JPH0568886A - Waste gas cleaning catalyst from diesel engine - Google Patents

Abstract

PURPOSE:To purify hydrocarbon, CO and SOF and, at the same time, to reduce an exhausted quantity of diesel particulate and to reduce an exhausted quantity of a sulfate. CONSTITUTION:A waste gas cleaning catalyst for diesel engine consists of a carrier base substance 1, a coating layer 2 being formed with at least one kind of material selected from alumina, titania and silica on the surface of the carrier base substance and obtains an oxide 3 of at least one kind of metal selected from Cu, Fe, Ni, Ce, Mg and Ca, and a catalystic metal 4 carried on a coating layer.

Description

Detailed Description of the Invention

[0001]

The present invention relates to H contained in exhaust gas from a diesel engine (hereinafter referred to as DE).
The present invention relates to a catalyst that can purify C, CO and SOF (Soluble Organic Fraction), reduce the emission amount of diesel particulates, and reduce the emission amount of sulfate.

[0002]

2. Description of the Related Art With respect to gasoline engines, toxic substances in exhaust gas have been steadily reduced due to strict regulations on exhaust gas and progress in technology capable of coping with the regulations. But DE
With respect to the above, due to the peculiar circumstances in which harmful components are mainly discharged as particulates, the regulations and the development of technology are behind that of a gasoline engine, and it is desired to develop an exhaust gas purification device that can surely purify.

As a DE exhaust gas purifying apparatus that has been developed so far, there are roughly known methods using a trap (without a catalyst and with a catalyst) and an open type SOF decomposition catalyst. Of these, the method that uses a trap is
Diesel particulates are trapped to control emissions, which is especially effective for exhaust gas with a high proportion of dry suits. However, a regeneration treatment device is required, and many problems remain in practical use, such as cracking of the catalyst carrier during regeneration, blockage due to ash, or complicated system.

On the other hand, as the open type SOF decomposition catalyst, as disclosed in, for example, Japanese Patent Application Laid-Open No. 1-171626, a catalyst carrying an oxidation catalyst such as a platinum group metal is used as in a gasoline engine, and it is used together with CO and HC in diesel. SOF in particulates is oxidatively decomposed and purified. This open type SOF decomposition catalyst has the drawback that the removal rate of dry suit is low, but the amount of dry suit can be reduced by improving the DE and the fuel itself, and there is a great merit that a regeneration treatment device is not required. Therefore, further improvement in technology is expected in the future.

[0005]

Open type S
With the OF decomposition catalyst, it was difficult to reduce the emission amount of diesel particulates. That is, the activated alumina layer formed on the open type SOF decomposition catalyst is
It has the property of adsorbing SO ₂ . Therefore, SO ₂ contained in the exhaust gas of DE is adsorbed by the activated alumina layer, and when the temperature of the catalyst becomes high, the SO ₂ adsorbed
Is oxidized by the catalytic action of the catalytic metal and is discharged as SO ₃ , and SO _{2 in} the exhaust gas is directly oxidized and discharged, so that there is a problem that the amount of particulates increases. This is because SO ₂ is not measured as particulates, but SO ₃ is measured as particulates. Particularly in DE, oxygen gas is sufficiently present in the exhaust gas, and the SO ₂ oxidation reaction easily occurs.

Further, the higher the oxidation catalytic action of the catalytic metal, the more S
Since the emission amount of O ₃ is also increased, the oxidation activity of the catalyst metal is also reduced, but in this case, the purification performance of HC, CO and SOF is also reduced. That is, it has been difficult to satisfy both purification of HC, CO and SOF and regulation of SO ₃ emission amount. SO ₃ easily reacts with water vapor present in a large amount in the exhaust gas to form sulfate.

The present invention has been made in view of the above circumstances, and purifies HC, CO and SOF, and
The purpose is to reduce the emission amount of diesel particulates and also the emission amount of sulfates.

[0008]

The exhaust gas purifying catalyst for DE according to the present invention, which solves the above-mentioned problems, comprises a carrier base material, alumina,
Cu, Fe, Ni, Ce, formed on the surface of the carrier substrate from at least one material selected from titania and silica
It is characterized by comprising a coat layer containing an oxide of at least one metal selected from Mg and Ca, and a catalyst metal supported on the coat layer.

The carrier base material is the same as the carrier base material of the exhaust gas purifying catalyst used in the conventional gasoline engine, and a monolith carrier base material, a foam filter, a honeycomb filter, a pellet or the like is used. The material is selected from ceramics such as cordierite, or metal. The greatest feature of the present invention is that Cu, F is formed on the surface of the carrier substrate.
formed from at least one material selected from alumina, titania, and silica containing an oxide of at least one metal selected from e, Ni, Ce, Mg, and Ca and carrying a catalyst metal. It has a coat layer.

