Purification of residual glycerol recovered from biodiesel production

Abstract

Transesterification is the most widely used reaction in the production of biodiesel. It involves the breaking of the triglyceride structure and the exchange of alkyl groups with the hydroxide groups of the alcohol to obtain the new ester (biodiesel). In this process residual glycerol is also produced, but since it is of low purity few alternatives for its application have been identified. In this context, a methodology for the purification of the residual glycerol was developed with a view to adding value to this product and making the process more economically attractive. In this study, residual glycerol was obtained from the transesterification of waste frying oil and of virgin soybean oil in bench scale. The purification method was also applied to residual glycerol obtained from a similar process on industrial scale. The product obtained after each step was characterized to evaluate the contribution of each unit of the operation to the quality of the final product. The results obtained show an increase in the degree of the glycerol purity in each step. It can thus be concluded that the method presented herein can be used to increase the quality of residual glycerol obtained from the biodiesel production process resulting in its acceptable commercial value.