Magnetic Fe-Ca oxide as a solid base catalyst for transesterification of rapeseed oil to produce biodiesel

Fe-Ca bifunctional magnetic solid base (CaO·γ-Fe₂O₃) was prepared via in-situ coprecipitation and used as catalyst in transesterification of rapeseed oil to produce biodiesel. The catalyst was characterized by XRD, BET, TG-DTA, SEM and VSM and the amounts of Ca and Fe leached in fatty acid methyl ester were measured through ICP-AES. The results indicated that Ca and Fe components are well composited; the CaO·γ-Fe₂O₃ catalyst exhibits good magnetic properties with high saturation magnetization (45.7emu/g), much higher than that of those magnetic base catalysts reported up to now. Under the mild conditions of 64℃, catalyst amount of 2.5%, methanol/oil mol ratio of 15, and reaction time of 2h, the oil conversions for first three cycles remain above 95%.