One-pot synthesis of lactic acid from glycerol over a Pt/L-Nb2O5 catalyst under base-free conditions

Highly efficient and selective transformations of glycerol to valuable chemicals are currently an attractive and challenging target reaction in biorefineries. A bifunctional catalyst consisting of Pt nanoparticles (Pt NPs) and layered-Nb2O5 (L-Nb2O5) efficiently catalyzed the one-pot conversion of glycerol to lactic acid (LA) in water under an oxygen atmosphere without the use of any additives such as strong bases. Mechanistic studies revealed that glycerol was initially oxidized to dihydroxyacetone and glyceraldehyde through dehydrogenation on Pt NPs. After the dehydration step catalyzed by acid sites on L-Nb2O5, the dehydrated intermediate pyruvic aldehyde was converted exclusively on Lewis acid sites, rather than a Brønsted acid, to produce LA through the Cannizzaro reaction. These experimental results represent the successful development of a binary catalyst consisting of metal NPs and solid acid, Pt/L-Nb2O5, for one-pot synthesis of LA from glycerol under additive-free conditions. [Display omitted] •Glycerol conversion to lactic acid by Pt-based catalysts on supports was examined.•Layered-structure-type Nb2O5 was synthesized and applied as a support.•Pt/L-Nb2O5 possessed the highest acid sites and strongest Lewis acid strength.•The Lewis acid on Pt/L-Nb2O5 catalyzed conversion of pyruvic aldehyde to lactic acid.•Pyruvic aldehyde to lactic acid conversion via the Cannizzaro reaction.