WO2014178632A1

WO2014178632A1 - Catalyst system for purifying exhaust gas from gasoline engine

Info

Publication number: WO2014178632A1
Application number: PCT/KR2014/003822
Authority: WO
Inventors: 김홍래; 송진우; 한현식
Original assignee: 희성촉매 주식회사
Priority date: 2013-05-02
Filing date: 2014-04-30
Publication date: 2014-11-06

Abstract

The present invention relates to a catalyst system for purifying exhaust gas from a gasoline engine, and more specifically, to a catalyst system for purifying exhaust gas from a gasoline engine in which a wall flow-type porous carrier is applied as a three-way catalyst carrier, and a gasoline particulate filter (GPF) is installed, and thus is capable of rapidly and efficiently progressing oxidation and reduction of the exhaust gas by improving contact properties with a three-way catalyst ingredient and the exhaust gas.

Description

Catalyst system for gasoline engine exhaust gas purification

The present invention relates to a catalyst system for purifying exhaust gas of a gasoline engine, and more particularly, to a wall-flow porous carrier as a three-way catalyst carrier, followed by a gasoline engine exhaust gas equipped with a catalytic filter (GPF) for gasoline engine soot filtration. The present invention relates to a catalyst system for purification, and to a catalyst system for gasoline engine exhaust gas purification, in which contact between the three-way catalyst component and the exhaust gas is improved, so that the exhaust gas oxidation and reduction reaction can proceed quickly and efficiently.

A three-way catalyst that simultaneously reduces CO, HC and NOx in gasoline engine exhaust gas by more than 90% is applied to the aftertreatment device. In three-way catalysts, CO and HC are converted into an oxidative reaction and at the same time, NOx is converted into a harmless component by a reduction reaction, and the related reaction mechanism is well known. In the three-way catalyst, Pt / Pd / Rh noble metal components including palladium (Pd) are used. Pd mainly promotes oxidation reactions to reduce CO and HC, and Rh promotes reduction of NOx. Methods of preparing and constituting the three-way catalyst are well known in the art.

In order to increase the reactivity of the noble metal catalyst to a substrate made of ceramic or metal, an alumina wash cord, which is an intermediate medium, is applied, and a catalyst material which reacts directly with the exhaust gas is applied to the outermost side. The three-way catalyst carrier is an open-flow (flow-through) type carrier.

1 is a partial cutaway perspective view of an open-flow type carrier, and FIG. 2 is a cross-sectional view of a catalytic converter coated with a three-way catalyst layer on an inner surface thereof. The converter 10 is composed of an open-flow honeycomb formed by separating a plurality of

exhaust gas passages

11a and 11b into porous partitions 12 on the inlet and

outlet sides

15 and 16. The three-way catalyst layer 30 is coated so that HC, CO are oxidized and NOx is reduced to N2.

Gasoline direct injection (GDI) engines are one of the most efficient gasoline engines in terms of fuel efficiency and power output, but have a problem of generating more particulate matter (PM) and particle count (PN) than conventional port fuel injection methods. . However, such open-flow carriers have a problem that they do not effectively remove particulate matter.

Thus, a catalytic purification system for a new gasoline engine that ensures good contact with the exhaust gases and three-way catalyst components emitted from the gasoline engine, while at the same time meeting the Euro-6 regulations, is also possible. need. In particular, in the case of filters, conventional DPF configurations for the removal of diesel particulate matter cannot be applied to gasoline (GDI) engine exhaust. The particulate matter generated in the GDI engine is finer (10 to 100 nm) than the particulate matter of the diesel engine, and therefore more sensitive to the problem of pressure loss due to cell wall blockage, and the GDI engine is also compared with the diesel engine exhaust gas. Since there is a lack of oxygen for burning the deposited particulate matter, a catalyst configuration is necessary to compensate for this.

The present inventors propose a wall-flow porous carrier as a three-way catalyst support structure in order to improve the contact between the gasoline engine exhaust gas and the catalyst layer. In addition, the rear end of the three-way catalyst module optionally controls the coating position and coating amount of the catalyst to be coated in the cell longitudinal direction inside the filter, thereby improving contact with the GDI engine exhaust gas and the catalyst and reducing the engine pressure due to the exhaust gas. It is to propose a catalytic purification system equipped with a catalytic filter that can lower the.

