Biodiesel synthesis from vegetable oil using eggshell waste as a heterogeneous catalyst

Abstract

A reusable heterogeneous catalyst was obtained from eggshell by a simple heat treatment method. Calcined eggshell was used in the transesterification of vegetable oil with methanol to produce biodiesel. To explain the effect of calcination temperature, we investigated the calcination process of eggshell with thermal gravity analysis (TGA), X-ray diffraction (XRD) pattern, Fourier transform infrared spectroscopy (FT-IR), atomic emission spectrometry (ICP-AES), and scanning electron microscopy (SEM). The yield of biodiesel was affected by the reaction variables (methanol/oil ratio, catalyst amount and reaction time). Reusability of eggshell catalyst was systematically studied in detail. For the following reactions, all catalyst was prepared by calcining eggshell at 800 °C for 2 h. The produced biodiesel was characterized by FT-IR spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The experimental results showed that the yield increased with an increase in the methanol/oil molar ratio, and reached a maximum when the ratio was above 9 with 3% catalyst. The produced eggshell catalyst can easily recovered and reused up to 8 times in the transesterification reaction with no apparent loss of activity. Reusing eggshell waste to prepare catalyst could minimize contaminants by recycling the waste, reducing the catalyst cost, and producing an economic and ecologically friendly biodiesel.