Low-Temperature C-H Bond Activation: Ethylbenzene-to-Styrene Conversion on Rutile TiO2(110)

The low-temperature C-H bond activation of alkanes remains a big challenge in alkane dehydrogenation. In this work, ethylbenzene (EB) oxidative dehydrogenation has been investigated on rutile(R)-TiO2(110) under both ultrahigh vacuum (UHV) and ambient conditions. Under UHV conditions, styrene is produced with nearly 100% selectivity in a stepwise manner, in which the first C-H bond dissociation of EB occurs at <285 K with the help of surface O22- species, followed by the second C-H bond dissociation at about 400 K. However, styrene, acetophenone, and 2,3-diphenylbutane products are produced from EB oxidative dehydrogenation under ambient conditions, suggesting that α-H dissociation is the initial step of EB oxidative dehydrogenation. This may be also possible for EB oxidative dehydrogenation on R-TiO2(110) under UHV conditions. The different pathways of EB oxidative dehydrogenation under UHV and ambient conditions may originate from different intermediates and O2 concentrations. This work provides new insight into the fundamental understandings of the low-temperature C-H bond activation of alkyl chains of aromatic hydrocarbons, which may promote the development of new catalysts for efficient styrene production from EB oxidative dehydrogenation under mild conditions.