Catalytic purification system according to the present invention is more efficient than the conventional purification system employing a conventional open-flow carrier by improving the contact between the catalyst component and the exhaust gas, it is possible to significantly reduce particulate matter by attaching a catalytic filter have.

1 and 2 are partial cutaway perspective views and cross-sectional views of the open-flow ternary catalyst carrier, respectively.

3 and 4 are respectively a perspective view and a cross-sectional view of the wall-flow porous three-way catalyst carrier according to the present invention.

5 is a partially enlarged cross-sectional view of a catalytic GPF according to the present invention.

In order to achieve the above object, the structure for supporting the three-way catalyst in the present invention is a wall-flow type porous carrier. For convenience in the drawings, the three-way catalyst component is illustrated on the inner wall of the carrier for convenience, but the porous catalyst carrier according to the present invention is deposited with the three-way catalyst active material in the carrier, and the catalytically active material is substantially on the inner wall surface of the carrier. It has a porous carrier structure that does not exist. As used herein, the term 'deposition' means that the catalytically active material penetrates into the pores formed in the carrier and is supported within the pores, and the catalytically active material is substantially coated on the surface of the carrier inner wall.

In the description of the present invention, "cross section" is defined as a cross section perpendicular to the exhaust gas flow direction unless otherwise specified. On the other hand, in the context of the GPF structure, the second half may be understood as the side through which the exhaust gas is discharged to the outside through the filter, the first half is defined as the side into which the exhaust gas discharged from the engine is introduced. Further, the 'first half' and 'second half' are not necessarily terms for dividing the filter in the longitudinal direction, and may be understood as some of the first half and some of the second half depending on the exhaust gas and engine conditions.

Figure 3 is a perspective view of the porous wall-flow catalytic converter partial cutaway according to the present invention, Figure 4 is a cross-sectional view of the catalytic converter coated or deposited three-way catalyst layer on the inner surface. The three-way catalytic converter 100 is formed by dividing the plurality of

exhaust gas passages

110a and 110b into the porous partition wall 120 and having a mutually zigzag pattern on the inlet side 150 and the outlet side 160. Both ends are plugged 130. Meanwhile, the three-way catalyst layer 300 is coated or deposited on the porous partition wall on the inner surface of the partition wall, and HC, CO are oxidized and NOx is reduced to N ₂ via the catalyst layer.

In the present invention, in order for the catalytically active material to be deposited in the carrier to achieve the object of the present invention, the porosity of the pore charge volume in the total volume of the carrier is preferably 20% to 80%. If the porosity is 20% or less, the three-way catalyst function sufficient for the oxidation and reduction reaction cannot be provided, and if it is 80% or more, the mechanical strength is lowered, so that the porous carrier of 40 to 70%, more preferably 65% is preferable. Do.

The carrier according to the present invention is made of a ceramic material capable of providing a high porosity, cordierite, silicon carbide, cordierite-α-alumina, silicon nitride, alumina-silica-magnesia, zircon silicate, silicate, magnesium silicate , Zircon, petalite, α-alumina, aluminosilicate, and the like, preferably made of cordierite. The catalytically active material is deposited in a plurality of pores formed in the carrier. Substances deposited inside the carrier are, but not limited to, three-component precious metals of Pt / Pd / Rh.

In addition, the present invention is a GPF (gasoline catalytic filter, 1100) is mounted to the rear end of the catalytic converter (100). Such GPFs can effectively remove particulate matter in addition to HC, CO and NOx in the exhaust gas. The GPF module is a structure similar to the wall-flow carrier, and the filter forming material may be metal, alloy or ceramic. When the exhaust gas passes through the filter, the particulate matter is trapped by the cell wall, and as a result, the particulate matter is removed from the gas component of the exhaust gas. However, in the honeycomb filter, the pressure loss due to the deposition of particulate matter increases with the use time. Therefore, when the pressure loss increases, the deposited particulate matter is removed by burning.

The optimal GPF 1100 according to the present invention is formed by dividing the plurality of through cells 1112 into the porous cell walls 1113, and directly injecting gasoline directly injected with both ends zigzag on the inlet and outlet sides 1115. In the catalyst filter for engine soot filtration, the first catalyst coating layer 1130 is formed in the first half of the cell wall surface of the inlet side opening cell, and the second catalyst layer 1130 'is formed in the second half inside the cell wall of the outlet side opening cell. It features. Such GPF may be implemented with other following features, but is not limited thereto.

