NO decomposition over a new type of low metal content fiberglass catalysts studied by the TAP technique

Abstract

NO absorption and decomposition over novel type of leached fiberglass catalysts containing very small amounts of platinum were studied by means of the temporal analysis of products (TAP) technique. In the temperature range of 200–400 °C NO was reversibly absorbed on the catalyst. At higher temperatures NO consumption and N 2 release occurred, indicating the proceeding of direct NO decomposition. However, in the temperature range of 400–500 °C the rate of NO decomposition declined with the quantity of NO dosed, i.e., with the number of pulses introduced, so that steady-state NO conversion was close to zero. This drop in catalyst activity is related to the negligible oxygen desorption during NO decomposition in this temperature range, making it reasonable to assume a blocking of the catalyst active sites by accumulating oxygen. Nevertheless, as temperature was raised above 500 °C, steady-state NO conversion increased sharply with temperature reaching a value of 45% at 550 °C. Apparently, a thermal desorption of oxygen beyond that temperature allows to free sites, which were covered during NO decomposition, sustaining in this way the overall reaction. Based on the obtained data activation energies of NO desorption and decomposition were estimated.