Factors Affecting Kinetics and Equilibrium of Biodiesel Transesterification

Biodiesel fuel is produced by the transesterification of triglycerides from renewable resources such as animal and plant oils. Aspects of the kinetics and equilibrium of the transesterification reaction using waste vegetable oil (WVO) were studied. Variables included properties of the WVO, such as water content and free fatty acid content, along with other process parameters and inputs. Reactions were performed in 50 g batches and 0.10 g samples were taken at intervals and quenched by catalyst neutralization and cooling. Conversion was analyzed using 1H NMR, while water contents of reactants and products were measured using coulometric Karl Fischer titrations. Water content of the alcohol/methoxide reactant was observed to have little effect on the reaction rate or equilibrium. An unexpected exotherm was observed during reaction following isopropyl alcohol extraction of free fatty acids from the WVO. Biodiesel made using a recycled glycerol/methanol/methoxide reactant appeared similar to product made from fresh methanol/methoxide reactant, but analysis of the kinetics and equilibrium composition was inconclusive in verifying the suitability of recycling waste into subsequent reaction batches. Further studies of reactions following isopropyl alcohol wash of WVO and using recycled waste are recommended