Calcium and tin oxides for heterogeneous transesterification of Babasssu oil (Attalea speciosa)

Abstract

Non-edible oils and waste cooking oils are alternatives to uphold a sustainable large scale production of biodiesel considering large volumes and by-products. Babassu oil (Attalea speciosa) offers a challenging case study scenario for the preparation of a heterogeneous catalytic material. This study shows the binary synthesis of calcium and stannic oxide (CaO/SnO2) catalysts for transesterification of oils with high content of free fatty acids (FFAs). The catalysts were prepared with several mass ratios of CaO:SnO2 in the proportions of 1:4, 4:1, 7:3 and 1:1. The catalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and N2-physisorption analyses. Biodiesel production was tested using a 23 full factorial design with variables such as temperature, methanol/oil molar ratio, and catalyst weight relative to oil. Such design statistically proved that there was no significant effect over the response variable. Furthermore a Box-Behnken design surface response analysis using the same three variables with three levels was performed with MATLAB showing a non-linear relation and statistical response of the optimal conditions for biodiesel production. The optimal experimental conditions were found to be 54.1°C, agitation speed at 250rpm with 6wt.% of CaO/SnO2 (7:3 mass ratio of the binary catalyst) and 10:1 (methanol:oil) molar ratio. The catalyst has shown a high potential for conversion of Babassu oil by fine-tuning as a single step by simultaneous esterification and transesterification to biodiesel.