African oil bean seed as feedstock for bio-oil and biodiesel production and on the effects of thermal pre-treatments on the quality of the bio-oil

Abstract

This research is on the introduction and the effect of the pre-treatment method on oil recovery from African oil bean seeds for biodiesel production. Samples were dried in the solar dryer, open sun, and the oven at 50 °C, 60 °C, and 70 °C. The solvent extraction process with hexane was used to extract oil from the product, and their saponification value, peroxide value, acid value, iodine value, specific gravity, and the color of the bio-oil were analyzed. The oil was further used in acid-catalyzed esterification and alkaline transesterification for biodiesel production, and the effects of temperature, catalyst concentration, feedstock to methanol molar ratio, and reaction time on biodiesel conversion were investigated. Solar drying of the seed yielded the highest volume of oil compared with other drying methods. Peroxide values of the oil meet the standard values from CODEX but showed an increase in rancidity in the solar-dried and open sundried products. Bio-oil produced has good lubricating properties as its iodine properties showed that it is not a drying oil. The cetane number and heating value of the biodiesel produced are within the range when compared with the ASTM standard of diesel properties. By using a feedstock to methanol molar ratio of 1:6 and a sulfuric acid concentration of 0.8%, a biodiesel conversion of 81% was obtained after 6 h of reaction at 60 °C. The biodiesel produced by this process met the American Society for Testing and Materials (ASTM) standard.