The catalytic performance of Au-Pd nanoparticles (NP) prepared by colloidal synthesis and immobilised on titanate nanotubes (Ti-NT) in the selective oxidation of glucose to gluconic and glucaric acids has been studied under initially basic and relatively mild conditions. Catalysts with varying compositions displayed quite different product selectivity especially in relation to deeper oxidation. The yield of glucaric acid was found to be proportional to the atomic content of Au in the Au-Pd NPs: Au/Ti-NT exhibited the highest selectivity to glucaric acid, while Au15Pd85/Ti-NT displayed the highest selectivity to gluconic acid, SGLO > 98%. Catalyst recycling revealed deactivation, which appears to be due to a combination of metal leaching, particle size changes and product adsorption, and is associated with the gradual fall in pH of the reaction mixture. Results suggest that the leached Au species play a significant role in the oxidation of gluconic to glucaric acid.
- Selective oxidation
- Titanate nanotubes