Catalytic performance of nanostructured iron oxides synthesized by thermal decomposition technique

Nanostructured iron oxide was synthesized by a thermal decomposition reaction using Fe(NO3)(3)center dot 9H(2)O in the presence of citric acid (CA) as a template agent. The produced nanopowder was characterized by XRD, FT-IR, TEM, N-2 adsorption-desorption isotherms, and thermo-analytical methods. Nanostructured iron oxide with high surface area (244 m(2)/g) and pore diameter distribution in the range of 1-6 nm was successfully achieved. Both the particle size and phase structure are greatly influenced by the ratio of iron precursor-to-CA, operating temperature, and the reaction time. The results show also that amorphous or weak crystalline iron oxide appears at a low preparation temperature (100 degrees C) and turns to crystalline phase when the temperature rises to 120 degrees C. Pure hematite phase was obtained at 120 degrees C with molar ratio 2:1 Fe salt/CA, while magnetite/maghamite phase was formed at 140 degrees C with molar ratio 1:2 Fe salt/CA. The as-formed nanostructured iron oxide powder was tested for catalytic oxidation of carbon monoxide (CO) using advanced quadruple mass gas analyzer system. The catalytic efficiency of the process was investigated at different operating temperatures. The results show that CO is completely oxidized to CO2 at 200 degrees C. The catalytic process was essentially affected by the presence of maghamite phase, crystal size and surface area of the nanostructured iron oxide. Furthermore, the magnetic properties of some selected products were briefly addressed and thoroughly discussed. (C) 2009 Elsevier B.V. All rights reserved.