J. Phys. IV France 7 (1997) C2-907-C2-908
Evolution of Fe3+ from Framework to Extra-Framework Species in Fe-Silicate as a Function of the Template Burning TemperatureS. Bordiga1, D. Scarano1, C. Lamberti1, A. Zecchina1, F. Geobaldo2, G. Vlaic3, R. Buzzoni4, G. Tozzola4 and G. Petrini4
1 Dipartimento di Chimica I.F.M., Via P. Giuria 7, 10125 Torino, Italy
2 Dipartimento di Scienza dei Materiali e Ingegneria Chimica Politecnico Torino, Italy
3 Dipartimento di Scienze Chimice e Sincrotrone Trieste SCpA, Trieste, Italy
4 ENICHEM SpA, Centro di Ricerche di Novara, Via G. Fauser 4, Novara, Italy
We report a XAFS study of the Fe3+ local environment in Fe-silicalite as a function of the template burning temperature. We investigate the structural changes of the zeolitic structure, upon thermal treatments and interaction with NH3. Our XAFS results show that, before template burning, Fe3+ are in tetrahedral symmetry with 4 oxygens at 1.85 Å, while after template removal and in vacuum conditions, they exhibit a distorted tetrahedral symmetry with 3 oxygens at 1.87 Å, and one at 2.10 Å ; dosage of NH3 partially restore the tetrahedral symmetry of the site. These results are strongly supported by parallel IR, Raman, UV-Vis, TPR and EPR investigations and by recent theoretical simulations.
© EDP Sciences 1997