Selective catalytic reduction of NO over W–Zr-Ox/TiO2: performance study of hierarchical pore structure

Abstract

A series of W–Zr-O_x/TiO₂ catalysts with hierarchical pore structure were prepared and used for selective catalytic reduction of NO by NH₃. Results showed that the 5C-WZ/T had a hierarchical pore structure, and exhibited high catalytic activity and good resistance to water and sulfur poisoning. The activity of the 5C-WZ/T catalyst was close to 100% in the range of 350–500 °C. The hierarchical pore structure not only improved the specific surface area, redox performance, and acid quantity, but also enabled the catalyst to expose more active sites and improved the catalytic performance. Although the reducing atmosphere caused by citric acid monohydrate reduced the chemical adsorption oxygen concentration, it increased the oxygen mobility and Ti³⁺ ion concentration, which was more conducive to the improvement of catalytic activity. Finally, the NH₃-SCR reaction over 5C-WZ/T catalyst followed L-H and E-R mechanisms. The monodentate nitrite, bidentate nitrate, gas-phase NO₂, coordinated NH₃ and NH₄⁺ were the main reaction intermediates.