Biodiesel production from soybean oil by hydroesterification process: experimental study and kinetic modeling

Abstract This study aims to develop a kinetic model for the hydrolysis reaction of soybean oil based on experimental data. The development of studies involving the estimation of kinetic parameters of mechanistic models is fundamental for greater precision in controlling the desired product. A kinetic model for triglyceride hydrolysis is essential to optimize biodiesel production, improving efficiency and cost of industrial production. It must overcome the challenges of reversible reactions and limited kinetic data to enable better process control. The model describes the initial phase of biodiesel production via the hydroesterification process, involving hydrolysis of oil into FAtty acids and glycerin, followed by esterification of the FAtty acids into biodiesel and water. Experiments were conducted in a pressurized stainless-steel reactor with sampling throughout the reaction. Conditions included temperatures of 200, 230, and 250 °C, a 1:1 water-to-oil volumetric ratio, and 1 % H 2 SO 4 by weight as a catalyst. Reaction conversion was determined by titration, and molar fractions of reactants and products were calculated. A kinetic model for the hydroesterification reaction was proposed, assuming that the different steps for the production of FAtty acids and glycerol had forward and reverse reaction rates, which were solved using the Dassl subroutine. Thus, expressions for the consumption rates of the reactants and byproducts were derived. The obtained solution was compared with the experimental data to estimate the Arrhenius constants. Furthermore, the influence of temperature on hydrolysis was assessed by calculating the pre-exponential FActor and activation energy. The estimated pre-exponential FActor were 1.02·10 7 min −1 , 5.20·10 2 min −1 , 1.60·10 3 min −1 and 7.55·10 5 min −1 while the values for activation energy were 89.283 kJ mol −1 , 15.795 kJ mol −1 , 37.071 kJ mol −1 and 44.208 kJ mol −1 . The proposed model effectively described the kinetics of the hydrolysis reaction.