The effect of NaOH catalyst concentration and extraction time on the yield and properties of Citrullus vulgaris seed oil as a potential biodiesel feed stock

Abstract

In this work, oil was extracted from Citrullus vulgaris (watermelon) seeds for potential feedstock in biodiesel production. The results showed that the oil content from Citrullus vulgaris seeds oil during extraction reached an average yield of 50%. Biodiesel was produced via transesterification using NaOH as a catalyst. The effect of NaOH on the yield of the biodiesel was investigated at three different traditions; 0.13, 0.15, and 0.18 g, and oil to methanol ratio of 5:1 under different reaction times; 90, 120 and 150 min at 60 C. The yield of biodiesel from NaOH concentration of 0.13 g was found to be 70% compared to those of concentrations of 0.15 g and 0.18 g which were 53% and 49% respectively. Gas chromatography was used to identify the methyl ester groups present in the biodiesel and the results revealed both concentration and time-dependent increase in oil yield. The physicochemical properties of the watermelon seed oil such as flash point (141.3 ± 0.4e143.4 ± 0.2), density (0.86 ± 0.04 e0.91 ± 0.01 g/cm3 ), kinematic viscosity (30.50 ± 0.1e31.20 ± 0.04 mm2 /s) and acid value (mg KOH/g) are similar to conventional vegetable oils. This work, therefore, highlights the potential utility of watermelon seeds for biodiesel production.