JPH03157143A - Catalyst for purification of exhaust gas from motorcycle - Google Patents

Abstract

PURPOSE:To obtain a durable catalyst for a motorcycle having low back pressure and high purifying performance by sticking an inorg. metal oxide contg. a noble metal to a wire net or punched metal carrier made of ferritic stainless steel contg. Al and Cr. CONSTITUTION:Ferritic stainless steel stock contg. 0.5-10wt.% Al and 5-30wt.% Cr is fired to form whiskers on the surface and a wire net or punched metal carrier is produced. An inorg. metal oxide such as alumina or silica contg. a noble metal such as Pt or Pd is stuck to the carrier and this carrier is formed into a cylindrical shape enabling fixing in an exhaust cylinder. A catalyst for purification of exhaust gas from a motorcycle fixable in the exhaust pipe of the motorcycle and having superior exhaust gas purifying performance, back pressure characteristics and durability is obtd.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a catalyst for purifying motorcycle exhaust gas.

More specifically, the present invention relates to a catalyst for purifying motorcycle exhaust gas that can be installed in the exhaust pipe of a motorcycle and has excellent exhaust gas purification performance, back pressure characteristics, and durability.

(Prior art) Environmental pollution caused by exhaust gas from internal combustion engines has become a major social problem, and various exhaust gas purification methods have been studied in the past. Catalysts have become the mainstream method for purifying exhaust gas. This honeycomb-shaped catalyst has 300 to 400 cells/
It is a one-piece structure with a gas flow path of 1.5 in (square inch) and is housed in the converter and attached to the exhaust gas line, but when used for motorcycle exhaust gas purification, unlike in the case of automobiles, the converter is The problems of installation space and increased back pressure caused by the honeycomb catalyst are significant, and this impedes driving performance, especially for small motorcycles, making it difficult to use in practice.

Therefore, as a catalyst for purifying motorcycle exhaust gas,
JP-A-54mm, No. 17816, JP-A-50-891
As seen in No. 2, a catalyst purification device in which a cloth-like catalyst is installed on the inner wall of the exhaust pipe has been proposed, but the cloth-like catalyst wears out due to vibrations during motorcycle operation and vibrations in the exhaust gas flow. There was a problem with durability. Another possibility is to apply the catalyst substance directly to the inner wall of the exhaust pipe, but this method has the disadvantage that satisfactory purification performance cannot be obtained because there is little contact between the catalyst and the exhaust gas.

(Problems to be Solved by the Present Invention) The present invention overcomes these conventional drawbacks and provides a highly durable catalyst for purifying motorcycle exhaust gas, which has low back pressure and high exhaust gas purification performance. It is something to do.

(Means for solving the problem) The catalyst according to the present invention comprises a wire mesh or punched metal carrier of ferritic stainless steel containing AI and Cr,
an inorganic metal oxide containing a noble metal deposited thereon.

The present inventors made the catalyst shape cylindrical along the inner wall of the exhaust pipe to suppress the reduction in the effective inner diameter of the exhaust pipe as much as possible, thereby suppressing the increase in back pressure. plate) as a carrier to increase the surface area of the catalyst in contact with the exhaust gas,
We have discovered scales that improve exhaust gas purification ability. Wire mesh can be used as long as the wire diameter is 0.1 m or more and the gap between openings is 10 mm or less.For punched metal, the shape of the holes does not matter, but in the case of circular holes, the diameter is 1 m or less.
It is sufficient to have a pitch of 0 mm or less and a pitch of 15 mm or less, and the plate thickness is preferably 0.05 to 1.5 mm from the viewpoint of strength and workability.

The material of the wire mesh and punching metal is an important issue for the durability of the catalyst. Since catalysts are exposed to high temperatures when purifying exhaust gas, ordinary heat-resistant steel and stainless steel do not have sufficient durability. Therefore, in the present invention, ferritic stainless steel containing A1 and Cr is used as the material of the carrier. AI! The content of Cr and Cr is preferably 1 to 10% by weight and 5 to 30% by weight, respectively, and contains 0.01 to 1% by weight of other rare earth elements such as yttrium (Y) and cerium (Ce). It's okay. Further, in the present invention, the ferritic stainless steel cable material is heated to a temperature in the range of 800 to 1000°C, preferably 85°C.
It is fired at a temperature in the range of 0 to 970°C to form whiskers on its surface. This whisker has a length of 1 to 3 μm,
These lengths and numbers differ slightly depending on the composition of the ferritic stainless steel used.

The catalytic material is primarily composed of noble metals and inorganic metal oxides. At least one of Pt5Pd and Rh is used as the noble metal, and wire mesh or punching metal 100a
0.01-1.5 g per n', preferably 0.1-1.
5g is attached. Examples of inorganic metal oxides include alumina, silica, and zirconia, but in the present invention, activated alumina having a γ, δ, or θ crystal form is preferred. Also, the use of activated alumina stabilized by alkaline earth metals or rare earth metals, as well as nickel (
Ni), iron (Fe), cerium (Ce), lanthanum (L
a) The performance of the catalyst of the present invention is improved by the addition of co-catalyst components such as zirconium (Zr). These inorganic metal oxides are 0.05 to 2.0% per 100 c++2 of wire mesh or punching metal. Og attached young.

