Alkali transesterification of linseed oil for biodiesel production

The use of renewable vegetable oils derived from plant seeds has gained attention worldwide due to soaring petroleum-crude prices. Physical and/or chemical transformations are used to improve the vegetable oil properties to make it compatible for use in existing engines. Transesterification process reduces the poly-unsaturation of these vegetable oils which results in diesel like fuel (biodiesel). Alkali-catalyzed transesterification is most commonly used process for oils with low free fatty acids and low moisture content. In this study, the kinetics and simulation of alkali-catalyzed transesterification of linseed oil in a batch reactor is reported. The effects of temperature, catalyst concentration, and molar ratio of methanol to triglyceride were investigated experimentally. The equilibrium conversions of triglycerides were observed to be in the range of 88–96%. The equilibrium conversions were achieved within 40 min in all experiments. Increasing the temperature and molar ratio increased the equilibrium conversions; while catalyst concentration had no significant effect. A reversible kinetic model was applied to the observed conversion data. Model parameters for forward and backward reactions were estimated and optimized. Various simulations were also carried out at different conditions to show that beyond a critical molar ratio no significant effect on transesterification kinetics was observed. Characterization of biodiesel produced from linseed oil showed similar properties to mineral diesel.