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

Multiwall carbon nanotubes with different amounts of oxygenated functional groups were prepared and used as metal-free catalysts in direct dehydrogenation of propane to propylene, exhibiting enhanced catalytic activities with the extent of oxidation treatments. A good linear relation between the propylene formation rates and the amounts of CO groups, confirming the active sites of CO groups for the carbon catalysts in the direct dehydrogenation of propane. [Display omitted] •Multi-wall carbon nanotubes with different amounts of oxygenated groups are prepared.•The oxidized MWCNTs are used as metal-free catalysts for dehydrogenation of propane.•High activity of oxidized MWCNTs are attributed to the oxygen functional groups.•A good linearity between the propylene formation rates and the amounts of CO groups. 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, N2 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 CO groups on the surface of the MWCNTs.