| Summary: | This article combines a systematic literature review on the fabrication of macroporous α-Al<sub>2</sub>O<sub>3</sub> with increased specific surface area with recent results from our group. Publications claiming the fabrication of α-Al<sub>2</sub>O<sub>3</sub> with high specific surface areas (HSSA) are comprehensively assessed and critically reviewed. An account of all major routes towards HSSA α-Al<sub>2</sub>O<sub>3</sub> is given, including hydrothermal methods, pore protection approaches, dopants, anodically oxidized alumina membranes, and sol-gel syntheses. Furthermore, limitations of these routes are disclosed, as thermodynamic calculations suggest that γ-Al<sub>2</sub>O<sub>3</sub> may be the more stable alumina modification for <i>A<sub>BET</sub></i> > 175 m<sup>2</sup>/g. In fact, the highest specific surface area unobjectionably reported to date for α-Al<sub>2</sub>O<sub>3</sub> amounts to 16–24 m<sup>2</sup>/g and was attained via a sol-gel process. In a second part, we report on some of our own results, including a novel sol-gel synthesis, designated as <i>mutual cross-hydrolysis</i>. Besides, the Mn-assisted α-transition appears to be a promising approach for some alumina materials, whereas pore protection by carbon filling kinetically inhibits the formation of α-Al<sub>2</sub>O<sub>3</sub> seeds. These experimental results are substantiated by attempts to theoretically calculate and predict the specific surface areas of both porous materials and nanopowders.
|
|---|
