Ethyl ester production by homogeneous alkaline transesterification: Influence of the catalyst

In this work, the process for ethyl ester production is studied using refined sunflower oil, and NaOH, KOH, CH3ONa, and CH3OK, as catalysts. In all cases, the reaction is carried out in a single reaction step. The best conversion is obtained when the catalyst is either sodium methoxide or potassium methoxide. We found that during the transesterification with ethanol, soap formation is more important than in the case of methanol. The saponification reaction consumes an important fraction of the catalyst. The amount of catalyst consumed by this reaction is 100% in the case of using hydroxides as catalyst (KOH or NaOH), and 25%, and 28% when using CH3ONa and CH3OK as catalysts, respectively. Ethanol increases the catalyst solubility in the oil–ethyl ester phase, thus accelerating the saponification reaction. It is possible to obtain high conversions in a one-step reaction, with a total glycerine concentration close to 0.25%.