Biodiesel production from soybean oil and dimethyl carbonate catalyzed by potassium methoxide

A study of the soybean oil transesterification reaction with dimethyl carbonate (DMC) catalyzed by potassium methoxide prepared through recrystallization process in presence of methanol was done. Reaction variables were analyzed viz. temperature of 40, 60 and 80 °C, DMC to oil molar ratio of 2:1, 4:1, 6:1, 8:1 and 10:1, and catalyst concentration of 1, 1.5 and 2 wt% in relation to oil, aiming to obtain the best condition for reaction. Triglyceride conversion of 99% was achieved for 6:1 DMC:oil molar ratio, 2.0 wt% of catalyst concentration and 80 °C after 15 min of reaction. Experiments were carried out to investigate methanol effects in DMC/oil medium and also to compare reactions with recrystallized and heterogeneous catalysts. Potassium methoxide recrystallized in presence of methanol achieved a triglyceride (TG) conversion higher than 99% while only a 20% TG conversion was achieved from heterogeneous reaction at same condition. Potassium quantification in biodiesel phase was done in order to investigate the homogeneous pathway catalysis in recrystallized catalyst reaction.