Catalytic properties of Pd–Tl/SiO2 systems in the reaction of liquid phase oxidation of aldoses

The influence of thallium addition on the catalytic properties of palladium catalysts supported on SiO2 in the reaction of aldoses (glucose and lactose) oxidation to aldonic acid was studied. It was found that thallium does not have any activity by itself, but acts as “promoter” for the catalytic activity and selectivity of monometallic Pd/SiO2 catalysts. The XRD studies proved the presence of intermetallic compounds, which probably increases activity and selectivity of bimetallic catalysts in those reactions. The same interaction was found using ToF-SIMS. The TPO studies show that palladium oxidation occurs at much higher temperatures than in the case of thallium. A reaction involving bimetallic catalysts in oxidizing atmosphere at 333 K should not lead to surface oxidation of palladium and thus their deactivation.

Graphical abstractThis paper deals with the oxidation of aldoses (glucose and lactose) with palladium on SiO2 catalysts modified with thallium. The catalysts were characterized by XRD studies and temperature-programmed oxidation (TPO) method after their reduction at 533 K. Figure optionsDownload full-size imageDownload as PowerPoint slide