This study investigated the selective catalytic reduction (SCR) of nitrogen oxides (NOx) with hydrocarbon in the presence of excess oxygen using various composition ratios of Pt/Al2O3, Rh/Al 2O3catalyst mixtures. The composition ratios were 1:1, 1:2, 2:1, 1:3 and 3:1 of 1 wt% Pt/Al2O3and Rh/Al 2O3, which are known to exhibit efficient NO xreduction at low and high temperatures among the noble metal catalysts. Experiments conducted on a single reductant revealed that more efficient NOxconversion could be obtained when Pt/Al 2O3and Rh/Al2O3were mixed at a ratio of 3:1, rather than 1:1 or 1:3. In a single reductant condition, C 3H6800 ppm (2400 ppmC1) and 400 ppm (1200 ppmC1) exhibited 50% and 38% NOxconversion efficiency at 200 °C, respectively. However, NOxconversion efficiency gradually decreased when temperatures were increased above 250 °C. With regard to Pt/Al2O3and Rh/Al2O3ratio, higher ratios of Rh/Al2O3activated this Pt+Rh/Al 2O3catalyst in the high temperature range.
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