Transformation of Petroporphyrins-Enriched Subfractions from Atmospheric Residue during Noncatalytic Thermal Process under Hydrogen by Positive-Ion Electrospray Ionization FT-ICR Mass Spectrometry
Bibliographic record
Abstract
Nickel and vanadyl porphyrins were separated from atmospheric residue of Canadian oil sand bitumen by solvent extraction and column chromatography and then subjected to noncatalytic thermal process under hydrogen. The petroporphyrins before and after thermal process were characterized by UV–vis spectroscopy and positive-ion electrospray ionization FT-ICR mass spectroscopy to probe their structural transformation. Three main vanadyl porphyrins, including N 4 VO, N 4 VOS, and N 4 VO 2 and a fraction of N 5 VO 2 are identified in the feed fraction. With time increasing, the relative abundance of C n H 2 n –28 N 4 VO (DBE = 17) increases initially and then decreases, in contrast with C n H 2 n –26 N 4 VO (DBE = 18). It suggests the hydrogenation and rapid hydrogenolysis of petroporphyrins. The carbon number shifts to the lower mass range with increased process severity, indicating extensive thermal cracking reactions of petroporphyrins have occurred. N 4 VOS porphyrins show very similar variation of DBE and carbon number distribution as N 4 VO. A considerable proportion of new types of N 4 VO 2, N 4 VO 3 and N 5 VO 2 are identified in the product after 30 min by accurate mass measurement and isotopic distribution. Under more severe conditions, these new species gradually diminish. It is inferred that the new species could most possibly derive from disassociation of large molecules in addition to chemical transformation. H 2 S and high hydrogen pressure could promote the hydrogenation of petroporphyrins. H 2 S can also enhance their thermal cracking reaction while high hydrogen pressure inhibits it. Nickel porphyrins present almost the same phenomena with vanadyl porphyrins, though with low content. Analysis of the petroporphyrins at the molecular level reveals their behavior and transformation during thermal process under hydrogen and could also benefit the catalysts design in HDM process.
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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".