Modified Malleus malleus Shells for Biodiesel Production from Waste Cooking Oil: An Optimization Study Using Box–Behnken Design

Abstract

Biodiesel has been attracting the whole world in overcoming energy crisis due to stupendous advantages over petrochemical fuels. The high production cost hampered the applicability of biodiesel in replacing non-renewable fuels. The present study aims to reduce the cost by employing waste cooking oil as feedstock for biodiesel production using heterogeneous catalyst derived from waste Malleus malleus shells (MMS) via transesterification reaction. Catalytic activity of the MMS was enhanced by the calcination–hydration–dehydration method to increase the rate of biodiesel conversion. The developed catalyst was characterized by X-ray powder diffraction, Brunauer–Emmett–Teller, scanning electron microscope and Fourier-transform infrared spectroscopy techniques. Response surface methodology based on Box–Behnken design was applied to investigate the optimum transesterification process conditions. The effect of process variables such as catalyst concentration (4–8% w/w), methanol to oil molar ratio (6:1–12:1), and reaction time (30–120 min) was varied to obtain the maximum biodiesel conversion. A quadratic model was predicted and the obtained regression equation was expressed as three-dimensional response surfaces to study the interaction between independent variables on the response biodiesel conversion. The experimental results revealed that a maximum biodiesel conversion of 93.81% was obtained at optimal operating conditions of 7.5 wt% catalyst concentration, 11.85:1 methanol to oil molar ratio, and 86.25 min reaction time.