Selective Catalytic Reduction of NO by CO over Supported Iridium and Rhodium Catalysts

Abstract

The catalytic reduction of NO with CO was investigated in the presence of oxygen over 16 supported metallic catalysts. Ir/WO3, Ir/ZnO, and Rh/Al2O3 showed the pronounced activity even in excess amount of oxygen. The effect of preparation conditions on the activity of Ir catalysts was further studied and it was found that Ir/WO3 prepared by loading of H2IrCl6 at 0.5 wt % Ir is the most active for the NO reduction with CO.

Detailed surface reaction mechanism for reduction of NO by CO

“…Ir is found to be an effective catalyst with higher N 2 selectivity than Pt, Rh and Pd for the NO-CO reaction under lean burn conditions and is cheaper than Pt and Rh [28][29][30][31]. Therefore we mainly concentrate our attention on Ir rather than Pt for our analysis of NO reduction under lean burn conditions.…”

Geometrical Structures of Partially Oxidized Rhodium Cluster Cations, Rh6Om+ (m = 4, 5, 6), Revealed by Infrared Multiple Photon Dissociation Spectroscopy

“…[1][2][3][4][5] The mechanism of NO reduction by Rh has been studied for many years using gas-phase clusters. Their use is advantageous for understanding the behavior of N and O atoms at the atomic and molecular level, since the number of Rh, N, and O atoms involved in the reaction is well defined.…”

An Ir/WO3 catalyst for selective reduction of NO with CO in the presence of O2 and/or SO2

“…An impregnation method was used to prepare 5.0 wt.-% Ir/WO 3 catalysts [9,10]. WO 3 supports were prepared by thermal decomposition of H 2 WO 4 at 673 K in air for 3 h. WO 3 (4 g) was impregnated with 100 cm 3 of H 2 IrCl 6 aqueous solution in a rotary evaporator at 343 K. The sample so obtained was dried in air at 383 K for 12 h and further calcined in air at 673 K for 2 h.…”

“…It is interesting that the reduction of NO in the presence of O 2 is promoted by SO 2 , which normally poisons the active sites and significantly decreases the activity of catalysts, although the activity of those catalysts becomes lower in the presence of O 2 alone. The present authors have studied the activity of Ir/WO 3 catalyst for the reduction of NO with CO [9,10]. It is noteworthy that this catalyst is highly active even in the presence of excess O 2 or O 2 + SO 2 ; such resistance to oxidation is very useful for sulfur-free lean-burn engines.…”