The finished catalyst is usually prepared by depositing a sol of an inorganic metal oxide or a colloidal slurry obtained by wet milling of an inorganic metal oxide on a support, followed by depositing a predetermined amount of the noble metal.

The catalyst may be formed into various shapes such as along the inner wall of the exhaust pipe, but a cylindrical shape is preferable.

The area of wire mesh or punching metal is 25 to 10,000 a.
It is preferable that the catalyst be n2, but this will depend somewhat on the cross-sectional area of the exhaust pipe, and if the thickness of the catalyst is thin, it can be wound in double or triple layers as long as the back pressure allows.

This back pressure is less than 800 mm of water (mmH2O) when the catalyst is formed into a cylinder with a diameter of 33M and a length of 50 mm and air is flowed at a flow rate of 2 Nm'/min. If a catalyst with a back pressure greater than this is installed in the exhaust pipe of a motorcycle, it will interfere with the normal running of the motorcycle, and in the worst case scenario, it may become impossible to drive.

Further, when the wire mesh or punched metal is molded into a predetermined shape, the aperture ratio with respect to the cross section is 87% or more, and if it is less than this, it will cause problems in running the motorcycle as described above.

(Examples) Next, the present invention will be explained in more detail with reference to Examples, but it goes without saying that the present invention is not limited only to these Examples.

Example 1 Aluminum-containing ferritic stainless steel (AICr:
Fe=5:2O:75) type wire mesh (2O0mmW
(Width)X2O0mmL (Length), 22 mesh
h) A wire mesh having a wire diameter of 0135 mI11) was fired at 900° C. for 2 hours in air to obtain a wire mesh in which whisker-like alumina was generated.

Activated alumina was wet-pulverized to obtain an alumina slurry (solid content concentration 30%), a whisker-shaped alumina-generating wire mesh was immersed in this for 1 minute, and the excess slurry was blown off with pressurized air. After drying for 10 hours, it was fired at 600°C for 2 hours to obtain an alumina-coated wire mesh.

After immersing the alumina-coated wire mesh in a palladium nitrate solution (Pd concentration 100 g/I), the excess liquid was blown off with pressurized air, and then dried at 200°C for 10 hours,
The catalyst was obtained by calcining in air at ℃ for 2 hours.

This catalyst contains 2.49g of alumina and 2.49g of palladium.
．． 02 g was supported.

Example 2 A punching metal made of aluminum-containing ferritic stainless steel similar to Example 1 having holes with a diameter of 2 mm and a pitch of 3 mm (200 mm W x 200 mm L
m thickness (T)) was fired in air at 900° C. for 2 hours to generate whisker-like alumina on the punched metal.

Powder containing Pt and Pd supported on activated alumina is wet-pulverized. A punched metal with whiskers is immersed in the resulting slurry (solid content concentration 35%) for 1 minute, then pulled out, and the excess slurry is blown with pressurized air. It was blown away.

Next, the catalyst was dried at 200°C for 10 hours and calcined at 600°C for 2 hours.

This catalyst contains 1.64 g of alumina, 1.06 g of Pt,
0.53 g of Pd was supported.

Comparative Example 1 In Example 1, suspension 304 (SUS 304) was used instead of the aluminum-containing ferrite stainless steel wire mesh.
A catalyst was obtained in the same manner as in Example 1, except that a wire mesh was used and the whisker-like alumina generation treatment was omitted.

This catalyst contains 2.07g of alumina and 2.01g of Pd.
It was being carried.

This catalyst contains 2.92 g of alumina and 0.96 g of Pt.
0.48 g of g5Pd was supported.

Example 3 The catalysts obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were cut into 100 mmW x 100 mmL pieces, their weight was measured, and then an ultrasonic cleaner was filled with pure water to soak each catalyst. After being subjected to ultrasonic treatment for 20 minutes, it was pulled up, dried at 200° C. for 5 hours, and its weight was measured to determine the amount of peeling of the catalyst material. The results are shown in Table mm.

Table Comparative Example 2 A catalyst was prepared in the same manner as in Example 2, except that a punching metal made of 5US304 was used instead of the aluminum-containing ferrite stainless steel punching metal in Example 2, and the whisker-like alumina generation treatment was omitted. Obtained.

Example 4 Each of the catalysts prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was processed into a cylinder with a diameter of 33 mm x 100 mm L, and was placed along the inner wall of the exhaust pipe of a commercially available FFI 50 cc motorcycle. Insert it and fix it at the 200 position from the engine by spot welding. After running 5000k111 for each catalyst, the running conditions were determined by the Economic Commission for Europe (Economics Commission for Europe).
CE)40 mode was set, and the purification rate of hydrocarbons (HC) and -carbon oxides (CO) was determined. The results are shown in Table-2.

