Aluminum(III) triflate-catalyzed selective oxidation of glycerol to formic acid with hydrogen peroxide

Glycerol is a by-product of biodiesel production and is an important readily available platform chemical. Valorization of glycerol into value-added chemicals has gained immense attention. Herein, we carried out the conversion of glycerol to formic acid and glycolic acid using H 2 O 2 as an oxidant and metal (III) triflate-based catalytic systems. Aluminum(III) triflate was found to be the most efficient catalyst for the selective oxidation of glycerol to formic acid. A correlation between the catalytic activity of the metal cations and their hydrolysis constants ( K h ) and water exchange rate constants was observed. At 70 °C, a formic acid yield of up to 72% could be attained within 12 h. The catalyst could be recycled at least five times with a high conversion rate, and hence can also be used for the selective oxidation of other biomass platform molecules. Reaction kinetics and 1 H NMR studies showed that the oxidation of glycerol (to formic acid) involved glycerol hydrolysis pathways with glyceric acid and glycolic acid as the main intermediate products. Both the [Al(OH) x ] n + Lewis acid species and CF 3 SO 3 H Brønsted acid, which were generated by the in-situ hydrolysis of Al(OTf) 3 , were responsible for glycerol conversion. The easy availability, high efficiency, and good recyclability of Al(OTf) 3 render it suitable for the selective oxidation of glycerol to high value-added products.