JPS5982944A - Catalystic medium for eliminating fine particle in waste gas - Google Patents

Abstract

PURPOSE:To obtain a catalytic medium which burns the captured fine particles at such a low temp. at which no thermal impact is applied on the capturing medium itself by combining a catalyst combined with copper, etc., an alkali metal compd., Mo, etc., and platinum, etc. with titania, etc. CONSTITUTION:A catalyst combined with at least one kind selected from copper and a copper compd., at least one kind selected from an alkali metal compd., at least one kind selected from Mo, V and their compd., and further at least one kind selected from platinum, Rh, Pd and their compd. according to need and at least one kind selected from titania, gamma-alumina and silica-alumina are combined. As a result, the captured fine particles are burned at such a low temp. at which no thermal impact is applied to the capturing medium itself, and the catalytic medium which is highly resistant to heat with less decrease in activity at an elevated temp. is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst body for combusting particulates in exhaust gas, for example, particulates in diesel engine exhaust gas, and more specifically, the present invention relates to a catalyst body for combusting particulates in exhaust gas, such as particulates in diesel engine exhaust gas, and more specifically, the present invention relates to a catalyst body for combusting particulates such as particulates in exhaust gas from a diesel engine. The present invention relates to a catalyst for purifying particulates in exhaust gas, which can catalytically burn particulates at low temperatures.

In recent years, fine particles in exhaust gas, especially fine particles emitted from diesel engine exhaust gas (fine powder of carbides such as soot), have been increasing.
However, since it has been revealed that it contains carcinogenic substances such as pentsupyrene, it has been viewed as a pollution problem, and regulations are being put in place to control its emissions.

Conventionally, the use of heat-resistant trapping bodies such as ceramic honeycombs, ceramic foams, metal wire filling systems, pellet carrier filling systems such as alumina, and ceramic fiber systems have been proposed for trapping such fine particles. Even if fine particles can be effectively captured by these trapping bodies, the accumulation of particles can cause a blockage, so it is necessary to periodically dispose of the accumulated particles or burn them off using high-temperature treatment. .

However, among these methods, disposing of the deposits is complicated, it is impossible to remove them effectively, and there are problems in terms of pollution. Further, in the combustion removal treatment at high temperature, it is necessary to raise the temperature to nearly 700° C., and the combustion may give an unfavorable thermal shock to the dust trap itself, accelerating its deterioration. Furthermore, there is a risk of generating gases such as carbon oxide due to incomplete combustion. Therefore, there is a demand for efficient combustion of the particulates captured by the particulate trap or purifier at a lower temperature.

The present invention meets the above-mentioned needs, and allows the captured particles to be combusted at a low temperature that does not cause a thermal shock to the capture body itself, and has excellent heat resistance with little loss of activity at high temperatures. The present invention provides a novel catalyst having the following properties.

That is, in order to achieve the above object, the present invention includes at least one selected from copper and copper compounds, at least one selected from alkali metal compounds, and at least one selected from molybdenum, vanadium, and their compounds.
Furthermore, by combining a desired catalyst comprising at least one selected from platinum, radium, rhodium, and their compounds with at least one selected from titania, γ-alumina, and silica-alumina, the It is used as a catalyst for purifying particulates.

Catalysts, especially precious metal catalysts (platinum, palladium, etc.), for converting gases such as NOx, carbon oxides, and hydrocarbons, which are conventionally considered harmful, into harmless substances through catalytic oxidation of gasoline engine exhaust gas. is known. but,
The mechanism of action of this type of catalyst is completely different from that of the particulate purification catalyst according to the present invention. For example, even if a platinum catalyst, which is known to be the most effective catalyst for gasoline engine exhaust gas purification, is used, Particulates cannot be effectively burned.

