(114h) Gold Nanoparticles Deposited inside Hierarchical Zeolites Catalyze Diverse Groups of Aromatic Alcohols

The slow internal mass transport, induced by long diffusion path length, of reactants and corresponding products to and from the active site reduces transport efficiency of single-sized zeolite catalysts. Comparatively, hierarchical zeolites consist of two (or more) level of highly interconnected porosity (microporosity, mesoporosity, and macroporosity), which enhance the mass transport and molecular accessibility in catalytic reactions. Our previous work indicated that the oxidation of benzyl alcohol, catalyzed by the gold nanoparticles inside the mesopores of SBA-15 zeolites, could be potentially limited by internal mass transport due to the long and tortuous diffusion path of mesoporous zeolites. The goal of this work is to design flexible catalyst synthesis technique to tune catalysts’ performance. Herein, we demonstrate a catalyst synthesis technique, directly depositing SwiS-stabilized gold nanoparticles inside hierarchical zeolites to alleviate the internal mass transport limitation in zeolite-based catalysts. Previously, we had demonstrated the direct deposition of switchable surfactant (SwiS)-stabilized gold nanoparticles inside the mesoporous SBA-15 zeolites. We hypothesize that SwiS-stabilized gold nanoparticles can be directly diffused inside both micropores and mesopores of hierarchical zeolites via incipient wetness technique, and the synthesized material can catalyze the oxidation of diverse groups of aromatic alcohols. We used transmission electron microscopy (TEM) to verify whether the deposition is successful. Based upon the knowledge from our previous work of depositing gold nanoparticles inside mesoporous zeolites, we anticipated the deposition was successful. Next, we investigated if this deposition affected the size of gold nanoparticles. Our previous work had shown that SwiS-stabilized gold nanoparticles well maintain size during deposition. Hence, we expected the size of gold nanoparticles to be well preserved. To test the second half our hypothesis, we tested the catalytic activities of the synthesized material in the oxidation of aromatic alcohols with different molecular size. Comparatively, the catalytic activities of gold nanoparticles inside mesoporous zeolite were tested in the same reaction conditions. We expected the gold nanoparticles inside the hierarchical zeolites to catalyze more types of aromatic alcohol than those inside mesoporous zeolites in oxidation reaction.