Direct dehydrogenation of propane to propylene on surface-oxidized multiwall carbon nanotubes

Nanocarbon is an important metal-free catalyst for various applications including oxidative dehydrogenation and direct dehydrogenation reactions. The surface oxygen-containing groups of nanocarbon are regarded as active sites in oxidative dehydrogenation reaction. However, the active sites for direct dehydrogenation are still not totally clear. Herein, multiwall carbon nanotubes (MWCNTs) are activated by different oxidation processes and thermal treatments, and used as effective catalysts for direct dehydrogenation of propane to propylene. The physicochemical properties of the oxidized MWCNTs are characterized by SEM, TEM, XRD, N-2 sorption, Raman, TGA, TPD-MS and XPS techniques. It is revealed that the concentrations of the oxygen-containing groups could be well controlled by sequential acid oxidation and thermal treatment. The activities of these nanocarbon catalysts exhibit a good linear dependence on the number of carbonyl/quinone groups, confirming the active sites are C=O groups on the surface of the MWCNTs.