Highly Active and Water-Resistant Mn-Loaded Mgalox Catalysts for Nh3-Scr at Low Temperature

Abstract

The development of low-temperature NH3-SCR catalysts can effectively promote the technology as an end-of-pipe treatment unit for flue gas denitration under different operating conditions. Herein, a highly active and water resistant catalyst for low temperature SCR is fabricated by impregnating active component MnOx onto MgAlOx composite oxides supports with various Mg/Al ratios derived from LDH precursors. The obtained catalyst with the Mg/Al ratio of 2 (Mn/Mg2AlOx) possesses relatively high concentrations of active oxygen species (Oα) and Mn4+, and exhibits remarkable catalytic performance. Mn/Mg2AlOx has a broad temperature window for denitration, removing 80% of NOx at 100-300 °C, as well as satisfactory water resistance. The temperature-programed surface reactions and NO oxidation reactions are performed to elucidate that the promoting effect of water on N2 selectivity, which is not only due to inhibition of catalyst oxidation capacity at high-temperature, but also in related to the competing adsorption of water and NH3. According to in situ DRIFTS, the NH3-SCR process on Mn/Mg2AlOx satisfies the E-R mechanism. This work illustrates the high potential of Mn-loaded MgAlOx SCR catalysts to be utilized downstream of exhaust treatment equipment.

Keywords: NH3-SCR, low-temperature activity, composite oxide support, MnOx catalyst, water resistance