One-Pot Production of Lactic Acid from Acetol over Dealuminated Sn-Beta Supported Gold Catalyst

Abstract

Staged biomass pyrolysis or condensation of the pyrolysis vapor generates less complex and concentrated liquid product streams, which provide a very promising route to produce value-added chemicals. Acetol is one of the major light oxygenates in fractionated bio-oil. Here we report an efficient one-pot conversion of acetol to lactic acid, a key platform chemical and an important monomer of biodegradable polymer, in aqueous phase over a bifunctional dealuminated Sn-Beta supported gold catalyst. Under relatively mild conditions (393 K, 1.9 MPa N2 + 0.1 MPa O2), 93.4% acetol conversion and 73.2% selectivity toward lactic acid were achieved. On the basis of measured rate constants, the reaction pathway likely proceeds via kinetically relevant oxidation of acetol to form pyruvaldehyde, followed by hydration and 1,2-hydride shift (internal Meerwein–Ponndorf–Verley reduction and Oppenauer oxidation) on Sn-Lewis sites to produce lactic acid.