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EP-4737003-A1 - EXHAUST GAS PURIFICATION CATALYST DEVICE FOR GASOLINE ENGINE

EP4737003A1EP 4737003 A1EP4737003 A1EP 4737003A1EP-4737003-A1

Abstract

Provided is an exhaust gas purification catalyst device for a gasoline engine. The exhaust gas purification catalyst device has: a substrate; an NH 3 adsorption layer containing a proton-type zeolite; and a PGM layer containing a catalytic noble metal selected from among Pd, Pt, and Rh. The proton-type zeolite contained in the NH 3 adsorption layer has an average pore diameter of 0.60 nm or less. The NH 3 adsorption layer is disposed closer to the substrate than the PGM layer and is disposed at a length shorter than the entire length of the substrate from the upstream end of the substrate in the exhaust gas flow direction. The PGM layer is disposed at a length longer than the NH 3 adsorption layer from the upstream end of the substrate in the exhaust gas flow direction. The PGM layer has a first PGM layer containing a catalytic noble metal selected from among Pd and Pt, and a second PGM layer containing Rh. The first PGM layer contains ceria.

Inventors

  • TAKASU, Ryosuke
  • SUGAWARA, KO
  • SHIRAYAMA, Yodai
  • ITO, MASAYA
  • YAMAZAKI, YUYA

Assignees

  • CATALER CORPORATION

Dates

Publication Date
20260506
Application Date
20240528

Claims (12)

  1. An exhaust gas purification catalyst device for a gasoline engine, comprising: a substrate, an NH 3 adsorption layer containing proton-type zeolite, and a PGM layer containing a noble metal catalyst selected from among Pd, Pt and Rh, wherein the proton-type zeolite in the NH 3 adsorption layer has a mean pore size of 0.60 nm or smaller, the NH 3 adsorption layer is disposed further toward the substrate side than the PGM layer, and is disposed at a location with a shorter length than the full length of the substrate, from the upstream end of the exhaust gas flow on the substrate, and the PGM layer is disposed at a location with a longer length than the NH 3 adsorption layer, from the upstream end of the exhaust gas flow on the substrate, the PGM layer comprising a first PGM layer containing a noble metal catalyst selected from among Pd and Pt, and a second PGM layer containing Rh, and the first PGM layer comprising ceria.
  2. The exhaust gas purification catalyst device according to claim 1, wherein the proton-type zeolite comprises a small-ring proton-type zeolite in which the basic skeleton is composed entirely of rings selected from among 4, 6 and 8-membered rings, at 80 mass% or greater with respect to the total mass of the proton-type zeolite.
  3. The exhaust gas purification catalyst device according to claim 2, wherein the small-ring proton-type zeolite is one or more selected from among H-ACO, H-AEI, H-AEN, H-AFN, H-AFT, AFX, H-ANA, H-APC, H-APD, H-ATT, H-CDO, H-CHA, H-DDR, H-DFT, H-EAB, H-EDI, H-EPI, H-ERI, H-GIS, H-GOO, H-IHW, H-ITE, H-ITW, H-LEV, H-LTA, H-KFI, H-MER, H-MON, H-NSI, H-OWE, H-PAU, H-PHI, H-RHO, H-RTH, H-SAT, H-SAV, H-SIV, H-THO, H-TSC, H-UEI, H-UFI, H-VNI, H-YUG and H-ZON.
  4. The exhaust gas purification catalyst device according to claim 1, wherein the amount of ceria in the first PGM layer is 4.0 g/L or greater and 45.0 g/L or lower as the ceria mass per 1 L of substrate capacity.
  5. The exhaust gas purification catalyst device according to claim 2, wherein the amount of ceria in the first PGM layer is 4.0 g/L or greater and 45.0 g/L or lower as the ceria mass per 1 L of substrate capacity.
  6. The exhaust gas purification catalyst device according to any one of claims 1 to 5, wherein the first PGM layer is the uppermost layer in direct contact with the exhaust gas across a length of at least 10% of the full length of the substrate from the upstream end of the exhaust gas flow on the substrate, and the second PGM layer is the uppermost layer in direct contact with the exhaust gas across a length of at least 20% of the full length of the substrate from the downstream end of the exhaust gas flow on the substrate.
  7. The exhaust gas purification catalyst device according to claim 6, wherein the first PGM layer is disposed at a length of greater than 70% of the full length of the substrate from the upstream end of the exhaust gas flow on the substrate.
  8. The exhaust gas purification catalyst device according to claim 6, wherein the second PGM layer is disposed at a length of 20% or greater and 90% or less of the full length of the substrate from the downstream end of the exhaust gas flow on the substrate.
  9. The exhaust gas purification catalyst device according to claim 6, wherein the first PGM layer is disposed at a length of greater than 70% of the full length of the substrate from the upstream end of the exhaust gas flow on the substrate, the second PGM layer is disposed at a length of 30% or greater and 90% or less of the full length of the substrate from the downstream end of the exhaust gas flow on the substrate, the total of the length of the first PGM layer and the length of the second PGM layer exceeds the full length of the substrate, and the second PGM layer is the uppermost layer in direct contact with the exhaust gas in the region where the first PGM layer and the second PGM layer overlap.
  10. An exhaust gas purification method which comprises disposing an exhaust gas purification catalyst device according to any one of claims 1 to 5 in an exhaust system of a gasoline engine, to purify exhaust gas that has been emitted from the gasoline engine.
  11. An exhaust gas purification catalyst system for a gasoline engine, comprising: an upstream end purification catalyst device disposed at the upstream end of the exhaust gas flow in the exhaust system of the gasoline engine, and a downstream end purification catalyst device disposed at the downstream end of the exhaust gas flow in the exhaust system, wherein the upstream end purification catalyst device is a three-way exhaust gas purification catalyst device comprising a platinum group noble metal catalyst, and the downstream end purification catalyst device is an exhaust gas purification catalyst device according to any one of claims 1 to 5.
  12. An exhaust gas purification method which comprises disposing an exhaust gas purification catalyst system according to claim 11 in an exhaust system of a gasoline engine, to purify exhaust gas that has been emitted from the gasoline engine.

