Reaction Kinetics, Mechanisms and Catalysis | 2021
Box–Behnken design-based optimization for biodiesel production from waste cooking oil using Mahogany (Swietenia macrophylla) fruit shell derived activated carbon as a heterogeneous base catalyst
Abstract
In this study, activated carbon was derived from inexpensive and abundant biomass feedstock Mahogany fruit shell and activated with KOH to act as a heterogeneous base catalyst for transesterification of waste cooking oil to biodiesel. The catalyst was characterized by means of FT-IR, XRD, FESEM-EDS and particle size analysis techniques. Box–Behnken design optimization was carried out to study the complex interaction between reaction parameters. Catalyst concentration, methanol to oil molar ratio, and reaction time were varied from 0.5–2 wt%, 6:1–12:1, and 120–240 min, to obtain the maximum biodiesel conversion. Reaction parameters with the combination of 2 wt% catalyst concentration, 180 min reaction time, 12:1 methanol to oil molar ratio, and 65 °C temperature led to the best yield of 97.26%. The optimization study revealed methanol to oil molar ratio to be the most influential parameter to dictate the biodiesel conversion. High coefficient of determination (R2) value of 99.844% proved that the predicted biodiesel yields were very close to the experimental ones. Gas chromatography (GC) analysis disclosed methyl palmitate (41.18%) and methyl oleate (48.19%) to be the major composition of the synthesized biodiesel. Physicochemical properties of the biodiesel, such as viscosity (4.58 cSt), density (862 kg/m3), acid value (0.28 mg KOH/g), pour point (16 °C), and flash point (128 °C) were measured and found to be in compliance with the standards. The maximum yield coming from a quite low catalyst concentration and methanol to oil molar ratio is phenomenal from an industrial perspective.