Infrared spectroscopic study of pyridine adsorption on MoO3·NiO catalysts supported on fluorinated γ-Al2O3

Abstract

Infrared spectra of adsorbed pyridine have been used to characterize Brønsted- and Lewis-acidic sites on fluorinated γ-Al₂O₃(Al samples) and on MoO₃·NiO supported on fluorinated γ-Al₂O₃(MoNiAl samples). The Brønsted acidity of MoNiAl samples increased with increasing fluorine content. Also MoNiAl exhibited higher Brønsted acidity, but lower ability to form hydrogen bonds with pyridine, than Al samples. Partial desorption of pyridine at 673–873 K revealed the presence of acid centres of different strengths. The strongest acid centres were probably associated with higher oxidation states of Mo or Ni.