Mechanistic investigation of the enhanced SO2 resistance of Co-modified MnOx catalyst for the selective catalytic reduction of NOx by NH3

Abstract

For the effectively removal of NOx emissions in the practical flue gas, a highly active NH3-SCR catalyst with remarkable SO2 tolerance is desirable. Herein a novel MnCoOx sphere catalyst has been developed, which not only exhibited high low-temperature activity for the NH3-SCR of NOx but also significantly enhanced SO2 resistance. XPS analysis and in-situ DRIFTs revealed that the formation of abundant bulk MnSO4 species due to the present SO2 led to the irreversible poisoning of pure MnOx catalyst, which could change the Langmuir-Hinshelwood (L-H) mechanism of NH3-SCR reaction into the Eley-Rideal (E-R) mechanism and inhibit the low-temperature activity. While over MnCoOx sphere catalyst the formation of MnSO4 is significantly inhibited in the presence of SO2, so that the reaction over the SO2-poisoned Mn(5)Co(5)Ox catalyst can still proceed by the L-H mechanism and maintain its high catalytic performance. This work unravels the mechanistic promoting effect of Co on the SO2 tolerance of MnCoOx catalyst from sulfates as well as the reaction mechanism perspectives, which would guide an ingenious design of SO2 tolerant Mn-based NH3-SCR catalysts.