Preparation of Mesoporous–Macroporous Spherical\nAlumina with Enhanced Hydrothermal Stability via Dual-Template Coupling\nMethod

Maintaining\nan optimized pore structure of the spherical alumina\nsupport after hydrothermal treatment is crucial for catalytic efficiency,\nas the pore structure is intricately linked to the dispersion of catalytically\nactive components and the diffusion of reactants. In this work, a\nunique mesoporous–macroporous spherical γ-Al<sub>2</sub>O<sub>3</sub> material (γ-Al<sub>2</sub>O<sub>3</sub>-CD) with\na reduced amount of surface hydroxyl groups was successfully synthesized\nto address pore blockages and enhance hydrothermal stability. Dodecane\nand hydrophilic-modified activated carbon were used as dual-template\nagents and, as a result, γ-Al<sub>2</sub>O<sub>3</sub>-CD exhibits\na distinctive mesoporous–macroporous structure, which is beneficial\nfor specific surface area and stability. The mercury intrusion porosimetry\n(MIP) specific surface area is measured to be 256 m<sup>2</sup>·g<sup>–1</sup>, with a considerable pore volume of 0.62 mL·g<sup>–1</sup> and an impressive porosity of 58.4%. In contrast,\nuntreated γ-Al<sub>2</sub>O<sub>3</sub> possesses only a specific\nsurface area of 204 m<sup>2</sup>·g<sup>–1</sup> and a\npore volume of 0.40 mL·g<sup>–1</sup>. Additionally, the\nabundant pore structure greatly facilitates precursor dehydration,\nleading to the formation of γ-Al<sub>2</sub>O<sub>3</sub>. Remarkably,\nthe γ-Al<sub>2</sub>O<sub>3</sub> content in γ-Al<sub>2</sub>O<sub>3</sub>-CD reaches an impressive 70.7%, with a chemical\nshift of μ<sup>2</sup>-OH at 1.31 ppm, resulting in a decreased\nnumber of surface hydroxyl groups and ultimately enhanced hydrothermal\nstability. Even after a 120 h hydrothermal treatment, the MIP specific\nsurface area remains virtually unchanged at 255 m<sup>2</sup>·g<sup>–1</sup>.