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Pd model catalysts: Effect of aging environment and lean redispersion

Paper ID Volume ID Publish Year Pages File Format Full-Text
45164 46401 2016 18 PDF Available
Title
Pd model catalysts: Effect of aging environment and lean redispersion
Abstract

•Different aging environments at 700 °C lead to different catalyst structures.•The aging environment severity ranking was: redox > rich-only >> lean-only.•Aged catalysts exhibited metal oxidation effects and support/additive interactions.•Exposure of aged catalysts to 700 °C air improved activity despite low Pd dispersion.•Multiple 700 °C air treatments were needed to restore Pd dispersion on CZO.

The performance of automotive three-way catalysts (TWC) deteriorates with time, temperature and aging environment. Engine control methods are needed to minimize the extent of catalyst deactivation and provide an environment capable of partially redispersing noble metal catalyst particles. In this study, palladium-based model powder catalysts on ceria-zirconia or alumina supports were exposed to three different exhaust compositions, lean-only, rich-only and redox, each at 700 °C for 16 h. Catalyst activity was determined by CO oxidation with the water gas shift (WGS) reaction and oxygen storage capacity (OSC) measurements to probe the contact between the noble metal and support at a given state of catalyst deterioration. Lean catalyst treatments at 550 °C and 700 °C were applied to determine the effect on measured Pd size and catalyst activity. The lean-only gas environment was above the PdO decomposition condition, yet showed slightly deteriorated catalyst activity from the fresh state. The rich-only and redox gas environments significantly deteriorated catalytic activity through a combination of metal oxidation state effects and support/additive interactions, both with various degrees of reversibility depending on lean treatment time and temperature. The insight gained from this work could be used to develop engine control and after treatment design strategies to track (or infer) the aging process on the vehicle, avoid severe aging modes and actively intervene at various points to regenerate the catalyst.

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Keywords
Palladium; Redispersion; TWC; Regeneration
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 183, April 2016, Pages 343–360
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us