Waste Frying Oil Conversion to Biodiesel in Presence of Advanced Alumina Heterogeneous Catalyst

This paper reports experimental conversion of spent vegetable oil with bio-ethanol to long chain biodiesel fuel in presence of a new developed solid K₃PO₄ heterogeneous catalyst. Examined catalyst was synthesized following dipping impregnation of γ-Al₂O₃ solid support in an aqueous solution of potassium phosphate tri-basic K₃PO₄. K₃PO₄/γ-Al₂O₃ catalyst samples were distinguished based on their percentage loadings of K₃PO₄ (C_K3PO4) and averaged particle size (d_p). Produced catalyst samples were characterized in terms of their textural and surface properties using nitrogen adsorption-desorption isotherms and carbon dioxide & ammonia temperature programmed desorption techniques respectively. While the liquid phase of the product was analyzed using a GC-Mass spectroscopy technique. Ethanolysis runs were carried out following surface response methodology, central composite design (CCD). Parameters including catalyst percentage loading (C_K3PO4), catalyst particle size (d_p) as well as catalyst reactor weight (cat) were simulated the design factors. While percentage of ethyl ester yield (EEY%) was used as design response.

Experimental results revealed an optimal measured EEY% of 92% achieved at 15:1 reactants molar ratio, 70 °C reaction temperature, 1000r.min⁻¹ agitation speed, 25% percentage loading, 115 μm catalyst average particle size and 10 g/200 ml of catalyst weight in the reaction mixture. A high accuracy mathematical model was established for predicting the examined EEY% response results in terms of the above indicated operating parameters. Optimal EEY% of 95.43% was predicted under same operating conditions. The used catalyst was approved to be highly active, reliable and steady available solid heterogeneous catalyst that may promote the future of a more environmentally friendly biodiesel fuel.