Doped Layered Phosphate Catalysts for the Activation of Glycerol

Abstract

Glycerol is a plentiful chemical side-product from many industrial processes including the production of biofuels, simple fermentations and reactions used to synthesise alkenes such as propene. The rising cost of safely disposing of chemical waste is forcing companies to find new and innovative ways of either reusing waste products or ways to minimise the amount of waste produced. Waste glycerol can be converted into more highly desirable compounds such as glycerol carbonate. However, the most common method of converting glycerol to glycerol carbonate is to react it with phosgene which is highly toxic. Glycerol carbonate is a highly sought after compound because of the magnitude of its uses from polymers and cleaning solvents to cosmetics and curing agents.

Recent research has started to focus on finding new green methods for synthesising glycerol carbonate, by way of catalysis. Previous work in this area was carried out by Aresta et al. in which γ-zirconium phosphate was used to catalyse the reaction between glycerol and urea to form glycerol carbonate. It is thought that the reaction proceeds via a two-step reaction. Firstly the glycerol and urea react forming glycerol carbamate, this intermediate then cyclicises around to form the carbonate. The advantage in using urea for this reaction as opposed to carbon dioxide is that ammonia gas is evolved during the reaction, allowing for a potentially greener method to synthesise another valuable industrial chemical. The work presented here is the synthesis of a library of novel metal-substituted layered phosphate catalysts and the assessment of their potential as catalysts, in the synthesis of glycerol carbonate via the glycerolysis of urea.