The first catalyst coating amount coated on the first half of the cell wall surface of the present invention may be present in a larger amount than the second catalyst deposition amount deposited on the second half inside the cell wall. The first catalyst coating layer 1130 component and the second catalyst layer 1130 'may be the same or different. The first catalyst coating layer component and the second catalyst layer are characterized by supporting at least one species selected from the group consisting of noble metals of platinum group such as Pt, Rh, Pd, and the second catalyst layer 1130 'includes ceria and the like. It may further comprise an oxygen storage component (OSC). According to such a catalytic filter, a large amount of catalyst components exposed to the first half of the cell longitudinal direction (exhaust gas inlet side) promotes the oxidation and reduction reactions of the exhaust gas components, ie, HC, CO, and NOx. In the latter part through which particulate matter passes, a small amount of catalyst is formed inside the cell wall, thereby minimizing pressure loss due to exhaust gas. In addition, since a relatively small amount of the catalyst component is supported in the latter half of the cell wall, it is possible to prevent rapid temperature rise in the latter half of the cell wall in the regeneration operation by burning particulate matter, to eliminate the temperature longitudinal unevenness in the cell longitudinal direction, and to crack due to thermal stress. It can prevent occurrence.

The entire GPF 1100 structure cross section according to the present invention exhibits a checkerboard shape. The density of the cell is set at around 200 / inch ² and the thickness of the cell wall 1113 is set at about 0.3 mm. Exhaust gas entering the cell 1112 opened at the inlet end passes through the cell wall, and particulate matter is filtered out (trap, deposited), and only the remaining gas component is opened at the outlet end through the cell wall pores (pore). It is discharged through the outside. In the GPF structure according to the present invention, the first catalyst coating layer 1130 made of a platinum group element, other metal elements, oxides thereof, or the like is coated on the front surface of the inlet-side opening cell inner cell wall 1113 across the cell wall surface. A second catalyst layer 1130 ′ having the same or different composition as that of the catalyst is formed in the inner half of the cell wall of the side opening cell. In addition, the structure of the above structure is that a small amount of thin second catalyst layer 1130 'is formed in the latter half of the first catalyst layer 1130 in the first half of the cell longitudinal direction, and more specifically, the inlet-side opening cell in the first half of the cell longitudinal direction. A coating layer 1130 having a thickness L is formed on the cell wall surface of the cell wall, and a coating layer 1130 'having a thickness l is formed inside the outlet side cell wall in the latter half of the cell longitudinal direction, wherein the thickness L is larger than the thickness l. The structure of the above configuration can change the exhaust gas flow direction flowing into the filter cell. In other words, the exhaust gas entering the inlet opening cell flows into adjacent cells through the cell wall pores (30-70% porosity) of the latter oxide layer, which is relatively thinner than the thicker first half coating layer, resulting in a decrease in pressure loss to the engine. . The particulate matter accompanying the gaseous components in the exhaust gas is thus trapped in a large amount in the latter half cell wall in which the coating layer is formed relatively thinly compared to the first half, and there is a large amount of accumulated particulate matter in the second half over time. In this respect. The second catalyst layer 1130 ′ may include a large amount of OSC components as compared to the first catalyst layer 1130. This OSC component triggers the accumulation of cumulative particulate matter, prevents rapid temperature rise inside the latter cell wall due to relatively small amount of catalyst components, and eliminates cracking due to thermal stress by eliminating cell longitudinal temperature unevenness. Can be.

