KR20120054447A - Perovskite-based catalyst with improved sulfur resistance - Google Patents

Perovskite-based catalyst with improved sulfur resistance Download PDF

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KR20120054447A
KR20120054447A KR1020100115822A KR20100115822A KR20120054447A KR 20120054447 A KR20120054447 A KR 20120054447A KR 1020100115822 A KR1020100115822 A KR 1020100115822A KR 20100115822 A KR20100115822 A KR 20100115822A KR 20120054447 A KR20120054447 A KR 20120054447A
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catalyst
perovskite
oxide
zro
particles
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KR1020100115822A
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Korean (ko)
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정창호
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현대자동차주식회사
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals

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Abstract

PURPOSE: A perovskite-based catalyst with improved sulfur resistance is provided to shorten rich spike time and to reduce the loss of fuel by decomposing exhaust gas components based on hydrogen generating materials and smoothly supplying generated hydrogen. CONSTITUTION: A perovskite-based catalyst includes one or more of a catalyst support supporting perovskite particles, an oxygen absorbing and releasing material, a complex oxide support, and a hydrogen generating material. The oxygen absorbing and releasing material is composed of Ce oxide, Si oxide, sulfur oxide, or the mixture of the same or is composed of Ti/ZrO_2, Hf/ZrO_2, or the mixture of the same. The hydrogen generating material is composed of Rh/ZrO_2 particles, Pt/CeO_2 particles, or the mixture of the same. The catalyst support is one or the mixture of two or more selected from a group including alumina, ceria, titania, magnesia, silica, and zirconia.

Description

Perovskite-based catalyst with improved sulfur resistance

The present invention relates to a perovskite-based catalyst used for automobile engine purification, and more particularly, to suppress the growth of sulfur poisoning particles and to promote decomposition of the sulfur poisoning particles generated, thereby reducing the energy consumed for sulfur poisoning regeneration. It relates to a perovskite catalyst that can improve the.

Hazardous emissions from automobiles include hydrocarbons, carbon monoxide and nitrogen oxides (NO x ). Among these, nitrogen oxides (NO x ) are representative harmful emissions, and are known as one of the main causes of environmental problems such as acid rain and smog, and when released into the atmosphere, they are oxidized to form various nitrogen oxides such as nitrogen dioxide (NO 2 ). .

In order to prevent such nitrogen oxide diseases and environmental problems, Europe has declared strong regulations that lead to EURO III, IV, V, VI, etc., and in the United States, the legislation of air regulations such as LEV II is applied.

Three-way catalysts, which have been used to remove nitrogen oxides from automobile engines, can effectively remove nitrogen oxides from fule-lean exhaust gas from lean burn engines or diesel engines. it became the nO x storing catalyst is a nO x storage-reduction characteristics in the reinforcing properties of an existing three-way catalysts in the 1990's it appeared to solve this problem. (Catalysis Today 96, 2004, 43-52)

Storing catalyst technology, such as an excess of oxygen (fuel-lean) adsorbing the NO x under the condition, the storage was added to the reducing gas is rich conditions, that is, the NO x storing and at the fuel oversupply condition (fuel-rich) nitrogen and carbon dioxide, The technology of converting to harmless materials. The occlusion type catalyst technology not only enables normal operation even under conditions of high oxygen and lean gas, but also has an advantage that it can be used with little change in the exhaust system used in the three-way catalyst.

Conventional occlusion catalysts allow nitrogen monoxide to be oxidized to nitrogen dioxide through a noble metal catalyst such as platinum (Pt) in a fuel lean condition to be chemically adsorbed to adsorption components on the surface of the catalyst in the form of nitrogen compounds, and reducing agents such as hydrocarbons, carbon monoxide and hydrogen. It is an oxidation / reduction catalyst for reducing nitrogen and carbon dioxide by using a noble metal catalyst such as rhodium in a sufficient supply of.

However, these catalysts were economically disadvantaged surface because it contains a lot of precious metals such as platinum, rhodium, a problem to be improved, such as the problem of catalyst poisoning caused by SO x is found there were a lot of efforts to resolve it.

