Microwave synthesis, characterization and transesterification activities of Ti-MCM-41

A series of Ti-MCM-41 mesoporous materials with different titanium content (Si/Ti ratio varying from 100 to 5) were prepared using a microwave irradiation method. Physicochemical and structural properties of the materials were investigated using small angle X-ray powder diffraction (SAXRD), N2 adsorption–desorption, Fourier transform infrared (FT-IR) spectroscopy, transmission electron micrograph (TEM), inductively coupled plasma optical emission spectrometry (ICP-OES), diffuse reflectance UV–visible (DRUV–vis) spectroscopy, X-ray photoelectron spectroscopy (XPS), FT-IR measure of adsorbed pyridine and ammonia temperature programmed desorption (NH3-TPD) techniques. Merging results of those characterizations mentioned above, it indicates that, with the decrease of Si/Ti ratio from 100 to 5, Ti-MCM-41 samples exhibit typical long-range order of hexagonal structure with a certain decrease of structure ordering; titanium species incorporate into the framework entirely and are mainly in tetrahedral coordination. As the titanium content increases gradually, the amount of framework Ti(IV) sites, which could result in the formation of weak Lewis acid sites on the surface, also rises correspondingly. The rich weak Lewis acid sites and mesoporous structure with large pore diameter are significant factors affecting the catalytic properties of Ti-MCM-41 materials for transesterification of dimethyl oxalate and phenol.

For Ti-MCM-41, titanium species incorporate into the framework entirely and mainly exist in tetrahedral coordination. As the titanium content increases gradually, the amount of framework Ti(IV) sites, which could result in the formation of weak Lewis acid sites on the surface, are also increased correspondingly. The rich weak Lewis acid sites and mesoporous structure with large pore diameter are significant factors affecting the catalytic properties of Ti-MCM-41 materials.Figure optionsDownload as PowerPoint slideHighlights
► A series of Ti-MCM-41 were prepared by a microwave irradiation method with different titanium content.
► Ti-MCM-41 samples exhibited typical long-range order of hexagonal structure.
► Titanium species incorporated into the framework and mainly existed in tetrahedral coordination.
► The increase of framework Ti(IV) sites resulted in the formation of more weak Lewis acid sites.
► The rich weak Lewis acid sites and mesoporous structure are favorable for the catalytic performances.