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Mechanism and Kinetics for the Initial Steps of Pyrolysis and Combustion of 1,6-Dicyclopropane-2,4-hexyne from ReaxFF Reactive Dynamics

Liu, Lianchi and Bai, Chen and Sun, Huai and Goddard, William A., III (2011) Mechanism and Kinetics for the Initial Steps of Pyrolysis and Combustion of 1,6-Dicyclopropane-2,4-hexyne from ReaxFF Reactive Dynamics. Journal of Physical Chemistry A, 115 (19). pp. 4941-4950. ISSN 1089-5639. https://resolver.caltech.edu/CaltechAUTHORS:20110607-080239665

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Abstract

We report the kinetic analysis and mechanism for the initial steps of pyrolysis and combustion of a new fuel material, 1,6-dicyclopropane-2,4-hexyne, that has enormous heats of pyrolysis and combustion, making it a potential high-energy fuel or fuel additive. These studies employ the ReaxFF force field for reactive dynamics (RD) simulations of both pyrolysis and combustion processes for both unimolecular and multimolecular systems. We find that both pyrolysis and combustion initiate from unimolecular reactions, with entropy-driven reactions being most important in both processes. Pyrolysis initiates with extrusion of an ethylene molecule from the fuel molecule and is followed quickly by isomerization of the fuel molecule, which induces additional radicals that accelerate the pyrolysis process. In the combustion process, we find three distinct mechanisms for the O2 attack on the fuel molecule: (1) attack on the cyclopropane, ring expanding to form the cyclic peroxide which then decomposes; (2) attack onto the central single bond of the diyne which then fissions to form two C_5H_5O radicals; (3) attack on the alkyne-cyclopropane moiety to form a seven-membered ring peroxide which then decomposes. Each of these unimolecular combustion processes releases energy that induces additional radicals to accelerate the combustion process. Here oxygen has major effects both as the radical acceptor and as the radical producer. We extract both the effective activation energy and the effective pre-exponential factor by kinetic analysis of pyrolysis and combustion from these ReaxFF simulations. The low value of the derived effective activation energy (26.18 kcal/mol for pyrolysis and 16.40 kcal/mol for combustion) reveals the high activity of this fuel molecule.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/jp110435pDOIUNSPECIFIED
http://pubs.acs.org/doi/abs/10.1021/jp110435pPublisherUNSPECIFIED
ORCID:
AuthorORCID
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2011 American Chemical Society. Received: November 1, 2010. Revised: December 16, 2010. Published: April 21, 2011. We thank Jonathan E. Mueller for helpful discussions and comments. Financial support from the National Science Foundation of China (No. 20473052), NSAF funding (No. 10676021), and National Basic Research Program of China (No. 2003-CB615804 and 2007CB209701) is gratefully acknowledged. We acknowledge the funding from China Scholarship Council (No. 2009623057). Funding from ONR (N00014-09-1-0634) and ARO-MURI (W911NF-08-1-0124 and W911NF-05-1-0345) and Los Alamos National Labs. is acknowledged.
Funders:
Funding AgencyGrant Number
National Science Foundation of China20473052
NSAF10676021
National Basic Research Program of China 2003-CB615804
National Basic Research Program of China 2007CB209701
China Scholarship Council2009623057
Office of Naval Research (ONR)N00014-09-1-0634
Army Research Office (ARO) Multidisciplinary University Research Initiative (MURI)W911NF-08-1-0124
Army Research Office (ARO) Multidisciplinary University Research Initiative (MURI)W911NF-05-1-0345
Alamos National LabsUNSPECIFIED
Issue or Number:19
Record Number:CaltechAUTHORS:20110607-080239665
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20110607-080239665
Official Citation:Mechanism and Kinetics for the Initial Steps of Pyrolysis and Combustion of 1,6-Dicyclopropane-2,4-hexyne from ReaxFF Reactive Dynamics Lianchi Liu, Chen Bai, Huai Sun, William A. Goddard III The Journal of Physical Chemistry A 2011 115 (19), 4941-4950
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23919
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:14 Jun 2011 18:22
Last Modified:03 Oct 2019 02:51

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