JPH03221125A - Exhaust gas cleaning apparatus for alcohol-fuelled automobile - Google Patents

Abstract

PURPOSE:To clean formaldehyde for a long duration by installing a noble metal- carrying catalyst in the upper stream side of an exhaust gas passing route, a base metal oxide-carrying catalyst in the lower side, and an air supplying apparatus to supply air to the catalyst in the lower side. CONSTITUTION:There are installed an upper side catalyst 2 carrying a noble metal in the upper stream side of an exhaust gas passing route, a lower side catalyst 3 in the lower stream side than the upper side catalyst 2, and an air supplying apparatus 4 which supplies air to the lower side catalyst 3. The lower side catalyst 3 is composed of a support substrate, a supporting layer formed on the support substrate, and oxides selected from vanadium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, and zinc oxide which are supported on the supporting layer. As a result, formaldehyde in an exhaust gas from an alcohol-fuelled engine is surely removed for a long duration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for purifying exhaust gas emitted from a motor vehicle equipped with an engine using alcohol as fuel.

[Prior Art] In recent years, due to the tightening of petroleum resources and pollution problems, research has been actively conducted on alternative energy sources to replace gasoline for automobiles. Among these, alcohol can be synthesized at low cost and has high expectations as a next-generation energy source.

However, even though alcohol is used, various harmful substances are generated as a result of combustion in the engine, so it is necessary to purify the exhaust gas.

[Problem to be solved by the invention] Prior to the present invention, the present inventors developed an exhaust gas purification catalyst supporting a noble metal, which is used in the exhaust system of a conventional Kallin fuel engine (see JP-A-63-162043). The purification performance of the exhaust system of an alcohol-fueled engine was investigated using this method. As a result, the engine exhibited excellent purification performance for C, CO, and NOX contained in the exhaust gas, similar to the case of the Kallin fuel engine. It was also confirmed that the amount of unburned alcohol could be reduced. However, with respect to formaldehyde, which is a component specific to the exhaust gas of alcohol-fueled engines, the catalyst had almost no effect in reducing it.

In the case of a Kallin-fueled engine, the stoichiometric air-fuel ratio <A/'> is 14.5 to 14.6. In contrast, in an alcohol-fueled engine, A/F is
is about 6.5, and when the fuel is 15% Karin-85% alcohol, the A/F is about 7°6. Therefore, if the engine is operated under the same conditions as a gasoline fuel engine, there will be an excess of fuel, and unburned methyl alcohol will cause the following dehydrogenation reaction on the catalyst to produce formaldehyde.

On the other hand, if air is supplied in front of the catalyst, the following oxidation reaction occurs on the catalyst with unburned methyl alcohol discharged from the engine, producing formaldehyde. . Further, even if the air-fuel ratio is adjusted appropriately, formaldehyde is generated in the engine due to this reaction.

C 30 RO + 1/202 → CHO + 口 20 As described above, it is difficult to avoid formaldehyde emissions from an alcohol fuel engine, and there is a strong desire for a catalyst that can purify the emitted formaldehyde. The alcohol fuel automatic heavy-duty exhaust gas purification device of the present invention meets these demands, and aims to purify formaldehyde over a long period of time.

[Means for Solving the Problems] The exhaust gas purification device for alcohol-fueled automobiles of the present invention includes an upstream catalyst provided upstream of an exhaust gas passage and supporting a precious metal, and a downstream catalyst provided downstream of the upstream catalyst. A device for purifying exhaust gas emitted from an alcohol-fueled vehicle, consisting of a catalyst and an air supply device that supplies air to the downstream catalyst, the downstream catalyst comprising a carrier base material and a surface of the carrier base material. and an oxide selected from vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, and zinc oxide supported on the support layer. It is characterized by

Further, the exhaust gas purification device for an alcohol-fueled vehicle according to the second invention includes: an upstream catalyst provided on the upstream side of the exhaust gas passage and supporting a precious metal; a downstream catalyst provided downstream of the upstream catalyst; A device for purifying exhaust gas emitted from an alcohol-fueled vehicle, comprising: an air supply device that supplies air to an alcohol-fueled vehicle; It is characterized by being comprised of a mixed layer consisting of an oxide selected from silica, titania and zirconia and a perovskite type composite oxide.

