Activation processes of highly ordered carbon nanofibers in the oxidative dehydrogenation of ethylbenzene

Highly graphitized multiwalled carbon nanofibers (CNFs) were used as a carbon-based model catalyst to study the oxidative dehydrogenation (ODH) of ethylbenzene. Their stability as well as the evolution of catalytic performance as well as structural and textural properties under robust operation conditions were studied. The catalyst was characterized by TEM, TPO, XPS, and N2 physisorption techniques. Highly ordered CNFs provide a low initial catalytic activity owing to the low degree of surface functionalization. The rate of ethylbenzene conversion increases by factor of 5 as the catalyst is exposed to the reaction conditions at 475 °C for a period of 30 h time on stream. A similar catalytic performance is obtained after short-term oxidation treatment of the pristine CNFs. The in situ formation of surface defects is attributed to the activation of the catalyst, whereas the generation of an active carbonaceous deposit on the catalyst surface is found to be less relevant.