Deactivation of zeolite catalysts used for NOx removal

The deactivation of Ce-zeolite deNO(x) catalysts has been studied. Catalyst s were aged in exhaust gases of a diesel engine and a natural gas engine. T he deactivation in real exhaust gas has been compared to deactivation in si mulated exhaust gas. Ammonia and urea were used as reducing agent. Deactiva ted catalysts were characterized with amongst others XPS, XRF and DRIFT. Ze olite deNO(x) catalysts show different types of deactivation apart from hyd rothermal dealumination. Deactivation may occur at low and at higher temper atures. Several depositions were found on the catalysts: coke, CxHy, S, Zn, P, N and Ca. Coke, CxHy and N containing species can be removed by heating under oxygen rich (deNO(x)) conditions resulting in (partial) recovery of the catalyst activity. The type of lubricating oil used in the internal com bustion engine might be an important factor in the deactivation of the deNO (x) catalyst. (C) 2000 Elsevier Science B.V. All rights reserved.