Characterization of intrazeolitic Fe3+ prepared by chemical vapor deposition of [(C5H5)Fe(CO)2]2 inside NaY and FSM-16 zeolites and their catalytic activities towards phenol hydroxylation

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, N-2 adsorption and Mossbauer measurements were used to characterize the various materials. An isomorphous substitution of Fe3+ into the framework of NaY zeolite was accomplished as determined from the Mossbauer results (IS less than or equal to 0.3) as well as from the increase in the unit cell volume. As a further confirmation, some framework IR bands (780 and 574 cm(-1)) showed a shift towards lower frequencies upon iron incorporation along with the existence of a band at 686 cm(-1) 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 Fe3+ components were revealed in FSM-16 and del-NaY samples specified as intrazeolitic iron oxide clusters and alpha-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. (C) 2003 Published by Elsevier Ltd.