One-pot catalytic hydrolysis/hydrogenation of cellobiose into hexitols over Ru/Al-MCM-48

Abstract

The simultaneous catalytic hydrolysis and hydrogenation of cellobiose, as a model constituent of biomass has been studied over Ru/Al-MCM-48. The catalyst, presenting both acidic and hydrogenating functions has been synthesized and characterized by means of N2 adsorption-desorption, SAXS, H2-TPR, XRD, TEM and NH3-TPD. A kinetic model is proposed, and possible reaction pathways and key intermediate compounds of conversion of cellobiose to hexitols are discussed. In the kinetic study the effects of pressure, temperature and time on the one-pot reaction were evaluated. A maximum yield around 91% of hexitols was achieved at 180 °C, 5 MPa of H2 and 7 min, where sorbitol was the main compound in the final product with 82% yield. Cellobitol was the main reaction intermediate. Temperatures in the range of 140–180 °C and pressures in the range of 3–5 MPa of H2 were studied and it was concluded that higher temperatures and pressures had a positive effect in order to maximize the production of hexitols. The developed kinetic model predicted with high accuracy the concentration of the different compounds involved in the proposed reaction pathway and served to calculate the reaction rate constant and activation energy values for the different steps of the catalytic process.