(196a) Micro/Mesoporous Au@SiO2 Core-Shell Nanoparticles for Alkalinity-Independent Selective Benzyl Alcohol Oxidation

Authors: 
Hammond-Pereira, E. - Presenter, Washington State University
Saunders, S. R., Washington State University
Wu, D., Washington State University
Bryant, K., Washington State University
Graham, T. R., Voiland School of Chemical Engineering and Bioengineering, Washington State University
Silica-encapsulated gold core-shell nanoparticles (Au@SiO2) were synthesized via a bottom-up synthesis to catalyze the selective oxidation of benzyl alcohol. The pore size, morphology, and composition of Au@SiO2 was evaluated using N2 gas adsorption, transmission electron microscopy, and inductively-coupled plasma mass spectroscopy, respectively. The nanoparticles exhibit a pore size distribution with a peak at 27 Å, a size which enhances selectivity via preferential transport of the desired product (i.e. benzaldehyde) relative to larger, undesired products (i.e. benzoic acid/benzyl benzoate). GC-FID analysis revealed the addition of potassium carbonate during the catalytic oxidation of benzyl alcohol increased conversion from 58% to 75% while only decreasing selectivity from 98.5% to 97.7%.

These results suggest that the pore size distribution within the inert silica shell of Au@SiO2 physically inhibits the formation of undesired products to facilitate the selective oxidation of benzaldehyde despite a basic environment which would drastically reduce selectivity under typical conditions. An activation energy study revealed an unusually low activation energy of 23 kJ/mol. Combined with overwhelmingly rate-limited Thiele moduli, the particles appear to have a lower activation energy as a result of a catalyst that is not only product selective, but mechanism selective. As such, these particles are a promising platform for analysis of the impact of functionalization on mass transport and surface chemistry discretely.