Alkali metal ion assisted preparation of zeolite encapsulated small cobalt cluster CoOx for direct styrene oxidation to benzaldehyde

Zeolites with metal clusters encapsulated within the pore structure have attracted more attention because of their unique properties with high stability, but diffusion resistance is the bottleneck limiting the utilization efficiency of active centers, especially in macromolecular reactions. Hollow zeolites could effectively improve mass transport by reducing the wall thickness. In this work, cobalt-base hollow silicate-1 zeolite was obtained by mother liquid treatment with sodium chloride. Various characterization results show that the CoOx@HS-1-0.5Na + crystals have completely hollow structure and small cobalt cluster highly dispersed encapsulated in it. The presence of Lewis acid sites and the unique hollow structure resulted in enhanced selectivity to benzaldehyde in the styrene oxidation . The effect of various factors including cobalt loading, the concentration of sodium ion , reaction solvents and H 2 O 2 /styrene molar ratio on the catalytic performance were systematically investigated. The yield of benzaldehyde can achieve 73.8% with 83.59% styrene conversion and 88.29% benzaldehyde selectivity.