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

    Research output: Contribution to journalArticleScientificpeer-review

    11 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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    author = "Antti Paajanen and Jukka Vaari",
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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

    TY - JOUR

    T1 - High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study

    AU - Paajanen, Antti

    AU - Vaari, Jukka

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    N2 - 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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