF (fluorescence X-ray analysis). XRF (energy dispersive X-ray fluorescence analyzer “SEA1200VX”, manufactured by SSI Nanotechnology Co., Ltd.) was performed under the conditions of vacuum atmosphere, acceleration voltage 15 kV (using Cr filter) or acceleration voltage 50 kV (using Pb filter). .
XRF is a method of calculating the abundance of a metal by fluorescence intensity, and a quantitative value (mass% conversion) cannot be calculated with XRF alone. Therefore, the amount of metal in the catalyst structure added with metal at Si / M = 100 was quantified by ICP analysis, and the amount of metal in the catalyst structure added with metal at Si / M = 50 and less than 100 was determined by XRF measurement results. And calculated based on the ICP measurement results.
As a result, it was confirmed that the amount of metal included in the structure increased as the amount of the metal-containing solution added increased at least in the atomic ratio Si / M in the range of 50 to 1000. .

[D] Performance evaluation About the catalyst structure of the said Example and comparative example provided with a support | carrier and solid acid microparticles | fine-particles, the catalyst ability (performance) which a solid acid microparticle has was evaluated. The results are shown in Tables 1-6.

(1) Catalytic activity The catalytic activity was evaluated under the following conditions.
First, 0.2 g of the catalyst structure was charged into an atmospheric pressure flow reactor, and a gas containing NO (nitrogen monoxide) was flowed at a flow rate of 1.0 ml / h to perform a reduction reaction.

  After completion of the reaction, the components of the collected product gas were analyzed by gas chromatography mass spectrometry (GC / MS). Note that TRACE1310GC (manufactured by Thermo Fisher Scientific Co., Ltd., detector: thermal conductivity detector) was used as the product gas analyzer.

Furthermore, the yield (mol%) of N ₂ (nitrogen) was determined based on the analysis results. The yield of the above compound was calculated as a percentage (mol%) of the total amount (mol) of the amount of N ₂ contained in the product gas with respect to the amount (mol) of NO before the start of the reaction.

In this example, when the yield of N ₂ contained in the product gas is 80 mol% or more, it is determined that the catalytic activity (resolution) is excellent, and “」 ”is 50 mol% or more and less than 80 mol%. The case where the catalytic activity is good is judged as “◯”, and the case where it is 20 mol% or more and less than 50 mol% is judged that the catalytic activity is not good but the acceptable level is “△”, and 20 mol. The case where it was less than% was judged that the catalyst activity was inferior (impossible), and was set as “x”.

(2) Durability (life)
The durability was evaluated under the following conditions.

  First, the catalyst structure used in the evaluation (1) was collected and heated at 650 ° C. for 12 hours to produce a heated catalyst structure. Next, using the obtained catalyst structure after heating, a reduction reaction of NO is performed by the same method as in the above evaluation (1), and the components of the product gas are further processed by the same method as in the above evaluation (1). Was analyzed.

Based on the analysis results, the yield (mol%) of N ₂ was determined by the same method as in the evaluation (1). Furthermore, how much the yield of N ₂ by the catalyst structure after heating is maintained as compared with the yield of N ₂ by the catalyst structure before heating (the yield obtained in evaluation (1)) Compared. Specifically, the yield of N ₂ by the catalyst structure after heating (determined by evaluation (2)) relative to the yield of N ₂ by the catalyst structure before heating (the yield determined by evaluation (1)). %) Was calculated.

In this example, the yield of N ₂ by the catalyst structure after heating (the yield determined by evaluation (2)) was determined by the yield of N ₂ by the catalyst structure before heating (determined by evaluation (1)). The yield is determined to be excellent when the durability (heat resistance) is excellent when it is maintained at 80% or more, and the durability (when it is maintained at 50% or more and less than 80%). It is determined that the heat resistance is good, and the case where it is maintained at 20% or more and less than 50% is determined to be a pass level (possible) although the durability (heat resistance) is not good. “△” and the case where it was lowered to less than 20% was judged as “poor” because the durability (heat resistance) was judged to be inferior (impossible).

  In Comparative Example 2, the same performance evaluation as in the evaluations (1) and (2) was performed. Comparative Example 2 is a carrier itself and does not have solid acid fine particles. Therefore, in the performance evaluation, only the support of Comparative Example 2 was filled instead of the catalyst structure. The results are shown in Table 6.

  As is clear from Tables 1 to 6, the catalyst structures (Examples 1 to 288) in which the solid acid was confirmed to be retained inside the support by cross-sectional observation, the solid acid fine particles were simply formed on the outer surface of the support. As compared with the catalyst structure (Comparative Example 1) that is only attached to the catalyst, it was found that the catalyst showed excellent catalytic activity in the NO reduction reaction and was excellent in durability as a catalyst.

  On the other hand, the support itself of Comparative Example 2, which does not have any solid acid, shows almost no catalytic activity in the reduction reaction of NO. Compared with the catalyst structures of Examples 1 to 288, the carrier activity and durability are relatively low. Both were inferior.