For example, Republic of Korea Patent No. 10-0892520 proposed a catalyst containing an active material such as ruthenium, potassium as a catalyst that can replace precious metals such as platinum, Korean Patent No. 10-2009-0044925 A catalyst comprising together palladium and potassium has been proposed.

In addition, Korean Patent Laid-Open Publication No. 1998-077049 discloses the use of a perovskite catalyst as a catalyst for decomposing nitrogen oxides discharged from a diesel engine.

Korean Patent Laid-Open Publication No. 10-2009-0119610 proposes that the problem of catalyst poisoning by SO x can be solved by using a metal titanate-based carrier as a carrier for the NO x removal catalyst.

Perovskite is a metal oxide generally having the chemical structure of ABO 3 and is widely applied in the field of electronic materials. In particular, the composite perovskite structure represented by AB ' x B " 1- x O 3 has many uses in many fields. Has been attracting attention.

Because perovskite materials can accommodate large amounts of oxygen vacancies, in some cases transition elements can be introduced into the lattice, and these transition elements exhibit multiple valences resulting in high proton conductivity. The use of such a property has been studied as a conventional NO x storage catalyst and has been in the spotlight as a material capable of replacing Pt as a NO x storage catalyst.

However, in the case of a catalyst using a conventional perovskite material, a substance such as barium sulfate is inevitably generated by a reaction between SO x present in the exhaust gas and an alkali metal oxide (eg, barium oxide) present in the storage catalyst. These sulfates are very stable and do not easily desorb even in a high temperature reducing atmosphere. For this reason, desulfurization regeneration of the catalyst usually requires a high temperature of 700 ° C. or higher, and a rich spike time has to be lengthened for such high temperature desulfurization.

The present invention was derived to solve the problems of the prior art as described above, by increasing the reaction temperature to increase the catalyst regeneration efficiency, suppress the growth of sulfur poisoning particles, and decomposes the sulfur poisoning particles themselves, rich spike (storage) It is an object of the present invention to provide a perovskite catalyst for exhaust gas post-treatment purification that can reduce energy consumption by reducing the time of operating the engine in fuel-rich for NO x regeneration and sulfur poisoning regeneration.

The present invention to achieve the above object

(1) On the catalyst support which supported the perovskite particle,

(2) an oxygen storage and releasing material consisting of Ce oxide, Si oxide, sulfur oxide or mixtures thereof;

(3) a composite oxide support consisting of Ti / ZrO 2 , Hf / ZrO 2, or mixtures thereof; And

(4) Provided is a perovskite catalyst comprising any one or more of hydrogen generating materials consisting of Rh / ZrO 2 particles, Pt / CeO 2 particles, or mixtures thereof.

In the present invention, the catalyst carrier is one or two selected from the group consisting of alumina (Al 2 O 3 ), ceria (CeO 2 ), titania (TiO 2 ), silica (SiO 2 ), zirconia (ZrO 2 ) It may be a mixture of the above, each carrier may contain up to 20wt% additives such as La, Y, Hf and various rare earths. Preferred examples include a total of 5 to 15 wt% of La, Ti, Y, Hf and rare earths (Pr, Nd, Eu, Er) for strengthening physical properties in the form of alumina, ceria and zirconia alone or in a mixture.

In the present invention, the Ce oxide is a composite oxide containing 10 wt% or more of CeO 2 , the silicon oxide is L 10 Si 6 O 27 (L: lanthanide element), the sulfur oxide is M 2 O 2 SO 4 It is preferable that it is (M: rare earth element).

In the present invention, (3) In the Ti / ZrO 2 particles or the Hf / ZrO 2 particles (composite oxide support), Ti or Hf is preferably 1 to 50% by weight relative to Zr. Each support may further include up to 20 wt% of additives such as La, Y, Hf and various rare earths. A preferred example is a form in which 5-15 wt% of La, Ti, Y, Hf and rare earths (Pr, Nd, Eu, Er) for strengthening physical properties are included in the form of these composite oxide supports alone or in a mixture.

