Infrared investigation on surface properties of alumina obtained using recent templating routes

El-Nadjar, Widad; Bonne, Magali; Trela, Emmanuelle; Rouleau, Loı̈c; Miňo, Andres; Hocine, Smaïn; Payen, Edmond; Lancelot, Christine; Lamonier, Carole; Blanchard, Pascal; Courtois, Xavier; Can, Fabien; Duprez, Daniel; Royer, Sébastien

doi:10.1016/j.micromeso.2012.03.006

Cited by 22 publications

(16 citation statements)

References 38 publications

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“…Generally speaking, it enables introduction of macroporosity into otherwise mesoporous or even non-porous materials, and for a relatively precise adjustment of macropore size. Common phase separating agents in alumina synthesis are polymers such as polyethylene oxide [64], polyacrylamide [76], or Pluronic P123 [77,78]. With the aid of P123 and additional tetrabutyl ammonium hydroxide, López Pérez et al were able to obtain pure α-Al 2 O 3 with A BET in the range of 16-24 m 2 /g by evaporation induced self-assembly [79], while Zhang et al report a value of 18 m 2 /g with additional PEG8000 after calcination at 1200 • C [80,81].…”

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

confidence: 99%

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: Introducing Porosity Via Soft Templating In Sol-gel Synthesesmentioning

confidence: 99%

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

2020

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“…Active alumina (γ-Al 2 O 3 ) is widely used in the chemical industry as catalysts for petrochemical and refinery processes, catalyst supports and adsorbents [1][2][3][4][5]. χ-Al 2 O 3 is one of the most acidic modifications of alumina.…”

Section: Introductionmentioning

confidence: 99%

Formation of Phases and Porous System in the Product of Hydrothermal Treatment of χ-Al2O3

et al. 2018

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Abstract:The presence of χ-Al 2 O 3 resulting from thermal decomposition gibbsite as part of alumina catalysts is unfavorable because of its acid characteristics. One of the available techniques of χ-Al 2 O 3 removal is crystallization under hydrothermal conditions into boehmite, which is a main precursor of active γ-Al 2 O 3 . The influence of products of the hydrothermal treatment of χ-Al 2 O 3 obtaining in result of thermal decomposition gibbsite under T = 150-200 • C, P = 0.5-1.5 MPa and pH = 4.0-9.2 were studied. The hydrothermal treatment products in these conditions are gibbsite and boehmite phases which are formed coincidently by parallel ways. In the alkaline medium at pH = 8.0-9.2 three-dimensional parallelepiped boehmite crystals with the edge length > 200 nm are formed, at pH = 4.0 two-dimensional rhombic-shaped plates with thickness 20-100 nm and with the edge length~80-500 nm are formed. Crystallization of coarse boehmite particles promotes the formation of large and closed mesoporous.

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“…It allows for determining the total acidity of the surface. However, the proton affinity energy of the strongest Brønsted sites of alumina is not sufficient for the protonation of ammonia molecules [26].…”

Section: Resultsmentioning

confidence: 99%

Influence of the Obtaining Method on the Properties of Amorphous Aluminum Compounds

et al. 2019

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Amorphous aluminum compounds are formed during the synthesis of the γ-Al2O3 catalyst precursor. Amorphous compounds influence on the alumina catalyst variously due to different physicochemical properties, which depend on the method of their preparation. In this research, the comparative analysis of physicochemical properties of amorphous aluminum compounds that were obtained by the precipitation method, the thermal decomposition of aluminum nitrate, and alcoxide hydrolysis product were studied. It is the first time that a new method for calculating of quantitative phase composition of amorphous aluminum compounds using the X-ray powder diffraction, thermogravimetric and differential scanning calorimetry analysis, mass-spectrometry, and CHN-analysis was described. Properties of obtaining samples were studied using scanning electron microscopy, low-temperature nitrogen adsorption, and temperature programmed desorption of ammonium analyses. The methods of precipitation and thermal decomposition of aluminum nitrate allows for obtaining non-porous samples consisting of a mixture of amorphous phases (hydroxide and basic salt) that contain the metals impurities and have low acidity of the oxides obtained from them. The highly porous amorphous alumina formed by the thermal decomposition of the alcoxide hydrolysis product with the least amount of impurities and a high acidity of the surface was observed.

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Infrared investigation on surface properties of alumina obtained using recent templating routes

Cited by 22 publications

References 38 publications

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Formation of Phases and Porous System in the Product of Hydrothermal Treatment of χ-Al2O3

Influence of the Obtaining Method on the Properties of Amorphous Aluminum Compounds

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