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

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/Ce_xZr_1−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/Ce_xZr_1−xO₂) and exchanged copper zeolite (Cu_2.5–FER) were selected as model NH₃-SCR catalysts. Results shows that WO₃/Ce_xZr_1−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 Cu_2.5–FER.