Mg‐Ion Inversion in MgO@MgO−Al2O3 Oxides: The Origin of Basic Sites

Although MgO−Al2O3 is well known as having a spinel structure, the inversion of which occurs by exchange of the trivalent (Al3+) and divalent (Mg2+) cations, little analytical study of the degree of inversion has been carried out. This study concerns a simple methodology to identify the inversion by...

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Bibliographic Details
Published in:ChemSusChem 2019-06, Vol.12 (12), p.2810-2818
Main Authors: Hiremath, Vishwanath, Kwon, Hyuk Jae, Jung, In‐Sun, Kwon, Soonchul, Kwon, Sung Hyun, Lee, Seung Geol, Lee, Hyun Chul, Seo, Jeong Gil
Format: Article
Language:English
Subjects:
Aluminum oxide
Basic oxides
carbon capture
Carbon dioxide
Carbon sequestration
Magnesium oxide
metal oxides
NMR spectroscopy
Sorbents
Sorption
Spectrum analysis
Spinel
spinel phases
structure elucidation
Thermogravimetric analysis
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Summary:Although MgO−Al2O3 is well known as having a spinel structure, the inversion of which occurs by exchange of the trivalent (Al3+) and divalent (Mg2+) cations, little analytical study of the degree of inversion has been carried out. This study concerns a simple methodology to identify the inversion by solid‐state NMR spectroscopy, whereby its correlation with the CO2 capture capacity of MgO‐rich MgO@MgO−Al2O3 spinel structures is verified. Through 27Al and 25Mg NMR spectroscopy, temperature‐programmed CO2 desorption, and thermogravimetric analysis, higher inversion is found to occur at low Mg/Al ratios and the inversion is found to decrease as the Mg/Al ratio increases. Moreover, the degree of inversion correlates with CO2 sorption, which is associated with the medium‐strength basic sites induced by formation of the unsaturated O2− species. These results will open new pathways to exploit defects in complex oxides beyond spinels and their derivatives for desired applications. This demonstration of MgO−Al2O3 for CO2 sorption can contribute to the design of future CO2 sorbents. Turn up the base: A simple methodology to identify the inversion of MgO‐rich MgO@MgO−Al2O3 spinel structures by solid‐state NMR spectroscopy provides a correlation with their CO2 capture capacity. Through NMR spectroscopy, temperature‐programmed CO2 desorption, and thermogravimetric analysis, higher inversion is found to occur at low Mg/Al ratios and the inversion is found to decrease as the Mg/Al ratio increases.
ISSN:1864-5631
1864-564X
DOI:10.1002/cssc.201900072