In situ infrared study of NO reduction over Pd/Al2O3 and Ag-Pd/Al2O3 catalysts under H2 rich and lean-burn conditions
Catalytic reduction of NO under H2-rich and lean-burn conditions over Pd/Al2O3 and Ag-Pd/Al2O3 has been studied by temperature programmed reaction (TPR) coupled with in situ infrared (IR) and mass spectrometry (MS) techniques. Under H2-rich conditions, Pd/Al2O3 produces, Pd-NCO, Pd+-NO, Pd0-NO, and adsorbed nitrate at temperatures below 398 K. N2 and adsorbed NH3 are produced at temperatures above 400 K. Addition of Ag to Pd/Al2O3 suppresses the Pd+-NO formation and lowers the formation temperature of NH3 species to 373 K. Under lean-burn conditions, Pd/Al2O3 produces Pd-NCO, Pd+-NO, Pd0-NO, and adsorbed nitrate at temperatures below 373 K, while the addition of Ag suppresses the Pd-NCO and Pd+-NO formation, and enhances the Pd0-NO formation. Infrared results reveal that oxygen under lean-burn conditions does not oxidize Pd0 sites to Pd+ on the Ag-Pd/Al2O3 catalyst. Addition of Ag enhances NO2 formation and shifts the N2 formation to lower temperatures, suggesting that NO2 is effectively reduced to N2.
Journal of the Taiwan Institute of Chemical Engineers
Miller, Duane D. and Chuang, Steven, "In situ infrared study of NO reduction over Pd/Al2O3 and Ag-Pd/Al2O3 catalysts under H2 rich and lean-burn conditions" (2009). Polymer Science Faculty Research. 202.