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This article combines a systematic literature review on the fabrication of macroporous α-Al2O3 with increased specific surface area with recent results from our group. Publications claiming the fabrication of α-Al2O3 with high specific surface areas (HSSA) are comprehensively assessed and critically reviewed. An account of all major routes towards HSSA α-Al2O3 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-Al2O3 may be the more stable alumina modification for ABET > 175 m2/g. In fact, the highest specific surface area unobjectionably reported to date for α-Al2O3 amounts to 16–24 m2/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 mutual cross-hydrolysis. 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-Al2O3 seeds. These experimental results are substantiated by attempts to theoretically calculate and predict the specific surface areas of both porous materials and nanopowders.

One of the major routes to synthesize macroporous α-Al2O3 is the sol-gel process in presence of templates. Templates include polymers as well as carboxylic acids, such as citric acid. By careful choice of the template, pore diameters can be adjusted between 110 nm and several µm. We report the successful establishment of plain short-chain dicarboxylic acids (DCA) as porogenes in the sol-gel synthesis of macroporous α-Al2O3. By this extension of the recently developed synthesis route, a very precise control of pore diameters is achieved, in addition to enhanced macropore volumes in α-Al2O3. The formation mechanism thereof is closely related to the one postulated for citric acid, as thermal analyses show. However, since branching in the DCA-linked alumina nuclei is not possible, close monomodal pore width distributions are attained, which are accompanied by enhanced pore volumes. This is a significant improvement in terms of controlled enhanced porosity in the synthesis of macroporous α-Al2O3.

Ceramic alumina foams are suitable catalyst supports with high temperature stability used, for example, in catalytic cracking processes or combined heat and power units. Herein, such replica foams are generated from macroporous α‐Al2O3 powder synthesized by a sol–gel process. The foam windows, constituting intrinsic (macroscopic) foam porosity, are supplemented by an additional porosity within the struts of the foams. These pores, originating from the sol–gel process, are preserved during sintering at 1350 °C. This results in less dense foams compared with foams from conventional alumina powders. Foams sintered at 1350 °C exhibit an increased strut porosity of ≈62%, of which ≈84% are open, with pore diameters in the range of 200–500 nm and a compressive strength of 0.2 MPa. Foams sintered at 1600 °C or higher possess an almost tenfold compressive strength but no additional strut porosity. Due to the use of carboxylic acids as porogenes in the sol–gel process, all samples generated from sol–gel‐derived alumina powder exhibit significantly higher porosity values than the respective reference foams made from commercial alumina powder. Although specific surface areas of ≈3 m2 g−1 are still small, this value is significantly improved by additional strut porosity.

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