Infrared investigation on surface properties of alumina obtained using recent templating routes

Porous aluminas were prepared according to recent mesostructuration routes, and compared in terms of structural, textural and surface properties with classical precipitated and sol–gel alumina supports. Among the different materials, the precipitation in presence of P123 triblock copolymer as pore directing agent does not allow to strongly improve textural properties which remains close to these obtained using classical precipitation. In addition, morphology and surface properties remains similar. By sol–gel procedure, the P123 leads to completely different pore properties, with extremely large pore size and pore volume, even if the pore directing agent is suggested to act differently than in classical mesostructuration synthesis. In this case, the emergence of heterogeneous Lewis acidic sites of higher strength is also observed over the sample prepared with P123. Finally, hexagonal structured materials, issued from Evaporation Induced Self Assembly routes, are the only to present a well-defined pore structure. Unfortunately, physical properties remain less interesting than over the sol–gel materials. In addition, alumina remains amorphous while the materials are presenting the lowest OH density and highest LAS strength.

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► Mesoporous alumina is synthesized using precipitation, sol–gel or EISA procedures.
► Only EISA allows the formation of organized mesoporous alumina.
► Large differences in structure and texture are obtained.
► EISA-based materials exhibit changed surface properties with LAS of higher strength.