Abstract
The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al2O3 catalysts. Comparing to γ-Al2O3, θ-Al2O3 can not only reduce the amount of occluded Rh but also better stabilize Rh during hydrothermal aging treatment. When the aging time was prolonged to 70 h, all the non-interacting Rh was transformed into strongly-interacting Rh and occluded Rh. The XPS results indicated that non- and strongly-interacting Rh might exist in the form of Rh/Rh3+ and Rh4+, respectively. CO-NO reaction was chosen as a probe reaction to research more information about non- and strongly-interacting Rh. The two Rh species had similar apparent activation energy (Eapp) of 170 kJ/mol, which indicated that non- and strongly-interacting Rh follow the same reaction path. The non-interacting Rh was removed from aged samples by the acid-treated method, and obtained results showed that only 2.5% and 4.0% non-interacting Rh was maintained in aged Rh/γ-Al2O3 and Rh/θ-Al2O3.
Highlights
Three-way catalysts (TWCs) are widely used for the exhaust treatment in gasolineengine powered vehicles since 1979 [1,2]
Ceria-zirconia solid solutions are a kind of material with excellent oxygen storage capacity (OSC), used in the exhaust gas treatment of gasoline vehicles, and used as the support of Rh-based TWCs according to published information [13]
The aged Rh/θ-Al2 O3 catalyst showed higher NO reduction activity at low temperature owing to the weaker interaction of θ-phase with Rh
Summary
Three-way catalysts (TWCs) are widely used for the exhaust treatment in gasolineengine powered vehicles since 1979 [1,2]. Γ-Al2 O3 , with high surface area, is usually used as Rh-based catalyst support. The low surface area of α-Al2 O3 limits the usage as catalyst supports, but some researchers [11,12] synthesized α-Al2 O3 with a high surface area (>140 m2 /g), which will allow α-Al2 O3 to play a more important role in catalyst supports in the future. Ceria-zirconia solid solutions are a kind of material with excellent oxygen storage capacity (OSC), used in the exhaust gas treatment of gasoline vehicles, and used as the support of Rh-based TWCs according to published information [13]. Several researches indicated that metal phosphate supports (such as ZrP2 O7 , AlPO4 ) show good performance in stabilizing
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