PRODUCTION OF BIODIESEL FROM THE TRANSESTERIFICATION OF WASTE COOKING OIL USING BIOBASED SULPHONATED CATALYST PREPARED FROM COCONUT SHELLS

ABSTRACT

The effects of various transesterification process variables were investigated in this work for the production of biodiesel from waste cooking oil using a biobased sulphonated catalyst prepared from waste coconut shells. The catalyst was characterized for its surface morphology, elemental compositions, surface area, pore volume and pore size using standard procedure. The transesterification process variables considered and their range of values include reaction time of 30 to 180 mins, catalyst loading of 1 to 6 wt% and reaction temperature of 45 to 65. The transesterification reaction was designed employing the Box Behnken design of response surface methodology. The waste cooking oil and biodiesel produced were analyzed using standard procedures. The surface morphology of the catalyst revealed a catalyst with an irregular pore structure with large pore space. Elemental composition of the catalyst gave the following compositions of metal oxides; Al₂O₃ (%), SiO₂ (%), P₂O₅ (%), K₂O (%), CaO (%), Fe₂O₃ (%), SrO (%), Nb₂O₃ (%) and Sb₂O₃ (). The surface area, pore volume and pore size of the catalyst were found to be 474.4 m².g^-1, 0.295 cm³.g^-1 and 2.144 nm respectively. Reaction time and temperature were found to have significant effects on biodiesel yield while the effect of catalyst dosage was insignificant. The maximum percentage yield of biodiesel of 96.22% was obtained after a reaction time of 147.73 mins using catalyst dosage of 2.18 wt% at a reaction temperature of 65. The high R² value of 0.9799 of the transesterification reactions of waste cooking oil to biodiesel indicates that the model obtained from this study can account for 98% of the variability in biodiesel yield. There was also a reasonable agreement between the adjusted R² (0.9541) and predicted R² (0.7705) values which indicates that response surface methodology can be efficiently used to model the transesterification process using a quadratic polynomial. The high yield of biodiesel indicates that waste cooking oil is a potential low cost biobased feed stock for biodiesel formulations. The properties of biodiesel prepared from waste cooking oil compared reasonable well with the standards of biodiesel.