An Application of the Selective Contact Reduction Method by NO_x-NH₃ Reaction to a Methanol Fueled S. I. Engine Exhaust System

Abstract

The catalytic reduction of NO_x by NH₃ generated from NO_x has been applied to methanol engine exhaust system. In an automotive three-way catalyst (Pt-Rh coated) a large amount of NO_x is converted to NH₃ in a temperature range of 500-550K and an excess air ratio of 0.9-1.0. On the other hand, NO_x reduction by NH₃ in methanol engine exhaust gas is efficiently performed under the condition of O₂= 2-4%, gas temperature= 450-500K, and NH₃ ≥ the stoichiometry of NO_x. Finally, about half an amount of NO_x is converted to NH₃ in a three-way catalyst and the formed NH₃ ratio is around 55%. On the basis of these results, some systems using the application of NO_x-NH₃ reactions to practical engines are proposed and their potential is discussed.