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 NH3-TPD correlated with the conversion of cornstalk and products distribution. It is found that the Ru/C catalyst reduced at 300 degrees 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 degrees C. The detailed investigations reveal a synergistic effect between Ru and RuO2 species in the conversion of lignocellulosic biomass, where metallic Ru is responsible for hydrogenation and RuO2 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.