Xylitol Production from Xylose by Catalytic Hydrogenation over an Efficient Cu–Ni/SiO2 Bimetallic Catalyst

Xylitol is a value-added health product from the hemicellulose component in biomass. In this work, highly efficient Cu–Ni/SiO2 catalysts are developed for the production of xylitol by means of xylose hydrogenation. The bimetallic catalysts exhibit higher activity compared to the corresponding monometallic nickel or copper catalyst and the currently used industrial Raney nickel catalyst. The bimetallic catalyst with a higher ratio of nickel to copper shows a better performance. The 5Cu15Ni/SiO2 catalyst exhibits a xylose conversion of 96% accompanied by higher than 99% selectivity to xylitol under the moderate conditions of 100 °C and 3MPa H2. The bimetallic catalysts show improved performances when they are activated at a low temperature. The apparent activation energies of xylose hydrogenation over the 5Cu15Ni/SiO2 and 20Ni/SiO2 catalysts are 16.6 and 25.2 kJ/mol, respectively. The formation of the Cu–Ni alloy leads to a lower activation energy and thus superior performance for xylose hydrogenation to xylitol.