Iron-Silicalite and FAPO-5 were synthesized by hydrothermal reaction and characterized by measns of physico-chemical methods such as XRD, SEM, EPR, DRS and oxygen isotope reaction.
Only limited amounts of iron ions are isomophously substituted into framwork structures even in as synthesized form. By calcination to remove the template, some of framework iron ions seemed to be removed from its framework position.
The nature of nonframework iron species in Iron-Silicalite seems to be different from that of FAPO-5. In Iron-Silicalte, the nonframework species are located in cationic positions and they are easily reduced by vacuum dehydration process. In FAPO-5, they are located in internal pore probably as Fe(III)-phosphate clusters or ferromagnetic iron clusters and are hardly reduced even by strong reductive treatment. These differences may be due to the presence of framework charge arising from isomorphous substitution of Fe(III) ions.
Iron-Silicalite and FAPO-5 showed similar dependence on iron content and different dependence on the degree of thermal treatment in its CO oxidation and oxygen isotope exchange reactions. This may be attributed to the difference in the nature of nonframework iron species in iron-Silicalite and FAPO-5.