The exhaust gas purification device for an alcohol-fueled vehicle of the present invention includes: an upstream catalyst provided on the upstream side of an exhaust gas passage and supporting a precious metal; a downstream catalyst provided downstream of the upstream catalyst; An air supply device is provided between the catalysts and supplies air to the downstream catalyst.

The upstream catalyst is similar to that provided in the exhaust system of conventional gasoline fuel engines, and contains Pt, Rh, and Pd.
It is loaded with precious metals.

Further, in addition to noble metals, a catalyst in which oxides of rare earth components such as cerium and lanthanum are supported can also be used. This upstream catalyst mainly handles HC in exhaust gas,
Purify Co and NOX.

The most distinctive feature of the present invention lies in the configuration of the downstream catalyst. One of the downstream catalysts is composed of a carrier base material, a support layer, and an oxide. The carrier base material is similar to the catalyst carrier used in the exhaust system of conventional gasoline-fueled engines.
Honeycomb-shaped monolith carriers, pellet-shaped carriers, etc. are used.

The material is not particularly limited, and ceramics such as cordierite, mullite, alumina, magnesia, and spinel, or heat-resistant metals such as ferritic steel can be used.

The carrier substrate is coated with a carrier layer. This support layer is similar to the catalyst support layer of conventional purification catalysts, and is formed of alumina, silica, titania, zirconia, etc., each having a large specific surface area. Generally, γ-alumina, θ-alumina, etc. are often used. The support layer may be formed only on the surface of the carrier base material, or the entire carrier base material may be formed of such a material.

An oxide is supported on the support layer. Examples of this oxide include vanadium oxide represented by VO, VO2, etc.
Chromium oxide, MnO, Mn2 expressed as r2O3, etc.
O3, Mn3O4 etc. oxidized mankan, Fe
Iron oxide represented by 01Fe203, Fego+, etc.
coo, c.

Cobalt oxide represented by 304 etc., nickel oxide represented by NiO etc., copper oxide represented by CuO, Cu2O etc., zinc oxide represented by ZnO etc., singly or in plural kinds. Can be used in combination.

The other downstream catalyst is composed of a carrier base material and a mixed coat layer. The carrier substrate can be formed from the same materials as the downstream catalyst described above.

The mixed layer is composed of a mixture of an oxide selected from alumina, silica, titania, and zirconia and a perovskite-type composite oxide represented by the general formula ABO3. In addition, the perovskite-type composite oxide has an ionic radius of element B..."a, an ionic radius of element B...rb
, the ionic radius of oxygen..."If O, ra>0.
09nmSrb>Q.

051 nm, −(ra+ro)/2 (rb+rO
) must be 0.75≦t≦1.0, and it is preferable that element B is a transition metal element, and in general, 20% or less of the B element is substituted with strontium.

The base metal oxide and perovskite type composite oxide described above are 0.01 to 1.0 m01 to the carrier base material IQ.
Q, 01mo is preferably supported in the range of
If it is less than 1, the formaldehyde purification performance will be poor,
1. □The effect is saturated even if more than mo+ is supported. 0.
A range of 0.03 to 0.6 m○1 is particularly preferable.

Note that in order to support the base metal oxide on the support layer, the support layer is impregnated with a solution such as a salt of the metal constituting the oxide.
A method can be used in which the material is then fired to form an oxide.

The air supply device supplies air to the downstream catalyst.

As a result, the atmosphere of the downstream catalyst becomes oxygen-rich, and formaldehyde is efficiently oxidized and purified.

[Function] In the exhaust gas purification device of the present invention, the exhaust gas of an alcohol fuel engine first enters the upstream catalyst, and the contained CO, CO, and NOx are purified by the catalytic action of the supported noble metal. The purified exhaust gas then enters the downstream catalyst. Here, air is supplied to the downstream catalyst from an air supply device,
The atmosphere is hot and crisp. Due to the presence of oxides, the formaldehyde contained in the exhaust gas undergoes a strong oxidation effect and is purified into water and carbon dioxide.

