Kinetics evaluation of the ethyl esterification of long chain fatty acids using commercial montmorillonite K10 as catalyst

Abstract

This study reports an assessment of free fatty acid esterification reactions with ethanol using montmorillonite K10 as catalyst, a commercial solid catalyst known for having high performance in several catalytic processes. Therefore, the main objective of this work is to perform reactions of FFA (lauric, stearic and oleic acids) ethyl esterification, checking how different chain lengths and unsaturation presence affect the reaction kinetics. The catalyst was characterized by different techniques, in which the structure and acidic properties were evaluated. Esterification reactions were systematically evaluated by a factorial design (effects of temperature, molar ratio and catalyst content) to determine optimal conditions to be used in the reaction kinetics study. In addition, kinetics reactions without montmorillonite K10 were also carried out in order to evaluate the autocatalytic (or thermal) reaction contribution. The kinetic data obtained for all FFAs was used to adjust kinetic parameters and the model was capable to correlate the experimental data, providing values of the root mean square deviation (rmsd) around 3.5% in terms of fatty acid conversions. The low values obtained for the rmsd indicate the possibility to achieve a reactor design to process complex fatty matrices using data generated for a pure FFA without quality loss. Furthermore, due to the high activity presented in the free fatty acid esterification under the studied conditions, montmorillonite K10 proves to be a suitable catalyst for industrial-scale biodiesel obtention from raw materials with high content of free fatty acids.