JPS62140647A - Catalyst for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To enhance the oxidation activity of the titled catalyst on SO3 and SO2 in exhaust gas by combining >=1 kind among (a) Cu or Cu compd., (b) V or V compds., and (c) Zn, Pb, Ce, or their compds., and depositing the combined material on a porous carrier. CONSTITUTION:Alumina, titania, zirconia, etc., are previously coated on the internal surface of a fine particle collecting body such as a ceramic porous body. Then the material obtained by combining at least one kind among (a) Cu or Cu compds., (b) V or V compds., and (c) Zn, Pb, Ce, or their compds. is deposited on the coated film of the fine particle collecting body to form the catalyst for purifying exhaust gas. Furthermore, >=1 kind among platinum, rhodium, and palladium is preferably deposited on the fine particle collecting body. The amts. of the metallic catalytic components to be deposited on the fine particle collecting body are controlled to 1-20wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a catalyst for burning off particulates contained in exhaust gases, particularly diesel engine exhaust gases.

BACKGROUND OF THE INVENTION In recent years, it has been discovered that fine particles in exhaust gas, especially diesel engine exhaust gas, contain carcinogenic substances such as pentupyrene and nitropyrenna.

Removal of these fine particles is a problem from the perspective of pollution prevention.

Particulate capture bodies (hereinafter referred to as capture bodies) that capture and remove such fine particles from exhaust gas include ceramic honeycombs, ceramic foam, metal wire filling systems, pellet carrier filling systems such as alumina, ceramic fiber systems, etc. A heat-resistant capture body has been proposed.

However, in such a trap, the captured particles gradually accumulate and become clogged. Therefore, it is necessary to unclog the trap by burning the particles after using it for a certain period of time. There is.

For this combustion treatment, various regeneration methods using additional equipment such as Hoehner have been proposed, but they have the disadvantage of increasing costs. For this reason, a proposal has been made to carry a catalyst on a trap, lower the combustion temperature of the particulates using the catalyst, and burn and remove the particulates using only the temperature of the exhaust gas.

According to this method, I! ) The cost will not increase because the additional equipment for production is not secure.

4. As a result of intensive research based on this idea, the inventors found a catalyst that matched 1.
-143840. This catalyst is characterized by "1. Particulates (fine particles 7 -) purification catalyst;
” “2.Claim 1-1 in which the copper compound is copper oxide
The particulate purification catalyst described in "3. Metals capable of having multiple oxidation states include germanium, tin, vanadium, niobium, antimony, bismuth, chromium, molybdenum, tungsten, selenium, tellurium, lanthanum, cerium, praseodymium, and rhenium. 2. The catalyst for purifying particulates according to claim 1, which is selected from , ruthenium, rhodium, and compounds thereof.

”. Among them, a catalyst consisting of two components, Cu and (2), has particularly high activity. In order to maximize the effect of this catalyst, place the particulate trap containing the catalyst in a position as close to the engine as possible where a high exhaust gas temperature can be obtained.9! Delicious.

Problems to be Solved by the Invention However, when the temperature of the exhaust gas is high, the carbon dioxide in the exhaust gas is oxidized by the catalyst, resulting in the formation of sulfuric acid. This is a particular concern for trucks and buses that are frequently operated under high loads and therefore have high exhaust gas temperatures. There were m topics.

The present invention can reduce the temperature required to burn and remove the particulates captured by the particulate trap, and when the exhaust gas passing through the particulate trap becomes appropriately hot due to engine operation, the exhaust gas It is an object of the present invention to provide an exhaust gas purifying catalyst capable of promoting the combustion removal of particulates trapped in a trap without converting the sulfur dioxide contained therein into sulfate.

Means for Solving the Problems The exhaust gas purifying catalyst of the present invention contains at least the following three components.
It is a combination of (a), (b), and (c).

(a) At least one selected from copper or copper compounds.

(b) At least one selected from vanadium or its compounds.

