With the mandated reduction of NOx from heavy-duty trucks, advanced emission control technologies are being implemented in order to comply with these lower standards. One of these strategies is the adaptation of selectivecatalytic reduction (SCR) units. These units are modified in various ways, with use of new reductants being among them. Currently the focus has been on use of urea due to its many advantages. Urea however suffers from several issues itself including its stability at elevated temperatures (>50°C) and its tendency to form deposits in the exhaust gas stream. Therefore, the use of compounds with amine functional groups has been proposed as reductants. Amines, such as methylamine (CH3-NH2), have a distinct advantage as they can thermally degrade to form ammonia, thereby eliminating the need for expensive catalysts in SCR units. However, during periods where the exhaust gas is insufficiently heated, complete conversion to ammonia notachieved and excess amine reductant will be emitted with the exhaust gas. Here we present a series of experiments focusing on the fate of four common primary amines in atmospheric conditions with the nitrate radical. This system shows potential for significant particle formation as evidenced by our previous work (1). It is found that ultrafine particles are formed with mass based yields ranging from <2% for methylamine to greater than 44%for butyl and ethylamine. Lower bounds for rate constants range from 1.39x10-16 cm3/molec/sec for methylamine to 7.75x10-17 cm3/molec/sec for ethylamine, indicating that these reactions are competitive with acid-base reactions.
Samenvatting