An efficient, recoverable solid base catalyst of magnetic bamboo charcoal: Preparation, characterization, and performance in biodiesel production

A novel bifunctional bamboo charcoal-based magnetic solid base catalyst (K/BC-Fe2O3) was successfully prepared by an in-situ synthesis-impregnation-calcination method. Scanning electron microscopy and Brunauer-Emmett-Teller results show that the synthesized bamboo charcoal-based magnetic catalyst possesses a mesoporous structure and high specific surface area. X-ray diffraction and X-ray photoelectron spectroscopy results indicate that after calcination of the precursor at 500 °C, the magnetic particles were finely fixed to the carbon skeleton of the bamboo charcoal, and the iron oxide was present as γ-Fe2O3. The vibrating sample magnetometer results demonstrate that the superparamagnetic catalyst could be easily separated and recovered after reaction with the aid of an external magnetic field. The possible formation mechanism of the alkaline site (K2O species) on the catalyst surface can be summarized as a transverse activation at low temperature and a radial activation at high temperature. It was determined that the following are the optimum conditions for biodiesel production: an amount of added catalyst 2.5 wt%, a molar ratio of methanol/oil of 8:1, a reaction time of 1 h, and a reaction temperature 60 °C with a maximum yield of 98.0%. Regeneration experiments reveal that the magnetic catalyst can maintain high catalytic activity even after being reused four times. This study presents a novel bifunctional heterogeneous catalyst with potential applications in biodiesel production.