Abstract
A new rapid, very simple and one-step sol-gel strategy for the large-scale preparation of highly porous γ-Al2O3 is presented. The resulting mesoporous alumina materials feature high surface areas (400 m2 g−1), large pore volumes (0.8 mL g−1) and the γ-Al2O3 phase is obtained at low temperature (500 °C). The main advantages and drawbacks of different preparations of mesoporous alumina materials exhibiting high specific surface areas and large pore volumes such as surfactant-nanostructured alumina, sol-gel methods and hierarchically macro-/mesoporous alumina monoliths have been analyzed and compared. The most reproducible synthesis of mesoporous alumina are given. Evaporation-Induced Self-Assembly (EISA) is the sole method to lead to nanostructured mesoporous alumina by direct templating, but it is a difficult method to scale-up. Alumina featuring macro- and mesoporosity in monolithic shape is a very promising material for in flow applications; an optimized synthesis is described.
Highlights
The industrial interest of alumina is highlighted by its intensive use as catalyst or as catalytic support materials for the petroleum refinement and as automobile emission controller [1,2]
It is important to develop strategies to design simple, reproducible and easy to scale-up procedures leading to high surface area, high pore volume and high pore size alumina by simple methods to be implemented in industrial processes
By employing amphiphilic block copolymers such as Pluronic® P123 and F127 formed of ethylene-oxide (EO) and propyleneoxide (PO) groups (EO20PO70EO20 and EO100PO65EO100, respectively) in an evaporation-induced self-assembly process (EISA), highly ordered mesoporous organic-inorganic nanocomposites were obtained under controlled evaporation at 60 °C
Summary
The industrial interest of alumina is highlighted by its intensive use as catalyst or as catalytic support materials for the petroleum refinement and as automobile emission controller [1,2]. The nanocasting method gives a large spectrum of possible mesoporous aluminas by the diversity of hard templates available [11] These synthetic routes are rather time consuming as it uses a double replica route through a carbon phase and rely on multi-step synthesis and are difficult to scale up. The macropore sizes in combination with a delicate alumina skeleton seem to limit their applicability as stationary phases in catalysis in flow, as the macropore size reduces the mass transfer within the monolith and the backbone probably can not withstand the resulting back pressure Hierarchical systems such as macro and mesoporous monoliths with large macropores (3 microns) based on silica or alumina-lined silica have recently shown their potentiality as catalytic flow microreactors for the fine chemical production with low pressure drop (
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