Reduction of lean NO2 with diesel soot over metal-exchanged ZSM5, perovskite and gamma-alumina catalysts

Abstract

The catalytic performances of metal-exchanged ZSM5, perovskite and gamma-alumina catalysts for the reduction of nitrogen dioxide (NO,) by diesel soot were investigated. The reaction tests were performed through temperature-programmed reaction (TPR), in which NO2 and O-2, were passed through a fixed bed of catalyst-soot mixture. On the three types of catalyst, NO2 was reduced to N-2 by model soot (Printex-U) and most of the soot was converted into CO2 Pt-, Cu- and Co-exchanged ZSM5 catalysts exhibited reduction activities with conversions of NO2 into N-2 of about 20%. Among the perovskite catalysts tested, La0.9K0.1FeO3 showed a 32% conversion of NO2 into N-2. The catalytic activities of the perovskite catalysts were largely influenced by the number and stability of oxygen vacancies. For the alumina catalyst, the peak reduction activity appeared at a relatively high temperature of around 500 degrees C, but the NO2 reduction was more effective than the NO reduction, in contrast to the results of the ZSM-5 and perovskite catalysts.