In the filter structure according to the present invention, the first and second catalyst compositions coated on the inlet-side opening cell inner cell wall surface and / or supported on the inner half of the outlet-side opening cell wall are known. For example, the catalyst layer can be formed in the following manner. The oxide powder or composite oxide powder is slurried together with a binder component such as alumina sol and water. The slurry is dipped in the inflow direction to coat the catalyst on the inner wall of the inlet-side opening cell 1112 of the catalytic filter structure, followed by drying and firing. Subsequently, the structure is dipped in the outflow direction, but this time, the catalyst is supported only on the second half cell wall inside the outflow cell of the catalytic filter structure, and then dried and calcined. As the catalyst component supported on the catalyst layer, a catalyst component capable of reducing NOx by catalytic reaction and promoting the oxidation of HC (hydrocarbon), CO, and particulate matter can be used. Preferably, the first and second catalyst layers are preferably loaded with one or more components selected from the group consisting of noble metals of platinum group such as Pt, Rh, Pd. However, as described above, the second catalyst layer 1130 ′ may include a large amount of OSC (oxygen storage material, eg, ceria) component as compared to the first catalyst layer 1130. The OSC component is a component for compensating for the exhaust gas of the GDI engine due to the ultra-lean combustion inevitably lacks the oxygen component, it can trigger the combustion of the deposited particulate matter.

Hereinafter, the three-way catalytic action and the particulate matter trapping action of the catalyst system according to the present invention will be briefly described. Exhaust gas is supplied to the cross section of the inlet side 150 of the catalytic converter 100 composed of the porous carrier of the catalyst system accommodated in the casing mounted on the GDI engine vehicle, and enters the exhaust gas passage 110a opened in the cross section. When the flowable exhaust gas passes through the porous partition wall 120, it is contacted with the three-way catalyst layer 300 to be converted into a harmless gas by a predetermined oxidation and reduction reaction. At this time, the exhaust gas vortex due to the plugging 130 occurs in each exhaust gas passage so that the exhaust gas has improved contact with the catalyst layer. Exhaust gas and converted harmless gas and particulate matter passing through the converter 100 enter the GPF inlet side. At this time, in contact with the first catalyst component 1130 exposed to the first half of the cell wall 1113, oxidation and reduction of the harmful HC and CO NOx gas proceed. Purified gaseous components and entrained particulate matter components collide with the lasting longitudinal point of plugging 1115 to reach the second half of the cell wall. Unlike the first half, a relatively thin coating layer 1130 ′ is formed in the second half of the cell wall, so that the gas component and the particulate matter component may easily pass through the second half cell wall pores. Therefore, a large amount of particulate matter accumulation is observed in the latter half compared to the first half. Meanwhile, while passing through the second half cell wall, components such as HC, CO, and / or NOx included in the gas are further oxidized, reduced, and purified by the second catalyst layer 1130 ', and the trapped particulate matter has a predetermined internal temperature of the filter. When the temperature is reached, it is complexed and combusted by the action of a noble metal catalyst such as Pt. In this case, since the second catalyst layer 1130 ′ includes a large amount of oxygen storage material, the particulate matter may be easily combusted in a GDI engine in which exhaust gas lacks an oxidizing material.

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.

Claims

A plurality of exhaust gas passages (110a, 110b) is formed divided into a porous partition wall 120, both ends of the plugging 130 in an in a stagged way on the inlet side 150 and outlet side 160 And a catalytic converter (100) in which a three-way catalyst (300) is deposited inside a wall-flow porous carrier partition wall.
The catalyst system for gasoline engine exhaust gas purification according to claim 1, wherein a gasoline catalytic filter (GPF) 1100 is further attached to the rear end of the catalytic converter (100).
The catalyst filter 1100 of claim 2, wherein the plurality of through-cells 1112 are formed by dividing the porous cell walls 1113, and both ends of the catalytic filter 1100 are formed in a stagged way on the inlet side and the outlet side. The plugging 1115 is performed, and the first catalyst coating layer 1130 is formed on the first half of the cell wall surface of the inlet-side opening cell, and the second catalyst layer 1130 'is formed on the inner half of the cell wall of the outlet-side opening cell. , Catalytic system for gasoline engine exhaust gas purification.
The catalyst for purifying gasoline engine exhaust gas according to claim 3, wherein the coating amount of the first catalyst coating layer 1130 coated on the first half of the cell wall surface is larger than the amount of the second catalyst layer 1130 'supported on the second half inside the cell wall. system.
The method according to claim 3 or 4, wherein the first catalyst coating layer 1130 and the second catalyst layer 1130 'carry at least one species selected from the group consisting of precious metals of platinum group such as Pt, Rh, and Pd. A catalyst system for purifying exhaust gas of a gasoline engine, characterized in that.
5. The catalyst system of claim 4, wherein the second catalyst layer (1130 ') further comprises an oxygen storage component (OSC).