Manganese-Zinc Ferrite Synthesis by the Sol-Gel Autocombustion Method. Effect of the Precursor on the Ferrite's Catalytic Properties

Manganese-zinc ferrites were obtained through combined coprecipitation and sol-gel autocombustion methods. The effect of the precursor used in the sol gel autocombustion synthesis on the ferrite's structural and catalytic properties was examined. The ferrite powders were characterized by XRD, BET, SEM, TG/DTA, and TPR-H-2, and their acidic-basic properties were determined using cyclohexanol and the TPD-NH3 test. The ferrite powder obtained from the hydroxide precursor (SC1-OH) has a larger specific surface area (16.41 m(2)/g), a larger crystallite size (35.6 nm), and a more heterogonous structure, which make it a more active catalyst. This is also achieved because of the existence of both acidic and basic centers on its surface. The ferrite obtained from the oxalate precursor (SC2-C2O4) has smaller (29.6 nm) but more aggregated particles. As a catalyst, it is more selective to dehydrogenation, which is related to its higher reducibility. The SC2-C2O4 sample also exhibits higher selectivity to ketone, and it is a much more efficient catalyst at higher temperatures.