On the role of aluminum in the selective oxidation of benzene to phenol by nitrous oxide over iron-containing MFI zeolites: an in situ Fe XANES study

Hensen, Emiel J. M.; Zhu, Qingjun; Liu, Pang-Hung; Chao, Kuei‐Hsiang; Santen, Rutger A. van

doi:10.1016/j.jcat.2004.06.010

Cited by 61 publications

(17 citation statements)

References 23 publications

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“…With the introduction of extralattice Al ions, Mul et al [29] observed an infrared absorption peak at 1635 cm -1 and assigned it to the Fe-OAl linkage. The presence of the Fe-O-Al species in Fe/ ZSM-5 zeolite was confirmed by the latter studies of van Santen et al [30][31][32]. It is believed that the Fe-O-Al species is one of the competing active sites in Fe/ZSM-5 zeolite, because the concentrations of the ''a-O'' species increase linearly with the amounts of the extra-lattice Al ions.…”

Section: Introductionmentioning

confidence: 68%

“…The 18 O-isotope labeling studies [15,16] supported the Eley-Rideal mechanism. Various experimental techniques have been used to characterize the ''a-O'' species [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. As the IR, EXAFS, TPD and TPR results [17][18][19][20] indicated, the mono-iron species does exist in the Fe/ZSM-5 zeolite, especially at low Fe loadings (Fe/Al \ 1.0).…”

Section: Introductionmentioning

confidence: 99%

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Active Sites in Fe/ZSM-5 Zeolite

et al. 2010

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Fe/ZSM-5 zeolite has shown great potential in the selective oxidations of hydrocarbons such as methane and benzene. The various competing active sites of Fe/ ZSM-5 zeolite are reviewed, including the mono-iron, oxygen-bridged [Fe, X] (X = Fe, Al) and peroxide species; in addition, the influences of H 2 pretreatment are considered. For the mono-iron species, the H 2 molecules are chemisorbed on the Fe(III) sites via the g 2 -binding mode. Both high-and low-spin Fe(III) ions play an important role during the H 2 reduction process whereas the former predominates in the N 2 O decomposition process. As the calculated energy barriers indicate, the Fe(III) ions are facile to be reduced by H 2 pretreatment and therefore the active site of the mono-iron species should be in the FeO(OH) form. Instead, the oxygen-bridged [Fe, X] and peroxide species remain stable by H 2 pretreatment. The suitable oxygenbridged [Fe, X] structures are screened out by comparisons with the experimental data and energy considerations from computational aspects. The geometries are in good agree-

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Section: Introductionmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Active Sites in Fe/ZSM-5 Zeolite

et al. 2010

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“…The next nearest-neighbour atoms are silicon (or aluminium) atoms. The characterization techniques that display typical spectral features for Fe F (Fe III in T d symmetry) and which are most widely used to prove its presence are EPR [17][18][19], Mössbauer [20][21][22] and XAFS [23,24].…”

Section: Framework Fe Fe Fmentioning

confidence: 99%

New frontiers in X-ray spectroscopy in heterogeneous catalysis: Using Fe/ZSM-5 as test-system

et al. 2005

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We have applied a number of novel X-ray spectroscopic tools to Fe/ZSM-5 systems. Fe/ZSM-5 can be considered as an ideal test-system for the characterization techniques in heterogeneous catalysis. The existence of a large range of sites and structures creates a good testing ground to determine which experimental tools are able to resolve such complex system. In situ soft X-ray absorption provides important information on the valence and electronic structure of iron during treatments, with a time scale down to 30 s. Kb-detected XANES yields unprecedented resolution for pre-edge structures and using hard X-rays can be used under any condition and treatment, including high-pressures. It can be expected that both in situ soft X-ray absorption and Kb-detected XANES become 'standard' tools for catalysis research, similar to traditional XANES and EXAFS today. The X-MCD is also used in this paper but it will probably remain a rather specialized technique in the field of heterogeneous catalysis. Further new developments for catalysis characterization are for all to be expected from X-ray spectro-microscopy, where one will have the possibility to perform the in situ soft X-ray absorption and Kb-detected XANES experiments with nanometer size spatial resolution. #

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“…It can be seen clearly that a pre-edge peak P appears at approximately 7112 eV, which corresponds to the 1s-3d electron transition due to the hybridization of the O 2p orbit and the Fe 3d orbit. 19,20) Peak S at approximately 7127.2 eV corresponds to the 1s-4p electron transition. 21) At first glance, there is very little difference in the XANES spectra between the two samples.…”

Section: Resultsmentioning

confidence: 99%

Structures and Dielectric Properties of Pb(Fe_1/2Nb_1/2)_1-xTi_xO₃Single Crystals

Liu¹,

Zhang²,

Wei³

et al. 2012

Jpn. J. Appl. Phys.

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The structures and dielectric properties of Pb(Fe 1=2 Nb 1=2 ) 1Àx Ti x O 3 (PFNT, x ¼ 0:07 and 0.48) single crystals were investigated using a combination of temperature-dependent dielectric, X-ray diffraction (XRD), Raman, and X-ray absorption fine structure (XAFS) spectra. Detailed structure analyses reveal that the crystal structure of PFNT (x ¼ 0:48) is single-phase tetragonal perovskite, whereas that of PFNT (x ¼ 0:07) is a mixture of rhombohedral and tetragonal phases. The structural differences are found to have significant connections with the dielectric properties in the temperature range of 90-300 K. Both samples exhibit a frequency-dependent dielectric anomaly, arising primarily from the 3d electrons hopping between Fe 2þ and Fe 3þ . The second dielectric anomaly, which is a weak frequency dispersion and observable only for PFNT (x ¼ 0:07), was probably caused by a dipole glass behavior near the morphotropic phase boundary. #

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On the role of aluminum in the selective oxidation of benzene to phenol by nitrous oxide over iron-containing MFI zeolites: an in situ Fe XANES study

Cited by 61 publications

References 23 publications

Active Sites in Fe/ZSM-5 Zeolite

Active Sites in Fe/ZSM-5 Zeolite

New frontiers in X-ray spectroscopy in heterogeneous catalysis: Using Fe/ZSM-5 as test-system

Structures and Dielectric Properties of Pb(Fe_1/2Nb_1/2)_1-xTi_xO₃Single Crystals

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On the role of aluminum in the selective oxidation of benzene to phenol by nitrous oxide over iron-containing MFI zeolites: an in situ Fe XANES study

Cited by 61 publications

References 23 publications

Active Sites in Fe/ZSM-5 Zeolite

Active Sites in Fe/ZSM-5 Zeolite

New frontiers in X-ray spectroscopy in heterogeneous catalysis: Using Fe/ZSM-5 as test-system

Structures and Dielectric Properties of Pb(Fe1/2Nb1/2)1-xTixO3Single Crystals

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Structures and Dielectric Properties of Pb(Fe_1/2Nb_1/2)_1-xTi_xO₃Single Crystals