Dynamics of a Combined DOC−NSRC−SCR Exhaust Gas Aftertreatment System with Periodic Regenerations

A combined exhaust gas aftertreatment system, consisting of a diesel oxidation catalyst (DOC), an NOx storage and reduction catalyst (NSRC, which also is called lean NOx trap, LNT), and a catalyst for selective catalytic reduction of NOx by NH3 (NH3-SCR) is studied experimentally. The catalyst samples are placed in series in an almost isothermal laboratory minireactor. Dynamic behavior of the system is examined under periodic lean/rich operation in temperature range of 200−400 °C with varying composition of the rich mixture, containing CO, H2 and C3H6. Concentrations of gas components are measured at the inlet, outlet, and between the individual catalysts. The individual DOC, NSRC, SCR, NSRC−SCR, and DOC−NSRC subsystems are also examined. The DOC is used as the first element in the exhaust aftertreatment line. It is responsible for the oxidation of CO and unburned hydrocarbons (HC), and it also supports the oxidation of NO to NO2. NSRC and SCR converters are employed for the abatement of nitrogen oxides. ...