Design and identify the confinement effect of active site position on catalytic performance for selective catalytic reduction of NO with NH3 at low temperature

Abstract

In heterogeneous catalysis, the migration and aggregation of active nanoparticles has always been a challenging problem in catalyst design. Two types of confined catalysts, including the pore confined Pore-CeW/OMT and framework confined FW-CeW/OMT were successfully designed for NH3-SCR process in this work. Experimental results revealed that the framework confined structure could effectively prevent the migration and aggregation of highly dispersed nanoparticles on catalyst. Benefiting from the structural advantages of ordered mesopores TiO2 (OMT), large specific surface area as well as abundant active sites could be supplied for catalytic reaction. It should be noted that citric acid pretreatment was essential for confined catalyst activation. The activation treatment could dramatically enhance catalyst surface acidity, especially a large number of strong acid sites were supplemented, resulting in significantly enhancement of catalytic activity at high temperature. Furthermore, it could also accelerate reduction of Ce4+ to Ce3+ and generate more active oxygen species, which resulted in a significant improvement in its low-temperature catalytic activity. Owning with strong surface acidity as well as framework confinement effect, the unique ordered mesoporous TiO2 framework could inhibit SO2 adsorption and protect active sites from SO2 attacking. Thus, the framework confined FW-CeW/OMT exhibited wide operating temperature window, good thermal stability, as well as strong sulfur resistance in NH3-SCR process.