JPH0463141A - Production of carrir having poisoning preventive layer, and production of catalyst having poisoning preventive layer - Google Patents

Abstract

PURPOSE:To improve the purification performance of the catalyst for exhaust gas by coating a specified carrier surface with a soln. containing a specified amt. of compd. containing group IIa elements in the periodic table, and drying the coating film to form a poisoning preventive layer. CONSTITUTION:A soln. containing a compd. 13 containing group IIa elements is applied on the surface of a specified carrier 11 and dried to form a poisoning preventive layer. The amt. of the compd. 13 in the soln. in 2-15wt.% in terms of the group IIa elements. As for the carrier to be coated with the poisoning preventive layer, pellet type ceramic carrier, monolith type ceramic carrier, pellet type metal carrier, monolith type metal carrier or a metal catalyst carrier is used. The group IIa elements are preferably Ca and Mg in order to obtain the preventive effect against Si-poisoning. Thereby, purification performance for exhaust gas can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 2] The present invention relates to a method for producing a carrier with a poison prevention layer and a method for producing a catalyst with a poison prevention layer. INDUSTRIAL APPLICABILITY The present invention is widely used in automobile exhaust gas purification devices and the like.

[Conventional technology]

Exhaust gas purification devices for automobiles, which are used for the purpose of pollution prevention, have become established as automobile parts because they significantly reduce air pollutants such as carbon oxides and nitrogen oxides, and do not reduce engine output or fuel efficiency. are doing. As exhaust gas purification devices, thermal reactors and catalytic converters are known, but catalytic converters have become mainstream as unburned components in exhaust gas are diluted due to recent improvements in engine combustion systems. Catalysts used for this include oxidation catalysts, reduction catalysts, and three-way catalysts in which predetermined catalyst components are supported on ceramic pellet-type or monolith-type carriers, and the catalyst components include noble metals such as Pt and Rh. is used.

[Problem to be solved by the invention]

However, nowadays, silicon (broadly referred to as a Si component) and phosphorus compounds may be mixed into exhaust gas because silicon is often used as a sealing material for automobile parts. Therefore, noble metals such as Pt and Rh, which are catalytic components, are easily poisoned or clogged by the silicon, so there is a problem that the function as a catalyst is significantly reduced.

The present invention solves the above problems, and provides a carrier with a poisoning prevention layer and a carrier that prevents poisoning of precious metals as catalyst components by silicon and/or phosphorus compounds and does not reduce catalyst performance. An object of the present invention is to provide a method for producing a catalyst with a poison prevention layer.

[Means to solve the problem]

The present inventor has conducted various studies to prevent poisoning, and has found that poisoning by 81 or phosphorus compounds in exhaust gas is
By forming a poisoning prevention layer made of a non-oxide compound containing a group Ia element, such as a chloride or a nitrate compound,
The present invention was completed by discovering that great effects can be obtained.

The method for producing a carrier with a poisoning prevention layer according to the first to fifth aspects of the present invention includes applying a compound (
A solution containing 2 to 15% by weight (hereinafter simply referred to as %) of a group IIa element (hereinafter referred to as a group IIa element compound) is applied and dried to form a poisoning prevention layer. do.

The method for producing a catalyst with a poisoning prevention layer according to the sixth to eleventh inventions includes:
A solution containing 2 to 12% by weight of a group IIa element compound in terms of the group IIa element is applied onto a catalyst layer made of a noble metal catalyst component formed on the surface of a predetermined carrier, and dried to form a poisoning prevention layer. It is characterized by forming.

In the present invention, after drying, for example, 500 to 600°C
It is also possible to provide a process in which the material is heated to a certain degree.

Here, the carriers on which the poisoning prevention layer or the catalyst layer is formed include ceramic pellet-type carriers (first and sixth inventions, etc.), ceramic monolith-type carriers (second and seventh inventions, etc.).
invention, etc.), metal pellet type carrier (third, eighth invention, etc.)
, a metal monolith type carrier (4th, 9th invention, etc.) or a metal catalyst carrier (1st O invention, etc.) is used.

Further, as the ceramic carrier, it is preferable to use a so-called wash-coated carrier, that is, a carrier coated with T-alumina fine particles to increase the specific surface area and to activate the carrier.

