Effect of Chemical Structure on the Cracking and Coking of Archipelago Model Compounds Representative of Asphaltenes
Bibliographic record
Abstract
Cracking and coke formation of a series of pyrene-based model compounds were investigated by thermogravimetric analysis (TGA) and microreactor experiments. The structure of the model compounds is that of a three-island archipelago, consisting of two pyrenyl groups joined to a central aromatic or heteroaromatic group by ethano bridges. The molecular weights of these compounds range from 459–679 g/mol and have sufficiently high boiling points to remain liquid under the reaction conditions. TGA measured the cracking kinetics and the coke yield of each compound, where coke yield was defined as the solid residue remaining after a 10 °C/min ramp to 500 °C, followed by isothermal heating at 500 °C for 15 min. Microreactor experiments provided the yield and structure of both cracked and addition products. Analysis of the reaction products by gas chromatography, mass spectrometry (MS), high-pressure liquid chromatography, matrix-assisted laser desorption/ionization MS, and tandem MS/MS show that the initial cracked fragments combined to form larger structures through a process of alkyl–alkyl and, to a lesser extent, alkyl–aryl C–C bond-forming reactions. The most likely mechanism for these processes includes a sequence of free-radical addition reactions to an unsaturated bond, followed by rearrangement(s), dehydrogenation, and/or further cracking. Compounds with heteroatoms incorporated in the central ring typically gave higher yields of coke and different selectivity of the cracked products, compared to hydrocarbon compounds. The change in cracking selectivity is attributed to several possible factors including a neophyl–like rearrangement, while the coke yield is governed by the rate of addition reactions, as well as the nature and reactivity of both the starting compound and the initially formed products. To test the hypothesis that molecular alignment and aggregation play a role in the observed coke yield, six model compounds were examined for liquid crystalline behavior under cross-polarized light microscopy. In this series of compounds, the coke yield increased as the isotropic temperature decreased.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".