Roles of ZnO in Cu/Core–Shell Al–MCM-41 for NO Reduction by Selective Catalytic Reduction with NH3: The Effects of Metal Loading and Cu/ZnO Ratio

Cu–ZnO/Al–MCM-41 catalysts were studied for NO x reduction. The total metal loading was varied as 3, 5, and 7 wt %, whereas the Cu-to-ZnO ratio was fixed at 1:1. Too high metal loading led to lower reducibility of Cu2+, as CuO and ZnO covers on the catalyst surface could partially block pores and hinder gas molecules to access the Cu2+ ions. Subsequently, Cu loading was fixed at 2.5 wt %, whereas ZnO content was varied as 0, 2.5, and 3.5 wt %. The results demonstrated that 2.5Cu–2.5ZnO catalyst exhibits the best catalytic activity, as it gave the average NO conversion of 87%.