Effect of Pressure on Visbreaking Product Composition and Properties
Bibliographic record
Abstract
Visbreaking is a thermal conversion process employed to decrease the viscosity of residual oils, and cracking occurs mainly in the liquid phase. The impact of pressure on thermal cracking is expected to be minor, yet several observations in the literature indicate that pressure may affect coking, the olefin-to-paraffin ratio, and product composition. In this study, the impact of pressure on coil visbreaking at 400 °C was evaluated in a closed system at a severity sufficient to cause the onset of coking. The products from thermal conversion with initial pressures of 0.5–2.0 MPa (low pressure) differed from those with initial pressures of 2.5–4.0 MPa (high pressure). High pressure suppressed coking, and at comparable vacuum residue conversion, the coke yield was lower at high pressure than at low pressure. Pressure had a minor impact on the distillation profile of the products. Under conditions of controlled space time, pressure did not affect the olefin-to-paraffin ratio, H/C molar ratio, or microcarbon residue. Pressure had an impact on composition-dependent properties, such as the first derivative of density and refractive index with respect to temperature, viscosity, and aromatic hydrogen content. No relationship was found between initial pressure and free radicals, n -pentane insoluble content, and molar element ratios measured in the study.
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 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 | 0.001 |
| 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".