Catalyst for purifying exhaust gases
US6217831A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 11, 1997 |
| Grant date | Apr 17, 2001 |
| Priority date | — |
| Expiry date | Aug 11, 2017 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02T10/12
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
A catalyst for purifying exhaust gases which aims to efficiently purify NO.sub.x in exhaust gases in oxygen-rich atmospheres whose oxygen concentrations are more than required for oxidizing CO and HC, and to attain improved NO.sub.x purifying performance after used for a long time. The catalyst includes, being arranged in an order from the upstream to the downstream of exhaust gas flow, a first catalyst 1 in which a noble metal catalyst 12 is loaded on a porous acidic support, a second catalyst 2 in which at least one kind of metal 22 selected from the group consisting of alkali metals, alkaline-earth metals, and rare earth metals is loaded on a porous support, and a third catalyst 3 in which a noble metal catalyst 32 is loaded on a porous support. Since SO.sub.2 is not adsorbed or oxidized by the first catalyst 1, SO.sub.2 is discharged downstream from the second catalyst 2 without generating sulfate. Therefore, since the NO.sub.x absorber is free from degradation even after used for a long time, the second catalyst 2 maintains high NO.sub.x adsorbing performance on the fuel-lean side, and the third catalyst 3 reduces NO.sub.x which are emitted from the second catalyst 2 on the st…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.