Preparation and property of a MCM-41 surface neopentyl-titanium and surface titanium oxides

The grafting of tetraneopentyl-titanium onto the surface of MCM-41 mesoporous molecular sieves prior to pretreatment at 500 degreesC under 10(-2) Pa vacuum generated a well-defined bigrafted surface complex (equivalent to Si - O)(2)Ti((CH2CMe3)(2). The Si - O)(2)Ti(CH2CMe3)(2) readily reacts with CH3OH, H2O and O-2 to produce (equivalent to Si - O)(2)Ti(OCH3)(2), ( equivalent to Si - O)(2)Ti(OH)(2) and ( equivalent to Si - O)(2)Ti(OCH2CMe3)(2) at room temperature, respectively. Further calcination in oxygen at 500 degreesC of the hydrolyzed products, ( equivalent to Si - O)(2)Ti(OH)(2), resulted in surface titanium oxides. All the above reactions were followed by in situ FTIR and the resulted products were characterized by elemental analysis, XRD, nitrogen adsorption, FTIR and DRS. It is showed that the grafting reaction and post-treatments did not affect the characteristic structure of MCM-41. The surface area and pore diameter of the Ti-MCM-41 are slightly less than that of MCM-41. The Ti atoms are tetrahedrally coordinated on the surface of MCM-41. Catalytic test revealed that the Ti-MCM-41 has evident photocatalytic activity toward ethylene. The reason for photocatalytic activity of the molecular sieve was discussed by comparing for the structure and properties of Ti-MCM-41 with that of [Ti]-MCM-41.