JPH02144148A - Catalyst for purification of fine particles in exhaust gas - Google Patents

Abstract

PURPOSE:To prevent the lowering of the activity of a catalyst for purification of exhaust gas at high temp. by combining one or more among copper or a compd. thereof, an alkali metal or a compd. thereof and an iron family metal or a compd. thereof to form the catalyst. CONSTITUTION:An aq. soln. contg. one or more among copper or at least one kind of compd. thereof, an alkali metal or at least one kind of compd. thereof and an iron family metal or at least one kind of compd. thereof is dried and calcined to obtain a catalyst for purification of fine particles in exhaust gas. In the catalyst, the atomic ratio of the iron family metal to Cu is preferably regulated to 0.4-1.2. It is preferable that molybdenum or at least one kind of compd. thereof is further added to the aq. soln.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a catalyst for purifying particulates in exhaust gas, and particularly to a catalyst for purifying particulates that captures and efficiently burns particulates emitted by diesel engines.

[Conventional technology]

In recent years, diesel engines have been widely used not only in transportation systems such as automobiles, ships, and trains, but also as industrial engines for power generation. Diesel engines are superior in terms of fuel consumption, but on the other hand, particulate matter called particulates or particulates is emitted from the exhaust gas3! [Since it emits
Due to concerns about the impact on the environment, particulate emission regulations have been implemented in the United States and smoke regulations have been implemented in Japan.

Under these circumstances, the technologies known to date to reduce particulates in exhaust gas can be roughly divided into two types: combustion improvement systems that reduce the amount inside the engine, and aftertreatment systems that install particulate collectors in the exhaust system. However, at present, it is not possible to completely reduce particulates in exhaust gas by taking measures inside the engine alone, and it is necessary to equip the exhaust system with an after-treatment system.

Conventionally, as an exhaust system after-treatment system, it has been proposed to collect fine particles containing metals and heavy hydrocarbons using a trapping body such as a ceramic foam or ceramic honeycomb. Collecting increases pressure loss and requires periodic replacement and regeneration of the trap. Regeneration of the trap requires high-temperature treatment at about 550 to 650° C. because the collected material is difficult to ignite, which often causes problems such as deterioration of the trap. Attempts have also been made to install a burner in the engine exhaust system to raise the temperature of the exhaust gas and burn the particulates emitted from inside the engine, but this is not practical as it would complicate the device and reduce fuel efficiency.

As a countermeasure against this, a method has been proposed in which the above-mentioned fine particles can be combusted near the engine exhaust temperature using a trapping body in which a catalyst is supported on a ceramic 7 ohm, ceramic honeycomb, or the like.

For example, Japanese Patent Application Laid-Open No. 58-1859
Publication No. 45 discloses burning fine particles by supporting a ternary catalyst consisting of vanadium or molybdenum, an alkali metal, and copper on a trapping body, but this technology has a high combustion temperature and cannot be used in diesel engines. If the low-load special exhaust temperature is low, particulates may not burn and be trapped in the trap, causing increased pressure loss in the trap, or even during re-burning, combustion heat may cause the trap to evaporate. There are concerns about durability and the associated frequency of replacement.

[Problem to be solved by the invention]

If technology were developed to burn particulates at a low temperature close to the engine exhaust temperature, it would be possible to keep the heat of combustion low, extend the life of the trap, and keep the trap carrying the catalyst clean at all times. , the frequency of replacement is reduced, and in some cases, regeneration operations are no longer necessary, but as mentioned above, with the conventional technology,
Selection of catalyst effective for re-combustion of particulates 1. The durability of the catalyst and trap when reburned was a problem.

The present invention addresses the above-mentioned problems and makes it possible for fine particles in exhaust gas to start and complete combustion at a lower temperature, and is less likely to lose activity even when exposed to high temperatures, and is heat resistant. The purpose of the present invention is to provide a catalyst for purifying particulates in exhaust gas that has excellent properties.

