Production of xylitol from acidic hydrolysates of lignocellulosic biomass by catalytic hydrogenation over a Ni–Ru/C catalyst

Abstract

Acid hydrolysis and hydrogenation reactions were capable to convert xylose obtained from biomass materials using heterogeneous catalysts based on Ni and Ru. Xylose was extracted from sugar cane bagasse using dilute acid sulfuric solutions, and then xylitol was obtained through xylose catalytic hydrogenation. A bimetallic catalyst (Ni 10.0 wt.% and Ru 1.0 wt.%) was prepared by the wet impregnation method, supporting the metallic phase in activated carbon. Sugarcane bagasse was delignified in a three-step pretreatment (acid, basic and organic extractions, respectively), allowing effective hydrolysis of the resulting holocellulose. The acid hydrolysis process for xylose extraction was more effective at the highest concentration of sulfuric acid in the study (2.5% v/v), obtaining a xylose-rich hydrolysate with concentration over 10 g L−1. For the xylose hydrogenation process, conversion of xylose and selectivity to xylitol was near 90 % after 1 h of reaction. Kinetic evolutions were evaluated through a mathematical model in terms of operating time and temperature, providing hydrogenation activation energy values of the order of 40.76 kJ mol−1.