Synthesis, characterization, and catalytic properties of Ti-containing mesoporous molecular sieves prepared using a fluorosilicon compound

Titanium substituted mesoporous molecular sieves were prepared using H2SiF6 as a silicon source with the mole ratio of SiO2:TiO2:HF:NH4OH:CTMABr:H2O = 1:0.011-0.043:5.40:6.48:0.49:246. Titanium substituted silica-based mesoporous molecular sieves (Ti-MMS) with good crystallinity and narrow pore size distribution could be prepared at atmospheric pressure in several hours. The material obtained was characterized by using XRD, N-2 physisorption, TEM, and UV-VIS spectroscopy. Its structural property is very much like MCM 41 with one-dimensional hexagonal lattice geometry. Titanium environment in Ti-MMS is believed to be very uniform relative to other types of titanium substituted M41S type materials, and titanium seems to exist mostly in isolated tetrahedral sites. Catalytic conversions for 2,6-DTBP (di-tert-butyl phenol) oxidation and cyclohexene epoxidation with H2O2 increased linearly with titanium contents in Ti-MMS within Si/Ti = 89-22 range. Ti-MMS showed catalytic activity close to that of Ti-MCM 41 of the same metal loading, but less active than Ti-HMS or Ti-MCM 48, because of the one-dimensional channel system of the Ti-MMS. (C) 2001 Elsevier Science B.V. All rights reserved.