Thulium modified MnOx/TiO2 catalyst for the low-temperature selective catalytic reduction of NO with ammonia

Abstract

A new thulium (Tm) modified Mn/TiO 2 catalyst is firstly prepared to remove NO at low temperature, where the TiO 2 with relatively high specific surface area (184.3 m 2 /g) is used as carrier to support the active component MnO x , and Tm is utilized as promoter to modify the MnO x . The developed Tm–Mn/TiO 2 catalyst presents significantly improved selective catalytic reduction (SCR) de-NO x performance at low temperature with NH 3 as reducing agent. It is found that after an appropriate content of Tm is introduced, the surface concentration of Mn 4+ , the chemical adsorbed oxygen, the chemisorption of NH 3 and NO, and the reducibility of the Tm–Mn/TiO 2 catalyst are improved, which are helpful to the enhancement of NH 3 -SCR de-NO x performance. Moreover, it is discovered that, over Tm–Mn/TiO 2 catalyst, an Eley-Rideal (E-R) mechanism occurs in the reaction between adsorbed NH 3 species connected by Lewis acid sites and gaseous NO, meanwhile, a Langmuir-Hinshelwood (L-H) mechanism occurs between adsorbed NH 3 species and adsorbed NO species, where the E-R mechanism dominates the NH 3 -SCR de-NO x process. • Tm was used as a dopant to modify Mn/TiO 2 catalyst for the SCR de-NO x for the first time. • The effects of Tm on the physical and chemical properties of Mn/TiO 2 were well disclosed. • Tm 0.1 Mn/TiO 2 exhibited excellent low-temperature de-NO x performance and N 2 selectivity. • The reaction mechanisms over the Tm 0.1 Mn/TiO 2 were fully revealed by in-situ DRIFTS.