Production of Biodiesel from Crotalaria juncea (Sunn-Hemp) Oil Using Catalytic Trans-Esterification: Process Optimisation Using a Factorial and Box–Behnken Design

Abstract

This study consists of the production of biodiesel from methanolysis of Sunn-hemp (Crotalaria juncea) oil, using homogeneous and heterogeneous catalysts. Calcium carbonate enriched sea shells like capiz and conch shell are used as natural catalysts after calcination for trans-esterification. These heterogeneous catalysts are physically characterized in order to locate the active sites using X-ray powder diffraction. Gas chromatography mass spectrometry is used to identify and estimate the fatty acid methyl esters of the biodiesel. Basic fuel properties like specific gravity, moisture content, kinematic viscosity, saponification value, iodine value, flash point, fire point, aniline point, cetane number and heat content are determined to establish this biodiesel as a diesel substitute for a fuel. The fuel properties indicate that after some modifications, Sunn-hemp seed oil based biodiesel could be a promising new source for the production of biofuel. Response Surface Methodology is used to optimize the operating parameters of the process. A Factorial and Box–Behnken Design is used to study the effects of time of reaction, type of catalyst, catalyst concentration and oil to methanol mole ratio on the yield of biodiesel. Statistical analysis shows that the model is significant with a R 2 value of 0.997 having achieved the optimum conditions after 4.15 h, with an oil to methanol molar ratio of 11. 2 wt% catalyst concentration and potassium hydroxide as the best catalyst for the production of 90.25 % biodiesel.