Chemical synthesis and thermal evolution of MgAl2O4 spinel precursor prepared from industrial gibbsite and magnesia powder

Reverón, Helen; Gutiérrez-Campos, Delia; Rodríguez, Rosa; Bonassin, J.C

doi:10.1016/s0167-577x(02)00425-1

Cited by 28 publications

(15 citation statements)

References 23 publications

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“…It can be noted that the support (MA800 sample) showed peaks typical of magnesium aluminate spinel (ICSD 21-1152) and no peak related to alumina or magnesium oxide (periclase) was noted. This finding is agreement with previous works [42][43][44], which claim that at temperatures as high as 800 o C, the crystalline phase of magnesium aluminate spinel (MgAl 2 O 4 ) is the only compound produced in the MgO-Al 2 O 3 system, which is more thermodynamically stable than alumina. After nickel addition, the peaks became narrower and more intense, indicating the increase of the crystalline domains and/or nickel aluminate formation (ICSD 77-1877).…”

Section: Catalysts Evaluationsupporting

confidence: 93%

Evaluation of nickel and copper catalysts in biogas reforming for hydrogen production in SOFC

Silva

Martins

Ballarini³

et al. 2017

Matéria (Rio J.)

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The solid oxide fuel cells (SOFC) enable the efficient generation of clean energy, fitting the current requirements of the growing demand for electricity and for the environment preservation. When powered with biogas (from digesters of municipal wastes), the SOFCs also contribute to reduce the environmental impact of these wastes. The most suitable route to produce hydrogen inside SOFC from biogas is through dry reforming but the catalyst is easily deactivated by coke, because of the high amounts of carbon in the stream. A promising way to overcome this drawback is by adding a second metal to nickel-based catalysts. Aiming to obtain active, selective and stable catalysts for biogas dry reforming, solids based on nickel (15%) and copper (5%) supported on aluminum and magnesium oxide were studied in this work. Samples were prepared by impregnating the support with nickel and copper nitrate, followed by calcination at 500, 600 and 800 o C. It was noted that all solids were made of nickel oxide, nickel aluminate and magnesium aluminate but no copper compound was found. The specific surface areas did not changed with calcination temperature but the nickel oxide average particles size increased. The solids reducibility decreased with increasing temperature. All catalysts were active in methane dry reforming, leading to similar conversions but different selectivities to hydrogen and different activities in water gas shift reaction (WGSR). This behavior was assigned to different interactions between nickel and copper, at different calcination temperatures. All catalysts were active in WGSR, decreasing the hydrogen to carbon monoxide molar ratio and producing water. The catalyst calcined at 500 o C was the most promising one, leading to the highest hydrogen yield, besides the advantage of being produced at the lowest calcination temperature, requiring less energy in its preparation.

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Section: Catalysts Evaluationsupporting

confidence: 93%

Evaluation of nickel and copper catalysts in biogas reforming for hydrogen production in SOFC

Silva

Martins

Ballarini³

et al. 2017

Matéria (Rio J.)

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“…Spinel powders can be prepared from a variety of methods including direct reaction of MgO with various Al 2 O 3 polymorphs, 4-6 sol-gel synthesis, 7-9 freeze drying of alkoxide precursors, 10 combustion synthesis, 11,12 and calcination of co-precipitated salts (e.g., hydroxides, 13,14 chlorides, 15 and sulfates 16 ). Spinel powders can be prepared from a variety of methods including direct reaction of MgO with various Al 2 O 3 polymorphs, 4-6 sol-gel synthesis, 7-9 freeze drying of alkoxide precursors, 10 combustion synthesis, 11,12 and calcination of co-precipitated salts (e.g., hydroxides, 13,14 chlorides, 15 and sulfates 16 ).…”

Section: Introductionmentioning

confidence: 99%

The Production of Transparent MgAl₂O₄ Ceramic Using Calcined Powder Mixtures of Mg(OH)₂ and γ‐Al₂O₃ or AlOOH

Sutorik

Gilde

Swab

et al. 2012

Int J Applied Ceramic Tech

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Magnesium hydroxide, Mg(OH)2 (both 99% and 99.99% purity grades), γ‐Al2O3, and AlOOH have been investigated for the direct production of transparent MgAl2O4. The highest average in‐line transmittance through 3.5–4 mm thick samples is 84.2 ± 1.0% at 550 nm, attained by using mixtures of 99.99% pure Mg(OH)2 and γ‐Al2O3. Other formulations exhibited 77–80% visible transmission, suggesting that further optimization can improve sample consistency. All samples exhibited a Knoop hardness of ~12 GPa, and elastic modulus of ~280 GPa. Biaxial flexural strength measurements ranged from 85 to 136 MPa depending on starting materials.

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“…The synthesis of the spinel powder is consequently a critical step in the fabrication of transparent specimens. The conditions for the synthesis of a single spinel phase powder with various levels of purity and particle size distributions have been reported in numerous publications 4–13 . A large number of additives such as CaCO 3 +LiF, 14,15 CaO, 16 LiF, 17,18 B 2 O 3 , 19 AlCl 3 , 20 AlF 3 , 20 Na 3 AlF 6 21 were suggested for enhancing spinel formation during calcination and densification.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Densification of Transparent Magnesium Aluminate Spinel by SPS Processing

Meir

Kalabukhov

Froumin

et al. 2009

Journal of the American Ceramic Society

128

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Mixtures of elementary oxides, MgO–Al2O3, were used to fabricate transparent polycrystalline magnesium aluminate spinel specimens by means of the spark plasma sintering technique. A sintering aid, 1 wt% of LiF, was added to the mixed powder. The presence of the additive promotes the synthesis of spinel that starts at 900°C and is completed at 1100°C. The LiF additive wets spinel on its melting and promotes densification, which is completed at 1600°C. LiF vapor plays a cardinal role in eliminating residual carbon contamination and in the fully dense state, allows attaining a 78% level of optical transmittance. The optimal conditions for achieving adequate transparency were determined and the role of the LiF addition in the various stages of the process is discussed.

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Chemical synthesis and thermal evolution of MgAl2O4 spinel precursor prepared from industrial gibbsite and magnesia powder

Cited by 28 publications

References 23 publications

Evaluation of nickel and copper catalysts in biogas reforming for hydrogen production in SOFC

Evaluation of nickel and copper catalysts in biogas reforming for hydrogen production in SOFC

The Production of Transparent MgAl₂O₄ Ceramic Using Calcined Powder Mixtures of Mg(OH)₂ and γ‐Al₂O₃ or AlOOH

Synthesis and Densification of Transparent Magnesium Aluminate Spinel by SPS Processing

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Chemical synthesis and thermal evolution of MgAl2O4 spinel precursor prepared from industrial gibbsite and magnesia powder

Cited by 28 publications

References 23 publications

Evaluation of nickel and copper catalysts in biogas reforming for hydrogen production in SOFC

Evaluation of nickel and copper catalysts in biogas reforming for hydrogen production in SOFC

The Production of Transparent MgAl2O4 Ceramic Using Calcined Powder Mixtures of Mg(OH)2 and γ‐Al2O3 or AlOOH

Synthesis and Densification of Transparent Magnesium Aluminate Spinel by SPS Processing

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The Production of Transparent MgAl₂O₄ Ceramic Using Calcined Powder Mixtures of Mg(OH)₂ and γ‐Al₂O₃ or AlOOH