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Pyrolysis of a large-scale molecular model for Illinois no. 6 coal using the ReaxFF reactive force field

Evidence and attribution

Authority of statements

Prose sections below (Summary, Methods, Findings, etc.) are curated summaries of the publication identified by doi, title, and pdf_path in the front matter above. They are not new primary claims by this wiki.

For definitive numerical values, reaction schemes, and interpretations, use the peer-reviewed article (and optional records under normalized/papers/ when present)—not this page alone.

Summary

The study applies ReaxFF reactive molecular dynamics to pyrolyze a large-scale molecular assembly of Illinois No. 6 coal represented by 728 diverse molecules in a simulation cell exceeding 50,000 atoms. Pyrolysis is conducted at 2000 K for 250 ps and continued until roughly 60% of cross-links have been thermally cleaved, a condition chosen so that chemistry occurs within a tractable simulation time at this elevated temperature. Initiation chemistry is attributed in the abstract to hydroxyl release, dehydrogenation of hydroaromatic moieties, and cleavage of heteroatom-containing cross-links. Reported volatile product classes include hydrogen, methyl, ethylene, acetylene, formaldehyde, ethynol, alkylphenols, alkylnaphthalenes, and alkylnaphthols, described as consistent with experimental tar and gas signatures. Molecular-weight distributions shift toward lower molar mass as thermal fragmentation proceeds, and tar structural motifs are compared with literature data.

Methods

Relationship to other ingests

  • Same JAAP article and scientific protocol as [[2014castro-marcano-journal-of-a-pyrolysis-large-scale]], but this pdf_path points at an Elsevier proof PDF (papers/Castro_JAAP_3246_proofs.pdf).

ReaxFF coal pyrolysis setup

  • ReaxFF reactive MD with the group’s coal/CHONS parameterization tracks bond-order-based bond formation/scission in the assembled Illinois No. 6 molecular model (abstract on sibling page).

Thermal schedule and stopping criterion

  • 2000 K for 250 ps, continued until ~60% of cross-links are disrupted (abstract).

Sulfur-free control

  • A sulfur-free duplicate model is run under the same schedule to isolate organic sulfur chemistry effects (abstract).

Canonical detail

  • For timestep/thermostat and analysis scripts, use the final JAAP issue PDF on [[2014castro-marcano-journal-of-a-pyrolysis-large-scale]] when available—not proof boilerplate alone.

1 — MD application (ReaxFF reactive MD)

  • Engine / code: Reactive molecular dynamics with ReaxFF per the shared JAAP abstract; specific MD package is N/A in the pages 1–2 extract—confirm in the final PDF.
  • System size & composition: >50,000 atoms; 728 diverse Illinois No. 6 molecules (abstract; extract for sibling slug).
  • Boundaries / periodicity / ensemble / timestep / thermostat / barostat: N/A — not stated in the indexed extract; confirm in the version-of-record PDF.
  • Duration / stages: 250 ps at 2000 K until ~60% of cross-links are disrupted primarily by thermolysis (abstract).
  • Temperature: 2000 K (abstract).
  • Pressure / electric field / enhanced sampling: N/A — not summarized in the abstract excerpt used here.

2 — Force-field training

N/A — application paper in the abstract framing (parameter provenance in the main text).

3 — Static QM

N/A — not the primary methodology in the abstract framing summarized here.

Findings

1 — Outcomes and mechanisms

The abstract reports that heteroatom-linked cross-links (sulfurated and oxygenated) thermally degrade more extensively than purely alkyl linkages, indicating higher reactivity near heteroatoms. Sulfur form analysis distinguishes aliphatic sulfur as more rapidly mobilized than thiophenic sulfur, matching qualitative experimental expectations. Quantitative heterocycle decomposition extents in the abstract include ~57% for pyrrolic, ~47% for thiophenic, and ~29% for furanic five-membered rings in the surveyed structures. Comparing sulfur-bearing versus sulfur-free trajectories, aryl/alkyl C–S bonds are found weaker than corresponding C–C bonds, so C–S cleavage yields greater fragmentation and higher evolution of inorganic gases and tars when sulfur is present—interpreted as sulfur accelerating pyrolysis kinetics in this model. The authors position ReaxFF plus representative coal structures as a practical probe of complex pyrolysis chemistry despite known force-field limitations.

2 — Comparisons

Qualitative alignment of volatile/tar chemistry and sulfur speciation trends with experiment is stated in the abstract (same scientific text as the issue PDF).

3 — Sensitivity

Sulfur-free duplicate trajectories isolate organic sulfur effects on gas/tar generation rates (abstract).

4 — Limitations (authored framing)

High T and short ps window vs laboratory pyrolysis timescales; see ## Limitations for corpus-specific proof-PDF caveats.

5 — Corpus / KB honesty

This slug’s pdf_path is an Elsevier proof (papers/Castro_JAAP_3246_proofs.pdf). Prefer [[2014castro-marcano-journal-of-a-pyrolysis-large-scale]] for version-of-record bytes and for Methods details not carried in short extracts.

Limitations

The corpus pdf_path is an Elsevier proof (Castro_JAAP_3246_proofs.pdf) with author-query boilerplate on page 1; pagination and figure placement may differ from the final issue. A single high-temperature, short-time window cannot represent full reactor residence-time distributions or pressure effects in industrial pyrolysis.

Relevance to group

van Duin and Russo coauthorship on ReaxFF for fossil energy and coal devolatilization chemistry aligned with group combustion and pyrolysis modeling.

Citations and evidence anchors

  • “Please cite this article in press as…” DOI http://dx.doi.org/10.1016/j.jaap.2014.07.011 (extract).
  • Structured abstract fields (extract).