Cooperative effect of Pt–Rh/Ba/Al and CuZSM-5 catalysts for NOx reduction during periodic lean-rich atmosphere

NOx removal efficiency was investigated with a combination of model Pt–Rh/Ba/Al and Cu-ZSM-5 catalysts using periodic fluctuations between lean (100 s) and rich (10 s) atmosphere. NOx removal is greatly improved at 250 °C and 300 °C by physically mixing the two catalysts. The mixed catalyst shows a NOx removal activity almost double as compared to a system where Pt–Rh/Ba/Al catalyst is situated upstream and CuZSM-5 downstream the gas flow. FT-IR characterisation shows that CuZSM-5 catalyst enhances the formation of NCO species on alumina during rich conditions. These NCO are further hydrolyzed to NH3 under lean condition which acts as a reductant for NOx.