In addition, in a high-temperature, cool atmosphere, sintering of PT is promoted, so that conventional catalysts have problems in durability. However, in the catalytic device of the present invention, oxides are relatively stable against high temperatures and oxidizing atmospheres;
Not easily affected by atmosphere. Therefore, predetermined performance can be maintained for a long period of time.

[Effects of the Invention] Therefore, the exhaust gas purification device of the present invention can reliably purify formaldehyde in the exhaust gas of an alcohol fuel engine, and is extremely practical. In addition, because of its excellent durability, formaldehyde can be purified stably for a long period of time.

Furthermore, base metal oxides and perovskite-type composite oxides are cheaper than noble metals, and the catalyst device of the present invention is advantageous in terms of cost.

[Example] Hereinafter, this will be explained in detail using examples.

FIG. 1 shows the configuration of the exhaust gas purification device of this embodiment. This exhaust gas purification device includes an upstream contact 11 provided on the upstream side of an exhaust system of an alcohol fuel engine 1 having an electronic fuel control device 10, a downstream catalyst 3 provided on the downstream side, and a downstream catalyst 2. and an air supply device 4 for supplying air to the air conditioner 3.

The upstream catalyst 2 and the downstream catalyst 3 are each held within a catalyst inverter 5.

In the upstream catalyst 2, a cordierite honeycomb-shaped monolith carrier base material is coated with a catalyst support layer made of activated alumina, and the catalyst support layer has PT and Rh of 1.5Q/R and C9: ll/Q supported, and cerium oxide and lanthanum oxide each have a metal equivalent of 0.
3 mol/Q and 0.03 mol/Q were supported.

In the exhaust gas purification device configured as described above, the configuration of the oxide of the downstream catalyst 3 was variously changed to create examples.

(Example 1) 100 parts by weight of activated alumina powder and alumina content of 10
An alumina slurry is prepared by mixing and stirring 0 parts by weight of alumina silua and 50 parts by weight of water. A commercially available cordierite monolith carrier base material having a large number of honeycomb cells was immersed in this slurry, pulled up and the excess slurry was blown off, and then dried at 200°C for 1 hour.
Bake at 00°C for 1 hour. This is repeated several times to form a support layer of 100Q per 1Q of carrier base material.

Next, vanadium chloride (VCQ2), chromium chloride (
CrCR2), manganese chloride (MnCQ2), iron chloride (FeCQ2), cobalt chloride (Co(J2),
Nickel chloride (NiCQ2), copper chloride (CuCQ2),
Each aqueous solution of zinc chloride (ZrlC522> was prepared, and the carrier base material with the above-mentioned support layer was immersed in each aqueous solution, then pulled up to blow off excess water, dried at 100°C for 1 hour, and then dried at 650°C for 1 hour. Eight types of catalysts No. 1 to No. 8 were prepared by baking and supporting each base metal oxide.The supported amount of each base metal oxide was calculated in terms of metal per 1Q of carrier base material. 0.3mO
It is.

(Example 2) Lanthanum acetate, strontium acetate, and cobalt acetate are weighed in a stoichiometric ratio to form a mixed aqueous solution. This aqueous solution was dried, decomposed at 150 to 300°C, and then heated to 850°C for 50 minutes.
A velorskite-type composite oxide powder is prepared by firing for a time and pulverizing.

Next, zirconia sol 10 with a zirconia content of 20%
0 parts by weight, 50 parts by weight of water, and 5 parts by weight of the perovskite type composite oxide are mixed and stirred to prepare a slurry. Then, the same carrier base material as in Example 1 was immersed in this slurry, pulled up, and the excess slurry was blown off.
2 After drying, it was fired at 300°C for 1 hour. Repeat this several times,
A mixed coating layer of 100 g was formed per carrier substrate IQ.

