JPS61129030A - Filter for collecting and purifying fine particles - Google Patents

Abstract

PURPOSE:To suppress the formation of sulfate, by forming the catalyst supported by the surface of a filter substrate from oxides of Pd, Rh and one of a metal selected from Cu, Zn, Mn and La and setting the catalyst to an amount constant to the apparent volume of the filter substrate. CONSTITUTION:A fine particle collection and purification filer is formed by supporting a catalyst for burning a particulate by a filter substrate. Pd for aiming the enhancement of ignitability and Ph for aiming to suppress the formation of sulfate and to enhance durability are supported by said catalyst in a respective amount of 0.1-5g to 1l of the apparent volume of the filter substrate. In addition thereto, 0.5-50g of oxide of one or more of metal selected from Cu, Zn, Mn and La is supported.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a particulate collection and purification filter that collects and purifies particulates contained in exhaust gas from a diesel engine, etc. The present invention relates to a particulate combustion catalyst supported on a filter and effective in regenerating the particulate collection and purification filter.

[Prior Art] Exhaust gas from an internal combustion engine such as a diesel engine contains particulates mainly composed of carbon. As particulate collecting and purifying filters that collect and purify these particulates, ceramic honeycomb structures (honeycomb filters), foam filters having a three-dimensional network structure, and the like are known. These filters are designed to prevent particulates from accumulating in the exhaust passage as the mileage of the vehicle increases, resulting in an increase in pressure (Ω loss) and a decrease in engine output. Since most of them are carbon particles, they can be burned and removed by heating to about 580°C or above, which makes it possible to regenerate the particulate filter. Regeneration methods include burning the collected particulates using a burner, electric heater, etc., or reducing the intake air amount of the engine using a throttle valve to increase the ratio of fuel to air. There are known methods to burn the collected particulates by raising the temperature of the exhaust gas.In these cases, a catalyst is added to the particulate filter to ensure the combustion of the particulates. It is also well known that supported catalysts are effective, and platinum metal catalysts, JP-A-55-2
The palladium catalyst disclosed in Publication No. 4597, platinum-
A rhodium catalyst or a noble metal-chromium catalyst disclosed in Japanese Patent Application Laid-Open No. 57-24640 is known.

[Problems to be solved by the invention] The above catalyst improves the ignitability of particulates,
Although it has excellent catalytic performance, it has strong oxidizing power and has the effect of oxidizing sulfur dioxide contained in diesel engine exhaust gas. Therefore, the particulates that are discharged without being collected by the particulate collection purification filter may contain sulfates, which not only reduces the apparent collection rate but also is not favorable from an environmental sanitary perspective. .

As a result of intensive research, the present inventor has suppressed the production of ra salt,
The present invention was completed by discovering a catalyst composition that also has excellent regeneration performance.

[Means for Solving the Problems 1] The particulate collecting and purifying filter of the present invention is composed of a ceramic filter base and a catalyst supported on the surface of the filter base, and is capable of reducing the particulate matter contained in the engine gas. In a particulate collection purification filter that collects curates, the catalyst contains 0.1 to 59 paranine cum, 0.1 to 5 rhodium, copper, It is characterized in that the oxide of at least one metal selected from zinc, manganese and lanthanum is composed of O85 and -50!11.

The filter base of the particulate collection and purification filter of the present invention is made of a ceramic material such as cordierite, mullite, spinel, etc., as in the conventional filter. The shape of the particulate collection and purification filter of the present invention is such that one end face has a checkered pattern [=1] and the other end face is a closed introduction passage, and the other end face has a checkered frontage, and the other end face has a checkered opening and an exhaust passage is closed. There are honeycomb-shaped structures with channels arranged adjacent to each other, or three-dimensional network structure (1ζ form ε), and both can be used, but they are not limited to these. .

It is desirable that a support layer made of a porous ceramic body be formed on the foam-like filter base fi. The purpose of these ten holding layers is to improve the collection performance or to prevent the collected particulates from scattering again, and various materials can be selected from alumina, titania, magnesia, etc., but γ-alumina is particularly preferred.

In the particulate collection and purification filter of the present invention, a particulate combustion catalyst is supported directly on the filter base or on the porous ceramic support layer. The most distinctive feature of the present invention lies in the composition of this catalyst.

Palladium (P(1) and rhodium (R1)) as catalysts used in the particulate filter of the present invention are conventionally known catalysts, but in the present invention, the apparent volume of the filter base is 1 liter. 0.1-5g each for
It is carried by hanging. Note that the apparent volume means the total volume including the volumes of the introduction passage and the discharge passage in the case of a honeycomb filter, and the total volume including the internal space of the three-dimensional network structure in the case of a foam filter. Among these, palladium is mainly used to improve ignitability, and rhodium is used mainly to suppress sulfate formation and improve durability, and exhibits the best performance when supported within the above range. Further, within the above range, it is desirable that palladium supports 1 to 10 times as much M as rhodium. Palladium is 1 of rhodium (1!I
If the value exceeds n, the amount of silicate produced tends to increase, and if the amount of palladium is less than that of rhodium, the ignitability becomes undesirable.