As described above, the catalyst for particulate purification according to the present invention can burn particulates at low temperatures, so it can be carried on a particulate trapping or purifying body such as a ceramic honeycomb or a ceramic porous body. In addition to reliably trapping particulates in exhaust gas, it is also possible to catalytically burn (regenerate) the particulates at a much lower temperature, thus requiring less energy for combustion and extending the life of the trapping body or purifying body. can. - Also, in some cases, the combustion temperature of particulates can be lowered to the exhaust gas temperature, so particulates in the exhaust gas can be captured and combusted at the same time, thereby eliminating clogging of the trapping body or purifying body and regenerating them. This eliminates the need for any operations, or at least eliminates the need for frequent playback operations. Furthermore, it is also possible to prevent the generation of toxic gases such as carbon monoxide during combustion of particulates.

Further, the catalyst for purifying particulates according to the present invention has excellent side heating properties and exhibits little decrease in activity at high temperatures. That is, according to the studies of the present inventors, high temperatures based on exhaust gas are often applied to the catalyst supported on the capture body, and when the catalyst is exposed to such high temperatures, the catalyst deteriorates. It was observed that a phenomenon of easy deactivation occurred. Therefore, it is desirable to have a catalyst that can reliably burn particulates at low temperatures, is less likely to deactivate even when exposed to high temperatures, and maintains its original activity. As mentioned above, the catalyst has high activity regarding the low temperature combustibility of fine particles, has little deactivation at high temperatures, maintains high activity even when exposed to high temperatures, and has very good heat resistance. . That is, at least one selected from copper and copper compounds, at least one selected from alkali metal compounds, at least one selected from molybdenum, vanadium, and their compounds, and optionally platinum, rhodium, .9radium, and these. A catalyst formed by combining at least one compound selected from compounds has an excellent effect of burning fine particles at a low temperature and has high heat resistance itself.
By combining it with at least one selected from γ-alumina and silica-alumina, extremely high heat resistance is imparted.

The present invention will be explained in more detail below.

The catalyst body for purifying particulates in exhaust gas according to the present invention is (
) at least one selected from copper and copper compounds; (b) at least one selected from alkali metal compounds; and (c) at least one selected from molybdenum, vanadium, molybdenum compounds, and vanadium compounds. In addition to the components (a), (b), and (e), if necessary, (d) a catalyst that is a combination of at least one selected from platinum, palladium, rhodium, and compounds thereof, and (e) titania, γ-alumina. and at least one selected from silica and alumina.

Here, as the copper compound (a), copper oxides, nitrates, halodanes such as chlorides and bromides, carboxylates,
Examples include sulfites, jaates, phosphates, etc., among which halodides, nitrates, oxides, etc. are preferably used. Note that copper may be monovalent or divalent.

In addition, as the alkali metal compound of component (b), compounds of ligram, sodium, potassium, rubidium, cesium, such as oxides, nitrates, halodides, carboxylates, sulfites, sulfates, phosphates, etc. can be mentioned. Among these, sodium and potassium compounds are preferred, and their halides and nitrates are particularly preferred, with potassium chloride being most preferred.

Furthermore, examples of the molybdenum compound and vanadium compound (C) include molybdenum and vanadium oxides, nitrates, halides, carbo/acid salts, sulfites, sulfates, phosphates, and complex salts. Specifically, molybdenum compounds include molybdenum trioxide, molybdic acid, ammonium molybdate, molybdenum chloride, molybdenum sulfide, molybdenum sulfate, sodium molybdate, potassium molybdate, and the like. In addition, vanadium compounds include ammonium vanadate, pananol dichloride, vanadium oxytrichloride, 9nanol sulfuric acid, vanadium pentoxide, vanadium trioxide, vanadium dichloride,
Examples include vanadium trichloride, vanadium tetrachloride, lithium panasinate, sodium panasinate, potassium panazonate, and oxides and calcined products thereof.

Note that when a double salt or complex salt with an alkali metal is used as the copper compound, molybdenum compound, or vanadium compound, the alkali metal compound is combined at the same time, so the alkali metal compound does not necessarily need to be added separately.

