III International Conference

PP-III-96INTERACTION OF N 2 O WITH ZSM-5 TYPE ZEOLITES – A TRANSIENTTAP STUDYLöffler M., Ates Ayten 1 , Breitkopf C.Institute of Technical Chemistry, University of Leipzig, Germany1 Department of Chemical Engeering, Cumhuriyet University, Sivas, TurkeyE-mail: loeffler@chemie.uni-leipzig.deIron-containing zeolites of the ZSM-5 type are an important catalyst class for the removal ofnitrous oxides from waste gases and in partial oxidations [1]. The catalytic performance isstrongly dependent on the formation of surface oxygen species. There is an ongoing discussion inthe literature about the influence of different iron species on the formation of those surface oxygenspecies. However, only few studies addressed the problem of surface oxygen concentration.Generally, these studies are limited by the experimental setup. Therefore it was started to employtransient methods to investigate zeolites [1]; these multipulse experiments were done by injectionof 0.31 µmol of N 2 O into a continuous flow of inert gas.In this study, we applied another transient technique, the temporal analysis of products(TAP) method [2], in which we decreased the pulse size by two orders of magnitudecompared to [1]. Thereby, we tried to enable a more detailed elucidation of active surfacecentres and their change in the course of the reaction. Additionally, we investigated theinfluence of the catalysts´ pre-treatment with different gases (He, O 2 , N 2 ) during the activationprocedure. The TAP method was also suitable for studies of kinetics, diffusion and sorptionprocesses occurring on the catalyst.Intensity (28)01000200016300014400012500010864200 0,05 0,1 0,15 0,2 0,25 0,3t [s]N 2 response curves with growing amount of pulsed N 2 OIntensity (44)623 K16573 K14523 K12473 K10423 K864200 0,1 0,2 0,3 0,4 0,5t [s]N 2 O response curves at different temperaturesReferences1. [1] A. Ates, A. Reitzmann. J. Catal. 235 (2005) 164.2. [2] C. Breitkopf. J. Mol. Chemical 226, 269 (2005).648