Selective Catalytic Reduction of NO in Diesel Exhaust over Anodic Alumina Catalyst

Abstract

A series of Cu-Mn-Ce/Al₂O₃ anodic alumina catalysts synthesized using the multi-impregnation method were employed to investigate the selective reduction of NO with C₃H₆ in the presence of excess O₂. The presence of Cu additive greatly promoted the low-temperature de-NO_x activity. A moderate loading of copper gave the most promising NO_x conversion. In contrast, no promotional effect on low-temperature de-NO_x activity was found when Mn was added to the alumina support. Although the Mn-supported catalyst exhibited a higher activity for the oxidation of NO to NO₂, the addition of Mn to the Cu-Ce/Al₂O₃ catalyst had no positive effect on NO_x reduction, due to the wasteful consumption of propene. The de-NO_x activity of the Cu-Ce/Al₂O₃ catalyst was maintained at a relatively high level, even in the presence of excess SO₂ (500 ppm) and H₂O (10 vol%). Furthermore, the presence of SO₂ was observed to greatly promote NO_x reduction at 723 K.