Treatment of nitrogen oxide at an Otto engine supplied with a lean mixture

摘要

A lean-burn engine exhaust gas NOx treatment process uses a NOx store (4) and an independent upstream catalyst (2) which is supplied with returned NOx-laden exhaust gas resulting from regeneration of the NOx store. A lean-burn i.c. engine exhaust gas NOx treatment process comprises storing NOx in a NOx store (4) during lean-burn operation of the engine, switching the engine to a fuel/air ratio (lambda ) of about 1 to regenerate the NOx store and returning at least part of the NOx released by the resulting temperature increase to an independent catalyst (2) located between the engine (1) and the NOx store (4). An independent claim is also included for equipment for carrying out the above process, including a return line (7) for returning NOx-laden exhaust gas from the NOx store (4) to the upstream catalyst (2) during regeneration of the NOx store (4).