Thereafter, it was calcined at 700° C. for 3 hours to prepare catalyst No. 9. This catalyst has 0.0% metal equivalent in the mixed coat layer.
31 mol/Q of (Lao, +Sro.

b) COO3 is contained as a velorskite type composite oxide.

Further, aqueous ammonia is added to a mixed aqueous solution of lanthanum nitrate, strontium nitrate, and manganese nitrate to form a coprecipitated hydroxide. This was filtered, washed with water, dried, calcined and pulverized to prepare a perovskite type composite oxide, and catalyst No. 10 was prepared in the same manner as above. This catalyst has
In the mixed coat layer, 0.42 mol/Q (L
ao, 5Sro, s) MnOa is supported as a perovskite type composite oxide.

(Comparative Example) A monolith carrier base material having a support layer made of activated alumina similar to that in Example 1 was prepared, and cerium nitrate and fII! Ii
! ! It was immersed in a mixed aqueous solution of lanthanum to support cerium and lanthanum in amounts of 0.3 mO and 0.3 mO, respectively in terms of metal, per carrier base material 19. After drying at 100°C, it was fired at 700°C for 1 hour. After that, it was immersed in a dinitrodiammine platinum solution and a rhodium chloride solution sequentially, and 1.5 CI and 0.3Q of Pt in terms of metal per 1Q of the carrier base material were immersed.
and Rh were supported to prepare catalysts of comparative examples.

(Evaluation) The catalysts of each of the Examples and Comparative Examples described above were placed at the position of the downstream catalyst 3 in FIG. 1, and their initial formaldehyde purification performance was measured under the following conditions.

Fuel used: 15% gasoline: 85% alcohol Air-fuel ratio (A/F): 7.6 (stoichiometric) Space velocity (SV)
)-50000h-1 (always!> Temperature of entering waste...40
0℃ (at upstream catalyst) Air supply amount from air supply device
...10052/min Each catalyst was also subjected to an endurance test under the following conditions, and then the formaldehyde purification performance after the endurance test was measured under the above conditions. The results are shown in Table 1.

Fuel used: 15% gasoline: 85% alcohol Air-fuel ratio (A/F): 7.6 (stoichiometric) Space velocity (SV)
)...90000h-1 (room temperature) Catalyst bed temperature...90
Durability time at 0°C (upstream catalyst): 50 hours From Table 1, the initial formaldehyde purification rate of the catalysts of each example is the same as that of the comparative example, but the catalyst of the comparative example has a lower purification rate after durability. However, it is clear that the catalysts of each example exhibited good purification performance even after the durability test. It should be noted that the purification rates of C1C0 and NOX were at the same excellent level as the conventional catalysts for each catalyst.

Margin below

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an exhaust gas purification device for an alcohol-fueled vehicle according to an embodiment of the present invention. Go...alcohol fuel engine

Claims (2)

[Claims] (1) an upstream catalyst provided on the upstream side of an exhaust gas passage and supporting a precious metal; a downstream catalyst provided downstream of the upstream catalyst; and an air supply device that supplies air to the downstream catalyst; A device for purifying exhaust gas emitted from an alcohol-fueled vehicle, wherein the downstream catalyst comprises a carrier base material, a support layer coated on the surface of the carrier base material, and a support layer supported on the support layer. Vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide,
An exhaust gas purification device for an alcohol-fueled vehicle, characterized in that it is comprised of an oxide selected from nickel oxide, copper oxide, and zinc oxide. (2) an upstream catalyst provided on the upstream side of the exhaust gas passage and supporting a precious metal; a downstream catalyst provided downstream of the upstream catalyst; and an air supply device that supplies air to the downstream catalyst; An apparatus for purifying exhaust gas emitted from alcohol fueled vehicles, the downstream catalyst comprising a carrier base material and a catalyst selected from alumina, silica, titania and zirconia coated on the surface of the carrier base material. 1. An exhaust gas purification device for an alcohol-fueled vehicle, comprising: a mixed coating layer comprising a perovskite-type composite oxide and a perovskite-type composite oxide.