Photon Factory Activity Report 2005 #23Part B (2006)
Surface and Interface

10B,13C/2005G192

Development of New Catalysts for Ultra Deep HDS Using TiO2-Al2O3 CompositeSupportsTakumi HARADA1, Masaya WATANABE1, Takako FUNAMOTO1, Motoyasu IMAMURA2,Nobuyuki MATSUBAYASHI2, Kohichi SEGAWA*1
1
Department of Chemistry, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan
2
National Metrology Institute of Japan, AIST, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, JapanExperimental
The two different supports investigated in this study areas follows: γ- Al2O3 and TiO2-coated alumina supports
prepared by CVD. The supported Ni and NiMo catalysts
were prepared by successive impregnation with citric acidat 1.16 mol ratio of citric acid per Ni. These catalysts
were sulfided with a mixture of H2S (5%) and H2 at 673 K
without calcination. Both before and after sulfied
catalysts were characterized with XAFS. Spectra at Mo
K-edge and Ni K-edge were measured in a transmission
mode at room temperature at the BL-10B using Si (311)
as a crystal monochromator. XPS spectra of Mo 3d, S 2pand Al 2p were also measured by using the excitationenergy-variable XPS at the BL-13C.
Result and discussions
We started from an XAFS study for clarification of theeffects of both Ni and citric acid addition into Mo
catalysts by using alumina supports. Figure1 shows thefourier transforms of Mo K-edge XAFS of Ni/Al2O3 andNiMo/Al2O3 catalysts with citric acid. The phase shift andback scattering amplitude were corrected as Mo-O bondusing FEFF8. The peak around 0.17 nm was assigned to2Mo-O bonds of MoO4 with tetrahedral structureconsidering the intensity and the width of the peak. This2indicates that Mo was impregnated on Al2O3 as MoO4
before sulfidation. The peaks assigned to Mo-S (0.24 nm)
and Mo-(S)-Mo (0.32 nm) of the spectra of aftersulfidation in the Fig. 1 show that Mo mostly changed toMoS2 by sulfidation.

72

Users' Report

Power of FT

1.5

1Mo-O

Ni:Mo=0:10 before sulfidation

Mo-S

Ni:Mo=2:8 before sulfidation
Ni:Mo=0:10 after sulfidation
Ni:Mo=2:8 after sulfidation

Mo-Mo
Mo-(O)-Mo or Ni
0.5000.20.40.6

0.8

1.0R/ nmFig. 1 Mo K-edge XAFS spectra of NiMo/Al2O3 withcitric acid catalysts before and after sulfidation.
3Ni-O

Ni:Mo=10:0 with citric acid
Ni:Mo=2:8 with citric acid
Ni:Mo=10:0 without citric acidPower of FTIntroduction
Because of the new environmental regulations
regarding the sulfur content of diesel, the ultra-deephydrodesulfurization (HDS) of gas oil is currentlydemanded. To improve catalytic HDS activity, we havestudied a new preparation method of NiMo catalysts
using the citric acid as a chelate agent. We found that
addition of citric acid into the NiMo impregnation step iseffective in improving HDS activity of 4,6-dimethdibenzothiophene. We assumed that the higher activity ofHDS was correlated with the increase of the number ofcatalytic active sites on NiMo catalysts from our HDS
reaction data, but no detailed structural study wasavailable. In this research, we have studied both
NiMo/Al2O3 and NiMo/TiO2-Al2O3 with citric acidcatalysts by using XAFS measurements.

Ni:Mo=2:8 without citric acid

2Ni-Ni of nickel aluminate
Ni-Ni of nickel oxide
1000.2

0.4

0.6

0.8

1.0

R/ nmFig. 2 Ni K-edge XAFS spectra of NiMo/Al2O3 with andwithout citric acid catalysts before sulfidation.

Fourier transforms of Ni K-edge XAFS of NiMo
catalysts with and without citric acid addition are shownin Fig. 2. The peak at 0.30 nm was assigned to Ni-(O)-Niof nickel aluminate with spinel structure and the peak at
0.32 nm to Ni-(O)-Ni of Ni2O3. The results show that
addition of citric acid inhibited the formation of nickelalminate and nickel oxide. The existence of Mo also
suppressed the formation of nickel alminate. Nickel
aluminate was so stable that it remained after sulfidation.
NiMo catalysts are activated by sulfidation, therefore,
nickel alminate decreases the catalytic active sites. This
result was well aligned with our reaction result, whichindicated an increase of catalytic acidic sites for NiMo
catalysts with citric acid.
The depth profile of Mo/Al ratios in XPS spectra of
NiMo catalysts with and without citric acid suggests thatthe migration of Mo into the alumina support wassuppressed in the case of catalysts with citric acid.
*k-segawa@sophia.ac.jp