Effect of Ring-Configuration on Pyrolysis and V<sub>2</sub>O<sub>5</sub>Catalyzed Oxidation of Polycyclic Aromatic Hydrocarbons
Bibliographic record
Abstract
Conversion of polycyclic aromatic hydrocarbons (PAHs) through oxidative ring-opening can be used as a potential strategy for upgrading of aromatic-rich fractions of heavy oil and bitumen. At the core of such a process is the oxidation of PAHs to produce quinonoids, further oxidation of quinonoids to form ring-opened carboxylic acids, and finally decarboxylation of the carboxylic acids. The fused ring systems in PAHs include linear and angular ring-configurations, which affect pyrolysis and oxidation selectivity. This study evaluated the effect of the ring-configuration of PAHs on pyrolysis and on oxidation over a metal oxide catalyst (V 2 O 5 ). Pyrolysis takes place in parallel with catalytic oxidation, and so it has an effect on the observed conversion chemistry. Liquid-phase pyrolysis and V 2 O 5 -catalyzed conversion of anthracene, phenanthrene, anthraquinone, and phenanthrenequinone were studied individually. All experimental work was conducted under a nitrogen atmosphere to avoid autoxidation. Results from high-pressure differential scanning calorimetry (HP-DSC) as well as from batch oxidation reactions indicated differences in reactivities due to the ring-configurations of both PAHs and their corresponding quinonoids. The reactivity sequence over V 2 O 5 for PAHs was anthracene > phenanthrene as the increase in π-sextets in anthracene provided additional driving force toward oxidation. On the contrary, the reactivity over V 2 O 5 of the corresponding quinonoids was phenanthrenequinone > anthraquinone. The angular configuration of phenanthrenequinone led to the carbonyl groups to be adjacent and to the carbons participating in that C–C bond to have an aliphatic nature, which increased the reactivity of the bond. The angular ring-configuration of phenanthrenequinone favored intramolecular ring-closing reactions, while the linear ring-configuration of anthraquinone exhibited higher stability toward oxidation. Conversion of anthraquinone led to products of oxygen removal via anthrone as well as to some ring-opened products. Compared to pyrolysis, V 2 O 5 accelerated the conversion of PAHs and their corresponding quinonoids. Regardless of the ring-configuration, catalytic oxidation of PAHs over V 2 O 5 did not favor production of ring-opened products. The study highlighted the importance of a hydrogen source, possibly water, for a successful ring-opening.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".