Studies on the structural evolution of highly active Ir-based catalysts for the selective reduction of NO with reductants in oxidizing conditions

Catalytic reduction of NO over in situ synthesized Ir/ZSM-5 monoliths

“…Therefore, in both cases, the dispersion of the Ir metal was increased and the deNO x activity was enhanced. Nakatsuji's results [15] showed that a particle size of the Ir metal of about 40-60 nm on inert supports exhibited excellent deNO x activities. Although, the particle size of Ir on the in situ synthesized Ir/ZSM-5 monoliths has not been examined in our work, the correlation between the dispersion of Ir and the deNO x activity of the catalysts is explicit.…”

“…However, after pretreatment with N 2 [15] or 10% H 2 O-N 2 [16] at high temperatures (1173 or 973 K), the Ir-based catalysts exhibited very high deNO x activities under oxidizing atmosphere when C 3 H 6 was used as reducing agent. Moreover, the wider operation window and the higher selectivity to N 2 make it an attractive candidate for the deNO x process under lean conditions.…”

Reduction of NO by propene over supported iridium catalysts under lean-burn conditions: an in situ FTIR study

“…Supported platinum catalysts have shown significant activity toward the HC-SCR at low temperature but large amounts of N 2 O are produced with N 2 and the range of temperatures within which the NO reduction proceeds is narrow [1][2][3][4][5]. Iridium-based catalysts have been also reported to be active and durable catalysts for HC-SCR of NO x [6][7][8][9][10][11][12][13][14][15]. N 2 is formed between 623 and 873 K over Ir/Al 2 O 3 [16], i.e., at higher temperatures than over Pt-based catalysts which are active between 473 and 623 K. An advantage of Ir-based catalysts over Pt-based catalysts is that the selectivity of NO reduction toward N 2 formation is high.…”

Unique properties of Ir/ZSM-5 catalyst for NO reduction with CO in the presence of excess oxygen

“…However, in comparison with the other noble metal catalysts, such as Pt, Pd and Rh [13][14][15][16], which have been intensively studied for the removal of NO x , Ir catalysts have received only little attention [17][18][19]. Many questions still exist regarding the intrinsic reasons why the Ir catalysts exhibit such superior properties for the reaction of NO/CO/O 2 .…”