SPring-8, the large synchrotron radiation facility

Inquiry number

SOL-0000001205

Beamline

BL01B1 (XAFS I)

Scientific keywords

A. Sample category	inorganic material
B. Sample category (detail)	amorphous, glass
C. Technique	absorption and its secondary process
D. Technique (detail)	XAFS, EXAFS, XANES
E. Particular condition	polarization (linear), low-T (~ liquid He)
F. Photon energy	X-ray (> 40 keV)
G. Target information	chemical state, chemical bonding, local structure, function and structure, function

Industrial keywords

level 1---Application area	display, environment, Chemical product, others
level 2---Target	catalysis, Environmental material
level 3---Target (detail)
level 4---Obtainable information	local structure, chemical state
level 5---Technique	XAFS, NEXAFS

Classification

A80.34 catalysis, M40.10 XAFS

Body text

In this solution, EXAFS method was applied to study local environments of Re(9.2 wt%)/Fe₂O₃, catalysts for methanol partial oxidation reaction to produce methylal. The EXAFS method is a powerful technique to study local structure (distance, coordination number, species of neighbor atoms) of selected elements both in crystalline states and in non-crystalline states. For this sample, Re L₃-edge EXAFS is difficult to measure due to large absorption by Fe₂O₃ support. High quality EXAFS spectrum could be measured at high energy Re K-edge (Fig. 1). EXAFS analysis revealed that Re and Fe atoms form a Re-Fe binary oxide and stabilize an active ReO₄ structure (Fig. 2).

Fig. 1 Re K-edge EXAFS spectrum of Re(9.2 wt%)/Fe₂O₃.

Fig. 2 Proposed structure oｆ Re active site on Re/Fe₂O₃.

Source of the figure

Bulletin from SPring-8

Bulletin title

SPring-8 Research Frontiers, 2000-2001

Page

53,54

Technique

XAFS spectra of dense samples are taken in a transmission mode. This method is performed by measuring x-ray absorption as a function of x-ray energy around an absorption edge of a selected element. Since EXAFS oscillation is smeared in high-energy region, XAFS spectra at more than 50 keV are usually measured at low temperature (10 K) to get high quality data by lowering temperature factor. Acquisition time per XAFS spectrum using QXAFS mode is 30-45 min in this solution.

Source of the figure

No figure

Required time for experimental setup

2 hour(s)

Instruments

Instrument	Purpose	Performance
XAFS Measurement System	Measurement of XAFS spectra	3.8-113 keV
Ionization Chamber	Measurement of transmission mode XAFS	concentration > 1000 ppm

References

Document name
T. Shido et al., SPring-8 Reserch Frontiers, 2000-2001, (2001) 53

Related experimental techniques

Questionnaire

The measurement was possible only in SPring-8. Impossible or very difficult in other facilities.
This solution is an application of a main instrument of the beamline.

Ease of measurement

Easy

Ease of analysis

Middle

How many shifts were needed for taking whole data in the figure?

Less than one shift