Flame-made MgAl2−xMxO4 (M = Mn, Fe, Co) mixed oxides: Structural properties and catalytic behavior in methane combustion

Spinel-like oxides with the general formula MgAl2−xMxO4 (M = Mn, Fe, Co) were synthesized in a single step by flame-spray pyrolysis. High surface area materials were obtained, which showed improved resistance to sintering upon increasing the Al-content. XPS showed surface enrichment of the transition metal constituent, which favorably increased the fraction of transition metal exposed to the environment. By tuning the fraction of transition metal in the mixed oxide, materials were obtained with a good balance between thermal stability and activity in the catalytic combustion of methane. The activity of the materials increased in the order Fe < Co < Mn.