Waste Cooking Oil Methyl Ester: Transesterification and Evaluation of Corrosion Rates of Aluminium Exposed to Blended Biodiesel and Automotive Gas Oil

Olusegun D. Samuel & Taofeek A. Yusuf

Abstract


This study investigated the corrosion of aluminum exposed to biodiesel produced from Waste Cooking Oil (WCO) and Automotive Gas Oil (AGO) blends. Response Surface Methodology (RSM) with three level-three factor central composite design was used in investigating the effects of transesterification variables such as reaction time, catalyst amount and oil/methanol molar ratio on the yield of waste cooking oil methyl ester (WCOME). Reaction time between 40 - 80 min., catalyst amount of 0.5 - 1.5% wt. and methanol to oil molar ratio of 4 - 8 were used in the transesterification experiment. Optimization of process variables was done using RSM. The fuel properties of biodiesel at optimum level in terms of density, kinematic viscosity, flash, pour and cloud points and sulphur content were obtained using standard method as described by ASTM. Blends of WCO biodiesel 0, 10, 20, 40 and 100% of AGO were designated as B0, B10, B20, B40 and B100 respectively. Corrosion characteristics of blends on aluminium (Al) were studied by static immersion test at room temperature. Mechanical properties of the Al were investigated before and after corrosion test. Changes in the morphology of coupons were also investigated. The optimization technique predicted WCOME yield of 97.1% at the optimal level of 78 minutes, 5.99, 1.1% wt. for the reaction time, methanol to oil molar ratio and catalyst amount respectively. The fuel properties at the optimal level were within the limits specified by ASTM D6751 and EN 14214 standards. The ranges of corrosion rates obtained for the blends were 0-0.2830 mpy. The Brinell hardness ranged for the blends were 105.012, 109.177, 133.717, 155.393, 166.803 N/mm2 while the tensile strength for the blends were 371.20, 386.12, 484.62, 495.22 and 592.89 MPa for B0, B10, B15, B20, B40 and B100 respectively. As the percentage of biodiesel in the blends increased, crack and pits on the morphology of the coupons become pronounced. The blend B10 was detected to perform close to B0 with respect to the Brinell hardness and tensile strength. 


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