Selective aqueous phase hydrogenation of xylose to xylitol over SiO2-supported Ni and Ni-Fe catalysts: Benefits of promotion by Fe.

[Display omitted] • Stable and selective bimetallic Ni-Fe catalyst was study in the aqueous phase hydrogenation of xylose to xylitol. • The benefits of using Fe as a promoter of Ni: increasing the catalyst activity and chemical stability of the catalyst. • Reduced Fe at the surface increased both the first-order apparent rate constant and the adsorption constant of xylose. • The restructuring of the bimetallic nanoparticles occurred as the metal particles sizes and the Fe proportion in the surface layers increased. A monometallic Ni and a bimetallic Ni-Fe catalyst were used in the aqueous phase hydrogenation of xylose in batch conditions (T = 50–150 °C, P H2 = 10–30 bar, xylose mass fraction in water = 3.7–11.0 wt.%) to evidence the benefits of promoting Ni by Fe. The activity of the catalysts increased with temperature, but a temperature of 80 °C allowed minimizing nickel leaching at full conversion. The presence of reduced Fe at the surface of the bimetallic nanoparticles increased both the first-order apparent rate constant and the adsorption constant of xylose. The catalytic activity of Ni/SiO 2 strongly declined and no deactivation was found for the Ni-Fe catalyst. A restructuring of the bimetallic nanoparticles took place, as the size of the metal particles and the Fe proportion in the surface layers increased, suggesting a flattening and coalescing of the particles over the silica surface. [ABSTRACT FROM AUTHOR]