The catalyst of the present invention includes the above (a), (b), and (c).
By combining these three components, it exhibits excellent performance as a low-temperature combustion catalyst for exhaust gas particles such as diesel engine exhaust gas, and has extremely high heat resistance. However, for example, although the performance as a low-temperature combustion catalyst can be satisfied by just combining components (a), p, and (b),
It is somewhat unsatisfactory in terms of heat resistance.

In the present invention, the above (a), (b), (c)
When these components are combined, their proportions are not particularly limited and can be used in combination in any proportion, but it is preferable that each component is contained in the catalyst in an amount of 5 mol or more. With a molar ratio within this range, very efficient low-temperature combustion treatment of fine particles can be performed, and high heat resistance can be achieved.

In the present invention, the above (a) # (b), (e
In addition to the components (d), at least one selected from platinum, palladium, rhodium, and these compounds can be further blended as a fourth component (d), and the (d) component can be added to the components (a) to (c). By combining these, it is possible to further increase the low-temperature combustion activity of small particles in the exhaust gas. In this case, compounds of platinum, palladium, and rhodium include oxides, halides, nitrates, carbo/acid salts, phosphates, and double salts, but halodides, especially chlorides, are preferably used. It will be done.

In addition, when combining component (d), the ratio is not particularly limited, but 0.01 weight to 100 weight based on the total M amount of component (a), (b), and (C). It is preferable to have a person in charge.

The above-mentioned catalyst is used in combination with at least one oxide selected from chikunia, γ-alumina, and silica-alumina to form a catalyst body, and the combination thereof provides improved heat resistance. A catalyst body can be obtained. Here, the amount of the oxide is not necessarily limited, but (a)
, C';) , 10 for the total weight of component (C)
It is preferable that the weight is at least % by weight. In the present invention, the above-mentioned oxides also include those in the form of double salts, such as potassium titanate and sodium titanate.

In accordance with the present invention, 111 may be integrated with a suitable carrier, capture body, such as ceramic foam, ceramic 45. It can be used by forming a trap on a trapping body such as a honeycomb, a metal wire-filled system, a carrier pellet-filled system such as alumina, etc. In this case, the above catalyst components and chikunia, γ-
1 +, i selected from alumina, silica-alumina
: Any method can be used to make the compound compatible, but the above-mentioned carrier or trapping body is coated with an oxide selected from titania, γ-alumina, and silica-alumina, and the catalyst of the present invention is supported on the surface of the oxide. ), or the catalyst of the present invention is coated with titania, γ-alumina, or silica.
Preferably, a method is employed in which an oxide selected from alumina is mixed and the mixture is supported on the surface of the carrier or trapping body.

Furthermore, for example, when the above component (d) is combined with the components (a) to (c), the component (d) may be mixed with the components (a) to (c) in advance. Finally, component (d) may be impregnated.

A preferable trapping body is a ceramic foam, but a specific example is one in which the internal communication space is 1
It is formed at a ratio of 96 to 150 pieces per inch length, and its bulk specific gravity is in the range of 0.25 to 1.0. Although it is possible to arrange only one of these ceramic foams of a desired size, a plurality of ceramic foams can also be used in combination. For example, it is also possible to construct the internal communication spaces by sequentially stacking them in order from coarser to denser internal communication spaces. Of course, the method of depositing the catalyst may also be changed as necessary.

The catalyst body of the present invention can be used more effectively in combination with a known catalyst, such as a catalyst for gasoline engine exhaust gas (with or without precious metals).

The trapping body supporting the catalyst of the present invention is used by being placed in a predetermined flow path for exhaust gas from an engine, etc., and the exhaust gas from the engine, etc. is purified by the trapping body or purifying body placed in the middle of the flow path. Exhaust gas from the body passes through the flow path, and during the passage, particulates such as soot and pentupyrene in the exhaust gas are well captured, and the captured particles are absorbed by the catalyst of the present invention. 200 to 300°C if no catalyst is used.
Complete combustion occurs at a moderately low temperature.

