Oxidative dehydrogenation of ethylbenzene to styrene over ultra-dispersed diamond and onion-like carbon

The catalytic properties of sp3-hybridized ultra-dispersed diamond and sp2-hybridized onion-like carbon in the oxidative dehydrogenation of ethylbenzene to styrene were investigated, highlighting the structure sensitivity of the reaction. The sp3-carbon led initially to C–C cleavage and benzene formation, while a switchover of the main reaction pathway into the styrene formation occurred with time on stream due to the formation of surface sp2 carbon, required for the selective styrene formation. This was confirmed by the behavior and the high stable styrene selectivity shown by onion-like carbons. High temperature oxygen pre-treatment created catalytically active species at the sp2 carbon surface, confirming that a high thermal stability carbon–oxygen complex was the active surface site for forming styrene.