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

A new thulium (Tm) modified Mn/TiO2 catalyst is firstly prepared to remove NO at low temperature, where the TiO2 with relatively high specific surface area (184.3 m(2)/g) is used as carrier to support the active component MnOx, and Tm is utilized as promoter to modify the MnOx. The developed Tm-Mn/TiO2 catalyst presents significantly improved selective catalytic reduction (SCR) de-NOx performance at low temperature with NH3 as reducing agent. It is found that after an appropriate content of Tm is introduced, the surface concentration of Mn4+, the chemical adsorbed oxygen, the chemisorption of NH3 and NO, and the reducibility of the Tm-Mn/TiO2 catalyst are improved, which are helpful to the enhancement of NH3-SCR de-NOx performance. Moreover, it is discovered that, over Tm-Mn/TiO2 catalyst, an Eley-Rideal (E-R) mechanism occurs in the reaction between adsorbed NH3 species connected by Lewis acid sites and gaseous NO, meanwhile, a Langmuir-Hinshelwood (L-H) mechanism occurs between adsorbed NH3 species and adsorbed NO species, where the E-R mechanism dominates the NH3-SCR de-NOx process. (C) 2021 Elsevier Ltd. All rights reserved.