One-Pot Catalytic Transformation of Lignocellulosic Biomass into Alkylcyclohexanes and Polyols

The direct transformation of lignocellulosic biomass into valuable chemicals and fuels, which is recognized as a promising strategy for easing the present situation of energy depletion, has brought a hot-spot of research. Here we describe the one-pot catalytic conversion of cornstalk into liquid alkylcyclohexanes (from lignin fraction) and polyols (from cellulose and hemicellulose components) over Ru/C catalysts, which are prepared by oxidized commercial Ru/C and then reduced at different temperature. These Ru/C catalysts are well-characterized by the techniques of X-ray photoelectron spectroscopy, H 2 -TPR, and NH 3 -TPD correlated with the conversion of cornstalk and products distribution. It is found that the Ru/C catalyst reduced at 300 °C has the best performance for cornstalk conversion; the mole yield of liquid alkylcyclohexanes reached 97.2% (based on lignin monomers in cornstalk) with 52.7% polyols (24.5% sorbitol, 12.2% xylitol, and 16.0% C 2 –C 4 polyols) at 200 °C. The detailed investigations reveal a synergistic effect between Ru and RuO 2 species in the conversion of lignocellulosic biomass, where metallic Ru is responsible for hydrogenation and RuO 2 species plays crucial roles in cleaving the interlinkages of lignin–carbohydrate (ester and ether linkages) efficiently and in promoting the retro-aldol condensation of carbohydrates. Furthermore, the Ru/C-300 catalyst can be reused for five runs and can be extended to several different raw biomass substrates, indicating that this Ru/C catalysts-based reaction system is promising for the total conversion of lignocellulosic biomass into liquid alkylcyclohexanes and polyols.