Lean NOx Removal by a Bifunctional (EtOH + NH3) Mixture Dedicated to (Ag/Al2O3 + NH3-SCR) Dual-Bed Catalytic System: Comparison Between WO3/CeZrO2 and Cu–FER as NH3-SCR Catalyst

Abstract

In a previous study, a drastic enhancement of the NOx conversion in EtOH-SCR process was achieved by means of ammonia and ethanol co-feeding over Ag/Al2O3 catalyst to avoid the NO2/NOx ratio dependency of conventional implemented urea-SCR technology. The ammonia activation was mainly attributed to the availability of hydrogen H* species resulting from EtOH dehydrogenation, which promoted the H2 assisted NH3-SCR over Ag/Al2O3. Additional conversion gain was reached with a dual-bed configuration in which a NH3-SCR catalyst (WO3/CexZr1−xO2) was added downstream to the silver-based sample (Ag/Al2O3 + NH3-SCR catalyst). This study deals with the influence of the SCR catalyst formulation on the catalytic performances of the dual-bed system. Oxide-based sample (WO3/CexZr1−xO2) and exchanged copper zeolite (Cu2.5–FER) were selected as model NH3-SCR catalysts. Results shows that WO3/CexZr1−xO2 in more appropriate in dual-bed configuration for (EtOH + NH3)-SCR process because ammonia and ethanol (or its by-products) strongly interacted together on Cu2.5–FER.