21454_ftp.pdf

Thermal Dissociation of Tripropylamine as the First Step in the Growth of Carbon Nanotubes Inside AlPO4 −5 Channels J. W. LIU, Z. F. LIU Department of Chemistry and Centre for Scientific Modeling and Computation, Chinese University of Hong Kong, Shatin, Hong Kong, China Received 29 May 2009; Revised 21 August 2009, 28 September 2009; Accepted 30 September 2009 DOI 10.1002/jcc.21454 Published online 7 January 2010 in Wiley InterScience (). Abstract: Tripropylamine (TPA) is a template for the synthesis of porous AlPO −5, whose calcination in the absence 4 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–Cα and the Cα –Cβ 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 31: 1681–1688, 2010 Key words: density functional theory; first principles