ELECTRON-SPIN-RESONANCE STUDY OF THE INCORPORATION OF IRON IN FERRISILICALITE AND FAPO-5

Ferrisilicalite and FAPO-5 were synthesized hydrothermally with iron c ontents from 0.1 to 1% on a molar basis and investigated by X-ray diff raction and electron spin resonance (e.s.r.) in the as-synthesized, ox idized, and reduced forms. The amount of Fe in the solid, the degree o f crystallinity, and the Fe3+ e.s.r, signal intensity all increase wit h synthesis time in the same manner, indicating a gradual incorporatio n of Fe3+. At the same Fe content, different spectral behaviors of Fe3 + in Fe-silicalite and in FAPO-5 are attributed to the differences in the degree of isomorphous substitution, in the amount of Fe3+ in defec t sites, and in the form of oxidic clusters.