Synergistic effect of VOx and MnOx surface species for improved performance of V2O5/Ce0.5Ti0.5−xMnxO2−δ catalysts in low-temperature NH3-SCR of NO

Abstract

Supported V₂O₅/Ce_0.5Ti_0.5−xMn_xO_2−δ (x = 0, 0.01, 0.05, 0.1, and 0.2) catalysts and bare supports were investigated in the selective catalytic reduction (SCR) of NO by NH₃ between 100 and 300 °C. Incorporation of Mn into Ce_0.5Ti_0.5O₂ increased the NO removal efficiency, reaching both NO and NH₃ conversions above 85% between 175 to 300 °C at remarkably high N₂ selectivities of ≥95%. Moreover, Mn-modified supports were also much more stable against deactivation in the presence of water. Deposition of vanadia on the Ce_0.5Ti_0.5−xMn_xO_2−δ supports enhanced the N₂ selectivity, reaching ≥98% in the whole temperature range for Mn percentages of ≤0.1. Characterization results revealed that incorporation of Mn leads to supports with higher lattice disorder and smaller crystallite size and enhances the oxygen mobility and the reducibility of the supports. Operando EPR studies show that the synergistic effect of VO_x and MnO_x surface species in moieties containing Mn³⁺/Mn²⁺ and VO³⁺/VO²⁺ in close vicinity contributes to the prevention of undesired NH₃ oxidation, thus improving the N₂ selectivity of these catalysts.