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TiO2-coated mesostructured SiO2 nanocomposite as thermally stable catalyst supports.

Magali Bonne ,  Stephane Pronier ,  Sabine Valange ,  Jean-Michel Tatibouët ,  Sebastien Royer ,  Patrice Marécot ,  Daniel Duprez 

LACCO, UMR CNRS 6503,, Poitiers ESIP, France

Abstract

Since the first synthesis of silica M-41S type mesostructured silica by researchers from Mobil in 1992, many attempts are made to generalize the synthesis to other oxidic solids. Thus, the mesostructuration of transition-metal oxides is the subject of much scientific and technological attention, and particularly titanium dioxide due to its numerous applications among those photocatalysis and support for catalytic reactions like gas phase depollution, hydrodesulfurization… While specific surface areas (SSA) of commercial titania samples rarely exceed 200 m2.g-1, some recent synthesis procedures sol-gel based mesostructuration allow to obtain largely higher SSA (up to 700 m2.g-1).1 Unfortunately, thermal stability of the solids remains low, and calcination generally results in the crystallization of the solid with the collapse of the porosity (and consequently an important decrease in SSA). In this work, we report an original synthesis procedure leading to the preparation of TiO2 supported mesostructured SiO2 nanocomposite. The procedure used consists in a sol-gel synthesis of TiO2 nanocrystals inside the porosity of the SBA-15 type silica host support. A series of TiO2/SiO2 (TiO2 loading from 10 to 55 wt.%) is then prepared from titanium isopropoxide as titania precursor in anhydrous ethanol as solvent. A systematic study of the impregnation steps evidences the difficulty to avoid titania segregation outside the silica porosity. A careful impregnation allows to synthesize 2-3 nm crystallized TiO2 nanoparticles dispersed inside the silica host support. TEM analysis clearly evidences the preservation of the initial hexagonal structure of the parent support and allows to observe crystallized anatase particles anchored onto the silica walls. As an example, the 55 wt.%TiO2/SiO2 sample display a SSA of 480 m2.g-1, a pore volume of 0.47 cm3.g-1 and a pore diameter of 4.5 nm (sample calcined at 400 °C).

References

1. Yoshitake, H.; Tatsumi, T. Chem. Mater., 2003, 15, 1695.

 

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Related papers

Presentation: Oral at E-MRS Fall Meeting 2008, Symposium D, by Sebastien Royer
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-28 10:59
Revised:   2009-06-07 00:48