Highly tunable selectivity to benzaldehyde over Pd/ZrO2 catalysts in Oppenauer oxidation of benzyl alcohol using acetone as H-acceptor

The development of novel bifunctional catalysts with high selectivity is the key to achieving the goals of sustainable chemical synthesis. Here, we report the synthesis of mesoporous zirconia and transition metal-doped zirconia by inverse micelle approach. Also, meso-zirconia supported Pd nanocatalysts via the deposition-precipitation method. Highly crystalline Pd/ZrO2 nanoparticles were formed, as evidenced in the pXRD and TEM analyses. The acid-base quantification was investigated using TPD-NH3 and TPD-CO2. Interestingly, the integration of the intrinsic chemical properties of the multi-component catalyst is significant in tailoring the catalytic activities. Interactions between the adsorbates and the moderate acid-base pair sites rather than a single dominating acid or base site mediate the higher selectivity for the aldehyde product. The 100 % chemoselectivity to benzaldehyde is ascribed to the strong synergy between Pd-Zr, which generated the moderate acid-base property. The Pd/ZrO2 is reusable, with selectivity retained after ten cycles.

Automated summary

The development of novel bifunctional catalysts with high selectivity is essential for sustainable chemical synthesis. This study successfully synthesized mesoporous zirconia, transition metal-doped zirconia, and meso-zirconia supported Pd nanocatalysts. The interaction between different acid-base pair sites in the multi-component catalyst significantly affected the selectivity, leading to 100% chemoselectivity to benzaldehyde through the strong synergy between Pd-Zr. The Pd/ZrO2 catalyst showed retained selectivity after ten cycles, demonstrating its reusability.