The rhodium (Rh) component in automotive three way catalysts (TWC) experiences severe thermal deactivation during fuel shutoff, an engine mode (e.g., at downhill coasting) used for enhancing fuel economy. In a subsequent switch to a slightly fuel rich condition,
in situ catalyst regeneration
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The rhodium (Rh) component in automotive three way catalysts (TWC) experiences severe thermal deactivation during fuel shutoff, an engine mode (e.g., at downhill coasting) used for enhancing fuel economy. In a subsequent switch to a slightly fuel rich condition,
in situ catalyst regeneration is accomplished by reduction with H
2 generated through steam reforming catalyzed by Rh
0 sites. The present work reports the effects of the two processes on the activity and properties of 0.5% Rh/Al
2O
3 and 0.5% Rh/Ce
xO
y-ZrO
2 (CZO) as model catalysts for Rh-TWC. A very brief introduction of three way catalysts and system considerations is also given. During simulated fuel shutoff, catalyst deactivation is accelerated with increasing aging temperature from 800 °C to 1050 °C. Rh on a CZO support experiences less deactivation and faster regeneration than Rh on Al
2O
3. Catalyst characterization techniques including BET surface area, CO chemisorption, TPR, and XPS measurements were applied to examine the roles of metal-support interactions in each catalyst system. For Rh/Al
2O
3, strong metal-support interactions with the formation of stable rhodium aluminate (Rh(AlO
2)
y) complex dominates in fuel shutoff, leading to more difficult catalyst regeneration. For Rh/CZO, Rh sites were partially oxidized to Rh
2O
3 and were relatively easy to be reduced to active Rh
0 during regeneration.
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