Copper and calcium-based metal organic framework (MOF) catalyst for biodiesel production from waste cooking oil: A process optimization study

Abstract

Due to the diminution of conventional fuels, biodiesel has attracted acute attention due to its renewable and zero-emission features. However, cleaner production of biodiesel on an industrial scale requires a stable heterogeneous, low cost and recyclable catalyst. This study presents the preparation and application of copper and calcium-based metal organic frameworks (MOFs) as catalysts in the esterification and transesterification reactions for biodiesel production from waste cooking oil (WCO). The synthesized catalysts are characterized using XRD, SEM, TGA, FTIR and BET. The catalyst characterization indicates the formations of the cubical structure of MOFs with a crystallite size of <50 nm and thermal stability below 600 °C. The catalyst has been tested for WCO to biodiesel production and the biodiesel samples comply with the ASTM standards. Furthermore, the process parameters i.e catalyst loading (X1), reaction temperature (X2) and alcohol-oil ratio (X3) are optimized employing response surface methodology (RSM) via central composite design (CCD). The second-order regression model is employed to investigate the dynamic interaction between the process parameters and biodiesel yield (YBD %). The optimum process values are determined i.e catalyst loading = 1.0 g/100 mL, reaction temperature = 60 °C and alcohol-oil ratio = 20 with optimum biodiesel yield of 84.5 (vol%). The experimental results and predicted results are in good agreement with percentage error less than ± 5%. The regenerated catalyst demonstrates a significant biodiesel yield up to 7% reduction for 3 cycles.