Oxygen breaks into carbon nanotubes and abstracts hydrogen from propane

We have revealed that molecular oxygen breaks into carbon nanotubes forming active sites to abstract hydrogen from propane. Various carbonaceous species (carbon defects and debris) on carbon nanotubes were identified and their effects on the oxo-functionalization as well as the catalytic performance in the oxidative dehydrogenation of propane were thoroughly investigated. The results indicate that certain amount of accessible skeleton defects is beneficial to the selective introduction of ether and ketonic carbonyl groups. However, amorphous carbons are poorly selective during oxo-functionalization and the related functionalities decompose easily during the long-term catalytic test. The proportion of ether and ketonic carbonyl groups obtained from oxygen functionalization reaches to 93%, which is twice more than that obtained from acidic solution treatment. Turnover frequency of 1.5 h(-1) in the oxidative dehydrogenation of propane is successfully correlated with ketonic carbonyl groups (C=O), while there is no obvious correlation between the activity and the amount of ether groups (C-O-C). (C) 2015 Elsevier Ltd. All rights reserved.