Dual-catalyst system to broaden the window of operability in the reduction of NOx with ammonia

The objective of this research was to determine if a dual-catalyst system for NO reduction with NH3 can achieve a given percent NO reduction over a wider range of temperatures and space velocities than either catalyst used alone in the same total reactor volume. Hydrogen mordenite (20/32 mesh) and copper-ion-exchanged hydrogen mordenite (2.2% Cu) were used in series at temperatures from 200 to 600°C and space velocities from 100 000 to 450 000 h-1 (STP). The superiority of the dual-catalyst system was demonstrated experimentally, and a model was developed which predicted its performance very well from data on the individual catalysts. A technique was then developed for predicting quantitatively the dual-catalyst enhancement of the space velocity versus temperature window for achieving a given percent NO conversion. The higher the conversion required, the greater is the enhancement provided by this system.