Kinetic study of the esterification of unsaturated free fatty acids

Abstract

The kinetics and thermodynamics of the esterification of oleic, linoleic and linolenic acids using a batch reactor are described in this study. The effect of relevant factors on ester conversion, such as reaction temperature, dose of sulfuric acid as a catalyst and methanol/free fatty acids (FFAs) (oleic, linoleic and linolenic acid) mole ratios are studied. The results show that the maximum conversion of oleic and linoleic acids was 88% at 40:1 methanol/FFAs molar ratio, temperature of 68°C, catalyst 2 wt% of FFAs and reaction time of 30 min. A pseudo-homogeneous kinetic model was proposed for the esterification. The effect of temperature on the rate constants is represented by Arrhenius equation, and the activation energy was found to be 13·35, 43·42 and 45·51 kJ/mol for linolenic, linoleic and oleic acids, respectively. The thermodynamic parameters including ΔG, ΔS and ΔH were determined. Thermodynamic studies have revealed that the reaction was a non-spontaneous and endothermic one.

Balance between Catalyst Acidity and Hydrophilicity in Biofuel Production from Fatty Acid Esterification over Al-SBA-15

“…Figure 6 shows that the catalyst was active for all those fatty acids, but higher conversion was reached with unsaturated ones (oleic acid > linoleic acid > stearic acid). A similar behavior has indeed been reported by other authors in the literature [51][52][53]. This trend may be ascribed to the polarity of the double bonds in the carbon chain leading to a higher reactivity of the carboxylic acid group [53][54][55].…”

Surface‐modified NiFe2O4 nanoparticles for the production of biodiesel from fatty acids and microalgae lipids Dunaliella salina

“…The reaction has been carried out with different quantities of water like 2.0, 3.0, and 4.0 mL with keeping constant ration of oleic acid to methanol (1:29) at 70°C under reaction conditions. The conversions obtained as 14%, 8%, and 0.5%, respectively, indicate that water inhibited the rate of reaction 34–36 . This is due to blockage of active sites of catalyst, and hence, it could hinder diffusion of reactant and product from the surface.…”

“…The conversions obtained as 14%, 8%, and 0.5%, respectively, indicate that water inhibited the rate of reaction. [34][35][36] This is due to blockage of active sites of catalyst, and hence, it could hinder diffusion of reactant and product from the surface. The equilibrium of the reaction is affected due to the formation of water, and hence, reversible reaction occurs.…”

Kinetic model for the esterification of free fatty acids from palm oil with methanol using sulfuric acid as catalyst and sensitivity analysis in tubular reactors

“…However, they proposed an irreversible first-order kinetic model. Recently, Hawash et al (2019) also suggested irreversible first-order kinetic models for the esterification of linolenic, linoleic, and oleic acids with methanol and sulfuric acid at 2 wt% as the catalyst. The activation energies found were 3.19, 10.37, and 10.88 kcal/mol, respectively, proving that FFA composition also affects esterification kinetics.…”

“…However, the catalyst concentration effect was also not explicit in none of them. Among other studies focused on kinetic models of FFA esterification to produce biodiesel, those reported by Sendzikiene et al (2004) and Hawash et al (2019) deserve to be mentioned. However, both studies proposed irreversible first-order kinetic models.…”