One-pot Synthesis of Gluconic Acid from Biomass-derived Levoglucosan Using a Au/Cs2.5H0.5PW12O40 Catalyst
The selective conversion of levoglucosan to gluconic acid, wildly used in food and pharmaceutical, has been achieved in one-pot by a heterogeneous bifunctional catalyst comprising gold on Cs salts of tungstophophates. With the concerted operation of active Au sites and acidic sites of Cs2.5H0.5PW12O40, gluconic acid was obtained with a high selectivity of 93.1% under nearly complete conversion. The gluconic acid product itself was found to accelerate the overall reaction rate, since the homogeneous Brønsted acidity introduced by gluconic acid could enhance the hydrolysis step of levoglucosan to glucose, a rate-limiting step as revealed by further kinetics analysis. This work provides a new and effective approach for the production of gluconic acid from levoglucosan, potentially enabling the efficient utilization of lignocellulose biomass to value-added chemicals.