Comparative NOx Reduction Behavior of Pt, Pd, and Rh Supported Catalysts in Simulated Exhaust Gases as a Function of Oxygen Concentration

Shinjoh, Hirohumi; Tanabe, Toshitaka; Yokota, Kouji; Sugiura, Masahiro
July 2004
Topics in Catalysis;Jul2004, Vol. 30/31 Issue 1-4, p319
Academic Journal
NOx reduction activity on Pt and Pd catalysts had a maximum for S value as stoichiometry number at a fixed temperature, and the S value at the maximum NOx conversion increased with decreasing temperature. NOx conversion on Rh catalyst increased with decreasing S value, but independent of temperature. As for the effect of HC on NOx reduction behavior, it was concluded that, for Pt and Pd catalysts, HC adsorbs strongly on the catalysts surface to cause the self-inhibition. Increasing O2 concentration lead to oxidation of HC, but decreased the value of NO/O2 ratio. The balance point of the two factors generated a maximum NOx conversion. For Rh catalyst, the strongly adsorbed oxygen is more reactive with decreasing S value, and thus NOx conversion is increased.


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