Chemical modification of Terminalia catappa L. kernel oil methyl ester using epoxidation-esterification approach, for application as bio-transformer fluid – Physicochemical characterization, kinetics and thermodynamics

Abstract

Epoxidation-esterification of fatty acid methyl ester obtained from Terminalia catappa L. kernel oil (TCKO), its characterization, kinetics and thermodynamics were the main focus of this study. The methyl ester obtained via base catalyzed transesterification was used for epoxidation-esterification modification process. Epoxidation kinetics and thermodynamics parameters were also investigated. The properties of the TCKO and epoxidized-esterified Terminalia catappa L. kernel oil methyl ester (MTCKO^e) were determined using standard methods. MTCKO^e was analyzed using Dissolved Gas Analysis equipment, so as to determine its constituent gases compositions. The order ${10}^{-5}$Lmol⁻¹s⁻¹ and 39.97 KJ/mol were the respective rate constant K and activation energy Ea, obtained for the epoxidation process. ΔG, ΔH, and ΔS values for the epoxidation process were (136.00–148.82 kJ mol⁻¹), 37.24 kJ mol⁻¹, and $-$320.64 J mol⁻¹ K⁻¹, respectively, indicating non-spontaneous, endothermic, and endergonic process. The properties of MTCKO^e sample were: -8°C, 280°C, 820 Kg/dm³, 8.56 mm²/s, 0.80 mgKOH/g, 0.65 mg/Kg and 50.05 KV for pour point, flash point, density, viscosity, acid value, moisture content and dielectric strength, respectively. The dissolved gas analysis result (in ppm) of the key gases for MTCKO^e sample are: <5, 87, 1441, <1, 6, 84, 3, <0.5 for H₂, H₂O, CO₂, CO, C₂H₄, C₂H₆, CH₄, C₂H₂, respectively. The characteristics met acceptable standard limits. The MTCKO^e properties indicated its possible use as bio-transformer oil.