RSM Optimization of Biodiesel Production by Oil Ethanolysis over CaO Catalyst

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CaO is a well know catalyst to produces biodiesel by oil methanolysis (FAME). Ethanol, instead methanol, will allow to obtain a completely renewable diesel (FAEE), but oil ethanolysis reaction its much more difficult than methanolysis. Ethanolysis of soybean oil was carried out over lime catalyst produced by calcination of scallop shells food wastes. The as prepared catalyst showed XRD lines belonging to lime, whereas post reaction samples presented XRD lines belonging to Ca(OH)2.The influence of the reaction parameters, such as ethanol:oil molar ratio (10:1-14:1), catalyst loading (10-15 %, based in oil weight) and time reaction (6-10 h), on the FAAE yield was analyzed by response surface methodology. A polynomial model was fitted using Minitab software, showing a correlation between predicted and experimental FAEE yields of 0.921. The maximum FAEE yield of 99.2 % was computed for optimal reaction parameters of 11:1 ethanol:oil molar ratio; 13.8 % catalyst loading and 9.1 h of reaction time. The fitted model was verified for the optimal conditions, using three replicas, given 99.0% of FAEE yield instead of the 99.2% predicted.