Production of Biodiesel from the Transesterification of Waste Cooking Oil using Biobased Sulphonated Catalyst prepared from Coconut Shells

Abstract

This study investigated the effects of transesterification process factors on biodiesel yield from waste cooking oil using a biobased sulphonated catalyst made from waste coconut shells. The catalyst was characterized in terms of surface structure, elemental compositions, surface area, pore volume and pore size. Reaction duration was varied from 30 to 180 minutes, catalyst loading varied from 1 to 6 wt%, and reaction temperature varied from 45 to 65°C are among the transesterification process variables studied. The Box Behnken design (BBD) of response surface methods was used to design the transesterification reaction. The catalyst surface morphology revealed that it has an uneven pore structure while elemental composition revealed that it is mainly composed of CaO (17.32%), SiO₂ (21.40%), SO₃ (21.04%), and Al₂O₃ (13.68%). The catalyst surface area, pore volume, and pore size were determined to be 474.4 m².g^-1, 0.295 cm³.g^-1, and 2.144 nm, respectively. Reaction time and temperature had significant effect on the biodiesel yield while the influence of catalyst dosage was minimal. After a reaction time of 147.73 minutes and a catalyst dosage of 2.18 wt % at a reaction temperature of 65°C, a maximum yield of 96.22 percent of biodiesel was produced. The predicted R² (0.9541) and actual R² (0.7705) values were found to be in good agreement. Due to the high output of biodiesel, waste cooking oil could be a low-cost biobased feedstock for biodiesel formulations. The characteristics of biodiesel made from waste cooking oil were comparable to those of conventional biodiesel.