Synthesis, characterization and application of MTS-9 with different content of titanium

Heteroatom of Ti is effectively incorporated into the framework of ordered mesoporous silica materials in strong acidic media by a two-step procedure. The synthesized samples (designated as MTS-9) are characterized by many methods. Results indicate that MTS-9 synthesized maintains mesoporous structure, and MTS-9 (Si/Ti = 53) possesses the more tetrahedrally coordinated titanium species. The catalysts are applied for oxidation of propene and styrene in methanol with hydrogen peroxide as the oxidant. As the ratio of Si to Ti is below 53, the increase of titanium content benefits to the formation of benzaldehyde.

The paper aims at synthesizing MTS-9 with the high titanium content and studying the effect of titanium content on the oxidation of propene and styrene. The spectra of samples are shown in figure. Samples have obvious adsorption band at 210 nm, which is similar to that of TS-1. An absorption band in the wavelength region of 200–260 nm is attributed to the ligand-to-metal charge transfer (LMCT) band of the highly dispersed tetrahedrally coordinated titanium. As the ratio of Si to Ti is below 37, width of peak increases, which indicates that octahedral coordinate titanium is present. And sample (Si/Ti = 26) displays an absorption band centered at 320 nm, suggesting the presence of another kind of titanium oxide species, i.e., an aggregated bulk titanium oxide species .Figure optionsDownload as PowerPoint slideHighlights
► The oxidation of propene and styrene is investigated on TS-1 and MTS-9 with different ratios of silica to titanium.
► For small-molecule reactant, TS-1 and MTS-9 with the same titanium content possess the similar activity.
► However, MTS-9 holds the higher activity than TS-1 for bulk reactant.