Supported Ni catalysts prepared by intercalation of layered double hydroxides: investigation of acid-base properties and nature of Ni phases
Articolo
Data di Pubblicazione:
2012
Abstract:
Supported nickel catalysts were obtained by exchange of Mg/Al Layered Double Hydroxides (LDHs) compensated
with NO3- ions with negatively charged Ni complexes, followed by thermal reduction. With this
aim, suspensions of Ni complexes were prepared by controlled hydroxylation of Ni2+ cations in the presence
of citrate (obtaining [Ni(C6H5O7)(OH)]y2y- species) or chloride (obtaining [NiCl4]2- species) complexing
ions. For comparative purposes, other two supported Ni catalysts were prepared starting from Mg/Al
LDHs compensated with Cl- ions and thereafter exchanged with [Ni(C6H5O7)(OH)]y2y- species (nominal
degree of exchange: 100% and 20%).
XRD and HRTEM techniques were employed for studying nickel phases and dispersion. CH3CN adsorption
at RT followed by FT-IR spectroscopy gave information on surface acid–base properties. CO adsorption
at 77 K followed by FT-IR spectroscopy was employed to deepen the characterization of the metal
phase.
On the basis of the results obtained, it is possible to evidence a correlation between the metal phase
morphologies and the surface acid–base properties of the reduced catalysts. High surface basicity
revealed by the presence of strongly basic O2- sites stabilizes small nickel particles (<4 nm), in spite of
the high metal loading (>11 Ni wt.%), whereas, when the basicity is suppressed by Cl- ions, a dramatic
Ni sintering occurs even at low metal loading (in the range 3–10 Ni wt.%).
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
Ni; Layered Double Hydroxides; FT-IR; HRTEM
Elenco autori:
S. Morandi; M. Manzoli; F. Prinetto; G. Ghiotti; C. Gérardin; D. Tichit
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