Highly efficient production of lactic acid from xylose using Sn-beta catalysts

Abstract

The efficient conversion of xylose into lactic acid, especially with the novel contribution of C₂ components, was revealed over the heterogeneous Sn-beta catalyst in water with a very high lactic acid yield of 70.0 wt% at 200 °C for 60 min. The ¹³C NMR results indicated that glycolaldehyde (C₂), the cleavage species of xylose condensate to erythrose (C₄), subsequently, erythrose converts to lactic acid (C₃) and to formic acid (C₁) with the removal of a carbon atom. In this catalytic process, Sn acts as the Lewis acid site in the Si–O–Sn framework, and participates in the coupling and cracking of C–C bonds (C₂ → C₄ → C₃) through the adsorption of α-protons to generate carbonium anions. Thus, more than 10 wt% lactic acid was obtained based on above pathway through the synergy of aldol addition, isomerization and retro-aldol condensation over the Sn-beta catalyst.