Preparation of Mesoporous–Macroporous Spherical Alumina with Enhanced Hydrothermal Stability via Dual-Template Coupling Method

Abstract

Maintaining an optimized pore structure of the spherical alumina support after hydrothermal treatment is crucial for catalytic efficiency, as the pore structure is intricately linked to the dispersion of catalytically active components and the diffusion of reactants. In this work, a unique mesoporous–macroporous spherical γ-Al₂O₃ material (γ-Al₂O₃-CD) with a reduced amount of surface hydroxyl groups was successfully synthesized to address pore blockages and enhance hydrothermal stability. Dodecane and hydrophilic-modified activated carbon were used as dual-template agents and, as a result, γ-Al₂O₃-CD exhibits a distinctive mesoporous–macroporous structure, which is beneficial for specific surface area and stability. The mercury intrusion porosimetry (MIP) specific surface area is measured to be 256 m²·g^–1, with a considerable pore volume of 0.62 mL·g^–1 and an impressive porosity of 58.4%. In contrast, untreated γ-Al₂O₃ possesses only a specific surface area of 204 m²·g^–1 and a pore volume of 0.40 mL·g^–1. Additionally, the abundant pore structure greatly facilitates precursor dehydration, leading to the formation of γ-Al₂O₃. Remarkably, the γ-Al₂O₃ content in γ-Al₂O₃-CD reaches an impressive 70.7%, with a chemical shift of μ²-OH at 1.31 ppm, resulting in a decreased number of surface hydroxyl groups and ultimately enhanced hydrothermal stability. Even after a 120 h hydrothermal treatment, the MIP specific surface area remains virtually unchanged at 255 m²·g^–1.