Density functional theory molecular modelling and experimental particle kinetics for CO2-char gasification

Mokone J. Roberts, Raymond C. Everson, George Domazetis, Hein W.J.P. Neomagus, J. M. Jones, Cornelia G.C.E. Van Sittert, Gregory N. Okolo, Daniel Van Niekerk, Jonathan P. Mathews

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Experimental measurements and DFT atomistic modelling were conducted to elucidate the mechanisms for gasification chemistry of char with CO2 gas. The molecular models used were based on experimental representations of coal chars derived from the vitrinite- and inertinite-rich South African coals at 1000°C. The HRTEM and XRD techniques were used to construct parallelogram-shaped PAH stacks of highest frequency in the vitrinite-rich (7 × 7) and intertinite-rich (11 × 11) char structures. Computations were executed to get the nucleophilic Fukui functions, at DFT-DNP level, to elucidate the nature and proportions of carbon active sites and quantify their reactivity. The DFT-DNP-computed reaction pathways and transition states, to obtain the energy of reaction and activation energies for the gasification reactions of CO2 with active carbon sites were examined. These results were compared with TGA experimental results at 900-980°C. The mean nucleophilic Fukui function of the H-terminated char models and active sites located at similar edge positions decreased with increasing size of char molecules and followed the sequence: zigzag > armchair > tip active sites. The mean DFT-DNP values for the activation energy of 233 kJ mol-1 at the reactive carbon edge was in agreement with the experimental 191 ± 25 kJ mol-1 and 210 ± 8 kJ mol-1 for the respective chars.

Original languageEnglish (US)
Pages (from-to)295-314
Number of pages20
JournalCarbon
Volume93
DOIs
StatePublished - Aug 8 2015

Fingerprint

Molecular modeling
Gasification
Discrete Fourier transforms
Density functional theory
Kinetics
Carbon
Coal
Activation energy
Polycyclic aromatic hydrocarbons
Gases
Molecules

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)

Cite this

Roberts, M. J., Everson, R. C., Domazetis, G., Neomagus, H. W. J. P., Jones, J. M., Van Sittert, C. G. C. E., ... Mathews, J. P. (2015). Density functional theory molecular modelling and experimental particle kinetics for CO2-char gasification. Carbon, 93, 295-314. https://doi.org/10.1016/j.carbon.2015.05.053
Roberts, Mokone J. ; Everson, Raymond C. ; Domazetis, George ; Neomagus, Hein W.J.P. ; Jones, J. M. ; Van Sittert, Cornelia G.C.E. ; Okolo, Gregory N. ; Niekerk, Daniel Van ; Mathews, Jonathan P. / Density functional theory molecular modelling and experimental particle kinetics for CO2-char gasification. In: Carbon. 2015 ; Vol. 93. pp. 295-314.
@article{1afb371312c8400298f09d0150f1fd8d,
title = "Density functional theory molecular modelling and experimental particle kinetics for CO2-char gasification",
abstract = "Experimental measurements and DFT atomistic modelling were conducted to elucidate the mechanisms for gasification chemistry of char with CO2 gas. The molecular models used were based on experimental representations of coal chars derived from the vitrinite- and inertinite-rich South African coals at 1000°C. The HRTEM and XRD techniques were used to construct parallelogram-shaped PAH stacks of highest frequency in the vitrinite-rich (7 × 7) and intertinite-rich (11 × 11) char structures. Computations were executed to get the nucleophilic Fukui functions, at DFT-DNP level, to elucidate the nature and proportions of carbon active sites and quantify their reactivity. The DFT-DNP-computed reaction pathways and transition states, to obtain the energy of reaction and activation energies for the gasification reactions of CO2 with active carbon sites were examined. These results were compared with TGA experimental results at 900-980°C. The mean nucleophilic Fukui function of the H-terminated char models and active sites located at similar edge positions decreased with increasing size of char molecules and followed the sequence: zigzag > armchair > tip active sites. The mean DFT-DNP values for the activation energy of 233 kJ mol-1 at the reactive carbon edge was in agreement with the experimental 191 ± 25 kJ mol-1 and 210 ± 8 kJ mol-1 for the respective chars.",
author = "Roberts, {Mokone J.} and Everson, {Raymond C.} and George Domazetis and Neomagus, {Hein W.J.P.} and Jones, {J. M.} and {Van Sittert}, {Cornelia G.C.E.} and Okolo, {Gregory N.} and Niekerk, {Daniel Van} and Mathews, {Jonathan P.}",
year = "2015",
month = "8",
day = "8",
doi = "10.1016/j.carbon.2015.05.053",
language = "English (US)",
volume = "93",
pages = "295--314",
journal = "Carbon",
issn = "0008-6223",
publisher = "Elsevier Limited",

