Support-Enhanced Selective Aerobic Alcohol Oxidation over Pd/Mesoporous Silicas

Abstract

The influence of silica mesostructure upon the Pd-catalyzed selective oxidation of allylic alcohols has been investigated for amorphous and surfactant-templated SBA-15, SBA-16, and KIT-6 silicas. Significant rate enhancements can be achieved via mesopore introduction, most notably through the use of interconnected porous silica frameworks, reflecting both improved mass transport and increased palladium dispersion; catalytic activity decreases in the order Pd/KIT-6 ≈ Pd/SBA-16 > Pd/SBA-15 > Pd/SiO 2 . Evidence is presented that highly dispersed palladium oxide nanoparticles, not zerovalent palladium, are the catalytically active species.