Description

FIELD The present invention relates to an exhaust gas purification catalyst device for a gasoline engine. BACKGROUND Exhaust gas emitted from gasoline engines includes HC (hydrocarbon), CO (carbon monoxide) and NOx (nitrogen oxide) gases, which are discharged into the atmosphere after having been purified by an exhaust gas purification catalyst device disposed in the exhaust system of the engine. Three-way catalysts are known, as exhaust gas purification catalyst devices that can purify all three gases, HC, CO and NOx. For example, PTL 1 describes an exhaust gas purification catalyst comprising an alumina layer with a multilayer structure on a substrate, with rhodium supported on the inner alumina layer, and with at least one from among platinum and palladium supported on the alumina layer on the front side. [CITATION LIST] [PATENT LITERATURE] [PTL 1] Japanese Unexamined Patent Publication SHO No. 63-039633 SUMMARY [TECHNICAL PROBLEM] When a mixture of gasoline and air is in an enriched state in a gasoline engine, reduction of NOx by a three-way catalyst tends to produce ammonia (NH3). A greater amount of ammonia tends to be generated during engine start-up. The produced ammonia can be purified with a three-way catalyst. However, in the low temperature state before the catalyst is warmed, such as during engine start-up, a portion of the produced ammonia is often emitted without being purified. The EU Vehicle Emission Standard "Euro7" sets restrictions for ammonia emissions, not only for large vehicles but also for passenger vehicles and vans. The present invention has been completed in light of these circumstances. It is an object of the present invention to provide an exhaust gas purification catalyst device for a gasoline engine with reduced ammonia emissions even in a low-temperature state such as during engine start-up. [SOLUTION TO PROBLEM] The present invention is as follows. <Aspect 1> An exhaust gas purification catalyst device for a gasoline engine, comprising: a substrate,an NH3 adsorption layer containing proton-type zeolite, anda PGM layer containing a noble metal catalyst selected from among Pd, Pt and Rh, whereinthe proton-type zeolite in the NH3 adsorption layer has a mean pore size of 0.60 nm or smaller,the NH3 adsorption layeris disposed further toward the substrate side than the PGM layer, andis disposed at a location with a shorter length than the full length of the substrate, from the upstream end of the exhaust gas flow on the substrate, andthe PGM layer is disposed at a location with a longer length than the NH3 adsorption layer, from the upstream end of the exhaust gas flow on the substrate,the PGM layer comprising a first PGM layer containing a noble metal catalyst selected from among Pd and Pt, and a second PGM layer containing Rh, andthe first PGM layer comprising ceria. <Aspect 2> The exhaust gas purification catalyst device according to aspect 1, wherein the proton-type zeolite comprises a small-ring proton-type zeolite in which the basic skeleton is composed entirely of rings selected from among 4, 6 and 8-membered rings, at 80 mass% or greater with respect to the total mass of the proton-type zeolite. <Aspect 3> The exhaust gas purification catalyst device according to aspect 2, wherein the small-ring proton-type zeolite is one or more selected from among H-ACO, H-AEI, H-AEN, H-AFN, H-AFT, AFX, H-ANA, H-APC, H-APD, H-ATT, H-CDO, H-CHA, H-DDR, H-DFT, H-EAB, H-EDI, H-EPI, H-ERI, H-GIS, H-GOO, H-IHW, H-ITE, H-ITW, H-LEV, H-LTA, H-KFI, H-MER, H-MON, H-NSI, H-OWE, H-PAU, H-PHI, H-RHO, H-RTH, H-SAT, H-SAV, H-SIV, H-THO, H-TSC, H-UEI, H-UFI, H-VNI, H-YUG and H-ZON. <Aspect 4> The exhaust gas purification catalyst device according to aspect 1, wherein the amount of ceria in the first PGM layer is 4.0 g/L or greater and 45.0 g/L or lower as the ceria mass per 1 L of substrate capacity. <Aspect 5> The exhaust gas purification catalyst device according to aspect 2, wherein the amount of ceria in the first PGM layer is 4.0 g/L or greater and 45.0 g/L or lower as the ceria mass per 1 L of substrate capacity. <Aspect 6> The exhaust gas purification catalyst device according to any one of aspects 1 to 5, wherein the first PGM layer is the uppermost layer in direct contact with the exhaust gas across a length of at least 10% of the full length of the substrate from the upstream end of the exhaust gas flow on the substrate, andthe second PGM layer is the uppermost layer in direct contact with the exhaust gas across a length of at least 20% of the full length of the substrate from the downstream end of the exhaust gas flow on the substrate. <Aspect 7> The exhaust gas purification catalyst device according to aspect 6, wherein the first PGM layer is disposed at a length of greater than 70% of the full length of the substrate from the upstream end of the exhaust gas flow on the substrate. <Aspect 8> The exhaust gas purification catalyst device according to aspect 6, wherein the second PGM layer is