One-Pot Selective Conversion of Hemicellulose to Xylitol

Converting hemicellulose into valuable platform chemicals is a key step in developing an integrated biorefinery. Traditionally, hemicellulose conversion into xylitol is done in two steps, using mineral acids and enzymes. Here we report a one pot hydrolysis-hydrogenation of hemicellulose to xylitol. We used a combination of either heteropoly acid or biomass-derived organic acid and Ru on carbon as catalyst. Silicotungstic acid, phosphotungstic acid, and lactic acid can be used efficiently in the hydrolysis part. Phosphomolybdic acid was not very active (<5% yield). The reduction can be done using either hydrogen gas or isopropanol as the reductant. The entire process runs in water, at relatively mild temperatures and pressures (140 degrees C and 20 bar). Lactic acid or phosphotungstic acid combined with Ru/C gave around 70% xylitol yield in 3 h using H-2 as a reductant. With isopropanol as a reductant, phosphotungstic acid and Ru/C gave a high xylitol yield (82%), while only similar to 20% xylitol yield was obtained with lactic acid.