Dynamics of SO_2 adsorption-oxidation in SO_x traps for the protection of NO_x adsorbers in diesel engine emissions

摘要

The SO_2 uptake behaviour at different temperature and SO_2 concentration of a reference SO_x trap is studied in a thermobalance apparatus and in a flow reactor under reaction conditions close to those in the emissions from a diesel engine.The data of the latter apparatus are also kinetically modelled to derive which controlling regime dominates the performances.The results evidence that at 200 deg C the behaviour is largely controlled by the slow solid-state diffusion of the sulphate species,while above 300 deg C there is an initial region controlled by the surface reaction,although for levels of SO_2 uptake above a weight increase of 4-5%(due to sulphation)the solid-state diffusion dominates the performances also at high temperature.