Optimization of two-step transesterification production of biodiesel from neem (Azadirachta indica) oil

This work investigated the optimization of biodiesel production from neem (Azadirachta indica) oil using a two-step transesterification process and determination of the qualities of the neem oil biodiesel. This was with a view to establish its production and viability potentials. Biodiesel production was carried using a two-step transesterification process. The first step was carried out using 0.60 w/w methanol-to-oil ratio in the presence of 1% w/w H2SO4 as an acid catalyst in 1 h at 50°C. The second step was base (NaOH) transesterification of the product from the first step using conditions specified in the optimization design. The central composite design optimization conditions for the second step were temperature (45°C to 65°C), catalyst amount (0.45% to 1.45% w/w), reaction time (45 to 65 min), and methanol/oil molar ratio (1.5 to 7.5). The physicochemical properties of the neem biodiesel were carried out using standard methods, while the fatty acid profile was determined using gas chromatography. Optimized biodiesel yield of 89.69% was produced at reaction time of 65 min, catalyst amount of 0.95 g, temperature of 55°C, and methanol/oil molar ratio of 4.5:1. The values for the physicochemical properties are 0.05% moisture content, 0.9 specific gravity at 25°C, 5.5 mm2/S kinematic viscosity, 207 mg KOH/g, 70.7 g I2/100 g iodine value, 55.31 cetane number, 39.85 MJ/Kg calorific value, 4 pour point, 8 cloud point, and 110 flash point. These values conform to international standards, in particular, American Society Testing Materials (ASTM). It can be concluded that neem biodiesel showed a general compliance with known standards judging from its physicochemical properties and the engine test. These, coupled with its high yield, attested to the production viability and efficiency of neem biodiesel using two-step transesterification process.