Evidence of Surface Properties by Isopropanol Decomposition Reaction and NH3-TPD over Ni-Fe Spinel Nanoparticles Prepared via Hydrothermal Route

In this work, surface properties evaluated by catalytic conversion of isopropanol and by ammonia Temperature Programmed Reduction (NH3-TPD) over ferrite spinel nanoparticles was investigated. Bulk NiFe2O4 with specific surface area 114 m(2)/g and crystallites size 6 nm was prepared by hydrothermal synthesis using nitrates as precursors. X-ray diffraction (XRD), Raman spectroscopy, specific surface area by B.E.T, Scanning Electron Microscopy (SEM) and X-ray energy dispersive microanalysis (EDS), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS) techniques were used for their structural and textural characterizations. The reducibility by hydrogen at variable temperatures was investigated by Temperature Programmed reduction (H-2-TPR) and Thermal Gravimetric Analysis- Differential Scanning Calorimetry (TGA-DSC). The total acidity and acid strength distribution was determined by NH3-TPD. The synthesized oxide showed the presence of mixed phases containing the inverse spinel structure NiFe2O4 as the major phase and iron oxide alpha-Fe2O3 as an additional phase. It was shown that the surface of the powder was richer in Ni2+ species. The surface acidity (Bronsted and Lewis) determined by NH3-TPD showed that the number of acidic sites increased dramatically with the temperature. The catalytic conversion of isopropanol yields both acidic and redox/basic sites were available. A good correlation between textural, structural, redox and acid-base properties of catalyst is established.