(c) At least one selected from zinc, lead, cerium, or a compound thereof.

The fourth component may be a combination of (d) at least one selected from platinum, rhodium, palladium, or compounds thereof.

Each component will be explained in detail below.

Component (a) used here is gold Ii1 copper or a copper compound. The copper ions constituting the copper compound may be either -valent or divalent. Copper compounds include copper nitrate, copper chloride,
Copper oxide, copper sulfate, copper oxalate, copper acetate, copper carbonate, copper hydroxide, cupric ammonium chloride, cupric ammonium sulfide, cupric ammonium phosphate, etc. can be used, among which copper nitrate, copper chloride and copper ammonium phosphate can be used. Copper oxide is preferred.

Component (b) is vanadium or a compound thereof. Specific examples of vanadium compounds include ammonium vanadate, vanadyl dichloride, vanadium oxytrichloride, vanadyl sulfate, vanadium pentoxide, vanadium dioxide, henadium dichloride, vanadium trichloride, and 7 chloride.
These include heselium, lithium/zeta nadate, sodium vanadate, potassium vanadate, and baked products thereof.

Component (C) is salivary lead, lead, cerium, or a compound thereof. Examples of zinc compounds include zinc nitrate, zinc chloride, lead in vinegar, ammonium chloride, zinc carbonate,
These include zinc oxalate, zinc sulfate, zinc ammonium sulfate, zinc oxide, and zinc hydroxide.

Examples of lead compounds include lead nitrate, lead chloride, lead sulfate, lead carbonate, lead sulfate, lead oxalate, lead phosphate, lead oxide, and lead hydroxide.

Examples of cerium compounds are cerium nitrate, cerium chloride, cerium carbonate, and cerium oxalate.

Examples include cerium oxide.

In the exhaust gas purifying catalyst of the present invention, (a) component and (b)
The blending ratio of component ) and component (c) is not particularly limited;
They can be blended in this ratio, but usually the atomic ratio (a + b) / (c) is 99, / 1 to 20
/80, preferably 90/10 to 50, /50. The blending ratio of component (a) and component (b) is not particularly limited and can be blended in any ratio, but usually (a)/(b) (atomic ratio) is 99/
The range is 1 to 1/99, preferably 80/20 to 20/80.

Further, the catalyst adhesion ratio is 1 to 20 wL% relative to the particulate capture body such as a ceramic porous body.

Preferably it is 3 to 10 wt%.

Furthermore, in addition to the catalyst consisting of the above three components, a fourth component and a
(d) At least one selected from platinum, rhodium, palladium, or a compound thereof may be blended.

The particulates in the exhaust gas are composed of carbon components and j↓'' hydrocarbon oil components, and the proportion of hydrocarbon oil components varies in the range of about 1 to 30 wt% depending on the engine operating conditions. (d) Component The added exhaust gas purification catalyst exhibits an excellent catalytic effect on the combustion of fine particles containing a large amount of hydrocarbon oil.

The catalyst for converting exhaust gas M of the present invention is supported on a suitable trapping body L and used. In order to support the catalyst of the present invention on the trapping body, alumina, titania, zirconia, silica, magnesia, titanic acid,
It is coated with potassium or a solid acid, and the catalyst is supported through the coating.

In addition, these powders and catalysts are mixed to form a slurry,
By coating the trapping body with this, the catalyst can be supported on the trapping body.

Examples of solid acids include silica-alumina, silica-zirconia, natania-zirconia, titania-silica,
Examples include alumina and boria.

Next, the exhaust gas purifying catalyst of the present invention is applied to (If
We will explain tests to demonstrate that it has the effect of burning particulates at low temperatures without oxidizing acid gas to sulfate.

First, 91 ceramic porous bodies were provided as particulate trapping bodies, and a catalyst to be described later was supported thereon. The catalyst-equipped ceramic porous body was then exposed to high-temperature exhaust gas in order to stabilize the catalyst. This was done by exposing the catalyst-equipped ceramic porous body to exhaust gas from a burner using light oil as fuel for 30 minutes.

