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 mesopo rous molecular sieves (Ti-MMS) with good crystallinity and narrow pore size distribution could be prepared at atmospheric pressure in several hours. T he 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 T i-MMS is believed to be very uniform relative to other types of titanium su bstituted M41S type materials, and titanium seems to exist mostly in isolat ed tetrahedral sites. Catalytic conversions for 2,6-DTBP (di-tert-butyl phe nol) oxidation and cyclohexene epoxidation with H2O2 increased linearly wit h titanium contents in Ti-MMS within Si/Ti = 89-22 range. Ti-MMS showed cat alytic activity close to that of Ti-MCM 41 of the same metal loading, but l ess 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.