Improvements in the N2 selectivity of Pt catalysts in the NO–H2–O2 reaction at low temperatures

Abstract The selective reduction of NO with H 2 in the presence of excess O 2 (the NO–H 2 –O 2 reaction) over noble metal catalysts, with a particular emphasis on the use of Pt, was investigated. The conversion of NO x exceeded 98% with Pt catalysts at between 350 and 500 K in the presence of 1% H 2 . Pd, Ir, and Rh catalysts were also highly active in the presence of 1% H 2 . NH 3 was formed as a byproduct over Pt catalysts between 350 and 400 K. The formation of NH 3 increased over Pt supported on ZrO 2 . The NH 3 formed at around 400 K was effectively converted to N 2 by the selective reduction of NO with NH 3 over H-ZSM-5, which was physically mixed with the Pt catalyst.