Improving the Alkene Selectivity of Nanocarbon-Catalyzed Oxidative Dehydrogenation of n-Butane by Refinement of Oxygen Species

Nanocarbon materials are promising catalysts of oxidative dehydrogenation (ODH) of alkanes, but improving the alkene selectivity remains a challenge. A deep understanding and thorough identification of oxygen species on nanocarbons are strongly required for approaches to nanocarbon modification. Successful application of iodometric titration in quantitative determination of the amount of electrophilic oxygen on the surface of carbon nanotubes has been performed in this work. Electrophilic oxygen species have been identified as the main culprits for deep oxidation of ODH of n-butane via a clear correlation between the amount of electrophilic oxygen and combustion reaction rate. By chemical reduction and annealing in nitrogen, the alkene selectivity is significantly improved. Phenol groups are found to play an essential role in improving alkene selectivity. The study reveals that higher alkene selectivity can be achieved by both eliminating deep oxidation active sites and facilitating the formation of phenol and carbonyl groups.