Predicting the surface tension of biodiesel fuels by a mixture topological index method, at 313 K

This paper described a method to predict the surface tension of a biodiesel fuel from the molecular structure of its fatty acid methyl ester (FAME) components. A topological index was proposed that used a combination of the distance matrix and adjacency matrix of the molecular structure. The topological index contains information on the molecular structure for the FAMEs, such as the carbon number and unsaturated bonds. The mean topological index values of five FAME mixtures (peanut, canola, coconut, and palm, soybean oil) were calculated by an integration using a modified Dalton-type mass-average equation. The relationship between the mean topological index and mean surface tension of FAME mixtures of biodiesel of known composition at 313 K was linear, and its regression equation allowed the surface tension of biodiesel fuels to be calculated. The relative error between the predicted surface tensions of the above biodiesel fuels and their measured values was within 2.19%. The surface tensions of five biodiesel fuels (corn, safflower, sunflower, and cottonseed, lard oil) were further predicted.