Alkali-Catalyzed Transesterification of Thevetia Peruviana Seed Oil: Comparative Evaluation of NaOH and KOH Catalysts and Fuel Property Characterization

Abstract

Rising energy costs and growing concern over greenhouse gas emissions continue to drive research into alternative fuel sources, and biodiesel derived from triglycerides remains one of the most promising options. This study investigates crude Thevetia peruviana (yellow oleander) seed oil as a biodiesel feedstock, produced via alkali-catalyzed methanolysis using sodium hydroxide (NaOH) and potassium hydroxide (KOH) as catalysts. The resulting biodiesel was characterized for key fuel properties, including kinematic viscosity at 40°C, density, flash point, fire point, acid value, saponification value, iodine value, and moisture content. NaOH produced a higher biodiesel yield and marginally better cetane index, flash point, and fire point than KOH, though excessive NaOH concentration promoted soap formation and emulsification during purification. KOH-catalyzed biodiesel, by contrast, retained substantially higher moisture content, a disadvantage for long-term storage stability. Both catalysts yielded biodiesel with viscosity, density, acid value, and iodine value within accepted limits for conventional biodiesel, and with flash points well above that of petroleum diesel, indicating safer handling and storage. These findings, considered alongside comparable studies on yellow oleander and other alkali-catalyzed feedstocks, confirm Thevetia peruviana seed oil as a viable, non-edible biodiesel feedstock capable of meeting conventional fuel-quality standards while offering the added environmental benefits of biodegradability and reduced emissions of carbon monoxide, particulate matter, and unburned hydrocarbons relative to petroleum-based diesel.