Iron-modified mesoporous and microporous zeolite materials, namely FSM-16 and NaY as well as dealuminated
NaY (del-NaY), were prepared using cyclopentadienyl iron dicarbonyl diamer [(C5H5)Fe(CO)2]2 via a
chemical vapor deposition (CVD) technique. XRD, FTIR, TG/DSC, N2 adsorption and Mo¨ssbauer measurements
were used to characterize the various materials. An isomorphous substitution of Fe3þ into the framework of NaY
zeolite was accomplished as determined from the Mo¨ssbauer results (IS 0:3) as well as from the increase in the
unit cell volume. As a further confirmation, some framework IR bands (780 and 574 cm1) showed a shift
towards lower frequencies upon iron incorporation along with the existence of a band at 686 cm1 ascribed to
Si–O–Fe linkages. The latter band was emphasized on the basis of comparison of NaY before and after the CVD
treatment with the precursor of the Fe complex. Two types of octahedral Fe3þ components were revealed in
FSM-16 and del-NaY samples specified as intrazeolitic iron oxide clusters and a-Fe2O3 species, which were
localized on the external surfaces of zeolites and occupied small percentages (18–22%) compared with the former
species. The surface area of the support NaY was preserved after the CVD treatment rather than FSM-16 that
showed a reduction (24%). The catalytic activities of various samples for the liquid phase hydroxylation of
phenol using H2O2 were found to be in the order: Fe/NaY > Fe/FSM-16 > Fe/del-NaY. The higher activity of the
Fe/NaY sample was attributed to the high dispersity of Fe ions that are located in framework positions and to the
high crystallinity. |
