Photon Factory Activity Report 2005 #23 Part B (2006)
Chemistry

9C,12C/2004G280

Preparation and Characterization of the Ni/CeO2/Al2O3 Catalyst for
Steam gasification of Biomass
Tomohisa MIYAZAWA*1, Takeo KIMURA1, Jin NISHIKAWA1,Kazu OKUMURA2, Kimio KUNIMORI1, Keiichi TOMISHIGE1
1
Institute of Materials Science, Univ. of Tsukuba, Tsukuba Ibaraki 305-8573, Japan2
Department of Materials Science, Tottori Univ., Koyama-cho, Minami, Tottori 680-8552, Japan
Introduction
Conversion of biomasses to hydrogen and synthesis gas
becomes more and more important in terms of theutilization of renewable sources. Our group has beenreported that Rh/CeO2/SiO2 was very effective to thegasification of biomass [1]. However, the catalyst has
problems in high cost and limited availability originatedfrom the usage of Rh. Recently, we have investigatedvarious oxide supported Ni catalysts in steam gasification.
As a result, it is found that CeO2 support played animportant role on the decrease of coke deposition. Here
we show the results of the EXAFS analysis of theNi/CeO2/Al2O3 catalysts prepared by co-impregnation andsequential impregnation methods and we discuss therelation between the results and catalyst activity for steam
gasification of real biomass.
Experimental
Ni/CeO2/Al2O3 catalysts were prepared by two differentmethods. One was co-impregnation method, and the otherwas sequential impregnation method. In the coimpregnation method, an Al2O3 support (JRC-ALO-1)
was impregnated with the aqueous solution ofNi(NO3)2•6H2O and Ce(NH4)2(NO3)6 (Wako) mixture by
the incipient wetness method. In the case of the sequential
impregnation, the CeO2 was loaded on the Al2O3 and after
the calcination at 773 K for 3 h, Ni was loaded on thisCeO2/Al2O3. After the impregnation, both catalysts weredried at 383 K for 12 h, followed by the calcination at 773
K for 3 h under air atmosphere. The loading amount of Ni
was 4 wt%, and that of CeO2 was 30 wt%. The catalysts
prepared by the co-impregnation method and thesequential impregnation method are denoted as
Ni/CeO2/Al2O3 (CI) and Ni/CeO2/Al2O3 (SI), respectively.
EXAFS spectra were measured by transmission mode at
377 K. After back ground subtraction, k weighted EXAFS
functions were Fourier transformed into R space and theone or two-shell fitting were analyzed by curve fitting.

Results and Discussion
3The Fourier transforms of k -weighted Ni K-edge
EXAFS oscillations for reduced Ni/CeO2/Al2O3 (CI),
Ni/CeO2/Al2O3 (SI) and Ni/Al2O3 catalyst are shown inFig. 1 and the fitting results are summarized in Table 1.
From the fitting results of EXAFS data, we could fit thespectrum only Ni-Ni species. The coordination number ofNi-Ni on the Ni/CeO2/Al2O3 (SI) was similar to that of Ni/
Al2O3. On the other hand, Ni/CeO2/Al2O3 (CI) gave much
lower coordination number of Ni-Ni than other catalysts.
This result indicates that the Ni particles were highly
dispersed on the CeO2/Al2O3 by co-impregnation and theparticle size of Ni on the Ni/CeO2/Al2O3 (CI) was much
lower than that of Ni/CeO2/Al2O3 (SI) and Ni/Al2O3 due tothe strong interaction of CeO2 and Ni. And this can berelated to the high performance of Ni/CeO2/Al2O3 (CI) on
the steam gasification of biomass.

Fig. 1. Results of Ni K-edge EXAFS analysis of Ni catalysts
Reference[1] K. Tomishige, et al. Appl. Catal. A: Gen. 246 (2003) 103*tkmyzw@ims.tsukuba.ac.jp

Table1 Curve fitting results of Ni-K edge EXAFS of various Ni catalysts after reduced at 773 K.

aCoordination number. bBond distance. cDebye-Waller factor. dDifference in the origin of photoelectron energyebetween the reference and the sample. Residual factor. Fourier filtering range: 0.129-0.295 nm.

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