Formation of better catalytically active titanium species in Ti-MCM-41 by vapor-phase silylation

Calcined Ti-MCM-41 was silylated by trimethylchlorosilane in the vapor phase for 2-9 h. 29Si MAS NMR spectroscopic study showed that Ti-MCM-41 silylated for 2-5 h exhibited a peak at 11 ppm, which was assigned to (CH3)3SiOSi(OSi)3 species. Further silylation of Ti-MCM-41 for 5-9 h gave an additional peak at 5.1 ppm, which was assigned to novel titanium species of (CH3)3SiOTi(OSi)3. Ti-MCM-41 silylated for 5 h showed relatively high activity in hydroxylation of benzene and epoxidation of 1-octene compared with calcined Ti-MCM-41. More important, Ti-MCM-41 silylated for 9 h gave much higher activity than Ti-MCM-41 silylated for 5 h. 29Si MAS NMR spectra showed the presence of the titanium species of (CH3)3SiOTi(OSi)3 in Ti-MCM-41 silylated for 5-9 h, and these can be better catalytically active sites than conventional titanium species in Ti-MCM-41.