Roles of Acid Sites on Pt/H-ZSM5 Catalyst in Catalytic
Oxidation of Diesel soot
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Abstract
Pt/H-ZSM5 and Pt/Al<sub>2</sub>O<sub>3</sub> with similar surface
Pt particle sizes and chemical states were prepared by incipient wetness
impregnation as catalysts for soot oxidation. Pt/H-ZSM5 exhibits obviously
higher activities in both O<sub>2</sub> and NO + O<sub>2</sub> than
Pt/Al<sub>2</sub>O<sub>3</sub>. On the basis of the results obtained
with in situ DRIFT and other structural and surface property characterizations,
the high catalytic activity of Pt/H-ZSM5 is currently attributed to
two main factors. First, the acidic H-ZSM5 support inhibits NO<sub>2</sub> adsorption on the catalyst, leading to a preferential adsorption
of NO<sub>2</sub> on the surface of soot and providing more chances
for NO<sub>2</sub>–soot reactions. Second, the strong acid
sites on the surface of Pt/H-ZSM5 can participate in the catalytic
formation and decomposition of surface oxygenated complexes. Consequently,
a high catalytic efficiency for soot oxidation is achieved on the
Pt/H-ZSM5 catalyst
