KR100680184B1 - Diesel particulate filter - Google Patents

Abstract

The present invention relates to a filter for a diesel engine particulate filter, by coating a platinum catalyst in the first half of the oxidation catalyst filter as in the prior art, and by replacing a portion of the Pt component with an excellent thermal durability in the second half of the oxidation catalyst filter. It is possible to prevent catalyst deterioration at the rear end by exothermic reaction at the front part of the filter, and it is possible to solve the activity and cost problems by using the NO2 oxidizing power generated at the front part so that the combustion reaction proceeds smoothly at the latter part. It is about useful filters.

Oxidation catalyst filter, soot filtration

Description

Diesel particulate filter {diesel particulate filter}

1 is a partial cutaway perspective view of an oxidation catalyst filter;

2 is a cross-sectional view of a conventional oxidation catalyst filter,

3 is a cross-sectional view of an oxidation catalyst filter according to the present invention.

* Brief description of drawings *

 10: oxidation catalyst filter 11a, 11b: exhaust gas passage

 12 porous porous wall 13 plugging

 15: inlet side 16: outlet side

 30: oxidation catalyst coating layer 40: first oxidation catalyst coating layer

 41: first half 50: second oxidation catalyst coating layer

 51: second half

The present invention relates to a filter for a diesel engine particulate filter, and more particularly, to a filter for a diesel engine particulate filter coated with a different catalyst composition in the first half and the second half of the porous filter.

The utilization of transportation including automobiles is explosively increasing, and various problems are raised due to the increase of traffic volume, among which the pollution problem caused by the use of fossil fuel is particularly important in large cities. Carbon dioxide, sulfides and nitrides (NOx, NOx) generated by the combustion of fossil fuels used as fuels for automobiles are becoming the main culprit of environmental pollution. In particular, significant environmental pollution occurs due to ozone layer destruction by Freon and N2O gas, and acid rain by SOx and NOx components. In addition, the human body mainly affects the respiratory and neurological disorders. In particular, ozone generation due to the photochemical reaction between HC and NOx and PM (particulate matter) have recently been found to be the cause of lung cancer. Interest in the impact on the public is increasing. Therefore, research and development to reduce this have been conducted.

In order to reduce harmful emissions due to the combustion of fossil fuels, technologies for reducing pollutants in the engine itself, that is, engine technology and pretreatment technology, have been developed. There are limitations to satisfying regulations alone, making it necessary to apply after-treatment technology to treat exhaust gases already burned in engines. Examples of post-treatment technologies for diesel vehicles include oxidation catalysts, NOx catalysts, and soot filters. Among them, diesel particulate filter trap (DPF) is the most efficient and practical approach. This device is a technology that collects particulate matter and soot discharged from diesel engine in filter, burns it, recycles it, and collects particulate matter and keeps using it. Economics are acting as a barrier to practical use.

The soot filtration device is basically composed of three parts: a filter, a regeneration device, and a control device. The regeneration device is a device necessary for collecting particulate matter in the filter, removing it, and continuing to use the filter. The regeneration method is an active regeneration type that burns particulate matter by electrically supplying a heat source to burn and collect the collected particulate matter, and a passive regeneration method that regenerates only exhaust gas without supplying a separate heat source. type). The forced regeneration method heats the collected particulate matter with an external heat source up to the ignition temperature of 550 ℃ ~ 600 ℃. Electric heater method, burner method, etc. are used. Severe and shorten the life, there is a problem in that the abnormal combustion (burn normal) occurs when a large amount of smoke is collected and recycled to break the filter. The natural regeneration method is a method of lowering the ignition temperature of particulate matter by using a catalyst and continuously burning it with an engine exhaust gas.An oxidation catalyst filter trap which burns particulate matter by coating precious metals such as platinum on the inner surface of the filter. ) And the catalyst collecting filter at the front end has a catalyst-trap combinations installed at the rear end.

The present invention relates to a diesel engine filter employing an oxidation catalyst filter method. Figure 1 is a partial cutaway perspective view of the oxidation catalyst filter, Figure 2 is a cross-sectional view of a conventional oxidation catalyst filter. The oxidation catalyst filter 10 is formed by dividing the plurality of exhaust gas passages 11a and 11b into the porous partition 12 and having an in-stagged way on the inlet side 15 and the outlet side 16. Both ends are plugged (13). On the other hand, the inner surface of the partition is coated with an oxidation catalyst 30, preferably NO is oxidized to NO 2 and the particulate matter collected in the filter can be easily oxidized (burned) at about 350 ℃. Conventional oxidation catalysts are known to be effective as platinum components as noble metals. However, in order to meet environmental regulations, platinum content is rapidly increased to increase the cost, and platinum is poor in thermal resistance due to its low thermal resistance. It is pointed out as a problem.

In order to solve this problem, a part of platinum is partially replaced with palladium having a high temperature durability, thereby reducing a filter cost and developing a filter having improved durability. On the other hand, the Pt component has better NO oxidizing power than the Pd component, and the conversion rate of NO to NO2 is excellent at about 300 ° C., which is the exhaust gas discharge temperature. In the same way, the platinum catalyst is coated at the same time, and the internal late part is coated with a Pd component having excellent thermal durability in place of a part of the Pt component, thereby preventing the catalyst deterioration in the latter part due to the exothermic reaction in the first half of the filter, and in the first half. By using the NO2 oxidation power, the combustion reaction in the second half can be smoothly performed.

The reaction scheme in the present invention having the above structure is as follows.

