Abstract: Through steam-assisted method, we achieved in situ reconstruction of commercial alumina to synthesize a core-shell alumina support with abundant penta-coordinated Al³⁺. By optimizing the reconstruction conditions, the irregular nanoparticles on the commercial alumina surface were transformed into the micron-thick layer of columnar alumina, increasing the specific surface area from 148 m²/g to 377 m²/g. The proportion of unsaturated penta-coordinated aluminum species reached 16.25%. Using the alumina as the catalyst support, Pd-based noble metal catalysts were fabricated; the unsaturated penta-coordinate Al³⁺ active sites on the support exhibited a strong anchoring effect on the noble metal species, effectively inhibiting their agglomeration. Compared with commercial alumina, the Pd species supported on the optimally restructured alumina exhibited improved dispersion and a reduced particle size, which decreased from 2.5 nm to 1.0 nm. The as-prepared noble metal catalyst was employed for the anthraquinone hydrogenation reaction, and its hydrogen efficiency was improved by 12% compared with the commercial noble metal catalyst. These results demonstrate the feasibility of synthesizing the core-shell alumina support with five-coordinate Al³⁺ via the steam-assisted method, and provide guidance for the development of industrial noble metal catalysts.

Key words: penta-coordination, active sites, metal particle size, anthraquinone hydrogenation