Furthermore, the material of the metal carrier is not particularly limited as long as it can withstand the conditions of use and can directly or indirectly support the self-poisoning prevention layer or the catalyst layer. This is usually a heat-resistant alloy with a higher Af content than usual, and by oxidizing it, the surface becomes A
12O5 is generated, and the poisoning prevention layer etc. can be directly formed on this surface, or an active porous layer such as T-Al2O3 can be formed and a poisoning prevention layer can be formed thereon. In addition, the shape of this carrier is not particularly limited, but it is usually
A honeycomb type as shown in FIG. 6 is used.

Further, the metal catalyst carrier is made of a material having a catalytic action for gas purification, such as Pt, P
It can be made of an alloy containing d, Rh, Ag, etc. However, since there is a large difference in thermal expansion between the poisoning prevention layer and the metal catalyst carrier, problems such as peeling occur, so in the case of a catalyst using a noble metal, a ceramic carrier is preferable.

The reason for using the above-mentioned rI [a compound containing a group A element] is that silicon contained in the exhaust gas and the group IIa element react with each other at the temperature at which the noble metal in the catalyst is used.
Since low melting point crystals are generated, silicon will not penetrate into the noble metal located downstream (viewed from the exhaust gas inlet side) or inside (side not exposed to exhaust gas) of this group IIa element, and as a result, the noble metal will not be covered. This is because it can prevent poison.

Here, "compounds containing group IIa elements" refer to Mg, C
It is a water-soluble compound containing elements such as a and Sr, and for example, chlorides such as calcium chloride, nitrates such as calcium nitrate, or acetates are used. Among these elements, C
a, Mg is preferable. This is because it is more effective in preventing Si poisoning than other elements. Further, the above chlorides, particularly Ca Cl 2 .2H20, are preferred. This is an aqueous solution with excellent homogeneity, and after being attached to the catalyst, very fine particles are formed, which prevents silicon from passing through Group IIa components and is active against silicon. This is because it becomes high.

The solution may be a mixture of two or more types of compounds (regardless of whether they are of the same type or different types of elements).

In addition, the concentration of this solution is 2 to 12% in terms of Na group elements in the production of a catalyst with a poisoning prevention layer. If it is less than 2%, the effect of preventing silicon poisoning or phosphorus compound poisoning is small, and if it exceeds 12%, the surface of the catalyst becomes clogged and the catalyst cannot function as an acid. Furthermore, the concentration of this solution in the production of the carrier with a poison prevention layer is 2 to 15% in terms of group IIa elements.

If it is less than 2%, the effect of preventing silicon poisoning or phosphorus compound poisoning is small, and if it exceeds 15%,
Since the surface of the carrier becomes dense or thickened by the Group IIa compound, sintering progresses in the coating layer during use, which may reduce adhesion to the carrier and cause peeling. As a result, not only the poisoning prevention function deteriorates, but also problems such as peeling off of the coating layer scattering to the catalyst section disposed at a later stage, filling the space.

The method for forming the poisoning prevention layer includes, for example, (1) immersing a carrier with a catalyst layer etc. in a predetermined mixed solution, drying and heat-treating, (2) applying the predetermined mixed solution by spraying, etc. Examples include methods of drying and heat treatment.

Generally, in a catalyst with a poisoning prevention layer, the poisoning prevention layer is formed directly on the surface of the catalyst layer, but a porous protective layer is formed on the surface of the catalyst layer to protect the catalyst layer. An anti-poisoning layer may also be formed.

Furthermore, the poisoning prevention layer is preferably formed as the outermost layer, but is not limited thereto.

In the case of a catalyst made of the monolithic carrier, the Group IIa element compound is placed on the entire surface of the carrier or on a part of the exhaust gas introduction side, on the side that is more exposed to the exhaust gas than the catalyst component. This is achieved by forming a poisoning prevention layer containing. When it is formed "on a part of the surface", it is preferable that the surface extends to 1/1o or more of the total length of the honeycomb as viewed from the exhaust gas introduction side. This is to ensure the ability to prevent Si from poisoning the catalyst components. Furthermore, for the same reason, when forming a poisoning prevention layer on a monolithic carrier, the layer should be formed on the surface up to 1/1o or more of the total length of the honeycomb as seen from the exhaust gas introduction side, and on the other surface. A catalyst layer may be formed thereon.