[Means to solve the problem]

In order to develop a particulate purification catalyst that enables low-temperature combustion of particulates in exhaust gas and has excellent heat resistance, the present inventors conducted intensive research on a large number of catalysts made of combinations of various metals and their compounds. We discovered that by combining the copper component and the alkali total loss component with the iron group metal component and furthermore with the molybdenum component, each component acts synergistically and contributes to lower combustion temperatures and heat resistance. The invention was completed.

That is, the present invention is characterized by having a composition that combines at least one selected from copper and its compounds, at least one selected from alkali metals and their compounds, and at least one selected from iron group metals and their compounds. It is a catalyst for purifying particulates in exhaust gas.

The present invention also provides at least one selected from steel and its compounds, at least one selected from alkali metals and their compounds, at least one selected from iron group metals and their compounds, and molybdenum and its compounds. A catalyst for purifying particulates in exhaust gas, characterized by having a composition combining at least one of the following.

Misfire # below! A will be explained in detail.

Copper and copper compounds used in the present invention include copper, copper oxides, nitrates, halogen compounds such as chlorides and bromides, and specific examples include oxidized steel, nitrate steel, copper chloride, Can be used to remove copper bromide, etc.

Alkali metals include lithium, sodium, potassium, rubidium, and cesium, and their compounds include halides such as fluoride, chloride, bromide, and iodide, nitrates, oxides, phosphates, and carbonates. Examples include acetates, cyanides, ands, hydrides, etc., but chlorides, nitrates, and oxides are particularly preferred, and potassium chloride, lithium chloride, etc. are preferably used.

Examples of iron group metals and their compounds include halides, nitrates, phosphates, oxides, and complex salts of iron, cobalt, and nickel. Specifically, iron chloride, cobalt chloride, nickel chloride, Iron nitrate, cobalt nitrate, nickel nitrate, iron phosphate, cobalt phosphate, nickel phosphate,
Examples include iron oxide, cobalt oxide, and nickel oxide.

In the present invention, when a catalyst is produced by combining the copper component, alkali metal component, and iron group metal component, the order of the component combinations is not particularly limited. In addition, the proportion of each component in the catalyst is usually about 10 m0 as a metal component in the catalyst.
It is used in the range of 1% or more, but the content of iron group metals and their compounds relative to copper and its compounds is such that the elemental ratio [iron group metals]/[Cu) is approximately α4 to 1.2,
Preferably, each component is adjusted to a range of about [L5 to 1].
It is preferable to turn it inside out. By adding an iron group metal component to the steel component and alkali metal component, and by setting the element ratio [iron group metal]/ICu) in the range of approximately ct4 to 1.2, the -l- sufficiency of each component can be improved. It is possible to obtain a mutually beneficial effect, and it is possible to burn at a much lower temperature than a system containing a copper component and 2g of alkali metal.

In addition, in the present invention, a molybdenum component is further added to the steel component, alkali metal component, and iron group metal component as catalyst components.
By using a component system, the activity decreases less at high temperatures than the five-component system described above, and the combustion temperature can be lowered.

Molybdenum and molybdenum compounds used in the present invention include molybdenum, ammonium salts of molybdenum,
Oxides, nitrates, halides, molybdic acid, molybdates, etc. are used, specifically ammonium molybdate, molybdenum dioxide, molybdenum trioxide, molybdenum pentoxide, molybdenum chloride, molybdenum oxalate, molybdate) IJ um, potassium molybdate, etc.

When the above-mentioned catalyst is manufactured by combining four components, the order of combining the components is not particularly limited. The primary component ratio is usually about 10 m as a metal component in the catalyst for each component.
In particular, the content of iron group metals and their compounds relative to molybdenum and its compounds is such that the elemental ratio [iron group metals]/(MO) is approximately 1.1 to 1.9. Preferably in the range of about 1.2 to 1.8, and furthermore, the blending amount of iron group metal and its compound to copper and its compound is [iron group gold hAE/[
It is preferable to prepare each component so that the value of Cu] is in the range of about α4 to t2, preferably about 0.5 to 1.

