Dual-layer AdSCR monolith catalysts: A new solution for NOx emissions control in cold start applications

A new dual layer monolithic AdSCR system (adsorption + selective catalytic reduction) constituted by Cu/CHA (top) and BaO/Al2O3 (bottom) was prepared and studied as a potential solution to improve the low-T performances of NH3-SCR catalysts. Two washcoat formulations were considered. The samples were characterized through optical microscopy and SEM-EDX; the ammonia storage capacity and the catalytic activity in the standard NH3-SCR reaction were also studied. When using water as solvent during the deposition, migration of Ba into the Cu-zeolite layer was observed, resulting in a decay of both ammonia storage capacity and NH3-SCR activity. On the other hand, when water was replaced by n-butanol, the two layers were well segregated, and no loss of SCR performances was noted. The butanol-based formulation exhibited promising performances in the NOx abatement during cold-start transients, with a NO removal efficiency of 31%, prior to ammonia injection, and of 52% after ammonia injection. [Display omitted] •Dual-layer SCR+BaO/Al2O3 monolith for NOx abatement in cold-start transients.•At low-T, NO is stored on the BaO/Al2O3 component in the presence of oxygen.•NOx stored on the BaO/Al2O3 layer can be decomposed by NH3 on the SCR layer.•Ba migration during the washcoat deposition deactivates Cu zeolite NH3-SCR activity.•Replacing H2O with butanol in washcoating prevents Ba contamination of Cu zeolite.