Optimized biodiesel production from waste cooking oil using a functionalized bio-based heterogeneous catalyst

Abstract

Bio-based waste materials are important sources of elements such as calcium and potassium that can be used as active phases for preparing heterogeneous catalysts for biodiesel production. In this study, the potential of a composite bio-based heterogeneous catalyst of fused crab shell and plantain peels was assessed for the transesterification of waste cooking oil. The catalyst and the precursor materials were characterized to assess their structural, compositional, morphological and thermal characteristics. Biodiesel production was carried out via a single step transesterification process while the experimental variables were optimized using response surface methodology (RSM). The morphological properties revealed an aggregated catalyst surface with clearly defined pores. The catalyst was bifunctional as evidenced by the presence of basic (calcium and potassium) and acidic oxides (silicon and iron). The catalyst had a high surface area (260.35 m2/g) and pore volume (0.65 cm3/g) which contributed to the maximum biodiesel yield of 93% obtained at a reaction temperature of 60 °C, catalyst loading of 5 wt%, reaction time of 149.94 min and methanol to oil ratio of 13.03:1. The RSM model was found to be very adequate in modeling biodiesel production (R2 = 0.9939). The catalyst was highly stable with high biodiesel yields (>80%) recorded after six cycles. The properties of the biodiesel were found to be comparable with standards. The synthesized catalyst holds numerous advantages over conventional catalysts because of its reusability, ease of synthesis, stability, high surface area and ready availability of the precursor materials.

Keywords

• Biodiesel
• Transesterification
• Response surface methodology
• Crab shells
• Plantain peels