Abstract: With the aid of CO and pyridine as probe molecules, infrared spectrophotometer. was ern-ployed to characterize the industrial catalyst Pd (Pt)/Al₂O₃ used for eliminating H₂ from feed CO₂ in urea synthesis. It is concluded that the factor which directly causes the deactivation of the catalyst comes from S^2- and S₂^2-,and the last factor resulting in the deactivation are S(Ⅵ)species; SO₄^2- and Al₂O₃-SO₃-H₂0 compounds.

Key words: supported noble metal catalyst, sulfur poisoning, deactivation mechanism, feed gas for urea synthesis