Biodiesel Production by Transesterification of Corn Oil with Dimethyl Carbonate Under Heterogeneous Base Catalysis Conditions Using Potassium Hydroxide

We have studied the process of transesterification of corn oil with dimethyl carbonate (DMC) in the presence of a heterogeneous catalyst: potassium hydroxide (KOH). Response surface methodology was used to optimize the three transesterification variables: reaction time, dimethyl carbonate:oil ratio, and catalyst loading. The Box–Behnken design was used to study the influence of these variables on the yield of fatty acid methyl esters (FAMEs) and an empirical model was developed. The maximum yield of FAMEs (90.9%) with low pour point (–11°C) was achieved by boiling a mixture of dimethyl carbonate and the oil (mole ratio 9:1) and 16.3 wt.% catalyst (based on oil weight) for 9 hours. The kinetics of KOH-catalyzed transesterification of triglyceride (TG) and diglyceride (DG) with DMC was studied in the temperature range 65°C-75°C. We found that both reactions are pseudo-second order, and the activation energy for transesterification of triglycerides and diglycerides is equal respectively to 83.3 and 89.8 kJ/mol.