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

10B/2005G220

Characterization of rhodium-molybdenum catalysts supported on mesoporous
silica for highly selective hydroformylation of propene
Yasuo Izumi* and Masayasu Tsukahara
Tokyo Institute of Technology, Nagatsuta 4259-G1-16, Midori-ku, Yokohama 226-8502
Introduction
Mesoporous silica crystalline, e.g. MCM and FSM
families, bears the possibility of various kinds of shapeand chemo-selective catalysis inside the space of 2 – 50
nm. The low population of silanol groups in the mesopore
hampered to accommodate enough metal active site in themesopore. The anchoring using alkyl alkoxysilane withphosphine, amine, halogens, or thiol group requires
complicating synthetic procedure to fix greater amount ofmetal active site.
In this work, simplified procedure to use heteropolyacid as a binder of rhodium metal complex site and FSM16 was investigated. The series of model Rh-Mo catalysts
were characterized using Rh and Mo K-edge synchrotron
XAFS.
Experimental section
Preparation of [Rh(COD)2]-[AlMo6]/FSM-16+3–[NH4] 3[AlMo6O18(OH)6] was dissolved in water and2 –1
mixed with FSM-16 (specific surface area 1294 m g ,+–Fuji Sylysia). After evaporation, [Rh(COD)2] [BF4](COD = cyclooctadiene) in ethanol was added and reacted
for 12h. Obtained cake was washed well with ethanol. As+–a control, [Rh(COD)2] [BF4] solution was directly mixed
with FSM-16 and obtained powder was washed well withethanol.
Preparation of [RhMo6]/FSM-16+
3–[NH4] 3[RhMo6O18(OH)6] was dissolved in water andmixed with FSM-16 for 12h. After evaporation, obtained
cake was washed well with ethylene glycol (EG). The Rh
amount introduced was fixed to 3.0 wt% but a part of Rh,
Al, and Mo introduced may be lost during washing withethanol/EG for [AlMo6O18(OH)6]/FSM-16, [Rh(COD)2][AlMo6O18(OH)6]/FSM-16, and [RhMo6O18(OH)6]/FSM16.

XAFS spectra were measured at beamline 10B intransmission mode at 30 – 290 K. The data was analyzed
using a package XDAP version 2.1.2 from XAFS
Software International.
Results and discussion
The EXAFS analysis results were summarized in Table+1. [Rh(COD)2] was bound on the surface in FSM-16
mesopore with two surface oxygen atoms (NRh-O = 2.0) in
the absence of binder. The loading amount was 0.3 wt%
3–Rh. When [AlMo6O18(OH)6] was used as binder,+[Rh(COD)2] was bound on the surface with three oxygenatoms (NRh-O = 3.0), possibly bridging oxygen atoms on
3–
the dish-shaped Anderson-type [AlMo6O18(OH)6]
molecule. The loading amount was 1.2 wt% Rh. Two
COD ligands seems to be maintained upon supporting(NRh-C, NRh•••C).
The curve fit analyses of EXAFS measured for[RhMo6]/FSM-16 are in progress. The χ function and its
associated Fourier transform of the Rh K-edge spectra
were perturbed compared to the data for+3–
[NH4] 3[RhMo6O18(OH)6] crystal, suggesting the induced
distortionduetotheinteraction
between3–[RhMo6O18(OH)6] and mesopore surface.
This catalyst exhibited specific catalysis: exclusive
formation of n-butanol and i-butanol starting frompropene, carbon monoxide, and hydrogen at 433 K. TheRh K-edge EXAFS after the catalysis indicated theformation of rhodium nanoparticles, presumably inside
nanopores based on HR-TEM measurements. Systematic
Rh and Mo K-edge XAFS study on these series of Rh-Mo
catalysts supported on FSM-16 before and afterhydroformylation is in progress.
* yizumi@chemenv.titech.ac.jp

Rh and Mo K-edge XAFS measurements
Table 1: Best fit results of Rh K-edge EXAFS for various rhodium-molybdenum
catalysts supported on FSM-16 and for reference sample
Rh-CRh-O
Rh•••CNRNRNR
Sample(Å)(Å)(Å)
2.088 3.0
2.063 8.0
2.955
[Rh(COD)2]-[AlMo6]/FSM-16 8.0
8.0
2.125 2.01.940 8.0
3.047[Rh(COD)2]/FSM-16+–82.228
83.043[Rh(COD)2] [BF4]Users' Report37