Chitosan derived N-doped carbon nanotubes for selective hydrogenation of nitroarenes to anilines

Selective hydrogenation of nitroarene to aniline is a key reaction for the manufacture of fine chemicals, pharmaceuticals, and dyes. In this study, N-doped carbon nanotubes (NCNTs) are prepared by the pyrolysis of chitosan-CNTs composite. The outside diameter of CNTs, concentration of chitosan, pyrolysis temperature and heating rate are tuned to improve the catalytic performance. The catalyst of CS/CNTs-800 doped with 0.33% pyrrolic N and 0.30% graphitic N exhibits good activity and high selectivity for the hydrogenation of nitroarenes. The kinetics data reveal that the hydrogenation reaction is zero-order for 4-nitrophenol and first-order dependence to H2 pressure, and H2 dissociation on the active sites is the rate-determining step. On CS/CNTs-800, the nitro groups of 12 different substrates can be selectively reduced with the protection of the other reducible groups. Nonpolar H radicals are found to be formed on CS/CNTs-800 for efficient hydrogenation. In addition, the catalyst showed good stability.