Nanocrystalline AMn2O4 (A=Co, Ni, Cu) spinels for remediation of volatile organic compounds—synthesis, characterization and catalytic performance

Nanocrystalline AMn2O4 (A = Co, Ni, Cu) manganite spinels were prepared using the sol-gel auto combustion method under the same synthesis conditions and their physico-chemical properties were studied by XRD, UV-VIS spectroscopy, SEM, BET method and FTIR. The reducibility of the oxides was studied by temperature-programmed reduction. The relationship between the properties and the activity of the spinels for the oxidation of 2-propanol and toluene was investigated. Nickel manganite showed the most promising activity, in which the completed conversion of 2-propanol and toluene occurred at 250 and 350 C, respectively. The higher activity of nickel manganite oxide is explained in terms of the synergetic effect between Mn3+ and Ni2+ phases in the nickel manganite oxide. No direct relationship was observed between the activity with either specific surface area or particle size of the manganite oxides and no correlation was found between the activity and the energy band gap of the oxides. It was shown that nickel manganite nano oxides could be promising catalysts for VOC removal. A relationship between the VOC's structure and reactivity for conversion over catalysts was revealed, in which 2-propanol showed more reactivity than toluene for conversion over these catalysts.