Mesoporous carbon nanotubes for use as support in catalysis and as nanosized reactors for one-dimensional inorganic material synthesis Original Research Article

Mesoporous multi-walled carbon nanotubes (MWNTs) with an average inner diameter of about 50 nm were successfully used as a one-dimensional catalyst support either in gas-phase, i.e. selective oxidation of H2S into elemental sulfur in a thrickle-bed configuration, or in liquid-phase reactions, i.e. selective hydrogenation of nitrobenzene into aniline or Friedel-Crafts benzoylation reactions. On one hand, the combination of the small size, i.e. high external surface area, and of the tube structure, i.e. confinement effect, allowed a significant improvement of the catalytic performance when compared to that obtained on traditional grain shaped catalysts as observed in the selective oxidation of H2S and the selective hydrogenation of nitrobenzene reactions. On the other hand, the confinement effect induced by the high aspect ratio of the tubes could, in addition, be effectively used for the synthesis of one-dimensional nanowire zeolitic materials under non-hydrothermal macroscopic conditions. Carbon nanotubes template were removed by combustion leaving behind zeolite nanowires which were made up of zeolite particles of about 10–20 nm. The zeolitic catalysts exhibit a high benzoylation activity compared to that of the commercial one due to its high external surface area.