Abstract
Though γ-Al2O3 has played a central role in heterogeneous catalysis for more than two centuries, its microstructure continues to be debated. Specifically, the positions of Al3+ cations within the crystal lattice have been discussed extensively in the literature. Many authors uphold that the cations primarily occupy spinel sites, while others endorse the occupation of non-spinel sites. The other main point of dispute is whether the structure contains interstitial hydrogen, with some authors supporting a partially hydrated model and others claiming that the structure must be completely dehydrated. The use of different structural models directly affects the predicted geometry of γ-Al2O3 at the surface, which in turn has significant implications for its catalytic utility. A comparison of theoretical data to experimental infrared (IR), X-ray diffraction (XRD), and selected area electron diffraction (SAED) evidence suggests that γ-Al2O3 features cations primarily in spinel positions, while IR and nuclear magnetic resonance (NMR) data indicate that interstitial hydrogen is present within the bulk structure.
Highlights
Alumina (Al2 O3 ) is an abundant material that is under continuous study due to the vast number of industrial and technological applications in which it finds use and its role in geological processes
Transition aluminas are most often utilized as adsorbents, catalysts, and catalytic supports, though they progressively degrade into α-alumina upon heating [1]
The question as to the completeness of dehydration is important because the presence/absence of hydrogen directly affects the shape of the unit cell, which positions cations occupy, and the surface structure of γ-alumina
Summary
Alumina (Al2 O3 ) is an abundant material that is under continuous study due to the vast number of industrial and technological applications in which it finds use and its role in geological processes It can exist either as the thermodynamically stable polymorph α-alumina (corundum) or as any one of several metastable/transitional phases (η, γ, χ, δ, κ, and θ) [1]. Γ-alumina has the most commercial/industrial utility due to its high specific surface area and defect crystal structure It is regularly employed as a catalyst support and washcoat in automotive catalytic converter systems [2] because of its exemplary electrical insulating properties (favorable for exothermic catalytic reactions) [3]. Consensus on which unit cell most represents interior structure so that consistent predictions can be made about its surface structure and properties
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
