Solvent-Free Synthesis of Zeolite Crystals Encapsulating Gold-Palladium Nanoparticles for the Selective Oxidation of Bioethanol.

The conversion of bioethanol into valuable products is an important area in the conversion of biomass. We demonstrate the successful synthesis of bimetallic gold-palladium (Au-Pd) nanoparticles encapsulated within S-1 zeolite crystals (AuPd@S-1) by a solvent-free strategy. This strategy allows highly efficient use of the noble metals, with more than 96 % of the gold and palladium being loaded into the final samples. Electron microscopy characterization and investigations with probe molecules confirm that the Au-Pd nanoparticles are encapsulated inside the S-1 crystals. The AuPd@S-1 catalyst is very active for the aerobic oxidation of bioethanol, giving 100 % conversion and 99 % selectivity to acetic acid. Even in the presence of 90 % water, the catalyst still gives a conversion higher than 80 % and a selectivity of 95 %. More importantly, the AuPd@S-1 catalyst exhibits excellent stability in the oxidation of bioethanol. These features are important for future practical applications of the AuPd@S-1 catalyst.