The catalyst metal supported on the coat layer contributes to the oxidation reaction of SOF, HC, and CO, and one or more kinds of conventional metals such as Pt, Rh, and Pd can be used. .. The supported amount of the catalyst metal is preferably about 0.05 to 2 g per liter of the carrier substrate volume. The metal oxide contained in this coat layer may be an oxide of one kind of metal selected from Cu, Fe, Ni, Ce, Mg and Ca, or may be a mixture of a plurality of metal oxides. Good. The content of this metal oxide is
The range of 0.05 to 3 mol is suitable. If it is less than this range, the SO ₂ adsorption performance is lowered, and if it is more than this range, the adsorption performance is increased, but conversely the oxidation activity of the catalyst metal is lowered, which is not preferable.

In the purifying catalyst of the present invention, SO ₂ is selectively chemically adsorbed by the metal oxide particles in the coating layer, so that the oxidizing action of SO ₂ by the catalytic metal is hard to work. Further, since the metal oxide exists in the form of particles, SO ₂ is further prevented from coming into contact with the catalyst metal. Therefore SO ₃
Since the generation of diesel is suppressed, the emission amount of diesel particulates is reduced.

[0012]

The exhaust purification catalyst of DE according to the present invention has at least one coat layer selected from alumina, titania and silica on the surface of the carrier substrate, and the coat layer contains a catalyst metal and Cu. , Fe, Ni, Ce, Mg, Ca
At least one metal oxide selected from the above is contained. Since SO ₂ in the exhaust gas is selectively adsorbed by this metal oxide, contact with the catalyst metal is prevented. Therefore, the oxidation reaction of SO ₂ is prevented,
Emission of SO ₃ is prevented.

Therefore, it is not necessary to reduce the oxidation activity of the catalyst metal in order to suppress the oxidation of SO ₂ , and a high oxidation activity can be obtained. Therefore, HC, CO and SO
The purification performance of F can be improved.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples. The manufacturing method will be described instead of the detailed description of the configuration. (Embodiment 1) FIG. 1 is a schematic view of a main portion of an exhaust gas purification catalyst of this embodiment. γ-alumina powder, aluminum nitrate,
26 g of copper oxide powder was added to 100 g of γ-alumina in a slurry composed of alumina sol and distilled water. A commercially available columnar cordierite honeycomb carrier substrate 1 (30 mm in diameter, 50 mm in length) was immersed in this slurry, and the slurry was pulled up to blow off excess slurry.
Alumina coat layer 2 was formed by drying at 0 ° C for 2 hours and firing at 600 ° C for 2 hours. The alumina coat layer 2 is formed in an amount of about 120 g per liter of the carrier substrate 1, and the alumina coat layer 2 contains 0.4 mol of copper oxide 3 per liter of the carrier substrate 1.

Next, after the water absorption treatment, it was immersed in an aqueous solution of platinum dinitrodiammine for 60 minutes and dried at 250 ° C. for 2 hours to support platinum 4 on the alumina coat layer 2. At this time, the amount of platinum 4 supported is 1 g per 1 liter of the carrier volume. (Example 2) Example 1 except that a slurry obtained by adding 26 g of copper oxide powder to 100 g of SiO ₂ in a slurry composed of SiO ₂ powder, SiO ₂ sol, and distilled water was used.
Is the same as.

In the exhaust gas purifying catalyst of Example 2, the silica coat layer 2 was about 120 per liter of the carrier substrate 1.
The silica coat layer 2 thus formed contains 0.4 mol of copper oxide 3 per liter of the carrier substrate 1. The amount of platinum 4 supported is 1 g per liter of carrier volume. (Example 3) Example 1 except that a slurry prepared by adding 26 g of copper oxide powder to 100 g of TiO ₂ in a slurry composed of TiO ₂ powder, TiO ₂ sol, and distilled water was used.
Is the same as.

In the exhaust gas-purifying catalyst of Example 3, the titania coat layer 2 was about 12 per volume of the carrier substrate 1.
The titania coat layer 2 contained 0.4 g of copper oxide 3 in an amount of 0.4 mol per liter of the carrier substrate 1. The amount of platinum 4 supported is 1 g per liter of carrier volume. (Example 4) Instead of copper oxide powder, iron oxide powder 36
The same as Example 1 except that g was used.

In the exhaust gas purifying catalyst of Example 4, the alumina coat layer 2 was about 12 per volume of the carrier substrate 1.
The alumina coat layer 2 contained 0.4 g of iron oxide 3 in an amount of 0.4 mol per liter of the carrier substrate 1. The amount of platinum 4 supported is 1 g per liter of carrier volume. (Example 5) The same as Example 1 except that 25 g of nickel oxide powder was used instead of the copper oxide powder.

