Cyclopentadiene (CPD) and cyclopentadienyl radical (CPDyl) reactions are known to provide fast routes to naphthalene and other polycyclic aromatic hydrocarbon (PAH) precursors in many systems. In this work, we combine literature quantum chemical pathways for the CPDyl + CPDyl recombination reaction and provide pressure dependent rate coefficient calculations and analysis. We find that the simplified 1-step global reaction leading to naphthalene and two H atoms used in many kinetic models is not an adequate description of this chemistry at conditions of relevance to pyrolysis and steam cracking. The C10H10 species is observed to live long enough to undergo H abstraction reactions to enter the C10H9 potential energy surface (PES). Rate coefficient expressions as functions of T and P are reported in CHEMKIN format for future use in kinetic modeling.
A combined experimental
and kinetic modeling study is presented
to improve the understanding of the formation of polycyclic aromatic
hydrocarbons at pyrolysis conditions. The copyrolysis of cyclopentadiene
(CPD) and ethene was studied in a continuous flow tubular reactor
at a pressure of 0.17 MPa and a dilution of 1 mol CPD/1 mol ethene/10
mol N2. The temperature was varied from 873 to 1163 K,
resulting in cyclopentadiene conversions between 1 and 92%. Using
an automated reaction network generator, RMG, we present an elementary
step kinetic model for CPD pyrolysis that accurately predicts the
initial formation of aromatic products. The model is able to reproduce
the product yields measured during the pyrolysis of pure cyclopentadiene
and the copyrolysis of cyclopentadiene and ethene. The addition of
ethene as coreactant increases the benzene and toluene selectivity.
In the absence of ethene, benzene formation is initiated by addition
of a cyclopentadienyl radical to cyclopentadiene, following a complicated
series of isomerizations and loss of a butadienyl radical. In the
presence of ethene, the main pathway for the formation of benzene
+ CH3 shifts to ethene + cyclopentadiene. Toluene formation
is initiated by vinyl radical addition to cyclopentadiene. Without
the addition of ethene, vinyl radicals are mainly formed by hydrogen
radical addition to ethyne. When ethene is added as coreactant, vinyl
radical production happens via hydrogen abstraction from ethene.
Simulation of quasi one-dimensional reacting flow is a standard in many combustion studies. Here Ember, a new open-source code for efficiently performing these calculations using large, detailed chemical kinetic models is presented. Ember outperforms other standard software, such as Chemkin, in computation time by leveraging rebalanced Strang operator splitting which does not suffer the steady-state inaccuracies of most splitting methods. The splitting approach and implementation used in Ember is described. Ember is validated for computation of flame extinction through imposed strain, extinction strain rate (ESR), and shown to be capable of modeling three typical experimental strained flame configurations: premixed twin flames, premixed single flames opposing inert, and diffusion flames. As further demonstration, Ember is used to investigate Lewis number effects on ESR using a detailed chemical kinetic model with 500 species for simulation of strained extinction of lean (Le > 1) and rich (Le < 1) propane/air flames. Primary trends predicted by Law [1] using asymptotic theories of strained flames are accurately reproduced with the large, detailed chemical kinetic model. However, the complicated chemistry introduces some subtle phenomena not seen with single-step models. The Ember software is open-source and freely available to any user online.
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