Low temperature glycerolysis as a high FFA pre-treatment method for biodiesel production

A novel low temperature glycerolysis process for lowering free fatty acid (FFA) in crude jatropha oil for alkali cata-lyzed transesterification has been developed. The response surface methodology (RSM) based on central composite design was used to model and optimize the glycerolysis efficiency under three reaction variables namely; reaction time, temperature and glycerol to oil mass ratio. The optimum conditions for highest glycerolysis efficiency of 98.67% were found to be temperature of 65°C, reaction time of 73 minutes and 2.24 g/g glycerol to oil mass ratio. These conditions lower the high free fatty acid of crude jatropha oil from 4.54% to 0.0654% which is below 3% recommended for alkali catalyzed transesterification. The pre-treated crude jatropha oil was then transesterified by using homogeneous base transesterification resulting to a conversion of 97.87%. The fuel properties of jatropha biodiesel obtained were found to be comparable to those of ASTM D6751 and EN 14214 standards. The process can also utilize the crude glycerol from the transesterification reaction, hence lowering the cost of biodiesel. The glycerolysis is easier implemented than acid esterification thereby avoiding the need for neutralization and alcohol removal step.
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Biodiesel, Glycerolysis, Free Fatty Acid, FFA, Re-esterification, Low temperature glycerolysis
Kombe, G. G., Temu, A. K., Rajabu, H. M., Mrema, G. D., & Lee, K. T. (2013). Low temperature glycerolysis as a high FFA pre-treatment method for biodiesel production. Advances in Chemical Engineering and Science, 2013.