Au@h-Al2O3 analogic yolk–shell nanocatalyst for highly selective synthesis of biomass-derived d-xylonic acid via regulation of structure effects

Abstract

Selective oxidation of biomass-based monosaccharides into value-added sugar acids is highly desired, but limited success of producing D-xylonic acid has been achieved. Herein, we report an efficient catalyst system, viz., Au nanoparticles anchored on the inner walls of hollow Al₂O₃ nanospheres (Au@h-Al₂O₃), which could catalyze the selective oxidation of D-xylose into D-xylonic acid under base-free conditions. The mesoporous Al₂O₃ shell as the adsorbent first adsorbed D-xylose. Then, the interface of Au nanoparticles and Al₂O₃ as active sites spontaneously dissociated O₂, and the exposed Au nanoparticle surface as the catalytic site drove the transformation. With this catalyst system, the valuable D-xylonic acid was produced with excellent yields in the aerobic oxidation of D-xylose. Extensive investigation showed that Au@h-Al₂O₃ is an efficient catalyst with high stability and recyclability.