Promoting effect of Ti addition on three-dimensionally ordered macroporous Mn-Ce catalysts for NH_3-SCR reaction: Enhanced N_2 selectivity and remarkable water resistance

摘要

A series of 3DOM-MnxCeyTiz catalysts with three-dimensionally ordered macroporous (3DOM) structure were synthesized by a soft template method. The high SCR activity of the 3DOM-Mn3Ce1 catalyst at low temperature was owing to the excellent redox ability and rich Lewis and Bronsted acid sites of the catalysts, which were beneficial to improve the catalytic activity. However, the strong oxidizability of MnOx resulted in the nonse-lective oxidation of NH3 and generation of N2O, decreasing the N-2 selectivity. After addition of Ti, the redox capacity of the 3DOM-Mn3Ce1Ti1 catalyst decreased, and the NH3 were strongly adsorbed on the acid sites, which enhanced the N-2 selectivity with a broadened temperature window of 240-440 degrees C and a high GHSV of 120000 h(-1). Furthermore, both the 3DOM-Mn3Ce1 and 3DOM-Mn3Ce1Ti1 catalysts showed remarkable tolerance of H2O. Finally, through in situ DRIFT analysis, the Langmuir-Hinshelwood (L-H) mechanism was confirmed as the dominant reaction pathway over the 3DOM-Mn3Ce1Ti1 catalyst.