 First half:

 NO2 + C-> NO + CO

      NO + CO + O2-> NO2 + CO2

Second half:

 NO2 + C-> NO + CO

      CO + O2-> CO2

The present invention is achieved by an oxidation catalyst filter in which a noble metal component including platinum and palladium is coated inside the rear porous partition, and Pt is coated inside the porous porous partition in the first half. Platinum and palladium coated in the second half is characterized in that 1: 5 to 5: 1 parts by weight. The 'first half' is defined as the side into which the exhaust gas discharged from the engine is introduced, and the 'second half' may be understood as the side through which the exhaust gas is discharged to the outside through the filter. In addition, the "first half" and "second half" are not necessarily terms dividing the filter, it may be understood as part of the first half and part of the second half depending on the exhaust gas and engine conditions. 3 is a schematic cross-sectional view of an oxidation catalyst filter according to the present invention.

The oxidation catalyst coated on the second half of the filter includes a noble metal component including platinum and palladium, and these catalysts are supported on a high surface area refractory oxide support such as high surface area alumina. Such supported catalysts can be used with oxygen storage components including rare earth metal oxides such as oxides of Ce, La, Pr, and Nd. High surface area refractory oxides are BET (Brunauer, Emmett and Teller) of high surface area alumina materials, also referred to as 'gamma alumina' or 'activated alumina', for example, and the surface area is typically at least 60 square meters (m2 / g) per gram. Such activated alumina is a gamma and delta phase mixture of alumina but may contain significant amounts of eta, kappa and theta alumina phases. Platinum and palladium components are usually supported in parts by weight of about 1: 5 to 5: 1, and a method for producing an oxidation catalyst containing platinum and palladium is known.

In a preferred embodiment of the present invention, the first half of the inside of the filter is coated with a first support carrying a precious metal component containing platinum; The second half of the inside of the filter is coated with a second support carrying a precious metal component including platinum and palladium components. In addition, the first support and the second support may include an oxygen storage component that is optional as a rare earth metal component. The first or second support may be selected from the group consisting of silica, alumina and titania compounds. Preferably it is an activating compound selected from the group consisting of alumina, silica, silica-alumina, alumino-silicate, alumina-zirconia, alumina-chromia and alumina-ceria. More preferably, it is activated alumina.

Hereinafter, the oxidation catalyst filter according to the present invention will be described in detail.

a. Pt-Pd-impregnated activated alumina mixed with platinum and palladium in a 2: 1 ratio by using chloroplatinic acid and palladium nitrate in gamma alumina powder was prepared, dispersed in water, and dispersed in water. And a second support carrying Pd.

b. Pt-impregnated activated alumina in which 2 parts by weight of platinum was mixed with chloroplatinic acid was prepared using gamma alumina powder, and dispersed in water to prepare a first support having a slurry of Pt.

c. About 90% of the first support and the second support were ball milled to have a particle size of 8-10 μm.

d. The ball milling slurry b was coated on the inner front portion 41 of the cordierite honeycomb 10 and dried at 150 ° C. to 160 ° C. for about 10 minutes, and then the slurry a was not coated with the slurry b. (51) and dried under the same conditions, and then fired at 530 ° C. to 550 ° C. for about 40 minutes to obtain an oxidation catalyst filter coated with Pt / Al 2 O 3 (40) // Pt-Pd / Al 2 O 3 (50) in the first half. Completed.

The filter structure for the diesel engine particulate filter according to the above can be expected to have a relatively high CO and HC oxidation activity compared to the oxidation catalyst filter coated on the inner partition of the platinum only as a noble metal component, a portion of the platinum is relatively high temperature durability Partial replacement with palladium reduces the filter cost, prevents catalyst deterioration at the rear end by exothermic reaction at the front end of filter, and smoothes the combustion reaction at the rear end by using NO2 oxidation power generated at the front end. Can be obtained. This production example illustrates the case of 2: 1 parts by weight of platinum and palladium as the coating material for the second half of the filter, but in the catalyst supporting platinum and palladium in a single layer, platinum and palladium are 1: 5 to 5: Since the composition composed of 1 part by weight has been known, the platinum and palladium compositions of the coating material of the latter part of the oxidation catalyst filter may also be expected to correspond to the conventional compositions.

While the invention has been described in detail with reference to specific embodiments, these embodiments are for illustration only, the scope of the invention being based on the appended claims.

In the present invention, in the oxidation catalyst filter, the platinum content is rapidly increased in recent years, thereby causing a cost increase, and in order to solve the problem of the thermal durability of the filter, a portion of platinum is converted into palladium having high temperature durability. According to the present invention, the Pt component has superior NO oxidation power compared to the Pd component, and the conversion rate of NO to NO2 is about 300, which is an exhaust gas discharge temperature. In consideration of this, in the conventional filter structure, the platinum catalyst is coated on the first half of the oxidation catalyst filter in the same manner as the conventional one, and the Pd component having excellent thermal durability is coated on the second half of the Pt component with excellent thermal durability. Deterioration of the catalyst due to exothermic reaction in the first part can be prevented, Using the NO2 generated oxidative document can be obtained an effect that smoothly combustion reaction in the second half is a useful filter to solve the activity and cost issues.

Claims (2)

A plurality of exhaust gas passages (11a, 11b) is formed by dividing the porous partition wall 12, plugging both ends in an in a stagged way on the inlet side (15) and the outlet side (16) (13) In the oxidation catalyst filter, the first half of the inside of the filter is coated with a first support 40 carrying a precious metal component containing platinum; The second half of the inside of the filter 51 is coated with a second support 50 loaded with a noble metal component including platinum and palladium components, wherein the first and second supports are composed of an activated powder having the same surface area. Filter for soot filtration. The filter for a diesel engine particulate filter according to claim 1, wherein the platinum and palladium supported on the second support are 1: 5 to 5: 1 parts by weight.

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