Cause and Effect of Reversible Deactivation of Diesel Oxidation Catalysts

Paper #:
  • 2014-01-1518

Published:
  • 2014-04-01
DOI:
  • 10.4271/2014-01-1518
Citation:
Ahari, H., Zammit, M., Cattani, L., Jacques, J. et al., "Cause and Effect of Reversible Deactivation of Diesel Oxidation Catalysts," SAE Technical Paper 2014-01-1518, 2014, doi:10.4271/2014-01-1518.
Pages:
8
Abstract:
To meet TierII/LEVII emissions standards, light duty diesel (LDD) vehicles require high conversion efficiencies from the Aftertreatment Systems (ATS) for the removal of both Hydrocarbon (HC) and Nitrogen Oxide (NOx) species. The most populous configuration for LDD ATS have the Selective Catalytic Reduction (SCR) catalyst positioned on the vehicle behind the close coupled Diesel Oxidation Catalyst (DOC) and Catalyzed Diesel Particulate Filter (CDPF). This SCR position may require active heating measures which rely on the DOC/CDPF to provide heat through the combustion of HC and CO in the exhaust. Although DOCs are always impacted by their aging conditions, some aging conditions are shown to be both reversible and irreversible. Under continuous, high speed and high mileage conditions such as experienced in a modified Standard Road Cycle (SRC) or as it is better known, the High Speed Cycle (HSC), it is shown that the DOC's activity can deteriorate initially but significantly recover over repeated FTP-75 test cycles on fully aged catalysts. The stable, lean and hot environment experienced during these durability cycles, create a temporary condition on the PGM sites that can be reversed when the system is exposed to cooler, transient environment in the presence of additional reductant. This mechanism is similar to that experienced with lean NOx traps (LNT) under NOx regeneration conditions.1,2 Mechanisms of shifting PGM oxidation states have been observed in PdO containing methane oxidation when exposed to various thermal conditions3, 4, 5, 6. This phenomenon is successfully recreated under controlled laboratory settings utilizing both oven and engine aging methods. Furthermore, the performance of the aged catalyst was evaluated to highlight the re-activation of the catalyst for HC/CO and NO oxidation.The advantage of using the HSC cycle is self-evident. The cycle's high speed allows the required 120k miles to be reached at a significantly shorter period of time, realizing substantial savings in time and program development costs. The harsher thermal environment of the cycle creates a worst case aging scenario that is discussed in this paper.
Access
Now
SAE MOBILUS Subscriber? You may already have access.
Buy
Select
Price
List
Download
$27.00
Mail
$27.00
Members save up to 40% off list price.
Share
HTML for Linking to Page
Page URL

Related Items

Technical Paper / Journal Article
2010-04-12
Article
2016-09-06
Training / Education
2017-12-18
Article
2016-08-24