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 by using the sol–gel auto combustion method under the same synthesis conditions and their physico-chemical properties were studied by XRD, UV–vis DRS, SEM, BET and FTIR. Besides, the reducibility of oxides was studied by temperature-programmed reduction (TPR). The relationship between the properties and activity of spinels in oxidation of 2-propanol and toluene was investigated. Among all, nickel manganite exhibited the most promising activity, in which the completed conversion of 2-propanol and toluene occurred at 250 and 350 °C, respectively. Higher activity of nickel manganite oxide was explained in terms of the synergetic effect between Mn3+ and Ni2+ phases in nickel manganite oxide. No direct relationship was resulted between activity with either specific surface area or particle size of manganite oxides. No correlation was found between activity and energy band gap of the oxides. The study showed that the nickel manganite nano oxides could be promising catalysts for VOC removal. A relationship between VOCʹs structure and reactivity for conversion over catalysts was revealed, in which 2-propanol showed more reactivity than toluene to be converted over these catalysts.