High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study

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7 Citations (Scopus)

Abstract

The kinetics and products of cellulose pyrolysis can be studied using large-scale molecular dynamics simulations at high temperatures, where the reaction rates are high enough to make the simulation times practical. We carried out molecular dynamics simulations employing the ReaxFF reactive force field to study the initial step of the thermal decomposition process. We gathered statistics of simulated reactive events at temperatures ranging from 1400 to 2200 K, considering cellulose molecules with different molecular weights and initial conformations. Our simulations suggest that, in gas-phase conditions at these high temperatures, the decomposition occurs primarily through random cleavage of the β(1 → 4)-glycosidic bonds, for which we obtained an activation energy of (171 ± 2) kJ mol −1 and a frequency factor of (1.07 ± 0.12) × 10 15 s −1. We did not observe dependency of the kinetic parameters on the molecular weight or initial conformation. Some of the decomposition reactions involved the release of low-molecular-weight products. Excluding radicals, the most commonly observed species were glycolaldehyde, water, formaldehyde and formic acid. Many of our observations are supported by the existing experimental and theoretical knowledge. We did not, however, observe the formation of levoglucosan, which is the dominant product in conventional pyrolysis experiments at much lower temperatures. This is understandable, since the high temperatures can force the dominance of radical reactions over pericyclic reactions. Nevertheless, our results support further use of ReaxFF-based molecular dynamics simulations in the study of cellulose pyrolysis.

Original languageEnglish
Pages (from-to)2713-2725
Number of pages13
JournalCellulose
Volume24
Issue number7
DOIs
Publication statusPublished - 1 Jul 2017
MoE publication typeA1 Journal article-refereed

Fingerprint

Cellulose
Molecular dynamics
Decomposition
Pyrolysis
Molecules
formic acid
Molecular weight
Conformations
Computer simulation
Temperature
Formic acid
Kinetic parameters
Formaldehyde
Reaction rates
Activation energy
Gases
Statistics
Kinetics
Water
Experiments

Keywords

  • cellulose
  • pyrolysis
  • molecular dynamics
  • stochastic simulation
  • reaxFF
  • ProperTune

Cite this

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title = "High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study",
abstract = "The kinetics and products of cellulose pyrolysis can be studied using large-scale molecular dynamics simulations at high temperatures, where the reaction rates are high enough to make the simulation times practical. We carried out molecular dynamics simulations employing the ReaxFF reactive force field to study the initial step of the thermal decomposition process. We gathered statistics of simulated reactive events at temperatures ranging from 1400 to 2200 K, considering cellulose molecules with different molecular weights and initial conformations. Our simulations suggest that, in gas-phase conditions at these high temperatures, the decomposition occurs primarily through random cleavage of the β(1 → 4)-glycosidic bonds, for which we obtained an activation energy of (171 ± 2) kJ mol −1 and a frequency factor of (1.07 ± 0.12) × 10 15 s −1. We did not observe dependency of the kinetic parameters on the molecular weight or initial conformation. Some of the decomposition reactions involved the release of low-molecular-weight products. Excluding radicals, the most commonly observed species were glycolaldehyde, water, formaldehyde and formic acid. Many of our observations are supported by the existing experimental and theoretical knowledge. We did not, however, observe the formation of levoglucosan, which is the dominant product in conventional pyrolysis experiments at much lower temperatures. This is understandable, since the high temperatures can force the dominance of radical reactions over pericyclic reactions. Nevertheless, our results support further use of ReaxFF-based molecular dynamics simulations in the study of cellulose pyrolysis.",
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High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study. / Paajanen, Antti; Vaari, Jukka.

In: Cellulose, Vol. 24, No. 7, 01.07.2017, p. 2713-2725.

Research output: Contribution to journalArticleScientificpeer-review

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