Table Example 5 Some of the catalysts prepared in Examples 1 and 2 (the catalyst of Example 1 was 100 mmW x 100 mmL, the catalyst of Example 2 was 1
00mmWX 50mmL), diameter 33n+m.

It was rolled and formed into a cylindrical shape with a length of 50 plates, and this was placed in a circumscribing pipe. Further, the catalyst prepared in Comparative Example 3 was similarly placed in the pipe, air was flowed at 2 Nm'/min, and the back pressure was measured. The results are shown in Table-3.

Comparative Example 3 Cordierite honeycomb carrier (diameter 33 mm x 5
Approximately 43 cc (0 mm L, 400 cells/in', wall thickness 6-1000 cells/in') of activated alumina preloaded with PT and Pd (solids concentration, 37%
) for 1 minute, then pulled out, and excess slurry was blown off with pressurized air. Then, heat it with hot air at 12O℃ for 5 minutes.
The mixture was air-dried for 1 minute, dried in a dryer at 200°C for 10 hours, and then calcined at 600°C for 2 hours to obtain a finished catalyst.

The total amount of catalyst material supported at this time was 52 Og. Of these, 0.49 g and 0.24 g of Pt and Pd were supported, respectively. The back pressure of the obtained catalyst was measured in the same manner as in Example 5, and the results are shown in Table 3.

Table 3 (Effects of the Invention) As is clear from Table 2, the catalysts of Examples 1 and 2 according to the present invention exhibit superior exhaust gas purification performance compared to the catalysts of Comparative Examples 1 and 2. .

When the catalysts of Comparative Examples 1 and 2, which had poor purification performance, were taken out and analyzed, it was found that the metal carriers themselves were severely damaged, and the attached catalyst material was peeling off, whereas the catalysts of Examples 1 and 2 Almost no changes were observed in the state of adhesion of the metal carrier and catalyst substance from the initial state of the catalyst.

Further, it can be seen from the peel test of Example 3 regarding the adhesion strength of the catalyst substance, and from the test of Example 5 regarding the back pressure that the present invention exhibits excellent effects.

From the above, the catalyst of the present invention has sufficient durability for practical use as a catalyst for purifying motorcycle exhaust gas in terms of purification performance, stability of the metal carrier, adhesion of the catalyst material, and tube strength. That is clear.

Claims (1)

[Claims] 1. 0.5 to 10% by weight of aluminum (Al); and 5
Using a cylindrical wire mesh or punched metal as a carrier, on which whisker-like alumina is formed on the surface of a ferritic stainless steel material containing ~30% by weight of chromium (Cr), a catalyst substance is attached onto the surface of the carrier. A catalyst for purifying motorcycle exhaust gas, which is characterized in that it can be installed in an exhaust pipe. 2. Firing the ferritic stainless steel material at a temperature of 800~
The catalyst according to claim 1, wherein the catalyst is calcined at a temperature of 1000°C to form whisker-like alumina having a length of 1 to 3 μm. 3. Claim in which the firing temperature is in the range of 850 to 970°C (
2) The catalyst described. 4. The catalyst material is at least one selected from the group consisting of platinum (Pt), palladium (Pd), and rhodium (Rh).
The catalyst according to claim 1, comprising a noble metal and an inorganic metal oxide. 5. The catalyst according to claim 1, wherein the ferritic stainless steel material is in the form of a wire mesh or punched metal. 6. Wire mesh wire diameter 0.1mm or more, opening interval 10mm
or less, and the precious metal content per 100cm^2 of the wire mesh is 0.
．． 01-1.5g, inorganic metal oxide 0.05-2.0g
The catalyst according to claim (1), (4) or (5), wherein g is attached. 7. The thickness of the punching metal is 0.05 to 1.5 mm, the punching hole diameter is 10 mm or less, and the pitch is 15 mm or less, and 0.01 to 1.5 g of noble metal is supported per 100 cm^2 of the punching metal, and inorganic metal oxide. is 0.05~
Claim (1), (4) or (
5) Catalyst as described. 8. The area of wire mesh or punching metal is 25 to 1000
Claims (1), (4), (5), (6
) or the catalyst described in (7). 9. Wire mesh or punching metal with a diameter of 33 mm and a length of 5
Form into a 0mm cylinder and fill it with air at 2Nm^3/(min)
Claim (1), (5), (6), (7) or (8), wherein the back pressure when flowing min is less than 800 mmH_2O.
Catalysts as described. 10. Claims (1), (5), wherein the wire mesh or punched metal has an aperture ratio of 87% or more when formed into a cylindrical shape.
The catalyst described in (6), (7), (8) or (9).