Magnetic and reusable MgO/MgFe2O4 nanocatalyst for biodiesel production from sunflower oil: Influence of fuel ratio in combustion synthesis on catalytic properties and performance

The successful synthesis of magnetic MgO/MgFe2O4 nanocatalyst via combustion method was achieved that has far less time and cost than the other methods. This catalyst was used in biodiesel production reaction from vegetable oil. By changing the fuel to nitrates ratio, proper structure of catalyst was obtained to produce biodiesel. Physiochemical analysis including XRD, FESEM, EDX dot-mapping, BET-BJH, FTIR and Surface Particle Size Distribution (SPSD) were used to define the characteristics of synthesized catalysts and optimum fuel ratio in combustion synthesis method. To evaluate the performance of the synthesized nanoceramics, all samples were used in the biodiesel production reaction. The results of XRD analyses showed the successful synthesis of MgFe2O4 crystals and also determined that other materials peaks (iron oxide phases) does not exist in the catalyst structure. BET-BJH analyses reveal the structures with large pore (more than 10 nm) and relatively good surface area (97.8 m2/g) for synthesized catalysts by combustion method. By biodiesel production reaction in the conditions of temperature = 110 °C, methanol-to-oil molar ratio = 12, catalyst concentration = 4 wt.% and reaction time = 4 h, it was found that the catalyst has great potential to produce biodiesel and also maximum conversion of 91.2% was obtained. For the stability test of catalyst, after convenient catalyst separation by magnet, it was used for five consecutive transesterification reactions that the results were very acceptable and finally the lowest conversion was achieved to be 82.4%. By the simultaneous consideration of analyses and reactor tests results, it was found that synthesized catalyst with fuel ratio of 1.5 has the best performance and it is very suitable for biodiesel production reaction.