Co-ZSM-5 Zeolites: Characterization and Magnetic Properties

L. PIERELLA; C. SAUX; M. FERNÁNDEZ GARCÍA; P. G. BERCOFF; H. R. BERTORELLO

Rio de Janeiro, Brasil

Congreso; 2nd Mercosur Congress on Chemical Engineering - 4th Mercosur Congress on Process Systems Engineering (ENPROMER 2005); 2005

ZSM-5 zeolites modified with Co cations were synthesized. They were characterized by AA, XRD, Raman Spectroscopy, TPR, FTIR and BET. The Co ions were introduced in the zeolitic matrix by wet impregnation or ion-exchange methods, followed by thermal treatments. The incorporation of cobalt ions onto ZSM-5 does not affect the high degree of purity, cristallinity and orthorhombic symmetry of the samples, verified at long range by XRD and at short range by FTIR. According to FTIR experimental data of pyridine adsorbed (at room temperature and 3 Torr) and desorbed at different temperatures, in all the samples can be observed the presence of both Brönsted (1550 cm-1) and Lewis (1450 cm-1) acidic sites. Co-ZSM-5 materials show the formation of new and strong Electron-Donor-Acceptor Adduct (EDA) of pyridine to Lewis sites, compared with the H-ZSM-5 (sample A), since they retain more pyridine after outgassing at 400°C. The Raman spectra and TPR profiles showed significant differences between Co-impregnated (sample B) and Co-exchanged (sample C) materials. The Raman spectroscopy clearly indicated that Co3O4 species were present only in the sample B. No evidence of reduction of Co3O4 to CoO and Co0 by TPR was observed in the sample C. The magnetic properties were studied, analyzing the effect of the built-in cation type. Hysteresis loops were measured at room temperature, and the results were correlated with the nature of the present ions in the zeolite. The magnetic properties will be correlated with the catalytic properties of the Co-ZSM-5 materials.