Effect of preparation conditions of benzene bridged Ti incorporated periodic mesoporous organosilicas on selectivity improvement of cyclohexene epoxidation

Benzene bridged Ti incorporated periodic mesoporous organosilicas (Ti-PMOs) was prepared following an in situ hydrothermal method by using P123 as a structure directing agent in acidic condition, tetrabutyl titanate (TBOT) as titanium source, tetraethoxysilane (TEOS) as inorganic Si-source and 1, 4-bis(triethoxysilyl)benzene (BTEB) as organic Si-source. The effects of preparation conditions of Ti-PMOs, mole ratio of TEOS/BTEB and ageing time, on the catalytic performance for the cyclohexene epoxidation with tertbutyl hydroperoxide as an oxidant agent were investigated. By means of a variety of characterized method, the results showed that the proper mole ratio of TEOS/BTEB was 3:1, which was favor of maintaining good mesoporous structure, ageing time of preparation mixture solution was a key factor to improve the catalytic performance of Ti-PMOs. NH3-TPD indicated that sample prepared at ageing time 48h had more readily exposed active titanium site, which significantly improve the selectivity of cyclohexene oxide to 97.7% from 37.7% at 24h ageing time. The hydrophobic group of benzene bridged on the pore wall was benefit for the approach of cyclohexene and formation of the active tetravalent titanium.