In addition to the above-mentioned palladium and rhodium, the filter base also contains copper (Cu), zinc (Zn), and ngan (Mn).
) and lanthanum (La). The supported metal may be one of these metals, or two or more metals may be used.

The above metals are usually supported as oxides, and 0.5 to 5
0 g, preferably 5 to 20 (+). If the supported amount is less than 0.5 (l), no effect will be obtained, and if it is more than 50 g, the supporting process will become complicated. There is no substantial performance improvement effect and this is not preferable.

In the particulate collection and purification filter of the present invention, a filter base such as a honeycomb filter or a foam filter is formed in the same manner as before, and a porous ceramic support layer is preferably formed in a rough manner, and then a solution containing palladium and rhodium chlorides, etc. The catalyst can be supported by immersing the substrate in a solution containing , nitrates of the above-mentioned metals, etc. to impregnate the substrate with the solution, and then calcining the solution.

Moreover, the supported amount can also be changed by changing the concentration of the solution. Note that palladium, rhodium, and the above metals may be in solution form, and are not limited to chlorides and nitrates. Moreover, various solvents such as water and alcohol can be selected.

The catalyst compounds may be supported all at once using a mixed solution, or each catalyst may be supported in separate solutions and supported in stages by dipping and baking each catalyst.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

In addition, hereinafter, the term "catalyst supported" refers to an oxide, excluding palladium and rhodium.

As a filter base, it has a large number of passages parallel to the axial direction inside, and the passages are open at both ends.The diameter is 3Q mm, the length is 50 mm, and one end surface is open.
A cordierite honeycomb structure of 1.0 mm/cm 2 was used. Then, using a plugging material made by kneading 8!5 parts of cordierite powder, 5 parts of methyl hirulose, and 10 parts of distilled water, the passages opening at one end were connected to each other in a substantially checkerboard pattern. r+ at a depth of about 5 mrI+
A was blocked. In addition, the passages that were not closed at the other end surface were similarly closed with the same closing material, dried at 120° C. for 2 hours, and then fired at 1400° C. for 4 hours to obtain a honeycomb filter. Next, the honeycomb filter is immersed in a suspension consisting of 37.51 parts of γ-alumina powder, 37.5 small parts of alumina sol, 5 parts of aluminum chloride, 6 parts of distilled water, and 207 parts of distilled water. After pulling it up and blowing away the excess liquid layer, it was dried at 120°C for 21'I for 1 hour and fired at 700°C for 3 hours to form porous holes made of γ-alumina on the passage walls.
Ramic lfT 1. iFi was formed.

Next, 10 aqueous solution containing 0.0351a% of palladium
The above-mentioned filter in which a γ-alumina support layer was formed in 0 ml was immersed for 1 hour while being rocked up and down, and after being reduced with an aqueous sodium borohydride solution, it was washed with water. It was roughly dried at 120°C for 2 hours and fired at 500°C for 30 minutes to support palladium.

Furthermore, the above-mentioned filter in which palladium was supported in an aqueous solution of rhodium chloride of O, O'35% by weight was crushed for 1 hour while rocking up and down, and after being reduced with an aqueous sodium borohydride solution, the filter was washed with water.

It was further dried at 120°C for 2 hours and fired at 500°C for 30 minutes to support rhodium.

Next, the filter carrying palladium and rhodium was crushed in an aqueous solution containing 3,050,000 m% of copper 611ate for 3 minutes, and after blowing off excess droplets, it was dried at 120°C for 2 hours, and then heated to 600°C for 1 hour. The fine particle collection and purification filter of Example 1 was obtained by firing for a time to support copper.

The particulate collection and purification filter of Example 1, which had a quantity of 1 q, contained 1 g of palladium per 1 liter of honeycomb filter volume.
19 rhodium and 29 copper were supported.

Exhaust the particulate collection and purification filter of Example 1 ff12
Installed in the exhaust system of a 200cc swirl chamber type diesel engine, engine speed 2500. rom, torque 11
100 to 150 liters of exhaust gas immediately after passing through the filter was collected under the conditions of 100 to 150 liters of exhaust gas having a temperature of 450° C. at the inlet of the filter. After extracting this ion, the amount of sulfate was determined by photometric titration. The results are shown in the table.

After the above exhaust gas collection is completed, the engine speed is 2000 rpm.
The filter was operated for an additional 3 hours under the conditions of m, f-lux of 3 kg/nl, and 0.45 to 0.55 g of particulates were collected in the filter. Thereafter, the filter in which the particulates were collected was placed in the experimental apparatus shown in FIG. 1, and the regeneration temperature was measured. Note that the regenerator temperature is the temperature at which the upstream end face of the filter is heated by the heater, which is necessary for burning and burning out 70% or more of the collected particulates, and it is preferably a lower value. The results are shown in the table.