By adding an iron group metal component and a molybdenum component to the copper component and alkali metal component, there is little activity loss at high temperatures.
Although the combustion temperature can be lowered and exhibits excellent low-temperature combustion activity, the element ratio of [iron group metal]/(MO) and [iron group metal]/[,Cu] must be within the above range. It is possible to obtain a sufficient mutually beneficial effect of the molybdenum, iron group metal component, and molybdenum component, and to obtain a catalyst with excellent heat resistance and low-temperature combustion activity.

The catalyst of the present invention can be used by being supported on a suitable trapping body, for example, a heat-resistant filter such as a ceramic 7 ohm filter, a ceramic honeycomb filter, a ceramic pellet, or a metal mesh filter. In this case, the method for supporting the catalyst is to coat the inner surface of the trapping body with an oxide selected from alumina, titania, zirconia, silica, and composites thereof, and to support the catalyst thereon. ,
The catalyst of the present invention may be directly supported on the capture body. It is also possible to mix alumina, titania, zirconia, silica, and composites thereof with the components of the present invention in advance and support them on the capture body. The supported catalyst is preferably calcined in an electric furnace at about 500 to 900° C. for about 1 to 4 hours.

Preferably, the trapping body is a ceramic foam. Ceramic 7 ohm, for example, has internal communication spaces formed at a ratio of about 10 to 100 fc/inch, and has a bulk specific gravity of about 0.25 to 1.
It is within the range of 0. Although it is possible to arrange only one of these ceramic foams in a desired size, it is also possible to use a combination of a plurality of them by changing the method of supporting the catalyst as necessary. For example, it is also possible to construct the structure by sequentially stacking the inner communication spaces starting from the ones with the coarsest ones and the ones with the densest ones.

In addition, the catalyst of the present invention can reduce hydrocarbons, nitrogen oxides, carbon oxides, etc. contained in exhaust gas by combining with a known catalyst, such as a catalyst for gasoline engine exhaust gas, Good sea layer can be used effectively.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Jito! Dilute the stone chips with distilled water to make a mixed water bath solution. This mixed aqueous solution is placed in an evaporating dish and evaporated to dryness over about 1 hour while stirring on a hot plate. Next, after drying in a hot air dryer at 120°C for about 5 hours, drying in an electric furnace at 600°C
The mixture was calcined at ℃ for about 5 hours and pulverized to obtain a six-component catalyst in the form of a powder. Combustion temperature was measured using this catalyst, and the results are shown in Table 1.

The combustion temperature was measured as follows. The sample was a homogeneous mixture of fine particles collected from diesel engine exhaust gas and catalyst at a weight ratio of 1:2, and a thermal analysis measurement device f
The degree of combustion was measured using it under the measurement conditions shown below.

The measurement method is to heat the sample part in an air stream and read the weight loss start temperature and layer weight loss stop temperature.
These temperatures were used as the catalyst activity index as the combustion start temperature and combustion completion temperature of the fine particles, respectively. Further, the combustion midpoint temperature Tm indicates one measure of complete combustion of the particulates. Thermal analysis measurement flexibility is sample amount 10rR9, air flow j
ii2004 m1n, and the temperature increase rate was 211 U/m1n.

Example 2 Ferric chloride fA 37.7 mmol, potassium chloride 42.
5 mmol1, nickel chloride #21h 8 mmol f
c% It was prepared in the same manner as in Example 1, and the combustion temperature was completely measured in the same manner as in Example 1. The results are shown in Table 1.

Example 5 Cupric chloride 5 (L 5 mmol, lithium chloride 13
i9mmo1, nickel chloride 2&8mmoli Example 1
The combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 1.

Example 4 Cupric chloride 25.1 mmol, lithium chloride 13.59
1 mmol and 2 a Ommol of ferric nitrate were prepared in the same manner as in Example 1, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 1.

Example 5 Cupric chloride 65.4 mmol, potassium chloride 42.5
mmo1. , 18.7 mmol of cobalt chloride was prepared in the same manner as in Example 1, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 1.

Example 6 27.7 mmol of cupric chloride, 13.59 mmol of lithium chloride, and 5.9 mmol of nickel chloride were heated in the same manner as in Example 1, and the combustion temperature was measured in the same manner as in Example 1. added. The results are shown in Table 1.