In the exhaust gas purifying catalyst of Example 5, the alumina coat layer 2 is about 12 per volume of the carrier substrate 1.
0 g of nickel oxide 3 was contained in the alumina coat layer 2 in an amount of 0.4 mol per liter of the carrier substrate 1. The amount of platinum 4 supported is 1 g per liter of carrier volume. (Example 6) The same as Example 1 except that 57 g of cerium oxide powder was used instead of the copper oxide powder.

In the exhaust gas purifying catalyst of Example 6, the alumina coat layer 2 was about 12 per volume of the carrier substrate 1.
The alumina coating layer 2 contained 0.4 g of cerium oxide 3 in an amount of 0.4 mol per liter of the carrier substrate 1. The amount of platinum 4 supported is 1 g per liter of carrier volume. (Example 7) The same as Example 1 except that 13 g of magnesium oxide powder was used instead of the copper oxide powder.

In the exhaust gas-purifying catalyst of Example 7, the alumina coat layer 2 was about 12 per volume of the carrier substrate 1.
The alumina coat layer 2 contained 0.4 g of magnesium oxide 3 in an amount of 0.4 mol per liter of the carrier substrate 1. The amount of platinum 4 supported is 1 g per liter of carrier volume. (Example 8) The same as Example 1 except that 19 g of calcium oxide powder was used instead of the copper oxide powder.

In the exhaust gas purifying catalyst of Example 8, the alumina coat layer 2 was about 12 per volume of the carrier substrate 1.
The alumina coat layer 2 contains 0.4 g of calcium oxide 3 per liter of the carrier substrate 1. The amount of platinum 4 supported is 1 g per liter of carrier volume. (Comparative Example 1) The same as Example 1 except that the copper oxide powder was not used.

In the exhaust gas-purifying catalyst of Comparative Example 1, the alumina coat layer 2 was about 12 per volume of the carrier substrate 1.
The amount of platinum 4 supported is 1 g per 1 liter of the carrier volume, and the amount of platinum 4 supported is 1 g per 1 liter of the carrier volume. (Comparative Example 2) Using the same carrier substrate as in Example 1, using TiO 2
_After dipping in a slurry consisting of ₂ powders, TiO ₂ sol and distilled water, pulling up and blowing off the excess slurry,
It was dried at 0 ° C. for 2 hours and calcined at 700 ° C. for 2 hours to form a TiO ₂ layer of about 120 g per liter of carrier volume. This carrier was immersed in an aqueous solution of ammonium metavanadate, dried and calcined to carry 20 g of V ₂ O ₅ per liter of the carrier. Further, platinum was loaded in the same manner as in Example 1 to obtain a catalyst of Comparative Example 2. (Test Example 1) Each of the above catalysts was subjected to a displacement of 2400
It was attached to the exhaust system of a cc swirl chamber type DE, and the purification rate of HC was measured under an exhaust temperature condition of 400 ° C. At the same time, the conversion rate of SO ₂ into SO ₃ was determined by the following equation using a non-dispersive infrared analyzer. The results are shown in Table 1.

[0024]

[Table 1] From Table 1, the conventional catalyst of Comparative Example 1 is not preferable because the conversion rate to SO ₃ is high because the HC purification rate is good. Moreover, in the catalyst of Comparative Example 2, although the conversion rate to SO ₃ is low, H 2
C Purification rate is low and not preferable.

On the other hand, all the catalysts of the examples are SO ₂ SO ₃
It can be seen that the conversion to is prevented. It is clear that this is an effect due to the inclusion of the metal oxide 3 in the coat layer 2. That is, SO ₂ is chemically adsorbed by the metal oxide in the coat layer, and is not converted to SO ₃ without being subjected to the catalytic action of platinum. Also HC, CO and SO
F etc. are efficiently purified.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a catalyst of an example of the present invention.

FIG. 2 is a schematic sectional view of a conventional catalyst of Comparative Example 1.

[Explanation of symbols]

1: Carrier substrate 2: Coating layer 3: Metal oxide 4: Platinum

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B01J 23/58 A 8017-4G

Claims (1)

[Claims] 1. A carrier substrate and at least one selected from alumina, titania, and silica.
Cu, Fe, formed on the surface of the carrier substrate from a seed material
At least 1 selected from Ni, Ce, Mg, and Ca
A catalyst for exhaust emission purification of a diesel engine, comprising a coat layer containing an oxide of one kind of metal and a catalyst metal supported on the coat layer.