Application of waste chalk/CoFe2O4/K2CO3 composite as a reclaimable catalyst for biodiesel generation from sunflower oil

Abstract

This investigation aimed to produce a new composited catalyst from a waste chalk powder, a waste generated by the construction industry, to produce biodiesel from sunflower oil. The waste chalk was modified by CoFe₂O₄ nanoparticles and K₂CO₃. The surface tests showed that the obtained catalyst has been successfully synthesized with desired surface properties. The surface areas of waste chalk, waste chalk/CoFe₂O₄, and waste chalk/CoFe₂O₄/K₂CO₃ were determined 20.8, 77.8, and 5.8 m²/g, respectively. This indicates that the waste chalk/CoFe₂O₄/K₂CO₃ catalyst has a lower surface area due to K₂CO₃ being placed on the catalyst. Results showed the efficiency of RSM-CCD (R² = 0.992) compared to ANN (R² = 0.974). It was shown that a contact time of 180 min, a temperature of 65 °C, a waste chalk/CoFe₂O₄/K₂CO₃ mass of 2 wt%, and methanol to oil mole ratio of 15:1 gave the highest efficiency (98.87%) of biodiesel production at the laboratory conditions. The kinetic results of the process showed the energy of activation and frequency factor of 11.8 kJ/mol and 0.78 min^-1, respectively. Also, the values of ΔH°, ΔS°, and ΔG° at 65 °C was calculated to be 9010.7 J/mol, -256.3 J/mol and 95.7 kJ/mol, respectively, indicating that the biodiesel production process is endothermic requiring high energy for proceeding. The generated catalyst has an efficiency of over 90% up to 6 steps of reuse. The generated biodiesel was met most of the international standard levels.

Keywords: Artificial neural network; Biodiesel; Heterogeneous catalyst; Thermodynamic study; Waste chalk.