High temperature transition aluminas in δ-Al2O3/θ-Al2O3 stability range: Review

High temperature treated transition aluminas display adsorptive and catalytic properties that are in many ways comparable to those of their low temperature counterpart gamma-Al2O3. While being important industrial catalysts as well as catalytic supports, their very basic crystallographic and structural characteristics remain actively studied. In this review, we critically examine the crystallography and structural complexity of these materials. Specifically, we review the crystallography of delta- and theta-Al2O3 polymorphs and show how structural intergrowth and disorder are accommodated in these phases. The structural complexity at the scale of overall microstructure is also examined, and the challenges and recent progress in quantification of the structure at ensemble level are discussed. Most pertinently to catalysis, we review the surfaces properties of high temperature treated Al2O3 and discuss the implications for understanding attributes relevant to heterogeneous catalysis. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

This review critically examines the crystallography and structural complexity of high temperature treated transition aluminas, including the crystallography of delta- and theta-Al2O3 polymorphs, structural intergrowth and disorder accommodation, overall microstructure complexity, as well as challenges and recent progress in quantifying the structure at ensemble level. The review also discusses the surface properties of high temperature treated Al2O3 and their implications for understanding attributes relevant to heterogeneous catalysis.