The catalyst of the present invention can be used not only for the removal of particulates from the exhaust gas of automobile engines, but also from the engines of transportation systems such as tillers, ships, and trains, industrial engines, and the exhaust gas of combustion furnaces and dylers. can do.

EXAMPLES Hereinafter, the present invention will be explained in more detail by showing Examples and Comparative Examples.

[Example 1, Comparative Examples 1 to 3] Copper chloride 1.5 m mot and potassium chloride 1.5 m mot
Put the mob in a 10ml beaker and dissolve it in distilled water.
Ammonium molybdate prepared separately 0.73 m
Mix the aqueous solution of mot, and add 0.0% titania to this.
5F was added and dried on a hot plate for about 10 minutes while stirring. Next, this sample was dried in a vacuum dryer at 200°C for 120 minutes, and then in an electric furnace for 70 minutes.
A catalyst body was obtained by firing at 0°C for 30 minutes.

A catalyst body was obtained by calcining at 900°C for 30 minutes using the same procedure.

Next) These catalyst bodies (Example 1 r Cu- to-Mo
) and particulates collected in advance from a diesel engine were mixed at a weight ratio of 1:1, and the combustion temperature of the diesel exhaust gas particulates was measured using a hot blood amount measuring device. In this case, the test conditions are: sample weight is 40 mg;
Air supply is 0.5 t/min, vortex rising speed is 2
0°C/+nin, and the midpoint of combustion (Tm,°C) was determined from the weight loss curve. In addition, the value of this midpoint - is a:'! 1.21'7. This shows one indication of complete combustion of the particles.

For comparison, a combination of copper chloride and potassium chloride (Comparative Example 1)
Similarly, lyl! When preparing the medium, the total amount of catalyst components was 3.72 m mot ,
(Titania 0.5I) was used, and the Tm of the easel exhaust gas particles was determined when these were used.

The results are shown in Table 1.

Table 1 As is clear from Table 1, the catalyst body of the present invention has 70
It shows an excellent combustion temperature reduction effect in both 0°C firing and 900°C firing, and therefore is difficult to deactivate even when exposed to high temperature exhaust gas when used as a catalyst. In contrast, Cu of Comparative Example 1 - In the two table systems, those fired at 700°C show excellent effects, but those fired at 900°C are deactivated and have poor heat resistance. It was found that the effect was not sufficient.

[Examples 2 to 7, Comparative Examples 4 to 7] In the same manner as in Example 1, copper chloride-hydrium chloride-ammonium molybdate (Cu-ni-Mo) and copper chloride-potassium chloride-ammonium vanadate (Cu The combustion behavior of diesel exhaust gas particulates was evaluated under the same conditions as in Example 1 using a catalyst body in which V) was used as the catalyst element and titania, silica-alumina, and r-alumina were combined. It was measured.

In addition, catalyst bodies were prepared in which the above catalyst components were combined with cordierite and magnesia, respectively, and the combustion behavior was similarly measured.

Incidentally, the calcination temperature during the preparation of the catalyst body was 900C.

N for the result! It is shown in Table 2.

As is clear from Table 2, it was found that the ternary catalyst of the present invention is preferably combined with titania, silica-alumina, and γ-alumina.

Applicant: Pridestone Tire Hayashiki Company Representative Patent Attorney: Takashi Kojima

Claims (1)

[Claims] 1. A catalyst made of a combination of at least one selected from copper and copper compounds, at least one selected from alkali metal compounds, and at least one selected from molybdenum, vanadium, and these compounds. ,
A catalyst for purifying fine particles in exhaust gas, characterized in that it is combined with at least one selected from γ-alumina and silica-alumina. 2. At least one selected from copper and copper compounds, at least one selected from alkali metal compounds, at least one selected from molybdenum, vanadium and these compounds, and platinum, rhodium, palladium and these compounds A catalyst for purifying fine particles in exhaust gas, characterized in that the catalyst is a combination of at least one of titania, γ-alumina, and silica-alumina.