Supported Pt and Pd are most commonly used for oxidation catalysts. They have similar and different characteristics for deactivation factors. The catalytic activity of Pt and Pd catalysts supported on c-Al 2 O 3 was studied in the presence and absence of H 2 O and SO 2 during CO oxidation under simulated conditions of diesel exhaust gas. Without the addition of H 2 O and SO 2 to the feed gas, Pd/Al 2 O 3 had a superior catalytic activity compared to Pt/Al 2 O 3 . The addition of H 2 O to the feed gas strongly and negligibly affected the activity of Pd and Pt, respectively, while the addition of SO 2 to the feed gas had a strong poisoning effect on the catalytic activity of both Pt and Pd catalysts. Although being the most active, Pd catalysts exhibited a strong sensitivity to water and sulfur-containing compounds. Fe was added to the Pt and Pd catalysts to introduce sulfur resistance. The addition of Fe enhanced the activity of the catalysts by suppressing the phase transition of Al 2 O 3 to Al 2 (SO 4 ) 3 and by hindering metal sintering.

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