Enhanced catalytic activity of benzene hydrogenation over nickel confined in carbon nanotubes

6.0 wt.% Ni was filled in the channel or deposited on the outer surface of carbon nanotubes (CNTs) by capillarity or deposition to obtain two kinds of catalysts (denoted as Ni-filled-CNTs and Ni-deposited-CNTs, respectively). The catalysts were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), nitrogen adsorption–desorption isothermal, thermogravimetric analysis (TGA), H2-temperature programmed reduction (H2-TPR), and Raman spectroscopy. The catalytic performance was evaluated by the hydrogenation of benzene to cyclohexane in the gas phase at 160 °C and under atmospheric pressure. The conversion of benzene on the Ni-filled-CNTs catalyst is 4.6 times as that of Ni-deposited-CNTs. The research results indicate that the enhanced catalytic activity can be attributed to the confinement of CNTs with more defects which provides facile reduction, reinforced reactivity and increased reactants concentrations due to larger charge transfer and deficient electron in tubular micro-reactor. And the gaps formed on the sidewall of CNTs during the treatment process also play an important role for decreasing the diffuse resistant kinetically.

Graphical abstractThe dramatic increase of the catalytic activity over the Ni confined in the inner of multi-walled carbon nanotubes with more defects has been interpreted by the facile reduction, reinforced reactivity, increased reactants density, and larger gaps formed on sidewall of carbon nanotubes which could reduce the diffusion resistance kinetically.Figure optionsDownload full-size imageDownload high-quality image (295 K)Download as PowerPoint slide