Chemistry and Properties of Carbon Fiber Feedstocks from Bitumen Asphaltenes
Notice bibliographique
Résumé
Carbon fibers are materials of paramount importance for composites applied in fields such as aerospace engineering, medicine, and renewable energy. Currently, most of the production of carbon fibers uses polyacrylonitrile, which incurs significant greenhouse gas emissions and high production costs. Therefore, carbon fiber manufacturing from asphaltene-enriched feedstocks is attractive as it could add value to extra-heavy fossil fuels and cut down precursor costs by ∼90%. Recent studies indicate that some asphaltene-rich samples feature rheological properties that make them optimal for melt-spinning and carbon fiber production; in other cases, the spun asphaltene feedstocks are unsuitable for such applications. In this work, bitumen asphaltenes were subjected to upgrading processes under three distinctive conditions to tweak their rheological properties in order to produce carbon fibers. The treated samples were comprehensively studied by separations based on solubility and extrography, and subsequently characterized by ultrahigh-resolution mass spectrometry, gas-phase fragmentation, and thermogravimetric analysis. The results indicate that upon thermal processing, asphaltene-rich feedstocks produced a mixture with diverse solubility, i.e., maltenes, asphaltenes, and toluene-insoluble material. The molecular composition of remnant asphaltenes suggests that thermal treatment dramatically decreased molecular polydispersity in terms of the content of heteroatoms, alkyl chains, and structural motifs, i.e., single-core vs multicore, also known as island vs archipelago. The processed asphaltenes revealed high abundances of alkyl-depleted island species. Such thermally treated samples produced no stable carbon fibers. Conversely, a feedstock treated with molten sodium in a proprietary process designed to remove sulfur, revealed increased content of alkyl-side chains and archipelago structural motifs. This sample produced stable carbon fibers. Furthermore, thermal analysis coupled with mass spectrometry (TGA-HRMS) was conducted to understand thermal desorption and pyrolysis profiles for the samples, as well as the presence of occluded compounds and carbon residue formation. The TGA-HRMS results are consistent with extrography and IRMPD FT-ICR MS studies and confirmed the ultrahigh abundance of multicore compounds in the desulfurized sample. Although the sample size is limited, and thus, correlations between molecular composition and rheology properties are not achieved, this is the first study that aims to understand the role of feed composition in the ability to generate carbon fibers from asphaltene-enriched feedstocks. Collectively, the results indicate that samples comprised of abundant highly aromatic asphaltenes, dominant in alkyl-depleted single-core structures, are unlikely optimal for carbon fiber applications. Conversely, a sample with a marked increase in H/C, a significant decrease in S content, and abundant multicore species could generate stable carbon fibers. More studies are underway to find correlations between molecular features and carbon fiber production.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».