Synthesis, characterization of high Ti-containing Ti-MCM-41 catalysts and their activity evaluation in oxidation of cyclohexene and epoxidation of higher olefins

A novel route for preparation of Ti-containing mesoporous silica with high catalytic performance by using a molecular precursor tetrakis(tris-tert-butoxysiloxy)titanium

“…Table 3 exhibits the representative results of catalytic performances (catalytic activity, estimated as turnover frequencies (TOF), and selectivity of cyclohexene oxide) reported in this study as well as in the literature. Previous studies using monomeric titanium alkoxide precursor, tetrabutoxytitanium 39 and tetraisopropyltitanium, 40 to introduce titanium into the mesoporous silica framework exhibit lower TOF (49-68) and lower selectivities (62-68%, 39 96% 40 ) of epoxide compared with TMS-TS4-x (x ¼ 28, 51, and 121). The catalysts reported here, containing Si/Ti ratios similar to those reported previously, show higher TOF (174-352) and selectivity of epoxide (98%).…”

Science and Technology of Framework Metal-Containing Zeotype Catalysts

“…Unfortunately, compared with the microporous MFI-type titanium silicates, the mesoporous materials exhibit low activity for epoxidation reactions. In another approach, a modified synthesis procedure was developed to obtain Ti-MCM-41 with high titanium content (202). Various attempts have been made to improve the activity.…”

“…The hydrophilic nature of mesoporous silica catalysts with isomorphous titanium substitution is considered to be one of the major reasons for the low activity (179). Indeed, the activity (on a per catalyst weight basis) for the epoxidation of olefins was improved significantly as a result of incorporation of a large amount of titanium (202). Using a different synthetic procedure, titanium species have been grafted onto MCM-41 to generate more accessible titanium sites for selective epoxidation (201).…”

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

“…The band at 450 cm −1 is attributed to tetrahedral bending vibration of Si-O-Si bonds. It has been demonstrated that the band at about 960 cm −1 could be ascribed to the stretching vibration of SiO 4 tetrahedra bonded to a titanium atom through Si-O-Ti bonds [32,33]. However, this absorption band is sometimes associated with silanol groups (Si-OH) at the defect sites.…”