Optimization by response surface methodology of the reaction conditions in 1,3-selective transesterification of sunflower oil, by using CaO as heterogeneous catalyst

Abstract

In this work, the experimental conditions for the transesterification reaction of sunflower oil, over commercial calcium oxide (CaO) as heterogeneous catalysts, have been optimized employing a multi-factorial design based on the response surface methodology (RSM). Hence, the effects of temperature, methanol/oil molar ratio and have been considered. The partial transesterification of sunflower oil produces one mol of monoglyceride (MG) and two moles of fatty acids methyl esters (FAME). This blend constitutes a new type of biofuel called Ecodiesel which can be applicable to diesel engines. This Ecodiesel integrates the glycerol as MG removing by-products and increasing the lubricity of the biofuel. Thus, the reaction conditions, obtained by Response surface methodology (RSM), that promote the highest values of selectivity to Ecodiesel are 65 °C of reaction temperature, 0.7 g of CaO and methanol/oil molar ratio of 5.3. On the other hand, in order to get a biofuel with lower viscosity, 65 °C and 0.7 g of CaO were also employed, although a lower methanol/oil molar ratio of 2 was employed. Operating under these selected experimental conditions, a high conversion value (70 %), a selectivity value to Ecodiesel of 35 % and a viscosity value around 15 cSt can be achieved. The biofuel thus obtained can be used in blends with diesel because in order to accomplish the viscosity limits stablished in the EN 14214. Consequently, this methodology could represent an advance in the technical and economic feasibility in the process of replacing fossil fuels by renewable fuels.