Mesostructured Forms of the Transition Phases η- and χ-Al2O3

摘要

Transition phases of alumina are metastable polymorphs of aluminum oxide formed through the thermal dehydration of aluminum trihydroxide (bayerite and gibbsite) and aluminum oxyhydroxide (boehmite) at temperatures between 230 and 1100 °C. These oxides are used widely as catalyst components and adsorbents. The chemical properties of a transition alumina phase are determined by a combination of surface acidity, which is directly related to the structure of the polymorph, the degree of surface hydroxylation, and textural properties, in particular, the surface area, pore volume, and pore-size distribution. η-Al2O3 is one of the most effective catalysts for the isomerization of unsaturated hydrocarbons owing to its exceptional surface acidity.