Lean NOx reduction over Rh/ZrP2O7 catalyst under steady-state and perturbation conditions

Abstract Catalytic lean NO x reduction performance was studied over Rh supported on ZrP 2 O 7 and ZrO 2 under steady-state and perturbation conditions. The ZrP 2 O 7 support significantly enhanced the NO x purification efficiency at the air-to-fuel (A/F) ratio between 14.6 and 15.0 compared with the ZrO 2 support, because of the higher activity toward C 3 H 6 oxidation and the higher stability of metallic Rh against reoxidation. The lean NO x purification efficiency was further enhanced by switching two simulated gas feeds with stoichiometric (A/F = 14.6) and lean (A/F = 14.9) compositions with shorter intervals (∼1 s). Considering faster reduction of Rh oxide in contrast to slower reoxidation of Rh on ZrP 2 O 7 , the perturbation effect could be rationalized by the stabilization of metallic Rh species, which is more active than Rh oxide for the catalytic NO x reduction.