In a device using the catalyst with a poisoning prevention layer of the present invention, this catalyst with a poisoning prevention layer can be used alone, but it is also possible to arrange this catalyst with a poisoning prevention layer on the exhaust gas introduction side. However, it is also possible to arrange a conventional catalyst that does not have a poisoning prevention effect on the exhaust gas outlet side. For the same reason as mentioned above, it is preferable that the length of the catalyst with the poisoning prevention layer is 1ZIC1 above the total length when viewed from the exhaust gas introduction side. Devices using the carrier with a poisoning prevention layer of the present invention include:
It is also possible to arrange this carrier with a poisoning prevention layer on the exhaust gas inlet side and arrange a conventional catalyst on the exhaust gas outlet side. The length of the carrier with the poison prevention layer is set to be 1/10 or more of the total length when viewed from the exhaust gas introduction side as described above.
It is preferable for the above reason.

〔Example〕

The present invention will be specifically explained below using Examples.

Example 1 In this example, the silicon toxicity of a catalyst with a poison prevention layer was investigated.

(1) Preparation of pellet type catalysts No. 1 to 12 P was added as a catalyst component to a spherical activated alumina carrier.
Noble metal-supported pellets (particle size approximately 3 mm) supporting t (0.13%) and Ph (0.14%) are prepared.

Next, as shown in Table 1, CaCf2 ・2H20(
Reagent grade), Ca (NO=)a '4H30, Ca
(CH,Coo), ・H,O,Mg (N.

, ) 2 . Then, each pellet was immersed in each solution, then taken out, dried, and heat-treated at about 500 to 600°C to produce catalysts Nα1 to Nα12.

Note that N1112 is a comparative product and does not form a poisoning prevention layer.

(2) Preparation of monolith type catalysts k 13 to 19 As shown in Table 1, the catalysts were prepared in the same manner as described above, except that a monolith type (honeycomb type) carrier was used instead of the pellet type carrier.

Note that this monolithic catalyst has a rectangular cross section (16×1.
A catalyst layer is formed by supporting the catalyst component on a honeycomb-shaped carrier made of cordierite (total length: approximately 200 mm, number of cells: approximately 400 cells per square inch, manufactured by Nippon Tokushu Tokugyo Co., Ltd.). Furthermore, on this surface, each 11a element compound layer shown in the same table was formed.

(3) Fabrication of a purification device As shown in FIG. 4, the catalyst 1 (Nα1 to 19) is placed in a predetermined metal container 2 to fabricate a purification device.
This was placed in place.

(4) Preparation of carriers Nα20 to 32 with poisoning prevention layer Instead of the carrier with a catalyst layer, a solution having the concentration shown in Table 2 was prepared on a carrier without a catalyst layer, and in the same manner as above, a solution with a concentration shown in Table 2 was prepared. Formed an anti-poison layer. Note that the carriers Nα20 to 26 are pellet-shaped products, and the carriers Nα27 to 32 are honeycomb-shaped products.

(5) Preparation of purification device B
As shown in the figure, the catalyst IA is placed in a predetermined metal container 2B and placed on the exhaust gas introduction side, and then the catalyst IA is placed in the predetermined metal container 2A to produce a purification device, and this is placed in a predetermined position. Placed. In addition, regarding the pellet type assemblies of Nos. 20 to 26, honeycomb type catalysts No. 19 were placed at the rear. For the honeycomb carriers No. 27 to 32, the pellet catalyst No. 12 was arranged at the rear.

(6) Performance test As shown in FIG. 4 or 5, the engine is operated (3000 rpm) in the predetermined purification device,
Si from the silicon injection port 32 on the exhaust vibe 3
Oil (rKF-96-100 manufactured by Shin-Etsu Silicone Co., Ltd.)
C3J) was injected for 1 hour (20 cc/hr).

In addition, the oxygen sensor mounting part 3 on this exhaust vibe 3
1, an oxygen sensor is arranged to determine the oxygen concentration in the exhaust gas and maintain it near the theoretical air/fuel efficiency. In the figure, 4 indicates an exhaust manifold, and 5 indicates a main muffler.

From the above, the C01NOx purification rate (initial stage, after Si test) was measured, and each catalyst and carrier was evaluated. The results are shown in Tables 1 and 2. Note that this purification rate is calculated by determining the concentration A1 of CO or NOx before passing through the catalyst and the concentration A of CO or NOx after passing through the catalyst, and using the following formula.

C(AI-A2 N/A + TS
100 (%) According to these results, the comparative product that does not form a poisoning prevention layer (No, 12.19.26.32)
And in the case of aqueous solution concentration 1% (No, 1, 13.20),
The purification rate after the Si test decreased. On the other hand, CaCl22
In a 15% aqueous solution of H20 (catalyst No. 4.16),
The initial purification rate decreased slightly.

