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 gamma-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 degrees C (Ea similar to 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.