Effect of aluminum on the nature of the iron species in Fe-SBA-15

Y. Li, Z. Feng, H. Xin, F. Fan, J. Zhang, P.C.M.M. Magusin, E.J.M. Hensen, R.A. Santen, van, Q. Yang, Can Li

Research output: Contribution to journalArticleAcademicpeer-review

61 Citations (Scopus)

Abstract

We report the preparation of highly ordered mesoporous Fe-Al-SBA-15 with isolated extraframework Fe species under acidic conditions. The materials were characterized by means of UV resonance Raman spectroscopy, in conjunction with BET, XRD, TEM, UV-vis, H2-TPR, FT-IR, and 27Al MAS NMR spectroscopy. The addition of both Fe and Al to the synthesis gel of SBA-15 results in the formation of isolated extraframework Fe species located close to the framework Al ions and the Fe content an order of magnitude higher than that in Fe-SBA-15 synthesized without Al. The existence of anchored extraframework Fe species was confirmed by the presence of a strong absorption band at 270 nm, hydrogen reduction at relatively low temperature, and the presence of a resonance Raman band at 1140 cm-1. The location of Fe in close proximity to framework Al nuclei is further supported by 27Al MAS NMR measurements. Two characteristic UV Raman bands at 510 cm-1 and 1090 cm-1 excited by 244-nm laser are assigned to Fe-O-Si symmetric and asymmetric stretching modes of isolated tetrahedral Fe ions in the silica framework for Fe-SBA-15. The resonance Raman band at 1140 cm-1 excited by 325-nm laser is attributed to the asymmetric stretching mode of the isolated extraframework iron species in Fe-Al-SBA-15. The isolated Fe species close to framework Al species are stable in acidic HCl solution, whereas the majority of Fe species in Fe-SBA-15 can be easily removed. [on SciFinder (R)]
Original languageEnglish
Pages (from-to)26114-26121
JournalJournal of Physical Chemistry B
Volume110
Issue number51
DOIs
Publication statusPublished - 2006

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