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, widely used in food and pharmaceutical industries, has been achieved in one pot by using a heterogeneous bifunctional catalyst comprising gold on Cs salts of tungstophosphates. 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% in 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 kinetic 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 obtain value-added chemicals.