Interaction of Cobalt Nanoparticles with Oxygen- and
Nitrogen-Functionalized Carbon Nanotubes and Impact on Nitrobenzene
Hydrogenation Catalysis
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Abstract
The type and the amount of functional
groups on the surface of
carbon nanotubes (CNTs) were tuned to improve the activity of supported
Co nanoparticles in hydrogenation catalysis. Surface nitrogen species
on CNTs significantly promoted the decomposition of the cobalt precursor
and the reduction of cobalt oxide, and improved the resistance of
metallic Co against oxidation in ambient atmosphere. In the selective
hydrogenation of nitrobenzene in the gas phase, Co supported on CNTs
with the highest surface nitrogen content showed the highest activity,
which is ascribed to the higher reducibility and the lower oxidation
state of the Co nanoparticles under reaction conditions. For Co nanoparticles
supported on CNTs with a smaller amount of surface nitrogen groups,
a repeated reduction at 350 °C was essential to achieve a comparable
high catalytic activity reaching 90% conversion at 250 °C, pointing
to the importance of nitrogen species for the supported Co nanoparticles
in nitrobenzene hydrogenation