Alkali-catalyzed Transesterification of Hibiscus sabdariffa (Roselle) Seed Oil for Biodiesel Production
Eman H. Ahmed
Department of Applied and Industrial Chemistry, Faculty of Pure and Applied Science, International University of Africa (IUA), Sudan.
Azhari H. Nour
Department of Applied and Industrial Chemistry, Faculty of Pure and Applied Science, International University of Africa (IUA), Sudan.
Omer A. Omer Ishag *
Faculty of Chemical and Process Engineering Technology, College of Engineering Technology, University Malaysia Pahang (UMP), Malaysia.
Abdurahman H. Nour
Faculty of Chemical and Process Engineering Technology, College of Engineering Technology, University Malaysia Pahang (UMP), Malaysia.
*Author to whom correspondence should be addressed.
Abstract
The need of energy never comes to an end so; the challenge is to procure power source sufficient to offer for our energy needs. Besides, this energy source must be dependable, renewable, recurring and non-contributing to climate change.
Aims: This study was aimed to produce biodiesel from Roselle seed oil and to investigate its quality. Methodology: The Roselle seeds were clean from dirt, milled to proper size and the oil was extracted using soxhlet with n-hexane as solvent. The extracted oil was subjected to physiochemical analysis tests and then transesterified using methanol and potassium hydroxide as catalyst; with ratio of oil to alcohol 1:8 at 65°C. The quality of produced biodiesel was investigated and compared to international standards. The fatty acid composition of the produced biodiesel was determined by GC-MS.
Results: Based on the experimental results, the yellow with characteristic odor oil was obtained from the seeds had the following physicochemical properties: yield, 12.65%; refractive index (25°C), 1.467 m ; free fatty acids, 5.5%; saponification value, 252 mg KOH/g of oil; density, 0.915 g/mL and ester value, 241 mgKOH/g. Also the biodiesel yield achieved was 96%, with density, 0.80 g/mL; API, 44.63; Kinematics viscosity @ 40˚C, 0.742; Pour point, < -51˚C; and Micro Carbon Residual (MCR), 0.65%; which conformed to the range of ASTM D6751 and EN 14214 standard specifications. However, the GC-MS analysis result revealed that the biodiesel produced was methyl ester and free other undesired products such as linoleic acid (33%), elaidic acid (29%) and palmitic acid (17%) and other biomolecules.
Conclusion: Based on the obtained results, Roselle seed oil had potential for biodiesel production due to its high contains of free fatty acids. Therefore, in the future, more investigations in alcohol: oil ratio and the concentration of catalyst may be warranted to increase the yield much more.
Keywords: Biodiesel, Hibiscus sabdariffa (Roselle), methanolysis, linoleic acid, transesterification