Selective Oxidative Dehydrogenation of Cyclohexene into 1,3-Cyclohexadiene on TiO2
Tianyue Wang1, Xinning Gu1, Zhiyong Xiao1
1Shenzhen Key Laboratory of Energy Chemistry & Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
Abstract:
The selective C-H bond activation remains a big challenge in hydrocarbon dehydrogenation. Herein, the selective oxidative dehydrogenation of cyclohexene (C6H10) has been investigated on a model rutile(R)-TiO2(110) surface. In the thermal conversion process, 1,3-cyclohexadiene (1,3-C6H8) is produced with nearly 100% selectivity in a stepwise manner, where the initial α-sp3 C-H bond dissociation of C6H10 occurs at <300 K with the help of surface O22- species. Under UV irradiation, a new reaction pathway for 1,3-C6H8 formation occurs via the dehydration of 2-cyclohexen-1-olate (1,2-C6H9O) groups, which is formed by the reaction of surface oxygen species (predominantly O2) with a cyclohexenyl radical (C6H9•) intermediate. In addition, different surface oxygen species give rise to different products in the oxidative conversion of C6H10 under UV irradiation. The findings not only elucidate the reaction mechanism of C6H10 oxidative dehydrogenation but also provide new insights for the C-H bond activation of cyclic hydrocarbons over TiO2-based catalysts.
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