Next, the concentrations of the copper nitrate aqueous solution were adjusted to 7.5% by weight and 15% by weight, respectively.
The same materials as in Example 1 were used except for overlaying and making the weight 30%, and the same amount of palladium and rhodium was supported by the same method. Particulate collection and purification filters of Example 2, Example 3, and Example 4 were obtained in which 5 g, 10 g, and 200 particles were supported in the apparent volume of 1 liter of the filter, respectively. Also, in place of the aqueous copper nitrate solution, an aqueous solution containing 18.5% by weight of zinc nitrate and 20% by weight of manganese nitrate were used.
13.3L of aqueous solution containing 2% and lanthanum nitrate
Example 1 except that each aqueous solution containing 1% was used.
Example 5, in which the same materials were used, the same amounts of palladium and rhodium were supported by the same method, and 10 g of zinc was supported in 1 liter of the apparent volume of the filter; Example 6, in which 100 of manganese was supported; 1 lantern
The particle collection and purification filter of Example 7 carrying 0(l) was
It was 9.

Furthermore, in the same manner as in Example 1, in order to compare with a conventional particulate collection and purification filter, after loading rhodium, 10g of chromium catalyst was supported in 1 liter of the apparent volume of the filter using an aqueous solution containing 26.31ft1% of 6r1M chromium. The particulate collection and purification filter of Comparative Example 1 contains 10% of cobalt using an aqueous solution containing 19.4% by weight of cobalt nitrate.
The particulate collection and purification filter of Comparative Example 2 which supported 1 g of palladium, and the particulate 1111 of Comparative Example 3 which supported only 1 g of palladium.
A collection and purification filter was used to remove 0.0% rhodium using an aqueous solution containing 19% palladium and 0.0035% by weight rhodium chloride.
Particulate bli collection and purification filter of Comparative Example 4 carrying 1g,
Using an aqueous solution containing 1 g of palladium and 0.0175% of rhodium chloride, 0.5% rhodium (supported particle collection of Comparative Example 5) P7 filter, 1 g of palladium.
A particulate collection and purification filter of Comparative Example 6 was manufactured according to Example 1, in which 19% of rhodium was supported and no metals such as 19% copper and 11% lead were supported.

The amount of sulfate produced and the regenerator temperature of the particulate collection and purification filters of the above Examples and Comparative Examples were measured in the same manner as in Example 1, and the results are shown in the table.

From the table, even in Comparative Example 6, which supported a palladium-rhodium catalyst and produced the least amount of sulfate, the 6M salt was 26 m (1
/m3, which means that the collection rate is reduced by more than 30% when compared with the collected particulate matter. Moreover, in Comparative Example 1 in which chromium was added to the palladium-rhodium system, Iiii! Although the amount of i-acid acid produced is reduced to 15 mq/m 3 , the regenerator temperature is as high as 525° C., and the regeneration performance is reduced. In addition, in IC Comparative Example 2 in which cobalt was added, the amount of sulfate produced was as high as 68 m (1/m3).On the other hand, the particle collection and purification filter of the example
! The acid salt production rate is 8 to 24 mq/m3, which is a preferable 1 shift, and the renewable temperature is also as low as 375 to 475°C.

Furthermore, as is clear from comparing Comparative Example 6 and Examples 1 to 4, as shown in FIG. 2, as the amount of copper supported increases, the FM salt production rate decreases, and the regenerator temperature also decreases. This is clearly an effect of copper.

[Operations and Effects of the Invention] In the particulate collection and purification filter of the present invention, sulfate generation is suppressed by adding metals such as copper and zinc that have low reactivity with sulfur dioxide to palladium, which has high reactivity with sulfur dioxide. It became possible. Therefore, the apparent collection rate is improved, which is also favorable from the viewpoint of environmental hygiene. Further, the above-mentioned metals also have the effect of propagating the combustion of particulates, and have the effect of lowering the regeneration temperature, which is a great effect of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an experimental apparatus used to evaluate the regeneration performance of the catalyst. FIG. 2 is a graph showing the relationship between the amount of copper supported, the amount of sulfate produced, and the renewable temperature in Examples. Patent applicant: Toyota Motor Corporation Representative Patent attorney: Hirodo Okawa Patent attorney: Shudo Fujitani Patent attorney: Akio Maruyama

Claims (4)

[Claims] (1) In a particulate collection and purification filter that is composed of a ceramic filter base and a catalyst supported on the surface of the filter base and that collects particulates contained in engine exhaust gas, the catalyst is 0.1 to 5 g of palladium, 0.1 to 5 g of rhodium, and 0.1 to 5 g of an oxide of at least one metal selected from copper, zinc, manganese, and lanthanum per 1 liter of apparent volume of the substrate. 5-5
A particulate collection and purification filter comprising: 0g. (2) The particulate collection and purification filter according to claim 1, which comprises a porous ceramic support layer on the surface of the filter base. (3) The particulate collection and purification filter according to claim 1, wherein palladium is contained 1 to 10 times as much as rhodium. (4) The particulate collection and purification filter according to claim 2, wherein the porous ceramic coating layer is made of γ-alumina.