Optimization of Biodiesel Production from the Transesterification of Rubber Seed Oil

Abstract

The high cost of feedstock for biodiesel production limits the competitive potential of the fuel as a substitute for the petroleum diesel. The current study investigated the optimization of biodiesel yield from the transesterification of rubber seed oil. The operating parameters such as temperature, reaction time and methanol-to-oil ratio were optimized using Central Composite Design in Design Expert software. The physicochemical properties of the biodiesel produced were analyzed using appropriate ASTM methods and the fatty acid composition was determined with the help of a gas chromatography equipped with mass selective detector. The highest biodiesel yield was 76.6 % obtained at optimum operating conditions of temperature (60 oC), reaction time (75 min), and methanol-to-oil ratio (4:1). The physichochemical properties of the biodiesel included density (848.4 g/m3), specific gravity (0.8675), viscosity at 40 oC (2.030), kinematic viscosity (1,722 mm2/s), acid value (1.604 mg KOH/g), free fatty acid (0.802 %), flash point (89.4 oC), pour point (-3.8 oC), cloud point (-5.2 oC), calorific value (40.1042 MJ/kg), and cetane number (46.9). The predominant fatty acid esters in the biodiesel included methyl tetradecanoate, hexadecanoic acid, methyl ester, 8-Octadecenoic acid, methyl ester, 9-octadecenoic acid, methyl ester, (E)-, (E)-11-Octadecenoic acid, methyl ester, and methyl stearate. The result of the physicochemical analysis revealed that the biodiesel produced is in agreement with the ASTM standards except that the fuel is slightly acidic. The composition of the fatty acid methyl ester revealed that the biodiesel produced possessed desired properties required for enhancing the performance of engines.