For diesel oil, 10kg of diesel oil is used under strict test conditions.
Approximately 1.4 kg of dodecanethiol is mixed in,
The sulfur content was approximately 2 wt%.

Further, the flow rate of the exhaust gas was 800 centimeters per minute in terms of room temperature, the a,)s'e degree in the exhaust gas was about 10%, and the exhaust gas temperature was 720°C at a position 1 cm in front of the ceramic porous body.

Next, we reduced the gas oil supply a little while leaving the exhaust gas flow as it was, and set the exhaust gas temperature to 600°C, and measured the concentration of sulfuric acid gas by infrared absorption at two locations, one just before the exhaust gas passes through the ceramic porous body, and one just after it passes through the ceramic porous body. The temperature of 600° C. is the temperature that the manifold output temperature easily reaches when the truck is operated at high speed and under high load.

Next, the fine particles were captured in the catalyst-equipped ceramic porous body that had undergone the above exposure test. To capture fine particles, install a porous ceramic body at a distance of 1.5 m from the exhaust of a diesel engine, and use Niacin at a speed of 100 rpm
The test was performed 0 times under the condition of a torque of 10 kg/m.

In this way, the ceramic porous body is produced! 1.0 in j ratio
After capturing wt% of fine particles in a ceramic porous body with a catalyst, this material was transferred to a thermal analyzer,
Air hole 1! ; The relationship between the amount of fine particles captured on the fibers and the temperature was determined at a heating temperature of 20° C./min. The catalytic activity was then compared using the temperature at which 50 wt% of the attached fine particles were removed as Tso.

Next, we will discuss the catalyst of the present invention used in this experiment and the conventional catalyst as a comparative example. First, three types of exhaust gas purification catalysts of the present invention were prepared, and these were attached to the trapping body. did.

Example 1 First (copper hexate [Cu CNO:+)2 skewer 3H20]
An aqueous solution was prepared by dissolving 171 g in 86 mJ1 of purified water.

Further, 83 g of ammonium vanadate [NH4VO3] was added to 745 m of purified water, and while heating and stirring, 178 g of oxalic acid was added little by little to create a homogeneous aqueous solution of oxalic acid/henadium.

Also, zinc nitrate [Z n (NO3) 2 ・6H20]
An aqueous solution was prepared by dissolving 105 g in 420+nJ1 of purified water.

Furthermore, 50g of titania was added as a catalyst carrier to 335tnJ.
A solution was prepared by dispersing No. 1 in purified water.

The four liquids prepared separately as described above were placed in a container No. 51 and stirred vigorously with a high-speed homomixer to prepare a slurry of the catalyst containing titania.

The catalyst slurry thus obtained has two exhaust gas inlet surfaces.
80x120mm race track shape, length 60mm
mm, the fineness of the filter 11 is 20 mesh (the uniform number of cells per inch of length is 20), and the bulk specific gravity is 0.4
After impregnating the three-dimensional network porous ceramic material mainly composed of cordierite in No. 5 and shaking off the excess adhesion slurry, it was dried in hot dry air at 150°C, and then heated in air at 600°C for 2 hours. Firing was performed. hl of attached catalyst
is a ceramic porous body H ratio of 4.5 wt%, and the catalyst composition (atomic ratio) Cu/V/Z n/T i=1/L10
．． It was 510.89.

Example 2 A catalyst was prepared using the following aqueous solution instead of the aqueous solution of 105 g of zinc nitrate dissolved in 420 mM purified water used in Example 1 above, and it was adhered to a porous ceramic body by the same operation as in Example 1. I let it happen.

Lead nitrate [Pb (NO3) 21 117g Purified water 468m The amount of catalyst deposited on the ceramic porous body was 1rr, rM ratio was 4.3wt%,
The catalyst composition (atomic ratio) is Cu/V/Pb/
T i = 1/l/0, 5/0, 8
9 There was a te.

