Hydrogenation Of Chloronitrobenzenes Over Carbon Nanotubes-Supported Amorphous Alloy Catalysts

With carbon nanotubes?CNTs?as the carrier and concerning the different surface tensions between water and ethanol,we succeeded in intratubal or extratubal loading of CoCl₂ or NiCl₂ into CNTs.Thus,amorphous Co-B/CNTs and Ni-B/CNTs catalysts in different loading methods were prepared via a chemical reduction method.The physiochemical properties of the catalysts were characterized.With the hydrogenation from chloronitrobenzenes?CNBs?to chloroanilines?CANs?as the probe,we tested the effects of loading method of active components and high-temperature crystallization on the catalytic performances of Co-B/CNTs and Ni-B/CNTs.After that,the reaction kinetics was deduced and the effects of metal ions on catalytic performances were further studied.As for Co-B/CNTs,we find?1?intratubal loading versus extratubal loading is affected by the intratubal confinement effect.The intratubal nano-space can effectively inhibit the growth and aggregation of Co-B particles,relieve the loss of active components,and improve the thermal stability of amorphous alloy.?2?Compared with the extratubally-loaded catalysts?Co-B-out/CNTs?,the intratubally-loaded catalysts?Co-B-in/CNTs?exhibit significantly higher m-CNB hydrogenation activity?6.41 mmol/g·h vs.4.30 mmol/g·h?,but high-temperature crystallization would reduce the catalytic activity.?3?Kinetic study showed m-CNB hydrogenation over Co-B-in/CNTs to be a first-order reaction with an apparent activation energy of 32.11 kJ·mol^-1.As for Ni-B/CNTs,we find?1?compared with extratubally-loaded catalysts?Ni-B-out/CNTs?,the intratubally-loaded catalysts?Ni-B-in/CNTs?exhibit small and uniform distribution of amorphous Ni-B particles as well as high thermal stability.?2?Ni-B-in/CNTs show significantly higher m-CNB hydrogenation activity than Ni-B-out/CNTs?37.64 mmol/g·h vs.29.88 mmol/g·h?,and high-temperature crystallization would reduce the catalytic activity too.?3?Kinetic study showed m-CNB hydrogenation over Ni-B-in/CNTs to be a first-order reaction with an apparent activation energy of 32.11 kJ·mol^-1.As for the effects of metal ions,we find?1?addition of Fe³⁺or Ce³⁺could significantly improve the m-CNB hydrogenation activity of Co-B-in/CNTs.The m-CNB hydrogenation rates were improved from 7.49 mmol/g·h to 10.44mmol/g·h at the Fe:Co molar ratio of 1:100 and to 10.61mmol/g·h at the Ce:Co molar ratio of1:125.?2?Addition of Fe³⁺or Tm³⁺could significantly improve the m-CNB hydrogenation activity of Ni-B-in/CNTs.The m-CNB hydrogenation rates were improved from 43.44 mmol/g·h to 63.04 mmol/g·h at the Fe:Ni molar ratio of 1:100and to 64.40 mmol/g·h at the Tm:Co molar ratio of 1:125.