Pr-modified MnOx catalysts for selective reduction of NO with NH3 at low temperature

Background: Manganese oxides (MnOx) are a promising catalyst in selective catalytic reduction of NO with NH3 due to their excellent low-temperature catalytic activities. However, MnOx still suffer from poor N-2 selectivity and SO2 resistance. Methods: In this work, rare earth element Pr was used to modify MnOx catalysts via co-precipitation method, and the effects of Pr modification on SCR performance of MnOx catalysts had been investigated. Significant findings: The temperature window of MnPrOx-0.1 catalyst with nearly 100% NO conversion efficiency ranged from 120 to 220 degrees C, and Pr modification on MnOx catalyst had improved the resistance to SO2 obviously. The characterization results indicated that Pr modification on MnOx catalyst could increase the specific surface area, dispersity, reducibility, relative percentages of surface Mn4+ and chemisorbed oxygen species (O-alpha). NH3-TPD and in-situ DRIFTS results revealed that Pr modification increased the adsorption of NH3 on catalyst surface, resulting in more amount of Lewis acid sites on the surface of MnPrOx-0.1 catalyst. All of these factors led to an excellent catalytic performance of Pr-modified MnOx catalysts. In-situ DRIFTS results implied that SCR reactions over Pr-modified MnOx catalyst followed both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. (C) 2021 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.