Deactivation of Accelerated Engine-Aged and Field-Aged Fe-Zeolite SCR Catalysts

Journal Article · Fri Jan 01 04:00:00 EST 2010 · Catalysis Today

DOI:https://doi.org/10.1016/j.cattod.2010.01.019· OSTI ID:981420

Toops, Todd J ^[1]; Nguyen, Ke ^[2]; Foster, Adam ^[2]; Bunting, Bruce G ^[1]; Jiao, Jian ^[1]

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

A single-cylinder diesel engine with an emissions control system - diesel oxidation catalyst (DOC), Fe-zeolite selective catalytic reduction (SCR) catalyst, and diesel particulate filter (DPF) - was used to perform accelerated thermal aging of the SCR catalyst. Cyclic aging is performed at SCR inlet temperatures of 650, 750 and 850 degrees C for up to 50 aging cycles. To assess the validity of the implemented accelerated thermal aging protocol, a field-aged SCR catalyst of similar formulation was also evaluated. The monoliths were cut into sections and evaluated for NO{sub x} performance in a bench-flow reactor. While the rear section of both the field-aged and the accelerated engine-aged SCR catalysts maintained high NO{sub x}conversion, 75-80% at 400 degrees C, the front section exhibited a drastic decrease to only 20-35% at 400 degrees C. This two-tiered deactivation was also observed for field-aged samples that were analyzed in this study. To understand the observed performance changes, thorough materials characterization was performed which revealed two primary degradation mechanisms. The first mechanism is a general Fe-zeolite deterioration which led to surface area losses, dealumination of the zeolite, and Fe{sub 2}O{sub 3} crystal growth. This degradation accelerated above 750 degrees C, and the effects were generally more severe in the front of the catalyst. The second deactivation mechanism is linked to trace levels of Pt that are suspected to be volatizing from the DOC and depositing on the front section of the SCR catalyst. Chemical evidence of this can be seen in the high levels of NH{sub 3} oxidation (80% conversion at 400 degrees C), which coincides with the decrease in performance.

• 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: 981420
• Journal Information: Catalysis Today, Journal Name: Catalysis Today Journal Issue: 3-4 Vol. 151; ISSN CATTEA; ISSN 0920-5861
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
AGING
CATALYSTS
CONTROL SYSTEMS
CONVERSION
CRYSTAL GROWTH
DEACTIVATION
DIESEL ENGINES
FILTERS
MATERIALS
OXIDATION
PARTICULATES
PERFORMANCE
SELECTIVE CATALYTIC REDUCTION