Transition Metal Catalysts for the Glycerol Reduction: Recent Advances

Glycerol (GL) represents a widespread agro-industrial waste. Its valorization is pivotal for a sustainable society because GL is a renewable compound deriving from biomass, but it has a high oxygen to carbon ratio, compared with feedstock used in the energy and chemistry sectors. Oxygen-poor derivatives are easily and immediately transferable to the industry, avoiding a deep and pressing modification of the plants. From this perspective, keeping the carbon content but with an oxygen content reduction, we could effectively obtain the enhancement of the recovery and the use of GL converting it into attractive industrial building-blocks. In this Review, we present and discuss the up-to-date results about the chemical reduction of GL into products with 3 carbon and 0, 1, or 2 oxygen atoms. The focus is on the transition metal (TM) catalysts that have made the hydrogenation reactions of GL possible, partitioning the metals into early and late, based on their position in the periodic table. This discussion will contribute to select and develop new catalysts aimed at the improvement of the yield and of the selectivity in the hydrogenation reactions of GL. The large availability of glycerol could make convenient to deoxygenate it to obtain chemicals that can be used for applications such as energy, polymers, and fine chemistry. Transition metals are efficient catalysts to perform such transformations and here we explored the recent literature to understand which metals could represent the economical, green and effective candidates to transform glycerol into C3 compounds, otherwise obtainable from fossil resource.image