H 2O 2-based selective oxidations over titaniumsilicates of SBA-15 type

Abstract

Hexagonally packed mesostructured titanosilicates of the SBA-15 type have been prepared in moderately acidic aqueous media starting from sodium disilicate Na 2Si 2O 5, TiOSO 4, and olefin oxide co-polymer of the Pluronic type (P123) as a template. Structure–texture parameters of the synthesised materials were characterised by using X-ray diffraction and nitrogen adsorption techniques. The titanium state in the silicate matrix was characterised by DR-UV, IR, Raman spectroscopy, and XPS. The catalytic properties of the new titaniumsilicates were tested in oxidation reactions with aqueous H 2O 2 using methyl phenyl sulfide and 2,3,6-trimethylphenol as model substrates and compared with the catalytic properties of TS-1 and Ti-MMM (titaniumsilicate of the MCM-41 type). The structure of the Ti-SBA-15 materials, by contrast to Ti-MMM catalysts, was proved to be hydrolytically stable towards aqueous H 2O 2. The catalytic activity of Ti-SBA-15 is considerably lower than that of Ti-MMM, most likely due to a lower titanium dispersion and higher wall thickness of the former material, which makes part of titanium sites unavailable for the reactants.