Beneficial role of the nitrogen-doped carbon nanotubes in the synthesis of the active palladium supported catalyst

The use of nitrogen doped carbon nanotubes (N-CNTs) as a palladium catalyst support resulted in the formation of isolated palladium ions and metal nanoparticles, depending on the Pd content. It was found that the formation of isolated palladium ions is due to the presence of pyridinic nitrogen centers in the N-CNTs and does not depend on the method of palladium deposition (impregnation or reductive deposition). These ions possess high thermal stability in hydrogen atmosphere, poorly adsorb CO even at subambient temperature and are low active in catalytic hydrogenation of nitrobenzene to aniline. The beneficial role of the N-CNTs was found to be in the stabilization by graphitic nitrogen of the metallic Pd nanoparticles of similar to 1.5 nm size showing high activity towards aniline formation at atmospheric pressure. The possibility of the tailored synthesis of different metal species by means of the N-CNTs as a support opens a wide room for use of these carbon nanomaterials in various catalytic applications.