Pyrolysis kinetics for long-chain n-alkylcyclohexanes

S. Ratz, Phillip E. Savage, L. Tan

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

We report new experimental data and a general, mechanism-based structure - reactivity relationship for the pyrolysis of long-chain n-alkylcyclohexanes. The relationship has as its foundation the previously deduced free-radical reaction mechanism for alkylcyclohexane pyrolysis. The model is general because it incorporates the effect of the alkyl chain length on the global kinetics by accounting for the chain-length-dependent reaction path degeneracy of the initiation, β-scission, and hydrogen-abstraction steps. The global kinetics determined from the model for pyrolyses at 400 °C and an initial reactant concentration of 0.13 mol/L are in good accord with the experimentally determined rate constants for nine different n-alkylcyclohexanes with aliphatic substituents ranging from butyl (n-C4) to octadecyl (n-C18). A sensitivity analysis reveals that the rate constants for initiation, termination, and β-scission to form a primary radical had the greatest influence on the calculated pyrolysis rate. This work provides an example of how a mechanism-based analytical rate equation, rather than some empirical reactivity index, can be used as the basis for a structure - reactivity relationship for hydrocarbon pyrolysis.

Original languageEnglish (US)
Pages (from-to)1805-1810
Number of pages6
JournalIndustrial and Engineering Chemistry Research
Volume40
Issue number8
StatePublished - Apr 18 2001

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Pyrolysis
Kinetics
Chain length
Rate constants
Free radical reactions
Hydrocarbons
Sensitivity analysis
Hydrogen

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering

Cite this

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abstract = "We report new experimental data and a general, mechanism-based structure - reactivity relationship for the pyrolysis of long-chain n-alkylcyclohexanes. The relationship has as its foundation the previously deduced free-radical reaction mechanism for alkylcyclohexane pyrolysis. The model is general because it incorporates the effect of the alkyl chain length on the global kinetics by accounting for the chain-length-dependent reaction path degeneracy of the initiation, β-scission, and hydrogen-abstraction steps. The global kinetics determined from the model for pyrolyses at 400 °C and an initial reactant concentration of 0.13 mol/L are in good accord with the experimentally determined rate constants for nine different n-alkylcyclohexanes with aliphatic substituents ranging from butyl (n-C4) to octadecyl (n-C18). A sensitivity analysis reveals that the rate constants for initiation, termination, and β-scission to form a primary radical had the greatest influence on the calculated pyrolysis rate. This work provides an example of how a mechanism-based analytical rate equation, rather than some empirical reactivity index, can be used as the basis for a structure - reactivity relationship for hydrocarbon pyrolysis.",
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Pyrolysis kinetics for long-chain n-alkylcyclohexanes. / Ratz, S.; Savage, Phillip E.; Tan, L.

In: Industrial and Engineering Chemistry Research, Vol. 40, No. 8, 18.04.2001, p. 1805-1810.

Research output: Contribution to journalArticle

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N2 - We report new experimental data and a general, mechanism-based structure - reactivity relationship for the pyrolysis of long-chain n-alkylcyclohexanes. The relationship has as its foundation the previously deduced free-radical reaction mechanism for alkylcyclohexane pyrolysis. The model is general because it incorporates the effect of the alkyl chain length on the global kinetics by accounting for the chain-length-dependent reaction path degeneracy of the initiation, β-scission, and hydrogen-abstraction steps. The global kinetics determined from the model for pyrolyses at 400 °C and an initial reactant concentration of 0.13 mol/L are in good accord with the experimentally determined rate constants for nine different n-alkylcyclohexanes with aliphatic substituents ranging from butyl (n-C4) to octadecyl (n-C18). A sensitivity analysis reveals that the rate constants for initiation, termination, and β-scission to form a primary radical had the greatest influence on the calculated pyrolysis rate. This work provides an example of how a mechanism-based analytical rate equation, rather than some empirical reactivity index, can be used as the basis for a structure - reactivity relationship for hydrocarbon pyrolysis.

AB - We report new experimental data and a general, mechanism-based structure - reactivity relationship for the pyrolysis of long-chain n-alkylcyclohexanes. The relationship has as its foundation the previously deduced free-radical reaction mechanism for alkylcyclohexane pyrolysis. The model is general because it incorporates the effect of the alkyl chain length on the global kinetics by accounting for the chain-length-dependent reaction path degeneracy of the initiation, β-scission, and hydrogen-abstraction steps. The global kinetics determined from the model for pyrolyses at 400 °C and an initial reactant concentration of 0.13 mol/L are in good accord with the experimentally determined rate constants for nine different n-alkylcyclohexanes with aliphatic substituents ranging from butyl (n-C4) to octadecyl (n-C18). A sensitivity analysis reveals that the rate constants for initiation, termination, and β-scission to form a primary radical had the greatest influence on the calculated pyrolysis rate. This work provides an example of how a mechanism-based analytical rate equation, rather than some empirical reactivity index, can be used as the basis for a structure - reactivity relationship for hydrocarbon pyrolysis.

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