Comparative example 1 2 chloride @ 5 CL 5 mmol, potassium chloride 4
2.5 mmol was prepared in the same manner as in Example 1,
Combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 1.

Table 1 Vi, % The following results are obtained by changing only the components under the same catalyst preparation conditions as described in Example 1. Comparative Example 1 shows a catalyst consisting of a copper component and an alkali metal component.
It shows the component catalyst.

Example 7 Cupric chloride 5α5 mmol, potassium chloride 42.5 mm
ol, and ferric nitrate 2! Measure out t l mmol into the same beer, dissolve it in distilled water to make an aqueous solution, and add 2.0 mmol of ammonium molybdate to the beer separately. Mix with an aqueous solution of Ommox dissolved in distilled water to obtain a mixed aqueous solution. Thereafter, 11 il of this mixed aqueous solution was prepared in the same manner as in Example 1, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 8g2.

Example 8 Cupric chloride 57.7 mmol, potassium chloride 657 m
mol, 25.1 mmol of ferric nitrate and 14.0 mmol of molybdenum chloride f: Polished in the same manner as in Example 7, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 2.

Example 9 Cupric chloride 51.4 mmol, potassium chloride 551 m
51.5 mmol of ferric nitrate and 2.5 mmol of ammonium molybdate were prepared in the same manner as in Example 7, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 2.

Examples 8 and 9 are examples in which the proportions of each component were changed compared to Example 7.

Example 10 Cupric chloride 5α3mm01, potassium chloride 42.5mm
ol, 26.7 mmol of cobalt chloride, and 2.5 mmol of ammonium molybdate were prepared in the same manner as in Example 7, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Part 2.

Example 11 Cupric chloride 5α5 mmol, potassium chloride 425 mm
o1, nickel chloride 2 & 8 mmol. Molybdenum chloride 1
7.5 mmol f: W was added in the same manner as in Example 7, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 2.

Example 12 Cupric chloride 515 mmol, lithium chloride Al 15 mm
ol, 51.5 mmol of nickel chloride, and ammonium molybdate A5 mrnol were prepared in the same manner as in Example 7, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Figure 2.

Examples 10 and 11 show examples using cobalt chloride and nickel chloride as iron group metal components.
c Example 12 shows an example in which lithium was used as the alkali metal component.

Example 13 Cupric chloride 5α3 mmol, potassium chloride 42.5 m
mo1 and ferric chloride 25. Weigh out 1 mmol to the same beer strength, dissolve it in distilled water to make a water bath solution, and add 2.0 mmol of ammonium molybdate separately. Dissolve Ommol in distilled water and then mix with the aqueous solution to make a mixed aqueous solution. Weigh out 24.5 mmol of r-alumina from this mixed solution, put it in an evaporating dish, and evaporate to dryness over FJ 1 hour while stirring on a hot plate. Next, in the hot air dryer 1
After drying at 20° C. for about 5 hours, it was calcined at 600° C. for 5 hours in an electric furnace to obtain a four-component catalyst. The combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 2.

This example shows an example in which a catalyst was prepared by mixing γ-alumina with four components.

Example 14 A catalyst fi was obtained in the same manner as in Example 5, except that the firing temperature of the catalyst was 900° C., and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 2.

Example 15 Example 10 except that the catalyst was fired at a temperature of 900°C.
The catalyst was prepared in the same manner as above, and the combustion temperature was measured in the same manner as for the actual 1M chestnut 1. The results are shown in Table 2.

Example 16 Example 11 except that the catalyst was fired at a temperature of 900°C.
A catalyst was obtained in the same manner as in Example 1, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 2. Example 1
Nos. 2 to 14 are examples in which the catalyst was fired at a temperature of 900° C., which shows that the catalyst of the present invention is unlikely to suffer from a decrease in activity even when exposed to high temperatures.

Example 17 Second steel chloride 6α4 mmol, potassium chloride 42.5 m
mol, 50 mmol of ammonium molybdate, and 21.4 mmol of ferric nitrate were prepared in the same manner as in Example 7, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 3.

