Iron Clusters Occluded in Zeolite ZSM5 Micropores
E. J. M. Hensen, Q. Zhu, P. C. M. M. Magusin and R. A. van Santen
Schuit Institute of Catalysis, Laboratory of Inorganic Chemistry and Catalysis,
Eindhoven University of Technology,
P.O. Box 513, 5600 MB, Eindhoven (The Netherlands), E-mail: e.j.m.hensen@tue.nl
Abstract
The effect of high temperature calcination and steaming on iron-containing zeolite was studied. Iron was introduced by sublimation of FeCl3. FTIR measurements clearly show the disappearance of Broensted acid sites upon such treatments. This is attributed to a reaction between small occluded Fe oxide clusters obtained after initial low temperature calcination and the zeolite protons to give cationic Fe species compensating the negative zeolite charge. High temperature calcination and especially steaming considerably increase the catalyst activity in nitrous oxide decomposition. The two treated catalysts exhibit a higher apparent activation energy than the original sample. This high apparent activation energy is compensated by a high pre-exponential factor. In Fe/ZSM5 the activity mainly derives from small Fe oxide clusters, while upon treatment more active cationic species are generated. The kinetic parameters point to a stronger Fe–O bond for the latter case.
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