Improving the Hydrogenation Performance of Nano‐Catalysts by Constructing a Cavity‐Constrained Fluidized System

Abstract Nano‐catalysts demonstrate exceptional performance in heterogeneous reactions, yet their potential is often underutilized due to a lack of attention to engineering design. In this study, an innovative encapsulated structure is presented for nano‐catalysts and a corresponding catalytic system. Using an oil‐in‐water droplet strategy, millimeter‐sized hollow spherical alumina (Al ₂ O ₃ ‐HS) is fabricated with an average diameter of ≈3 mm and a hollow void size of ≈1 mm. This approach enables the one‐step encapsulation of nanoscale Pd/Al ₂ O ₃ within the Al ₂ O ₃ ‐HS. The resulting assembly is immobilized within a tubular reactor for the hydrogenation of 2‐ethylanthraquinone, with hydrogen introduced from the bottom of the reactor. Remarkably, the encapsulated catalyst achieved twice the H ₂ O ₂ productivity of conventional supported catalysts. This enhancement is attributed to the cavity‐constrained fluidization behavior of Pd/Al ₂ O ₃ within the hollow alumina spheres. The design introduces a novel catalytic system that combines shell‐immobilization with the fluidization of encapsulated nano‐catalysts. As the gas velocity exceeds the minimum fluidization velocity, the Pd/Al ₂ O ₃ particles remain highly accessible while allowing efficient gas and product flow. This hybrid approach integrates the advantages of fixed‐bed and fluidized‐bed systems, offering a promising solution to the technical challenges limiting the industrial application of nano‐catalysts.