Example 18 Cupric chloride 5a8 mmol, potassium chloride 657 mmol
1. , 17.0 mmol of molybdenum chloride, and 47.1 mmol of ferric nitrate were prepared in the same manner as in Example 7, and 5j! Combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 5.

Example 19 2% chloride 455.8 mmol, potassium chloride 657
mmol1, ammonium molybdate7, Ommol
.

Copal chloride) 47.1 mmol vI4 was produced in the same manner as in Example 7, and the combustion temperature was measured in the same manner as in Example 1. The results will be shown to the fifth group.

Example 20 Example 1 except that the firing temperature of the catalyst was ft900°C.
A catalyst was obtained in the same manner as in Example 7, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 5.

Examples 14 to 16% and Example 20 are examples in which the catalyst was calcined at a temperature of 900°C, and show that the catalyst of the present invention is unlikely to lose activity even when exposed to high temperatures. .

Comparative Example 2 Cupric chloride 75.4 mmol, potassium chloride tZ5m
mo1, ammonium molybdate2. Ommol
A five-component vI4AL catalyst was obtained in the same manner as in Example 7 using f, and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 5.

Comparative Example 3 A catalyst was obtained in the same manner as in Comparative Example 2, except that the firing temperature of the catalyst was 900° C., and the combustion temperature was measured in the same manner as in Example 1. The results are shown in Table 5.

Reference example Particulates collected from diesel engine exhaust gas 3~
f! : The temperature was raised in the same manner as in Example 1, and the combustion temperature was measured. The results are shown in Figure 5.

This example shows the temperature when fine particles are burnt alone without a catalyst.

As is clear from Table 1, Table 2, and Table 3, the catalyst according to the present invention has a low combustion start temperature and a combustion completion temperature of around 400°C, which is the midpoint of combustion that indicates complete combustion. The temperature Tm is 400°C or less. In addition, high temperature firing (9
00°C), the activity at 600°C calcination was maintained, indicating that the catalyst of the present invention is unlikely to lose its activity even when exposed to high temperatures.

〔Effect of the invention〕

When the catalyst of the present invention is used as a supported trap, it can be placed in a predetermined flow path of an engine exhaust system, reliably traps particulates in exhaust gas, and starts combustion at a lower temperature. , and combustion can be completed.

As a result, less combustion energy is required, extending the life of the trapping body, and preventing the trapping body from becoming clogged! By eliminating ll, the frequency of replacement can be reduced, and in some cases, regeneration operations can be eliminated. Since the catalyst of the present invention has excellent heat resistance, there is little decrease in activity even when exposed to high temperatures due to engine operating conditions.

Claims (1)

[Claims] 1. It has a composition that combines at least one selected from copper and its compounds, at least one selected from alkali metals and their compounds, and at least one selected from iron group metals and their compounds. A catalyst for purifying particulates in exhaust gas. 2. It has a composition that combines at least one selected from copper and its compounds, at least one selected from alkali metals and their compounds, and at least one selected from iron group metals and their compounds, and The blending amount of the iron group metal and its compound with respect to the compound is such that the element ratio [iron group metal]/[Cu]=0.4 to 1.
2. A catalyst for purifying particulates in exhaust gas. 3. At least one selected from copper and its compounds, at least one selected from alkali metals and their compounds, at least one selected from iron group metals and their compounds, and further at least one selected from molybdenum and its compounds. A catalyst for purifying particulates in exhaust gas, characterized by having a combination of compositions. 4. At least one selected from copper and its compounds, at least one selected from alkali metals and their compounds, at least one selected from iron group metals and their compounds, and further at least one selected from molybdenum and its compounds. and the blending amount of the iron group metal and its compound with respect to the copper and its compound, and the blending amount of the iron group metal and its compound with respect to molybdenum and its compound, in element ratio [iron group metal]/ A catalyst for purifying particulates in exhaust gas, characterized in that [Cu]=0.4 to 1.2 and [iron group metal]/[Mo]=1.1 to 1.9.