Initial reaction mechanisms of cellulose pyrolysis revealed by ReaxFF molecular dynamics

Mo, Zhaolan; Wang, Ze; Li, Xiaoxia; Qiao, Xianjie; Song, Wenli; Guo, Li

doi:10.1016/j.fuel.2016.03.008

Cited by 213 publications

(111 citation statements)

References 57 publications

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“…This is in line with previous experimental and theoretical evidence suggesting that cellulose pyrolysis begins with depolymerisation reactions that ultimately lead to the oligoand monosaccharide level (Pouwels et al 1989;Várhegyi et al 1994;Mamleev et al 2006;Lin et al 2009;Lédé 2012;Agarwal et al 2012;Mayes and Broadbelt 2012;Hosoya and Sakaki 2013;Zhou et al 2014;Zheng et al 2016). …”

Section: Depolymerisation Reactionssupporting

confidence: 92%

“…The ReaxFF-MD study by Zheng et al (2016) provides a relevant point of comparison to our results. Firstly, they report glycolaldehyde and water among the major products, which is in agreement with our results.…”

Section: Depolymerisation Reactionsmentioning

confidence: 55%

“…the elementary reaction mechanisms underlying pyrolysis, is regarded as one of the fundamental challenges for a thorough understanding of cellulose (and in general polymer) pyrolysis (Mettler et al 2012b). In the recent years, there have been attempts to complement the experimental data on cellulose pyrolysis through electronic structure calculations and atomistic simulations that are capable, one way or the other, of capturing individual chemical reactions that occur during the decomposition process (Liu et al 2011b;Zhang et al 2011b;Mayes and Broadbelt 2012;Agarwal et al 2012;Hosoya and Sakaki 2013;Zhang et al 2014;Murillo et al 2015;Zhang et al 2015a, b;Zheng et al 2016). This is a formidable challenge, as the pyrolysis chemistry of cellulose is highly complex, involving thousands of chemical reactions and yielding hundreds of volatile species (Zhou et al 2014).…”

Section: Introductionmentioning

confidence: 99%

“…At high temperatures, the most favourable pathway was glycosidic bond cleavage and subsequent formation of an epoxide precursor to LGA. Recently, Zheng et al (2016) used ReaxFF-based RMD simulations to study the initial reaction mechanisms of cellulose pyrolysis, and the effect of temperature on the product distribution. Their model system consisted of an amorphous arrangement of six cellulose chains, each having 60 b-D-glucopyranose units.…”

Section: Introductionmentioning

confidence: 99%

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

Paajanen

Vaari

2017

Cellulose

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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 b(1 ? 4)-glycosidic bonds, for which we obtained an activation energy of (171 ± 2) kJ mol -1 and a frequency factor of 1:07 AE 0:12 ð ÞÂ10 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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Section: Depolymerisation Reactionssupporting

confidence: 92%

Section: Depolymerisation Reactionsmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Paajanen

Vaari

2017

Cellulose

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“…The connectivity between atoms in the molecule of the reactive force field (ReaxFF) is determined by the interatomic bond order at that time, which means the chemical bond can be broken and formed freely, so that the chemical reaction process can be obtained . The ReaxFF method has been successfully applied to reaction kinetics simulation researches, including applications of the organic micromolecular system, the polymer system, and the high energy material system . The result of ReaxFF method has been verified to be consistent with that of the quantum mechanics (QM) method and the experiment .…”

Section: Introductionmentioning

confidence: 80%

The Constructions and Pyrolysis of 3D Kerogen Macromolecular Models: Experiments and Simulations

et al. 2019

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Kerogens are extracted from deep shales to study pyrolysis of deep shale samples. The 2D molecular models of kerogens are obtained by a series of physical and chemical experiments by which the macromolecular models of kerogens are constructed. Then, the reasonable 3D macromolecular models are established by molecular mechanics and global energy minimization. The effects of temperature and heating rate on the chemical kinetics of kerogen pyrolysis are studied using reactive force field (ReaxFF). The hybrid molecular dynamics/force‐biased Monte Carlo (MD/fbMC) approach is used to simulate the pyrolytic process at the experimental temperature, which is lower than the conventional one. The gaseous products and residues obtained by the simulations agree with the experimental results, which means a reliable simulation method for pyrolysis at experimental temperature is provided. This study constructs the rational macromolecular models of kerogen by experiments, and proposes the mechanisms of typical reactions of kerogen pyrolysis, which may help in understanding the formation of shale oil and gas.

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Influence of n‐butanol and isomers on the combustion mechanisms of isooctane and coke formation based on ReaxFF simulation

et al. 2022

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Fuel additives play a significant role in enhancing the thermal stability of fuel combustion. The effect of additives on the combustion of hydrocarbon fuels and the combustion performances of isooctane with three different isomer additives, (n‐butanol (1‐BuOH), diethyl ether (DEE), and 2‐butanol(2‐BuOH)), and additive‐free isooctane were explored by ReaxFF simulation in this work. The simulation system was heated to 3000 K at a heating rate of 10 K/ps and kept stable at 3000 K. A variety of combustion products (e.g., small gas molecules and C1‐C8 hydrocarbon compounds) in each system were analyzed, and the reaction paths were speculated based on the computed trajectory. The simulation results showed that the CC bond scission reaction dominated the combustion process of the three additives. All three additives promote the formation of toxic carbonyl compounds such as formaldehyde, while the pure DEE additive has the best inhibition effect on the formation of the coke precursor, C2H2, C3H4, and C3H6. The pure 1‐BuOH additive can shorten the initial reaction time of the reactants. The effects of DEE/1‐BuOH additive on the combustion of isooctane were investigated to obtain a desirable additive mixture with good performance. The expansion of the DEE proportion (80%/20% DEF/1‐BuOH) shows a slightly better coke (C3H4 and C3H6) reduction effect, while the inhibition effect is not as obvious as that of a pure DEE additive.

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Initial reaction mechanisms of cellulose pyrolysis revealed by ReaxFF molecular dynamics

Cited by 213 publications

References 57 publications

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

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

The Constructions and Pyrolysis of 3D Kerogen Macromolecular Models: Experiments and Simulations

Influence of n‐butanol and isomers on the combustion mechanisms of isooctane and coke formation based on ReaxFF simulation

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