Decoupling the role of carbon counterparts in Pickering emulsifier for an enhanced selective oxidation of benzyl alcohol

Abstract

Pickering emulsion, a novel medium and reaction platform, has great potential for applications in interfacial catalysis. Although various efforts have been made to modulate suitable catalysts for such reactions, unveiling the intrinsic role of a catalyst in enhanced catalytic activity is highly desired. In this aspect, biomass-derived carbon was combined with hydrophilic zeolite particles to decouple the role of catalysts under Pickering interfacial catalysis (PIC) conditions for enhanced performance. The surface properties of the as-made nanocomposites were engineered and optimized in detail. This also modulated the emulsion capabilities and showed the volcano distribution of catalytic efficiency towards the selective oxidation of benzyl alcohol, indicative of the optimal activity with a conversion of up to >95% and good reusability under base-free conditions with molecular oxygen. It was found that the catalytic efficiency was strongly dependent on the interfacial area provided by the Pickering emulsion and followed the pseudo-first-order rate kinetics. The large biphasic interfacial area was in favor of mass transfer in the reaction process and reduced the external diffusion resistance. The quantitative measurements by electrochemical quartz crystal microbalance (EQCM) and temperature-programmed desorption of oxygen (O₂-TPD) revealed that the combined carbon was able to enhance the adsorption capability towards benzyl alcohol five-fold and oxygen as compared to pristine S-1 during the reaction process. These integrated superiorities are responsible for enhanced catalytic efficiency.