Soybean oil ethanolysis was initial

Soybean oil ethanolysis was initially investigated through a factorial experimental design in which three variables were considered in the following levels: ethanol–oil molar ratio (MR) of 6:1 and 12:1, NaOH at 0.3 and 1.0 wt% in relation to the oil mass and reaction temperatures of 30 and 70 °C. A triplicate was carried out at the center point of the experimental design (MR of 9:1, NaOH at 0.65 wt% and 50 °C) and their corresponding ester yields were used to calculate the relative standard deviation of the overall procedure. Once the best reaction condition was identified, experiments were carried out to evaluate whether KOH could be used to replace NaOH as the reaction catalyst. KOH was used at the concentrations of 0.42, 1.0 and 1.4 wt% under the same reaction conditions applied earlier (MR of 6:1 and/or 12:1 and reaction temperatures of 30 and/or 70 °C).Reactions were carried out in 500 mL three-necked round-bottom flasks adapted to a water bath, a reflux condenser and a mechanical stirrer set at 600 rpm. Initially, 100 g of soybean oil were added to the flask reactor and heated up to the desired reaction temperature. In another flask, the appropriate amount of catalyst was added to a predetermined amount of anhydrous ethanol and the mixture was stirred up until the solids were completely dissolved. The resulting solution was conditioned to the desired temperature and immediately added to the pre-heated oil, when the reaction began. The mixture was stirred vigorously for a total reaction time of 60 min. Afterwards, the ethanol was evaporated at 50–60 °C under low pressure and the glycerin phase was recovered after phase separation, carrying most of the dissolved catalyst with it. The upper layer, containing the desired product, was washed thoroughly with water at 80 °C (three washing steps with 10 mL of water) and the water-washed ester layer was dehydrated with anhydrous sodium sulfate. Solids were then removed by filtration and the resulting ethyl esters were stored under nitrogen for further analysis. This procedure was referred to as one-stage ethanolysis of refined soybean oil.