A new mesoporous titanium-silicate Ti-MMM-2: a highly active and hydrothermally stable catalyst for H2O2-based selective oxidations

Physicochemical characterisation and catalytic properties of a new hydrothermally stable mesoporous mesophase titanium-silicate, denoted as Ti-MMM-2, synthesised under moderately acidic conditions are reported. Structure and texture were characterised by using X-ray diffraction, N2 adsorption and TEM. The state of titanium was characterised using DRS-UV and XANES techniques. Catalytic properties of Ti-MMM-2 were tested in oxidation of three large organic substrates, 2,3,6-trimethylphenol, caryophyllene and methyl phenyl sulfide, and compared with catalytic properties of TS-1 and Ti-MMM (titanium-silicate of the MCM-41-type synthesised under weakly alkaline conditions). The catalytic activity of Ti-MMM-2 is considerably higher compared to the activity of microporous TS-1 and similar to that of Ti-MMM. The performed physicochemical study implicated that Ti-MMM-2 combines marked accessibility of titanium and its high dispersion that ensure high catalytic activity of this material. By contrast to Ti-MMM, Ti-MMM-2 is hydrothermally stable and can be used repeatedly without deterioration of catalytic properties. A blend of high catalytic activity and hydrothermal stability allows to consider Ti-MMM-2 as a promising catalyst for the selective oxidation of large organic molecules with aqueous H2O2.