Process optimization, kinetics, thermodynamics and kinetic Monte Carlo modeling of catalyzed biodiesel production in supercritical medium

This study initially focused on optimizing the oleic acid esterification in supercritical methyl alcohol using sodium hydroxide as a catalyst. Subsequently, the kinetics related to this process were investigated. The study examined various variables affecting the esterification process, such as temperature, reaction time, oil to alcohol ratio and the quantity of sodium hydroxide (catalyst) used. The GCMS analysis confirmed the formation of mixture of alkyl esters (methyl oleate, methyl linoleate, methyl palmitate) as biodiesel. Using RSM and BBD, the process conversion was modeled and the optimum condition obtained as 573.0 K, 30.0 min, 1:30 ratio, and 0.11 % for temperature, reaction time, the oil to alcohol molar ratio and catalyst concentration, respectively. Also, a kinetic model was suggested and matched with the experimental results. Results showed the kinetics parameters of Ea = 21.13 kJ mol−1, A = 424 L mol−1.min−1 as well as the reaction order of pseudo-first-order. Comparison of the results of this work with kinetic studies of biodiesel production at normal (under critical point) conditions shows that the activation energy at supercritical conditions can decrease by up to nearly 3 times. This observation can serve as confirmation of a significant improvement in mass transfer enhancement under critical conditions. These kinetic parameters were further validated through Monte Carlo simulation. The process was explored at different methyl alcohol to oleic acid ratios and temperatures using the established kinetic parameters of the proposed mechanism, followed by result evaluation.