Microwave-assisted rapid valorization of glycerol towards acetals and ketals

Biodiesel appears as one of the most promising and feasible alternatives among the non-conventional sources of energy; however, its production ends up with a huge amount of glycerol, a financial shortcoming for the expansion of its production. In this context herein we demonstrated an unprecedented catalyst- and solvent-free protocol for the microwave assisted acetalization of glycerol and carbonyl compounds to achieve high yields of cyclic acetals or ketals including commercially valuable hyacinth fragrance and fuel additive precursors. Comparative studies with conventional heating suggest that microwave irradiation plays a crucial role for the acetalization reactions. Moreover, several heterogeneous catalysts on the acetalization reaction have also been screened. The present work thus dispenses with excessive amount of solvents, precious catalysts and provides a clean and green approach towards the valorization of glycerol. Considering the commercial importance of the acetalization reactions the model reaction was scaled up to 150 ml, is evidence for 90 +/- 5% conversion and consistent selectivity. C) 2013 Elsevier B.V. All rights reserved.