}

Roberts, MJ, Everson, RC, Domazetis, G, Neomagus, HWJP, Jones, JM, Van Sittert, CGCE, Okolo, GN, Niekerk, DV & Mathews, JP 2015, 'Density functional theory molecular modelling and experimental particle kinetics for CO2-char gasification', Carbon, vol. 93, pp. 295-314. https://doi.org/10.1016/j.carbon.2015.05.053

Density functional theory molecular modelling and experimental particle kinetics for CO2-char gasification. / Roberts, Mokone J.; Everson, Raymond C.; Domazetis, George; Neomagus, Hein W.J.P.; Jones, J. M.; Van Sittert, Cornelia G.C.E.; Okolo, Gregory N.; Niekerk, Daniel Van; Mathews, Jonathan P.

In: Carbon, Vol. 93, 08.08.2015, p. 295-314.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Density functional theory molecular modelling and experimental particle kinetics for CO2-char gasification

AU - Roberts, Mokone J.

AU - Everson, Raymond C.

AU - Domazetis, George

AU - Neomagus, Hein W.J.P.

AU - Jones, J. M.

AU - Van Sittert, Cornelia G.C.E.

AU - Okolo, Gregory N.

AU - Niekerk, Daniel Van

AU - Mathews, Jonathan P.

PY - 2015/8/8

Y1 - 2015/8/8

N2 - Experimental measurements and DFT atomistic modelling were conducted to elucidate the mechanisms for gasification chemistry of char with CO2 gas. The molecular models used were based on experimental representations of coal chars derived from the vitrinite- and inertinite-rich South African coals at 1000°C. The HRTEM and XRD techniques were used to construct parallelogram-shaped PAH stacks of highest frequency in the vitrinite-rich (7 × 7) and intertinite-rich (11 × 11) char structures. Computations were executed to get the nucleophilic Fukui functions, at DFT-DNP level, to elucidate the nature and proportions of carbon active sites and quantify their reactivity. The DFT-DNP-computed reaction pathways and transition states, to obtain the energy of reaction and activation energies for the gasification reactions of CO2 with active carbon sites were examined. These results were compared with TGA experimental results at 900-980°C. The mean nucleophilic Fukui function of the H-terminated char models and active sites located at similar edge positions decreased with increasing size of char molecules and followed the sequence: zigzag > armchair > tip active sites. The mean DFT-DNP values for the activation energy of 233 kJ mol-1 at the reactive carbon edge was in agreement with the experimental 191 ± 25 kJ mol-1 and 210 ± 8 kJ mol-1 for the respective chars.

AB - Experimental measurements and DFT atomistic modelling were conducted to elucidate the mechanisms for gasification chemistry of char with CO2 gas. The molecular models used were based on experimental representations of coal chars derived from the vitrinite- and inertinite-rich South African coals at 1000°C. The HRTEM and XRD techniques were used to construct parallelogram-shaped PAH stacks of highest frequency in the vitrinite-rich (7 × 7) and intertinite-rich (11 × 11) char structures. Computations were executed to get the nucleophilic Fukui functions, at DFT-DNP level, to elucidate the nature and proportions of carbon active sites and quantify their reactivity. The DFT-DNP-computed reaction pathways and transition states, to obtain the energy of reaction and activation energies for the gasification reactions of CO2 with active carbon sites were examined. These results were compared with TGA experimental results at 900-980°C. The mean nucleophilic Fukui function of the H-terminated char models and active sites located at similar edge positions decreased with increasing size of char molecules and followed the sequence: zigzag > armchair > tip active sites. The mean DFT-DNP values for the activation energy of 233 kJ mol-1 at the reactive carbon edge was in agreement with the experimental 191 ± 25 kJ mol-1 and 210 ± 8 kJ mol-1 for the respective chars.

UR - http://www.scopus.com/inward/record.url?scp=84931274320&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84931274320&partnerID=8YFLogxK

U2 - 10.1016/j.carbon.2015.05.053

DO - 10.1016/j.carbon.2015.05.053

M3 - Article

AN - SCOPUS:84931274320

VL - 93

SP - 295

EP - 314

JO - Carbon

JF - Carbon

SN - 0008-6223

ER -

Roberts MJ, Everson RC, Domazetis G, Neomagus HWJP, Jones JM, Van Sittert CGCE et al. Density functional theory molecular modelling and experimental particle kinetics for CO2-char gasification. Carbon. 2015 Aug 8;93:295-314. https://doi.org/10.1016/j.carbon.2015.05.053