Experimental investigation on the estimation of the viscous thermodynamic activation energy parameters of vegetable oils extracted from Cocos nucifera, Calophyllum inophyllum and Canarium indicum

Abstract

Knowledge about of the viscous thermodynamic properties of vegetable oils is important for better understanding for the development of biodiesels. In this work, temperature dependent dynamic viscosities and densities of vegetable oils extracted from Cocos nucifera, [Copra oil (CPO) and Virgin Coconut Oil (VCO)], Calophyllum inophyllum (CaliO) and Canarium indicum (CiO) were determined experimentally. CaliO and CiO exhibited high viscosity compared to CPO/VCO due to the presence of long unsaturated fatty acid chains. Polar lipids dominated CaliO resulting in high density while non-polar lipids resulted in low density of CiO. The Eyring model was used to estimate the viscous thermodynamic activation energy parameters; ΔEa (kJ mol−1) ΔH‡ (kJ.kg−1), ΔS‡ (J.kg−1.K−1) and ΔG‡ (kJ). For CPO/VCO: ΔEa = 24.4, ΔH‡ = 23.8, ΔS‡ = 927. For CaliO: ΔEa = 26.0, ΔH‡ = 25.9, ΔS‡ = 924 and for CiO: ΔEa = 27.5, ΔH‡ = 26.7, ΔS‡ = 921. The positive and high ΔH‡ value in CiO corresponded to high ordering in the oil while the high value of ΔS‡ in CPO/VCO signified high disorientation during flow. The viscosity and the activation energy parameters correlated well with the nature and the proportion of the different types of fatty acids present in the oils.