Pyrolysis of norbornadiene: An experimental and kinetic modeling study

Pyrolysis of norbornadiene (NBD) was investigated in a jet-stirred reactor at 760 torr and within the temperature range of 560 to 1100 K. 37 products and intermediates ranging from m/z = 26 to 178 were identified and quantified by using synchrotron radiation photoionization molecular-beam mass spectrometry accompanied by gas chromatography. The C 7 H 8 isomers, including NBD, cycloheptatriene (CHT) and toluene (A1CH 3 ), were differentiated. Acetylene (C 2 H 2 ), cyclopentadiene (C 5 H 6 ), C 7 H 8 isomers and other aromatics are abundant during the pyrolysis process. A detailed kinetic model was developed with reasonable predictions against the measured results, involving 264 species and 1259 reactions, which is helpful to understand the kinetic and heat features of initial consumption as well as the synergistic effect of C 2 H 2 , C 5 H 6 and A1CH 3 to the formation of aromatics. Rate-of-production analysis shows that the pyrolysis of NBD experiences two stages. The first stage involves the isomerization and decomposition of NBD, yielding A1CH 3 , CHT, C 5 H 6 and C 2 H 2 . Branching ratio analysis shows that C 5 H 6 and C 2 H 2 are dominant products in the first stage. Heat release analysis indicates that the first stage is endothermic. The second stage involves the pyrolysis and interactions of first-stage products to produce light hydrocarbons and polycyclic aromatic hydrocarbons like indene, naphthalene, acenaphthylene, fluorene and phenanthrene. Three routes dominate the formation of indene, including C 5 H 6 + C 5 H 5 , benzyl radical + C 2 H 2 and cycloheptatrienyl radical + C 2 H 2 , the last one of which has been scarcely considered in the previous investigation. Sensitivity analysis indicates the reactions in the first stage exhibit strong promoting effects for the consumption of NBD, while the second-stage reactions play minor roles in NBD consumption. This work would enrich the understanding of NBD consumption, PAH formation and heat release. (c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

Pyrolysis of norbornadiene (NBD) was studied using synchrotron radiation photoionization molecular-beam mass spectrometry. A detailed kinetic model was developed to predict the species and reactions involved in the pyrolysis process. The results reveal a two-stage process with the formation of acetylene, cyclopentadiene, C7H8 isomers, and other aromatics in the first stage, followed by the formation of light hydrocarbons and polycyclic aromatic hydrocarbons in the second stage. Sensitivity analysis shows that the reactions in the first stage play a significant role in NBD consumption.