Optimization of coconut oil ethyl esters reaction variables and prediction model of its blends with diesel fuel for density and kinematic viscosity

This paper presents the synthesis of biodiesel from coconut oil sourced from Nigeria through base-catalyzed transesterification using potassium hydroxide (KOH) as catalyst and ethanol as solvent. Direct transesterification reactions were carried out due to low free fatty acid value (0.65 mg KOH/g oil). The reaction variables optimized were: KOH amount (0.5–2.25 wt.%), reaction temperature (30–80 °C), reaction time (30–70 min) and ethanol to oil molar ratio (3–12). Physico-chemical properties of the coconut oil and fuel properties of the coconut oil ethyl esters (CNOEE) were determined using standard test methods, and the properties of the latter were compared with biodiesel standards. Also, the density and viscosity of diesel fuel blends (B5, B10, B20 and B50) with CNOEE were determined and the viscosities compared with that of the Grunberg and Nissan model. In this study, the optimum reaction variables obtained (KOH amount = 1.0 wt.%, ethanol/oil molar ratio = 6:1, reaction temperature = 70 °C, reaction time = 60 min) gave a biodiesel yield of 97.20% and the fuel properties of CNOEE at the optimum conditions conformed to both ASTM D6751 and EU 14214 standards. There was agreement between the measured and estimated values for the density and viscosities of CNOEE–diesel blends. The results indicate that the density and viscosities of the blends increased with the increased of biodiesel percentage in the blends.