TiO2-SiO2 mixed oxide modified with H2SO4I. Characterization of the microstructure of metal oxide and sulfate

A series of titania and silica mixed metal oxide samples modified by H2SO4 has been characterized by BET, XRD, XPS, FT-IR and compared with non sulfat ed samples. The XPS results show the appearance of a titanium silicate phas e in all samples. After sulfuric acid treatment the decrease of BET surface area, the appearance of the TiO2 crystalline in XRD and the enrichment of Si on the surface in XPS indicate that the strong bond between TiO2 and sul fate ions induces the migration of Ti ions from the titanium silicate phase . The total contents of sulfate ions depend on the TiO2-SiO2 mole ratio. Th e shift of the S=O characteristic peak in FT-IR shows that the bond strengt h of S=O is influenced by the TiO2-SiO2 microstructure. (C) 2001 Elsevier S cience B.V. All rights reserved.