Petroleum Processing and Petrochemicals ›› 2014, Vol. 45 ›› Issue (10): 41-46.
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Abstract: Fe-ZRP zeolites were synthesized through solid state ion exchange, ion exchange and impregnation method. The zeolites were characterized by XRD, XPS, SEM and pyridine adsorption IR spectra to investigate the physico-chemical properties and the distributions, compositions and transfer cases of iron in the ion exchanged zeolites. The catalytic performance of zeolites by different methods and the functions of Fe2O3 loading introduced by solid ion exchange were examined as well. The results show that the surface Lewis acid and weak acid content are increased, resulting more total acid. The amount of Bronst acid is reduced in cases of impregnation and solid ion exchange. A less effect on total acid amount by liquid ion exchange is observed. Three forms of iron: isolate Fe3+ species, iron oxide clusters and α-Fe2O3 particles are found in the samples. Iron is mainly on the skeleton by liquid ion exchange method; while only part of iron are exchanged into the skeleton and more surface α-Fe2O3 particles are formed by solid state ion exchange. As increase of Fe2O3 loading, the areas and volumes of micro-pores of zeolites decrease due to the occupation of part of micropores by iron oxide. Ion exchanges low down the crystallinity of the zeolite for local excess acid. The change of acid is not linear with increase of iron. The threshold of loading amount is 2%-3% of iron that does not make particles gather. Lewis acid amount exists a maximum value within the loading amount tested.
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