Powder Chalk as a Solid Base Heterogeneous Catalyst for Biodiesel Generation: Process Optimization via Box-Behnken Model

Abstract

In order to produce biodiesel from waste palm oil (WPO), a calcium oxide (CaO) catalyst was developed using waste powder chalk and tested as a transesterification catalyst for the biofuel process. Generating CaO catalyst required a calcination method that was carried out at 900 °C for 3 h. Further investigation was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The transesterification procedure was carried out applying response surface methodology (RSM) based on box-Behnken design (BBD). The BBD experimental design was employed, and the 3 process parameters investigated were catalyst concentration (3-5 wt.%), methanol/oil mole ratio (12-18), and reaction time (60-120 min). Experiments conducted under the optimal conditions predicted yielded over 97%, which was in excellent agreement with the expected value (a relatively small margin of error). This study demonstrates that WPO and waste chalk as low-cost feedstock are excellent sources of raw material for biodiesel production, and that a sustainable generation of biodiesel can be accomplished by optimizing process variables.