Sol-gel synthesis of α-Al2O3 with enhanced porosity via dicarboxylic acid templating

Carstens, Simon; Splith, Christian; Enke, Dirk

doi:10.1038/s41598-019-56294-1

Cited by 15 publications

(14 citation statements)

References 15 publications

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“…Branched molecules like citric acid form larger but also more irregular primary particles than linearly composed dicarboxylic acids. Although this mechanism hypothesis cannot be proven with absolute certainty, it is strongly supported by several analyses [68,91]. The most definite and significant results are found in SEM imaging in Figure 6.…”

Section: Epoxide-mediated Sol-gel Synthesis Of Porous α-Al 2 Omentioning

confidence: 65%

“…Not only does it enable pore volumes of up to 1.2 cm 3 /g with macropores ranging from 0.1-5.3 µm but A BET were also increased up to 12 m 2 /g with the aid of citric acid. Similar effects can be achieved by addition of dicarboxylic acids, though with even better tunability of pore widths [91].…”

Section: Introducing Porosity Via Soft Templating In Sol-gel Synthesesmentioning

confidence: 77%

“…Different additives were used as porogenes: PEO (M w 900,000) was dissolved with the educts, while di-and tricarboxylic acids were added immediately before the reaction. The respective amounts are listed inor can be drawn from [68] and [91]. The solution was placed in an ice bath and cooled down to 4 • C while stirring.…”

Section: Epoxide-mediated Sol-gel Synthesis Of Porous α-Al 2 O 3rementioning

confidence: 99%

“…Tokudome et al extended this route to polymer-induced phase separation, thus yielding alumina monoliths with increased porosity and a hierarchical pore structure [64]. Further improvements in terms of pore size control and increasing porosities along with a greener route have been published recently by our group [68,91]. In this sub-section, we present an overview of the new possibilities offered by using di-and tricarboxylic acids as porogenes, as well as some new results concerning the influence of the gel-ageing temperature.…”

Section: Epoxide-mediated Sol-gel Synthesis Of Porous α-Al 2 Omentioning

confidence: 99%

“…Table 4. Pore diameters and volumes for different amounts of selected additives in the sol-gel synthesis of macroporous α-Al 2 O 3 after calcination at 1200 • C. Most data are adapted from [68] and [91]. Samples SG-Ref0- (80) and SG-C3- (80) are presented here for the first time.…”

Section: Epoxide-mediated Sol-gel Synthesis Of Porous α-Al 2 Omentioning

confidence: 99%

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Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

2020

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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.

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Section: Epoxide-mediated Sol-gel Synthesis Of Porous α-Al 2 Omentioning

confidence: 65%

Section: Introducing Porosity Via Soft Templating In Sol-gel Synthesesmentioning

confidence: 77%

Section: Epoxide-mediated Sol-gel Synthesis Of Porous α-Al 2 O 3rementioning

confidence: 99%

Section: Epoxide-mediated Sol-gel Synthesis Of Porous α-Al 2 Omentioning

confidence: 99%

Section: Epoxide-mediated Sol-gel Synthesis Of Porous α-Al 2 Omentioning

confidence: 99%

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Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

2020

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Reticulated Alumina Replica Foams with Additional Sub‐Micrometer Strut Porosity

et al. 2019

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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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