In the present invention, one or more selected from the group consisting of Pt, Pd and Rh on the composite oxide support of (3) may be further included in a content of 10 ~ 60g / ft 3 .

In the present invention, the specific surface area of the catalyst carrier is not particularly limited but is preferably maintained in the range of 40 to 350 m 2 / g for effective catalytic activity.

As described above, the engine aftertreatment catalyst according to the present invention can increase the catalyst temperature by the heat of reaction by oxygen absorbing material occludes oxygen in the lean region and then releases it in the rich spike stage, thereby improving the regeneration efficiency. The oxide support is located adjacent to the perovskite to inhibit the growth of sulfur poisoning particles, and to facilitate the supply of hydrogen (a powerful reducing agent for sulfur poisoning) generated by the hydrogen generating substance decomposing the exhaust gas components. By decomposing the poisoned particles themselves, the rich spike time can be drastically reduced, which significantly reduces fuel loss.

1 is a schematic diagram showing an example of the configuration of a perovskite catalyst according to the present invention.
2 is a schematic diagram showing catalyst poisoning by sulfur components in a lean running state in the perovskite catalyst according to the present invention.
3 is a schematic diagram showing catalyst regeneration at the rich spike stage in the perovskite catalyst according to the present invention.
Figure 4 is a schematic diagram showing the principle of generating oxygen by the oxygen storage material of the perovskite catalyst according to the present invention.
5 is a schematic diagram showing that sulfur poisoning particles continuously rise when the composite oxide support of component (3) according to the present invention is not included.
FIG. 6 shows sulfur by a composite oxide support (Ti x Pr y Zr 1 -x- y O 2 , 0 ≦ x <1, 0 ≦ y <1) as a component (3) in the perovskite catalyst according to the present invention. It is a schematic diagram which shows that growth of poisoning particle is suppressed.

Hereinafter, the present invention will be described in more detail.

The present invention relates to an automotive engine aftertreatment catalyst comprising a perovskite material, comprising: (1) a catalyst support supporting perovskite particles, (2) an oxygen storage and releasing material; (3) a composite oxide support; And (4) a hydrogen generating material. In the present invention, the effect is best when all of the components (2) to (4) are included in the component (1), but only one or more of the components (2) to (4) are included in the scope of the present invention. Included in

The catalyst carrier serving as a support in the present invention may be used alone alumina, or may be used in the form of a complex oxide with other metal oxides such as CeO 2 , ZrO 2, and the like. In addition, it may include La, Y, Hf and rare earths (Pr, Nd, Eu, Er) to improve the physical properties while containing more than 90wt% of alumina, ceria, zirconia.

The catalyst carrier is preferably used in the range of 65 to 95% by weight based on the total weight of the catalyst to maintain thermal stability and catalyst activity. In addition, it is preferable that its BET specific surface area likewise maintain a range of 40-350 m 2 / g for maintaining thermal stability and catalytic activity.

In the present invention, the perovskite material is a composite oxide having a chemical structure of ABO 3 , which is advantageous in terms of economical efficiency because it can reduce the amount of precious metal used in the existing engine after-treatment catalyst. However, perovskite materials are easily poisoned by sulfur, such as SOx, and desulfurization requires high energy consumption for catalyst regeneration. This high temperature desulfurization process causes the fuel economy of the automobile engine to be reduced.

The present invention starts from the concept of raising the reaction temperature, inhibiting the growth of sulfur poisoning particles, and decomposing sulfur poisoning particles themselves to reduce energy consumption.

