Photon Factory Activity Report 2014 #32 (2015) B

NW10A/2013G197

XAFS Characterization of Oxide-Supported Ru Nanoparticle Catalysts
for Selective Nitrile Hydrogenation

Satoshi MURATSUGU1,2, Sutasinee KITYAKARN1,3, Fei WANG1,2, Nozomu ISHIGURO1,3,Mizuki TADA*1,2,3
1
Department of Chemistry, Graduate School of Science, Nagoya University, Furo, Chikusa, Aichi
464-8602, Japan.
2
Institute for Molecular Science, Myodaiji, Okazaki, Aichi 444-8585, Japan.
3
Research Center for Materials Science, Nagoya University, Furo, Chikusa, Aichi 464-8602, Japan.
1 Introduction
Several supported ruthenium nanoparticle catalysts
were prepared by the attachment of Ru3(CO)12 on various
oxide supports, and catalytic performance onhydrogenation of valeronitrile highly depended on thetype of oxide supports of catalysts. It was found out that
K-doped ΑluC-supported Ru nanoparticle catalyst (Ru3CO/K-AluC) exhibited the highest activity and selectivity
to corresponding primary amine for the hydrogenation ofvaleronitrile
among
other
oxide-supported
Runanoparticles we prepared.[1] The local coordination
structures of Ru catalysts after the catalytic reaction wereinvestigated by Ru K-edge EXAFS analysis to obtain the
structural change in Ru nanoparticles.[1]2 Experiment
Catalysts were prepared by a wet impregnation method,and valeronitrile hydrogentaion reactions were conducted
in n-heptane under 101.3 kPa of H2 at 343 K. After thecatalytic reaction, the samples were collected. Ru K-edge
XAFS was measured in transmission mode at 20 K at theNW10A station with a Si(311) double-crystal
monochromator. The energy and current of electrons inthe storage ring were 6.5 GeV and 60 mA, respectively.
Ionization chambers filled with pure Ar and pure Kr wereused to monitor incident and transmitted X-rays,respectively. EXAFS spectra were analysed withIFEFFIT (Athena and Arthemis) ver. 1.2.11. k3-Weighted
EXAFS oscillations (30–150 nm−1) were Fouriertransformed into R-space, and curve-fitting analysis wascarried out in k-space. Fitting parameters werecoordination number (CN), interatomic distance (R),Debye-Waller factor (σ2), and correction of-edge energy(∆E0). Phase shifts and backscattering amplitudes for RuRu and Ru-O were calculated by using Ru metal andRuO2, respectively.
3 Results and Discussion
The local coordination structures of catalysts wereexamined by Ru K-edge EXAFS analysis, and structuralparameters are listed in Table 1. The Ru3-CO/K-AluC (Ru:2 wt%, K: 4 wt%) before the hydrogenation reaction had
Ru-Ru interaction at 0.265 ± 0.001 nm (Its coordination
number (CN) was estimated to be 4.6 ± 0.6.), and Ru-O

interaction at 0.200 ± 0.003 nm (Its CN was estimated tobe 2.1 ± 0.8.). The Ru-O interaction disappeared after thehydrogenation reaction of high primary amine selectivity,and only Ru-Ru interaction was observed. The CN of RuRu of Ru3-CO/K-AluC after the reaction at 0.264 ± 0.001
nm was 5.3 ± 0.8, which was increased a little comparedwith the value before the reaction.
On the other hand, the Ru-O interaction was stillobserved on the Ru catalyst prepared on AluC without Kdoping (Ru3-CO/AluC (Ru: 2 wt%)) after thehydrogenation reaction. The CN of Ru-O at 0.204 ± 0.002
nm was 2.2 ± 0.6, and the CN of Ru-Ru at 0.262 ± 0.001
nm was 2.5 ± 0.4, which was smaller than that of Ru3CO/K-AluC. This result suggests that the oxidized Ru
species still existed after the catalytic reaction, whichmight result in the low selectivity of the primary amine.
When MgO was used as the support, the selectivity ofprimary amine on Ru3-CO/MgO was also lower than thatof Ru3-CO/K-AluC. The local coordination analysis of Ru
K-edge EXAFS of Ru3-CO/MgO after the reaction
exhibited the similar trends as Ru3-CO/AluC.
Table 1 Curve-fitting results of Ru K-edge EXAFS Fourier transformsof the oxide-supported Ru nanoparticle catalysts (Ru: 2 wt%) aShell

CNR /nm∆E0 /eVσ2 /× 10-5 nm2

Ru3-CO/K-Alu C (Rf = 0.8%) Before reaction
2.1 ± 0.8
0.200 ± 0.003
2±58±4Ru-O
4.6 ± 0.6
0.265 ± 0.001
1±19±1
Ru-Ru
Ru3-CO/K-Alu C (Rf = 1.9%) After reaction
Ru-Ru
5.3 ± 0.8
0.264 ± 0.001
2±27±1
Ru3-CO/MgO (Rf = 1.2%) After reaction
Ru-O
2.4 ± 0.9
0.204 ± 0.003
5±59±4Ru-Ru
4.0 ± 0.7
0.269 ± 0.001
5±19±1
Ru3-CO/Alu C (Rf = 1.5%) After reaction
Ru-O
2.2 ± 0.6
0.204 ± 0.002
6±48±3Ru-Ru
2.5 ± 0.40.262 ± 0.001
1±28±1ak range and R range were 30-150 nm-1 and 0.13-0.30 nm,
respectively.

References[1] S. Muratsugu, S. Kityakarn, F. Wang, N. Ishiguro, T.
Kamachi, K. Yoshizawa, O. Sekizawa, T. Uruga, M. Tada,
Phys. Chem., Chem. Phys., Accepted.
* mtada@chem.nagoya-u.ac.jp