High surface area hierarchical porous Al sub(2)O sub(3) prepared by the integration of sol-gel transition and phase separation

• Published in: RSC advances 2016-06, Vol.6 (62), p.57217-57226
• Main Authors: Passos, A R, Pulcinelli, SH, Briois, V, Santilli, C V
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum oxide; Boehmite; Ceramics; Networks; Phase separation; Sol gel process; Surface area
• ISSN: 2046-2069
• DOI: 10.1039/c6ra11477f

Hierarchical porous gamma -Al sub(2)O sub(3) samples were prepared by a soft template method based on the integration of sol-gel transition with spinodal phase separation, using aluminum isopropoxide combined with low molecular weight poly(ethylene oxide) (PEO, M sub(w) = 4 10 super(3) g mol super(-1)) as phase separation inducer. The boehmite structure formed from the hydrolysis and condensation of aluminum isopropoxide was investigated by means of FTIR and time-resolved SAXS analyses. The boehmite layers acted as the primary building blocks of the gel phase networks. The growth of the gel network reduced the compatibility with PEO, inducing spinodal phase separation between the gel-rich and solvent-rich phases. The results of the TG and FTIR analyses indicated that the PEO was preferentially dissolved in the solvent-rich phase. Mercury porosimetry, N sub(2) physisorption, and SEM measurements revealed that the porous gamma -Al sub(2)O sub(3) possessed an interconnected macro-mesoporous hierarchical structure. Appropriate selection of the starting composition enabled control of the average pore sizes and the volume fractions of the macro- and mesopore families present in the gamma -Al sub(2)O sub(3) ceramics. The high Al sub(2)O sub(3) surface area (675 m super(2) g super(-1)) obtained in this work could be explained by the high mesopore volume (3.3 cm super(3) g super(-1)) and the fine structure of the ceramic skeleton.