Effects of Rapid High Temperature Cyclic Aging on a Fully-Formulated Lean NOx Trap Catalyst

Journal Article · Thu Jan 01 04:00:00 EST 2009 · Journal of the Society of Automotive Engineers of Japan

OSTI ID:962630

Ottinger, Nathan ^[1]; Nguyen, Ke ^[1]; Bunting, Bruce G ^[2]; Toops, Todd J ^[2]; Howe, Janet E ^[2]

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1. University of Tennessee, Knoxville (UTK)
2. ORNL

In this study, high-temperature deactivation of a fully-formulated lean NOx trap (LNT) is investigated with an accelerated aging protocol where accelerated aging is accomplished by rapid temperature cycling and by higher temperatures. Thermal aging is carried out in a bench-flow reactor at nominal temperatures of 700, 800, 900, and 1000 C using an aging cycle consisting of a 130s lean-phase and a 50s rich-phase. After a prescribed number of lean/rich aging cycles, the NOx conversion of the aged LNT is evaluated at 200, 300, and 400 C. The NOx performance is obtained at a GHSV of 30,000 h-1 using an evaluation cycle consisting of a 60s lean-phase and 5s rich-phase. The effects of aging on the LNT washcoat are determined with EPMA, XRD, STEM/EDS, and BET. Aging at 700 and 800 C has a minimal effect on LNT performance and material properties. However, at aging temperatures of 900 and 1000 C reduction in surface area and sintering of PGM particles are observed and result in a drastic reduction in NOx conversion. Additionally, after aging at 900 C and 1000 C the NOx storage medium, BaCO3, is no longer visible in the XRD patterns, even though a Ba-phase identified by EPMA still exists in all aged samples. BaAl2O4 is not identified at any aging temperatures; possibly due to stabilization effects provided by washcoat additives present in this particular LNT.

• Research Organization: Oak Ridge National Laboratory (ORNL); High Temperature Materials Laboratory
• Sponsoring Organization: EE USDOE - Office of Energy Efficiency and Renewable Energy (EE)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 962630
• Journal Information: Journal of the Society of Automotive Engineers of Japan, Journal Name: Journal of the Society of Automotive Engineers of Japan
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
54 ENVIRONMENTAL SCIENCES
AGING
AIR POLLUTION CONTROL
CATALYSTS
DEACTIVATION
NITROGEN OXIDES
PERFORMANCE
TEMPERATURE DEPENDENCE
THERMAL CYCLING