4. Conclusion
The best operation condition for the two-step biodiesel production catalyzed by SrFe2O4/SiO2-SO3H
and NaOH, respectively, was 100oC & 90 min for esterification and 60oC & 40 min for transesterification.
The overall conversion of the mixed oil consisting of 20% oleic acid and 80% soybean oil almost achieved 100%.
The SrFe2O4/SiO2-SO3H catalyst could be easily separated by applying a magnetic field and be reused many times, thereby having the potential to be commercialized. Moreover, the proposed two-step biodiesel production method is effective in converting FFAs-rich oil (such as waste cooking oil) into biodiesel and can also be applied in practical applications.