Spinel Mixed Oxides Prepared by Soft Chemistry Methods for Catalytic Hydrogenation of 2-Nitrophenol to 2-Aminophenol.

Mixed oxides of Ni0.65Zn0.35Fe2O4 stoichiometry (Ni + Zn/Fe = 1:2) were prepared by citrate and coprecipitation methods, characterized by TGA-TD, XRD, FTIR and SEM, and its catalytic properties were investigated in hydrogenation of 2-nitrophenol (2-NP) to 2-aminophenol (2-AP) counterparts under ambient conditions. The methods of preparation influenced the textural, the structural and the reactivity properties. All the preparations show the presence of mixed phases containing spinel structure and γ-Fe2O3 oxide. The crystallite sizes increase with increasing calcination temperatures due to the coalescence of nanoparticles by solid-state diffusion. All samples exhibited high catalytic activity with first-order kinetic; the sample issued from citrate method and annealed at 800 °C (Ea ~ 31.6 kJ/mol) is the most active system with a high X-ray density and a low force constant at tetrahedral sites. For this catalyst, 99.7% of 2-NP was reduced to 2-AP within 6.5 min and the recycled catalyst shows a very good activity for five catalytic runs. It could remain more than 88% activity after it was used five times. [ABSTRACT FROM AUTHOR]