Synthesis of Methyl Esters Employing a DBD Plasma Reactor with Liquid-Phase Discharge

The use of a dielectric barrier discharge plasma reactor with liquid-phase discharge was investigated in the production of methyl esters by transesterification reaction at room temperature, atmospheric pressure and without any previous reactant stirring step. The effects of applied voltage, reaction time and catalyst content were analyzed on ester production. The transesterification reactions of vegetable oil and monoesters were compared to understand the effect of dielectric barrier discharge plasma on miscible and poorly miscible liquid phases. The power transmitted to the plasma was evaluated for different conditions in order to evaluate the energy expenditure of the plasma reactor in the transesterification reaction and the factors that influence it. Results of the transesterification of vegetable oil were analyzed through sustainability indicators regarding mass productivity, energy consumption and cost of production. The transesterification of monoester showed higher conversion rates when compared to the transesterification of vegetable oil due to the fact that reactants are miscible. The analysis of the power transmitted to the plasma showed that conditions with lower energy expenditure are obtained with more polar solutions and with lower applied voltages to the plasma. Conditions with low plasma applied voltage showed significantly better results in the energy indicators. The results with sustainability indicators suggest that an optimized route using a plasma-assisted catalytic reactor is competitive when compared with conventional reactors for biodiesel production.