Thermal dissociation of tripropylamine as the first step in the growth of carbon nanotubes inside AlPO4‐5 channels

Tripropylamine (TPA) is a template for the synthesis of porous AlPO₄‐5, whose calcination in the absence of air leads to the formation of 4 Å single‐walled carbon nanotubes. The thermal dissociation of TPA is the first step in this remarkable process. We examined the dissociation mechanisms of TPA by first principles calculations, under three types of conditions. In the gas phase, the unimolecular dissociation was a complex process initiated by the breaking of either the N? C^α and the C^α? C^β bonds. Within a confined space inside neutral zeolitic channels, the diffusion of H radicals enhanced a cycle of reactions to produce dipropylamine and monopropylamine, in agreement with experimental observations. In the presence of an acidic site, the dissociation of TPA was catalyzed to produce ammonia and propylene molecules, which were identified as the precursors for the eventual formation of carbon nanotubes. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010