Cu-ZSM5 based monolith reactors for NO decomposition

Micronic ZSM5 (Si/Al = 25) powder has been deposited on cordierite monoliths by dip-coating technique using colloidal alumina or silica as binders with different zeolite/binder ratios in aqueous suspension determining the parameters to obtain the best adhesion and mechanical resistance of the washcoat layer. For monolithic catalysts with washcoat containing 10 wt% SiO2 the following alternative preparation procedures have been used: (i) deposition of a pre-exchanged Cu-ZSM5 powder on the ceramic monolith; (ii) deposition of a H-ZSM5 powder on the ceramic monolith followed by copper exchange of the structured catalyst. The monolithic catalysts have been investigated by morphological (SEM), physical (BET and porosity), chemical (ICP-MS, EDX, XRD, H2 TPR) and catalytic (NO decomposition tests in flow reactor under dry and wet conditions) analyses. Results have been compared with those obtained on the corresponding Cu-ZSM5 powder sample with the same copper content and Si/Al ratio in order to define the effect of the preparation procedure on the chemical and catalytic properties of the monoliths.