Abstract
Imogolite is a tubular clay mineral with a typical chemical composition of (OH)3Al2O3SiOH. This material has been expected as a shape selective catalyst, however, because of its chemical stability, an incorporation of another element is necessary to generate a chemical function. Thus Fe containing imogolite was prepared using NaSiO4, FeCl3 and AlCl3. In the case of the ratio of Fe/(Al+Fe) =0.1 in the starting solution, the product was amorphous. In the case of the sample with the ratio of Fe/(Al+Fe) =0.05 named “Fe-imo”, we obtained the XRD profile and the IR spectrum which were similar to those of the imogolite. The state of iron was found to be octahedral Fe3+ ion in the sample from the UV-VIS diffuse reflectance spectrum and X-ray absorption spectrum. The EXAFS function of Fe-imo is different from that of Fe3+ ion adsorbed on the imogolite (abbrev. Fe/imo). In the catalytic oxidation of cyclohexene, it was found that the catalytic properties were different for Fe-imo and Fe/imo. It is an interesting finding that Fe-imo catalyzed the oxidation of benzene to yield phenol. It is considered that state of Fe3+ in Fe-imo is different from that of Fe/imo and has higher potential toward oxidation reaction.