  In addition, the catalyst structure of Comparative Example 1 in which the solid acid is attached only to the outer surface of the carrier has a catalytic activity in the reduction reaction of NO as compared with the carrier of Comparative Example 2 that does not have any solid acid. Although improved, the durability as a catalyst was inferior to the catalyst structures of Examples 1 to 288.

1,2 catalytic structure 10 support 10a outer surface 11 passages 11a hole 12 enlarged diameter portion 20 solid acid 30 NO _x reduction catalyst

Claims (22)

A porous structure carrier composed of a zeolite-type compound;
A NO _x reduction catalyst comprising a solid acid inherent in the carrier;
With
The carrier has passages communicating with each other;
A reduction catalyst structure for automobiles, wherein the NO _x reduction catalyst is held in at least the passage of the carrier. The passage has an enlarged diameter portion, and
2. The reduction catalyst structure for an automobile according to claim 1, wherein the NO _x reduction catalyst is included in at least the enlarged diameter portion.   The reduction catalyst structure for an automobile according to claim 2, wherein the enlarged-diameter portion communicates a plurality of holes constituting any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. .   The solid acid is a fine particle, and an average particle diameter of the fine particle is larger than an average inner diameter of the passage and is equal to or smaller than an inner diameter of the enlarged diameter portion. 2. A reduction catalyst structure for automobiles according to item 1.   5. The reduction catalyst structure for automobile according to claim 4, wherein the fine particles have an average particle diameter of 0.1 nmn to 50 nm.   6. The reduction catalyst structure for automobile according to claim 5, wherein an average particle diameter of the metal oxide fine particles is 0.45 nm to 18.5 nm.   The reduction catalyst structure for automobile according to claim 4 or 5, wherein a ratio of an average particle diameter of the fine particles to an average inner diameter of the passage is 0.06 to 500.   8. The reduction catalyst structure for automobile according to claim 7, wherein the ratio of the average particle diameter of the fine particles to the average inner diameter of the passage is 0.1 to 36. 9.   9. The reduction catalyst structure for automobile according to claim 7, wherein a ratio of an average particle diameter of the fine particles to an average inner diameter of the passage is 1.7 to 4.5.   The metal element (M) of the metal oxide fine particles of the solid acid is contained in an amount of 0.5 to 2.5% by mass with respect to the catalyst structure. The reduction catalyst structure for automobiles according to claim 1. The passage is any one of a one-dimensional hole, a two-dimensional hole, and a three-dimensional hole defined by a skeleton structure of the zeolite-type compound, and any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. With a different enlarged diameter part,
The average inner diameter of the passage is 0.1 nm to 1.5 nm, and the inner diameter of the enlarged diameter portion is 0.5 nm to 50 nm. Reduction catalyst structure for automobiles. The reduction catalyst structure for automobile according to any one of claims 1 to 11, further comprising at least one other NO _x reduction catalyst held on an outer surface of the carrier. The content of the NO _x reduction catalyst inherent in the carrier is greater than the content of the at least one other NO _x reduction catalyst held on the outer surface of the carrier, according to claim 12, The reduction catalyst structure for automobiles described.   The reduction catalyst structure for automobile according to any one of claims 1 to 13, wherein the zeolite-type compound is a silicate compound.   An automobile exhaust gas treatment apparatus comprising the automobile reduction catalyst structure according to claim 1.   A catalyst molded body comprising a honeycomb substrate and the oxidation catalyst structure for exhaust gas purification according to any one of claims 1 to 15, which is provided on a surface of the honeycomb substrate. A firing step of firing the precursor material (B) obtained by impregnating the precursor material (A) with a metal-containing solution to obtain a porous structure carrier composed of a zeolite-type compound;
A hydrothermal treatment step of hydrothermally treating the precursor material (C) obtained by firing the precursor material (B);
The manufacturing method of the reduction catalyst structure for motor vehicles characterized by having.   The reduction catalyst structure for automobile according to claim 17, wherein a nonionic surfactant is added in an amount of 50 to 500 mass% with respect to the precursor material (A) before the firing step. Manufacturing method.   Before the firing step, the precursor material (A) is impregnated with the metal-containing solution by adding the metal-containing solution to the precursor material (A) in a plurality of times. The manufacturing method of the reduction catalyst structure for motor vehicles of Claim 17 or 18.   When the precursor material (A) is impregnated with the metal-containing solution before the firing step, the amount of the metal-containing solution added to the precursor material (A) is changed to the precursor material (A). 10 to 1000 in terms of the ratio of silicon (Si) constituting the precursor material (A) to the metal element (M) contained in the metal-containing solution added to (atom ratio Si / M) It adjusts so that it may become, The manufacturing method of the reduction catalyst structure for motor vehicles of any one of Claims 17-19 characterized by the above-mentioned.   The method for producing a reduction catalyst structure for an automobile according to claim 17, wherein the precursor material (C) and a structure directing agent are mixed in the hydrothermal treatment step.   The method for producing a reduction catalyst structure for an automobile according to claim 17, wherein the hydrothermal treatment step is performed in a basic atmosphere.

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