Valorisation of Glycerol by Acetalization Reactions Using Heterogeneous Catalysts

Abstract

The production of biodiesel has increased considerably during the last few years. About 100 kg of glycerol is produced for every 900 kg of biodiesel formed. Glycerol is considered a byproduct, but it can be converted into new compounds with high commercial value, which leads to increased sustainability of the biodiesel industry. Different processes, such as esterification, etherification, and oxidation reactions, can be used to improve the glycerol commercial value. Glycerol can be transformed into oxygenate compounds through acetalization reactions with ketones and aldehydes. The products of these processes can be applied as additives fuels. Usually, these reactions occur using homogeneous catalysts, such as sulphuric, fluoridric, chloridric and p-toluensuphonic acids. However, heterogeneous catalysts present some benefits over homogenous catalysts. Heterogeneous catalysts can be separated from the liquid phase and reused several times. They are less harmful to the environment, such as they are less corrosive. The present work presents a review that focuses on the use of a diversity of solid materials as heterogenous catalysts for glycerol valorisation by acetalization reactions.