Glycerol byproduct utilisation during transesterification process

In the transesterification process of biodiesel production, the carbon chain of a molecule of vegetable oil is broken into three. At each break, a hydrogen atom from methanol is substituted for the link to the adjacent carbon atom. The production of biodiesel, however, leads to the formation of large quantities of crude glycerol – around 10% of the mass of biodiesel created – but is generally uneconomical to refine. Researchers are seeking ways to convert this waste product into something useful, and some efforts have focused on the dehydration reaction to acrolein – used as a herbicide and polymer precursor. 

The remain glycerol could be reduced back to methanol by carbon–carbon bond scission and reduction using water as a hydrogen source. This reaction can take place by either of two mechanisms: the first begins with double dehydration to acrolein and the second proceeds via the ethylene glycol radical and hydroxyethanal. It's a new chemistry, which has never been discussed in the literature before. Further investigations show that cerium dioxide is a more effective catalyst than magnesium oxide, achieving complete conversion with methanol selectivity of 60%. In this way sustainability loop for the transesterification process of biodiesel could be closed.