Microwave preparation of Ti-containing mesoporous materials. Application as catalysts for transesterification

Titanium-containing mesoporous (Ti-MCM-41) materials were prepared by microwave irradiation method at different temperature (from 353 K to 413 K) in 40 min, a much shorter period of crystallization time than that by hydrothermal method. Various characterization techniques, including XRD, FT-IR, N2 adsorption and desorption, ICP, DRUV-vis, pyridine-FTIR, NH3-TPD and particle size analysis were carried out to investigate the physicochemical properties of these samples. Results showed that the samples prepared by microwave irradiation method have typical long-range order of hexagonal MCM-41 structure. Titanium incorporates into the silica framework and Ti species are mostly in tetrahedral coordination. Ti-MCM-41 molecular sieves were active as catalysts for transesterification of dimethyl oxalate and phenol to produce diphenyl oxalate and the optimal heating temperature is 393 K. The small particle size, large surface area and plenty of Ti(IV) active centers inside the framework, which provide more weak acid sites, are favorable for improving the catalytic properties.