In the present invention, the role of the reaction temperature rise is performed by the oxygen storage material. In the present invention, the oxygen absorbing material absorbs oxygen in the lean region and increases the reaction heat by exotherm as oxygen is released from the rich spike region. Examples of the oxygen storage material in the present invention is in the form of silicon oxide, sulfur oxide or a mixture thereof containing Ce, specifically, the silicon oxide is L 10 Si 6 O 27 (L: lanthanide element), the sulfur oxide is M It is preferably 2 O 2 SO 4 (M: rare earth element), but is not limited thereto. As can be seen in Figure 4, rare earth metals such as Ce, Pr, etc. can change the number (oxidation number) of oxygen coordinated trivalent (3+), tetravalent (4+), oxygen in the lattice on this principle Atoms can be released / occluded. In the rich spike stage, HC and CO are enriched in the exhaust gas. At this time, lattice oxygen atoms are released to oxidize HC and CO, thereby raising the catalyst temperature and promoting sulfur poisoning decomposition.

In the present invention, the role of inhibiting the growth of sulfur poisoning particles is performed by the composite oxide support. In the present invention, the composite oxide support is composed of Ti / ZrO 2 , Hf / ZrO 2, or a mixture thereof, and the Ti and Hf are present in a dispersed form on the ZrO 2 support. In the present invention, the sulfur poisoning particles formed near the perovskite particles by the Ti and Hf are suppressed from growth, and the regeneration temperature may be lowered due to the catalytic action of the Ti and Hf components during regeneration.

In the present invention, the hydrogen generating material plays a role of decomposing the sulfur poisoning particle itself. The hydrogen generating material is preferably in a state in which Rh is highly dispersed in ZrO 2 particles or in a state in which Pt is highly dispersed in CeO 2 particles. In the present invention, the hydrogen generating material itself does not contain hydrogen, but serves to facilitate the generation of hydrogen by promoting the reaction of the reducing gas in the rich spike step.

That is, in the case of Pt / CeO 2 , it promotes the reaction of CO + H 2 O → CO 2 + H 2 ,

In the case of Rh / ZrO 2 , C 3 H 6 + 6H 2 O → 3CO 2 + 9H 2 promotes the reaction.

The poisoned component in the form of BaSO 4 is produced by the hydrogen produced as above.

The BaSO 4 + 2H 2 → Ba + SO 2 ( gas) + 2H BaSO 4 by the reaction of the 2 O is decomposed is reproduced Ba.

By the above process, there is an advantage of the present invention that sulfur poisoning particles can be decomposed by directly generating H 2 on a catalyst rather than an external supply.

Due to the above characteristics, the perovskite catalyst according to the present invention can reduce the rich spike time by more than 10% compared to the case of using the conventional perovskite catalyst when used for automobile engine purification. have.

Claims (5)

(1) On the catalyst support which supported the perovskite particle,
(2) an oxygen storage and releasing material consisting of Ce oxide, Si oxide, sulfur oxide or mixtures thereof;
(3) a composite oxide support consisting of Ti / ZrO 2 , Hf / ZrO 2, or mixtures thereof; And
(4) A perovskite catalyst comprising at least one of a hydrogen generating substance consisting of Rh / ZrO 2 particles, Pt / CeO 2 particles, or a mixture thereof.
The method according to claim 1,
The catalyst support is one or two selected from the group consisting of alumina (Al 2 O 3 ), ceria (CeO 2 ), titania (TiO 2 ), magnesia (MnO 2 ), silica (SiO 2 ) and zirconia (ZrO 2 ). Perovskite-based catalyst, characterized in that a mixture of more than one species.
The method according to claim 1,
The Ce oxide is a composite oxide containing 10 wt% or more of CeO 2 , the silicon oxide is L 10 Si 6 O 27 (L: lanthanide element), and the sulfur oxide is M 2 O 2 SO 4 (M: rare earth element) Perovskite catalyst, characterized in that.
The perovskite catalyst of claim 1, wherein in the Ti / ZrO 2 particles or the Hf / ZrO 2 particles, Ti or Hf is 1 to 50% by weight relative to Zr.
The method according to claim 1,
Perovskite-based catalyst, characterized in that the at least one selected from the group consisting of Pt, Pd and Rh on the composite oxide support of (3) further comprises a content of 10 ~ 60g / ft 3 .
KR1020100115822A 2010-11-19 2010-11-19 Perovskite-based catalyst with improved sulfur resistance KR20120054447A (en)

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