jp072616h_si_001.pdf (2.75 MB)
Selective Butanol Synthesis over Rhodium−Molybdenum Catalysts Supported in Ordered Mesoporous Silica
journal contribution
posted on 2007-07-12, 00:00 authored by Yasuo Izumi, Kazushi Konishi, Masayasu Tsukahara, Diaa Mosbah Obaid, Ken-ichi AikaRhodium catalysts were synthesized in ordered mesoporous silica FSM-16 using Rh/Al heteropolyacid anions
and/or [Rh(COD)2]+ complex. The hydroformylation activity of propene was compared to impregnated Rh/FSM-16 catalysts prepared from rhodium chloride. The catalysts were very selective to produce butanols due
to the effect of two-dimensional mesoporous reaction space (effective internal pore diameter 27 Å). The
selectivity to butanols (n-butanol and i-butanol) was as much as >98% over [RhMo6O18(OH)6]3-/FSM-16
catalysts and 73% over RhCl3/FSM-16 catalysts. Under the hydroformylation reaction conditions at 433 K
and 60 kPa, 22−28 Å of supported nanoparticles were present based on Rh K-edge extended X-ray absorption
fine structure (EXAFS) and high-resolution transmission electron microscopy (HR TEM) measurements. Rh
metallic nanoparticles atomically mixed with Mo atoms and distorted heteropolyacid species coexisted in the
[RhMo6O18(OH)6]3-/FSM-16 catalysts based on Rh and Mo K-edge EXAFS and HR TEM measurements.
The population of metallic nanoparticles increased as the metal loading amount decreased from 5.2 to
0.22 wt % Rh. Thus, metallic nanoparticles in FSM-16 were essential for the butanol synthesis and Mo
played an additional promoter role to increase the selectivity further. A reaction mechanism was proposed in
which the metallic nanoparticle surface was predominantly adsorbed with CO and multiple-step hydrogenations
of oxygenate intermediates proceeded to form butanols during slow diffusion in the two-dimensional
mesoporous space.
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EXAFSheteropolyacid species coexistedhydroformylation activityform butanolsmesoporous reaction spacerhodium chloridemesoporous spacereaction mechanismoxygenate intermediatesFSMmetal loading amountHR TEMnanoparticles atomicallyRhMo 6O catalystshydroformylation reaction conditionsMo atomstransmission electron microscopyHR TEM measurementsMesoporous SilicaRhodium catalystsSelective Butanol Synthesisbutanol synthesisCO433 K60 kPapromoter rolenanoparticle surface
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