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

The efficient conversion of xylose into lactic acid, especially with the novel contribution of C-2 components, was revealed over the heterogeneous Sn-beta catalyst in water with a very high lactic acid yield of 70.0 wt% at 200 degrees C for 60 min. The C-13 NMR results indicated that glycolaldehyde (C-2), the cleavage species of xylose condensate to erythrose (C-4), subsequently, erythrose converts to lactic acid (C-3) and to formic acid (C-1) 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 (C-2 -> C-4 -> C-3) through the adsorption of alpha-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.