The pH effect on the preparation of MFI type ferrisilicate zeolites

Ferrisilicates with MFI type structure were hydrothermally synthesized. The structural environments of iron in the ferrisilicates were characterized b y XRD, SEM, IR, EPR, and ammonia-TPD. It has been shown that pH of the fina l gel mixture during the synthesis affects the crystal size, morphology, ch emical composition and catalytic activity. The results of the lattice param eters, IR, and EPR indicate the existence of a framework iron and the conte nt of framework iron depends on pH of the synthesis gel. Finally, the catal ytic activity of these zeolites was examined for the cyclohexane oxidation to cyclohexanol and cyclohexanone in the liquid phase. The conversion of th is reaction was increased with increasing iron content of the framework lat tice positions.