However, carrier N023.29 with a poison prevention layer showed good purification performance, although the aqueous solution concentrations were 16% and 15%, respectively.

Example 2 In this example, phosphoric acid toxicity was investigated. Instead of the silicone oil in Example 1, a 30% concentration solution of phosphoric acid (orthophosphoric acid reagent) was added at a rate of 20 cc/hour to a similar purification apparatus using the catalyst and carrier shown in Table 3. Injected for hours. The subsequent purification rates are shown in Table 3.

According to the results, the catalyst exhibited better performance than Comparative Product No. 12, except for Nα4, which had a concentration of 15%. In addition, for the carrier/catalyst, the comparative amount Nα26
It showed good performance, except for k16, which had a concentration of 15%.

Table 3. This test was conducted by arranging each of the catalyst devices using the catalysts or carriers shown in Table 4 as described above, idling rotation (lean) for 10 seconds, then 3000 rpm, A/F
=12 (rich) 60 seconds then 11000 rpm
, A/F=14.5 (λ=1).

The results are shown in Table 4. According to this result, compared with 1f and each comparison amount Nα12.26, No. 23 (CaC1,
・2H,O; concentration 16%, excluding carrier/catalyst), 30
Good purification performance was shown even after 0 hours.

(Hereinafter, blank spaces) Example 3 This example was tested for durability. From Table 4 and above, in the case of a catalyst with a poisoning prevention layer, the concentration of Group IIa element compound was 2 to 12%. In the case of the carrier/catalyst with a poisoning prevention layer, the concentration may be a little higher, and good performance was shown at 2 to 15%.

It should be noted that the present invention is not limited to those shown in the above-mentioned specific embodiments, and may be modified in various ways within the scope of the present invention depending on the purpose and use. That is, the shape, material and size of the pellet type carrier or monolith type carrier, porosity in the case of ceramic, etc. are not particularly limited. For example, the shape is not limited to a spherical shape, but can also be a cylindrical pellet, or a monolith shape other than a cylindrical shape, such as a prismatic shape. In the case of a monolith shape, it can be a so-called honeycomb shape. In this case, the other end may not be sealed, or the other end may be sealed and the exhaust gas may pass through the wall. The material may be ceramic or metal, and the type of ceramic or metal can be selected depending on the purpose and use.

Further, the shape of the metal carrier or the metal catalyst carrier can usually be a honeycomb type 6 as shown in FIG. That is, the outer cylindrical body 61a and the intermediate cylindrical body 61b
and the inner cylindrical body 61c, each corrugated plate part 62a, 6 supports a catalyst component etc. in the shape of a circularly bent corrugated plate.
2b may be arranged. Note that this cylindrical body may or may not be made of the same material as the corrugated plate portion. Each contact point between the cylindrical body 61 and the corrugated plate portion 62 is appropriately joined by welding or the like. Furthermore,
The number of cylindrical bodies (the number of laminated bodies), the pitch or height of bending, the interval between them, etc. are not particularly limited. Further, in the purification device, a modification may be made in which a catalyst using a metal carrier is disposed on the exhaust gas outlet side.

〔Effect of the invention〕

When using the catalyst with a poisoning prevention layer or the carrier with a poisoning prevention layer manufactured according to the present invention, IIa
Since it is captured by the group element compound, this catalyst component is less likely to be poisoned or clogged by silicon or the like. Therefore, even if the catalyst of the present invention is used repeatedly, the catalyst performance will not deteriorate significantly (exhaust gas purification performance will be maintained for a long period of time without deterioration).

Further, when a metal carrier or a metal catalyst carrier is used as the carrier, the metal is less likely to crack or break, and has excellent durability.

