Combustion of volatile organic compounds on manganese iron or nickel mixed oxide catalysts

Manganese iron or nickel mixed oxide catalysts (MnFe or MnNi, respectively) were obtained by coprecipitation varying the aging time. A detailed description of the bulk and surface structure of each system was achieved by means of measurements of specific surface area, XRD, XPS, FT-IR, and Mössbauer spectroscopies. The characterisation results show that MnNi catalysts are formed by NiMnO3 and Ni6MnO8 mixed oxides besides a little amount of Mn2O3. In contrast, MnFe catalysts consist of an oxide mixture (Fe2O3, Mn2O3 and Mn5O8) forming incipiently a solid solution. The catalytic activity was evaluated in the combustion of propane and ethanol, selected as model volatile organic compounds. In propane combustion, the best results were obtained with MnNi catalysts whereas MnFe catalysts showed the best performance in ethanol combustion. The catalytic behaviour was correlated with catalyst affinity by oxygen, which was determined by studies of O2-TPD and TPR. The variation of the precipitated aging time modifies neither the catalyst structure nor the catalytic performance.