Pillared
clay-supported NiMo catalysts were synthesized in their
reduced and sulfided forms and applied to the hydrodeoxygenation of
guaiacol (2-methoxyphenol) as a bio-oil model compound. The sulfided
catalyst displayed better activity and selectivity as compared to
the reduced catalyst, yielding phenol as the major product. Quasielastic
neutron scattering demonstrated that jump diffusion of guaiacol was
seen after adsorption on both the sulfide catalyst and pillared clay.
Inelastic neutron scattering was carried out in conjunction with an
infrared study and reveal that there were two types of interaction
of guaiacol with the catalyst. The first is guaiacol adsorbed via
various types of H-bonding interaction, as observed in the sulfided
catalyst. The second type of interaction is guaiacol adsorbed on the
surface, presumably at a Mo vacant site, by chemisorption through
formation of a methoxyphenate species as seen in the reduced catalyst.
The interactions were greater in the sulfided catalyst by which guaiacol
was selectively adsorbed in coordination with the Ni–Mo–S
site.
The vibrational spectroscopy of CS2 has been investigated many times in all three phases. However, there is still some ambiguity about the location of two of the modes in the solid state. The aim of this work was to locate all of the modes by inelastic neutron scattering (INS) spectroscopy, (which has no selection rules), and to use periodic density functional theory to provide a complete and unambiguous assignment of all the modes in the solid state. A comparison of the observed and calculated INS spectra shows generally good agreement. All four of the ν2 bending mode components are calculated to fall within 14 cm−1. Inspection of the spectrum shows that there are no bands close to the intense feature at 390 cm−1 (assigned to ν2); this very strongly indicates that the Au mode is within the envelope of the 390 cm−1 band. Based on a simulation of the band shape of the 390 cm−1 feature, the most likely position of the optically forbidden component of the ν2 bending mode is 393 ± 2 cm−1. The calculations show that the optically inactive Au translational mode is strongly dispersed, so it does not result in a single feature in the INS spectrum.
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