Effect of preparation conditions of benzene bridged Ti incorporated periodic mesoporous organosilicas on selectivity improvement of cyclohexene epoxidation
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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 48 h had more readily exposed active titanium site, which significantly improve the selectivity of cyclohexene oxide to 97.7% from 37.7% at 24 h 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.
KeywordsTitanium PMOs 1,4-Bis(triethoxysilyl)benzene Aging time Cyclohexene epoxidation
The authors thank the financial support from the National Natural Science Foundation of China (No. 21776237) and Hunan 2011 Collaborative Innovation Center of New Chemical Technologies for Environmental Benignity and Efficient Resource Utilization.
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