Example 3 105g of zinc nitrate used in Example 1 was placed in a 420 m
A catalyst was prepared using the following aqueous solution instead of the aqueous solution dissolved in purified water, and it was attached to a ceramic porous body in the same manner as in Example 1.

Cerium nitrate [Ce (NO3) 3 II 6H20
]54g 1 old ice
6
1 6 m 1 of the catalyst deposited; 11 is the ceramic porous body iTr.
Atomic ratio) is Cu/V/Ce/T i = 1
/l/0, 5/0, 89.

Comparative Example 1 A catalyst was prepared that differed from the catalyst of Example 1 in that 111j lead nitrate was not used.

The rll- of the catalyst with 6° is 4.6 wt% in ceramic porous weight ratio, and the catalyst MI composition (atomic ratio) is C
u/V/T i = 1/1/0,
89 There was te.

Comparative example 2 Only ceramic porous bodies were used.

Table 1 shows the results of the above tests using the samples of Examples 1-3 and Comparative Examples 1-2.

υ From Table 1, the combustion temperature T so of fine particles when using only a ceramic porous body and no catalyst is 495°C, but compared to the catalyst made of copper and vanadium in Comparative Example 1 (JP-A-58-1
43840) is used, the combustion temperature T s of the particulates.

is reduced to 340°C. However, S02 in the combustion exhaust gas
33% of is converted to 303.

On the other hand, in addition to copper and vanadium components, further (C
) When using the catalysts of Examples 1 to 3 containing Zn, Pb, or CeJ& as a component, SO in the combustion exhaust gas
The conversion rate of 2 to 303 was 20 to 23%, which was reduced to two-thirds of the level in Comparative Example 1 using a catalyst without (C)I&, (c) The effect of addition of t&min is recognized. In addition, the combustion temperature Tso of fine particles when using the catalysts of Examples 1 to 3 is 335° C., which is the same as that of Comparative Example 1. (c) There is no decrease in the activity of the catalyst due to the addition of J&.

Effects of the invention (a) At least one selected from copper or a copper compound; (b) At least one selected from vanadium or a compound thereof; (C) At least one selected from zinc, lead, cerium, or a compound thereof. 3
Exhaust gas purification catalysts made of a combination of components are capable of converting sulfur dioxide gas [SO2] contained in exhaust gas into carbon dioxide [S
O3] (which reacts with moisture in the air to form VL acid mist) is less oxidized than the conventional 6M, so it can solve the problem of resistant mountains, which is currently considered a problem from the perspective of deforestation. Despite having the following characteristics, the catalyst that can contribute to this invention has catalytic activity and durability that are comparable to conventional catalysts. From the above, by holding this catalyst in a trapping body such as a ceramic honeycomb or ceramic foam, and placing the trapping body in a place where the exhaust gas temperature is high, for example near the manifold, it is possible to not only trap fine particles in the exhaust gas but also to Since the injected particulates can be spontaneously combusted during engine operation without generating sulfates, special additional equipment for regenerating the trapping body can be omitted.

For exhaust gas purification, a catalyst consisting of the three components (a), (b), and (C) above is blended with (d) at least one selected from platinum, rhodium, palladium, or a compound thereof as a fourth component. Since the catalyst contains noble metal elements such as platinum, it not only provides the same effect as the three-component catalyst described above, but also improves the combustion removal efficiency of fine particles containing a large amount of hydrocarbon oil. It is possible to make a purchase.

Claims (1)

[Claims] 1. (a) at least one selected from copper or a copper compound, (b) at least one selected from vanadium or a compound thereof, and (c) selected from zinc, lead, cerium, or a compound thereof. An exhaust gas purifying catalyst comprising at least one of: 2. The exhaust gas purifying catalyst according to claim 1, further comprising (d) at least one selected from platinum, rhodium, palladium, or compounds thereof.