Electron spin resonance study of the incorporation of iron in ferrisilicalite and FAPO-5

Ferrisilicalite and FAPO-5 were synthesized hydrothermally with iron contents from 0.1 to 1% on a molar basis and investigated by X-ray diffraction and electron spin resonance (e.s.r.) in the as-synthesized, oxidized, and reduced forms. The amount of Fe in the solid, the degree of crystallinity, and the Fe3+ e.s.r. signal intensity all increase with synthesis time in the same manner, indicating a gradual incorporation 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 defect sites, and in the form of oxidic clusters.