Transesterification, Modeling and Simulation of Batch Kinetics of Non-Edible Vegetable Oils for Biodiesel Production

Biodiesel derived from renewable plant sources is monoalkyl esters of long chain fatty acids which fall in the carbon range C12-C22. It has similar properties as mineral diesel. Various processes exist to convert vegetable oils (mainly triglycerides) into biodiesel. Transesterification of vegetable oils using alcohol in a catalytic environment is most commonly used method for producing biodiesel. The equilibrium conversions of Triglycerides (TG) is affected by various factors, namely, type of alcohol used, molar ratio of alcohol to TG, type of catalyst, amount of catalyst, reaction temperature, reaction time and feedstock quality (like free fatty acid content, water content etc.). The present work reports the characterization of non-edible feedstock oils of Indian origin, production, separation, characterization of biodiesel and byproduct. This study also reports the optimal operating parameters for different oils in batch reactor. The main thrust of the present work was to study the kinetics, modeling and simulation of alkali-catalyzed transesterification of Linseed and Jatropha curcas oils. Experiments were carried out in a 2.0 l batch reactor to generate kinetic data and a reversible kinetic model was developed. The effects of temperature, catalyst concentrations, and molar ratios of methanol to TGs and stirring rates were investigated. A few fuel properties were also measured for biodiesel to observe its competitiveness with conventional diesel fuel. The equilibrium conversions of TG were observed to be in the range of 88-96 %. (Linseed) and 50-83% (Jatropha). The equilibrium conversions were achieved in less than 45 minutes for both oils. It was also observed that increasing the temperature and molar ratio increased the equilibrium conversions; while increase in catalyst concentration had no significant effect on reaction time. Characterization of the feedstock oils and biodiesel produced were carried out. It was observed that the biodiesel produced had similar properties to mineral diesel. Model parameters (order and rate constants) for the reversible model were calculated. Gear’s technique was used to solve the initial value problem and genetic algorithm was used with the mathematical model to minimize the error between experimental and model predicted conversions. Activation energies for forward and backward reactions were estimated. Model fitness values were observed to be more than 0.9. Various simulations were also carried out at different conditions and showed that beyond a critical molar ratio there is no significant effect on transesterification kinetics.