Decomposition of nitrous oxide over a low-cost catalyst

Abstract

Nitrous oxide (N2O) is a significant greenhouse gas and its emissions from fluidized bed combustion systems can be controlled using catalytic conversion and decomposition. The catalytic decomposition of N 2O was studied in a quartz fixed-bed reactor at 450-700 °C. The low-cost catalyst was prepared from fly ash and iron oxides, and was characterized in terms of the BET specific surface area and XRD. This study showed that both the Fe content on the catalyst surface and the calcination temperature during the preparation of the catalyst should be optimized in order to significantly improve the catalyst performance when used for N2O decomposition. The influences of O2, H2O, CO2 and SO2 on the N2O decomposition were investigated at the most reactive temperature. Experimental results showed that O2 had a small negative effect on the catalytic activity, while CO2 had no obvious effect on the N2O decomposition. The N2O conversion was still high even when H2O was present. However, the N2O conversion dropped sharply when H2O and O2 were both present. The catalytic activity was reduced by SO2 because of its reaction with the catalyst. The difference between the N2O conversion with H2O present and with both H2O and O 2 present was analyzed in order to determine the N2O decomposition mechanism. Two mechanisms for the N2O catalytic decomposition mechanism have been considered, of which the one with formation of oxygen atoms at two sites with migration and recombination shows better agreement with our experimental results. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.