[Brief Description of the Drawings] Fig. 1 is a cross-sectional view of a pellet-type catalyst manufactured in an example, Fig. 2 is a cross-sectional view of a monolith-type catalyst manufactured in an example, and Fig. 3 is a cross-sectional view of a monolith-type catalyst manufactured in an example. An enlarged right side view of the main part of the catalyst, FIG. 4 is an explanatory diagram showing a state in which a purification device in which the catalyst of the embodiment is placed in a container is installed, and FIG. An explanatory diagram showing the installed state,
FIG. 6 is a front view of the honeycomb metal carrier. 1, IA; catalyst, 11; carrier, 12; catalyst component layer, 13
; Group IIa element compound layer, IB; Structure for preventing Si poisoning, 2; Metal container, 3; Exhaust pipe, 31; Oxygen sensor mounting part, 32; Silicon injection port, 4; Exhaust manifold, 5; Main muffler 6 ; Metal carrier. Patent applicant: NGK Spark Plug Co., Ltd. Representative: Patent attorney: Kiyoji Kojima 1! ] i! 1 Figure 4 F Figure 5 Procedural amendment (voluntary) Figure 6 1, Display of the case 1990 Patent Application No. 172432 2, Name of the invention Method for manufacturing carrier with poison prevention layer and poison prevention layer attached Catalyst manufacturing method 3, relationship with the case of the person making the amendment Patent applicant 14-18 Takatsuji-cho, Mizuho-ku, Nagoya (454) NGK SPARK PLUG Co., Ltd. Representative Suzukitei - 1c 4゜

Claims (11)

[Claims] (1) Periodic table I on the surface of the ceramic pellet type carrier
A compound containing a group Ia element is 2 to 1 in terms of the group IIa element.
A method for producing a carrier with a poisoning prevention layer, comprising applying a solution containing 5% by weight and drying to form a poisoning prevention layer. (2) A solution containing 2 to 15% by weight of a compound containing a group IIa element of the periodic table in terms of the group IIa element is applied on the entire surface of the ceramic monolithic carrier or on a part of the surface on the exhaust gas introduction side. A method for producing a carrier with a poisoning prevention layer, which comprises coating and drying to form a poisoning prevention layer. (3) 2 to 15% by weight of a compound containing a group IIa element of the periodic table on the surface of a metal pellet carrier, calculated as the group IIa element.
1. A method for producing a carrier with a poisoning prevention layer, which comprises applying a solution containing the carrier and drying it to form a poisoning prevention layer. (4) A solution containing 2 to 15% by weight of a compound containing a group IIa element of the periodic table, calculated as the group IIa element, is applied on the entire surface of the metal monolithic carrier or on a part of the surface on the exhaust gas introduction side. A method for producing a carrier with a poisoning prevention layer, which comprises coating and drying to form a poisoning prevention layer. (5) The method for producing a carrier with a poisoning prevention layer according to any one of claims 1 to 4, wherein the group IIa element of the periodic table is Ca or Mg. (6) A catalyst layer made of a noble metal catalyst component is formed on the surface of a ceramic pellet-type carrier, and then a compound containing a group IIa element of the periodic table is applied to the surface of the catalyst layer in an amount of 2 to 12% in terms of the group IIa element. 1. A method for producing a catalyst with a poisoning prevention layer, which comprises applying a solution containing % by weight and drying to form a poisoning prevention layer. (7) A catalyst layer made of a noble metal catalyst component is formed on the entire surface of the ceramic monolithic carrier or on a part of the surface on the exhaust gas introduction side, and then the surface of the catalyst layer is coated with a group IIa element of the periodic table. 1. A method for producing a catalyst with a poisoning prevention layer, which comprises applying a solution containing 2 to 12% by weight of a compound containing the group IIa element, and drying to form a poisoning prevention layer. (8) A catalyst layer made of a noble metal catalyst component is formed on the surface of a metal pellet type carrier, and then a compound containing a group IIa element of the periodic table is added to the surface of the catalyst layer in terms of the group IIa element.
A method for producing a catalyst with a poisoning prevention layer, comprising applying a solution containing ~12% by weight and drying to form a poisoning prevention layer. (9) A catalyst layer made of a noble metal catalyst component is formed on the entire surface of the metal honeycomb-type carrier or on a part of the surface on the exhaust gas introduction side, and then the surface of the catalyst layer is coated with a group IIa element of the periodic table. 1. A method for producing a catalyst with a poisoning prevention layer, which comprises applying a solution containing 2 to 12% by weight of a compound containing the group IIa element, and drying to form a poisoning prevention layer. (10) A solution containing 2 to 12% by weight of a compound containing a group IIa element of the periodic table in terms of the group IIa element is applied to the surface of a metal catalyst carrier containing a noble metal element and having a catalytic action for exhaust gas purification. A method for producing a catalyst with a poisoning prevention layer, which comprises drying to form a poisoning prevention layer. (11) The method for producing a catalyst with a poisoning prevention layer according to any one of claims 6 to 10, wherein the group IIa element of the periodic table is Ca or Mg.